Diazinon Mitigation in Constructed Wetlands: Influence of Vegetation

In intensively cultivated areas, agriculture is a significant source of pesticides associated with storm runoff. When these pollutants enter aquatic receiving waters, they have potential to damage nearby aquatic ecosystems. Constructed wetlands are a best management practice (BMP) designed to help alleviate this potential problem. A constructed wetland system (180×30 m) comprised of a sediment retention basin and two treatment cells was used to determine fate and transport of a simulated storm runoff event containing the insecticide diazinon and suspended sediment. Wetland water, sediment, and plant samples were collected spatially and temporally over 55 d. Results indicated that 43% of the study’s measured diazinon mass was associated with plant material, while 23 and 34% were measured in sediment and water, respectively. Mean diazinon concentrations in water, sediment, and plants for the 55-d study were 18.1±4.5 μg/l, 26.0±8.0 μg/kg, and 97.8± 10.7 μg/kg, respectively. Aqueous concentrations fluctuated in the wetlands between 51–86 μg/l for the first 4 h of the experiment; however, by 9 h, aqueous concentrations were approximately 16 μg/l. During the 55 d experiment, 0.3 m of rainfall contributed to fluctuations in diazinon concentrations. Results of this experiment can be used to model future design specifications for mitigation of diazinon and other pesticides.