Analysis of Chemical Composition

The atmosphere contains complex mixtures of chemical species. Evaluation of the mixture composition can reveal the nature of the sources contributing to ozone formation and the extent of chemical reactions. Analyses of particle composition and gas/aerosol partitioning can provide insights into the sources of particulate matter and the limiting factors for secondary aerosol formation. Since ozone is a secondary pollutant formed by the reaction of nitrogen oxides and hydrocarbons, it is often fruitful to examine both the chemical composition of the hydrocarbon and carbonyl species and other indicator ratios, such as VOC/NO_x, NO/NO₂ , O₃/NO_y, HNO₃/NO_y, PAN, NO_y, and H₂O₂/HNO₃, in order to improve the understanding of controlling processes. Motor vehicle exhaust, industrial emissions, gasoline vapors, biogenic hydrocarbon emissions, and chemical solvents are some of the major sources of NO_x and hydrocarbons leading to ozone and secondary aerosols. These precursors have both anthropogenic and biogenic origins. Each hydrocarbon reacts at a different rate and with different reaction mechanisms. STI analysts investigate the chemical composition of emission sources and the ambient samples in order to better understand the possible impacts of emission control strategies.