Ruiz-Aguilar Graciela M L, Fernandez-Sanchez Jose M, Kane Staci R, Kim Donguk, Alvarez Pedro J J
Department of Civil and Environmental Engineering, University of Iowa, 4119 Seamans Center, Iowa City, Iowa 52245, USA.
Environ Toxicol Chem. 2002 Dec;21(12):2631-9.
Aquifer microcosms were used to determine how ethanol and methyl-tert-butyl ether (MtBE) affect monoaromatic hydrocarbon degradation under different electron-accepting conditions commonly found in contaminated sites experiencing natural attenuation. Response variability was investigated by using aquifer material from four sites with different exposure history. The lag phase prior to benzene, toluene, ethylbenzene, and xylenes (BTEX) and ethanol degradation was typically shorter in microcosms with previously contaminated aquifer material, although previous exposure did not always result in high degradation activity. Toluene was degraded in all aquifer materials and generally under a broader range of electron-accepting conditions compared to benzene, which was degraded only under aerobic conditions. The MtBE was not degraded within 100 d under any condition, and it did not affect BTEX or ethanol degradation patterns. Ethanol was often degraded before BTEX compounds and had a variable effect on BTEX degradation as a function of electron-accepting conditions and aquifer material source. An occasional enhancement of toluene degradation by ethanol occurred in denitrifying microcosms with unlimited nitrate; this may be attributable to the fortuitous growth of toluene-degrading bacteria during ethanol degradation. Nevertheless, experiments with flow-through aquifer columns showed that this beneficial effect could be eclipsed by an ethanol-driven depletion of electron acceptors, which significantly inhibited BTEX degradation and is probably the most important mechanism by which ethanol could hinder BTEX natural attenuation. A decrease in natural attenuation could increase the likelihood that BTEX compounds reach a receptor as well as the potential duration of exposure.
含水层微观模型被用于确定乙醇和甲基叔丁基醚（MtBE）如何在经历自然衰减的受污染场地常见的不同电子受体条件下影响单环芳烃的降解。通过使用来自四个具有不同暴露历史场地的含水层材料来研究响应变异性。在含有先前受污染含水层材料的微观模型中，苯、甲苯、乙苯和二甲苯（BTEX）以及乙醇降解之前的滞后期通常较短，尽管先前的暴露并不总是导致高降解活性。与仅在好氧条件下才降解的苯相比，甲苯在所有含水层材料中都能降解，并且通常在更广泛的电子受体条件下进行。在任何条件下，MtBE在100天内都不会降解，并且它不影响BTEX或乙醇的降解模式。乙醇通常在BTEX化合物之前降解，并且作为电子受体条件和含水层材料来源的函数，它对BTEX降解具有可变的影响。在硝酸盐无限的反硝化微观模型中，乙醇偶尔会促进甲苯的降解；这可能归因于乙醇降解过程中甲苯降解细菌的偶然生长。然而，通过流通式含水层柱进行的实验表明，这种有益效果可能会被乙醇驱动的电子受体消耗所抵消，这会显著抑制BTEX的降解，并且这可能是乙醇阻碍BTEX自然衰减的最重要机制。自然衰减的降低可能会增加BTEX化合物到达受体的可能性以及潜在的暴露持续时间。
