@article {SONG20061526,
	title = {Source apportionment of PM2.5 in Beijing by positive matrix factorization},
	journal = {Atmospheric Environment},
	volume = {40},
	number = {8},
	year = {2006},
	pages = {1526 - 1537},
	abstract = {Air pollution associated with atmospheric fine particulate matter (PM2.5, i.e., particles with an aerodynamic diameter of 2.5μm or less) is a serious problem in Beijing, China. To provide a better understanding of the sources contributing to PM2.5, 24-h samples were collected at 6-day intervals in January, April, July, and October in 2000 at five locations in the Beijing metropolitan area. Both backward trajectory and elemental analyses identified two dust storm events; the distinctly low value of Ca:Si (\&lt;0.2) and high Al:Ca (\&gt;1.7) in Beijing PM2.5 appear indicative of contributions from dust storms. Positive matrix factorization (PMF) was used to apportion sources of PM2.5, and eight sources were identified: biomass burning (11\%), secondary sulfates (17\%), secondary nitrates (14\%), coal combustion (19\%), industry (6\%), motor vehicles (6\%), road dust (9\%), and yellow dust. The lower organic carbon (OC), elemental carbon (EC), SO42-, and Ca values of yellow dust enable it to be distinguished from road dust. The PMF method resolved 82\% of PM2.5 mass concentrations and showed excellent agreement with a previous calculation using organic tracers in a chemical mass balance (CMB) model. The present study is the first reported comparison between a PMF source apportionment model and a molecular marker-based CMB in Beijing.},
	keywords = {Backward trajectories},
	issn = {1352-2310},
	doi = {http://dx.doi.org/10.1016/j.atmosenv.2005.10.039},
	url = {http://www.sciencedirect.com/science/article/pii/S1352231005010174},
	author = {Yu Song and Yuanhang* Zhang and Shaodong Xie and Limin Zeng and Mei* Zheng and Lynn G. Salmon and Min Shao and Sjaak Slanina}
}
