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

氮氧化物，NOx(=NO+NO2)，是一种普遍存在的污染物，可以催化臭氧的形成，并可以参与臭氧的破坏。当NOx被氧化成硝酸并沉积到地球表面时，它会增加酸度，并通过添加固定氮来肥沃生态系统。NOx主要在白天与羟基(OH)自由基反应，晚上转化为更高级的氮氧化物(NO3和N2O5)来去除。然后，N2O5与水发生多相反应生成硝酸，为脱除NOx提供了一条“暗”途径。大气化学模型表明，在高纬度冬季，夜间时间长，温度低，N2O5的非均相水解途径占主导地位。在这个项目中，研究人员将测量高纬度污染羽流中N2O5与NOx、臭氧、一氧化碳、气溶胶化学成分和雪化学成分的混合比率，作为离污染源距离的函数，以了解夜间氮氧化物化学的机制。来自费尔班克斯的污染羽流将通过使用仪表式拖车跟踪顺风向气团来研究。秋季、冬季和春季的活动将探讨积雪、温度和不同日长的作用。研究生和本科生将在这个项目中发挥关键作用。

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.