## Materials and Methods
### Experimental Study on Dynamic Adsorption Characteristics of Solute  
The bacterial and cementation solutions used in MICP technology are the solutes migrated in the second confined aquifer sand layer in Shanghai. At present, the process of solute adsorption is mostly described by the isothermal adsorption curve and equation, but isothermal adsorption can only describe the solute in the adsorption equilibrium and not the adsorption speed or the adsorption equilibrium process [23]. Meanwhile, when the MICP technology is used to form the HSRB, water flow is involved, and the solute is in a state of motion [38]. Therefore, the kinetics of the solute adsorption process must be studied by using the silty fine sand from layer 1 of Shanghai collected from the No. 4 well to determine the solute adsorption process and the time required to reach the adsorption equilibrium. (1) Adsorption kinetics of _S. pasteurii_  
In a 20 mL centrifuge tube, 5 g of Shanghai layer 1 fine sand and 10 mL of _S. pasteurii_ with OD\({}_{600}\) = 0.8 were added. In addition to the actual working conditions of the site, the test environment temperature was set at 20 \({}^{\circ}\)C and the sample was oscillated at 200 rpm. To determine the adsorption characteristics of _S. pasteurii_ with time, the oscillation time gradient was set to 0, 20, 40, 60, 80, 100, and 120 min. After shaking, the tube was taken out and left to stand for 2 h to determine the concentration of the bacteria in the supernatant. To reduce the test error, triplicate samples were taken at each point and the average value was represented as the final one. Meanwhile, to eliminate the influence of the wall of the centrifuge tube on the adsorption of the bacterial solution, a centrifuge tube with only 10 mL of bacterial solution was set as the blank control group. The _S. pasteurii_ adsorption ratio (\(\gamma_{a}\)) of Shanghai layer 1 fine sand was defined and calculated using the following formula:  
\[\gamma_{a}=\frac{c_{0}-c_{t}}{c_{0}}\times 100\% \tag{1}\]  
where \(\gamma_{a}\) is the adsorption rate of _S. pasteurii_, %; \(c_{0}\) is the initial concentration of _S. pasteurii_, cfu/mL; and \(c_{t}\) is the equilibrium concentration of _S. pasteurii_ adsorbed by layer 1 fine sand from Shanghai after different times, cfu/mL. The below Formula (2) was utilized to convert the OD value (UV spectrophotometer) of the microbes into the cell concentration (cells/mL) [39]. \[Y=8.59\times 10^{7}Z^{1.3627}, \tag{2}\]  
where \(Z\) is the OD\({}_{600}\) value, and \(Y\) is the cell concentration (cells ML\({}^{-1}\)). When using this formula for conversion, OD\({}_{600}\) must be in the range of 0.2-0.8. When the OD\({}_{600}\) value exceeds this range, it needs to be diluted before conversion. The mass concentration of _S. pasteurii_ is an important parameter for the analysis of bacterial migration in aquifers, so it was necessary to design a test to determine the mass concentration of the _S. pasteurii_ solution. Forty-five mL of the bacterial solution with OD\({}_{600}\) values of 0.4, 0.6, 0.8, 1.0, and 1.2 were, respectively, added into 50 mL centrifuge tubes and centrifuged in the centrifuge at a speed of 13,000 r/min for 30 min. After centrifugation, the supernatant was removed to obtain _S. pasteurii_. To reduce the error, triplicate samples were taken for each OD\({}_{600}\) value, and the average value was considered as the final one. The mass \(m_{\mathrm{s}}\) corresponding to each OD\({}_{600}\) value of _S. pasteurii_ was calculated by \(m_{\mathrm{s}}=m_{2}-m_{1}\), where \(m_{1}\) was the mass of the centrifuge tube dried before centrifugation, and \(m_{2}\) was the mass of the centrifuge tube containing bacteria with the supernatant removed after centrifugation and dried in the even at 105 \({}^{\circ}\)C. The mass concentration of _S. pasteurii_ was obtained by dividing the mass of _S. pasteurii_ by the corresponding volume.