【摘要】 为更好地研究太原市冬季大气细颗粒物(PM_2.5)中硫酸盐(SO₄^2-)的污染特征及形成机制，于2020年1月采用在线设备对小时分辨率的PM_2.5及其化学组分（水溶性离子、金属元素）、气态污染物进行观测，分析了不同污染水平下SO₄^2-变化特征，评估了不同形成机制对硫酸盐形成的贡献.结果表明，观测期间太原市ρ(PM_2.5)平均值为（108.7±72.1）μg·m^-3,SO₄^2-、NO₃^-和NH₄⁺在PM_2.5中的占比分别为18.0%±7.9%、16.8%±4.9%和13.1%±3.5%.清洁天、污染天和严重污染天ρ(SO₄^2-)分别为（9.2±5.3）、（17.9±9.2）和（46.3±17.7）μg·m^-3，污染天（0.33）和严重污染天（0.51）硫氧化率(SOR,n(SO₄^2-)/(n(SO₄^2-)+n（SO₂）))明显高于清洁天（0.26）.SOR与RH呈显著正相关（r=0.65,p<0.05），与O_x（O_x=O₃+NO₂）相关性较弱（r=0.10,p<0.05），表明SO₄^2-主要来源于液相和非均相反应.观测期间pH范围为4.0～4.7,pH影响的敏感性分析显示Mn表面催化和H₂O₂途径主导硫酸盐的形成.污染案例分析表明硫酸盐产生速率范围为1.5～7.1μg·m^-3·h^-1，数值计算结果显示Mn表面催化和H₂O₂途径对SO₄^2-产生的平均贡献分别为37.7%和36.0%.更多还原

【Abstract】 In order to better study the pollution characteristics and formation mechanism of sulfate (SO₄^2-) in atmospheric fine particulate matter(PM_2.5) in winter of Taiyuan,hourly PM_2.5 and its chemical components （water-soluble ions,metal elements） and gaseous pollutants were monitored by online equipment during January 2020.The characteristics of SO₄^2-under different pollution levels were analyzed and the contribution of different formation mechanisms to sulfate formation was evaluated.The results showed that the average concentration of PM_2.5 was （108.7±72.1）μg·m^-3 during the observation period in Taiyuan,and the proportions of SO₄^2-,NO₃^-and NH₄⁺in PM_2.5 were 18.0%±7.9%,16.8%±4.9%and 13.1%±3.5%,respectively.The mean mass concentrations of SO₄^2-were （9.2±5.3）,（17.9±9.2） and （46.3±17.7）μg·m^-3 during clean,polluted and heavily polluted days,respectively.SOR (n(SO₄^2-)/(n(SO₄^2-)+n（SO₂）)) were significantly higher during polluted days （0.33） and heavily polluted days （0.51） than clean days （0.26）.SOR was significantly positively correlated with relative humidity （RH）（r=0.65,p<0.05）,weakly correlated with O_x （O_x=O₃+NO₂）（r=0.10,p<0.05）,indicating that the formation of SO₄^2-was mainly originated from aqueous-phase and heterogeneous reaction.The pH range was 4.0～4.7 during the observation period,and the sensitivity analysis of pH effect showed that Mn surface catalysis and H₂O₂ pathway dominated the formation of sulfate.The results of the pollution case analysis show that the sulfate production rate ranges from 1.5μg·m^-3·h^-1 to 7.1μg·m^-3·h^-1.The numerical calculations show that the average contributions of Mn-surface catalysis and H₂O₂ pathway to SO₄^2-production were 37.7%and 36.0%,respectively.更多还原