UNDERSTANDING AND PREDICTING THE IMPACT OF AGRICULTURE ON THE ENVIRONMENTAL INTEGRITY OF MANAGED WATERSHEDS
Location: Water Quality and Ecology Research
Title: Effects of vegetation in mitigating the toxicity of pesticide mixtures in sediments of a wetland mesocosm
Submitted to: Water, Air, and Soil Pollution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 21, 2010
Publication Date: August 11, 2011
Citation: Lizotte Jr, R.E., Moore, M.T., Locke, M.A., Kroger, R. 2011. Effects of vegetation in mitigating the toxicity of pesticide mixtures in sediments of a wetland mesocosm. Water, Air, and Soil Pollution. 220(1):69-79.
Interpretive Summary: We measured sediment pesticide effects on an aquatic invertebrate animal, Hyalella azteca, living in and on sediment. The study took place in a divided constructed wetland, one half with plants and one half without any plants. We looked at how well this wetland with or without plants could decrease the effects of two pesticides, diazinon and permethrin in sediment on aquatic animals living in and on sediment. The study showed that plants were better at decreasing the effects of pesticides in sediment within the first 5 hours. Also, we showed that holding the pesticide contaminated water in the constructed wetland for 21 days was needed to remove sediment toxicity. Our results are of interest to regulatory and other agencies and the pesticide industry by providing additional information to improve and sustain river, stream and lake water quality and overall environmental quality using constructed wetlands as an effective conservation practice.
This study assessed effects of a mixture of two pesticides, diazinon and permethrin, on 48-h sediment toxicity to Hyalella azteca in a constructed wetland mesocosm containing non-vegetated and vegetated sections. Sediment samples were collected at inflow, middle, and back points within each section 5 h, 24 h, 72 h, 7 d, 14 d, and 21 d post-amendment. Pesticides were detected in sediments throughout non-vegetated and vegetated wetland sections. Hyalella azteca 48-h survival varied across sampling period, wetland location, and vegetation type with lowest survival occurring within the first 72 h of the inflow and middle locations of the non-vegetated section. Sediment toxicity was ameliorated by 14 d and 7 d within the non-vegetated and vegetated sections, respectively. Associations of pesticides with animal survival indicated toxicity was from both diazinon and cis-permethrin in the non-vegetated section and primarily cis-permethrin in the vegetated section. Results show that vegetation ameliorated pesticide mixture 48-h sediment toxicity to H. azteca sooner and to a greater extent than no vegetation throughout the constructed wetland. A 21 d retention time is necessary to improve 48-h H. azteca sediment survival to =90% in wetlands of this size.