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An investigation of cadmium, zinc and lead isotope signatures and their use as tracers in the environment Shiel, Alyssa Erin 2010

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AN INVESTIGATION OF CADMIUM, ZINC AND LEAD ISOTOPESIGNATURES AND THEIR USE AS TRACERS IN THE ENVIRONMENTbyAlyssa Erin ShielB.Sc., The University of Arizona, 2003A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR THE DEGREE OFDOCTOR OF PHILOSOPHYinThe Faculty of Graduate Studies(Oceanography)THE UNIVERSITY OF BRITISH COLUMBIA(Vancouver)August 2010©Alyssa Erin Shiel, 2010AbstractEnvironmental monitoring and remediation require techniques to identify thesource and fate of metals emissions. In this study, Cd and Zn isotopes were evaluated astools for the identification of metal sources through (1) the assessment of metallurgicalprocessing as a source of Cd and Zn isotopic fractionation and (2) the measurement ofisotopic compositions in bivalves from sites receiving variable metal contributions fromnatural and anthropogenic sources. This study was facilitated by the successfuldevelopment of a technique to measure Cd and Zn isotopes (MC-ICP-MS) inenvironmental and anthropogenic samples.Cadmium, Zn and Pb isotopic ratios were measured for samples from anintegrated Zn–Pb smelting/refining complex in B.C. (British Columbia, Canada).Significant fractionation of Cd and Zn isotopes during processing is demonstrated by thetotal isotopic variation in δ114/110Cd (1.04‰) and δ66/64Zn (0.42‰) among smelter samples.Characterization of Cd and Zn isotopic compositions in emissions as fractionated relativeto ores demonstrates the tracing capability of this new tool. Moreover, Pb isotopicsignatures may be used to identify sources contributing metals to environmental samples.Combined Cd, Zn and Pb isotope systematics were used to trace the source anddistribution of these metals in bivalves from western Canada (B.C.), the USA and France.Variability in δ114/110Cd of bivalves (-1.20 to -0.09‰) is attributed to differences in therelative contributions of Cd from natural and anthropogenic (e.g., smelting) sourcesbetween sites. High Cd levels in B.C. oysters are identified as primarily natural, withsome additional variability attributed to anthropogenic sources. In contrast, high Cdlevels in French bivalves (Gironde estuary and Marennes-Oléron basin) are primarilyanthropogenic. Variability in δ66/64Zn values exhibited by bivalve samples is small (0.28to 0.46‰), with the exception of oysters from the polluted Gironde estuary (1.03 to1.15‰). Lead isotopes are used to identify emissions from industrial processes and theconsumption of unleaded gasoline and diesel fuel as metal sources to bivalve samples.This study demonstrates the effective use of Cd and Zn isotopes to traceanthropogenic sources in the environment and the benefit of combining these tools withPb “fingerprinting” techniques.iiTable of ContentsAbstract ..........................................................................................................................iiTable of Contents...........................................................................................................iiiList of Tables ................................................................................................................viiList of Figures................................................................................................................ ixAcknowledgements........................................................................................................ xiCo-authorship Statement ..............................................................................................xiiiCHAPTER 1 Introduction............................................................................................ 11.1 Introduction......................................................................................................... 21.1.1 Anthropogenic perturbations of natural Cd, Zn and Pb distributions............ 31.1.2 Radiogenic isotope tracer– Pb stable isotopes.............................................. 41.1.3 Mass-dependent fractionation ..................................................................... 51.1.4 Cd and Zn isotope variations in the environment......................................... 71.1.5 Metal Pollution in British Columbia (Canada)............................................. 91.1.6 High Cd levels in oysters from British Columbia ........................................ 91.2 Overview of the dissertation .............................................................................. 101.3 References......................................................................................................... 17CHAPTER 2 Matrix effects on the multi-collector inductively coupled plasma massspectrometric analysis of high-precision cadmium and zinc isotope ratios .............. 242.1 Introduction....................................................................................................... 252.2 Experimental ..................................................................................................... 272.2.1 Reagents and standards ............................................................................. 282.2.2 Isotopic standards ..................................................................................... 282.2.3 Ion exchange chemistry ............................................................................ 282.2.4 Mass spectrometry .................................................................................... 302.2.4.1 Trace element analyses..................................................................... 302.2.4.2 Isotopic analyses .............................................................................. 302.2.5 Isotope data presentation........................................................................... 312.2.6 Description of the matrix experiments....................................................... 322.2.7 Matrix components ................................................................................... 322.3 Results and discussion ....................................................................................... 332.3.1 Bulk column blank matrix addition ........................................................... 332.3.2 Inorganic elements introduced during cadmium column chemistry............ 352.3.3 Inorganic matrix effects ............................................................................ 352.3.4 Chemical treatment of resin-derived organics............................................ 36iii2.3.5 Correction of delta values ......................................................................... 372.3.6 Consequences for natural samples............................................................. 382.4 Conclusions....................................................................................................... 392.5 Acknowledgements ........................................................................................... 402.6 References......................................................................................................... 50CHAPTER 3 Evaluation of zinc, cadmium and lead isotope fractionation duringsmelting and refining .................................................................................................. 553.1 Introduction....................................................................................................... 563.2 Materials and methods....................................................................................... 593.2.1 Sample materials and collection................................................................ 593.2.2 Sample preparation ................................................................................... 623.2.2.1 Reagents........................................................................................... 623.2.2.2 Sample digestion .............................................................................. 633.2.2.3 Anion exchange chromatography ..................................................... 633.2.3 Standards .................................................................................................. 643.2.4 Data presentation ...................................................................................... 653.2.5 Analytical techniques................................................................................ 653.2.5.1 Elemental analysis............................................................................ 653.2.5.2 Isotopic analysis............................................................................... 663.2.5.2.1 Zn and Cd isotopes .................................................................. 663.2.5.2.2 Pb isotopes .............................................................................. 673.2.5.2.3 Spectral and non-spectral interferences .................................... 683.3 Results............................................................................................................... 693.3.1 Zn, Cd and Pb isotopes ............................................................................. 693.3.1.1 Zn isotopes....................................................................................... 693.3.1.2 Cd isotopes....................................................................................... 693.3.1.3 Pb isotopes....................................................................................... 703.4 Discussion ......................................................................................................... 713.4.1 Fractionation of Zn, Cd and Pb isotopes during Zn refining ...................... 713.4.1.1 Zn isotope variation.......................................................................... 713.4.1.2 Cd isotope variation ......................................................................... 733.4.1.3 Pb isotope variation.......................................................................... 753.4.2 Implications for local environmental samples............................................ 773.5 Conclusions....................................................................................................... 783.6 Acknowledgements ........................................................................................... 793.7 References......................................................................................................... 89ivCHAPTER 4 Tracing cadmium, zinc and lead pollution in bivalves from the coastsof western Canada, the USA and France using isotopes............................................ 944.1 Introduction....................................................................................................... 954.1.1 Cd, Zn and Pb emission sources in Canada, the USA and France .............. 984.2 Materials and methods..................................................................................... 1014.2.1 Sample materials and collection.............................................................. 1014.2.2 Sample preparation ................................................................................. 1024.2.2.1 Reagents......................................................................................... 1024.2.2.2 Sample digestion ............................................................................ 1034.2.2.3 Anion exchange chromatography ................................................... 1034.2.3 Standards ................................................................................................ 1034.2.4 Data presentation .................................................................................... 1044.2.5 Analytical methods ................................................................................. 1044.3 Results............................................................................................................. 1054.3.1 Cd isotopes ............................................................................................. 1054.3.2 Zn isotopes ............................................................................................. 1074.3.3 Pb isotopes.............................................................................................. 1084.4 Discussion ....................................................................................................... 1094.4.1 Isotopic variations in bivalves from the Pacific Coast of Canada andHawaii .................................................................................................... 1094.4.1.1 Cd isotope systematics ................................................................... 1094.4.1.2 Zn isotope systematics.................................................................... 1104.4.1.3 Pb isotope systematics.................................................................... 1114.4.2 Isotopic variations in bivalves from the USA Atlantic Coast ................... 1134.4.2.1 Cd isotope systematics ................................................................... 1134.4.2.2 Pb isotope systematics.................................................................... 1154.4.3 Isotopic variations in bivalves from the Atlantic and Mediterranean Coastsof France................................................................................................. 1174.4.3.1 Cd isotope systematics ................................................................... 1174.4.3.2 Zn isotope systematics.................................................................... 1194.4.3.3 Pb isotope systematics.................................................................... 1204.5 Conclusions..................................................................................................... 1224.6 Acknowledgements ......................................................................................... 1234.7 References....................................................................................................... 142vCHAPTER 5 Conclusions......................................................................................... 1525.1 Introduction..................................................................................................... 1535.2 Key findings of this study................................................................................ 1545.3 Suggestions for future research........................................................................ 1585.4 References....................................................................................................... 161Appendices ................................................................................................................ 162Appendix A List of publications and presentations during Ph.D. ................................ 163Appendix B Cd and Zn separation chemistry.............................................................. 165Appendix C Column matrix effects on Cd and Ag ion-signal intensities and delta Cdvalues .............................................................................................................. 166Appendix D Column matrix effects on Zn and Cu ion-signal intensities and delta Znvalues .............................................................................................................. 167Appendix E Inorganic column-derived matrix effects on Cd and Ag ion-signal intensitiesand delta Cd values.......................................................................................... 168Appendix F Matrix effects from metallic elements on Cd and Ag ion-signal intensitiesand delta Cd values.......................................................................................... 169Appendix G Matrix effects from metallic elements on Zn and Cu ion-signal intensitiesand delta Zn values.......................................................................................... 170Appendix H Plot of δ114/110Cd vs. δ111/110Cd for B.C. oyster soft tissues and gutcontents ........................................................................................................... 171Appendix I Method for the measurement of Cd isotopes in environmental and geologicalsamples............................................................................................................ 172Appendix J Stanley Park trees.................................................................................... 175Appendix K Stanley Park trees, sampling locations.................................................... 178Appendix L Stanley Park trees, core sampling of the fallen trees................................ 179Appendix M Stanley Park trees, photographs ............................................................. 180Appendix N Stanley Park trees, Pb concentrations and isotopic compositions ............ 181Appendix O Stanley Park trees, Pb concentrations and 206Pb/207Pb values ................... 182viList of TablesCHAPTER 1Table 1.1 Metal (Zn, Cd and Pb) abundances in continental crust, ocean seawaterand human blood.................................................................................... 13CHAPTER 2Table 2.1 Inorganic contents of column chemistry blanks are shown for three resincleaning methods, the routine clean was used in this study ..................... 41Table 2.2 Cadmium isotope data for secondary Cd isotopic standards and formeasurement of a "zero-delta" by back-to-back analysis of the PCIGR-1Cd standard............................................................................................ 42Table 2.3 Zinc isotope data for the in-house secondary Zn isotopic standard and formeasurement of a "zero-delta" by back-to-back analysis of the PCIGR-1Zn standard ............................................................................................ 43Table 2.4 First and second ionization energies (eV) and atomic weights for analytesand matrix elements relevant in this study .............................................. 44CHAPTER 3Table 3.1 Zinc and Cd contents and isotopic compositions .................................... 80Table 3.2 Lead contents and isotopic compositions................................................ 81CHAPTER 4Table 4.1 Estimated Pb emissions from the consumption of petroleum products andcoal in B.C. (2008) and all of Canada (1970 and 2008) ........................ 125Table 4.2 Estimated Pb emissions from the consumption of petroleum products andcoal in Canada, the USA and France (2005) ......................................... 126Table 4.3 Cadmium concentrations (µg g-1 dry weight) and isotopic compositions ofbivalve tissues...................................................................................... 127Table 4.4 Zinc concentrations (µg g-1 dry weight) and isotopic compositions ofbivalve tissues...................................................................................... 128viiTable 4.5 Lead concentrations (µg g-1 dry weight) and isotopic compositions ofbivalve tissues...................................................................................... 129viiiList of FiguresCHAPTER 1Figure 1.1 Variations in the Cd isotopic composition of select geological, marine andanthropogenic samples ........................................................................... 14Figure 1.2 Variations in the Zn isotopic composition of select geological, marine andanthropogenic samples ........................................................................... 15CHAPTER 2Figure 2.1 Matrix effects on Cd isotope ratio measurements as a function of bulkcolumn blank matrix addition................................................................. 45Figure 2.2 Matrix effects on Zn isotope ratio measurements as a function of bulkcolumn blank matrix addition................................................................. 46Figure 2.3 Matrix effects for solutions doped with metallic elements: (a) 110Cd and109Ag ion signal intensities and (b) 64Zn and 63Cu ion signal intensities .. 47Figure 2.4 Matrix effects for solutions doped with metallic elements: (a) δ114/110CdSSBand δ114/110CdAg-corr. values and (b) δ66/64ZnSSB and δ66/64ZnCu-corr. values . 48Figure 2.5 Matrix effects as a function of the dilution of the Cd eluate cut for abivalve sample ....................................................................................... 49CHAPTER 3Figure 3.1 Schematic depiction of Zn and Pb operations at Teck’s integrated Zn andPb smelting and refining complex in Trail (B.C., Canada)...................... 82Figure 3.2 Mass-dependent Zn and Cd isotopic fractionation for all Zn and Cdsamples.................................................................................................. 84Figure 3.3 Plots of (a) 208Pb/206Pb vs. 206Pb/207Pb and (b) 208Pb/204Pb vs. 206Pb/204Pbfor all smelter and refinery Pb samples................................................... 85Figure 3.4 Variations in Zn isotopic composition of samples from the smelting andrefining operations depicted in Fig. 3.1 and published geological andanthropogenic materials ......................................................................... 86ixFigure 3.5 Variations in Cd isotopic composition of samples from the smelting andrefining operations depicted in Fig. 3.1, recycled Cd metal, CdS pigmentand published geological and anthropogenic materials ........................... 88CHAPTER 4Figure 4.1 Pie charts of the relative Pb emission contributions from petroleumproducts and coal consumption in Canada, the USA and France in2005..................................................................................................... 130Figure 4.2 Map of SW British Columbia showing the locations of samplingsites...................................................................................................... 131Figure 4.3 Map of the USA East Coast and Hawaii (inset) showing the locations ofsampling sites ...................................................................................... 132Figure 4.4 Map of France showing the locations of sampling sites ........................ 133Figure 4.5 Histogram of the Cd concentrations of oyster and mussel samplescollected between 2002 and 2006......................................................... 134Figure 4.6 Plot of variations in the Cd isotopic composition of bivalve samples,inclusive of those from western Canada (B.C.), Hawaii, the USA EastCoast and France.................................................................................. 135Figure 4.7 Mass-dependent Cd and Zn isotopic fractionation for all bivalvesamples................................................................................................ 136Figure 4.8 Plot of 208Pb/206Pb vs. 206Pb/207Pb for the B.C. and Hawaiianoysters ................................................................................................. 137Figure 4.9 Plot of 208Pb/206Pb vs. 206Pb/207Pb for the USA East Coast bivalves........ 138Figure 4.10 Plot of 208Pb/206Pb vs. 206Pb/207Pb for the French bivalves ...................... 139Figure 4.11 Variations in the (a) Cd and (b) Zn isotopic compositions of oysters(oyster gut contents indicated by a star) from the North Pacific Ocean,seawater, plankton, geological and anthropogenic materials ................. 140Figure 4.12 Variations in the (a) Cd and (b) Zn isotopic compositions of bivalves fromthe North Atlantic Ocean, seawater, plankton, geological andanthropogenic materials ....................................................................... 141xAcknowledgementsThere are many people I would like to thank for their support and encouragement,not only of my decision to pursue a Ph.D. but also during the journey, as all of themcontributed to my success. First, I would like to thank my supervisors Dominique Weisand Kristin Orians for the opportunity to conduct this research and for their supportthroughout this project. I am especially grateful to Dominique, who, in addition tokeeping my office stocked with Belgian chocolate, always had an open door, wasavailable for scientific discussions and pushed me to progress. Her support andunderstanding, especially at the end, will not be forgotten. I would like to give a specialthanks to Kristin for her contributions to this work, her advice and her commitment to myacademic development. I would like to thank Roger Francois, who provided expertise andencouragement, especially when I was first undertaking work with Cd isotopes. I wishalso to thank James Scoates for contributing to my overall academic growth, giving meadvice and providing comments on my writing and presentations.I am especially grateful to Jane Barling, who in addition to training me to operatethe Nu and helping me set-up a Cd measurement method, has always shown a keeninterest in my work and has asked probing questions that have benefited my research. Myscientific writing has been improved greatly by comments from Jane. I am thankful forthe help of Bert Mueller and Maureen Soon, who helped whenever asked, sharing a lot oftheir time and expertise. I am also grateful to many other talented researchers and supportstaff in EOS and PCIGR including Rich Friedman, Vivian Lai and Bruno Kieffer. Iwould like to thank George Kruzynski and Bill Heath for providing the B.C. oystersamples, for their interest in the Cd isotope study of B.C. oysters and for answering allmy questions (especially while I was preparing for my candidacy exam). I would alsolike to thank all the EOS administrative staff for their friendliness and dedication,especially Cecilia Li, Carol Leven, Alex Allen and Cary Thomson.I am thankful for the friendships of many other grad students in EOS andChemistry, this experience would not have been the same without them. During my firstfew years, I was fortunate to share an office with Cheryl Wiramanaden, Sabrina Crispoand Anka Lekhi. I am grateful for their help in solving analytical problems, as well asxitheir friendships. Cheryl and Sabrina are especially thanked for teaching me how to workin a trace metal clean lab and how to survive as a grad student. After Cheryl, Sabrina andAnka graduated, I was welcomed into the “bowling alley” and I am grateful for the manysupportive friends I have made during my residence there, especially Inês, Elspeth,Katrin, Caroline, Laure and Diane. Inês Nobre Silva and Elspeth Barnes helped groundme during the crazy period at the end and were there to congratulate me at each milestone(often with a glass of wine).I am very thankful for the support of my family and friends. Very special thanksgo to my parents, Wally and Holly, for raising me to work hard and to embracechallenges, and together with my sister, Diana, for the encouragement, frequent phonecalls and visits. Another special thanks goes to Mike for his understanding and support,especially during the more stressful periods. Many thanks go to my very supportiveextended family Anne, Arisia, Ajana and Alan Lee. Many of my best memories includethem, including camping and backpacking trips, especially the trip to Europe, and theirvisits to Vancouver. I would like to extend my gratitude to Ann Marie Wolf and AnnaSpitz, for allowing me to participate in the wonderful work being done at the SonoraEnvironmental Research Institute, Inc. (SERI) and for encouraging me to go to gradschool. Last but not least, I would like to thank my best friends in the world, Mel, Mindieand Will in Tucson, Debbie and Eric in Austin and Leila and Jamie in London, for theirfriendships and support over the years, as well as for endless memories of good times.xiiCo-authorship StatementThis dissertation includes three manuscripts (Chapters 2, 3 and 4); I am the leadauthor of each of the three manuscripts. The three manuscripts are all co-authored by mysupervisor, Dominique Weis, and my co-supervisor, Kristin J. Orians. They bothprovided financial support to the research carried out in this dissertation. Specificcontributions to each manuscript are described below.In preliminary efforts that facilitated the results presented in each of the manuscriptchapters, the lead author:• designed the set-up of the Cd isotopic method on the Nu Plasma MC-ICP-MS atPCIGR (UBC) with Jane Barling, based on a published method and adapted themethod for the purpose of this dissertation;• prepared samples for chemical analysis, including sample digestion and analyticalseparation techniques, as appropriate;• performed all elemental and Cd, Zn and Pb isotopic analyses;• interpreted all data;• wrote up research results and prepared all figures and tables;• prepared manuscripts for publication in peer-reviewed international scientificjournals.Chapter 2Matrix effects on the multi-collector inductively coupled plasma mass spectrometricanalysis of high-precision cadmium and zinc isotope ratiosAuthors: Alyssa E. Shiel, Jane Barling, Kristin J. Orians and Dominique WeisIn addition to the above, the lead author:• identified compromised Cd and Zn isotopic data quality;• reviewed existing literature of matrix effects on MC-ICP-MS analysis;• investigated the source of identified inaccuracies and imprecision through a seriesof experiments evaluating matrix effects on Cd and Zn isotopic analyses;xiii• developed and implemented solutions, including modifications to the Cd and Znisotopic sample preparation techniques.Jane Barling co-authored this manuscript; she and my supervisor, DominiqueWeis, contributed to the development of this project, the interpretation of the results andprovided comments on multiple versions of the manuscript. My co-supervisor, Kristin J.Orians, provided comments on the final version of the manuscript.Chapter 3Evaluation of zinc, cadmium and lead isotope fractionation during smelting and refiningAuthors: Alyssa E. Shiel, Dominique Weis and Kristin J. OriansIn addition to the above, the lead author:• identified the opportunity for unique study;• initiated the participation of Teck;• selected smelter samples;• developed an understanding of smelting processes;• undertook literature review of fractionation of Cd and Zn isotopes;• evaluated smelting and refining operations as sources of isotopic fractionation.I initiated this project with my supervisor, Dominique Weis, to assess theanthropogenic contribution to Cd and Zn isotope systematics in B.C. Smelter sampleswere provided by John F.H. Thompson (Teck Resources Ltd., VP Technology andDevelopment). Michael Heximer (Teck Metals Ltd.) significantly contributed to thisstudy by assisting with sample selection, providing expertise on smelting processes andreviewing the manuscript. My supervisor, Dominique Weis, provided comments onmultiple manuscript versions. The manuscript significantly benefited from commentsprovided by Jane Barling. My co-supervisor, Kristin J. Orians, provided comments on thefinal version of the manuscript.xivChapter 4Tracing cadmium, zinc and lead pollution in oysters from the coasts of western Canada,the USA and France using isotopesAuthors: Alyssa E. Shiel, Dominique Weis and Kristin J. OriansThe lead author:• coordinated the participation of bivalve samples from the USA and France• investigated natural variability of Cd and Zn isotopes and evaluated their use astracers of anthropogenic emissions• traced anthropogenic Pb using Pb isotopes.The initial premise (B.C. part) for the study came from my co-supervisor, KristinJ. Orians, George M. Kruzynski (Fisheries and Oceans Canada) and my supervisor,Dominique Weis. The expansion of the study to include bivalves from France and theUSA and to broaden the scope of the isotopic study by integrating Pb isotopiccompositions (fingerprinting) was developed through my discussions with DominiqueWeis.B.C. oyster tissue samples, as well as assistance with sample selection, wereprovided by George M. Kruzynski, William Heath (B.C. Ministry of Agriculture Foodand Fisheries) and Leah I. Bendell (Simon Fraser University). Didier Claisse and DanielCossa (IFREMER, France) from the French monitoring network (RNO) provided bivalvesamples from coastal France. Gunnar Lauenstein (NOAA, U.S.A.) from the MusselWatch Project of the U.S. National Status and Trends Program provided bivalve samplesfrom the USA East Coast and Hawaii. This manuscript benefited from my discussionswith Dominique Weis, Kristin J. Orians, George Kruzynski, William Heath and DanielCossa and the review of multiple manuscript versions by Dominique Weis. In addition,Kristin J. Orians and Jane Barling provided constructive reviews of this manuscript.In addition to that provided by the supervisory committee, noteworthy academicsupport was provided regularly by James S. Scoates, who also reviewed portions of eachmanuscript chapter.xvCHAPTER 1Introduction11.1 IntroductionMetal contamination of the environment poses a risk to the health of naturalecosystems and resident organisms and can have devastating implications for humanhealth. Environmental monitoring and assessment techniques, which evaluate the source,transport and fate of metals in the environment, are instrumental in assessing the impactof metal emissions and maximizing the efficiency of remediation strategies. Some tracemetals, e.g., zinc (Zn), are essential micronutrients (biologically necessary), whereas,cadmium (Cd), and lead (Pb) are non-essential metals and may be toxic even at lowconcentrations. The concentration of the micronutrient Zn is much higher than those ofCd and Pb in human blood (Table 1.1), reflecting its significance in human nutrition andhealth. Cadmium and Pb compounds are carcinogenic and can cause birth defects(Emsley, 1998). There is a low risk of severe or fatal Cd poisoning from ingestion due tothe associated emetic action (i.e., induces vomiting). However, cumulative exposures toCd cause accumulation in the kidneys and eventually renal dysfunction (Elinder andJärup, 1996). Endemic outbreaks of renal disease have been reported in areas of Japanfrom repeated Cd exposures consequent to the consumption of rice grown on soilspolluted by mining and ore processing (Nogawa and Ishizaki, 1979). In the case of Pbingestion, most Pb passes through the body without being absorbed but Pb poisoning iscumulative; e.g., Pb poisoning is reported in children from exposures to soil and dustcontaminated with Pb from leaded gasoline and lead-based paints (Mielke and Reagan,1998).Cadmium, Zn and Pb are present in the natural environment (e.g., continentalcrust and seawater) at trace levels (Table 1.1), with the exception of the much higherconcentrations found in ores. Environmental sources of these metals include naturalsources (e.g., for all these metals, the weathering of rocks and volcanic activity, and inthe case of Pb, radioactive decay) and anthropogenic sources. Major metal pollutionresults from the combustion of fossil-fuels by stationary (e.g., power plants) and mobile(e.g., automobiles and air planes) sources, mining, smelting, manufacturing and wasteincineration. In the USA, national emission standards exist for the release of hazardousair pollutants (Clean Air Act) and Priority Pollutants (Clean Water Act), which include2Cd, Zn and Pb. In addition, industrial and federal facilities must report releases ofchemicals on the toxic release inventory list (e.g., Cd, Zn and Pb) to the USEnvironmental Protection Agency (US EPA).1.1.1 Anthropogenic perturbations of natural Cd, Zn and Pb distributionsSignificant anthropogenic emissions may be much larger than natural inputs andthus greatly impact the natural geochemical cycling of heavy metals. Anthropogenicactivities have long lead to disturbances in natural Pb levels and distributions. At least5,000 years ago, Pb was produced as a by-product of silver metal production, which wasrefined from sulfide ores using smelting and cupeling techniques (Settle and Patterson,1980). Mining and smelting operations, for the sole intention of refining Pb, haverepresented a significant portion of total Pb production only during the past century(Settle and Patterson, 1980). Globally, modern anthropogenic sources account for ~91%of total (sum of natural and anthropogenic) atmospheric Pb emissions to the environment(Pacyna and Pacyna, 2001).In 1976, Pb concentrations in the bones of Americans were revealed to be ~500×higher than those measured in the bones of Ancient Peruvians (Ericson et al., 1979).Between the early 1980s and mid-1990s, a global decline (~64%) in Pb emissions to theatmosphere was observed (Pacyna and Pacyna, 2001). Reductions in atmospheric Pbemissions are related primarily to the introduction of unleaded gasoline and the phase-outof leaded gasoline for use in automobiles in Canada (banned in 1990), the USA (bannedin 1996), and Europe (e.g., banned in France in 2000). In the USA, Pb consumption was10× larger when Pb was used as antiknock additive in gasoline (Reuer and Weiss, 2002).Combustion of unleaded and leaded gasoline (the latter being gasoline treated with anorganolead compound, most commonly tetraethyl lead) remains the major source ofglobal atmospheric Pb emissions, accounting for approximately 74% of totalanthropogenic Pb emissions (Pacyna and Pacyna, 2001).Similarly, global anthropogenic emissions of Cd and Zn to the atmosphere areestimated to account for the majority (70% for Cd and 56% for Zn) of total (i.e., sum ofnatural and anthropogenic) emissions of these metals (Pacyna and Pacyna, 2001). Thelargest source of Cd and Zn emissions to the atmosphere is non-ferrous metal smelting3and refining, accounting for approximately 72–73% of anthropogenic emissions of thesemetals (Pacyna and Pacyna, 2001). Emissions of trace metals, including Cd and Zn, to theatmosphere from non-ferrous metal smelting and refining in North America and Europedecreased during the 1980/90s due to increasingly strict government regulations and theestablishment of more efficient technologies for emission control. As a result, betweenthe early 1980s and mid-1990s, a global decline (~61 or 57%, respectively) inatmospheric emissions of Cd and Zn was observed (Pacyna and Pacyna, 2001).Recent studies have demonstrated the global impact of anthropogenic trace metalemissions to the atmosphere. In a study examining metal levels in ice from Greenland,Candelone et al. (1995) reported that levels of Cd and Zn were undetectable before theIndustrial Revolution, in contrast, recorded Pb levels were already an order of magnitudeabove natural levels (compared with levels in ice deposited ~7760 yrs BP) by the late 18thcentury. Levels of Cd, Zn and Pb were reported to have increased from the beginning ofthe record (1774) until the 1960/70s and then to decrease during the following decades(Candelone et al., 1995). Planchon et al. (2002) measured trace metals in Antarcticsnow/ice deposited from 1834 to 1990. They report enhancements during recent decadesof Cr, Cu, Zn, Ag, Pb, Bi and U related to anthropogenic activities (largely non-ferrousmetal smelting and refining) in the Southern Hemisphere, especially in South America,Southern Africa and Australia. They found no clear temporal trend for Cd.Potential exists for the measurement of metal isotopic compositions tounequivocally trace the source of metal emissions. Identification of the source and fate ofthese anthropogenic metal emissions, and differentiation between natural andanthropogenic metals in the environment will aid in reducing environmental exposuresand lead to improved environmental and human health.1.1.2 Radiogenic isotope tracer– Pb stable isotopesLead has four stable isotopes with masses between 204 and 208, three (206Pb, 207Pband 208Pb) are the stable end products of radioactive decay chains (238U, 235U and 232Th,respectively), while one is a non-radiogenic isotope (204Pb). The Pb isotopic compositionof anthropogenic emissions resulting from high temperature processes (e.g., fossil fuelcombustion, smelting and refining) reflects the isotopic composition of the source4materials. As a result, Pb isotopic composition can be used to trace the source of Pbemissions in a technique called “fingerprinting”. In addition, the relative contributions ofboth natural and anthropogenic Pb sources may be determined when the isotopiccompositions of the sources are well constrained. This fingerprinting technique hasproven to be a very useful tracer of Pb pollution (and other associated metals) in theenvironment for over the past three decades.The utility of Pb isotopes as a tracer of anthropogenic emissions was firstsuggested by the work of Chow and co-workers (i.e., Chow et al., 1975), whichdemonstrated the large range in Pb isotopic composition found in leaded gasoline (i.e.,ores), coals and aerosols (Reuer and Weiss, 2002). In an early study, Shirahata et al.(1980) discovered chronological co-related variations in both Pb concentration andisotopic composition; elevated Pb concentrations in surface sediment layers (~4× higherthan the levels found in layers 130 yr old) were linked to industrial sources using Pbisotopes. Lead isotopes have been used to trace the source of Pb in, e.g., blood, animaltissues, groundwater, seawater and soils (see the review article: Weiss et al., 1999). Inaddition, Pb isotope measurements of various environmental archives (e.g., ice, peatbogs, sediments, corals, trees and lichens) have provided records of temporal changes inPb emission sources (Weiss et al., 1999).1.1.3 Mass-dependent fractionationAlthough the isotopic compositions of other heavy metals, e.g., Cd and Zn, arenot controlled by radioactive decay, mass-dependent fractionation of these elements maybe used to trace the source of these elements in the environment. For elements with morethan one isotope, mass-dependent fractionation can lead to natural variations in theisotopic composition of the element. The stable isotopic composition of a sample reflectsthat of the source plus any isotopic fractionation introduced by physical and chemicalreactions (Peterson and Fry, 1987). Mass-dependent fractionation for an element isdependent on the relative mass difference for the isotope pair (the difference in massbetween the isotopes, Δm, relative to the average mass of the element’s isotopes). As aresult, the relative mass difference decreases with increasing mass for Δm=1. For thetraditional light stable isotopes, C and N, the relative mass differences for Δm=1 are 8%5and 7%, respectively. For heavier elements, such as Zn and Cd, the relative massdifferences for Δm=1 are much smaller, 1.5% and 0.9%, respectively.The light stable isotope systems, such as H, C, N, O and S, have been traditionallystudied using isotope ratio mass spectrometry instruments; however, use of this techniqueis limited to light elements, which can easily be converted to common gases. Heavyisotope systems, both radiogenic and stable, have been studied using thermal ionizationmass spectrometry (TIMS); recent TIMS instruments are equipped with multiplemoveable collectors allowing the simultaneous collection of several masses, overcomingsome earlier limitations associated with temporal stability of the ion beam. Isotopicanalysis using TIMS instruments is limited to elements that can be ionized using thethermal source, which has a low ion yield (much less than 1%, usually less than 0.3%)(Felton, 2003). The ICP source, which can ionize 95% of the periodic table (Felton,2003), affords the high ionization efficiency needed for the measurement of elementswith high ionization potentials such as Zn and Cd.The precision needed to measure the small natural variations in the isotopiccompositions of heavy elements (produced by mass-dependent fractionation) has onlybeen feasible in the last 15 yrs since the first multi-collector inductively coupled plasmamass spectrometry (MC-ICP-MS) instrument was introduced (Halliday et al., 1995).Prior to the MC-ICP-MS instrument, detection of the small variations in the isotopiccompositions of elements with masses >40 was difficult or impossible (Weiss et al.,2008). MC-ICP-MS has become the preferred method for non-traditional stable isotopeanalysis and has facilitated the measurement of the small isotopic variations of most non-traditional stable elements (e.g., Zn and Cd) in terrestrial materials. Elements reported asunder investigation using MC-ICP-MS include all elements, with two or more stableisotopes (i.e., excludes the listed elements: As, Be, Co and Mn), listed by the US EPA ashazardous air pollutants (Sb, Cd, Cr, Pb, Hg, Ni, Se) under the Clean Air Act and/or asPriority Pollutants (Sb, Cd, Cr, Cu, Pb, Hg, Ni, Se, Ag, Tl and Zn) under the Clean WaterAct.61.1.4 Cd and Zn isotope variations in the environmentVariations in the Cd and Zn isotopic compositions1 of select geological, marineand anthropogenic samples are shown in Fig. 1.1 and 1.2, respectively. Maréchal et al.(1999) and Wombacher et al. (2003) developed MC-ICP-MS techniques for the accurateand precise determination of Zn and Cd isotopic compositions, respectively, laying thefoundation for the numerous MC-ICP-MS studies of these elements that have followed.At the time this Ph.D. project was proposed, few studies had looked at natural variationsin Cd isotopes using MC-ICP-MS. Terrestrial rock and mineral samples were reported toexhibit only small variations (Δδ114/110Cd = 0.88‰; Fig. 1.1) in Cd isotopic composition(Wombacher et al., 2003) with the exception of the value reported for a layered tektite(impact-related rock) (δ114/110Cd = 3.04‰; not shown in Fig. 1.1). High temperatureprocesses (i.e., evaporation of Cd) were identified as a source of Cd isotopic fractionation(Wombacher et al., 2004).  Cloquet et al. (2005) measured Cd isotopic variations ingeological materials as well as anthropogenic samples (the latter shown in Fig. 1.1). Asignificant difference was reported (Cloquet et al., 2005) between the Cd isotopiccompositions of smelter produced dust and slag (Δδ114/110Cd = 1.00‰; Fig. 1.1).More recent work has included the determination of the Cd isotopic compositionof seawater; first by Lacan et al. (2006) who measured Cd isotopes in depth profiles fromthe Northwest Pacific Ocean and Northwest Mediterranean Sea, and then by Ripperger etal. (2007), who measured seawater samples from the Atlantic, Southern, Pacific andArctic Oceans (samples from the Atlantic and Pacific Oceans and the Mediterranean Seaare shown in Fig. 1.1). In addition, Lacan et al. (2006) demonstrated the preferentialuptake of light Cd by phytoplankton in culture experiments (Δδ114/110Cd = -1.35‰).Schmitt et al. (2009) and Horner et al. (2010) measured the Cd isotopic compositions inferromanganese crusts in an evaluation of their archiving of deep-water Cd isotopic                                                  1 Cd and Zn isotopic compositions of samples are reported in the standard delta (δ) permil (‰) notation relative to the JMC Cd (Wombacher and Rehkämper, 2004) and “Lyon-JMC” Zn reference standards (Maréchal et al., 1999):€ δ114 /110Cd =  (114 /110Cd)sample(114 /110Cd)standard−1       x 1,000€ δ66/64Zn =  (66 / 64Zn)sample(66 / 64Zn)standard−1       x 1,0007composition. The large study by A.-D. Schmitt et al. (2009) also measured Cd isotopes inMORB, OIB, loess and sphalerite (select samples are shown in Fig. 1.1). Systematicvariations in Cd isotopic composition (Fig. 1.1) were reported for polluted topsoil near aPb smelter and refinery in Northeast France (Cloquet et al., 2006b) and allowed theauthors to trace the Cd source. Gao et al. (2008) used Cd isotopes to identify sediments assmelting polluted (Fig. 1.1).Early work on Zn isotopes included measurements of marine samples, e.g.,ferromanganese nodules (representative of overlying waters; Fig. 1.2) and sediment trapmaterial (Maréchal et al., 2000) (Fig. 1.2). Large variations in the Zn isotopiccomposition of the carbonate fraction of a sediment core from the equatorial Pacificdeep-ocean suggested potential for use as a paleoceanography proxy for surfaceproductivity (Pichat et al., 2003). More recently, Zn isotopes have been measured inseawater from the North Pacific (Bermin et al., 2006; John, 2007) and the North Atlantic(John, 2007) and in seafloor hydrothermal vent fluids and chimneys (John et al., 2008)(Fig. 1.2). Heavy Zn isotopes have been demonstrated to preferentially absorb ontodiatom frustules in culturing experiments (Gélabert et al., 2006; John et al., 2007a).A restricted range of Zn isotopic composition (Fig. 1.2) has been established forsphalerite samples (ZnS) of worldwide origin (Albarède, 2004; Wilkinson et al., 2005;Mason et al., 2005; Sonke et al., 2008). In an attempt to quantify Zn isotopic fractionationintroduced by industrial processes, Zn isotopes have been measured in anthropogenicsamples (Fig. 1.2), e.g., polluted lichens, urban waste incineration flue gases and urbanaerosols from Northeast France (Cloquet et al., 2006a); Zn metals, health products andhardware (John et al., 2007b) and polluted sediments, soils and tailings from a now-closed Zn ore processing facility in Southwest France (Sivry et al., 2008). Sonke et al.,(2008) measured historical variations of Zn isotopes in two sediment cores fromNortheast Belgium. Mattielli et al. (2009) examined process samples from a Pb–Znsmelter and refinery in Northeast France (Fig. 1.2) in an evaluation of anthropogenicfractionation processes of Zn isotopes and their subsequent tracing in the environment.81.1.5 Metal Pollution in British Columbia (Canada)British Columbia is home to one of the world’s largest fully integrated Zn and Pbsmelting and refining complexes (Trail, B.C.). In 2008, this facility (Teck) reported thelargest provincial on-site releases to air and water of the metals, Cd, Zn and Pb, and theircompounds (235 kg, 97 tonnes, 3,065 kg; respectively) (Environment Canada, 2009).Even so, the quantities of Cd, Zn and Pb released from the smelting and refiningoperations in Trail declined considerably, by a factor of 21, between 1994 and 2008 (in1994: 11 tonnes, 4,466 tonnes, 246 tonnes; respectively) (Environment Canada, 2009).Decreasing metal emissions levels from Teck’s Trail facility reflect the vast improvementin efficiency of emission control technologies employed at the facility in an to improvetheir environmental performance.1.1.6 High Cd levels in oysters from British ColumbiaHigh Cd levels have been found in oysters (Crassostrea gigas) along the coasts ofBritish Columbia (B.C.), western Canada (Kruzynski, 2001, 2004; Lekhi et al., 2008;Bendell and Feng, 2009). High Cd levels are found not only in oysters but also in otherresident shellfish, e.g., scallops and mussels (Lares and Orians, 1997; Kruzynski, 2004).Coastal communities (including First Nations communities) are concerned about thepotential health problems associated with the consumption of these shellfish (which mayrepresent a significant proportion of their diet) and the potential loss of markets thatsupport local shellfish aquaculture (Kruzynski, 2004). In B.C., the expansion of theaquaculture industry has the potential to create jobs and build revenue for the Provincewhere declines in the forestry industry and natural fisheries have meant the losses of both(Kruzynski, 2004). In an effort to promote the expansion of shellfish aquaculture in B.C.,the Provincial Government announced the Shellfish Development Initiative, in 1997,which doubled the amount of crown land made available for shellfish aquaculture(Kruzynski, 2004). At this time, the largest export markets of B.C. bivalve shellfish werethe US (~80%) and Hong Kong (~10%) (Carswell, 2001). In 1999/2000, Hong Kongrejected several shipments of B.C. oysters for exceeding their Cd limit of 2 µg g-1 (tissue,wet weight). As a result, the Canadian Food Inspection Agency (CFIA) conducted asurvey of B.C. oysters and found a mean Cd concentration of 2.6 µg g-1 (tissue, wet9weight) (Schallié, 2001). Over 60% of the oyster samples, as well as the means of majoroyster farming areas had Cd levels exceeding 2 µg g-1 (tissue, wet weight); oysters withrelatively high Cd levels were not limited to populated areas but rather included thoseharvested from sparsely inhibited or “pristine” areas (Schallié, 2001). In contrast, acomplimentary study by the CFIA reported a mean Cd concentration of 0.33 µg g-1(tissue, wet weight) for oysters (C. virginica) collected from the eastern coast of Canada(Schallié, 2001). In addition, no change has been observed in the Cd concentrations ofB.C. oysters (C. gigas) over the past 30 years (Kruzynski et al., 2002). This is in contrastto reports of declining Cd concentrations of oysters (C. virginica) collected from theSoutheastern USA (Gulf of Mexico) which are attributed to decreasing inputs ofindustrial and urban waste to those waters (Beliaeff et al. 1997).Potential sources of high Cd levels found in B.C. bivalves include natural sources,primarily the upwelling of nutrient-rich deep-waters found in the North Pacific Ocean,and anthropogenic sources (e.g., smelting and refining operations in B.C.).1.2 Overview of the dissertationThis dissertation was written in manuscript-style format, where each of the threemanuscript chapters was prepared for publication in international scientific journals. As aresult, a few repetitions exist between chapters, especially between the methods sectionsof Chapters 2, 3 and 4. Chapter 2 is published in Analytica Chimica Acta under the title“Matrix effects on the multi-collector inductively coupled plasma mass spectrometricanalysis of high-precision cadmium and zinc isotope ratios.” Chapter 3 is published inScience of the Total Environment under the title “Evaluation of zinc, cadmium and leadisotope fractionation during smelting and refining.” Aspects of this study have also beenpresented at international and national scientific conferences as oral and posterpresentations. A list of peer-reviewed publications (including those listed above) andconference abstracts related to this study is provided in Appendix A. Contributions toeach manuscript by Alyssa E. Shiel, her co-authors (including her supervisor, DominiqueWeis, and co-supervisor, Kristin J. Orians) and other individuals are detailed in the Co-authorship Statement.10All chemical and analytical work in this study was performed by Alyssa E. Shielat the Pacific Centre for Isotopic and Geochemical Research (PCIGR) at the Universityof British Columbia (UBC). Elemental analyses were performed on the ELEMENT2(Thermo Finnigan, Germany) High Resolution Inductively Coupled Mass Spectrometer(HR-ICP-MS) and the Varian 725-ES (Varian, Inc., USA) Inductively Coupled PlasmaOptical Emission Spectrometer. Isotopic analyses were performed on the Nu Plasma (Nu021; Nu Instruments, UK). Multi-collector Inductively Coupled Plasma MassSpectrometer. Jane Barling (MC-ICP-MS), Bert Mueller (HR-ICP-MS) and MaureenSoon (ICP-OES) provided assistance with the operation of the instruments, as well astraining.In Chapter 2, an investigation is undertaken of non-spectral interferences, ormatrix effects, on Cd and Zn isotope measurements by MC-ICP-MS resulting from thepresence of (1) resin-derived contaminants (both organics and inorganic elements) addedto samples during chromatographic separations and (2) inorganic elements in relativelylarge quantities (matrix element molar concentration is 5× that of the analyte). In additionto the results of these matrix experiments, the analytical results include elementalconcentrations (ICP-MS) of chromatographic column blanks, evaluating the cleanlinessof different batches of the same resin and the effectiveness of on-column and batch resincleaning methods. This study was motivated by the need to measure high-precision,accurate Cd and Zn isotopic ratios. Identification of potentially compromised dataquality, related to matrix effects on Cd and Zn isotopic measurements, made this studyhighly relevant, especially with the organic matrix of our samples. The results of thisstudy were used to improve the quality of Cd and Zn isotopic measurements explored inthe following two chapters.In Chapter 3, in the light of the regional importance of the smelting and refiningcomplex in Trail, B.C., metallurgical processing is evaluated as a source of Cd, Zn andPb isotope fractionation and dispersion into the environment. The analytical resultsinclude Cd, Zn and Pb concentrations (ICP-OES) and isotopic compositions (MC-ICP-MS) of smelter process samples, recycled Cd metal and CdS pigments. Cd and Znisotopes are identified as effective tracers of smelting and refining air emissions andeffluent. The combined use of Pb isotopes allows the identification of source ores. The11results demonstrated the closed nature of the integrating processing, with the exception ofthe reported emissions. The characterization of the isotopic compositions ofanthropogenic sources allows tracing of these signals in natural samples, e.g., bivalves, inthe next chapter.In Chapter 4, Cd, Zn and Pb concentrations and isotopic compositions are used totrace anthropogenic metal pollution in bivalves from western Canada, the USA andFrance. This study evaluates the usefulness of these isotopic tracers individually and incombination. The analytical results include Cd, Zn and Pb concentrations (ICP-MS) andisotopic compositions (MC-ICP-MS) of bivalve (oyster and mussel) tissue samples. Theoriginal motivation for this study was the high Cd content of B.C. oysters; the sources ofthis high Cd are evaluated through the combined use of Cd, Zn and Pb isotopes in thisstudy and shown to be mostly natural. The study was then extended to include oystersand other bivalves collected from France and the USA East Coast to broaden the scope ofthe study to include locations with different anthropogenic processes at play.In Chapter 5, significant findings presented in each manuscript chapter aresummarized and implications from the entire study are discussed. Finally, suggestions forfurther research are made.12Element Zn Cd PbAtomic number 30 48 82Atomic weight 65.39 112.4 207.2Upper continental crust abundance(ppm)aSurface ocean seawater concentration ( ppm)bHuman blood (mg dm-3)c7.0 0.0052 0.21aWedepohl, 1995.cEmsley, 1998, and references within.bSurface water concentrations for both the Atlantic and Pacific Oceans; [Zn] and [Cd] in the Pacific Ocean (Bruland, 1980); [Pb] in the Pacific Ocean (Boyle et al., 2005) and [Zn], [Cd] and [Pb] in the Atlantic Ocean (Kremling and Streu, 2001).Table 1.1. Metal (Zn, Cd and Pb) abundances in continental crust, ocean seawater and human blood.52 0.102 170.8-314 x 10-6 0.08-19 x 10-6 2.3-21 x 10-6 13Fig. 1.1. Variations in the Cd isotopic composition of select geological, marine and anthropogenic samples. The grey ellipses indicate error as reported by referenced authors. In several cases the error is smaller than the symbol. Data sources: 1Ripperger et al., 2007; 2Lacan et al., 2006; 3Schmitt et al., 2009; 4Wombacher et al., 2003; 5Cloquet et al., 2005; 6Cloquet et al., 2006b; 7Gao et al., 2008.-1.00 -0.50 0.00 0.50 1.00-1.50-1.00 -0.50 0.00 0.50 1.00-1.50d114Cd/110Cd (‰)Slag5Smelter dust5Polluted soils,Pb-Zn refinery (France)6 Industrial samples:Environmental samples:Marine samples:Polluted sediments,Pb-Zn refinery (China)7 Mediterranean seawater2N Atlantic Ocean seawater1Waste incineration dust5N Pacific Ocean seawater Stn. ALOHA1NE Pacific Ocean seawaterStn.K12N Pacific Ocean seawater Stn. 71 1.6‰, 3.8‰11.501.50Sphalerite/Greenockite4Sphalerite (ZnS)3Greenockite (CdS)3Otavite/Smithsonite4Graywacke4Shale4Continental carbonates and sulfides:Basalt4Diorite4Terrestrial rocks:Mixed sphalerite assemblages3Oceanic sulfides:14Fig. 1.2. Variations in the Zn isotopic composition of select geological, marine and anthropogenic samples. The grey ellipses indicate error as reported by referenced authors. In several cases the error is smaller than the symbol. Data sources: 1Bermin et al., 2006; 2John, 2007; 3Maréchal et al., 1999; 4John et al., 2008; 5Sonke et al., 2008; 6Mason et al., 2005; 7Albarède, 2004; 8Wilkinson et al., 2005; 9Mattielli et al., 2009; 10Sivry et al., 2008; 11Cloquet et al., 2006a; 12John et al., 2007b.15Galena5Sphalerite5Environmental samples9Zn-Pb enriched ores9Pb enriched ores9Zn refining emissions (roasting, blast furnace)9Pb refining emissions (roasting, blast furnace)9Main chimney emissions9Polluted lichens, (Metz, NE France)11Urban waste incinerator flue gases, REFIOM (NE France)11Urban aerosols (Metz, NE France)11-1.00 -0.50 0.00 0.50 1.00 1.50 2.00d66Zn/64Zn (‰)-1.00 -0.50 0.00 0.50 1.00 1.50 2.00Pb-Zn metallurgical plant (NE France):Environmental samples (NE France):Zn ore treatment plant (SW France):Mineral samples:Marine samples:N Atlantic Ocean seawater2Plankton tows, worldwide2Sediment cores10:Unpolluted PollutedTailings10Coal ashes10Percolating water10Polluted stream sediments10Polluted soils10Sulfide ores, mixed assemblages(Urals, Russia)6Oceanic sulfides, mixed assemblages:Fe-Zn chimney4Cu-rich chimney4Anthropogenic Zn samples:"Common" anthropogenic Zn;Zn metals and health products12Electroplated hardware12Galvanized hardware12NE Pacific Ocean seawater Stn. 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Geochimica et Cosmochimica Acta 67: 4639–4654.23CHAPTER 2Matrix effects on the multi-collectorinductively coupled plasma massspectrometric analysis of high-precisioncadmium and zinc isotope ratios11A version of this chapter has been published. Shiel, A.E., Barling, B., Orians, K.J., Weis,D. (2009) Matrix effects on the multi-collector inductively coupled plasma massspectrometric analysis of high-precision cadmium and zinc isotope ratios. AnalyticaChimica Acta 633: 29–37.242.1 IntroductionThe multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS)has enabled the measurement of small differences in the isotopic composition of manyheavy stable elements. In particular, the enhanced ionization efficiency inherent to theinductively coupled plasma source has enabled the ionization of elements, such as Cd andZn, that have been difficult to ionize by other methods, e.g., TIMS (Rosman and deLaeter, 1976; Rosman et al., 1980; Rosman and de Laeter, 1988; Loss et al., 1990).Recent MC-ICP-MS investigations have revealed small Cd and Zn isotopic variations interrestrial (Maréchal et al., 1999; Maréchal et al., 2000; Wombacher et al., 2003; Cloquetet al., 2005; Weiss et al., 2005; Wilkinson et al., 2005; Dolgopolova et al., 2006; Weiss etal., 2007), marine (Maréchal et al., 1999; Maréchal et al., 2000; Pichat et al., 2003;Bermin et al., 2006; Lacan et al., 2006; Ripperger et al., 2007; John, 2007; Shiel et al.,2007; John et al., 2008; Shiel et al., 2008), anthropogenic (Cloquet et al., 2005;Dolgopolova et al., 2006; Shiel et al., 2007; Shiel et al., 2008; Cloquet et al., 2006a;Cloquet et al., 2006b; Sivry et al., 2006; John et al., 2007; Sivry et al., 2008; Sonke et al.,2008) and extraterrestrial samples (Wombacher et al., 2003; Luck et al., 2005; Moynier etal., 2006). The largest isotopic variations are of anthropogenic (e.g., ore processing andsmelting) and extraterrestrial (e.g., chondrites, meteorites and lunar samples) origins.Reported isotopic variations range from δ114/110Cd = -7.8 to +14.8‰ (Wombacher et al.,2003; Cloquet et al., 2005; Lacan et al., 2006; Ripperger et al., 2007; Shiel et al., 2007;Shiel et al., 2008; Cloquet et al., 2006b; Sivry et al., 2006) relative to the “JMC Cd”reference standard (Johnson Matthey Company) (Wombacher and Rehkämper, 2004) andfrom δ66/64Zn = -3.83 to +6.39‰ (Maréchal et al., 1999; Maréchal et al., 2000; Weiss etal., 2005 Wilkinson et al., 2005; Dolgopolova et al., 2006; Weiss et al., 2007; Pichat etal., 2003; Bermin et al., 2006; John, 2007; John et al., 2008; Shiel et al., 2008; Cloquet etal., 2006a; John et al., 2007; Sivry et al., 2008; Sonke et al., 2008; Luck et al., 2005;Moynier et al., 2006) relative to the “JMC Zn-Lyon” reference standard (Maréchal et al.,1999).Resolution of these small differences in Cd and Zn isotopic compositions requiresa high degree of accuracy and precision and therefore careful attention must be paid to25potential spectral and non-spectral interferences (Evans and Giglio, 1993; Douglas andTanner, 1998; Horlick and Montaser, 1998; Rehkämper et al., 2004). Spectralinterferences include isobaric interferences of singly (e.g., 114Sn+ on 114Cd+) and doubly(e.g., 136Ba2+ on 68Zn+) charged elements and polyatomic species from the recombinationof argon, atmospheric gases, solvents and sample matrix (e.g., 68Zn40Ar+ on 108Cd+)(Douglas and Tanner, 1998; Tan and Horlick, 1986). These interferences on isotopes ofthe analyte result in non-mass-dependent isotopic variations that are readily identified bycomparing the per amu delta values calculated from the different analyte isotope ratios.Non-spectral interferences, or ‘matrix effects’, are changes in the instrument response(signal intensity and mass bias) to the analyte resulting from the presence of matrixcomponents (Rehkämper et al., 2004; Carlson et al., 2001; Galy et al., 2001). In contrastto spectral interferences, these interferences are difficult to identify because the effectsare mass-dependent and may obscure small natural mass-dependent fractionations(Carlson et al., 2001). Recently, efforts have been made to evaluate non-spectralinterferences in the analysis of non-traditional stable isotopes by MC-ICP-MS; e.g., Ir onAg–Pd (Carlson et al., 2001); Na, Al, Ca on Mg (Galy et al., 2001); Nb, Cd, Sb, W, Tl,Na, Mg on Mo–Zr (Pietruszka et al., 2006. However, their origin and mode of occurrenceand formation are not yet well understood.Correction of measured ratios for instrumental mass-dependent fractionation ormass bias (f) is required to resolve small natural mass-dependent isotopic variations (e.g.,Rehkämper et al., 2004). Two methods for mass bias correction were used in this study:(1) sample-standard bracketing of measured ratios (SSB) and (2) combined externalnormalization–SSB (Ag-corrected for Cd, Cu-corrected for Zn) (Maréchal et al., 1999;Wombacher et al., 2003; Rehkämper et al., 2004; Longerich et al., 1987). The firstmethod, SSB requires that instrumental mass bias remains stable or varies systematicallywith time and that mass bias behavior is the same for the samples and bracketingstandards (Albarède and Beard, 2004). The second method, combined externalnormalization–SSB, assumes that the mass bias response of the analyte (Cd or Zn) variessystematically with the mass bias response of the mass bias-correcting element (Ag orCu) (Maréchal et al., 1999). For reliable external normalization data f(Ag)/f(Cd) andf(Cu)/f(Zn) must be constant in samples and standards during an analytical session.26Therefore, any matrix effect that causes mass bias variations in samples relative tostandards must be investigated.This study was motivated by observations made during the investigation of Cdand Zn isotopic variation in biological samples (Shiel et al., 2007; Shiel et al., 2008).Namely: (1) ion signal intensity enhancement in samples of known concentration, (2)differences in mass bias of normalizing elements between samples and bracketingstandards and (3) isotopic signatures in samples that varied depending on the dilutionfactor of the analyzed solution. This latter observation strongly suggested a matrix effectrelated to column-derived material and motivated this study of non-spectral matrix effectsassociated with column-derived matrix. These experiments were designed to separate thematrix effects resulting from the inorganic and organic components of the column blank.To do this, Cd and Zn cuts, eluted from blank column loads, were used to dope purestandard solutions in proportions reflecting the presence of eluted column blank in dilutedsamples. This methodology is in contrast to experiments comparing pure standards tostandards that have been passed through chemistry in that a single column blank is usedto dope standards in a sequence of dilutions similar to those found inchromatographically processed samples. Although the experiments described here arespecific to Cd and Zn, the results may be applicable to any isotopic system wheresamples are purified by ion exchange chromatography and analyzed by MC-ICP-MS.2.2 ExperimentalExperimental work was carried out in metal-free Class 1,000 clean labs at thePacific Centre for Isotopic and Geochemical Research (PCIGR), University of BritishColumbia. The high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) and MC-ICP-MS are housed in Class 10,000 labs. Sample preparation for traceelement and isotopic analysis was performed in Class 100 laminar flow hoods, in both theclean labs and instrument rooms.272.2.1 Reagents and standardsNitric (HNO3) and hydrofluoric (HF) acids used in this study were purified in-house from concentrated reagent grade acids by sub-boiling distillation. Baseline®hydrobromic (HBr), hydrochloric (HCl) and perchloric (HClO4) acids produced bySeastar Chemicals Inc. (Canada) were also utilized. Standard solutions used for traceelement concentration determination by HR-ICP-MS were prepared from 1,000 µg mL-1single-element solutions from High Purity Standards, Inc. (USA) and Specpure® Plasma(Alfa Aesar®, Johnson Matthey Company, USA). These single-element standards werealso used in the matrix experiments on the MC-ICP-MS. Ultrapure water (≥18.2 MΩcm), prepared by de-ionization of reverse osmosis water using a Milli-Q system(Millipore, USA), was used to prepare all solutions. All labware was washed successivelywith a ~2% extran® 300 (Merck KGaA, Germany) solution (alkaline cleanser), analyticalgrade HCl and environmental grade HNO3.2.2.2 Isotopic standardsThe in-house primary and secondary Cd reference standards (PCIGR-1 Cd andPCIGR-2 Cd) are from High Purity Standards, Inc. (USA) (lots 291012 and 502624,respectively). The “JMC Cd” (Wombacher et al., 2003; Wombacher and Rehkämper,2004), “Münster Cd” (Wombacher and Rehkämper, 2004) and BAM-1012 Cd (FederalInstitute for Materials Research and Testing, Germany) (Wombacher and Rehkämper,2004) reference materials were also analyzed. All Cd isotopic solutions were prepared as2:1 Cd and Ag solutions, with a single analysis consuming 150 ng Cd.The in-house primary and secondary Zn reference standards (PCIGR-1 Zn andPCIGR-2 Zn) are from High Purity Standards, Inc. and Specpure® (lots 505326 and011075A, respectively). Zinc isotopic solutions were prepared as 3:1 Zn to Cu solutions,with a single analysis consuming 100 ng Zn.2.2.3 Ion exchange chemistryColumn blanks for the matrix experiments were prepared using the Cd and Znanion exchange chromatography purification procedure of Mason (2003), identically toreal samples (Appendix B). The Cd and Zn eluate cuts were collected in Savillex® PFA28vials, dried, treated with 0.100 mL ~15 M HNO3 (standard treatment) in an effort todigest organic column residue, then redried and dissolved in 1 mL 0.05 M HNO3 inpreparation for isotopic analysis. Alternative refluxed HNO3 and HClO4/HNO3 digestionsfor removal of organic residue were also tested. Column blanks for Cd and Zn arenegligible (Table 2.1). However, HR-ICP-MS analysis of these blanks identified anumber of non-coeluting elements present at levels that cannot be attributed to the acidsused in the procedure (Table 2.1) but rather derive from the resin (Straßburg et al., 1998;personal communication, D. Hardy, Bio-Rad Laboratories, 2008).Magnesium was the most significant contaminant element in the Cd eluate cut ofthe column blank, with Ca, Fe, Al and Zn all present at ng levels (Table 2.1). Of these theonly potential Cd or Ag spectral interference was Zn (67Zn40Ar+, 70Zn40Ar+). The mostsignificant contaminant element in the Zn eluate cut of the column blank was Al followedby Fe, Mg, Ca and Cr at ng levels (Table 2.1). Aluminum (27Al36Ar+, 27Al38Ar+, 27Al40Ar+)was the only potential Zn or Cu spectral interference.Inorganic contaminants in both the Cd and Zn eluate cuts, despite carefulcleaning, were variable (Table 2.1). We therefore investigated three resin-cleaningprotocols. In the first method, the resin was cleaned on-column using the routine on-column cleaning (Appendix B). Two other resin-cleaning methods (used in addition tothe routine on-column cleaning) were tested to see if the inorganic content of the columnblanks could be reduced: (1) an on-column cleaning method utilizing 10 mL each of theeluting acids (full clean) and (2) the batch cleaning method of De Jong et al. (2007).Neither cleaning procedure significantly reduced the inorganic content of the blanks(Table 2.1). Previously, Straßburg et al. (1998) reported that Na, Mg, Al, K, Cr, Fe, Znand Ba occur as contaminants in the anion exchange resin AG 1-X8 (Bio-RadLaboratories, Inc., USA). Bio-Rad Laboratories AG (Analytical Grade) resins aregenerated by extensive acid and base cleaning of technical grade Dowex resins. However,even after this cleaning, a background of elements persists due to variable purity ofcomponents used in the initial manufacture of the technical grade resin [personalcommunication, D. Hardy, Bio-Rad Laboratories, 2008]. As a result, resin-derivedinorganic elements and organics (e.g., styrene divinylbenzene; personal communication,29D. Hardy, Bio-Rad Laboratories, 2008) may be leached out during column chemistryproducing non-reproducible blanks.2.2.4 Mass spectrometry2.2.4.1 Trace element analysesTrace element analyses of column blanks were performed on an ELEMENT2(Thermo Finnigan, Germany) HR-ICP-MS. Measurements were made using a Conikalglass concentric nebulizer (Glass Expansion, USA) and a Scott-type glass spray chamber.Elemental concentrations were quantified using multi-element calibration curves withindium, measured at mass 115, as an internal standard. All solutions were prepared with0.15 M HNO3.2.2.4.2 Isotopic analysesIsotope ratios were measured by multi-collection on a Nu Plasma MC-ICP-MS(Nu 021; Nu Instruments, UK) using the DSN-100 (Nu Instruments, UK) membranedesolvator for sample introduction. The standard dry plasma cones (type B; NuInstruments, UK) were used, with the exception of one experiment, where the standardwet plasma cones (type A; Nu Instruments, UK) were used. A standard SSBmeasurement protocol (Rehkämper et al., 2004) was followed, where samples were runalternately with standards.The Cd isotope measurement method was adapted from Wombacher et al. (2003)and consisted of a dynamic run with main and interference cycles that enabled collectionof masses 106 to 118 (isotopes of Cd, Ag and Sn). Correction of the Sn interference on112Cd, 114Cd and 116Cd was enabled by measurement of 118Sn. An analysis comprised 2blocks of 15 × 5 s integrations with a 20 s ESA deflected baseline before each block.Zinc isotope measurements consisted of a single cycle to collect masses 62 to 68(isotopes of Zn, Cu and Ni). Correction of the Ni interference on 64Zn was permitted bycollection of 62Ni. Each measured ratio comprised 2 blocks of 15 × 10 s integrations. Anon-peak zero was measured before each Zn analysis in order to correct for backgroundsignal.302.2.5 Isotope data presentationCadmium and Zn isotopic compositions are expressed relative to the PCIGR-1 Cdand PCIGR-1 Zn reference standards in the standard delta (δ) notation as follows:€ δiCd =  (iCd)sample(iCd)standard−1       x 1,000€ δjZn =  (jZn)sample(jZn)standard−1       x 1,000where i and j are the measured isotope ratios, for Cd i = 111/110, 112/110, 113/110 or114/110 and for Zn j = 66/64, 67/64, 68/64 or 68/66. Isotopic compositions are reportedin terms of δ114/110Cd (‰) and δ66/64Zn (‰). However, these and the other isotope ratiosare also reported as delta values per atomic mass unit (amu) in Appendices C, D, E, F, G;these values are used for diagnostic purposes to (1) control quality and (2) monitor forspectral interferences. Delta values per amu are calculated by dividing the delta value bythe difference in mass of the two isotopes. Although monitored, low abundance Cdisotopes, 106Cd (1.25%) and 108Cd (0.89%), are not reported, as they are associated withpoor precision. Although relatively abundant, 116Cd (7.49%) is omitted because it is notmeasured in the same cycle as the mass bias–correcting element (Ag).Delta values are reported as (1) SSB and (2) combined externalnormalization–SSB corrected. For SSB, delta values are calculated from measured ratiosin samples referenced to the mean of their two bracketing standards (Rehkämper et al.,2004). For combined external normalization–SSB, the external normalization of Cd or Znsamples and standards was made using Ag or Cu, respectively.  The measured 107Ag/109Agor 65Cu/63Cu ratios are then used to calculate the instrumental mass bias, f(Ag) and f(Cu),and these values are used to correct the measured Cd and Zn ratios using the exponentialform of the General Power Law (GPL) (Maréchal et al., 1999; Rehkämper et al., 2004).Delta values were then calculated by referencing exponentially corrected sample ratios toexponentially corrected standard ratios using the SSB method. The graphicalnormalization method of Maréchal et al. (1999) was not used here because there wasinsufficient instrumental mass bias drift during Cd and Zn measurement sessions.31Reproducibility of measurements of in-house Cd and Zn secondary standards anda zero-delta by back-to-back measurement of the PCIGR-1 Cd and PCIGR-1 Znstandards is reported in Tables 2.2 and 2.3, respectively. In-house secondary standardmeasurements were made systematically before and during each analytical session. Deltavalues for Cd reference standards (Table 2.2) agreed within uncertainty with δ114/110Cdvalues in the literature.2.2.6 Description of the matrix experimentsThe pure Cd and Zn standards (PCIGR-1) and doped standard solutions forisotopic analysis were prepared daily. Three categories of dopant were investigated: (1)bulk organic and inorganic column-derived components, (2) mock column-derivedinorganic components prepared from pure standard solutions and (3) various singlemetallic element matrix components. All doped standards were treated as samples.Matrix effects were assessed by examining changes in signal intensities (110Cd,109Ag, 64Zn and 63Cu), mass biases (f(Cd), f(Ag), f(Zn), f(Cu)) and delta values betweendoped and undoped standards. Matrix effects on the δ114/110Cd and δ66/64Zn values weredeemed significant when they were outside the 2S.D. reproducibility of the in-housesecondary standards; i.e., for δ114/110CdSSB ± 0.33‰, δ114/110CdAg-corr. ± 0.14‰, δ66/64ZnSSB ±0.06‰ and δ66/64ZnCu-corr. ± 0.19‰ (Tables 2.2 and 2.3, respectively).2.2.7 Matrix componentsBulk column blank material (i.e., organic and inorganic) was added to pure Cdand Zn standards in proportions (0.2–50%) consistent with the range of dilutions neededfor the real samples that motivated this study.  For example, typical digested bivalvesamples contain 300 ng of Cd and 5,000 ng Zn, while 150 ng of Cd and 100 ng of Zn arerequired for a MC-ICP-MS isotopic analysis. Therefore, with 100% column yield, 50%of the Cd eluate cut or 2% of the Zn eluate cut are present in the analyzed solution.In order to investigate the effect of the inorganic component of the bulk columnblank, two doping experiments were performed for Cd. In the first, the matrix effectinduced by Mg (the major component of the blank) was determined. In the second, thecombined effect of the major contaminant elements was investigated using a “mock32column inorganic matrix” solution. In both experiments, elements were doped at thehighest quantities measured in the blanks (October 2006, Table 2.1). Therefore, the Cdstandard (150 ng mL-1) was doped with 42 ng mL-1 of Mg corresponding to a molarconcentration of 1.3 times the molar concentration of Cd. The “mock column inorganicmatrix” was prepared similarly resulting in a total matrix element concentration of 1.7times the molar concentration of Cd.In the final set of experiments, large quantities of metallic elements, five times themolar concentration of Cd or Zn, were added to the Cd and Zn standards to approximatesample-derived inorganic matrix components and characterize the matrix effectsassociated with individual inorganic element additions. The matrix elements in theseexperiments were chosen on the basis of their abundance in biological or geologicalmaterials as well as to cover a wide range in mass and ionization potential (IP) (Table2.4; Sansonetti and Martin, 2005).2.3 Results and discussionThe results for the bulk column blank matrix addition experiments for Cd and Znare given in tables in Appendices C and D, respectively. The results for the inorganiccolumn blank matrix addition experiments are given in Appendix E with results of themetallic elements doping experiments for Cd and Zn in Appendices F and G,respectively.2.3.1 Bulk column blank matrix additionIon signal enhancement relative to the undoped standards results from thepresence of bulk column blank matrix during isotopic analysis by MC-ICP-MS. Ionsignal intensity changes, for Cd–Ag (Fig. 2.1a and b) and for Zn–Cu (Fig. 2.2a and b),vary considerably from run to run but are generally somewhat larger for the element pairZn–Cu as compared to the pair Cd–Ag. For both pairs the mass bias-correcting elements(Ag and Cu) (Figs. 2.1b and 2.2b) generally experience larger signal enhancement thanthe analytes (Cd and Zn) (Figs. 2.1a and 2.2a).33More importantly, column matrix induces changes in the instrumental mass biasof both analytes and mass bias-correcting elements, resulting in inaccurate Cd and Znisotope ratios (Figs. 2.1c, d and 2.2c, d). These effects, like the ion signal intensityenhancement, vary from one session to the next.For SSB corrected Cd delta values, with the addition of up to 20% matrix tostandards, mass bias changes are insignificant and δ114/110CdSSB values are within error ofundoped standard values (Fig. 2.1c). However, column matrix concentrations of 50%result in heavy δ114/110CdSSB values due to higher f(Cd) in the presence of matrix (Fig.2.1c). Use of the wet plasma cones (A cones) for Cd isotopic analysis does not reducethis mass bias change. Low matrix levels (0.2–2%) have little effect on f(Zn) and thusδ66/64ZnSSB values are within error of matrix-free values (Fig. 2.2c). However as with Cd,mass bias effects result in heavy δ66/64ZnSSB values for 10% and 50% column matrix (Fig.2.2c).For the combined external normalization–SSB (instrumental mass bias correctionusing f(Ag) and f(Cu)) f(Ag) and f(Cu) overcorrect the measured Cd and Zn isotopicratios, i.e., f(Ag)>f(Cd) and f(Cu)>f(Zn), resulting in light δ114/110CdAg-corr. (Fig. 2.1d) andδ66/64ZnCu-corr. (Fig. 2.2d) values even at low matrix levels. The δ114/110CdAg-corr. andδ66/64ZnCu-corr. values per amu are similar in magnitude, suggesting the matrix-induced massbias effects may be largely related to the relative ionization potentials of the elementpairs, Cd–Ag and Zn–Cu, which unlike mass are similar (Table 2.4).Differences in mass bias between analytes and their mass bias-correctingelements, such as these, have been reported in previous studies (Wombacher et al., 2003;Carlson et al., 2001; Pietruszka et al., 2006) and result in discrepancies between the deltavalues derived from the SSB and the combined external normalization–SSB instrumentalmass bias correction methods. Such discrepancies may be used to identify the presence ofmatrix effects. Importantly, as we demonstrate here, it cannot be assumed that thecombined external normalization–SSB correction produces more accurate results thanSSB correction alone.342.3.2 Inorganic elements introduced during cadmium column chemistryAlthough the relative contribution of inorganic elements is small, their effect onion signal intensity and mass bias can be significant. Doping with Mg (column blanklevel) increases the ion signal intensities of both Cd and Ag (4.5–14.9%) as does dopingwith “mock column inorganic matrix” (8.6–15.7%) (Appendix E). Doping with Mg aloneleads to insignificant changes in mass bias and delta values for both mass bias correctionmethods. The “mock column inorganic matrix” produces changes in f(Cd) that areinsignificant or, in one of four tests, result in a heavy delta value (δ114/110CdSSB = 0.47‰).This suggests that the larger changes in f(Cd) introduced by bulk column blank matrix arelargely related to resin-derived organics.The combined external normalization–SSB mass bias correction method usingf(Ag) results in δ114/110CdAg-corr. values that are heavy in two tests (δ114/110CdAg-corr. = 0.24‰,0.37‰) and light in one test (δ114/110CdAg-corr. = -0.26‰). For these three tests, themagnitude of the change in the δ114/110CdAg-corr. values is 28–71% of that observed for thebulk column blank matrix, again suggesting inorganic elements alone are not responsiblefor the mass bias effects introduced by bulk column blank matrix.2.3.3 Inorganic matrix effectsAdditions of metallic matrix elements to the analyte in larger quantities than arepresent in the “mock column inorganic matrix” cause ion signal intensity enhancement inthe majority of cases and suppression in a few cases. In contrast to bulk column blankmatrix, ion signal intensity changes are greater for the higher mass pair Cd–Ag than forZn–Cu. Both Cd and Zn ion signals are suppressed by Al and enhanced by Sr (two ofthree results for Sr-doped Cd standards), Ba and Pb (Fig. 2.3a and b). Aluminum, Sr andBa enhance both Ag and Cu ion signal intensities (Fig. 2.3a and b), while Pb causessuppression of the Cu ion signal, but not of the Ag ion signal, suggesting that themechanism for suppression is more effective for lower mass analyte ions (Fig. 2.3a andb). Silver ion signal intensity is always more enhanced than Cd and Cu ion signalintensity is usually more enhanced than Zn perhaps due to the lower ionization potentialsof the mass bias-correcting elements (Table 2.4).35With few exceptions, both mass bias correction methods produce light Cd and Zndelta values indicating that f(Cd), f(Ag), f(Zn) and f(Cu) are all reduced when metallicelements are present. Correction of measured Cd with SSB alone produces light deltavalues with few exceptions (one heavy result each for Al, Ir and Pb) (Fig. 2.4a).Fractionation correction using f(Ag) for doped Cd runs only partially compensates for thematrix effect on f(Cd) (i.e., f(Cd) > f(Ag)) and δ114/110CdAg-corr. values are still all light. Oneexception is for Sr-doped Cd standards (two of three results), where the resultingδ114/110CdAg-corr. value is within error of the undoped Cd standard. The lightest δ114/110CdSSBand δ114/110CdAg-corr. values (Fig. 2.4a) result from the tested matrix elements with thelowest ionization potentials, Rb and Cs (Table 2.4). Changes in the ion signal intensity of110Cd and the calculated δ114/110CdSSB and δ114/110CdAg-corr. values for Zn-doped solutions arein part due to the formation of ZnAr+ ((m/z) = 107, 110) from minor isotopes of Zn (Figs.2.3a and 2.4a). However, the small contributions from ZnAr+ do not significantly changeeither the magnitude of the delta values or the difference between the δ114/110CdSSB andδ114/110CdAg-corr. values (Appendix F).All doped Zn standard runs are isotopically light (Fig. 2.4b), with the exception ofthe Ba-doped Zn standards where heavy isotopic values for some isotope ratios can beattributed to the isobaric interference of Ba2+ on 65Cu, 66Zn, 67Zn and 68Zn (Appendix G).The apparently light Zn isotope ratios observed for Sr-doped Zn standards (Fig. 2.4b) arelargely attributed to a spectral interference (SrAr2+) that affects 63Cu and 64Zn (AppendixG). The lightest δ66/64ZnSSB values result from doping with Al and Ca, elements withionization potentials lower than those of both Zn and Cu (Table 2.4). In contrast toCd–Ag, fractionation correction using f(Cu) produces δ66/64ZnCu-corr. values that areovercorrected and are even lighter than δ66/64ZnSSB values for Al, Ca, Cd and Pb (i.e.,f(Zn) < f(Cu)) (Fig. 2.4b).2.3.4 Chemical treatment of resin-derived organicsThe magnitude of the matrix effect varied with analytical session and socomparisons between our standard column matrix treatment and the refluxed HNO3 andHClO4/HNO3 treatments are made for experiments run in the same session (seeAppendices C and D). Chemical treatment with refluxed HNO3 (Blank 5 compared to36standard treatment Blank 2) or HClO4/HNO3 (Blank 6 compared to standard treatmentBlank 4) does not reduce signal enhancement but column blank matrix-induced mass biasvariation and associated inaccuracy in δ114/110Cd values are reduced (Fig. 2.1c and d). TheHClO4/HNO3-treated column matrix results in signal enhancements and delta valuesidentical to those of the HClO4/HNO3 acid blank, suggesting residual HClO4 or inorganicelements introduced with the HClO4 are the source of the mass bias effect. Similarly forZn, chemical treatment with refluxed HNO3 (Blank 3 compared to standard treatmentBlank 1) or HClO4/HNO3 (Blank 4 compared to standard treatment Blank 1) reduces thematrix effect on the mass bias (Fig. 2.2c and d) and in the case of the refluxed HNO3-treated column blank the matrix effect on the mass bias is insignificant.After refluxed HNO3 digestion, remaining matrix effects are attributed to thepresence of residual refractory organics and the inorganic column matrix. The HClO4treatment should remove residual organics, but introduces additional inorganiccontamination (Table 2.1). In addition, residual HClO4 may be present, due to its highboiling point (~203 °C), and may itself be the source of mass bias effects.The reduction of the mass bias effects, observed for bulk column blanks that haveundergone more oxidizing treatments than our standard column blank treatment, supportsthe conclusion that organics are partially responsible for the observed matrix effects. Theremaining mass bias effects, observed as delta values, for the more aggressively digestedcolumn blanks are approximately equal to the effect observed for the “mock columninorganic matrix.” Therefore, inaccurate delta values from column matrix treated by ourstandard digestion are attributed to a combination of organics and inorganic elementsleached from the resin.2.3.5 Correction of delta valuesCorrection of delta values may be possible if delta values resulting from thepresence of column matrix are consistent over time (during a given run or between runs).Archer and Vance (2004) suggested (for Zn) that referencing samples to standards, whichthemselves have been through columns, could effectively compensate for a columnmatrix effect. Our experiments show that the magnitude of the matrix effect is dependenton the dilution of the column matrix and the associated organic and inorganic37contaminants, and that the column blank itself is variable. Therefore, for this method towork column blank would need to be added to standards in similar proportions to columnmatrix present in the samples and even so some variability would be expected due to thevariability of the inorganic component of the column blank.2.3.6 Consequences for natural samplesThese experiments demonstrate that resin-derived organics and inorganicelements, introduced to the sample during column chemistry, create a mismatch betweensample and bracketing standard matrices leading to inaccurate delta values. The degree ofinaccuracy increases with the amount of column blank matrix added to the pure standardsolutions. One of the original motivations for this investigation was the observation thatisotopic signatures in samples varied depending on the dilution factor of the analyzedsolution. In order to test whether the observed inaccuracy could be accounted for by thecolumn blank matrix effect, an experiment was devised in which replicate purifications ofvariable column loads enabled variable dilution of the Cd eluate cut (Fig. 2.5). Thedegree of inaccuracy introduced by our matrix experiment was identical in magnitude tothat seen in our natural samples (cf. Fig. 2.1c and d).The range of dilutions investigated in these experiments is not necessarilyrestricted to biological materials. For example, at one extreme samples may contain highCd and/or Zn concentrations but be limited in availability (e.g., lunar samples; Moynier etal., 2006). Also, there are samples with extremely low Cd and/or Zn concentrationswhere large quantities of sample are needed for a single analysis (e.g., seawater; Lacan etal., 2006; John, 2007). In both these scenarios sample dilution may be limited, resultingin analyses vulnerable to the type of matrix effects described here. However, for manysample materials (e.g., anthropogenic materials; Cloquet et al., 2006b; Sivry et al., 2008;Sonke et al., 2008 and Zn ores; Wilkinson et al., 2005; Dolgopolova et al., 2006), samplesize and analyte concentration do not limit dilution and these materials are not expectedto be subject to these matrix effects as long as sufficient sample material is loaded on thecolumn.Inorganic and organic resin-derived contaminants and associated matrix effectsare expected to vary with the resin, volume of the resin bed, eluents and volumes of38eluents used in the column chemistry. Similar chemistries using AG MP-1M resin,employed for the purification of Zn, Cu and Fe (e.g., Maréchal et al., 1999), may producepurified samples susceptible to these matrix effects during MC-ICP-MS analysis. Inaddition, chromatography procedures utilizing other resins, including the Bio-Rad AG 1anion exchange resins, are expected to introduce similar matrix effects. Indeed, the onlysimilar study to this one has found that AG 1-X8 resin-derived contaminants cause matrixeffects in MC-ICP-MS analysis of Mo isotopes (Pietruszka and Reznik, 2008).Ultimately, each ion exchange purification method will need to be assessed individually.Based on our experiments, we recommend, that for accurate delta values, sufficientquantities of sample material be loaded on the column so that no more than 20% of theCd or Zn eluate cut is in the analyzed solution.2.4 ConclusionsMatrix effects are particularly significant in the measurement of isotopicfractionation in systems with small natural variations, such as Cd and Zn. Our studydemonstrates that column matrix and even low-levels of metallic elements must beevaluated as potential sources of error during Cd and Zn isotopic analysis. The mainfindings of our investigation are:(1) Bulk column blank matrix and metallic elements cause signal enhancement. In bothCd–Ag and Zn–Cu systems, enhancements are greater for the lower ionizationpotential mass bias-correcting elements (Ag and Cu) than for the analytes (Cd andZn). Signal enhancement and suppression indicate matrix problems and are associatedwith inaccurate Cd and Zn isotope ratios.(2) Mass bias changes result from bulk column blank matrix introduced during standardcolumn chemistry. For both Cd and Zn these mass bias changes result in heavy SSBcorrected delta values and light combined external normalization–SSB corrected deltavalues.39(3) The inorganic content of bulk column blank matrix is variable and even smallquantities can cause significant effects. However, the effects are not large enough toaccount for those of the bulk column blank matrix.(4) Residual resin-derived organics are a significant source of column-induced matrixeffects.(5) Chemical treatment of column blanks, aimed at destroying resin-derived organics,with either refluxed HNO3 or HClO4/ HNO3 reduced the mass bias effect relative tothe standard HNO3 dry down.(6) In both Cd–Ag and Zn–Cu systems, the mass bias responses of the analyte and massbias-correcting element differ in the presence of matrix. This results in disagreementbetween δ114/110CdSSB and δ114/110CdAg-corr. and δ66/64ZnSSB and δ66/64ZnCu-corr. values. Insuch cases the externally normalized values cannot be assumed to give the moreaccurate result.2.5 AcknowledgementsThis work benefited from discussions on matrix effects with Bert Mueller and wealso thank him for his assistance with the ELEMENT2 HR-ICP-MS. We are grateful toJames Scoates, Laure Aimoz and six anonymous reviewers for comments on variousversions of this manuscript. We also thank Frank Wombacher for providing aliquots ofthe “JMC Cd”, the “Münster Cd” and the BAM-1012 Cd reference standards. This studywas funded by NSERC Discovery grants to Dominique Weis and Kristin J. Orians.40Table 2.1. Inorganic contents of column chemistry blanks are shown for three resincleaning methods, the routine clean was used in this study (see Appendix B). Perchlorictreatment of a column blank after routine cleaning (Cd Blank 6 and Zn Blank 4) wasevaluated for additional contamination.    Routine   Full Batch HClO4- [Matrix element]5/clean clean clean treated [Cd]6 or [Zn]7Element (ng) Oct 06 Jun 07 Apr 08 Jun 07 Apr 08 Jun 07 in real samplesCd fraction (0.5 M HNO3)Mg142 17 0.2 21 2.7 74 0.095-0.447Al13.3 0.83 1.1 2.1 1.1 2.5 0.007-0.032Ca18.2 ND 0.46 3.3 0.97 7.3 0.011-0.053Cr10.7 0.33 0.2 0.61 0.15 41 0.001-0.003Fe23.8 1.5 0.61 1.3 0.44 2.8 0.003-0.015Zn31.9 1 0.14 0.67 0.43 1.6 0.001-0.004Cd4ND ND ND ND ND NDZn fraction (0.1 M HBr + 0.5 M HNO3)Mg11.7 ND 4.2 19 ND 11 0.002-0.011Al166 42 21 108 10 42 0.078-0.368Ca11.7 ND 0.15 5.3 ND 3.5 0.001-0.006Cr11.3 1.9 0.92 1.5 0.47 42 0.001-0.003Fe25.2 4.4 7.6 8.6 4.4 5.0 0.003-0.012Zn31.4 2.6 0.67 0.60 3.7 0.90 0.000-0.002               Not Detected (ND)Element should elute in 1the first 10 mL of 7 M HCl, 28 M HF + 2 M HCl, 30.1 M HBr + 0.5 M HNO3 or40.5 M HNO3.5Molar concentrations of matrix elements in the highest blank, chemistry performed Oct. 2006.B.C. oyster Cd6 (2.9-13.7 ppm dry weight) and Zn7 (197-1082 ppm dry weight) concentrations used incalculation, assume 0.150 g tissue digested and loaded on column.41Table 2.2. Cadmium isotope data for secondary Cd isotopic standards and formeasurement of a "zero-delta" by back-to-back analysis of the PCIGR-1 Cd standard.    Sample-standard bracketing   External normalization withsample-standard bracketingSample   δCd/amuaδ114/110Cd   δCd/amuaδ114/110CdPCIGR-1 Cd relative to PCIGR-1 Cdmean (n=33) -0.00 -0.01 0.00 0.002SD 0.04 0.17 0.03 0.08PCIGR-2 Cd relative to PCIGR-1 Cdmean (n=42) -0.37 -1.43 -0.37 -1.472SD 0.08 0.33 0.04 0.14JMC Cd relative to PCIGR-1 Cdmean (n=3) -0.02 -0.07 -0.01 -0.032SD 0.03 0.11 0.02 0.05BAM-1012 relative to PCIGR-1 Cdmean (n=4) -0.33 -1.29 -0.38 -1.472SD 0.10 0.35 0.04 0.12BAM-1012 relative to JMC Cd – literature -1.08bmean (n=5) -0.28 -1.11 -0.34 -1.372SD 0.08 0.36 0.08 0.25Münster Cd relative to JMC Cd-literature 4.65b, 4.48cmean (n=4) 1.13 4.50 1.13 4.502SD 0.06 0.27 0.02 0.03Münster Cd relative to BAM-1012-literature 5.74bmean (n=3) 1.44 5.75 1.44 5.762SD 0.03 0.13 0.02 0.09                     a δCd/amu is calculated from the mean of 4 ratios (111Cd/110Cd, 112Cd/110Cd, 113Cd/110Cd, 114Cd/110Cd).b Wombacher and Rehkämper (2004).c Cloquet et al. (2005).42Table 2.3. Zinc isotope data for the in-house secondary Zn isotopic standard and formeasurement of a "zero-delta" by back-to-back analysis of the PCIGR-1 Zn standard.    Sample-standard bracketing   External normalization withsample-standard bracketingSample   δZn/amuaδ66/64Zn   δZn/amuaδ66/64ZnPCIGR-1 Zn relative to PCIGR-1 Znmean (n=52) 0.001 0.00 0.00 0.002SD 0.020 0.05 0.03 0.05PCIGR-2 Zn relative to PCIGR-1 Znmean (n=18) -5.15 -10.37 -5.10 -10.282SD 0.03 0.06 0.10 0.19                     a δZn/amu is calculated from the mean of 4 ratios (66Zn/64Zn, 67Zn/64Zn, 68Zn/64Zn).43Table 2.4. First and second ionization energies (eV) and atomic weights for analytes andmatrix elements relevant in this study (Sansonetti and Martin, 2005).Atomic Weight Element 1st IP 2nd IP24.3 Mg 7.65 15.0427.0 Al 5.98 18.8340.1 Ca 6.11 11.8763.6 Cu 7.73 20.2965.4 Zn 9.39 17.9685.5 Rb 4.18 27.2987.6 Sr 5.69 11.03107.9 Ag 7.58 21.48112.4 Cd 8.99 16.91132.9 Cs 3.89 23.16137.3 Ba 5.21 10.00175.0 Lu 5.43 13.9192.2 Ir 8.97207.2 Pb 7.42 15.03       44-505102025300 10 20 30 40 50 60% of column blank matrix diluted for analysisChange in 110Cd ion signal intensity (a)15-505102025300 10 20 30 40 50 60% of column blank matrix diluted for analysisChange in 109Ag ion signal intensity (b)15% of column blank matrix diluted for analysisd114/110Cd SSB (‰)% of column blank matrix diluted for analysisd114/110Cd Ag-corr. (‰)-1.0-0.8-0.4-0.20.20.81.00 10 20 30 40 50 60(d)0-0.60.60.4-1.0-0.8-0.4-0.20.20.81.00 10 20 30 40 50 60(c)0-0.60.60.4Blank 1 Blank 2 Blank 3 Blank 4 Blank 5 (HNO3) Blank 6 (HClO4) Blank 7 (A-cones) HClO4 blankCadmiumFig. 2.1. Matrix effects on Cd isotope ratio measurements as a function of bulk column blank matrix addition: (a) percent changes in 110Cd ion signal intensity, (b) percent changes in 109Ag ion signal intensity, (c) d114/110CdSSB and (d) d114/110CdAg-corr. values. For (a) and (b), the grey areas denote 2 standard deviation (SD) on the mean 110Cd and 109Ag ion signal intensities during measurement of a “zero-delta” by back-to-back analysis of the PCIGR-1 Cd standard (n = 33). For (c) and (d), the grey areas denote 2SD on the mean d114/110CdSSB and d114/110CdAg-corr. values for the in-house secondary Cd standard (Table 2.2). Note that in (b) for Blanks 1 and 2 with 2% matrix, the values (7.48% and 7.51%, respectively) are overlapping. 450 10 20 30 40 50 60-20-10102030400Change in 64Zn ion signal intensity (%)(a)% of column blank matrix diluted for analysis0 10 20 30 40 50 60-20-10102030400Change in 63Cu ion signal intensity (%)(b)% of column blank matrix diluted for analysis0 10 20 30 40 50 60-0.6-0.400.20.40.6-0.2(c)% of column blank matrix diluted for analysisd66/64Zn SSB (‰)0 10 20 30 40 50 60-0.6-0.400.20.40.6-0.2(d)% of column blank matrix diluted for analysisd66/64Zn Cu-corr. (‰)Blank 1 Blank 2 Blank 3  (HNO3) Blank 4 (HClO4)ZincFig. 2.2. Matrix effects on Zn isotope ratio measurements as a function of bulk column blank matrix addition: (a) percent changes in 64Zn ion signal intensity, (b) percent changes in 63Cu ion signal intensity, (c) d66/64ZnSSB and (d) d66/64ZnCu-corr. values. For (a) and (b), the grey areas denote 2 standard deviation (SD) on the mean 64Zn and 63Cu ion signal intensities during measurement of a “zero-delta” by back-to-back analysis of the PCIGR-1 Zn standard (n = 52). For (c) and (d), the grey areas denote 2SD on the mean d66/64ZnSSB and d66/64ZnCu-corr. values for the in-house secondary Zn standard (Table 2.3). 46-30-20-100102030405060110Cd 109AgRbSr CsBa LuIrPbAlZnChange in ion signal intensity (%)(a)-4-20246810121416Change in ion signal intensity (%)64Zn 63Cu(b)AlCaSrCd PbBaFig. 2.3. Matrix effects for solutions doped with metallic elements: (a) 110Cd and 109Ag ion signal intensities and (b) 64Zn and 63Cu ion signal intensities, calculated as the variation (%) of the doped solution ion signal intensity from the mean ion signal intensity of the two bracketing undoped standards. For (a), the grey area denotes 2 standard deviation (SD) on the mean 110Cd and 109Ag ion signal intensities during measurement of a “zero-delta” by back-to-back analysis of the PCIGR-1 Cd standard (n = 33). For (b), the grey area denotes 2SD on the mean 64Zn and 63Cu ion signal intensities during measurement of a “zero-delta” by back-to-back analysis of the PCIGR-1 Zn standard (n = 52). 47-10-8-6-4-202d114/110Cd (‰)AlRbZn SrCsBaLu Ir Pb(b)-12-10-8-6-4-202d 66/64Zn (‰)Al Ca Sr Cd Pb-30-20-10010(a)BaSSBAg-corr.SSBCu-corr.Fig. 2.4. Matrix effects for solutions doped with metallic elements: (a) d114/110CdSSB and d114/110CdAg-corr. values and (b) d66/64ZnSSB and d66/64ZnCu corr. values. Matrix effects on the d114/110Cd and d66/64Zn values are discussed as significant when outside the 2 standard deviation (SD) of the in-house secondary Cd and Zn standards (Tables 2.2 and 2.3, respectively), not shown in (a) and (b). 482SD Ag-corr.2SD SSB-1.00-0.80-0.60-0.40-0.200.000.200.400.600.800 10 20 30 40 50 60d114/110CdSSB (‰)d114/110CdAg-corr. (‰)% of column blank matrix diluted for analysisdCdexpected - dCdmeasured0 10 20 30 40 50 60% of Cd cut diluted for analysis1.00Fig. 2.5. Matrix effects as a function of the dilution of the Cd eluate cut for a bivalve sample. For this experiment, variable quantities of a single bivalve digest were loaded on columns such that the analyzed solutions contained 2–50% of the eluted Cd and column matrix. The shift from the expected delta value is represented by d114/110Cdexpected - d114/110Cdmeasured. 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Chemical Geology 255: 295–304.Sonke, J.E., Sivry, Y., Viers, J., Freydier, R., Dejonghe, L., André, L., Aggarwal, J.K.,Fontan, F., Dupré, B. (2008) Historical variations in the isotopic composition ofatmospheric zinc deposition from a zinc smelter. Chemical Geology 252:145–157.Straßburg, S., Wollenweber, D., Wünsch, G. (1998) Contamination caused by ion-exchange resin!? Consequences for ultra-trace analysis. Fresenius Journal ofAnalytical Chemistry 360: 792–794.Tan, S.H., Horlick, G. (1986) Background Spectral Features in Inductively CoupledPlasma Mass-Spectrometry. Applied Spectroscopy 40: 445–460.Weiss, D.J., Mason, T.F.D., Zhao, F.J., Kirk, G.J.D., Coles, B.J., Horstwood, M.S.A.(2005) Isotopic discrimination of zinc in higher plants. New Phytologist 165:703–710.Weiss, D.J., Rausch, N., Mason, T.F.D., Coles, B.J., Wilkinson, J.J., Ukonmaanaho, L.,Arnold, T., Nieminen, T.M. (2007) Atmospheric deposition and isotope53biogeochemistry of zinc in ombrotrophic peat. Geochimica et Cosmochimica Acta71: 3498–3517.Wilkinson, J.J., Weiss, D.J., Mason, T.F.D., Coles, B.J. (2005) Zinc isotope variation inhydrothermal systems: Preliminary evidence from the Irish Midlands ore field.Economic Geology 100: 583–590.Wombacher, F., Rehkämper, M. (2004) Problems and suggestions concerning thenotation of cadmium stable isotope compositions and the use of referencematerials. Geostandards and Geoanalytical Research 28: 173–178.Wombacher, F., Rehkämper, M., Mezger, K., Munker, C. (2003) Stable isotopecompositions of cadmium in geological materials and meteorites determined bymultiple-collector ICPMS. Geochimica et Cosmochimica Acta 67: 4639–4654.54CHAPTER 3Evaluation of zinc, cadmium and lead isotopefractionation during smelting and refining 11A version of this chapter has been published. Shiel, A.E., Weis, D., Orians, K.J. (2010)Evaluation of zinc, cadmium and lead isotope fractionation during smelting and refining.Science of the Total Environment 408: 2357–2368.553.1 IntroductionWorldwide production of refined Zn, Cd and Pb metals in 2007 was 11,500,000 t(Tolcin, 2009), 20,400 t (Tolcin, 2008) and 8,280,000 t (Guberman, 2009), respectively.The majority of Zn is used as an anti-corrosion coating (40%), e.g., galvanized steel(Greenwood and Earnshaw, 2001). The majority of Cd is used to produce the metallic Cdelectrode plate found in nickel-cadmium (Ni-Cd) batteries (67%); significant Cd is alsoused in pigments (15%), plastic stabilizers (10%) and coatings (7%) (Greenwood andEarnshaw, 2001). Today, lead-acid battery production accounts for the largest use of Pb;Pb is also used to produce ammunition, building construction materials, communicationand power cable coverings and leaded gasoline (still sold for use in automobiles in partsof Eastern Europe, Africa, the Middle East, Asia and Latin America and used to fuelsmall general aviation aircrafts) (Greenwood and Earnshaw, 2001).Zinc, Cd and Pb are all chalcophile elements. Zinc and Pb are the majorconstituents of the ore minerals sphalerite (ZnS) and galena (PbS). Cadmium is theconstituent element of the mineral greenockite (CdS) and also occurs as a significantimpurity (usually ~0.2–0.4%) in the ore mineral sphalerite, sphalerite being the importantcommercial source (Greenwood and Earnshaw, 2001). Sphalerite and galena ores arecommonly associated and mined together. The main metallic Zn and Pb components ofthese ores are separated from other ore and gangue minerals, using methods such asgrinding and sulfide flotation, to produce Zn and Pb ore concentrates. These oreconcentrates undergo smelting and refining to produce high purity metals. Most of theworld’s refined Zn is produced from Zn ore concentrates using an electrowinningprocess, while most Pb is produced from Pb ore concentrates and secondary Pb materials(e.g., spent Pb-acid batteries) using pyrometallurgical processes. Cadmium is recoveredprimarily as a byproduct of Zn smelting and refining and from the recycling of spent Ni-Cd batteries, alloys and electric arc furnace dust.In 2007, Canada was the second largest producer of refined Zn and the fourthlargest producer of refined Cd in the world, producing ~7% (Tolcin, 2009) and ~10%(Tolcin, 2008), respectively. Canada also produced ~3% of the world’s Pb (Guberman,2009). Teck is Canada’s largest mining, mineral processing and metallurgical company.56Their operations in Trail, British Columbia (B.C.) include one of the world’s largest fullyintegrated Zn and Pb smelting and refining complexes, which contributed an estimated36%, 33% and 67% of Canada’s Zn, Pb and Cd metals production in 2007, respectively(calculated from Fthenakis, 2004; Teck Cominco Ltd., 2008; Tolcin, 2008, 2009;Guberman, 2009).Zinc and Pb smelters, together with refineries, are large contributors toanthropogenic Zn, Cd and Pb emissions. Releases to air and water vary with the Zn andPb ores used, type of metallurgical processing and the abatement measures in place. Inthis contribution, we endeavor to better understand the behavior of Zn, Cd and Pbisotopes during metallurgical processing and we explore the potential use of newgeochemical tools, such as Zn and Cd isotopes, to source and trace these metals in theenvironment.For elements with two or more stable isotopes, physical and chemical reactionsmay result in mass-dependent isotopic fractionation. This leads to natural variations inthe isotopic compositions of many elements. The stable isotopic composition of a samplereflects that of the source and/or isotopic fractionation introduced by physiochemicalreactions (Peterson and Fry, 1987). The extent of natural isotopic variability for anelement is primarily determined by the relative mass difference for isotopes of thatelement (i.e., the mass difference for an isotope pair, Δm, relative to the average mass ofthe isotopes of the element) (Johnson et al., 2004). The extent of isotopic variability foran element will decrease with increasing atomic weight; for Δm = 1, the relative massdifference is, e.g., 8.0% for C, 1.5% for Zn, 0.9% for Cd and 0.5% for Pb. However,heavier elements tend to have more isotopes, and so the Δm, and subsequently therelative mass difference, for two isotopes of an element, may be much larger than that forΔm = 1. Due to the extended mass range of Cd isotopes relative to that of Zn isotopes,both Zn and Cd have total relative mass differences of 9.0% for Δm = 6 and Δm = 10(i.e., Δm = mass range for all isotopes of the given element), respectively, despite theheavier mass of Cd. For Pb, this total relative mass difference is significantly smaller,1.9% for Δm = 4. Only with modern instruments, primarily the multi-collectorinductively coupled plasma mass spectrometer (MC-ICP-MS) with its enhancedionization efficiency, has the precision needed to measure the small isotopic variations of57most heavy stable elements (e.g., Zn and Cd) in terrestrial materials been available. In thecase of Pb, any isotopic mass-dependent fractionation is very small in contrast to thevariation in isotopic abundance among the world’s ore deposits (0.61% for 204Pb, 6.64%for 206Pb, 6.03% for 207Pb and 4.93% for 208Pb; Böhlke et al., 2005). Lead has four stableisotopes, three (206Pb, 207Pb and 208Pb) the stable end products of radioactive decay chains(238U, 235U and 232Th, respectively) and one non-radiogenic isotope (204Pb). The Pbisotopic composition of an ore deposit is that of the initial Pb-isotopic composition of thehost-rock/source material at the time of formation, plus new radiogenic Pb if any, whichwould have accumulated from the radioactive decay of U and Th since the time offormation (i.e., the age of the deposit; Faure and Mensing, 2005). The Pb isotopiccomposition of anthropogenic emissions resulting from high temperature processes (e.g.,fossil fuel combustion, smelting and refining) reflects the isotopic composition of thesource. As a result, Pb isotopic composition can be used to trace the source of Pbemissions in a technique called Pb isotope fingerprinting.A few previous studies have examined the Zn and Cd isotopic variability amongsulfide ores (Wombacher et al., 2003; Mason et al., 2005; Sonke et al., 2008; Mattielli etal., 2009; Schmitt et al., 2009), constraining the range in isotopic compositions of smeltersource materials. Potential use of Zn and Cd isotopes as tracers has been increasinglyexplored since Wombacher et al. (2004) and Cloquet et al. (2005) identified that hightemperature processes (e.g., evaporation of Cd) cause isotopic fractionation. Morerecently, Mattielli et al. (2009) identified successive steps of pyrometallurgicalprocessing, particularly evaporation, as a source of Zn isotopic fractionation in resultingairborne particles. Zinc isotopes can therefore be used as a tracer of atmospheric Znemissions released from these processing plants. Most recent studies have focused on theisotopic fractionation imparted to environmental samples taken from the vicinity of oreprocessing plants (Dolgopolova et al., 2006) and refineries (Cloquet et al., 2006b; Gao etal., 2008; Sivry et al., 2008; Sonke et al., 2008; Mattielli et al., 2009). By contrast,process samples have been the focus of fewer studies (Cloquet et al., 2005; Sivry et al.,2008; Mattielli et al., 2009).Several studies have evaluated the use of Zn or Cd isotopes to sourceanthropogenic emissions of these elements in the environment. The coupled use of Zn58and Pb isotopes traced the source of enriched Zn in lichens and leaves (Russia) to localactivities related to mining and ore processing as well as long-range transport of dustfrom other anthropogenic activities or natural processes (Dolgopolova et al., 2006).Enriched Zn in sediments and soils was traced using Zn isotopes to emissions from localmetallurgical processing plants in the polluted Lot watershed in SW France (Sivry et al.,2008) and in a peat bog lake near Lommel, Belgium (Sonke et al., 2008). A trendbetween proximity to a Pb and Zn refinery plant (N France) and Cd isotopic compositionwas identified in topsoils (from proximal and a light Cd isotopic composition consistentwith emissions from the refinery, to distal and a heavier isotopic composition consistentwith natural sources) demonstrating Cd isotopes can be used as an environmental tracer(Cloquet et al., 2006b).The primary focus of this study is to determine the presence and degree of Zn, Cdand Pb isotopic fractionation introduced during the metallurgical processing of Zn and Pbore concentrates in one of the world’s largest integrated Zn and Pb processing plants(Teck’s operations in Trail, B.C.). We obtained samples of source materials, end productsand intermediate products (e.g., roaster calcine) chosen to represent significant steps inprocessing (especially high temperature processes), which may result in isotopicfractionation. The thermal recovery of Cd in the recycling of Ni-Cd batteries wasevaluated as a source of Cd isotopic fractionation by comparing the Cd isotopiccompositions of recycled Cd metal, recovered from Ni-Cd batteries at INMETCO’s Cdrecovery plant (Ellwood City, PA), and refined Cd metal (Teck), chosen to exemplify therefined Cd metal used to make the metallic Cd electrode plate found in Ni-Cd batteries.The process of calcination, used to produce CdS pigments, was evaluated as a source ofisotopic fractionation by comparing the Cd isotopic compositions of CdS pigment and Cdbearing minerals.3.2 Materials and methods3.2.1 Sample materials and collectionSamples were collected from the Zn and Pb operations at Teck’s integrated Znand Pb smelting and refining complex in Trail, B.C. in December 2008. Teck’s Trail59facility also produces Cd, Ge and In as byproducts of Zn production and Ag, Au, Bi, Cuand As as byproducts of Pb production and sulfuric acid (H2SO4) produced from SO2 off-gases. Zinc and Pb ore concentrates comprise the primary feeds for Zn and Pb operations.These ore concentrates are produced at mining sites from ores using crushing, grindingand selective flotation to isolate ZnS and PbS and reject gangue minerals (including FeS)to mine tailings (Fthenakis, 2004). Although the focus of this paper is to study the Zn, Cdand Pb isotopic fractionation imparted by smelting and refining of Zn and Cd, due to theintegrated nature of the processing at Teck’s Trail facility, both Zn and Pb processingmust be considered as sources of Zn, Cd and Pb isotopic fractionation in smelting andrefining products and emissions.Zinc and Cd refining, as relevant to this study, is summarized in Fig. 3.1. For Zn,Teck’s Trail facility employs an electrolytic Zn process, which consists of parallel hightemperature roasting (Z1) and pressure leaching (not shown in Fig. 3.1), leaching withH2SO4 (Z2), purification (Z4), electrodeposition (Z5) and melting/casting (Z6)(Fthenakis, 2004). Although, Zn ore concentrates are normally treated in parallel withtwo processes, roasting (80–85%) and pressure leaching (20–25%), the pressure leachingplant was not in operation during the sampling period and any contributions frompreviously processed inventory are negligible (personal communication, M. Heximer,Teck Metals Ltd., 2009). During roasting (Z1), much of the Zn in the ZnS ore concentrateis oxidized to form ZnO (calcine). The sulfur in the ZnS is converted to SO2 gas, which isisolated in the SO2 gas treatment plant and converted to H2SO4. Iron impurities present inthe Zn ore concentrates form Zn ferrite (ZnFe2O4; Graydon and Kirk, 1988) (~11% of theZn; personal communication, M. Heximer, Teck Metals Ltd., 2009). The roaster calcineis leached in H2SO4 (Z2) to dissolve the ZnO (~89% of the Zn; personal communication,M. Heximer, Teck Metals Ltd., 2009) and form a ZnSO4 solution, while the ZnFe2O4 isseparated as a solid and directed to Pb operations for treatment. The ZnSO4 solution issent to the purification circuit (Z4), where cementation is used to remove other metals. Znmetal is recovered from the sulfate solution by electrowinning (Z5). The Zn stripped offthe cathodes is melted and cast (99.995% Zn or different Zn alloys; Z6). Cadmium cake,resulting from the purification of the ZnSO4 solution, is directed to the Cd plant (Z7),where additional leaching and vacuum distillation are used to purify the Cd metal (≥6099.99% Cd). Residues from the Cd plant (Z7) are directed to the sulfide leaching plant(Z2), these residues result from the Cd plant processes of leaching and prilling (used toform Cd pellets), which take place before the distillation step. The effluent from Znoperations is treated with milk of lime (Ca(OH)2), to precipitate out dissolved metals ashydroxides, filtered (Z8) and reprocessed in Zn and Pb operations for metal recovery.For Pb, Teck’s Trail facility uses a Kivcet (flash smelting technology) furnace toproduce Pb bullion and slag (P2). This smelting furnace is fed a mixed feed comprised ofPb ore concentrates and residues from Zn operations; this feed mixture is prepared in thefeed plant (P1). Smelting separates impure Pb bullion from the slag metals (P2). The Pbbullion is directed to the drossing plant and Pb refinery (not shown in Fig. 3.1), while themolten slag is treated in a slag-fuming furnace (P3) to remove Zn as ZnO fume (alsoremoving Cd as CdO). The remaining fumed slag is sold as ferrous granules for use as aniron supplement in cement production. The ZnO fume is dehalogenated (F and Cl areremoved) in a fume leach plant (P4) and then fed into the oxide leaching plant (Z3). Inthe oxide leaching plant the fume is treated with H2SO4 to remove impurities of In andGe, which are directed to the In/Ge Plant (not shown in Fig. 3.1), and impurities of Pb,As and Sb, which are recycled back into Pb operations. The ZnSO4 and CdSO4 solution isfed into the sulfide leaching plant (Z2).Samples include a variety of Zn smelting operation feeds: Zn ore concentrates(primarily ZnS) (S1) produced at (a) the black shale hosted Red Dog Zn–Pb mine(Alaska, USA), the world’s largest source of Zn and the primary source of Zn oreconcentrate for Teck’s Trail facility; (b) the carbonate hosted Pend Oreille Zn–Pb mine(Washington, USA) and (c) Bolivian Zn–Pb mines in the Oruro and Potosi regions. Theroaster (Z1) feed typically comprises: Red Dog Zn ore concentrates (40–60%), PendOreille Zn ore concentrates (20%) and other Zn ore concentrates (20–40%), e.g., theBolivian blend. In addition to the three Zn ore concentrate samples, six samples from Znand Pb smelting operations were included in this study: (S2) calcine, primarily zinc oxide(ZnO), produced by roasting the Zn ore concentrates (965–980 °C; Z1); (S3) Pb smeltermixed feed, produced in the feed plant (P1), includes Pb ore concentrates and residuesfrom Zn operations (effluent treatment plant, Z8; sulfide leaching plant, Z2; oxideleaching plant, Z3); (S4) ZnO fume, resulting from slag fuming (P3), before61dehalogenation (P4); (S5) refined zinc metal and (S6) refined cadmium metal productsand (S7) effluent from Zn smelting operations, primarily originating from the roasters(Z1) and associated SO2 gas treatment, sampled prior to treatment at the EffluentTreatment Plant (Z8).In addition, recycled cadmium metal (S8), reclaimed primarily from Ni-Cdbatteries (not shown in Fig. 3.1), was obtained from The International MetalsReclamation Company, Inc. (INMETCO) in Ellwood City, PA, USA. INMETCOrecycles consumer and commercial Ni-Cd batteries by thermal recovery in their Cdrecovery plant, which came on line in December 1995. In the Cd recovery process, Cdmaterials are reduced, using carbon, to Cd metal, vaporized and condensed into Cd metalshot (99.750–99.999% Cd; Hanewald et al., 1996). Cadmium sulfide (CdS) pigment (S9;not shown in Fig. 3.1) was obtained as true cadmium yellow light pigment (PébéoFragonard, France) manufactured from zinc salts calcinated at 600 ºC (personalcommunication, Pébéo Fragonard, 2009).3.2.2 Sample preparationExperimental work was carried out in metal-free Class 1,000 clean labs at thePacific Centre for Isotopic and Geochemical Research (PCIGR), University of BritishColumbia (UBC). Sample preparation for elemental and isotopic analyses was performedin Class 100 laminar flow hoods in the clean labs and instrument rooms.3.2.2.1 ReagentsNitric (HNO3), hydrochloric (HCl) and hydrofluoric (HF) acids used in this studywere purified in-house from concentrated reagent grade acids by sub-boiling distillation.Baseline® hydrobromic (HBr) acid and hydrogen peroxide (H2O2) produced by SeastarChemicals Inc. (Canada) were also utilized. Ultra-pure water (≥ 18.2 MΩ cm), preparedby de-ionization of reverse osmosis water using a Milli-Q system (Millipore, USA), wasused to prepare all solutions. All labware was washed successively with a ~2% extran®300 (Merck KGaA, Germany) solution (alkaline cleanser), analytical grade HCl andenvironmental grade HNO3.623.2.2.2 Sample digestionFor powdered smelter samples, between 9.63 and 25.5 mg was weighed out intoSavillex® PFA vials. For the CdS pigment, 0.5 mg was weighed out. Refined Cd and Znmetals were cleaned with Citranox® detergent (Alconox, Inc., USA), leached with 1 MHCl and resulting leachates were collected to represent the metals. Powdered samples(S1, S2, S3, S4, S9), metal leachates (S5, S6, S8) and effluent (S7) were digested in twosteps: (1) 3 mL ~15 M HNO3 and 2 mL ~29 M HF and (2) 5 mL ~6 M HCl. Digestionwas carried out on a hotplate except in the case of the Pb smelter mixed feed (S3, highlyrefractory sample) for which digestion was carried out in an oven at 190 °C in a steel-jacketed high-pressure PTFE bomb. From each digested sample solution, three separatealiquots were taken for (1) elemental analysis, (2) the isolation of Cd and Zn and (3) theisolation of Pb.3.2.2.3 Anion exchange chromatographyThe anion exchange chromatography procedure used to isolate Zn and Cd followsthe method of Mason (2003) and is presented in Shiel et al. (2009). Column blanks for Znand Cd are negligible (Zn detected in the column blank corresponds to 8.5 × 10-5% or 9.4× 10-4% of the total sample Zn loaded on the column; calculated using the Zn content oftwo different column blanks and the smallest quantity of sample Zn loaded on thecolumn; Cd was not detected in the column blanks). In this study, the resin was batchcleaned using the method of De Jong et al. (2007) prior to packing the column. The resinwas then cleaned in the column before loading and purifying samples.  Fresh resin wasused for each sample. The Cd and Zn eluate cuts were collected in Savillex® PFA vials,dried, treated with HNO3 and H2O2 and close-vessel digested on a hotplate in an effort todigest any resin-derived organics (Shiel et al., 2009), then dried again driving off anytraces of eluent acids (i.e., trace HF, HCl or HBr), and redissolved in 1 mL 0.05 M HNO3in preparation for isotopic analysis. Recovery of Cd and Zn was monitored to ensure~100%, in order to avoid introduction of isotopic fractionation associated withchromatographic separation (as observed for numerous ion exchange chromatographyprocedures: Maréchal et al., 1999; Anbar et al., 2000; Maréchal and Albarède, 2002;63Wombacher et al., 2003; Schönbächler et al., 2007). Quantitative yields for Cd and Znwere 100 ± 4% and 100 ± 7%, respectively.Sample Pb was isolated by anion exchange chromatography using the AG 1-X8(100–200 mesh) resin (Bio-Rad Laboratories, Inc.), as previously described (Weis et al.,2006). Briefly, the sample is loaded onto the column in 0.5 M HBr and the resin absorbsPb while bulk elements are eluted. Lead is then recovered using 6 M HCl. The Pb eluatecuts were collected in Savillex® PFA vials, dried, treated with HNO3 and H2O2 and close-vessel digested on a hotplate in an effort to digest any resin-derived organics (Shiel et al.,2009), then dried again driving off any traces of eluent acids (i.e., trace HCl or HBr), andredissolved in 1 mL 0.05 M HNO3 in preparation for isotopic analysis. Yield for Pb was± 6%.3.2.3 StandardsStandard solutions used for element concentration determination were preparedfrom 1,000 µg mL-1 single-element solutions from High Purity Standards, Inc. (USA),Specpure® Plasma (Alfa Aesar®, Johnson Matthey Company, USA) and PlasmaCAL(SCP Science, Canada).The in-house primary and secondary reference Zn isotopic standards (PCIGR-1Zn and PCIGR-2 Zn) are from High Purity Standards, Inc. and Specpure® (lots 505326and 011075A, respectively). The “Lyon-JMC” Zn standard (Maréchal et al., 1999) wasanalyzed and is isotopically identical, within uncertainty, to the PCIGR-1 Zn standard(δ66/64Zn = -0.01 ± 0.22‰, n = 7). The in-house primary and secondary reference Cdisotopic standards (PCIGR-1 Cd and PCIGR-2 Cd) are from High Purity Standards, Inc.(USA) (lots 291012 and 502624, respectively). The JMC Cd, “Münster Cd” and BAM-1012 Cd (Federal Institute for Materials Research and Testing, Germany) referencematerials (Wombacher and Rehkämper, 2004) were analyzed and results agree withvalues reported in the literature (Shiel et al., 2009). JMC Cd and PCIGR-1 Cd areidentical within uncertainty (δ114/110Cd = -0.03 ± 0.05‰, n = 3). The NIST (USA) SRM981 natural Pb (isotopic) standard is used for monitoring analytical run instrument driftand normalization of all measured Pb isotopic ratios.643.2.4. Data presentationZinc and Cd isotopic compositions are expressed relative to the PCIGR-1 Zn andPCIGR-1 Cd reference standards in the standard delta (δ) per mil (‰) notation asfollows:€ δiZn =  (iZn)sample(iZn)standard−1       x 1,000€ δjCd =  (jCd)sample(jCd)standard−1       x 1,000where i and j are the measured isotope ratios, for Zn i = 66/64, 67/64 or 68/64 and for Cdj = 111/110, 112/110, 113/110 or 114/110. Isotopic compositions for all the ratiosmentioned above are reported here, although discussion will revolve around δ114/110Cd andδ66/64Zn values, as these are the most widely reported. For Pb, the 206Pb/204Pb, 207Pb/204Pb,208Pb/204Pb, 206Pb/207Pb and 208Pb/206Pb ratios are reported. To assess the importance ofmass-dependent isotopic fractionation for Pb, some discussion for Pb will focus ondeviations in a given Pb isotope ratio between two samples, expressed in delta (δ) per mil(‰) notation per atomic mass unit (amu) as follows:€ δkPb =  (kPb)A(kPb)B−1       x 1,000 x (mass1- mass2)-1where k is the measured isotope ratio, mass1/mass2 = 206/207 or 208/206, for twosamples, A and B.3.2.5 Analytical techniques3.2.5.1 Elemental analysisElement concentration analyses of sample digests and Zn, Cd and Pb eluate cutswere performed on a Varian 725-ES (Varian, Inc., USA) inductively coupled plasmaoptical emission spectrometer (ICP-OES) housed in the Earth and Ocean Sciencesdepartment, UBC. Emission line wavelengths of 213.857 nm, 226.502 nm and 220.353nm were used to determine the concentrations of Zn, Cd and Pb, respectively. Elementconcentrations were quantified using multi-element calibration curves with europium(Eu), measured at 420.504 nm, as an internal standard. All solutions were prepared with650.3 M HNO3. Measured Zn, Cd and Pb concentrations agree with product compositioninformation provided by Teck.3.2.5.2 Isotopic analysisIsotope ratios were measured by multi-collection on a Nu Plasma (Nu 021; NuInstruments, UK) multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS) using the DSN-100 (Nu Instruments, UK) membrane desolvator for sampleintroduction. The MC-ICP-MS is housed in a Class 10,000 lab at the PCIGR, UBC. Allstandard and samples solutions were prepared fresh for each Zn, Cd and Pb measurementsession by diluting with 0.05 M HNO3. Copper, Ag and Tl were doped into all measuredsolutions of Zn, Cd and Pb, respectively, and used to monitor and correct for instrumentalmass bias.3.2.5.2.1 Zn and Cd isotopesZinc and cadmium isotope measurements were obtained following the proceduresdescribed by Shiel et al. (2009). In brief, a standard sample-standard bracketing (SSB)measurement protocol was followed, where samples were run alternately with standards.Each sample was measured a minimum of three times during at least two differentanalytical sessions. Zinc isotopic solutions were prepared as 3:1 Zn and Cu solutions,typically at 70 µg L-1 Zn and 23 µg L-1 Cu. Ion signal intensities were measured formasses 62–68 (isotopes of Zn, Cu and Ni). The isobaric Ni interference on 64Zn wascorrected by monitoring 62Ni. Ion signal intensities for 62Ni were ≤ 0.12 mV for allmeasurements (samples and standards), corresponding to ≤ 0.03 mV on mass 64 with a64Zn ion signal intensity ranging from 4.2 to 5.1 V, making the Ni contributioninsignificant for all analyses. Cadmium isotopic solutions were prepared as 2:1 Cd andAg solutions, typically at 60 µg L-1 Cd and 30 µg L-1 Ag. Ion signal intensities weremeasured for masses 106–118 (isotopes of Cd, Ag and Sn) in two cycles. Thecontribution of Sn on Cd isotopes 112 and 114 was corrected by monitoring the intensityof 118Sn. Ion signal intensities for 118Sn were ≤ 0.40 mV for all samples and standards,excluding the Pb smelter mixed feed (S3), corresponding to ≤ 0.01 mV on mass 114 witha 114Cd ion signal intensity ranging from 3.3 to 5.4 V, making the Sn contribution66insignificant even before correction. For the Pb smelter mixed feed, a 118Sn ion signalintensity of 36 mV was measured and used to correct for the corresponding 0.98 mV onmass 114 with a 114Cd ion signal intensity of ~ 5.1 V.Two methods were used to correct for instrumental mass bias: (1) SSB ofmeasured ratios and (2) combined external normalization–SSB. For Zn, the SSB methodresulted in more precise results and is reported. This can be attributed to differences inthe behaviors of Zn and Cu in the presence of residual sample matrix (Shiel et al., 2009).For Cd, combined external normalization–SSB corrected delta values are reportedbecause they are the most reproducible. This can be attributed to similar behaviors of Cdand Ag in the presence of residual sample matrix (Shiel et al., 2009).3.2.5.2.2 Pb isotopesLead isotope measurements were obtained following the procedures described inmore detail elsewhere (Weis et al., 2006; Barling and Weis, 2008). At the start of eachanalytical session a batch (≥ 5) of the NIST SRM 981 standard was run. Samples wererun following a modified SSB measurement protocol, where the standard was run afterevery two samples. Lead isotopic solutions, both samples and standards, were prepared as4:1 Pb and Tl solutions, typically at 15 µg L-1 Pb and 3.75 µg L-1 Tl. Ion signal intensitieswere measured for masses 202–208 (isotopes of Pb, Tl and Hg). Instrumental massfractionation was corrected using a Tl standard (Specpure®, lot 205081F) with a 205Tl/203Tlratio of 2.3885 (Weis et al., 2006). Corrected Pb ratios for the NIST SRM 981 standardwere within error of the triple spike Pb ratios (Galer and Abouchami, 1998). The isobaricHg interference on 204Pb was corrected by monitoring 202Hg and assuming naturalabundances, 202Hg/204Hg = 4.350 (de Laeter et al., 2003). Ion signal intensities for 202Hgwere ≤ 0.24 mV for all measurements (samples and standards), corresponding to ≤ 0.05mV on mass 204 with a 204Pb ion signal intensity ranging from 0.12 to 0.15 V, making theHg contribution insignificant for all analyses. The ion signal intensity for 208Pb wasbetween 4.6 and 6.1 V and for 204Pb was ≥ 0.12 V for all analyzed samples. Measured,instrumental mass bias corrected ratios were normalized to the triple spike values ofGaler and Abouchami (1998) using the ln–ln method or the SSB normalization method67(White et al., 2000; Albarède and Beard, 2004), depending on the level of instrumentalmass bias drift during the analytical session.3.2.5.2.3 Spectral and non-spectral interferencesCare was taken to avoid spectral and non-spectral interferences on measuredisotopes. All samples were processed through chromatography columns to isolate theanalytes as described in Section 3.2.2.3. The high analyte concentrations of these samplesmeant that it was possible to dilute the purified samples by at least 4,600×, 35× or 73× forZn, Cd or Pb, respectively. By measuring these dilute purified samples, the non-spectralmatrix effects associated with residual sample and resin-derived organic and inorganiccontaminants (Shiel et al., 2009) were limited or avoided. Removal of elements that causeisobaric interferences was confirmed by monitoring eluate cuts prior to analysis. Prior todoping sample Zn, Cd and Pb solutions with their mass bias correcting elements (Cu, Agand Tl, respectively) for isotopic analysis, each was analyzed on the MC-ICP-MS toensure their mass bias correcting elements were at levels consistent with the acid blank.This was especially important in this study as Cu, Ag and Tl are all byproducts of Zn andPb smelting and refining operations in Trail.Zinc is a special concern for Cd analysis, due to the formation of ZnAr+, which isan isobaric interference on 107Ag and 110Cd. In the majority of the samples, the Znconcentration is much higher than the Cd concentration, the [Zn] is as much as 540× the[Cd] (Table 3.1); thus even a small percentage of Zn in the neighboring Cd eluate cutmay have detrimental effects. For the purified Cd samples, the highest relativeconcentration of Zn to Cd, i.e., [Zn]/[Cd], was ~8.0% and Zn was not detected in themajority of purified Cd samples. In an experiment on the MC-ICP-MS, ~0.1% of Zn wasdetermined to form ZnAr+ (determined by comparing the 64Zn and 64Zn40Ar+ ion signalintensities for a 35 µg L-1 Cd and 18 µg L-1 Ag solution undoped and doped with 30 µgL-1 Zn). For the purified Cd sample with the highest [Zn]/[Cd], 67Zn40Ar+ and 70Zn40Ar+would result in insignificant changes to the δCd values (affecting the SSB and combinedexternal normalization–SSB delta values in the fourth and third decimal places,respectively).683.3 Results3.3.1 Zn, Cd and Pb isotopesZinc and Cd concentrations and delta values are reported in Table 3.1 and shownin Fig. 3.2a and b, respectively. Lead concentrations and isotopic ratios are reported inTable 3.2 and shown in Fig. 3.3. The δ66/64Zn, δ114/110Cd and 206Pb/207Pb values of smeltingand refining samples are summarized in Fig. 3.1.3.3.1.1 Zn isotopesThe Zn isotopic composition varies among analyzed samples with a total range ofδ66/64Zn = 0.09 to 0.51‰ (see Table 3.1 for the other ratios). The total range representssignificant differences in Zn isotopic compositions. The linear data array for Zn ratios inFig. 3.2a is consistent with mass-dependent fractionation. Zinc ore concentrates (S1)exhibit the lightest Zn isotopic compositions of all smelter samples (δ66/64Zn = 0.09 to0.17‰; Fig. 3.2a). The Zn isotopic composition of the calcine (S2) is within error of thatof the Zn ore concentrates (S1; Fig. 3.2a). The Pb smelter mixed feed (S3), the ZnO fumefrom Pb smelting operations (S4) and the Zn operations’ effluent (S7) exhibit the heaviestZn isotopic compositions (δ66/64Zn = 0.33 to 0.51‰; Fig. 3.2a). The Zn metal product(S5) has an intermediate Zn isotopic signature (δ66/64Zn = 0.22‰), which can beexplained as resulting from the mixing of the isotopically lighter Zn ore concentrates (S1)and the isotopically heavier Zn (S3, S4; Fig. 3.2a) introduced to Zn smelting operationsby the Pb smelter mixed feed (P1) via the oxide leaching plant (Z3).3.3.1.2 Cd isotopesThe Cd isotopic composition varies among analyzed samples with a total range ofδ114/110Cd = -0.52 to 0.52‰ (see Table 3.1 for the other ratios). The total range representssignificant differences in Cd isotopic compositions. The linear data array for Cd ratios inFig. 3.2b is consistent with mass-dependent fractionation. Zinc concentrates (S1) have Cdisotopic compositions ranging from δ114/110Cd = -0.13 to 0.18‰ (Fig. 3.2b). The Cdisotopic composition of calcine (S2) is within error of that of the Zn ore concentrates (S1;Fig. 3.2b). The lightest sample Cd isotopic compositions (S3, S4; δ114/110Cd = -0.52 to69-0.38‰) are introduced from the Pb smelter via the oxide leaching plant (Z3). Theheaviest Cd isotopic composition is exhibited by the Cd metal product (S6; δ114/110Cd =0.39 to 0.52‰; Fig. 3.2b). As with Zn, the smelting operations’ effluent (S7) exhibits aheavy Cd isotopic composition (Fig. 3.2b). A significant shift in the Cd isotopic signatureis observed between the Zn ore concentrates (S1) and the Cd metal product (S6; Fig.3.2b).The recycled Cd metal from INMETCO (S8) has a Cd isotopic signature similarto that of the smelter-refined Cd metal product (S6; Fig. 3.2b). The CdS pigment fromFrance (S9), resulting from the calcining of zinc salts, exhibits a Cd isotopic signaturewithin the range of Cd isotopic compositions observed for the Zn ore concentrates (S1)and the smelter-produced calcine (S2; Fig. 3.2b).3.3.1.3 Pb isotopesThe Pb isotope values of the analyzed samples range from 1.15174 to 1.24642 for206Pb/207Pb and 2.04842 to 2.10703 for 208Pb/206Pb (see Table 3.2 for the other ratios). Themost radiogenic samples are characterized by high 206Pb/207Pb ratios and low 208Pb/206Pbratios and vice-versa for the least radiogenic samples (Fig. 3.3a). Zinc ore concentrates(S1) exhibit the most radiogenic Pb isotopic values of the analyzed samples (Fig. 3.3a,b).Calcine (S2) has a slightly less radiogenic Pb isotopic composition (Fig. 3.3a,b). Themixed feed (S3) for the Kivcet Pb smelter and the ZnO fume from Pb smelting operations(S4) exhibit the least radiogenic Pb isotopic values (Fig. 3.3a,b). Zinc smeltingoperations’ effluent (S7) has an intermediate Pb isotopic composition. The intermediatePb isotopic composition of the effluent (S7) may be attributed to mixing of the moreradiogenic isotopic compositions of the calcine (S2) and Zn ore concentrates (S1) and theless radiogenic isotopic compositions of the Pb smelter mixed feed (S3) and ZnO fume(S4; Fig. 3.3a,b). Samples form a trend from low Pb concentration and more radiogenicPb isotopic composition (Zn ore concentrates, S1) to high Pb concentration and lessradiogenic Pb isotopic composition (Pb smelter mixed feed, S3; ZnO fume, S4) (inset ofFig. 3.3a).703.4 Discussion3.4.1 Fractionation of Zn, Cd and Pb isotopes during Zn refining3.4.1.1 Zn isotope variationZinc ore concentrates (S1; δ66/64Zn = 0.09 to 0.17‰), primarily composed of ZnS,exhibit Zn isotopic compositions that are consistent with those reported in the literaturefor sphalerites and other ore grade sulfide minerals (Fig. 3.4) (Mason et al., 2005; Sonkeet al., 2008; Mattielli et al., 2009) and are within error of the global average Zn isotopiccomposition (δ66/64Zn = 0.16 ± 0.20‰, 2SD, n = 10 mines) for major ore body sphaleritesproposed by Sonke et al. (2008). The δ66/64Zn value for the roaster calcine (S2; δ66/64Zn =0.17‰) falls within the range of the Zn ore concentrates (S1) included in this study (Fig.3.4), indicating a near 100% yield from this step. The δ66/64Zn value for the Pb smeltermixed feed (S3; δ66/64Zn = 0.33‰) falls at the heavier end of the range reported for oregrade sulfide minerals (Mason et al., 2005; Sonke et al., 2008; Mattielli et al., 2009) andis heavier than those measured for the Zn ore concentrates included in this study (Fig.3.4). This discrepancy indicates a significant contribution of relatively heavy Zn to the Pbsmelter mixed feed (Fig. 3.4), which may originate from Zn introduced as (1) Pb oreconcentrates not included in this study, e.g., from the Cannington mine, Queensland,Australia and/or (2) stockpiled Zn residues, derived from the past processing, sulfideleaching (Z2) and effluent treatment (Z8), of Zn ore concentrates not included in thisstudy, e.g., from the now closed, nearby Sullivan mine, B.C. (see Section 3.4.1.3;personal communication, M. Heximer, Teck Metals Ltd., 2009). This explanationrequires the unaccounted ores have Zn isotopic compositions among the heaviest reported(i.e., ZnS: δ66/64Zn ≤ 0.37‰, PbS: δ66/64Zn ≤ 0.25‰; Sonke et al., 2008). The differencebetween the Zn isotopic compositions of the Pb smelter mixed feed (S3; δ66/64Zn =0.33‰) and the relatively heavy Zn found in the ZnO fume (S4; δ66/64Zn = 0.43‰) likelyreflects variability in the composition of the Pb smelter mixed feed with time, althoughthis is unclear given the measurement uncertainties.Zinc isotopic fractionation occurring during the processing of Zn ore concentrates(S1) is reflected in the significantly heavy δ66/64Zn values of the Zn operations’ effluent71(S7; δ66/64Zn = 0.41 to 0.51‰). This relatively heavy δ66/64Zn value is expected tooriginate from high temperature roasting (Z1; Fig. 3.1), the primary source of Zn to theeffluent, although due to the relatively small Zn loss during roasting, the differencebetween the Zn isotopic compositions of the Zn ore concentrates (S1) and calcine (S2) isnegligible (Fig. 3.2a). Heavy δ66/64Zn values, similar to those found for the Zn operations’effluent (S7; Fig. 3.4), have been observed in smelting and refining polluted lichens(Cloquet et al., 2006a), sediments and soils (Sivry et al., 2008).Although significant fractionation of Zn isotopes occurs during smelting andrefining processes, as observed in the effluent (S7) and particulate atmospheric emissions(as light as δ66/64Zn = -0.73‰; Mattielli et al., 2009), due to the high Zn recovery (~98%overall Zn recovery; personal communication, M. Heximer, Teck Metals Ltd., 2009) theZn isotopic composition of the Zn metal product (S5) is not significantly different fromthat of the source material (S1) (Fig. 3.4). The vast majority of the unrecovered Zn (~2%)is lost in Pb operations as ferrous granules. Effluent (0.003%) and atmospheric emissions(0.030%) (calculated from Environment Canada, 2007 and Teck Cominco Ltd., 2008) areisotopically heavy and light, respectively, but represent a very small percentage of theoverall Zn budget. Therefore, these losses, although isotopically fractionated relative tothe source materials, are not large enough to significantly shift the isotopic compositionof the remaining Zn. The Zn isotopic composition of the Zn metal product (S5) can beaccounted for by variable mixing of the Zn ore concentrates (S1) and the Pb smeltermixed feed (S3) (Fig. 3.2a). A mixture of 80% and 20% for the Zn ore concentrates (S1)and Pb smelter mixed feed (S3) would account for the observed Zn isotopic compositionof the Zn metal product (S5; Fig. 3.1). As a result of this high recovery, variability of theZn isotopic composition of the Zn metal product is expected to result primarily fromisotopic variability inherent to the Zn and Pb ore concentrates used to feed smelting andrefining operations rather than from the small Zn losses due to emissions and incompleterecovery of Zn during slag fuming. The relatively small range of Zn isotopiccompositions reported for “common” anthropogenic Zn products relative to that reportedfor ore samples (Fig. 3.4; John et al., 2007) results from smelting and refining operationswhich homogenize the mixture of Zn ore concentrates (S1) feeding Zn operations (asdiscussed in Section 3.2.1). The Zn isotopic composition of the Zn metal product (S5;72Fig. 3.4) is consistent with that of “common” anthropogenic Zn (Zn metal and healthproducts, between δ66/64Zn = 0.1 and 0.3‰), including electrochemically refined highpurity Zn shot (99.995% purity) from the Canadian Electrolytic Zinc refinery (Salaberry-de-Valleyfield, Québec) and thermal distillation refined Zn metal dust (98.5% purity)(John et al., 2007).3.4.1.2 Cd isotope variationThe Zn ore concentrates (S1) studied here exhibit Cd isotopic compositions(δ114/110Cd = -0.13 to 0.18‰) consistent with those reported for continental and oceanicsulfides, including sphalerite (ZnS) and greenockite (CdS) minerals (Wombacher et al.,2003; Schmitt et al., 2009) and all δ114/110Cd values fall within the range of those reportedfor terrestrial rocks (Wombacher et al., 2003) (Fig. 3.5). The δ114/110Cd values of the Znore concentrates (S1) and the roaster-produced calcine (S2; δ114/110Cd = 0.05‰) cannot bedistinguished due to the near 100% yield from roasting (roaster products are separated ina subsequent step of processing). It is therefore unclear from this comparison as towhether roasting fractionates Cd isotopes.The δ114/110Cd value of the Pb smelter mixed feed (S3; δ114/110Cd = -0.38‰) islighter than that of the Zn ore concentrates (S1). Its Cd isotopic composition is withinerror of the lightest reported for continental sulfides (Wombacher et al., 2003; Schmitt etal., 2009), with a δ114/110Cd value similar to a greenockite mineral (Schmitt et al., 2009)(Fig. 3.5). It falls within the lighter end of the range reported for oceanic sulfides(Schmitt et al., 2009) and terrestrial rocks (Wombacher et al., 2003) (Fig. 3.5). Therelatively light signature of the Pb smelter mixed feed (S3) as compared to the Zn oreconcentrates (S1) may reflect, in part, the use of ore concentrates not included in thisstudy (see Section 3.4.1.1 and Section 3.4.1.3; Fig. 3.5). However, given the overallpicture constructed by the Cd isotopic compositions of the smelter samples, we suggestthe source of light Cd isotopes in the Pb smelter mixed feed (S3) is more likely to be Znresidues resulting from the treatment of roaster-produced calcine in the sulfide leachingplant (Z2). These Zn residues (primarily partially reacted sphalerite particles andZnFe2O4) are filtered from the ZnSO4 electrolyte solution in the sulfide leaching plant(Z2) and directed to Pb operations, where they are included in the Pb smelter mixed feed73(S3). Roasting (Z1) is therefore suggested to impart different Cd isotopic compositions tothe different mineralogical phases formed.The ZnO fume (S4) has a light Cd isotopic composition (δ114/110Cd = -0.52‰)within error of that of the Pb smelter mixed feed (S3) (Fig. 3.5). The δ114/110Cd value ofthe ZnO fume (S4) is similar to that reported for smelting dust (Cloquet et al., 2005) (Fig.3.5). The Zn operations’ effluent (S7) has a relatively heavy Cd isotopic composition,which is expected to result from the high temperature roasting process, similar to Zn. Theδ114/110Cd value for the effluent is identical to that reported for Pb–Zn refinery plant slag(Cloquet et al., 2005) and the heaviest of the values observed in smelting and refiningpolluted sediments (Gao et al., 2008) (Fig. 3.5).Significant Cd isotopic fractionation results from the refining of Cd as abyproduct of Zn and Pb smelting and refining and is reflected in the Cd isotopiccompositions of the effluent (S7), ZnO fume (S4), particulate atmospheric emissions(Cloquet et al., 2005) and Cd metal product (see below). Effluent (0.012%) andatmospheric emissions (0.010%) are isotopically heavy and light (Fig. 3.5), respectively,however, these represent a very small percentage of the overall Cd budget. The loss inheavy Cd isotopes to the effluent during roasting is not significant enough to result in adifference between the Cd isotopic compositions of the Zn ore concentrates and roastercalcine. Although the overall recovery for Cd is not available, it is presumed to be lowerthan that of Zn, as Cd is recovered as a byproduct and the processing is optimized forrecovery of Zn. Cadmium recovery is calculated as 72–92% using the Zn, Cd and Pbcontents of Red Dog mine Zn and Pb ore concentrates and annual Zn, Pb and Cd metalproduction (Fthenakis, 2004; Teck Cominco Ltd., 2008).The δ114/110Cd value of the Cd metal product (S6; δ114/110Cd = 0.39 to 0.52‰) isheavier than that of the Zn ore concentrates (S1; Fig. 3.2b). Processes occurring in theCadmium Plant (Z7), mainly the use of vacuum distillation to purify Cd, were consideredas potential sources of Cd isotopic fractionation. Evaporation and condensation duringfractional distillation have been demonstrated to be sources of Cd isotopic fractionation(Wombacher et al., 2004). However, this explanation is not favored here, as there is not alarge loss of Cd associated with the distillation and this explanation does not account forthe relatively light isotopic signature of the Pb smelter mixed feed. Rather, a significant74loss of light Cd, by means of a mass loss during Pb operations of Cd originating fromboth Pb ore concentrates and Zn residues from Zn operations (e.g., Cd is lost to the Pbbullion and ultimately the Cu cake), is expected to account for the relatively heavyisotopic composition of the Cd metal product (S6). In this scenario, the primary source ofCd isotopic fractionation is roasting (Z1), as discussed above, and Zn residues, comingfrom the sulfide leaching plant (Z2), are expected to account for the light Cd isotopicsignature of the Pb smelter mixed feed (S3).The Cd isotopic signature of the INMETCO recycled Cd metal (S8; δ114/110Cd =0.23 to 0.34‰) is within error of that of Teck’s Cd metal product (S6; Fig. 3.2b), and isexpected to vary primarily with that of the Cd recovery plant feed (commercial andconsumer Ni-Cd batteries). The ability to assess the Cd isotopic fractionation associatedwith the thermal recovery of Cd, as part of Ni-Cd battery recycling, is limited due to anunknown Cd loss during processing and the inaccessibility of the plant feed andintermediate products for sampling. The Fragonard CdS pigment (S9) has a δ114/110Cdvalue consistent with the heaviest Zn ore concentrates (S1a) included in this study, theroaster calcine (S2; Fig 3.2b) and continental and oceanic sulfides (Wombacher et al.,2003; Schmitt et al., 2009) (Fig. 3.5). This similarity suggests that the calcination of zincsalts does not fractionate Cd isotopes and/or the recovery of the process is ~100%,similar to roasting.3.4.1.3 Pb isotope variationThe three Zn ore concentrates (S1) are the most radiogenic Pb samples includedin this study (Fig. 3.3a,b). Those from the Red Dog mine (S1a) exhibit the leastradiogenic Pb isotopic signature of the three (Fig. 3.3a,b), with isotope ratios within therange of literature values for ore from the Red Dog mine: 206Pb/207Pb = 1.1805 and208Pb/206Pb = 2.0764 (mean calculated by Sangster et al., 2000, from references within).The 206Pb/207Pb ratio of the roaster calcine (S2; 206Pb/207Pb = 1.16784) is significantly lessradiogenic than those of the Zn ore concentrates (S1a,b,c; 206Pb/207Pb = 1.17988 to1.24642), by between -63 and -10‰ (Fig. 3.3a). Therefore, the mixture of Zn oreconcentrates used to feed the roasters is presumed to have also included a Zn oreconcentrate with a radiogenic Pb isotopic composition not included in this study. The75similarity between the Pb isotopic compositions of the calcine (S2; representative of themixture of Zn ore concentrates used to feed the roasters) and Zn operations’ effluent (S7)corroborates Teck’s identification of roasting as the largest source of Zn operations’effluent (personal communication, M. Heximer, Teck Metals Ltd., 2009). The Pb smeltermixed feed (S3) is among the least radiogenic samples included in this study (Fig.3.3a,b), its Pb isotopic composition requires the mixing of Pb from the Red Dog depositwith Pb from a much less radiogenic source. As Pb ore concentrates were not included inthis study, we can not unequivocally identify this less radiogenic source, however, twolikely sources are: (1) Pb ore concentrates from the Cannington mine, Queensland,Australia (206Pb/207Pb = ~1.041; Huston et al., 2006) and/or (2) stockpiled Zn residuesresulting from the processing of ore concentrates from the nearby Sullivan mine, B.C.(personal communication, M. Heximer, Teck Metals Ltd., 2009). The Sullivan mine wasthe largest source of Pb ore concentrates to Teck’s Trail facility prior to the mine’sclosure in 2001: 206Pb/207Pb = 1.0679 and 208Pb/206Pb = 2.1889 (Fig. 3.3a,b; meancalculated by Sangster et al., 2000, from references within). A mixture of Pb and Zn oreconcentrates, with 74% and 26% of the total processed Pb originating from the Red Dogand Sullivan mines, respectively, can account for the observed Pb isotopic composition ofthe Pb smelter mixed feed (S3).Lead isotopes are not likely to undergo significant mass-dependent fractionationduring Zn or Pb smelting operations due to the element’s heavy mass and subsequentlyits small relative mass difference. This is evidenced by: (1) the lack of internalconsistency among the delta values per amu calculated for the different Pb isotope ratios(e.g., for the calcine and effluent: δ206/207Pb = 1.88‰ amu-1 and δ208/206Pb = 0.60‰ amu-1and for the Pb smelter mixed feed and the ZnO fume: δ206/207Pb = 0.45‰ amu-1 andδ208/206Pb = -0.41‰ amu-1), (2) the discrepancy between the slope of the trend defined byall analyzed samples and that of the mass-dependent fractionation line (Fig. 3.3a) and (3)the extent of the variations observed in Pb isotopes in this study (δ206/207Pb = 76‰ amu-1for all samples). Kinetic fractionation of Pb would be expected to therefore be smallerthan that of Cd due to its heavier mass, a worse case scenario for Pb would be 0.30‰(this is the total variation, per amu, observed here for Cd), which corresponds to avariation less than the symbol size in Fig. 3.3a (~0.01 for 206Pb/207Pb and 208Pb/206Pb).76In Pb–Pb diagrams (Fig. 3.3a,b), all Pb samples form a mixing trend, where thePb isotopic compositions of the smelting and refining intermediate products and effluentcan be explained by the mixing of Zn and Pb ore concentrates of different origins.Therefore, mixing, rather than mass-dependent fractionation, accounts for the vastmajority of the variation among the Pb isotopic compositions of samples. Lead and Znisotopes agree when the signature reflects the source, departures from this general trendoccur when the Zn isotopic composition is fractionated during processing, e.g., Znoperations’ effluent (S7; Fig. 3.1). In such cases, pairing the use of Zn and Pb isotopeswill allow the assessment of Zn isotopic fractionation and tracing of the source.3.4.2 Implications for local environmental samplesThe implementation of aggressive pollution abatement policies in response toincreasingly strict regulations and the availability of new technologies in North Americaand Western Europe has led to dramatic reductions in the metals (including Zn, Cd, Pb)released into environments neighboring, downstream and downwind of smelters andrefineries in these regions. However, high metal levels are expected to persist inenvironments adjacent to historical polluters. Historical levels of air and water releasesfrom smelting and refining operations in Trail were much higher than today. Forexample, the direct disposal of granulated slag, resulting from Pb operations (Fig. 3.1),into the Columbia River was ceased in 1995 and this slag is now sold to cementmanufacturers (Teck Cominco Ltd., 2007).The results of this study support the use of Zn and Cd isotopes to trace smeltingand refining air emissions and effluent in the local environment, at storage sites and atdisposal sites. The use of Pb isotopic signatures may complement the use of Zn and Cdisotopes, because the Pb isotopic signature reflects the source. Several recent studies haveused Zn and Cd isotopic signatures to identify the source of enriched metal levels inreservoirs representative of natural environments (e.g., lichens, sediments, soils) thathave been affected by historical or modern smelters and refineries (e.g., for Zn: Cloquetet al., 2006a; Sonke et al., 2008; Sivry et al., 2008; Mattielli et al., 2009 and for Cd:Cloquet et al., 2006b; Gao et al., 2008). Distinguishing between historic and recentreleases may not be possible, as shifts in the source Zn and Pb ore concentrates over time77may not be accompanied by significant changes in the Zn and Cd isotopic compositions.However, well documented temporal changes in the Pb isotopic composition of oreconcentrates consumed by smelters and refineries may allow differentiation betweenhistoric and recent Pb smelting emission related depositions in the environment.3.5 ConclusionsOur investigation of Zn, Cd and Pb isotopic fractionation in smelting and refiningprocesses resulted in the following conclusions:(1) Significant fractionation of Zn isotopes occurs systematically throughout thehydrometallurgical processing of Zn ore concentrates as evidenced by the significantshift between the Zn isotopic compositions of the Zn ore concentrates and theeffluent. The effluent represents only a very small overall loss of Zn duringprocessing; as a result there is no significant difference between the δ66/64Zn values ofthe Zn ore concentrates and the refined Zn metal. The δ66/64Zn value of the refined Znmetal is therefore expected to reflect the δ66/64Zn value of the ore concentrate feed.(2) The same observation holds for Cd, where significant fractionation of Cd isotopesresults from the metallurgical processing of Zn ore concentrates. This is evidenced bythe larger total variation in Cd isotopic composition exhibited by the Zn oreconcentrates, Pb smelter mixed feed, ZnO fume, refined Cd metal and effluent.(3) Recycling of Ni-Cd batteries is not associated with a significant shift in the Cdisotopic composition between the metallic Cd electrode plate (as represented by therefined Cd metal) and the recycled Cd metal product.(4) No significant fractionation of Pb isotopes results from the smelting and refining ofZn and Pb ore concentrates. Significant Pb isotopic variation between the Zn oreconcentrates and the Pb smelter mixed feed reflects the contribution to the latter ofvarious Pb ore concentrates not included in this study and/or stockpiled residues fromZn operations.(5) The results of this study suggest Zn and Cd isotopes can be used to tracemetallurgical processing emissions of these metals in the environment.783.6 AcknowledgementsWe especially want to thank Teck and John F.H. Thompson for providing smeltersamples and are grateful to Michael Heximer for his assistance with sample selection andfor providing valuable discussion regarding smelting processes. We thank INMETCO,especially Frank Przywarty and Al Hardies, for the recycled Cd metal sample and adescription of their Cd recovery process. We are grateful to Jane Barling for commentson this manuscript and for her assistance with the Nu Plasma MC-ICP-MS and toMaureen Soon for her assistance with the Varian 725-ES ICP-OES. We thank JamesScoates for comments on this manuscript and his support. We are grateful to JeroenSonke and Alla Dolgopolova for their insightful and constructive reviews. We also thankFrancis Albarède for providing an aliquot of the “Lyon-JMC” Zn standard solution. Thisstudy was funded by NSERC Discovery grants to Dominique Weis and Kristin J. Orians.79Table 3.1. Zinc and Cd contents and isotopic compositions.Sample IDaSample[Zn](%)bδ66Zn/64Zncδ67Zn/64Zncδ68Zn/64Zncnd[Cd](%)bδ111Cd/110Cdcδ112Cd/110Cdcδ113Cd/110Cdcδ114Cd/110CdcndZinc ore concentratesS1a Red Dog mine 52.2 0.12 ± 0.00 0.19 ± 0.03 0.23 ± 0.07 2 0.302 0.03 ± 0.07 0.08 ± 0.13 0.14 ± 0.17 0.18 ± 0.27 3S1aRed Dog mine dup.e52.2 0.17 ± 0.05 0.27 ± 0.18 0.33 ± 0.16 3 0.302 0.05 ± 0.05 0.10 ± 0.07 0.13 ± 0.07 0.17 ± 0.15 3S1b Pend Oreille mine 64.2 0.09 ± 0.07 0.13 ± 0.14 0.20 ± 0.17 5 0.118 0.04 ± 0.04 0.08 ± 0.06 0.10 ± 0.04 0.14 ± 0.12 3S1c Bolivian blend 51.7 0.12 ± 0.11 0.16 ± 0.11 0.19 ± 0.23 3 0.233 -0.04 ± 0.04 -0.09 ± 0.12 -0.12 ± 0.18 -0.13 ± 0.24 3Zinc smelter, Trail, B.C.S2 Calcine 58.4 0.17 ± 0.06 0.24 ± 0.13 0.31 ± 0.08 3 0.286 0.02 ± 0.02 0.05 ± 0.02 0.06 ± 0.17 0.05 ± 0.12 2S5 Refined Zn alloy 95.0 0.22 ± 0.04 0.31 ± 0.13 0.45 ± 0.10 3S6Refined Cd metalf100 0.08 ± 0.01 0.19 ± 0.06 0.30 ± 0.19 0.39 ± 0.18 3S6Refined Cd metal dup.e,f100 0.15 ± 0.09 0.27 ± 0.14 0.40 ± 0.19 0.52 ± 0.19 3S7 Effluent (ppm) 109 0.51 ± 0.02 0.74 ± 0.09 1.02 ± 0.11 2 1.34 0.09 ± 0.02 0.18 ± 0.01 0.24 ± 0.06 0.31 ± 0.07 3S7Effluent dup.e (ppm)109 0.41 ± 0.08 0.64 ± 0.13 0.82 ± 0.19 3 1.34 0.12 ± 0.01 0.24 ± 0.00 0.35 ± 0.07 0.46 ± 0.08 2Lead smelter, Trail, B.C.S3Mixed feed8.68 0.33 ± 0.15n/agn/ag3 0.155 -0.11 ± 0.07 -0.19 ± 0.12 -0.29 ± 0.20 -0.38 ± 0.25 3S4ZnO fume  (feed material for Zn operations)46.3 0.43 ± 0.03 0.63 ± 0.07 0.85 ± 0.08 3 0.354 -0.14 ± 0.03 -0.26 ± 0.02 -0.40 ± 0.03 -0.52 ± 0.02 3Inmetco, Inc., Ellwood City, PAS8Recycled Cd metalf100 0.05 ± 0.11 0.12 ± 0.14 0.18 ± 0.32 0.23 ± 0.34 3S8Recycled Cd metal dup.e,f100 0.08 ± 0.04 0.17 ± 0.04 0.28 ± 0.13 0.34 ± 0.12 3Cadmium productsS9 CdS yellow pigment 8.5 45.3 0.02 ± 0.04 0.06 ± 0.02 0.12 ± 0.10 0.16 ± 0.01 3aColumn 1 identifies sample ID as described in section 3.2 Materials and methods and shown in Fig. 3.1.bElemental concentration given as % by weight, except where noted.cRatios are reported as the mean ± 2 standard deviation (SD).dn refers to the number of replicate isotopic measurements.edup. refers to a full procedural duplicate, inclusive of the analytical separation and isotopic analysis.fConcentrations provided by manufacturer.gDeltas calculated for ratios with masses 67 and 68 in the numerator are omitted due to a Ba2+ interference.80Table 3.2. Lead contents and isotopic compositions.Sample IDaSample[Pb](%)c 206Pb/204Pbd,e 207Pb/204Pbd,e 208Pb/204Pbd,e 206Pb/207Pbd,e 208Pb/206Pbd,eZinc ore concentratesS1a Red Dog mine 2.81 18.4161 ± 0.0008 15.6077 ± 0.0007 38.262 ± 0.002 1.17991 ± 0.00002 2.07766 ± 0.00003S1aRed Dog mine dup.b2.81 18.4192 ± 0.0008 15.6112 ± 0.0007 38.269 ± 0.002 1.17988 ± 0.00001 2.07766 ± 0.00004S1b Pend Oreille mine 0.779 19.7144 ± 0.0010 15.8166 ± 0.0009 40.383 ± 0.002 1.24642 ± 0.00001 2.04842 ± 0.00003S1c Bolivian blend 1.16 18.7984 ± 0.0010 15.6808 ± 0.0009 39.106 ± 0.003 1.19880 ± 0.00002 2.08028 ± 0.00003Zinc smelter, Trail, B.C.S2 Calcine 2.57 18.1980 ± 0.0010 15.5826 ± 0.0008 38.135 ± 0.002 1.16784 ± 0.00002 2.09553 ± 0.00004S7 Effluent (ppm) 4.08 18.1760 ± 0.0010 15.5931 ± 0.0009 38.134 ± 0.002 1.16564 ± 0.00001 2.09806 ± 0.00004Lead smelter, Trail, B.C.S3Mixed feed20.6 17.9372 ± 0.0009 15.5668 ± 0.0008 37.794 ± 0.002 1.15226 ± 0.00002 2.10703 ± 0.00003S4ZnO fume  (feed material for Zn operations)18.1 17.9243 ± 0.0008 15.5627 ± 0.0008 37.736 ± 0.002 1.15174 ± 0.00001 2.10529 ± 0.00003aColumn 1 identifies sample ID as described in section 3.2 Materials and methods and shown in Fig. 3.1.bdup. refers to a full procedural duplicate, inclusive of the analytical separation and isotopic analysis.cElemental concentration given as % by weight, except where noted.dRatios are reported as the mean ± 2 standard error (SE).eAll data have been normalized to the NIST SRM 981 triple spike Pb ratios of Galer and Abouchami (1998).81Fig. 3.1. Schematic depiction of Zn and Pb operations at Teck’s integrated Zn and Pb smelting and refining complex in Trail (B.C., Canada). Processes employed during Zn and Pb operations are indicated by a circle and designated by Z and P, respectively, followed by a number corresponding to the step in the process (Z1, Z2, etc. and P1, P2, etc., respectively). Samples are indicated by a star and are designated by an S followed by a number (S1, S2, etc.). d66/64Zn, d114/110Cd and 206/207Pb values are given for each sample. This figure is adapted from http://www.metsoc.org/virtualtour/processes/zinclead.asp and personal communication, M. Heximer, Teck Metals Ltd., 2009.82Zn concentratesRoasterPlant(965-980ºC)CalcineSulfide Leaching PlantPurificationCircuitZnSO4 electrolyte ElectrolyticPlantMeltingPlantZn metalCd Plant (distillation)Cd metalOxide LeachingPlantLeached fumeEffluent Treatment PlantTreated effluentColumbia RiverFeed PlantSlag FumingPlantKivcet SmelterFume LeachPlantPb bullionZn operationsPb operationsP4Slag FumePb concentratesResiduesResiduesPureZn206/207Pb = 1.15174d114/110Cd = -0.52d66/64Zn = 0.43d114/110Cd = 0.39, 0.52d66/64Zn = 0.22206/207Pb = 1.15226d114/110Cd = -0.38d66/64Zn = 0.33SolidsRecycled to Zn and Pb smelting operationsSolids from contaminated water Ferrous slag 206/207Pb = 1.17988 to 1.24642d114/110Cd = -0.13 to 0.18d66/64Zn = 0.09 to 0.17206/207Pb = 1.16784d114/110Cd = 0.05d66/64Zn = 0.17Z1 Z2Z3Z4Z5Z7Z6Z8S4Mixed feed206/207Pb = 1.16564d114/110Cd = 0.31, 0.46d66/64Zn = 0.41, 0.51Zinc operations' effluentP1 P2 P3S3S1S7S6S5S2Solids from contaminated water Drossing Plant and Pb RefineryCement production (Fe supplement)Cd cakeImpure Zn solutionZn residues83Pend Oreille ore (S1b)Red Dog ore (S1a)Bolivian ore (S1c)Calcine (S2)Effluent (S7)Pb smelter mixed feed (S3)ZnO fume (S4)Cd metal (S6)Recycled Cd metal (S8)CdS pigment (S9)Zn metal (S5)-0.80-0.60-0.40-0.200.000.200.400.600.80-0.20 -0.10 0.00 0.10 0.20 0.30d111Cd/110Cdd114Cd/110Cd0.60d66Zn/64Znd68Zn/64Zn0.000.200.400.600.801.001.200.00 0.10 0.20 0.30 0.40 0.50(b)(a)Source materialEnd productEffluent and fumesEnd productFumesSource materialEffluentEffluentFumesSource materialFig. 3.2. Mass-dependent Zn and Cd isotopic fractionation for all Zn and Cd samples, respectively: (a) d68/64Zn vs. d66/64Zn and (b) d114/110Cd vs. d111/110Cd. Error bars denote – 2 standard deviation (SD) on the mean delta value for replicate analyses of each sample. The calculated regression lines (for (a), r2 = 0.9953; for (b), r2 = 0.9857) are coherent with mass-dependent isotopic fractionation, indicating spectral interferences are insignificant with one exception. For (b), the d68/64Zn value for the Pb smelter mixed feed is biased by a significant Ba2+ interference on mass 68, as a result this sample is excluded from the linear regression. The d68/64Zn value plotted for the Pb smelter mixed feed is calculated from the d66/64Zn value. Inset shows d114/110Cd vs. d66/64Zn for all samples for which both Zn and Cd isotopic measurements were made. Error bars denote – 2SD on the mean delta value for replicate analyses of each sample, except when this value is less than the long-term reproducibility calculated for the in-house secondary Zn and isotopic standards (Shiel et al., 2009), and then the latter is used. Source material (i.e., Zn ore concentrates) for both Zn and Cd isotopes falls in a narrow range. Processing of Zn ore concentrates through Teck’s Trail operations leads to heavier isotopic compositions of both Zn and Cd in the effluent, suggesting a similar mechanism of isotopic fractionation during processing. On the contrary, the Pb smelter mixed feed and ZnO fume are isotopically light for Cd and heavy for Zn, perhaps suggesting the two elements behave differently during roasting.-0.80-0.400.000.400.800.00 0.20 0.40 0.60d66Zn/64Znd114Cd/110Cd84208Pb/206Pb2.042.062.082.102.122.141.12 1.14 1.16 1.18 1.20 1.22 1.24 1.26Ores (Canada)Emissions (Canada)Lichens (B.C., Canada)Pend Oreille ore (S1b)Red Dog ore (S1a)Bolivian ore (S1c)Calcine (S2)Effluent (S7)Pb smelter mixed feed (S3)ZnO fume (S4)Source materialEffluentFume(b)(a)35.536.036.537.037.538.038.539.039.540.040.541.016.0 16.5 17.0 17.5 18.0 18.5 19.0 19.5 20.0206Pb/204Pb208Pb/204PbSource materialEffluentFume206Pb/207PbMass-dependent fractionation lineFig. 3.3. Plots of (a) 208Pb/206Pb vs. 206Pb/207Pb and (b) 208Pb/204Pb vs. 206Pb/204Pb for all smelter and refinery Pb samples. For all samples, 2 standard error is smaller than the symbol size. The data are compared with the Pb isotope ratios of Canadian Pb ores including Sullivan mine ore (Sangster et al., 2000), lichens from B.C. (Simonetti et al., 2003) and Canadian emissions (Carignan and Gariépy, 1995; Bollhöfer and Rosman, 2001). Error bars indicate error as reported by referenced authors; in several cases this error is smaller than the symbol size. The dashed line in (a) corresponds to mass-dependent fractionation of Pb isotopes. Inset in (a) shows 206Pb/207Pb vs. 1/[Pb](%) for all samples except the effluent.Sullivan oreSullivan ore(1.0679, 2.1889)1.141.161.181.201.221.240 0.20 0.40 0.60 0.80 1.00 1.201/[Pb](%)206Pb/207Pb85Fig. 3.4. Variations in Zn isotopic composition of samples from the smelting and refining operations depicted in Fig. 3.1 and published geological and anthropogenic materials. The grey ellipses indicate error as reported by referenced authors; for this study the grey ellipses denote – 2 standard deviation on the mean d66/64Zn value for replicate analyses of each sample, except when this value is less than the long-term reproducibility calculated for the in-house secondary Zn isotopic standard,  –0.06‰, and then the latter is used. In several cases the error is smaller than the symbol. Data sources: 1Sonke et al., 2008; 2Mason et al., 2005; 3John et al., 2008; 4Mattielli et al., 2009; 5Cloquet et al., 2006a; 6Sivry et al., 2008; 7John et al., 2007.86Oceanic sulfides, mixed assemblages:Pb-Zn Metallurgical plant, Metaleurop Nord S.A.(NE France):-1.00 -0.50 0.00 0.50 1.00 1.50 2.00d66Zn/64Zn (‰)This study:Zn ore concentrates (S1)Calcine (S2)Refined Zn (S5)Effluent (S7)Pb smelter mixed feed (S3)ZnO fume (S4)Galena (PbS)1Sphalerite (ZnS)1Continental sulfides:Fe-Zn chimney3Cu-rich chimney3Sulfide ores, mixed assemblages(Urals, Russia)2Environmental samples4Zn-Pb enriched ores4Pb enriched ores4Zn refining emissions (roasting, blast furnace)4Pb refining emissions (roasting, blast furnace)4Main chimney emissions4Zn ore treatment plant (Riou-Mort-Lot river system, SW France):Polluted lichens, (Metz, NE France)5Urban waste incinerator flue gases, REFIOM (NE France)5Urban aerosols (Metz, NE France)5Anthropogenic Zn samples:Sediment cores6:Unpolluted PollutedTailings6Coal ashes6Percolating water6Polluted stream sediments6Polluted soils6"Common" anthropogenic Zn;Zn metals and health products7Electroplated hardware7Galvanized hardware7Polluted environmental samples (NE France):-1.00 -0.50 0.00 0.50 1.00 1.50 2.0087-1.00 -0.50 0.00 0.50 1.00 1.50d114Cd/110Cd (‰)Zn ore concentrates (S1)Calcine (S2)Refined Cd (S6)Effluent (S7)Pb smelter mixed feed (S3)ZnO fume (S4)CdS pigment (S9)Recycled Cd (S8)Smelter slag3Smelter dust3Polluted soils,Pb-Zn refinery (France)4 Polluted sediments, Pb-Zn smelter (China)5Sphalerite (ZnS)1 Greenockite (CdS)1Sphalerite (ZnS)2Greenockite (CdS)2Otavite (CdCO3)1Smithsonite (ZnCO3)1Mixed sphalerite assemblages:(ZnS, ZnS+FeS2 or ZnS+BaSO4)2Graywacke1Shale1Continental carbonates and sulfides:Oceanic sulfides:Basalt1Diorite1Terrestrial rocks:Industrial samples:Environmental samples:Incinerator fly ash (BCR 176)3This study:-1.00 -0.50 0.00 0.50 1.00 1.50Fig. 3.5. Variations in Cd isotopic composition of samples from the smelting and refining operations depicted in Fig. 3.1, recycled Cd metal, CdS pigment and published geological and anthropogenic materials. The grey ellipses indicate error as reported by referenced authors; for this study the grey ellipses denote – 2 standard deviation on the mean d114/110Cd value for replicate analyses of each sample, except when this value is less than the long-term reproducibility calculated for the in-house secondary Cd isotopic standard,  –0.14‰, and then the latter is used. In several cases the error is smaller than the symbol. Data sources: 1Wombacher et al., 2003; 2Schmitt et al., 2009; 3Cloquet et al., 2005; 4Cloquet et al., 2006b; 5Gao et al., 2008.883.7. ReferencesAlbarède, F., Beard, B.L. (2004) Analytical methods for non-traditional isotopes.Reviews in Mineralogy and Geochemistry 55: 113–152.Anbar, A.D., Roe, J.E., Barling, J., Nealson, K.H. (2000) Nonbiological fractionation ofiron isotopes. 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(2000) High-precision analysis of Pb isotoperatios by multi-collector ICP-MS. Chemical Geology 167: 257–270.Wombacher, F., Rehkämper, M. (2004) Problems and suggestions concerning thenotation of cadmium stable isotope compositions and the use of referencematerials. Geostandards and Geoanalytical Research 28: 173–178.Wombacher, F., Rehkämper, M., Mezger, K. (2004) Determination of the mass-dependence of cadmium isotope fractionation during evaporation. Geochimica etCosmochimica Acta 68: 2349–2357.Wombacher, F., Rehkämper, M., Mezger, K., Münker, C. (2003) Stable isotopecompositions of Cd in geological materials and meteorites determined bymulticollector-ICPMS. Geochimica et Cosmochimica Acta 67: 4639–4654.93CHAPTER 4Tracing cadmium, zinc and lead pollution inbivalves from the coasts of western Canada,the USA and France using isotopes 11A version of this chapter will be submitted for publication. Shiel, A.E., Weis, D., Orians,K.J. (2010) Tracing cadmium, zinc and lead pollution in bivalves from the coasts ofwestern Canada, the USA and France using isotopes.944.1 IntroductionCoastal and marine pollution impact the global environment and haveimplications for the health of ecosystems and organisms. Marine pollution, includingheavy metal pollution, adversely affects local fisheries and associated economies. Insome cases, however, high metal concentrations in the environment and residentorganisms may not derive from an anthropogenic source. The source of high Cd levelsreported in the tissues of oysters (Crassostrea gigas) harvested from British Columbia(B.C., western Canada) (e.g., Kruzynski, 2001, 2004; Lekhi et al., 2008; Bendell andFeng, 2009) is unknown but thought to be largely natural. In B.C., the Federal andProvincial Governments have encouraged pursuits in aquaculture as the forest industryand wild fisheries have declined. In 1997, the Provincial Government made plans todouble the crown lands available for bivalve aquaculture through the ShellfishDevelopment Initiative (Kruzynski, 2004). In 1999/2000, however, several shipments ofB.C. oysters were rejected by Hong Kong for exceeding their import Cd limit of 2 µg g-1wet weight (Kruzynski, 2004). This generated concerns over the potential loss of marketssupporting the expanding aquaculture industry as well as health concerns related to theconsumption of B.C. shellfish with high Cd levels. The subsequent survey of B.C.oysters, harvested from the western coast of Canada, by the Canadian Food InspectionAgency (CFIA) found a mean Cd concentration of 2.63 µg g-1 wet weight (n = 81), with60% of samples over 2 µg g-1 wet weight (Schallié, 2001). Oysters with relatively highCd levels were not limited to populated areas but rather included those harvested fromsparsely inhibited or “pristine” areas. In contrast, a complimentary investigation ofoysters (Crassostrea virginica) harvested from the eastern coast of Canada found Cdconcentrations ranging from 0.07 to 0.56 µg g-1 wet weight, with a mean Cdconcentration of only 0.33 µg g-1 wet weight (n = 18) (Schallié, 2001). Using the Cdconcentrations reported for B.C. oysters by the CFIA, Health Canada conducted a formalHealth Risk Assessment. Based on this assessment, they recommended consumption belimited to a dozen 40 g oysters per month for an adult (Kruzynski, 2004). However, noconsideration was made for nutritional and other risk factors in their assessment. In95addition, major gaps exist in the knowledge related to Cd bioavailability from oysters andpotential health effects (Kruzynski, 2004).Potential sources of Cd to B.C. coastal waters and bivalve molluscs (e.g., oystersand mussels) include natural sources, such as the upwelling of deep oceanic waters or theweathering of mineral outcrops, or anthropogenic sources, such as erosion-related runoff(e.g., in logging areas), municipal storm water, effluent from wastewater treatment, pulpand paper mills or mining. The disparity between the Cd concentrations found in oystersfrom the Pacific and Atlantic coasts of Canada (with the exception of polluted estuarieson the Atlantic coast) suggests the source of high Cd in the North Pacific region may benatural. Seawater in the North Pacific has higher dissolved Cd concentrations due to theglobal thermohaline circulation of the ocean. Upwelling of intermediate waters rich innutrients and nutrient-type trace metals (e.g., Cd and Zn) could bring this water to theregions where oysters are grown. In global thermohaline circulation, deep water forms inthe North Atlantic Ocean, sinks, flows south, around Antarctica, moves east through theIndian Ocean, and then northward from the South Pacific Ocean to the North PacificOcean, accumulating nutrients and trace metals along the way. Cadmium concentrationsof North Pacific deep waters (1.04 nmol kg-1 or 117 ng kg-1; Bruland, 1980) are ~3–4×those of the North Atlantic (0.32 nmol kg-1 or 36 ng kg-1; Bruland and Franks, 1983).Similarly, Zn concentrations of North Pacific deep waters (9.07 nmol kg-1 or 593 ng kg-1;Bruland, 1980) are ~4–6× those of the North Atlantic (1.61 nmol kg-1 or 105 ng kg-1,Bruland and Franks, 1983). On the west coast of Vancouver Island, variations in the Cdconcentrations of mussel tissues were found to be associated with variations in dissolvedCd related to upwelling events (Lares and Orians, 1997). The US Mussel Watch Program(NOAA, USA) did not find a correlation between high Cd concentrations in oysters andmussels and high human population density; this was in contrast to Pb concentrations, forwhich a fairly strong correlation with high human population density was reported(O’Connor, 2002). The US Mussel Watch Program reported high Cd concentrations inmussels inhabiting coastal Northern California and suggested coastal upwelling as thesource (O’Connor, 2002). Further, Cd concentrations in scallops from Antarctica are high(14–49 µg g-1 dry weight); high concentrations in this remote area were suggested to96result from the upwelling of Cd-rich deep-waters (Berkman and Nigro, 1992; Viarengo etal., 1993).In contrast to Cd and Zn, which have nutrient–type depth profiles in the ocean andincrease in concentration as deep waters flow from the Atlantic to the Pacific, Pb has ascavenged-type depth profile (Chester, 2003). Lead concentrations are high at the surface,due to atmospheric input, and decrease with depth and deep water age, as Pb is scavengedonto particles and removed to the sediments. Most Pb in the modern ocean isanthropogenic in origin (Chester, 2003). The worldwide decline in the consumption ofleaded gasoline has been associated with significant reductions in the atmosphericdeposition of Pb to the surface oceans. In the central North Pacific, Pb concentrationsdecreased by a factor of ~2 in surface waters from ~65 pmol kg-1 (~13 ng kg-1) in 1976(Schaule and Patterson, 1981) to ~30 pmol kg-1 (~6.2 ng kg-1) in 1999 (Boyle et al.,2005), correlated with the phase-out of leaded gasoline in the USA. Similarly, Pbconcentrations in surface waters of the western North Atlantic decreased by a factor of ~4during the 1980s (Boyle et al., 1994), with lead concentrations from ~40 to 60 pmol kg-1(~8.3 to 12 ng kg-1) reported for 1995/6 in surface waters from the western North Atlantic(Wu and Boyle, 1997). A decreasing trend in Pb concentrations continues in the oceans.Oysters and mussels are bioaccumulators and have much higher metalconcentrations than seawater. As sessile organisms, their tissue metal concentrations arerepresentative of time-integrated metal concentrations at the collection site. As a result,these bivalves are used to monitor coastal contamination, including contamination ofheavy metals (e.g., Cd, Zn and Pb) in national mussel watch programs such as those ofthe USA and France. These programs monitor both spatial and temporal trends inchemical concentrations. However, some limitations are associated with the evaluation ofchemical contamination using concentrations alone, e.g., it is difficult to differentiatebetween anthropogenic and natural metal sources or to determine if relatively low metalconcentrations represent the natural baseline level, in addition, for some metals,concentrations vary depending on the species. For example, in B.C., estimates of annualcoastal Cd loading from local anthropogenic inputs failed to explain observed variationsin the Cd concentrations of B.C. oysters (Kruzynski et al., 2002). New geochemical tools,such as Cd and Zn isotopic signatures, may provide strong evidence as to metal sources.97The ionization efficiency needed for the precise measurement of small natural variationsin Cd and Zn isotopic composition has been afforded by the introduction of the multi-collector inductively coupled plasma mass spectrometer (MC-ICP-MS). Cadmium andZn are among a growing number of non-traditional stable isotope systems (i.e., Li, Mg,Ca, Si, Ti, Cr, Fe, Ni, Cu, Ge, Se, Zr, Mo, Ru, Ag, W and Tl) under investigation. Thesetools may be especially powerful in combination with radiogenic isotope tracers, e.g., Pb,which are used to trace the source.In this study, we evaluate the use of Cd, Zn and Pb isotopes as tracers of sourcesof these metals to the marine environment and bivalves. These elements are often foundtogether in solid wastes, wastewaters and emissions from industrial sources, e.g., oremining, smelting (Shiel et al., 2010) and steelmaking (Ketterer et al., 2001). Thecorrelation of these isotopic tracers from a common source is used to resolve ambiguitiesencountered with the use of only one of these isotope systems. Our investigation centerson determining the origin of these metals in oysters harvested from sites in B.C.(Canada). In order to gain a broader perspective on Cd and Zn isotopic variability inmarine environments, these isotopic compositions are compared to those of bivalvemolluscs (i.e., oysters and mussels) from Hawaii, the Atlantic coast of the USA and theAtlantic and Mediterranean coasts of France. This allows the assessment of Cd and Znisotopic compositions of bivalves from sites impacted, to various degrees, by differentnatural and anthropogenic sources. Lead isotopes are used to “fingerprint” importantanthropogenic sources, narrowing the identified potential anthropogenic sources of Cdand Zn at marine sites. Finally, Pb isotopes are used to determine the relative importanceof natural and anthropogenic Pb sources to bivalves post leaded gasoline phase-out.4.1.1 Cd Zn and Pb emission sources in Canada, the USA and FranceGlobal anthropogenic emissions of Cd and Zn to the atmosphere are estimated toaccount for the majority (70% for Cd, and 56% for Zn) of total (i.e., sum of natural andanthropogenic) atmospheric emissions of these metals (Pacyna and Pacyna, 2001). Non-ferrous metal smelting and refining is the largest source of Cd and Zn emissions to theatmosphere, accounting for approximately 72–73% of anthropogenic emissions of thesemetals (Pacyna and Pacyna, 2001). British Columbia is home to one of the world’s98largest fully integrated Zn and Pb smelting and refining complexes (Trail, B.C.). In 2008,this facility (Teck) reported the largest on-site releases to air and water of the metals, Cd,Zn and Pb, and their compounds (235 kg, 97 tonnes, 3,065 kg; respectively)(Environment Canada, 2009). Even so, the quantities of Cd, Zn and Pb released from thesmelting and refining operations in Trail declined considerably, by ~98–99%, between1994 and 2008 (in 1994: 11 tonnes, 4,466 tonnes, 246 tonnes; respectively) (EnvironmentCanada, 2009). Decreasing levels of metal emissions from Teck’s Trail facility reflectfacility upgrades (including the implementation of new technologies, which increasedinternal recycling between operations) and the vast improvement in efficiency ofemission controls employed at the facility in an effort to improve their environmentalperformance and demonstrate a commitment to environmental sustainability.B.C. oysters were collected from two regions, Desolation Sound and BarkleySound, which are located ~540 km northwest and west of the facility in Trail, B.C.Atmospheric emissions from smelting and refining operations in Trail may be a source ofCd, Zn and/or Pb to the oyster farms in Desolation Sound, both currently and moreimportantly in the past, as the most frequent wind direction near the site (in Powell River,45 km southeast of Desolation Sound) is east (i.e., toward the west). The oyster farms inBarkley Sound are not likely to receive significant Pb emissions from smelting andrefining operations as the most frequent wind direction over the Georgia Strait (separatesthe B.C. mainland from Vancouver Island) is northwest (i.e., toward the southeast).Anthropogenic sources account for ~91% of total (sum of natural andanthropogenic) global atmospheric Pb emissions to the environment (Pacyna and Pacyna,2001). Globally, the major source of atmospheric Pb emissions is the combustion ofunleaded and leaded gasoline (the latter being gasoline treated with an organoleadcompound, most commonly tetraethyl lead), which accounts for approximately 74% ofanthropogenic Pb emissions (Pacyna and Pacyna, 2001). Summaries of estimated Pbemissions from the consumption of petroleum products and coal are presented in Table4.1 (for B.C. in 2008 and Canada in 1970/2008) and Table 4.2 and Fig. 4.1 (for Canada,the USA and France in 2005). In Canada, Pb emissions resulting from the consumption ofrefined petroleum products and coal in 2008 are estimated to be <1% of those emitted in1970 (Table 4.1). In 1970, almost 100% of the total Pb emissions from the consumption99of refined petroleum products and coal are attributed to the widespread use of leadedgasoline in motor vehicles (Table 4.1). The phase out of the use of leaded motor gasolinein on-road vehicles began in Canada and the USA in the 1970s and continued through the1980s, with the introduction of unleaded gasoline in 1975. Leaded gasoline has beenprohibited in motor vehicles since 1990 and 1996 in Canada and the USA, respectively.The phase-in of unleaded motor gasoline began in France in 1989 and was completed in2000. The shift to the use of unleaded gasoline is overwhelmingly responsible for thereduction in Pb emissions over that time. In the wake of the phase-out of leaded motorgasoline, other anthropogenic Pb emission sources are left as dominant Pb contributors,albeit with total anthropogenic Pb emission levels much smaller than those before thephase-out (Table 4.1). The use of aviation gasoline (avgas), which contains the antiknockadditive tetra-ethyl lead (TEL), in piston type aircraft engines and the consumption ofdiesel fuel and heavy fuel oil by the marine transportation sector are now relativelyimportant anthropogenic sources of Pb emissions to the environment (Tables 4.1 and4.2). In B.C., the most significant Pb sources include Pb emissions from industry (e.g.,smelting and refining operations and mining), the combustion of various refinedpetroleum products (e.g., avgas and diesel fuel oil; Table 4.1) and the storage andhandling of large volumes of petroleum products, chemicals and coal.In 2008, British Columbia (B.C.) was responsible for ~10.6% of Canada’s Pbemissions resulting from the consumption of refined petroleum products and coal (Table4.1). For both Canada and B.C., the consumption of avgas (59.6 and 67.6% of the totalPb emissions, respectively) was the most important of these Pb emissions sources (Table4.1). Although, the second most important of these Pb emission sources was coal (17.4%)in Canada and diesel fuel oil (16.3%) in B.C. (Table 4.1). Across Canada, the primary useof coal is for the production of electricity, however, in B.C. most electricity is producedusing hydroelectric dams and coal is used primarily for industrial purposes (Ménard,2005). The relative importance of these Pb emissions sources in the USA is strikinglysimilar to Canada, where avgas accounts for more than half of the total Pb emissionsfrom the consumption of petroleum products (Fig. 4.1). In contrast to Canada and theUSA, diesel fuel oil is the most important source of these Pb emissions in France,accounting for almost 50% (Fig. 4.1).1004.2 Materials and methodsBivalve samples from western Canada (B.C., Fig. 4.2), the USA (Fig. 4.3) andFrance (Fig. 4.4) were selected to gain an appreciation for the global variability of the Cd,Zn and Pb isotopic compositions recorded in bivalve tissues. Selected sites represent awide range of coastal health, from relatively “pristine” (i.e., sparsely inhabited) to highlypolluted (i.e., populated and/or industrial presence) environments. The majority ofbivalve samples were analyzed for both Cd and Pb isotopic compositions, whereas Znisotopic analyses were performed only on a subset of samples chosen to exemplify totalvariability and extremes in environmental site conditions (i.e., select sites in B.C. andFrance). The observed limited variability in Zn isotopic compositions did not justify amore detailed study.4.2.1 Sample materials and collectionThis study includes B.C. oysters (Crassostrea gigas) from oyster farming siteswithin Desolation Sound (B.C. mainland) and Barkley Sound (west coast of VancouverIsland) (Fig. 4.2). These oysters (dried powders) were provided by George M. Kruzynski(Fisheries and Oceans Canada), William Heath (B.C. Ministry of Agriculture & Lands)and Leah I. Bendell (Simon Fraser University). These oysters were collected in early2004, with the exception of the oyster from Thor’s Cove (Desolation Sound) collectedlate in 2002 (included in the Cd and Zn isotope studies) and one of the two oysters fromSeddall Island (Barkley Sound) collected in late 2003 (included in the Pb isotope study).Details regarding sample collection are provided by Kruzynski (2004).Oyster and mussel tissue samples (dried powders) from the USA and France (Fig4.3 and 4.4, respectively) have been provided by their respective national Mussel Watchprojects; these projects are handled by the National Status and Trends (NS&T) programof the National Oceanic and Atmospheric Administration (NOAA) and the RéseauNational d’Observation de la qualité du milieu marin (RNO) of the Institut Français deRecherche pour l’Exploitation de la Mer (IFREMER), respectively. Information about theNOAA (USA) and IFREMER (France) mussel watch projects, including details about the101sampling sites and sample collection are provided by NOAA (1998) and O’Connor andLauenstein (2006) and Claisse (1989), respectively. The oyster and mussel samples fromthe USA (Fig. 4.3) were collected between 2003 and 2006. The majority of the oyster andmussel samples from France (Fig. 4.4) were collected in 2004 and 2005. However,archived samples from 1984 (Boyardville, Marennes Oléron basin) and 1987 (La Fosse,Gironde estuary) are also included to provide a temporal dimension to our study. As noone species exists at all sites, the mussel watch programs of both the USA and France useseveral species of both oysters (Crassostrea gigas, Crassostrea virginica, Ostreasandvicensis) and mussels (Mytilus edulis, Mytilus galloprovincialis). The species of eachsample is indicated in Tables 4.3, 4.4 and 4.5.4.2.2 Sample preparationDetailed descriptions of the sample preparation, which lead to the dried oystertissue powders provided for use in this study, are provided by Christie and Bendell(2009) for B.C. samples, NOAA (1998) for the USA samples and Claisse (1989) for theFrench samples. For B.C., oyster individuals, rather than pooled samples were provided.These individuals were separated into guts contents and the remaining soft tissues. Forthe USA and France, samples from each site were pooled as 20 oysters or 30 mussels and>10 oysters or >50 mussels, respectively. Small differences in the sampling andprocessing of bivalves are not expected to affect the results of this study.4.2.2.1 ReagentsNitric (HNO3), hydrochloric (HCl) and hydrofluoric (HF) acids used in this studywere purified in-house from concentrated reagent grade acids by sub-boiling distillation.Baseline® hydrobromic (HBr) acid and hydrogen peroxide (H2O2) produced by SeastarChemicals Inc. (Canada) were also utilized. Ultra-pure water (≥ 18.2 MΩ cm), preparedby de-ionization of reverse osmosis water using a Milli-Q system (Millipore, USA), wasused to prepare all solutions.All labware was washed successively with a ~2% extran® 300 (Merck KGaA,Germany) solution (alkaline cleanser), analytical grade HCl and environmental gradeHNO3. Savillex® PFA vials used for sample digestions and to collect purified Cd and Zn102samples were cleaned in an additional step with ~1.5 M sub-boiled HNO3.  Savillex® PFAvials used to collect purified Pb samples were cleaned in an additional step with ~6 Msub-boiled HCl.4.2.2.2 Sample digestionFor dried and powdered bivalve tissue samples, 100–600 mg was weighed outinto Savillex® PFA vials. Closed-vessel digestion was carried out on a hotplate usingsuccessive steps of HNO3 and HNO3+H2O2. Separate sample digests were used for thepurification of sample Cd and Zn and the purification of sample Pb.4.2.2.3 Anion exchange chromatographySample Cd and Zn was isolated using the anion exchange chromatographymethod of Mason (2003), and is presented in detail in Shiel et al. (2009). In this study,the resin was batch cleaned, prior to loading on the column, using the method of De Jonget al. (2007) and then cleaned on column before loading and purifying samples.Treatment of the purified samples (Cd and Zn eluate cuts) before Cd and Zn isotopicanalysis on the mass spectrometer is described by Shiel et al. (2010). Sample Pb wasisolated by anion-exchange chromatography using the AG 1-X8 (100–200 mesh) resin(Bio-Rad Laboratories, Inc.), as previously described (Weis et al., 2006; Shiel et al.,2010).4.2.3 StandardsStandard solutions used for element concentration determination were preparedfrom 1,000 µg mL-1 single-element solutions from High Purity Standards, Inc. (USA) andSpecpure® Plasma (Alfa Aesar®, Johnson Matthey Company, USA).Source information and isotope data for the in-house primary and secondaryreference Cd and Zn isotopic standards as well as reference materials are provided byShiel et al. (2009). The JMC Cd standard (Wombacher et al., 2003; Wombacher andRehkämper, 2004) and the in-house primary reference Cd standard (PCIGR-1 Cd) areidentical within uncertainty (δ114/110Cd = -0.03 ± 0.05‰, n = 3). The “Lyon-JMC” Znstandard (Maréchal et al., 1999) and the in-house primary reference Zn standard (PCIGR-1031 Zn) are isotopically identical within uncertainty (δ66/64Zn = -0.01 ± 0.22‰, n = 7). TheNIST (USA) SRM 981 natural Pb (isotopic) standard is used for monitoring analyticalrun instrument drift and normalization of all measured Pb isotopic ratios relative to thetriple-spike values of Galer and Abouchami (1998).4.2.4 Data presentationCadmium and Zn isotopic compositions are expressed relative to the PCIGR-1 Cdand PCIGR-1 Zn reference standards in the standard delta (δ) per mil (‰) notation asfollows:€ δjCd =  (jCd)sample(jCd)standard−1       x 1,000€ δkZn =  (kZn)sample(kZn)standard−1       x 1,000where j and k are the measured isotope ratios, for Cd j = 111/110, 112/110, 113/110 or114/110 and for Zn k = 66/64, 67/64 or 68/64. Isotopic compositions for all the ratiosmentioned above are reported. However, discussion will revolve around 114Cd/110Cd and66Zn/64Zn. These isotopes are selected for their high relative isotopic abundances, thelarge relative mass difference between the isotope pair and to avoid or minimize isobaricinterferences.For Pb, the 206Pb/204Pb, 207Pb/204Pb, 208Pb/204Pb, 206Pb/207Pb and 208Pb/206Pb ratios arereported. However, most discussion will focus on the 206Pb/207Pb and 208Pb/206Pb ratios, tobe consistent with the majority of environmental studies, which in the past, have omittedreporting 204Pb values or report values with large errors due to various combinations ofthe following: limited instrument sensitivity, the low relative isotopic abundance (1.4%;Bölke et al., 2005) of 204Pb and limited Pb availability in samples (Sangster et al., 2000,and references within).4.2.5 Analytical methodsExperimental work was carried out in metal-free Class 1,000 clean laboratories atthe Pacific Centre for Isotopic and Geochemical Research (PCIGR), University of BritishColumbia (UBC). Sample preparation for elemental and isotopic analyses was performed104in Class 100 laminar flow hoods in the clean labs and instrument rooms. Elementalanalysis was carried out on an ELEMENT2 (Thermo Finnigan, Germany) high-resolutioninductively coupled plasma mass spectrometer (HR-ICP-MS). The trace element analysismethod and instrument set-up are described by Shiel et al. (2009). Isotopic analysis wasperformed on a Nu Plasma (Nu 021; Nu Instruments, UK) multi-collector inductivelycoupled plasma mass spectrometer (MC-ICP-MS). The isotopic analysis methods for Cd,Zn and Pb are described in Shiel et al. (2010).4.3 ResultsCadmium and Zn concentrations and delta values for bivalve samples are reportedin Tables 4.3 and 4.4, respectively. Cd concentrations for all samples collected between2002 and 2006 are given in a histogram (Fig. 4.5). Variations in bivalve Cd tissueconcentrations and isotopic composition are shown in Fig. 4.6. Mass dependentfractionation is shown for Cd and Zn isotopes in Fig. 4.7a and b, respectively. Leadconcentrations and isotopic ratios are reported in Table 4.5 and shown in Figures 4.8, 4.9and 4.10 for bivalve samples from B.C. (Canada) and Hawaii (North Pacific Ocean), theUSA East Coast (Northwest Atlantic Ocean) and France (Northeast Atlantic Ocean andMediterranean Sea), respectively.4.3.1 Cd isotopesThe Cd isotopic composition varies among bivalve samples by 0.99‰ with a totalrange from δ114/110Cd = -1.08 to -0.09‰ (Fig. 4.6; see Table 4.3 for the other ratios). Thetotal range represents significant differences in Cd isotopic compositions. The linear dataarray for Cd ratios in Fig. 4.7a is consistent with mass-dependent fractionation.Oysters from the southern coast of B.C. (Canada) have Cd contents of 2.9 to13 µg g-1 dry weight (tissues) and of 39 to 78 µg g-1 dry weight (gut contents) (Table 4.3;Fig. 4.5). Their Cd isotopic compositions range from δ114/110Cd = -0.69 to -0.09‰ (Fig.4.6). For the three B.C. oysters for which both tissues and gut contents were measured,the δ114/110Cd values of the tissues and gut contents are within error (Appendix H). For theB.C. oysters, the heaviest δ114/110Cd value is exhibited by one of the Barkley Sound (west105coast of Vancouver Island) oyster samples (Seddall Island; δ114/110Cd = -0.09‰), thelightest by one of the Desolation Sound (B.C. mainland) oyster samples (Gorge Harbor;δ114/110Cd = -0.69‰) (Fig. 4.6). The average δ114/110Cd value of Desolation Sound oysters(-0.54‰) is lighter than that of Barkley Sound oysters (-0.31‰). The Hawaiian oystersample (Honolulu Harbor) has a Cd concentration of 1.0 µg g-1 dry weight, which islower than those of the other Pacific Ocean samples (i.e., B.C. oysters) (Fig. 4.5). Theδ114/110Cd valve of the Hawaiian oyster sample (-0.46‰) is comparable to those exhibitedby the B.C. oyster samples (Fig. 6). B.C. oysters tend to have the highest Cd tissueconcentrations, excluding bivalves from the highly polluted Gironde estuary (Fig. 4.5).Also, their Cd isotopic compositions are among the heaviest exhibited by all bivalvesamples (Fig. 4.6).Oysters and mussels from the USA East Coast have Cd concentrations rangingfrom 1.5 to 16 µg g-1 dry weight (Table 4.3; Fig. 4.5). Their Cd isotopic compositionsrange from δ114/110Cd = -1.20 to -0.46‰ (Fig. 4.6). For USA East Coast bivalves, theheaviest δ114/110Cd value is exhibited by mussels from Cape Arundel, ME (δ114/110Cd =-0.54‰), the lightest by oysters from Charleston Harbor, SC (δ114/110Cd = -1.20‰) (Fig.4.6). This is the lightest Cd composition reported, with the exception of values reportedfor ordinary chondrites and a layered tektite (impact-related rock) (Wombacher et al.,2003).Oysters from the English Channel and the French Atlantic Coast have Cdconcentrations ranging from 1.4 (Abers Benoît, English Channel) to 29 µg g-1 dry weight(Gironde estuary, Atlantic Ocean) for samples collected in 2004/5 (Fig. 4.5) and up to129 µg g-1 dry weight (Gironde estuary) including samples collected in 1984/7 (Table4.3). French mussels have Cd concentrations ranging from 0.37 (Etang du Prevost,Mediterranean Sea) to 5.7 µg g-1 dry weight (Etang de Bages, Mediterranean Sea) (Fig.4.5). Cadmium isotopic compositions of the French bivalve samples range fromδ114/110Cd = -1.08 to -0.20‰ (Fig. 4.6). The heaviest δ114/110Cd value (-0.20‰) is exhibitedby mussels from Oye Plage (English Channel), the lightest by French oysters from theAtlantic Coast, Les Palles (-1.08‰) and the Gironde estuary (-0.99 to -1.06‰, includesoysters collected both in 1987 and 2005) (Fig 4.6). For French bivalves, δ114/110Cd valuesvary from –0.88 to –0.20‰ for sites on the English Channel, from –1.08 to –0.62‰ for106sites on the Atlantic Coast and from –0.52 to –0.29‰ for sites on the MediterraneanCoast (Fig. 4.6). The Cd isotopic values exhibited by bivalves from the Marennes-Oléronbasin and Gironde estuary (Atlantic Coast) are among the lightest of the whole study(Fig. 4.7a). For bivalves collected from Boyardville (Atlantic Coast) in 1984, the Cdconcentration of the oyster sample is ~6.3× that of the mussel sample, while aninsignificant difference is observed between their δ114/110Cd values (Fig. 4.6).4.3.2 Zn isotopesThe Zn isotopic composition varies among bivalve samples by only 0.18‰ with atotal range of δ66/64Zn = 0.28 to 0.46‰, except for the significantly heavier oyster samplesfrom the Gironde estuary (Atlantic Coast; 1987/2005), which are as heavy as 1.15‰ (Fig.4.7b; see Table 4.4 for the other ratios). The narrow total range in Zn isotopiccomposition exhibited by the majority of the bivalve samples is much smaller than thatreported for seawater and plankton tow samples (Bermin et al., 2006; John, 2007) (Fig.4.11b, 4.12b). The much heavier Zn isotopic compositions of the oysters from theGironde estuary (Atlantic Coast) are consistent with compositions from smelter tailings(Sivry et al., 2008) and polluted sediments (Sonke et al., 2008) (Fig. 4.12b). The lineardata array for Zn ratios in Fig. 4.7b is consistent with mass-dependent fractionation.Oysters from the southern coast of B.C. (Canada) have Zn contents of 390 to490 µg g-1 dry weight (tissues). There is no significant difference between the δ66/64Znvalues of oysters from Desolation Sound (B.C. mainland) and Barkley Sound (west coastof Vancouver Island) (total range of 0.28 to 0.36‰; Table 4.4).Oysters from the English Channel and the Atlantic Coast of France have Znconcentrations ranging from 1320 (Abers Benoît, English Channel) to 3570 µg g-1 dryweight (Gironde estuary, Atlantic Coast) for samples collected in 2005 and up to 8350 µgg-1 dry weight (Gironde estuary) for samples collected in 1987 (Table 4.4). Mussels fromthe French Mediterranean Coast have Zn concentrations ranging from 90.0 (Etang deBages) to 116 µg g-1 dry weight (Etang du Prévost) (Table 4.4). Zinc isotopiccompositions of the French bivalve samples range from δ66/64Zn = 0.39 to 1.15‰ (Fig.4.7b). The lightest δ66/64Zn value is exhibited by the oyster sample from the EnglishChannel (Abers Benoît; 0.39‰) (Fig. 4.7b). The heaviest δ66/64Zn values are exhibited by107the oysters from the Gironde estuary on the Atlantic Coast (1.03 to 1.15‰, for oysterscollected both in 1987 and 2005) (Fig. 4.7b). For French bivalves, δ66/64Zn values varyfrom 0.39 to 1.15‰ for sites on the English Channel and Atlantic Coast and from 0.43 to0.46‰ for sites on the Mediterranean Coast (Fig. 4.7b). The Zn isotopic compositions ofthe oysters from the Gironde estuary (Atlantic Coast) are by far the heaviest of the wholestudy. Due to the limited overall variation in the Zn isotopic compositions of bivalves,with the exception of the oysters from the highly polluted Gironde estuary, the USAsamples were excluded from the Zn isotopic composition study.4.3.3 Pb isotopesThe Pb isotope values of the bivalve samples range from 1.14832 to 1.21783 for206Pb/207Pb and 2.03564 to 2.10931 for 208Pb/206Pb (Table 4.5). The most radiogenicsamples are characterized by high 206Pb/207Pb and low 208Pb/206Pb ratios.Oysters from the southern coast of B.C. (Canada) have Pb contents of 0.05 to0.22 µg g-1 dry weight. Their Pb isotopic compositions range from 206Pb/207Pb = 1.14832to 1.17442, within the range of those reported for B.C. lichens (Simonetti et al., 2003)(Fig. 4.8). The lowest 206Pb/207Pb value is exhibited by one of the Desolation Sound (B.C.mainland) oyster samples (Gorge Harbor; 206Pb/207Pb = 1.14832), the highest by one ofthe Barkley Sound (west coast of Vancouver Island) oyster samples (Seddall Island;206Pb/207Pb = 1.17442). In general, the oysters from Desolation Sound (B.C. mainland)have higher Pb contents and lower 206Pb/207Pb values than those from Barkley Sound(west coast of Vancouver Island) (Fig. 4.8). The Hawaiian oyster sample (HonoluluHarbor) has a much higher Pb concentration (5.7 µg g-1 dry weight) than those of theother Pacific Ocean samples (i.e., B.C. oysters) (Table 4.5). Despite this, the 206Pb/207Pbvalue of the Hawaiian oyster sample (1.16521 ± 0.00001) is within the range of thosemeasured for the B.C. oysters (Fig. 4.8).Oysters and mussels from the USA East Coast have Pb concentrations rangingfrom 0.11 to 2.2 µg g-1 dry weight (Table 4.5). The Pb isotopic compositions of thesebivalves range from 206Pb/207Pb = 1.17949 to 1.21783 over a range similar to that of NorthAmerican coals (Fig. 4.9). The lowest of these 206Pb/207Pb values is exhibited by oystersfrom Charleston Harbor (SC), the highest by oysters from Mobile Bay (AL) (Fig. 4.9).108Despite the difference between the Pb concentrations of the Chesapeake Bay (MD)oysters (the Bodkin Point oyster sample has a Pb concentration 2.6× that of the ChoptankRiver oyster sample), the Pb isotopic compositions of the oysters are almost within error(Fig. 4.9).Bivalve samples from the coasts of France have Pb concentrations ranging from0.40 (Etang de Bages, Mediterranean Coast) to 3.1 µg g-1 dry weight (Gironde estuary,Atlantic Coast) for samples collected in 2004/2005 and up to 34 µg g-1 dry weight(Gironde estuary) for samples collected in 1984/7 (Table 4.5). Lead isotopic signatures ofthe same bivalve samples range from 206Pb/207Pb = 1.16076 to 1.18134, intermediatebetween those of French aerosols and pre-industrial sediments (Fig. 4.10). The lowest206Pb/207Pb value is exhibited by Loire estuary (Atlantic Coast) mussels (206Pb/207Pb =1.16076 to 1.18134), the highest by Gironde estuary (Atlantic Coast) oysters(206Pb/207Pb = 1.18134; 2005 sample) (Fig. 4.10). For French bivalves, 206Pb/207Pb valuesvary from 1.16355 to 1.17534 for sites on the English Channel, from 1.16076 to 1.18134for sites on the Atlantic Coast and from 1.17374 to 1.18064 for sites on theMediterranean Coast (Fig. 4.10). A shift is observed between the Pb isotopiccompositions of bivalves sampled in 1984/7 and 2004/5 from the Gironde estuary andMarennes-Oléron basin (Fig 4.10). For bivalves collected from Boyardville in 1984, thePb concentration and isotopic composition of oysters (Fig. 4.10) is similar but notidentical to that of mussels (1.97 µg g-1 dry weight, 206Pb/207Pb = 1.17739 and 1.76 µg g-1dry weight, 206Pb/207Pb = 1.17433; respectively).4.4 Discussion4.4.1 Isotopic variations in bivalves from the Pacific Coast of Canada and Hawaii4.4.1.1 Cd isotope systematicsB.C. oyster tissues (δ114/110Cd = -0.55 to -0.29‰) and associated gut contents(δ114/110Cd = -0.64 to -0.26‰) exhibit Cd isotopic signatures within the range of thelightest reported for North Pacific seawater (Lacan et al., 2006; Ripperger et al., 2007)(Fig. 4.11a). The Cd isotopic compositions of the B.C. oysters and their gut contents109(δ114/110Cd = -0.69 to -0.09‰) are within error (Appendix H). An evaluation of theimportance of preferential uptake of light Cd by phytoplankton (as observed inphytoplankton culture experiments, Δδ114/110Cd = -1.35 between culture media andphytoplankton cultures; Lacan et al., 2006) in determining the Cd isotopic compositionsof oysters in the North Pacific is not possible given the scale of this study and the poorlyconstrained Cd isotopic compositions of local waters. We expect small variations in therelative contributions of Cd sources through time (e.g., seasonally variable upwelling ofdeep nutrient-rich waters or shifts in the relative contributions of anthropogenic Cdemissions) to be reflected in subtle differences between the δ114/110Cd values of the gutcontents (potentially transient Cd source) and the oyster tissues (Cd is accumulated overtime).The relatively light Cd isotopic compositions of the oysters from DesolationSound (B.C. mainland), as compared to those of oysters from Barkley Sound (west coastof Vancouver Island), are attributed to the mixing of seawater Cd with anthropogenic Cdemissions characterized by a light Cd isotopic composition (Cloquet et al., 2005; Shiel etal., 2010) (Fig. 4.11a). Alternatively, differences between the Cd isotopic compositionsof oysters from Desolation Sound and Barkley Sound may potentially reflect naturaldifferences between the Cd isotopic compositions of waters in the Strait of Georgia andalong the west coast of Vancouver Island. However, mixing with a light Cd sourcerelated to anthropogenic emissions is strongly supported by the positive correlationbetween the δ114/110Cd and 206Pb/207Pb values of B.C. oysters (inset of Fig. 4.7a), whereincreasing values reflect an increasing contribution of natural Cd and Pb and decreasingvalues reflect an increasing contribution from anthropogenic sources of Cd and Pb (seeSection 4.4.1.3). The Hawaiian oyster sample from Honolulu Harbor exhibits a Cdisotopic composition within the range of those of B.C. oysters (Fig. 4.6), indicating acommon natural Cd source across the Northwest Pacific Ocean.4.4.1.2 Zn isotope systematicsThe δ66/64Zn values of B.C. oysters (0.28 to 0.36‰) from Desolation Sound (B.C.mainland) and Barkley Sound (west coast of Vancouver Island) are within error (Fig.4.11b). The limited range of δ66/64Zn values exhibited by B.C. oysters falls within the110range reported for North Pacific seawater and plankton tows (-0.16 to 0.62‰ and 0.08 to0.57‰, respectively; John, 2007) (Fig. 4.11b). As natural Zn concentrations are muchhigher than those of Cd in bivalve tissues (e.g., for two B.C. oysters, the Zn concentrationis 68× or 94× higher than the Cd concentration; Tables 4.3 and 4.4), any anthropogeniccontribution will need to be correspondingly larger to be recorded in the Zn isotopicsignature. Therefore, it is not surprising that the Zn isotopic compositions exhibited byB.C. oysters are within error (Fig. 4.11b), despite the total variability observed in the Cdisotopic compositions.4.4.1.3 Pb isotope systematicsIn Pb–Pb diagrams (Fig. 4.8), the Pb isotopic ratios of bivalve samples from thePacific Coast of B.C. and Hawaii form a linear trend, between several modernanthropogenic Pb emissions (discussed in detail below) and natural Pb (e.g., Chineseloess; Jones et al, 2000). The Pb isotopic compositions of the oysters can be explained bymixing of these end-members. Unlike Cd and Zn, Pb isotopes are not likely to undergosignificant mass dependent fractionation during anthropogenic processing due to theelement’s heavy mass and as a consequent its small relative mass difference (Shiel et al.,2010). The Pb contents of oysters from both Desolation Sound (B.C. mainland) andBarkley Sound (west coast of Vancouver Island) are comparably low (0.05-0.22 µg g-1dry weight) and below the median concentration of Pb in oysters from the USAestablished by the US Mussel Watch Program (0.5 µg g-1 dry weight in 1993; Beliaeff etal., 1998). However, oysters from Desolation Sound (B.C. mainland) are characterized bylower 206Pb/207Pb and higher 208Pb/206Pb ratios than those from Barkley Sound (west coastof Vancouver Island). The Pb isotopic composition of the Hawaiian oyster sample fromHonolulu Harbor is comparable to those of the oysters from Barkley Sound, however, thePb content of this sample is significantly greater (5.7 µg g-1 dry weight) than those of theB.C. oysters or the median concentration for oysters from the USA (0.5 µg g-1 dry weightin 1993; Beliaeff et al., 1998).The relatively radiogenic Pb isotopic signatures of the oysters from BarkleySound are consistent with those of road dust from highways in the lower mainland(representative of the average modern Pb isotopic signature of unleaded gasoline111consumed by passenger automobiles and diesel fuel consumed by trucks mixed with localnatural Pb; Preciado et al., 2007). The Pb isotopic signature of B.C. mainland oysters isattributed to a relatively large contribution of anthropogenic Pb emissions from a sourcethat is characteristically unradiogenic (low 206Pb/207Pb). This unradiogenic anthropogenicPb source is suggested to be Pb ore from Mt. Isa (Australia) and/or the Sullivan mine(B.C., Canada), although the latter has become increasing less important as a source overtime as the mine was closed in 2001. Two plausible mechanisms for the dispersion of thisunradiogenic Pb source in the B.C. lower mainland are (1) Pb emissions resulting fromthe smelting and refining operations in Trail, B.C. (1,563 kg Pb released to the air in2008; Environment Canada, 2009) of ore concentrates from the Cannington mine (Mt. Isainlier, Eastern Succession, Australia; 206Pb/207Pb 1.041; Huston et al., 2006) and theSullivan mine (B.C.; 206Pb/207Pb 1.0679; Sangster et al., 2000, and references within)(Shiel et al., 2010) (Fig. 4.8), and (2) Pb emissions resulting from the consumption ofavgas (responsible for an estimated 4,860 kg Pb emissions in B.C.; Table 4.1) in smallgeneral aircrafts (e.g., personal aircrafts, seaplanes, crop dusters and bush planes). Avgas,similar to leaded motor gasoline, uses the antiknock additive, TEL, which is nowmanufactured by only a few companies worldwide. Much of the Pb used to produce TELoriginates from Australia (Mt. Isa and Broken Hill) and formerly B.C., Canada (Sullivanmine) (Monna et al., 1995, 1997), i.e., relatively old terrains, with distinctly unradiogenicPb isotopic compositions. Further testing is needed to determine the Pb isotopiccomposition of locally consumed avgas; this is especially important as there is a part ofthe general aviation fleet that can not use existing alternative fuels and will continue touse avgas until an alternative is available. Atmospheric emissions of Pb (1,563 kg Pb in2008; Environment Canada, 2009) from smelting and refining operations in Trail arethought to be an important source of Pb to the lower B.C. mainland and by extrapolation,to the oyster farms in Desolation Sound as the most frequent wind direction near the siteis east. Historic releases of Pb from smelting and refining in Trail were much greater thancurrent Pb releases and therefore historically these operations were responsible for arelatively larger contribution of Pb pollution to the B.C. lower mainland. Historicalreleases of Pb from operations in Trail decreased substantially in the late-1990s and early2000s; e.g., total on-site Pb emissions in 2008 were ~1.2% of those released in 1994112(Environment Canada, 2009). The positive correlation between the δ114/110Cd and206Pb/207Pb values of B.C. oysters (inset of Fig. 4.7a), suggests a source that exhibits botha light Cd isotopic composition and an unradiogenic Pb isotopic composition (e.g.,emissions from smelting and refining operations in Trail; see 4.4.1.1). The similaritybetween the Pb isotopic compositions of oysters from B.C. and Hawaii suggestscomparable anthropogenic Pb sources across the NE Pacific, i.e., the consumption ofpetroleum products, such as unleaded motor gasoline and diesel fuel, characterized bycomparable Pb isotopic compositions.The use of diesel fuel oil and heavy fuel oil by container ships, cargo ships, ferriesand cruise ships represents another important source of modern anthropogenic Pbemissions in B.C. (Table 4.1). The Pb isotopic composition of these fuels is not wellconstrained and will vary with that of the crude oil source (few studies have measured thePb isotopic composition of crude oils; e.g., Dreyfus et al., 2007). In addition, anevaluation needs to be made of other significant provincial Pb polluters, including theVancouver Wharves (released 1,602 kg Pb to the air and 129 kg Pb to the water in 2008),wastewater treatment facilities (1,064 kg released to waters in 2008 by facilities servingthe Greater Vancouver area, Victoria and Nanaimo) and smaller Pb polluters locatedadjacent to the oyster collection sites, e.g., pulp and paper mills located in Elk Falls(released 89 kg Pb to the air and water in 2008) and Port Alberni (released 11 kg Pb tothe air and water in 2008) (Environment Canada, 2009). Testing of the Pb isotopicsignatures of these emissions is needed to confirm their relative importance in B.C.oysters.4.4.2 Isotopic variations in bivalves from the USA Atlantic Coast4.4.2.1 Cd isotope systematicsSignificant variability in the Cd isotopic compositions is exhibited amongbivalves from the USA East Coast and δCd values of these samples include values amongthe lightest ever reported. The bivalves from the USA East Coast are enriched in light Cdrelative to those from the North Pacific (i.e., B.C. and Hawaii) (Fig. 4.6). Cadmiumconcentrations in the USA East Coast bivalves likely result from the significantly denser113industrial presence on the USA East Coast. This is in contrast to the attribution ofcomparable Cd concentrations in North Pacific oysters to natural sources. The relativelylight isotopic compositions of the USA East Coast bivalves suggest contributions of lightCd enriched emissions from anthropogenic processes, e.g., smelting (e.g., Cloquet et al.,2005; Shiel et al., 2010). Primary and secondary smelting and refining of non-ferrousmetals and iron and steel mills report the largest Cd emissions regionally (US EPA,2010); the variable importance of anthropogenic emissions from these facilities betweensites is expected to account for the majority of the variability observed in the Cd isotopiccompositions of the USA East Coast bivalves. As compared to bivalves from theNorthwest Pacific, bivalves from the North Atlantic have lower natural Cd contents andas a result, similar contributions from anthropogenic sources will be more apparent in theCd isotopic signatures of North Atlantic bivalves than in Northwest Pacific bivalves.An overall positive correlation exists between the δ114/110Cd and 206Pb/207Pb valuesof bivalves from the USA East Coast (inset of Fig. 4.7a), similar to the one observed forB.C. oysters, but displaced towards lower δ114/110Cd values. For oyster and musselsamples, the NS&T Program Mussel Watch found that Cd tissue concentrations were notstatistically correlated to human population density (O’Connor, 2002), rather high Cdconcentrations may represent natural enrichments of this element, as observed in theNorthwest Pacific. For the oyster and mussel samples included in this study, there is noclear relationship between the Cd concentration and isotopic composition of tissues.Mussels from Cape Arundel (Gulf of Maine) are characterized by both the lowestCd concentration (1.5 µg g-1 dry weight) and the heaviest Cd isotopic composition of theUSA East Coast bivalve samples (Fig. 4.12a), closest to those of Atlantic Ocean seawater(Ripperger et al., 2007), ferromanganese nodules (Schmitt et al., 2009) and terrestrialrocks and minerals (Wombacher et al., 2003). All other USA East Coast bivalves (Fig.4.3) are collected from sites more proximal to industries reporting significant Cd releases(Fig. 4.3). Steelmaking, using electric arc and blast furnaces, needs to be evaluated as asource of Cd isotopic fractionation. Iron and steel mills populate the USA East Coast;mills are located (near bivalve collection sites) in, e.g., Baltimore (MD), Charleston (SC),Tuscaloosa (AL) and Axis (AL) (Fig. 4.3). Baltimore Harbor, which feeds intoChesapeake Bay, receives metal pollution from local industries including a local iron and114steel mill (Fig. 4.3; US EPA, 2010). In Chesapeake Bay, the Cd concentration of theoyster sample from Bodkin Point (located where Baltimore Harbor enters ChesapeakeBay) is ~3.5× that of the oyster sample from the mouth of the Choptank River (a majortributary of Chesapeake Bay located ~60 km south of Baltimore Harbor). In addition tohaving the higher Cd concentration, the oyster sample from Bodkin Point has a lighter Cdisotopic composition (δ114/110Cd = -0.74‰) than that of the oyster sample from ChoptankRiver (δ114/110Cd = -0.56‰). A similarly light δ114/110Cd value is exhibited by the oystersample from Mobile Bay (-0.78‰; Fig. 4.6) suggesting contributions of light Cd enrichedatmospheric emissions from the nearby secondary smelter or iron and steel mills (Fig.4.3).The Cd concentrations (2.1 and 4.2 µg g-1 dry weight) of the oyster samples fromCharleston Harbor (SC) are higher than the average concentration reported for the state(NOAA, 2010). Bivalves from Charleston Harbor (SC) exhibit the lightest Cd isotopicsignatures (δ114/110Cd = -1.20 and -1.05‰) of this study. The relatively light Cd isotopiccompositions of these bivalves suggest contributions from a Cd emission source that ischaracterized by a light isotopic composition (Fig. 4.12a), e.g., emissions from Znsmelting and refining operations (Cloquet et al., 2005; Shiel et al., 2010) in Clarksville,TN (Fig. 4.3; discussed in Section 4.4.2.2).4.4.2.2 Pb isotope systematicsA strong correlation between Pb concentration and human population densityexists for oyster and mussel tissues collected as apart of the NS&T program MusselWatch (O’Connor, 2002). The Pb isotopic compositions of these bivalves (Fig. 4.9) areconsistent with values measured for NE USA emissions (Bollhöfer and Rosman, 2001;Carignan et al, 2002). The range in Pb isotopic compositions of the bivalves from theUSA East Coast suggests significant contributions from varied and regional industrial Pbemission sources and corroborates the lighter Cd isotopic signatures. Post-leaded gasolinephase-out, facilities that release significant quantities of Pb are shown to dictate the Pbisotopic signature of local environments. The relative contribution of Pb emissions fromthe combustion of coal, to the total Pb emissions from fuel consumption (Table 4.2), issimilar for the USA (21.9%) and Canada (18.9%). Combustion of coal therefore is115expected to be a significant Pb source to bivalves from the USA East Coast. B.C. is instrong contrast to the rest of the Canada and the USA, as there is a much smallercontribution of Pb emissions from coal combustion (Table 4.1) and this source istherefore not a significant contributor of Pb to the B.C. oysters. The importance of Pbemissions from coal combustion on the USA East Coast is reflected in the Pb isotopiccompositions of the USA East Coast bivalves, which are largely overlapping with thoseof North American coals (Díaz-Somoano et al., 2009). The electric power sector is thelargest USA consumer of coal (US EIA, 2010) and therefore the largest source of thesePb emissions.On the USA East Coast, significant Pb releases are reported by several industries,e.g., primary Zn and Pb smelting and refining of non-ferrous metals, secondary smeltingand refining of lead (e.g., car batteries, ammunition, electric arc furnace dust from steelmills) and steelmaking (Fig. 4.3). The range of Pb isotopic compositions exhibited byUSA East Coast bivalves suggests mixing with a Pb emission source characterized by aradiogenic signature such as that of SE Missouri Pb ore (206Pb/207Pb = 1.3390; calculatedby Sangster et al., 2000, from references within) (Fig. 4.9). There was an increase in theusage of SE Missouri Pb ore in primary Pb production post-1980 in the USA (Shirahataet al., 1980; Ketterer et al., 2001). Primary Pb smelting operations in Herculaneum, MO(Doe Run Co. Herculaneum Smelter), reported the highest quantity of air emissions of Pbcompounds (17,501 kg, sum of on-site point source and fugitive emissions) in the USA in2008 (US EPA, 2010). Secondary Pb smelting and refining operations may be in part orwholly responsible for the radiogenic Pb found in the surrounding areas. A secondary Pbsmelting facility in Iron, MO (Buick Resource Recycling Facility), which processes carbatteries and ammunition, reported significant air emissions of Pb compounds (11,487kg, sum of on-site point source and fugitive emissions) in 2008, second only to theprimary Pb smelting operations in Herculaneum (MO) (US EPA, 2010). This radiogenicPb component is seen most significantly in the oyster sample from Alabama (Fig. 4.9).Secondary Pb smelting operations in Troy (AL) and/or Baton Rouge (LA) may besignificant sources of Pb emissions deposited at this site. The iron and steel millspopulating the USA East Coast may be another important source of radiogenic Pb in theUSA East Coast bivalves, as regional steel mill electric arc furnace dust is expected to116have a radiogenic Pb isotopic signature (for electric arc furnace process materials,206Pb/207Pb = 1.214; Ketterer et al., 2001) (Fig. 4.9).Oysters from Charleston Harbor (SC) are characterized by the lowest 206Pb/207Pbvalues of the USA East Coast bivalves (Fig. 4.9). Identification of the dominant Pbsources to the sites in Charleston Harbor (Shutes Folly and Fort Johnson) is especiallyimportant as an increasing temporal trend in Pb concentration was identified at these sites(O’Connor and Lauenstein, 2006). The Pb isotopic composition of these bivalves, incombination with their relatively light Cd isotopic composition, is consistent withemissions from primary smelting of ores with less radiogenic Pb compositions (i.e.,relatively low 206Pb/207Pb) (Fig. 4.9), e.g., Zn smelting and refining in Clarksville, TN(~802 km NW on Charleston Harbor) of ores from Australia (e.g., Broken Hill:206Pb/207Pb = 1.0407, Mount Isa: 206Pb/207Pb = 1.0431), Central and South America (e.g.,for Argentina 206Pb/207Pb  = 1.1530 to 1.1535) and Ireland (206Pb/207Pb = 1.1581 to 1.1717for 20th century producing mines) (Sangster et al., 2000, and references within; Nyrstar,2010).4.4.3 Isotopic variations in bivalves from the Atlantic and Mediterranean Coasts ofFrance4.4.3.1 Cd isotope systematicsBivalves from the French coasts (Fig. 4.4) exhibit the most overall variation inδ114/110Cd (Fig. 4.6), from relatively light isotopic compositions, such as those observed inbivalves from sites within the polluted Marennes-Oléron basin and the Gironde estuary(Atlantic Coast), to relatively heavy isotopic compositions, such as observed in bivalvesfrom Oye Plage (English Channel) and Etang du Prévost (Mediterranean Sea). This rangein isotopic composition reflects the large variability of coastal health and anthropogenicinputs among French sites included in this study.For bivalve samples collected from the English Channel, increasing Cdconcentrations correspond to increasing light Cd compositions (Fig. 4.6). The musselsample from Oye Plage (English Channel) has the lowest Cd concentration and exhibitsthe heaviest Cd isotopic composition of the French bivalves (δ114/110Cd = -0.20‰), closest117to that of Atlantic seawater (Ripperger et al., 2007; Fig. 4.12a). In contrast, mussels fromthe Seine estuary have the highest Cd concentration and exhibit the lightest Cd isotopiccomposition for the English Channel samples (Fig. 4.6). The Seine River and estuaryreceive wastewater and industrial effluents from neighboring urban areas including Paris,Rouen and Le Havre (Fig. 4.4). Cadmium contamination in the estuary is largelyattributed to the disposal (banned in 1992) of calcium sulfate (high Cd content), a wastebyproduct produced by phosphoric acid plants located near Rouen and Le Havre (Fig.4.4), into the Seine River and estuary (Nakhlé et al., 2007).The Cd isotopic compositions (δ114/110Cd = -1.08 to -0.62‰) of the bivalves fromthe Atlantic coast of France reflect the relatively large anthropogenic presence near thecollection sites (Fig. 4.6). The heaviest Cd isotopic composition of the French AtlanticCoast bivalves is that of the mussels collected from the Loire estuary (δ114/110Cd =-0.62‰); however, this isotopic composition is still relatively light when compared tothose of bivalves from the other coasts studied here. The Gironde estuary and theadjacent Marennes Oléron basin are famous for their oysters, the latter being the locationof the largest oyster farming area in Europe. As a result, concern exists over thedocumented history of metal contamination from local industries (e.g., mining, smelting,foundries, battery manufacturing) along the Garonne River and its tributaries (especiallythe Lot River), which feed into the Gironde estuary (Grousset et al., 1999; Audry et al.,2004). Cadmium contamination is primarily attributed to smelting activities (1842 to1987) near Decazeville (Audry et al., 2004). Cadmium, Zn and Pb concentrations ofoysters from the Gironde estuary show a marked decrease between 1987 and 2005,corresponding to the shutdown of the smelter near Decazeville. Despite the significantdecrease in the Cd concentrations over this time (from 129.1 to 28.7 µg g-1 dry weight),the Cd isotopic signatures (δ114/110Cd = -1.02, -1.03‰) of the oyster samples are stillwithin error of each other and of smelting dust (from the Metaleurop Pb smelter andrefinery in Noyelles-Godault, Northeast France, closed in 2003; Cloquet et al., 2005)(Fig. 4.4, 4.12a). This suggests the dominant source of Cd pollution in the Girondeestuary remains historical Cd emissions from the now-closed, metallurgical industry(Jouanneau et al., 1990) likely via remobilization of sediments and associated metals by,e.g., flooding, riverbed dredging and other anthropogenic activities, especially from the118Lot River (Audry et al., 2004). Although the Cd concentrations of bivalves from thenearby sites in the Marennes-Oléron basin, La Moucliere and Les Palles, (1.1 and 2.8 µgg-1 dry weight, respectively) are much lower than those of the oyster sample from theGironde estuary (28.7 µg g-1 dry weight), their Cd isotopic compositions are within error,suggesting the dominant source of Cd is also historic smelting emissions (Fig. 4.6).Both oyster and mussel samples from Boyardville (1984) were included in thisstudy. Cadmium metal concentrations in bivalves for this collection year are the highestreported for this site (IFREMER, 2010), reflecting the strength of local industrial Cdemissions at the time (discussed above). Consistent with previous findings that significantdifferences exist between the accumulation of Cd in oyster verses mussel tissues incontaminated environments (Claisse et al., 1989), the Cd concentration of the Boyardvilleoyster is ~6.3× that of the mussel. Despite this difference in Cd concentration, theδ114/110Cd values of the oyster and mussel samples are within error (Fig. 4.6), suggestingthat differences in Cd uptake among bivalve species do not affect the Cd isotopiccomposition of the accumulated Cd.The French Mediterranean sites are coastal lagoons and will therefore have thetendency to accumulate pollutants with time. The significantly higher Cd concentration ofthe mussels from Etang de Bages (5.7 µg g-1 dry weight), as compared to those fromEtang du Prévost (0.4 µg g-1 dry weight), is accompanied by a significantly lighter Cdisotopic composition (δ114/110Cd = -0.51 as compared to -0.29‰, respectively). The Cdcontamination at Etang de Bages is attributed largely to Cd emissions associated with Cdpigment plant activities in the nearby city of Narbonne (Fig. 4.4), which ceased in theearly 1990s (Claisse, 1989). In contrast, the Cd isotopic composition of mussels collectedfrom Etang du Prévost is consistent with the lightest δCd values reported forMediterranean seawater (Lacan et al., 2006) (Fig. 4.12a).4.4.3.2 Zn isotope systematicsFrench bivalves from the English Channel and the Mediterranean Coast have Znisotopic compositions within error of each other and seawater from the English Channeland Atlantic Ocean (Bermin et al., 2006; John, 2007) (Fig. 4.12b). Oysters from thepolluted Gironde estuary have distinctly heavier Zn isotopic compositions, which are119consistent with a large Zn contribution from local smelting operations as demonstrated bythe similarity between the δ66/64Zn of these oyster samples (1.03‰) and smelting pollutedsediments and mine tailings (Sonke et al., 2008) (Fig. 4.12b). Similar to Cd, for theGironde estuary oyster samples from 1987 and 2005, despite the significant decrease inthe Zn concentrations over time (from 8350 to 3570 µg g-1 dry weight, respectively), theZn isotopic signatures (δ66/64Zn = 1.15 and 1.03‰, respectively) are within error,suggesting that the dominant source of Zn pollution in the Gironde estuary remainshistorical Zn emissions from the now-closed, metallurgical industry (Fig. 4.12b).4.4.3.3 Pb isotope systematicsAll French bivalve samples have Pb isotopic compositions consistent withindustrial, as opposed to automotive (leaded gasoline, which in Europe is lessradiogenic), Pb sources as defined by Deboudt et al. (1999). Lead deposited in theenvironment from the use of leaded gasoline (banned in France in 2000) is characterizedby a low radiogenic Pb isotopic signature (e.g., auto exhaust collected in 1987 before theintroduction of unleaded gasoline in France in 1989; Monna et al., 1995) (Fig. 4.10). Thisis because the TEL additive was produced primarily from Pb ores from the Broken Hilland Mt. Isa (Australia) and Sullivan (B.C.) mines (Monna et al., 1995), which all exhibitunradiogenic Pb isotopic signatures. In Europe, the decrease in the Pb concentration ofaerosols, associated with the progressive phase-out of leaded gasoline, is linked with asystematic change in 206Pb/207Pb, i.e., increasing since 1979 (Grousset et al., 1994).Nationally, diesel fuel oil (18,194 kg Pb in 2005) and avgas (~13,750 kg Pb in 2005) arethe two most important sources of Pb emissions from the consumption of petroleumproducts and coal (Fig. 4.1). Industrial facilities that report significant Pb emissions (of asimilar magnitude to those produced by fuel consumption) proximal to the bivalvecollection sites are discussed below.Bivalve samples from Northeast France (Oye Plage and Ambleteuse) and theSeine and Loire estuaries are characterized by relatively low 206Pb/207Pb values ascompared to other French bivalve samples. Although the Metaleurop Pb smelter inNoyelles-Godault (Northeast France) closed in 2003, Pb emissions (~29,000 kg Pb in2002; DRIRE Nord Pas-de-Calais, 2003) from the smelter are expected to represent a120significant contribution of Pb to the bivalves collected in 2004 at proximal sites. Anearby iron and steel mill (Sollac Atlantique, now ArcelorMittal Dunkerque, NortheastFrance) emitted a similar magnitude of Pb, 15,319 kg in 2002 (DRIRE Nord Pas-de-Calais, 2003). A mixture of Pb emissions from these two facilities may be largelyresponsible for the Pb isotopic signatures exhibited by the bivalve samples from theNortheast French coast. The Pb isotopic signature of the oyster sample from Abers Benoît(English Channel) is closer to that of the radiogenic pre-industrial sediments (Sun, 1980)endmember than to those of the other bivalves sampled from the English Channel (Fig.4.10), indicating a larger contribution of natural Pb at Abers Benoît.The Pb isotopic compositions of the bivalves from the Atlantic Coast of France(Fig. 4.10) plot with the values for the Garonne River and its tributaries (SPM andsediments) in the late 1990s, which are not different from those reported for waterscollected by Elbaz-Poulichet et al. (1986) in the same area in the mid-1980s. Lead inoysters from the Gironde estuary and the Marennes-Oléron basin (Atlantic Coast) issuggested to derive largely from local industries, e.g. mining and smelting operations(closed in 1987; Audry et al., 2004). A shift in the Pb isotopic composition toward theradiogenic natural endmember (pre-industrial river sediments; Elbaz-Poulichet et al.,1986) is observed between the mid-1980s and 2004/5 for samples from both the Girondeestuary and the Marennes-Oléron basin (Fig. 4.10). However, insignificant change isobserved in the Pb concentrations of the bivalve tissues over the same time (Table 4.5).This shift is consistent with increasing contributions from a natural endmember andresults from the banning of Pb addition to gasoline in France (Grousset et al., 1994). Thisis in contrast to the insignificant change observed in the Cd and Zn isotopic compositionsof bivalve tissues over that time (see sections 4.4.3.1 and 4.4.3.2), which indicate thedominant Cd and Zn sources to those oysters have not changed. This striking differencebetween the reaction rates to environmental changes of Pb versus Cd and Zn isotopicsignatures is a strong argument for the combined use of these isotope systems to trace thesources, fate and behavior of these metals in the environment.For French Mediterranean collection sites (coastal lagoons/semi-enclosed basin)the Pb concentration increases as the Pb isotopic compositions become less radiogenic(Table 4.5; Fig. 4.10). This trend indicates increasing relative contributions from121anthropogenic Pb sources and decreasing contributions from natural Pb sources (e.g., pre-industrial sediments; Sun, 1980). Mussels from the coastal lagoon, Etang du Prévost,have the highest Pb concentrations and least radiogenic Pb signatures of these sites,indicating the largest anthropogenic input, likely resulting from metal pollutionassociated with harbor operations accumulating due to the enclosed nature of the site.These results are consistent with the Pb isotopic compositions for recent and ancientshells (the latter being relatively radiogenic) of Mediterranean mussels (Labonne et al.,1998).4.5 ConclusionsOur investigation of Cd, Zn and Pb isotopic signatures in oysters and mussels from thewestern coast of Canada, the USA and France resulted in the following conclusions:(1) High Cd levels in B.C. oysters are largely attributed to the natural upwelling ofnutrient (and Cd) rich deep waters in the North Pacific as the Cd isotopic compositionof B.C. oysters falls within the light end of those reported for North Pacific seawater.Variability in the Cd isotopic compositions of B.C. oysters is attributed to variable Cdcontributions from anthropogenic emission sources (e.g., smelting). We suggestlimiting consumption of B.C. oysters to ensure dietary Cd remains within safe limits.The Zn isotopic compositions of B.C. oysters fall within a narrow range of thosereported for North Pacific seawater, indicating a primarily natural Zn source.(2) For B.C. oysters, Pb isotopic signatures identify unleaded gasoline and diesel fuel asthe primary Pb sources, despite low Pb concentrations (lowest of the study). The Pbisotopic composition of the oyster from Hawaii falls within the range of those of B.C.oysters (despite its much higher Pb concentration) suggesting a common Pb sourcefor the North Pacific. Pb isotopic signatures of B.C. mainland oysters reveal, incomparison to those of the west coast of Vancouver Island and Hawaii, additionalcontributions from a characteristically unradiogenic source such as Pb emissions fromB.C. smelting and refining operations.122(3) The Cd isotopic compositions of the USA East Coast bivalves include some of thelightest compositions ever measured, and reflect significant anthropogenic Cd inputs(e.g., primary/secondary smelting or steelmaking).(4) Lead isotopic signatures of USA East Coast bivalves are consistent with those of UScoals and industrial Pb emission sources (e.g., primary/secondary smelting orsteelmaking).(5) Significant variation in Cd concentrations, as well as δ114/110Cd values, exists betweencoastal sites of France, from relatively pristine (relatively heavy δ114/110Cd; e.g., OyePlage) to heavily polluted (relatively light δ114/110Cd; e.g., Marennes-Oléron basin andGironde estuary). For the smelting polluted sites in the Marennes-Oléron basin andthe Gironde estuary, decreases in the Cd concentrations between 1984/7 and 2004/5are not accompanied by a shift toward natural isotopic compositions suggesting thedominant Cd source remains historical smelting activities. The Zn isotopiccomposition of French bivalves falls within a narrow range of that of seawater andplankton tows, with the exception of the oysters from the smelting polluted Girondeestuary, which exhibit characteristically heavy Zn isotopic compositions.(6) The Pb isotopic compositions of French bivalves are consistent with industrial asoppose to automotive Pb sources. Shifts are observed in the Pb isotopic compositionsof French bivalves between 1984/7 and 2004/5 related to the complete phase-out ofleaded gasoline in automobiles in France.(7) The results of this study demonstrate the effective use of Cd isotopes, and to a lesserextent Zn isotopes, to trace industrial emissions of these metals in the environment.The combined use of Cd and Pb isotopes allows the assessment of Cd isotopicfractionation and tracing (fingerprinting) of the source.4.6 AcknowledgementsWe especially want to thank George M. Kruzynski (Fisheries and Oceans Canada)and William Heath (B.C. Ministry of Agriculture & Lands) for providing the B.C. oystersamples and are grateful to them for numerous valuable discussions. We thank DidierClaisse and Daniel Cossa at IFREMER and Gunnar Lauenstein at NOAA for providing123the bivalve samples for France and the USA, respectively. We want to especially thankDaniel Cossa for providing helpful comments and suggestions. We are grateful to JaneBarling for her assistance with the Nu Plasma MC-ICP-MS and to Bert Mueller for hisassistance with the ELEMENT2 HR-ICP-MS. This study was funded by NSERCDiscovery grants to Dominique Weis and Kristin J. Orians.124Table 4.1. Estimated Pb emissions from the consumption of petroleum products and coal in B.C. (2008) and all of Canada (1970 and 2008).B.C. Canada Canada Pb fraction B.C. Canada Canada B.C. Canada CanadaFuel 2008 2008 1970 emitted 2008 2008 1970 2008 2008 1970Petroleum producta,bAvgasc,d6480 53760 0.75-1.00e4860 40320 67.57 58.89Leaded gasolined,f312 668 11585620 0.75-1.00e234 501 8689215 3.25 0.73 99.87Unleaded gasolinePremiumg333 2618 0.75-1.00e250 1963 3.47 2.87Mid-gradeg74 376 0.75-1.00e56 282 0.77 0.41Regularg395 3766 0.75-1.00e296 2824 4.12 4.12Diesel fuel oilh1232 9322 2772 0.95i1170 8856 2634 16.27 12.93 0.03Heavy fuel oilj4041 25586 44672 0.045k182 1151 2010 2.53 1.68 0.02Light fuel oill3 152 448 NAmJet fueln11 45 14 0.75-1.00e8 33 11 0.12 0.05 <0.01Coalb,o,p7194 660000 341836 0.019q137 12540 6495 1.90 18.31 0.07TOTAL 20075 756291 11975362 7192 68471 8700364aConsumption of petroleum products in B.C. and Canada in 2008; Statistics Canada, 2010. bConsumption of petroleum products and coal in Canada in 1970; Quirin, 1999.cAviation gasoline [Pb], 100 low lead (100LL); ConocoPhillips, 2007.dLeaded gasoline for 1970 inlcudes both motor vehicle and aircraft consumption; referenceb.fMedian [Pb] of range used to calculate values in the following columns; Quickert et al., 1972; Jungers et al., 1975; Parekh et al., 2002.gMid-grade value assumed to be the average of the Pb concentrations given for premium and regular gasolines; Sanders, 1998.hAverage [Pb] of diesel samples used to calculate values in the following columns; Reyes and Campos, 2005.iFraction Pb emitted for diesel calculated from Pb consumption rate and emission rate for diesel engines; Wang et al., 2003.jLow sulfur fuel [Pb] used to calculate values in the following columns; Miller et al., 1996.kFraction Pb emitted for heavy fuel oil calculated from emission rate of 0.182 kg Pb/million L fuel consumed (1.5 x 10-3 lb/1000 US gallon fuel consumed); US EPA, 1998.l[Pb] from Miller et al., 1996.mFraction Pb emitted not available for light fuel oil; Pb emissions are not calculated due to uncertainty. Small relative contributions are expected.nMedian [Pb] of range used to calculate values in the following columns; Shumway, 2000, in Murphy et al., 2007.oCoal consumption is given for 2007, 2008 data is unavailable; no significant change is expected for 2008; Stone, 2009.pAverage [Pb] for North American coals (143 samples); Chow and Earl, 1972.qFraction Pb emitted for coal calculated from emission factor of 0.21 mg Pb/1 kg coal feed (2.1 x 10-4 kg Pb/1 Mg coal feed); US EPA, 1998.Pb emissions , % of totalPb emissions (kg) Fuel Pb (kg)eFraction Pb emitted for both motor and aviation gasolines assumed to be between the historically used, US EPA esimate of 0.75 and 1. The same fraction is assumed for jet fuel. In the following columns, 0.75 is used to calculate Pb emissions.125Table 4.2. Estimated Pb emissions from the consumption of petroleum products and coal in Canada, the USA and France (2005).Canada USA France Pb fraction Canada USA France Canada USA FranceFuel 2005 2005 2005 emitted 2005 2005 2005 2005 2005 2005Petroleum productaAvgasb52500 805833 183330.75-1.00c39375 604375 13750 56.58 62.01 34.68Motor gasolined7328 95673 26190.75-1.00c5496 71755 1964 7.90 7.36 4.95Diesel fuel oile10395 78860 191510.95f9875 74917 18194 14.19 7.69 45.89Heavy fuel oilg37416 213546 274200.045h1684 9610 1234 2.42 0.99 3.11Jet fueli45 633 540.75-1.00c34 475 40 0.05 0.05 0.10Coala,j690646 11236170 2349380.019k13122 213487 4464 18.86 21.90 11.26TOTAL 798330 12430715 302515 69586 974618 39646aUS EIA, 2008.bAviation gasoline [Pb], 100 low lead (100LL); ConocoPhillips, 2007.dCalculated motor gasoline [Pb] calculated based on those of premium and regular gasolines and the estimated relative consumption of each; Sanders, 1998.eAverage [Pb] of diesel samples used to calculate values in the following columns; Reyes and Campos, 2005.fFraction Pb emitted for diesel calculated from Pb consumption rate and emission rate for diesel engines; Wang et al., 2003.gLow sulfur fuel [Pb] used to calculate values in the following columns; Miller et al., 1996.hFraction Pb emitted for heavy fuel oil calculated from emission rate of 0.182 kg Pb/million L fuel consumed (1.5 x 10-3 lb/1000 US gallon fuel consumed); US EPA, 1998.iMedian [Pb] of range used to calculate values in the following columns; Shumway, 2000, in Murphy et al., 2007.jAverage [Pb] for North American coals (143 samples); Chow and Earl, 1972.kFraction Pb emitted for coal calculated from emission factor of 0.21 mg Pb/1 kg coal feed (2.1 x 10-4 kg Pb/1 Mg coal feed); US EPA, 1998.Fuel Pb (kg) Pb emissions (kg) Pb emissions , % of totalcFraction Pb emitted for both motor and aviation gasolines assumed to be between the historically used, US EPA esimate of 0.75 and 1. The same fraction is assumed for jet fuel. In the following columns, 0.75 is used to calculate Pb emissions .126Table 4.3. Cadmium concentrations (µg g-1 dry weight) and isotopic compositions of bivalve tissues.Sample collection sitea, yearBivalve species [Cd] δ111Cd/110Cdbδ112Cd/110Cdbδ113Cd/110Cdbδ114Cd/110CdbncWestern CanadadDesolation Sound, B.C.Gorge Harbor 2004 C. gigas 7.3 -0.17 ± 0.03 -0.36 ± 0.01 -0.51 ± 0.03 -0.69 ± 0.01 2Redonda Bay 2004 C. gigas 4.6 -0.14 ± 0.03 -0.28 ± 0.07 -0.42 ± 0.12 -0.55 ± 0.14 3Redonda Bay* 2004 C. gigas 78 -0.17 ± 0.08 -0.35 ± 0.07 -0.43 ± 0.24 -0.64 ± 0.28 3Teakerne Arm 2004 C. gigas 13 -0.17 ± 0.06 -0.32 ± 0.11 -0.47 ± 0.05 -0.64 ± 0.20 3Thor's Cove 2002 C. gigas 5.5 -0.09 ± 0.03 -0.17 ± 0.11 -0.24 ± 0.19 -0.34 ± 0.25 3Trevenen Bay 2004 C. gigas 11 -0.11 ± 0.07 -0.21 ± 0.07 -0.28 ± 0.19 -0.38 ± 0.14 3Barkley Sound, B.C.Effingham Inlet 2004 C. gigas 2.9 -0.08 ± 0.04 -0.15 ± 0.04 -0.21 ± 0.14 -0.29 ± 0.15 3Effingham Inlet* 2004 C. gigas 39 -0.07 ± 0.09 -0.13 ± 0.10 -0.25 ± 0.09 -0.26 ± 0.07 3Fatty Basin 2004 C. gigas 6.5 -0.11 ± 0.07 -0.17 ± 0.11 -0.24 ± 0.18 -0.33 ± 0.13 3Poett Nook 2004 C. gigas 6.0 -0.11 ± 0.11 -0.20 ± 0.10 -0.30 ± 0.19 -0.37 ± 0.18 3Poett Nook* 2004 C. gigas 40 -0.14 ± 0.12 -0.26 ± 0.23 -0.40 ± 0.34 -0.52 ± 0.41 3Seddall Island 2004 C. gigas 5.2 -0.05 ± 0.06 -0.06 ± 0.12 -0.10 ± 0.18 -0.09 ± 0.23 4FranceeEnglish ChannelOye plage, Dunkerque-Calais 2004 M. edulis 0.48 -0.09 ± 0.13 -0.10 ± 0.16 -0.21 ± 0.25 -0.20 ± 0.22 3Ambleuteuse-Boulogne 2004 M. edulis 0.57 -0.15 ± 0.07 -0.28 ± 0.16 -0.34 ± 0.31 -0.49 ± 0.36 3Cap de la Hève, Seine estuary 2004 M. edulis 2.2 -0.22 ± 0.08 -0.44 ± 0.11 -0.68 ± 0.16 -0.88 ± 0.23 3Aber Benoît, North Brittanyf2005 C. gigas 1.4 -0.15 ± 0.11 -0.29 ± 0.17 -0.49 ± 0.06 -0.63 ± 0.14 2Aber Benoît, North Brittany dup.f,g2005 C. gigas 1.4 -0.14 ± 0.10 -0.25 ± 0.19 -0.42 ± 0.18 -0.52 ± 0.31 3Atlantic OceanPointe de Chemoulin, Loire estuary 2004 M. edulis 1.8 -0.15 ± 0.05 -0.31 ± 0.06 -0.47 ± 0.21 -0.62 ± 0.20 3Boyardville, Marennes-Oléron basinh1984 C. gigas 12 -0.13 ± 0.07 -0.33 ± 0.21 -0.51 ± 0.24 -0.63 ± 0.35 3Boyardville, Marennes-Oléron basinh1984 M. edulis 1.9 -0.20 ± 0.10 -0.36 ± 0.14 -0.62 ± 0.23 -0.72 ± 0.21 3La Mouclière, Marennes-Oléron basin 2004 M. edulis 1.1 -0.22 ± 0.06 -0.45 ± 0.08 -0.70 ± 0.04 -0.92 ± 0.07 3Les Palles, Marennes-Oléron basin 2004 C. gigas 2.8 -0.28 ± 0.05 -0.55 ± 0.05 -0.81 ± 0.12 -1.08 ± 0.09 3La Fosse, Gironde estuaryf1987 C. gigas 129 -0.27 ± 0.06 -0.51 ± 0.02 -0.74 ± 0.13 -0.99 ± 0.12 4La Fosse, Gironde estuary dup.f,g1987 C. gigas 129 -0.27 ± 0.04 -0.52 ± 0.13 -0.81 ± 0.31 -1.06 ± 0.30 3La Fosse, Gironde estuaryf2005 C. gigas 29 -0.26 ± 0.04 -0.52 ± 0.05 -0.79 ± 0.12 -1.03 ± 0.17 5Mediterranean SeaEtang de Bages, Roussillonf2005 M. galloprovincialis 5.7 -0.14 ± 0.08 -0.25 ± 0.05 -0.40 ± 0.04 -0.51 ± 0.11 5Etang de Bages, Roussillon dup.f,g2005 M. galloprovincialis 5.7 -0.13 ± 0.13 -0.26 ± 0.14 -0.41 ± 0.07 -0.51 ± 0.20 3Etang du Prévost, Thauf2005 M. galloprovincialis 0.37 -0.09 -0.17 -0.19 -0.27 1USAeAtlantic OceanKennebunkport, Cape Arundel, ME 2005 M. edulis 1.5 -0.15 ± 0.08 -0.30 ± 0.15 -0.40 ± 0.15 -0.54 ± 0.21 2Arnolds Point Shoal, Delaware Bay, NJ 2005 C. virginica 12 -0.19 ± 0.05 -0.41 ± 0.13 -0.63 ± 0.24 -0.81 ± 0.32 3Arnolds Point Shoal, Delaware Bay, NJ dup.g2005 C. virginica 12 -0.22 ± 0.09 -0.45 ± 0.16 -0.67 ± 0.30 -0.91 ± 0.36 3Bodkin Point, Chesapeake Bay, MD 2005 C. virginica 16 -0.19 ± 0.07 -0.37 ± 0.11 -0.55 ± 0.23 -0.74 ± 0.26 4Choptank River, Chesapeake Bay, MD 2005 C. virginica 4.6 -0.13 ± 0.05 -0.29 ± 0.04 -0.41 ± 0.05 -0.56 ± 0.10 2Fort Johnson, Charleston Harbor, SC 2006 C. virginica 2.1 -0.33 ± 0.04 -0.60 ± 0.05 -0.87 ± 0.21 -1.20 ± 0.27 2Shutes Folly Island, Charleston Harbor, SC 2006 C. virginica 4.2 -0.29 -0.56 -0.82 -1.05 1Dog River, Mobile Bay, AL 2006 C. virginica 3.9 -0.18 ± 0.06 -0.41 ± 0.11 -0.62 ± 0.09 -0.78 ± 0.19 3Pacific OceanKeehi Lagoon, Honolulu Harbor, HI 2004 O. sandvicensis 1.0 -0.13 ± 0.10 -0.25 ± 0.10 -0.36 ± 0.18 -0.46 ± 0.12 3aSample collection sites labelled to be consistent with those assigned by the NS&T (NOAA, USA) and the RNO (IFREMER, France), where appropriate.bRatios are reported permil (‰) as the mean ± 2 standard deviation (SD).cn refers to the number of replicate isotopic measurements.eBivalve samples from France and the USA are pooled samples rather than individuals (see Section 4.2.2).f[Cd] provided by the RNO (IFREMER).gdup. refers to a full procedual duplicate, inclusive of the analytical separation and isotopic analysis.dB.C. oyster samples are soft tissues of individuals, exclusive of the gut contents, except where guts are indicated (*) and these samples include only the gut and its contents.127Table 4.4. Zinc concentrations (µg g-1 dry weight) and isotopic compositions of bivalve tissues.Sample collection sitea, yearBivalve species [Zn] δ66Zn/64Znbδ67Zn/64Znbδ68Zn/64ZnbncWestern CanadadDesolation Sound, B.C.Thor's Cove 2002 C. gigas 390 0.28 ± 0.05 0.45 ± 0.16 0.59 ± 0.17 2Barkley Sound, B.C.Fatty Basin 2004 C. gigas 439 0.36 ± 0.13 0.55 ± 0.22 0.74 ± 0.26 5Seddall Island 2004 C. gigas 490 0.30 ± 0.15 0.47 ± 0.14 0.62 ± 0.29 3Francee,fEnglish ChannelAber Benoît, North Brittany 2005 C. gigas 1320 0.39 ± 0.04 0.60 ± 0.07 0.78 ± 0.07 3Atlantic OceanLa Fosse, Gironde estuary 1987 C. gigas 8350 1.15 ± 0.10 1.73 ± 0.12 2.27 ± 0.12 3La Fosse, Gironde estuary 2005 C. gigas 3570 1.03 ± 0.04 1.54 ± 0.08 2.05 ± 0.08 3Mediterranean SeaEtang de Bages, Roussillon 2005 M. galloprovincialis 90.0 0.43 ± 0.06 0.62 ± 0.10 0.85 ± 0.07 4Etang du Prévost, Thau 2005 M. galloprovincialis 116 0.46 ± 0.07 0.69 ± 0.16 0.91 ± 0.13 3aSample collection sites are labelled to be consistent with those assigned by the RNO (IFREMER, France), where appropriate.bRatios are reported permil (‰) as the mean ± 2 standard deviation (SD).cn refers to the number of replicate isotopic measurements.eBivalve samples from France are pooled samples rather than individuals (see Section 4.2.2).dB.C. oyster samples are soft tissues of individuals, exclusive of the gut content.128Table 4.5. Lead concentrations (µg g-1 dry weight) and isotopic compositions of bivalve tissues.Sample collection sitea, year Bivalve species [Pb]Western CanadadDesolation Sound, B.C.Gorge Harbor 2004 C. gigas 0.13 17.8791 7 15.5702 6 37.625 3 1.14832 2 2.10447 3Redonda Bay 2004 C. gigas 0.05 17.9159 12 15.5708 11 37.697 3 1.15061 2 2.10409 5Teakerne Arm 2004 C. gigas 0.09 17.9232 9 15.5771 8 37.731 2 1.15059 2 2.10522 4Barkley Sound, B.C.Effingham Inlet 2004 C. gigas 0.22 18.1930 13 15.5946 11 38.024 3 1.16659 2 2.09001 4Fatty Basin 2004 C. gigas 0.11 18.2745 15 15.5965 12 38.070 3 1.17167 2 2.08312 6Fatty Basin rep.e2004 C. gigas 0.11 18.2707 15 15.5940 15 38.065 4 1.17165 3 2.08343 7Poett Nook 2004 C. gigas 0.05 18.0245 12 15.5857 12 37.822 3 1.15649 2 2.09831 6Poett Nook* 2004 C. gigas 0.10 18.0816 16 15.5857 15 37.875 4 1.16020 3 2.09465 6Seddall Island 2003 C. gigas 0.16 18.0302 15 15.5842 18 37.787 3 1.15695 2 2.09567 5Seddall Island* 2003 C. gigas 0.11 18.2433 23 15.5850 21 37.997 5 1.17059 4 2.08271 10Seddall Island 2004 C. gigas 0.14 18.3149 9 15.5947 9 38.089 2 1.17442 2 2.07973 4FrancefEnglish ChannelOye plage, Dunkerque-Calais 2004 M. edulis 1.8 18.2015 10 15.6226 9 38.176 2 1.16508 1 2.09742 4Oye plage, Dunkerque-Calais rep.e2004 M. edulis 1.8 18.2009 9 15.6220 7 38.175 2 1.16509 2 2.09743 4Ambleuteuse-Boulogne 2004 M. edulis 1.4 18.2225 11 15.6262 11 38.206 3 1.16615 2 2.09662 4Cap de la Hève, Seine estuary 2004 M. edulis 5.7 18.1819 6 15.6271 7 38.194 2 1.16355 1 2.10053 3Cap de la Hève, Seine estuary rep.e2004 M. edulis 5.7 18.1837 6 15.6277 6 38.197 2 1.16358 1 2.10046 3Aber Benoît, North Brittanyg2005 C. gigas 0.90 18.3787 9 15.6390 7 38.351 2 1.17518 1 2.08670 3Aber Benoît, North Brittany dup.g,h2005 C. gigas 0.90 18.3798 12 15.6378 12 38.350 3 1.17534 2 2.08657 4Atlantic OceanPointe de Chemoulin, Loire estuary 2004 M. edulis 1.5 18.1476 8 15.6343 8 38.150 2 1.16076 1 2.10223 3Boyardville, Marennes-Oléron basin 1984 C. gigas 2.0 18.4302 6 15.6536 5 38.828 1 1.17739 2 2.10673 3Boyardville, Marennes-Oléron basin 1984 M. edulis 1.8 18.3860 6 15.6567 6 38.782 1 1.17433 1 2.10931 4La Mouclière, Marennes-Oléron basin 2004 M. edulis 1.6 18.4534 7 15.6636 6 38.742 2 1.17810 1 2.09943 3Les Palles, Marennes-Oléron basin 2004 C. gigas 1.2 18.4639 6 15.6571 6 38.729 2 1.17927 1 2.09758 3La Fosse, Gironde estuaryg1987 C. gigas 3.4 18.3920 9 15.6556 9 38.478 3 1.17479 1 2.09209 4La Fosse, Gironde estuary rep.e,g1987 C. gigas 3.4 18.3917 10 15.6547 9 38.477 2 1.17485 2 2.09202 3La Fosse, Gironde estuary dup.g,h1987 C. gigas 3.4 18.3917 8 15.6536 7 38.474 2 1.17488 2 2.09190 4La Fosse, Gironde estuary 2004 C. gigas 2.6 18.4855 7 15.6636 6 38.596 2 1.18019 1 2.08789 3La Fosse, Gironde estuaryg2005 C. gigas 3.1 18.5035 12 15.6623 10 38.678 3 1.18134 2 2.09047 4Mediterranean SeaEtang de Bages, Roussillong2005 M. galloprovincialis 0.40 18.4924 10 15.6630 9 38.488 2 1.18064 1 2.08130 4Etang du Prévost, Thaug2005 M. galloprovincialis 1.7 18.3733 6 15.6523 5 38.432 2 1.17385 1 2.09169 4Etang du Prévost, Thau dup.g,h2005 M. galloprovincialis 1.7 18.3716 12 15.6522 11 38.429 3 1.17374 1 2.09175 3Anse de Carteau, Golfe de Fos 2004 M. galloprovincialis 1.1 18.4451 8 15.6580 6 38.446 2 1.17801 1 2.08435 3USAfAtlantic OceanKennebunkport, Cape Arundel, ME 2005 M. edulis 2.0 18.8412 9 15.6585 6 38.574 2 1.20326 1 2.04734 3Dover Point, Great Bay, NH 2005 M. edulis 2.2 18.8415 7 15.6629 6 38.594 2 1.20295 1 2.04838 3Arnolds Point Shoal, Delaware Bay, NJ 2005 C. virginica 0.65 18.9200 16 15.6783 15 38.754 4 1.20675 2 2.04829 4Bodkin Point, Chesapeake Bay, MD 2005 C. virginica 0.29 18.7752 11 15.6712 11 38.582 3 1.19810 2 2.05488 4Choptank River, Chesapeake Bay, MD 2005 C. virginica 0.11 18.7642 11 15.6559 9 38.577 2 1.19854 2 2.05591 4Cape Hatteras, Pamlico Sound, NC 2006 C. virginica 0.56 18.9586 7 15.6713 7 38.867 2 1.20976 1 2.05031 3Fort Johnson, Charleston Harbor, SC 2006 C. virginica 0.75 18.4078 8 15.6066 8 38.155 2 1.17949 2 2.07269 4Shutes Folly Island, Charleston Harbor, SC 2006 C. virginica 0.72 18.5151 11 15.6140 11 38.284 3 1.18580 1 2.06773 3Dog River, Mobile Bay, AL 2006 C. virginica 0.27 19.0807 12 15.6681 9 38.842 2 1.21783 2 2.03564 4Pacific OceanKeehi Lagoon, Honolulu Harbor, HI 2004 O. sandvicensis 5.7 18.1721 8 15.5959 7 37.933 2 1.16521 1 2.08734 3fBivalve samples from France and the USA are pooled samples rather than individuals (see Section 4.2.2).g[Pb] provided by the RNO (IFREMER).erep. refers to a replicate analysis of the Pb sample solution.206Pb/204Pb  2SEb,c 208Pb/206Pb  2SEb,c206Pb/207Pb  2SEb,c208Pb/204Pb  2SEb,c207Pb/204Pb 2SEb,cbRatios are reported as the mean ± 2 standard error (SE). Reported error values are the ten-thousandth (206Pb/204Pb, 207Pb/204Pb), thousandth (208Pb/204Pb) or hundred-thousandth (206Pb/207Pb, 208Pb/206Pb) decimal digit.aSample collection sites labelled to be consitent with those assigned by the NS&T (NOAA, USA) and the RNO (IFREMER, France), where appropriate.cAll data have been normalized to the NIST SRM 981 triple spike Pb ratios of Galer and Abouchami, 1998.dB.C. oyster samples are soft tissues of individuals, exclusive of the gut contents, except where guts are indicated (*) and these samples include only the gut and its contents.129Fig. 4.1. Pie charts of the relative Pb emission contributions from petroleum products and coal consumption in Canada, the USA and France in 2005. Table 4.2 includes the references for data used to calculate these contributions.CanadaAvgasDiesel fuel oil Heavyfuel oilCoalUSA FranceAvgasMotor gasolineHeavy fuel oilCoalAvgasMotor gasolineDiesel fuel oil Heavy fuel oilCoalMotor gasolineDiesel fuel oil 130Fig. 4.2. Map of SW British Columbia showing the locations of sampling sites. The integrated Zn and Pb smelting and refining complex (black star) in Trail is located ~400 km from Vancouver.100 kmCanadaBarkley SoundDesolation Soundaa Effingham Inletb Fatty Basinc Poett Nookd Seddall Islandcb,dhiefgPort AlberniCampbell RiverVictoriaVancouverVancouver IslandB.C. mainlandStrait of Georgia Pacific OceanGorge Harbor Teakerne ArmThor's CoveRedonda BayTrevenen Baye f g h  i N 49.0 N 50.0 W 126 W 124 W 122 W 127 W 125 W 123 N 48.0 USATrail131Fig. 4.3. Map of the USA East Coast and Hawaii (inset) showing the locations of sampling sites. Facilities (not comprehensive) reporting emissions which are relevant in the discussion of Cd and Pb sources to the bivalve samples are indicated by stars; a and b: Lorain, OH; c: Monaca, PA; d: Lyon Station, PA; e: Baltimore, MD; f: Herculaneum, MO; g: Boss, MO; h: Clarksville, TN; i: Tuscaloosa, AL; j: Charleston, SC; k: Troy, AL; l: Axis, AL. Black star: primary smelting of non-ferrous metals; black star, grey border: copper foundry; white star: iron and steel mill; grey star: secondary smelter.W 70  W 65  W 60  W 75  W 80  W 85  N 45.0  N 40.0  N 35.0  lcabdefghi jkCanadaAtlantic OceanBaltimoreMobileCharlestonCape Arundel, MEGreat Bay, NHCharleston Harbor, SCMobile Bay, ALPamlico Sound, NCChesapeake Bay, MD200 kmGulf of MexicoUSA East Delaware Bay, NJChoptank RiverBodkin PointOahuHonolulu HarborPacific OceanHawaiian Islands100 kmHawai'iN 20.0  W 158  W 156  N 21.0  N 22.0  Lorain, OHMonaca, PALyon Station, PAAxis, ALTroy, ALTuscaloosa, ALClarksville, TNBoss, MOHerculaneum, MO1320  W 2  E 4  E 6  E 8  W 4  ParisBordeauxLyon200 kmAtlantic OceanFig. 4.4. Map of France showing the locations of sampling sites. The sites along the French Mediterranean coast are unique in that they are coastal lagoons (Etang de Bages and Etang du Prévost) and a semi-enclosed basin (Anse de Carteau). Note the Marennes-Oléron basin and Anse de Carteau are sites of major oyster and mussel production, respectively. Facilities of significance in the discussion are shown here. Black star: smelting and refining of Pb and Zn near Noyelles-Godault and of Zn near Decazeville (both now closed); white star: iron and steel mill near Dunkerque; grey star: Cd pigment plant near Narbonne (now closed).English ChannelMediterranean SeaN 44.0  N 46.0  N 50.0  N 42.0  Etang du PrévostAnse de CarteauEtang de BagesLa Fosse, Gironde estuaryBoyardville, La Mouclière, Les Palles,Marennes-Oléron basinPointe de Chemoulin, Loire estuaryAber BenoîtCap de la Hève, Seine estuaryOye Plage, Dunkerque-CalaisAmbleteuse-BoulogneDecazevilleNoyelles-GodaultNarbonneRouenLe HavreDunkerque1330246810121416<5 <15 <20 <25 <30<10Fig. 4.5. Histogram of the Cd concentrations of oyster and mussel soft tissue samples collected between 2002 and 2006. Oyster (solid color) and mussel (color gradient) samples are differentiated, as significant differences in Cd accumulation exist between the two species in polluted environments (Boutier et al., 1989). Unlike the bivalve samples from the USA and France, the B.C. oyster samples do not include gut contents. Due to the high relative Cd concentration of gut contents, B.C. whole oysters (inclusive of the gut) will have somewhat higher Cd concentrations than those shown here. B.C. whole oyster Cd concentrations are reported to range from 3.78 to 22.1 mg g-1 dry weight for oyster farming areas (Bendell and Feng, 2009). The data is also given in Table 4.3.France-musselsFrance-oystersUSA East Coast-musselsUSA East Coast-oystersHawaii (USA)-oystersB.C. (Canada)-oysters012345678<2 <4 <6 <8 <10[Cd] (mg g-1 dry weight)Frequency134-1.00 -0.50 0.00 0.50 1.00-1.50-1.00 -0.50 0.00 0.50 1.00d114Cd/110Cd (‰)-1.50Fig. 4.6. Plot of variations in the Cd isotopic composition of bivalve samples, inclusive of those from western Canada (B.C.), Hawaii, the USA East Coast and France. The grey ellipses denote 2 standard deviation on the mean Cd value, except when this value is less than the long-term reproducibility calculated for the in-house secondary standards (–0.14‰), and then the latter is used. Cadmium concentrations in bivalve tissues are given on the left in red (oysters) and blue (mussels). For the Marennes-Oléron, samples collected in 1984 are from Boyardville and in 2004 are from La Mouclière (top) and Les Palles (bottom). The data is also given in Table 4.3.Desolation Sound, B.C. (Canada)Barkley Sound,B.C. (Canada)7.34.613.25.5112.95.26.56.0English Channel-FranceAtlantic Ocean-FranceGironde estuaryMediterranean Sea-France(1987)(2005)0.5[Cd] (mg g-1 dry weight)0.62.21.41.8121.91.12.81290.4295.7Atlantic Ocean-USA164.62.14.23.91.512Marennes-Oléron(1984)(2004)Loire estuaryCharleston Harbor (SC)Cape Arundel (ME)Delaware Bay (NJ)Chesapeake Bay (MD)Mobile Bay (AL)Oye PlageAmbleteuseSeine estuaryAber BenoîtPacific Ocean-Canada/USAEtang de BagesEtang du Prévost1.0 Hawaii (USA)135Fig. 4.7. Mass-dependent Cd and Zn isotopic fractionation for all bivalve samples: (a) d114/110Cd vs. d111/110Cd and (b) d68/64Zn vs. d66/64Zn. The calculated regression lines (for (a), r2=0.9624; for (b), r2=0.9995) are coherent with mass-dependent isotopic fractionation, indicating spectral interferences are insignificant. Inset in (a) shows d114/110Cd vs. 206Pb/207Pb; best fit lines are shown for the B.C oysters and USA East Coast bivalves. The error on each sample is not shown in (a) for clarity; in (b), error bars denote 2 standard deviation (SD) on the mean dZn value for replicate analyses of each sample. The long-term reproducibility, calculated as the 2SD on the mean dCd and dZn values for the in-house secondary Cd and Zn isotopic standards (Shiel et al., 2009), is shown. For Pb, the error (2SE) is smaller than the symbol size. Note that in (a) for Aber Benoît (English Channel-France) and the Loire estuary (Atlantic Ocean-France), the values (---0.15‰, -0.63‰ and -0.15‰, -0.62‰, respectively) overlap.0.000.501.001.502.002.500.00 0.25 0.50 0.75 1.00 1.25-1.40-1.20-1.00-0.80-0.60-0.40-0.200.00d66Zn/64Zn (‰)d68Zn/64Zn (‰)d114Cd/110Cd (‰)(b)(a)-0.35 -0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00d111Cd/110Cd (‰)d114Cd/110Cd (‰)206Pb/207Pb–2s-1.20-0.80-0.400.001.14 1.16 1.18 1.20 1.22–2sB.C. mainland Vancouver IslandHawaii (USA)Atlantic Ocean-USAAtlantic Ocean-FranceEnglish Channel-FranceMediterranean Sea-France–2s136Fig. 4.8. Plot of 208Pb/206Pb vs. 206Pb/207Pb for the B.C. and Hawaiian oysters. These Pb isotope ratios are compared with those of B.C. lichens (representative of atmospheric Pb fall-out, collected in 1995-7; Simonetti et al., 2003); aerosols from Victoria (collected in 1998/9; Bollhöfer and Rosman, 2001); road dust from the lower B.C. mainland (Preciado et al., 2007); B.C. smelter ZnO fume and effluent (Shiel et al., 2010); Red Dog mine (AK) ore (Shiel et al., 2010); Bathurst district ore (representative of Canadian leaded gasoline) and Sullivan mine (B.C.) ore (Sangster et al., 2000, and references within); loess-China (Jones et al., 2000); Pacific Ocean deep water (ferromanganese crust from the N. Pacific Ocean, last 2 Ma years of time series shown; van de Flierdt et al., 2003). For this study, the error (2SE) is smaller than the symbol size.2.042.062.082.102.121.14 1.16 1.18 1.20206Pb/207Pb208Pb/206PbB.C. mainland Vancouver IslandRed Dog mine oreRoad dust-B.C. mainlandPacific Ocean deep waterLichens-B.C. mainlandLichens-Vancouver Is.Aerosols-Victoria, B.C.HawaiiLoess-China(1.0679, 2.1889)Sullivan oreOyster samples:Bathurst district Pb oreSmelter effluent-B.C.Gut contentsSmelter ZnO fume-B.C.137Fig. 4.9. Plot of 208Pb/206Pb vs. 206Pb/207Pb for the USA East Coast bivalves. The data are compared with the Pb isotope ratios of road dust from the lower B.C. mainland (collected in 2002/3; Preciado et al., 2007), aerosols from New York and Woods Hole (collected in 1997/8; Bollhöfer and Rosman, 2001), NE USA lichens (representative of atmospheric Pb fall-out, collected in 1994-6; Carignan et al., 2002), electric arc furnace (EAF) dust (steel mill; Ketterer et al., 2001), US coal samples (Díaz-Somoano et al., 2009), Mt. Isa and SE Missouri Pb ores (Sangster et al., 2000, and references within), N. Atlantic Ocean seawater (collected in 1988; Véron et al., 1994) and Atlantic Ocean sediments (Sun, 1980). For this study, the error (2SE) is smaller than the symbol size.1.961.982.002.022.042.062.082.102.122.141.12 1.14 1.16 1.18 1.20 1.22 1.24 1.26206Pb/207Pb208Pb/206PbCape Arundel (ME)/Great Bay (NH)Bivalve samples:Delaware Bay (NJ)Chesapeake Bay (MD)Pamlico Sound (NC)Charleston Harbor (SC)Mobile Bay (AL)Atlantic Ocean sedimentsRoad dustCoal-USAAerosols-NY/Woods HoleN. Atlantic Ocean seawaterNE USA emissions(1.3390, 2.5282)SE Missouri oreEAF dust (steel mill)Coals-USA(1.0431, 2.2224)Mt. Isa ore1382.042.062.082.102.122.142.162.181.08 1.10 1.12 1.14 1.16 1.18 1.20 1.22Fig. 4.10. Plot of 208Pb/206Pb vs. 206Pb/207Pb for the French bivalves. These Pb isotope ratios are compared with those of pre-industrial sediments (Sun, 1980; Elbaz-Poulichet et al., 1986), Garonne River and its tributaries (Elbaz-Poulichet et al., 1986; Grousset et al., 1999), Seine and Loire Rivers (Elbaz-Poulichet et al., 1986), aerosols from western Europe and France (1994-1998; Bollhöfer and Rosman, 2001), auto exhaust (1987) and highway runoff (1992/3) (France; Monna et al., 1995) and Mt. Isa Pb ores (Sangster et al., 2000, and references within). There is an insignificant difference between the Pb isotope ratios of the Garonne River and its tributaries collected in the early 1980s and the late 1990s (Elbaz-Poulichet et al., 1986; Grousset et al., 1999). For this study, the error (2SE) is smaller than the symbol size.206Pb/207Pb208Pb/206PbGaronne River and tributariesPre-industrial sedimentsLoire RiverAerosols (W. Europe)Seine RiverHighway runoff-FranceAerosols-FranceAuto exhaust-FranceEtang de BagesEtang du PrévostAnse de CarteauMarennes-Oléron basinLoire estuaryAbers BenoîtSeine estuaryOye PlageAmbleteuseMediterranean SeaBoyardville, 1984La Moucliere/Les Palles, 2004Gironde estuary19872004/5Bivalve samples:French gasoline(1.0431, 2.2224)Mt. Isa ore139Fig. 4.11. Variations in the (a) Cd and (b) Zn isotopic compositions of oysters (oyster gut contents indicated by a star) from the North Pacific Ocean, seawater, plankton, geological and anthropogenic materials. The grey ellipses indicate error as reported by referenced authors; for this study the grey fields denote 2 standard deviation on the mean Cd value in (a) or Zn value in (b) for replicate analyses of each sample except when this value is less than the long-term reproducibility calculated for the in-house secondary standards (for (a), –0.14‰; for (b), –0.06‰), and then the latter is used. In several cases the error is smaller than the symbol and so no grey field is shown. Data sources: 1Lacan et al., 2006; 2Ripperger et al., 2007; 3Schmitt et al., 2009; 4Shiel et al., 2010; 5Cloquet et al., 2005; 6Cloquet et al., 2006b; 7Bermin et al., 2006; 8John, 2007.North Pacific Ocean-0.60 -0.40 -0.20 0.00 0.20 0.40 0.60 0.80 1.00-0.60 -0.40 -0.20 0.00 0.20 0.40 0.60 0.80 1.00(b)Marine samples:Plankton tows, worldwide8NE Pacific Ocean seawater Stn. P47This study:B.C. mainland oystersVancouver Is. oystersN Pacific Ocean seawater8d66Zn/64Zn (‰)-1.00 -0.50 0.00 0.50 1.00d114Cd/110Cd (‰)Smelter ZnO fume4Slag5Smelter dust5Polluted soils,Pb-Zn refinery (France)6 Sphalerite (ZnS)3Mineral/Industrial samples:Environmental samples:This study:-1.50Zn ore concentrates4-1.00 -0.50 0.00 0.50 1.00-1.50Marine samples:N Pacific Ocean seawater Stn. ALOHA2NE Pacific Ocean seawaterStn.K11N Pacific Ocean seawater Stn. 72B.C. mainland oystersVancouver Is. oystersHawaii oysters(a)1.6‰, 3.8‰2140Fig. 4.12. Variations in the (a) Cd and (b) Zn isotopic compositions of bivalves from the North Atlantic Ocean, seawater, plankton, geological and anthropogenic materials. The grey ellipses indicate error as reported by referenced authors; for this study the grey fields denote 2 standard deviation on the mean Cd value in (a) or Zn value in (b) for replicate analyses of each sample except when this value is less than the long-term reproducibility calculated for the in-house secondary standards (for (a), –0.14‰; for (b), –0.06‰), and then the latter is used. In several cases the error is smaller than the symbol and so no grey field is shown. Data sources: 1Ripperger et al., 2007; 2Lacan et al., 2006; 3Schmitt et al., 2009; 4Shiel et al., 2010; 5Cloquet et al., 2005; 6Cloquet et al., 2006a; 7Gao et al., 2008; 8John, 2007; 9Sonke et al., 2008; 10Mattielli et al., 2009; 11Sivry et al., 2008; 12Cloquet et al., 2006a. -1.00 -0.50 0.00 0.50 1.00-1.50(a)-1.00 -0.50 0.00 0.50 1.00-1.50d114Cd/110Cd (‰)Smelter ZnO fume4Slag5Smelter dust5Polluted soils,Pb-Zn refinery (France)6 Sphalerite (ZnS)3Mineral/Industrial samples:Environmental samples:Zn ore concentrates4Marine samples:English Channel-France bivalvesUSA East Coast bivalvesMediterranean Sea-musselsAtlantic coast-France bivalvesPolluted sediments,Pb-Zn refinery (China)7 Mediterranean seawater2N Atlantic Ocean seawater1Waste incineration dust5North Atlantic OceanThis study: This study:Zn ore concentrates4Effluent4ZnO fume4Galena (PbS)9Sphalerite (ZnS)9Environmental samples10Zn-Pb enriched ores10Pb enriched ores10Zn refining emissions (roasting, blast furnace)10Pb refining emissions (roasting, blast furnace)10Main chimney emissions10Polluted lichens, (Metz, NE France)12Urban waste incinerator flue gases, REFIOM (NE France)12Urban aerosols (Metz, NE France)12-1.00 -0.50 0.00 0.50 1.00 1.50 2.00d66Zn/64Zn (‰)-1.00 -0.50 0.00 0.50 1.00 1.50 2.00Pb-Zn metallurgical plant (NE France):Environmental samples (NE France):Zn ore treatment plant (Riou-Mort-Lot River system, SW France):Mineral/Industrial samples:English Channel-France bivalvesMediterranean Sea-musselsAtlantic coast-Gironde estuary, France-oysters(b)Marine samples:N Atlantic Ocean seawater8Plankton tows, worldwide8Sediment cores11:Unpolluted PollutedTailings11Coal ashes11Percolating water11Polluted stream sediments11Polluted soils111414.7 ReferencesAudry, S., Blanc, G., Schafer, J. 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(1998) Chapter 1: External CombustionSources in AP 42, fifth edition, Compilation of Air Pollutant Emission Factors,Volume 1: Stationary Point and Area Sources.(Available at http://www.epa.gov/ttnchie1/ap42/ch01/index.html)US EPA (Environmental Protection Agency). (2010) Toxics Release Inventory (TRI)Explorer: Release reports: http://www.epa.gov/triexplorer/chemical.htm.151CHAPTER 5Conclusions1525.1 IntroductionMetal emissions to the natural environment from anthropogenic sources may bemuch larger than those from natural sources as is the case for atmospheric emissions ofCd, Zn and Pb globally; Pacyna and Pacyna, 2001). This can disturb the natural cycles forthese metals. For many metals anthropogenic emissions have lead to higher levels thanoccur naturally even in remote regions, such as Greenland and Antarctica (Pacyna andPacyna, 2001). Both the health of ecosystems and humans depend on achievingsustainable metal emission levels. The accomplishment of this goal requires diligentenvironmental monitoring, implementation of increasingly efficient industrial processesand improved emission controls and a reduction of our dependence on fossil fuels.Globally, non-ferrous metal smelting is the largest contributor to anthropogenicatmospheric emissions of Cd and Zn (Pacyna and Pacyna, 2001). This study hasdemonstrated Cd and Zn isotopes to be effective tracers of Cd and Zn emissions in theenvironment, as the isotopic compositions of these metal emissions are fractionatedrelative to source materials (i.e., ores). The use of the stable isotope systematics of Cdand Zn (and potentially those of other heavy elements) to evaluate the relative strengthand extent of metal emissions to the environment from anthropogenic sources, andclearly demonstrate their impact on environmental health has the potential to:(1) establish the need for stricter regulations for polluting industries;(2) put pressure on reluctant facilities to invest in more efficient technologies andemission control;(3) determine the impact of anthropogenic emissions from laxly regulatedindustrial sources, even when emissions cross political borders;(4) demonstrate the effectiveness of remediation strategies in industriallyimpacted environments or the successful natural recovery of ecosystem healthwhen strategies are emplaced to reduce metal emissions.The efficiency of Cd and Zn isotopes as new tools will improve with the expansion of thenatural and anthropogenic materials’ isotopic compositions database and knowledgeregarding sources and mechanisms of isotopic fractionation.1535.2 Key findings of this studyThis study began with the successful establishment of a technique to measure Cdand Zn isotopes in bivalve molluscs, environmental and anthropogenic samples. Thedevelopment of this technique facilitated the evaluation of Cd and Zn isotopes as a toolfor the identification of natural and anthropogenic metal sources and assessment of theirrelative contributions in the environment. A multi-tracer approach is used to resolveambiguities inherent to the interpretation of single element stable isotope data (similar tolight stable isotope studies; Peterson and Fry, 1987). The combined use of Pb isotopes,along with the Cd and Zn isotopes, allows the processes contributing metals to beidentified through “fingerprinting”. Cadmium and Zn stable isotope systematics aresuccessfully used to trace the source of natural and anthropogenic emissions of theseelements. The major contributions of this study are the following: (1) establishment ofsmelting and refining processes as sources of Cd and Zn isotopic fractionation; (2)characterized Cd, Zn and Pb isotopic end members — providing a link to ore sources; (3)characterized the Cd and Zn isotopic compositions of smelter effluent and fumes asdifferent from those of source materials; (4) demonstrated the overall closed nature of theintegrated smelting and refining facility in Trail due to internal recycling betweenoperations; (5) established high Cd concentrations of B.C. oysters as mostly natural withsome local variability due to anthropogenic sources; (6) identified greater anthropogeniccontributions of Cd in USA East Coast bivalves due to high prevalence of industry; (7)documented relatively large variability among bivalves from the coasts of Franceresulting from the large variability of environmental health at collection sites; (8)established oysters and mussels from sites in the Marennes-Oléron basin and Girondeestuary (French Atlantic Coast) as having the largest anthropogenic Cd contribution ofFrench sites (this region is the largest oyster farming area in Europe and produces someof the most prized in the world!). This study has contributed substantially to ourunderstanding of Cd and Zn cycling and distribution processes in the environment andthe relative importance of natural and anthropogenic sources.154A summary of each chapter including major contributes follows:Matrix effects on the multi-collector inductively coupled plasma mass spectrometricanalysis of high-precision cadmium and zinc isotope ratiosResin-derived contaminants added to samples during column chemistry are shownto cause matrix effects that lead to inaccuracy in multi-collector inductively coupledplasma mass spectrometry (MC-ICP-MS) measurement of small variations in Cd and Znisotopic compositions observed among terrestrial samples. These matrix effects wereevaluated by comparing pure Cd and Zn standards and standards doped with bulk columnblank from the anion exchange chromatography procedure. Doped standards exhibitsignal enhancements (Cd, Ag, Zn and Cu), instrumental mass bias changes and inaccurateisotopic compositions relative to undoped standards, all of which are attributed to thecombined presence of resin-derived organics and inorganics. The matrix effect associatedwith the inorganic component of the column blanks was evaluated separately by dopingstandards with metals at the trace levels detected in the column blanks. Mass bias effectsintroduced by the inorganic column blank matrix are smaller than for the bulk columnblank matrix but can still lead to significant changes in ion signal intensity, instrumentalmass bias and isotopic ratios. Chemical treatment with refluxed HNO3 or HClO4/HNO3removes resin-derived organic components resulting in matrix effects similar inmagnitude to those associated with the inorganic component of the column blank.Mass bias correction using combined external normalization-SSB does not correctfor these matrix effects because the instrumental mass biases experienced by Cd and Znare decoupled from those of Ag and Cu, respectively. These results demonstrate that ionexchange chromatography and associated resin-derived contaminants can be a source oferror (up to 0.23‰ amu-1 for δ114/110CdAg-corrected and 0.28‰ amu-1 for δ66/64ZnCu-corrected) inMC-ICP-MS measurement of heavy stable element isotopic compositions. As a result ofthese experiments, all samples were loaded on to anion exchange chromatographycolumns in sufficient quantities to allow significant dilution of the purified samples (andresin-derived matrix) in the analyzed solutions, thus minimizing the associated matrixeffects. In addition, purified samples (i.e., Cd and Zn eluate cuts) were dried and close-155vessel digested on a hotplate using HNO3 and H2O2 in an effort to remove any resin-derived organics before bringing the samples up in dilute HNO3 for isotopic analysis.Evaluation of zinc, cadmium and lead isotope fractionation during smelting andrefiningTo evaluate metallurgical processing as a source of Zn and Cd isotopicfractionation and to potentially trace their distribution in the environment, high-precisionMC-ICP-MS Zn, Cd and Pb isotope ratio measurements were made for samples from theintegrated Zn–Pb smelting and refining complex in Trail, B.C., Canada. Significantfractionation of Zn and Cd isotopes during processing of ZnS and PbS ore concentrates isdemonstrated by the total variation in δ66/64Zn and δ114/110Cd values of 0.42‰ and 1.04‰,respectively, among all smelter samples.No significant difference is observed between the isotopic compositions of the Znore concentrates (δ66/64Zn = 0.09 to 0.17‰; δ114/110Cd = -0.13 to 0.18‰) and the roastingproduct, calcine (δ66/64Zn = 0.17‰; δ114/110Cd = 0.05‰), due to ~100% recovery fromroasting. The overall Zn recovery from metallurgical processing is ~98%, thus the refinedZn metal (δ66/64Zn = 0.22‰) is not significantly fractionated relative to the startingmaterials despite significantly fractionated fume (δ66/64Zn = 0.43‰) and effluent (δ66/64Zn= 0.41 to 0.51‰). Calculated Cd recovery from metallurgical processing is 72–92%, withthe majority of the unrecovered Cd lost during Pb operations (δ114/110Cd = -0.38‰). Therefined Cd metal is heavy (δ114/110Cd = 0.39 to 0.52‰) relative to the starting materials. Inaddition, significant fractionation of Cd isotopes is evidenced by the relatively light andheavy isotopic compositions of the fume (δ114/110Cd = -0.52‰) and effluent (δ114/110Cd =0.31 to 0.46‰). In contrast to Zn and Cd, Pb isotopes are homogenized by mixing of Pbsources during processing. The total variation observed in the Pb isotopic compositionsof smelter samples is attributed to mixing of ore sources, with different radiogenicsignatures, during processing.156Tracing cadmium, zinc and lead in bivalves from the coasts of western Canada, theUSA and France using isotopesIn a multi-tracer study, Cd, Zn and Pb isotopic compositions (MC-ICP-MS) andelemental concentrations (HR-ICP-MS) are used to distinguish between natural andanthropogenic sources of these metals in bivalves collected from western Canada (B.C.),Hawaii, the USA East Coast and France.B.C. oyster tissues and gut contents have identical Cd isotopic compositions(δ114/110Cd  = -0.69 to -0.09‰) that fall within the light end of the range reported for NorthPacific seawater, suggesting the high Cd levels in these oysters primarily results fromnatural upwelling of Cd-rich deep-waters in the North Pacific. We suggest limitingconsumption of B.C. oysters to ensure Cd intake remains within safe levels. Variability inthe Cd isotopic compositions of B.C. oysters is attributed to variable contributions fromanthropogenic sources; the lightest of these oysters are from the B.C. mainland. Therange of Zn isotopic composition exhibited by B.C. oysters (δ66/64Zn  = 0.28 to 0.36‰) isconsistent with that of North Pacific seawater. Despite relatively low Pb levels in B.C.oysters (0.05 to 0.22 µg g-1 tissue dry weight), their Pb isotopic compositions reflectprimarily anthropogenic sources, likely mixing between Pb emissions from theconsumption of unleaded automotive gasoline and diesel fuel (high 206Pb/207Pb) andsmelting (potentially historical) of Pb ores in Trail, B.C. (low 206Pb/207Pb source). Boththe Cd and Pb isotopic compositions of the Hawaiian oysters fall within the rangeexhibited by the oysters from Vancouver Island suggesting similar metal sources.All bivalve samples from the Atlantic coasts exhibit Cd isotopic compositionslighter than reported for North Atlantic seawater suggesting the widespread importanceof anthropogenic sources. USA East Coast bivalves exhibit relatively light Cd isotopiccompositions (δ114/110Cd  = -1.20 to -0.54‰) due to the high prevalence of industry on thiscoast. The δ114/110Cd values of USA East Coast bivalves include the lightest ever reportedfor terrestrial materials (with the exception of that reported for a tektite sample, i.e., in acompletely different set of conditions). The Pb isotopic compositions of bivalves fromthe USA East Coast indicate Pb emissions from the combustion of coal are an importantsource of Pb; this is consistent with the high consumption of coal for power productionon this coast.157The large variability of environmental health among coastal areas in France isreflected in the broad range of Cd isotopic compositions exhibited by French bivalves(δ114/110Cd  = -1.08 to -0.20‰). Oysters and mussels from the Marennes-Oléron basin andGironde estuary have the lightest Cd isotopic compositions of the French oystersconsistent with significant historical Cd emissions from the now-closed proximal Znsmelter. In these bivalves, significant declines in the Cd levels between 1984/7 and2004/5 are not accompanied by a shift in the Cd isotopic composition toward naturalvalues. The Mediterranean samples have isotopic compositions within error of the lighterend of the range reported for Mediterranean seawater. The Zn isotopic compositions ofFrench oysters and mussels (δ66/64Zn  = 0.39 to 0.46‰) are identical to those reported forNorth Atlantic seawater, with the exception of the much heavier compositions of oysters(δ66/64Zn  = 1.03 to 1.15‰) from the polluted Gironde estuary. The French bivalvesexhibit Pb isotopic compositions that indicate primarily industrial (as opposed toautomotive) sources; this is consistent with the collection of most of the French bivalvesamples in 2004, after the complete phase-out of leaded gasoline in France.This study demonstrates the effective use of Cd and Zn isotopes to traceanthropogenic sources in the environment and the benefit of combining these tools withPb isotope “fingerprinting” techniques to identify processes contributing metals. 5.3 Suggestions for future researchThis work represents significant contributions to our understanding of Cd and Znisotopes as source tracers and provides direction for future research. Measurement of thesmall differences observed in the isotopic compositions of heavy stable elements has onlybeen possible in recent years, primarily with the MC-ICP-MS. Improved techniques andinstrumentation are expected to facilitate increasingly precise measurement of these smalldifferences. Potential applications for heavy stable isotopes are early in theirdevelopment. Prospective research includes:(1) The evaluation of isotopic fractionation for other metals duringsmelting and refining and the potential use of these elemental isotopes158for tracing emissions in the environment. For example, aninvestigation of Cu, Ni and/or Sb isotope fractionation (depending onstarting materials processed by the facility) during Cu smelting andrefining to produce Cu and Ni metals and associated byproducts, e.g.,Sb.(2) The evaluation of isotopic fractionation for heavy metals duringvarious anthropogenic processes and the assessment of the potential totrace those anthropogenic metal emission sources. For example, aninvestigation of isotopic fractionation of Cd, Cr, Cu, Hg and/or Znduring waste incineration, which contributes between 1 and 5% oftotal global atmospheric emissions of these metals (mid-1990s; Pacynaand Pacyna, 2001). Initial investigation of the Cd isotopic compositionof urban waste incineration fly ash suggests incineration mayfractionate Cd isotopes (Cloquet et al., 2005).In addition, this study has exposed several opportunities for Pb “fingerprinting” orthe combined use of Cd and Pb isotopes to trace these metals in the environment.Prospective research includes:(1) A thorough investigation of anthropogenic metal sources in theGreater Vancouver area, focusing on Pb. The consumption ofpetroleum products accounts for substantial contributions to totalatmospheric Pb emissions in B.C. (e.g., consumption of avgas by smallplanes and diesel and heavy fuel oils by boats). An investigation of thePb isotopic signatures of these emissions would allow the precisedetermination of their relative importance as anthropogenic Pb sourcesin Southwestern B.C. In particular, the impact of significant Pbemissions, resulting from the consumption of avgas (accounts for~68% of total Pb emissions from the consumption of fossil fuels inB.C.; Table 4.1), on local environmental health needs to be assessed.(2) An evaluation of the historical evolution of Pb pollution in theVancouver area and its sources through a tracer study of Pb in159available environmental archives, such as tree cores (Stanley Park ishome to trees that are hundreds of years old) or peat cores (a core fromBurns Bog, located within the Greater Vancouver area, could provide arecord of thousands of years).(3) Regional studies of Cd and Pb isotope systematics in bivalves andother environmental samples in order to provide clear links betweenhigh metal levels and anthropogenic sources; e.g., oysters fromCharleston Harbor exhibit Cd isotopic compositions among the lightestin the study–a regional study of broader scope may allow the preciseidentification of the important anthropogenic sources.1605.4 ReferencesCloquet, C., Rouxel, O., Carignan, J., Libourel, G. (2005) Natural cadmium isotopicvariations in eight geological reference materials (NIST SRM 2711, BCR 176,GSS-1, GXR-1, GXR-2, GSD-12, Nod-P-1, Nod-A-1) and anthropogenicsamples, measured by MC-ICP-MS. Geostandards and Geoanalytical Research29: 95–106.Pacyna, J.M., Pacyna, E.G. (2001) An assessment of global and regional emissions oftrace metals to the atmosphere from anthropogenic sources worldwide.Environmental Reviews 9: 269–298.Peterson, B.J., Fry, B. (1987) Stable isotopes in ecosystem studies. Annual Review ofEcology and Systematics 18: 293–320.161Appendices162Appendix A List of publications and presentations during Ph.D.Peer-reviewed publicationsShiel, A.E., D. Weis and K.J. Orians. Tracing cadmium, zinc and lead pollution inoysters from the coasts of western Canada, the USA and France using isotopes (inpreparation).Shiel, A.E., D. Weis and K.J. Orians (2010) Evaluation of zinc, cadmium and leadisotope fractionation during smelting and refining. Science of the Total Environment 408:2357-2368.Shiel A.E., J. Barling, K.J. Orians and D. Weis (2009) Matrix effects on the multi-collector inductively coupled plasma mass spectrometric analysis of high-precisioncadmium and zinc isotope ratios.  Analytica Chimica Acta 633: 29-37.Conference abstractsOral presentationsShiel, A.E., K.J. Orians, D. Cossa and D. Weis (2008) Sourcing Metals in BivalvesUsing Combined Pb, Zn and Cd Isotopic Compositions. Geochimica et CosmochimicaActa 72(12) Supplement 1: A859.Shiel, A.E., K.J. Orians, D. Cossa and D. Weis (2007) Anthropogenic contamination ofbivalves revealed by Cd isotopes. Geochimica et Cosmochimica Acta 71(15) Supplement1: A928.PostersShiel, A.E., D. Weis and K.J. Orians. (2010) Pb, Cd and Zn Isotopes as Source Tracers inPacific/Atlantic Bivalves. Geochimica et Cosmochimica Acta 74(11) Supplement 1:A952.163Torchinsky, A., A.E. Shiel, M. Price and D. Weis. (2010) Pb, Cd and Zn Isotopes asSource Tracers in Pacific/Atlantic Bivalves. Geochimica et Cosmochimica Acta 74(11)Supplement 1: A1050.Verheyden, S., C. Maerschalk, A.E. Shiel and N. Mattielli (2007) Single columnprocedure for quantitative separation and recovery of Cd for high precision isotopeanalysis by MC-ICP-MS. Geochimica et Cosmochimica Acta 71(15): Supplement 1:A1063.Shiel, A.E., D. Weis, J. Barling and K.J. Orians (2006) Matrix effects on the MC-ICP-MS Analysis of Zn and Cd isotopes. Eos Trans. AGU, 87(52), Fall Meet. Suppl., AbstractV21B-0583.Barling, J., A.E. Shiel and D. Weis (2006) The Influence of Non-spectral Matrix Effectson the Accuracy of Isotope Ratio Measurement by MC-ICP-MS. Eos Trans. AGU,87(52), Fall Meet. Suppl., Abstract V21B-0584.Barling, J., A.E. Shiel, B. Mueller and D. Weis (2006) An Investigation of Non-SpectralMatrix Effects on the Accuracy of Non-Traditional Stable Isotope Measurements by MC-ICP-MS. Geophysical Research Abstracts, 8, 10261.Shiel, A.E., J. Barling, D. Weis and K.J. Orians (2005) Potential Use of CadmiumIsotopes to Source Cadmium in Oysters, Eos Trans. AGU, 86(52), Fall Meet. Suppl.,Abstract OS51C-0574.164Appendix B Cd and Zn separation chemistry, designed by Mason(2003).  Eluent  Acid Volume (ml) Eluted2 mL AG MP-1M resin, 100-200 mesh size, chloride form (Bio-RadLaboratories, Inc.)aResin cleaning1 M HNO3 10≥18.2 MΩ cm water 21 M HNO3 10≥18.2 MΩ cm water 21 M HNO3 10≥18.2 MΩ cm water 10Resin conditioning7 M HCl 10Load sample solution7 M HCl 1Elution sequence7 M HCl 10 Matrix (e.g. Mg, Al, Ca, Cr)7 M HCl 20 Cu8 M HF+2 M HCl 10 Fe, Mo, Sn0.1 M HBr+0.5 M HNO310 Zn0.5 M HNO310 Cd       aResin was loaded into single use, acid washed PolyPrep® columns (Bio-Rad Laboratories, Inc.).165Appendix C Column matrix effects on Cd and Ag ion-signal intensities and delta Cd values. Table includes values shown in Fig. 2.2. Sample Volume (%)110Cd109Agδ111/110CdSSB/amuδ112/110CdSSB/amuδ113/110CdSSB/amuδ114/110CdSSB/amuδ114/110CdSSBδ111/110CdAg-corr./ amuδ112/110CdAg-corr./ amuδ113/110CdAg-corr./ amuδ114/110CdAg-corr./ amuδ114/110CdAg-corr.   Blank 12 8.28 7.48 -0.07 -0.05 -0.06 -0.04 -0.16 -0.08 -0.08 -0.08 -0.07 -0.2710 21.30 24.45 -0.09 -0.10 -0.12 -0.12 -0.46 -0.11 -0.11 -0.13 -0.11 -0.4520 14.11 19.04 0.03 0.01 0.03 0.01 0.04 -0.09 -0.10 -0.09 -0.10 -0.4050 13.94 21.99 0.12 0.14 0.15 0.14 0.57 -0.17 -0.14 -0.14 -0.14 -0.57Blank 22 6.58 7.51 0.01 0.00 0.01 0.01 0.05 -0.05 -0.06 -0.04 -0.04 -0.1810 11.92 14.50 0.03 0.01 0.00 0.00 0.00 -0.03 -0.07 -0.08 -0.08 -0.3050 16.18 3.63 0.16 0.21 0.24 0.22 0.90 -0.18 -0.15 -0.12 -0.13 -0.52Blank 32 0.69 -0.16 0.02 -0.03 -0.03 -0.03 -0.11 -0.02 -0.05 -0.06 -0.06 -0.2310 8.20 12.36 0.04 0.03 0.00 0.02 0.07 -0.08 -0.08 -0.10 -0.09 -0.3650 9.85 23.50 0.03 0.02 0.03 0.02 0.09 -0.19 -0.19 -0.19 -0.19 -0.77Blank 450 10.45 26.36 -0.13 -0.10 -0.10 -0.11 -0.44 -0.25 -0.22 -0.23 -0.23 -0.92Blank 5 (fluxed HNO3 treatment, run during same analytical session as Blank 2)2 3.95 4.10 -0.07 -0.08 -0.09 -0.08 -0.31 -0.03 -0.05 -0.05 -0.04 -0.1410 12.52 15.95 -0.01 0.00 0.01 0.00 -0.02 -0.06 -0.06 -0.04 -0.05 -0.2150 15.04 23.29 0.12 0.11 0.10 0.11 0.43 -0.09 -0.11 -0.10 -0.10 -0.39Blank 6 (HClO4 treatment; run during same analytical session as Blank 4)50 11.47 25.62 0.08 0.08 0.10 0.09 0.37 -0.11 -0.11 -0.10 -0.10 -0.41HClO4 acid blank (run during same analytical session as Blank 4)50 13.10 22.48 0.10 0.09 0.10 0.10 0.38 -0.10 -0.11 -0.09 -0.08 -0.34Blank 7 (A-type skimmer)2 4.10 -0.90 -0.01 -0.01 0.02 0.00 0.00 -0.02 -0.03 0.01 -0.02 -0.0810 6.34 8.18 0.05 0.04 0.05 0.05 0.19 -0.11 -0.10 -0.09 -0.09 -0.3650 10.25 17.09 0.06 0.06 0.04 0.06 0.24 -0.15 -0.15 -0.16 -0.15 -0.60Change in ion-signal (%) Sample-standard bracketing External normalization with sample-standard bracketing166Appendix D Column matrix effects on Zn and Cu ion-signal intensities and delta Zn values. Table includes values shown in Fig. 2.1. SampleRun #64Zn63Cuδ66/64ZnSSB/ amuδ67/64ZnSSB/ amuδ68/64ZnSSB/ amuδ68/66ZnSSB/ amuδ66/64ZnSSBδ66/64ZnCu-corr./ amuδ67/64ZnCu-corr./ amuδ68/64ZnCu-corr./ amuδ68/66ZnCu-corr./ amuδ66/64ZnCu-corr.Blank 10.2 8.86 3.14 -0.02 0.02 -0.02 -0.01 -0.04 -0.14 -0.10 -0.14 -0.13 -0.282 16.28 9.62 0.01 0.05 0.01 0.02 0.01 -0.28 -0.24 -0.27 -0.25 -0.5610 25.98 25.56 0.10 0.13 0.10 0.11 0.20 -0.16 -0.12 -0.15 -0.14 -0.3350 26.20 31.87 0.10 0.22 0.14 0.18 0.21 -0.24 -0.12 -0.19 -0.15 -0.49Blank 250 14.98 25.06 0.15 0.42 0.27 0.39 0.30 -0.12 0.16 0.00 0.12 -0.24Blank 3 (fluxed HNO3 treatment; run during same analytical session as Blank 1)2 10.73 12.61 0.05 0.05 0.04 0.04 0.10 -0.03 -0.03 -0.03 -0.03 -0.0610 -16.23 21.73 0.10 0.17 0.12 0.13 0.20 0.01 0.07 0.02 0.03 0.0150 -10.30 28.17 0.02 0.29 0.10 0.17 0.05 0.04 0.29 0.11 0.18 0.08Blank 4 (HClO4 treatment; run during same analytical session as Blank 1)2 10.28 11.22 0.04 0.05 0.04 0.04 0.08 -0.20 -0.19 -0.20 -0.20 -0.4010 18.34 25.64 0.04 0.08 0.05 0.06 0.08 -0.22 -0.18 -0.21 -0.20 -0.4450 -13.56 35.66 0.05 0.29 0.13 0.21 0.10 -0.20 0.04 -0.12 -0.05 -0.40Blank 5 (HClO4 treatment; run during same analytical session as Blank 2-not shown in Fig. 2.2)50 3.07 15.92 0.09 0.37 0.22 0.34 0.18 -0.14 0.14 -0.03 0.11 -0.28Change in ion-signal (%) Sample-standard bracketing External normalization with sample-standard bracketing167Appendix E Inorganic column-derived matrix effects on Cd and Ag ion-signal intensities and delta Cd values. Table includes values given in the Results section.Sample Run #110Cd109Agδ111/110CdSSB/amuδ112/110CdSSB/amuδ113/110CdSSB/amuδ114/110CdSSB/amuδ114/110CdSSBδ111/110CdAg-corr./ amuδ112/110CdAg-corr./ amuδ113/110CdAg-corr./ amuδ114/110CdAg-corr./ amuδ114/110CdAg-corr.   Mg-doped1 4.66 4.53 -0.08 -0.04 -0.04 -0.04 -0.17 -0.02 0.00 0.01 0.00 0.002 6.78 6.20 -0.09 -0.07 -0.05 -0.05 -0.22 -0.03 -0.01 0.01 0.01 0.033 10.29 14.87 -0.04 -0.03 -0.03 -0.03 -0.11 -0.01 -0.01 0.00 0.00 0.00Mock Col Inorg 1 8.58 9.46 0.00 -0.03 -0.03 -0.03 -0.12 0.08 0.06 0.06 0.06 0.242 12.93 13.98 0.03 0.04 0.00 0.01 0.06 0.10 0.12 0.07 0.09 0.373 11.26 15.74 0.00 -0.04 0.00 -0.01 -0.02 -0.06 -0.07 -0.07 -0.07 -0.264 8.55 14.77 0.14 0.12 0.11 0.12 0.47 0.04 0.02 0.01 0.03 0.10Change in ion-signal (%) Sample-standard bracketing External normalization with sample-standard bracketing168Appendix F Matrix effects from metallic elements on Cd and Ag ion-signal intensities and delta Cd values. Table includes values shown in Figs. 2.2(a) and 2.4(a).Doping ElementVolume (%)110Cd109Agδ111/110CdSSB/amuδ112/110CdSSB/ amuδ113/110CdSSB/ amuδ114/110CdSSB/ amuδ114/110CdSSBδ111/110CdAg-corr./ amuδ112/110CdAg-corr./ amuδ113/110CdAg-corr./ amuδ114/110CdAg-corr./ amuδ114/110CdAg-corr.   Al1 -24.12 9.14 0.16 0.18 0.19 0.19 0.76 -0.13 -0.12 -0.12 -0.11 -0.452 -22.30 12.67 -0.19 -0.17 -0.18 -0.17 -0.69 -0.30 -0.30 -0.31 -0.31 -1.223 -23.86 10.34 -0.10 -0.07 -0.07 -0.07 -0.28 -0.26 -0.24 -0.23 -0.23 -0.934 -9.58 17.56 -0.26 -0.24 -0.22 -0.23 -0.92 -0.39 -0.37 -0.36 -0.36 -1.44Zn11 5.46 12.12 -0.10 -0.09 -0.09 -0.09 -0.35 -0.17 -0.17 -0.16 -0.17 -0.672 3.92 10.48 -0.10 -0.10 -0.10 -0.09 -0.37 -0.14 -0.13 -0.13 -0.12 -0.483 2.18 27.62 -0.10 -0.08 -0.08 -0.08 -0.32 -0.19 -0.17 -0.18 -0.17 -0.684 2.50 11.70 -0.12 -0.09 -0.09 -0.08 -0.32 -0.19 -0.16 -0.16 -0.15 -0.59Rb1 -1.55 8.12 -1.91 -1.93 -1.98 -1.96 -7.84 -0.35 -0.37 -0.43 -0.43 -1.702 7.12 16.36 -0.17 -0.16 -0.18 -0.17 -0.67 -0.07 -0.06 -0.07 -0.07 -0.27Sr1 -10.72 35.48 -0.26 -0.29 -0.31 -0.31 -1.25 0.10 0.08 0.06 0.06 0.222 4.48 -3.40 -0.21 -0.20 -0.17 -0.19 -0.76 -0.06 -0.05 -0.03 -0.04 -0.163 11.09 26.55 -0.30 -0.32 -0.31 -0.33 -1.33 0.11 0.09 0.10 0.08 0.32Cs1 1.03 12.94 -2.23 -2.20 -2.30 -2.23 -8.92 -0.33 -0.35 -0.43 -0.40 -1.602 2.73 12.88 -0.62 -0.64 -0.66 -0.65 -2.58 -0.15 -0.18 -0.19 -0.18 -0.713 17.57 33.18 -0.22 -0.22 -0.21 -0.20 -0.82 -0.19 -0.19 -0.18 -0.18 -0.724 -6.74 -1.09 -0.04 -0.06 -0.07 -0.07 -0.27 -0.08 -0.09 -0.09 -0.09 -0.38Ba1 8.87 14.73 -0.71 -0.73 -0.73 -0.74 -2.95 -0.25 -0.28 -0.27 -0.29 -1.172 2.00 8.45 -0.47 -0.46 -0.47 -0.47 -1.89 -0.35 -0.34 -0.34 -0.35 -1.403 7.29 12.24 -0.15 -0.15 -0.15 -0.15 -0.58 -0.16 -0.17 -0.17 -0.16 -0.66Lu1 15.98 13.48 -0.19 -0.23 -0.20 -0.21 -0.85 -0.10 -0.16 -0.14 -0.15 -0.582 -1.01 53.37 -0.07 -0.09 -0.08 -0.08 -0.32 -0.22 -0.22 -0.21 -0.21 -0.853 11.64 -8.59 0.03 0.03 0.02 0.01 0.05 0.02 0.01 0.01 -0.01 -0.034 8.77 -7.64 -0.06 -0.10 -0.14 -0.12 -0.48 0.01 -0.02 -0.03 -0.03 -0.10Ir1 0.71 4.66 0.32 0.37 0.38 0.38 1.53 -0.24 -0.21 -0.20 -0.19 -0.76Pb1 8.22 10.63 -0.39 -0.41 -0.40 -0.40 -1.62 -0.10 -0.11 -0.11 -0.11 -0.432 5.21 1.03 0.12 0.11 0.09 0.10 0.40 0.02 0.02 0.03 0.02 0.07mass 110 and that this contributes -0.03‰ to the observed δ114/110CdSSB = -0.32‰. Assuming that the zinc argides are present roughly in proportion to the isotopic abundances of Zn, then the  ZnAr+ contribution on 107Ag would be approximately 0.316 mV on a 3.676206 V beam. Fractionation correction using f(Ag) results in δ114/110CdAg-corr. = -0.59‰, removing the 67Zn40Ar+ contribution on 107Ag results in δ114/110CdAg-corr. = -0.72‰.Change in ion-signal (%) Sample-standard bracketing External normalization with sample-standard bracketing1Based on comparison of the delta values of 114/110Cd with interference free ratio 114/111Cd, it is estimated that the contribution of ZnAr+ on mass 110 is 0.046 mV for a run with 1.593724 V on 169Appendix G Matrix effects from metallic elements on Zn and Cu ion-signal intensities and delta Zn values. Table includes values shown in Figs. 2.3(b) and 2.4(b).Doping ElementRun #64Zn63Cuδ66/64ZnSSB/ amuδ67/64ZnSSB/ amuδ68/64ZnSSB/ amuδ68/66ZnSSB/ amuδ66/64ZnSSBδ66/64ZnCu-corr./ amuδ67/64ZnCu-corr./ amuδ68/64ZnCu-corr./ amuδ68/66ZnCu-corr./ amuδ66/64ZnCu-corr.Al11 0.92 12.66 -0.28 -0.01 -0.27 -0.26 -0.57 -0.33 -0.05 -0.31 -0.30 -0.652 -2.68 14.46 -0.34 0.14 -0.33 -0.33 -0.68 -0.56 -0.08 -0.55 -0.54 -1.12Ca1 4.60 6.50 -0.32 -0.33 -0.33 -0.34 -0.65 -0.73 -0.74 -0.73 -0.72 -1.462 3.12 0.31 -0.27 -0.26 -0.26 -0.26 -0.54 -0.72 -0.69 -0.70 -0.69 -1.44Sr21 6.90 4.30 -4.73 -3.21 -2.46 -0.18 -9.46 -3.27 -1.77 -1.02 1.24 -6.542 10.68 13.26 -5.69 -3.86 -2.96 -0.23 -11.37 -4.46 -2.63 -1.75 0.98 -8.93Cd1 4.56 0.92 -0.24 -0.24 -0.25 -0.25 -0.48 -0.72 -0.71 -0.71 -0.71 -1.432 4.82 -0.89 -0.23 -0.24 -0.24 -0.24 -0.46 -0.75 -0.75 -0.75 -0.74 -1.50Ba31 4.85 3.48 6.10 693.04 371.31 727.64 12.21 -15.29 629.08 320.61 677.21 -30.582 8.91 9.81 5.19 616.32 330.01 648.07 10.38 -12.89 566.46 289.81 608.17 -25.77Pb1 4.00 -2.73 -0.14 -0.15 -0.14 -0.14 -0.29 -0.51 -0.51 -0.50 -0.49 -1.022 3.26 -3.30 -0.03 -0.04 -0.02 -0.01 -0.05 -0.65 -0.66 -0.63 -0.62 -1.301Changes in the calculated delta value for 67Zn/64Zn are in part due to the formation of AlAr+ (m/z = 67).2Changes in the intensities of 63Cu and 64Zn and the calculated delta values are in part due to the formation of SrAr2+ (m/z = 63, 64).3Changes in the calculated delta values are in part due to the formation of significant Ba2+ (m/z = 65, 66, 67, 68). Change in ion-signal (%) Sample-standard bracketing External normalization with sample-standard bracketing170-1.00-0.80-0.60-0.40-0.200.00-0.30 -0.25 -0.20 -0.15 -0.10 -0.05 0.00d114Cd/110Cd (‰)d111Cd/110Cd (‰)Appendix H Plot of d114/110Cd vs. d111/110Cd for B.C. oyster soft tissues and gut contents. The error bars denote 2 standard deviation (2SD) on the mean dCd value for replicate analyses of each sample.B.C. mainland oysters Vancouver Island oystersRedonda Bay:soft tissuesgut contentsPoett Nook:soft tissuesgut contentssoft tissuesgut contentsEffingham Inlet:171Appendix I Method for the measurement of Cd isotopes in environmentaland geological samples.These methods are appropriate for the preparation of biological, environmental andgeological samples for Cd isotope MC-ICP-MS analysis. Small modifications to theprocedure will be necessitated by differences between sample materials.1. Sample preparation:a. Homogenize sample material. For B.C. oyster samples, homogenization isaccomplished by processing tissues in a commercial blender equipped with anacid-washed polycarbonate container and a stainless steel blade.b. Dry sample material in a drying oven or freeze-dryer.c. Weigh out dry sample material into digestion vessels.d. Digest sample material using closed-vessel hot-plate techniques or microwavedigestion. For dried and powdered bivalve tissue samples, 100–600 mgsample is weighed out into Savillex PFA vials. Closed-vessel digestion iscarried out on a hotplate using successive steps of HNO3 and HNO3+H2O2. Todetermine the appropriate amount of sample material to be digested andloaded onto anion exchange chromatography columns the following must beconsidered: i. The quantity of analyte needed for the MC-ICP-MS isotopic analysisand trace element concentration determination. To avoid non-spectralmatrix effects related to the presence of resin-derived organics andinorganic elements, sufficient quantities of sample material need to beloaded on the column so that no more than 20% of the Cd eluate cut isin the analyzed solution. ii. The column capacity for the analyte and matrix elements.e. Isolation of the analyte, i.e., Cd. The anion exchange chromatographyprocedure is given in Appendix B. The digested sample is loaded in 7 M HClafter being centrifuged to ensure undigested material is removed. Smallvolumes of the eluent (e.g., 2 mL) are loaded on the column to reduce the flow172rate of the solvent through the column and achieve better chromatographicseparations. In addition, eluent volumes larger than those listed in Appendix Bare used in some cases to ensure that the matrix elements and analytes areproperly separated. For bivalve tissue samples, where [Zn]>>[Cd], ~16 mL ofthe eluent 0.1 M HBr+0.5 M HNO3 is added 2 mL at a time, to ensure ~100%of the Zn is eluted before eluting the Cd and minimizing the quantity of Znfound in the Cd eluate cut. Cadmium is typically eluted using 14–16 mL of0.5 M HNO3 to ensure ~100% Cd recovery.f. Cadmium eluate cuts were dried dry in Savillex PFA vials. Dried eluate cutsare treated with HNO3+H2O2, close-vessel digested overnight in an effort todigest any resin-derived organics and then dried again, driving off any tracesof eluent acids (i.e., trace HCl, HF or HBr) and redissolved in 1 mL of 0.05 MHNO3 in preparation for isotopic analysis.2. Isotope analysis:a. Isotope ratios are measured by multi-collection on a Nu Plasma MC-ICP-MS(Nu 021; Nu Instruments, UK) using the DSN-100 (Nu Instruments, UK)membrane desolvator for sample introduction.b. The standard dry plasma cones (type B; Nu Instruments, UK) are used.c. A standard SSB measurement protocol is followed, where samples are runalternately with standards.d. The Cd isotope measurement method was adapted from Wombacher et al.(2003) and consists of a dynamic run with main and interference cycles thatenable collection of masses 106 to 118 (isotopes of Cd, Ag and Sn).Correction of the Sn interference on 112Cd, 114Cd and 116Cd is enabled bymeasurement of 118Sn. An analysis comprises 2 blocks of 15 × 5 s integrationswith a 20 s ESA deflected baseline before each block.e. Each sample is measured at least three times during at least two analyticalsessions. Each analytical session is preceded by the measurement of (1) azero-delta, by back-to-back analysis of the PCIGR-1 Cd standard (batch run of≥7 runs, often run overnight), and (2) the PCIGR-2 Cd standard (n≥3). The173PCIGR-2 Cd standard is measured several more times during the analyticalsession, typically as every fourth sample.f. The presence of matrix elements in analyzed solutions is routinely monitoredto ensure any spectral and non-spectral matrix effects are minimal. Particularattention is paid to potential isobaric interferences on isotopes of the analyteof singly and doubly charged elements and polyatomic species. Analyzed Cdsolutions are monitored for ZnAr+ by measuring the intensity at mass 104(64Zn40Ar+; 64Zn is the most abundant Zn isotope).ReferencesWombacher, F., Rehkämper, M., Mezger, K., Munker, C. (2003) Stable isotopecompositions of cadmium in geological materials and meteorites determined bymultiple-collector ICPMS. Geochimica et Cosmochimica Acta 67: 4639–4654.174Appendix J Stanley Park treesIntroductionStanley Park was established in 1888 and is the largest and most visited park inVancouver, B.C. Windstorms during the winter of 2006–2007 resulted in the loss of morethan 10,000 trees (between 5 and 10% of all trees) in Stanley Park. Three fallen treesfrom Stanley Park were sampled in order to reconstruct the history of Pb pollution for theVancouver area. Lead isotope ratios of the annual growth rings of these trees will be usedto identify the sources of atmospheric lead through time.Sample selectionAlyssa E. Shiel obtained permission for the sampling of fallen trees in StanleyPark from Jim Lowden and Yuna Flewin. Trees were selected for sampling by Alyssa E.Shiel with the assistance of Paul Lawson (Forest Manager, Malcolm Knapp ResearchForest, UBC) on April 11, 2007. Samples were selected from the north side of StanleyPark near Prospect Point (Appendix K), which suffered moderate to severe forest damageduring the 2006–2007 winter storms. Three trees were selected for sampling: (1) aWestern Hemlock, (2) a Douglas Fir (located closest to Prospect Point, adjacent to aparking lot) and (3) a Western Red Cedar. Cookie samples (Appendix L) were takenusing chainsaws, April 12 and 13, 2007, by park staff (Eric Meagher, Supervisor, StanleyPark Maintenance). Samples were picked up from the park and transported to UBC onApril 13, 2007 and left to dry (exposed to rainwater and hosed off at the park prior topick up). Photographs of the fallen trees in Stanley Park and of sample selection areshown in Appendix M.Sample preparation and analytical methodsCookie samples of each tree were quartered and then cut down to manageablesizes (core samples) using a band saw (Appendix M) with the help of Dr. Kyu-YoungKang (Department of Forestry, UBC). Core samples were scanned to create a digitalrecord of each before processing. Tree-ring counting was used to determine the age ofeach tree and was accomplished by direct observation and using the digital images. Tree-175rings of the Western Hemlock (tree 1) and the Western Red Cedar (tree 3) were formedbetween 1881 and 2006 (over 125 years) and between 1801 and 2006 (over 205 years),respectively. Photographs of sample preparation are shown in Appendix M.The core was separated into tree-ring samples, representing between one and nineyears (depending on the size of the individual rings), using a stainless steel knife.Samples were blown off with N2 gas, transferred to pre-weighed vials (cleaned withCitranox® detergent and 1 M HCl, analytical grade), freeze-dried and weighed. Selectedsamples were transferred to savillex® vials and then close-vessel digested on a hotplateusing successive treatments of HNO3 and HNO3+H2O2. An aliquot of each sample wasset aside for Pb concentration determination. Sample Pb was isolated from the remainingsample by anion exchange chromatography using the AG 1-X8 (100–200 mesh) resin(Bio-Rad Laboratories, Inc.).Experimental work was carried out in metal-free Class 1,000 clean laboratories atthe Pacific Centre for Isotopic and Geochemical Research (PCIGR), University of BritishColumbia (UBC). Sample preparation for elemental and isotopic analyses was performedin Class 100 laminar flow hoods in the clean labs and instrument rooms. Elementalanalysis was carried out on an ELEMENT2 (Thermo Finnigan, Germany) high-resolutioninductively coupled plasma mass spectrometer (HR-ICP-MS). The trace element analysismethod and instrument set-up are described in Section 2.2.4.1. Isotopic analysis wasperformed on a Nu Plasma (Nu 021; Nu Instruments, UK) multi-collector inductivelycoupled plasma mass spectrometer (MC-ICP-MS). The isotopic analysis method for Pb isdescribed in Section 3.2.5.2.2.ResultsPreliminary results for the Western Hemlock (tree 1) and the Western Red Cedar(tree 3) are in Appendices N and O. Lead concentration data needs to be interrupted withcaution as growth rate of the tree-rings can influence the concentration of elements in thewood. Neighboring trees should display similar radial (i.e., across the tree-rings) patternsin Pb concentration and isotopic composition. Differences observed between the temporalrecords in Pb isotopic composition (Appendices N and O) of the Western Hemlock (tree1) and the Western Red Cedar (tree 3) may be attributed to the movement of Pb in a176radial direction. Further study is needed to determine if the temporal record of Pbpollution is preserved in the annual tree-rings of the three sampled Stanley Park trees.Recommendations for future work1. Combust tree-ring samples prior to digestion.2. Compare temporal trends recorded in the tree-rings of the Douglas Fir (tree 2)with the results for the Western Hemlock (tree 1) and the Western Red Cedar(tree 3).3. Compare the Pb distribution patterns recorded in several radial cores of thesame tree sample.4. Calculate Pb enrichment factors in the tree-rings by measuring the ratio of Pband a lithogenic element (e.g., Sc).  Critically evaluate the significance oftrends in Pb enrichment factors and [Pb].177Stanley ParkBurrard InletBeaver LakeLions Gate BridgeCoal HarbourLost LagoonEnglish BayStanley Park CausewayProspect PointN500 m123Appendix K Stanley Park trees, sampling locations of three trees are indicated by green stars and identified as tree 1 (Western Hemlock), tree 2 (Douglas Fir) and tree 3 (Western Red Cedar).178Appendix L Stanley Park trees, core sampling of the fallen trees. Fallen trees (a) were sampled first as cookies or disks (b). These cookie samples (b) were then quatered (c). A straight cut was made across each of the cookie quarters (c) creating boards (d). These boards (d) were then cut into strips (e), where each strip (e) is the equivalent of a core, which samples across the tree rings.(a)(b) (c) (d) (e)179Appendix M Stanley Park trees, photographs of fallen trees, sample selection and preparation.180Appendix N Stanley Park trees, Pb concentrations and isotopic compositions of tree-ring samples.[Pb] ppma Western Red Cedar (tree 3)1917 1920 0.02 17.7462 49 15.5333 45 37.544 14 1.14252 6 2.11575 111928 1932 17.8309 19 15.5477 14 37.600 4 1.14687 2 2.10872 61936 1940 0.04 17.8766 20 15.5480 19 37.640 5 1.14972 3 2.10558 71950 1953 0.07 17.7624 9 15.5506 11 37.512 3 1.14227 2 2.11179 51964 1972 17.7375 7 15.5501 7 37.499 2 1.14065 1 2.11408 41979 1984 2.3 17.6517 8 15.5452 7 37.406 2 1.13550 1 2.11909 41991 1994 5.7 17.6856 8 15.5480 7 37.444 2 1.13748 1 2.11723 32002 2006 0.27 17.7180 7 15.5506 6 37.481 2 1.13936 1 2.11546 3Western Hemlock (tree 1)1930 1933 17.4911 7 15.5434 8 37.255 2 1.12528 1 2.12997 41949 1953 17.5624 8 15.5426 7 37.325 2 1.12994 1 2.12535 31960 1963 17.5616 8 15.5412 9 37.324 2 1.12998 1 2.12536 31971 1971 17.5453 6 15.5436 7 37.325 2 1.12878 2 2.12738 41972 1972 17.5834 6 15.5492 7 37.370 4 1.13085 2 2.12518 41980 1981 17.6153 7 15.5538 7 37.392 2 1.13253 2 2.12270 41990 1990 17.6029 13 15.5505 13 37.382 3 1.13193 3 2.12369 41991 1991 17.6114 8 15.5537 7 37.396 2 1.13229 1 2.12341 42002 2006 17.7279 45 15.5601 45 37.532 10 1.13922 5 2.11707 4aPb concentrations were measured for a subset of samples.bRatios are reported as the mean ± 2 standard error (SE). Reported error values are the ten-thousandth (206Pb/204Pb, 207Pb/204Pb), thousandth (208Pb/204Pb) or hundred-thousandth (206Pb/207Pb, 208Pb/206Pb) decimal digit.cAll data have been normalized to the NIST SRM 981 triple spike Pb ratios of Galer and Abouchami, 1998.206Pb/207Pb  2SEb,c 208Pb/206Pb  2SEb,cTree-ring years206Pb/204Pb  2SEb,c 207Pb/204Pb 2SEb,c 208Pb/204Pb  2SEb,c181206Pb/207PbTree-ring yearAppendix O Stanley Park trees, Pb concentrations and 206Pb/207Pb values for tree-ring samples. For tree-ring year, (youngest tree-ring year + oldest tree-ring year) /2 is plotted. The error (2SE) on the 206Pb/207Pb value is smaller than the symbol size.2.1002.1052.1102.1152.1202.1252.1302.1351910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010Western Hemlock (Tree 1)Western Red Cedar (Tree 3)206Pb/207PbTree-ring year2.1002.1052.1102.1152.1202.1252.1302.1351910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010Western Red Cedar (Tree 3)0125643Pb concentration (mg g-1)206Pb/207PbPb concentration182

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