AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
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Particle-Phase Chemistry Leading to Sulfate Product
RENYI ZHANG, Texas A&M University
Abstract Number: 216 Working Group: There Must be Something in the Water: Cloud, Fog and Aerosol Aqueous Chemistry for Aerosol Production
Abstract Sulfate (SO42-) is ubiquitous and is a key constituent of fine particulate matter (PM) in the atmosphere. Hygroscopic sulfate aerosols serve as efficient cloud condensation nuclei, affecting cloud formation, precipitation, and climate. A major fraction of regional acid deposition is attributed to the sulfate content that exerts debilitating effects on acid sensitive ecosystems. Furthermore, high levels of fine PM have been implicated in adverse human health issues, as exemplified by high fatality during the 1952 London Fog. Sulfur compounds are emitted globally from many natural and anthropogenic sources, and there have been high SO2 emissions from combustion of coal and petroleum products in developing countries (such as China) spurred on by fast economic development. Gaseous SO2 is converted to particulate sulfate through gas-phase oxidation or aqueous reactions, but the detailed chemical mechanisms remain controversial. The gas-phase oxidation of SO2 is dominated by its reaction with the OH radical, with a lifetime of about 1 week at the typical tropospheric level of OH radicals. The aqueous pathways of SO2 oxidation include the reactions with dissolved ozone, hydrogen peroxide, organic peroxides, OH, and NO2 via catalytic or non-catalytic pathways involving mineral oxides. Most recently, an interfacial SO2 oxidation mechanism involving O2 on acidic microdroplets has been suggested. Atmospheric measurements have revealed high sulfate production during severe haze events in China, which cannot be explained by current atmospheric models and suggests missing sulfur oxidation mechanisms. In this talk the sulfate formation is discussed, by combining field measurements of gaseous pollutants and aerosol particle properties in two Chinese Megacities and complementary laboratory experiments