CAREER: Constraining Atmospheric Nitrate Precursors and Chemistry Across the United States (US)

This CAREER project seeks to improve the prediction of atmospheric nitrate by focusing on nitrogen oxide precursor emissions and oxidation pathways. Isotope observations from national atmospheric monitoring sites will be combined with the next generation of atmospheric chemistry models, that include the ability to simulate isotope compositions, to fill critical knowledge gaps regarding nitrogen oxide sources and chemistry.

This information will enable the development of more effective regulatory strategies for improving air quality.

The research objectives of this project are to quantify nitrate formation pathways and characterize the variability of nitrate precursor emissions across the US. The primary loss pathway of nitrogen oxide (NOx) is through its oxidation to atmospheric nitrate, mainly in the form of nitric acid (HNO3) and particulate nitrate (pNO3), with organic nitrates (RONO2) also contributing significantly to some regions.

Atmospheric chemistry and transport models are often unable to accurately replicate observed concentrations of HNO3 and pNO3, including their magnitude, seasonality, and urban-rural gradients, posing significant challenges for predicting air quality responses under policy change. Stable isotope analyses of nitrogen and oxygen will be used to quantify precursor emissions and oxidation chemistry across the contiguous US.

By integrating these novel isotopic measurements with 3-D chemistry transport modeling, this project will provide insights into the spatial and temporal patterns of precursor emissions and chemical formation pathways contributing to nitrate across diverse regions in the US, enhancing model predictions of nitrate.

An environmental chemistry summer camp, the first of its kind in South Carolina, will be developed leveraging the existence of an established summer camp entitled the Carolina Master Scholars Adventure Series (CMSAS), designed to attract academically talented middle and high school students. The project also will support around 3-5 undergraduate and 1-2 graduate students and 1 postdoctoral scholar.

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.