| The pollution of urban atmospheric fine particles has become one of the major public health problems in China.Polycyclic aromatic hydrocarbons（PAHs）,as one of the most important toxic organic compounds in the atmospheric environment,are easily adsorbed on PM2.5with smaller particle size,which seriously endangers human health.Jiangsu Province is located in the core area of the Yangtze River Delta,with dense population and relatively serious pollution of atmospheric fine particles.Because of different geographical location,economic development,meteorological factors and other conditions in southern and northern Jiangsu,the pollution characteristics of atmospheric fine particles and PAHs in atmospheric fine particles in different cities are also different.Therefore,the following studies were carried out:（1）comparative analysis of PM2.5concentration in different seasons in five cities of southern and northern Jiangsu;（2）analysis on the temporal and spatial distribution characteristics of PAHs in PM2.5;（3）the distribution characteristics of PAHs with different ring-number in PM2.5from five cities of southern and northern Jiangsu in different seasons were explored;（4）the pollution source of PAHs in PM2.5from five cities of southern and northern Jiangsu was analyzed preliminarily;（5）the health risk assessment of PAHs in PM2.5from five cities of southern and northern Jiangsu in different seasons was carried out.ObjectivesTo understand the pollution characteristics and differences of PAHs in atmospheric fine particles and atmospheric fine particles in southern and Northern Jiangsu,and further explore the source differences and health risks of PAHs in the two regions,so as to provide the basis for the local government to formulate the atmospheric pollution prevention and control measures.MethodsIn this study,atmospheric PM2.5samples were collected from five cities（South-A,South-B,North-A,North-B,North-C）in southern and Northern Jiangsu,and PM2.5data of each sampling point were collected at the same time.During the whole sampling period,PM2.5samples were collected from December 2017 to August 2019 for 21 months.The PAHs were extracted by ultrasonic extraction method with high extraction efficiency,and PAHs were quantitatively analyzed by gas chromatograph-mass spectrometer（GC/MS/MS）.The pollution characteristics of PAHs in PM2.5and PM2.5in different seasons in southern and northern Jiangsu were compared.The spatial and temporal distribution characteristics of PAHs and the distribution characteristics of PAHs with different ring-number were emphatically analyzed.In addition,the source analysis and health risk assessment of PAHs in PM2.5from five cities were carried out.Results1.Concentration levels of PM2.5in five cities of Jiangsu provinceFrom the perspective of area distribution,the PM2.5pollution level of the three cities in northern Jiangsu is higher than that of the two cities in southern Jiangsu.Compared with the second-level limit of 24-hour average concentration of Environmental Air Quality Standard（gb3095-2012）,North-B has the highest over-standard rate and South-A has the lowest.From the perspective of seasonal distribution,PM2.5concentration showed obvious seasonal variation,which was high in winter and low in summer.The monthly average concentration of PM2.5was the highest in January,and the lowest in July and August.The seasonal variation of PAHs concentration in five cities of Jiangsu province was greater in winter than in summer,and higher in northern Jiangsu than in southern Jiangsu.2.Temporal and spatial changes of PAHs in PM2.5in five cities of Jiangsu provinceFrom the perspective of regional distribution,the annual average value ofΣPAHs in PM2.5from the five cities in 2018 from big to small was as follows:North-A（13.83ng/m3）,North-C（13.19ng/m3）,North-B（10.76ng/m3）,South-A（5.94ng/m3）and South-B（4.52ng/m3）.Generally speaking,the pollution of PAHs in northern Jiangsu was higher than that in southern Jiangsu.In spring 2019,the average PAHs in PM2.5from the five cities showed similar phenomenon,but not obvious in summer.From the perspective of seasonal distribution,PAHs in PM2.5from five cities of Jiangsu showed seasonal change characteristics,namely the highest in winter,the lowest in summer.3.The component spectral characteristics of PAHs in PM2.5in five cities of Jiangsu provinceAmong the 16 PAHs monomers in South-A and South-B,Bb F,Bghi P and Icd P have a significant advantage,which indicates that South-A and South-B are relatively more affected by vehicle exhaust pollution.However,Pyr,Flt and Ba A have obvious advantages in North-C,which indicates that North-C is greatly affected by coal sources.North-A and North-B are affected by both.4.Distribution characteristics of PAHs in PM2.5in five cities of Jiangsu provinceIn the five cities of 2018,except North-C,the PAHs in the other four cities in the whole year are mainly 5 rings and 6 rings.The proportion of PAHs in the winter ring4 rings is slightly higher than that in the other three seasons.Four seasons of North-A in northern Jiangsu show the characteristics of rich 4 rings.5.Source analysis of PAHs in PM2.5in five cities of Jiangsu provinceThe PAHs from five cities of Jiangsu mainly resulted from combustion sources.The sources of PAHs in South-A were mainly diesel vehicle exhaust,coal and biomass combustion;those in South-B were mainly diesel vehicle exhaust and oil combustion;those in North-A were diesel vehicle exhaust,coal and biomass combustion;those in North-B were diesel vehicle exhaust,coal and biomass combustion;those in North-C were gasoline vehicle exhaust,coal and biomass combustion.In addition,except North-B,the sources of PAHs in the other four cities also show some seasonal characteristics,that is,there are different degrees of coal and biomass burning pollution in winter and spring,and oil burning sources in summer and autumn.6.Health risk assessment of PAHs in PM2.5in five cities of Jiangsu province（1）The TEQ of five cities was high in winter and low in summer.From the perspective of regional distribution,the TEQ of five cities in the whole year from big to small was as follows:North-B（3.26ng/m3）>North-A（3.11ng/m3）> South-A（1.41ng/m3）>North-C（0.68ng/m3）>South-B（0.62ng/m3）.（2）In 2018,the average daily exposure level of PAHs of five cities in the whole year from big to small was as follows:North-B(9.99×10-6mg/（kg·d）)>North-A(7.52×10-6mg/（kg·d）)>South-A(3.42×10-6mg/（kg·d）)>North-C(1.93×10-6mg/（kg·d）)>South-B(1.60×10-6mg/（kg·d）).（3）In 2018,the life-long carcinogenic excess risk of PAHs exposure in atmospheric PM2.5to adult was the highest in South-B,which reached 3.10×10-5,2.33×10-5in North-A,1.06×10-5in South-A,5.99×10-6in North-C and 4.95×10-6in South-B.The life-long carcinogenic excess risk in five cities was more than 1×10-6,which indicates that there is a certain potential risk of carcinogenesis.（4）In 2018,the life expectancy loss caused by PAHs exposure to adult in five cities from high to low was as follows:North-B（192.52min）,North-A（144.91min）,South-A（65.78min）,North-C（37.24min）and South-B（30.75min）.Conclusion（1）In Jiangsu Province,the pollution of PM2.5and its element PAHs in the three cities in Northern part is higher than that in the two cities in Southern part.In addition,the pollution of PM2.5and its element PAHs in the five cities changes with the seasons,that is,the pollution reaches its peak in winter and its lowest point in summer.The PAHs in these five cities mainly comes from coal and vehicle exhaust.（2）In 2018,PAHs pollution in the five cities of Jiangsu Province,especially North-A and North-B,posed a certain threat to the health of adult residents within their jurisdiction,which should be paid enough attention to. |
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