Collaborative Research: The Role of Loess Weathering in Global Geochemical Cycles

合作研究：黄土风化在全球地球化学循环中的作用

• 批准号: 0240919
• 负责人: Daniel Mann
• 金额: $ 8.73万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-06-01 至 2006-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0240919&HistoricalAwards=false
• 关键词: Collaborative; Research; Role; Loess; Weathering

ABSTRACTAnderson OPP-0240676MannOPP-0240919This is a collaborative proposal by Principal Investigators at the Universities of California-Santa Cruz and Alaska -Fairbanks. This award will be jointly supported by the Arctic Natural Sciences Program and Geology and Paleontology Program in the Division of Earth Sciences. Glaciers produce large amounts of fine-grained sediment, exposing vast amounts of mineral surface area to chemical weathering processes. Despite the tremendous potential for glaciers to influence global weathering rates and hence atmospheric carbon dioxide (CO2) levels, this effect has not yet been demonstrated. Silicate weathering rates underneath glaciers are subdued, and rates in recently deglaciated terrain are below average. The hypothesis is that loess weathering provides the key link between the physical erosion done by glaciers and global geochemical cycles. This project is to study silicate weathering fluxes from glacial loess, and assess their global significance. Loess is a silt-clay sized sediment, transported by wind off unvegetated braid plains of glacier-fed rivers, and deposited over broad vegetated areas. Both the fine grain size and vegetation should render loess deposits highly susceptible to silicate weathering. These deposits effectively extend the impact of glaciation to a much broader area than the extent of glacier ice. Weathering of loess has never been examined from the perspective of contribution to global geochemical cycles. The project is designed to answer two questions: 1) does loess deposition increase the silicate weathering flux from a soil profile, and 2) does the weathering of loess occur at rates that can affect global weathering rates, and hence, global CO2 levels? Laboratory experiments, field measurements, and modeling will be used to address these questions. The field site is the Delta River valley in central Alaska, a glacial outwash system with on-going loess deposition at variable rates. Results from lab and fieldwork will be synthesized in a one-dimensional model of soil weathering fluxes as a function of loess deposition rate, precipitation rate, organic matter content, and grain size distributions. The model will be extended to the landscape scale to assess the global significance of loess deposition on CO2 consumption. Weathering of loess may be a significant, but it is still an unrecognized, component of carbon cycling. If this proves to be the case, then loess formation and weathering over timescales much longer than the duration of glaciation must be considered in models of atmospheric CO2 variation.

Anderson OPP-0240676 MannOPP-0240919这是加州大学圣克鲁斯分校和阿拉斯加大学费尔班克斯分校的首席研究人员共同提出的建议。该奖项将由北极自然科学计划和地球科学部地质古生物学计划联合支持。冰川产生了大量的细粒沉积物，使大量的矿物表面积暴露在化学风化过程中。尽管冰川极有可能影响全球风化速率，从而影响大气二氧化碳(CO2)水平，但这种影响尚未得到证实。冰川下面的硅酸盐风化速率很低，最近冰川消融地区的风化速率低于平均水平。该假说认为，黄土风化作用是冰川物理侵蚀和全球地球化学循环之间的关键环节。本项目旨在研究冰川黄土的硅酸盐风化通量，并评价其全球意义。黄土是一种粉质粘土大小的沉积物，被风从冰川滋养的河流的未植被的辫子平原上输送，并沉积在广阔的植被繁茂的地区。细小的粒度和植被都应该使黄土沉积物非常容易受到硅酸盐风化的影响。这些沉积物有效地将冰川作用的影响扩大到比冰川冰的范围更广的区域。黄土的风化作用从来没有从对全球地球化学循环的贡献的角度来研究。该项目旨在回答两个问题：1)黄土沉积是否增加了土壤剖面的硅酸盐风化通量；2)黄土的风化速度是否会影响全球风化速率，从而影响全球二氧化碳水平？将使用实验室实验、现场测量和建模来解决这些问题。现场地点是阿拉斯加中部的三角洲河谷，这是一个冰川喷发系统，不断以不同的速度沉积黄土。实验室和野外工作的结果将被综合在土壤风化通量的一维模型中，该模型是黄土沉积速率、降水速率、有机质含量和粒度分布的函数。该模型将扩展到景观尺度，以评估黄土沉积对二氧化碳消耗的全球意义。黄土的风化可能是重要的，但它仍然是碳循环的一个未被认识的组成部分。如果事实证明是这样，那么在大气二氧化碳变化模型中必须考虑比冰川持续时间长得多的时间尺度上的黄土形成和风化。