An Seongnam, Woo Heesoo, Kim Sang Hyun, Yun Seong-Taek, Chung Jaeshik, Lee Seunghak
Water Cycle Research Center, Korea Institute of Science and Technology (KIST), Seoul, 02792, South Korea.
Geo-technical Team, ECO Solution Business Unit, SK Ecoplant, Seoul, 03143, South Korea.
Chemosphere. 2023 Jun;326:138417. doi: 10.1016/j.chemosphere.2023.138417. Epub 2023 Mar 14.
The migration of petroleum hydrocarbons in vadose zone involves complex coupled processes such as downward displacement and natural attenuation. Despite its significance in determining groundwater vulnerability to petroleum contamination and optimizing the remedial strategy, it has not been comprehensively studied in terms of overall processes under field-relevant conditions. In this study, a series of unsaturated soil column experiments were conducted by simulating subsurface diesel contamination within a vadose zone using different soil textures at different soil bulk densities and initial diesel concentrations, while partly exposing them to simulated precipitation. The results showed that the soil column with less fine fraction was favorable for the downward migration of diesel but unfavorable for its natural degradation. However, precipitation complicated the relative conductivities of multiple fluids (water, air, and diesel) through the pore network, therby decreasing diesel migration and degradation. For example, the downward migration of diesel in the SL column decreased by 8.4% under precipitation, while the overall attenuation rate dropped to almost 0.24% of its original state. Lowering bulk density (from 1.5 to 1.23 g/cm3), however, could enhance the attenuation rate presumably due to the secured void space for the incoming fluids. A high initial concentration of diesel (2%; w/w) inhibited its natural attenuation, while its influence on its vertical propagation after the precipitation was not significant. The present findings provide a mechanistic basis for approximating the behavior of petroleum hydrocarbons in a random vadose zone.
石油烃在包气带中的迁移涉及向下位移和自然衰减等复杂的耦合过程。尽管其在确定地下水对石油污染的脆弱性以及优化修复策略方面具有重要意义，但在实际现场条件下，尚未对其整体过程进行全面研究。在本研究中，通过使用不同土壤质地、不同土壤容重和初始柴油浓度模拟包气带内的地下柴油污染，并使部分土壤柱暴露于模拟降水，进行了一系列非饱和土柱实验。结果表明，细颗粒含量较少的土柱有利于柴油向下迁移，但不利于其自然降解。然而，降水使多种流体（水、空气和柴油）通过孔隙网络的相对传导率变得复杂，从而降低了柴油的迁移和降解。例如，在降水条件下，SL柱中柴油的向下迁移减少了8.4%，而总体衰减率降至其原始状态的近0.24%。然而，降低容重（从1.5降至1.23 g/cm³）可能会提高衰减率，这大概是由于为进入的流体提供了有保障的孔隙空间。高初始柴油浓度（2%；w/w）抑制了其自然衰减，但其对降水后垂直传播的影响并不显著。本研究结果为估算石油烃在随机包气带中的行为提供了一个机理基础。
