Atmospheric PM_2.5and PM₁₀ Pollutions And Their Components Characteristics Before And After The Youth Olympic Games And Health Risk Assessment In Nanjing City

PM2.5 and PM10 are the primary pollutants affecting urban ambient air quality.Their serious impacts on ecology,climate and economy have caused many environmental and healthy effects,thus attracting widespread public attention.It has become the urgent problem for the society and government to improve air quality.In the present study,the objectives were to explore the pollution features of atmospheric PM2.5 and PMlo in Nanjing,and analyze the characteristics and harm of heavy mental and water-soluble ions pollution.Therefore,we carried out an experiment to observe the dynamic changes in the concentrations of PM2.5 and PM10,and test the health risk assessment and the water-soluble ions and heavy metal compositions of them,from April,2014 to August,2015.Weight method was adapted to analyze PM2.5 and PM10 concentrations;ICP-OES was adapted to measure the heavy metal content of PM2.5;The principal component analysis was applied to analyze general source of heavy metals of PM2.5 and PM10;The method of health risk assessment was used to evaluate the hazard of the heavy metals in PM2.5 and PM10.The main results are as follows:(1)The distribution characteristics of PM2.5 and PM10 in Nanjing showed obviously seasonal variations.The highest monthly mean value of PM2.5 and PM10 concentrations appeared in winter while the minimum were observed in summer.The ratios of PM2.5 to PM10(PM2.5/PM10)ranged from 0.38 to 0.75,the mean is 0.58,indicating that PM2.5 was the main composition of PM10,the pollution of PM2.5 should not be ignored.(2)Three main water-soluble ions were SO42-,NO3-and NH4+,account for 29.8%,11.2%,8.5%in PM2.5,and 20.6%,8.7%,6.5%in PM10 respectively.In general,the higest values were mainly observed in winter.There were both reduction of SO42-and NO3-observed during the Youth Olympic Games(YOG)and after the implementation of"Jiangsu Province Air Pollution Prevention Act",but NH4+ don't show the same trend,suggesting that SO42-and NO3-were greatly influenced by artificial factors,while NH4+was mainly impacted by the agricultural production and meteorological factors.(3)The PCA analytical results indicated that motor vehicle exhaust and the vent gases of coal burning were the main soures of heavy metals in PM2.5 and PM10.(4)The health risk values of Cd,Cu and Ni in PM2.5 and PM10 via breathing and dermal contact exposure were all within the acceptable ranges,but potential carcinogenic risk was existed for Cr and there was potential non-carcinogenic health risk via breathing for adult males of Mn.Meanwhile,Pb in PMlohad greater non-carcinogenic health risk for children via dernal contact exposures.