中文摘要：

青海湖是我国环境研究中的一个热点地区，近年来^137Cs计年技术已在这一地区得到广泛的应用。已报道的青海湖沉积物中^137Cs垂直分布盐线显示，剖面最表层0-1cm泥沙的^137Cs浓度约60Bq／kg，大致为峰值浓度的2／3，远超过近年来大气沉降^137Cs所应带来的沉积水平。为查明青海湖表层底泥中放射性同位素^137Cs的来源，深入理解湖泊沉积过程，本文对青海湖沉积剖面的^137Cs面积活度与^137Cs本底值、湖泊表层底泥的137Cs浓度与入湖河流洪水沉积泥沙开展了比对研究．结果表明核爆期间的大气直接沉降是青海湖东南湖湾表层沉积物中的^137Cs主要来源，约占4／5，风沙和人湖径流河沙的间接输入的^137Cs仅占1／5，而最表层0-1cm的沉积物中^137Cs很可能主要来源于底泥扰动，在这样的情况下，利用沉积岩芯开展青海湖环境研究时，分辨率的选取需要慎重考虑这一因素。

英文摘要：

The ^137Cs dating technique has been applied widely in Lake Qinghai,one of the highlighted areas of envi- ronmental studies in China. The investigated vertical profiles indicate the ^137Cs content in the upmost surface sediment （the upper 1 cm layer of the surface） is about 60 Bq/kg （2/3 of the peak value）, which is much higher than the supposed content caused by ^137Cs from atmosphere in recent years. In order to investigate the source of ^137Cs isotope and understand the process of the sediments forming, this paper focused on comparative studies of ^137Cs inventory, both in background samples and in the sediments of Lake Qinghai. Comparative studies of ^137Cs content in sediments on the surface and in sediments at the confluence of contributing streams of Lake Qinghai were also carried out. The results indicate that atmosphere precipitation during the nuclear explosion is the major source of ^137Cs in the sediments of Lake Qinghai, causing 4/5 content of the total ^137Cs in the sediments of Lake Qinghai, with just 1/5 content from source of dust sands and contributing streams indirectly. ^137Cs in the upmost sediments mainly comes from bottom sediments. In such case, when the sediment core was used to study the environment of the Lake Qinghai, precautions should be taken when seeking for high resolution.