|Smith Jr, Sammie|
Submitted to: Environmental Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/1/2004
Publication Date: 10/1/2004
Citation: Milam, C.D., Bouldin, J.L., Farris, J.L., Schulz, R., Moore, M.T., Bennett, E.R., Cooper, C.M., Smith Jr, S. 2004. Evaluating acute toxicity of methyl parathion application in constructed wetland mesocosms. Environmental Toxicology. 19(5):471-479. Interpretive Summary: Pesticides associated with agricultural storm runoff can damage populations of fish and other organisms in receiving aquatic systems such as rivers, lakes, and streams. This study analyzed water and sediment samples collected from constructed wetlands (one with plants, one without plants) which were amended with a simulated storm event containing the pesticide, methyl parathion. Less toxic effects upon standard test organisms were noted in the wetland with plants, as opposed to the wetland without plants. Results indicate the important role that aquatic plants play in cleaning up water contaminated with pesticides.
Technical Abstract: Wetland ecosystems have served to reduce ambient levels of various organic and metallic compounds, although their effectiveness on agricultural pesticides is not well documented. Five stations within each of four 10 x 50 m constructed wetlands (two vegetated; two non-vegetated) were selected to measure fate and effects of methyl parathion (MeP). Following a simulated storm event, aqueous, sediment, and plant samples were collected and analyzed spatially (5,10,20, and 40 m from inlet) and temporally (3 h - 10 d) for MeP concentrations and impact to the aquatic fauna. Aqueous toxicity to fish decreased spatially and temporally in the vegetated mesocosm. Pimephales promelas survival was significantly reduced to 68% in non-vegetated mesocosms at the 10 m station (3 h post application) with pesticide concentrations averaging 9.6 ug MeP/L. Ceriodaphnia in both vegetated and non-vegetated mesocosms were sensitive to pesticide exposures through 10 d post-application. Mean MeP concentrations in water ranged from 0.5 to 15.4 ug/L and 0.1 to 27 ug/L in vegetated and non-vegetated mesocosms, respectively. Hyalella azteca aqueous tests resulted in significant mortality at the 5 m vegetated segment following 10 d post exposure of MeP (2.2 ug/L). Solid phase (10 d) sediment toxicity tests showed no significant reduction in Chironomus tentans survival or growth with the exception of the sediments sampled 3 hours post application in the non-vegetated mesocosm (65% survival). Thereafter, midge survival averaged more than 87% in sediments sampled from both treated mesocosms. These data suggest wetlands play a significant role in mitigating MeP exposures to sensitive aquatic biota.