汾渭平原秋冬季PM2.5化学组分特征及其来源

汾渭平原是我国空气污染最严重的区域之一，2018年被列为重点区域. 本研究针对汾渭平原11城市开展PM_2.5化学组分连续观测，分析PM_2.5浓度和主要化学组分的时空分布规律，并利用PMF模型解析PM_2.5污染来源. 结果表明:①2018—2019年秋冬季汾渭平原11城市ρ(PM_2.5)平均值为(101.4±65.4)μg/m3，是京津冀及周边地区“2+26”城市的1.1倍. 临汾市ρ(PM_2.5)最高(216.8 μg/m3)，是汾渭平原的2.1倍. ②2018—2019年秋冬季汾渭平原PM_2.5的主要化学组分是有机物、硝酸根离子、地壳物质和硫酸根离子，其中地壳物质占比是京津冀及周边地区的1.6倍. ③受污染物排放、气象条件以及地理位置的影响，汾渭平原PM_2.5中有机物、硝酸根离子、地壳物质、硫酸根离子、铵根离子和氯离子的空间分布具有明显的差异性. ④随着污染的加重，硝酸根离子、硫酸根离子和氯离子在PM_2.5中的占比均逐渐增加，地壳物质、元素碳、微量元素等与一次排放相关的组分占比随污染加重逐渐减少，表明污染期间燃煤源管控仍需进一步加严，而对扬尘源和机动车等污染源的管控起到了良好的效果. ⑤重污染过程期间，相对湿度增加、风速减小是影响PM_2.5浓度上升的客观因素，二次组分以及与燃煤源和生物质燃烧源有关的化学组分的增长是影响PM_2.5浓度上升的重要原因，二次源和燃烧源是PM_2.5的主要来源. 研究显示，汾渭平原秋冬季PM_2.5污染较重，尤其需要关注燃烧源的管控. 

Chemical Composition Characteristics and Source Apportionment of PM2.5 in the Fenwei Plain in Autumn and Winter

The Fenwei Plain was one of the areas with the most serious air pollution issue in China, and was listed as the key air pollution control area in 2018. This study carried out continuous observation of PM_2.5 chemical components in 11 cities in the Fenwei Plain, analyzed the temporal and spatial distribution of PM_2.5 concentration and main chemical components, and used PMF model to analyze the source of PM_2.5 pollution. It showed that the average concentration of PM_2.5 was (101.4±65.4) μg/m3 in the Fenwei Plain in autumn and winter of 2018-2019, which was 1.1 times higher than that in the Beijing-Tianjin-Hebei and its surrounding areas. The average concentration of PM_2.5 in Linfen City was the highest, the concentration value reached 216.8 μg/m3, which was 2.1 times higher than that of the Fenwei Plain. The main chemical components of PM_2.5 in the Fenwei Plain in autumn and winter were organic matter, nitrate, crustal materials and sulfate. And the proportion of the crustal materials was 1.6 times of the Beijing-Tianjin-Hebei and its surrounding areas. Affected by pollutant emissions, meteorological conditions and geographical location, the spatial distribution of organic matter, nitrate, crustal materials, sulfate, ammonium and chloride ions in PM_2.5 in the Fenwei Plain were obviously different. With the aggravation of pollution level, the proportion of nitrate, sulfate and chloride ions in PM_2.5 gradually increased, and the proportion of crustal materials, elemental carbon, trace elements and other components related to primary emissions gradually decreased with the aggravation of pollution. It showed that the control of coal combustion sources still needed to be further tightened during the pollution period, and the control of dust sources, motor vehicles and other pollution sources had achieved good results. In the heavy pollution process, the increase of relative humidity and the decrease of wind speed were the objective factors leading to PM_2.5 concentration increase, and the increase of secondary components and chemical components related to coal combustion sources and biomass combustion sources were the important reasons for the increase in PM_2.5 concentration. Secondary source of pollution and combustion were the main source of PM_2.5 during heavy pollution. The research showed that PM_2.5 pollution in the Fenwei Plain was heavy in autumn and winter, and special attention should be paid to the control of combustion sources and dust sources.