Experimental Investigation of the Reactivity of Organic Acids in Geologic Environments

建议的研究是在与地质环境相关的条件下对有机酸反应性的实验研究。有机酸是地质流体中含量最丰富的溶解性有机化合物，在石油和天然气的生成和运移、成矿溶液中金属的迁移、沉积盆地孔隙度的演化、风化作用和地下微生物活动等地质过程中起着重要作用。 以前试图评估乙酸和其他有机酸的分解速率，在地质条件下这些化合物的行为留下了很大的不确定性。 这些不确定性将通过一种新的实验方法来解决，该方法涉及更好的反应装置和更全面的反应产物分析。 具体问题包括：（1）脱羧和氧化对乙酸酯和长链羧酸热分解的相对贡献;（2）化学环境（氧化态、pH、溶解硫化合物的存在）对分解途径的影响;（3）CO2和乙酸酯在某些情况下能否达到亚稳态热力学平衡;（4）有机酸或其反应产物在水溶液中的缩合反应能否导致长链烃的合成。 我们希望这些实验能够解决有机酸反应性中突出的不确定性，并对有机酸在地质过程中的作用进行定量评价。

McCollomEAR-0073850The proposed research is an experimental investigation of the reactivity of organic acids at conditions pertinent to geologic environments. Organic acids are frequently the most abundant dissolved organic compounds in geologic fluids, and have been implicated to play a significant role in a number of geologic processes including the generation and migration of oil and natural gas, transportation of metals in ore-forming solutions, evolution of porosity in sedimentary basins, weathering, and subsurface geomicrobial activities. Previous attempts to evaluate decomposition rates of acetic acid and otherorganic acids have left large uncertainties in the behavior of these compounds under geologic conditions. These uncertainties will be addressed in the proposed research through a new experimental approach that involves a better reaction apparatus and a more comprehensive analysis of reaction products. Specific issues to be addressed include:(1) the relative contributions of decarboxylation and oxidation to the thermal decomposition of acetate and longer chain carboxylic acids, (2) the impact of chemical environment (oxidation state, pH, presence of dissolved sulfur compounds) on which decomposition pathway predominates, (3) whether CO2 and acetate can attain a state ofmetastable thermodynamic equilibrium under some circumstances, (4) whether condensation of organic acids or their reaction products can lead to synthesis of longer chain hydrocarbons in aqueous solutions. We expect these experiments to resolve the outstanding uncertainties in the reactivity of organic acids and allow quantitative evaluations to be made of the role of organic acids in geologic processes.