Núcleo Ressacada de Pesquisas Em Meio Ambiente (REMA) - Department of Sanitary and Environmental Engineering, Federal University of Santa Catarina (UFSC), Campus Universitário Sul da Ilha - Rua José Olímpio da Silva, 1326 - Bairro Tapera, 88049-500 Florianópolis, SC, Brazil.
J Contam Hydrol. 2019 Apr;222:17-30. doi: 10.1016/j.jconhyd.2019.01.003. Epub 2019 Jan 11.
Gasohol spills may easily descend through the soil column down and impact sensitive receptors as contaminants dissolve into the groundwater. Gasoline formulations are commonly blended with ethanol to alleviate environmental and economic issues associated with fossil fuels. However, the amount of ethanol added to gasoline and the groundwater hydraulic regime can significantly affect BTEX plume dynamics and lifespan. In this study, two long-term (5 and 10 years) field-scale gasohol releases with ethanol contents of 85% (E85) and 24% (E24), respectively, were assessed to discern the different dynamics undergone by gasohol blends. Statistical, geochemical, microbiological and trend approaches were employed to estimate the influence of groundwater flow variations on ethanol and dissolved BTEX transport, and the associated biodegradation rates of different gasohol blend spills. Ethanol and BTEX groundwater flow were quantified in terms of breakthrough curve characteristics, plume centroid positions and spreading, source depletion and mass degradation rates. In addition, bromide migration was evaluated to address the contribution of flow-driven dissolution. Results revealed that the high amount of ethanol along with a fast and dynamic flow exerted a flushing behavior that enhanced BTEX dissolution, migration (vertical and horizontal) and concentrations in groundwater. The higher amount of ethanol in E85 enhanced BTEX dissolution (and bioavailability) relative to E24 site and led to faster biodegradation rates, which can be explained by the cosolvency effect and metabolic flux dilution. Therefore, flow field dynamics and high ethanol content in gasohol blends enhance BTEX migration and biodegradation in gasohol-contaminated sites. The balance of these factors is crucial to determine fate and transport of contaminants in field sites. These findings suggest that hydraulic regime should be spatially and temporally characterized to support decisions on appropriate monitoring plan and remedial strategies for gasohol spills.
乙醇汽油泄漏可能很容易沿着土壤柱向下渗透，并随着污染物溶解到地下水中而对敏感受体造成影响。为了缓解与化石燃料相关的环境和经济问题，通常将乙醇与汽油混合制成乙醇汽油。然而，加入汽油中的乙醇量和地下水水力条件会显著影响 BTEX 羽流的动态变化和寿命。在这项研究中，评估了两个长期（5 年和 10 年）野外尺度的乙醇汽油泄漏，乙醇含量分别为 85%（E85）和 24%（E24），以区分不同乙醇汽油混合物经历的不同动态变化。采用统计、地球化学、微生物学和趋势方法来估计地下水流动变化对乙醇和溶解 BTEX 运移的影响，以及不同乙醇汽油混合物泄漏的相关生物降解率。以突破曲线特征、羽流质心位置和扩散、源耗竭和质量降解率来量化乙醇和 BTEX 地下水流动。此外，评估了溴化物迁移以解决流动驱动溶解的贡献。结果表明，大量的乙醇以及快速和动态的流动会产生冲洗作用，从而增强 BTEX 的溶解、迁移（垂直和水平）以及地下水中的浓度。E85 中较高的乙醇含量增强了 BTEX 的溶解（和生物利用度），与 E24 点相比，导致更快的生物降解率，这可以通过共溶剂效应和代谢通量稀释来解释。因此，混合汽油中的流动场动态和高乙醇含量会增强混合汽油污染场地中 BTEX 的迁移和生物降解。这些因素的平衡对于确定现场污染物的归宿和运移至关重要。这些发现表明，应从空间和时间上对水力条件进行表征，以支持针对乙醇汽油泄漏的适当监测计划和补救策略的决策。
