Characterizing Chemical Production and Loss of Nitrous Acid (HONO) Via Stable Isotopes

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This award from the Environmental Chemical Sciences Program supports Professor Meredith Hastings at Brown University to study nitrous acid. Nitrous acid is a key species in atmospheric chemistry, with important implications for air quality both indoors and outdoors. This project focuses on addressing the difficult-to-resolve sources and sinks of atmospheric nitrous acid. Nitrous acid is typically produced on an environmental surface by reactions of nitrogen dioxide, nitric acid or particulate nitrate. The project uses stable isotopic analysis of these species to determine potential pathways of gaseous nitrous acid production. It builds on measurements of isotopic signatures from previous work and leads to improved understanding of the relative contributions from each source and pathway to the atmospheric nitrous acid budget. This has strong implications for understanding air quality, climate change, and their impact on human and ecosystem health. It also provides a potential tool for better prediction and decision making related to emissions that lead to nitrous acid production. This award also advances the career development of a postdoctoral scientist and a graduate student. Results are being integrated into a newly developed course on air quality at Brown University. A new method has been developed and verified in Professor Hasting's lab to efficiently capture nitrous acid in the air for stable isotopic characterization of nitrogen and oxygen isotopes. This technique has been used to distinguish the isotopic signature of nitrous acid from major sources including vehicle, soil and biomass burning emissions. In this project, a flow reactor is being designed and built to couple with the collection technique to isotopically characterize the nitrous acid heterogeneously produced on environmentally representative surfaces that are both prepared in the lab and collected in the actual environment. The results from this project will constrain atmospheric nitrous acid budget and trace reactive nitrogen species cycling from regional to global scales.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.