Effects Of Fresh And Aged Sea Salt On The Chemistry Of Urban And Remote Regions

现在人们普遍认识到卤素原子在对流层化学中起着重要作用。然而，模型至少低估了光化学活性前体的浓度一个数量级。该项目旨在通过对海盐的热和光化学反应的一系列实验室研究来解决这一差异，这些研究以前没有被研究过。目的是：(1)测量新鲜海盐和陈年海盐混合物反应产生的氯（Cl2）；(2)定量评估海盐颗粒的光化学变化，因为其化学成分的变化类似于在空气中运输的变化；(3)阐明硝酸盐和亚硝酸盐离子光化学过程中微粒内外羟基自由基“自下而上”氧化有机物对海盐的动力学和机理。智力上的优点在于对海盐化学的深刻理解，这可以用于海洋边界层和其他有悬浮盐颗粒的地区的模型，这将有助于解决对流层中卤素原子前体的测量和模型预测之间的巨大差异。这种巨大的脱节很重要，因为对流层卤素化学影响臭氧的形成和去除，臭氧是一种有毒的空气污染物，温室气体和高活性OH自由基的前体，以及影响公众健康，能见度和气候的颗粒形成和生长。这项研究将对硝酸盐和亚硝酸盐阴离子光化学的重要性和影响提供新的见解，这些阴离子在海盐在空气中运输时被纳入海盐，以及据信存在于这些颗粒上的有机涂层的影响。这项研究还将为本科生、研究生和博士后科学家提供培训，这些培训在大气化学方面是广泛的，但在具体化学知识的发展和实验经验方面是深入的。

It is now widely recognized that halogen atoms play a major role in tropospheric chemistry. However, models under-predict the concentrations of photochemically active precursors by at least an order of magnitude. This project is directed to resolving this discrepancy through a series of laboratory studies of the thermal and photochemical reactions of sea salt that have not before been investigated. The objectives are to: (1) measure chlorine (Cl2) production from reactions of salt mixtures representative of fresh and aged sea salt; (2) quantitatively assess the change in the photochemistry of sea salt particles as their chemical composition changes in a manner similar to that during transport in air; (3) elucidate the kinetics and mechanisms of oxidation of organics on sea salt "from the bottom up" by hydroxyl radicals generated in and on particles from nitrate and nitrite ion photochemistry. The intellectual merit lies in a deep understanding of sea salt chemistry that can be used in models of the marine boundary layer and other regions having suspended salt particles, and that will help to resolve the large discrepancies between measurements and model predictions of halogen atom precursors in the troposphere. This large disconnect is important to elucidate because tropospheric halogen chemistry impacts the formation and removal of O3, a toxic air pollutant, greenhouse gas and precursor to highly reactive OH radicals, as well as particle formation and growth that impacts public health, visibility and climate. The research will provide new insights into the importance and impacts of the photochemistry of the nitrate and nitrite anions which are incorporated into sea salt as it is transported in air, and into the impacts of organic coatings believed to exist on these particles. This research will also provide training to undergraduates, graduate students and postdoctoral scientists that is both broad in terms of atmospheric chemistry, yet deep in terms of the specific chemical knowledge that is developed and experimental experience gained.