Ambient levels and temporal variations of PM 2.5 and PM 10 at a residential site in the mega-city, Nanjing, in the western Yangtze River Delta, China.

The deteriorating air quality in eastern China including the Yangtze River Delta is attracting growing public concern. In this study, we measured the ambient PM10and fine PM2.5in the mega-city, Nanjing at four different times. The 24-h average PM2.5and PM10mass concentrations were 0.033–0.234 and 0.042–0.328 mg/m3, respectively. The daily PM10and PM2.5concentrations were 2.9 (2.7–3.2, at 95% confidence interval) and 4.2 (3.8–4.6) times the WHO air quality guidelines of 0.025 mg/m3for PM2.5and 0.050 mg/m3for PM10, respectively, which indicated serious air pollution in the city. There was no obvious weekend effect. The highest PM10pollution occurred in the wintertime, with higher PM2.5loadings in the winter and summer. PM2.5was correlated significantly with PM10and the average mass fraction of PM2.5in PM10was about 72.5%. This fraction varied during different sampling periods, with the lowest PM2.5fraction in the spring but minor differences among the other three seasons. [ABSTRACT FROM AUTHOR]