Controlling soil hydraulic conductivity with the control of microbial activity

这项研究的目的是开发一种技术，通过增加或减少土壤中的微生物来控制土壤的透水性到所需的值。在模型试验中，测量了不同直径玻璃微珠的水力传导性变化。颗粒直径越小，上层渗透系数下降越快，因为营养物质主要在上层消耗，导致下层营养物质较少。在北海道地区碧柏泥炭地的现场测量中，细菌产生的甲烷气体积累在地下。为了模拟这一产甲烷过程，进行了实验室立柱实验。地下水位降低10 cm时，渗流开始后第6天，5 cm深度处的氧化还原电位降至-150 mV以下。结果，观测到大量甲烷排放到大气中。根据上述试验结果和现场测试结果，建立了微生物活动降低土壤导水率的数学模型。颗粒直径的不同会影响微生物的生长速度，并用该模型解释了菌落形成现象。

This research aims at developing a technique to control water permeability of soils to required values by multiplying the microbe in soil or making it decrease. In a model experiment, hydraulic conductivity changes of the glass beads of different diameters were measured. Hydraulic conductivity at the upper layer decreased more rapidly for smaller particle diameter beads, because the nutrient was mainly consumed at the upper layer resulting in less nutrient at the lower layer. In on-site measurement at Bibai peatland in Hokkaido District, methane gas produced by bacteria is accumulated in the ground. To simulate this methane producing process, a laboratory column experiment was conducted. When the groundwater level was lowered by 10cm, the redox potential at the 5cm depth decreased to less than -150mV at 6 day after the start of percolation. As a result, a lot of methane emission into the atmosphere was observed. Based on the result of the above experiment and on-site measurement a mathematical model explaining the hydraulic conductivity decrease by microbial activity was built. The difference in particle diameter influences microbial growth rate and a colony formation phenomenon was expalined by this model.