|Smith Jr, Sammie|
Submitted to: Archives of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/15/2003
Publication Date: 12/1/2003
Citation: Schultz, R., Moore, M.T., Bennett, E.R., Milam, C.D., Bouldin, J.L., Farris, J.L., Smith Jr, S., Cooper, C.M. 2003. Acute toxicity of methyl-parathion in wetland mesocosms: influence of aquatic plants. Archives Of Environmental Contamination And Toxicology. 45(3): 331-336. Interpretive Summary: Following rainfall events, some agricultural pesticides are known to be washed off the field and enter surrounding rivers, lakes, and streams. To decrease the amount of pesticides and other types of pollutants entering these water bodies, certain best management practices have been evaluated with (and at the edge of) agricultural fields. One such best management practice involves placing a constructed wetland at the edge of an agricultural field to collect the runoff before it enters a river or stream. This research compared the capability of a constructed wetland with plants to one without plants, in order to see which system worked best at decreasing the amount of a pesticide (methyl parathion) entering rivers, lakes, and streams. It was discovered that the wetland with plants was ten times better at decreasing the pesticide as opposed to the one without plants. By decreasing the amount of pesticide reaching the rivers, lakes, and streams, fewer non-target animals (e.g. fish)would be affected.
Technical Abstract: The acute toxicity of methyl-parathion (MeP) introduced into constructed wetlands for the purpose of assessing the importance of emergent vegetation was tested using Hyalella azecta (Crustacea: Amphipoda). A vegetated (90% cover, mainly Juncus effuses) and a non-vegetated wetland (each with a water body of 50 m x 5.5 m x 0.2 m) were dosed with 6.5 cubic meters of water containing 6.6 mg per liter a.i. MeP associated with 400 mg per liter suspended soil to simulate a storm runoff event. H. azteca was exposed for 48 h in the laboratory to water samples taken from the wetlands at 5,10,20, and 40 m distance from the pesticide inlet 3 h, 24h, 96h, and 10 d following contamination. MeP was detected throughout the non-vegetated wetland, whereas the pesticide was not transported through the vegetated wetland. A three way analysis of variance (ANOVA) usiing time, location (both repeated measure variables) and vegetation indicated a significantly lower toxicity in the vegetated wetland. Furthermore, the mortality decreased significantly with both increasing distance from the inlet and time. A significant three-way interaction of time x vegetation x location confirmed a higher toxicity at the inlet are of the non-vegetated wetland at short time periods after contamination. These results demonstrate the importance of vegetation for pesticide mitigation in constructed wetlands.