兰州市大气降尘的化学特性

对定期收集的兰州市降尘样品，用X射线荧光法分析了其中24种元素的相对浓度，并用富集因子法对数据进行了处理，分析，结果表明兰州市现代降尘中主要有SiO2,Al2O3,CaO,铁的氧化物，MgO,Na2O,K2O,TiO2等，同时含有微量P,Mn,Zn,Ba,Pb等元素，从元素浓度的年内变化情况看，Fe,Co,Cu,Cr,As等元素在采暖期（11月－次年3月）浓度均高于非采暖期，Al,Si,Ca,Pb等元素浓度年内差异不大，而Na,Mg,K等元素浓度在采暖期明显降低，在降尘中富集程度最高的元素Zn,Pb,As主要来自人为污染，Si,Al,Mg,K,Na,V,Co,Ni则基本源于本地和邻近地区的土壤表土，Fe,Ca,Ti,P,Cu,Ba,Cr,Mn人为污染亦占有一定比例。

Chemical characteristics of atmospheric dust in Lanzhou

samples of atmospheric dust were collected in Lanzhou City and analyzed for 24 elements by X-ray fluorescence.Enrichment factor was used in this study to identify different sources.SiO 2,Al 2O 3,CaO and Iron Oxides etc composed the major composition in the dust,while P,Mn,Zn,Ba etc were trace elements.According to the monthly variations of concentration,Fe,Cu,Co,Cr and As were higher during the heating period(Nov.to next Mar.).Na,Mg and K etc had an opposite pattern.The concentrations of Al,Si,Ca,Pb and some other elements showed no great changes within the whole year.Enrichment factor analyses indicated that anthropogenic sources were the major source of Zn,Pb,As and also contributes to Fe,Ca,Ti,P,Cu,Ba,Cr,Mn in a certain extent.On the contrary,elements such as Si,Al,Mg,K,Na,V,Co and Ni were generally from crustal soil.