Effects of Vegetation in Mitigating the Toxicity of Pesticide Mixtures in Sediments of a Wetland Mesocosm

Abstract

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 nonvegetated 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 nonvegetated constructed wetlands. A 21-day retention time is necessary to improve 48-h H. azteca sediment survival to ≥90% in wetlands of this size.

Mitigating with macrophytes: Submersed plants reduce the toxicity of pesticide‐contaminated water to zooplankton

“…Although previous studies have reported the mitigating effects of emergent vegetation contained within agricultural constructed wetlands and drainage ditches on the toxicity of insecticides to aquatic taxa [37], the present study appears to be the first experimental demonstration that submersed macrophytes can strongly mitigate the lethal effects of insecticides on an aquatic species. Specifically, we discovered that the common macrophyte E. canadensis substantially reduced the lethality of the popular insecticide malathion to the keystone herbivore, D. magna, [26] and also increased the rate at which water treated with malathion was detoxified.…”

A Literature Review of Wetland Treatment Systems Used to Treat Runoff Mixtures Containing Antibiotics and Pesticides from Urban and Agricultural Landscapes

“…Constructed wetland systems included horizontal flow The primary studies that showed high removal efficiencies (greater than 75%) were larger for mesocosm studies. Of the studies that analyzed the mesocosm scale, 68% had at least one contaminant removed at an efficiency greater than or equal to 75% [16,23,45 182,183,185,192,193,195,[201][202][203]209,210,[217][218][219]. Additionally, 54% of microcosm studies resulted in high removal efficiencies [30,60,76,78,83,90,94,97,119,129,131,143,146,164,168,177,181,188,194,200,207] and 59% of field studies resulted in high removal efficiencies [3,46,50,53,62,63,68,74,77,…”

Mitigation of Wastewater-Borne Chlorpyrifos in Constructed Wetlands: the Role of Vegetation on Partitioning

“…Peak concentrations of mixed pesticides are reportedly reduced by 72% in non-vegetated CWs and 91% in vegetated CWs, representing toxic unit (TU) reductions of 79% and 95%, respectively [9]. Vegetation also plays an important role in resisting algal blooms in surface flow CWs installed to handle both nutrients and pesticides [20]. The presence of emergent vegetation is critical for managing large wetland treatment systems, especially those with low P loadings [21].…”