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

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，但对造岩矿物上的吸附在全球CO2汇中可能发挥的作用或它如何影响地下水中的14C测年知之甚少。 初步结果表明，CO2的吸附可以占一个小的，但显着的百分比陆地CO2汇，和水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。 在钻探时将岩心样品与大气隔离，然后打开并在真空下加热，以从岩石孔隙中的水中提取无机溶解碳（DIC）。 碳回收率超过可用DIC表明，这些岩石中存在相当大的吸附碳库。 使用前，将对样品的表面积、孔隙对称性和矿物学进行表征。 对于干和湿实验，将在2000 ℃下预热碎石以产生吸附等温线，并再次在6000 ℃下预热，以量化可能存在的痕量有机涂层的影响。 将在干燥条件下和存在单层吸附水的情况下测量吸附等温线。 通过在平衡后收集顶空气体并测量初始和平衡CO2的d13 C来评价同位素分馏。 通过重新引入具有独特d13 C特征的CO2并在平衡后再次测量顶空气体来评价同位素交换。 通过将CO2引入饱和浆液的顶部空间并监测顶部空间CO2浓度和pH值来测量饱和系统中的吸附，以计算分配到水相和吸附相中的质量。 同位素分馏和交换将被测量在相同的方式为干和湿experiments.Results从这项工作将被用作第一步，在估计的CO2吸附作为大气CO2的陆地汇的幅度，在何种程度上adsortion和交换可能改变地下水中的14C活动。 研究结果还将用于制定更有针对性的吸附位点和机制研究。 这项研究的教育影响包括研究生和本科生两级的学生培训。

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.