Effects of Vegetation in Mitigating the Toxicity of Pesticide Mixtures in Sediments of a Wetland Mesocosm
2011
Lizotte, Richard E., Jr | Moore, Matthew T. | Locke, Martin A. | Kroger, Robert
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, 24, 72 h, 7, 14, and 21 days post-amendment. Pesticides were detected in sediments throughout non-vegetated and vegetated wetland sections. H. 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 and 7 days within the non-vegetated and vegetated sections, respectively. Relationships between pesticide concentrations and 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 earlier and to a greater extent than non-vegetated constructed wetlands. A 21-day retention time is necessary to improve 48-h H. azteca sediment survival to ≥90% in wetlands of this size.
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