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

氮氧化物NOx（=NO+NO2）是催化臭氧形成并可参与臭氧破坏的普遍存在的污染物。当氮氧化物被氧化成硝酸并沉积在地球表面时，它通过添加固定氮来提供酸性并使生态系统肥沃。氮氧化物主要在白天通过与羟基（OH）自由基反应而被去除，并在夜间转化为更高的氮氧化物（NO3和N2O5）。然后N2O5与水发生非均相反应形成硝酸，为NOx去除提供了“黑暗”途径。大气化学模型表明，N2O5的非均相水解途径是占主导地位的高纬度冬季，当夜晚长，温度低。在这个项目中，研究人员将测量N2O5混合比沿着氮氧化物，臭氧，一氧化碳，气溶胶化学成分，雪的化学成分在高纬度污染羽流作为一个函数的距离，从源头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装有仪器的拖车跟踪顺风的空气团来研究。积雪、温度和日长变化的作用将通过秋季、冬季和春季的活动来探讨。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.