Department of Computational Hydrosystems, UFZ-Hlelmholtz Centre for Environmental Research, Leipzig, Germany.
Environ Sci Technol. 2010 Mar 15;44(6):2064-71. doi: 10.1021/es902489q.
Reactive transport simulations are a common approach for the quantitative assessment of contaminant biodegradation in the subsurface. To use knowledge on microbial kinetics for the simulation of in situ biodegradation, the mass transfer processes controlling the bioavailability of the contaminants need to be described appropriately. A common approach to account for this problem is using a linear exchange model controlling the link between bulk and bioavailable concentration. Assuming that the subsequent degradation is controlled by the bioavailable concentration, only, these two steps can be combined to an analytical expression for the overall reaction rate know as the Best-Equation. In our work, we evaluate this approach for its ability to describe biodegradation kinetics limited by pore-scale mass transfer. Results from explicit numerical and analytical simulations of mass transport and reactive consumption at the pore scale are used to test the accuracy of results obtained using the Best-Equation. Our analysis shows that strictly spoken the Best-Equation is not valid. However, a good approximation can be achieved with errors of less than 6% in cases of moderate bioavailability and much lower errors in cases of either low or high bioavailability. These results support the description of mass transfer processes used in many reactive transport models. Furthermore, we present a method to obtain an accurate estimate of the unknown rate parameter controlling the diffusive mass transfer processes at the pore scale.
反应迁移模拟是定量评估地下环境中污染物生物降解的常用方法。为了在模拟原位生物降解时利用微生物动力学知识，需要适当描述控制污染物生物可利用性的传质过程。解决此问题的常用方法是使用线性交换模型来控制体相和生物可利用浓度之间的联系。假设随后的降解仅受生物可利用浓度控制，这两个步骤可以组合成一个整体反应速率的解析表达式，称为最佳方程。在我们的工作中，我们评估了该方法在描述受孔尺度传质限制的生物降解动力学方面的能力。使用显式数值和分析模拟在孔尺度上的传质和反应消耗的结果来测试使用最佳方程获得的结果的准确性。我们的分析表明，严格来说，最佳方程并不成立。但是，在生物可利用性适中的情况下，可以达到小于 6%的误差的良好近似值，而在生物可利用性较低或较高的情况下，误差要小得多。这些结果支持了许多反应迁移模型中使用的传质过程描述。此外，我们提出了一种方法，可以准确估计控制孔尺度扩散传质过程的未知速率参数。
