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Apatite in a glacial lake Reid, Ruth Pamela 1979

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APATITE IN A GLACIAL LAKE by RUTH PAMELA RE ID B.Sc. Queen's University, 1972 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES Department of Geological Science We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA Apri l , 1979 © Ruth Pamela Reid, 1979 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of Geological Sciences The University of British Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1W5 Date April 12, 1979 i i ABSTRACT Apatite is a common accessory mineral in the source rocks for the glacial debris supplying recent sediments to many Canadian lakes. Chemical analyses of sediments in Kamloops Lake, British Columbia suggest that this apatite may comprise a significant portion of the total phosphorus load to the lake, thereby overestimating the trophic state that would be predicted by the relationship between total phosphorus load and the ratio of mean depth to flushing time. A method has been developed which uses scanning electron microscopy and energy dispersive X-ray spectrometry for direct identification of apatite. This method has been used to examine the apatite content of various size fractions in Kamloops Lake sediments. Apatite concentrations obtained by this direct examination correlate well with the apatite concentrations of the indirect chemical analyses and indicate that, in addition to comprising as much as 70% of the total phosphorus load, apatite may comprise as much as 20% of the "dissolved" (<0.45 urn) inorganic phosphorus load. Therefore, estimates of lake productivity could be erroneous even if dissolved rather than total phosphorus values are used for the estimation. CONTENTS PAGE Abstract i i Contents i i i List of Figures iv List of Tables v Acknowledgements vi Introduction 1 Methods Physical Separation, Identification and Quantification of Apatite 8 Selective Chemical Extraction of Apatite 12 Analytical Results Physical Separation 13 Chemical Extraction 18 Conclusions 25 References 27 Appendix 1. Size Separation of Silt Particles 30 Appendix 2. Procedure for Heavy Liquid Separation of Apatite . . . 31 Appendix 3. The Apatite Fraction: S.E.M. Sample Preparation and Examination 35 Appendix 4. Data from Heavy Liquid Separation 36 Appendix 5. Data from S.E.M. Examination 38 Appendix 6. Observed Apatite Concentrations 40 Appendix 7. Contribution of Apatite to the "Dissolved" Phosphorus i v LIST OF FIGURES PAGE Figure 1. The Vollenweider Relationship 2 Figure 2. Location Map; Kamloops Lake, B.C 4 Figure 3. The Selective Chemical Extraction of Inorganic Phosphorus 4 Figure 4. Heavy Liquid Separation of Apatite 9 Figure 5. S.E.M. X-ray Identification of Phosphate Grains 9 Figure 6. Particle Size Distribution, Total Sample 14 Figure 7. Particle Size Distribution, Individual Size Fractions . . 14 Figure 8. Typical Kamloops Lake Apatites 15 Figure 9. X-ray Emission Spectrum of Apatite 15 Figure 10. 0.45 ym Apatite and Monazite 19 Figure 11. X-ray Emission Spectrum of Monazite 19 Figure 12. Correlation between Apatite Concentrations from Chemical Extraction and Physical Separation 23 Figure 13. Apatite Concentration vs. Grain Size 24 LIST OF TABLES PAGE Table 1. Apatite Concentrations from Physical Separation 17 Table 2a. Extraction of Apatite Standards 20 Table 2b. Extraction of Apatite from Spiked Sediment Samples 20 Table 3. Extraction of Apatite from Kamloops Lake Sediments 22 Table 2-1. Centrifligation Times 34 Table 4-1. Data from Heavy Liquid Separation 37 Table 5-1. Data from S.E.M. Examination 39 Table 6-1. Observed Apatite Concentrations 41 vi ACKNOWLEDGEMENTS The author gratefully acknowledges both the technical assistance and personal support given throughout this project by thesis supervisor Dr. W.C. Barnes. Discussions of techniques with Dr. M.A. Barnes and Dr. L.M. Lavkulich were very useful. The author would like to thank Dr. C.H. Pharo for the suggestion of the research topic and Dr. C.H. Pharo, C.B.J. Gray, R. Kirkland and V. Chamberlain at the National Water Research Institute, West Vancouver for stimulating discussion of phosphorus extraction techniques. Chemical extractions of apatite and particle size analyses for this study were performed by R. Kirkland and V. Chamberlain at N.W.R.I. Field assistance in sample collection was provided by Dr. C.H. Pharo and V. Chamberlain. Laboratory expenses for the project were met by National Science and Engineering Research Council Grant A-7027 held by Dr. W.C. Barnes. The author was supported throughout the project by a National Research Council Postgraduate Scholarship (1976-1978) and a Gulf Oil Graduate Fellowship (1978-1979). The manuscript was improved by the suggestions of Dr. C.H. Pharo and Dr. W.C. Barnes. 1 INTRODUCTION Phosphorus is often the limiting nutrient controlling organic growth in aquatic systems in temperate zones (Gakstatter et al_., 1975). Vollenweider (1968) and Vollenweider and Dillon (1974) have developed an empirical rela-tionship for lakes which relates annual total phosphorus load, mean depth and flushing time to the trophic state, or productivity of the lake. This rela-tionship, seen in Figure 1, has been used in North America and in Europe as a guide to the degree of eutrophication of lakes and to permissible loading levels (Dillon and Kirchner, 1975; Yeasted and Morel, 1978). Recent investigations of forms of phosphorus in lake sediments have shown that a Targe portion of the total phosphorus in some lakes is present as apatite (Williams and Mayer, 1972; St. John et aj_., 1976). The most abun-dant form of primary apatite in nature is fluorapatite [CastPO^F] (Williams et aj_.,1976, Deer et aj_., 1966) and since the solubility of fluorapatite in lake water is extremely low, it is unlikely to be more than a minor source of phosphorus for biological growth. This conclusion is supported by Sagher and Harris (1972), Sagher et al_. (1975), Syers et a l . (1973), and Wil 1 iams et a]_. (1976). Sagher and Harris (1972) and Sagher et al_. (1975) investigated the availability of sediment phosphorus and concluded that the non-occluded Fe-bound phosphorus was the most available form of sediment phosphorus, whereas the apatite phosphorus was of limited availability. Syers et al_. (1973, p.8) conclude that Ca-P (apatite) in lake water is "essentially immobile". Williams et a l . (1976) comment that a high input of apatite-P to Lake Erie prior to 1850 did not render the lake eutrophic. However, Smith et aj_. (1978) have shown that naturally occurring apatites may provide a source of orthophosphate for growth of bacteria and algae. At present, the question 2 10. -i 1 — i — i i i 111 1 1—i—i—i i i i i 1 i i i i i i 11 1967/70 "1 1 1—l I I I I I a. 1.0 cr (3 Z D g CO 0,1 EUTROPHIC KOOTENAY 1960/64 0 ERIE ONTARIO c »-r - O V* 1940 OKANAGAN'' . £ ~ WOOI HURON 5 ^ # 5 OLIGOTROPHIC ,01' 1 1 — i — i i i i 11 1 i i i i i i 11 i i i ' ' 'iti i ' i i i i 11 1 1 10 100 1000 z / t w = qs • Figure 1. The relationship (Vollenweider,1968) between trophic state, annual total phosphorus load, mean depth (z) and flushing time ( t w ) shown for some Canadian lakes. Kamloops Lake is not plotted due to the difficulties discussed in the text, (from St. John et a l . 1976) 3 of how much phosphorus detrital apatite contributes to the nutrient budget of a lake remains controversial. If apatite phosphorus is largely unavailable for biological growth (or of very limited availability), it should not be included in the total phos-phorus loading values used to estimate trophic state. This problem was recognized by Dillon and Kirchner (1975), Peters (1978), and Vollenweider himself (Vollenweider, 1968). Dillon and Kirchner (1975, p. 143) summarized as follows: "However there will undoubtedly be certain cases where total phosphorus is not the most suitable fraction to work with; for example, some streams may carry a high total phosphorus content that is largely the result of erosion of apatite-bearing rock. In these cases, soluble phosphorus may be biologically a more important consideration. Such a condition exists in the Rhine as described by Vollenweider (1968)." Fluorapatite is a common accessory mineral in the source rocks for the glacial debris supplying sediments to many Canadian lakes. Kamloops Lake, the subject of the present study, is a 25 km x 2.1 km fjord lake which oc-cupies a glacial valley in the semi-arid, south-central region of British Columbia (Figure 2). Chemical analyses of water and sediment in the lake im-ply that 70% of the total phosphorus entering the lake is in the form of apa-tite and that apatite may occur in all size fractions of the lake sediment (St. John et j}].., 1976). This latter suggestion is significant, for if apa-tite is present in the lake as particles smaller than 0.45 pm, apatite par-ticles could pass through the membrane filters used to separate "dissolved" from "particulate" materials and be included in the "dissolved" phosphorus 4 depth >120m i . . . . i • • i • i 0 5 10 k m Figure 2. Sample location in Kamloops Lake, British Columbia, Canada. Sediment 0.5 g Residue Residue Res 1 M NaOH 0.5 M HCI Extract due discarded 0.22 M Na CITRATE 0.11 M Na BICARBONATE 1.0 g Na DITHIONITE Extract 1 Extract (Colourimetric \ Determination/ APATITE P NON-APATITE INORGANIC P Figure 3. The selective chemical extraction scheme for identification of apatite phosphorus and Non-Apatite Inorganic Phosphorus developed by Williams et al_. (1976). N.W.R.I. used 1M HCI, rather than 0.5M HCI, to extract apatite phosphorus from Kamloops Lake sediments, as discussed in text. 5 pool. Therefore, estimates of productivity could be erroneous even if dis-solved rather than total phosphorus values are used for the estimation, as suggested by Dillon and Kirchner (1975). Both Williams et aj_. (1976) and Smith et al_. (1978) state that the solubility of apatite increases with de-creasing particle size, but no estimates have been made of the availability of phosphorus in apatite that is smaller than 0.45 pm. The method used to identify apatite in the 1976 Kamloops Lake study was the selective chemical extraction technique of Wil 1 iams et a]_. (1976) (Figure 3). In this procedure, sodium dithionite-sodium citrate-sodium bicarbonate (DCB) and NaOH release phosphorus associated with iron and aluminum com-plexes. The amount of orthophosphate released is determined colourimetrical-ly in a reaction involving the formation of molybdophosphoric acid. The sum of the DCB and NaOH phosphorus is referred to by Williams et a l . (1976) as Non-Apatite Inorganic Phosphorus (NAIP). Apatite phosphorus is then released as orthophosphate by dissolution of the apatite in 0.5 M HC1, and the ortho-phosphate is again measured colourimetrically. There are, however, problems associated with specificity of the colourimetric method for analysis of orthophosphate (Harwood and Hattingh, 1973). Complexes of silicate, arsenate and germanate can form heteropoly acids with molybdenum and interfere with the phosphorus determination. Labile organic phosphorus compounds may also interfere. In general, the chemical extraction technique for identifying forms of phosphorus in soils and sediments has developed as a result of ex-tracting standard compounds in the laboratory and from statistical chemical correlations (Fisher and Thomas, 1935; Williams, 1937; Dean, 1938; Williams, 1950; Chang and Jackson, 1957; Williams et 1967; Williams et a l . , 1971a; Williams et al_., 1971b). 6 Direct methods for identifying and quantifying phosphate minerals in soils and sediments have met with limited success because of the small quantities of these minerals and because of difficulties in petrographic determination (Lindsay and Vlek, 1977). Shipp and Matelski (1960) developed a technique whereby 2 to 3 drops of 10.7 N H 2 S O 4 added to sediment on a glass slide caused needle-like calcium sulphate crystals to grow on the surface of apatite grains, thereby facilitating their recognition. In the presence of H 2 S O 4 however, carbonate minerals also develop this needle-like growth and differentiation of the carbonates from the apatites is based on a difference in birefringence. Shipp and Matelski (1960) used this method to quantify apatite in a soil profile in Nebraska and correlated the results with the acid soluble phosphorus in a profile in an "adjacent quarter of the same section". The correlation would be more convincing i f the measurements were made on samples from the same locality. Sawhney (1973) used the electron microprobe to examine the composition of phosphate grains, but his work is not quantitative. Kingston (1973, p.l) examined the "feasibility of detecting and quantitatively estimating phosphate minerals in lacustrine sediments by mineralogical methods". Kingston concentrated phosphate grains by heavy liquid and magnetic separations and suggested that the microprobe could be used effectively to obtain particle size distribution, relative abundance, and mineralogy of discrete phosphate grains. However, Kingston's method is not quantitative. The purpose of the present study was to develop a method of physical separation, identification and quantification of apatite in lake sediments and to use this method to investigate the size distribution of apatite in Kamloops Lake. The apatite concentrations of various size fractions of Kamloops Lake sediment obtained by this method of direct observation would be 7 compared to the apatite concentrations obtained by the selective chemical extraction of the same size fractions. In addition, an attempt would be made to estimate the amount of apatite which may be contributing to the "dissolved" phosphorus load of the lake. 8 METHODS Physical Separation, Identification and Quantification of Apatite A sample of sediment was collected with a Shipek Grab Sampler from the basin floor of Kamloops Lake at a depth of 130 m in the pro-delta region of the Thompson River Delta at the east end of the lake (Figure 2). The particle size distribution of the total sediment was determined by hydrometer analysis. The sample was divided into eight size fractions from 125 ym to <2 urn. The 125 to 62 urn fraction was obtained by sieving, the five fractions between 62 and 10 urn by separation in a hydraulic cyclone elutriator (see Appendix 1) and the 10 to 2 and <2 ym fractions by centrifugation. Sedigraph analyses of the 6 fractions from 62 to 2 pm were performed by the National Water Research Institute, (formerly the Canada Centre for Inland Waters) West Vancouver. Each of the eight size fractions was further subdivided on the basis of density by separation with heavy liquids. As seen in Figure 4, 250 mg of sediment were centrifuged in 50 ml of diiodomethane to remove the particles with density >3.3 g.cm"3. The light particles from this separation were then centrifuged in 50 ml of an acetone diiodomethane mixture with a density of 3.05 g.cm"3. Apatite was concentrated in the heavy fraction, which will be referred to as the apatite fraction and contains minerals with densities between 3.05 and 3.3 g.cm~3. The theoretical density of fluorapatite is 3.199 g.cnr^ (McConnell, 1973); however, isomorphous substitutions in naturally occurring "fluorapatites" result in a range of densities from 3.1 to 3.2 g.cm"3 (Berry and Mason, 1959). Densities of some igneous apatites reported by McConnell (1973) range from 3.17 3.22 g.cm"3. S e d i m e n t 1.5 kq r T 1 t r 125-52 62-4 5 4 5 3 3 33-25 25-17 17-10 "I " r - r ^ — n ' ^ r r 10-2 treated similarly 250 rr.fi C H 2 I 2 3.3 • g c m" treated similarly I L i g h t ' ] 3. Heavy C H 2 I 2 3.0 5 gcrr f 3 1 [Tight Heavy| / Inc lud ing \ A P A T I T E i: 2 50 mg C H 2 I 2 g e m - 3 j Heavy / I n c l u d i n g x APATITE & VF^ONAZITE Figure 4. Scheme for heavy liquid separation of apatite. Figure 5. Identification of phosphate grains using a scanning electr microscope equipped with an energy dispersive X-ray spectrometer. Bar in (A) and (B) is 500 uin long. (A) S.E.M. image. Apatite grains are circled. (B) Phosphorus Ka image. 10 The separation procedure described above was followed for all size fractions of the Kamloops Lake sediment except the <2 ym fraction. Because of the very long centrifugation times required for separation of the <2 ym fraction, only the 3.05 g.cm"^ separation was done. A detailed description of the separation procedure is presented in Appendix 2. Triplicate or quadruplicate heavy liquid separations of the 5 size fractions from 62 to 10 ym were performed; single separations were done for the other 3 size fractions. A subsample of each apatite fraction obtained by the heavy liquid separation was mounted on a graphite disc and examined at low magnification with an ETEC autoscan scanning electron microscope equipped with an ORTEC X-ray analytical system. The procedure for the S.E.M. sample preparation and examination is outlined in Appendix 3. Grains in the apatite fraction which contain phosphorus are easily identified in the X-ray image of the phosphorus K a emission, as shown in Figure 5. Once identified, the phosphorus-containing grains may be examined individually at increased magnification and their elemental compositions determined from their X-ray emission spectra. Since the grains in each sample are approximately equivalent in size and density, the number of grains containing phosphorus divided by the total number of grains in any one S.E.M. ' f ie ld' , such as that of Figure 5, is a measure of weight per cent apatite in that particular apatite fraction. For each apatite fraction, five fields, each containing approximately 100 to 200 grains, were examined. The five apatite concentrations from the five fields were averaged to obtain a value representing the apatite concentration in the apatite fraction. This number was multiplied by the weight proportion of sample represented by the apatite fraction to obtain a measure of the concentration of apatite in the original size fraction. 11 Since the heavy liquid separation of fine-grained sediment may be incomplete, a weighed amount of fluorapatite of appropriate size was added to each of the five size fractions from 62 to 10 ym as an internal standard ("spike") to test the recovery of apatite in the apatite fraction. The apatite used for this internal standard was a single inclusion-free crystal of fluorapatite from Durango, Mexico (Sample S-4024, obtained from J . Nagel, U . B . C ) . The apatite crystal was crushed and separated into the five size fractions by gravity settling and decantation. As in the unspiked samples for these 5 size fractions, triplicate or quadruplicate analyses (heavy liquid separation and S.E.M. examination) of the 5 spiked fractions were performed. As seen in equation 1, K 0b, the mean concentration of apatite observed in the spiked sample should be equal to a recovery factor, p, times the amount of apatite added (I) plus p times the apatite in the original sediment (M). However, since p times the apatite in the original sediment is equal to M0b» the mean value observed for apatite in the unspiked sample (equation 2), the two equations can be combined to solve for p. K0b = Pi + pM (1) But pM = M o b (2) l<ob -M0b , , so p = (3) I Analysis of apatite from Durango, Mexico which were performed by the U.S.G.S. are reported by Young et aj_. (1969). The density of the apatite analyzed by Young et al_. (1969) was 3.216 g.cm - 3 . 12 Selective Chemical Extraction of Apatite Selective chemical extractions of apatite for this study were performed by the National Water Research Institute, West Vancouver. N.W.R.I. modified the extraction scheme of Williams et aj_. (1976), Figure 3, in that 1 M HCI, rather than 0.5 M HCI, was used for the apatite extraction. Initial verification of the technique using apatite standards was followed by extraction of seven of the size fractions of Kamloops Lake sediments. Verification of the selective chemical extraction technique involved extraction of an apatite standard, extraction of sediment with apatite added as an internal standard, and S.E.M. examination of the extracted sediment. The apatite used as the standard was the same crushed fluorapatite from the single crystal from Durango, Mexico which was used in the physical separation spiking procedure. Analyses of apatite from Durango by Young et al_. (1969) suggest that impurities in the apatite are less than 1.5 weight per cent and that phosphorus comprises 17.8 weight per cent of the apatite. 13 ANALYTICAL RESULTS Physical Separation Particle size distributions for the total sample and for 6 size fractions are shown in Figures 6 and 7. The weights of each of the three density fractions obtained by heavy liquid separation of each size fraction are summarized in Appendix 4, and the results of point counting apatite grains in the apatite fraction with the scanning electron microscope are summarized in Appendix 5. Four typical phosphorus-containing grains identified in Kamloops Lake sediment are shown in Figure 8. The phosphorus-containing grains observed in all size fractions, with one exception which will be discussed later, contained both Ca and P in proportions equivalent to those observed in an apatite standard. Some grains have X-ray emission spectra indicating the additional presence of minor amounts of Al , Si , and/or Fe, which are probably present as coatings on the apatite as the grains were not treated to remove sesquioxides. The numbers of grains with these coatings increased slightly in the <10 ym sizes. A typical X-ray emission spectrum for the phosphorus-containing grains is shown in Figure 9. The X-ray energy from fluorine is not detected by the X-ray emission method used. The observed apatite concentrations calculated for each sample are reported in Appendix 6. Observation with the scanning electron microscope showed that the "125 to 62 ym" fraction contains a large proportion of grains smaller than 62 ym. When point counting grains in the apatite fraction of this size fraction, only grains of approximate size 125 to 62 ym were counted. 14 100-O 8 0 o CI 0. 6 0 -a 3 40 E 3 o 101 - ' , , , 1—,—, , , 1 2 10 17 2 3 3 3 45 62 10 0 Equivalent Spher ica l Diameter, jum Figure 6. Hydrometer analysis showing particle size distribution of sediment from the pro-delta region of Kamloops Lake. 100-§ 8 0 -o 0. 6 0 -V > 3 4 0 -E 3 o 2 0 -D C B A 2 10 17 25 3 3 tS 62 10 0 Equivalent Spherical Diameter, um Figure 7. Sedigraph analyses showing particle size distribution of 6 size separated fractions of sediment from Kamloops Lake. Analyses performed at N.W.R.I. A = "62 to 45 ym" fraction B = "45 to 33 ym" fraction C = "33 to 25 ym" fraction D = "25 to 17 ym" fraction E = "17 to 10 ym" fraction F = "10 to 2 ym" fraction 15 16 Heavy liquid separation and S.E.M. examination of the five size fractions of both unspiked and spiked samples from 62 to 10 urn were performed in triplicate or quadruplicate. The observed apatite concentrations calculated for these repeated analyses (Appendix 6) were averaged to obtain a mean observed apatite concentration for each of the five fractions. These mean concentrations (Mo^  and K0h) are summarized in Table 1. The relative standard error of each mean observed apatite concentration is generally about 5%. This error reflects differences between subsamples and variability in estimates of the weight per cent apatite in the apatite fraction. The mean observed apatite concentration, M0b, of the unspiked sample represents the amount of apatite in the size fraction if the heavy liquid separation of apatite is 100% complete. However, complete separation of fine-grained sediments is unlikely and the means of the spiked and unspiked samples for each size fraction were substituted in equation 3 to calculate the recovery factor, p. The observed apatite concentrations of the 5 unspiked samples were then corrected for incomplete separation in order to estimate the amount of apatite in the original size fraction (M, Table 1). Recovery of apatite in the apatite fraction (p, Table 1) is seen to decrease with decreasing grain size. The relative standard errors of the recoveries, and consequently of the corrected apatite concentrations (M), are about 20%. However, the minimum apatite concentration for any size fraction is that observed in the unspiked fraction (Mq^). No attempt was made to quantify the apatite in the <2 ym fraction by point counting phosphorus-containing grains. Detection of phosphorus-containing grains smaller than 1 ym by X-ray spectrometry is extremely difficult since there is very l i t t l e X-ray emission from these tiny grains. 17 TABLE 1 Apatite Concentrations from Physical Separation Method Sample 125-62 v m 62-45 iim 45-33 ym 33-25 urn 25-17 vm 17-10 pm 10-2 urn "ob -1 ng.g 1180 (single observation) 7080±320 4600±180 3430±130 3260±240 2220*200 1030 (single observation) Kob, wg.g-' U430±590 7280±530 6220±210 5350*610 3790±150 ug.g-4616 2795 3401 2699 2264 0.94±.15 0.96+.20 0.82±.07 0.77±.24 0.69*.11 ug.g-' 7500*1400 4800*1100 4200±500 4200±1500 3200*500 Note: Numbers are not rounded to 2 significant figures until the final calculation (H). H0jj« Mean observed apatite concentration of unspiked sample (from Appendix 6), ± the standard error of the mean. ^ob° e^an observed apatite concentration of spiked sample (from Appendix 6), ± the standard error of the mean. I» Amount of apatite added as an Internal standard. p» Recovery factor, calculated using equation 3 in text, ± the calculated standard error. M* Apatite concentration in the size fraction, corrected for Incomplete recovery of apatite 1n the apatite fraction, * the standard error. H « M0t>/P 18 Since only a 3.05 g.cm"3 density separation was attempted for this fraction, the apatite in the <2 ym fraction was less concentrated than in the apatite fractions for the other grain sizes. Two phosphorus-containing grains from the <2 ym fraction which have dimensions approaching 0.45 ym are shown in Figure 10. Monazite is a cerium, lanthanum phosphate with small amounts of thorium and yttrium. Calcium substitutes in minor amounts for Ce and La. The X-ray emission spectrum of a monazite grain is shown in Figure 11. Monazite has a density of 4.6 to 5.5 g.cm"^ and so would not be included in the apatite fraction (3.05 to 3.3 g.cm"3) of the other sizes. Monazite, like apatite, is an accessory mineral in igneous and metamorphic rocks and, again like apatite, has an extremely low solubility and is unlikely to be an important source of biologically available phosphate. Chemical Extraction The results of the chemical extraction of apatite standards are presented in Tables 2a and 2b. The phosphorus content of the apatite standard was assumed to be 17.8%, as measured in fluorapatite from the same locality by Young et a l . (1969). Errors involved in weighing the apatite are less than 0.5%. Recoveries of pure apatite ranged from 86 to 97%, with 2 to 5% of the apatite being extracted as Non-Apatite Inorganic Phosphorus (see Table 2a). Theoretical recoveries of apatite in the spiked sediment ranged from 75 to 102% (see Table 2b). However, the standard error of the mean sediment apatite extract values is about 3%, and the theoretical recoveries of the apatite added may be exaggerated by errors in the spiked and unspiked values. A spiked and an unspiked sample of 62 to 45 ym sediment from 19 15 Figure 10. Apatite and monazite grains with dimensions approaching 0.45 ym are circled. Bar in (A) and (B) is 0.45 ym long, (A) Apatite (B) Monazite i i h o O to O 't.... -f H -t 1 I 1 I I 10 15 Energy,keV Figure l l . X-ray emission spectrum for Kamloops Lake monazite. 20 TABLE 2a Extraction of an Apatite Standard Apatite Size Initial Wt. ug P NAIP-P ug P NAIP-P x 100 Initial Ht.P Apat1te-P Apatlte-P x 100 ug Initial Wt.P All sizes 2081 10-2 um 2183 25-17 urn 2096 33-25 uM 2580 105 51 85 41 Not extracted 54 21 1800 2100 2000 2500 861 961 951 971 TABLE 2b Extraction of Apatite from Spiked Sediment Samples Recovery of Apatite Spike Sample U I S (Assumes 31 error In Unspiked Sample Amt. Ap. Added Spiked Sample S and U) (vg ap-P).(g sed.)"1 (ug ap-P).(g sed.)"1 (ug ap-P).(9 sed.)"1 M x 100 KT Gen 1A 549 143 696 102I±18I (AP) KT Gen 1A 549 148 660 751±181 (AP+IP+OP) (CAM 62-45 um 1293 821 2017 881±91 (AP) 21 Kamloops Lake were separated with heavy liquids (as above) after being extracted for apatite and NAIP and were examined with the scanning electron microscope. No apatite grains were observed in the apatite fraction, indicating that all of the apatite was dissolved in the extraction. In general, the Williams et aQ_. (1976) technique of selective chemical chemical extraction of apatite seems to be >85% effective in recovering a fluorapatite standard. WiIdung et aj_. (1977) found that the Williams method generally gave recoveries of >90% of inorganic phosphorus added to lake sediments. The results of the apatite extractions of the seven size fractions of Kamloops Lake sediment are summarized in Table 3. The concentration of apatite is the concentration of apatite-phosphorus divided by 0.18, since the weight per cent of phosphorus in apatite is approximately 18%. The apatite concentrations indicated by chemical extraction are plotted against those of the physical separation in Figure 12. The two methods give similar results (within 7%) for the five size fractions from 62 to 10 pm. The 10 to 2 pm point count value is considerably lower than the extraction value since this sample was not spiked to estimate recovery of apatite in the apatite fraction. Since the point count value for the 10 to 2 pm sediment has not been corrected for incomplete separation and is too low, the chemical extraction numbers are plotted in Figure 13 to estimate the concentration of apatite in sediment smaller than 0.45 pm. Extrapolation of the extraction data suggests that this concentration may be as high as 1800 pg apatite per gram sediment. Therefore, apatite smaller than 0.45 pm probably contributes to the "dissolved" phosphorus load in Kamloops Lake. Data are not available to calculate how much this apatite is contributing to the "dissolved" load, but estimates (see Appendix 7) suggest that it is about 20%. TABLE 3 Extraction of Apatite from Kamloops Lake Sediments Sample Mean Cone. Ap.-P t Std.Error Mean Apatite Cone. ± Std.Error pg.g pg.g T 62-45 urn 1293±13 7180±72 45-33 pm 912±57 5070±318 33-25 pm 738*19 4100±105 25-17 pm 756±19 4200±105 17-10 pm 607±11 3370±61 10-2 pm 571±23 3170±128 <2 pm 352±26 1960*144 23 c .2 800CH o 00 62-45xjm >< UJ E o sz O 6000-45-33 ;jm»y 4000-C0 o c o o o CO < 25-17ijnV y/%3-25 urn 10-2 aim 17X10 ijm 20 0 0-20'00 40'0 0 60'0 0 8000 Apatite cone, ojg-g - 1 Physical Separation Figure 12. Correlation between apatite concentrations obtained by chemical extraction and by physical separation. Dashed line equals 100 per cent correlation. 24 .2 sooo-o 6 0 0 0 -r -O 4 0 0 0 4 cn o o o o 2C0O-0.45 10 62 G r a i n S i z e mr\ F igure 13. A p a t i t e c o n c e n t r a t i o n (by chemical e x t r a c t i o n ) versus g r a i n s i z e . 25 CONCLUSIONS A method has been developed which shows that the concentrations of apatite obtained by indirect chemical extraction of phosphorus in Kamloops Lake sediments are comparable to the values obtained by direct physical observation. The method developed is time consuming, tedious, and expensive, and is not recommended as a general procedure for evaluating concentrations of apatite in sediments. Rather it is a method which could be used to verify "apatite" concentrations from chemical extractions, and could, of course, be used for identification of other minerals as well. The scanning electron microscope with energy dispersive X-ray spectrometer has proven to be extremely useful and may be more versatile than the electron microprobe used in previous phosphate studies (eg., Kingston 1973) since it is capable of scanning at lower magnifications than most microprobes. The general technique of using an internal standard to test the recovery of a mineral in heavy liquid separation was also an important part of this study. The apatite which has been observed in the sediments of Kamloops Lake accounts for a significant portion (approximately 70%, St. John et aj_., 1976) of the phosphorus in the total phosphorus load to the lake. In 1953, Kurtz summarized the use of total phosphorus measurements in soil science as fol 1 ows: "Except for research studies, determinations of total phosphorus in soils have been made rarely in recent years, since total phosphorus is generally recognized as of l i t t le value in assessing the phosphorus fert i l i ty of a soil." (Kurtz, 1953, p.61). 26 Total phosphorus measurements in lakes receiving sediment from glaciated igneous and metamorphic terrains are similarly likely to be of l i t t le value in assessing the "phosphorus fertility" of a lake. The results of this study indicate that apatite smaller than 0.45 ym may be abundant in Kamloops Lake, comprising as much as 20% of the "dissolved" phosphorus load. The biological availability of phosphorus in apatite grains smaller than 0.45 ym requires investigation. REFERENCES 27 Berry, L.G. and B. Mason. 1959. Mineralogy. W.H. Freeman and Co., San Francisco, p.453-55. Chang, S.C. and M.L. Jackson. 1957. Fractionation of soil phosphorus. Soil Sci . 84:133-143 Cyclosizer, Operating Manual. 34p. Dean, L.A. 1938. An attempted fractionation of the soil phosphorus. J . of Agricultural Sci . 28:234-246 Deer, W.A., R.A. Howie and J . Zussman. 1966. An introduction to the rock forming minerals. Longman, London, p.504-509. Dillon, P .J . and W.B. Kirchner. 1975. The effects of geology and land use on the export of phosphorus from watersheds. Water Research 9:135-148 Fisher, R.A. and R.P. Thomas. 1935. The determination of the forms of inorganic phosphorus in soils. J . of the Am. Soc. of Agronomy 27:863-873 Gakstatter, J . H . , M.O. Allum and J.M. Omernik. 1975. Lake eutrophication: results from the national eutrophication survey. Corvallis Environmental Research Laboratory, USEPA, Corvallis, Oregon. 32p. Harwood, J . E . and W.H.J. Hattingh. 1973. Colorimetric methods of analysis of phosphorous at low concentrations in water. _In Environmental Phosphorus Handbook. John Wiley and Sons. p.289-339. Jackson, M.L. 1956. Soil chemical analysis - advanced course. (Fifth Printing 1969) Published by the author, Dept. of Soil Sc i . , University of Wisconsin, Madison, Wisconsin, p.101-168. Kelsal l , D .F . , C . J . Restarick and P.S.B. Stewart. 1974. Technical note on an improved cyclosizing technique. Proc. Australas. Inst. Min. Metall. No. 251. p.9-10. Kingston, P.W. 1973. (unpubl.) Phosphate minerals in lacustrine sediments. Report of Contract No. KW111-2-0686/5-03-3040-101-0432 to Dep. Environ., Can. Cent. Inland Waters. 40p. Kurtz, L .T . 1953. Inorganic phosphorus in acid and neutral soils. Agronomy 4: 59-88 Lindsay, W.L. and P.L.G. Vlek. 1977. Phosphate minerals. J_n Minerals in Soil Environments. Soil Sci . Soc. Am. Inc. p.639-672. McConnell, D. 1973. Apatite. Springer-Verlag, New York. l l l p . Peters, R.H. 1978. Concentrations and kinetics of phosphorus fractions in water from streams entering Lake Mepmhremagog. J. Fish. Kes. Board Can. ' 35:315-328. 28 Sagher, A . and R . F . H a r r i s . 1972. M i c r o b i a l a v a i l a b i l i t y of phosphorus i n lake sediments. Abstracts of 15th conf . on Great Lakes Research, p.193 • Sagher, A . , R . F . Har r i s and D . E . Armstrong. 1975. A v a i l a b i l i t y . o f sediment phosphorus to microorganisms. Mater Resources Center, Un ive r s i t y of Wisconsin Technical Report WIS WRC 75-01. 57p. Sawhney, B . L . 1973. E l e c t i o n microprobe analys is of phosphates in s o i l s and sediments. S o i l S c i . Soc. Am. Proc . 37:658-660. Shipp, R . F . and R . P . M a t e l s k i . 1960. A microscopic determination of apa t i t e and a study of phosphorus i n some Nebraska s o i l p r o f i l e s . S o i l S c i . Soc. Am. P r o c . 24:450-452. Smith, E . A . , C . I . Mayf ie ld and P . T . S . Wong. 1978. Na tu ra l ly occurr ing apa t i t e as a source of orthophosphate for growth of bac ter ia and a lgae. M i c r o b i a l E c o l . 4:104-117. S t . John, B . E . , E . C . Carmack, R . J . Daley, C . B . J . Gray, and C H . Pharo. 1976. The limnology of Kamloops Lake, B . C . Dep. E n v i r o n . , Inland Waters D i r e c t o r a t e , P a c i f i c and Yukon Region, Vancouver, Canada. 167p. Syers , J . K . , R . F . Har r i s and D . E . Armstrong. 1973. Phosphate chemistry in lake sediments. J . Env i ron . Q u a l i t y 2:1-14. Vol lenweider , R . A . 1968. S c i e n t i f i c fundamentals of the eut rophica t ion of lakes and f lowing waters, wi th p a r t i c u l a r reference to nitrogen and phosphorus as factors in eu t roph ica t ion . Par i s Tech. Rep. 0ECD, DAS/SCI/68.27. 192p. Vol lenweider , R . A . and P . J . D i l l o n . 1974. The app l i ca t ion of the phosphorus loading concept to eu t rophica t ion research. National Research Council Associa ted Committee on S c i e n t i f i c C r i t e r i a for Environmental Q u a l i t y , NRCC#13690. 42p. Wildung, R . E . , R . L . Schmidt and R . C . Routson. 1977. The phosphorus status of eutrophic lake sediments as re la ted to changes in l imnolog ica l condi t ions - phosphorus mineral components. J . Envi ron . Qua l i ty 6:100-104. W i l l i a m s , C H . 1950. Studies "on S o i l Phosphorus I . A method for the p a r t i a l f r a c t i o n a t i o n of s o i l phosphorus. J . of A g r i c u l t u r a l S c i . 40:233-242. W i l l i a m s , R.W. 1937. The s o l u b i l i t y of s o i l phosphorus and other phosphorus compounds in sodium hydroxide s o l u t i o n s . J . of A g r i c u l t u r a l S c i . 27:259-270. W i l l i a m s , J . D . H . and T . Mayer. 1972. Effects of sediment diagenesis and regeneration of phosphorus wi th spec ia l reference to Lakes E r i e and O n t a r i o . _In H . E . A l l e n and J . R . Kramer Ced . ] , Nutrients i n Natural . Waters, Wi ley - In t e r sc i ence , New.York. p.281-315. W i l l i a m s , J .D .H . . , J . K . Syers and T.W. Walker. 1967. F rac t i ona t ion of s o i l inorganic phosphate by a mod i f i ca t ion of Chang and Jackson's procedure. S o i l S c i . Soc. Am. P roc . 31:736-739. 29 Williams, J .D.H. , J.K. Syers, S.S. Shukla and R.F. Harris. 1971b. Levels of inorganic and total phosphorus in lake sediments as related to other sediment parameters. Environ. Sci. Technol. 5:1113-1120. Williams, J .D.H. , J.M. Jaquet and R.L. Thomas. 1976. Forms of phosphorus in the surficial sediments of Lake Erie. J . Fish. Res. Board Can. 33:413-429. Yeasted, J.G. and F.M.M. Morel. 1978. Empirical insights into lake response to nutrient loadings with application to models of phosphorus in lakes. Environ. Sci. Technol. 12:195-201. Young, E . J . , A.T. Myers, E .L . Munson and N.M. Conklin. 1969. Mineralogy and geochemistry of fluorapatite from Cerro de Mercado, Durango, Mexico. U.S.G.S. Prof. Paper 650-D. p.85-93. 30 APPENDIX 1. Size Separation of Silt Particles The Cyclosizer is a hydraulic cyclone elutriator which separates sediment into five specific size fractions from 62 urn to 10 pm. The elutriation action takes place in a hydraulic cyclone where the fluid is spinning and centrifugal forces many times those due to gravity are acting on the particles (Cyclosizer, Operating Manual). In a comparatively short time (15 - 20 min.) the Cyclosizer is capable of yielding highly reproducible sub-sieve size divisions of sediment. Material rejected by the fifth cyclone (approximately 10 pm quartz) normally passes to waste (Kelsall et a l . , 1974). If this <10 pm material is needed for study, it may be decanted and collected before the cyclosizing procedure. Approximately 430 grams of Kamloops Lake sediment from 62 to 10 pm were separated in the cyclosizer. Before cyclosizing, the >62 pm fraction was removed by sieving and the <10 pm fraction by settling and decantation. Thirty gram subsample.s of the sediment were cyclosized for 15 minutes, with a water temperature of 11°C and a flow rate of 180 cm3.sec"1. 31 APPENDIX 2. Procedure for Heavy Liquid Separation of Apatite. For grain sizes from 62 to 2 ym, the following procedure was followed: 1. Shake a dry sediment sample in a Spex Mixer for 20 minutes to homogenize. 2. Add 0.25 g sediment to a Pyrex 50 ml conical centrifuge tube. 3. Add 5 ml of acetone, which has been dried with anhydrous magnesium sulphate, to the sediment in the tube. Disperse the sediment in the acetone by hand swirling in an ultra sonic bath. Centrifuge and decant the acetone. Discard the used acetone. This step replaces water adsorbed onto grains with acetone, which is miscible with diiodomethane. 4. Add 50 ml of diiodomethane (density 3.32 g.cm"3) to the tube. Centrifuge for the appropriate time (Table 2-1). Stir the light fraction from this separation with a thin glass rod to allow any heavy minerals to free themselves and settle. Centrifuge again. 5. Freeze the heavy fraction (density >3.3 g.cm"3) in the centrifuge tube by placing the lower half of the tube in liquid nitrogen. Decant the light fraction (density <3.3 g.cm"3) into a second 50 ml Pyrex conical centrifuge tube which contains 5 ml of dried acetone. 6. Thaw the >3.3 g.cm - 3 fraction. Disperse this fraction in the diiodomethane remaining in the tube and recentrifuge. Refreeze the heavy fraction and add the light fraction from this separation to the light fraction of Step 5. Save the heavy fraction. 7. F i l l the second centrifuge tube (Step 5) to 47 ml with diiodomethane. This tube now contains 5 ml acetone (density 0.7899 g.cm - 3), plus 42 ml diiodomethane (density 3.32 g.cm -3) so that the solution has a density 3.05 g.cm"3. Centrifuge for the appropriate time. Stir the light fraction and recentrifuge. The heavy minerals from this separation have 32 densities between 3.05 g.cm"3 and 3.3 g.cm"3. This is the "apatite fraction". The lights have densities <3.05 g.cm - 3. 8. Collect the 3 fractions (the >3.3 g.cm - 3 fraction from step 6, and the apatite fraction and the <3.05 g.cm"3 fraction from step 7) on preweighed 5.5 cm f i l ter paper by vacuum filtration using a 47 mm Millipore 300 ml Pyrex funnel with stainless screen f i l ter support. Freeze the apatite fraction in the bottom of the tube with liquid nitrogen while the <3.05 g.cm - 3 fraction is decanted. Use acetone to wash the diiodomethane from the sediment and f i l ter paper. For grain sizes > 10 urn, use Whatman No. 1 Filter paper; for grain sizes between 2 and 10 pm use Whatman No. 42 f i l ter paper. Preweigh the f i lter papers on a Mettler H20 balance. 9. Allow the f i l ter papers and sediments to dry and then weigh on a Mettler H20 balance. The time elapsed between preweighing the paper and weighing the paper plus sediment should be kept to a minimum since humidity changes in the laboratory may significantly affect the weight of the f i l ter paper. For grain sizes <2 pm, only the 3.05 g.cm"3 separation is performed. The procedure is as follows: 1. Steps 1, 2, 3 as above. 2. Add 5 ml of fresh dry acetone to the sediment from Step 3 and f i l l the tube to 47 ml with diiodomethane. Centrifuge, stir the light fraction and recentrifuge. 3. Collect the 2 fractions (>3.05 g.cm - 3 and <3.05 g.cm - 3). The <3.05 g.cm"3 fraction is collected on Whatman No. 42 f i l ter paper and is washed with acetone. However, this f i l ter paper has a pore size of 1 to 2 pm and some sediment may pass through the paper. Therefore, the >3.05 33 g.crrr3 fraction (in this case, the "apatite fraction") is collected on a preweighed 0.01 urn cellulose acetate membrane f i l ter . Since this f i l ter is soluble in acetone, the diiodomethane is first decanted from the apatite fraction and 20 ml of acetone are added to the centrifuge tube. The sediment is dispersed in the acetone and is then centrifuged. The acetone is decanted and water is added. The water-sediment mixture is filtered through the 0.01 pm membrane f i l ter paper to collect the apatite fraction. The weight of the apatite fraction may be determined but no quantitative S.E.M. point counting of apatite is possible for this size fraction. 34 TABLE 2-1 Centrifugation Times for Settling Apatite in Diiodomethane or Diiodomethane-acetone Mixture, as in Appendix 2. IEC International Centrifuge, #240 Head Minimum Particle Size Centrifuge Speed Centrifugation Time RPM Calculated Recommended 25 pm 900 0.86 min 2 min 17 ura 900 1.87 m1n 4 min 10 ura 900 5.39 min 10 m1n 2 im 1500 48.00 m1n 1 hr 40 min 0.2 ura 1500 75 nr. NOTE: Calculated centrifugation times, based on Stokes law, are given by Jackson (1956, p.127) as follows: (63.0 x 1Q8) (log 1 0 R/S) (n)  t m 1 n " ' (Nm)2 (Du)2 Us) where tg,in " time 1n minutes n • viscosity 1n poises at the existing temperature (.028 for diiodomethane at 20°C) R • radius of rotation (In cm) of the top of the sediment 1n the tube (23cm for 50 ml centrifuge tube) S • radius of rotation (In cm) of the surface of the suspension in the tube (13cm for 50 ml centrifuge tube) N,,, » centrifuge speed in rotations per minute. D g • particle diameter 1n microns is • difference 1n specific gravity between the particle and the suspension liquid (approximately 0.1 for both diiodomethane and di iodomethane-acetone mixture)-Recoirmended centrifugation times are generous to allow settling of apatites with specific gravities from 3.1 - 3.25. 35 APPENDIX 3. The Apatite Fraction: S.E.M. Sample Preparation and Examination. The amount of apatite in the apatite fraction of the heavy liquid separation is determined by point counting apatite grains in this fraction with a scanning electron microscope equipped with an energy dispersive X-ray spectrometer. The sample preparation and method of examination is described below. 1. Cut a pie shaped wedge (approximately one eighth of the f i l ter paper) from the paper on which the apatite fraction of the separated sediment has been collected. 2. Water wash the sediment from this wedge onto a 0.45 ym cellulose acetate membrane f i l ter supported by the 13 mm diameter stainless steel screen of a Millipore Vacuum filtration apparatus. Disperse the sediment evenly on the f i l ter paper. 3. Allow the 13 mm fi l ter paper and sediment to dry and then use double sided paper tape to mount the paper on a circular carbon button (diameter 13 mm, thickness 5 mm). 4. Apply a carbon coat (approximately 25 nm) to the f i l ter paper and sample. 5. Examine the sample with an ETEC autoscan scanning electron microscope with an ORTEC X-ray analytical system. Set the "region of interest" at 1.96 - 2.06 keV. Scan 5 fields, each containing 100 to 200 grains, in the north, south, east, west and middle of each button. The number of apatite grains in each field divided by the total number of grains in the field and multiplied by 100 gives an estimate of the weight per cent apatite in the apatite fraction. Average the weights per cent apatite for the five fields to obtain a single estimate of the weight percent apatite in the apatite fraction. 36 APPENDIX 4. Data from Heavy Liquid Separation. The weights of each density fraction obtained by heavy liquid separation of each size fraction are summarized in Table 4-1. In general, 2 to 3% sediment loss occurred during the separation procedure. The weight per cent of each sample which is represented by the apatite fraction is calculated by dividing the weight of the apatite fraction by the sum of the weights of the three density fractions. This calculation assumes that the sediment loss from each density fraction during separation is proportional to the weight of the fraction. In sample 33-25 ym (subsamples 1,2 and 3), the <3.05 g.cm"3 separations spilt before being weighed, and the total0sediment separated (E) was obtained by assuming a 2% loss during separation. 37 TABLE 4-1 Data From Heavy Liquid Separation Sample A Initial Wt.(g) Wt.<3.05g.ccT3 Fraetlon(g) Wt.>3.3g.cm"3 Fraction(g) Wt.apatite Fraction(g) Wt.Total Sed. Sep.(g) (B + C + 0) % Loss or Gain E-A x 100 A  Wt.* Apatite Fraction D x 100 E  125-62 pm 0.25831 0.24542 0.00294 0.00643 0.25479 -1.4 2.52 62-45 pm 1 2 3 0.25181 0.25385 0.25718 0.20006 0.21569 0.20070 0.02240 0.01996 0.02190 0.01955 0.02052 0.02157 0.24201 0.25617 0.24417 -3.9 +0.9 -5.1 8.08 8.01 8.83 62-45 pm (Spiked) 1 2 3 0.24360 0.21864 0.23004 0.20188 0.17861 0.18932 0.02095 0.01720 0.01843 0.02169 0.01800 0.01932 0.24452 0.21381 0.22707 +0.4 -2.2 -1.3 8.87 8.42 8.51 45-33 pm 1 2 3 4 0.25165 0.24928 0.26193 0.24674 0.21149 0.21761 0.23069 0.21643 0.01367 0.01034 0.01005 0.01093 0.01506 0.01819 0.01562 0.01502 0.24022 0.24614 0.25636 0.24238 -4.5 -1.3 -2.1 -1.8 6.27 7.39 6.09 6.20 45-33 pm (Spiked) 1 2 3 0.18169 0.25467 0.24560 0.15554 0.21766 0.21169 0.00812 0.01048 0.01006 0.01239 0.01722 0.01591 0.17605 0.24536 0.23766 -3.1 -3.7 -3.2 7.04 7.02 6.69 33-25 pm 1 2 3 4 0.24666 0.24901 0.24501 0.22805 spilt spilt spilt 0.19959 0.01049 0.00966 0.01005 0.01030 0.01612 0.01547 0.01401 0.01671 0.24173 0.24402 0.24010 0.22660 -2 assumed -2 assumed -2 assumed -0.6 6.67 6.34 5.84 7.37 33-25 pm (Spiked) 1 2 3 4 0.25940 0.24479 0.25472 0.24575 0.22401 0.21716 0.22796 0.21839 0.00910 0.01014 0.00657 0.00869 0.01702 0.01318 0.01345 0.01361 0.25013 0.24048 0.24798 0.24069 -3.6 -1.8 -2.6 -2.1 6.80 5.48 5.42 5.65 25-17 pm 1 2 3 0.23664 0.24425 0.25687 0.20550 0.21264' 0.22090 0.01067 0.00949 0.00927 0.01561 0.01843 0.01809 0.23178 0.24056 0.24826 -2.1. -1.5 -3.4 6.73 7.66 7.29 25-17 pm (Spiked) 1 2 3 0.22912 0.25073 0.24885 0.19873 0.22064 0.21342 0.01079 0.01241 0.01017 0.01756 0.01422 0.01643 0.22708 0.24727 0.24002 -0.9 -1.4 -3.5 7.73 5.75 6.85 17-10 pm 1 2 3 0.25598 0.25542 0.26694 0.23392 0.23531 0.23938 0.00959 0.00967 0.00818 0.01012 0.00972 0.00945 0.25363 0.25470 0.25701 -0.9 -0.3 -3.7 3.99 3.82 3.68 17-10 pm (Spiked) 1 2 3 0.26723 0.25574 0.26782 0.24192 0.23114 0.25131 0.00899 0.00944 0.00915 0.01155 0.01019 0.00827 0.26246 0.25077 0.26873 -1.8 -1.9 +0.3 4.40 4.06 3.08 10-2 pm <2 urn 0.25204 0.25299 0.24294 0.22744 0.00260 0.01028 0.0O257 0.25582 0.23001 +1.5 -9.1 4.02 1.12 38 APPENDIX 5. Data from S.E.M. Examination For each apatite fraction, five independent fields each containing 100-200 grains were examined with the scanning electron microscope, in the north, west, south, east and middle of each button (except for one sample in the 17-10 pm size fraction and 3 samples in the spiked 17-10 pm size fraction in which only 4 independent fields were examined). For each field, a measure of the weight per cent apatite in the apatite fraction is obtained by dividing the number of apatite grains observed by the total numbers of grains in the field. The 5 results are averaged to obtain a mean weight per cent apatite for each separation. The results are summarized in Table 5-1. The weight per cent apatite numbers for each of the five fields are uncertain in the first decimal place and therefore the average of these five numbers is accurate only to the first decimal place. Data in Table 5-1 are reported to two decimal places but the final calculations obtained using these numbers are rounded to two significant figures (see Table 1). TABLE 5-1 Data From S.E.M. Examination Sample North Wt. % Apatite 1n Apatite Fraction West South East Middle Mean 125-62 ym 62-45 62-45 nm (Spiked) 1 2 3 45-33 vm la lb 2 3 4a 4b 45-33 wm (Spiked) 1 2 3 33-25 um 1 2 3 4 33-25 ym (Spiked) 1 2 3 4 25-17 ym 1 2 3 25-17 ym (Spiked) 1 2 3 17-10 ym 1 2 3 17-10 ym (Spiked) 1 2 . 3a 3b 10-2 um 4.03 7.75 12.23 8.49 11.77 12.00 14.75 4.22 10.19 4.07 5.62 6.08 5.67 12.14 10.35 7.69 3.37 5.18 4.73 5.71 9.73 13.42 9.20 12.27 2.45 4.58 2.91 5.53 7.01 6.38 4.49 4.52 5.89 8.92 9.66 16.05 10.53 4.17 5.56 6.96 10.86 6.59 13.73 15.65 12.77 8.08 6.11 4.00 10.42 3.76 9.48 11.06 11.96 8.76 5.88 6.31 5.21 6.28 7.64 9.09 11.65 11.98 7.46 4.73 6.79 9.96 5.56 9.85 4.94 6.10 5.09 9.15 9.60 13.48 9.80 2.16 4.92 10.38 6.82 9.35 11.77 14.27 11.77 8.81 8.33 10.07 5.70 6.25 7.87 8.33 12.37 10.19 6.79 4.45 4.87 3.14 12.50 9.38 15.04 10.71 7.14 2.96 1.65 9.90 10.43 7.98 12.50 4.88 3.72 7.61 7.74 14.78 11.39 1.52 5.61 7.47 6.55 8.41 7.14 11.61 15.91 3.33 10.97 7.79 11.36 5.17 8.73 9.52 10.97 10.44 5.45 5.23 6.79 5.28 9.47 12.11 13.74 7.27 6.59 4.08 4.79 5.21 9.55 2.75 5.48 7.64 3.97 8.00 8.38 18.42 13.04 2.53 3.23 9.25 5.79 10.79 13.94 15.00 17.60 6.22 13.79 4.96 5.11 7.20 6.64 12.78 11.43 9.63 2.78 5.76 6.75 5.21 8.26 7.53 11.11 12.12 3.57 5.26 3.20 11.33 5.81 10.69 4.88 6.81 9.52 2.49 4.67 8.36 8.45 8.73 11.67 13.71 14.56 6.13 9.88 6.18 7.64 5.69 7.68 10.77 11.42 9.34 4.85 5.39 5.67 5.12 9.52 10.31 12.15 10.87 5.44 4.32 3.87 8.39 7.67 7.53 6.46 5.78 5.10 8.42 8.85 15.68 10.86 2.57 40 APPENDIX 6. Observed Apatite Concentrations The numbers involved in the calculation of observed apatite concentrations are presented in Table 6-1. In three instances (45 to 33 pm, subsamples 1 and 4; and 17 to 10 pm, subsample 3) a second sample for S.E.M. examination was prepared from a single apatite fraction in order to check an anomalously high or low calculated apatite concentration. In these cases, the average concentration from the duplicate analyses from a single separation was the value used with the concentrations calculated for the other separations of the same size fraction to obtain an average observed apatite concentration for the fraction. Explanation of Terms in Table 6-1 F = Wt. of Apatite Fraction as in Appendix 4. Wt.% Ap in Ap. Frac. Mean of 5 observations, as in Appendix 5. Ob. Ap. Cone. = Observed apatite concentration; Wt% Ap. in Ap. Fraction x F. Av. Duplicate = Average observed apatite concentration of duplicate analyses of a single separation. This average is used with the apatite concentrations from the repeated separations to calculate the mean for the size fraction. Std. Error of Mean = Standard error (deviation) of the mean observed apatite concentration; JSX^ /n where x is each observed apatite concentration and n is the number of x's. 41 TABLE 6-1 Observed Apatite Concentrations Sample F X (Appendix 4) Wt. X Ap. 1n Ap. Fraction (Appendix 5) Ob.Ap.Cone, ug.g-' Av. Duplicate ug.g"1 Mean Ob.Ap Cone, pg.g" Std. Error of Mean ug.g-^ 125-62 um 62-45 um 1 2 3 62-45 um (Spiked) 1 2 3 45-33 pm la lb 2 3 4a 4b 45-33 um (Spiked) 1 2 3 33-25 pm 1 . 2 3 4 33-25 pm (Spiked) 1 2 3 4 25-17 um 1 2 3 25-17 pm (Spiked) 1 2 3 17-10 m 1 2 3 17-10 pm (Spiked) 1 2 3a . 3b 2.52 8.08 8.01 8.83 8.87 8.42 8.51 6.27 6.27 7.39 6.09 6.20 6.20 7.04 7.02 6.69 6.67 6.34 5.84 7.37 6.80 5.48 5.42 5.65 6.73 7.66 7.29 7.73 5.75 6.85 3.99 3.82 3.68 4.40 4.06 3.08 3.08 4.67 8.36 8.45 8.73 11.67 13.71 14.56 6.13 9.88 6.18 7.64 5.69 7.68 10.77 11.42 9.34 4.85 5.39 5.67 5.12 9.52 10.31 12.15 10.87 5.44 4.32 3.87 8.39 7.67 7.53 6.46 5.78 5.10 8.42 8.85 15.68 10.86 1180 6750 6770 7710 10350 11540 12390 3840 6190 4570 4660 3530 4760 7580 8020 6250 3230 3420 3310 3770 6480 5650 6590 6140 3660 3310 2820 6490 4410 5160 2580 2210 1880 3700 3590 4830 3340 7080 11430 4600 320 S90 180 5015 4145 7280 3430 6220 3260 5350 2220 3790 530 130 210 240 610 200 150 4085 10-2 pm 4.02 2.57 1030 42 APPENDIX 7. Contribution of Apatite to the "Dissolved" Phosphorus Load. Three stations in Kamloops Lake, each representative of approximately one third of the lake, have mean grain sizes of 10.2 ym with no sediment smaller than 0.45 ym, 4.2 ym with 4% of the sediment smaller than 0.45 ym, and 2 ym with 16% of the sediment smaller than 0.45 ym (Dr. C H . Pharo, personal communication). The total phosphorus load to Kamloops Lake is 23 g.rrf^.y-1 (St. John et aj[., 1976). 90% of this load, or 20.7% g.rrf 2 .y _ 1 is "particulate" phosphorus i .e . >0.45 ym and 10% or 2.3 g.m.~ 2.y-l is "dissolved" phosphorus i .e. <0.45 ym. If the size distribution of particulate phosphates is similar to that of the general sediment, 7% of the true particulate matter may be <0.45 ym, and the loading of 20.7 g.m.~2.y""l would represent only 93% of the true particulate phosphorus. In this case, 1.5 g.m."2.y-l of particulate phosphate <0.45 ym would be entering the lake. Approximately 80% of the particulate phosphate in the total sediment is apatite; however, the proportion of Non-Apatite Inorganic Phosphorus increases with decreasing sediment size. If 35% of the particulate phosphorus <0.45 ym is apatite (as indicated by extraction analyses of the <2 ym fraction by N.W.R.I.), this would represent a loading of 0.5 g.m."2.y-1. Therefore, about 20% of the so called "dissolved" phosphorus load of 2.3 g.m"2.y"l may be particulate apatite. Cautionary Note: This calculation is extremely approximate. 


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