Shallow groundwater salinization hydrogeochemical process simulation and analysis method

Abstract

The invention discloses a shallow groundwater salinization hydrogeochemical process simulation and analysis method. The method comprises the following steps: 1, carrying out a simulation experiment on a shallow groundwater salinization hydrogeochemical process; 2, carrying out hydrological earth process analysis on salinization of underground water under the condition of irrigation-evaporation circulation; 3, ion equalization calculation is carried out under the irrigation-evaporation circulation condition; according to the method, the shallow groundwater salinization hydrogeochemical process is simulated and analyzed through a simulation experiment process, a groundwater salinization hydrogeochemical process analysis process under the condition of irrigation-evaporation circulation and an ion equilibrium calculation process under the condition of irrigation-evaporation circulation; according to the invention, the influence rule of different irrigation conditions on the underground water-soil hydrogeochemical action process can be effectively researched, and the influence rule of different irrigation conditions on the underground water-soil hydrogeochemical action process can be analyzed; and a foundation is laid for researching underground water-soil hydrogeochemical action processes in different regions.

Description

Technical Field

[0001] The invention relates to the technical field of geological engineering, and in particular to a simulation and analysis method for the hydrogeochemical process of shallow groundwater salinization. Background Art

[0002] Groundwater is one of the main sources of water for industrial and agricultural production and residents' daily life. The chemical composition and mineralization of groundwater directly affect its use value. There are great differences in the chemical composition and mineralization of groundwater in different regions. Analyzing the temporal and spatial variation of groundwater chemistry is of great significance to the rational development, utilization and management of groundwater.

[0003] In the groundwater system, groundwater interacts with the surrounding media during its runoff, and its chemical composition is constantly changing. By studying the hydrochemical characteristics of groundwater, we can find out important information such as its occurrence environment, runoff pathways, and material exchange, and reveal the origin and formation process of groundwater. In order to reveal and study the origin and formation process of groundwater, the study of hydrogeochemical simulation officially began in the early 1960s. At the end of the 20th century, my country's hydrogeochemical simulation research began to develop. Guo Yonghai and others took the groundwater in the Hebei Plain as the research object, and used the method of hydrogeochemical simulation to analyze the water-rock interaction and hydrogeochemical process of groundwater on the flow path under the influence of human activities, and revealed its evolution mechanism. Using groundwater salinity, we can effectively distinguish between salinized and desalinated areas of groundwater.

[0004] In the process of land irrigation, we know that different irrigation conditions have different effects on the groundwater-soil hydrogeochemical process, but there are no written materials and limiting conditions for the specific influence rules and the means to simulate the shallow groundwater salinization hydrogeochemical process. Therefore, there are still insurmountable technical barriers in the study of the influence rules of different irrigation conditions on the groundwater-soil hydrogeochemical process.

[0005] Therefore, in view of the above problems, it is urgent to design a simulation and analysis method of the hydrogeochemical process of shallow groundwater salinization to solve the problems existing in the above-mentioned prior art. Summary of the invention

[0006] In view of the above problems, the present invention aims to provide a method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization. This method simulates and analyzes the hydrogeochemical process of shallow groundwater salinization through the simulation experiment process, the analysis process of the hydrogeological process of groundwater salinization under irrigation-evaporation cycle conditions, and the ion balance calculation process under irrigation-evaporation cycle conditions. It can effectively study the influence law of different irrigation conditions on the groundwater-soil hydrogeochemical action process, analyze the influence law of different irrigation conditions on the groundwater-soil hydrogeochemical action process, and thus lay a foundation for studying the groundwater-soil hydrogeochemical action process in different regions.

[0007] In order to achieve the above object, the technical solutions adopted by the present invention are as follows:

[0008] A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization, including

[0009] Step 1: Use the simulation device for the hydrogeochemical process of shallow groundwater salinization to conduct a simulation experiment on the hydrogeochemical process of shallow groundwater salinization;

[0010] Step 2: Based on the results of the simulation experiment, analyze the hydrogeological process of groundwater salinization under irrigation-evaporation cycle conditions;

[0011] Step 3: Based on the analysis of the hydrogeological process of groundwater salinization under irrigation-evaporation cycle conditions, perform ion balance calculation under irrigation-evaporation cycle conditions.

[0012] Preferably, the simulation device for the hydrogeochemical process of shallow groundwater salinization described in Step 1 includes an experimental cylinder and a measuring cup;

[0013] The experimental cylinder is a transparent tubular structure provided with scales, and a piezometer tube, a water inlet, and a water intake are provided on the experimental cylinder. Multiple groups of piezometer tubes are provided on the tube body of the experimental cylinder, the water inlet is provided at the lower end of the experimental cylinder, and the water intake is provided at the bottom of the experimental cylinder;

[0014] The measuring cup is connected to the water intake through a hose, and stop valves are provided on both the water inlet and the water intake.

[0015] Preferably, the simulation experiment of the hydrogeochemical process of shallow groundwater salinization described in Step 1 includes the steps

[0016] Step101. Column filling;

[0017] Step102. Water level stabilization

[0018] Cover the top of the soil column with a cover. Inject the groundwater water sample from the irrigation area into the gravel layer in the experimental cylinder through the water inlet until the water level burial depth is stable at the height of the gravel layer, then close the water stop clamp, and weigh the total weight M0 of the column body;

[0019] Make multiple groups of soil columns in the same way;

[0020] Step103. Evaporation;

[0021] Step104. Irrigation;

[0022] Step105. Circulation

[0023] Repeat steps Step103 and Step104. Before each evaporation, weigh the total mass of the experimental soil column, which is M0 each time. The end point of evaporation is the water level burial depth of 60 cm. Weigh the total mass of the soil column after evaporation as M1. Repeat the above experiment until the soil column experiment with multiple irrigations is completed;

[0024] Step106. Testing;

[0025] Step107. Change the mixing ratio and repeat steps Step101 - Step106 to test the influence of different mixing ratios on the chemical components of groundwater.

[0026] Preferably, the evaporation process described in Step103 includes

[0027] (1) After removing the cover, place the soil column in a constant temperature and humidity chamber with a temperature of T = 25°C and a humidity of h = 70%, and regularly observe the water level burial depth in the soil column through the piezometer tube;

[0028] (2) When the water level burial depth in the experimental cylinder reaches 60 cm, weigh the remaining weight M1 of each group of soil columns, calculate the evaporation amount M2 = M0 - M1, and end the soil column experiment with 0 irrigations.

[0029] Preferably, the irrigation process described in Step104 includes

[0030] (1) According to the set mixing ratio, inject the mixed solution with a mass of M2 into the soil column from the upper part;

[0031] (2) After irrigation, cover the cover and seal the experimental cylinder. After the solution completely infiltrates into the soil column and the water level in the piezometer tube is stable, remove the cover and place the soil column in the constant temperature and humidity chamber to simulate the evaporation process of irrigation.

[0032] Preferably, the testing process described in Step106 includes

[0033] (1) After each group of soil column experiments, collect water samples at different depths in the soil column and analyze the chemical and isotope indexes;

[0034] (2) Take out the soil columns, collect soil samples every 10 cm, and conduct mineral composition and soluble salt analysis.

[0035] Preferably, the hydrogeological process analysis process of groundwater salinization under the irrigation-evaporation cycle conditions described in Step 2 includes

[0036] Step201. Based on the water quality analysis results of the water samples at the initial and final moments of each group of soil columns in Step 1, calculate the equilibrium distribution of aqueous solution components and the mineral saturation index;

[0037] Step202. On the basis of determining the dissolution or precipitation trend of mineral components in the aqueous solution, use the PHREEQC software to simulate the hydrogeochemical process of groundwater salinization under different mixing ratios and different irrigation times, calculate the reaction amounts of each mineral component, and verify the calculation and simulation results in combination with the changes in the corresponding mineral components in the soil before and after irrigation;

[0038] Step203. On the basis of Step202, use the single variable method to analyze the influence of the mixing ratio and irrigation times on the hydrogeochemical process of groundwater salinization, and determine the key chemical reactions affecting the groundwater salt content; at the same time, based on the mineral composition and soluble salt content of the soil samples at different horizons in the soil columns after the experiment, analyze the influence of irrigation activities on the salt migration law in the soil.

[0039] Preferably, the process of ion balance calculation under the irrigation-evaporation cycle conditions described in Step 3 includes

[0040] Step301. Use the hydrogeochemical reaction amount to build a bridge between salt balance and ion balance. For a certain ion in the irrigation-evaporation cycle soil column experiment, there is:

[0041] Water balance: V G0 = V’ G0 + V E0

[0042] V p + V I + V’ G0 = V’ G1 + V E1

[0043] i×(V p + V I ) + V’ G0 = V’ G i + V Ei (i = 0, 1, 2…7)

[0044] Where: V p + V I = V in

[0045] V’ G i = V’ G0

[0046] Salt balance: V G0 C G0 = V’ G0 C’ G0 + R0

[0047] V in C in + V G0 C G0 = V’ G1 C’ G1 + R1

[0048] 2×(V in C in ) + V G0 C G0 = V’ G2 C’ G2 + R2

[0049] i×(V in C in ) + V G0 C G0 = V’ Gi C’ Gi + R i (i = 0, 1, 2…7)

[0050] In the formula, V G0 , V’ Gi respectively represent the volumes of groundwater before irrigation and after the evaporation experiment at the end of the i-th irrigation. C G0 and C’ Gi respectively represent the concentrations of a certain ion in the corresponding groundwater; V in and C in respectively represent the volume and the concentration of a certain ion in the mixed solution of atmospheric precipitation and irrigation water; R i is the chemical reaction amount of the corresponding ion during the evaporation process of the i-th irrigation. R i = R i1 + R i2 +…+ R in ; R in is the dissolution or precipitation amount of the n-th mineral during the i-th irrigation;

[0051] Step302. Based on the above equations and iterative calculations, it is further deduced that:

[0052] V in C in = V’ G0 (C’Gi -C’ Gi-1 ) + R i -R i-1

[0053] α E / (1 - α E )C in =ΔC’ Gi +ΔR i / V’ G0 。

[0054] The beneficial effects of the present invention are as follows: The present invention discloses a method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization. Compared with the prior art, the improvements of the present invention are as follows:

[0055] 1. The present invention designs a method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization, including a simulation experiment process, a hydrogeological process analysis process of groundwater salinization under irrigation-evaporation cycles, and an ion balance calculation process under irrigation-evaporation cycles. When in use, by using the above method to simulate and analyze the hydrogeochemical process of shallow groundwater salinization, it can effectively study the influence law of different irrigation conditions on the groundwater-soil hydrogeochemical action process; at the same time, based on the ion concentration and evaporation amount changes of the soil and water samples measured in the irrigation cycle soil column experiment, combined with mathematical analysis, the correlation relationships among the irrigation times, the change amount of groundwater salinity, and the hydrogeochemical reaction amount under different mixing ratios are drawn and fitted to establish, and the influence law of different irrigation conditions on the groundwater-soil hydrogeochemical action process is analyzed, thus laying a foundation for studying the groundwater-soil hydrogeochemical action process in different regions;

[0056] 2. The present invention designs a simulation device for the hydrogeochemical process of shallow groundwater salinization to implement the above method. When in use, this device can be used to measure the specific gravity of soil samples by the pycnometer method, test the initial moisture content of the soil by the drying method, calculate the saturated moisture content by the mass difference before and after the soil sample is saturated, and determine the porosity by the water retention method, with the advantages of simple structure, convenient use, and good simulation effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 is a flowchart of the method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization of the present invention.

[0058] Figure 2 is a schematic structural diagram of the simulation device for the hydrogeochemical process of shallow groundwater salinization of the present invention.

[0059] Wherein: 1. experimental cylinder, 2. piezometric tube, 3. water inlet, 4. water intake, 5. measuring cup, 6. stopcock, 7. geotextile, 8. soil column, 9. gravel layer, 10. cover body. Detailed implementation manners

[0060] In order to enable ordinary technicians in the field to better understand the technical solution of the present invention, the technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0061] Example 1: Refer to the Figure 1-2 A simulation device for the hydrogeochemical process of shallow groundwater salinization shown in the figure, including an experimental cylinder 1 and a measuring cup 5; wherein

[0062] The experimental cylinder 1 is a transparent tubular structure provided with scales, and a piezometric tube 2, a water inlet 3 and a water intake 4 are provided on the experimental cylinder 1. Multiple groups of the piezometric tubes 2 are provided on the tube body of the experimental cylinder 1 for observing the change of the groundwater level at any time; the water inlet 3 is provided at the lower end of the experimental cylinder 1 for injecting groundwater into the experimental cylinder 1; the water intake 4 is provided at the bottom of the experimental cylinder 1.

[0063] The measuring cup 5 is connected to the water intake 4 through a rubber hose to facilitate the release of the water in the experimental cylinder 1 and weighing in the measuring cup 5.

[0064] Stopcocks 6 are provided on both the water inlet 3 and the water intake 4 to control the opening and closing of the pipelines of the water inlet 3 and the water intake 4.

[0065] Preferably, a cover body 10 is also detachably provided on the experimental cylinder 1 to prevent the evaporation of the water in the experimental cylinder 1 during the experiment.

[0066] A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization using the above-mentioned simulation device for the hydrogeochemical process of shallow groundwater salinization. The experimental scheme of this method is: the dry density of the designed experimental soil column 8 is 1.5 g / cm 3 ; the groundwater depth before evaporation is 20 cm, and after a single evaporation, it is 60 cm; the temperature of the constant temperature and humidity box is fixed at 25 °C and the humidity is 70%; six groups of mixing ratios of irrigation water and atmospheric precipitation are designed, V p :V I are 4:3, 5:2, 6:1, 1:6, 2:5, 3:4 respectively; the number of irrigation cycles is 0, 1, 2, 3, 4, 5, 6, 7 times respectively; the experimental steps include

[0067] Step 1: Simulate the experimental process

[0068] Step101. Soil column filling

[0069] (1) Before filling, calculate the required soil mass based on the designed dry density of the soil sample and the initial water content of the soil;

[0070] (2) After calculating the soil mass, evenly load the soil sample onto the gravel layer 9 in the experimental cylinder 1 in layers of 10 cm thickness each and compact it successively. The surface of the soil sample needs to be scraped smooth between each layer until the designed filling height is reached, and the filling of the soil column 8 is completed;

[0071] Step102. Water level stabilization

[0072] (1) Cover the top of the soil column 8 with a cover body 10 to prevent water evaporation. Slowly inject the groundwater water sample in the irrigation area into the gravel layer in the experimental cylinder 1 from the water inlet 3 until the water level burial depth is stable at 20 cm, then close the stopcock 6 on the water inlet 3, and weigh the total weight of the column body 8 as M0;

[0073] (2) Use the same method to make 8 groups of the same soil columns 8;

[0074] Step103. Evaporation

[0075] (1) After removing the cover body 10, place the 8 groups of soil columns in a constant temperature and humidity chamber with a temperature of T = 25 °C and a humidity of h = 70%, and regularly observe the water level burial depth in the soil column through the piezometer tube 2;

[0076] (2) When the water level burial depth in the experimental cylinder 1 reaches 60 cm, weigh the remaining weight M1 of each group of soil columns 8, and calculate the evaporation amount M2 = M0 - M1, and end the soil column experiment with 0 irrigation times;

[0077] Note: In steps Step102(1) and Step103(2), during the experiment, since the single weight of the column body 8 cannot be weighed, the overall weight including the experimental cylinder 1 is weighed;

[0078] Step104. Irrigation

[0079] (1) According to the set mixing ratio, inject the mixed solution with a mass of M2 into the soil column 8 from the upper part;

[0080] Among them, the set mixing ratio includes the mixing ratio of irrigation water and atmospheric precipitation, V p :V I are 4:3, 5:2, 6:1, 1:6, 2:5, 3:4 respectively;

[0081] (2) After irrigation, cover the cover body 10 to seal and let the experimental cylinder 1 stand still. After the solution completely infiltrates into the soil column 8 and the water level in the piezometer tube 2 is stable, remove the cover body 10 and place the soil column 8 in a constant temperature and humidity chamber to simulate the evaporation process of 1 irrigation;

[0082] Among them, the evaporation process is the same as the process described in Step103;

[0083] Step105. Loop

[0084] Repeat steps Step103 and Step104. Each time before evaporation, the total mass of the experimental soil column 8 is M0. The end point of evaporation is the water table depth of 60 cm. After evaporation, weigh the total mass of the soil column 8 as M1. Repeat the above experiment until the soil column experiment of the eighth group with 7 irrigations is completed;

[0085] Step106. Test

[0086] (1) After each group of soil column 8 experiments, collect water samples at different depths in the soil column 8 and analyze chemical and isotope indicators;

[0087] (2) Take out the soil column 8, collect soil samples every 10 cm and conduct mineral composition and soluble salt analysis;

[0088] Step107. Change the mixing ratio and repeat steps Step101 - Step106 to test the influence of different mixing ratios on the chemical components of groundwater;

[0089] And during the simulation experiment in step 1, lay a geotextile 7 on the soil column 8 to prevent erosion of the top of the soil during the simulated irrigation process; and set a filter layer of gravel layer 9 with a height of 20 cm at the bottom of the soil column 8 for soil filtration and drainage, and lay 2 - 3 layers of geotextiles 7 on it to prevent soil samples from falling into the gravel layer 9;

[0090] Step Two: Hydrogeological Process Analysis of Groundwater Salinization under Irrigation - Evaporation Cycle

[0091] Step201. Based on the water quality analysis results of the water samples at the initial and final moments of each group of soil columns 8, calculate the equilibrium distribution of aqueous solution components and the mineral saturation index;

[0092] Step202. On the basis of judging the dissolution or precipitation trend of mineral components in the aqueous solution, use the PHREEQC software to simulate the hydrogeochemical process of groundwater salinization under different mixing ratios and different irrigation times, calculate the reaction amounts of each mineral component, and combine the changes in the corresponding mineral components in the soil before and after irrigation to verify the calculation and simulation results;

[0093] Step203. On this basis, use the single - variable method to analyze the influence of the mixing ratio and irrigation times on the hydrogeochemical process of groundwater salinization, and determine the key chemical reactions affecting the groundwater salt content; in addition, based on the mineral composition and soluble salt content of the soil samples at different horizons in the soil column 8 after the experiment, analyze the influence of irrigation activities on the salt migration law in the soil, and provide an experimental basis for the mutual feedback between groundwater salinization and soil salinization;

[0094] Step 3: Ion balance calculation under irrigation-evaporation cycle conditions

[0095] Step301. From the perspective of salt balance, irrigation simultaneously brings the salts in irrigation water and soil into groundwater. Therefore, the impact mechanism of different irrigation frequencies on groundwater salinization needs to be considered in the salt balance term; in this embodiment, a hydrogeochemical reaction quantity is used to build a bridge between salt balance and ion balance. For a certain ion in the irrigation-evaporation cycle soil column test, there is:

[0096] Water balance: V G0 = V’ G0 + V E0

[0097] V p + V I + V’ G0 = V’ G1 + V E1

[0098] i × (V p + V I ) + V’ G0 = V’ Gi + V Ei (i = 0, 1, 2…7)

[0099] Where: V p + V I = V in

[0100] V’ Gi = V’ G0

[0101] Salt balance: V G0 C G0 = V’ G0 C’ G0 + R0

[0102] V in C in + V G0 C G0 = V’ G1 C’ G1 + R1

[0103] 2 × (V in C in ) + V G0 C G0 = V’ G2 C’ G2 + R2

[0104] i × (V in C in ) + VG0 C G0 = V' Gi C' Gi + R i (i = 0, 1, 2…7)

[0105] In the formula, V G0 , V' Gi respectively represent the volumes of groundwater before irrigation and after the evaporation experiment for the i-th irrigation, C G0 and C' Gi respectively represent the concentrations of a certain ion in the corresponding groundwater; V in and C in respectively represent the volume of the mixed solution of atmospheric precipitation and irrigation water and the concentration of a certain ion; R i is the chemical reaction amount of the corresponding ion during the evaporation process of the i-th irrigation, R i = R i1 + R i2 +……+ R in (R in is the dissolution or precipitation amount of the n-th mineral during the i-th irrigation);

[0106] Step302. Based on the above equations and iterative calculations, further derivation gives:

[0107] V in C in = V' G0 (C' Gi - C' Gi-1 ) + R i - R i-1

[0108] α E / (1 - α E )C in = ΔC' Gi + ΔR i / V' G0

[0109] It can be seen that the irrigation times i, the irrigation water quality C in , the evaporation ratio α E , the groundwater volume V' G0 and the hydrogeochemical reaction amount R i all have a certain impact on the change amount of groundwater salinity;

[0110] According to the ion concentration and evaporation amount change conditions of the soil and water samples measured in the irrigation cycle soil column experiment, combined with mathematical analysis, draw and fit the correlation relationships between the irrigation times, the change amount of groundwater salinity, and the hydrogeochemical reaction amount under different mixing ratios, and analyze the influence law of different irrigation conditions on the groundwater-soil hydrogeochemical action process.

[0111] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization, characterized in that: including Step 1: Conduct a simulation experiment on the hydrogeochemical process of shallow groundwater salinization using a simulation device for the hydrogeochemical process of shallow groundwater salinization; Step 2: Analyze the hydrogeological process of groundwater salinization under irrigation-evaporation cycle conditions based on the results of the simulation experiment; Step 3: Conduct ion balance calculations under irrigation-evaporation cycle conditions based on the analysis of the hydrogeological process of groundwater salinization under irrigation-evaporation cycle conditions.

2. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization according to claim 1, characterized in that: The simulation device for the hydrogeochemical process of shallow groundwater salinization described in Step 1 includes an experimental cylinder and a measuring cup; The experimental cylinder is a transparent tubular structure with scales, and a piezometer tube, a water inlet, and a water sampling port are provided on the experimental cylinder. Multiple groups of piezometer tubes are provided on the tube body of the experimental cylinder. The water inlet is provided at the lower end of the experimental cylinder, and the water sampling port is provided at the bottom of the experimental cylinder; The measuring cup is connected to the water sampling port through a hose, and stop valves are provided on both the water inlet and the water sampling port.

3. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization according to claim 1, characterized in that: The simulation experiment on the hydrogeochemical process of shallow groundwater salinization described in Step 1 includes the steps Step101. Soil column filling; Step102. Water level stabilization Cover the top of the soil column, inject the groundwater water sample from the irrigation area into the gravel layer in the experimental cylinder through the water inlet until the water level depth is stable at the height of the gravel layer, then close the stop valve, and weigh the total weight M0 of the column body; Make multiple groups of soil columns in the same way; Step103. Evaporation; Step104. Irrigation; Step105. Cycle Repeat Step103 and Step104. Before each evaporation, the total mass of the experimental soil column is weighed as M0. The end point of evaporation is a water level depth of 60 cm. Weigh the total mass of the soil column after evaporation as M1. Repeat the above experiment until the soil column experiment with multiple irrigations is completed; Step106. Testing; Step107. Change the mixing ratio, and repeat Step101 - Step106 to test the influence of different mixing ratios on the chemical components of groundwater.

4. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization according to claim 3, characterized in that: The evaporation process described in Step103 includes (1) After removing the cover, place the soil column in a constant temperature and humidity chamber with a temperature of T = 25°C and a humidity of h = 70%, and regularly observe the water level depth in the soil column through the piezometer tube; (2) When the water level depth in the experimental cylinder reaches 60 cm, weigh the remaining weight M1 of each group of soil columns, calculate the evaporation amount M2 = M0 - M1, and end the soil column experiment with 0 irrigations.

5. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization according to claim 3, characterized in that: The irrigation process described in Step104 includes (1) According to the set mixing ratio, inject a mixed solution with a mass of M2 into the soil column from the upper part; (2) After irrigation, cover the lid and seal the experimental cylinder. Wait until the solution completely infiltrates into the soil column and the water level in the piezometer tube is stable, then remove the lid and place the soil column in a constant temperature and humidity chamber to simulate the evaporation process of irrigation.

6. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization according to claim 3, characterized in that: The testing process described in Step106 includes (1) After each group of soil column experiments, collect water samples at different depths in the soil column and analyze chemical and isotope indicators; (2) Take out the soil column, collect soil samples every 10 cm and conduct mineral composition and soluble salt analysis.

7. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization according to claim 1, characterized in that: The analysis process of the hydrogeological process of groundwater salinization under irrigation-evaporation cycle conditions described in Step 2 includes Step201. Based on the water quality analysis results of the water samples at the initial and final moments of each soil column in Step 1, calculate the equilibrium distribution of aqueous solution components and the mineral saturation index; Step202. On the basis of determining the dissolution or precipitation trend of mineral components in the aqueous solution, use the PHREEQC software to simulate the hydrogeochemical process of groundwater salinization under different mixing ratios and different irrigation frequencies, calculate the reaction amounts of each mineral component, and verify the calculation and simulation results in combination with the changes in the corresponding mineral components in the soil before and after irrigation; Step203. On the basis of Step202, use the single variable method to analyze the influence of the mixing ratio and irrigation frequency on the hydrogeochemical process of groundwater salinization, and determine the key chemical reactions affecting the groundwater salt content; at the same time, based on the mineral composition and soluble salt content of the soil samples at different horizons in the soil column after the experiment, analyze the influence of irrigation activities on the salt migration law in the soil.

8. A method for simulating and analyzing the hydrogeochemical process of shallow groundwater salinization according to claim 1, characterized in that: The process of ion balance calculation under the irrigation-evaporation cycle conditions described in Step 3 includes Step301. Use the hydrogeochemical reaction amount to build a bridge between salt balance and ion balance. For a certain ion in the irrigation-evaporation cycle soil column experiment, there is: Water balance: V G0 = V' G0 + V E0 V p +V I +V’ G0 = V’ G1 +V E1 i×(V p +V I )+V’ G0 =V’ Gi +V Ei (i = 0, 1, 2…7) where: V p +V I =V in V’ Gi = V’ G0 Salt balance: V G0 C G0 = V’ G0 C’ G0 + R0 V in C in +V G0 C G0 = V' G1 C' G1 + R1 2×(V in C in )+V G0 C G0 =V’ G2 C’ G2 +R2 i×(V in C in ) + V G0 C G0 = V’ Gi C’ Gi + R i (i = 0, 1, 2…7) Where, V G0 , V’ Gi respectively represent the volumes of groundwater before irrigation and after the evaporation experiment of the i-th irrigation, C G0 and C’ Gi respectively represent the concentrations of a certain ion in the corresponding groundwater; V in and C in respectively represent the volume of the mixed solution of atmospheric precipitation and irrigation water and the concentration of a certain ion; R i is the amount of chemical reaction that occurs for the corresponding ion during the evaporation process of the i-th irrigation, R i =R i1 +R i2 +…+R in , R in is the amount of dissolution or precipitation of the n-th mineral during the i-th irrigation;​ Step302. Based on the above equations and iterative calculations, further deduce and obtain: V in C in = V' G0 (C' Gi - C' Gi-1 ) + R i - R i-1 α E / (1 - α E )C in = ΔC’ Gi + ΔR i / V’ G0 。

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