|Smith jr, Sammie|
Submitted to: Environmental Pollution
Publication Type: Peer reviewed journal
Publication Acceptance Date: 10/3/2005
Publication Date: 5/1/2006
Citation: Moore, M.T., Bennett, E.R., Cooper, C.M., Smith Jr, S., Farris, J.L., Drouillard, K.G., Schulz, R. 2006. Influence of vegetation in mitigation of methyl parathion runoff. Environmental Pollution. 142 (2006) 288-294. Interpretive Summary: Pesticides associated with agricultural runoff may contaminate downstream rivers and lakes, causing damage to fish and other organisms. The current study used a simulated runoff exposure on two constructed wetlands-one with vegetation and one without vegetation to determine if the BMP (constructed wetlands) are efficient at reducing pesticide concentrations in runoff. After only 30 minutes of simulated runoff, pesticide concentrations were detected leaving the non-pesticide vegetated wetland outflow. At the same time in the vegetated wetland, the modeling indicated that a much smaller wetland length (three times) would be needed to clean the runoff if plants were present as opposed to plants being absent. This research indicates the importance of vegetation in the role of pesticide mitigation.
Technical Abstract: Even though they possessed water quality enhancement capabilities, many wetlands in the United States and elsewhere were drained in the early 20th century (with heavy losses in the 1960s and 1070s) to allow for increased agricultural prodcution acreage. In the last two decades, researchers have focused on the capacity of constructed wetlands for reducing the concentrations of both point and non-point source pollutants. In this study, a pesticide runoff event was simulated using two 10 m x 50 m constructed wetlands (one non-vegetated; one vegetated with Juncus effusus and Leersia oryzoides) to evaluate the fate of methyl parathion (Penncap-M0. A partition wall divided each wetland longitudinally into replicate cells. Water, sediment, and plant samples were collected at five sites downstream on the inflow for a period of approximately 120 days. Additionally, semi-permeable membrane devices (SPMDs) were deployed at the outlfow of each wetland cell to determine the total load of pesticide reaching that distance. Results for the non-vegetated wetland cells indicated that methyl parathion was detected in water throughout the entire system (50 m) 30 minutes post-exposure and was still detected at 10 days. In the vegetated wetland, methyl parathion was detected 20 m from the inflow 30 minutes post-exposure, while after 10 days it was detected 20 m from the inflow 30 minutes post-exposure, while after 10 days it was detected only at 10 m. Methyl parathion was measure only in SPMDs deployed in the non-vegetated wetland cells, which further suggests that detectable levels were not present near the vegetated wetland outflow. Regression formulas on necessary wetland length for mitigation indicated that 18.8 m would be needed to decrease the outlfow concentrations to 0.1% of the inflow concentration (8.01 mg/L) in vegetated systems. In non-vegetated systems, for the same circumstances, a wetland length of 62.9 m would be necessary to achieve sufficient mitigation. These results demonstrate the importance of vegetation as sorption sites for pesticide mitigation in constructed wetlands.