Indoor monitoring method and system for underground solute or colloid migration

Abstract

The invention discloses an indoor monitoring method and system for underground solute or colloid migration, and the method comprises the steps: decoupling a complex conductivity spectrum through a Cole-Cole model, building a quantitative mapping relation between the complex conductivity spectrum and the distribution of solutes or colloids in different time-space and different phase states output by a one-dimensional convection-dispersion equation, and carrying out the indoor monitoring of the underground solute or colloid migration. A regulation and control mechanism of solute or colloid adsorption kinetics on an interface polarization effect can be disclosed; according to the invention, indoor simulation experiments of underground solute or colloid migration under various hydrological conditions can be realized, geoelectric response is associated with specific changes of underground solute or colloid in physical and biogeochemical processes, and an underground solute or colloid migration monitoring method with micro-intervention, real-time monitoring and spatial linear continuous measurement is provided. The solute or colloid migration process is transparentized, and the cost is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil and groundwater pollution remediation, in particular to an indoor monitoring method and system for underground solute or colloid transport. BACKGROUND

[0002] Geophysical methods are methods for detecting the internal structure and distribution of geological bodies of the earth by studying geophysical fields such as gravity field, magnetic field, electric field, seismic wave field, etc. It is based on the principle of physics, uses various instruments to measure the changes of geophysical field, and then analyzes and interprets these measured data to infer the underground geological structure, rock-soil properties, mineral resources distribution and other information. Compared with the traditional drilling method for exploring the characteristics and state of underground system, geophysical methods have the characteristics of micro-intervention, real-time monitoring, spatial linear continuous measurement and cost-effectiveness. Geophysical methods can be used in geoscience, environmental science and agricultural science to characterize underground properties. At present, it is more commonly used in oil and gas and mineral exploration, but its application in soil and groundwater pollution remediation is relatively lacking. Among them, the monitoring of underground transport behavior of solute or colloid has always been a heavy and difficult point due to the difficulty of sampling and spatial and temporal discontinuity, as well as the hysteresis of testing.

[0003] The frequency spectrum induced polarization method in geophysical methods injects alternating current into the target porous medium, and obtains the geophysical signal caused by the porous medium according to the different space-time conductivity and polarization effect in the porous medium, which has high sensitivity and high selectivity. Compared with the traditional direct current resistivity method, the frequency spectrum induced polarization method can provide additional information about the change of multi-phase interface. This method has been proved to be sensitive to underground solute or colloid-mediated processes, but there are still some problems: first, the dynamic monitoring is insufficient: there is a lack of real-time capture of the spatio-temporal transport law of solute or colloid under various hydrological conditions by using the frequency spectrum induced polarization method. Second, the mechanism correlation is missing: the frequency spectrum induced polarization method is difficult to link the geoelectric response to specific changes in the physical and biogeochemical processes of underground solute or colloid. SUMMARY

[0004] In view of the problems existing in the prior art, the present application provides an indoor monitoring method and system for underground solute or colloid transport, which can simulate various hydrological conditions, establish the correlation mechanism between soil geoelectric properties and macroscopic transport process, and realize the spatio-temporal positioning of underground solute or colloid transport location by analyzing the frequency spectrum characteristic differences of different space-time complex conductivity signals.

[0005] The technical scheme of the present application is as follows: In the first aspect of the present application, an indoor monitoring method for underground solute or colloid transport is provided, comprising the following steps: Step one, building an indoor experimental device to obtain the geometric factor of the experimental device; Step 2: Fill the experimental device with soil from the target detection area, and then pre-wash it from bottom to top with a salt solution that does not contain the target solute or colloid to obtain the soil porosity, dispersion coefficient, geoelectric signal background value and chemical content background value in the effluent of the target detection area. Step 3: Inject solutes or colloids into the experimental device to simulate the dynamic process of solutes or colloids being injected into the soil saturation zone or vadose zone of the target detection area, and obtain the concentration data of solutes or colloids in the effluent of the target detection area, as well as geoelectric signal data at different times and locations. Step 4: Based on the dispersion coefficient obtained in Step 2 and the concentration data of solute or colloid in the effluent obtained in Step 3, a one-dimensional convection-dispersion equation is used to fit the transport of solute or colloid in the target detection area, invert the transport characteristic parameters, and then deduce the concentration of solute or colloid in the liquid and solid phases at different times at the location monitored by the geoelectric signal. Step 5: Calculate the complex conductivity signal value based on the geometric factors of the experimental setup and the geoelectric signal data; and obtain the Cole-Cole model characteristic parameters by fitting the complex conductivity signal value through the Cole-Cole model, which characterizes the spectral characteristics of the complex conductivity. Step 6: By analyzing the statistical correlation between the concentration of solute or colloid in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, the geoelectric signal and the chemical content in the effluent during pre-rinsing and solute or colloid injection are compared to obtain the transport characteristics of solute or colloid.

[0006] In some embodiments of the present invention, the experimental apparatus adopts a cylindrical structure with the cylinder arranged vertically. The top and bottom of the cylinder are provided with openings, and multiple pairs of measuring electrodes are provided on the side of the cylinder. The multiple pairs of measuring electrodes are arranged at equal intervals along the axial direction of the cylinder, and each pair of measuring electrodes is connected to a spectrum excitation polarization instrument through a wire.

[0007] In some embodiments of the present invention, the geometric factors of the experimental apparatus are obtained in the following manner: A solution with known conductivity was injected into the experimental apparatus using a peristaltic pump, and the complex impedance of the solution was determined by spectral excitation polarization. The geometric factor of the experimental apparatus was then calculated using the following formula:

[0008] Where G represents the geometric factor, m -1 ; Z represents the complex conductivity, S / m; Z represents the measured complex impedance, Ω.

[0009] In some embodiments of the present invention, the soil porosity, dispersion coefficient, geoelectric signal background value, and chemical substance content background value in the effluent of the target detection area are obtained by the following methods: Soil was filled into the target detection area of ​​the experimental device. A salt solution without target solutes or colloids was injected into the soil column from bottom to top using a peristaltic pump as a pre-flushing fluid. The pre-flushing fluid discharged from the soil column was collected, and the influent and effluent mass was measured. After the soil column was saturated, the pore volume of the soil column was calculated to obtain the soil porosity. The injection of pre-flushing fluid continued until the conductivity of the influent and effluent was balanced. The concentration of tracer in the pre-flushing fluid at different times was inverted using a one-dimensional convection-dispersion equation to obtain the dispersion coefficient. After the conductivity of the influent and effluent was balanced, 10 times the pore volume of the soil column of pre-flushing fluid was injected. During the entire pre-flushing process, the background value of the geoelectric signal was obtained by continuously measuring multiple frequencies in the range of 0.01-10000 Hz using a spectrum excitation polarization instrument with multiple pairs of measuring electrodes. The chemical content in the effluent was measured using an analytical instrument as the background value of the chemical content in the effluent. In some embodiments of the present invention, when simulating the dynamic process of injecting solutes or colloids into the soil saturation zone of the target detection area, the transport concentration data and geoelectric signal data after the injection of solutes or colloids are obtained in the following ways: A peristaltic pump is used to inject a solute or colloidal suspension into the soil column from bottom to top. An automatic partial collector is used to collect the solute or colloidal suspension discharged from the soil column and measure its mass. At the same time, a spectrum excitation polarization instrument is used to continuously measure geoelectric signal data at multiple frequencies in the range of 0.01-10000 Hz through multiple pairs of measuring electrodes. Simultaneously, the concentrations of solutes or colloids in the effluent and in the soil at the end of the experiment were measured.

[0010] In some embodiments of the present invention, when simulating the dynamic process of injecting solutes or colloids into the vadose zone of the soil in the target detection area, the transport concentration data and geoelectric signal data after the injection of solutes or colloids are obtained in the following ways: After the pre-flushing of the soil column from bottom to top is completed, the water inlet direction is switched, and the pre-flushing liquid is injected into the soil column from top to bottom. By adjusting the two peristaltic pumps at the inlet and outlet, a speed difference is created to reduce the water content of the soil column from saturated conditions to the specified unsaturated conditions. After the soil column reaches the specified water content, the pre-flushing liquid is switched to the target solute or colloidal suspension, and the two peristaltic pumps are adjusted to the same speed to ensure that the effluent meets the required flow rate. Subsequently, the effluent from the soil column is collected by an automatic partial collector and the mass is measured. At the same time, a spectrum excitation polarization instrument is used to continuously measure geoelectric signal data at multiple frequencies in the range of 0.01-10000 Hz using multiple pairs of measuring electrodes. At the same time, the concentration of solute or colloid in the effluent and the concentration of solute or colloid in the soil at the end of the experiment were measured. Alternatively, after pre-flushing the soil column from bottom to top, connect the lower section of the soil column to a low-pressure chamber, exposing the upper end to air. Switch the water inlet direction and use a peristaltic pump to inject pre-flushing fluid into the soil column from top to bottom. Simultaneously, turn on the vacuum pump and the control valve for adjusting the pressure inside the chamber to create a low-pressure environment in the low-pressure chamber. Because there is a pressure difference between the upper and lower ends of the soil column, unsaturated conditions are formed in the soil column. After the soil column reaches the specified moisture content, switch the pre-flushing fluid to the target solute or colloidal suspension. Adjust the speed of the peristaltic pump and the control valve for the pressure inside the chamber to ensure that the effluent meets the required flow rate. Subsequently, collect the effluent from the soil column using an automatic partial collector and measure its mass. At the same time, use a spectrum excitation polarization instrument to continuously measure geoelectric signal data at multiple frequencies in the range of 0.01-10000 Hz using multiple pairs of measuring electrodes. Simultaneously, the concentrations of solutes or colloids in the effluent and in the soil at the end of the experiment were measured.

[0011] In some embodiments of the present invention, the transport characteristic parameters include the primary adhesion coefficient of the first type of site, the primary adhesion coefficient of the second type of site, the primary separation coefficient of the first type of site, the primary separation coefficient of the second type of site, the solid solute or colloidal retention concentration of the first type of site, and the maximum solid solute or colloidal retention concentration of the second type of site. In some embodiments of the present invention, the complex conductivity signal value of the injected solute or colloid is calculated using the following formula:

[0012]

[0013] The conductivity value is S / m. S is the real part of conductivity, S / m; The imaginary part of conductivity is S / m; Furthermore, by fitting the complex conductivity signal value using the Cole-Cole model, the characteristic parameters of the Cole-Cole model are obtained, including the normalized charge rate, relaxation time, and the Cole-Cole constant reflecting the relaxation time distribution.

[0014] In some embodiments of the present invention, the process of obtaining the transport characteristics of the solute or colloid includes: Determine the statistical correlation between solute or colloid concentrations in liquid and solid phases at different times and locations and geoelectric characteristic parameters; among which, geoelectric characteristic parameters include complex conductivity signal values ​​and Cole-Cole model characteristic parameters; The measurement of the background value of geoelectric signal and the background value of chemical substances in effluent is to compare the influence of target solutes or colloids on geoelectric signal and chemical substances in effluent; Based on the above correlation analysis and comparison, and combined with the spatiotemporal variation of complex conductivity signal values ​​and characteristic parameters of the Cole-Cole model, the transport characteristics of solutes or colloids are obtained.

[0015] In a second aspect of the invention, an indoor monitoring system for underground solute or colloidal transport is provided, comprising: The geometric factor acquisition module is configured to: build an indoor experimental setup and acquire the geometric factors of the experimental setup. The background value acquisition module is configured to: fill the target detection area with soil into the experimental device, and then pre-wash it from bottom to top with a salt solution that does not contain target solutes or colloids to acquire the soil porosity, dispersion coefficient, geoelectric signal background value and chemical content background value in the outflow of the target detection area. The first data acquisition module is configured to: inject solute or colloid into the experimental device to simulate the dynamic process of solute or colloid being injected into the soil saturated zone or vadose zone of the target detection area, and acquire the concentration data of solute or colloid in the effluent of the target detection area, as well as geoelectric signal data at different times and locations. The second data acquisition module is configured to: fit the transport of solute or colloid in the target detection area using a one-dimensional convection-dispersion equation based on the obtained dispersion coefficient and the obtained concentration data of solute or colloid in the effluent, invert the transport characteristic parameters, and then invert the concentration of solute or colloid in the liquid and solid phases at different times at the location monitored by the geoelectric signal. The Cole-Cole model feature parameter acquisition module is configured to: calculate the complex conductivity signal value based on the geometric factors and geoelectric signal data of the experimental setup; and obtain the Cole-Cole model feature parameters by fitting the complex conductivity signal value through the Cole-Cole model, which characterize the spectral features of the complex conductivity. The transport characteristic acquisition module is configured to: obtain the transport characteristics of solutes or colloids by analyzing the statistical correlation between the concentration of solutes or colloids in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, and by comparing the geoelectric signal and the chemical content in the effluent during pre-rinsing and solute or colloid injection.

[0016] One or more technical solutions of the present invention have the following beneficial effects: (1) The indoor testing method for monitoring underground solute or colloidal transport based on complex conductivity signals under multiple frequencies provided by this invention can realize indoor simulation experiments of underground solute or colloidal transport under various hydrological conditions, link the geoelectric response with specific changes in the physical and biogeochemical processes of underground solute or colloidal transport, propose a micro-intervention, real-time monitoring, and spatial linear continuous measurement method for monitoring underground solute or colloidal transport, make the solute or colloidal transport process transparent, and greatly reduce costs.

[0017] (2) This invention decouples the complex conductivity spectrum through the Cole-Cole model, and establishes a quantitative mapping relationship between the complex conductivity spectrum and the transport parameters output by the one-dimensional convection-dispersion equation for the distribution of solutes or colloids in different phases in different times and spaces. This can reveal the regulation mechanism of solute or colloid adsorption kinetics on the interface polarization effect, and fill the geophysical gap in the interpretation of geoelectric signals.

[0018] (3) The experimental device provided by this invention unifies the device scale effect through the geometric factor G, enabling the parameter relationships calibrated indoors to be directly applied to field scenarios, thus promoting the spectral excitation polarization method as a universal technology for solute / colloid monitoring. By adjusting the water flow direction, peristaltic pump, and vacuum device, the experimental device can simulate various hydrological conditions, including water saturation conditions, water unsaturation conditions, steady-state flow, and transient flow, to achieve indoor monitoring of underground solute or colloid transport under various hydrological conditions. Attached Figure Description

[0019] Figure 1 This is a flowchart of the indoor monitoring method for underground solute or colloidal transport according to the present invention; Figure 2 This is a schematic diagram showing the connection between the experimental apparatus of the present invention and the spectrum excitation polarization instrument; Figure 3 This is a schematic diagram of the experimental apparatus for injecting solutes or colloids under saturated conditions according to the present invention; Figure 4 This is a schematic diagram of the experimental setup used in the first method to obtain relevant data under unsaturated conditions according to the present invention. Figure 5 This is a schematic diagram of the experimental setup used in the second method to obtain relevant data under unsaturated conditions according to the present invention.

[0020] In the diagram: 1. Upper end cap; 2. Cylinder body; 3. Lower end cap; 4. Electrode port; 5. First opening; 6. Second opening; 7. Copper wire; 8. Power supply electrode; 9. Non-polarized measuring electrode; 10. Cable; 11. Reference resistor; 12. Signal generator; 13. Measuring platform; 14. Peristaltic pump; 15. Water inlet bottle; 16. Water inlet pipe; 17. Automatic partial collector; 18. Soil in the target detection area; 19. Water outlet pipe; 20. Vacuum pump; 21. Low-pressure chamber; 22. Vacuum gauge; 23. Control valve inside the chamber. Detailed Implementation

[0021] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this disclosure. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.

[0022] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this disclosure. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0023] For ease of description, the use of the words "up," "down," "left," and "right" in this disclosure only indicates that they are consistent with the up, down, left, and right directions of the accompanying drawings themselves. They do not limit the structure and are only used to facilitate the description of this disclosure and to simplify the description. They do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0024] Example 1 In a typical embodiment of the present invention, an indoor monitoring method for underground solute or colloidal transport is proposed, such as... Figure 1 As shown, it includes the following steps: Step 1: Construct the indoor experimental setup and obtain the geometric factors of the setup; Step 2: Fill the experimental device with soil from the target detection area, and then pre-wash it from bottom to top with a salt solution that does not contain the target solute or colloid to obtain the soil porosity, dispersion coefficient, geoelectric signal background value and chemical content background value in the effluent of the target detection area. Step 3: Inject solutes or colloids into the experimental device to simulate the dynamic process of solutes or colloids being injected into the soil saturation zone or vadose zone of the target detection area, and obtain the concentration data of solutes or colloids in the effluent of the target detection area, as well as geoelectric signal data at different times and locations. Step 4: Based on the dispersion coefficient obtained in Step 2 and the concentration data of solute or colloid in the effluent obtained in Step 3, a one-dimensional convection-dispersion equation is used to fit the transport of solute or colloid in the target detection area, invert the transport characteristic parameters, and then deduce the concentration of solute or colloid in the liquid and solid phases at different times at the location monitored by the geoelectric signal. Step 5: Calculate the complex conductivity signal value based on the geometric factors of the experimental setup and the geoelectric signal data; and obtain the Cole-Cole model characteristic parameters by fitting the complex conductivity signal value through the Cole-Cole model, which characterizes the spectral characteristics of the complex conductivity. Step 6: By analyzing the statistical correlation between the concentration of solute or colloid in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, the geoelectric signal and the chemical content in the effluent during pre-rinsing and solute or colloid injection are compared to obtain the transport characteristics of solute or colloid.

[0025] The aforementioned monitoring method, through the experimental setup, can simulate the underground environment of the target detection area. It uses a one-dimensional convection-dispersion equation to calculate the concentration of solutes or colloids in the liquid and solid phases at different times and locations, and uses the Cole-Cole model to obtain characteristic parameters. By analyzing the statistical correlation between the concentration of solutes or colloids in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, and combining the spatiotemporal variation patterns of the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, it compares the geoelectric signals and the chemical content in the effluent during pre-flushing and solute or colloid injection to determine and analyze the transport characteristics of substances. This method enables the connection between geoelectric response and specific changes in the physical and biogeochemical processes of underground solutes or colloids in an indoor environment, solving the problem of the lack of a correlation mechanism in the real-time capture of the spatial transport patterns of solutes or colloids using the spectral excitation polarization method.

[0026] Specific monitoring methods include: Step 1: Construct an indoor experimental setup and obtain the geometric factors of the setup.

[0027] Specifically, the indoor experimental setup is as follows: Figure 2As shown, the experimental device adopts a cylindrical structure, filled with soil from the target detection area. The top and bottom of the cylinder 2 are sealed by an upper end cover 1 and a lower end cover 3, respectively. The upper end cover 1 has a first opening 5 and the lower end cover 3 has a second opening 6. Multiple electrode ports 4 are provided on the side of the cylinder. Each power supply electrode 8 and non-polarized measurement electrode 9 is inserted into the electrode port 4. The power supply electrode 8 extends into the cylinder 2 through a connecting copper wire 7. The non-polarized measurement electrode 9 only contacts the surface of the soil 18 in the cylinder 2. Both the power supply electrode 8 and the non-polarized measurement electrode 9 are connected to a spectrum excitation polarization instrument through a cable 10. The spectrum excitation polarization instrument includes a signal generator 12, a reference resistor 11, and a measurement platform 13 connected in sequence. The positive and negative terminals of the signal generator are connected to the power supply electrode 8 on the experimental device, and the measurement platform 13 is connected to the non-polarized measurement electrode 9 on the experimental device. The spectrum excitation polarization instrument is an existing device, and its use is also existing technology.

[0028] It is understood that the cylindrical body of the experimental apparatus can take other shapes or sizes. For ease of observation, the cylindrical body can be made transparent, and those skilled in the art can choose according to their needs. The number of electrode ports can be selected by those skilled in the art; in this embodiment, three pairs of electrode ports are used as an example. In addition, during the operation of the experimental apparatus, the openings on the upper and lower end caps can both serve as water inlets or outlets, and can be replaced according to experimental needs.

[0029] Furthermore, the geometric factors of the experimental setup are obtained in the following manner: A solution with known conductivity was injected into the cylinder of the experimental apparatus using a peristaltic pump. The complex impedance of the solution was measured by spectral excitation polarization, and the geometric factor of the experimental apparatus was calculated using the following formula:

[0030] Wherein G(m) -1 () represents the geometric factor; (S / m) represents complex conductivity; Z (Ω) represents the measured complex impedance.

[0031] Step 2: Fill the experimental device with soil from the target detection area, and then pre-wash it with a salt solution that does not contain the target solute or colloid to obtain the soil porosity, dispersion coefficient, geoelectric signal background value, and chemical content background value in the effluent from the target detection area.

[0032] Specifically, firstly, soil 18 from the target detection area is filled into the cylinder of the experimental device. Then, a peristaltic pump 14 is used to inject pre-rinsing liquid (a salt solution without target solutes or colloids) into the soil column from bottom to top, and the pre-rinsing liquid discharged from the soil column is collected, and the mass of the inlet and outlet water is measured. After the soil column is saturated, the mass of the inlet and outlet water bottles is weighed using a balance, and the pore volume of the soil column is calculated based on their mass difference. The soil porosity is obtained by dividing the pore volume by the volume of the cylinder 2 of the experimental device. Pre-rinsing liquid is injected again, and soil effluent of 0.5 times the pore volume of the soil column is collected by an automatic collector 17 (it can be understood that 0.5 times the pore volume of the soil column is used as an example here, but other values ​​can also be used). The conductivity is measured by a conductivity meter until the conductivity of the inlet and outlet water is balanced. The concentration of tracer in the pre-rinsing liquid at different times is inverted by a one-dimensional convection-dispersion equation to obtain the dispersion coefficient. After the conductivity of the inlet and outlet water is balanced, pre-rinsing liquid of 10 times the pore volume of the soil column is injected again. Throughout the pre-rinse, geoelectric signal data were continuously measured using a SIP instrument at 43 frequencies (7 points per order of magnitude) in the range of 0.01-10000 Hz across 3 channels, and the chemical content in the effluent was measured using an analytical instrument as background values.

[0033] In other embodiments, the experimental setup can be continuously monitored along its length, not limited to three channels. Furthermore, the sampling frequency of the instrument used by the applicant can range from 1 to 120 points. Of these, 31 points is the minimum number of points required for subsequent analysis (5 points per order of magnitude). The more measurement points, the longer the measurement time; those skilled in the art can set this as needed. No further restrictions are placed on the number of channels or the sampling frequency here.

[0034] Step 3: Inject solutes or colloids into the experimental device to simulate the dynamic process of solutes or colloids being injected into the soil saturation zone or vadose zone of the target detection area, and obtain the concentration data of solutes or colloids in the effluent of the target detection area, as well as geoelectric signal data at different times and locations.

[0035] Specifically, when simulating the dynamic process of solute or colloid injection into the soil saturation zone (saturation condition) of the target detection area, the transport concentration data and geoelectric signal data after solute or colloid injection are obtained through the following methods: After calculating soil porosity and pre-flushing to achieve equilibrium of influent and effluent electrical conductivity as per step two, inject a solute or colloidal suspension into the soil column, such as... Figure 3 As shown, the water inlet bottle 15 contains a solute or colloidal suspension. The solute or colloidal suspension is injected into the soil column from bottom to top through the peristaltic pump 14. The solute or colloidal suspension discharged from the soil column is collected by the automatic collector 17 and its mass is measured. At the same time, the geoelectric signal data is continuously measured at 43 frequencies in the range of 0.01-10000 Hz using a SIP instrument in 3 channels.

[0036] Specifically, when simulating the dynamic process of solute or colloid injection into the vadose zone (unsaturated conditions) of the soil in the target detection area, the transport concentration data and geoelectric signal data after solute or colloid injection can be obtained in the following two ways: The method is the same Figure 4 As shown, after the pre-rinsing of the soil column from bottom to top is completed, the water inlet direction is switched, and the pre-rinsing liquid is injected into the soil column from top to bottom. By adjusting the two peristaltic pumps 14 at the inlet and outlet, a speed difference is formed to reduce the water content of the soil column from saturated conditions to specified unsaturated conditions. After the soil column reaches the specified water content, the pre-rinsing liquid is switched to the target solute or colloidal suspension, and the two peristaltic pumps 14 are adjusted to the same speed so that the effluent meets the required flow rate. Subsequently, the effluent from the soil column is collected by the automatic partial collector 17 and the mass is measured. At the same time, the geoelectric signal data is obtained by measuring with reference to the saturation conditions. Simultaneously, the concentration of solute or colloid in the effluent and the concentration of solute or colloid in the soil at the end of the experiment are measured.

[0037] Method 2, as Figure 5 As shown, after the pre-rinsing of the soil column from bottom to top is completed, the lower section of the soil column is connected to the low-pressure chamber 21, with the upper end exposed to the air. The water inlet direction is switched, and the pre-rinsing liquid is injected into the soil column from top to bottom through the peristaltic pump 14. At the same time, the vacuum pump 20 is turned on to create a low-pressure environment in the low-pressure chamber 21. The low-pressure chamber 21 is equipped with a vacuum gauge 22 and a valve 23 to control the pressure inside the chamber. Because there is a pressure difference between the upper and lower ends of the soil, unsaturated conditions are formed in the soil column. After the soil column reaches the specified moisture content, the pre-rinsing liquid is switched to the target solute or colloidal suspension, and the peristaltic pump 14 and valve 23 are adjusted to make the effluent meet the required flow rate. Subsequently, the effluent from the soil column is collected by the automatic collector 17 and the mass is measured. At the same time, the concentration of solute or colloid in the effluent and the concentration of solute or colloid in the soil at the end of the experiment are measured.

[0038] Furthermore, the concentrations of tracer, solute or colloid in the effluent collected by the collection tube and the concentration of solute or colloid in the soil were determined by relevant instruments; the tracer concentration was determined by ion chromatography; the solute or colloid concentration was determined by inductively coupled plasma atomic emission spectrometry; the solute or colloid in the soil was first extracted and then also determined by inductively coupled plasma atomic emission spectrometry.

[0039] Based on the above steps, the saturated and unsaturated conditions of the soil column are adjusted. At the same time, the steady-state flow and transient flow in the soil column are realized by adjusting the peristaltic pump, so as to simulate the transport of solutes or colloids in the soil under various hydrological conditions.

[0040] Step 4: Based on the dispersion coefficient obtained in Step 2 and the concentration data of solute or colloid in the effluent obtained in Step 3, a one-dimensional convection-dispersion equation is used to fit the transport of solute or colloid in the target detection area, invert the transport characteristic parameters, and then deduce the concentration of solute or colloid in the liquid and solid phases at different times at the location monitored by the geoelectric signal.

[0041] Specifically, the soil volumetric water content is calculated by dividing the pore volume of the soil column obtained in step two by the volume of the experimental apparatus cylinder. [%], based on the tracer concentration of the soil effluent collected in the collection tube in step three, the hydrodynamic dispersion coefficient is calculated by substituting it into the one-dimensional convection-dispersion equation. D [cm 2 min -1 ].

[0042] The one-dimensional convection-dispersion equation is as follows: ; in, C (mg·L) -1 () represents the concentration of the solute or colloid in the liquid phase; t (min) is time; z (cm) is the distance between the solute or colloid and the water inlet of the soil column; q (cm·min) -1 () is the water flow rate.

[0043] Furthermore, based on the data obtained in steps two and three, a one-dimensional convection-dispersion equation is used to fit the transport of solute or colloid in the target detection area, yielding transport characteristic parameters including the first-order adhesion coefficients of the first and second types of sites. k a1 and k a2 First-order segregation coefficients of the first and second types of loci k d1 and k d2 Solid solute or colloidal retention concentration at the first and second type sites S 1 and S 2; ; ; ; Ψ a = 1- S / S max or Ψ b = [( d + z) / d ] -β or Ψ c = (1- S / S max )[( d + z ) / d ] -β ; in, S 1 and S 2 (mg·g) -1 These are the solid solute or colloid concentrations of the first and second type sites, respectively. (g·cm) -3 ( ) is the soil bulk density; k a1 (min) -1 )and k a2 (min) -1 These are the first-order adhesion coefficients for the first and second types of sites, respectively; k d1 (min) -1 )and k d2 (min) -1 () is the first-order segregation coefficient of the first and second type loci; Ψ It is the retention function that determines the site attachment mechanism; S max (mg·g) -1 () is the maximum solute or colloidal retention concentration at the first / second type site; d (cm) represents the median particle size; β (-) represents an empirical parameter controlling the spatial distribution.

[0044] The obtained transport characteristic parameters include the first-order adhesion coefficient of the first type of site. k a1 Primary adhesion coefficient of the second type of site k a2 First-order segregation coefficient of the first type of locus k d1 The first-order segregation coefficient of the second type of loci k d2 Maximum solute or colloidal retention concentration at the first type of site S max1 Maximum solute or colloidal retention concentration at the second type of site S max2 Based on the obtained transport characteristic parameters, the concentrations of solutes or colloids in the liquid and solid phases at different times and locations can be calculated. The measured solute or colloid concentrations in the soil at the end of the experiment can be used to verify the fitted model.

[0045] It should be noted that, in order to achieve better fitting results, professionals can decide for themselves the number of retention sites (1 or 2), and whether each site has an adhesion coefficient. k a and separation coefficient k d And the choice of the form of the retention function ( Ψ a , Ψ b or Ψ c ).

[0046] Step 5: Based on the geometric factors of the experimental setup and the geoelectric signal data after injecting the solute or colloid, calculate the complex conductivity signal value of the injected solute or colloid; and obtain the Cole-Cole model characteristic parameters by fitting the complex conductivity signal value through the Cole-Cole model to characterize the spectral characteristics of the complex conductivity.

[0047] Specifically, the complex conductivity signal value of the injected solute or colloid is calculated using the following formula:

[0048]

[0049] The conductivity value is S / m. S is the real part of conductivity, S / m; denoted as the imaginary part of conductivity, S / m.

[0050] Furthermore, by fitting the complex conductivity signal value using the Cole-Cole model, the characteristic parameters of the Cole-Cole model, including charge rate, relaxation time, and the Cole-Cole constant reflecting the relaxation time distribution, are obtained. These parameters are calculated using the following formula:

[0051]

[0052] in, , (S / m) represent the low and high frequency conductivity, respectively (select representative low and high frequencies and calculate based on the complex impedance corresponding to the frequency multiplied by the geometric factor G); m(-) represents the charge rate. (s) represents the relaxation time; c (-) represents the Cole-Cole constant, which reflects the relaxation time distribution. m n (S / m) is the normalized charging rate, which can be expressed as m × get.

[0053] Step 6: By analyzing the statistical correlation between the concentration of solute or colloid in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, the geoelectric signal and the chemical content in the effluent during pre-rinsing and solute or colloid injection are compared to obtain the transport characteristics of solute or colloid.

[0054] Specifically, the transport characteristics of the solute or colloid are obtained in the following ways: Determine the statistical correlation between solute or colloid concentrations in liquid and solid phases at different times and locations and geoelectric characteristic parameters; among which, geoelectric characteristic parameters include complex conductivity signal values ​​( , ) and Cole-Cole model feature parameters ( , ); The measurement of the background value of geoelectric signal and the background value of chemical substances in effluent is to compare the influence of target solutes or colloids on geoelectric signal and chemical substances in effluent; Based on the above correlation analysis and comparison, and combined with the spatiotemporal variation of complex conductivity signal values ​​and characteristic parameters of the Cole-Cole model, the transport characteristics of solutes or colloids are obtained.

[0055] Example 2 In a typical embodiment of the present invention, an indoor monitoring system for underground solute or colloidal transport is provided, comprising: The background value acquisition module is configured to: fill the target detection area with soil into the experimental device, and then pre-wash it from bottom to top with a salt solution that does not contain target solutes or colloids to acquire the soil porosity, dispersion coefficient, geoelectric signal background value and chemical content background value in the outflow of the target detection area. The first data acquisition module is configured to: inject solute or colloid into the experimental device to simulate the dynamic process of solute or colloid being injected into the soil saturated zone or vadose zone of the target detection area, and acquire the concentration data of solute or colloid in the effluent of the target detection area, as well as geoelectric signal data at different times and locations. The second data acquisition module is configured to: fit the transport of solute or colloid in the target detection area using a one-dimensional convection-dispersion equation based on the obtained dispersion coefficient and the obtained concentration data of solute or colloid in the effluent, invert the transport characteristic parameters, and then invert the concentration of solute or colloid in the liquid and solid phases at different times at the location monitored by the geoelectric signal. The Cole-Cole model feature parameter acquisition module is configured to: calculate the complex conductivity signal value based on the geometric factors and geoelectric signal data of the experimental setup; and obtain the Cole-Cole model feature parameters by fitting the complex conductivity signal value through the Cole-Cole model, which characterize the spectral features of the complex conductivity. The transport characteristic acquisition module is configured to: obtain the transport characteristics of solutes or colloids by analyzing the statistical correlation between the concentration of solutes or colloids in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, and by comparing the geoelectric signal and the chemical content in the effluent during pre-rinsing and solute or colloid injection.

[0056] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An indoor monitoring method for underground solute or colloidal transport, characterized in that, Includes the following steps: Step 1: Construct the indoor experimental setup and obtain the geometric factors of the setup; Step 2: Fill the experimental device with soil from the target detection area, and then pre-wash it from bottom to top with a salt solution that does not contain the target solute or colloid to obtain the soil porosity, dispersion coefficient, geoelectric signal background value and chemical content background value in the effluent of the target detection area. Step 3: Inject solutes or colloids into the experimental device to simulate the dynamic process of solutes or colloids being injected into the soil saturation zone or vadose zone of the target detection area, and obtain the concentration data of solutes or colloids in the effluent of the target detection area, as well as geoelectric signal data at different times and locations. Step 4: Based on the dispersion coefficient obtained in Step 2 and the concentration data of solute or colloid in the effluent obtained in Step 3, a one-dimensional convection-dispersion equation is used to fit the transport of solute or colloid in the target detection area, invert the transport characteristic parameters, and then deduce the concentration of solute or colloid in the liquid and solid phases at different times at the location monitored by the geoelectric signal. Step 5: Calculate the complex conductivity signal value based on the geometric factors of the experimental setup and the geoelectric signal data; and obtain the Cole-Cole model characteristic parameters by fitting the complex conductivity signal value through the Cole-Cole model, which characterizes the spectral characteristics of the complex conductivity. Step 6: By analyzing the statistical correlation between the concentration of solute or colloid in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, the geoelectric signal and the chemical content in the effluent during pre-rinsing and solute or colloid injection are compared to obtain the transport characteristics of solute or colloid.

2. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, The experimental apparatus adopts a cylindrical structure with the cylinder set vertically. The top and bottom of the cylinder are set with openings. Multiple pairs of measuring electrodes are set on the side of the cylinder. The multiple pairs of measuring electrodes are set at equal intervals along the axis of the cylinder. Each pair of measuring electrodes is connected to a spectrum excitation polarization instrument through a wire.

3. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, The geometric factors of the experimental setup were obtained in the following manner: A solution with known conductivity was injected into the experimental apparatus using a peristaltic pump, and the complex impedance of the solution was determined by spectral excitation polarization. The geometric factor of the experimental apparatus was then calculated using the following formula: Where G represents the geometric factor, m -1 ; Z represents the complex conductivity, S / m; Z represents the measured complex impedance, Ω.

4. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, The soil porosity, dispersion coefficient, geoelectric signal background value, and chemical substance content background value in the effluent of the target detection area were obtained through the following methods: Soil was filled into the target detection area of ​​the experimental device. A salt solution without target solutes or colloids was injected into the soil column from bottom to top using a peristaltic pump as a pre-flushing fluid. The pre-flushing fluid discharged from the soil column was collected, and the influent and effluent mass was measured. After the soil column was saturated, the pore volume of the soil column was calculated to obtain the soil porosity. The injection of pre-flushing fluid continued until the conductivity of the influent and effluent was balanced. The concentration of tracer in the pre-flushing fluid at different times was inverted using a one-dimensional convection-dispersion equation to obtain the dispersion coefficient. After the conductivity of the influent and effluent was balanced, 10 times the pore volume of the soil column of pre-flushing fluid was injected. During the entire pre-flushing process, the background value of the geoelectric signal was obtained by continuously measuring multiple frequencies in the range of 0.01-10000 Hz using a spectrum excitation polarization instrument with multiple pairs of measuring electrodes. The chemical content in the effluent was measured using an analytical instrument as the background value of the chemical content in the effluent.

5. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, When simulating the dynamic process of solute or colloid injection into the soil saturation zone of the target detection area, the transport concentration data and geoelectric signal data after solute or colloid injection are obtained through the following methods: A peristaltic pump is used to inject a solute or colloidal suspension into the soil column from bottom to top. An automatic partial collector is used to collect the solute or colloidal suspension discharged from the soil column and measure its mass. At the same time, a spectrum excitation polarization instrument is used to continuously measure geoelectric signal data at multiple frequencies in the range of 0.01-10000 Hz through multiple pairs of measuring electrodes. Simultaneously, the concentrations of solutes or colloids in the effluent and in the soil at the end of the experiment were measured.

6. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, When simulating the dynamic process of solute or colloid injection into the vadose zone of the soil in the target detection area, the transport concentration data and geoelectric signal data after solute or colloid injection are obtained through the following methods: After the pre-flushing of the soil column from bottom to top is completed, the water inlet direction is switched, and the pre-flushing liquid is injected into the soil column from top to bottom. By adjusting the two peristaltic pumps at the inlet and outlet, a speed difference is created to reduce the water content of the soil column from saturated conditions to the specified unsaturated conditions. After the soil column reaches the specified water content, the pre-flushing liquid is switched to the target solute or colloidal suspension, and the two peristaltic pumps are adjusted to the same speed to ensure that the effluent meets the required flow rate. Subsequently, the effluent from the soil column is collected by an automatic partial collector and the mass is measured. At the same time, a spectrum excitation polarization instrument is used to continuously measure geoelectric signal data at multiple frequencies in the range of 0.01-10000 Hz using multiple pairs of measuring electrodes. At the same time, the concentration of solute or colloid in the effluent and the concentration of solute or colloid in the soil at the end of the experiment were measured. Alternatively, after pre-flushing the soil column from bottom to top, connect the lower section of the soil column to a low-pressure chamber, exposing the upper end to air. Switch the water inlet direction and use a peristaltic pump to inject pre-flushing fluid into the soil column from top to bottom. Simultaneously, turn on the vacuum pump and the control valve for adjusting the pressure inside the chamber to create a low-pressure environment in the low-pressure chamber. Because there is a pressure difference between the upper and lower ends of the soil column, unsaturated conditions are formed in the soil column. After the soil column reaches the specified moisture content, switch the pre-flushing fluid to the target solute or colloidal suspension. Adjust the speed of the peristaltic pump and the control valve for the pressure inside the chamber to ensure that the effluent meets the required flow rate. Subsequently, collect the effluent from the soil column using an automatic partial collector and measure its mass. At the same time, use a spectrum excitation polarization instrument to continuously measure geoelectric signal data at multiple frequencies in the range of 0.01-10000 Hz using multiple pairs of measuring electrodes. Simultaneously, the concentrations of solutes or colloids in the effluent and in the soil at the end of the experiment were measured.

7. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, The transport characteristic parameters include the primary adhesion coefficient of the first type of site, the primary adhesion coefficient of the second type of site, the primary separation coefficient of the first type of site, the primary separation coefficient of the second type of site, the solid solute or colloidal retention concentration of the first type of site, and the maximum solid solute or colloidal retention concentration of the second type of site.

8. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, The complex conductivity signal value of the injected solute or colloid is calculated using the following formula: The conductivity value is S / m. S is the real part of conductivity, S / m; The imaginary part of conductivity is S / m; Furthermore, by fitting the complex conductivity signal value using the Cole-Cole model, the characteristic parameters of the Cole-Cole model are obtained, including the normalized charge rate, relaxation time, and the Cole-Cole constant reflecting the relaxation time distribution.

9. The indoor monitoring method for underground solute or colloidal transport as described in claim 1, characterized in that, The process of obtaining the transport characteristics of the solute or colloid includes: Determine the statistical correlation between solute or colloid concentrations in liquid and solid phases at different times and locations and geoelectric characteristic parameters; among which, geoelectric characteristic parameters include complex conductivity signal values ​​and Cole-Cole model characteristic parameters; The measurement of the background value of geoelectric signal and the background value of chemical substances in effluent is to compare the influence of target solutes or colloids on geoelectric signal and chemical substances in effluent; Based on the above correlation analysis and comparison, and combined with the spatiotemporal variation of complex conductivity signal values ​​and characteristic parameters of the Cole-Cole model, the transport characteristics of solutes or colloids are obtained.

10. An indoor monitoring system for underground solute or colloidal transport, characterized in that, include: The geometric factor acquisition module is configured to: build an indoor experimental setup and acquire the geometric factors of the experimental setup. The background value acquisition module is configured to: fill the target detection area with soil into the experimental device, and then pre-wash it from bottom to top with a salt solution that does not contain target solutes or colloids to acquire the soil porosity, dispersion coefficient, geoelectric signal background value and chemical content background value in the outflow of the target detection area. The first data acquisition module is configured to: inject solute or colloid into the experimental device to simulate the dynamic process of solute or colloid being injected into the soil saturated zone or vadose zone of the target detection area, and acquire the concentration data of solute or colloid in the effluent of the target detection area, as well as geoelectric signal data at different times and locations. The second data acquisition module is configured to: fit the transport of solute or colloid in the target detection area using a one-dimensional convection-dispersion equation based on the obtained dispersion coefficient and the obtained concentration data of solute or colloid in the effluent, invert the transport characteristic parameters, and then invert the concentration of solute or colloid in the liquid and solid phases at different times at the location monitored by the geoelectric signal. The Cole-Cole model feature parameter acquisition module is configured to: calculate the complex conductivity signal value based on the geometric factors and geoelectric signal data of the experimental setup; and obtain the Cole-Cole model feature parameters by fitting the complex conductivity signal value through the Cole-Cole model, which characterize the spectral features of the complex conductivity. The transport characteristic acquisition module is configured to: obtain the transport characteristics of solutes or colloids by analyzing the statistical correlation between the concentration of solutes or colloids in the liquid and solid phases at different times and locations and the complex conductivity signal value and the characteristic parameters of the Cole-Cole model, and by comparing the geoelectric signal and the chemical content in the effluent during pre-rinsing and solute or colloid injection.

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