摘要
本文基于西安市2021年9月1日至11月14日利用Sunset Model 4/OCEC(RT-4)Lab有机碳元素碳在线分析仪实时采集PM_(2.5)中的OC和EC,分析了PM_(2.5)、OC和EC的质量浓度特征,结合湿清除率探究降水强度与PM_(2.5)的关系,利用OC/EC比值、OC与EC相关性以及二次有机碳(SOC)估算探究OC和EC的排放来源.结果表明,西安市秋季PM_(2.5)、OC和EC平均浓度分别为(29.6±28.1)μg·m^(−3)、(6.1±4.3)μg·m^(−3)、(1.2±0.9)μg·m^(−3);OC和EC浓度质量变化都呈夜间高于白天和中度污染>轻度污染>清洁天的特征.污染物清除率受到降水强度和污染物浓度的综合影响.降水强度小但PM_(2.5)及其碳质气溶胶浓度较高的情况下,降水的正清除作用较弱.西安市OC/EC比值的平均值为3.15,说明大气中存在着较为明显的二次有机碳污染;不同污染程度下OC,EC的来源复杂程度为清洁天>中度污染天气>轻度污染天,从排放源来看,不同污染程度下均是燃烧直接排放大于非燃烧排放.SOC的平均值为4.3μg·m^(−3),对OC的贡献率为71.7%,SOC与NO_(2)、SO_(2)的相关性显著,说明研究期间西安有机碳的二次污染转化较为明显且主要来源于机动车尾气,生物质燃烧和工业排放.
In this paper,Sunset Model 4/OCEC(RT-4)Lab Organic Carbon online analyzer was used to determine OC and EC in PM_(2.5)from September 1 to November 14,2021 in Xi'an in real time.The mass concentration characteristics of PM_(2.5),OC and EC were analyzed,and the relationship between precipitation intensity and PM_(2.5)was explored based on the wet clearance rate.The emission sources of OC and EC were estimated by the ratio of OC/EC,correlation between OC and EC,and secondary organic carbon(SOC).The results showed that:(1)the average concentrations of PM_(2.5),OC and EC in Xi'an in autumn were(29.6±28.1)μg·m^(−3),(6.1±4.3)μg·m^(−3)and(1.2±0.9)μg·m^(−3),respectively.OC and EC concentrations at night were significantly higher than those at day,and presented a trend of moderate pollution>light pollution>clean days.(2)The pollutant removal rate is influenced by precipitation intensity and pollutant concentration.When the precipitation intensity is small but PM_(2.5)and its carbon aerosol concentration is high,or when precipitation intensity is large but PM_(2.5)concentration is low,the positive clearance effect of precipitation is weak.(3)The average value of OC/EC ratio in Xi’an is 3.15,indicating the obvious secondary organic carbon pollution in the atmosphere.The trend of source complexity of OC and EC was clean>moderate pollution>light pollution days.Direct combustion emissions were greater than non-combustion emissions under different pollution levels.(4)The mean value of SOC was 4.3μg·m^(−3),and the contribution rate to OC was 71.7%.The correlation between SOC and NO_(2)and SO_(2)was significant,indicating that the secondary pollution transformation of organic carbon in Xi'an was obvious and mainly came from vehicle exhaust,biomass burning and industrial emissions during the study period.
作者
杨震
曹磊
高飞
王敏
李春燕
吕婧
李毅辉
蒙瑞丽
牛天田
周变红
YANG Zhen;CAO Lei;GAO Fei;WANG Min;LI Chunyan;LYU Jing;LI Yihui;MENG Ruili;NIU Tiantian;ZHOU Bianhong(Shaanxi Environmental Monitoring Center Station,Shaanxi Key Lab for Environmental Monitoring and Forewarning of Trace Pollutants,Xi’an,710054,China;Shaanxi Environmental Monitoring Technical Service and Consultation Center,Xi’an,710043,China;Shaanxi Provincial Key Laboratory of Disaster Monitoring and Mechanism Simulation,School of Geography and Environment,Baoji University of Arts and Sciences,Baoji,721013,China)
出处
《环境化学》
CAS
CSCD
北大核心
2023年第10期3461-3472,共12页
Environmental Chemistry
基金
国家大气重污染成因与治理攻关项目(DQGG-05-36)
陕西省自然科学基础研究项目(2019JM-120)
中国科学院气溶胶化学物理重点实验室项目(KLACP2004)
宝鸡文理学院重点项目(ZK2018049)资助.
