Study of Chemical Composition and Pollution Level of Fine Aerosol in Tianjin City

To investigate the chemical characters of PM2.5,a serial sampling work was made from Aug.to Dec.in 2006 in Tianjin.Concentrations and monthly variation characteristics of water-soluble ions,element carbon(EC),organic carbon(OC) and inorganic elements were determined respectively.The results showed that the average concentration of PM2.5 was 165.90 μg/m3,and OC,SO42-and soil were the main components of PM2.5,accounting for 37.0% of PM2.5,while SO42-,NO3-,NH4+ and Cl-were the dominant water-soluble chemical,accounting for 88.6% of total water soluble ions.The results also showed that the average ratio of OC/EC was 4.21,and secondary organic carbon(SOC) concentration was 13.98 ug/m3,accounting for 34.5% of OC,suggesting that second reaction was more active in winter.Trace elements took less than 10% of the detected elements in concentration,of which Zn and Pb were of high contents,with a concentration of 623.8 and 302.3 ng/m3,accounting for 3.6% and 1.8% of all the elements,which showed that coal burning and engine exhaust may be the main contributor.