Formation and exchange of nitrous acid at atmospheric interfaces: Understanding a critical reactive air quality intermediate

点击翻译按钮获取中文摘要

Human activities have dramatically increased and altered the cycling of reactive nitrogen (Nr) at a global scale. Mobilized Nr causes a cascade of environmental cycling and exchange. Fundamental understanding of the chemical, physical, and biological processes driving the movement of Nr within and between Earth system compartments is critical to effectively utilize Nr in modern society, while mitigating both its legacy and future detrimental impacts. Recently, the Nr species nitrous acid (HONO) has been determined to undergo exchange between the Earth's surface and atmosphere. Photolysis of HONO in the early morning can initiate and/or dominate the oxidative capacity of the atmosphere, depending on environment and season. Oxidation sets the lifetime of chemicals emitted into the atmosphere and is fundamental to chemical models used to predict climate and air quality. At the interface, HONO exchange perturbs the Nr pool of the local environment and connected components via the cascade. Chemical, physical, and biological mechanisms that might contribute to exchange of HONO have been found from many laboratory studies. Real world observations, however, are not currently capable of distinguishing which, if any, of these are the major mechanism(s). Under ambient conditions exchange processes are expected to vary across diurnal to seasonal timescales, making prediction of HONO chemistry a critical issue in atmospheric chemistry and biogeochemistry. My research group is customizing state-of-the-science analytical tools to achieve the HONO measurements needed at the interface under real-world conditions. We will advance the state of measuring HONO exchange to make eddy covariance fluxes, by customizing and optimizing its detection with a time-of-flight chemical ionisation mass spectrometer (ToF-CIMS). We will innovate an optimal sampling inlet, as well as automation of standard additions for calibration and interference tracking when deployed for field measurements. The platform will undergo validation through field intercomparison before being used to quantify HONO flux measurements over Nr-rich agricultural soils. The ToF-CIMS platform will be integrated with automated interface flux chambers for reactive gases to bridge the limitations of current lab and field capabilities. The chambers will be used to conduct exchange mechanism experiments under ambient environmental conditions, allowing us to systematically discern the major processes controlling HONO exchange at the interface. Our chambers will be also be used to investigate HONO exchange mechanisms on materials found throughout the indoor environment, where very high HONO levels are regularly found. This work will involve a total of 7 graduate (4 PhD, 3 MSc) and 8 undergraduates. Through development and application of innovative new analytical methods in the lab and field, my group will provide fundamental chemical understanding that is essential to effective environmental regulation.