Nitrogen oxide and radical reservoir species in the troposphere

这项研究计划的目标是提高对对流层(大气的最低层)中控制臭氧(O3)和二次有机气溶胶(SOA)丰度的化学过程的科学理解，这些化学过程在高浓度时会对人类健康和地球气候造成不利影响。*对流层臭氧的产生是通过NOx(=NO+NO2)和Hox(=OH+HO2)催化自由基链光氧化挥发性有机化合物(VOC)来实现的。这项研究计划旨在消除NOx和Hox自由基的产生、清除和运输(以储存物种的形式)中的不确定性。在这种情况下，烷基硝酸盐(含有-ONO2基团的有机化合物)至关重要，因为它们要么作为储存物，暂时储存NOx并将其重新分配到全球各地，要么作为NOx下沉，通过将其水解为酸雨的主要成分硝酸永久地将其清除。由于烷基硝酸盐的挥发性低于其VOC前体，它们的形成也与SOA的增长有关。然而，许多细节(例如，空气-水分配系数)还没有确定，特别是来自生物VOC的烷基硝酸盐。*我们将通过独一无二的新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、自由基及其储存物种的化学，包括亚硝酸、有机过氧基和硝酸氯(ClNO3)。我们将使用我的实验室首创的方法，例如腔衰荡和腔增强吸收光谱，系统地研究来自人为和生物来源的烷基硝酸盐。具体地说，我们将测量它们在RO2与NO(α)和不饱和VOCs与NO3的反应中的产率，确定它们的亨利定律常数，量化它们与OH自由基(β)反应时回收的NOx的量，并测量它们的气溶胶吸收参数(γ)。我们还将研究多相光氧化过程，这些过程会被光敏剂显著改变，例如最近发现的唯一咪唑类化合物。这些实验室研究的结果将被参数化为大气模型。*此外，我们还将建造一个过氧基化学放大器(PECA)来检测过氧化氢爆炸物。这些化合物很容易用家用化学品合成，但目前通过常规方法避免了微量蒸汽的检测。*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。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利益。

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 (α) and unsaturated VOCs with NO3, determine their Henry's law constants, quantify the amount of NOx recycled when they are reacted with OH radicals (β), and measure their aerosol uptake parameters (γ). 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.**