细菌密度对微生物诱导的CaCO3沉淀物生长速率和特性影响的颗粒尺度实验研究
Effects of bacterial density on growth rate and characteristics of microbial-induced CaCO3 precipitates: a particle-scale experimental study
摘要：
微生物诱导碳酸盐沉淀（Microbial-Induced Carbonate Precipitation，MICP）作为一种有前途的土壤改良技术已经被探索了十多年。然而，它仍然是具有挑战性的预测和控制的CaCO 3沉淀的生长速度和特性，这直接影响到MICP处理的土壤的工程性能。在这项研究中，我们采用了基于微流体的孔隙尺度模型，观察细菌密度的影响，在MICP过程中发生在砂粒尺度的碳酸钙沉淀物的生长速率和特性。结果表明，在0.6e8 ~ 5.2e8个/ml细菌浓度范围内，CaCO_3沉淀率随细菌浓度的增加而增加。细菌密度也影响CaCO 3晶体的大小和数量。0.6e8个细胞/ml的低细菌密度产生1.1e6个晶体/ml，平均晶体体积为8，000 μ m 3，而5.2e8个细胞/ml的高细菌密度产生更多晶体（2.0e7个晶体/ml），但平均晶体体积较小，为450 μ m 3。当菌体密度为0.6e8个/ml时，所产生的碳酸钙晶体稳定。当细菌密度高4-10倍时，晶体首先不稳定，然后转化为更稳定的CaCO 3晶体。这表明细菌密度应该是设计MICP方案时的重要考虑因素。
英文摘要：
Microbial-Induced Carbonate Precipitation (MICP) has been explored for more than a decade as a promising soil improvement technique. However, it is still challenging to predict and control the growth rate and characteristics of CaCO3 precipitates, which directly affect the engineering performance of MICP-treated soils. In this study, we employ a microfluidics-based pore scale model to observe the effect of bacterial density on the growth rate and characteristics of CaCO3 precipitates during MICP processes occurring at the sand particle scale. Results show that the precipitation rate of CaCO3 increases with bacterial density in the range between 0.6e8 and 5.2e8 cells/ml. Bacterial density also affects both the size and number of CaCO3 crystals. A low bacterial density of 0.6e8 cells/ml produced 1.1e6 crystals/ml with an average crystal volume of 8,000 um3, whereas a high bacterial density of 5.2e8 cells/ml resulted in more crystals (2.0e7 crystals/ml) but with a smaller average crystal volume of 450 um3. The produced CaCO3 crystals were stable when the bacterial density was 0.6e8 cells/ml. When the bacterial density was 4-10 times higher, the crystals were first unstable and then transformed into more stable CaCO3 crystals. This suggests that bacterial density should be an important consideration in the design of MICP protocols.
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