Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL, 60607, USA.
Department of Civil and Materials Engineering, University of Illinois at Chicago, Chicago, IL, 60607, USA.
J Environ Manage. 2020 Oct 1;271:110997. doi: 10.1016/j.jenvman.2020.110997. Epub 2020 Jul 2.
Gas ebullition in sediment results from biogenic gas production by mixtures of bacteria and archaea. It often occurs in organic-rich sediments that have been impacted by petroleum hydrocarbon (PHC) and other anthropogenic pollution. Ebullition occurs under a relatively narrow set of biological, chemical, and sediment geomechanical conditions. This process occurs in three phases: I) biogenic production of primarily methane and dissolved phase transport of the gases in the pore water to a bubble nucleation site, II) bubble growth and sediment fracture, and III) bubble rise to the surface. The rate of biogenic gas production in phase I and the resistance of the sediment to gas fracture in phase II play the most significant roles in ebullition kinetics. What is less understood is the role that substrate structure plays in the rate of methanogenesis that drives gas ebullition. It is well established that methanogens have a very restricted set of compounds that can serve as substrates, so any complex organic molecule must first be broken down to fermentable compounds. Given that most ebullition-active sediments are completely anaerobic, the well-known difficulty in degrading PHCs under anaerobic conditions suggests potential limitations on PHC-derived gas ebullition. To date, there are no studies that conclusively demonstrate that weathered PHCs can alone drive gas ebullition. This review consists of an overview of the factors affecting gas ebullition and the biochemistry of anaerobic PHC biodegradation and methanogenesis in sediment systems. We next compile results from the scholarly literature on PHCs serving as a source of methanogenesis. We combine these results to assess the potential for PHC-driven gas ebullition using energetics, kinetics, and sediment geomechanics analyses. The results suggest that short chain <C alkanes are the only PHC class that alone may have the potential to drive ebullition, and that PHC-derived methanogenesis likely plays a minor part in driving gas ebullition in contaminated sediments compared to natural organic matter.
沉积物中的气体鼓泡是由细菌和古菌混合产生的生物成因气体引起的。它通常发生在受到石油烃 (PHC) 和其他人为污染影响的富含有机物的沉积物中。鼓泡在相对狭窄的生物、化学和沉积物地质力学条件下发生。这个过程分三个阶段进行：I）主要产生甲烷的生物成因过程和气体在孔隙水中溶解相的迁移到气泡成核点，II）气泡生长和沉积物破裂，以及 III）气泡上升到表面。在第一阶段中生物成因气体的产生速度和第二阶段中沉积物对气体破裂的阻力在鼓泡动力学中起着最重要的作用。对于驱动气体鼓泡的甲烷生成速率中底物结构所起的作用了解较少。已经确定甲烷菌只能利用非常有限的化合物作为底物，因此任何复杂的有机分子都必须先分解为可发酵的化合物。鉴于大多数鼓泡活跃的沉积物是完全厌氧的，在厌氧条件下难以降解 PHC 这一众所周知的事实表明，PHC 衍生的气体鼓泡可能存在潜在限制。迄今为止，没有研究能够明确证明风化的 PHC 可以单独驱动气体鼓泡。本综述包括对影响气体鼓泡的因素以及沉积物系统中厌氧 PHC 生物降解和甲烷生成的生物化学的概述。我们接下来汇编了关于 PHC 作为甲烷生成源的学术文献中的结果。我们将这些结果结合起来，使用能量学、动力学和沉积物地质力学分析来评估 PHC 驱动的气体鼓泡的潜力。结果表明，短链 <C 烷烃是唯一可能单独具有驱动鼓泡潜力的 PHC 类别，与天然有机物相比，PHC 衍生的甲烷生成在污染沉积物中驱动气体鼓泡的作用可能较小。
