Ambient concentrations and elemental compositions of PM10 and PM2.5 in four Chinese cities

Abstract

Three size fractions of particulate matter (PM), i.e., fine particles (PM2.5), coarse particles (PM2.5-10), and PM10, were measured at the school yards of eight elementary schools in four large Chinese cities during 1995 and 1996. These schools, one located in an urban district and one in a suburban district in each city, served as principal bases for an air pollution epidemiologic study. All PM samples were collected on Teflon filters using dichotomous samplers and analyzed gravimetrically for PM mass concentrations. A subset of the samples collected were analyzed for elements using a standard XRF technique. Annual means of PM10 concentrations, in which 52-75% were PM2.5, ranged from 68 to 273 μg/m3 across the eight sampling sites. Within each city, the urban site had higher annual means of all measured PM size fractions. Reported in the paper were also the concentrations of eight elements which were likely to be associated with urban pollution sources. The concentrations of these elements were found to be substantially higher in fine particles than in coarse particles, suggesting that urban pollution may have a larger impact on fine particles. This is further supported by the results from comparing elemental enrichment factors for fine particles with those for coarse particles. It is clearly demonstrated that the elements were enriched more in fine particles than in coarse particles.