Carbon in karst: Investigating sources, transport mechanisms and isotopic fractionation to advance the interpretation of speleothem climate records

喀斯特中的碳：研究来源、传输机制和同位素分馏，以推进对洞穴气候记录的解释

• 批准号: 1124514
• 负责人: Daniel Breecker
• 金额: $ 22.39万
• 依托单位: University of Texas at Austin
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-08-15 至 2015-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1124514&HistoricalAwards=false
• 关键词: Carbon; karst; Investigating; sources; transport

The project will investigate the environmental controls on carbon isotopic composition of speleothem in order to refine this tool for paleo-environmental analysis. The transfer of carbon from vegetation to speleothem calcite is mediated by multiple processes, many of which are poorly understood and some heretofore unrecognized. Understanding of these processes can be significantly improved though careful empirical examination of a well-characterized karst setting. Project will study the sources, transport mechanisms and isotopic fractionation of carbon in multiple caves of the karst system in central Texas. Specific hypotheses to be tested are: 1) the carbon isotope composition of dissolved inorganic carbon in cave drip water is strongly influenced by deeply rooted plants (C3 trees) and only minimally by shallowly rooted plants (grasses and herbs;, 2) CO2 is transported into these caves in both the gas and liquid phases; 3) calcite precipitated in the caves is not in C isotope equilibrium with water entering the caves and the kinetic isotope effects responsible for this disequilibrium occurs primarily by degassing of CO2 from drip water rather than by calcite precipitation; and 4) the magnitude of kinetic isotope effects varies seasonally, can be quantified, and may thus provide new applications to paleoclimatology. The most important impact of the proposed research will be to provide a more useful tool for the speleothem and paleoclimate research community. In addition, the research will support and train students and results will be communicated to high school students and teachers through a well-established educational program at the University of Texas Austin.

该项目将研究环境对岩石层碳同位素组成的影响，以完善这一古环境分析工具。碳从植被到洞穴方解石的转移是由多个过程介导的，其中许多过程知之甚少，有些迄今尚未认识到。通过对具有良好特征的岩溶环境进行仔细的实证研究，可以显著提高对这些过程的理解。该项目将研究德克萨斯州中部喀斯特系统多个洞穴中碳的来源、输运机制和同位素分异。需要验证的具体假设有：1)洞穴滴水中溶解无机碳的碳同位素组成受深根植物（C3树）的强烈影响，而受浅根植物（草和草本植物）的影响很小；2)CO2以气相和液相两种形式被输送到洞穴中；3)溶洞中沉淀的方解石与溶洞中水的碳同位素不平衡，导致这种不平衡的动力学同位素效应主要是由滴水中的CO2脱气引起的，而不是由方解石沉淀引起的；4)动力学同位素效应的强度随季节变化而变化，可以量化，从而为古气候学提供新的应用。建议的研究最重要的影响将是为洞穴和古气候研究界提供更有用的工具。此外，这项研究将支持和培训学生，结果将通过德克萨斯大学奥斯汀分校一个完善的教育项目传达给高中生和教师。