Rasa Ehsan, Bekins Barbara A, Mackay Douglas M, de Sieyes Nicholas R, Wilson John T, Feris Kevin P, Wood Isaac A, Scow Kate M
Department of Civil and Environmental Engineering, University of California-Davis, One shield Avenue, Davis, California, 95616, USA.
U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, California, 94025, USA.
Water Resour Res. 2013 Aug;49(8):4907-4926. doi: 10.1002/wrcr.20382.
In a field experiment at Vandenberg Air Force Base (VAFB) designed to mimic the impact of a small-volume release of E10 (10% ethanol and 90% conventional gasoline), two plumes were created by injecting extracted groundwater spiked with benzene, toluene, and -xylene, abbreviated BTX (No-Ethanol Lane) and BTX plus ethanol (With-Ethanol Lane) for 283 days. We developed a reactive transport model to understand processes controlling the fate of ethanol and BTX. The model was calibrated to the extensive field dataset and accounted for concentrations of sulfate, iron, acetate, and methane along with iron-reducing bacteria, sulfate-reducing bacteria, fermentative bacteria, and methanogenic archaea. The benzene plume was about 4.5 times longer in the With-Ethanol Lane than in the No-Ethanol Lane. Matching this different behavior in the two lanes required inhibiting benzene degradation in the presence of ethanol. Inclusion of iron reduction with negligible growth of iron-reducers was required to reproduce the observed constant degradation rate of benzene. Modeling suggested that vertical dispersion and diffusion of sulfate from an adjacent aquitard were important sources of sulfate in the aquifer. Matching of methane data required incorporating initial fermentation of ethanol to acetate, methane loss by outgassing, and methane oxidation coupled to sulfate and iron reduction. Simulation of microbial growth using dual Monod kinetics, and including inhibition by more favorable electron acceptors, generally resulted in reasonable yields for microbial growth of 0.01-0.05.
在范登堡空军基地（VAFB）进行的一项野外试验中，旨在模拟小体积释放E10（10%乙醇和90%传统汽油）的影响，通过注入添加了苯、甲苯和二甲苯（简称BTX）的提取地下水，创建了两条羽流，一条是无乙醇通道（No-Ethanol Lane），另一条是BTX加乙醇通道（With-Ethanol Lane），持续了283天。我们开发了一个反应性输运模型来理解控制乙醇和BTX归宿的过程。该模型根据广泛的野外数据集进行了校准，并考虑了硫酸盐、铁、乙酸盐和甲烷的浓度，以及铁还原菌、硫酸盐还原菌、发酵菌和产甲烷古菌。在含乙醇通道中苯羽流的长度约是无乙醇通道中的4.5倍。要匹配两条通道中这种不同的行为，需要抑制乙醇存在时苯的降解。为了再现观测到的苯的恒定降解速率，需要纳入铁还原且铁还原菌生长可忽略不计的情况。建模表明，来自相邻隔水层的硫酸盐的垂直扩散和弥散是含水层中硫酸盐的重要来源。要匹配甲烷数据，需要纳入乙醇最初发酵为乙酸盐、通过排气损失甲烷以及与硫酸盐和铁还原耦合的甲烷氧化。使用双莫诺德动力学模拟微生物生长，并包括更有利电子受体的抑制作用，通常会得到0.01 - 0.05的合理微生物生长产量。
