| PM2.5 samples were collected at five sites in BTH (Beijing Tianjin and Hebei) area (four urban sites of Beijing, Tianjin, Shijiazhuang, Chengde, and one site of Shangdianzi background station) from 2009 to 2010. The inorganic water-soluble ions were analyzed and spatio-temporal characteristics of ions were concluded. The concentrations of PM2.5 were quite high, with annual average more than 100μg/m3 in Beijing, Tianjin and Shijiazhuang. The annual average concentrations of secondary ions (SO2-4, NO-3, NH+4) were 22-75 μg/m3 at five sites, and higher in the spring and summer. In BTH, SO2-4 concentrations were much higher than NO-3 in the summer,and Mg2+ and Ca2+ were higher in the spring. Mg2+ and Ca2+ were much higher in Tianjin and Shijiazhuang, reflecting more crust materials pollution. The characteristics of PM2.5 and water-soluble ions for Beijing in this paper were very different from the similar studies before 2004, showing more stable PM2.5 concentrations in four seasons, higher secondary ions in summer, and higher NO-3/SO2-4 than before. The results of Shangdianzi background station (SDZ) also showed that the aerosol pollution of SDZ was largely influenced by Beijing urban area. |
