Winter and Summer PM_2.5Chemical Compositions in Fourteen Chinese Cities

PM2.5in 14 of China's large cities achieves high concentrations in both winter and summer with averages >100 μg m-3being common occurrences. A grand average of 115 μg m-3was found for all cities, with a minimum of 27 μg m-3measured at Qingdao during summer and a maximum of 356 μg m-3at Xi'an during winter. Both primary and secondary PM2.5are 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 μg m-3in 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 PM2.5deriving 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.PM2.5mass 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 PM2.5emissions and gaseous precursors to attain China's recently adopted PM2.5national air quality standards.