Source, long‐range transport, and characteristics of a heavy dust pollution event in Shanghai

Abstract

Daily particulate matter with particles less than 2.5 μm in aerodynamic diameter (PM2.5) and total suspended particulates (TSP) were analyzed for chemical composition and daily PM10, SO2, and NO2 were monitored by automatic monitoring systems on the seven sites over China along the pathway of the long‐range transport of the dust from 20 March to 19 April 2007. The highest recorded dust and daily Air Pollution Index topped 500 for the first time since 2002, when the routine continuous monitoring of PM10 was initiated in Shanghai. The daily 24 h average PM10 concentration of 648 μg m−3 was observed on 2 April 2007. The ratios of SO2/PM10, NO2/PM10, and PM2.5/PM10 were 0.066, 0.077, and 15.5% on 2 April 2007, which were significantly different from the nondust day and could be used as the index to judge the occurrence of dust in Shanghai. On the peak dusty day, the ratios of crustal matter rose to 70% and 64% of the total mass of PM2.5 and TSP, respectively, while the ratios were 13% and 37% on nondust days. The ratio of Ca/Al in the dust aerosol in Shanghai was much closer to that in Duolun and Yulin near Mongolia Gobi rather than that in Tazhong of Taklimakan desert, indicating that the dust was transported from Mongolia Gobi instead of Taklimakan desert in Xinjiang province. The compositions of sea salt aerosol in PM2.5 and TSP, combined with back trajectories, indicated that the dust passed through the East China Seas before reaching Shanghai, which is one of the typical dust pathways that lead to heavily polluted days in Shanghai due to dust transport. The anthropogenic sources along the pathway also partially contributed to the PM pollution in Shanghai during this dust event.