LAUSR

Abstract The mass concentration and the elemental composition of PM2.5 and polycyclic aromatic hydrocarbons were measured in 30 residential apartments during spring in the city of Xian and Chongqing, China. A total of 45 major, minor and trace elements were determined by X-Ray Fluorescence analysis. The carbonaceous species were determined with the thermal–optical transmittance technique. The daily PM2.5 mass concentration ranged from 25 to 140 µg/m3. The following compounds had higher concentrations outdoors than indoors and had higher concentrations in Xi'an than in Chongqing: Na, Al, Si, K, Mn, Fe, Cu, Zn, Br. Sulfur had higher concentrations in Chongqing than in Xi'an and had higher concentrations outdoors than indoors. For the strongly enriched elements (enrichment factor > 100) like S, Cl, Zn, Br, an anthropogenic origin can be suggested. In this study, the average ratio of organic carbon to elemental carbon was 4.9, indicating the possible presence of secondary organic carbon.