Pollution characteristics of PM_(2.5) and secondary components in the winter in Tianjin

Secondary inorganic water-soluble ions(NH+4,NO-3 and SO2-4),organic carbon(OC)and elemental carbon(EC) were studied using particulate sample data in Tianjin during November to December of 2011.The secondary organic carbon(SOC) mass concentrations were estimated with the minimum ratio method of OC/EC.The results showed that the mean mass concentrations of PM2.5 were respectively 166.9 μg · m-3 in urban area and 180.0 μg · m-3 in Wuqing.SO2-4,NO-3 and OC were the main components,accounting for about 19.4%,16.7% and 15.4% of the total PM2.5 in urban area,19.2%,15.5% and 20.4% of the total PM2.5 in Wuqing,respectively.The secondary components(SNA+SOM) accounted for 47%(urban) and 46%(Wuqing) of the PM2.5 mass concentration,and higher concentration in fog and haze day.Adverse weather conditions such as high humidity and static light wind primarily contributed to the continuing increase of PM2.5 and the secondary component concentration.