Development of a Laser Photofragmentation/ Laser-Induced Fluorescence Instrument for Tropospheric Measurements of Nitrous Acid

该项目涉及开发激光光破碎/激光诱导荧光仪器，用于测量对流层中HONO的浓度。环境空气将膨胀成低压电池，HONO将在355nm光解作用下分解成OH和NO。OH光片段将使用308 nm的气体膨胀荧光法（FAGE）进行定量。预计这种新仪器将结合光谱技术的选择性和化学技术观察到的低检测限，使其成为科学界的主要兴趣。这种新仪器将在实验室中进行充分的表征，预计将在城市大气中进行初步的实地测量。除了OH和NO外，还将测量HONO，以确定是否有未知来源的HONO出现在印第安纳州布卢明顿的大气中。当前大气化学模型中对HONO主要来源的不完整描述可能会对空气质量控制策略产生重要影响，因为它可能导致对光化学污染物浓度的低估。例如，臭氧和二次有机气溶胶由于对人类健康的有害影响而引起社会的特别关注。此外，准确描述自由基的主要来源对气候变化问题很重要，因为大气氧化过程控制着对地球辐射收支有重大影响的温室气体和替代氟氯化碳的寿命。该仪器在野外活动中的未来部署以及在实验室研究中的使用将为大气中发生的HONO化学提供更多的见解，并将有助于改进大气化学的实际模型。未来将该仪器与其他测量技术进行相互比较，也将有助于评估大气中HONO测量的准确性。

This project involves the development of a Laser Photofragmentation/Laser Induced Fluorescence instrument for measuring tropospheric concentrations of HONO. Ambient air will be expanded into a low-pressure cell and HONO will be fragmented into OH and NO by photolysis at 355 nm. The OH photofragment will be quantified using the Fluorescent Assay by Gas Expansion (FAGE) approach at 308 nm. It is anticipated that this new instrument will combine the selectivity of spectroscopic techniques and the low detection limit observed for chemical techniques, making it of prime interest for the scientific community. This new instrument will be fully characterized in the laboratory and it is anticipated to perform initial field measurements in an urban atmosphere. HONO will be measured in addition to OH and NO to determine if unknown sources of HONO are occurring in the atmosphere of Bloomington, IN.An incomplete description of the major sources of HONO in current models of atmospheric chemistry may have important implications for air quality control strategies as it may lead to an underprediction of the concentrations of photochemical pollutants. For example, ozone and secondary organic aerosols are of particular interest to the society due to detrimental effects on human health. In addition, an accurate description of the main sources of free radicals is important to issues of climate change as atmospheric oxidation processes control the lifetime of greenhouse gases and the alternative chlorofluorocarbons, which have a significant impact on the radiative budget of earth. Future deployments of this instrument during field campaigns as well as its use during laboratory studies will provide additional insights in the HONO chemistry occurring in the atmosphere and will help improve actual models of atmospheric chemistry. Future intercomparisons of this instrument with other measurement techniques will also help in assessing the accuracy of HONO measurements in the atmosphere.