Method for improving soda saline-alkali soil by applying electrodynamics in combination with aluminum sulfate

Abstract

The invention discloses a soda saline-alkali soil improvement method combining electrodynamics with aluminum sulfate application, which comprises the following steps: applying an aluminum sulfate modifier in soda saline-alkali soil to distribute the aluminum sulfate modifier in surface layer or plough layer soil; the method comprises the following steps: burying an anode on the surface layer of a soil body of soda saline-alkali soil, and burying a cathode below a target improvement depth to form a vertical or approximately vertical electrode system; and applying a direct-current electric field to the soil body to realize electric improvement of the soda saline-alkali soil, and supplying water to the soil body in the electric improvement process. According to the method, the soil structure is improved through aluminum sulfate, and the electroosmosis effect and the electromigration effect generated under the action of an external electric field are combined, so that the migration ability of moisture and salt in the low-permeability soil is enhanced; the aluminum-based ions migrate to the cathode side under the action of an electric field, so that the problems of salt enrichment and aggravation of the alkalization degree easily occurring in a cathode area in the electric improvement process are solved, and salt and exchangeable sodium in the soda saline-alkali soil are effectively removed.

Description

Technical Field

[0001] This invention relates to a method for improving soda saline-alkali soil by combining electrodynamics with aluminum sulfate application, belonging to the field of soil improvement technology. Background Technology

[0002] Soil salinization is a major issue concerning agricultural production safety. Currently, the global area of ​​saline-alkali soil is approximately 1.1 × 10⁻⁶. 9 hm 2 The area of ​​saline-alkali soil in China is approximately 3.69 × 10⁻⁶. 7 hm 2 Saline-alkali soils are characterized by poor pore connectivity, disrupted aggregate structure, and low organic matter content. They are typical low- to medium-yield soils, hindering land productivity and sustainable agricultural development. Improving saline-alkali land is crucial for enhancing agricultural productivity and ensuring food security.

[0003] Soda saline-alkali soil contains a large amount of exchangeable Na. + HCO3 - and CO3 2- The soil has a high pH and ESP (soil alkalinity). This is due to the high Na content in the soil. + Hydration of soil colloids makes them more easily dispersed upon contact with water, reduces soil pore size, and decreases permeability; CO3 2- Hydrolysis produces an alkaline environment, and the high pH increases the electrostatic repulsion between soil particles, further disrupting the soil's aggregate structure. This makes traditional irrigation and salt leaching methods ineffective for improving soda-alkali soils. Simultaneously, high pH and HCO3... - and CO3 2- The reduced content also decreases the activity of metal cations in the amendment, which means that chemical amendments (gypsum, aluminum sulfate, ferrous sulfate, etc.) need to be applied to severely soda saline-alkali soils, increasing the input cost.

[0004] In recent years, electro-optical soil remediation technology, which utilizes a direct current electric field to promote ion migration and electroosmotic flow, has been applied in the field of soil remediation and has shown potential in improving low-permeability soils. The advantages of electro-optical remediation lie in its ability to perform in-situ soil remediation, reducing physical disturbance during the process, and significantly enhancing water movement in low-permeability soils. Electro-optical remediation of saline-alkali soils has achieved good salt removal and alkali reduction effects at the anode; however, the electrode reaction generates a large amount of OH- at the cathode. - Salt ions migrate from the anode to the cathode and accumulate there, causing a further increase in soil salinity and exacerbating alkalization near the cathode. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for improving soda saline-alkali soil by combining electrodynamics with the application of aluminum sulfate.

[0006] The technical solution adopted in this invention is as follows: A method for improving soda-saline-alkali soil by combining electrodynamics with aluminum sulfate application, comprising the following steps: (1) Apply aluminum sulfate amendment to soda saline-alkali soil and distribute it in the topsoil or cultivated layer. The aluminum sulfate amendment can be mixed evenly by tilling, mechanical mixing and other methods. (2) An anode is buried on the surface of the soda saline-alkali soil and a cathode is buried below the target improvement depth to form a vertical or near-vertical electrode system. (3) Apply a DC electric field to the soil to achieve electro-modification of soda saline-alkali soil. During the electro-modification process, water is supplied to the soil so that the electrolysis reaction can continue.

[0007] Preferably, the application amount of the aluminum sulfate amendment is 0.1 wt.% to 2.0 wt.% based on the dry weight of the soil.

[0008] Preferably, the DC electric field is formed by connecting a regulated DC power supply to the anode and cathode.

[0009] Preferably, the potential gradient of the DC electric field is 0.6~2.4V / cm, and the continuous energizing time is 7~60 days.

[0010] Preferably, during the electric improvement process, sufficient moisture is supplied to the soil through surface irrigation or by maintaining shallow water accumulation.

[0011] Preferably, the standard for providing sufficient water supply is to keep the soil saturated or nearly saturated with water in order to maintain continuous pore water channels and facilitate the conduction of electric current.

[0012] Preferably, a drainage structure is provided at the cathode to drain water and salt that have migrated to the vicinity of the cathode.

[0013] The beneficial effects of this invention are as follows: (1) This invention provides a method for improving soda saline-alkali soil by combining electro-modification technology with the application of aluminum sulfate, thereby fully leveraging the synergistic effect of chemical modification and the application of an external electric field. Aluminum sulfate can improve the physical structure of the soil, promote the formation of aggregates, enhance water permeability, and promote the leaching and removal of salts; the applied DC electric field can generate electroosmotic flow and electromigration in the soil, accelerating water movement and the migration of salt ions. The synergistic effect of the two can effectively enhance the water and salt transport capacity in low-permeability soda saline-alkali soil, and has a better effect on reducing alkali and removing salts compared with chemical modification alone.

[0014] (2) During the process of electrically improving soil, the electrolytic reaction at the anode will produce H₂. + The electrolysis reaction at the cathode will produce OH- - This can easily lead to a decrease in pH and ESP on the anode side and an increase in pH and ESP on the cathode side when using electrodynamic remediation of saline-alkali soil. After applying aluminum sulfate, the electric field and the acidic environment generated near the anode promote the migration of aluminum-based ions towards the cathode. The aluminum-based ions that migrate to the cathode side can improve the soil structure near the cathode and promote the excretion of adsorbed sodium and soluble salts, thereby effectively alleviating the phenomenon of salt accumulation and intensified alkalization on the cathode side when using electrodynamic remediation alone, and improving the overall remediation effect of saline-alkali soil. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the vertical electric modification device used in Example 1; Figure 2 Soil profile salt content distribution and overall desalination rate under individual electrodynamic improvement, individual aluminum sulfate improvement, and combined electrodynamic and aluminum sulfate application treatments; Figure 3 Soil profile pH and ESP distribution under treatments of leaf electrokinetic improvement alone, aluminum sulfate improvement alone, and combined electrokinetic and aluminum sulfate application; Figure 4 This is a schematic diagram of the application of this method in the field; where 1-anode; 2-cathode; 3-flooded layer; 4-soil mixed with aluminum sulfate; 5-initial soil; 6-outlet.

[0016] The present invention will be further described below with reference to specific embodiments. Detailed Implementation

[0017] The present invention will be further described below with reference to the embodiments, but the description of the embodiments does not limit the scope of protection of the present invention in any way. Unless otherwise defined, 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 invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. Furthermore, while this document may provide examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but may approximate the corresponding values ​​within acceptable error tolerances or design constraints. Unless otherwise specified, all substances or instruments used in the following examples can be obtained from conventional commercial sources. Example 1: Soil column experiment Three improvement methods were set up: single electrodynamic improvement, single aluminum sulfate improvement, and electrodynamic combined with aluminum sulfate comprehensive improvement. The improvement effects of the three methods were compared through soil column experiments.

[0018] Severely soda-salt-alkali soil with an initial pH of 10.45 and an ESP of 76.9% was selected.

[0019] The electric soil amendment device is arranged vertically, with the anode positioned above the soil sample chamber and the cathode positioned below the soil sample chamber as a drainage outlet. The electrode spacing is 20 cm. Figure 1 A 300-mesh nylon mesh and permeable stone are laid sequentially above the cathode.

[0020] Soil samples were prepared at a concentration of 1.4 g / cm³. 3 The dry density of the sample was layered and filled into the electric soil amendment device. Water was supplied to the soil through the outlet to saturate it, and a constant water head of 5 mm was maintained from above the soil sample chamber using a Marshall bottle.

[0021] Under the same experimental conditions as above, the following three test treatments were set up: (1) Individual electric improvement treatment: Connect the electrode to a regulated DC power supply with a voltage gradient of 1.2V / cm and continuously power it on for 30 days at 25℃.

[0022] (2) Aluminum sulfate improvement treatment alone: ​​Analytical grade aluminum sulfate was selected and added at 0.8 wt.% of the dry weight of the soil. The aluminum sulfate was thoroughly mixed with the soil sample and then layered into the electric improvement device. The power supply was not connected, and the device was cultured for 30 days in the same environment as treatment (1).

[0023] (3) Electrodynamic combined aluminum sulfate improvement treatment: Analytical grade aluminum sulfate was selected and the amount added was 0.8 wt.% of the dry weight of the soil. The aluminum sulfate was thoroughly mixed with the soil sample and then filled into the electric improvement device in layers. The electrodes were connected to a regulated DC power supply with a voltage gradient of 1.2 V / cm. The device was continuously powered on for 30 days under the same conditions as treatment (1).

[0024] After cultivation, stratified samples were taken to measure the profile distribution of soil salinity, pH, and alkalinity.

[0025] Experimental results show that ( Figure 2 and Figure 3While electrokinetic soil conditioning (VEK) alone can significantly reduce salinity, pH, and ESP at a soil depth of 0-10 cm (anode side), it increases soil salinity and alkalinity at a depth of 10-20 cm (cathode side), resulting in an overall soil desalination rate of only 30.6%. Aluminum sulfate conditioning alone (Al2(SO4)3) can achieve overall soil profile desalination with a desalination rate of 69.5%, but its improvement on soil alkalization is very limited, and it is almost ineffective in reducing soil pH and ESP. The electrokinetic treatment combined with aluminum sulfate application (VEK-Al2(SO4)3) reduces soil salinity at all depths, achieving a desalination rate of 88.1%, while also reducing the overall soil profile ESP to below 2%. The electrokinetic treatment combined with aluminum sulfate application provided by this invention has good salt removal and alkalization effects, and effectively alleviates the phenomenon of salt accumulation and increased alkalization on the cathode side when electrokinetic conditioning is used alone.

[0026] Example 2: Field Application like Figure 4 As shown, in field application, aluminum sulfate amendment is evenly spread on the surface of soda-alkali soil. Through tilling, the aluminum sulfate amendment is evenly mixed into the topsoil layer 4. Anode electrodes 1 are buried shallowly on the soil surface, and cathode electrodes 2 are buried below the target improvement depth. The spacing between the electrode components can be adjusted according to soil type, salinity, and field conditions. The cathode electrodes are installed by partially excavating the soil to the target improvement depth at the electrode location, burying the cathode, and then backfilling with soil. The cathode uses a combination structure of a perforated electrode plate and a semi-circular PVC pipe, with the perforated electrode plate positioned on top of the semi-circular PVC pipe, both arranged along their length. During the electro-amendment process, water and salt migrating to the vicinity of the cathode are discharged through the semi-circular PVC pipe. Other methods for draining water and salt near the cathode can also be used. A shallow water layer 3 is maintained on the soil surface. The two electrodes are connected to a regulated DC power supply to create an approximately vertical electric field in the soil for electro-amendment. During the electric improvement process, the soil moisture is maintained at saturation through irrigation or pipeline water supply, and the high-concentration salt water near the cathode electrode 2 is discharged through the drainage structure 6 of the cathode electrode 2.

[0027] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for improving soda-saline-alkali soil by combining electrodynamics with aluminum sulfate application, characterized in that... The steps include: (1) Apply aluminum sulfate amendment to soda saline-alkali soil and distribute it in the topsoil or cultivated layer; (2) An anode is buried on the surface of the soda saline-alkali soil and a cathode is buried below the target improvement depth to form a vertical or near-vertical electrode system. (3) Apply a DC electric field to the soil to achieve electric modification of soda saline-alkali soil and provide water supply to the soil during the electric modification process.

2. The method for improving soda-saline-alkali soil according to claim 1, characterized in that: The application rate of the aluminum sulfate amendment is 0.1 wt.% to 2.0 wt.% based on the dry weight of the soil.

3. The method for improving soda-saline-alkali soil according to claim 1, characterized in that: The DC electric field is formed by connecting a regulated DC power supply to the anode and cathode.

4. The method for improving soda-saline-alkali soil according to claim 1, characterized in that: The potential gradient of the DC electric field is 0.6~2.4V / cm, and the continuous energizing time is 7~60 days.

5. The method for improving soda-saline-alkali soil according to claim 4, characterized in that: During the electric improvement process, sufficient moisture is supplied to the soil through surface irrigation or by maintaining shallow water accumulation.

6. The method for improving soda-saline-alkali soil according to claim 5, characterized in that: The standard for providing sufficient water supply is to keep the soil saturated or nearly saturated with water.

7. The method for improving soda-saline-alkali soil according to any one of claims 1-6, characterized in that: A drainage structure is installed at the cathode to drain water and salt that have migrated to the vicinity of the cathode.

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