• 关键词：PM_2.5  有机碳和元素碳  二次有机气溶胶  影响因素

• 基金项目：国家重点研发计划（No.2016YFC0202000，2017YFC0213000）；国家自然科学基金（No.21677002，41977179）；大气重污染成因与治理攻关项目（No.DQGG0103）

• 吴兴贺
• 1. 河北工程大学能源与环境工程学院, 邯郸 056038;2. 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871

• 殷耀兵
• 河北工程大学材料科学与工程学院, 邯郸 056038

• 谭瑞
• 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871

• 王甜甜
• 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871

• 许栩楠
• 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871

• 祖可欣
• 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871

• 陈士意
• 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871

• 曾立民
• 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871

• 郭松
• 1. 北京大学环境科学与工程学院, 环境模拟与污染控制国家重点联合实验室, 北京 100871;2. 南京信息工程大学, 江苏省大气环境与装备技术协同创新中心, 南京 210044

• 摘要：为探明二次有机气溶胶（SOA）的污染特征和影响因素，本研究于2018年11月-2019年1月对华北区域点（德州市郊区点）细颗粒物（PM_2.5）的化学组成进行了在线测量，并分析了PM_2.5中有机碳（OC）、元素碳（EC）和水溶性离子组分的污染特征及PM_2.5与气象要素之间的相关性.结果表明，观测期间德州PM_2.5污染严重，平均质量浓度为（115.6±24.6）μg·m^-3；其中，有机碳和元素碳是PM_2.5的主要成分，平均质量浓度分别为（8.2±5.8）μg·m^-3和（2.6±2.2）μg·m^-3，占PM_2.5总质量的7.1%和2.2%；PM_2.5与风速呈负相关，与相对湿度呈正相关，与气温的相关性较差，偏北风对PM_2.5浓度影响较大.同时，本研究利用EC示踪OC/EC比值法对PM_2.5中的二次有机碳（SOC）进行了估算，通过估算得到的SOC结果表明，华北区域点冬季SOC是OC的重要组成部分，平均浓度为（4.0±2.9）μg·m^-3，占OC的45.7%，SOC在白天占比较高（62.7%），早晚由于有局地生物质燃烧影响，SOC占比降低，约占OC的42.7%.本研究还分析了SOC生成的影响因素，分析了德州市冬季O₃、含水量、酸度与SOC的相关性.结果表明，SOC受臭氧浓度影响，但在白天和夜晚表现出不同的相关关系，可能存在不同的生成机制.最后，利用ISORROPIA模型估算了颗粒物的含水量和酸度，发现SOC在高含水量和低含水量下存在不同的关系，高含水量更能促进SOC生成；在高含水量下SOC与H⁺具有显著相关性，但在低含水量下则不相关，表明颗粒物含水量较高、H⁺浓度较高情况下液相酸催化反应可能对SOC具有重要贡献.

• Abstract：To investigate the characteristics and influencing factors of secondary organic aerosol (SOA), chemical composition of fine particulate matter (PM_2.5) was continuously measured at a reginal site of North China Plain, i.e. Dezhou site, from November 2018 to January 2019. Organic carbon (OC), Elemental carbon (EC), and water-soluble ions were measured. The relationship between PM_2.5 and meteorological conditions were further investigated. The results showed that Dezhou suffered severe particle pollution in winter, with an average PM_2.5 mass concentration of (115.6±24.6) μg·m^-3. Organic carbon and elemental carbon were the major components, with an average mass concentration of (8.2±5.8) μg·m^-3 and (2.6±2.2) μg·m^-3, respectively, accounting for 7.1% and 2.2% of PM_2.5. PM_2.5 is negatively correlated with wind speed, but positively correlated with relative humidity, suggesting the influence of wind scavenging, and aqueous-phase formation. Besides, the northerly wind has a greater impact on PM_2.5 concentration. However, temperature has no correlation with the particle concentration. In this study, secondary organic carbon (SOC) was estimated by using EC tracer OC/EC ratio method. SOC was an important component of OC in winter of Dezhou, with an average concentration of SOC was (4.0±2.9) μg·m^-3, accounting for 45.7% of OC. SOC accounted for 62.7% of OC in the daytime. Due to local biomass burning, the proportion of SOC was lower at night, accounting for 42.7% of OC. The influencing factors of SOC formation was investigated in the present work. SOC formation was affected by ozone concentration. The correlations during daytime and night were different, implying different formation mechanisms. The water content and acidity of particles were estimated by ISORROPIA model. It was found that higher water content can promote the SOC formation, and SOC is correlated well with H⁺ when water content was high. However, the correlation is weak when water content was low. Our study suggested that aqueous phase acid catalytic reaction may contribute significantly to SOC formation under high water content.

• Key words：PM_2.5  OC/EC  SOC  influencing factor

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