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.

Approctinganderson OPP-0240676MANNOPP-0240919这是加利福尼亚州圣克鲁斯大学和阿拉斯加大学-Fairbanks的首席研究人员的合作提案。 该奖项将由北极自然科学计划以及地球科学部的古生物学计划共同支持。 冰川会产生大量的细粒沉积物，使大量的矿物表面积暴露于化学风化过程中。尽管冰川具有影响全球风化速率的巨大潜力，因此尚未证明这种影响。冰川下方的硅酸盐风化速率被柔和，最近脱气的地形的速率低于平均水平。假设是，黄土风化提供了冰川所做的物理侵蚀与全球地球化学周期之间的关键联系。该项目是研究冰川黄土的硅酸盐风化通量，并评估它们的全球意义。 Loess是一种淤泥尺寸的沉积物，由冰川喂养的河流的绿色辫子平原运输，并沉积在宽阔的植被区域。细晶粒尺寸和植被都应使Loess沉积非常容易受到硅酸盐风化的影响。这些沉积物有效地扩展了冰川的影响到比冰川冰的程度更广泛的区域。从对全球地球化学周期的贡献的角度来看，从未对黄土的风化进行检查。 该项目旨在回答两个问题：1）黄土沉积是否会增加土壤剖面中的硅酸盐风化通量，而2）黄土的风化是否会以可能影响全球风化速率的速度发生，从而影响全球二氧化碳水平？实验室实验，现场测量和建模将用于解决这些问题。现场地点是阿拉斯加中部的三角洲河谷，这是一种冰川折断系统，具有可变速率的持续黄土沉积。实验室和现场工作的结果将在土壤风化通量的一维模型中合成，这是黄土沉积速率，降水速率，有机物含量和晶粒尺寸分布的函数。该模型将扩展到景观量表，以评估黄土沉积对CO2消费的全球意义。 黄土的风化可能是重要的，但它仍然是碳循环的未识别的组成部分。 如果事实证明是这种情况，那么在大气二氧化碳变化模型中，必须考虑黄土形成和在时间尺度上长得多得多。