Fluvial Geochemistry of the Arctic Rivers of Eastern Siberia

小行星9627613 这一持续项目的目的是：（1）确定东西伯利亚原始大河的化学成分及其流入北冰洋的通量;（2）与热带类似地质地形中的情况相比，研究控制低温环境中风化速率的因素;（3）限制以极盛冰期为特征的冰缘环境的大规模扩张对风化通量的影响;（4）为可能受未来温室效应影响最大的环境提供基线数据。 这项工作将提供对人类活动引起的全球变暖所引起的气候和水文变化所产生的地球化学影响的见解。 此外，这些结果将使人们能够估计气候恶化，即冰川最大条件对全球风化通量的影响，目前这是一个主要由于缺乏数据而引起很大争议的问题。 强有力的限制也将放置在地质过去的全球气候模型中使用的假设，调用pCO 2风化反馈，以稳定温室效应。 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外贝加尔高地的火成岩和变质基底岩石中排出的蒸汽数据给出的区域化学通量与奥里诺科河流域的瓜亚纳地盾的化学通量相当，尽管后者的年平均温度高约50 oC，降水量至少是后者的四倍。 虽然化学产率与风化的严重程度相当，如Na/K比值和 87 Sr/86 Sr比值在西伯利亚盆地中偏低。 在热带地区，基底风化基本完成，形成高岭石和三水铝石，但极其缓慢，“搬运有限”。在寒冷的气候中，霜冻作用在所有尺度上不断产生新的反应表面，导致基本上“暴露有限”的情况。 此外，河流排放的各种沉积岩类型的通量类似于在低纬度地区观察到的通量，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，Anabar河、Olenek河、Indigirka河和阿纳迪尔河，并对这一未冰川化但以寒冷为主的环境中河流体系的溶解和颗粒有机碳和氮系统的主要、次要和微量元素地球化学和同位素系统学进行完整的表征。

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.