苏州市大气PM_(2.5)中水溶性无机离子的源解析及其气象因子分析

为了探明PM_(2.5)中水溶性无机离子的来源和气象因子对其浓度变化的影响,利用2012年2、5、8和11月苏州市PM_(2.5)中水溶性无机离子浓度和本站气象观测数据,分析了苏州市水溶性无机离子的时间变化特征,解析了当地PM_(2.5)中水溶性无机离子的主要来源,探讨了气象因素对离子组分的影响。结果表明:(1)苏州市PM_(2.5)中水溶性无机离子年均浓度大小依次为:SO_4~(2-)NO_3~-NH_4~+Na~+Cl~-K~+Ca~(2+)Mg~(2+)F~-;SO_4~(2-)、NH_4~+和NO_3~-为PM_(2.5)中最重要的3种水溶性无机离子物种,其总和占PM_(2.5)总质量浓度的50.9%。各离子的季节浓度特征均为冬季最高、夏季最低。(2)通过运用主成分分析法对苏州市PM_(2.5)中水溶性无机离子进行来源分类解析,发现第一类为二次污染源和生物质燃烧,其贡献率为32.84;第二类为道路扬尘及工业排放,其贡献率为19.99%;第三类为海盐污染,其贡献率为18.43%。(3)通过水溶性无机离子与气象条件的相关性分析发现,风向、风速和温度与水溶性无机离子浓度的相关性较显著,这三者是颗粒物浓度变化的主要影响因子。(4)利用HYSPLIT后向轨迹模式对外来污染物进入苏州市的轨迹进行聚类分析后发现:因受季风气候影响,苏州市外来污染物的输入路径存在明显的季节性变化特征,其中夏半年输送主径源自海上,冬半年主径源自内陆。

Source resolution of water-soluble inorganic ions in PM2.5 in Suzhou city and impact of meteorological factors on their concentration change

In order to ascertain the sources of water-soluble inorganic ions in PM_2.5 and the impact of the meteorological factors on their concentration changes, in this paper, the data of water-soluble inorganic ions in PM_2.5 and the observed meteorological data at Suzhou Station during February, May, August and November in 2012 were analyzed. The temporal variation characteristics of water-soluble inorganic ions were revealed, their main sources were resolved and the influence of meteorological factors on these water-soluble inorganic ions concentration was investigated. The results were shown as follows:(1) The annual average concentrations of the water-soluble inorganic ions in PM_2.5 was in the order of SO₄^2- > NO₃^- > NH₄⁺ > Na⁺ > Mg²⁺ > K⁺ > F^- > Cl^- > Ca²⁺ and SO₄^2-, NH₄⁺ and NO₃^- were the most important ones, which contributes 50.9% of PM_2.5. The seasonal concentrations of all ions showed the highest concentration in winter and the lowest in summer. (2) The principal component analysis method was adopted to analyze the source apportionment of water-soluble inorganic ions in PM_2.5 at Suzhou Station. The analysis results displayed that the secondary pollution sources and the biomass combustion was the first category whose contribution rate was 32.84%, the road dust and the industrial emissions was the second category whose contribution rate was 19.99% and the sea salt pollution was the third category whose contribution rate was 18.43%. (3) The correlation between the water-soluble inorganic ions and the meteorological factors was analyzed. It was found that the most significant correlations existed between the concentrations of water-soluble ions and the wind direction, wind speed and temperature and the three meteorological factors were the most influential factors on the concentration of the particulate matters. (4) After the cluster analysis of the backward trajectory from HYSPLIT4.0 model, it is found that the enter paths of external pollutions in Suzhou had an obvious seasonal variation characteristics and they could be influenced by the monsoon climate. The main enter paths in the summer half year came from the sea and they came from the inland in the winter half year.