大同市大气颗粒物浓度与水溶性离子季度分布特征

为研究大同市大气颗粒物质量浓度与水溶性离子组成特征,于2013年2、7、9、12月,分别对大同市及其对照点庞泉沟国家大气背景点进行了PM2.5及PM10的采样,通过超声萃取-IC法测定了样品中的9种水溶性离子,结果表明,大同市大气颗粒物污染1、4季度重于2、3季度,PM2.5季度均值全年均未超标,PM10仅第1季度超标1.4倍,污染状况总体良好,PM2.5与PM10相关系数R为0.75,说明大同市颗粒物污染有较为相近的来源,且不同季节均以粗颗粒物为主;大同市PM2.5中水溶性离子浓度分布为SO2-4、NO-3、NH+4Cl-、Ca2+K+、Na+F-、Mg2+,PM10中Ca2+浓度仅次于SO2-4、NO-3,控制扬尘将有效降低PM10的浓度;PM2.5及PM10中的9种水溶性离子在不同季度的浓度与颗粒物浓度分布规律类似,1、4季度较高,2、3季度较低;由阴阳离子平衡计算结果可知,相关性方程的斜率K为1.045,表明大同市大气颗粒物中阳离子相对亏损,大气细粒子组分偏酸性。NO-3与SO2-4浓度比值均小于1,大同市以硫酸型污染为主,大气中的SO2-4主要来源于人类活动排放。

Characteristics of Mass and Water-Soluble Ionic Compounds of Atmospheric Fine Particles in Four Quarters of Datong

To investigate atmospheric fine particles and water-soluble components pollution in Datong, PM_2.5 and PM₁₀ samples were collected at city sites and National Atmospheric Back ground site of Pang Quangou in four seasons of 2013.The mass concentrations and inorganic water-soluble ions were analyzed. The results show that the mass concentrations and water-soluble ions were quite higher in the first and the fourth seasons. Only PM₁₀ exceeded to the Environmental standards 1.4 times, which indicate that the atmospheric fine particles pollution in Datong is not serious. The correlation coefficient (R) of PM_2.5 and PM₁₀ was 0.75, suggesting that the particulate pollution sources of Datong were similar. The coarse particle pollution is serious in this city.In this city the concentrations of water-soluble ion was NO₃^-, SO₄^2-, NH₄⁺>Cl^-, Ca²⁺>K⁺, Na⁺>F^-, Mg²⁺.The concentrations of Ca²⁺ is less than SO₄^2-, NO₃^- in PM₁₀, so controlling dust is the effective way to reduce the PM₁₀. The ions balance between total cations and total anions showed the Slope of correlation equation was 1.045, it meaned the airborne PM_2.5 at Datong was just a little acid, which was consistent with the results of pH measurement. The ratio of NO₃^-/SO₄^2- is less than 1 and sulfuric is mainly pollution in Datong. The SO₄^2-mainly come from the emissions of human activities.