Collaborative Research: Role of Organic Matter Source on the Photochemical Fate of Pharmaceutical Compounds

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PIs: Allison MacKay / Yu-Ping Chin / Charles SharplessProposal Numbers: 1133600 / 1133094 / 1132207Evaluating the impacts of human pharmaceutical compounds in the environment is a daunting task, given the wide variety of chemicals administered for medical conditions and the various wastewater management schemes that facilitate their release to aquatic systems. Prior studies suggest photodegradation reactions to be important attenuation processes for pharmaceutical compounds in the environment. The susceptibility of pharmaceuticals to photochemical reactions will be impacted by the co-release of these compounds with effluent organic matter (EfOM). EfOM is expected to have differing photoreactivity, relative to well-studied natural organic matter (NOM) sources, presumably because of its anticipated lower aromatic content and lower color, compared to NOM. The PIs hypothesize that pharmaceutical compound photodegradation will be altered with increasing proportion of wastewater effluent in natural channel flow because of the increased presence of EfOM, relative to NOM. The ultimate goal of the proposed research is to identify key environmental system characteristics that are associated with enhanced environmental photodegradation rates of pharmaceutical compounds. They propose three major research activities to evaluate their hypothesis. (1): Field measurements of environmental degradation rates and pathways will be obtained for representative wastewater discharge scenarios ? forested New England watershed (Pomperaug River, CT), agricultural Midwestern watershed (East Fork of the Little Miami River, OH), and an urban stream with combined sewer outfalls (Park River, CT). Flow-adjusted samples will be obtained downstream of the effluent discharge to measure pseudo-first order environmental degradation rates with differing seasonal EfOM-to-NOM ratios. Photolysis losses will be differentiated from other losses by comparing daytime and nighttime observations. Supporting lab degradation studies will resolve contributions of organic matter (OM) type to photochemical pathways. (2): OM will be isolated from the field sites, including from effluent streams directly. Isolation methods of XAD-8 resin and tangential flow ultrafiltration will be used for consistency with geochemistry methods. Isolates will be characterized for their biochemical constituents (thermochemolysis), and for optical and structural properties (UV-Vis, fluorescence, solid-state 13C NMR). (3): Quantum yields of singlet oxygen, hydrogen peroxide and excited triplet-state OM will be obtained for OM isolates and correlated to OM characteristics (Task 2). Together, the results of Tasks 2 and 3 will yield critical insights for interpreting differences in photodegradation rate constants (Task 1) among the sites and within seasons, as effluent contributions change at each site. This study will be the first to examine the fate of pharmaceutical compounds in New England and Midwestern rivers, expanding on prior fate studies from arid systems. They will establish an important body of knowledge about environmental system drivers of pharmaceutical compound fates that will contribute to robust science-based decisions about regulation, remediation, and/or ?green? design for pharmaceutical compounds. They will work closely with the Pomperaug River Watershed Coalition and the East Fork Watershed Cooperative to engage citizens in cutting-edge science through semi-annual project progress presentations, to involve water managers and community members in water quality sampling, and to organize a cross-disciplinary Roundtable to bring together environmental scientists and engineers, regulators, with ecologists and pharmacologists to discuss environmental management of pharmaceutical compounds in the environment. The PIs will mentor graduate and undergraduate researchers through the process of scientific discovery ? experimental design, manuscript preparation and national professional society presentations. The PIs will continue their record of engaging student researchers from groups underrepresented in the sciences and engineering. Students will have a unique opportunity to work with a guiding PI team with expertise in engineering (PI MacKay), geochemistry (PI Chin), photochemistry (PI Sharpless) and systems ecology (Collaborator Nietch), providing broad context for their own projects.