南京市秋季大气颗粒物中金属元素的粒径分布

Size distribution characteristics of metal elements in air particulate matter during autumn in Nanjing

在南京市仙林地区,采用ANDERSON八级撞击采样器,于2016年秋季采集了63个大气颗粒物有效样本,并利用ICP-MS分析了金属元素的含量.结合气象等资料,研究了大气颗粒物金属元素的粒径分布与富集特征,并对其来源进行了探讨.结果表明:南京秋季大气颗粒物质量浓度的粒径分布呈双峰型,峰值分别位于0.4～1.1和3.3～9μm;金属元素的粒径分布呈3种类型,一是粗粒子单峰型,峰值位于3.3～5.8μm,主要元素包括Na、Al、Ca、Mg、Co、Ce、Sr和Ba;二是细粒子单峰型,峰值位于0.4～1.1μm,主要元素包括Zn、As、Cd、Ag、Tl和Pb;三是粗细粒子双峰或多峰型,峰值位于1.1和5μm粒径段,主要元素包括K、Se、Li、Be、Mn、V、Cu、Cr、Ni和Fe.按富集因子的大小,可将元素分为3类,低富集元素包括Ba、Ca、Ce、Sr、Mg、Fe、Co、Mn、Be和V,中富集元素包括Li、Na、Ni、K和Cr,高富集元素包括Cu、Tl、Zn、As、Pb、Ag、Cd和Se.不同的粒径分布和富集水平反映了大气颗粒物的来源特征.研究结果可以为深入认识大气颗粒物金属元素的来源及其环境与健康效应提供科学依据.

Totally63samples of size-segregated particulate matter(PM)were collected using an8-stage Anderson cascade impactor in autumn2016at the Xianlin campus,Nanjing University.The concentrations of24metal elements were analyzed by the ICP-MS.Size distribution characteristics of mass concentrations,enrichment factors(EFs),and possible sources of different metal elements were studied.Results showed that the size distribution of the mass concentration was bimodal,peaking at0.4~1.1and5.8~9μm,respectively.With regard to the metal elements,we found three types of size distribution.The first type had a mono peak at coarse size segment(3.3~5.8μm),including Na,Al,Ca,Mg,Co,Ce,Sr and Ba.The second had a mono peak at fine size segment(0.4~1.1μm),including Zn,As,Cd,Ag,Tl and Pb,and the third had two peaks at fine(1μm)and coarse(5μm),respectively,including K,Se,Li,Be,Mn,V,Cu,Cr,Ni and Fe.According to the value of the EFs,the elements were divided into three groups.They were a slightly enriched group with EFs lower than5(Ba,Ca,Ce,Sr,Mg,Fe,Co,Mn,Be and V),a moderately enriched group with EFs between5and100(Li,Na,Ni,K and Cr),and a highly enriched group with EFs larger than100(Cu,Tl,Zn,As,Pb,Ag,Cd and Se).The characteristics of the size distribution and the EFs reflected different sources of atmospheric PM in Nanjing,which were meaningful for further researches on health effects and for policy making for air pollution control.