| 长株潭城市群PM2.5中二次无机离子特征及生成机制 |
| 摘要点击 3152 全文点击 860 投稿时间：2022-11-15 修订日期：2023-02-07 |
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| 中文关键词 二次无机离子 污染特征 二次转化 霾污染 长株潭城市群 |
| 英文关键词 secondary inorganic ions pollution feature secondary generation haze pollution Changsha-Zhuzhou-Xiangtan City Group |
| DOI 10.13227/j.hjkx.20231110 |
| 作者 | 单位 | E-mail | | 马杰利 | 湘潭大学环境与资源学院, 湘潭 411105
湖南省环境保护科学研究院, 长沙 410004 | 393133400@qq.com | | 罗达通 | 湖南省环境保护科学研究院, 长沙 410004 | | | 刘欣 | 湘潭大学环境与资源学院, 湘潭 411105
湖南省环境保护科学研究院, 长沙 410004 | | | 王蕾 | 湖南省环境保护科学研究院, 长沙 410004 | | | 王幸 | 湖南省环境保护科学研究院, 长沙 410004 | | | 刘湛 | 湖南省环境保护科学研究院, 长沙 410004 | | | 沈健 | 湘潭大学环境与资源学院, 湘潭 411105 | | | 张俊丰 | 湘潭大学环境与资源学院, 湘潭 411105 | | | 李晟 | 湖南省环境保护科学研究院, 长沙 410004 | 1157627670@qq.com |
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| 中文摘要 |
| 二次无机离子是大气PM2.5的主要组分，其对城市霾污染的驱动作用愈发明显.目前长株潭城市群秋冬季PM2.5污染形势依旧严峻，但该区域的二次转化对冬季霾污染过程以及秋冬季SNA差异特征的影响尚不明晰.2020年11月和2021年1月在长株潭城市群4个典型站点进行PM2.5连续采样，并定量分析了SO42-、NO3-和NH4+等组分.结果显示，秋季和冬季PM2.5中ρ（SO42-）、ρ（NO3-）、ρ（NH4+）平均值（μg·m-3）分别为（5.2±2.5）、（7.9±4.8）、（4.1±2.2）和（7.2±4.2）、（17.1±10.5）、（7.8±5.2）.在冬季霾污染过程中，ρ（SO42-）、ρ（NO3-）和ρ（NH4+）（SNA）的增量约占PM2.5浓度增量的72.7%，其中ρ（NO3-）占41.2%，因此霾污染形成主要由NO3-生成所驱动.在霾污染过程的"污染阶段"，较高的气溶胶含水量（AWC）促使SNA快速二次转化，同时不利气象条件导致污染物的本地累积，在"消散阶段"，硫氧化率（SOR）和氮氧化率（NOR）值仍较高，PM2.5浓度的降低并不是由于SNA的二次转化减弱，而是一次排放的削减以及利好气象条件的形成；长株潭城市群冬季较高的AWC浓度、pH值以及较低的温度是导致ρ（NO3-）/ρ（PM2.5）值、NOR高于秋季的主要原因，同时在高AWC浓度条件下区域NO3-的生成主要以非均相反应为主.而受气溶胶pH值与生成速率影响，H2 O2液相氧化SO2是长株潭城市群秋冬季SO42-的主要生成途径，冬季较高的AWC浓度也使得SOR高于秋季. |
| 英文摘要 |
| Secondary inorganic ions, the main components of atmospheric PM2.5, are a dominant contributor to haze formation. The detailed characteristics and main generation mechanism of secondary inorganic ions in PM2.5 are still unclear in the Changsha-Zhuzhou-Xiangtan City Group, which is suffering from severe haze pollution, particularly in the autumn and winter seasons. For our study, we collected PM2.5 samples in November 2020 and January 2021 from four urban sites in the Changsha-Zhuzhou-Xiangtan City Group. Secondary inorganic components such as SO42-, NO3-, and NH4+ in PM2.5 were quantified. The average values(μg·m-3) of ρ(SO42-), ρ(NO3-), and ρ(NH4+) in autumn and winter were(5.2±2.5) and(7.9±4.8),(4.1±2.2) and(7.2±4.2), and(17.1±10.5) and(7.8±5.2), respectively. During the heavy haze pollution events in winter, the sum of ρ(SO42-), ρ(NO3-), and ρ(NH4+)(SNA) contributed 72.7% to the growth of PM2.5 mass concentration, and ρ(NO3-) accounted for 41.2%. This result suggested that the generation of NO3- was the key factor leading to the formation of winter haze pollution. In the polluted stage, high aerosol water content(AWC) promoted the rapid secondary generation of SNA, whereas adverse meteorological conditions also led to the accumulation of pollutants. The values of sulfur oxidation rate(SOR) and nitrogen oxidation rate(NOR) were still high in the dissipation stage. It indicated that the PM2.5 concentration fell due to the reduction in primary emissions and favorable weather conditions in dissipation, instead of the weakening of secondary generation of SNA. Compared to that in autumn, the higher AWC concentration, pH value, and lower temperature in winter were the main factors for the higher ρ(NO3-)/ρ(PM2.5) and NOR values in the Changsha-Zhuzhou-Xiangtan City Group. At the same time, the heterogeneous reaction was the main generation pathway of NO3-, when the AWC concentration was high in winter. Affected by aerosol pH value and generation rate, the liquid-phase oxidation reactions of H2O2 and SO2 were the main generation pathways of SO42- in autumn and winter in the Changsha-Zhuzhou-Xiangtan City Group. Compared to that in autumn, the higher AWC was more conducive to forming SO42-, which led to higher SOR in winter. |
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