NSF Award
2310247
Synthetic organic compounds such as pesticides and pharmaceuticals can enter surface water systems (e.g., lakes and rivers) through point sources (e.g., effluents from wastewater treatment plants) and non-point sources (e.g., runoff from urban and agricultural watersheds). These organic pollutants can adversely affect both human and ecosystem health. Understanding how quickly sunlight reacts to degrade synthetic organic pollutants in aquatic systems is important for predicting and managing their health risks. However, laboratory experiments using simulated sunlight cannot be directly translated to environmental conditions and greatly overestimate how quickly sunlight reacts with synthetic organic chemicals in surface water systems including lakes and rivers. As a result, these chemicals may have longer lifetimes in surface waters than currently predicted. The overarching goal of this project is to advance the fundamental understanding of sunlight-induced photochemical degradations of synthetic organic pollutants in surface water systems. To advance this goal, the Principal Investigators (PIs) will study approximately 50 pesticides, pharmaceuticals, and industrial chemicals in the laboratory and outdoors and will use this information to make accurate predictions about sunlight-driven degradation reactions in rivers and lakes. The successful completion of this research will benefit society through the generation of new data and fundamental knowledge about the extents and rates of sunlight-driven photochemical reactions of synthetic organic pollutants in aquatic systems. This new data and knowledge will be critical for evaluating the fate and lifetime of potentially toxic organic chemicals in lakes and rivers. Additional benefits will be achieved through student education and training including the mentoring of one graduate student at the University of Wisconsin-Madison and two undergraduate students at the University of St. Thomas, a predominantly undergraduate institution.<br/><br/>Sunlight-mediated photodegradation is among the most important abiotic transformation processes in aquatic systems for synthetic organic compounds (SOCs) such as pesticides and pharmaceuticals. A major goal of this project is to test the hypothesis that laboratory-scale experiments overpredict the photolysis rates of SOCs in lakes and rivers by many orders of magnitude due to discrepancies between laboratory light sources and environmental conditions. To test this hypothesis, the Principal Investigators (PIs) propose to evaluate the direct photolysis of approximately 50 pesticides, pharmaceuticals, and industrial chemicals in relevant aquatic systems with the goal of developing a first principles kinetic model to relate laboratory direct photolysis rates to a variety of environmental conditions. The model will be validated using outdoor mid-scale experiments that quantify the impacts of diurnal variability, water depth, cloud cover, and seasonality on the rates of direct photolysis of SOCs in aquatic systems. Finally, the PIs propose to couple laboratory and outdoor experiments, and modeling to investigate the indirect photolysis rates of selected SOCs in the presence of dissolved organic matter (DOM), a natural photosensitizer in surface water systems that absorbs light to generate photochemically produced reactive intermediates such as hydroxyl radicals and singlet oxygen species. The successful completion of this project has the potential for transformative impact by linking laboratory-measured rates with expected photodegradation rates in lakes/rivers for a wide range of SOCs. To implement the educational and training goals of this project, the PIs propose to leverage existing programs at the University of Wisconsin (UW)-Madison and the University of St. Thomas to recruit and mentor undergraduate students, including those from underrepresented groups, to work on this project. In addition, the PIs plans to 1) integrate the research findings into existing undergraduate and graduate courses in the Department of Civil and Environmental Engineering at the UW-Madison and 2) develop a website that will include a database containing all the validated results of the project. These results will be disseminated to water resource managers, relevant stakeholders, and the public.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
