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

该项目涉及开发一台用于测量对流层HONO浓度的激光光解/激光诱导荧光仪。环境空气将被膨胀成低压槽，HONO将在355 nm处通过光解被裂解为OH和NO。OH光碎片将在308 nm处使用气体膨胀荧光分析(FAGE)方法进行定量。预计这一新仪器将结合光谱技术的选择性和化学技术的低检测下限，使其成为科学界最感兴趣的工具。这一新仪器将在实验室中得到充分鉴定，预计将在城市大气中进行初步现场测量。除了测量OH和NO外，还将测量HONO，以确定在印第安纳州布卢明顿的大气中是否存在未知的HONO来源。在当前的大气化学模型中，对HONO的主要来源的不完整描述可能会对空气质量控制战略产生重要影响，因为这可能导致对光化学污染物浓度的低估预测。例如，臭氧和二次有机气雾剂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温室气体和替代氯氟烃的寿命，这对地球的辐射收支有重大影响。今后在实地活动中部署该仪器以及在实验室研究中使用该仪器将提供对大气中发生的HONO化学的更多洞察，并将有助于改进大气化学的实际模型。今后对该仪器与其他测量技术的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.