[Assessing PM10 and SO2 networks using positive matrix factorization in Beijing city].

The aim of this study was to identify city areas with similar air pollution characteristics and determine which sites may be providing redundant information. Positive matrix factorization (PMF) was applied in this study to assess the mass concentrations of sulfur dioxide (SO2) and particulate matter with an aerodynamic diameter less than 10 microm (PM010), collected in the air quality monitoring network in the year of 2000. The analysis indicated that there were obviously seasonal variations for PM10 and SO2 in Beijing. The PM10 concentrations were higher in spring and lower in summer, but the SO2 concentrations were higher in winter and lower in summer. The results of the PMF showed that the sites of PM10 network in Beijing could be identified as three regions, which represented city areas characterized by the same specific air pollution. These three regions represented Gucheng site/Chegongzhuang site, Qianmen site/National Olympic Sports Center site/Tiantan site/Nongzhanguan site, and Ming Tombs site, respectively. Some sites in region 2 which included four sites may be redundant and can be removed. SO2 network can be divided into six regions including Chegongzhuang site/Qianmen site, Tiantan site/Nongzhanguan stie, Ming Tombs site, National Olympic Sports Center site, Dongsi site, and Gucheng site. It indicated that some sites in Beijing PM10 and SO2 monitoring networks might be redundant and could be removed or relocated to other areas.