西安市临潼区地表颗粒物重金属分布特征及生态风险评价

摘要

This study aims to examine the distribution characteristics and the potential ecological risk of heavy metals in road sediments across different land use areas of the city. 75 samples were collected from the industrial, residential, commercial, traffic and tourism areas of the Lintong District of Xi'an, respectively. The contents of Pb, Cd, Cu and Cr in each sample were determined by the flame atomic absorption spectrometry (A3). The distribution characteristics and sources of these heavy metals were analyzed for different land use areas. The potential ecological risk of these heavy metals was also evaluated using the potential ecological risk index. The results showed that the contents of Pb, Cd, Cu and Cr in road sediments in Lintong District of the city exceeded the limits to some extent with the average contents of Pb, Cd, Cu and Cr in the district were 258.52, 1.85, 92.30 and 83.39 mg·kg-1, respectively. The average contents were 12.08, 20.56, 4.31 and 1.33 times of the relevant background values in Xi'an, respectively, and were 9.94, 19.07, 4.08 and 1.37 times of their respective surface soil background values in China. Pb, Cd and Cr contents showed strong spatial variability, due to anthropogenic activities. The variation coefficient of Cu was 0.3, indicating weak impacts of anthropogenic activities. Great differences existed in the contents of heavy metals in road sediments among different land use areas. The characteristics were as follows: for Cu and Pb, the contents steadily decrease from the industrial, commercial, traffic, residential to tourism areas, whereas for Cr and Cd, the contents decline in a different order, i.e. from the traffic, industrial, to commercial, residential and then tourism areas. The potential ecological risk coefficients decreased from Cd to Cu followed by Pb and then Cr. The potential ecological risk of the five land use areas was all at the level of strong (Ⅲ). Among the five land use areas, the potential ecological risk of the traffic and industrial areas was the highest. Hence, optimizing industry and reducing traffic pollution are the main measures to lower the heavy metal pollution of surface particulates in the Lintong District.%为了研究地表颗粒物中重金属含量在城市不同功能区的分布特征及其潜在生态风险,以西安市临潼区为研究区,选择工业区、居民区、商业区、交通区和旅游休闲区5个不同功能区,共采集75组地表颗粒物样品,采用火焰原子吸收光谱(A3)测定了样品中重金属Pb、Cd、Cu、Cr的含量,分析了不同功能区地表颗粒物重金属的分布特征及其污染来源,并采用潜在生态指数评价法对不同功能区重金属潜在生态危害进行评价.结果表明:西安市临潼区地表颗粒物重金属Pb、Cd、Cu、Cr均存在一定程度超标,平均质量分数分别为258.52、1.85、92.30、83.39 mg·kg-1,分别是西安市表层土壤背景值的12.08、20.56、4.31、1.33倍,中国土壤背景值的9.94、19.07、4.08、1.37倍.4种重金属中Pb、Cd、Cr受人类活动影响导致空间变异性较大,而Cu的变异系数为0.3,表明其受人类活动干扰较小.不同功能区地表颗粒物重金属污染差异较大,Cu、Pb表现为工业区>商业区>交通区>居民区>休闲区;Cr、Cd表现为交通区>工业区>商业区>居民区>休闲区.重金属潜在生态危害系数大小顺序为Cd>Cu>Pb>Cr.5个功能区的生态危害水平均为强生态危害等级(Ⅲ级),其中,交通区与工业区潜在生态危害水平最高.优化工业生产和减少交通污染是改善临潼区地表颗粒物重金属污染的有效措施.