Eweis Juana B, Labolle Eric M, Benson David A, Fogg Graham E
E.L. Hydrologic Associates, Davis, California 95616, USA.
Environ Sci Technol. 2007 Oct 1;41(19):6822-7. doi: 10.1021/es071250j.
Tertiary butyl alcohol (TBA) is commonly found as an impurity in methyl tertiary butyl ether (MTBE) added to gasoline. Frequent observations of high TBA, and especially rising TBA/MTBE concentration ratios, in groundwater at gasoline spill sites are generally attributed to microbial conversion of MTBE to TBA. Typically overlooked is the role of volatilization in the attenuation of these chemicals especially in the vadose zone, which is a source of contamination to groundwater. Here we show that volatilization, particularly through remediation by vapor extraction, can substantially affect the trends in TBA and MTBE concentrations and the respective mass available to impact groundwater aquifers, through the preferential removal of more volatile compounds, including MTBE, and the apparent enrichment of less volatile compounds like TBA. We demonstrate this phenomenon through numerical simulations of remedial-enhanced volatilization. Results show increases in TBA/MTBE concentration ratios consistent with ratios observed in groundwater at gasoline spill sites. Volatilization is an important, and potentially dominant, process that can result in concentration trends similar to those typically attributed to biodegradation.
叔丁醇（TBA）通常作为杂质存在于添加到汽油中的甲基叔丁基醚（MTBE）中。在汽油泄漏场地的地下水中，经常观察到高浓度的TBA，尤其是TBA/MTBE浓度比不断上升，这通常归因于MTBE被微生物转化为TBA。通常被忽视的是挥发作用在这些化学物质衰减过程中的作用，特别是在包气带中，而包气带是地下水污染的一个来源。在此我们表明，挥发作用，尤其是通过蒸汽抽提修复，可通过优先去除挥发性更强的化合物（包括MTBE）以及使挥发性较弱的化合物（如TBA）明显富集，从而极大地影响TBA和MTBE的浓度趋势以及影响地下水含水层的各自质量。我们通过修复增强挥发的数值模拟来证明这一现象。结果表明，TBA/MTBE浓度比增加，与在汽油泄漏场地地下水中观察到的比值一致。挥发是一个重要且可能占主导地位的过程，它可导致与通常归因于生物降解的浓度趋势相似的结果。
