中文摘要：

沉积物是河流水环境中重金属污染物的主要储存载体,其磁化率特征具有一定的污染指示意义.本研究对澜沧江干流及其11条主要支流,开展河道床沙沉积物样品采集,并测定了样品中5种重金属元素铜（Cu）、砷（As）、铅（Pb）、锌（Zn）、铬（Cr）的含量和磁化率值.采用潜在生态危害指数法分析床沙的重金属污染程度,亦探讨了床沙重金属含量与磁化率关系.结果表明：（1）澜沧江流域自上而下,床沙中重金属含量呈减弱趋势,因流域内矿业开发、电站建设等人类活动的影响,使各断面重金属含量分布差异较大;（2）所有样点的综合潜在生态危害指数RI值均小于150,为低风险.潜在生态危害指数法和沉积物的磁化率特征分析结果表现一定的相似性,呈现中游磁化率值较高,污染指数值较高,而中下游磁化率值较低,污染指数值较低;（3）澜沧江床沙中重金属As含量与磁化率和频率磁化率有很好的相关性,在一定程度上对床沙污染具有一定的指示意义.研究结果揭示了澜沧江床沙重金属污染状况及其环境磁学指示,为澜沧江矿产资源与水能合理开发提供新的科学依据.

英文摘要：

River sediments are main storage for heavy metal pollutants in water environment, and their environmental magnetism characteristics have a role to demonstrate the situation of heavy metal pollution. This work aims to investigate heavy metal contamination with five elements （Cu,As,Pb,Zn,Cr） in the bed sands of the mainstream and 11 tributaries in Lancang Basin, in association with magnetic susceptibility characteristics as an indicator for the pollution. The metal contamination in bed sands was evaluated by applying potential ecological risk index. The relationship between heavy metal concentration and magnetic susceptibility was also discussed. The results show that （1） the heavy metal contents in bed sands present a decreasing trend from upstream to downstream but the variation is obvious in some sampling sites due to anthropogenic activities of mining exploitation and dam constructions. （2） The values of risk indices （RI） of heavy metals in all samplings are below 150, so the potential ecological risk of heavy metals is significantly low. The results of the potential ecological risk index and magnetic susceptibility show a certain similarity with high values in midstream and lower values in downstream. （3） The heavy metal contents, magnetic susceptibility and frequency magnetic susceptibility of As show identical correlationship, so magnetic susceptibility could act as an indicator of heavy metal pollution of bed sands in Lancang River. These results make clear the pollution status by heavy metal and magnetism characteristics of bed sands collected from the water system, providing a scientific reference for sustainable development of mineral and hydropower resources as well.