基于SPAMS探究南京市秋季大气中含草酸重金属颗粒的混合状态  

An investigation of the mixing state of oxalate-containing heavy metals in autumn in Nanjing using SPAMS

作　　者：谢芹惠 苏柏江 卓泽铭 杜绪兵 张国华[2] 李磊 周振 XIE Qinhui;SU Bojiang;ZHUO Zeming;DU Xubing;ZHANG Guohua;LI Lei;ZHOU Zhen(Institute of Mass Spectrometer and Atmospheric Environment,Jinan University,Guangzhou 510632;Guangzhou Institute of Geochemistry,Chinese Academy of Sciences,Guangzhou 510640;Guangdong Provincial Engineering Research Center for on-line Source Apportionment System of Air Pollution,Guangzhou 510632)

机构地区：[1]暨南大学,质谱仪器与大气环境研究所,广州510632 [2]中国科学院,广州地球化学研究所,广州510640 [3]广东省大气污染在线源解析系统工程技术研究中心,广州510632

出　　处：《环境科学学报》2022年第7期73-83,共11页Acta Scientiae Circumstantiae

基　　金：基于延时引出技术的单颗粒质谱分辨率提升及其影响研究项目(No.41905106)。

摘　　要：草酸是大气环境中重要的二羧酸,可以与多种非吸湿性的多价金属形成草酸-金属络合物,并对生物健康和大气环境产生重要的影响.众所周知,光化学反应可以促进草酸的形成.然而,考虑到草酸与重金属(Heavy Metals,HMs)潜在的络合反应,草酸与HMs颗粒的混合态目前尚不完全清楚.本研究利用单颗粒气溶胶质谱仪对南京市大气中含有草酸的HMs(Fe、Cu、Pb、Zn)的粒径和化学组成进行了分析.结果表明,与采样期间获得的整体颗粒相比(17.16%),HMs中草酸的数分数(Number fractions,Nfs)更高(29.88%).草酸在各类HMs中的Nfs值分别为20.84%(Fe)、45.59%(Cu)、37.16%(Pb)、36.51%(Zn).此外,草酸与Cu(r=0.53)、Pb(r=0.55)和Zn(r=0.79)之间存在良好的相关性,这可能归因于它们在环境中可以形成草酸-重金属配合物.值得注意的是,Fe与草酸在白天(r=0.29)和夜间(r=0.71)的相关性差异明显,这可能是因为Fe-草酸配合物在白天发生光解和Fe驱动的Fenton反应有关.此外,气溶胶酸度(Relative acidity,Ra)和相对湿度(Relative humidity,RH)对形成草酸-重金属配合物也有影响.Ra的增强可能抑制草酸-重金属配合物的形成.当RH>70%时,RH增大可能促进草酸-重金属配合物的形成.本研究为评估草酸在HMs中的增强提供了一些参考依据,同时提高了我们对大气环境中存在的草酸汇的认识.Oxalic acid is an important dicarboxylic acid that can form oxalate-metal complexes with different non-hygroscopic polyvalent metals in the atmosphere,which plays a critical role in biological health and atmospheric environment.It is well known that the formation of oxalic acid can be formed by photochemical reactions.Oxalic acid can potentially react with heavy metals(HMs),however,the mixing state of oxalic acid and HMs is unclear.In this study,a single particle aerosol mass spectrometer(SPAMS)was used to investigate the size and chemical composition of individual oxalate-containing HMs(i.e.,Fe,Cu,Pb,Zn)in autumn in Nanjing.The results showed that higher number fractions(Nfs)of oxalic acid were observed in HMs(29.88%),compared with all detected particles(17.16%).Nfs of oxalate in each type of HMs were 20.84%(Fe),45.59%(Cu),37.16%(Pb)and 36.51%(Zn).This phenomenon was probably attributed to the formation of oxalate-HMs complexes in the atmosphere,which was supported by the correlation between oxalic acid of Cu(r=0.53),Pb(r=0.55),and Zn(r=0.79).Notably,the correlation between Fe and oxalic acid was significantly different during the daytime(r=0.29)and nighttime(r=0.71),which was observed due to the photochemical degradation of Feoxalate complexes and the Fe-driven Fenton reactions in the daytime.Besides,aerosol relative acidity(Ra)and relative humidity(RH)also affect the formation of oxalate-HMs complexes.Ra is more likely to inhibit the formation of complexes.When RH>70%,the increased RH may promote the formation of oxalate-HMs complexes.This study provides reference for assessing the enhanced oxalic acid formation in HMs and improves our understanding of the sink of oxalic acid in the atmosphere.

关 键 词：重金属 草酸 络合物 混合态 相对酸度 相对湿度 

分 类 号：X51[环境科学与工程—环境工程]