Experimental Characterization of PM2.5 Organic Carbon by Using Carbon-fraction Profiles of Organic Materials

Organic aerosols (OA) in the atmosphere have complex emission sources and formation processes that must be determined to understand the OA composition and behavior. The thermal optical method is generally used to analyze organic carbon (OC) in OAs, and the resulting thermally fractionated OC profiles can be considered to be a synthesis of the organic materials contained in OAs. In this study, carbon-fraction profiles of 43 organic materials were determined and categorized into five types on the basis of their profile patterns. Then a chemical mass balance (CMB) analysis using the five types and the measured carbon-fraction profiles of particulate OC from various emission sources was conducted. The major sources thus determined were generally reasonable considering the known chemical properties of emission source particles. In addition, the seasonal organic matter composition in ambient particulate OC measured at a suburban site of Tokyo was experimentally estimated by a CMB analysis using the five types, and the potential of making good use of thermally fractionated OC data to understand the characteristics of OAs was discussed.