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UBC Theses and Dissertations

Pesticides in the aquatic environment. Hext, Herbert Daniel 1973

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I PESTICIDES IN THE AQUATIC ENVIRONMENT by HERBERT DANIEL HEXT B.A.Sc, University of Bri t i s h Columbia, 1970 A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in the Department of C i v i l Engineering We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA Ap r i l , 1973 In p r e s e n t i n g t h i s t h e s i s i n p a r t i a l f u l f i l m e n t o f the requirements f o r an advanced, degree a t the U n i v e r s i t y o f B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r r e f e r e n c e and study. I f u r t h e r agree t h a t p e r m i s s i o n f o r e x t e n s i v e c o p y i n g o f t h i s t h e s i s f o r s c h o l a r l y purposes may be g r a n t e d by the Head o f my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t c o p y i n g o r p u b l i c a t i o n o f t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be a l l o w e d w i t h o u t my w r i t t e n p e r m i s s i o n . Department o f C i v i l Engineer ing The U n i v e r s i t y o f B r i t i s h Columbia Vancouver 8, Canada Date A p r i l 13. 1933 A B S T R A C T A comprehensive literature review i s presented concerning pesticides; in particular the organochlorine insecticides, DDT and d i e l -drin, and their role in the pollution of water resources. The results of a laboratory study on the removal of DDT and dieldrin (HEOD) by adsorption onto a clay of the montmorillonite type (bentonite) are presented. For an i n i t i a l DDT concentration of 100 ygm/1, the addition of bentonite at concentrations of 1.0 gm/l and 10.0 gm/l results in the removal of about 60 and 72 per cent, respectively, of the insecticide. For an i n i t i a l HEOD concentration of 100 pgm/1, the addition of bentonite at concentrations of 1.0 gm/l and 10.0 gm/l brings about the removal of about 15 and 30 per cent, respectively, of this insecticide. The results of a laboratory study on the desorption of DDT and HEOD from the bentonite are presented. Both insecticides are desorbed from the clay, the HEOD being desorbed to the greater extent and the DDT desorp-tion being quite minimal. The results of a further laboratory study conducted to ascertain the a b i l i t y of bentonite clay to remove, by adsorption, insecticides from solution while settling through a quiescent water body are presented. Bento-nite at concentrations of 1.0, 5.0, and 10.0 gm/l removes about 44, 48, and 54 per cent, respectively, of DDT from the quiescent water body i n i t i a l l y containing 100 ygm/1 DDT. Bentonite at concentrations of 1.0, 5.0 and 10.0 gm/l removes about 14, 23, and 30 per cent, respectively, of the HEOD from * i i i i i the quiescent water body i n i t i a l l y containing 100 ugm/1 HEOD. The results of an inorganic blanketing study indicates that the addition of a layer of sand over DDT and HEOD contaminated benthic deposits w i l l block, somewhat, the desorption of these insecticides into the overlying waters. TABLE OF CONTENTS Page LIST OF TABLES. . . . . . v i i i LIST OF FIGURES i * CHAPTER I. INTRODUCTION. 1.1 SCOPE AND AIM OF STUDY 1 1.2 PESTICIDES . . . . . . 2 1.3 USE OF PESTICIDES 3 1.3.1 Benefits 3 1.3.2 Hazards 4 1.4 PESTICIDE FORMULATIONS . . . . . . 5 1.4.1 Powders 6 1.4.2 Wettable Powders 6 1.4.3 Granulated Preparations . . . 6 1.4.4 Solutions of Pesticides in Water and Organic Solvents 7 1.4.5 Emulsive Concentrates . . . . . . . 7 1.4.6 Aerosols 7 1.5 SOURCES OF WATER-BORNE PESTICIDES. . . . . . . . . . 8 1.5.1 Manufacture . . . . . . . 8 1.5.2 Application . . . . . . . . . . 9 1.5.3 Surface Drainage 9 1.5.4 Biota Transport . . . . . . 9 1.5.5 Atmospheric Deposition 10 II. DDT AND DIELDRIN 11 11.1 INTRODUCTION . . . . . . . 11 11.2 PROPERTIES OF DDT AND DIELDRIN 13 11.2.1 DDT 13 11.2.2 Dieldrin . . . . . . . . . . . 15 11.2.3 Aldrin . . . . . 16 11.3 USE OF DDT AND DIELDRIN 16 11.3.1 Use of DDT . 16 11.3.2 Use of Dieldrin 18 11.4 UBIQUITOUS NATURE OF DDT AND DIELDRIN. . . . . . . . 18 11.5 LETHAL EFFECTS . . . . . . . 20 11.5.1 On Man 20 11.5.2 On Wildlife 20 11.6 SUB-LETHAL EFFECTS . . . . . . 24 II.6.1 On Man 24 CHAPTER Page II.6.2 On Wildlife . 24 11.7 PERSISTENCE IN THE ENVIRONMENT 26 11.8 BIOLOGICAL MAGNIFICATION . . . . . . 28 11.9 EUTROPHICATION 31 III. INFLUENCE OF SEDIMENTS ON WATER QUALITY . . . . 33 111.1 ADSORPTION AND DESORPTION 33 111.2 EFFECT OF SUSPENDED SOLIDS . . . . . . . 35 111.3 EFFECT OF BOTTOM SEDIMENTS . . . . . . . . . . . . 38 IV. DETECTION OF DDT AND DIELDRIN 40 IV. 1 INTRODUCTION. 40 IV. 2 GAS LIQUID CHROMATOGRAPHY 40 IV.2.1 Definition 40 IV.2.2 Technique of Gas Liquid Chromatography . . 40 IV. 2.3 Carrier Gas 42 IV.2.4 Sample Introduction. . . . . . 42 IV.2.5 Column 42 IV.2.6 Solid Support 43 IV.2.7 Stationary Phase . 43 IV. 2.8 Temperature 43 IV.2.9 Detectors... 44 IV.3 THE ELECTRON CAPTURE DETECTOR USED WITH GAS LIQUID CHROMATOGRAPHY. . . . . . . . . . . . . 44 IV.3.1 Introduction . . . . . . . . . ° 44 IV.3.2 Operation: Mechanisms and Principles of the Electron Capture Detector . . . . . 46 IV.3.3 Electron Capture With A Nickel 63 Source . 47 IV.3.4 Potential. . . . . . . . . . . 49 IV.3.5 Standing Current 51 IV.3.6 Peak Area 51 TV.3.7 Calibration Curve 52 IV. 3.8 Linearity 52 IV.3.9 Sensitivity 52 IV.3.10 Carrier Gas 52 IV.3.11 Carrier Gas Flow Rate 54 IV.3.12 Detector Temperature . . . . 55 IV.3.13 Pulse Interval 56 v i CHAPTER Page V. METHODS OF ANALYSIS USING ELECTRON CAPTURE GAS CHROMATOGRAPHY 58 V. l GENERAL INFORMATION 58 V . l . l Sample Handling 58 V . l . 2 Glassware 58 V.l.3 Standards, Reagents and Solvents . 59 V. 1.4 Sample Transfer 60 V.l.5 Cleaning of Syringe 60 V. 2 GAS LIQUID CHROMATOGRAPHY: RESEARCH APPLICATIONS . . . . 61 V.2.1 The Gas Chromatograph System 61 V.2.2 Columns 62 V. 2.3 Column Efficiency 62 V.2.4 Extraction of Sample 64 V.2.5 Injection into the Gas Chromatograph System,. . . 64 V.2.6 Qualitative and Quantitative Analysis 65 V.2.7 Optimum Operating Conditions 66 VI. DESCRIPTION OF STUDY METHODS 70 VI. 1 ADSORPTION AND DESORPTION TESTS 70 VI.2 QUIESCENT REMOVAL TESTS 71 VI. 3 SAND BLANKETING TESTS . . . . . 72 VII. RESULTS OF THE STUDY 73 VII. l ADSORPTION TEST RESULTS 73 VII.2 DESORPTION TEST RESULTS . 79 VII.3 QUIESCENT REMOVAL TEST RESULTS 79 VII. 4 SAND BLANKETING TEST RESULTS 85 VIII. CONCLUSIONS AND RECOMMENDATIONS 88 VIII. 1 CONCLUSIONS 88 VI11. 2 RECOMMENDATIONS 90 REFERENCES 92 APPENDICES 100 APPENDIX A: COMPARATIVE CHROMATOGRAMS OF TWO HEXANES . . . . 102 APPENDIX B: THERMAL CLEANING RESULTS 104 APPENDIX C: EXAMPLES OF RECOVERY FROM SAMPLES CONTAINING KNOWN AMOUNTS OF INSECTICIDES 106 v i i Page APPENDIX D: EXAMPLES OP INJECTION TECHNIQUE PRECISION ANALYSIS TESTS 108 APPENDIX E: ADSORPTION, DESORPTION, QUIESCENT REMOVAL AND SAND BLANKETING TEST RESULTS. . . . . . . . . . . I l l APPENDIX F: SAMPLE CALCULATIONS . . . . . . . 166 LIST OF TABLES Table Page I. WORLDWIDE USAGE SURVEY FOR 1966 12 II. EFFECTS OF PESTICIDES ON FISH AND WILDLIFE . . . . . . 21 III. FISH KILLS, CALIFORNIA 1965-1969 . . . . . . . . . . . 23 \ IV. APPROXIMATE RELATIVE AFFINITIES OF ELECTRON-CAPTURE DETECTOR FOR SOME ORGANIC COMPOUNDS 45 V. SAND BLANKETING TEST RESULTS FOR HEOD. . . . . . . . . 86 VI. SAND BLANKETING TEST RESULTS FOR DDT . . . . . . . . . 87 v i i i LIST OF FIGURES Figure Page 1. Chemical Structure of DDT 13 2. Chemical Structure of HEOD 15 3. Persistence of Organochlorine Insecticides 27 4. Biological Concentration of DDT in the Food Web of a Long Island Estuary 30 5. Pesticide Adsorption Isotherms 37 6. Schematic Drawing of a Gas Chromatographic System. . . 41 7. Schematic Drawing of Two Electron A f f i n i t y Cells . . . 46 8. Diagram of Electron Capture C e l l 47 9. Illustration of Pulsed EC Ce l l Potential 50 10. Six Typical Linearity Plots 53 11. Electron Concentration vs. Time Between Pulses . . . . 54 12. Effect of Carrier Gas Flow Rate on Sensitivity . . . . 55 13. Linearity and Sensitivity at Various Pulse intervals . 57 14. Column Efficiency Parameters 63 15. Linearity Curve for DDT 67 16. Linearity Curve for HEOD 68 12.. HEOD Adsorption Curves: 1.0 gm/l Bentonite 74 18. HEOD Adsorption Curves: 10.0 gm/l Bentonite 74 19. HEOD Adsorption Curves: 1.0 gm/l Bentonite; Solution 0.01 Molar 76 20. HEOD Adsorption Curves: 10.0 gm/l Bentonite; Solution 0.01 Molar. 76 ix X Figure Page 21. DDT Adsorption Curves: 1.0 gm/l Bentonite 77 22.. DDT Adsorption Curves: 10.0 gm/l Bentonite 77 23. DDT Adsorption Curves: 1.0 gm/l Bentonite; Solution 0.01 Molar 78 24. DDT Adsorption Curves: 10.0 gm/l Bentonite; Solution 0.01 Molar 78 25. HEOD Desorption Curves: 1.0 gm/l Bentonite 80 26. HEOD Desorption Curves: 10.0 gm/l Bentonite 80 27. DDT Desorption Curves: 1.0 gm/l Bentonite. . . . . . . . 81 28. DDT Desorption Curves: 10.0 gm/l Bentonite . . . . . . . 81 29. HEOD Quiescent Removal Test Results 82 30. DDT Quiescent Removal Test Results . . . . . . 84 CHAPTER I INTRODUCTION 1.1 SCOPE AND AIM OF STUDY There i s much public concern about the widespread use of pesti-cides i n North America. This concern i s being expressed because pesticides, especially chlorinated hydrocarbon (organochlorine) insecticides, are highly toxic to w i l d l i f e and extremely persistent in the environment. This research i s directed towards finding a solution to a severe problem which i s occurring i n many natural water bodies today. The problem i s that of the release of pesticides from lake bottom sediments into overlying waters. 1 Certain clays, which are widespread constituents of bottom sediments, have been shown to adsorb pesticides and, under certain condi-tions, to permit desorption into overlying waters. This research i s directed towards identifying the quantity of these insecticides adsorbed onto the clays, finding a method to prevent the insecticides from being desorbed from the clay sediments, and i n using this clay to remove the insecticides already present i n the water. This thesis project i s also designed to provide a review of the available literature concerning pesticides (in particular, the organochlorine insecticides, DDT and dieldrin) and their role in the pollution of water re-sources. 1 2 1.2 PESTICIDES Our society has gained tremendous benefits from the use of pesticides. Their use has helped to increase food and fibre production and to prevent disease. Pesticides appear to be needed. They were developed in response to public needs and demands, and when used wisely and s k i l l f u l l y under responsible^leadership, have done much towards eradicating disease and improving agriculture. Improper care, however, through misuse or over-use, has resulted in unnecessary damage, especially to wildl i f e and fishery resources. The widespread public concern during the last decade about the environmental damage caused by organic pesticides, stems largely from the circulation of Rachel Carson's book, Silent Spring [1], Her book dramati-cally i l l u s t r a t e d the broad range of damage caused by the improper use of pesticides. Several reports and publications written after the appearance of Carson's book reinforced her principal point: that pesticides were being used i n massive quantities with l i t t l e or no regard to undesirable side effects. The persistence, toxicity and pervasiveness, particularly of the organochlorine pesticides, as well as the use of increased quanti-ties and new pesticide variants, further aroused public concern. In the United States, i n 1969, synthetic organic pesticide production was increas-ing at an annual rate of 15 per cent with an estimated $3 b i l l i o n in annual sales by 1975 [2]. At the same time there were some 900 active pesticidal chemicals formulated into over 60,000 preparations [2], 3 Benefits derived from pest control through pesticide use are measured by their effectiveness i n reducing populations of pest species. Detrimental effects are based on adverse effects on l i f e forms other than the specified pest. There is an abundance of recent evidence indicating the need to be concerned with the detrimental effects of pesticides on non-target organisms. The benefits of using pesticides must be weighed against present and future risks of using pesticides. The total problem of pesticide usage must be considered, not only in the context of what is known, but also in the context of the many unknowns that w i l l probably come to ligh t in the near future. There is a serious lack of information available on pesticide use patterns, especially for non-agricultural uses [2]. There i s a similar lack of information concerning the fate of pesticides i n the aquatic environment. The research of today must concentrate on the long-range effects of low-level doses and the possible synergistic and antagonis-t i c effects of pesticides. 1.3 USE OF PESTICIDES 1.3.1 Benefits. Increased control over the environment, including the use of pesticides i n organized agriculture, has greatly raised our material standard of l i v i n g . The domestication of food plants and large-scale, single-crop farming has brought about a concentration and localiza-tion of crops and animals. This concentration and localization has reduced the amount of energy required to be expended by pests in their search for i food and has resulted in a substantial increase in the pest problem. Pest 4 control has thus become a v i t a l part of man's trend towards the con-centrated monoculture system that he has adopted. Agricultural needs have entailed the largest applications of pesticides i n developed nations and productivity has increased to such an extent that famine is an unknown experience in such countries. Not only do pesticides reduce crop losses, but they also result in v i s -ually high quality foodstuffs. The average shoppers of today, for ex-ample, are accustomed to blemish-free products at their supermarkets. Besides enabling great increases in agricultural production, pesticides have freed man from several communicable diseases to an un-precedented extent. Examples of diseases that have been limited through pesticide use against their related insect vectors are yellow fever, malaria, and typhus. It has been estimated that, from the start of using DDT in World War II to 1953, over 5 million deaths from malaria have been prevented, and over 100 million related illnesses prevented [3]. 1.3.2 Hazards. Detailed examination of the hazards of pesti-cide use i s beyond the scope of this paper. Subsequent chapters w i l l , how-ever, give pertinent information on the environmental hazards associated with the use of DDT and dieldrin. This section w i l l , therefore, only b r i e f l y deal with general concepts. When pesticides were f i r s t introduced i t was apparent, at that time, that they were useful. However, armed with the knowledge we have today, one would be hard-pressed to justify their continued large-scale, indiscriminate use. It can be easily argued that large-scale, single-crop farming that needs an abundance of pesticides to work e f f i c i e n t l y may not be necessary. Perhaps i t would be wise to forsake some of this material 5 efficiency for an efficiency more closely related to the environment. After a l l , there is no use i n being e f f i c i e n t in producing foodstuffs i f the cost i s to slowly but steadily k i l l ourselves through the poison-ing of our environment. As mentioned in the benefits of using pesticides, we have high quality foodstuffs as far as visual aspects are concerned, but there may be a hidden low quality inherent in the product. For example, shoppers of today may in fact be accustomed to blemish-free products at their super-markets, but i f given the choice, they may opt for blemished, even wormy, but pesticide-free foodstuffs. This may especially be so i f the alter-natives of both are properly presented to the shopper. As mentioned, western man has modified agriculture and livestock rearing to the extent that he needs pesticides. The efficiency of this sys-tem i s such that i t has helped raise his material standard of l i v i n g , but with hidden costs that are just now coming to light. These hidden costs are the environmental effects of the large-scale use of pesticides and the consequences associated with this. I t i s time now to attempt to put values on these hidden costs and i f not enough i s known about them, to ban the use of the related pesticide, as has been done i n the case of certain organochlorine insecticides. Perhaps western man should sacrifice some of his Gross National Product-related efficiency in the production of food-stuffs for more diverse, more complex and smaller-scale agriculture that would not require the use of pesticides. In other words, western man should seek to enhance the quality of his l i f e , not just the quantity. 1.4 PESTICIDE FORMULATIONS [4] The amount of pesticide that gets into natural waters depends to a large extent on the pesticide formulations and methods of application. 6 Depending on the chemical properties of the pesticide, i t s purpose, and the means of application, the formulation considered most ef f i c i e n t i s selec-ted. There are a tremendous number of different formulations manufactured for use i n industry, agriculture, and health protection. In the United States alone there are over 1200 formulations manufactured that are based on DDT only, and about 1500 based on other organochlorine insecticides-The most important types of formulations are the following: 1.4.1 Powders (nusts). 1.4.2 Wettable Powders. 1.4.3 Granulated Preparations. 1.4.4 Solutions i n Water and Organic Solvents. 1.4.5 Emulsive Concentrates. 1.4.6 Aerosols. 1.4.1 Powders. The pesticidal powders or dusts consist of a mechanical mixture of the active ingredient and an inert diluent. The inert diluents are usually hydrophobic minerals of the talc and pyrophyllite type, although in dry climates hydrophilic minerals of the kaolin and bentonite clay types are also used. These powders are applied dry on the plants to be protected. 1.4.2 Wettable Powders. Wettable powders are powders that are diluted with water to yie l d stable suspensions. These suspensions are sprayed on plants and other surfaces and are gradually replacing the dusts, as they are usually more effective. The advantages of using wettable pow-ders over dusts are that less pesticide i s lost due to wind currents, being washed off by r a i n f a l l , or being applied on material that i s not to be treated. 1.4.3 Granulated Preparations. Granulated formulations are often used instead of dusts as they are frequently more convenient and 7 leave a smaller amount of undesirable contaminants on the plants. These formulations are prepared by the granulation of powders on a suitable diluent, with subsequent screening. Kaolin, bentonite, or similar clays are most often used as diluents. 1.4.4 Solutions of Pesticides in Water and Organic Solvents. Only compounds that are rather soluble i n water can be used in the form of aqueous solutions. The main pesticides used in aqueous solutions are herbicides and some organophosphorus insecticides and fungicides. Various solutions of pesticides i n organic solvents are widely used for so-called low-volume, finely-dispersed spraying of plants. The most frequently used solvents for the preparation of pesticide solutions are the petroleum hydrocarbons: dearomatized kerosene, white s p i r i t (turpentine substitute),mineral o i l s and diesel fuel. 1.4.5 Emulsion Concentrates. Emulsion concentrates are formu-lations that upon dilution with water give stable emulsions suitable for spraying plants and surfaces. These emulsions are usually more concentrated, than suspensions but otherwise are quite similar to the pesticide-organic solvent solutions. 1.4.6 Aerosols. Aerosols are a relatively new form of pesti-cide application used mainly in public health and agriculture. .' The simplest method of producing pesticide aerosols is by burn-ing, in special smoke pots, paper and other combustible products that have been impregnated with the pesticide. This method produces smoke and clouds poisonous to insects, fungi or bacteria. Another method of producing pesticide aerosols that i s recommended for control of f l i e s and other flying insects in enclosed areas i s aerosols 8 i n spray cans. The aerosols are obtained by p l a c i n g solutions of i n s e c t i c i d e s i n v o l a t i l e solvents, i n metal aerosol c y l i n d e r s equipped with an atomizing device. The solutions are forced out of the c y l i n d e r by the i n t e r n a l pressure created using carbon dioxide or a low-boiling solvent such as Freon, or methyl c h l o r i d e . As mentioned, the p e s t i c i d e formulation determines, to a large extent, the amount of p e s t i c i d e that enters the aquatic environ-ment. The l e s s soluble p e s t i c i d e s , such as the organochlorine i n s e c t i -cides and the phenoxy h e r b i c i d e s , are formulated with emulsions or sur-factants i n l i g h t o i l s o l u t i o n or i n organic solvents l i k e ethanol or acetone. These p e s t i c i d e s , which are formulated i n organic solvents, be-come suspensions i n water and disperse i n such f i n e p a r t i c l e s that they act much l i k e s o l u t i o n s . Other formulations have more d i f f i c u l t y i n spreading throughout the aquatic environment. Wettable powders and granular formulations, f o r example, tend to s e t t l e to the bottom i n water bodies [5]. Since many of the p e s t i c i d a l formulations are of such a nature t h a t the p e s t i c i d e can enter and disperse throughout the aquatic environment, an important consideration becomes the sources of entry of these p e s t i c i d e s i n t o water bodies. 1.5 SOURCES OF WATER BORNE PESTICIDES 1.5.1 Manufacture. The manufacture of p e s t i c i d e s may contribute a s i g n i f i c a n t amount of these p e s t i c i d e s to the aquatic environment. P e s t i -cides may enter the water through the wasting of clean-up water from p e s t i -cide manufacturing or formulating p l a n t s . P e s t i c i d e residues may be found i n wastewater from the washing of p r o t e c t i v e c l o t h i n g worn i n these p l a n t s . The extent to which formulating plants may contribute pesti-cides to a stream is il l u s t r a t e d by a survey conducted jointly by the United States Public Health Service and the United States Department of Agriculture. Of the 57 lower Mississippi River drainage basin formulating plants inspected, every one carried out some operating procedure which could cause contamination of the surface water [6]. 1.5.2 Application. The majority of pesticides found i n the aquatic environment probably result from their application for pest con-t r o l . They may have been directly applied to the natural waters for con-t r o l of filamentous algae, carp, or to k i l l mosquito larvae. Wind cur-rents during aerial applications may have carried them to an adjacent water body. Occasional accidental s p i l l s into water courses during treat-ment of large forested areas is a third p o s s i b i l i t y . 1.5.3 Surface Drainage. A source of pesticide residues in the aquatic environment not to be neglected would be contamination due to surface drainage. Surface drainage from treated crop lands may contain pesticides that have been desorbed from the s o i l in concentrations ranging from picograms to micrograms per l i t r e of water [7]. Rainfall of a high intensity w i l l not only carry pesticides that have been desorbed from s o i l particles, but w i l l also transport eroded, contaminated s o i l from the treated area [7, 8] . 1.5.4 Biota Transport. A minor route of pesticide contamina-tion, but one worth mentioning, is through biota transport. Living organ-isms may bring pesticides into water bodies, either i n the organisms them-selves or adsorbed onto their surfaces [9] and through release of waste material or death, deposit the pesticides in the aquatic environment. 10 Alternatively, the contaminated organism may form a lower link in the food chain and thus spread the pesticide through the biota. 1.5.5 Atmospheric Deposition. Another minor route for pesti-cide contamination of the aquatic environment is through atmospheric de-position. Evidence exists indicating that pesticides can become airborne, either as a vapour or adsorbed onto dust particles, and thus be trans-located far from the treated area [10, 11, 12]. It i s most l i k e l y that some of the errant pesticide would be deposited in water courses. CHAPTER II DDT AND DIELDRIN II.1 INTRODUCTION A pesticide i s a chemical used to k i l l non-human organisms considered by man to be a pest; i.e., hostile to human interests. In-cluded as pesticides are: insecticides, herbicides, fungicides and rodent-icides. DDT and dieldrin are two insecticides of the chlorinated hydro-carbon (organochlorine) family. Other members include: aldrin, endrin, toxaphene, lindane, methoxychlor, chlordane, and heptachlor. The United States Department of Agriculture has predicted that the domestic use of insecticides w i l l more than double in the period from 1969 to 1975, and that foreign use of pesticides w i l l likewise continue to increase. Organochlorine and organophosphorus insecticides w i l l con-tinue to represent a significant part of the market [2]. As late as 1967 the organochlorine insecticides made up approximately one-half of the total United States production of insecticides, of which about 50 per cent was DDT [2]. / Shell International Chemical Company's Worldwide Usage Survey for 1966 (Table I) illustrates the widespread usage of insecticides, par-t i c u l a r l y the organochlorine group, i n agriculture. Table I does not include the large amounts of insecticides used for reasons of public health. 11 12 TABLE I WORLDWIDE USAGE SURVEY FOR 1966 CROP TOTAL INSECTICIDE USAGE (lbs.) PER CENT CHLORINATED HYDROCARBON INSECTICIDES IN TOTAL Cotton 60,400 38 Rice 12,000 57 A l l Other Cereals 7,600 85 Vegetables 6,800 46 Potatoes 2,800 61 Sugar Beets 2,400 55 Sugar Cane 2,100 74 Tobacco 2,000 67 Oilseeds 1,900 77 Coffee 300 81 Tea 500 19 Sweet Potatoes 200 92 Source: Shell International Chemical Company [2] Since 1957 most of the persistent insecticides have shown a decline i n use, with DDT use rapidly declining i n domestic pest control programs. This s h i f t to non-persistent insecticides w i l l probably con-tinue at an accelerated rate. However, there w i l l be a continued need for the use of persistent materials, such as DDT and dieldrin, for the i control of selected pest problems. Although imaginative and exciting research concerning non-insecticidal control techniques i s in progress (including research into biological methods ) i t i s not l i k e l y to have a significant impact on the use of insecticides in the foreseeable future. There appears, however, to be an increased appreciation for the use of integrated control u t i l i z i n g less persistent insecticides in the management of pest problems [2]. t 13 II.2 PROPERTIES OF DDT AND DIELDRIN II.2.1 DDT. DDT i s a chlorinated hydrocarbon insecticide; or more precisely, i t i s a diphehyl aliphatic chlorinated hydrocarbon. Its chemical name i s 1,1,1 - Trichloro - 2,2 - di - (p-chlorophenyl) ethane and i t s chemical formula i s C, .H„Clr. DDT1s chemical structure i s shown 14 9 5 in Figure 1. Figure 1 [13] Chemical Structure of DDT 14 Pure DDT has a melting point of between 108.5 C and 109 C. A l -though the sol u b i l i t y of DDT in water is only 0.001 mg/l (1 ppb), evi-dence exists indicating that i t may occur at significantly higher concen-trations in natural waters. Wershaw et al. [14] show that the addition of sodium humate to d i s t i l l e d water (0.5% solution) increased the solubil -i t y of DDT about 20 times. Bowman et al. [15] showed that DDT may exist in aqueous solutions as molecular aggregates at a concentration approxi-mately 12 times greater than that in a true solution. Acree et al. [16] found that DDT c o d i s t i l l s with water at am-bient temperatures. This phenomenon, coupled with the DDT carried by wind currents from areas treated with aerial spraying, may help explain the appearance of DDT in regions where i t never has been used, such as the Antarctic. DDT penetrates through intact skin and exerts i t s toxic action when i t has entered into the respiratory tract. For this reason, the maximum permissible concentration i n the a i r i s only 1.0 mg/rn^ i n the 3 United States and 0.1 mg/m in the U.S.S.R. The maximum permissible con-centration i n seasonal foodstuffs i n the United States i s 1.0 mg/kg (ppm) [17]. In spite of the many investigations, the exact mechanisms of DDT's action on l i v i n g organisms s t i l l has not been determined. [4, 17, 18, 19], However, i t is known that i n soils and in l i v i n g organisms, DDT i s broken down to residues of DDD [1, 1-bis (4 - chlorophenyl) - 2 , 2 -dichloroethane) and other compounds [17, 19, 20]. i The principal formulations of DDT as i t i s applied are, as a 50 per cent wettable powder, as a 25 per cent emulsifiable concentrate, as a 15 five per cent dust, and as a 10~per cent aerosol [21]. II.2.2 Dieldrin. Dieldrin is a white cyrstalline substance which is highly toxic to both man and animals; i t s lethal oral dose for a 50 per cent mortality (LD^) for various animals being only 25 to 50 mg/kg of body weight [17]. Its melting point, when pure, i s between 175°C and 176°C and i t has a s o l u b i l i t y in water of 120 ppb at 20°C [22]. The technical grade product is a light brown material contain-ing not less than 85 per cent of the compound l,2,3,4,10,10-hexachloro-6,7-epoxy-1,4,4a,5,6,7,8,8a-octahydro-l,4-endo,exo-5-8-dimethanonaphthalene, con-veniently abbreviated as HEOD. The other 15 per cent of dieldrin is var-ious impurities. The chemical structure of HEOD i s shown in Figure 2. Analytical methods, particularly those involving gas-liquid chromatography, determine HEOD, not dieldrin [20]. Figure 2 [13] Chemical Structure of HEOD 16 As the toxicity of dieldrin has been shown to be high, the maximum permissible concentration allowed i n the a i r i s 0.01 mg/kg (ppm) in the United States and no residues are permitted on food or forage pro-ducts. The use of dieldrin i s not permitted i n the U.S.S.R. [17]. The principal formulations of dieldrin as i t i s applied are, as a 50 per cent wettable powder, as a 1.5 per cent dust, and as an emulsifiable concentrate containing 1.5 pounds per gallon [21]. II.2.3 Aldrin. No report about dieldrin would be complete without mentioning aldrin. Aldrin contains not less than 95 per cent of the compound 1,2,3,4,10,10 - hexachloro - 1,4,4a,5,8,8a - hexahydro -I, 4 - endo, exo - 5 - 8 - dimethanonaphthalene, commonly abbreviated as HHDN. HHDN i s rapidly epoxidized in animals and by s o i l microorganisms to HEOD [18,23,24], or in other words, aldrin i s rapidly epoxidized to dieldrin. In subsequent chapters, discussion of dieldrin w i l l apply equally to aldrin. Aldrin i s used extensively i n treating corn acreage as i t k i l l s a wide variety of corn pests. Roughly one-half of the total United States corn acreage was treated with aldrin in 1968. This use constituted over 81 per cent of the total aldrin and dieldrin manufac-tured i n the United States for that year [ 2 1 . In the U.S.S.R., the use of aldrin i s not permitted [17]. II. 3 USE OF DDT AND DIELDRIN II.3.1 Use Of DDT. In Canada, the general use of DDT has been i t banned by the Federal Government since January 1, 1970 [25]. Since early i n 1971, DDT and DDT-like products have been collected for disposal 17 at the Defense Research Establishment Suffield at Ralston, Alberta. Liquid DDT products are to be. thermally destroyed with powdered DDT products from the Western Provinces to be stored there for use i n case of health emergencies. There is also an eastern storage site for pow-dered DDT products from Eastern Canada [26]. In the United States, the use of DDT in domestic pest con-t r o l i s rapidly declining, with the major need reported to be associ-ated with cotton production i n the Southeastern United States. The Secretary's Commission on Pesticides and Their Relationship to Environ-mental Health [2, p. 8] recommended to "eliminate within two years a l l uses of DDT and DDD in the United States excepting those uses essential to the preservation of human health and welfare and approved unanimously by the Secretaries of the Departments of Health, Education and Welfare, Agriculture and Interior." Production of DDT i n the United States during 1967 was 103 million pounds of which 82 million pounds was exported. Over one-half of a l l DDT exports were in the form of wettable powders used primarily for mosquito control by agencies of the World Health Organization (WHO) and the Food and Agriculture Organization (FAO) of the United Nations for malaria eradication [2]. Although total production i s declining, an increasing amount of DDT is being purchased by these agencies for their foreign malaria control programs [2]. WHO and FAO use DDT for control of mosquitoes that spread yellow fever and malaria. It i s expected that this use of DDT w i l l decrease slightly as control programs become more sophisticated, but 18 DDT for this use is s t i l l expected to amount to about 40 million pounds per year [2]. The World Health Organization states, ". . . i t s (DDT) low cost makes i t irreplaceable i n public health at the present time. Limitations on i t s use would give rise to greater problems in the majority of developing nations." [2, p. 50] II.3.2 Use of Dieldrin. Due to i t s high toxicity, dieldrin has never enjoyed the widespread use that DDT has. In Canada, the use of dieldrin had declined from about 15,000 pounds per year in 1962 to about 6,000 pounds per year in 1968 [27]. In the United States dieldrin i s used when a long-lasting resid-ual effect is desired. These residual uses of dieldrin include i t s appli-cation for termite control, insect control on lawns and corn crops, and the permanent moth proofing of fabrics [2]. Dieldrin i s used by WHO and FAO for controlling mosquitoes which transmit yellow fever and malaria. It is also extensively used in Africa to control sleeping sickness caused by the Tsetse f l y [2]. As previously mentioned, the use of dieldrin i s not permitted i n the U.S.S.R. [17]. II.4 UBIQUITOUS NATURE OF DDT AND DIELDRIN One of the major properties of the organochlorine insecticides causing concern is the ubiquitous nature of these chemicals. In 1962 i n -secticides were distributed over nearly 90 million acres in the United States (nearly one i n every 20 acres) and the annual sale of aerosol spray cans of insecticides i n the same year exceeded more than one per household [18]. 19 Weaver et al. [28] divided the United States into 15 major drainage basins and sampled for pesticides. Dieldrin, DDT and DDE were found in a l l the major river basins, with dieldrin being the most preva-lent. The United States Public Health Service has monitored major river basins i n the United States for organochlorine pesticidal compounds since 1957 [29]. Breidenbach et al. [30] have reported that DDT and re-lated compounds have been present through the entire period and again dieldrin was the most prevalent. George and Frear [31] and Tatton and Ruzicka [32] found trace amounts of DDT in species taken in the Antarctic and Cohen and Pinkerton [10] found evidence of organochlorine compounds, including DDT, being transported on dust particles. In England, Wheatleyand Hardman [11] found organochlorine compounds in rain water. Schafer et al. [29] found dieldrin i n over 40 per cent of the samples of finished drinking water taken i n the Mississippi and Missouri River basins. More than 30 per cent of these samples contained detectable endrin, p, p* - DDT, and p, p' - DDE. DDT has been found i n the body fat of residents, who had no occu-pational exposure, in England, Germany, the United States and Canada with an average level of 12 ppm in the United States and two ppm in England and Germany [18]. Dieldrin has been found in the body fat of residents of England at an average of 0.2 ppm and is probably present i n the fat of North Americans as a result of the extensive use of this insecticide [18, 33]. The omnipresence of the persistent organochlorine insecticides with regard to non-target fi s h i s i l l u s t r a t e d by the report that a l l 16 20 commercial fi s h foods tested for use i n a Canadian fish hatchery contained DDT and i t s metabolites. Some of these commercial foods caused 30 to 90 per cent mortality of the fry and fingerlings [2]. II.5 LETHAL EFFECTS II.5.1 On Man. Each year approximately 150 deaths are attributed to the misuse of pesticides i n the United States, with over half dealing with children accidently exposed at home [18]. However, none of these deaths were attributed to either DDT or dieldrin. There have been numerous cases of acute poisoning due to DDT [17] but no mortality reported, as the toxicity of DDT to man i s com-paratively small [2, 17]. While dieldrin has caused many more cases of serious poisoning [2], no instances of mortality have been found i n the literature reviewed. II.5.2 On Wildlife. The misuse and overuse of pesticides has caused needless death to fis h and w i l d l i f e , and numerous cases of lethal effects of DDT and dieldrin have been well documented. The more notable incidents of mortality are l i s t e d in Table II. Pesticides cause approximately twice as many fis h to be k i l l e d per incident than a l l other forms of pollution combined (Table III) and as indicated in Table II, dieldrin and DDT and i t s metabolites account for most of the lethal incidents. The data in Table III refers only to f i s h k i l l s due to direct action of the pesticide and not to subtle effects on fis h reproduction i and behaviour. 21 TABLE II EFEECTS OF PESTICIDES ON FISH AND WILDLIFE NO. CHEMICAL RATE PURPOSE EFFECT 1. Aldrin Aldrin Rice seed protection. 2 lb/Acre (A) Japanese beetle control. Widespread mortality of fulvous tree ducks. Nearly complete elimina-tion of many species of songbirds. Heavy mor-t a l i t y of gamebirds. Some mortality of mam-mals. DDD DDT 50 - 70 ppm in water. Clear Lake gnat. Dutch elm disease control. Death of grebes and re-duction of breeding population. Heavy mortality of robins and songbirds. DDT DDT 7. DDT DDT 1/2 lb /A and 1 lb/A Gypsy moth and biting f l y . Forest protection. Agriculture drainage. Spruce bud-worm and blackheaded budworm. Cessation of reproductive successes of trout due to death of fry. Trout k i l l due to food depletion. Death of many f i s h , some birds. Salmon and trout popula-tions reduced and produc-tion curtailed. 10. DDT DDT 0.2 - 1. lb / A Rice pests. Mosquito control Some deaths of mallards, pheasants and other birds. Deaths of f i s h , crabs, frogs, lizards and snakes. 22 TABLE II (Continued) NO. CHEMICAL RATE PURPOSE EFFECT 11. Dieldrin 2-3 lbs/A White fringed beetle, Japa-nese beetle. Heavy mortality of song-birds, quail, and water-birds, rabbits and some other mammals. 12. Dieldrin, DDT and others Routine agricul-tural applica-tions . Pheasant production reduced. 13. 14. 15. Dieldrin Endrin 1 lb /A 0.8 lb /A Heptachlor or Dieldrin 2 lb /A 16. Heptachlor 2 lbs /A Sandfly larvae. Cutworm. Imported f i r e ant. Japanese beetle. Heavy fish mortality. Heavy rabbit mortality. Virtual elimination of birds. Populations of quail remained depressed for at least three years. Heavy songbird mortality. 17. Cotton D r i f t from Insecticides treated 18. Toxaphene fie l d s . Cotton insect control. Crop protection. Death of some rabbits, birds, snakes, fi s h and frogs. Heavy mortality of f i s h -eating birds.each year 1960-1963. 19. Cotton Surface Insecticides erosion from treated f i e l d s . Cotton insects. Heavy fish k i l l s in 15 streams. Source: Reference [12]. 23 TABLE III FISH KILLS CALIFORNIA, 1965-1969 PESTICIDES OTHER POLLUTANTS TOTAL NO. NO. KILLED TOTAL NO. NO. KILLED INCIDENTS KILLED PER INCIDENT INCIDENTS KILLED PER INCIDENT 48 408,457 8500 180 612,985 4700 Source: Reference [34] Dieldrin and aldrin are many times more toxic to vertebrates than DDT [18]. Unlike most other insecticides, an average dosage of dieldrin (one to three pounds per acre) produces high mortality of mammals in the treated area [18]. An interesting case of fish mortality i s the example of number 5 in Table II. In this case, over the one month period when the small fry have almost completely absorbed their yolk sac, over 350,000 fry died (close to 100 per cent mortality). This puzzling case was ultimately traced to fatty material i n their eggs. The newly hatched fry lived on this fatty material from the egg and when they had absorbed approximately 2.9 ppm of the DDT, i t was enough to cause death. This example illustrates the indirect manner i n which organochlorine insecticides may cause death in f i s h and wi l d l i f e . I 24 II.6 SUB-LETHAL EFFECTS II.6.1 On Man. Precisely because pesticide chemicals are designed to k i l l or metabolically upset some l i v i n g organism, they are potentially dangerous to other l i v i n g non-target organisms, including man. At the present time there is no evidence that the levels of pesticides in the en-vironment present an acute toxicity hazard to man. Not enough i s known, however, about the effects of long-term, low-level environmental exposures. Nor i s there enough known about the possible synergistic effects that two or more pesticides may have on man. In one study [18] people ingested 35 mgs of DDT per day. Over an 18 month period these test specimens showed no i l l effects. However, DDT and i t s metabolites averaged 270 ppm i n their fat tissues, more than 20 times the national average for that area. Many other studies conducted [2] show that DDT and i t s metabolites are stored in the fat tissues of people but an equilibrium level is attained despite continuing exposure. The pre-cise concentration at which this equilibrium level i s reached appears to be related to the level of exposure, but there are other determining factors such as the method of ingestion (orally, through the respiratory tract or absorption through skin), the form the DDT i s in; and others. A two-year study group [2] on dieldrin showed that no i l l effects were found in the test subjects at the highest level of ingestion of 0.22 5 mg/man/day. Again, like DDT, i t did exhibit a build-up in body fat and blood to an equilibrium level. This equilibrium concentration was also re-lated to the level of exposure and declined when the exposure was discontinued, i II.6.2 On Wildlife. The most noteworthy result of the exposure of wi l d l i f e to pesticides involve mortality. In such situations the connection 25 between cause and effect i s easily seen because they are usually closely re-lated i n time and space. When these mortalities occur, the course of action to remedy the situation is quite apparent. These dramatic wi l d l i f e mortalities are then highly publicized and very often may be wrongly considered the most serious effect of the pest-icides on f i s h and w i l d l i f e . In actual fact, the long-term, low-level con-centration of pesticides or the possible synergistic effects of pesticides may have a greater and farther-reaching effect on the environment. These many indirect effects may be much more serious and yet are usually much harder to comprehend. Some of these indirect effects that have to be studied include effects on the reproduction of non-target organisms, effects on the metabolism of s o i l and aquatic micro-organisms, persistence in the environ-ment, biological magnification, and the effects of population suppression. The effects of DDT on the reproduction of birds i s well docu-mented. Risebrough et al. [35] l i s t numerous studies that show birds have suffered reproduction losses due to DDT. Stickel and Rhodes [36] show that Coturnix quail fed dietary dosages of p,p'-DDT produced fewer eggs and their eggs had thinner shells than the control population. DDT has been found to be stored in the fat of birds [37,38]. Some birds may accumulate small amounts of DDT i n their fat tissues while eat-ing and when u t i l i z i n g these fats during winter or migration, these sub-lethal amounts could become lethal. It has been observed that dieldrin, after 10 hours exposure at 1 ppm, causes physiological i r r i a t i o n s in osyters [39]. Residues of only 4 i ppm i n the gonads of lake trout have been reported to have caused the death of the developing fry. 26 The effects of pesticides on the metabolism of s o i l and aquatic micro-organisms i s also well documented. The presentation of this abundance of information i s , however, beyond the scope of this paper. The reader i s directed to the work of Ware and Roan [40] and others [41,42] who f u l l y re-view the studies done on the interactions of insecticides with aquatic micro-organisms and to the ample literature [43,44,45,46,47,48,49,50,51,52,53] con-cerning the actions of various insecticides on s o i l micro-organisms. II.7 PERSISTENCE IN THE ENVIRONMENT An important characteristic of the organochlorine insecticides, particularly DDT and dieldrin, i s their persistence in the natural environ-ment in toxic form. The chemical half l i f e of these stable chlorinated hydro-carbons i s measured, not i n weeks nor months, but in years. DDT, dieldrin and related compounds have persisted in soils from three to 15 years or long-er [23,52,53]. It i s because of this s t a b i l i t y that these organochlorine i n -secticides present such a major residue problem. Edwards [47] presents an excellent review of the persistence of insecticide residues i n so i l s . Lichtenstein and Schultz [54] recovered up to 33 per cent of the DDT applied to a muck s o i l 3h years after the application. Wheatley et al. [55] indicate that the half l i f e of dieldrin -is approximately four years i n a mineral s o i l and five to seven years in an organic s o i l . Lich-tenstein et al. [56,57] found that aldrin was converted to dieldrin in the s o i l , and that eight to 10 per cent of the aldrin i n i t i a l l y applied was re-covered as dieldrin four years later. Woodwell and Martin [58] report that the s o i l from sprayed forest stands in New Brunswick and Maine contained DDT residues and these residues 27 increased between 1958 and 1961, although no new spray had been applied. This increase suggests that DDT residues may persist for several years in tree canopies, but are ultimately carried to the s o i l . Some of the chlorinated hydrocarbon insecticides are decom-posed slowly i f at a l l by s o i l organisms [52,59]. DDT and dieldrin have been found to be highly resistant to biological attack [40], although some micro-organisms have been isolated that degrade aldrin to dieldrin [60]. H i l l and McCarty [13] found that dieldrin, although extremely resistant to microbial degradation, was broken down in an anaerobic biological system. Figure 3 shows the relative persistence of several organo-chlorine insecticides. It must be remembered that although aldrin breaks down f a i r l y rapidly, a portion of i t i s converted to the highly stable dieldrin. Figure 3 [47] Persistence of Organochlorine Insecticides 28 II.8 BIOLOGICAL MAGNIFICATION The idea of biological magnification of insecticide residues i n the food chain refers to an accumulation of the insecticide to a higher con-centration than that in the preceding trophic le v e l . For this concept to work, two basic processes must occur: biological magnification of the insec-ticide at one trophic level and then biological transfer of the insecticide from that trophic level to the next highest. Several conditions [61] must be met by any insecticide before i t w i l l be accumulated by an organism: 1. The insecticide must persist in the physical environment long enough for assimilation by the organism to occur. 2. The insecticide must persist i n a form a v a i l -able to the organism considered . A—: 3. Once assimilated by the organism, the i n s e c t i -cide must be accumulated at a rate greater than that at which i t i s metabolized and/or excreted. From previous discussions, i t i s evident that DDT and dieldrin are persistent and therefore condition (1) i s met. Condition (2) i s easily satisfied by both DDT and dieldrin. Both DDT and dieldrin have been shown to be readily assimilated into organisms be-cause they are invariably much more soluble in the l i p i d part of any organism than in water [40, 61]. One example of this i s the study conducted by Chacko and Lockwood [9]. They found that over a 24-hour period, micro-organisms accumulated 70 to 90 per cent of the dieldrin and DDT from solutions contain-ing 0.1 to 1.0 ppm of these insecticides. Since both dead and l i v e micro-organisms accumulated nearly a l l the dieldrin and DDT from the medium, i t appears that this accumulation does not involve metabolism, but rather an 29 adsorption of the insecticide onto the surface of the micro-organism. Whether or not this process i s adsorption or absorption, these phenomena make these insecticides readily available to higher trophic levels, as micro-organisms are a lower.link i n the food chain of nearly a l l animals. Many other examples of DDT and dieldrin existing in forms easily assimilated are Illustrated by the occurrence of these organochlorine insecticides in numerous organisms [2, 18, 47]. Condition (3) is satisfied when considering the numerous examples of both DDT and dieldrin being accumulated at a rate greater than that at which i t is metabolized and/or excreted. DDT and dieldrin exhibit this property in both man (p. 24 this paper) and other organisms [38, 39, 45, 61, 62, 63] . Ko and Lockwood [45] added fungal and actinomycete mycelia to s o i l containing dieldrin, DDT and pentachloronitrobenzene (PCNB) and found that these s o i l micro-organisms accumulated a l l the insecticides to levels above ambient concentrations. Woodwell [63] shows that DDT and i t s residues have been biologi-cally magnified in an estuary on the east coast of the United States. Figure 4 shows the estuary flora and fauna and the residual concentrations of DDT and i t s metabolites found in them. In a study conducted by the United States Fish and Wildlife Department [62], DDT was found to be stored by oysters during a 40-day ex-posure period i n amounts 70,000 times greater than the 0.1 ppb concentration in the water. Earthworms, a major lower link in the food chain of many birds, have been shown to concentrate aldrin and dieldrin up to 10 times that of the surrounding s o i l [50] and DDT up to a thousandfold [38]. 30 NUMBERS INDICATE RESIDUES OF DDT AND ITS METABOLITES OBSERVED (IN FARTS PER MILLION, WET WEIGHT, WHOLE-BODY BASIS) Figure 4 [63] Biological Concentration of DDT in the Food Web of a Long Island Estuary 31 Evidence also exists that aquatic plants take up these organo-chlorine, insecticides. Wheeler et al. [64] showed that DDT and dieldrin can be sorbed through the root system of cereal crops and grasses. These insecticides are then distributed throughout the plant. It is obvious from the abundance of evidence presented that bio-logical magnification does indeed occur. In light of this conclusion, one should consider the possible increased effects insecticides would have on humans due to this process. Presently, the process of biological magnification appears to have a minimal impact on man because human food i s produced by a two- or three-link food chain i n which the process, i f recognized, can be controlled. For example, residues are permitted on feeds for domestic animals only i n amounts that w i l l not ultimately yield unacceptable levels i n meat, in milk, or i n other animal products. Thus, excessive levels of pesticide residues in agricultural products used for human consumption usually results only from accident or misuse. Of.course, by continuing to use such insecticides as DDT and dieldrin that can be biologically magnified, man cannot control the concentration of these insecticides i n fish and w i l d l i f e , and i n the future, w i l l exert a diminishing amount of control on the levels which develop in domestic animals. II.9 EUTROPHICATION An important action that the organochlorine insecticides may exert on aquatic organisms i s that of population suppression. This indirect lethal effect i s caused by changes in growth rates or changes in specific metabolic 32 processes, such as photosynthesis and carbon fixation. These indirect effects are ecologically very important. The insecticides exert stress on one or more organisms that may permit previously suppressed competitors to flourish. This may upset the environmental balance of the particular biological system. The diversity of species and the complexity of their interactions in the aquatic environment makes the evaluation of the effects of insecticides on these populations extremely d i f f i c u l t . Wurster [65] reports that concen-trations of p,p'-DDT as low as a few parts per b i l l i o n reduced photosynthesis in four species of coastal and oceanic phytoplankton representing four major classes of marine algae. Ware and Roan [40] report that in concentrations of one part per million during four hours exposure, dieldrin and DDT caused a reduction of carbon fixation by estuarine phytoplankton of 85 and 77 per cent respectively. It was found by Bishop [53] that the selective toxicity of DDT on certain a l g a e may alter the species composition of a natural phytoplankton community. The f l o r a l imbalances caused by these actions of insecticides could easily favour species that would normally be suppressed by others. This spec i f i c i t y could produce population explosions and dominance of the community by one or a few species, since their natural suppressors would have been k i l l e d by insecticides. This process could aggravate the problems of eutrophication caused by an excess of phosphates and nitrates i n natural water bodies. Thus the action of population suppression by insecticides may play an important yet rarely recognized role i n the eutrophication of lakes. CHAPTER III INFLUENCE OF SEDIMENTS ON WATER QUALITY I I I . l ADSORPTION AND DESORPTION The organochlorine insecticides are extremely hydrophobic and can be easily concentrated on soil s , particularly highly surface active clays. Such adsorption often leads to a diminution of the insecticide activity, but i t must be realized that there may be grave risks associated with the concept that what you do not see, w i l l not harm you. If the adsorption is irreversible then this detoxicification is essentially permanent. How-ever, i f this adsorption i s not irreversible, then complications could arise. The s o i l , together with i t s adsorbed insecticide, may be washed from treated areas into natural waters. Epstein and Grant [7] showed that runoff from treated plots contained significant amounts of the applied i n -secticides, DDT, endosulfan, and endrin, with the concentration and amounts of DDT being higher than the other insecticides during almost a l l the season. When these soil-insecticide combinations enter natural waters, there may be slow leakage of the insecticides back into the biological system. These concentrations may be too low to be of significance in pest control, but possibly s t i l l be at levels sufficiently high to be magnified in succes-sive steps in the food chain. Ultimately the insecticide may reveal or ex-press i t s e l f in terms of a harmful effect on some non-target organism. There have been several studies done on insecticide adsorption onto, and desorption from, s o i l s . H i l l and McCarty [13] showed that the adsorption 33 34 of several organochlorine insecticides, including DDT and dieldrin, onto bentonite clay did occur, and that this sorption was reversible. Eye [22] found that dieldrin was adsorbed from phosphate buffered water by various s o i l and clay-soil mixtures. Huang and Liao [66] found that DDT, dieldrin, and heptachlor were easily adsorbed by i l l i t e , kaolinite, and montmorillonite, with DDT being adsorbed in the largest quantity, heptachlor next, and dieldrin adsorbed the least. They found that at an i n i t i a l concentration of lOOngm/1 of insecti-cide, from 75 to 95 per cent was adsorbed onto the clay, depending upon the specific insecticide-clay combination used, and the amount of clay added. They also determined that the degree of desorption depended upon the mechan-isms through which adsorption i s attained. If adsorption i s attained by some weak forces of attraction, then a certain degree of desorption w i l l occur. Huang [67] found the adsorption of dieldrin onto montmorillo-nite was not significantly affected by water temperature changes in the range of 10°C to 30°C, and that the water pH only slightly affected the adsorption. He determined that several representative organic pollutants exerted no effect at a l l on the adsorption of dieldrin, heptachlor, and DDT by montmorillonite or i l l i t e . He also found that dieldrin adsorption by montmorillonite was not influenced by the soluble organic matter contained in a f i l t e r e d domestic wastewater. There are several conflicting theories and reports concerning the mechanisms of adsorption. Bailey and White [68,69] have presented two good reviews on the subject. In one of these reviews [69], the theory i s postu-lated that the expanding clay minerals, such as montmorillonite and vermiculite, have a high adsorptive capacity due to their high cation exchange capacity and 35 large specific surface area. The non-expanding clay minerals, such as i l l i t e , kaolinte, and chlorite, because of their low cation exchange capacity, and small specific surface area, do not have as large an adsorptive capacity. Eye [22], however, gives evidence indicating that the adsorp-tive capacity of soils i s more closely related to organic content than the specific surface area or the cation or base exchange capacities. He found that less dieldrin was adsorbed onto montmorillonite, a high cation exchange capacity and large specific surface area clay, than onto several other clays and clay-soil mixtures. Similarly, Huang and Liao [66] found that the adsorp-tive capacities of the clay used in their study; montmorillonite, kaolinite, and i l l i t e , did not correlate to their ion exchange capacities nor to their specific surface areas. The nature of the insecticide formulation may have an effect on the relative adsorption, desorption-, and a v a i l a b i l i t y of the insecticide. It has been reported that montmorillonite [70] and kaolinite [71] adsorb sur-factants to some degree. Since surfactants are present in most organochlorine insecticide formulations, these may result in competition for adsorption sites and thus would affect the adsorption and desorption of the insecticide. Whatever the mechanism, adsorption onto and desorption from soils does occur and therefore the role of suspended s o i l s becomes very important in water quality analysis with respect to the movement and bioactivity of insecticides. III.2 EFFECT OF SUSPENDED SOLIDS Suspended solids, washed from treated areas, may carry adsorbed insecticides far from their point of application. Freeden et al. [72] found 36 that DDT was adsorbed onto the suspended solids in the Saskatchewan River. These suspended solids contained from 0.24 to 2.26 ygms. of DDT per gram of solids as far as 68 miles downstream from their point of application. This event started with an i n i t i a l rate of application to the river of 0.09 ppm DDT, for 16 minutes, as a 10 per cent solution in methylated naphthalene and kerosene . The suspended solids in this case consisted mainly of clay and fine s i l t , and during the tests the suspended solids content of the river ranged as high as 551 ppm. As mentioned previously, Epstein and Grant [7] found that runoff from treated plots contained significant amounts of the applied insecticide. They showed that the total amount, the intensity, and the freguency of rain-f a l l or i r r i g a t i o n water received, not only affected the movement of the insecticide from the treated plots, but also affected the removal of the solids onto which these insecticides had been adsorbed. Adsorption isotherms, such as the one constructed by McCarty and H i l l [13] and reproduced i n Figure 5, can be used to estimate the potential pollutional load of pesticides in river waters. If the types and relative amounts of the material contained in the suspended solids is known, then the amount of potential pollution by the adsorbed insecticide can be estimated. McCarty and H i l l [13] give an example of this estimate based on Figure 5. If a turbid water contained 0.1 ugm/litre of DDT i n solution and carried a suspended so l i d load of 100 ygm/ml bentonite clay, there would be more DDT associated with the clay, than there would be in solution. Similar observations can be made for other insecticides and other clays or so i l s . Evidence exists which indicates that DDT is not as prevalent in natural waters as one might expect from the preceding discussion. Breiden-0.01 I : 1 1 1 1 1 0.01 0.1 I 10 100 1000 CONCENTRATION OF PESTICIDE IN WATER (PPB) Figure 5 [13] Pesticide Adsorption Isotherms bach and Lichtenberg [73], in studies of the major river basins of the United States, found dieldrin to be more prevalent than DDT. The sampling in their study was done by concentrating the pesticides from several thousand gallons of water by adsorption onto carbon. As Walker [74, p. 161] points out, however, ". . .when taking large samples using the adsorp-tive capacity of activated carbon, i t i s almost always necessary to remove the suspended solids with a sand f i l t e r f i r s t to avoid clogging the carbon cartridge," No mention of p r e - f i l t r a t i o n was made in the above study, but with turbid river waters, p r e - f i l t r a t i o n would seem l i k e l y . If p r e - f i l t r a t i o n did take place, the results of this study would be low and misleading. This fact is 38 of particular importance as i t illu s t r a t e s the lack of knowledge concerning the ultimate fate of insecticides in the aqueous environment. These adsorbed insecticides could possibly be desorbed and thus maintain small concentrations of these materials i n the water bodies. III.3 EFFECT OF BOTTOM SEDIMENTS Some of the suspended solids of natural waters eventually settle under quiescent conditions and become an integral part of the bottom sedi-ments. Thus the bottom sediments w i l l contain clays and soils that may have insecticides, especially the organochlorine ones, adsorbed onto them. Under certain conditions, part of the adsorbed insecticides may be desorbed and released onto overlying waters, where they would be maintained by a dynamic equilibrium system. As Woodwell [63, p. 30] states, ". . .DDT has only a low solubility in water, but as algae and other organisms in the water absorb the sub-stance in fats, where i t i s highly soluble, they make room for more DDT to be dissolved into the water. Accord-ingly, water that never contains more than a trace of DDT can continuously transfer i t from deposits on the bottom to organisms." It can be expected that the other organochlorine insecticides would behave in a similar manner. The concept of the bottom sediments providing a continuous supply of toxic material to the water, and thus to aquatic organisms, is reinforced by several studies [75,76,77,78,79] indicating higher concentrations of organochlorine insecticides in the mud than in the overlying waters. Bailey and Hannum [75] found that the pesticide concentrations in Califor-nia river sediments exceeded those i n water 20 to 100 times, with the concen-trations being proportionallyhigher as the sediments became finer. Bridges et 1 39 al. [77] found DDT and i t s metabolites were in significantly higher concen-trations in the mud bottom of a farm pond than in the water. Hickey et al. [78] found that the sediments obtained from Lake Michigan contained significant amounts of DDT and i t s metabolites. These samples were from relatively deep sections of the lake (33 to 96 feet) and i l l u s t r a t e the prevalent nature of DDT i n lake sediments. Methods may be available to cu r t a i l this release of toxic chemicals from the bottom sediments to the overlying waters. Sylvester and Seabloom [80] who found that the quality of the bottom s o i l had a detrimental effect on the overlying water's quality, determined that a well-placed mineral s o i l covering of about two inches in thickness effectively reduced the leach-ing and exchange of solutes from the bottom s o i l . Tenney and Echelberger [81] used f l y ash to develop a physical barrier at the mud-water interface which impaired the release of bottom pollutants into overlying waters. Similarly, a blanket of f l y ash or mineral s o i l over bottom sediments may effectively stop the release of organochlorine insecticides into the overlying waters. I CHAPTER IV DETECTION OF DDT AND DIELDRIN IV.1 INTRODUCTION The detection and measurement of the organochlorine insecticides is quite d i f f i c u l t due to their extremely low concentrations in the natural environment.and in biological tissues. Gas liquid chromatography with the electron capture detector, because of i t s extreme sensitivity with respect to electron capturing compounds such as the organochlorine insecticides, overcomes the d i f f i c u l t y of these low concentrations and has proven to be an ideal instrument for this analysis. 5LV.2 GAS LIQUID CHROMATOGRAPHY [82] IV.2.1 Definition. The basis for gas chromatographic separation i s the distribution of a sample between two phases. In gas liquid chromato-graphy (G.L.C.), one phase i s a liquid stationary bed spread as a thin film over an inert solid and the other phase i s a gas which percolates through this stationary bed. The basis for separation is the partitioning of the sample in and out of this l i q u i d film. IV.2.2 Technique of Gas Liquid Chromatography. In gas liquid chromato-graphy the components to be separated are carried through the column by an inert gas (Carrier Gas) as shown in Figure 6. The sample mixture is partitioned between the carrier gas and a non-volatile solvent (Stationary Phase) supported on an inert size-graded solid (Solid Support). The solvent selectively retards the sample components, according to their distribution coefficients [the ratio 40 41 of the concentration of the solute (sample component) in solvent one (the carrier gas) to that in solvent two (the liquid phase)], u n t i l they form separate bonds in the carrier gas. These component bands leave the column in the gas stream and are recorded as a function of time. Figure 6 [82] Schematic Drawing of a Gas Chromatographic System 42 IV.2.3 Carrier Gas. A high pressure gas cylinder serves as the source of carrier gas. A pressure regulator i s used to assure a uniform pres-sure to the column inl e t , and thereby a constant rate of gas flow. At a given column temperature, this constant rate w i l l elute components at a charac-t e r i s t i c time (the retention time) and thus qualitatively identify the compo-nents of the sample. The choice of carrier gas depends primarily on the detec-tor used. A purge flow may be introduced to the column effluent just after i t exits from the column. The purge gas is added to increase the linear velocity of the gas flow and thus decrease the residence time of the components as they are swept into the detector. This purge flow eliminates or minimizes band broadening due to the increase in the volume of the gas after exiting the column. At high flow rates (over 50 mls/min), band broadening i s not a fac-tor and thus purge flow i s not necessary. IV.2.4 Sample Introduction. The sample should be introduced instantaneously as a "plug" onto the column so as to have subsequent narrow chromatogram peaks and good separation of components. A standard technique for the introduction of gases and liquids i s to inject measured columns with a syringe, through a self-sealing septum located in the injection port (Figure 6) . IV.2.5 Column. The column tubing may be made of copper, stain-less steel, aluminum, or glass, in a straight, bent, or coiled form. The choice of column material i s dependent upon whether or not i t may adsorb or react with sample components. Straight columns are more eff i c i e n t , but at longer lengths may not f i t into the column oven and thus may have to be bent or coiled. If coiled, 43 the spiral diameter should be at least 10 times the column diameter to mini-mize diffusion and racetrack effects (the carrier gas finding a shorter route along the inside diameter of the column). IV.2.6 Solid Support. The purpose of tehe'solid support is to pro-vide a large,uniform, inert surface area for distributing the liquid phase. The solid support should be of regular size. There are several solid supports available commercially. IV.2.7 Stationary Phase. The correct choice of the partitioning solvent i s an important task. Ideally the solvent should have the following characteristics: (a) sample components must exhibit different d i s t r i -bution coefficients; (b) sample components should have a reasonable solubility in the solvent; (c) the solvent should have a negligible vapour pressure at the operating temperatures. The v e r s a t i l i t y and selectivity of gas liquid chromatography is largely due to the wide choice of solvents available. For the novice operator, the choice of solvents is best made after studying available literature concern-ing related work. IV.2.8 Temperature. Three different temperature controls, a sep-arate one each for the injection chamber, the column oven, and the detector, are needed on the gas chromatograph. The temperature of a l l three of these component parts serve different functions and thus must be able to be con-trolled independently. (a) Injection Port Temperature. The injection port must be hot enough to completely and rapidly vapourize the sample so that no loss of efficiency results from the injection technique. It must also be low 44 enough so that there is no thermal decomposition of the components in the sample. (b) Column Temperature. For most components the lower the column operating temperature, the higher the ratio of partition coefficients in the stationary phase. This results in better separation and longer reten-tion times. The column temperature should be optimized so that i t is high enough for analyses to be accomplished i n a reasonable length of time, and low enough so that the desired separation is obtained. (c) Detector Temperature. The influence of temperature de-pends considerably on the type of detector employed. As a general rule, how-ever, the detector, and the connections from the column exit to the detector, must be hot enough so that condensation of the sample does not occur. IV.2.9 Detectors. The detector indicates the presence and mea-sures the amounts of components in the column effluent. Desirable charac-t e r i s t i c s of a detector are high sensitivity, low noise level, a wide linear-ity of response, response to a l l types of compounds, ruggedness, and insen-s i t i v i t y to flow and temperature changes. There i s no ideal detector? however, the thermal conductivity c e l l and the flame ionization detector come close to satisfying the above c r i t e r i a . In addition, specific detec-tors such as the electron capture and the phosphorus detectors have the advan-tage of selectively measuring only certain types of compounds. This makes them extremely useful for trace and qualitative analysis. IV.3 THE ELECTRON CAPTURE DETECTOR USED WITH GAS LIQUID CHROMATOGRAPHY IV.3.1 Introduction. Lovelock and Lipsky [83] were the f i r s t to sug-gest the potential for electron capture use in gas liquid chromatography. 45 They noted that such a detector would excel in i t s a b i l i t y to selectively mea-sure certain compounds that show an a f f i n i t y for free electrons. The electron capture detector i s extremely sensitive to electron absorbing com-pounds such as organo-halides, conjugated carbonyls, n i t r i t e s , nitrates and organometallies. It i s vir t u a l l y insensitive to unsubstituted-hydrocarbons, amines, alcohols, and ketones. This selective sensitivity to chlorine contain-ing compounds makes the electron capture detector particularly valuable for the determination of organochlorine insecticides. It i s capable of detecting -12 picogram (10 grams) quantities of many organochlorine insecticides in a more concentrated matrix of a non-responding compound such as hexane (see Table IV). TABLE IV APPROXIMATE RELATIVE AFFINITIES OF ELECTRON-CAPTURE DETECTOR FOR SOME ORGANIC COMPOUNDSa COMPOUND DISC INTEGRATOR UNITS PER ygm. OF SAMPLE^ Hexane Chlorobenzene Atrazine 2,4-D Malathion DDT Heptachlor Dieldrin Lindane Carbon Tetrachloride 0.9 55.0 3,000 125,000 250,000 2,000,000 4,800,000 8,000,000 11,000,000 400,000,000 Marian-Aerograph Co., Walnut Creek, California. Disc Integrator Units are based on peak area measurement of chroma-tograms with a Disc Integrator. Source: Reference [84] 46 IV.3.2 Operation: Mechanisms and Principles of the Electron Capture Detector. In 1961 Lovelock [85] modified the geometry of his origi^-nal diode ion detector to that of two par a l l e l plates (Figure 7). In this new design the effluent from the G.L.C. column enters through the anode. The radioactive beta-source was tritium or nickel 63. When there i s only a non-electron absorbing gas in the c e l l , the high energy 3-particles (18 kev for tritium and 67 kev for nickel) produce posi-tive ions'and about a ten-fold increase of low-energy electrons due to the collisions of the 3-particles with the molecules of the carrier gas. By applying a potential to the electrodes these electrons w i l l migrate to the anode and thus establish a current. When a substance which can absorb these electrons enters the c e l l , part of the electrons w i l l be removed in the form of negative molecular ions. This decrease i n the number of electrons causes a corresponding decrease in the current which i s amplified and displayed on a strip chart recorder. A - ANODE AND GAS ENTRANCE C - CATHODE R - RADIOACTIVE p-SOURCE I c s-r-i — h PARALLEL PLATE DETECTOR CONCENTRIC TUBE Figure 7 [86] Schematic Drawing of Two Electron A f f i n i t y Cells 47 TV.3.3 Electron Capture With A Nickel 63 Source [82,87]. One of the more, common detectors in use today, and thus worthy of discussion in more detail, i s the Nickel 63 parallel plate detector. This par a l l e l plate electron capture detector is based on and quite similar to Lovelock's o r i -ginal design (Figure 8). Nickel 63 is used as the radioactive source be-cause i t can be operated at higher temperatures (360°C maximum) than can tritium (225°C maximum). This higher operating temperature offers greater selectivity in operating parameters of the gas chromatograph. The nickel 63 detector operates in much the same manner as Love-lock's par a l l e l plate detector; the radioactive source produces a current by emitting electrons (beta-radiations) which flow between an anode and a cathode. A-NICKEL FOIL B-GAUZE C-ANODE (INLET) D-CATHODE (OUTLET) E -PLASMA 2—o Figure 8 [87] Diagram of Electron Capture C e l l 48 With only purge gas i n the c e l l , an average current of 10 to -9 10 amps flows across the c e l l from A to B. This current is produced by electrons in the c e l l , which are derived from two sources: (a) primary electrons or beta-particles which are emitted by the nickel f o i l (A): (b) secondary electrons which are formed by the c o l l i s i o n between primary electrons and molecules of the carrier gas. The production of these secondary electrons occurs mainly i n the plasma (E). Positive ions are also formed in the plasma by these c o l l i s i o n s . When an electron capturing component i s introduced into the c e l l at C, i t moves into the plasma (E) where an abundance of free electrons exist. The eluted components capture electrons by several reactions, for example: AB + e -*• AB ± energy AB+e -* A + B~ ± energy AB + e -+• AB ± energy •* A + B ± energy The net result of this capturing i s the removal of electrons from the system and substitution of negative ions having a far greater mass. These ions w i l l combine with positive ions available in the plasma and be purged from the c e l l as a neutral complex. The ionization efficiency of certain compounds may approach 100 per cent, and the ionized molecules of these compounds that have a high electron a f f i n i t y may i n fact capture more than one electron. These two factors account, in part, for the extremely high sensitivity of the detector with respect to this type of compound. 49 When a potential is applied to the c e l l , essentially a l l the free electrons are collected at the anode (A, Figure 8). However, at least one electron has been captured for every molecule of electron capturing substance present. This loss of electrons results i n a corresponding decrease i n c e l l current which, after amplification, i s presented on a recorder. IV.3.4 Potential. The potential across the c e l l can be applied either as a continuous positive charge on one electrode (DC operation) or the charge may be applied periodically as i n "pulsed" operation. The pulsed mode has an advantage over the DC operation i n that with the DC operation large ions d r i f t , under the influence of a constant e l e c t r i c a l potential, toward the electrode of the opposite polarity. As a consequence, the current measured is a combination of both electrons and ion components with the resulting detector signal representing both electron capture and ion migration. With the pulsed mode this ion migration is negligible. During the pulsed operation, the applied voltage lasts only for 0.75 micro-seconds, as indicated in Figure 9. The electron concentration varies in a saw-tooth fashion. When the pulse is applied, the electrons are collected at the anode and their concentration drops rapidly to zero (point A, Figure 9). During the interval between pulses, the concentration gradually builds up as beta-.' particles are emitted from the Nickel 63 source (point B) . The magnitude of electron concentration then depends on the pulse interval (X). Decreased-detector sensitivity usually results from decreased pulse intervals. The collection of electrons at each pulse constitutes a current flow. Because of their small mass, the electrons accelerate, rapidly reaching the anode before the pulse terminates. The large ions formed hardly begin to 50 move during the 0.75 microsecond pulse and consequently their contribution to c e l l current i s negligible. Thus, as previously mentioned, the effect of ion migration i s negligible when using the pulsed mode. D-APPLIED POTENTIAL • TIME ( 3/4 U SEC.) X r PULSE INTERVAL (5,15,50,150 U SECj A TIME (MICROSECONDS) Illustration of Pulsed EC Ce l l Potential Figure 9 [87] The average or "standing" current noted in Figure 9 i s amplified in the electrometer and i s zeroed out to the recorder e l e c t r i c a l zero. The cap-ture of electrons by a sample component reduces the standing current and, as 51 mentioned, this reduction i s measured, amplified, and recorded. TV.3.5 Standing Current. The standing current of the electron capture detector i s related to: (a) detector cleanliness; (b) contamination, either from column or system bleed, or moisture or oxygen in the carrier or purge gas; (c) detector temperature; (d) gas flow rate; (e) pulse rate. With a relatively new and clean source, a standing current of about 4 - 6 x 10 ^ ° amps should be observed under the following conditionss (a) carrier gas flow rate: 60 ± 5 mis./min.; (b) carrier gas: 5% methane in argon; (c) purge flow: none; (d) detector temperature: 245 - 255°C,; (e) pulse interval: 50 u.secs. A value of less than 2.0 x 10 ^  amps for the standing current under the preceding conditions usually means that either the detector needs cleaning or there i s some contaminating material entering the detector. IV.3.6 Peak Area. The peak formed on the strip-chart recorder by the elution of an electron capturing component of a sample not only quali-tatively identifies the component by retention time, but also quantitatively mea-sures the sample weight by either peak height or peak area. The peak area may be measured by several methods, such as using a disc integrator, by triangulation using a ruler, or by a planimeter. 52 IV.3.7 Calibration Curve. A calibration curve for the pesticide being analyzed should be prepared by making a series of solutions of pesti-cide and pure (nanograde) hexane of varying concentrations and subjecting these solutions to gas chromatographic analysis. The most convenient curve constructed i s a plot of sample size versus disc integrator units on log-log paper. The curve should l i e on a precise 45 degree line and be linear over a weight range of about two log cycles. IV.3.8 Linearity. The electron capture detector i s inherently a non-linear device; however, as previously mentioned a plot of sample size versus peak area is linear over a weight range of about 100 times. It i s therefore essential that plots, such as those shown in Figure 10, be con-structed i n order to ensure one is working i n the linear range of the detec-tor. Significant errors may arise i n analysis, even though standards are frequently run, i f sampling occurs in the non-linear range. IV.3.9 Sensitivity. Under proper operating conditions ( a clean detector and no column or septum bleed, and no oxygen or water in the carrier gas) the electron capture detector has an extremely high sensitivity. This sensitivity i s illustrated by the plots i n Figure 10. For example, the smallest amount of aldrin that could be detected was 0.01 ngs which, in a one microlitre solution of water, amounts to 0.01 parts per million or 10 parts per b i l l i o n . IV.3.10 Carrier Gas. The pulsed detector requires a flow of argon/methane as either a carrier gas or a purge gas, or as both. Without a purge gas, the detector becomes overloaded (non-linear response) at an injection of approximately 10 ^ grams. Adding purge gas flow w i l l extend 53 FIGURE 10-SIX TYPICAL LINEARITY PLOTS [84] 54 linearity up to ten-fold (10 gram). As previously mentioned, however, at flow rates above about 50 mls/min., purge flow i s not needed in order to optimize detector sensitivity, and thus i t s inclusion i s not necessary. When used as a carrier gas, a composition of five per cent methane and 95 per cent argon i s the optimum, as shown in Figure 11. co TIME (USEC) Figure 11 [88] Electron Concentration vs. Time Between Pulses It i s essential that both the carrier gas and the purge flow, i f any, be dry and contain no oxygen. These two contaminants have a d e t r i -mental effect on the standing current as both w i l l absorb electrons. IV.3.11 Carrier Gas Flow Rate. The electron capture detector i s somewhat similar to the thermal conductivity detector with regard to carrier gas flow rate in that the signal increases as the flow rate is decreased. 55 However, as shown i n Figure 12, this i s not a linear relationship. 20 40 CARRIER GAS FLOW RATE (MLS/MIN) Figure 12 [88] Effect of Carrier Gas Flow Rate on Sensitivity It was found by Clark [89] that the pulsed mode detector i s insensi-tive to flow rate changes over the range of 40 to 200 mis. per minute. There-fore, i f the detector i s operated within this range, tests to optimize sensi-t i v i t y due to flow-rate changes need not be undertaken. IV.3."12 Detector Temperature. The detector temperature may have an incredible effect on sensitivity. The peak area may increase, decrease, or remain relatively constant as the detector temperature is changed [87]. 56 The detector operating temperature should be selected, in conjunction with other operating parameters, with the view to optimizing the sensitivity of the gas chromatograph system. This selection may encompass a wide range of detector temperatures with the only limitation being that this temperature be kept a few degrees above that of the column to prevent condensation of sample components in the detector. IV.3.13 Pulse Interval. The research gas chromatograph used i n this study offers a range of pulse intervals of 5, 15, 50 or 150 microseconds. The settings offer a control on sensitivity and linearity as shown in Figure 13. The longer the pulse interval, the greater the electron concen-tration grows, and thus sensitivity increases. However, other factors, such as detector, oven, and injection port temperatures and column bleed, also-play a part. Optimum sensitivity may therefore occur at shorter pulse intervals. 57 LINEARITY SAMPLE SIZE (GRAMS) Figure 13 [88] ! Linearity and Sensitivity at Various Pulse Intervals I CHAPTER V METHODS OF ANALYSIS USING ELECTRON CAPTURE GAS CHROMATOGRAPHY V.l GENERAL INFORMATION The methods described i n this section were chosen after an exten-sive review and analysis of a l l available literature exhausted the pos s i b i l -i t y of any further refinements. This section i s therefore limited to a discussion of the techniques used. Comprehensive treatment of analytical techniques are contained i n references [90, 91, 92 and 93]. V . l . l . Sample Handling. Samples taken for analysis were immedi-ately centrifuged and then subjected to extraction with nanograde hexane. Extracted samples were then analyzed by gas chromatography. Due to the possible i n s t a b i l i t y of DDT or dieldrin in water, the samples were not stored at a l l . V.l.2 Glassware. In order to avoid contamination i t i s of partic-ular importance that glassware used in pesticide analysis be scrupulously clean during use. Great care was therefore taken to ensure that this was the case. Glassware was cleaned as soon as possible after use, using a method recommended by Bevenue et al. [94] with several minor changes. Volumetric glassware was f i r s t washed with a strong soap solution and rinsed with tap water followed by a rinsing with a sodium dichromate-sulfuric acid solution. The glassware was then rinsed with tap water, dis-t i l l e d water, f i n a l l y with nanograde hexane and allowed to air-dry. Non-volumetric glassware was subject to the same thorough washing and rinsing 58 59 procedure, but after a i r drying i t was also heated overnight at 200°C. The glassware was stored immediately after cleaning to prevent accumulation of dust or other contaminants. If possible, the glassware was stored inverted. Several tests were undertaken to ensure that the glassware was thoroughly cleaned. At f a i r l y regular intervals during testing a sample blank was run which contained no insecticide. The resulting extract was subjected to gas chromatographic analysis and the chromatogram obtained studied for traces of insecticides. The results showed that the cleaning procedure employed was effective in removing possible adsorbed insecticides and any other interfering compounds. IV.1.3 Standards, Reagents and Solvents. Stock solutions were prepared by dissolving 100 mgs. of the insecticide in one l i t r e of pesticide grade acetone. Acetone is not recommended for pesticide use [92] as the pesticide may degrade upon standing in this solvent. However this infor-mation was not available at the start of the test and over the three month test period, neither DDT nor dieldrin showed any detectable degradation. The stock solution was transferred to one l i t r e , ground-glass stoppered, volumetric flasks and working standards prepared from these. The working standards were checked often for degradation and concentration and were renewed several times over the course of the study. A l l standards were stored in tightly stoppered flasks in a refrigerated incubator i n order to minimize evaporation losses. The standards were allowed to come to room temperature before opening. The solvent (hexane) used for extraction was of nanograde quality and was checked before use for degradation and/or interferences, by injection into the gas chromatograph. Other solvents and reagents used were also of 60 nanograde or pesticide grade quality. Solvents were stored in a cool dark place according to the manufacturer's instructions. Considerable d i f f i c u l t y was met in obtaining nanograde hexane of suitable quality for pesticide residue analysis. Hexane supplied by the f i r s t supplier was found to contain considerable quantities of interfering substances which were evidenced by poor chromatograms. Because i t was i n i t i a l l y thought that these poor chromatograms were due to machine or oper-ator error, considerable time was wasted in attempting to determine the cause of the problem. It was eventually found that the several gallons supplied were Of poor quality. Subsequently a second manufacturer was contacted who was able to supply high quality nanograde hexane. Comparative chromatograms of the two hexanes are shown i n Appendix A. The solvents used during the research undertaken in this thesis project were Fisher pesticide grade ace-tone (C H 0) and Mallinckrodt nanograde hexanes (C_H,.). 3 6 o 14 V.1.4 Sample Transfer. Extracted solutions of hexane were trans-ferred very carefully i n order to reduce the possible occurrence of inaccurat results. The internal wall of the transferring vessel was rinsed twice with hexane and the funnels used for transferring were also rinsed with hexane. Due to possible adsorption of the insecticide onto the ground glass sections of the volumetric flasks used [94], a l l transfers from such containers were made with clean, disposable glass pipettes. V.l.5 Cleaning of the Syringe. The syringe used in analysis was scrupulously cleaned after each sample injection. This was accomplished by several solvent (nanograde hexane) rinses. The plunger was., then removed and further cleaned by placing solvent on a tissue and carefully wiping the t 61 plunger, rinsing the plunger with d i s t i l l e d water and then wiping dry with a clean,' dry, lin t - f r e e tissue. The barrel was cleaned with copious amounts of solvents and then rinsed by drawing d i s t i l l e d water through the barrel with the aid of a low vacuum source. The barrel was dried then by forcing air from a clean compressed a i r source through i t . The syringe was checked periodically during a test for cleanliness. The syringe used during this study was a Unimetrics, 10 y l . syringe' with a replaceable needle. V.2 GAS LIQUID CHROMATOGRAPHY V.2.1 The Gas Chromatograph System. The gas chromatograph used in this study was a Hewlett-Packard research gas chromatograph with a Nickel 63 electron capture detector (pulsed mode) and a model 7127A strip chart recorder. The carrier gas used was a mixture of 95 per cent argon and five per cent methane supplied by Matheson of Canada, and guaranteed suitable for electron capture detector analysis. No purge flow was maintained. A molecular sieve gas-filter drier was used to remove any possible moisture in the carrier gas. The standing current test was used as a check of detector c l e a n l i -ness and contamination. As mentioned previously a standing current of about -10 4 - 6 xlO amps should be observed under specified conditions with a rel a -tively new and clean detector. A value of less than 2.0 x 10 ^  amps i n d i -cated the necessity for troubleshooting. Only once during the study period did the standing current f a l l below 3.5 x 10 ^  amps and this was due to detector uncleanliness. The de-, tector was thermally cleaned by operating i t at 50°C above i t s normal operating temperature of 265°C, with normal operating flow for 48 hours. The result of 62 this thermal cleaning i s shown in Appendix B. V.2.2 Columns. Since pesticides have been known to decompose upon contact with hot metals [84, 89], a borosilicate glass column was chosen for this study. The column was four feet long, with an inside diameter of four millimeters and packed with five per cent DOW-11 on 80/100 mesh high perform-ance Chromosorb W. The column was packed to a uniform density. Care was taken to avoid loose packing and consequent excessive void volumes and too dense pack-ing which would create excessive back pressure. The column tubing was rinsed with solvent and dried in the gas chromatograph oven before packing. The column was f i l l e d through a funnel connected by flexible tubing to one end. The other end of the column was plugged with silanized (made hydrophobic) glass wool and a slight vacuum was applied. The column was f i l l e d with the aid of an applied vibration and the applied vacuum. When f i l l e d , the open end was also plugged with silanized glass wool. The column was conditioned (prepared for use through removal of interfering materials) in the gas chromatograph oven, near i t s recommended maximum operating temperature for the l i q u i d phase, for 48 hours, under no flow conditions and not connected to the detector. V.2.3 Column Efficiency. The efficiency of the column and instru-ment systems is indicated by the narrowness of the eluted peaks and i s c a l -culated i n terms of the number of theoretical plates (N). High efficiency w i l l make a difference between good and poor quantitative results. A good column, operated under optimum conditions, should have an efficiency of at least 400 plates per foot [82]. 63 The expression for calculating the number of theoretical plates, as recommended by European and American Gas Chromatography Symposiums i s as follows [82, 87]: N = 16 (|) 2 where the distances X and Y are measured as shown in Figure 14. Figure 14 [87] Column Efficiency Parameters The efficiency of the column used in this study was about 1900 plates per foot for HEOD and about 1200 plates per foot for DDT. 64 V.2.4 Extraction of Sample.. Two extraction techniques were em-ployed in this study. Both techniques used hexane to extract the insecticide from the sample. In both cases, 25 m i l l i l i t r e s of sample (clay-insecticide solution) was withdrawn at the appropriate time, transferred to 50 ml. centri-fuge tubes, and centrifuged for 20 minutes at 2000 revolutions per minute. Ten mis. of the centratewas then extracted with hexane in a 50 ml, all-glass, separatory funnel. The f i r s t method consisted of making three separate 5 ml. extractions, collecting the extract in 25 ml. volumetric flasks and making the f i n a l sample up to exactly 25 mis. The efficiency of extraction from samples with known amounts of insecticide for this extraction technique ranged from 83 to 95 per cent for HEOD and 62 to 92 per cent for DDT. The second method of extraction involved making one extraction using 5 mis. of hexane and a second extraction using 2 mis. of hexane. The extract volume was made up to 10 mis. in volumetric flasks and the efficiency of extraction for this technique ranged from 88 to 93 per cent for HEOD and 72 to 84 per cent for DDT. The results of these recovery tests are shown in Appendix C. V.2.5 Injection Into The Gas Chromatographic System. The 10 micro-l i t r e syringe used in this study contained about 0.7 microlitre of sample in the needle after injection. Depending on the v o l a t i l i t y of the sample and the length of time the needle i s l e f t i n the injection port, part of this needle volume w i l l "bleed" into the injection port. Thus, total sample volumes injected may range from 10 to 10.7 microlitres, depending upon the operator's injection technique. Slower v o l a t i l i z a t i o n from the needle w i l l also result 65 in a broader injection plug and a consequent broadening of peaks. However, i f the injection technique i s well refined and the quickness of injection is good, this v o l a t i l i z a t i o n w i l l be minimized, i f not stopped altogether. Warnick and Gaufin [95] recommend that the operator practice injection tech-nique u n t i l he can make repeated injections with less than two per cent error. Extensive practice during this research enabled injection to be made with about one per cent error (Appendix D). The expertise developed resulted in very l i t t l e , i f any, of the needle volume being v o l a t i l i z e d in the injection port. To avoid bleed off that may have caused background interferences, the injection port septa were conditioned before use. This was accomplished by placing a new low-bleed septum in the unused injection port a day ahead of time and, with a low gas flow, allow this system to condition overnight. The two septa were rapidly interchanged the next morning resulting i n a short sys-tem stabilization time. As mentioned previously, pesticides have been known to decompose upon contact with hot metals and thus some pesticide may be lost in the i n -jection port. To make sure that this was not the case, on-column injections were carried out. In an on-column injection, the sample is injected directly into the glass column and does not make contact with the hot metal of the i n -jection port. V.2.6 Qualitative and Quantitative Analysis. Qualitative identi-fication of an unknown component is made by matching the retention time of the unknown with that of a standard obtained under identical conditions. i Usually this single gas chromatographic determination does not provide un-66 equivocal identification of the unknown component. However, in this study, since the insecticide was the only chemical added that could have been ex-tracted, i t is not actually an unknown, and thus the comparison of retention time with that of a standard would constitute positive identification,. The area of the eluted peak i s proportional to the quantity of the insecticide injected. This area was measured by a disc integrator, which is part of the strip chart recorder. The units of measurement are termed disc units. To improve precision, three injections of each sample were made and the areas calculated from each injection were averaged. Standards were run for each series of tests and calibration curves similar to those shown in Figures 15 and 16 were plotted. It was necessary to run these standards because neither detector sensitivity nor column v a r i -ables, such as the amount of liquid phase or temperature, may remain con-stant between tests. The concentration of insecticides i n the sample i s calculated as follows: A x _ . .micrograms. t Concentration (—, . ? ) = ________ l i t r e V. x V 1 s where A = sample size in nanograms as found from chromatograms; V. 1 = volume of extract injected (uls); V t = volume of total extract (uls); V s = volume of water extracted (mis). V.2.7 Optimum Operating Conditions. The optimum operating condi-tions, combining a relatively short retention time, good peak geometry, and no column packing breakdown, were as follows: 67 -10 ,000 ipoo z o CO Q < ID rr < < ID CL 1.0 SAMPLE SIZE (NANOGRAMS) FIGURE 15 - LINEARITY CURVE FOR DDT 10.0 68 10,000 jo ipoo o w Q < UJ cc < < LO 100 0.1 1.0 SAMPLE SIZE (NANOGRAMS) 10.0 FIGURE 16 - LINEARITY CURVE FOR HEOD 1 Detector temperature: Injection port temperature: Column temperature: Carrier gas flow rate: Purge gas flow rate: Rotameter setting: Carrier gas i n l e t pressure: Pulse interval: Range: Attenuation: Temperature program: Chart speed: Once these optimum operating conditions maintained throughout the study period. 69 225°C. 230°C. 230°C. 90 mis./min. none 4.0 40 p s i . 150 usees, 10 variable isothermal 0.25 inches/min. were determined, they were CHAPTER VI DESCRIPTION OF STUDY METHODS VI.1 ADSORPTION AND DESORPTION TESTS Adsorption and desorption tests were conducted in a series of 2 l i t r e Pyrex bottles. The test solutions were agitated with glass-covered s t i r r i n g bars which were operated by magnetic s t i r r e r s . Glass-coated s t i r -ring bars were used instead of teflon as the teflon-coated s t i r r i n g bars may have adsorbed some of the insecticide [93] . During each test the bottles were tightly sealed with foil-covered rubber stoppers. For each adsorption test, a 1.5 l i t r e , 100 yg/1 aqueous i n s e c t i c i -dal solution was placed i n each of the 2 l i t r e bottles. (Because of the low solubility of these insecticides, in a l l tests one ml. of pesticide-grade acetone per l i t r e of solution was used as a carrier solvent). An accurate-ly weighed quantity of clay was then added to each bottle and allowed to be mixed with the solution. The insecticide remaining in the water was deter-mined at frequent intervals, beginning from when the clay was added, u n t i l equilibrium was reached. For the desorption tests a suitable method of separating the re-maining clay from the water had to be found. This was accomplished by exact-ly repeating the above adsorption tests except that a l l solutions were made 0.01 molar with respect to CaCl 2 by the addition of CaCl 2 • 2H20. The addi-tion of this salt had the desired effect of causing the clay to flocculate i and settle. The addition of enough CaCl 2 to make the solution 0.01 molar 70 71 was undertaken as this procedure was shown to not affect the adsorption of another chlorinated hydrocarbon (Lindane) onto fine clays [96]. At the end of this second series of adsorption tests, the clay was allowed to settle overnight and the overlying water decanted and replaced with new d i s t i l l e d water. The test solutions were then mixed continuously for the remainder of the test and the insecticide concentration in the water was determined at frequent time intervals starting with the i n i t i a l replacement of the dis-t i l l e d water. Repeating the adsorption tests had the added advantage of deter-mining whether or not the addition of CaCl 2 • 2H20 affected the adsorption of the insecticides onto the clay particles. VI.2 QUIESCENT REMOVAL TESTS Quiescent removal tests were conducted in two l i t r e Pyrex beakers. The test solutions were well-mixed 1.5 l i t r e aqueous insecticidal solutions which had an i n i t i a l insecticide concentration of 100 ugms/litre. These again were made 0.01 molar with respect to CaCl 2. An accurately weighed amount of clay was l i g h t l y sprinkled on top of the test solutions and allowed to settle into and through the solutions. The insecticide concentration in the solution was determined at regular time intervals starting immediately following the addition of the clay. The test solutions were not agitated in any way during this test except for the i n i t i a l preparation of. the i n -secti c i d e - d i s t i l l e d water - CaCl^ * 2H20 solution. i 72 VI.3 SAND BLANKETING TESTS Sand blanketing tests were conducted immediately following the quiescent removal tests. The clay in the test solutions was allowed to further settle overnight. In one test solution the settled clay was covered with approximately 1/4 inch of sand while the settled clay of an identical test solution was l e f t uncovered. The water in the test solutions was then replaced, attempting not to disturb the settled clay or the sand layer. After 12 hours the water directly above the sand layer and directly above the settled clay was sampled for insecticide analysis. The water was again replaced and after a further 24 hours sampled and analyzed in the same manner. CHAPTER VII RESULTS OF THE STUDY VII.l ADSORPTION TEST RESULTS The results of the adsorption study indicate that significant amounts of the experimental insecticides were adsorbed onto the bentonite. Of the two insecticides, DDT i s adsorbed easier and in greater quantities than HEOD. The tabulated results of a l l the tests are presented in Appendix E. The spread in individual tests as illustrated by tests 1, 2, and 3 in Figure 17 when compared to tests 4, 5 and 6 in Figure 18, is due to several factors. The latter tests were more precise due to operator exper-tise gained, in operating the gas chromatograph, extracting the samples, and other research procedures, as the test program progressed. This spread was evident i n the several tests conducted during the i n i t i a l stages of the research. Also, a certain amount of the impreciseness noted in a l l tests conducted was due to the d i f f i c u l t y in maintaining exact operating condi-tions of the gas chromatograph throughout the test period. Figures 17 and 18 show that HEOD is adsorbed onto bentonite with the degree of adsorption depending upon the clay concentration. With a clay concentration of 1.0 gm/l about 15 per cent of the HEOD i s adsorbed while with a clay concentration of 10.0 gm/l about 30 per cent of the HEOD is adsorbed. These figures also show that the adsorption of HECD onto bento-i nite i s essentially instantaneous with the maximum adsorption occurring 73 74 2 3 4 5 TIME (HOURS) FIGURE 1 7 - H E O D ADSORPTION CURVES' 1.0 G M / L BENTONITE TEST NO. 5,6,7 BENTONITE CONC/IO.O GM/L HEOD CONC.: 100 pGM/L CONTF OL- . - > / < • 1 > ) TIME (HOURS) FIGURE 18-HEOD ADSORPTION CURVES' 10.0 G M / L BENTONITE 1 75 during the f i r s t 1/2 to 1 1/2 hours. Thereafter, a gradual desorption takes place u n t i l the equilibrium adsorption level i s attained about two hours after the start of the test. Figures 19 and 20 confirm that the addition of CaCl 2 • 2H20, enough to make the solution 0.01 molar, does not seriously alter the f i n a l equilibrium adsorption level of the HEOD onto the bentonite. However, the i n i t i a l adsorption levels are affected by the CaCl 2 * 2H20 addition and in the tests containing the higher clay concentrations the time required to reach the f i n a l equilibrium level is increased. Figures 21 and 22 indicate that DDT i s adsorbed onto bentonite to a much greater degree than HEOD. With a clay concentration of 1.0 gm/l about 60 per cent of the DDT is adsorbed while with a clay concentration of 10.0 gm/l the adsorption i s increased to about 72 per cent. These f i g -ures also show that the rate of adsorption of DDT onto bentonite is dependent upon the clay concentration. The solutions containing 1.0 gm/l clay take nearly four hours to reach equilibrium compared to about two hours for the 10.0 gm/l. clay solutions. This difference in the rate of adsorption is l i k e -ly due to the DDT having easier access to the adsorption sites located on the clay particles when there i s a higher clay concentration. As shown in Figures 23 and 24, the addition of enough CaCl 2 • 2H20 to make the solution 0.01 molar does not seriously alter the f i n a l equilibrium adsorption of DDT. However, the addition of this salt does slow the rate of DDT adsorption. It appears that the C a + + ion i s , in a l l probability, changing the structure of the layers of the clay molecule such that i t affects the rate of DDT adsorption. 76 40L-2 3 4 TIME (HOURS) FIGURE 19-HEOD ADSORPTION CURVES 1.0 GM/L BENTONITE; SOLUTION 0.01 MOLAR h T E S T NO. 10, 11,12 BENTONITE CONC. 10.0 G M / L HEOD CONC. 100 U G M / L WT. CaCI 2 < 2 H 2 0 = 2.205 GMS. ) & ____________ — -< ' ; < \ < I —• — MM TIME (HOURS) FIGURE 2 0 - H E O D ADSORPTION C U R V E S ' 10.0 GM/L BENTONITE; SOLUTION 0.01 MOLAR 77 4 0 o 5 3 0 or UJ o z 5 20 ui CO Y T R 0 L EQUILIB RWM CC >NC.= 73 U G M / TEST NO. 13, 14,15 BENTONITE CONC- 1.0 6 M / L DDT CONC. • 100 U G M / L i _ ( 3 <• ) / \ — i >• • - ( js ) • S 1 < IE r -Z Ul o z o o 10 2 3 4 TIME (HOURS) FIGURE 21- DDT ADS0RTI0N CURVES-. 1.0 G M / L BENTONITE 4 0 2 5 30 ui I a 20 z z < S u i rr z o Si cc r -Z Ul o z o o cor T R 0 L E QUILIBF IUM CO MC.= 81 J G M / L TEST NO. 16, 17, 18 BENTONITE CONC/10.0 G M / L DDT. CONC.: 100 p G M / L V »- * 8 1 p 10 TIME (HOURS) FIGURE 22 -DDT ADSORPTION CURVES 10.0 GM/L BENTONITE 45 5 I 1 1 1 1 1 1 1 1 1 1 1 U 0 1 2 3 4 5 6 TIME (HOURS) FIGURE 2 3 - DDT ADSORPTION CURVES 1.0 G M / L BENTONITE,- SOLUTION 0.01 MOLAR T E S T NO. 2 2 , 2 3 . 2 4 BENTONITE C O N C . 10.0 G M / L - 3 5 DDT CONC. 100 U G M / L t j WT. C a C I a - 2 H z O ; 2.205 GMS s O 30 , — , , , rr 0 1 1 1 1 1 1 1 1 1 1 L 0 I 2 3 , 4 6 TIME (HOURS) FIGURE 2 4 - DDT ADSORPTION CURVES 10.0 G M / L BENTONITE i SOLUTION 0.01 MOLAR 79 VII.2 DESORPTION TEST RESULTS The overlying water that was decanted during the adsorption tests was quite clear, with an average of 1.61 mg/l total solids. Thus very l i t t l e clay was removed with the decanted water. As a l l the overlying water could not be removed without disturbing and/or removing some of the clay, the water was only decanted to a specified level for each clay concentration. For the 1.0 gm/l clay, a maximum of 53 mis. of clay-water solution was l e f t in the bottles, and for the 10.0 gm/l clay concentration, a maximum of 310 mis of clay-water solution was l e f t . Therefore a certain portion of the insecticide measured during the desorption tests would come from the thin layer of water overlying the clay which was not decanted. This concentration however can be calculated from the adsorp-tion test results. It can therefore be calculated whether or not desorption does in fact occur. Such calculations are presented in Appendix F. Results of the adsorption tests i l l u s t r a t e d in Figures 25 and 26 show that the desorption of HEOD from bentonite does occur, with an e q u i l i -brium value of about 10 ygm/1 reached for both clay concentrations, 1.0 gm/l and 10.0 gm/l. Figures 27 and 28 indicate that DDT desorption from bentonite does occur; with a desorption concentration of 3 ygm/1 and 1 ycrm/1 for clay concentrations of 1.0 gm/l and 10.0 gm/l, respectively. VII.3 QUIESCENT REMOVAL TEST RESULTS The results of the quiescent removal tests for HEOD are presented I in Figure 29. The curves confirm that bentonite can be used to remove dis-solved HEOD. The clay, added to the solution under quiescent conditions, 80 s ca-rr ui < rr ui o z o u ; i TEST NO. 25, 26,27 BENTONITE CONC. 1.0 G M / L INITIAL HEOD CONC. .100 U G M / L i' — — — / 1 > _— 1 L , / / 1 — k y i >. — _ • —— / - • 3 ( *. ST* C » 1 / \ s o MAXIH rfUM POJ 5SIBLE C ONCENTf NATION C UE TO C ILUTION o TIME (HOURS) FIGURE 2 5 - H E O D D E S O R P T I O N C U R V E S ' 1.0 G M / L BENTONITE 2' o n. r r . ui < r-< < rr i-z U l o z o o JT 1 T E S T NO. 28,29,30 BENTONITE CONC. 10.0 G M / L IN1TIALHE0D CONC. 100 P G M / L 1 -© / { . i ) - ~f. '-/. < i i f . { i. •v. 2 o MAXI i MUM P 0 SSIBLE C lONCENT RATION DUE TO DILUTION 1 r o TIME (HOURS) FIGURE 2 6 - H E O D DESORPTION C U R V E S ' 10.0 G M / L BENTONITE 81 TEST NO. 31, 32,33 BENTONITE CONC. I.O G M / L INITIAL DDT CONC. 100 p G M / L _ l JS n . IO I — — i i MAX 1 MUM PC 1 3SSI8LE t CONCEIT 1 TRATIO t 1 ^ DUE -I 1 •0 DILU" i ION 7 I 2 3 4 TIME (HOURS) FIGURE 2 7 - D D T DESORPTION CURVES' I.O GM/L BENTONITE T E S T NO. 34 ,35 ,36 BENTONITE CONC. I0.0 G M / L INITIAL DDT CONC. I00 U G M / L S M WIMUM POSSIBL E CONC ENTRATi ON DUE . TO DIL UTION JS) i IS n . 7 1 <i m / / * 9 ^ 4 - I A C ) f TIME (HOURS) FIGURE 2 8 - DDT DESORPTION CURVES'-! 10.0 G M / L BENTONITE CONCENTRATION REMAINING IN WATER (UGM LITRE) 38 83 settled through the solution, and while settling adsorbed HEOD from i t . The amount of HEOD removed from the water i s dependent upon the amount of clay used as an adsorbing agent. Figure 30 il l u s t r a t e s the results of the tests using bentonite to remove DDT from quiescent water bodies. As i n the case for .HEOD, the bentonite removed DDT from the solution while settling through i t , and the amount removed i s dependent upon the amount of clay used as an adsorbing agent. The results of the quiescent removal tests for HEOD indicate that the same or sli g h t l y more HEOD was adsorbed during these tests while under quiescent conditions, than was adsorbed during the adsorption tests, while under constant mixing conditions. A possible explanation of this phe-nomenon is that the weak HEOD-clay bond was broken in some cases, due to the rapid mixing that was undertaken during the adsorption tests, and thus just slightly less HEOD was adsorbed during such tests than during the quies-cent removal tests. In the case of the adsorption tests for DDT, the stronger DDT-clay bond was not affected by the rapid mixing and thus the results for the adsorp-tion tests (mixing) and the quiescent removal tests (no mixing) compare quite closely. 1 85 VII.4 SAND BLANKETING TEST RESULTS . The sand blanketing tests were undertaken to see i f this method would stop the desorption of adsorbed insecticides from benthic clay de-posits into overlying waters. The results of these tests are presented in Tables V and VI for HEOD and DDT, respectively. In these tests, water samples were taken just prior to the addi-tion of the Ottawa sand and sample number one (time: 0 hours) was taken just after the sand addition. It was found by comparing the results from these samples that the sand i t s e l f did not adsorb any insecticides. As can be seen in Tables V and VI, the sand layer does in fact help prevent the desorption of the insecticides into the overlying water. Some of the insecticide present in the water i s due to dilution (as in the desorption tests, not a l l the water could be removed) but both test solutions, the solution with the sand blanket and the one without, were l e f t with essen-t i a l l y the same amount of water. Thus the differences in insecticidal concentration between the samples with a sand blanket and those without, as shown in Tables V and VI, cannot be attributed to dilution effects, but must be caused by desorption. Therefore, i t is apparent that the sand blanket used was at least somewhat effective in reducing desorption of the insecticides from the clay. The effectiveness of the sand blanket was due to the fact that i t acts as a physical block to the desorption of the insecticide into the over-lying waters. TABLE V SAND BLANKETING TESTS FOR HEOD TEST NUMBER 1 2 3 4 Sample Number : i 2 3 1 2 3 1 2 3 1 . 2 3 Bentonite Concentration (mg/l) 1.0 1.0 1.0 1.0 1.0 1.0 10.0 10.0 10.0 10.0 10.0 10.0 Time sample taken (hrs) 0 12 36 0 12 36 0 12 36 0 12 36 Time when over l y i n g water replaced (hrs) l 13 - 1 13 - 1 13 . - 1 13 -Cone, of HEOD i n overlying water f o r sample without sand blanket (ygm/1) 60.0 9.1 2.4 62.0 8.7 3.1 50.5 6.3 2.5 51.0 4.3 1.7 Cone, of HEOD i n overlying water f o r sample with sand blanket (vigm/1) 55.0 8.43 Trace 57.0 8.3 Trace 52.5 4.14 Trace 49.0 2.21 Trace CO TABLE VI SAND BLANKETING TESTS FOR DDT TEST NUMBER 1 2 3 4 Sample number 1 2 3 1 2 3 1 2 3 1 2 3 Bentonite Concentration (mg/l) 1.0 1.0 1.0 1.0 1.0 1.0 10.0 10.0 10.0 10.0 10.0 10.0 Time sample taken (hrs) 0 12 36 0 12 36 0 12 3.6 0 12 36 Time when overlying water replaced (hrs) 1 13 - 1 13 - 1 13 - 1 13 •• Cone, of DDT i n overlying water f o r sample without sand blanket (ygm/1) 19.0 2.64 16.2 3.7 2.8 9.4 3.4 2.6 9.5 3.2 2.5 Cone, of DDT i n overlying water for sample with sand blanket (ygm/1) 15.0 4.0 2.0 14.1 3.6 2.1 9.0 2.1 Trace 9.3 2.2 Trace CHAPTER VIII CONCLUSIONS AND RECOMMENDATIONS VIII.1 CONCLUSIONS 1. DDT and dieldrin are persistent i n the environment, can be biologically magnified, and may exist i n the natural habitat of man and animals, exerting their lethal and sub-lethal effects, for a long period of time. 2. The adsorption of DDT and HEOD onto bentonite does occur (Figures 17 to 24) with DDT being adsorbed to a greater extent. The rate of adsorption, and the f i n a l adsorption equilibrium level attained for both insecticides, are related to the clay concentration of the solution, with the higher clay concentration adsorbing more insecticide, and reaching i t s f i n a l adsorption equilibrium level faster. With a DDT concentration of 100 ygm/1 (ppb) in solution the addi-tion of bentonite at a concentration of 1.0 gm/l w i l l cause the removal of about 60 per cent of this insecticide, while the addition of bentonite at a concentration of 10.0 gm/l w i l l result i n removal of about 72 per cent. With a HEOD concentration of 100 ygm/1 in solution, the addition / of similar bentonite concentrations of 1.0 gm/l and 10.0 gm/l w i l l bring about the removal of about 15 and 30 per cent of the HEOD, respectively. The addition of a salt (CaCl 2 • 2H20) has relatively l i t t l e or no effect on the f i n a l insecticide adsorption level attained. However, due to the salt's i n i t i a l competition with the insecticide for the adsorp-88 89 tion sites on the clay particles, the time required to reach the f i n a l adsorption level i s increased. 3. The desorption of DDT and HEOD from bentonite does occur (Figures 25 to 28), with HEOD being desorbed to the greater degree and DDT desorption being quite minimal. The DDT appears to be much more tightly bound to the bentonite than the HEOD. The desorption equilibrium level attained for HEOD appears to be unrelated to the clay concentration, and thus to the amount of HEOD ad-sorbed, as essentially the same amount of HEOD was desorbed for both clay concentrations (1.0 gm/l and 10.0 gm/l). In the case of DDT, the results were inconclusive, except to say that some desorption does occur. 4. The insecticidal removal during quiescent removal tests was related to the amount of bentonite that was settled through the water. As expected from the adsorption tests, DDT was removed to a greater ex-tent than HEOD (Figures 29 and 30). The results indicate that bentonite at concentrations of 1.0, 5.0, and 10.0 gm/l, w i l l remove about 44, 48, and 54 per cent, respectively, of the DDT while settling through a quiescent water body that i n i t i a l l y con-tained DDT at a concentration of 100 ygm/1. Bentonite at similar concentrations of 1.0, 5,0, and 10.0 gm/l w i l l remove about 14, 23, and 30 per cent, respectively of the HEOD while settling through a quiescent water body that had an i n i t i a l HEOD concentra-tion of 100 ygm/1. 5. The addition of a layer of sand blocks the desorption of DDT and HEOD from benthic clays. The sand blanket i s somewhat effective 90 because i t acts as a physical block to the desorption of the insecticide. Suspended materials, onto which insecticides may be adsorbed, when settled make up an integral part of bottom sediments. Under certain condi-tions part of the adsorbed insecticides may be desorbed from these benthic deposits and released into the overlying waters where they would be main-tained by a dynamic equilibrium system. A sand layer over these benthic deposits, acting as a physical barrier, would materially reduce this de-sorption into the overlying waters. This sand layer would also reduce the potential for further contamination due to the transportation of these polluted bottom sediments to uncontaminated areas. VIII.2 RECOMMENDATIONS Pesticides, especially the organochlorine insecticides DDT and^  d i e l -drin, are highly toxic to w i l d l i f e and extremely persistent i n the natural environment. Due to the many instances of overuse and misuse, i t i s strong-ly recommended that research into the contamination of the aquatic environ-ment by the organochlorine insecticides be continued. It is of particular importance to examine the ultimate fate of these insecticides once they have entered the marine ecosystem. This research should be directed towards evaluating the long-range effects of low-level doses and the possible syner-g i s t i c and antagonistic effects of pesticides in the aquatic environment. The pollution of natural water bodies by contaminated benthic de-posits i s becoming an increasingly common occurrence. This contamination may be due to insecticides or other pollutants such as mercury, nutrients, radio-active isotopes, and others, and w i l l require further research into i t s pre-vention. The concept of using a blanket of inorganic material to act as a physical barrier to any re-solution is worthy of much more research. In the case of such research, the type of inorganic material to be used as the blanket should be studied, as should the optimum thickness of the blanket. The application of different types and thicknesses of inorganic materials should be studied for different contaminants. Different materials to be used as adsorbants for various soluble pollutants should also be researched. The research should eventually be undertaken with a dynamic system in order to duplicate as closely as possible the conditions in nature. It is f e l t that the knowledge gained from such research may have important engineering applications i n the not too distant future. 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A P P E N D I C E S APPENDIX A COMPARATIVE CHROMATOGRAMS OF TWO ..HEXANES 3 •• 2 •• I - -BOTH INJECTIONS ARE THE SAME SIZE, WITH THE SAME OPERATING CONDITIONS. THE CHROMATOGRAM ON LEFT (FROM SUPPLIER'A') SHOWS INTERFERENCES WHILE THE ONE ON THE RIGHT SHOWS NONE. APPENDIX B THERMAL CLEANING RESULTS i MEASUREMENT OF THE STANDING CURRENT [94] 1. Balance the electrometer to true recorder zero which should coincide to the chart 0 per cent. 2. Set the following range and attenuation: Nickel . . . . 10 x 6 4 3 . Disconnect the electrometer cable at the detector. 4. Zero the pen to 100 per cent using the electrometer zeroing controls. 5 . Reconnect the cable and note the recorder reading (R). 6. Calculate the Standing Current (S.C.) —12 100—R S.C. = [electrometer sensitivity (1x10 amps)] X Range X Attenuation X ^ A. Standing Current * ( l x l 0 ~ 1 2 ) ( 1 0 ) ( 6 4 ) ( 1 0 ° 0 Q 2 ) = 1.79 x 10~ 1 0 amps. B. Standing Current = ( l x l O - 1 2 ) (10) (64) (i~zH) = 4 . 3 5 x i o " 1 0 amps. 104 105 z LJ CC CC 13 O o z STANDING CURRENT TEST 1 A". STANDING CURRENT BEFORE THERMAL CLEANING = 1.79 x I0 _ l 0amps. in B STANDING CURRENT AFTER THERMAL CLEANING OVER WEEKEND = 4.35 x I0"'°amps. APPENDIX C EXAMPLES OF RECOVERY FROM SAMPLES CONTAINING KNOWN AMOUNTS OF INSECTICIDE * A. EXAMPLES FOR HEOD RECOVERY FROM SAMPLE CONTAINING 100 ugm/litre WITH NO CLAY ADDED 3-5 ml. extractions 1-5 ml., 12 ml. extraction Sample No. 1 2 1 2_ Volume Water Ext. (mis) 10 10 10 10 Volume Extract (mis) 25 25 10 10 Volume Inject (yls) 5 5 3 3 Disc Area (D.U.*s) 271 273 455 421 Sample Size (ngs) 0.167 0.169 0.286 0.267 Concentration (u. g/1) 83.5 84.5 95.3 89.0 Recovery Eff. (%) 83.5 84.5 95.3 89.0 * B. EXAMPLES FOR DDT RECOVERY FROM SAMPLES CONTAINING 100 u gm/litre WITH NO CLAY ADDED 3-5 ml. extractions 1-5 ml., 12 ml. extr Sample No. 1 2: 1_ 2_ Volume Water Ext. (mis) 10 10 10 10 Volume Extract (mis) 25 25 10 10 Volume Inject (uls) 5 5 3 3 Disc. Area (D.U.'s) 176 152 329 267 Sample Size (ngs) 0.143 0.125 0.278 0.221 Concentration (yg/1) 71.5 62.5 92.6 73.6 Recovery Eff. (%) 71.5 62.5 92.6 73.6 * In a l l recovery efficiency tests from spiked samples, the samples were extracted in the same manner as the actual test samples. Therefore, recovery efficiency includes loss of insecticide on centri-fuge tubes and walls of other vessels, as well as the efficiency of the extraction process. It appears that the loss on vessels walls i s a major factor in loss of insecticide, as the samples that were extracted the least, but also handled the least, had the highest recovery efficiencies. 107 APPENDIX D EXAMPLES OF INJECTION TECHNIQUE PRECISION ANALYSIS TESTS PEAK AREA REPRODUCIBILITY TESTS Operating Conditions: Pulse Interval - 50 u sees. Attenuation - 64 Range - 10 Oven Temperature - 230°C. Detector Temperature - 265°C. Injection Port Temperature - 230°C. Inlet Pressure - 40 p s i . Carrier Gas Flow Rate - 90 mls/min. EXAMPLE 1 INJECTION PEAK AREA X-X (X-X) 2 NO. (X) 1 762 6.2 38.44 2 747 -8.8 77.44 3 739 -16.8 283.00 4 758 2.2 4.84 5 763 7.2 51.84 6 751 -4.8 23.04 7 758 2.2 4.84 8 764 8.2 67.24 9 753 -2.8 7.14 10 763 -7.2 51.83 Total = 610.36 X 755.8 s 2 = 6 1 0 ; 3 6 = 67, s = 3.22 . X = 755.8 ± 8.2 error = (0.6745)(8.2) = 5.54 error , 4, .5.54 ( % > = (755.8 ) 1 0° = 0.73%. EXAMPLE 2 INJECTION PEAK AREA X-X (X-X) NO. (X) 1 444 -1.2 1.44 2 450 4.8 23.04 3 458 12.8 163.84 4 428 -17.2 295.84 5 438 7.2 51.84 6 452 6.8 46.24 7 451 5.8 33.64 8 447 1.8 3.24 9 444 -1.2 1.44 10 439 -6.2 38.44 Total = 659.00 X = 445.2 2 659.0 0_ s = — = 73.22 s = 8.55 .*. X = 445.2 ± 8.55 Probable error = (0.6745)(8.55) = 5.77 Probable error (%) - ( f ^ j ) 1 0 0 = 1.29%. \ APPENDIX E ADSORPTION, DESORPTION, AND QUIESCENT REMOVAL TESTS ADSORPTION TEST NO. 1 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF . -DISTILLED CaCl, • 2 H20 WATER ADDED (ugm/1) (ugm/1) (mg/l) (mis) (gms) 100 — 1.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 10 25 25 25 25 Volume Injected (uls) 5 5 5 5 5 5 Peak Area (Disc Units) 166 195 164 182 179 181 Sample Size (ngs) 0.131 0.155 0.128 0.145 0.141 .0.151 Concentration i n Water (ugm/1) 65.5 62.0 64.0 72.0 70.5 75.5 ADSORPTION TEST NO. 2 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 1.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 198 204 200 211 223 225 Sample Size (ngs) 0.15 0.155 0.i52 0.16 0.17 0.172 Concentration in Water (ygm/1) 75.0 77.5 76.0 80.0 85.0 86.0 ADSORPTION TEST NO. 3 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 1.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 227 203 229 236 259 272 Sample Size (ngs) 0.38 0.34 0.385 0.40 0.438 0.462 Concentration in Water (ygm/1) 76.0 68.0 77.0 80.0 87.6 92.4 ADSORPTION TEST NO. 4 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ugm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 10.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 160 169 177 161 180 163 Sample Size (ngs) 0.115 0.122 0.129 0.116 0.130 0.118 Concentration i n Water (ygm/1) 57.5 61.0 64.5 58.0 65.0 59.0 ADSORPTION TEST NO. 5 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (mis) CaCl- • 2 H20 ADDED (gms) 100 — 10.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected .(yls) 5 5 5 5 5 5 Peak Area (Disc Units) 146 159 153 169 167 180 Sample Size (ngs) 0.106 0.117 0.113 0.125 0.124 0.13 Concentration i n Water (ygm/1) 53.0 58.5 56.5 62.5 62.0 65.0 ADSORPTION TEST NO. 6 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 10.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 170 175 186 180 190 186 Sample Size (ngs) 0.11 0.113 0.12 0.117 0.122 0.12 Concentration in Water (ygm/1) 1 - , 55.0 56.5 60.0 58.0 61.0 60.0 ADSORPTION TEST NO. 7 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl, • 2 H20 WATER ADDED (ugm/1) (Ugm/1) (mg/l) (mis) (gms) 100 — 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 201 218 219 221 227 223 Sample Size (ngs) 0.138 0.148 0.149 0.151 0.156 0.153 Concentration in Water (ygm/1) 69.0 74.0 74.5 75.5 78.0 76.5 ADSORPTION TEST NO. 8 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl 2 • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 340 195 180 185 193 182 Sample Size (ngs) 0.29 . 0.156 0.142 0.147 0.155 0.143 Concentration in Water (ygm/1) 145 73.0 71.0 73.5 77.5 71.5 ADSORPTION TEST NO. 9 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl, • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 1.0 1500 2.2Q5 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 185 200 196 200 212 196 Sample Size (ngs) 0.152 0.164 0.16 0.164 0.168 0.16 Concentration i n Water (ygm/1) 76.0 82.0 80.0 82.0 84.0 80.0 ADSORPTION TEST NO. 10 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 ' 5 Peak Area (Disc Units) 222 231 203 207 210 211 Sample Size (ngs) 0.129 0.131 0.115 0.119 0.12 0.12 Concentration i n Water (ygm/1) 64.5 65.5 57.5 59.5 60.0 60.0 ADSORPTION TEST NO. 11 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl 2 • 2 H20 WATER ADDED (ugm/1) (ygm/1) (mg/l) (mis) (gms) 100 — 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 138 136 115 136 142 150 Sample Size (ngs) 0.115 0.113 0^096 0.113 0.119 0.124 Concentration i n Water (ygm/1) 57.5 56.5 48.0 56.5 59.5 62.0 ADSORPTION TEST NO. 12 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ugm/1) (ugm/1) (mg/l) (mis) (gms) 100 — 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (uls) 5 5 5 5 5 5 Peak Area (Disc Units) 209 210 209 215 217 217 Sample Size (ngs) 0.12 0.1205 0.12 0.123 Q.124 0.124 Concentration i n Water (ugm/1) 60.0 62.25 60.0 61.5 62.0 62.0 ADSORPTION TEST NO. 13 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) — 100 1.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 45 27 23 23 32 25 Sample Size (ngs) 0.04 0.0238 0.02 0.02 0.02E 0.023! Concentration i n Water (ygm/1) 20.0 11.9 10.0 10.0 10.0 8.4 ADSORPTION TEST NO. 14 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl 2 • 2 H20 WATER ADDED (ugm/1) (ygm/1) (mg/l) (mis) (gms) — 100 1.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 6 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 158 150 144 120 91 67 Sample Size (ngs) 0.129 0.115 0.111 0.092 0.084 0.052 Concentration i n Water (ygm/1) 25.8 23.0 22.2 18.4 16.8 10.4 ADSORPTION TEST NO. 1 5 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl, • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) — 100 1.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 51 42 42 40 32 31 Sample Size (ngs) 0.04 0.0336 0.0336 0.316 0.024E 0.024 Concentration in Water (ygm/1) 20.0 16.8 16.8 15.8 12.4 10.2 ADSORPTION TEST NO. 16 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) — 100 10.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 82 77 75 69 62 48 Sample Size (ngs) 0.063 0.059. 0.0575 0.0525 0.047 0.0365 Concentration in Water (ygm/1) 12.6 11.8 11.5 10.5 9.4 7.3 ADSORPTION TEST NO. 17 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCI- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) — 100 10.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 33 27 28 23 26 25 Sample Size (ngs) 0.025 0.0205 0.020E 0.0169 0.018E 0.0184 Concentration i n Water (ygm/1) 12.5 10.25 10.4 8.45 9.25 9.2 ADSORPTION TEST NO. 18 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl, • 2 H20 WATER ADDED (Ugm/1) (ygm/1) (mg/l) (mis) (gms) — 100 10.0 1500 — Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 68 74 70 66 59 58 Sample Size (ngs) 0.055 0.059 0.056 0.053 0.047 0.0465 Concentration in Water (ygm/1) 11.0 11.8 11.2 10.6 9.4 9.3 ADSORPTION TEST NO. 19 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) — 100 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 ' 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 163 142 100 114 61 51 Sample Size (ngs) 0.15 0.13 0.09 0.105 0.056! 0.047 Concentration i n Water (ygm/1) 30.0 26.0 18.0 21.0 11.3 9.4 ADSORPTION TEST NO. 20 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl 2 • 2 H20 WATER ADDED (ugm/1) (ygm/1) (mg/l) (mis) (gms) — 100 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 93 45 43 53 36 35 Sample Size (ngs) 0.079 0.038 0.036 0.045 0.029 0.028 Concentration i n Water (ygm/1) 39.5 19.0 18.0 22.5 14.5 14.0 ADSORPTION TEST NO. 21 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl. • 2 H-0 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) — 100 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 105 79 48 47 39 28 Sample Size (ngs) 0.084 0.063 0.0385 0.0375 0.031 0.0215 Concentration in Water (ygm/1) 42.0 31.5 19.25 18.75 15.5 12.75 ADSORPTION TEST NO. 22 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (pgm/1) (ugm/1) (mg/l) (mis) (gms) -- 100 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (uls) 5 5 5 5 5 5 Peak Area (Disc Units) 46 43 34 25 25 22 Sample Size (ngs) 0.042 0.0395 0.0315 0.024 0.024 0.0195 Concentration i n Water (ugm/1) 21.0 19.75 15.75 12.0 12.0 9.75 ADSORPTION TEST NO. 23 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl- • 2 H20 WATER ADDED (ygm/1) (ygm/1) (mg/l) (mis) (gms) — 100 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 25 25 25 25 25 25 Volume Injected (yls) 7 7 7 7 7 7 Peak Area (Disc Units) 30 23 31 34 30 24 Sample Size (ngs) 0.025 0.019 0.0262 0.0285 0.025 0.02 Concentration in Water (ygm/1) 8.93 6.78 9.36 10.2 8.93 7.15 ADSORPTION TEST NO. 24 HEOD CONC. DDT CONC. BENTONITE CONC. VOLUME OF DISTILLED CaCl 2 • 2 H20 r WATER ADDED (ugm/1) (ygm/1) (mg/l) (mis) (gms) — 100 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 Time (hours) 0 h 1 2 4 6 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 125 92 77 67 73 65 Sample Size (ngs) 0.101 0.073 0.062 0.053 0.058 0.052 Concentration in Water (ygm/1) 20.2 14.6 12.4 10.6 11.6 10.4 DESORPTION TEST NO. 1 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) 100 — 1.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 k h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 94 102 101 118 106 103 Sample Size (ngs) 0.053 0.057 0.057 0.067 0.061 0.058 Concentration in Water (ygm/1) 10.6 11.4 11.4 13.4 12.2 11.6 DESORPTION TEST NO. 2 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) 100 — 1.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 115 116 120 124 122 124 . Sample Size (ngs) 0.073 '0.073 0.077 0.08 0.078 0.08 Concentration in Water (ygm/1) 14.6 14.6 15.4 16.0 15.6 16.0 DESORPTION TEST NO. 3 INITIAL HEOD CONC. (ugm/1) INITIAL DDT CONC. (ugm/1) INITIAL BENTONITE CONC. (mg/l) 100 — 1.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 k h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 84 86 86 91 90 94 Sample Size (ngs). 0.057 0.059 0.059 0.062 0.062 0.084 Concentration in Water (ugm/1) 11.4 11.8 11.8 12.4 12.4 12.8 DESORPTION TEST NO. 4 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) 100 — 10.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 146 163 159 167 169 175 Sample Size (ngs) 0.098' 0.112 0.108 0.114 0.115 0.12 Concentration in Water (ygm/1) _ - - -19.8 -. -22.4 -21.6 22*3 23,0 24.0 I 1 DESORPTION TEST NO. 5 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (Ugm/1) INITIAL BENTONITE CONC. (mg/l) 100 — 10.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (uls) 5 5 5 5 5 5 Peak Area (Disc Units) 65 154 150 165 171 165 Sample Size (ngs) 0.038 0.102 0.098 0.11 0.115 0.11 Concentration i n Water (ugm/1) 7.6 20.4 19.6 22.0 23.0 22.0 DESORPTION TEST NO. & INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) 100 — 10.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 Peak Area (Disc Units) 120 176 193 205 199 196 Sample Size (ngs) 0.068 0.102 0.111 0.117 0.114 0.113 Concentration in Water (ygm/1) 12.6 20.4 22.2 23.4 22.8 22.6 DESORPTION TEST NO. 7 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) — 100 1.0 Sample Number 1 2 3 4 5 6 Time.(hours) 0 k h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 7 7 7 7 7 7 Peak Area (Disc Units) 33 34 35 35 35 36 Sample Size (ngs), 0.026 0.027 0.0275 0.0275 0.0275 0.0285 Concentration in Water (ygm/1) 3.71 3.85 3.93 3.93 3.93 4.07 DESORPTION TEST NO. 8 INITIAL HEOD CONC. (Ugm/1) INITIAL DDT CONC. (Ugm/1) INITIAL BENTONITE CONC. (mg/l) — 100 1.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (uls) 7 7 7 7 7 7 Peak Area (Disc Units) 33 32 33 30 33 30 Sample Size (ngs) 0.026 0.025 0.026 0.232 0.026 0.0232 Concentration i n Water (ugm/1) 3.71 3.57 3.71 3.31 3.71 3.31 DESORPTION TEST NO. 9 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) — 100 1.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 7 7 7 7 7 7 Peak Area (Disc Units) 32 34 30 33 35 36 Sample Size (ngs) 0.025 0.027 0.0232 0.026 0.0275 0.0282 Concentration in Water (ygm/1) 3.57 3.85 3.31 3.71 3.93 4.03 DESORPTION TEST NO. 10 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) — 100 10.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 \ h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 7 7 7 7 7 7 Peak Area (Disc Units) 21 25 27 27 29 28 Sample Size (ngs) o.oi6: 0.0195 0.021 0.021 0.0225 0.022 Concentration in Water (ygm/1) 2.71 2.78 3.0 3.0 3.21 3.1 DESORPTION TEST NO. 11 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) — 100 10.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 7 7 7 7 7 7 Peak Area (Disc Units) 23 ; 25 28 23 22 20 Sample Size (ngs) I 0.017< 0.0195 0.0215 0.0179 0.017 0.0155 Concentration in Water (ygm/1) 2.55 2.78 3.13 2.55 2.43 2.21 DESORPTION TEST NO. 12 INITIAL HEOD CONC. (ygm/1) INITIAL DDT CONC. (ygm/1) INITIAL BENTONITE CONC. (mg/l) — 100 10.0 Sample Number 1 2 3 4 5 6 Time (hours) 0 h h 1 2 4 Volume of Water Extracted (mis) 10 10 10 10 10 10 Extract Volume (mis) 10 10 10 10 10 10 Volume Injected (yls) 7 7 7 7 7 7 Peak Area (Disc Units) 21 24 28 27 29 28 Sample Size (ngs) 0.0164 0.0187 0.022 0.021 0.0227 0.022 Concentration i n Water (ygm/1) 2.34 2.67 3.1 3.0 3.18 3.1 QUIESCENT REMOVAL TEST NO. 1 VOLUME OF WEIGHT OF HEOD CONC. DDT CONC. BENTONITE CONC. DISTILLED WATER CaCl 2 • 2H20 ADDED (ygm/1) (ygm/1) (mg/l) (ml) (gms) 100 — 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 253 262 253 250 248 261 368 360 Sample Size (ngs) 0.147 0.152 0.147 0.145 0.143 0.151 0.215 0.21 Concentration in Water (ygm/1) 73,5 76.0 73.5 72.5 71.5 75.5 71.7 70.0 QUIESCENT REMOVAL TEST NO. 2 VOLUME OF WEIGHT OF HEOD CONC. DDT CONC. BENTONITE CONC. DISTILLED WATER CaCl 2 • 2H20 ADDED (ugm/1) (ygm/1) (mg/l) (ml) (gms) 100 — 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 245 246 249 256 252 250 258 256 Sample Size (ngs) 0.141 0.142, 0.144 0.148 0.146 0.145 0.149 0.148 Concentration in Water (ygm/1) 70.5 71.0 72.0 74.0 73.0 72.5 74.5 74.0 QUIESCENT REMOVAL TEST NO. 3 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) 100 — 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 255 260 258 262 251 251 248 250 Sample Size (ngs) 0.1485 0.15 0.149 0.151 0.146 0.146 0.144 0.145 Concentration i n Water (ygm/1) 74.25 75.0 74.5 75.5 73.0 73.0 72.0 72.5 QUIESCENT REMOVAL TEST NO. 4 HEOD CONC. (ugm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) 100 — 5.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 258 240 240 236 234 232 220 212 Sample Size (ngs) 0.149 0.138 0.138 0.136 0.134 0.132 0.126 0.122 Concentration in Water (ygm/1) 74.5 69.0 69.0 68.0 67.0 66.0 63.0 61.0 QUIESCENT REMOVAL TEST NO. HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) 100 — 5.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 238 238 239 238 236 224 218 210 Sample Size (ngs) 0.137 0.137 0.138 0.137 0.136 0.13 0.125 0.121 Concentration in Water (ygm/1) 68.5 68.5 69.0 68.5 68.0 65.0 62.5 60.5 QUIESCENT REMOVAL TEST NO. 6 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) 100 — 5.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 230 238 235 230 232 225 220 214 Sample Size (ngs) 0.132 0.137 0.135 0.132 0.133 0.13 0.126 0.122 Concentration in Water (ygm/1) 66.0 68.5 67.5 66.0 66.5 65.0 63.0 61.0 QUIESCENT REMOVAL TEST NO. 7 HEOD CONC. (ugm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) 100 — 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 4 4 4 4 4 4 4 4 Peak Area (Disc. Units) 186 183 193 180 169 171 168 170 Sample Size (ngs) 0.106 0.098 0.104 0.095 0.09 0.098 0.096 0.098 Concentration i n Water (ygm/1) 66.3 61.2 65.0 59.4 56.3 49.0 48.0 49.0 QUIESCENT REMOVAL' TEST NO. 8 HEOD CONC. (ugm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) 100 — 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 4 4 5 5 5 5 5 5 Peak Area (Disc. Units) 252 172 184 190 186 184 180 177 Sample Size (ngs) 0.145 0.098 0.105 0.109 0.106 0.105 0.103 0.101 Concentration in Water (ygm/1) 90.5 61.2 52.5 54.5 53.0 52.5 51.5 50.5 QUIESCENT REMOVAL TEST NO. 9 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) 100 — 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 k h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 236 153 148 144 135 124 126 122 Sample Size (ngs) 0.136 0.1245 0.12 0.117 0.11 0.10 0.101 0.098 Concentration in Water (ygm/1) 68.0 62.25 60.0 58.5 55.0 50.0 50.5 49.0 QUIESCENT REMOVAL T E S T N 0 « 1 0 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 96 70 54 58 52 146 123 114 Sample Size (ngs) 0.086 0.064 0.05 0.0535 0.048 0.132 0.113 0.105 Concentration in Water (ygm/1) 43.0 32.0 25.0 26.75 24.0 26.4 22.6 21.0 QUIESCENT REMOVAL TEST NO. 11 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 72 63 57 57 49 127 114 94 Sample Size (ngs) 0.067 0.058 0.053 0.053 0.045 0.116 0.105 0.086 Concentration i n Water (ygm/1) 38.5 29.0 26.5 26.5 22.0 23.2 21.0 17.2 QUIESCENT REMOVAL TEST NO. 12 HEOD CONC. (ugm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 1.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 112 85 72 65 60 57 50 54 Sample Size (ngs) 0.091 0.068 0.057 0.052 0.048 0.045 0.04 0.043 Concentration in Water (ygm/1) 45.5 34.0 28.5 26.0 24.0 22.5 20.0 21.5 QUIESCENT REMOVAL TEST NO. 13 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 5.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 k h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 10 10 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 120 111 117 108 93 91 89 105 Sample Size (ngs) 0.11 0.101 0.107 0.098 0.084 0.083 0.082 0.095 Concentration in Water (ygm/1) 22.0 -20.2 21.4 19.6 16.8 16.6 16.4 19.0 QUIESCENT REMOVAL TEST NO. 14 HEOD CONC. (ugm/1) DDT CONC. (Ugm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 5.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 10 10 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 111 110 114 106 109 99 93 89 Sample Size (ngs) 0.101 0.10' 0.105 0.096 0.10 0.91 0.084 0.082 Concentration in Water (ugm/1) 20.2 20.0 21.0 19.2 20.0 18.2 16.8 16.4 QUIESCENT REMOVAL TEST NO. 15 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 5.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 10 10 10 10 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 156 125 130 122 113 111 110 105 Sample Size (ngs) 0.128 0.101 0.104 0.099 0.092 0.09 0.088 0.086 Concentration in Water (ygm/1) 25.6 20.2 20.8 19.8 18.4 18.0 17.6 17.2 QUIESCENT REMOVAL TEST NO. 16 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 h h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 31 25 28 28 23 56 57 59 Sample Size (ngs) 0.0285 0.023 0.026 0.026 0.0215 0.0515 0.053 0.0521 Concentration i n Water (ygm/1) 14.25 11.5 13.0 13.0 10.75 10.3 10.6 10.42 QUIESCENT REMOVAL TEST NO. 17 HEOD CONC. (ygm/1) DDT CONC. (ygm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 k h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 25 25 25 25 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 42 41 40 36 35 32 29 31 Sample Size (ngs) 0.0335 0.023 0.031 0.0285 0.028 0.0245\ 0.023 0.024 | Concentration in Water (ygm/1) 16.75 16.5 15.5 14.25 14.0 12.25 11.5 12.0 QUIESCENT REMOVAL TEST NO. 18 HEOD CONC. (ugm/1) DDT CONC. (ugm/1) BENTONITE CONC. (mg/l) VOLUME OF DISTILLED WATER (ml) WEIGHT OF CaCl 2 • 2H20 ADDED (gms) — 100 10.0 1500 2.205 Sample Number 1 2 3 4 5 6 7 8 Time (hours) 0 k h 1 2 4 6 8 Volume of Water Extracted (mis) 10 10 10 10 10 10 10 10 Extracted Volume (mis) 25 25 25 25 10 10 10 10 Volume Injected (yls) 5 5 5 5 5 5 5 5 Peak Area (Disc. Units) 35 32 28 30 75 68 60 57 Sample Size (ngs) 0.0315 0.029 0.026 0.0275 0.068 0.063 0.055 0.053 Concentration in Water (ygm/1) 15.75 14.5 13.0 12.75 13.6 12.6 11.0 10.6 APPENDIX F SAMPLE CALCULATIONS t 167 (a) Concentration of Insecticide in Water where A x V Cone. = - — v (ygms/litre) i s A = sample size in nanograms; V = volume of total extract (yls); V\ = volume of extract injected (yls); V = volume of water extracted (mis) s For Test #1, Sample No. 1 A = 0.131 ngs V = 25,000 yls V ± = 5 yls V = 10 s (0.131) (25,000) c _ _ ._ Cone. = .—(5) (jo) = 65.5 ygm/1 l t r e (b) Calculation of Insecticide Left i n Solution After Removal of Water; Desorption Tests (i) For 1.0 gm/l Clay Concentration, for HEOD tests 25, 26, 27: Amount of water l e f t = 53 mis Maximum concentration in this water (from adsorption tests) = 80 ygms/litre 168 Amount of water in Desorption tests = 1350 mis maximum possible concentration due . . . . to dilution = i,c» =3.14 ygm/litre (ii) For 10 gm/l Clay Concentration, for HEOD tests 28, 29, 30: Amount of water l e f t = 310 mis. Maximum concentration i n this water (from desorption tests) = 62 ygm/litre Amount of water in desorption test (added after decanting) = 1350 mis. . . Maximum possible concentration due . . . to dilution = — 1 3 5 0 = 1 3 , 8 Vqm/Htre ( i i i ) For 1.0 gm/l Clay Concentration, for DDT tests 31, 32, 33: Amount of water l e f t = 53 mis. Maximum concentration i n this water = 14 ygm/litre Amount of water in desorption test = 1350 mis .*. Maximum possible concentration due (53)(14) to dilution = 1 3 5 Q = 0.55 ygms/litre 169 (iv) For 10.0 gm/l Clay Concentration, for DDT tests 34, 35, 36s Amount of water l e f t =310 mis Maximum concentration in this water = 10.5 ugm/litre Amount of water in desorption test = 1350 mis .*. Maximum possible concentration due c\ - • - . . l o l l ) ; t l U . S ; . ., . to dilution = ———- • =2.4 ygms/litre l O D U (c) Calculation of Amount of CaCl,, Added Gram Molecular Weight of CaCl 2 • 2H20 = 147 gms . Add 1.47 gms and bring solution up to one l i t r e by adding d i s t i l l e d water to make solution 0.01 molar. .". Add (1.47)(1.5) = 2.205 gms of CaCl 2 • 2H20 and bring solution up to 1.5 l i t r e s to make solution 0.01 Molar. 

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