With growing global use of methanol as a fuel additive and extensive use in other industrial processes, there is the potential for unintended release and spills into soils and aquifers. In these subsurface systems it is likely that methanol will be readily biodegraded; however, degradation may lead to the production of by-products, most importantly methane possibly resulting in explosion hazards and volatile fatty acids (VFAs) causing aesthetic issues for groundwater. In this study, the formation of these potentially harmful by-products due to methanol biodegradation was investigated in natural sand and silt sediments using microcosms inoculated with neat methanol (100%) ranging in concentration from 100 to 100,000 ppm. To assess the rate of degradation and by-product formation, water and headspace samples were collected and analyzed for methanol, volatile fatty acids (VFAs, including acetic, butyric, and propionic acid), cation (metal) concentrations (Al, Ca, Fe, K, Mg, Mn and Na), microbial community structure and activity, headspace pressure, gas composition (CH₄, CO₂, O₂ and N₂), and compound specific isotopes. Methanol was completely biodegraded in sand and silt up to concentrations of 1000 ppm and 10,000 ppm, respectively. Degradation was initially aerobic, consuming oxygen (O₂) and producing carbon dioxide (CO₂). When O₂ was depleted, the microcosms became anaerobic and a lag in methanol degradation occurred (ranging from 41 to 87 days). Following this lag, methanol was preferentially degraded to acetate, coupled with CO₂ reduction. Microcosms with high methanol concentrations (10,000 ppm) were driven further down the redox ladder and exhibited fermentation, leading to concurrent acetate and methane (CH₄) generation. In all cases acetate was an intermediate product, further degraded to the final products of CH₄ and CO₂. Carbonates present in the microcosm sediments helped buffer VFA acidification and replenished CO₂. Methane generation in the anaerobic microcosms was short-lived, but temporarily reached high rates up to 13 mg kg⁻¹ day⁻¹. Under the conditions of these experiments, methanol degradation occurred rapidly, after initial lag periods, which were a function of methanol concentration and sediment type. Our experiment also showed that methanol degradation and associated methane production can occur in a stepwise fashion.

随着全球越来越多地使用甲醇作为燃料添加剂以及在其他工业过程中的广泛使用，有可能意外释放和泄漏到土壤和含水层中。在这些地下系统中，甲醇很可能很容易被生物降解；然而，降解可能会导致副产品的产生，最重要的是甲烷可能导致爆炸危险和挥发性脂肪酸 (VFA) 导致地下水的美观问题。在这项研究中，使用接种浓度为 100 至 100,000 ppm 的纯甲醇 (100%) 的微观世界，在天然沙子和淤泥沉积物中研究了由于甲醇生物降解而形成的这些潜在有害副产物。为了评估降解和副产物形成的速率，收集水和顶空样品并分析甲醇，₄、CO ₂、O ₂和N ₂ )，以及化合物的特定同位素。甲醇在沙子和淤泥中完全生物降解，浓度分别高达 1000 ppm 和 10,000 ppm。降解最初是有氧的，消耗氧气 (O ₂ ) 并产生二氧化碳 (CO ₂ )。当 O ₂耗尽时，微观世界变得厌氧，甲醇降解出现滞后（从 41 天到 87 天不等）。在此滞后之后，甲醇优先降解为乙酸盐，再加上 CO ₂减少。具有高甲醇浓度 (10,000 ppm) 的微观世界被进一步推向氧化还原阶梯并表现出发酵，导致同时生成乙酸盐和甲烷 (CH ₄ )。在所有情况下，乙酸盐都是中间产物，进一步降解为最终产物 CH ₄和 CO ₂。微观沉积物中存在的碳酸盐有助于缓冲 VFA 酸化并补充 CO ₂。厌氧微观世界中的甲烷生成是短暂的，但暂时达到了高达 13 mg kg ^-1 天^{-1的高速率}. 在这些实验条件下，甲醇降解在初始滞后期后迅速发生，这是甲醇浓度和沉积物类型的函数。我们的实验还表明，甲醇降解和相关的甲烷产生可以逐步发生。