UC Riverside

Gas-phase reduced sulfur compounds (dimethylsulfide, dimethyldisulfide) and amines (trimethylamine, diethylamine, butylamine, ammonia) are both present in relatively high concentrations over agricultural land and are both thought to be important to new particle formation and particle growth. Despite this, there is a lack of knowledge on how amines oxidize in the atmosphere, there are discrepancies in results from studies focused on determining the oxidation products of reduced sulfur compounds, and there have been no investigations into how these co-emitted compounds interact to form aerosol. This thesis will begin to fill these information gaps. First, the major difficulties involved in running experiments on reduced sulfurs and amines is discussed. The methodology by which these compounds can be successfully oxidized in a 37.5 cubic meter Teflon environmental chamber is laid out. Next, results are presented from oxidation of reduced sulfur compounds under extreme dry conditions. The importance of nitrogen oxides was also probed. This marks the very first investigation of these compounds under dry conditions. The subsequent study is focused on these same oxidation experiment under humid conditions. These studies provide insight into the importance of water vapor to the mass concentration and composition of secondary aerosol. Results from both of these studies are used to update existing oxidation mechanisms as well as aerosol yields for dimethylsulfide and dimethyldisulfide. To date, this represents the most atmospherically relevant reduced sulfur oxidation study. Next, the physical and chemical properties of secondary aerosol formed through the oxidation of amines under both dry and humid conditions are discussed. Finally, results are discussed from interaction experiments involving the oxidation of an amine in the presence of a reduced sulfur compound. This study is the first of its kind and provides a more realistic look at how these compounds react in the atmosphere to form secondary aerosol. Chemical and physical aerosol properties measured during multiple precursor experiments are compared to results from individual precursor experiments to determine if the two compounds are interacting. Furthermore, when it is determined that an interaction occurred, the nature of this interaction is investigated and a mechanism by which aerosol forms is developed.