长江重庆城区段表层沉积物重金属污染特征分析

Characterization of heavy metal pollution in surface sediments of Chongqing section of the Yangtze River

采用污染负荷指数法、美国国家海洋大气管理局（NOAA）水体泥沙质量标准及香港公务局疏浚污泥重金属污染程度分类法，对长江重庆城区段（包括嘉陵江段（A）、汇合前长江段（B）与；12合后长江段（C））表层（0-10cm）沉积物重金属Pb、zn、Cu污染程度进行评价。结果表明：①重庆城区段长江水体表层沉积物重金属质量比变异较大，最低值均低于全球背景值而最高值则均超过全球背景值；②Pb、Zn、Cu平均质量比顺序为A〈B〈C且各江段均为Pb〈Zn〈Cu；③3段水道沉积物污染负荷指数分别是0．54（A）、0．76（B）和1．52（C），整个研究区域为0．85；④整个研究区域沉积物中Pb和Zn质量比均低于NOAA提出的低效应范围值，而Cu质量比远高于低效应范围值，其中两江汇合后超过中效应范围值，表明Pb、Zn对水体生物没有负面影响，而Cu对水体生物的负面影响较大；⑤沉积物Pb、Zn属于香港公务局疏浚污泥重金属污染程度分类中的A类，而Cu则属于C类，表明沉积物受到Cu的严重污染，因此，疏浚和转运中需加以特别注意防止该元素的迁移。

Using three evaluation methods, the Pollution Load Index （PLI）, the NOAA Sediment Quality Standard, and the Classification of Heavy Metal Pollution in Dredging Sludge by the Hongkong Works Bureau, heavy metal pollution in the surface sediments in the Chongqing section of the Yangtze River was studied. This section includes the Jialing River section （A）, and the sections before （B） and after （C） the confluence of the Jialing River and the Yangtze River. Results show that： （1） the heavy metal concentrations of the studied surface sediments varied greatly： the lowest values were lower than the global background values while the highest values were greater than the background values; （2） the mean concentrations of Pb, Zn and Cu in A were the highest, followed by those in B and C, and in each section, the Pb concentration was higher than that of Zn and the Cu concentration was the lowest; （3） the PLIs were 0.54, 0.76, and 1.52 for sections A, B, and C, respectively, and 0.85 for the whole study area; （4） the Pb and Zn concentrations of sediments were lower than the NOAA low effect range and the Cu concentration was far greater than the NOAA middle effect range, indicating no negative biological effects of Pb and Zn but significant negative effects of Cu; and （5） sediments were heavily polluted only by Cu according to the Hongkong Works Bureau, indicating that more attention must be paid to the dredging and transportation of sediments.