| To investigate the regional and source characteristics of the aerosol in Changzhou,fine particulate matter(PM2.5)samples were simultaneously collected at an urban site and an industrial site from October to December?autumn and winter?,2016.A total of 139 daily PM2.5samples were analyzed for various compositions,including carbonaceous species?elemental carbon?EC?,organic carbon?OC?,and water-soluble organic carbon?WSOC??,water-soluble inorganic ions?WSIIs?,inorganic elements,water-soluble organic nitrogen?WSON?,humic-like substances?HULIS?,polycyclic aromatic hydrocarbons?PAHs?and organic acids.Mass levels and source of chemical components in PM2.5 were discussed.Positive matrix factorization?PMF?model was employed to identify presumptive sources to the sampling sites.Moreover,we compared the chemical charcteristics of PM2.5 at two sites in order to elucidate reginal difference of PM2.5 pollution.The main conclusions were as follows:1.The air quality of urban was dominated by good and light pollution,accounting for 37% and 29%of the total days,respectively,and the heavy pollution days accounted for 5%.However,the air quality in industrial areas was dominated by light pollution,moderate pollution and heavy pollution,accounting for 30%,30%and 20%of the total days,respectively,and only 3%of excellent days.The daily average concentrations of PM2.5 were ?78.26±43.39?and?112.92±64.45??g·m?3 for urban and industrial site,respectively.The The PM2.5 concentrations exceeded 75?g·m?3?target-2 standard of the national ambient air quality standardof China?GB3095-2012??on more than 49%sampling days at urban site,and on more than 68%of sampling days at industrial site,indicating Changzhou suffered serious air pollution.2.The main water-soluble inorganic ions were SO42?,NO3?and NH4+?abbreviated as SNA?, accounting for 77.2%of the total WSIIs in the urban area.The change trend of Fe,Zn and Pb level was obvious among inorganic elements,and the three accounted for a relatively high proportion,with percentage of 31.5%,28.3%and 17.9%in the total inorganic elements, respectively;The ratio of OC/EC was basically greater than 2,and the overall winter OC/EC ratio was higher than that in autumn.It was confirmed that the source of OC was very complicated,and it was affected by secondary sources such as photochemical reaction and liquid phase reaction.Both NH4+?N and NO3??N were the main form of water-soluble nitrogen,whereas the contribution of WSON was relatively small,accounting for 14.0%of WSTN.The value of WSOC/OC was between 17.9%and 98.8%,with an average of 55.7%.It could be seen that WSOC was the main component of OC.3.SNA accounted for 83.3%of total WSIIs in industrial area,which was higher than that of in urban area.The content of Fe,Al and Zn was higher in industrial areas,with proportion of 48.3%,29.4%and 11.9%in total inorganic elements,respectively.The mass level of inorganic elements in winter was larger than that in autumn with more obvious temporal change.The OC/EC ratio was basically greater than 2,indicating that the OC may come from a secondary source.The WSON accounted for 16.0%of WSTN,slightly higher than the urban area.At the same time,the concentrations of HULIS-C and HULIS were determined in WSOA.The results showed that the daily average concentration of HULIS was?4.44±2.06??g·m?3,accounting for 4.5%of PM2.5,and the average value of HULIS-C/WSOC was 48.7%.The total concentration of PAHs was 235.29 ng·m?3,of which the highest concentration was benzofluoranthene?BbF+BjF+BkF?,accounting for 47.1%, followed by chrysene?11.3%?.The average daily mass concentration of hexadecanoic acid was the largest in the organic acids,and the octadecanoic acid was the second.The most abundant species of dicarboxylic acids was sebacic acid(205.05 ng·m?3),while other several types were low and the difference was small.4.Source apportionment results derived from PMF model indicate that the major contributors of PM2.5 in industrial site were secondary source?39.8%?,coal combustion?19.7%?,crust matter?13.9%?,mixed source of motor vehicles and ships?13.9%?and industrial emission ?8%?,while main sources in urban site were:secondary aerosol?63.7%?,coal combustion?19.7%?,motor vehicle exhausts?13.8%?and ship emissions?2.9%?.In summary,this study provided a detailed analysis of the chemical composition and source of atmospheric PM2.5 in urban and industrial areas,in order to provide detailed data for understanding the pollution status of fine particulate matter in Changzhou.At the same time,it also provided an important scientific support for the formulation of coordinated emission reduction policy in the Yangtze River Delta. |
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