hemical characteristics of particulate matter in the post-"coal substitution" policy atmospheric environment of coal
combustion cities and their surrounding areas
NIU Hongya SHI Lijie REN Xiulong JIN Niu WANG Shuo LI Shujiao HU Sihao WU
Chunmiao LU Yanqi FAN Jingsen SUN Yuzhuang
School of Earth Science and Engineering, Hebei University of Engineering
In October 2020, the policy of "coal-to-gas" and "coal-to-electricity" was completed in Handan, a coal-burning industrial city. In order to investigate the chemical characteristics of fine particulate matter (PM2.5) after the "coal substitution" policy, the PM2.5 samples were collected in the winter of Handan city during four pollution periods from 2018 to 2020 and one pollution period in Wei and Jize counties in 2020 to analyze the water-soluble ions and carbonaceous aerosols. In Handan city, the PM2.5 concentration in the winter decreased by 40.8% in 2020, compared with the initial stage of the implementation of the "coal substitution" policy in 2015. It indicated that the implementation of the "coal substitution" policy effectively improved the air quality. During the four pollution periods, the PM2.5 was alkaline with the average mass concentrations were (153.9±97.7), (164.5±78.7), (137.3±72.9), and (161.8±84.3)μg·m-3, respectively. The average mass concentration of PM2.5 in Wei and Jize counties were (123.5±47.3) and (124.5±53.4)μg·m-3, respectively. Analysis of water-soluble ions showed that the content of SNA (NH4+, NO3-, and SO42-) was the highest, accounting for 85.3%-90.0% of the total concentration of water-soluble ions. Compared with the winter of 2016 in Handan city, the concentration of Cl-, as a tracer of coal combustion, decreased by 48.0% after the "coal substitution" policy, explaining the good results of the "coal substitution" policy. The ratio of NO3- to SO42- mass concentration showed that the contribution of mobile sources (vehicle exhaust) was higher than that of stationary sources (coal combustion). Carbon aerosol analysis showed that the proportion of total carbon (TC) in PM2.5 decreased by 54.2%. In all survey regions, organic carbon (OC) to elemental carbon (EC) ratio was greater than 2, demonstrating the existence of secondary organic carbon (SOC) pollution. The results of correlation analysis and principal component analysis showed that the main sources of carbon aerosols in Handan city gradually changed from coal combustion and vehicle exhaust to biomass combustion during the implementation of the "coal substitution" policy. According to the potential source analysis, the main potential source areas of Handan city, Wei, and Jize counties were central Shanxi, northwest Shandong, and north Henan.
使用离子色谱仪对样品中的水溶性离子（阳离子：Na+、K+、Mg2+、NH4+、Ca2+；阴离子：Cl-、NO3-、SO42-）进行分析。使用美国沙漠研究所研制的热/光碳分析仪（DRI model 2001A）对PM2.5中碳质气溶胶进行分析。采样期间的气象因子（气温、相对湿度）通过慧聚大气网（http://airwise.hjhj-e.com/）获取，2015-2020年PM2.5通过真气网（http://www.aqistudy.cn）获取。
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