Collaborative Research: Determination of Nitrous Acid and Nitrogen Dioxide Flux and Concentration Over Forest Canopies Using Quantum Cascade Laser Absorption Spectroscopy

通过构建改进的仪器，能够对涡流协方差通量进行快速响应测量，并通过部署新的传感器对其进行现场测试，详细测量HONO浓度和通量及其与其他氮氧化物、氧化剂和环境条件的协方差，将研究氮气（HONO）向大气通量的产生和损失机制以及大小。亚硝酸光解（HONO）是边界层中OH自由基的主要来源，但人们对其了解甚少。PI将(1)构建并测试能够高频测量HONO和NO2的双通道量子级联激光吸收光谱仪（QCLAS），(2)在受车辆排放影响的郊区站点和农村森林冠层上方测量HONO、NO、NO2和NOy，以及(3)在基于GEOS-Chem的光化学模型框架内解释浓度和通量观测，以提供控制边界层HONO过程的新见解。这些研究活动将通过提供仪器开发和支持研究伙伴关系来加强现有的研究基础设施。该仪器满足了社会对可靠的快速响应仪器的关键需求，以测量连续运行中的HONO，以评估污染影响。HONO- no2 QCLAS将能够参与各种未来的现场测量活动，以检查HONO的生产和损失。这项工作将直接支持一项研究生论文项目，并将作为哈佛森林研究中心两名本科生和一名高中教师的研究课题，作为本科生研究经验（REU）项目和教师研究经验（RET）暑期项目的一部分。

The production and loss mechanisms, and the magnitude of nitrous acid (HONO) fluxes to the atmosphere, will be investigated by constructing improved instrumentation capable of fast response measurements suitable for eddy-covariance flux, and by deploying the new sensor to field test it by making detailed measurements of HONO concentrations and fluxes and their covariance with other nitrogen oxides, oxidants, and environmental conditions. Photolysis of nitrous acid (HONO) is a major source of OH radicals in the boundary layer but poorly understood. The PI's will (1) construct and test a 2-channel Quantum-Cascade laser absorption spectrometer (QCLAS) capable of high frequency measurement of HONO and NO2, (2) measure HONO, NO, NO2, and NOy at a suburban site influenced by vehicle emissions, and above a forest canopy at a rural site, and (3) interpret the concentration and flux observations within a photochemical model framework, based on GEOS-Chem, to provide new insights into the processes controlling HONO in the boundary layer. These research activities will enhance existing research infrastructure by providing instrument development and supporting research partnerships. The instrument addresses a critical societal need for a reliable fast-response instrument to measure HONO in continuous operation to assess pollution impacts. The HONO-NO2 QCLAS will enable participation in a variety of future field measurement campaigns to examine HONO production and loss. This work will directly support a graduate-student thesis project and will serve as a research topic for two undergraduate students and a high school teacher at the Harvard Forest LTER as part of Research Experience for Undergraduates (REU) program and Research Experience for Teachers (RET) summer programs.