The air-borne particulate pollution in Beijing - concentration, composition, distribution and sources

Aerosol samples of PM2.5 and PM10 were collected in both summer and winter seasons from 2002 to 2003 synchronously at a traffic site, an industrial site, and a residential site in Beijing, which could basically be the representatives over Beijing. Twenty-three elements and 15 ions together with organic carbon and elemental carbon were analyzed systematically for characterization of Beijing aerosol. PM2.5 was the major part of the inhalable particles (PM10), as the ratios of PM2.5/PM10 were 0.45-0.48 in summer and 0.52-0.73 in winter. SO42-, NO3-, NH4+, organic matter, crustal matter, and element carbon were the six dominant species, which totally accounted for 85.8-97.7% of Secondary aerosol, (SO42-, NO3-, and NH4+), road dust or/and long-range transported dust from outside Beijing, industry and motor vehicles emission, coal burning were the major contributors to the air-borne particulate pollution in Beijing. Overall, coal burning and the traffic exhausts, plus the dust from the long-range transport, could be the major sources of the aerosol pollution at Beijing. A relatively even spatial distribution of chemical species in PM2.5 was found while in PM10 a significant variation with the highest concentrations at the industrial site in summer and at the residential site in winter was observed. The concentrations of PM10, PM2.5 as well as various chemical species were higher in winter than in summer. The contributions of mineral aerosol from outside Beijing were first estimated with a newly developed element tracer technique, which accounted for 79% and 37% of the total mineral in PM10 and PM2.5 in winter, and 19% and 20% in summer, respectively. During the dust storm period from 20 to 22 March, it reached up to 97% in TSP, 79% in PM10 and 76% in PM2.5. This is the technique, firstly, developed for estimating the relative contributions of sources from inside and outside Beijing to the total mineral aerosol and it could provide the basic information in controlling the air-borne particulate pollution at Beijing. (C) 2004 Elsevier Ltd. All rights reserved.