Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 12/10/2006
Publication Date: 2/2/2007
Citation: Moore, M.T., Lizotte Jr, R.E., Smith Jr, S. 2007. Toxicity evaluation of diazinon contaminated leaf litter. Bulletin of Environmental Contamination and Toxicology. 78(2):168-171. Interpretive Summary: Pesticides in runoff from farm fields can contaminate rivers, lakes, and streams. Constructed wetlands are a suggested best management practice to help reduce the detrimental effects of pesticide runoff on downstream water resources. This study examined the fate and effects of diazinon within a constructed wetland, focusing primarily on leaf-litter contamination. Plant materials are an integral part of the constructed wetland mitigation process. Constructed wetlands are capable of holding a significant amount of detrital (leaf-litter) material throughout the year. This study demonstrated that while the leaf-litter may initially serve as sorption sites for pesticides, it has the potential to become contaminated and harmful to non-target organisms which may feed or live on such plant material.
Technical Abstract: Diazinon is an organophosphate pesticide with widespread use on a variety of agricultural crops. Because of its use, diazinon is a potential contributor to non-point source contamination of aquatic environments. A prominent feature within these aquatic environments includes leaf litter, especially during autumn. Leaf litter has extensive surface area available for sorption or organic chemicals. Leaf litter bags were placed in a constructed wetland system exposed to diazinon. Water, sediment, and leaf litter were collected at 8 h, 48 h, 7 d, 15 d, and 27 d after initial pesticide dosing. Chemical analyses and toxicity assessments using the benthic macroinvertebrate, Hyalella azteca, were conducted on the collected samples. Survival decreased significantly, compared to controls, in the first two wetland cells 8 h after diazinon exposure. A decrease within the final finishing cell was not apparent until the last sampling period (27 d). Based upon toxicity assessments, diazinon contaminated leaf litter, which initially serves as a contaminant sink, may change to a source of pesticide contamination for days to weeks after entering the constructed wetland.