Collaborative Research: Investigation of the Production of Nitrous Oxide by Sunlight in Ocean Surface Waters

Nitrogen is an essential element for all life on Earth. It exists in many chemical forms, and biological processes control most of the reactions that transform one form to another. This project will investigate the production of nitrous oxide (N2O) in ocean surface waters by non-biological reactions in which sunlight provides the energy needed for the reaction. Nitrous oxide is important for stratospheric ozone destruction and is also a strong greenhouse gas, and the ocean is a significant source of N2O to the atmosphere. Understanding N2O emissions is thus important for understanding air quality, the ozone layer, and biological cycles. The discovery that N2O can be produced by non-biological reactions as well as biological ones suggest a new pathway in the nitrogen cycle that may be important to global nitrogen budgets. Project results will be shared with non-scientific audiences to inform society of the findings and raise awareness of the ocean’s role in global biogeochemistry. The project will provide research opportunities for graduate and undergraduate students. Recent research provides experimental evidence for substantial and consistent abiotic production of N2O as a result of sunlight exposure in oxygenated surface water conditions. This discovery unveils a new process taking place in the surface waters of both freshwater and marine environments, and it offers an explanation for the persistent oversaturation of N2O in surface waters across the world's oceans. The project will address the following objectives: 1) to characterize the mechanism of photochemodenitrification, including the site preference; 2) to assess if there are additional substrates and reactions leading to the photochemical formation of N2O, 3) to determine the action spectrum and efficiency of the photochemical production of N2O; 4) to integrate the photochemical rates with N2O production from biological processes, and characterize their depth distributions with respect to light conditions. Isotope (nitrogen-15) tracer incubations will be used to measure the rate of N2O production using different substrates under controlled radiation conditions to determine the wavelength dependence in the laboratory. Incubations at sea with natural sunlight will be used to determine which pathways are important in the ocean and their depth distributions. 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. NSF Award ID: 2546863 | Program: 01002627DB NSF RESEARCH & RELATED ACTIVIT | Principal Investigator: Scott Wankel | Institution: Woods Hole Oceanographic Institution, WOODS HOLE, MA | Award Amount: $194,008 View on NSF Award Search: https://www.nsf.gov/awardsearch/show-award/?AWD_ID=2546863 View on Research.gov: https://www.research.gov/awardapi-service/v1/awards/2546863.html