Characterizing spatial distribution and temporal variation of PM10 and PM2.5 mass concentrations in an urban area of Southwest China

To investigate the temporal and spatial behavior of particulate matter (PM10 and PM2.5), daily data of PM10 and PM2.5 mass concentrations were collected from five air-quality monitoring stations in Chengdu from March 2013 to February 2014. In this period, the daily average concentrations of PM10 and PM2.5 were 156.6 and 99.5 mu g/m(3), respectively, which exceeded both the Chinese ambient air-quality standards for PM and the guidelines of the World Health Organization (WHO). Higher mass concentrations of both PM10 and PM2.5 were observed in winter and spring, indicating that meteorological parameters play an important role. Although PM mass concentrations were evidently lower than reported in previous studies, the average PM2.5/PM10 ratio in this study was higher, indicating that fine particulate (PM2.5) pollution has become more serious. Weekly variations of PM concentrations were analyzed to estimate the impact of traffic restriction policies. The results show that the highest concentrations of particles were observed on Mondays and the lowest on Thursdays. Weekend effects were also obvious, which were mainly attributed to human activities.