上海市灰霾天大气颗粒物浓度及富集元素的粒径分布

The concentration and size distribution of enriched elements of airborne particles in Shanghai as haze day

利用电称低压冲击仪(electric low pressure impactor,ELPI)在线监测上海市灰霾天和非灰霾天大气颗粒物浓度的粒径分布,并收集0.03～4.4μm粒径段的大气颗粒物.用同步辐射X荧光分析其中K,Ca,Ti,Mn,Cr,Ni,Cu,S,Cl,Zn,As,Pb和Fe等13种元素的粒径分布特征;以Fe为参比元素,根据富集因子定性确定各元素在灰霾天和非灰霾天的污染特征.结果显示,大气颗粒物的质量浓度在灰霾天显双模态结构,在非灰霾天显单模态结构;灰霾天大气颗粒物的粒子数浓度在0.07～0.3μm粒径段内出现明显的峰值.K,Ca,Ti,Cl,Mn,Cr,Zn,As,Pb在非灰霾天显单模态结构,在灰霾天除了K仍显单模态结构外,其余均显双模态结构;Ni,Cu和S在非灰霾天显双模态结构,在灰霾天除Ni出现三模态结构外,仍显双模态结构,但3个元素峰值在非灰霾天和灰霾天变化明显.K,Ca,Ti的富集因子在非灰霾天和灰霾天均为1左右,Mn,Cr的富集因子也小于10,表明K,Ca,Ti,Mn和Cr来自自然源;Cl,Pb,As,Ni,Cu,S,Zn的富集因子在非灰霾天和灰霾天均远大于10,且Ni,Cu,S,Zn的富集因子在灰霾天明显大于在非灰霾天的值.

The concentration of airborne particles （0.03-4.4 μm） in clear and haze days in Shanghai was online investigated by ELPI （electrical low pressure impactor）.The concentration of typical elements （K,Ca,Ti,Mn,Cr,Ni,Cu,S,Cl,Zn,As,Pb,Fe） was measured by synchrotron radiation X-ray fluorescence.In this work,Fe was used as the reference element to demonstrate the enrichment of other elements.Experimental results show that,the concentration of airborne particles appeared bi-modal in haze days while appeared single modal in clear days.Also,the particle number concentration showed more remarkable peaks in size segregated particles （0.07-0.3 μm） in haze days than in clear days.Ca,Ti,Cl,Mn,Cr,Zn,As,Pb exhibited single modal in clear days and exhibited bi-modal in haze days;K exhibited single modal in clear and haze days;Cu,S exhibited bimodal in clear and haze days;Ni exhibited bi-modal in clear days and exhibited tri-modal in haze days;Cu,S,Ni showed prominent differences in clear and haze days.For the reason that the enrichment factors of K,Ca,Ti,Mn,Cr were less than 10,they were mainly from natural sources.The enrichment factors of Cl,Pb,As,Ni,Cu,S,Zn were much larger than 10 in clear and haze days,and also the enrichment factors of Ni,Cu,S,Zn were obviously larger in haze days than in clear days.