Geoscience Research and Applications, Sandia National Laboratories , Albuquerque, New Mexico 87185, United States.
Civil, Architectural and Environmental Engineering, University of Texas at Austin , Austin, Texas 78712, United States.
Environ Sci Technol. 2015 Oct 20;49(20):12094-104. doi: 10.1021/acs.est.5b00152. Epub 2015 Oct 5.
The ability of Pseudomonas stutzeri strain DCP-Ps1 to drive CaCO3 biomineralization has been investigated in a microfluidic flowcell (i.e., micromodel) that simulates subsurface porous media. Results indicate that CaCO3 precipitation occurs during NO3(-) reduction with a maximum saturation index (SIcalcite) of ∼1.56, but not when NO3(-) was removed, inactive biomass remained, and pH and alkalinity were adjusted to SIcalcite ∼ 1.56. CaCO3 precipitation was promoted by metabolically active cultures of strain DCP-Ps1, which at similar values of SIcalcite, have a more negative surface charge than inactive strain DCP-Ps1. A two-stage NO3(-) reduction (NO3(-) → NO2(-) → N2) pore-scale reactive transport model was used to evaluate denitrification kinetics, which was observed in the micromodel as upper (NO3(-) reduction) and lower (NO2(-) reduction) horizontal zones of biomass growth with CaCO3 precipitation exclusively in the lower zone. Model results are consistent with two biomass growth regions and indicate that precipitation occurred in the lower zone because the largest increase in pH and alkalinity is associated with NO2(-) reduction. CaCO3 precipitates typically occupied the entire vertical depth of pores and impacted porosity, permeability, and flow. This study provides a framework for incorporating microbial activity in biogeochemistry models, which often base biomineralization only on SI (caused by biotic or abiotic reactions) and, thereby, underpredict the extent of this complex process. These results have wide-ranging implications for understanding reactive transport in relevance to groundwater remediation, CO2 sequestration, and enhanced oil recovery.
已在模拟地下多孔介质的微流控流动池（即微模型）中研究了施氏假单胞菌 DCP-Ps1 菌株驱动 CaCO3 生物矿化的能力。结果表明，在硝酸盐（NO3(-)）还原过程中会发生 CaCO3 沉淀，最大饱和指数（SIcalcite）约为 1.56，但当去除 NO3(-)、保持无活性生物量以及将 pH 值和碱度调节至 SIcalcite 约 1.56 时则不会发生 CaCO3 沉淀。代谢活跃的 DCP-Ps1 菌株培养物促进了 CaCO3 沉淀，在相似的 SIcalcite 值下，其表面电荷比无活性的 DCP-Ps1 菌株更负。采用两阶段硝酸盐（NO3(-) → NO2(-) → N2）还原的孔隙尺度反应传输模型来评估反硝化动力学，在微模型中，反硝化动力学表现为上部（NO3(-)还原）和下部（NO2(-)还原）生物量生长的水平带，而仅在下部区域观察到 CaCO3 沉淀。模型结果与两个生物量生长区一致，并表明沉淀发生在下部区域，因为 pH 值和碱度的最大增加与 NO2(-)还原有关。CaCO3 沉淀物通常占据孔隙的整个垂直深度，并影响孔隙度、渗透率和流量。本研究为在生物地球化学模型中纳入微生物活性提供了一个框架，生物地球化学模型通常仅基于 SI（由生物或非生物反应引起）来预测生物矿化，从而低估了这一复杂过程的程度。这些结果对理解与地下水修复、CO2 封存和提高石油采收率有关的反应传输具有广泛的意义。
