菏泽市秋冬季PM2.5水溶性离子化学特征分析

为深入研究菏泽市秋冬季PM_2.5中水溶性离子污染特征，于2017年10月15日-2018年1月31日对菏泽市3个监测点同步进行PM_2.5的采集和分析，分析探讨了不同污染程度下ρ（PM_2.5）及水溶性离子化学特征.结果表明:①菏泽市秋冬季PM_2.5呈区域污染特征.②整个观测期间，ρ（PM_2.5）范围为26.72~284.10 μg/m3，平均值为103.27 μg/m3，其中水溶性离子对ρ（PM_2.5）贡献率较大，为44.65%~49.87%；SNA（NO₃-、NH₄+、SO₄2-的统称）的占比较高，SNA占总水溶性离子质量浓度的86.88%，说明二次气溶胶为菏泽市大气PM_2.5中的重要组成部分.③SNA三角图解和水溶性离子相关性结果表明，采样期间大气中NO₃-、SO₄2-可能以NH₄NO₃、（NH₄）₂SO₄形式存在；ρ（Cl-）与ρ（K+）相关性较高（清洁天和污染天的相关系数分别为0.79和0.81），由此推测Cl-与K+具有同源性，二者主要源于生物质燃烧.④重度及以上污染天的SOR（硫氧化率）和NOR（氮氧化率）分别为0.54和0.37，分别是清洁天的2.08和2.06倍；轻/中污染天的SOR和NOR分别为0.37和0.29，分别是清洁天的1.42和1.61倍.随着污染程度的加重，SO₂和NO₂向SO₄2-和NO₃-的二次转化增强.重污染日SOR、NOR和相对湿度均大于清洁天和轻/中度污染天，而温度则未表现出相似的变化趋势，说明非均相反应是菏泽市秋冬季SO₄2-和NO₃-形成的重要原因.研究显示，菏泽市污染呈区域性污染特征，二次气溶胶是菏泽市大气PM_2.5的重要组成部分，污染天ρ（NO₃-）、ρ（SO₄2-）、ρ（NH₄+）均与相对湿度呈显著正相关（P < 0.05），均与温度呈负相关，表明在污染天高湿低温对SO₂、NO₂转化为SO₄2-、NO₃-有推动作用. 

Chemical Characteristics of Water-Soluble Ions of PM2.5 in Autumn and Winter in Heze City

In order to study the characteristics of water-soluble ions in PM_2.5 in autumn and winter in Heze City, PM_2.5 samples were collected simultaneously at 3 monitoring sites from October 15th, 2017 to January 31st, 2018. The chemical characteristics of water-soluble ions in PM_2.5 were analyzed at different pollution levels. The results showed that:(1) PM_2.5 shows regional pollution characteristics in autumn and winter in Heze City. (2) ρ(PM_2.5) was 26.72-284.10 μg/m3, with an average value of 103.27 μg/m3. The contribution rate of water-soluble ions to (PM_2.5) was 44.65%-49.87%; Secondary inorganic ions (NO₃-, NH₄+ and SO₄2-) have a large proportion of water-soluble ions, accounting for 86.88%. The results show that secondary inorganic aerosols are an important part of PM_2.5 in Heze City. (3) NO₃- and SO₄2- in the atmosphere may exist in the form of NH₄NO₃ and (NH₄)₂SO₄ during sampling period. The correlation between Cl- and K+ was relatively high (r is about 0.79 and 0.81 on clean days and polluted days, respectively), indicating that Cl- and K+ has same sources, which was mainly derived from biomass combustion. (4) sulful oxidation rate (SOR) and nitrogen oxidation rate (NOR) were 0.54 and 0.37 on heavy-polluted days, respectively, which were 2.08 and 2.06 times than that on clean days. The SOR and NOR of light/moderate-polluted days were 0.37 and 0.29, respectively, which were 1.42 and 1.61 times than that on clean days. The results showed that the secondary transformation of SO₂ and NO₂ to SO₄2- and NO₃- was enhanced with the increase of pollution level. The values of SOR, NOR and relative humidity on heavy pollution days are larger than clean days and light/moderate pollution days, while temperature show no similar change trend, indicating that heterogeneous reactions are an important reason for the formation of SO₄2- and NO₃- in autumn and winter in Heze City. The research shows that there is regional pollution in Heze City, secondary aerosols are an important part of atmospheric PM_2.5 in Heze City. NO₃-, SO₄2- and NH₄+ on polluted days have significant positive correlation with relative humidity (P < 0.05) and shows negative correlation with temperature, indicating that high humidity and low temperature on polluted days may promote the conversion of SO₂ and NO₂ to SO₄2- and NO₃-.