| 常州夏冬季PM2.5中无机组分昼夜变化特征与来源解析 |
| 摘要点击 3098 全文点击 899 投稿时间：2017-07-18 修订日期：2017-08-28 |
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| 中文关键词 常州 PM2.5 无机组分 季节性变化 昼夜特征 |
| 英文关键词 Changzhou PM2.5 inorganic components seasonal variation day-night variation |
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| 中文摘要 |
| 为探讨常州大气气溶胶中无机组分的昼夜变化特征，在夏冬两季分别连续采集1个月的PM2.5样品，对比分析了11种水溶性离子和13种重金属元素的昼夜特征和来源.结果表明，夏冬两季PM2.5平均质量浓度白天高于夜间，水溶性离子占比夜间稍高于白天.冬季水溶性离子占PM2.5的比例（44%~45%）高于夏季（31%~36%），而重金属元素呈现相反的季节性特征（冬季白天3.03%，夜间2.29%；夏季白天4.40%，夜间4.51%）.SO42-、NO3-、NH4+是主要的二次离子，占总水溶性离子77%~85%，说明常州市大气污染呈二次污染为主的复合污染特征.夏季强太阳辐射的光化学反应导致白天SO42-占比（49.0%）稍高于夜间（41.1%），而白天高温NH4NO3分解，使NO3-浓度白天（1.98 μg ·m-3）远低于夜间（5.10 μg ·m-3）.NH4+与SO42-、NO3-之间好的线性相关性及预测NH4+与实测NH4+的比值接近1，表明NH4+主要以（NH4）2SO4，NH4NO3和NH4Cl形态存在.离子平衡表明夏季颗粒物呈弱碱性，冬季呈中性.Fe、Al和Zn这3种重金属元素占比最大，Fe和Al元素白天占比明显高于夜间，Zn正好相反.无机组分相关性及主成分分析表明，无机组分都来自二次生成、扬尘和交通等排放源，表现一定的季节性和昼夜变化特征. |
| 英文摘要 |
| To investigate the day-night variation characteristics of inorganic components in atmospheric aerosol, PM2.5 samples were continuously collected for one month in Changzhou during summer and winter. Eleven water-soluble ions (WSⅡs) and 13 metal elements were compared in terms of their day-night character and sources. The results indicated that the day time average PM2.5 mass concentration was higher than the night time, while the percentage of the total WSⅡs in PM2.5 during the night was higher. The total WSⅡs fractions in PM2.5 were higher in winter (44%-45%) compared to summer (31%-36%), with an opposite seasonal character for metal elements (winter day 3.03%, winter night 2.29%, summer day 4.40%, summer night 4.51%). SO42-, NO3-, and NH4+, were the three main secondary ions, comprising 77%-85% of the total WSⅡs, suggesting that air pollution in Changzhou exhibits complex pollution characteristics dominated by secondary processes. The day time SO42-/WSⅡs ratio (49.0%) was slightly higher than that of the night (41.1%) due to the photochemical reaction under stronger solar radiation, while the lower NO3-(1.98 μg·m-3) in the day compared to the night (5.10 μg·m-3) was attributed to the decomposition of NH4NO3 during summer days. A good linear correlation among NH4+, SO42- and NO3-, accompanied by a ratio of predicted NH4+ to measured NH4+ near 1, illustrated that NH4+ ions mainly existed in the form of (NH4)2SO4, NH4NO3, and NH4Cl. It was concluded from the ion balance that PM2.5 was weakly alkaline in summer but neutral in winter. Fe, Al, and Zn were the largest contributors to the total metal elements, with higher concentrations of Fe and Al and lower levels of Zn in the day time. A correlation coefficient analysis and principle component analysis revealed that inorganic components come from sources that include secondary aerosol formation, suspended dust, and vehicle emissions, but there is some seasonal variation and day-night differences. |
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