Mahieu Koenraad, De Visscher Alex, Vanrolleghem Peter A, Van Cleemput Oswald
Laboratory of Applied Physical Chemistry ISOFYS, Ghent University, Coupure links 653, Ghent, Belgium.
Waste Manag. 2008;28(9):1535-42. doi: 10.1016/j.wasman.2007.06.003. Epub 2007 Sep 6.
A technique to measure biological methane oxidation in landfill cover soils that is gaining increased interest is the measurement of stable isotope fractionation in the methane. Usually to quantify methane oxidation, only fractionation by oxidation is taken into account. Recently it was shown that neglecting the isotope fractionation by diffusion results in underestimation of the methane oxidation. In this study a simulation model was developed that describes gas transport and methane oxidation in landfill cover soils. The model distinguishes between 12CH4, 13CH4, and 12CH3D explicitly, and includes isotope fractionation by diffusion and oxidation. To evaluate the model, the simulations were compared with column experiments from previous studies. The predicted concentration profiles and isotopic profiles match the measured ones very well, with a root mean square deviation (RMSD) of 1.7 vol% in the concentration and a RMSD of 0.8 per thousand in the delta13C value, with delta13C the relative 13C abundance as compared to an international standard. Overall, the comparison shows that a model-based isotope approach for the determination of methane oxidation efficiencies is feasible and superior to existing isotope methods.
一种用于测量垃圾填埋场覆盖土壤中生物甲烷氧化的技术正越来越受到关注，即测量甲烷中的稳定同位素分馏。通常为了量化甲烷氧化，只考虑氧化引起的分馏。最近研究表明，忽略扩散引起的同位素分馏会导致对甲烷氧化的低估。在本研究中，开发了一个模拟模型来描述垃圾填埋场覆盖土壤中的气体传输和甲烷氧化。该模型明确区分了(^{12}CH_4)、(^{13}CH_4)和(^{12}CH_3D)，并包括扩散和氧化引起的同位素分馏。为了评估该模型，将模拟结果与先前研究的柱实验进行了比较。预测的浓度分布和同位素分布与测量结果非常吻合，浓度的均方根偏差（RMSD）为(1.7)体积%，(\delta^{13}C)值的RMSD为(0.8‰)，其中(\delta^{13}C)是相对于国际标准的(^{13}C)相对丰度。总体而言，比较表明基于模型的同位素方法用于确定甲烷氧化效率是可行的，并且优于现有的同位素方法。
