Elemental Pollution Characteristics And Comprehansive Assessment Of Ambient PM_2.5 In Nanchong City

The paper collected Nanchong PM_2.5 samples during1, 4, 7, 10 months in 2015, and analyzed the concentrations of 11 kinds of elements of Al, Ba, Cd, Cr, Cu, Fe, Mn, Mo, Pb, Sb and Sr. The paper studied the characteristics of PM_2.5 mass concentration, analyzing elements pollution characteristics through Enrichment Factor, Correlation Analysis, Factor Analysis, and used Geo-accumulation Index Analysis, Potential Ecological Risk Assessment, and Health Risk Assessment to evaluate the heavy metal pollution. The conclusions were as follows: The average PM_2.5 concentration was 55.4 μg·m-3, lower than the secondary average mass concentration standard. There were 26 days higher than secondary average mass concentration standard, which counted 21.3%. The PM_2.5 mass concentration and the over standard rate in this study were lower than the monitoring data of Nanchong municipal party committee, but the variation trend was consistent. Compared with cities at home and abroad, Nanchong PM_2.5 concentration were relatively low, but still exceeded the standard, which was needed to be attended. The daily average concentration of Pb element did not exceed the standard quality. The Cd element daily average concentration did not exceed the standard quality, but there were 14 days exceeding the standard concentration, which was 28.6% of the total number, On the whole, inorganic element concentration was higher than in Shanghai and lower than in Wuhan. The heavy mental concentrations in Chengdu, Chongqing, Guangzhou were higher than Nanchong. The whole elemental concentration was similar to Beijing and Tianjin. Compared with foreign cities, the whole concentration of Nanchong was higher than Barcelona, Genoa, Zabrze. The quality concentrations of inorganic elements Pb, Sb, Sr, Mo were the highest during the winter, the Cu, Cd, Ba, Al, Mn, Fe, Cr mass concentrations were the highest in the autumn. Overall, the inorganic element concentrations in spring and summer were low. The results of Enrichment factor, Correlation analysis and Factor analysis showed that the inorganic element Al, Ba, Cr, Mn, Fe, Sr come from soil dust, Pb, Sb, Mo, Cd come from the road traffic emissions, Cu come from coal fuel sources. The Geo-accumulation Index and Potential Ecological Risk Assessment showed that the pollution levels of Cr, Mn were the lowest, the Cu belonged to the secondary pollution, Cd, Sb were strong or very strong polluted. Health Risk indicated that the heavy metals existed non-cancer health risks in children, the HI value reached 5.36, far greater than 1, showing that heavy metals in Nanchong PM_2.5 has became a serious health risk for children. For adults, HI value was 0.674, less than 1, showing that the heavy metals would not do harm for adults, but in winter, the HI value was greater than 1,showing that there existed non-cancer health risks for adults. For Cr and Cd, there did not exist non-carcinogenic health risk to the human body.