Experimental Investigation of the Reactivity of Organic Acids in Geologic Environments

拟议的研究是对有机酸在与地质环境有关的条件下的反应性的实验研究。有机酸通常是地质流体中最丰富的溶解有机化合物，在许多地质过程中起着重要作用，包括石油和天然气的产生和运移、成矿溶液中金属的运输、沉积盆地孔隙度的演化、风化和地下地质微生物活动。先前评估乙酸和其他有机酸分解速率的尝试，在地质条件下对这些化合物的行为留下了很大的不确定性。这些不确定性将在拟议的研究中通过一种新的实验方法来解决，这种方法包括更好的反应装置和更全面的反应产物分析。需要解决的具体问题包括：(1)脱羧和氧化对醋酸酯和长链羧酸热分解的相对贡献；(2)化学环境（氧化状态、pH值、溶解硫化合物的存在）对分解途径占主导地位的影响；(3)在某些情况下，CO2和醋酸酯是否能达到亚稳态热力学平衡状态。(4)有机酸或其反应产物的缩合是否会导致水溶液中长链烃的合成。我们期望这些实验能够解决有机酸反应性中突出的不确定性，并允许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.