Characteristics, Formation Mechanisms and Potential Transport Pathways of PM2.5 at a Rural Background Site in Chongqing, Southwest China
Characteristics, Formation Mechanisms and Potential Transport Pathways of PM2.5 at a Rural Background Site in Chongqing, Southwest China
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重庆农村背景点PM2.5特征、形成机制及潜在传输途径
DOI：
10.4209/aaqr.2019.01.0010
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发表时间：
2019-09-01
影响因子：
4
通讯作者：
Zhai, Chongzhi
中科院分区：
文献类型：
--
作者：
Peng, Chao;Tian, Mi;Zhai, Chongzhi
从2014年10月至2015年7月，在重庆的一个农村本底站（缙云）连续四个季节收集每日PM2.5样品。分析了主要水溶性无机离子（WSIIs）、有机碳（OC）和元素碳（EC）的化学特征、迁移途径和潜在源区。PM2.5年平均浓度为56.2 ± 31.0 µg m-3，其中二次无机气溶胶（SNA）和碳质气溶胶分别占41.0%和29.4%。SO 42-的浓度和贡献在夏季高于秋季和春季，这可能是由于SO2向SO 42-的二次转化。此外，重庆市区（渝北）的交通运输在该季节对SO 42-的升高起了重要作用。虽然PM2.5在冬季污染事件的积累也是由于水相反应，基于全年，NO3-形成可能主要是由均匀的气相反应驱动。此外，气溶胶环境是铵丰富的，和NH 4+的形成促进了在较低的温度下的NO3-的生产。碳质组分，其中包括81.0-84.6%的OC，表现出较高的浓度在冬季比其他季节;总OC的50.0-77.2%，反过来，由初级有机碳（POC）的贡献。潜在源贡献函数（PSCF）分析表明，该站点主要受到区域污染的影响，来自重庆西南和北方地区。
Daily PM2.5 samples were collected at a rural background station (JinYun) located in Chongqing across four consecutive seasons from October 2014 to July 2015. The major water-soluble inorganic ions (WSIIs), organic carbon (OC) and elemental carbon (EC) were analyzed, and their chemical characteristics, transport pathways and potential source regions were investigated. The average annual PM2.5 concentration was 56.2 ± 31.0 µg m–3, of which secondary inorganic aerosol (SNA) and carbonaceous aerosols composed 41.0% and 29.4%, respectively. Higher concentrations of and contributions from SO42–, which were likely caused by the secondary transformation of SO2 into SO42–, were observed in summer than in autumn and spring. Additionally, transportation from the urban area of Chongqing (Yubei) played an important role in elevating the SO42– during this season. Although the accumulation of PM2.5 during pollution episodes in winter was also due to aqueous-phase reactions, based on the entire year, NO3– formation may have been primarily driven by homogeneous gas-phase reactions. Furthermore, the aerosol environment was ammonium-rich, and NH4+ formation promoted the production of NO3– at lower temperatures. The carbonaceous component, which consisted of 81.0–84.6% OC, exhibited higher concentrations in winter than in the other seasons; 50.0–77.2% of the total OC, in turn, was contributed by primary organic carbon (POC). Potential source contribution function (PSCF) analysis suggests that the site was mainly affected by regional pollution originating in the southwestern and northern areas of Chongqing.