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HA10 Environmental Toxicology, Environmental Assessment
() Laboratory biomonitoring and in-situ biomarkers for the evaluation of diazinon toxicity in constructed wetlands.
Bouldin, J1, Farris, J1, Moore, M2, Smith, Jr, S2, Cooper, C2, 1 Arkansas State University, State University, AR, USA2 USDA-ARS National Sedimentation Laboratory, Oxford, MS, USA
ABSTRACT- Best management practices for the modification of agricultural associated non-point source runoff include constructed mitigation wetlands. Following a simulated runoff from a 1.3-cm rainfall event, a series of vertical wetlands was used to measure the fate and effect of the organophosphate insecticide diazinon. Water, sediment and plant samples from five sites spaced throughout the wetland, were analyzed for diazinon concentrations from 0.5-h to 26-d. Biomarkers for sublethal responses were extracted from Corbicula fluminea deployed in-situ at corresponding sites. While no acute toxicity to Pimphales promelas was measured upon exposure to site water, toxicity to Ceriodaphnia dubia progressed through the wetlands after 9-h. Toxicity was measured to C. dubia exposed to aqueous samples from the site nearest the runoff introduction through 7-d and in-situ organisms at these sites experienced complete mortality by the 26-d sampling. Survival of organisms placed at downstream sites was not reduced; however, growth and acetylcholinesterase activity were significantly reduced as compared to control clams, and C. dubia survival was reduced upon exposure to water from these sites throughout the 26-d sampling. While toxicity was measured in Chironomus tentans exposed to sediment from upstream sites at 26-d only, survival was reduced in sediments sampled after 48-h through 14-d at downstream sites. In this exposure, clam acetylcholinesterase, cellulase, and growth responses were indicative biomarkers of aqueous and sediment toxicity measured in laboratory tests, while chemical analyses confirmed the movement of diazinon through the wetland cells.
Key words: biomonitoring, mitigation wetlands, sublethal biomarkers, agricultural runoff
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