Kinetic Modeling of the Atmospheric Photooxidation of Reduced Sulfur and Nitrogen Compounds

Atmospheric aerosols encapsulate a wide variety of particles with different compositions, sizes and sources of origin. They also directly and indirectly affect climate by their interactions with sunlight, clouds, atmospheric chemical species, and even other suspended particles. To understand the atmospheric aerosol processes and the effects they have in global and regional climate is of utmost importance for the future establishment of environmental regulations and emission policies that affect aerosol precursor compounds in an effective and beneficial manner. In particular, aerosols are known to be formed from emissions from human activities, such as fossil fuel burning, agriculture, or concentrated animal feeding operations (CAFOs). Secondary organic aerosols (SOA) constitute a type of atmospheric aerosols that are formed from the atmospheric oxidation of organic compounds that are released from various sources into the atmosphere. Due to the complexity of the atmosphere and variability of its conditions, the direct study of SOA formation is a challenging task, but the implementation of atmospheric chamber facilities to study aerosol formation and growth under controlled conditions has provided a way to study the formation and growth of SOA. However, chamber experiments cannot study specific reactions or individual compounds from the aerosol formation mechanisms in isolation, they can only provide insight on what is produced and what it is produced from, and under what conditions. Thus, kinetic modeling of the mechanisms of gas-phase atmospheric oxidation of the compounds of interest is used to develop reliable and accurate chemical models that will help have precise estimations and determine the mechanisms by which volatile organic compounds interact to produce aerosol particles. Dimethyl sulfide (DMS), dimethyl disulfide (DMDS) and trimethylamine (TMA) are three relevant atmospheric compounds, due to their emissions from many natural and anthropogenic sources and recent studies on emissions of these compounds from animal waste from CAFOs has triggered the interests on the study of SOA formation from these and other similar compounds. In this study, kinetic modeling of the atmospheric oxidation mechanisms of DMDS, DMS and TMA is used to simulate atmospheric chamber studies of aerosol formation to develop accurate models and help determine the mechanisms of aerosol formation