Neonicotinoids are the most widely used insecticides in the world. The widespread application of neonicotinoids has led to their proliferation in waters across the U.S., including those used as drinking water sources. Although neonicotinoids exhibit relatively low toxicity towards mammals compared to some pesticides; however, formation of mammalian toxic metabolites is an exposure concern. Despite high solubility and polarity, our prior studies identified granular activated carbon (GAC) as a method for neonicotinoid and neonicotinoid metabolite removal from drinking water. Desorption tests of five-year-old used GAC (spent GAC) from the Iowa City DWTP revealed that although imidacloprid was present on the GAC surface, no desnitro-imidacloprid was observed even though it is capable of adsorbing to GAC; these results suggest desnitro-imidacloprid degradation on the GAC surface. The objective of the present study was to determine if imidacloprid and its mammalian toxic metabolite desnitro-imidacloprid that is adsorbed to black carbon can be mineralized into less toxic products via biofilm-coated (bio-augmented) black carbon. Experiments with soil-microbe coated corn biochar and spent DWTP GAC probed possible imidacloprid and desnitro-imidacloprid degradation on bio-augmented black carbon. Batch experiments revealed that bio-augmented corn biochar readily transformed imidacloprid into desnitro-imidacloprid. In solutions containing spent GAC, imidacloprid was rapidly adsorbed to the spent GAC surface without any metabolites detected in solution. Nevertheless, in solutions containing GAC-associated microorganisms without GAC, imidacloprid was degraded into desnitro-imidacloprid suggesting the adsorbed neonicotinoid may be degraded on the black carbon surface. Sacrificial batch experiments are underway to determine the rates and possible mechanisms behind these biotransformation reactions. Further experiments are elucidating whether the mammalian toxic metabolite is a dead-end product or if the metabolite is further transformed by bio-augmented black carbon. This research may provide a promising method to remove neonicotinoids from water in natural and engineered systems by coupling GAC sorption to biofilm degradation.<br/>

Biotransformation of neonicotinoid insecticides and their metabolites on biologically activated carbon: Implications for human exposure, treatment, and biofilm transformation

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.