Chemical Characteristics and Sources of Water-Soluble Organic Nitrogen Species in PM2.5 in Nanjing, China
Chemical Characteristics and Sources of Water-Soluble Organic Nitrogen Species in PM2.5 in Nanjing, China
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DOI：
10.3390/atmos12050574
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发表时间：
2021-04
期刊：
影响因子：
2.9
通讯作者：
Yue Liu;Haiwei Li;Shijie Cui;Dongyang Nie;Yanfang Chen;X. Ge
中科院分区：
文献类型：
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作者：
Yue Liu;Haiwei Li;Shijie Cui;Dongyang Nie;Yanfang Chen;X. Ge
水溶性有机氮（WSON）是PM2.5的重要组成部分，对空气质量、气候和人体健康有重要影响。本文在南京北方采集了一年（2017年6月-2018年5月）的大气PM2. 5现场样品。对PM2.5主要组分和WSON进行了化学表征，并通过Aerodyne烟尘颗粒气溶胶质谱仪（SP-AMS）以及正矩阵因子分解（PMF）的测量进一步研究了WSON的组成和来源。无机离子主要由铵、硫酸盐和硝酸盐组成，占PM2.5质量的58.7%，其次是有机物（OM）（22.6%）和元素碳（EC）（2.1%）。水溶性有机质占有机质总量的65.1%，其时间变化与次生有机质的时间变化密切相关，而水不溶性有机质的时间序列与原生有机质的时间序列密切相关。WSON平均浓度为2.15 μg/m3，冬季最高，夏季最低。WSON与PM2.5组分的相关分析也表明WSON主要来源于二次污染源。SP-AMS显示WSON质谱由CxHyNp+（91.2%）和CxHyOzNp+（8.8%）组成，表明胺和其他含氧ON化合物占主导地位。PMF分析解决了WSOM和WSON的两个主要来源（交通，生物质燃烧）和两个次要来源（氧化程度较低和氧化程度较高的因素），次要来源占主导地位的WSOM和WSON。在冬季，氧化程度较高的ON因子贡献很大，而氧化程度较低的ON因子在夏季的贡献很大，这表明冬季的水相过程和夏季的光化学氧化作用对WSON的形成可能起着重要作用。
Water-soluble organic nitrogen (WSON) is an important component of PM2.5 which may affect air quality, climate and human health. Herein, one-year field samples of atmospheric PM2.5 (June 2017–May 2018) were collected in northern Nanjing. Chemical characterization of PM2.5 major components as well as WSON were conducted, and WSON composition and sources were further investigated via measurements by a Aerodyne soot particle aerosol mass spectrometer (SP-AMS) as well as positive matrix factorization (PMF). Inorganic ions, mainly consisting of ammonium, sulfate, and nitrate, were found to dominate PM2.5 mass (58.7%), followed by organic matter (OM) (22.6%), and elemental carbon (EC) (2.1%). Water-soluble OM dominated OM (65.1%), and its temporal variation was closely correlated with that of secondary organic matter, while time series of water-insoluble OM concentrations correlated tightly with that of primary organic matter. Average WSON concentration was 2.15 μg/m3, which was highest in winter and lowest in summer. Correlation analysis of WSON with PM2.5 components also indicated that WSON was mainly from secondary sources. SP-AMS revealed that WSON mass spectrum was composed of CxHyNp+ (91.2%) and CxHyOzNp+ (8.8%), indicating dominance of amines and other oxygenated ON compounds. PMF analysis resolved two primary sources (traffic, biomass burning) and two secondary sources (less-oxidized and more-oxidized factors) of WSOM and WSON, and the secondary source dominated both WSOM and WSON. Contribution of the more-oxidized ON factor was very high in winter, and the less-oxidized factor was significant in summer, indicating a likely important role of aqueous-phase processing in winter as well as photochemical oxidation in summer to WSON.