珠江三角洲大气夜间非均相化学反应对二次气溶胶和臭氧的影响  

Effects of nighttime heterogeneous reactions on the formation of secondary aerosols and ozone in the Pearl River Delta

作　　者：牛英博 黄晓锋 王海潮 王少霞 林晓玉 陈瑶 朱波 朱乔 何凌燕 Yingbo Niu;Xiaofeng Huang;Haichao Wang;Shaoxia Wang;Xiaoyu Lin;Yao Chen;Bo Zhu;Qiao Zhu;Lingyan He(Laboratory of Atmospheric Observation Supersite,School of Environment and Energy,Peking University Shenzhen Graduate School,Shenzhen 518055,China;School of Atmospheric Sciences,Sun Yat-sen University,Guangzhou 510275,China;Chinese Society for Environmental Sciences,Beijing 100082,China)

机构地区：[1]北京大学深圳研究生院环境与能源学院大气观测超级站实验室,深圳518055 [2]中山大学大气科学学院,广州510275 [3]中国环境科学学会,北京100082

出　　处：《科学通报》2022年第18期2060-2068,共9页Chinese Science Bulletin

基　　金：国家重点研发计划(2018YFC0213901);深圳市科技计划项目(GXWD20201231165807007-20200808165742001)资助。

摘　　要：近年来,我国在PM_(2.5)治理方面取得了显著成效,而O_(3)污染问题日益突出.观测结果表明,珠江三角洲光化学反应活跃季PM_(2.5)与O_(3)呈现明显的正相关,但对两者之间耦合关系认识不清使得其协同控制具有很大难度.迄今为止,大部分研究主要关注日间光化学机制,而对夜间大气化学过程的认识明显不足.最新研究表明,夜间五氧化二氮(N_(2)O_(5))非均相反应是PM_(2.5)和O_(3)生成的重要潜在机制,不仅对二次硝酸盐生成具有重要贡献,而且其非均相反应产物硝酰氯(ClNO_(2))在次日清晨的光解对促进大气氧化性也有重要影响.本研究于2018年10月在臭氧污染较严重季节对深圳城市大气中N_(2)O_(5)和ClNO_(2)进行了在线测量,基于气相和颗粒相污染物变化对N_(2)O_(5)的非均相反应进行量化计算与活性评估.观测结果表明,夜间N_(2)O_(5)和ClNO_(2)的最高浓度可分别达到1524与477 pptv(5 min平均,1 pptv=10^(-3) mm^(3)/m^(3)),并受到前体物来源和成分的影响而呈现不同的污染特征.夜间通过N_(2)O_(5)生成的硝酸盐在污染时段可达到硝酸盐总量的24%~60%;清晨ClNO_(2)光解产生的Cl自由基对烷烃的最大去除效率可达OH自由基的2~3倍,Cl自由基氧化反应在上午时段可有效增加RO_(2)自由基产量,并通过HO_(x)自由基循环而促进O_(3)和二次气溶胶生成.研究结果揭示,珠江三角洲沿海地区大气中活跃的夜间非均相反应是PM_(2.5)和O_(3)耦合生成的重要潜在机制,亟须深入研究以便为PM_(2.5)和O_(3)协同防治提供科学依据.Fine particulate matter(PM_(2.5))and ozone(O_(3))are currently the most concerning air pollutants.Long-term exposure to PM_(2.5) and O_(3) can induce cardiovascular diseases,presbyopia,and preterm birth.Acute exposure to PM_(2.5) and O_(3) can also result in hypertension and decreased heart rate variability.In recent years,PM_(2.5) pollution abatement in China has achieved remarkable results,but O_(3) pollution issues have emerged.In the troposphere,O_(3) and PM_(2.5) have a close association,i.e.,O_(3) can oxidize gaseous precursors to form sulfate,nitrate,ammonium and secondary organic aerosols in PM_(2.5),and PM_(2.5) affects the generation and removal of O_(3) by providing surfaces for heterogeneous reactions.Recent studies show that PM_(2.5) and O_(3) have a significant positive correlation in the photochemically active season in the Pearl River Delta(PRD)region.However,it is still difficult to achieve cooperative control for PM_(2.5) and O_(3) due to our limited knowledge of their coupling relationship.To date,most studies have focused on the photochemical mechanism in the daytime,and our understanding of the chemical processes at night is insufficient.As an important reactive intermediate,N_(2)O_(5) mainly accumulates through the nocturnal reaction of NO_(2) and O_(3) and is removed by heterogeneous reactions to produce HNO_(3).These processes directly affect ozone production and particulate matter formation.In addition to losing NO_(x),the heterogeneous reaction of N_(2)O_(5) would lead to particulate nitrate formation and photolabile species(i.e.,ClNO_(2))release.ClNO_(2) is a reservoir of NO_(2) and chlorine,providing a connection between nitrogen oxide pollution and halogen activation.The formation of ClNO_(2) represents an activation process of chlorine from the aerosol phase to the gas phase.ClNO_(2) photolysis releases chlorine radicals and oxidizes VOCs,which could increase radical levels and promote ozone formation.Moreover,NO_(2) released via ClNO_(2) photolysis also promotes O_(3) formation in t

关 键 词：PM_(2.5) O_(3) 非均相反应 五氧化二氮 硝酰氯 

分 类 号：X51[环境科学与工程—环境工程]