title: Particulate pollution in urban Chongqing of southwest China: Historical trends of variation, chemical characteristics and source apportionment.
abstract: Chongqing, the largest megacity in southwest China, faces serious aerosol pollution but lacks information on particle characteristics and its sources. Official data released by Chongqing Environmental Protection Bureau demonstrated that urban PM10concentrations decreased remarkably from 150μgm-3in 2000 to 90μgm-3in 2012. However, only several peer-reviewed studies paid attention to local fine particle (PM2.5) pollution. In the study, PM2.5samples were obtained and subjected to chemical analysis in an urban site of the city during 2012 to 2013. The annual mean PM10and PM2.5concentrations in urban Chongqing were 103.9±52.5 and 75.4±42.2μgm-3, respectively. PM2.5showed a distinct seasonality of high concentration in winter and similar levels in other seasons. The average OC/EC (organic carbon/element carbon) ratio was 3.7 with more high-OC/EC ratio sources contribution in autumn and winter. The varying sources and formation mechanisms resulted in SO42-and NH4+peaks in both summer and winter, whereas high nitrate concentration was only observed in winter. In the average mass closure, PM2.5was composed of 23.0% SO42-, 11.7% NO3-, 10.9% NH4+, 30.8% OM (organic matter), 5.2% EC, 8.2% mineral dust, 0.6% TEO (trace elements), 1.0% Cl-and 1.1% K+, while exhibiting large seasonal variability. Using positive matrix factorization (PMF), six sources were apportioned in PM2.5: secondary inorganic aerosols, coal combustion, other industrial pollution, soil dust, vehicular emission, and metallurgical industry. The annual mean contribution of above sources to PM2.5was 37.5, 22.0, 17.5, 11.0, 9.8 and 2.2%, respectively. Coal combustion was identified by As tracer and dominated the primary sources of PM2.5, while the two different industrial sources were characterized by Cr and Mo, Co, Ni, and Se, respectively. The study is of great importance in characterizing the historical trends, current chemical characteristics and sources of fine particles in urban Chongqing.
authors.affiliation: School of Safety and Environmental Engineering, Capital University of Economics and Business,No.121 Zhangjialukou Rd, Fengtai District, Beijing 100070, PR China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: College of Environmental Science and Engineering, Peking University, No.5 Yiheyuan Rd, Haidian District, Beijing 100871, PR China. Electronic address: sdxie@pku.edu.cn.
authors.forename: Shao-Dong
authors.initials: SD
authors.lastname: Xie
authors.affiliation: Sichuan Provincial Environmental Monitoring Center, No.88 3(rd) East Guanghua Rd, Qingyang District, Chengdu 610041, Sichuan Province, PR China.
authors.forename: Bin
authors.initials: B
authors.lastname: Luo
authors.affiliation: Chongqing Environmental Monitoring Center, No.252 Qishan Rd, Yubei District, Chongqing 401147, PR China.
authors.forename: Chong-Zhi
authors.initials: CZ
authors.lastname: Zhai
keywords: Chemical composition; Chongqing; PM; Source apportionment