Particulate composition and source apportionment trends in winter in Chengdu

Air samples of ambient PM10and PM2.5were collected in 2010, 2011, and 2012 at eight sites during winter in Chengdu, Sichuan Province. The inorganic elements, water solvent ions and carbonaceous species were measured to identify the sources of the PM10and PM2.5. The trends of PM concentration, chemical composition and sources were investigated. The concentration of PM10was the highest in the industrial region, while PM2.5showed regional characteristics. The sources of PM10and PM2.5in Chengdu were determined by chemical mass balance iteration (CMB-iteration) receptor model. The results showed that the important sources of PM10in winter in Chengdu were suspended dust, sulfates, fly coal combustion, nitrates and vehicle exhaust, with contributions of 24%-29%, 17%-22%, 13%-16%, 6%-12% and 6%-11%, respectively, from 2010 to 2012. The important sources of PM2.5were sulfates, suspended dust, fly coal combustion, nitrates and vehicle exhaust, with contributions of 25%-27%, 19%-22%, 12%-15%, 11%-13% and 8%-11%, respectively, from 2010 to 2012. This work indicated that secondary particles and suspended dust were the major sources of PM in Chengdu. Suspended dust and cement dust, which were mainly composed of coarse particles, contributed less year by year, while the contribution of secondary particles, which were mainly composed of fine particles, increased year by year. Fine PM pollution was serious in winter in Chengdu.