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

Abstract

PM_2.5 in 14 of China's large cities achieves high concentrations in both winter and summer with averages >100 μg m⁻³ being common occurrences. A grand average of 115 μg m⁻³ was found for all cities, with a minimum of 27 μg m⁻³ measured at Qingdao during summer and a maximum of 356 μg m⁻³ 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 μg m⁻³ 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.

Acknowledgments

This work was supported by the Natural Science Foundation of China (NSFC40925009), projects from Chinese Academy of Sciences (KZCX2-YW-BR-10, O929011018, and KZCX2-YW-148). The authors thank Jo Gerrard of the Desert Research Institute for her assistance in assembling and editing the paper.