| 基于高分辨率MARGA分析成都市PM2.5中水溶性离子污染特征 |
| 摘要点击 1295 全文点击 614 投稿时间：2020-03-04 修订日期：2020-04-01 |
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| 中文关键词 水溶性离子 二次离子 PM2.5 气象参数 成都市 |
| 英文关键词 water-soluble ions secondary ions PM2.5 meteorological parameters Chengdu |
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| 中文摘要 |
| 利用高分辨率MARGA对2019年成都市PM2.5中水溶性离子展开连续监测，结合气象参数分析水溶性离子污染特征.结果表明，MARGA监测的8种水溶性离子质量浓度与PM2.5变化趋势一致，水溶性离子年均浓度为（23.1±13.6）μg ·m-3，在PM2.5中占比为48.6%，表明水溶性离子为PM2.5重要组分.各离子质量浓度大小顺序依次为：NO3-、SO42-、NH4+、Cl-、Ca2+、K+、Mg2+和Na+，其中二次离子（NO3-、SO42-和NH4+）年均质量浓度为（20.2±2.7）μg ·m-3，在水溶性离子占比为87.2%.水溶性离子质量浓度季节变化趋势为：冬季 > 春季 ≈ 秋季 > 夏季，逐月变化呈"U"型，1月和12月浓度最高，6~8月浓度最低.无论有无降雨，能见度均随水溶性离子浓度的增加呈幂指数递减规律，且SNA为首要影响因素.降小雨（日累计降雨量<10 mm）对水溶性离子无清除作用，中雨及以上时清除作用显著.SNA在0.01水平上显著相关（两两之间相关系数均大于0.7），表明二次离子生成机制及在大气中演变过程具有较高的相似性.硫氧化率（SOR）和氮氧化率（NOR）年均值分别为0.42和0.12，与温度和O3均呈负相关性，与湿度均呈正相关性，表明SO42-来源主要为液相非均相氧化反应，NO3-来源主要为夜间非均相氧化反应.阳离子和阴离子电荷比（CE/AE）年均值为1.2，二次离子中和率（NR）年均值为1.1，表明气溶胶整体呈弱碱性.成都市大气环境处于富氨状态，二次离子存在形式主要为（NH4）2 SO4和NH4NO3. |
| 英文摘要 |
| Water-soluble ions in PM2.5 were serially on-line monitored using the MARGA sampling and measurement system in Chengdu in 2019. Pollution characteristics of water-soluble ions were analyzed using the meteorological monitoring data. The results show that variations in the concentrations of eight water-soluble ions were consistent with the variations in PM2.5 in Chengdu. The annual average mass concentration of the total water-soluble ions was (20.2±12.7) μg ·m-3, accounting for 48.6% of the PM2.5 mass, which indicates that water-soluble ions were the major components of PM2.5. The mass concentrations of all the ions were in the order of NO3- > SO42- > NH4+ > Cl- > Ca2+ > K+ > Mg2+ > Na+. The annual average mass concentration of secondary ions was (20.2±12.7) μg ·m-3, accounting for 87.2% of total water-soluble ions. The concentrations of total water-soluble ions in different seasons were in the order of winter > spring ≈ autumn > summer. Monthly variations in total water-soluble ion concentrations followed a U-shaped curve; mass concentrations were the highest in January and December and lowest from June to August. Monthly variations in the concentrations of NO3-, SO42-, NH4+, Cl-, Na+, and K+ were consistent with the total water-soluble ion concentrations, while the concentrations of Ca2+ and Mg2+ were the highest in June. Visibility declined with the increase in the concentration of water-soluble ions, especially secondary water-soluble ions regardless of the rainfall. Light rain (accumulated rainfall in 24 h <10 mm) had no scavenging effect on water-soluble ions, while moderate and heavy rainfall had a significant effect. There was a significant positive correlation between NO3-, SO42-, and NH4+ (all the correlation coefficients were over 0.7), indicating that the mechanisms of evolution of secondary water-soluble ions in the atmosphere are highly similar to each other. The annual mean values of SOR and NOR were 0.42 and 0.12, respectively, which were negatively correlated with temperature and O3 and positively correlated with humidity, indicating that the main source of SO42- was heterogeneous oxidation reactions in the liquid phase and the main source of NO3- was heterogeneous oxidation reactions at night. The annual mean values of CE/AE and NR were 1.2 and 1.1, respectively, indicating that most aerosols in the study area were relatively alkaline. The atmospheric environment of Chengdu is rich in ammonia; thus, (NH4)2 SO4 and NH4NO3 were the main forms of secondary ions. |
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