Author : Sean Michael Staudt
Release : 2019
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Heterogeneous Reactions of Nocturnal Nitrogen Oxides at Atmospherically Relevant Aqueous Interfaces - read free eBook in online reader or directly download on the web page. Select files or add your book in reader. Download and read online ebook Heterogeneous Reactions of Nocturnal Nitrogen Oxides at Atmospherically Relevant Aqueous Interfaces write by Sean Michael Staudt. This book was released on 2019. Heterogeneous Reactions of Nocturnal Nitrogen Oxides at Atmospherically Relevant Aqueous Interfaces available in PDF, EPUB and Kindle. Dinitrogen pentoxide (N2O5) is a naturally occurring gas-phase nitrating agent that acts as a nocturnal NOx reservoir (NOx ≡ NO + NO2) in the atmosphere. The heterogeneous reaction of N2O5 at aqueous interfaces can serve as a chain terminating reaction in the catalytic cycling of NOx radicals that generate ozone in the lower atmosphere. A molecular mechanism for the heterogeneous reaction of N2O5 has remained elusive but is generally thought to proceed through hydrolysis forming nitrate in the condensed phase. It has been shown previously that N2O5 can also react with aqueous chloride, forming nitryl chloride (ClNO2). Upon evaporation to the gas phase, ClNO2 can photolyze, regenerating NO2 and a chlorine radical. The fraction of N2O5 that is converted to ClNO2 following reactive uptake to aqueous interfaces ([uppercase Phi]ClNO2) depends strongly on the chloride concentration. Although well established for aqueous solutions containing only chloride, recent field observations indicate that parameterizations of [uppercase Phi]ClNO2 based on laboratory measurements uniformly overpredict [uppercase Phi]ClNO2 for more chemically complex interfaces. In this thesis, I expand upon existing studies of N2O5 reaction with chloride in water to investigate alternative solutes and solvents as well as mixed salt solutions that are more relevant proxies for atmospheric interfaces. In chapters 2 and 3, I report and interpret measurements of the nitryl chloride (ClNO2) branching fraction following reactive uptake of N2O5 to mixed organic and inorganic solutions representative of atmospheric interfaces. For solutions containing 0.5 M NaCl, [uppercase Phi]ClNO2 is reduced from 0.85 +/- 0.03 to 0.32 +/- 0.14 upon the addition of 2.0 M Na2SO4, and to 0.18 +/- 0.03 upon the addition of 0.5 M NaAc. The results indicate that anions ubiquitous in atmospheric aerosol, commonly considered to be unreactive, may regulate the production of reactive gases such as ClNO2. In chapter 4, I investigate the parallel reaction of N2O5 with bromide (sodium bromide, NaBr, and tetrahexylammonium bromide, THABr) and compare the observed product branching fractions with those observed for aqueous chloride solutions. In the second part of chapter 4, I explore the product branching fractions for Br2 in a new solvent, glycerol, to represent the organic component of aerosol.