运城秋冬季大气细粒子化学组成特征及来源解析

Chemical Composition and Source Analysis of PM_(2.5)in Yuncheng,Shanxi Province in Autumn and Winter

为研究运城市秋冬季细颗粒物(PM_(2.5))的化学组成特征和污染来源贡献,于2018年10月15日至2019年3月15日利用四通道小流量颗粒物采样器在运城市对大气PM_(2.5)样品进行了连续采集.主要对水溶性离子、元素碳、有机碳和金属元素等化学成分进行了分析,并结合颗粒物化学质量重构法和正定矩阵因子分解模型(PMF)深入探讨.结果表明,采样期间PM_(2.5)质量浓度范围为29.37~370.11μg·m^(-3),期间有101 d高于我国《环境空气质量标准》(GB 3095-2012)中的二级标准,超标率为70.63%,说明秋冬季运城市大气污染较为严重.按照空气质量指数(air quality index,AQI)将采集样品分类为清洁,轻-中度污染和重度-严重污染,水溶性离子、有机碳、元素碳和金属元素分别占总PM_(2.5)浓度的40%、19%、5%、7%(清洁天),46%、18%、4%、5%(轻-中度污染)和46%、21%、4%、4%(重度-严重污染).二次离子NO^(-)_(3)、SO^(2-)_4和NH^(+)_4是水溶性离子主要成分,分别占总离子浓度的81%(清洁天)、87%(轻-中度污染)和87%(重度-严重污染).采样期间OC/EC的值分别为3.78(清洁天)、4.02(轻度-中度污染)和5.37(重度-严重污染).随着污染程度的加剧,大气中二次有机气溶胶的污染情况也越发严重.此外,随着大气污染程度的加深,Fe和Cr元素浓度逐渐下降,而其余金属元素的浓度总体呈上升趋势.化学质量重构结果表明在运城市的PM_(2.5)中,二次无机盐、海盐、重金属、矿物尘、建筑尘、有机物和元素碳的质量分数分别为40%、1%、1%、5%、1%、32%和5%,且随着污染的加剧,二次无机盐的占比有所升高,矿物尘的占比降低.PMF分析结果表明,二次相关源、燃煤源、交通源与生物质燃烧及二次有机物是运城市灰霾暴发的主要原因.

In order to reveal the chemical composition characteristics and pollution sources of fine particulate matter(PM_(2.5))in autumn and winter in Yuncheng,PM_(2.5)samples were continuously collected using a four-channel small-flow particulate sampler from October 15,2018 to March 15,2019.The study prediminantly analyzed the chemical components of water-soluble ions,elemental carbon,organic carbon,and metal elements.Additionally,the chemical mass reconstruction method of particulate matter and the positive matrix factorization model(PMF)were combined for an in-depth discussion.During the sample period,the PM_(2.5)mass concentrations range was 29.37-370.11μg·m^(-3),and 101 days during the sampling period exhibited concentrations that were higher than the secondary standard in China's Ambient Air Quality Standards(GB 3095-2012),with an exceeding rate of 70.63%.These results indicate that the air pollution in Yuncheng in autumn and winter is serious.According to the air quality index(AQI),the collected samples are classified as clean,light-moderate pollution,and heavy-severe pollution.Water-soluble ions,OC,EC and metal elements account for 40%,19%,5%,and 7%on clean days,46%,18%,4%,and 5%on days with light-moderate pollution,and 46%,21%,4%,and 4%on days with heavy-severe pollution,respectively.Secondary ions NO^(-)_(3),SO^(2-)_(4),and NH^(+)_(4)are the primary components of water-soluble ions,accounting for 81%(clean days),87%(light-moderate pollution),and 87%(heavy-severe pollution)of the total ion concentration,respectively.The OC/EC ratios during the sampling period were 3.78(clean days),4.02(light-moderate pollution),and 5.37(heavy-severe pollution).With the intensification of pollution,the pollution of secondary organic aerosols in the atmosphere becomes increasingly serious.In addition,as the air pollution increased,the concentration of Fe and Cr elements gradually decreased,while the concentration of other metal elements showed an overall upward trend.The results of the chemical mass reconstruction demonstrate that among the different pollution levels of atmospheric PM_(2.5)in Yuncheng,the mass percentages of secondary inorganic salt,sea salt,heavy metals,mineral dust,construction dust,organic matter,and elemental carbon were 36%,2%,2%,8%,1%,33%,and 5%(clean days),41%,1%,1%,5%,0.01%,31%,and 5%(light-moderate pollution),and 41%,1%,1%,4%,0.004%,34%,and 4%(heavy-severe pollution).The proportion of secondary inorganic ions increased and mineral dust decreased with the deterioration of air quality.The PMF analysis results suggest that secondary related sources,coal combustion sources,vehicle exhaust sources,biomass burning,and secondary organic matter are the predominant sources of PM_(2.5)during serious air pollution in Yuncheng.