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PM 2.5 in 14 of China's large cities achieves high concentrations in both winter and summer with averages >100 g m À3 being common occurrences. A grand average of 115 g m À3 was found for all cities, with a minimum of 27 g m À3 measured at Qingdao during summer and a maximum of 356 g m À3 at Xi'an during winter. Both primary and secondary PM 2.5 are important contributors at all of the cities and during both winter and summer. While ammonium sulfate is a large contributor during both seasons, ammonium nitrate contributions are much larger during winter. Lead levels are still high in several cities, reaching an average of 1.68 g m À3 in Xi'an. High correlations of lead with arsenic and sulfate concentrations indicate that much of it derives from coal combustion, rather than leaded fuels, which were phased out by calendar year 2000. Although limited fugitive dust markers were available, scaling of iron by its ratios in source profiles shows $20% of PM 2.5 deriving from fugitive dust in most of the cities. Multipollutant control strategies will be needed that address incomplete combustion of coal and biomass, engine exhaust, and fugitive dust, as well as sulfur dioxide, oxides of nitrogen, and ammonia gaseous precursors for ammonium sulfate and ammonium nitrate.Implications: PM 2.5 mass and chemical composition show large contributions from carbon, sulfate, nitrate, ammonium, and fugitive dust during winter and summer and across fourteen large cities. Multipollutant control strategies will be needed that address both primary PM 2.5 emissions and gaseous precursors to attain China's recently adopted PM 2.5 national air quality standards.

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