Fluvial Geochemistry of the Arctic Rivers of Eastern Siberia

9627613埃德蒙这一持续项目的目的是：(1)确定东西伯利亚原始大河流的化学成分及其流向北冰洋的通量；(2)调查控制低温环境中风化速率的因素，将其与在热带类似地质地形中运行的风化速率进行比较；(3)限制以冰川极大为特征的冰川周围环境的大幅扩张对风化通量的影响；(4)为未来受温室气体变暖影响最大的环境提供基线数据。这项工作将提供关于气候和水文变化所产生的生物地球化学效应的见解，这些变化预计将由人为全球变暖引起。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话题。过去地质时期的全球气候模型中使用的假设也将受到严格的限制，这些假设调用二氧化碳风化反馈来稳定温室效应。在Lena、Yana和Kolyma盆地进行了广泛的实地工作。来自勒纳源头Aldan Shield和Trans-Baikal Highland火成岩和变质基底岩石的蒸汽的数据显示，奥里诺科河排水中的面积化学通量与Guayana Shield的相当，尽管后者的年平均温度升高约50摄氏度，降雨量至少是瓜亚纳盾的四倍。虽然西伯利亚盆地的化学产率相当，但由Na/K比值和87Sr/86Sr值所指示的风化程度要小得多。热带地区基底风化基本完成，以高岭石和三水铝石为主，但速度极慢，“运移受限”。在寒冷的气候中，霜冻作用会在所有尺度上不断产生新的反应表面，导致基本上是一种“暴露受限”的情况。此外，排泄各种沉积岩类型的河流提供的通量与在较低纬度地区观察到的类似，例如中国的大河。建议将这项工作扩大到该区域的其他重要河流--阿纳巴尔河、奥莱纳克河、印地格尔卡河和阿纳迪尔河，并对这一未冰川但以冷为主的环境中河流体系中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体系进行完整的表征。

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.