(ESH) A Modern Test of the Assumptions Used for Determining Paleo-Atmospheric Carbon Dioxide from Goethite-Bound Carbon

(ESH) 用于从针铁矿结合碳中测定古大气二氧化碳的假设的现代测试

• 批准号: 9628035
• 负责人: Paul Schroeder
• 金额: $ 8.78万
• 依托单位: University of Georgia Research Foundation Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-08-01 至 2000-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9628035&HistoricalAwards=false
• 关键词: ESH; Modern; Test; Assumptions; Used

9628035 Schroeder The concept of using goethite-bound carbon isotopes as a proxy for estimating paleo-atmospheric pCO2 throughout the Phanerozoic has been a kingpin for modeling efforts such as the GEOCARB model used by Berner (1994). In this study we propose to test the underlying assumptions used by Yapp (1992) (developer of the goethite inferred paleo-atmospheric pCO2 method) in a modern goethite forming environment. The study will be performed using goethite forming in soil-saprolite found overlying granite terrains in the Piedmont of Georgia. The principal study site is the Panola Mountain Research Watershed (PMRW) located 25 km outside of Atlanta, Georgia. It is optimal for the test because of the abundance of soil goethite found and it is part of the large-scale U.S. Geological Survey (USGS) investigation known as the Water, Energy and Biogeochemical Budget (WEBB) Program. The PMRW has seen over 10 years of continuous collaborative hydrologic, climatic, geochemical and botanical research, thus providing a well-characterized contextual backdrop to examine the phenomenon of carbon inclusion in goethite. In this study we propose to: (1) conduct high-resolution sampling of the soil/caprolite/parent rock sequence at established monitoring stations with the PMRW; (2) detail the crystal-chemical nature of the authigenic goethite in order to account for such previously ignored effects such as the isomorphous A13+ substitution on the degree of CO3= substitution; (3) make stable carbon isotopic measurement of all carbon-bearing components in the system including atmosphere and soil CO2 at various depths, soil-respired CO2, live and subsurface degrading organic matter, as well as the carbon in goethite; (4) evaluate the mechanism of carbon inclusion in goethite in the context of observed carbon isotopic profiles and concentration gradients, and (5) understand the process in the context of local denudation rates using cosmogenic 10Be and 26Al and the heretofore untested idea of using 14C, bound in goethite. The principal goal of this work will be to establish the critical relationships between the stable carbon isotopic species (particularly goethite-bound carbon) and other carbon components in a soil/saprolite sequence. This work has important implications for the viability of using carbon-bound goethite as a proxy for paleo-atmospheric CO2. This proposal solicits $87,776 over a three-year period to be used for Summer salary, extraction line upgrades, mass spectrometer maintenance, funds for selected cosmogenic nuclide (10Be, 14C, 26Al) accelerator mass spectrometry, expendable supplies and funds to present scientific findings. ??

9628035 Schroeder 使用针铁矿结合的碳同位素作为估计整个显生宙古大气 pCO2 的代理概念一直是建模工作的主要支柱，例如 Berner 使用的 GEOCARB 模型（1994 年）。 在本研究中，我们建议在现代针铁矿形成环境中测试 Yapp（1992）（针铁矿推断古大气 pCO2 方法的开发者）使用的基本假设。 这项研究将利用在佐治亚州皮埃蒙特花岗岩地形上发现的土壤腐泥土中形成的针铁矿进行。 主要研究地点是位于佐治亚州亚特兰大郊外 25 公里的帕诺拉山研究流域 (PMRW)。 由于发现了丰富的土壤针铁矿，因此它是该测试的最佳选择，并且它是美国地质调查局 (USGS) 大规模调查的一部分，即水、能源和生物地球化学预算 (WEBB) 计划。 PMRW 已经进行了 10 多年的持续合作水文、气候、地球化学和植物学研究，从而为研究针铁矿中的碳夹杂现象提供了良好的背景背景。 在本研究中，我们建议：（1）利用 PMRW 在已建立的监测站对土壤/己酸钙石/母岩序列进行高分辨率采样； (2) 详细描述自生针铁矿的晶体化学性质，以解释以前被忽视的影响，例如同晶 A13+ 取代对 CO3= 取代程度的影响； (3) 对系统中所有含碳组分进行稳定碳同位素测量，包括不同深度的大气和土壤CO2、土壤呼吸CO2、活体和地下降解有机物以及针铁矿中的碳； (4) 在观察到的碳同位素分布和浓度梯度的背景下评估针铁矿中碳夹杂物的机制，以及 (5) 使用宇宙成因 10Be 和 26Al 以及迄今为止未经测试的使用 14C 的想法在局部剥蚀率的背景下了解该过程，束缚在针铁矿中。 这项工作的主要目标是建立稳定碳同位素物种（特别是针铁矿结合碳）与土壤/腐泥土序列中其他碳成分之间的关​​键关系。 这项工作对于使用碳结合针铁矿作为古大气二氧化碳替代物的可行性具有重要意义。 该提案在三年内筹集 87,776 美元，用于夏季工资、提取线升级、质谱仪维护、选定宇宙核素（10Be、14C、26Al）加速器质谱分析的资金、消耗品和展示科学发现的资金。 ??