Impact of Pollutant Transport on the Air Quality of Shanghai in 2007

Pollutant transport has a significant impact on the air quality of Shanghai. To quantify this impact, we comprehensively analyze the characteristics and formation mechanisms of air pollution in Shanghai, using a data set covering five selected air quality monitoring sites and a meteorological site. We find air pollution events occur ∼10% of the year. These events are classified into three typical categories, namely the local pollution case (LP), the dust storm case (DS) and the regional transport case (RT), based on temporal variations and spatial distributions of PM10 and gaseous pollutants as well as meteorological factors and backward trajectories. The ratios of SO2/PM10, NO2/PM10 and PM2.5/PM10 are used as indicators of long-range transport of mineral dust, while CO proves to be a good tracer of regional transport of anthropogenic pollutants. In 2007, 64% of all pollution events were RT and the mean PM10 concentration reached 220 μg m-3. 17% of all pollution events were DS and the mean PM10 concentration reached 310 μg m-3. We estimate that transport contribution to PM10 abundance was within the range of 34% to 64% by comparing the anomaly of the background concentration with the urban concentration.