Photo-oxidation and multiphase reactions of atmospheric reduced nitrogen

虽然分子N2占地球大气的78%，但通常以低得多的水平（十亿分之一或万亿分之一）存在的含氮分子对大气的辐射预算和反应性有重大影响。例如，一氧化二氮（N2 O）是一种有效且长期存在的温室气体，氨（NH3）控制颗粒物的形成和生长，氮氧化物自由基（NO和NO2）调节大气的氧化能力。全球粮食生产的很大一部分依赖于工业肥料中的固定氮，但人类对全球氮的地球化学循环的干预对社会产生了一系列重要后果，包括空气质量下降，臭氧消耗，酸雨和水体富营养化。* 本研究的总体目标是确定和量化大气中固定氮的化学转化率，以及其与底层生态系统的交换率（排放/沉积）。虽然预计在下一个世纪全球范围内人类活动导致的NO排放量将下降，但预计NH3的排放量将随着肥料生产而继续增加。在这种情况下，NH3的氧化可能成为大气中NO的重要来源，改变了我们对活性氮预算的看法。为了研究这一途径的重要性，我们需要更准确的信息，涉及NH3氧化的气相化学反应的速率和产物。这些反应中有许多是在与燃烧系统有关但与地球大气无关的条件下进行研究的。这种化学反应的一个特别有趣的方面是HNO分子的参与，以前没有人在大气中测量过。我们假设它应该以可测量的数量存在，并建议开发一个系统来测量它在不同的环境中。氨不仅在气相中反应，而且在环境中的一系列冷凝相中反应，例如露水、雾、云、雪、水性气溶胶和有机气溶胶。我们将在实验室中创建人工系统来研究潜在的反应，我们还将从环境中收集雾、露和气溶胶样本，并在其中进行反应。这种凝聚相化学的研究将扩展到其他形式的还原氮，如胺和异氰酸酯，它们可能参与产生有毒和/或吸光化合物的反应。因此，这项研究与了解大气活性氮对健康和气候的影响有关。

While molecular N2 comprises 78% of Earth's atmosphere, it is nitrogen-containing molecules typically present at much lower levels (parts per billion or trillion) that have major impacts on the radiative budget and reactivity of the atmosphere. For example, nitrous oxide (N2O) is a potent and long-lived greenhouse gas, ammonia (NH3) controls the formation and growth of particulate matter, and nitrogen oxide radicals (NO and NO2) regulate the atmosphere's oxidative capacity. A substantial fraction of global food production relies on fixed nitrogen from industrial fertilizer, but the intervention of humans in the global biogeochemical cycle of nitrogen has a series of important consequences for society including degraded air quality, ozone depletion, acid rain, and eutrophication of water bodies. ****The overall goal of this research is to identify and quantify the rates of chemical transformations of fixed nitrogen within the atmosphere, and the rates of its exchange (emission/deposition) with underlying ecosystems.******While emissions of NO resulting from human activity are predicted to decline globally over the next century, emissions of NH3 are expected to continue increasing with fertilizer production. In that scenario, the oxidation of NH3 could become a significant source of NO to the atmosphere, transforming the way we think about the reactive nitrogen budget. To investigate the importance of this pathway, we need more accurate information about the rates and products of gas phase chemical reactions involved in the oxidation of NH3. Many of these reactions have been studied under conditions that are relevant to combustion systems but not to Earth's atmosphere. One particularly interesting aspect of this chemistry is the involvement of the molecule HNO, which no one has measured in the atmosphere before. We hypothesize that it should be present in measurable quantities and propose to develop a system to measure it in different environments.******Ammonia does not only react in the gas phase, but also in a range of condensed phases in the environment such as dew, fog, clouds, snow, aqueous aerosol and organic aerosol. We will create artificial systems in the lab to study potential reactions, and we will also collect fog, dew and aerosol samples from the environment and carry out the reactions in them. The investigations of this condensed phase chemistry will be extended to other forms of reduced nitrogen, such as amines and isocyanates, which can be involved in reactions producing toxic and/or light-absorbing compounds. For this reason, the research is relevant to understanding the health and climate implications of atmospheric reactive nitrogen.***********