| In recent years, atmospheric fine particulate matters (PM2.5) has become theprimary pollutant in urban air, and organic carbon (OC), elemental carbon (EC) asimportant components of PM2.5, have drawn widespread attention. Chinese scientistsstarted to investigate PM2.5and carbonaceous aerosol in the atmosphere relatively latecompared to US and European scientists. Currently, the research of atmosphericparticulate matters from coarse particulates gradually turn to focus on fine particulatesas it is more harmful to human health. The smaller particulate matter size, the morecarbonaceous components. So the research on carbonaceous components also focuseson fine particulates such as PM2.5. Many researchers have investigated the healtheffects, spatial and temporal distribution, and polluted characteristics of carbonaceouscomponents in PM2.5. Because PM2.5is small in size and light in weight, it has along-distance transmission characteristics and pollutants from other regions couldimpact it easily. In this paper, the distribution characteristics of OC and EC inChangchun in2014have been studied by applying Stepwise Cluster Analysis (SCA)and Grid Analysis Method (GAM) to analysis their major sources. Through theanalysis, the main conclusions are as following:(1) The variation ranges of OC and EC concentrations in PM2.5in Changchun were9.08-31.96μg/m3and0.28-14.52μg/m3, with the annual mean17.07μg/m3and6.32μg/m3. Total carbon (TC) accounted for26.61-71.95%(annual mean42.79%) inPM2.5. Compared to other domestic cities, Changchun’s OC annual mean is inmedium level, while EC is relatively high.(2) From the point of view of seasons, the order of OC and EC concentrations fromhigh to low is spring>autumn>winter>summer and spring>autumn>summer>winter,respectively. The seasonal means of OC/EC present a variation ofwinter>summer>spring>autumn. From the point of view of space, OC and ECconcentrations in the north of Changchun is relatively high. There are variations in thespatial distribution of OC and EC concentration in different seasons. There is the mostobvious change in the spatial distribution of OC and EC concentrations in the spring,which the highest OC and EC concentrations were detected in the northern part. It isbecause that sandstorm from north filtered by trees and buildings in Changchun sothat it decreased while moving towards the south. (3) The average mass concentration of second organic carbon (SOC) is5.32g/m3，accounting for35.88%of OC. The seasonal mean of SOC presents a variation asspring>winter>autumn>summer, and the change of SOC/OC is different, which issummer>winter>spring>autumn. It is not difficult to see, SOC is easy to generate insummer. The concentration of SOC is significantly correlated with O3(R2=0.73). Itshows that photochemical reaction is an important way to form SOC, while there maybe other reaction mechanisms at other times.(4) Using SCA, all873648-hour backward trajectories of Changchun in2014wereclustered and8classes of average trajectory were obtained. Areas which the PM2.5haspassed through in its backward trajectories include Russia, Mongolia, Inner Mongolia,Liaoning Province, Heilongjiang Province, Shandong Province, the Bohai Sea andJilin Province, and no pollution source in eastern and southern regions. Theprobability of air mass from Liaoning and Russia are higher, accounting for16.21%and15.66%, respectively.(5) By applying GAM, it is found that short distance transmission of air mass fromthe northeast area of Inner Mongolia, Liaoning Province, Heilongjiang Province andthe long distance transmission from the southeast regions of Chinese bordering Russiahave the largest contribution to PM2.5. |
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