Characteristics and sources of lead pollution after phasing out leaded gasoline in Beijing

A 5-year long-term programme of Pb-monitoring from 2000 to 2004 was carried out at three representative urban sites (a traffic, an industrial, and a residential site), and a suburban site to evaluate the pollution level of Pb in Beijing. For comparison, aerosol samples were also collected in four other cities, Shanghai, Qingdao, Duolun, and Yulin in China. Pb pollution in Beijing has been very serious when compared with other sites over the world, as the concentration of Pb in Beijing remained as high as ∼100–300 ng m−3 in fine particles (PM2.5). Significant spatial variation of Pb in summer with the highest concentration at the industrial site was observed, while relatively even spatial variation was found in winter in urban area, although much heavier in the urban area than at suburban site. Strong seasonal variation of ∼2–3 times higher Pb concentration in winter than that in summer was found. Pb exhibited a unimodal size distribution with most of it in fine fraction. Pb in fine particles was enriched by a factor of 200–1600 relative to its abundance in crust. Besides industry emission, motor vehicle emission, and coal burning, long-range transported dust from outside Beijing and the re-suspended soil containing the deposition of those from previously emitted leaded gasoline could be the important sources of Pb in Beijing.