帕米尔高原冰川河流流域的现代化学风化过程、碳消耗通量及控制因素

The study of control factor on surface chemical weathering rate has long been the focus of earth science field. It is of great significance to explain global climate change over long time scale. Now the control factors remain controversial. Since glacier basin has a typical characteristic of high erosion rate just as since the Late Cenozoic Era, the research on glacial chemical weathering processes can be used to analog the past chemical weathering rate and its control mechanism. However, the current research on glacial basin is still lacking. .A glacial river (Gaizi River) basin on the Pamirs plateau, which has significant differences in topographic and climatic gradient, will be selected as research area. Space and high time resolution samples, including rain water, river water, groundwater, surface soil, bedrock and sediment samples will be systemically collected. Combined with detailed hydrological data, the objectives of this research program are to quantitatively calculate modern chemical weathering rate and carbon consumption flux in the Gaizi River under different erosion and climate conditions, and explore the main control factor and its control mechanism of silicate weathering rate of Asian inland at glacial conditions, and further to find out its relationship with the global climate change, thus provide regional examples and scientific basis for explaining the driving mechanism of chemical weathering under global warming condition.

地表化学风化速率控制因素的研究一直以来是地球科学领域研究的重点，它对于解释长时间尺度全球气候变化具有重大的意义。国际上对风化速率控制因子的研究仍存在很大的争议。冰川流域具有晚新生代以来高侵蚀速率的典型特征，对典型冰川流域化学风化过程的研究可以用来类比过去高侵蚀环境下化学风化速率的受控机制，但是目前对冰川流域现代化学风化过程和碳消耗的研究仍十分缺乏。. 本课题拟选取帕米尔高原具有显著地形和气候梯度差异的冰川河流（盖孜河）流域，通过空间上和高时间分辨率上的水（雨雪水、河水、地下水）、表土、基岩和河流沉积物样品的系统采集，并结合详细的水文数据，定量计算盖孜河流域不同侵蚀和气候条件下的现代化学风化速率和碳消耗通量，探讨冰川条件下亚洲内陆硅酸盐风化速率的主控因子及其与全球气候变化的关系，为全球变冷情形下化学风化的驱动机制解译提供区域实例及科学依据。

国际上对于晚新生代以来地表风化速率到底受到气候还是构造控制一直存在较大的争论。本课题因此选择了我国西部高侵蚀区的典型冰川流域来开展化学风化和CO2消耗速率的控制因素研究。通过对该流域系统的雨水、河水、地下水的时空采样，以及流域内沉积物、土壤、大气降尘、岩石样品的元素、同位素等的分析。我们利用forward模型量化了研究区的风化速率。本项研究的结果显示，该区域的CO2消耗速率为0.89-1.49 *105 t/km2/yr, 阳离子通量为373-1266 meq/m2/yr。这个结果是全球河流化学风化的2-7倍，说明即使在极端干旱区，低温低降雨条件下，冰川侵蚀产生的新鲜矿物表面也能极大增强地表的化学风化速率，气候的作用对硅酸盐风化的影响较弱。进一步指示了与物理侵蚀相关联的构造作用是地表风化速率的主要控制因素。这项研究为认识长时间尺度地表风化速率的控制因素提出了重要的数据支持。