锕系元素在定量化所参与的水体物理-化学过程具有显著的优势。青海湖水体锕系元素初步结果表明U含量和同位素呈现一致的分布特征，U含量约13.6ppb, 明显高于海水，(234U/238U)活度比约1.889。230Th-xs含量呈现明显的空间分布特征。那么230Th的空间分布差异到底受控于什么因素及环境指示意义的理解亟需我们结合湖水颗粒物，河水和沉积物钻孔深度研究来评估。基于此，本申请试图通过对青海湖27个深度剖面湖水和颗粒物、河水和沉积钻孔进行系统的U,Th和Pa的同位素分析，结合微量元素分析，评估青海湖水体U的来源，锕系元素在水体中的滞留时间，颗粒沉降速率和沉积物通量变化，深入理解锕系元素231Pa和230Th从水体到沉积物中的净化过程，进而评估湖泊沉积物U系不平衡特征是否能够提供流域古风化历史的潜力。

The natural radionuclides 231Pa and 230Th have potential advantage in tracing physico-chemical processes. Preliminary analysis of actinides in Qinghai Lake indicates that U concentration and isotopic distribution are consistent in spatial and depth profiles. The U concentration is about 13.6ppb, higher than that of seawater, (234U/238U) activity ratio is 1.889. The concentration of 230Th-xs showed obvious spatial distribution characteristics, but not for the depth profile. Then, what kind of factors affect the spatial distribution of 230Th, how about the Th and Pa distribution in water and particulate matter, the understanding about source and control mechanism of U in the water, and the particles in the water retention time and environmental significance, it is urgent for us to understand the above question. This paper aims to present measurements of dissolved and particulate (>0.45μm) 231Pa, 230Th, 232Th and 234U,235U,238U of dissolved from Qinghai Lake transect with multiple particulate type, combined with river and sediments of Qinghai Lake contribution in June and September, in conjunction with measurements of the mass concentration and major chemical composition of dissolved and particulate. With these measurements, we can understand the concentration and isotopic distribution of the water and particulates, assess the source of U of Qinghai Lake and the retention time of actinides in water, reveal particle sedimentation rate and sediment flux. There is an in-depth assessment of how particle types and flux affect the ultimate distribution of sedimentary 230Th and 231Pa, and evaluate the potential providing basin weathering history based on the disequilibrium of the U-Th.