• 关键词：二元羧酸  二次有机气溶胶(SOA)  稳定碳同位素  左旋葡聚糖  液相形成机制

• 基金项目：国家重点研发计划（No.2017YFC0212406；2016YFC0207505）；国家自然科学基金项目（No.41505112；41702373）；山东省自然科学基金项目（No.BS2015HZ002）

• 周瑞文
• 聊城大学环境与规划学院, 聊城 252000

• 孟静静
• 聊城大学环境与规划学院, 聊城 252000

• 王亚晨
• 聊城大学环境与规划学院, 聊城 252000

• 李政
• 聊城大学环境与规划学院, 聊城 252000

• 姚蒸蒸
• 黄山气象管理处, 黄山 245000

• 衣雅男
• 聊城大学环境与规划学院, 聊城 252000

• 刘晓迪
• 聊城大学环境与规划学院, 聊城 252000

• 燕丽
• 环境保护部环境规划院, 北京 100012

• 侯战方
• 聊城大学环境与规划学院, 聊城 252000

• 郭庆春
• 聊城大学环境与规划学院, 聊城 252000

• 摘要：为研究济南市冬季PM_2.5中二元羧酸类二次有机气溶胶（SOA）的来源、液相形成机制及影响因素，于2016年1-2月昼夜共采集46个PM_2.5样品，并对二元羧酸类SOA （包括二元羧酸、酮羧酸与α-二羰基化合物）与左旋葡聚糖的昼夜变化特征进行分析.研究结果表明，二元羧酸、α-二羰基化合物与左旋葡聚糖均呈昼低夜高的变化特征，而酮羧酸的昼夜变化特征与之相反.二元羧酸类SOA的分子组成特征以草酸（C₂）的浓度最高，其次是丁二酸（C₄）和丙二酸（C₃），与受生物质燃烧较显著的二元羧酸类SOA的分子组成是相同的.C₂/总二元羧酸的浓度（TDACs）、甲基乙二醛（mGly）/乙二醛（Gly）、C₂/SO₄^2-比值的昼夜变化特征与稳定碳同位素（δ¹³C）的组成特征均表明济南市冬季夜晚气溶胶的氧化程度比白天深.C₂及其前体物（Gly、mGly）与SO₄^2-、相对湿度（RH）、液相水含量（LWC）与气溶胶的实际酸度（pH_is）的相关性均较强，表明C₂及其前体物是在液相中经酸催化氧化反应产生的.夜晚二元羧酸类化合物的δ¹³C值高于白天，且随着含碳量的升高二元羧酸的δ¹³C值随之降低.C₂的δ¹³C值随气溶胶的老化而偏正，这是由于同位素动力学效应（KIEs）导致的.

• Abstract：To investigate the sources, formation mechanisms and influencing factors of dicarboxylic acids and related secondary organic aerosol (SOA) in PM_2.5 from Jinan City during winter, a total of 46 PM_2.5 samples were collected from January to February of 2017 on a day/night basis, and the diurnal variations of dicarboxylic acids, ketocarboxylic acids, α-dicarbonyls and levoglucosan in PM_2.5 were analyzed. The results showed that the concentrations of dicarboxylic acids, α-dicarbonyls and levoglucosan were higher in nighttime than those in daytime, but ketocarboxylic acids exhibited higher concentration during daytime than that during nighttime. Oxalic acid (C₂) is the most abundant species in the whole sampling period, followed by succinic acid (C₄) and malonic acid (C₃), which is similar to the molecular pattern observed biomass burning plumes. The diurnal variations of the mass ratios of C₂/TDCAs, mGly/Gly, C₂/SO₄^2- and stable carbon isotopic compositions (δ¹³C) of major dicarboxylic acids and related SOA suggested that the nighttime aerosols were more aged than those in daytime. C₂ and the precursors presented strong correlations with SO₄^2-, relative humidity (RH), liquid water content (LWC) and particle in-situ pH (pH_is), indicating that these SOA were mainly originated from the aqueous-phase oxidation driven by acid-catalyzed oxidation. δ¹³C of major dicarboxylic acids and related SOA were higher in nighttime than those in daytime, and the longer-chain dicarboxylic acids were more depleted in ¹³C than the shorter-chain dicarboxylic acids. An enrichment of δ¹³C of C₂ was found during the aging process of aerosol due to the kinetic isotope effects (KIEs).

• Key words：dicarboxylic acids  secondary organic aerosols (SOA)  levoglucosan  stable carbon isotope  aqueous formation mechanism

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