In situ destruction of halogenated Superfund contaminants with biological radical reactions

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PROJECT 3: SUMMARY/ABSTRACT Highly halogenated compounds include recently recognized pollutants such as per- and polyfluorinated alkyl substances (PFAS) as well as legacy contaminants, such as chlorinated solvents, polychlorinated biphenyls (PCBs) and Polybrominated diphenyl ethers (PBDEs). PFAS and other extremely persistent halogenated compounds do not exist alone in sites. For example, chlorinated solvents (e.g., trichloroethylene) often coexist with 1,4-dioxane and PFAS, as well as fuel components including benzene and xylene. Highly halogenated compounds remain in sites even when co-contaminants have been remediated, posing continued environmental health risks to human receptors through exposure via drinking water sources and food. As more highly halogenated chemicals are discovered, remediation strategies need to combine both selectivity and high reactivity. For decades bioremediation has been attractive due to selective enzymes targeting specific contaminants. Likewise, chemical redox treatment has garnered interest due to its high reactivity. However, it takes decades to evolve new specific enzymes in nature and the harsh site conditions after chemical treatment are drawbacks to both technologies when applied alone. Biological enzymatic systems that produce radicals are widespread in microbial systems in aerobic and anaerobic environments. We hypothesize that these biological- radical systems could become a novel remediation approach that combines both selectivity and high reactivity. In Aim 1, we propose to employ bioinformatics and molecular biology techniques to study known and putative laccase systems with multiple chemical mediator compounds in high throughput assays to determine optimized systems for PFAS treatment. Aim 2 focuses on studying the reactions of anaerobic radical systems, such as glycyl radical enzymes (GRE) and S-adenosylmethionine (SAM) to study their capability to be engineered future remediation strategies. We will combine Project 3 and 4 approaches in Aim 3, where chemical treatment will be used to prime pollutants that make them more amenable to subsequent biological radical treatment, as well as study the microbial community dynamics before and after chemical treatment. The findings of Project 3 could provide a new approach of remediation technologies to remediate highly halogenated emerging and legacy compounds in the environment to protect the environmental health of surrounding communities.