Chemical Transformations of Nitrogen Oxides in High Latitude Plumes: The Role of Dinitrogen Pentoxide (N2O5) Heterogeneous Hydrolysis

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Nitrogen oxides, NOx (=NO+NO2), are ubiquitous pollutants that catalyze ozone formation and can participate in ozone destruction. When NOx is oxidized to nitric acid and deposited to Earth's surface, it contributes acidity and fertilizes ecosystems by adding fixed nitrogen. NOx is removed by reaction with hydroxyl (OH) radicals, primarily in the day, and by conversion to higher nitrogen oxides (NO3 and N2O5) at night. N2O5 then undergoes heterogeneous reaction with water to form nitric acid, providing a "dark" pathway for NOx removal. Atmospheric chemistry models indicate that the N2O5 heterogeneous hydrolysis pathway is dominant during high latitude winter, when nights are long and temperatures are low. In this project, the investigators will measure N2O5 mixing ratios along with NOx, ozone, carbon monoxide, aerosol chemical composition, and snow chemical composition in high latitude pollution plumes as a function of distance from the source to understand the mechanism of nighttime nitrogen oxide chemistry. The pollution plume from Fairbanks will be studied by following air masses downwind using an instrumented trailer. The role of snow cover, temperature, and varying day length will be probed by campaigns in fall, winter, and spring. Graduate and undergraduate students will play key roles in this project.