Evaluating the Atmospheric Dynamics of Nitrate and Sulfate in Southern New England in Response to Emission Regulations

Atmospheric particulate nitrate and sulfate concentrations have decreased significantly during the last decades, yet, the processes that control their production from emitted precursor gases remain ill-defined. The project seeks to fill this knowledge gap by chemically and isotopically analyzing stored filter samples collected between 2005 and 2018 at various locations in southern New England. The 13-year record obtained through this study will help inform diverse fields including atmospheric chemistry, ecology, health, climate and policy. The project aims at using a unique combination of concentration and isotopic compositions to help constrain atmospheric mechanisms of nitrate and sulfate formation. Archived filters will provide a seasonal record that spans a period during which significant declines in emission of nitrogen oxide and sulfur dioxide gases have led to associated, albeit non-linear decreases in particulate nitrate and sulfate. The cause for non-linearity is investigated by using fractionation of stable isotopes of (i) nitrogen and sulfur for fingerprinting and source apportionment of emission sources, and (ii) oxygen to inform production pathways for nitrate and sulfate. Novel data generated from this work will impact fields beyond atmospheric chemistry by inferring trends in ecological systems and global climate. The PI team will work with staff at various facilities and supervise one graduate and several undergraduate students to complete this labor-intensive analytical study. Results will also be incorporated into the atmospheric chemistry curriculum and shared in an annual outreach event for local elementary schools. 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.