[Spatial Temporal Characteristics and Cluster Analysis of Chemical Components for Ambient PM_2.5 in Wuhan]

The characteristics of chemical components of particulate matter are good indicators for analyzing sources and causes of pollution. The spatial and temporal distribution characteristics of particulate matter can reflect regional pollution problems in urban development, providing a basic dataset to support effective control of particulate matter sources. We collected PM_2.5 and analyzed its concentration and chemical components at eight sites during different seasons. The results indicated that the average concentration of PM_2.5 in Wuhan reached 70.7 μg·m^-3. The concentration of PM_2.5 in winter (103.1 μg·m^-3) was significantly higher than that of other seasons, and the lowest concentration was in autumn (52.4 μg·m^-3). The concentrations of PM_2.5 in Donghu Gaoxin, Zhuankou New Area, and Qingshan Ganghua Station were significantly higher than those at the other sites. The main chemical components in PM_2.5 were OC and SO₄^2-, accounting for 15.4% and 14.2%, respectively. The OC concentration was the highest in winter, whereas SO₄^2-concentration was the highest in summer. The average annual OC/EC ratio was up to 2.80, lower in winter and spring, and higher in summer and autumn. Material reconstruction showed that secondary particles and organic matter (OM) were major substances, accounting for 32.34% and 20.44% of PM_2.5 mass, respectively. Coal combustion and vehicle exhaust might be the main contributors to ambient PM_2.5. The highest fractions for OM were at the Wujiashan and Donghu Gaoxin sites, whereas the fraction of secondary particles was higher at each site, suggesting that secondary pollution had obvious regional characteristics in Wuhan. Cluster analysis based on the characteristics of chemical components showed that the eight sites were divided into three clusters:1 Hanyang Yuehu, Haze, Donghu Liyuan, and Huangpi sites, where the main characteristics were that the concentrations of components at each point were low; ② Zhuankou New Area and Qingshan Ganghua, which were characterized by higher nitrogen components; and ③ Donghu Gaoxin and Wujiashan, where not only industrial sources were heavily polluted in Wuhan, but also motor vehicles and dust pollution greatly contributed.