| 大连市PM2.5中水溶性离子污染特征及高酸度成因 |
| 摘要点击 2460 全文点击 508 投稿时间：2023-09-18 修订日期：2023-12-13 |
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| 中文关键词 大连市 PM2.5 水溶性离子（WSI） 来源解析 气溶胶酸度 |
| 英文关键词 Dalian PM2.5 water-soluble ions （WSI） source identification aerosol acidity |
| 作者 | 单位 | E-mail | | 杨萌 | 辽宁省大连生态环境监测中心, 大连 116023 | yangm-kf@126.com | | 刘畅 | 辽宁省大连生态环境监测中心, 大连 116023 | | | 王笑欢 | 辽宁省大连生态环境监测中心, 大连 116023 | | | 刘莲莲 | 辽宁省大连生态环境监测中心, 大连 116023 | | | 张明明 | 辽宁省大连生态环境监测中心, 大连 116023 | | | 曹姗姗 | 辽宁省大连生态环境监测中心, 大连 116023 | | | 阎守政 | 辽宁省大连生态环境监测中心, 大连 116023 | | | 孙泽宇 | 中国科学院烟台海岸带研究所海岸带环境过程与生态修复重点实验室, 山东省海岸带环境过程重点实验室, 烟台 264003
中国科学院大学, 北京 100049 | zysun@yic.ac.cn | | 田崇国 | 中国科学院烟台海岸带研究所海岸带环境过程与生态修复重点实验室, 山东省海岸带环境过程重点实验室, 烟台 264003
中国科学院海洋大科学中心, 青岛 266071 | |
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| 中文摘要 |
| 为更加深入地了解大连市细颗粒物（PM2.5）及其水溶性离子（WSI）的污染状况及影响因素,进行霾、 酸雨等污染事件的精准管控,于2021年6月至2022年5月在大连市进行PM2.5样品的采集,分别采用重量法和离子色谱法测定了PM2.5和WSI的浓度,分析其污染特征和来源,并探讨了春季PM2.5高酸度的成因. 结果表明,采样期间大连市ρ（PM2.5）及其ρ（WSI）年均值分别为（33.24 ±28.87）μg·m-3和（18.66 ±20.52）μg·m-3,二次离子（SNA,即SO42-、 NO3-和NH4+）在WSI中占比最高[（86.2 ±9.3）%]. 受到气象条件和秋末至春初集中采暖期燃煤排放的影响,PM2.5及其WSI季节变化大小为：冬季>春季>秋季>夏季,SNA则为春季最高. 相关性和主成分分析结果表明,PM2.5中的WSI主要来自大气中SO2和NO2的二次转化、 燃烧和扬尘混合源以及沙尘和海盐源. 燃烧源在夏季主要为生物质燃烧,秋冬春则以燃煤为主；秋季到冬季风向的变化带来海盐源向土壤沙尘源的转变,与西北风有关的外来污染输送则导致春季WSI来源较为复杂. ISORROPIA-Ⅱ模型模拟得到NH4NO3是大连市PM2.5中存在最多的固体气溶胶形态,其次是CaSO4和（NH4）2SO4；PM2.5在夏秋冬三季pH值均接近中性,春季则明显呈酸性（2.03 ±3.18）. 春季的高酸度与低温高湿和高SNA浓度带来较高的气溶胶含水量及气-粒转化程度,最终形成贫氨环境. 后向轨迹和PSCF结果表明,春季高酸度PM2.5的外来输送主要来自西北（45.0%）和西南（40.8%）方向,前者主要与城市机动车和港口船舶排放有关,后者则受到相对较强的燃煤和工业源的影响. |
| 英文摘要 |
| To gain a deeper understanding of the pollution status and influencing factors of fine particles （PM2.5） and their water-soluble ions （WSI） in Dalian and to implement precise control of pollution events such as haze and acid rain, PM2.5 samples were collected in Dalian from June 2021 to May 2022. Then, the mass concentrations of PM2.5 and WSI were determined using the weight method and ion chromatography, respectively, and the pollution characteristics and sources were analyzed. Furthermore, the causes of the high acidity of PM2.5 in spring were discussed. The results showed that the annual average mass concentrations of PM2.5 and WSI in Dalian during the sampling period were （33.24 ±28.87） μg·m-3 and （18.66 ±20.52） μg·m-3, respectively, and the secondary ions （SNA, including SO42-, NO3-, and NH4+） accounted for the highest proportion of WSI [（86.2 ±9.3）%]. The order of ion concentration levels from highest to lowest was： NO3->SO42->NH4+>Cl->K+>Ca2+>Na+>Mg2+>F-. Due to the influence of meteorological conditions and coal combustion emissions during the concentrated heating period from late autumn to early spring, the seasonal variation in PM2.5 and WSI was winter>spring>autumn>summer, whereas SNA was the highest in spring and the lowest in summer. The results of correlation and principal component analysis showed that WSI in PM2.5 was mainly from the secondary transformation of atmospheric SO2 and NO2 （contributing to the majority of SNA）, mixed sources of combustion and dust （characterized by K+, Mg2+, Cl-, and F-）, and sources of sand and sea salt （characterized by Na+, Ca2+, and Mg2+）. In summer, the main combustion source was biomass burning, whereas in autumn, winter, and spring, coal combustion emissions were predominant. The change in wind direction from autumn to winter brought by a shift from the source of sea salt to soil dust； additionally, the external pollution transported by northwest winds contributed to the complexity of the sources of WSI in PM2.5 during spring in Dalian. ISORROPIA-II model simulations suggested NH4NO3 as the most present solid aerosol form in PM2.5 in Dalian, followed by CaSO4 and （NH4）2SO4； compared to that in solid aerosols, more SNA existed in liquid aerosols. The annual average pH of PM2.5 in Dalian was 5.65 ±3.00, with pH values close to neutral in summer, autumn, and winter but significantly acidic in spring （2.03 ±3.18）. The high acidity observed in spring was attributed to the combination of low temperature, high humidity, and high SNA concentrations. These conditions resulted in higher aerosol water content and increased gas-to-particle conversion rates, ultimately leading to an ammonia-deficient environment. The backward trajectory and PSCF results indicated that the external transport of high acidity PM2.5 in spring mainly came from the northwest （45.0%） and southwest （40.8%） directions. Mobile source emissions made the most significant contribution to the transportation of pollutants in the former, forming high-pollution source areas in the Beijing-Tianjin-Hebei Region, which may have been mainly related to urban motor vehicle and port vessel emissions； the latter was influenced by relatively strong stationary sources and showed higher SO2 emissions in the southern part of Henan Province and the central part of Jiangsu Province. |
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