中文摘要：

流域内矿山开采引起的河流系统重金属污染是流域开发及资源利用过程中的主要环境问题之一。本研究选取澜沧江水系底沙沉积物为介质，考察其干流及11条主要支流的5种重金属元素铜（Cu）、砷（As）、铅（Pb）、锌（Zn）和铬（Cr）含量的空间变化，并综合采用了单因子指数法和潜在生态危害指数法评价澜沧江干支流底沙沉积物中重金属污染分布现状。结果显示：（1）澜沧江水系自上游至下游，底沙重金属含量呈减弱趋势，但各支流重金属含量分布差异较大；（2）单因子指数法评价结果表明，干流最上游的旧州断面因区域背景值较高而致使As、Pb呈现重污染。支流黑惠江河口的As及勐戛河的Cu为重污染，沘江断面的Pb、Zn污染指数最大，属严重污染。其它干支流样点除了少数重金属元素有中度污染外，均为无污染状态；（3）潜在生态危害指数法指出，干流旧州断面的As及支流批江断面Pb的E值较高，其它各采样点值均未超出40，且各支流潜在生态危害指数（RI）值均小于150，属于低潜在生态危害的范围。本研究对澜沧江干流及其主要支流底沙沉积物中重金属污染状况进行分析与评价，分析干流主要的污染来源及各支流主要污染物，为澜沧江干支流的污染治理提供科学依据。

英文摘要：

Mining-induced heavy metal pollution in river system is one of the main environmental problems in the process of watershed development and resource utilization. This research investigated that the bed loads of the mainstream and its 11 tributaries in the Lancang River, aiming to examine the spatial distribution of heavy metal contents （Cu, As, Pb, Zn and Cr）, as well as to assess the heavy metal contamination status with the methods of Single Factor Index and Potential Ecological Risk Index. The results are shown as follows： （1） Heavy metal contents in sediments present a decreasing trend from upstream to downstream of the Lancang River system, while the heavy metal contents contained in the tributaries＇ bed sands are distinctly different. （2） The results of Single Factor Index indicate that sands at the Jiuzhou are seriously contaminated by As and Pb due to their high regional geological background. The two tributaries, the Heihui and Mengjia rivers, have been heavily polluted by As and Cu respectively. Especially, the single factor indexes of Pb and As are the highest with massive pollution in the Bijiang River. The other sampling sites, except for a few heavy metal elements with moderate pollution, present a pollution-free status in the main stream and tributaries. （3） The results of Potential Ecological Risk Index suggest that potential ecological risk factors （ E~ ） of the mainstream at Jiuzhou with As and the Bijiang tributary with Pb are relatively high, while the values in the other samples are below 40, and risk indices for all the tributaries investigated are less than 150, so the potential ecological risk of heavy metals is significantly low. Thus this work devotes to inspect and evaluate the spatial distribution of heavy metals in the bed loads throughout the river system of the Lancang River, in association with analyses of the pollution sources of the main stream from tributaries. So our conclusions could provide a scientific reference for pollution control during the basin d