Nitrogen oxide and radical reservoir species in the troposphere

对流层中的氮氧化物和自由基储存物种

• 批准号: RGPIN-2016-03849
• 负责人: Osthoff, Hans
• 金额: $ 2.19万
• 依托单位: University of Calgary
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=708867
• 关键词: Nitrogen; oxide; radical; reservoir; species

The goal of this research program is to improve the scientific understanding of chemical processes in the troposphere (the lowest layer of the atmosphere) that control the abundances of ozone (O3) and secondary organic aerosol (SOA), which in high concentration adversely affect human health and the Earth's climate. Tropospheric O3 production occurs through photo-oxidation of volatile organic compounds (VOC) via the NOx (=NO+NO2) and HOx (=OH+HO2) catalytic radical chains. This research program seeks to remove uncertainties in the production, removal, and transport (in the form of reservoir species) of NOx and HOx radicals. Alkyl nitrates (organic compounds containing the -ONO2 group) are critical in this context because they act either as reservoir species, temporarily storing NOx and redistributing it around the globe, or as NOx sinks, permanently removing it through hydrolysis to nitric acid, a major component of acid rain. Because alkyl nitrates are less volatile than their VOC precursors, their formation is also linked to SOA growth. However, many details have not been worked out (e.g., air-water partitioning coefficients), in particular for alkyl nitrates derived from biogenic VOC. We will accomplish our research objectives through novel, one-of-a-kind analytical methods and conduct laboratory experiments to investigate the chemistry of organic nitrates and of free radicals and their reservoir species, including nitrous acid, organic peroxy radicals, and chlorine nitrate (ClNO3). We will use methods pioneered in my lab, e.g., cavity ring-down and cavity-enhanced absorption spectroscopy, to systematically study alkyl nitrates derived from both anthropogenic and biogenic sources. Specifically, we will measure their yields in reactions between RO2 with NO () and unsaturated VOCs with NO3, determine their Henry's law constants, quantify the amount of NOx recycled when they are reacted with OH radicals (), and measure their aerosol uptake parameters (). We will also investigate heterogeneous photo-oxidation processes which are considerably altered by photosensitizers such as the only recently recognized imidazoles. Results from these laboratory studies will be parameterized for incorporation into atmospheric models. In addition, we will construct a peroxy-radical chemical amplifier (PERCA) to detect peroxide explosives. These are readily synthesized using household chemicals but currently escape trace vapor detection by routine methods. The information that this research program will provide will allow policy makers and stakeholders to make more informed decisions on pollution control strategies. The benefits to Canadians will be the training of experts to assist in this process. A reduction of environmental impacts of anthropogenic activities will have economic benefits to society though improved health and a reduced climate impact.

该研究计划的目标是提高对对流层（大气最低层）化学过程的科学认识，这些过程控制臭氧（O3）和二次有机气溶胶（SOA）的丰度，高浓度对人类健康和地球气候产生不利影响。 对流层O3的产生是通过挥发性有机化合物（VOC）经由NOx（=NO+NO2）和HOx（=OH+ HO 2）催化自由基链的光氧化而发生的。该研究计划旨在消除NOx和HOx自由基的生产，去除和运输（以水库物种的形式）中的不确定性。硝酸烷基酯（含有-ONO 2基团的有机化合物）在这方面至关重要，因为它们既可以作为储存物质，暂时储存NOx并将其重新分布在地球仪周围，也可以作为NOx沉降物，通过水解将其永久去除为硝酸，硝酸是酸雨的主要成分。由于硝酸烷基酯的挥发性低于其VOC前体，因此它们的形成也与SOA的生长有关。然而，许多细节还没有制定出来（例如，空气-水分配系数），特别是对于源自生物源VOC的硝酸烷基酯。 我们将通过新颖的，独一无二的分析方法来实现我们的研究目标，并进行实验室实验，以研究有机硝酸盐和自由基及其储库物种的化学，包括亚硝酸，有机过氧自由基和硝酸氯（ClNO 3）。我们将使用我的实验室开创的方法，例如，光腔衰荡和光腔增强吸收光谱，系统地研究来自人为和生物源的烷基硝酸盐。具体来说，我们将测量RO 2与NO（）和不饱和VOC与NO3之间反应的产率，确定它们的亨利定律常数，量化它们与OH自由基反应时再循环的NOx量（），并测量它们的气溶胶吸收参数（）。我们还将研究异质光氧化过程，这是相当大的光敏剂，如最近才认识到咪唑改变。将对这些实验室研究的结果进行参数化，以便纳入大气模型。 此外，我们将建立一个过氧自由基化学放大器（PERCA）检测过氧化物炸药。这些很容易用家用化学品合成，但目前通过常规方法逃避痕量蒸汽检测。 该研究计划将提供的信息将使政策制定者和利益相关者能够就污染控制战略做出更明智的决定。对加拿大人的好处将是培训专家协助这一进程。减少人类活动对环境的影响将通过改善健康和减少气候影响而给社会带来经济效益。