不同粒径近地表大气尘元素分配规律研究——以成都经济区为例

Elements distribution rule of air dust near the ground in diferent particle sizes: A case study of Chengdu Economic Region

将不同地貌单元和城市不同功能区的近地表大气尘机械筛分,分析其粒度组成和化学组成特征及其相互关系,以探讨元素在不同粒径大气尘颗粒中的分配规律。研究结果表明：近地表大气尘颗粒粒径主要集中在300-400目（38.5-54μm）,其中城市和丘陵地区质量分数最高,达56.596%-68.493%。化学组成上,人为扰动重金属元素,除Pb本底值比较高外,总体上城市高于丘陵和山区;Al2O3、Na2O、SiO2、Ti、Zr等稳定元素总体上,随粒径的减小,元素含量逐渐增大;Mn、P、S等元素,总体上随粒径的减小,元素含量逐渐减小。Pb、Zn、Cr等人为扰动元素,大粒径近地表大气尘元素含量稍大于小粒径元素含量,但小粒径元素含量总体上仍呈现随粒径的减小而逐渐增大的趋势。

By mechanical sieving air dust near the ground in different geomorphic units and functional areas, this paper mainly studied the particle size and chemical component of the air dust and their correlativity, the results show that the particle sizes mostly close to 300-400 mesh （38.5-54 μm）, and in city and hilly area, the mass content is highest, up to 56.596-68.493%. As for chemical component, the human-disturbed heavy metals are higher in city than that in uplands and mountainous area, with an exception of lead having higher background value. In total, the content of stable chemical components, such as Al2O3, Na2O, SiO2, Ti, Zr, etc, gradually increases with particle size reducing. However the content of Mn, P, S gradually decreases with size reducing. The content of human-disturbed elements, such as Pb, Zn, Cr etc., is slightly higher in the big air dust particles near the ground than that in the small particles, but concentration of these elements in the small particles, as a whole, still presents the trend of gradual increase along with the size decreasing.