Unraveling Chemical Sink Processes of Ammonia: Insights from Stable Isotopes

This award from the Environmental Chemical Sciences Program in the Division of Chemistry supports Professor Wendell Walters and his students for research on ammonia in the atmosphere. Ammonia is an important trace gas which impacts air quality, ecosystems, and climate. Ammonia helps neutralize acids in the atmosphere, forming particles that affect air quality and human health. Despite its importance, many uncertainties remain regarding ammonia emission sources and its chemical fate. This project will study ammonia and its interactions in the atmosphere, providing valuable data that will help improve air quality models and inform policies. Additionally, the project will involve educational and outreach activities, benefiting students and the broader community. By integrating hands-on learning and outreach activities, the project will enhance science education and community engagement. The nitrogen stable isotopic composition of ammonia has been demonstrated to be a potentially useful tool for tracking ammonia emissions, but limitations arise from a lack of knowledge about isotope effects associated with ammonia sink processes. This project aims to address these knowledge gaps from controlled laboratory experiments to elucidate nitrogen isotope fractionation associated with ammonia chemical sink processes, including gas-to-particle conversion and oxidation. The objectives are to determine nitrogen-stable isotope effects associated with aerosol nucleation involving ammonia, quantify nitrogen isotope fractionation during particle condensation under varying aerosol compositions, and quantify isotope effects and reaction mechanisms associated with ammonia oxidation. The resulting dataset will be instrumental in integrating nitrogen stable isotopes of ammonia and its secondary products into atmospheric chemistry models, advancing efforts to address the complex challenges posed by the atmospheric reactive nitrogen burden. 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.