| Atmospheric fine particles PM2.5 have a significant impact on global climate, regional environmental quality and human health etc. Water-soluble ions are important components of atmospheric fine particulate matter,accounting for the proportion of 40% more or less, which could affect the formation of cloud condensation nuclei(CNN) and then affect the global climate, meanwhile the role of extinction will reduce atmospheric visibility. This paper selected three sampling points of Wuhan such as industrial site,downtown traffic site and botanical garden site and collected samples in four seasons during 2011 and 2012. The variation of PM2.5 mass concentration were analyzed. Ion chromatography was used to analyze water-soluble ions. Characteristics of the pollution, spatial and temporal distribution and influence factors of several aspects of the water-soluble ions were analyzed,and the source apportionment was researched by principal component analysis(PCA).The main conclusions are as follows:(1) During 2011 to 2012 the samples of three sampling points in four seasons in Wuhan PM2.5 daily average concentration varied from 1.96 ?g·m-3~ 1243.08 ?g·m-3and annual average PM2.5 concentration is 144.71 ?g·m-3. PM2.5 have a significant spatial and temporal characteristics,distribution of spring and winter PM2.5 mass concentration changes represent the highest industrial, the lowest downtown traffic, the lowest pollution season is summer. And in autumn,the highest is industrial, botanical garden is lowest; The highest of PM2.5 mass concentration in industrial is spring, downtown traffic is fall, botanical garden is winter. Industrial emissions was an important atmospheric PM2.5 pollution sources of Wuhan.(2) Annual average concentrations of nine water-soluble ions were arranged in descending order: SO42-> NO3-> NH4+ > Ca2+> Cl- > K+> Na+> Mg2+ > F-, total concentration of water-soluble ions ranged 6.24~91.92 ?g·m-3, with an average of 36.39 ?g·m-3. PM2.5 samples of water-soluble ionic components accounted for 25.15% of the total mass. SO42-?NO3-?NH4+ and Ca2+ were the major water-soluble ions,four kinds of ions amounted to 32.16 ?g·m-3,accounting for 88.36% of water-soluble ion concentration.(3) The spatial and temporal distribution of water-soluble ions found: industrial and downtown traffic site were high in winter and low in autumn, while in the industrial site the spring was high and summer was low, the downtown traffic site contrast, botanic Garden winter was high followed by autumn and spring was low. Spring, summer and autumn showed that industrial site was the highest, botanical garden was lowest. Concentration of water-soluble ions in industrial site had a large affect to the whole Wuhan. Climatic conditions varied widely in Wuhan, pollutant sources were more complex, resulting in the concentration of water-soluble ions volatile.(4) Correlation analysis of water-soluble ions showed that correlation of autumn or winter was stronger than spring or summer, and the correlation coefficient showed that winter>autumn>summer>spring. Three secondary ions(SO42-, NO3-, NH4+) was mainly in the form of existence NH4HSO4 and NH4NO3 in spring and winter, summer,(NH4)2SO4 and NH4NO3 in summer and autumn. The annual average of NO3-/ SO42- was 0.84, showed that stationary sources of soluble ions was greater than the contribution of mobile sources. By ion balance calculation, Wuhan four seasons showed a relative loss of anions, the ions were alkaline the whole year.(5) Principal component analysis(PCA) was used to the source apportionment of water-soluble ions. The main pollution sources of industrial site were coal-fired, soil source and industrial emissions. The main pollution sources of downtown traffic site were soil source, secondary source and biomass combustion. The main sources of botanical garden site were industrial emissions of soot, waste incineration and soil sources. |
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