Collaborative Research: Evaluation of the Fundamental Photochemical Mechanisms Driving Carbonyl Sulfide and Carbon Disulfide Formation in Sunlit Natural Waters

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With support from the Environmental Chemical Sciences (ECS) Program in the Division of Chemistry, Amisha Shah and Christina Remucal of Purdue University and the University of Wisconsin-Madison, respectively, will study chemical reactions involving the element sulfur that occur at the surface of natural waters. These chemical reactions are important because they can produce small molecules containing carbon-sulfur (C-S) bonds that can then move into the atmosphere above. Once in the atmosphere, the small molecules can participate in other chemical reactions that impact climate warming and cooling. It is clear that exposing such waters to sunlight helps form the carbon-sulfur species, but the details of how the process occurs remains unclear, especially with regard to how other chemical compounds in water impact the process. In this project, Drs. Shah and Remucal will investigate the chemical mechanisms for production of carbonyl sulfide and carbon disulfide from precursors in natural waters. At present, models of the global sulfur budget for the production of these gases from these sources are inconsistent. In particular, sunlight is known to enhance production of these organosulfur species, but the mechanism for this enhancement remains unclear. The primary aim of this study is to develop a better understanding of the fundamental chemical mechanisms responsible for the photoproduction of carbonyl sulfide and carbon disulfide in natural waters. These goals will be met by conducting different types of lab-scale experiments using a reactor that simulates sunlight illuminating a water sample containing a variety of chemical precursors and reactants. Outcomes of this project will include outreach to the scientific community, students, and the public to educate them on the role aquatic chemistry and photochemistry processes have on the climate. The researchers will also engage in outreach to middle and high schools and provide research training to undergraduate and graduate students.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.