16 Pesticide Availability Influence of Sediment in a Simulated Aquatic Environment
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ALLAN R. ISENSEE Pesticide Degradation Laboratory, Beltsville Agricultural Research Center, U.S. Department of Agriculture, Beltsville, MD 20705
Sediment additions were made to model aquatic environments containing DDT equilibrated between sediment, water, and four species of aquatic organisms to determine i f pesticide a v a i l a b i l i t y to biota was reduced through normal sedimentation events. Soil treated with C-labeled DDT at 10, 100, and 1000 ppm was flooded and fish (Gambusia a f f i n i s ) , snails (Helosoma sp.), algae (Oedogonium cardiacum), and daphnids (Daphnia magna) were added. At two-week intervals, untreated sediment additions (equalling 1% of the water weight) were made. Samples of water and organisms, taken before and after sediment additions, were analyzed for DDT, DDE, and DDD and compared to equilibrated systems not treated with sediment. DDT content in water decreased 3-to 9fold by the f i r s t sediment addition. Polar metabolites in water increased as DDT decreased. Fish were k i l l e d at the 1000 ppm level and daphnids succembed at 100 and 1000 ppm levels. Sediment additions substantially reduced the toxicity at lower treatment levels. Sediment additions decreased total C by 6 to 13% in fish, 20 to 40% in algae, 45 to 50% in snails and 55% in daphnids (10 ppm rate). Measureable levels of DDT not diffuse through 1 cm or more of untreated s o i l into water in one year. Covering pesticide contaminated sediment with soil and sediment in situ is an effective contamination control method under certain aquatic conditions. 14
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P e s t i c i d e s that enter the aquatic environment from spills or improper treatment of manufacturing waste pose unusually difficult d i s p o s a l problems. For example, the volume of contaminated and d i s p o s a l methods are i m p r a c t i c a l and p r o h i b i t i v e l y expensive. In a d d i t i o n , the p h y s i c a l c o n d i t i o n This chapter not subject to U.S. copyright. Published 1984, American Chemical Society
Krueger and Seiber; Treatment and Disposal of Pesticide Wastes ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
TREATMENT AND
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of the s i t e may severely l i m i t the use of e s t a b l i s h e d techniques and heavy equipment. Thus some i n s i t u means of c o n t r o l l i n g the contamination i s h i g h l y d e s i r a b l e . One p o t e n t i a l i n s i t u abatement procedure i s to bury the contaminant i n place under s o i l or sediment. H i g h l y i n s o l u b l e , s t r o n g l y adsorbed contaminants would, i d e a l l y , be contained and b i o l o g i c a l l y i s o l a t e d by t h i s procedure. In a d d i t i o n , the anaerobic c o n d i t i o n s that develop under the o v e r l a y i n g s o i l or sediment r e s u l t i n a c c e l e r a t e d degradation of c e r t a i n compounds. D e c h l o r i n a t i o n of DDT under anaerobic conditions i s well known (1, 2). Dehalogenation of haloaromatic compounds has also been demonstrated under anaerobic c o n d i t i o n s ( 3 ) . The study was conducted to evaluate i n s i t u sedimentation as an abatement procedure. DDT was chosen as the t e s t p e s t i c i d e since i t i s a p e r s i s t e n t , w a t e r - i n s o l u b l e compound that has created d i f f i c u l t d i s p o s a l problems and since a contaminated s i t e e x i s t s i n Alabama where DDT r e s i d u e s estimated to exceed 500 tons have been found i n the bottom sediment of a 3-mile stream segment. Two experiments were conducted to (1) determine the e f f e c t of s o i l (sediment) a d d i t i o n s i n t o a simulated aquatic environment on the d i s t r i b u t i o n and b i o - a v a i l a b i l i t y of DDT and (2) determine the extent of DDT d i f f u s i o n through layers of untreated sediment. Methods and M a t e r i a l s Microecosystem Chambers The aquatic microecosystem i s shown i n Figure 1 and has been p r e v i o u s l y described ( 4 ) . For t h i s study, 160-g q u a n t i t i e s of a sandy c l a y loam s o i l (58.4, 18.0, 26.6 and 1.94 % sand, s i l t , c l a y and organic carbon, r e s p e c t i v e l y ) were t r e a t e d with [ ^ C - r i n g ] DDT (98+ % p u r i t y , 3.6 m Ci/mmole s p e c i f i c a c t i v i t y ) at 10, 100 and 1000 ppm and placed i n the bottom of 20-L c a p a c i t y glass tanks (41 χ 20 χ 24 cm). The s o i l was obtained from an uncontaminated l o c a t i o n upstream from the DDT contaminated s i t e i n Alabama. Three r e p l i c a t e s of each rate plus two c o n t r o l (160 g untreated s o i l ) were prepared and then flooded with 16-L a c t i v a t e d carbon f i l t e r e d tap water. One day l a t e r 20 f i s h (Gambusia a f f i n i s ) , 20 s n a i l s (Helisoma sp.) and 1-g algae (Oedogonium cardiacum) were added to the tank and about 200 daphnids (Daphnia magna) were placed i n the daphnid chamber (1.5-L c a p a c i t y tank with a s t a i n l e s s s t e e l screen bottom to r e s t r i c t daphnid passage) which was suspended i n the 20-L tank. Water was continuously pumped (about 10 ml/min) i n t o the daphnid chamber which ensured uniform mixing of the water and transport of food to the daphnids. Untreated (no DDT) s o i l a d d i t i o n s (160 g/tank) were made to two of the three r e p l i c a t e s at each c o n c e n t r a t i o n and to one of the c o n t r o l tanks 14, 28 and 42 days a f t e r the a d d i t i o n of organisms. S o i l was f i r s t suspended i n 2-L of water, then
Krueger and Seiber; Treatment and Disposal of Pesticide Wastes ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
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Figure 1. Microecosystem contains 16 L water and four o f organisms. The chamber measures 41 χ 20 χ 24 cm.
species
Krueger and Seiber; Treatment and Disposal of Pesticide Wastes ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
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TREATMENT AND DISPOSAL O F PESTICIDE WASTES
drained into tanks 3 cm below the water surface with the flow d i r e c t e d h o r i z o n t a l l y to minimize d i s r u p t i o n of the bottom treated s o i l . A water volume of 16-L was maintained v i a a properly located d r a i n . The ecosystem was t h e r e f o r e designed t o simulate an i n f l o w o f water and sediment into a p e s t i c i d e e q u i l i b r a t e d pond or l a k e . Sampling and A n a l y s i s Water samples ( t r i p l i c a t e 1-ml) were taken at 2-day i n t e r v a l s and analyzed by standard l i q u i d s c i n t i l l a t i o n (LS) methods f o r t o t a l ^ c - Larger water samples (100 ml) were taken each week and e x t r a c t e d using C 18 Sep-Paks (Waters Associates, Inc.)*. Samples were passed through Sep Paks at 2-4 ml/min. Recovery of *^c~DDT plus metabolites from the Sep Paks was achieved by e x t r a c t i n g with 10 ml acetone followed by 5 ml dichloromethane. DDT e x t r a c t i o n e f f i c i e n c y from water was 97+ %. Combined e x t r a c t s (acetone plus dichloromethane) were spotted on TLC p l a t e s (with unlabeled DDT, DDE and DDD) (20 χ 20 cm GF-254, E. Merck, Darmstadt) and developed f o r 10 cm using heptane:acetone (99:1). P l a t e s were then scraped and t o t a l ^ C determined by LS. Tissue samples (two f i s h , two s n a i l s , 100 mg algae and about 50 mg daphnids) were taken 1, 3, 8, 15, 22, 29, 36, 43, 50 and 57 days a f t e r the s t a r t of the experiment. Whole f i s h and s n a i l s were homogenized i n a c e t o n i t r i l e , and the homogenate was assayed d i r e c t l y by LS. F i l t e r e d samples of the homogenates were analyzed by TLC as described above. Daphnids were weighed, placed i n LS v i a l s , then ruptured with the c o c k t a i l and analyzed d i r e c t l y by LS. Algae samples were o x i d i z e d to determine t o t a l ^ C* DDT was a c u t e l y t o x i c to f i s h (1000 ppm treatment) and daphnids (100 + 1000 ppm treatment) which n e c e s s i t a t e d r e s t o c k i n g . Only l i v i n g f i s h and daphnids were analyzed. Water and organism c o n t r o l samples were taken, processed, and analyzed simultaneously with ^C"DDT t r e a t e d samples. F i n a l ^c-DDT v a l u e s were corrected using the appropriate c o n t r o l . No ^ c i n excess of background was recovered from any c o n t r o l sample. M
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D i f f u s i o n Experiment Twenty gram q u a n i t i e s of the Alabama s o i l were t r e a t e d with [ ^ c - r i n g ] DDT at 100 ppm and placed i n the bottom o f 1 L beakers. D u p l i c a t e beakers c o n t a i n i n g the t r e a t e d s o i l were covered with 0, 1, 2, or 3 cm o f untreated s o i l and flooded with 800 ml water. Four cm o f untreated s o i l i n d u p l i c a t e beakers flooded with 800 ml water served as c o n t r o l s . T r i p l i c a t e 1-ml water samples were taken p e r i o d i c a l l y . Two weeks a f t e r f l o o d i n g , 3 s n a i l s , 0.5 g algae and about 30 daphnids were ^Mention of a trade name or p r o p r i e t a r y product does not c o n s t i t u t e a guarantee or warranty o f product by the U.S. Dept. A g r i c . and does not imply i t s approval to the e x c l u s i o n of other products that may be s u i t a b l e .
Krueger and Seiber; Treatment and Disposal of Pesticide Wastes ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
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added to each beaker. DDT was acutely t o x i c to the daphnids i n the 0 cm treatments which n e c e s s i t a t e d p e r i o d i c r e s t o c k i n g . Results and D i s c u s s i o n DDT i n Water The e f f e c t of sediment a d d i t i o n s on DDT i n water i s shown i n Table I. There are two DDT data points f o r each sampling day; the f i r s t i s based on t o t a l a n a l y s i s and the second ( i n parentheses) i s based on TLC a n a l y s i s of the water extracts. Total c i n water was not g r e a t l y a f f e c t e d by the 1% (160 g s o i l per 16-L water) sediment a d d i t i o n s . T o t a l c i n the W/0 tanks (not r e c e i v i n g sediment) increased continuously with time while approximate plateau l e v e l s were maintained i n the W tanks ( r e c e i v i n g sediment). In c o n t r a s t , DDT l e v e l s (based on TLC a n a l y s i s ) were g r e a t l y reduced. For example, on day 22, the c o n c e n t r a t i o n of DDT i n W tanks was 9, 5 and 3 times lower than the concentration i n W/0 tanks f o r the 10, 100 and 1000 ppm treatments, r e s p e c t i v e l y . T o t a l by comparison, was 1.1, 1.7, and 1.5 times lower f o r the same treatments. C l e a r l y then, input of sediment w i l l reduce the concentration of DDT i n s o l u t i o n , p a r t i c u l a r l y at the lower concentrations. However, the r e s u l t s are complicated by the fact that DDT l e v e l s decreased with time ( a f t e r day 8 or 15) i n a l l tanks, i n c l u d i n g those not r e c e i v i n g sediment. TLC a n a l y s i s of e x t r a c t s from 100 ml water samples p a r t l y e x p l a i n t h i s decrease (Figure 2). DDT concentrations i n the e x t r a c t s averaged ( f o r the three treatment r a t e s ) 76, 67, 52 and 9% of the t o t a l recovered a c t i v i t y f o r days 3, 8, 15 and 22, r e s p e c t i v e l y . For days 29 through 57, DDT l e v e l s were below 5% o f the recovered Polar metabolites, remaining at the TLC p l a t e o r g i n , increased as DDT decreased. These data suggest that the DDT i n water was degraded to p o l a r metabolites and that l i t t l e or no a d d i t i o n a l DDT desorbed from the t r e a t e d bottom sediments. The slow increase i n c ( i n the W/0 tanks) with time may represent r e l e a s e of polar metabolites from the bottom sediment. T o t a l c i n water on day 57 represented 1 and 3% of the t o t a l C added to each tank at the s t a r t , for the W and W/0 sediment treatments, r e s p e c t i v e l y . In a d d i t i o n , C recovered from the 100 ml water samples decreased from 88% of the total c (1 ml samples) on day 3 to 51% on day 57. These r e s u l t s i n d i c a t e that polar metabolites increased with time s i n c e they are not recovered by Sep Paks. Only small amounts of DDE and DDD (7 and 13% o f t o t a l c by day 8 and 15, r e s p e c t i v e l y ) were detected i n water. The concentration of DDT i n s o l u t i o n (Table I) often exceeded the g e n e r a l l y accepted water s o l u b i l i t y o f 2 ppb. Two f a c t o r s may account f o r these d i f f e r e n c e s . F i r s t , the water samples were not f i l t e r e d before C 18 Sep Pak e x t r a c t i o n . 1 4
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Krueger and Seiber; Treatment and Disposal of Pesticide Wastes ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
Krueger and Seiber; Treatment and Disposal of Pesticide Wastes ACS Symposium Series; American Chemical Society: Washington, DC, 1984.
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