山西省四城市冬季PM_(2.5)中碳质组分特征及来源分析

CHARACTERISTICS AND SOURCES ANALYSIS OF CARBONACEOUS COMPONENTS IN PM_(2.5) IN WINTER IN FOUR CITIES OF SHANXI PROVINCE

为研究山西省太原、阳泉、长治和晋城冬季PM_(2.5)中碳质组分的污染特征和来源,于2017-11-15—12-31同步采集了冬季PM_(2.5)样品,采用热/光分析法分析了样品中有机碳(OC)和元素碳(EC)组分含量,使用最小相关系数法估算了二次有机碳(SOC)浓度,并利用相关分析及正定矩阵因子分析法(PMF)研究了各城市PM_(2.5)中碳质组分的来源。结果表明:采样期间各城市OC、EC的平均浓度分别为(13.5±5.7),(8.0±4.4)μg/m^(3),均呈阳泉((17.3±4.5),(13.6±3.0)μg/m^(3))>太原((16.5±7.0),(7.8±4.2)μg/m^(3))>长治((12.8±4.0),(7.7±2.8)μg/m^(3))>晋城((8.3±2.9),(2.9±1.3)μg/m^(3))的空间分布特点。各城市OC、EC与气态污染物SO2、NO2和CO均显著相关,表明燃煤源和机动车尾气对碳质组分的影响较大。OC和SOC与相对湿度均呈显著正相关,各城市SOC在OC的占比排序为太原(48%)>长治(45%)>晋城(36%)>阳泉(34%),与相对湿度一致,说明各城市冬季SOC的形成可能主要来自液相反应。PMF解析结果显示:各城市冬季PM_(2.5)中碳质组分主要来源于燃煤源(24.2%~30.4%)、汽油车尾气(21.0%~30.9%)、柴油车尾气(16.1%~24.3%)和扬尘源(17.2%~20.5%),其中燃煤源对长治冬季PM_(2.5)中碳质组分的贡献(30.4%)高于其他3个城市,汽油车尾气对太原的贡献(30.9%)高于其他城市,而柴油车尾气(24.3%)和扬尘(20.5%)对阳泉的贡献均高于其他城市。

Taiyuan, Yangquan, Changzhi, and Jincheng are four cities in Shanxi province in the Beijing-Tianjin-Hebei and its surrounding areas. To study the characteristics and sources of the carbonaceous components in PM_(2.5) in winter, PM_(2.5) samples were collected simultaneously from November 15 to December 31, 2017, and then the organic carbon(OC) and elemental carbon(EC) component contents of the samples were analyzed following the thermal/optical reflection protocol. The concentration of secondary organic carbon(SOC) was estimated using the minimum phase relation number method(MRS), and the source of carbonaceous components in PM_(2.5) was conducted using correlation analysis and positive matrix factorization(PMF). The average concentrations of OC and EC were(13.5±5.7) μg/m^(3) and(8.0±4.4) μg/m^(3) for each city during the sampling period, showing the spatial distribution order of Yangquan((17.3±4.5),(13.6±3.0) μg/m^(3))>Taiyuan((16.5±7.0),(7.8±4.2) μg/m^(3))> Changzhi((12.8±4.0),(7.7±2.8) μg/m^(3)) >Jincheng((8.3±2.9),(2.9±1.3) μg/m^(3)). OC and EC were significantly correlated with gaseous pollutants SO2, NO2 and CO in each city, indicating that coal-combustion and motor vehicle exhaust had a greater influence on the carbonaceous components. Both OC and SOC were significantly and positively correlated with relative humidity, and the ranking of SOC/OC was Taiyuan(48%)>Changzhi(45%)>Jincheng(36%)>Yangquan(34%), which was consistent with relative humidity in each city, indicating that the formation of SOC in winter in each city might mainly come from liquid phase reactions. The results of PMF analysis showed that carbonaceous components in PM_(2.5) in winter in each city mainly originated from coal-combustion sources(24.2%~30.4%), gasoline vehicle exhaust(21.0%~30.9%), diesel vehicle exhaust(16.1%~24.3%), and dust sources(17.2%~20.5%). The contribution of coal-combustion to carbonaceous components in PM_(2.5) in winter was higher in Changzhi(30.4%) than in the other three cities, gasoline vehicle exhaust was higher in Taiyuan(30.9%) than in the other cities, while diesel vehicle exhaust(24.3%) and dust sources(20.5%) were both higher in Yangquan than in the other cities.