A comparative study of the organic matter in PM2.5 from three Chinese megacities in three different climatic zones

Organic matter in PM2.5 collected in 2002 and 2003 from three megacities in different climatic zones in China, Beijing (40°N), Shanghai (31°N) and Guangzhou (23°N), was characterized. The focus was on solvent-extractable organic compounds (SEOC), which were used to identify the influences of geography, variation of the season, sources and transport on the concentration and distribution of these homologues. Organic carbon, elemental carbon, and water-soluble organic carbon concentrations were analyzed only for the substantiation of the SEOC findings. Analysis of the fossil fuel residues and the plant wax components in n-alkanes, PAHs, fatty acids and n-alkanols allowed the identification of anthropogenic (coal and petroleum combustion processes, and kitchen emissions) and biogenic (vegetation and microbial) sources. The influence of temperature on the distribution of the SEOC was exemplified by the negative correlation between the relative concentrations of the semivolatile homologues (alkanes and PAHs) and ambient temperature. This is attributable to gas–particle partitioning. Indirectly, ambient temperature dictates the type of vegetation that can grow in a geographical zone. This would influence the distribution of the plant waxes, and finally, it plays a role in the aerosol loading due to energy usage.