Adsorption of Inorganic Carbon on Volcanic Rock: Implications for Global CO2 Budgets and 14C-Dating of Groundwater (Pilot Study)

火山岩上无机碳的吸附：对全球二氧化碳预算和地下水 14C 测年的影响（试点研究）

• 批准号: 0210003
• 负责人: Gregg Davidson
• 金额: $ 10.41万
• 依托单位: University of Mississippi
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2002
• 资助国家: 美国
• 起止时间: 2002-09-01 至 2006-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0210003&HistoricalAwards=false
• 关键词: Adsorption; Inorganic; Carbon; Volcanic; Rock

Davidson-0210003Adsorption of inorganic carbon on mineral phases has been of interest to researchers in many different fields of study, but little is known about the role that adsorption on rock-forming minerals may play in global CO2 sink, or how it may affect 14C dating in groundwater. Preliminary results suggest that adsorption of CO2 could account for a small but significant percentage of the terrestrial CO2 sink, and exchange between the aqueous and adsorbed phase could influence 14C dating in groundwater. The preliminary data comes from experiments with tuff (felsic volcanic rock). Core samples were isolated from the atmosphere at the time of drilling, and were later opened and heated under vacuum to extract inorganic dissolved carbon (DIC) from water in the rock pores. Carbon recoveries in excess of available DIC suggest that a sizeable reservoir of adsorbed carbon exists in these rocks.A pilot project is proposed to investigate CO2 adsorption and associated isotopic fractionation on five volcanic rock materials representing suites of felsic and mafic minerals under dry, wetted, and saturated conditions. Samples will be characterized for surface area, porosymmetry and mineralogy before use. For dry and wetted experiments, crushed rock will be preheated at 2000C to generating adsorption isotherms, and again at 6000C in order to quatify the effect of trace organic coatings that may be present. Adsorption isotherms will be measured under drying conditions and in the presence of a mono-layer of adsorbed water. Isotopic fractionation will be evaluated by collecting head space gases after equilibration and measuring the d 13C of initial and equilibrated CO2. Isotopic exchange will be evaluated by reintroducing CO2 with a unique d13 C signature and measuring head space gases again after equilibration. Adsorption in saturated systems will be measured by introducing CO2 into the head space of a saturated slurry and monitoring the head space CO2 concentration and the pH to calculate the mass partitioned into the aqueous and adsorbed phases. Isotopic fractionation and exchange will be measured in the same fashion as for dry and wetted experiments.Results from this work will be used as a first step in estimating the magnitude of CO2 adsorption as a terrestrial sink of atmospheric CO2, and the extent to which adsoption and exchange may alter 14C activities in groundwater. The results will also be used to formulate a more targeted study of adsorption sites and mechanisms. Educational impacts of the study include student training at both the graduate and undergraduate level.

无机碳在矿物相上的吸附一直是许多不同研究领域的研究人员感兴趣的问题，但关于岩石矿物上的吸附在全球二氧化碳汇中可能起到的作用，或者它可能如何影响地下水中的14C测年，人们知之甚少。初步结果表明，二氧化碳的吸附可能占陆地二氧化碳汇的一小部分，但占很大比例，水相和吸附相之间的交换可能会影响地下水中的14C测年。初步数据来自凝灰岩(长英质火山岩)的实验。岩心样品在钻探时从大气中分离出来，随后打开并在真空下加热，从岩石孔隙中的水中提取无机溶解碳(DIC)。碳回收率超过可利用的DIC表明，这些岩石中存在相当大的吸附碳库。建议进行一个试点项目，研究在干燥、潮湿和饱和条件下，代表长英质和镁铁质矿物系列的五种火山岩材料对二氧化碳的吸附及其相关的同位素分馏。样品在使用前将进行表面积、孔隙对称性和矿物学表征。对于干燥和潮湿的实验，碎石将在2000℃预热到产生吸附等温线，然后在6000℃再次预热，以量化可能存在的微量有机涂层的影响。吸附等温线将在干燥条件下和在单层吸附水存在的情况下测量。将通过收集平衡后的顶部空间气体并测量初始和平衡的二氧化碳的d13C来评估同位素分馏。同位素交换将通过重新引入具有独特d13C特征的二氧化碳并在平衡后再次测量顶部空间气体来进行评估。饱和体系中的吸附将通过将二氧化碳引入饱和浆体的顶空并监测顶空CO2浓度和pH来计算分配到水相和吸附相中的质量来测量。同位素分馏和交换将以与干和湿实验相同的方式进行测量。这项工作的结果将作为第一步，估计作为大气二氧化碳汇的二氧化碳吸附的程度，以及吸收和交换可能改变地下水中14C活性的程度。研究结果还将用于制定更有针对性的吸附位置和机理研究。这项研究的教育影响包括研究生和本科生水平的学生培训。