title: Winter and summer PM2.5 chemical compositions in fourteen Chinese cities.
abstract: PM2.5 in 14 of China's large cities achieves high concentrations in both winter and summer with averages > 100 microg m(-3) being common occurrences. A grand average of 15 microg m(-3) was found for all cities, with a minimum of 27 microg m(-3) measured at Qingdao during summer and a maximum of 356 microg m(-3) at Xi 'an during winter. Both primary and secondary PM2.5 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 microg 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 PM2.5 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.
  
  
  CONCLUSIONS
  PM2.5 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 PM2.5 emissions and gaseous precursors to attain China's recently adopted PM2.5 national air quality standards.
authors.affiliation: Key Lab of Aerosol, SKLLQG, Institute of Earth Environment, Chinese Academy of Sciences, Xi 'an, China. cao@loess.llqg.ac.cn
authors.forename: Jun-Ji
authors.initials: JJ
authors.lastname: Cao
authors.forename: Zhen-Xing
authors.initials: ZX
authors.lastname: Shen
authors.forename: Judith C
authors.initials: JC
authors.lastname: Chow
authors.forename: John G
authors.initials: JG
authors.lastname: Watson
authors.forename: Shun-Cheng
authors.initials: SC
authors.lastname: Lee
authors.forename: Xue-Xi
authors.initials: XX
authors.lastname: Tie
authors.forename: Kin-Fai
authors.initials: KF
authors.lastname: Ho
authors.forename: Ge-Hui
authors.initials: GH
authors.lastname: Wang
authors.forename: Yong-Ming
authors.initials: YM
authors.lastname: Han
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D002681:China; D002947:Cities; D004784:Environmental Monitoring; D010316:Particle Size; D052638:Particulate Matter / Q000032:analysis*; D012621:Seasons; D013052:Spectrometry, X-Ray Emission
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter