Atmospheric lead pollution in fine particulate matter in Shanghai, China.

The Pb-monitoring program was extended for 6 years from 2002 to 2007 at 17 representative urban sites (6 traffic, 5 industrial, and 6 residential sites), and 3 suburban sites to assess the lead pollution in fine particulate matter (PM2.5) after phasing out leaded gasoline in Shanghai. Compared with Pb levels reported in other places, the Pb pollution in Shanghai is still serious after phasing out leaded gasoline, which remains at high concentration range (213-176 ng/m3) in PM2.5 in winter. Significant spatial variation of Pb concentrations and strong seasonal variation of higher Pb concentration in winter than that in summer were detected. The size distribution of Pb in particulate matter has a unimodal mode that peaks at approximately 0.154-1.59 microm particle diameter, indicating that Pb is mainly concentrated in fine fraction. Lead in the fine fraction is enriched by a factor of 10(3)-10(4) relative to Pb abundance in crust. Eight categories of Pb pollution sources were identified in the PM2.5 in the winter of 2007 in Shanghai. The important emission sources among them are vehicle exhaust derived from combustion of unleaded gasoline, metallurgic industry emission, and coal combustion emission.