Fluvial Geochemistry of the Arctic Rivers of Eastern Siberia

9627613埃德蒙这个持续项目的目标是；(1)确定东西伯利亚原始大河的化学成分及其流向北冰洋的流量；(2)与热带相似地质地形条件下的风化速率进行对比，探讨低温环境下的风化速率控制因素；(3)抑制以冰期极大期为特征的冰周环境的大规模扩张对风化通量的影响；(4)为未来可能受温室效应影响最大的环境提供基线数据。这项工作将为人类活动导致的全球变暖所带来的气候和水文变化所带来的生物地球化学效应提供见解。此外，这些结果将使人们能够估计气候恶化的影响，即冰川极值条件对全球风化通量的影响，这是目前主要由于缺乏数据而引起很大争议的一个话题。过去地质时期全球气候模型中使用的假设也将受到严格的限制，这些模型援引二氧化碳分压-风化反馈来稳定温室效应。在勒拿河、亚纳河和科雷马河流域进行了广泛的实地工作。从勒拿河源头的阿尔丹地盾和跨贝加尔湖高地的火成岩和变质基底岩中流出的蒸汽所获得的数据显示，该地区的化学通量与奥里诺科河流域瓜亚那地盾的化学通量相当，尽管后者的年平均气温要高出50摄氏度，降水量至少是前者的四倍。从Na/K比值和87 Sr/86Sr值可以看出，西伯利亚盆地的风化程度要小得多。在热带地区，基底的风化作用基本完成，以高岭石和三叠石为主，但极其缓慢，“运输有限”。在寒冷的气候中，霜冻作用不断地在所有尺度上产生新的反应表面，导致本质上的“暴露限制”情况。此外，流经所有沉积岩类型的河流的通量与在低纬度地区观测到的通量相似，例如中国的大河。建议将这项工作扩展到该地区的其他重要河流，即Anabar、Olenek、Indigirka和Anadyr，并在这一无冰川但以寒冷为主的环境中，对河流制度的主要、次要和微量元素地球化学以及溶解和颗粒有机碳和氮系统的同位素系统进行完整的表征。

9627613 Edmund The aims of this continuing project are; (1) to characterize the chemical compositions of the pristine large rivers of Eastern Siberia and their fluxes to the Arctic Ocean; (2) to investigate the factors controlling weathering rates in low temperature environments as compared to those operating in similar geologic terrains in the Tropics; (3) to constrain the effects that the large expansion of peri-glacial environments characteristic of the glacial maxima had on weathering fluxes; (4) to provide base-line data for the environment likely to be most impacted by future greenhouse warming. This work will provide insights on the biogeochemical effects that will result from the climatic and hydrologic changes to be expected from anthropogenic global warming. In addition the results will allow estimates to be made of the effects of climatic deterioration, i.e. glacial maximum conditions, on global weathering fluxes, presently a topic of much controversy owing, mainly, to lack of data. Strong constraints will also be place on the assumptions used in global climate models of the geologic past that invoke a pCO2-weathering feedback to stabilize the greenhouse effect. Extensive field work has been carried out in the basins of the Lena, Yana and Kolyma. Data from steams draining the igneous and metamorphic basement rocks of the Aldan Shield and Trans-Baikal Highland in the Lena headwaters give areal chemical fluxes comparable to those from the Guayana Shield in the drainage of the Orinoco, this despite the fact that latter has an annual average temperature~50oC warmer and receives at least four times the amount of precipitation. While the chemical yields are comparable the severity of weathering, as indicated by Na/K ratios and the 87 Sr/86Sr values, is much less in the Siberian basins. In the Tropics weathering of basement is essentially complete, to kaolinite and gibbsite, but extremely slow, "transport limited". In cold climates frost action continually generates fresh re action surfaces at all scales leading to essentially an "exposure limited" situation. In addition rivers draining the complete range of sedimentary rock types give fluxes similar to those observed in lower latitudes e.g. the large rivers of China. It is proposed to extend this work to the other important rivers of the region, the Anabar, Olenek, Indigirka and Anadyr, and to make a complete characterization of the major, minor and trace element geochemistry and of the isotopic systematics of the dissolved and particulate organic carbon and nitrogen systems of the fluvial regimes in this unglaciated but cold-dominated environment.