|Shields Jr, Fletcher|
Submitted to: Science of the Total Environment
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/9/2012
Publication Date: 5/4/2012
Citation: Lizotte Jr, R.E., Shields Jr, F.D., Murdock, J.N., Kroger, R., Knight, S.S. 2012. Mitigating agrichemicals from an artificial runoff event using a managed riverine wetland. Science of the Total Environment. 427-428:373-381. Interpretive Summary: We measured the ability of a water-level controlled natural wetland to trap sediment, nutrients and pesticides to see if the system could be used as an agricultural best management practice. The study was done to better understand how effective the wetland could be in trapping sediment nutrients and pesticides in runoff from agricultural fields. The study showed the wetland was effective in trapping sediment, nutrients and pesticides, preventing them from moving downstream and entering the adjacent Coldwater River. These results are of interest to regulatory and other agencies and farming stakeholders by providing additional information to improve and sustain lake and flood plain water quality and overall environmental quality using conservation practices.
Technical Abstract: We examined the mitigation efficiency of a managed riverine wetland amended with a mixture of suspended sediment, two nutrients (nitrogen and phosphorus), and three pesticides (atrazine, metolachlor, and permethrin) during a simulated agricultural runoff event. Hydrologic management of the 500 m-long, 25 m-wide riverine wetland was done by adding weirs at both ends. The agrichemical mixture was amended to the wetland at the upstream weir simulating a four-hour, 1.27 cm rainfall event from a 16 ha agricultural field. Water samples (1 L) were collected every 30 min within the first 4 h, then every 4 h until 48 h, and again on days 5, 7, 14, 21, and 28 post-amendment at distances of 0 m, 10 m, 40 m, 300 m and 500 m from the amendment point within the wetland for suspended solids, nutrient, and pesticide analyses. Peak sediment, nutrient, and pesticide concentrations occurred within 3 h of amendment at 0 m, 10 m, 40 m, and 300 m downstream and showed rapid removal of agrichemicals from the water column with 79-98%, 42-98%, and 63-98% decrease in concentrations of sediments, nutrients, and pesticides, respectively, within 48 h. By day 28, all amendments were near or below pre-amendment concentrations. Water samples at 500 m showed no changes in sediment or nutrient concentrations; pesticide concentrations peaked within 48 h but at =11% of upstream peak concentrations and had dissipated by day 28. Managed riverine wetlands can efficiently trap agricultural runoff during moderate rainfall events, mitigating impacts to receiving rivers.