CAS-MNP: Assessing the Controls of Plastic Photochemical Reactivity in the Surface Ocean

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With support from the Environmental Chemical Sciences Program in the Division of Chemistry at NSF, Collin Ward and Taylor Nelson at the Woods Hole Oceanographic Institution (WHOI) will study the fate of plastics in the sunlit surface ocean. Despite sustained attention from stakeholders, the ultimate fate of consumer plastics in the ocean remains an open question. Exposure to sunlight is a key degradation process (i.e., photo-degradation) for most consumer plastics but the controls that affect the rates and extents of plastic photo-degradation in the ocean are not well understood. This study aims to determine the factors that control photochemical degradation of consumer plastics and thus their fate in the ocean. The basic knowledge gained from this research will inform fate and transport models that estimate the amount, location, and persistence of plastics in the ocean, as well as their potential impacts on ecosystem processes. This project supports engagement with the Lincoln Laboratory Beaver Works Summer Institute and the Build a CubeSat Challenge, opportunities for high school students across the country to learn about marine plastic pollution. Moreover, numerous undergraduate, and graduate students will be trained and participate on this research project.It is widely understood that sunlight chemically transforms plastics in the ocean into a suite of polymer-, dissolved-, and gas-phase products. However, the governing controls of these photochemical processes are poorly constrained. This research will deconvolute the relative importance of varying controls on the photochemical reactivity of consumer plastics at sea, including particle size, plastic formulation (i.e., base polymer + inorganic additives such as titanium dioxide and zinc oxide), and sunlight wavelength. Specific measures to be tested include oxidation (molecular oxygen consumption), chain scission (decrease in molecular weight), and the production of dissolved organics. This project supports outreach activities with high school students, and the training of 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.