Chemical and Materials Sciences Division, Fundamental and Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, Washington, USA.
Environ Sci Technol. 2010 Apr 15;44(8):3085-92. doi: 10.1021/es903396h.
Microbial degradation of contaminants in the subsurface requires the availability of nutrients; this is impacted by porous media heterogeneity and the degree of transverse mixing. Two types of microfluidic pore structures etched into silicon wafers (i.e., micromodels), (i) a homogeneous distribution of cylindrical posts and (ii) aggregates of large and small cylindrical posts, were used to evaluate the impact of heterogeneity on growth of a pure culture (Delftia acidovorans) that degrades (R)-2-(2,4-dichlorophenoxy)propionate (R-2,4-DP). Following inoculation, dissolved O2 and R-2,4-DP were introduced as two parallel streams that mixed transverse to the direction of flow. In the homogeneous micromodel, biomass growth was uniform in pore bodies along the center mixing line, while in the aggregate micromodel, preferential growth occurred between aggregates and slower less dense growth occurred throughout aggregates along the center mixing line. The homogeneous micromodel had more rapid growth overall (2 times) and more R-2,4-DP degradation (9.5%) than the aggregate pore structure (5.7%). Simulation results from a pore-scale reactive transport model indicate mass transfer limitations within aggregates along the center mixing line decreased overall reaction; hence, slower biomass growth rates relative to the homogeneous micromodel are expected. Results from this study contribute to a better understanding of the coupling between mass transfer, reaction rates, and biomass growth in complex porous media and suggest successful implementation and analysis of bioremediation systems requires knowledge of subsurface heterogeneity.
微生物对地下污染物的降解需要营养物质的可用性；这受到多孔介质的非均质性和横向混合程度的影响。两种类型的微流控硅晶片刻蚀孔结构（即微模型），（i）圆柱柱体的均匀分布和（ii）大圆柱柱体和小圆柱柱体的聚集，被用来评估非均质性对纯培养物（Delftia acidovorans）生长的影响，该纯培养物降解（R）-2-（2,4-二氯苯氧基）丙酸（R-2,4-DP）。接种后，溶解的 O2 和 R-2,4-DP 作为两条平行流引入，在横向于流动方向混合。在均匀的微模型中，生物质在中心混合线的孔体中均匀生长，而在聚集微模型中，在聚集物之间发生优先生长，而在沿中心混合线的聚集物中发生较慢且较稀疏的生长。总的来说，均匀的微模型具有更快的生长速度（2 倍）和更多的 R-2,4-DP 降解（9.5%），而聚集孔结构的降解速度（5.7%）更慢。来自孔尺度反应传输模型的模拟结果表明，沿中心混合线的聚集物内部的传质限制降低了整体反应；因此，与均匀微模型相比，生物量生长速度较慢。这项研究的结果有助于更好地理解复杂多孔介质中传质、反应速率和生物量生长之间的耦合，并表明成功实施和分析生物修复系统需要了解地下非均质性。
