上海市地表灰尘与降水关系的分析

Analysis of relation between street dust and precipitation in Shanghai

为了探讨降水对上海市地表灰尘的影响,以上海市杨浦区6个不同功能区的地表灰尘为研究对象,采用环境磁学方法分析降雨前后地表灰尘的磁学特征变化,用电感耦合等离子体质谱仪(ICP-MS)分析其中11种重金属元素含量,采用富集因子法分析地表灰尘中各种重金属的富集情况,讨论分析降雨前后不同功能区地表灰尘的磁学特征变化及元素质量浓度的分布特征。结果表明:上海市杨浦区地表灰尘污染总体上呈现降雨后低于降雨前的变化趋势,其中降水对地表灰尘磁学参数影响最大的为频率磁化率χ_(fd)%,对重金属元素Pb的含量影响较大;在不同功能区中,工业区和交通区受降水影响均较大,而教学区受降水影响最小;重金属的富集程度为Pb>As>Cd>Zn≈Mn≈Cr>Cu>Ni>Ca>Mg,其中Pb、Cr、Mn、Ni、Cu、Zn、As、Cd等重金属已在环境中富集。众多结果显示,降水对城市地表灰尘的磁性特征和重金属含量均有一定的影响。

In order to investigate the influence of precipitation on street dust in Shanghai, the paper took the street dust of six different functional areas at Yangpu district of Shanghai as research object, and used environmental magnetic method to analyze the change of magnetism characteristics of street dust before and after precipitation. It measured the contents of eleven kinds of heavy metal element with ICP - MAS method, and used the enrichment factor method to analyze the enrichment condition of all kinds of heavy metals in the street dust. It analyzed the variation characteristics of street dust ＇s magnetism parameters and element concentrations at different functional areas with the factor of precipitation. The results showed that the street dust pollution in Yangpu district generally has higher level before the rain than that after the rain. Among all magnetic parameters involved, frequency - dependent susceptibility Xfd % is the most affected factor. The influence of precipitation on heavy metal element Pb is greater. In different functional areas, the industry and traffic area are more affected by precipitation, and the school area is less affected; degree of enrichment of heavy metal is Pb 〉 As 〉 Cd 〉 Zn ≈ Mn ≈Cr 〉 Cu 〉 Ni 〉 Ca 〉 Mg, some of these heavy metal had been enriched in the environment, such as Pb,Cr,Mn,Ni,Cu,Zn,As,Cd et al. The re- sults showed that precipitation has certain influence on magnetic feature and heavy metal content of street dust in city.