Comparison of Ozone and PM2.5 Concentrations over Urban,Suburban, and Background Sites in China |
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| Authors: | Lan GAO Xu YUE Xiaoyan MENG Li DU Yadong LEI Chenguang TIAN Liang QIU |
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| Abstract: | Surface ozone (O3) and fine particulate matter (PM2.5) are dominant air pollutants in China. Concentrations of these pollutants can show significant differences between urban and nonurban areas. However, such contrast has never been explored on the country level. This study investigates the spatiotemporal characteristics of urban-to-suburban and urban-to-background difference for O3 (ΔO3]) and PM2.5 (ΔPM2.5]) concentrations in China using monitoring data from 1171 urban, 110 suburban, and 15 background sites built by the China National Environmental Monitoring Center (CNEMC). On the annual mean basis, the urban-to-suburban ΔO3] is ?3.7 ppbv in Beijing–Tianjin–Hebei, 1.0 ppbv in the Yangtze River Delta, ?3.5 ppbv in the Pearl River Delta, and ?3.8 ppbv in the Sichuan Basin. On the contrary, the urban-to-suburban ΔPM2.5] is 15.8, ?0.3, 3.5 and 2.4 μg m?3 in those areas, respectively. The urban-to-suburban contrast is more significant in winter for both ΔO3] and ΔPM2.5]. In eastern China, urban-to-background differences are also moderate during summer, with ?5.1 to 6.8 ppbv for ΔO3] and ?0.1 to 22.5 μg m?3 for ΔPM2.5]. However, such contrasts are much larger in winter, with ?22.2 to 5.5 ppbv for ΔO3] and 3.1 to 82.3 μg m?3 for ΔPM2.5]. Since the urban region accounts for only 2% of the whole country’s area, the urban-dominant air quality data from the CNEMC network may overestimate winter PM2.5] but underestimate winter O3] over the vast domain of China. The study suggests that the CNEMC monitoring data should be used with caution for evaluating chemical models and assessing ecosystem health, which require more data outside urban areas. |
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| Keywords: | ozone PM2 5 urban suburban background |
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