西安东郊某废弃钢铁厂油松年轮记录的重金属含量变化过程

Content Variations of Heavy Metals Recorded by Tree Rings from a Displaced Steel Works in the Eastern Xi'an City

以西安市东郊某废弃钢铁厂为例,采用石墨炉原子吸收法、电感耦合等离子体原子发射光谱法、原子荧光法测定了废弃钢铁厂两棵油松(Pinus tabulaeformis Carr.)树盘及其根部土壤中重金属Cr、Mn、Hg、Zn、Pb、Cd和类金属As以及P等8种元素的含量.土壤测定结果表明,该地区Cr、Zn、As等元素含量超过了西安市郊区土壤背景值,Cr、Mn等元素易在深层土壤中积累,Hg、Zn等元素不易在深层土壤中积累.两个树盘年轮中这8种元素的含量随着年代的推移总体呈现上升的趋势,这表明该地区由这些元素引起的污染状况日益加重.Hg、Pb、Cd等元素于1996年左右吸收达到最高峰,与该钢铁厂生产历史相一致.这两个树盘中Mn、Hg、Zn、As、P等元素自1993年后均呈现比较一致的增长趋势.通过计算各元素的自相关系数,从统计学角度发现这8种元素在油松年轮中的迁移特征:Mn、Zn、As等元素均存在着3年的横向迁移趋势,Pb、P存在2年的迁移趋势,Hg、Cd有1年的迁移,而Cr几乎不迁移,其中Zn、Cd、P等元素在油松中的迁移趋势与西安市西部某地区椿树和桐树中的迁移趋势表现一致.

Using graphite furnace atomic absorption spectrometry （GFAAS）, inductively coupled plasma-atomic emission spectrometry （ICP）and atomic fluorescence spectrometry （AFS）, we analyzed the contents of eight trace elements （Cr, Mn, Hg, Zn, Pb, Cd, As and P）for two tree rings of Chinese pines trees （Pinus tabulaeformis Carr.）, and nearby soil in different depths from a displaced steel works in the eastern Xi＇an city. Results showed that the contents of Cr, As and Zn in the soil were higher than the background values of the suburban soil in Xi＇an. The contents of eight elements in two tree rings showed increasing trends with time, which indicated that environmental contamination caused by these elements was increasing seriously. The contents of Pb, Cd and Hg elements in annual rings had a positive correlation with the production of the steel works. The contents of Mn, Hg, Zn and As elements showed the same increasing trends since 1993. Autocorrelation analysis showed that Mn, Zn and As elements displayed three year moving between rings, Pb and P two years and Hg and Cd one year. Cr element was stable without lag effects. The results of Zn, Cd and P elements were quite similar to those found in other tree species（ Toona sinensis and Firmiana simplex ）in western Xi＇an.