Water treatment and reuse initiatives are essential to combat declining water supplies in a changing climate, especially in arid and semi-arid regions such as California. Pollution of water resources intensifies the search for strategies to provide water for potable and non-potable reuse that mitigates detrimental ecological and human health effects. Fipronil and synthetic pyrethroids are common urban-use insecticides that have aquatic toxicity at trace levels and have been often found in urban surface streams. In this study, we systematically evaluated the spatial and temporal occurrence and distribution of fipronil, fipronil degradates and pyrethroids in the Prado Wetlands - the largest constructed wetland system on the west coast of the U.S. Concentration-based removal rates and changes in mass flux were calculated to determine the efficacy of constructed wetland treatment. Observed water concentrations were further used to calculate toxicity units for invertebrates <i>Hyalella azteca</i> and <i>Chironomus dilutus</i>. Pesticide concentrations in water, sediment, and plant samples consistently decreased as the water passed through the wetland cells at all time points. Removal rates for fipronil desulfinyl, fipronil sulfide, fipronil, fipronil sulfone, bifenthrin, and cyfluthrin were 100%, 99.7-100%, 57.8-88.1%, 75.6-100%, 74.7-100%, and 36.6-82.2%, respectively, and there was a general net attenuation of pesticides by the wetland. Toxicity units decreased in every instance for both aquatic invertebrates. The results of this study further indicated that settling of contaminated particles, adsorption to sediment, plant uptake or adsorption, and subsequent on-site degradation contributed to the effective removal of these urban-use insecticides. These findings highlight the potential of constructed wetlands for protecting urban water quality by removing trace contaminants.

Evaluation of a large wetland for removing urban-use insecticides

ACS Fall 2020 Virtual Meeting

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