Bauer Robert D, Maloszewski Piotr, Zhang Yanchun, Meckenstock Rainer U, Griebler Christian
Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Groundwater Ecology, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany.
J Contam Hydrol. 2008 Feb 19;96(1-4):150-68. doi: 10.1016/j.jconhyd.2007.10.008. Epub 2007 Nov 17.
Various abiotic and biotic processes such as sorption, dilution, and degradation are known to affect the fate of organic contaminants, such as petroleum hydrocarbons in saturated porous media. Reactive transport modeling of such plumes indicates that the biodegradation of organic pollutants is, in many cases, controlled by mixing and therefore occurs locally at the plume's fringes, where electron donors and electron-acceptors mix. Herein, we aim to test whether this hypothesis can be verified by experimental results obtained from aerobic and anaerobic degradation experiments in two-dimensional sediment microcosms. Toluene was selected as a model compound for oxidizable contaminants. The two-dimensional microcosm was filled with quartz sand and operated under controlled flow conditions simulating a contaminant plume in otherwise uncontaminated groundwater. Aerobic degradation of toluene by Pseudomonas putida mt-2 reduced a continuous 8.7 mg L(-1) toluene concentration by 35% over a transport distance of 78 cm in 15.5 h. In comparison, under similar conditions Aromatoleum aromaticum strain EbN1 degraded 98% of the toluene infiltrated using nitrate (68.5+/-6.2 mg L(-1)) as electron acceptor. A major part of the biodegradation activity was located at the plume fringes and the slope of the electron-acceptor gradient was steeper during periods of active biodegradation. The distribution of toluene and the significant overlap of nitrate at the plume's fringe indicate that biokinetic and/or microscale transport processes may constitute additional limiting factors. Experimental data is corroborated with results from a reactive transport model using double Monod kinetics. The outcome of the study shows that in order to simulate degradation in contaminant plumes, detailed data sets are required to test the applicability of models. These will have to deal with the incorporation of existing parameters coding for substrate conversion kinetics and microbial growth.
诸如吸附、稀释和降解等各种非生物和生物过程会影响有机污染物的归宿，例如饱和多孔介质中的石油烃。此类羽流的反应性输运模型表明，在许多情况下，有机污染物的生物降解受混合作用控制，因此发生在羽流边缘的局部区域，即电子供体和电子受体混合的地方。在此，我们旨在检验这一假设是否能通过二维沉积物微观世界中需氧和厌氧降解实验获得的实验结果得到验证。选择甲苯作为可氧化污染物的模型化合物。二维微观世界填充有石英砂，并在模拟未受污染地下水中污染物羽流的受控流动条件下运行。恶臭假单胞菌mt-2对甲苯的需氧降解在15.5小时内使连续8.7毫克/升的甲苯浓度在78厘米的输运距离内降低了35%。相比之下，在类似条件下，芳香烃油杆菌菌株EbN1以硝酸盐（68.5±6.2毫克/升）作为电子受体，降解了98%渗入的甲苯。生物降解活性的主要部分位于羽流边缘，在活跃生物降解期间电子受体梯度的斜率更陡。甲苯的分布以及羽流边缘硝酸盐的显著重叠表明，生物动力学和/或微观尺度输运过程可能构成额外的限制因素。实验数据与使用双莫诺德动力学的反应性输运模型的结果相佐证。研究结果表明，为了模拟污染物羽流中的降解，需要详细的数据集来测试模型的适用性。这些数据集将必须处理编码底物转化动力学和微生物生长现有参数的纳入问题。
