The fate of atrazine and a hexachlorobiphenyl isomer in naturally‐derived model stream ecosystems

Abstract

AbstractCurrent emphasis in hazard assessment is being placed on the development of quick and inexpensive methods to identify chemicals with potentially harmful properties. The present study was designed to test the validity of simple microcosms that have been proposed to predict chemical behavior in aquatic systems.Six laboratory streams were used to study the fate and effects of atrazine and 2, 4, 5, 2′, 4′, 5′, ‐ hexachlorobiphenyl (HCBP) in a naturally derived aquatic community during one annual period. Two streams were treated with the HCBP (0.100 μg/L), two received atrazine (25 μg/L) and two streams served as solvent controls. The chemicals were administered for 30 days during the fall, winter, spring, and summer; a 60 day depuration phase followed each treatment.The substrates and benthic organisms accumulated HCBP rapidly and concentrations increased with duration of exposure. Uptake of HCBP by the biota was biphasic; the most rapid rate of accumulation occurred during the initial three hours of exposure. Maximum HCBP concentrations in the biota occurred on day 30. Bioaccumulation factors at this time ranged from 300,000 for amphipods to 1200 for clams. Fish, crayfish and other macroinvertebrates had intermediate values. There was no evidence that residue concentrations were increased by trophic transfer.Atrazine was not accumulated in the laboratory stream communities. Atrazine bioaccumulation factors in the biota ranged from 3.5 in annelids to 480 in mayfly nymphs. Residue concentrations declined to pretreatment levels within a few days of depuration.These results are significant in that (1) they are consistent with predictions derived from physical‐chemical data and (2) the compounds behaved similarly to closely related compounds in simpler model systems. Based on our results, simpler model ecosystems and/or models based on physicalchemical data are probably adequate for predicting the fate of toxicants in aquatic systems.