Abstract
Abstract. Concentrations of PM10, PM2.5 and PM1 were monitored at 24 CAWNET (China Atmosphere Watch Network) stations from 2006 to 2014. The highest particulate matter (PM) concentrations were observed at the stations of Xian, Zhengzhou and Gucheng, on the Guanzhong Plain and the Huabei Plain (HBP). The second highest PM concentrations were observed in northeast China, followed by southern China. According to the latest air quality standards of China, 14 stations reached the PM10 standard, and only 7 stations, mainly rural and remote stations, reached the PM2.5 standard. The ratios of PM2.5 to PM10 showed a clear increasing trend from northern to southern China, because of the substantial contribution of coarse mineral aerosol in northern China. The ratios of PM1 to PM2.5 were higher than 80 % at most stations. PM concentrations tended to be highest in winter and lowest in summer at most stations, and mineral dust influenced the results in spring. A decreasing interannual trend was observed on the HBP and in southern China for the period 2006 to 2014, but an increasing trend occurred at some stations in northeast China. Bimodal and unimodal diurnal variation patterns were identified at urban stations. Both emissions and meteorological variations dominate the long-term PM concentration trend, while meteorological factors play a leading role in the short term.
Highlights
Tropospheric aerosols are important because of their strong influence on the climate system through both direct and indirect effects
Based on a data set across 19 Canadian sites, most of the PM2.5 concentrations were found to be below 26 μg m−3, and PM2.5 accounted for 49 % of the measured PM10 (Brook et al, 1997)
Eldred et al (1997) reported that PM2.5 and PM10 particulate concentrations measured at 42 sites of the Interagency Monitoring of Protected Visual Environments (IMPROVE) network over the 1993 seasonal year (March 1993 to February 1994) showed the PM2.5 concentration had a large gradient from west to east in the US, averaging 3 μg m−3 in most of the west compared with 13 μg m−3 in the Appalachian region
Summary
Tropospheric aerosols are important because of their strong influence on the climate system through both direct and indirect effects These include the direct effect of scattering and absorbing radiant energy, and the indirect effect of modifying the microphysical properties of clouds, and their radiative properties and lifetime (Haywood and Boucher, 2000). At the coarse end of the spectrum (PM10), the spatial distribution and interannual variation of concentrations has been comprehensively studied using a data set accumulated from 86 Chinese cites (Qu et al, 2010). The spatial pattern of average PM concentration levels and the relationships among them are reported Their seasonal and interannual variations are presented
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