|Smith jr, Sammie|
Submitted to: Archives of Environmental Contamination and Toxicology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/12/2007
Publication Date: 6/27/2007
Citation: Bouldin, J.L., Farris, J.L., Moore, M.T., Smith Jr, S., Cooper, C.M. 2007. Assessment of diazinon toxicity in sediment and water of constructed wetlands using deployed corbicula fluminea and laboratory testing. Archives of Environmental Contamination and Toxicology 53(2):174-182. Interpretive Summary: Pesticides in runoff can harm fish and other organisms living in nearby streams or lakes. By using constructed wetlands as a buffer between agricultural fields and nearby water sources, the runoff can be cleaned before making contact with the river, lake or stream. An insecticide was applied to a mixture of sediment and water and pumped into a constructed wetland. Using live, caged organisms in five locations throughout the wetland, an assessment of the potential harm to organisms was monitored. Although the wetlands reduced the pesticide concentration to acceptable levels for survival, long-term growth effects were noted for wetland-exposed organisms. For this reason, it is important to combine chemical and physical information with biological data to determine the overall impact of pesticide runoff.
Technical Abstract: Constructed wetlands proposed as best management practices for the mitigation of non-point agricultural runoff have been assessed for their ability to reduce potential toxicity from associated contaminants. Following a simulated runoff from a 1.3-cm rainfall event, constructed wetlands positioned in series were used to measure the effects of the organophosphate insecticide diazinon [O,O-diethyl 0-2-isopropyl-6-methyl 9pyrimidine-4-yl) phosphorothioate]. Water, sediment, and plant samples from five sites spaced throughout the wetland were analyzed for diazinon concentrations from 0.5 h to 26 d. Cholinesterase activity and changes in shell growth were measured from Corbicula fluminea deployed at corresponding sites. Water collected after 9 h from sites throughout the wetland contained diazinon concentrations sufficient to cause toxicity to Ceriodaphnia dibua, but not to Pimephales promelas. Ceriodaphnia dubia survival was reduced in water sampled through 7 d from the site nearest the runoff introduction, while C. fluminea deployed at this same site experienced 100% mortality after 26 d. Clams from lower sites survived wetland conditions, although their growth and ChE activity were significantly reduced below that of clams from a control site. Ceriodaphnia dubia exposed to water from these sites continued to have reduced survival throughout the 26-d sampling. Sediment sampled from 48 h through 14 d at the lowest wetland site reduced survival in laboratory testing with Chironomus tentans, and sediment from upper sites elicited effects only on day 26. While wetland mitigation resulted in concentrations of aqueous diazinon reduced below toxic thresholds after 26 d, reduced ChE activity in deployed clams provided evidence of residual diazinon effects to resident communities.