Natural force driven saline-alkali soil negative pressure desalination system and method of use thereof

Abstract

This invention discloses a natural force-driven negative pressure desalination system for saline-alkali soil and its application method, belonging to the technical field of saline-alkali soil treatment equipment. It includes a water supply system, a soil tank, and a negative pressure water suction system. The soil tank is a rectangular plexiglass container with an open top, used to store saline-alkali soil. The water supply system is located outside the soil tank, with its outlet end placed inside the saline-alkali soil within the tank, providing water at a constant pressure to the soil. The inlet end of the negative pressure water suction system is placed inside the saline-alkali soil within the tank, used to draw water from the saline-alkali soil to the outside. This invention utilizes the natural force of soil-water potential to dissolve, absorb, and recover salts from the soil, achieving both soil desalination and the resource utilization of water and salt. It effectively solves the problems of large engineering costs, long construction periods, soil salinization, and secondary degradation associated with existing saline-alkali land improvement technologies.

Description

Technical Field

[0001] This invention relates to the technical field of saline-alkali soil treatment equipment, specifically to a natural force-driven negative pressure desalination system for saline-alkali soil, and also to a method of using the natural force-driven negative pressure desalination system for saline-alkali soil. Background Technology

[0002] Analysis of saline-alkali land improvement technologies reveals that the high-pressure salinity physical improvement technology, which involves water leaching and underground pipe drainage, provides fresh (or slightly brackish) water to the soil to dissolve the salts. The dissolved salts are then temporarily driven below the topsoil or to the outside using the natural potential energy of the soil water, achieving short-term improvement. However, this method often requires significant engineering and investment, has a long construction period, and without long-term control and management, the soil will quickly re-salinate or develop secondary salinity problems. While chemical, biological, and agronomic saline-alkali land improvement technologies also exist, they are limited to improvement, adding various agents, microbial agents, and fertilizers to the soil to achieve the desired effect. These methods primarily involve adding to the soil, with few reports on methods that subtract from it to remove soil salinity. There is an urgent need for a highly efficient, long-lasting, and low-energy-consumption soil desalination method. Summary of the Invention

[0003] The first objective of this invention is to provide a natural force-driven negative pressure desalination system for saline-alkali soil, which solves the problems of large engineering and investment, long construction period, soil salinization and secondary degradation in existing saline-alkali land improvement technologies.

[0004] To achieve the first objective, the technical solution adopted by this invention is as follows: a natural force-driven negative pressure desalination system for saline-alkali soil, comprising a water supply system, a soil tank, and a negative pressure water absorption system. The soil tank is a rectangular plexiglass container with an open top, used to store saline-alkali soil. The water supply system is located outside the soil tank, with one end of the water outlet placed inside the saline-alkali soil within the soil tank, used to provide water at a constant pressure to the soil inside the soil tank. The water inlet of the negative pressure water absorption system is placed inside the saline-alkali soil within the soil tank, used to draw water from the saline-alkali soil to the outside of the soil.

[0005] Furthermore, the aforementioned water supply system includes a Marshall bottle and a linear water source emitter. The Marshall bottle is equipped with an air inlet pipe, a water supply valve, a scale, an air outlet, and a water outlet valve. The water outlet valve is connected to a water distributor via a first water supply pipe. The water distributor is installed on a soil tank and is connected to multiple linear water source emitters via multiple second water supply pipes. The multiple linear water source emitters are spaced apart in the saline-alkali soil within the soil tank for supplying water to the saline-alkali soil.

[0006] Furthermore, the water inlet of the aforementioned water distributor is equipped with an inlet valve, and multiple outlets are equipped with outlet valves.

[0007] Furthermore, the aforementioned linear water source emitter includes a shell, a pagoda connector, a plug, micropores, and an inner liner. The shell is a cylindrical structure with openings at both ends. The inlet of the pagoda connector is connected to the second water supply pipe. The pagoda connector and the plug are fixedly connected to the upper and lower ends of the shell, respectively. The shell wall is covered with multiple micropores. The inner liner is a tubular structure with openings at both ends. The upper end is connected to the outlet of the pagoda connector and maintains a gap with the shell, while the lower end maintains a gap with the inner end of the plug.

[0008] Furthermore, the aforementioned negative pressure water intake system includes a negative pressure pump, a water collector, an electronic scale, and a negative pressure filter. The negative pressure filter is placed in the middle of the saline-alkali soil. Linear water emitters are symmetrically arranged around the negative pressure filter. The outlet at the top of the negative pressure filter is connected to the negative pressure pump through a third water supply pipe. The negative pressure pump is connected to the water collector through a fourth water supply pipe. The water collector is installed on the electronic scale.

[0009] Furthermore, the aforementioned negative pressure filter includes a negative pressure interface, a semi-permeable membrane, and a water-permeable layer. The water-permeable layer is a barrel-shaped structure with an open top. The semi-permeable membrane is placed inside the water-permeable layer, and the top of the semi-permeable membrane is connected to the negative pressure interface, which is connected to the third water supply pipe.

[0010] Furthermore, the soil box is provided with sensor installation holes and sampling holes on its four sides. The sensor installation holes and sampling holes are used to install sensors (soil temperature, humidity, and conductivity sensors, model: RS-ECTH-N01) and to take soil samples, respectively. The sensor installation holes and sampling holes are detachably sealed with sealing caps. The bottom of the soil box is designed with uniform small holes (φ3mm) to facilitate the infiltration of soil for venting. The sensor adopts a three-in-one sensor for temperature, humidity, and moisture.

[0011] Furthermore, the aforementioned sensors are connected to a controller, which is also connected to a negative pressure pump, a Mascher bottle, and a water distributor. The controller is used to control the water supply and negative pressure absorption based on the sensor's detection signals. The controller is connected to a storage battery, which is connected to a photovoltaic panel.

[0012] The second objective of this invention is to provide a method for using a natural force-driven negative pressure desalination system for saline-alkali soil, which facilitates precise desalination and improves desalination efficiency.

[0013] Regarding the second objective, the technical solution adopted by this invention is: a method for using a natural force-driven negative pressure desalination system for saline-alkali soil, the method comprising the following steps:

[0014] Step 1: Soil sample filling and sensor installation

[0015] First, lay qualitative filter paper at the bottom of the soil box and seal all sampling holes and sensor installation holes on the soil box with a sealing cap. After the saline soil sample is sieved through a 2mm sieve, it is loaded into the soil box according to the set bulk density, and evenly loaded into the soil box in seven layers, each layer being 10cm thick, with roughened between layers. After the soil sample is filled, remove the sealing piece of the sensor installation hole, insert the sensor horizontally into the sensor installation hole, and ensure that the sensor probe is fully inserted into the soil sample. After the sensor is installed, connect the sensor to the controller.

[0016] Step Two: Water Supply System Installation

[0017] Using a screwdriver, drill four bottom holes from the top surface of the soil sample downwards at the four corners of the soil sample surface. The four holes are axially symmetrical. Slowly insert four linear water emitters into the four bottom holes. Then connect the Mascher bottle, water distributor and linear water emitter using the first water supply pipe and the second water supply pipe.

[0018] Step 3: Installation of the negative pressure system

[0019] Using a screwdriver, make a bottom hole in the center of the soil sample from the top surface downwards. Slowly insert the negative pressure filter. Then, use the third and fourth water supply pipes to connect the pagoda head of the negative pressure filter, the negative pressure pump, and the water collector. Place the water collector on the electronic scale, set the electronic scale to tare, and finally connect the negative pressure pump and controller to test the negative pressure system.

[0020] Step 4: Linear infiltration into the soil

[0021] First, open the water supply valve of the Marble bottle, add an appropriate amount of test water to the Marble bottle, then close the water supply valve and record the water level value with a ruler. Adjust the lower end of the air outlet of the Marble bottle's air inlet pipe to be flush with the upper surface of the soil sample. Open the first water outlet valve of the Marble bottle and the water inlet valve of the distributor. Water flows from the Marble bottle into the distributor under constant pressure along the first water supply pipe. Open the second of the four subdivision water outlet valves of the distributor in sequence, and fine-tune the second of the four subdivision water outlet valves to make the water flow evenly into the linear source irrigation device. Observe the linear source infiltration process, record the trend of the wetting peak change and the water level value on the ruler. During the linear source infiltration process of the soil sample, the following should be noted: ① During the linear source infiltration process, the second water outlet valve should be adjusted to a smaller value. ① Ensure the opening of the valve is adjusted to allow for slow infiltration, preventing excessive water velocity from creating preferential flow in the soil; ② Observe the water level in the Marshall bottle. When the water level is low, promptly close the outlet valve of the Marshall bottle, record the water level value on the scale, open the water supply valve of the Marshall bottle to replenish water, record the water level value on the scale again after replenishment, and open the outlet valve of the Marshall bottle to continue water supply; ③ When leakage occurs at the bottom of the soil tank, adjust the outlet valve to reduce the amount of infiltrated water; ④ When flowing water appears near a certain linear irrigator on the soil sample surface, adjust the outlet valve to balance the water supply of the four linear irrigators and avoid excessive irrigation by a single irrigator;

[0022] Step 5: Negative pressure suction control

[0023] When water seeps out from the bottom of the soil tank, turn on the controller of the negative pressure system and adjust the controller parameters to a smaller (15%-30%) flow rate to reduce soil infiltration. When the soil moisture sensor indicates that the soil is completely saturated, increase the controller parameters to increase the speed of the negative pressure pump, creating a negative pressure environment inside the negative pressure filter. Under the stress of water potential and negative pressure, the salt solution in the soil permeates through the permeable layer and semi-permeable membrane into the filter, and then enters the water collector through the third water supply pipe, the negative pressure pump, and the fourth water supply pipe. The mass of the water collector is recorded by an electronic scale. During use, it is important to ensure that the soil sample is saturated to promote the dissolution of salts in the soil sample. Therefore, when the moisture content of the soil sample changes, adjust the parameters of the linear irrigator and the negative pressure filter (including valve opening or pump pressure) through the controller to coordinate the water supply intensity of the linear irrigator and the suction of the negative pressure pump.

[0024] Step Six: Stabilizing Desalination Control

[0025] Once the soil sample source infiltration and negative pressure absorption reach equilibrium, record the mass of the electronic scale. Start the stopwatch and record the stopwatch time once for each change in the displayed value of the electronic scale (e.g., 0.1 kg). When the cumulative change in the displayed value of the electronic scale reaches 0.9 kg, take a 50g water sample from the outlet of the fourth water pipe using a disposable cup and measure the conductivity value using a conductivity measuring device. This is recorded as a desalination process. If the conductivity of the day is... When the conductivity changes reach a very small set threshold for 7 consecutive times, the negative pressure pump is turned off, the soil is soaked, and the next set of desalination is carried out after 24 hours. The desalination process ends when the conductivity changes for 3 consecutive sets are very small.

[0026] Step 7: Data Processing

[0027] Calculate the mean value of desalination for each group. , upper deviation and lower deviation As in formula (1):

[0028] (1),

[0029] The measurement data were then fitted with non-uniform rational B-spline curves. For example, in formula (2):

[0030] (2),

[0031] In the formula, For node vectors, The vector called node i The vector of node p, The vector for node n+1, Control point The corresponding weighting factor, Indicates the first indivual Sub-B spline basis, The derivative of the B-spline basis functions. ≥0 and not all of them are 0. There are n+1 control points, forming a control polygon.

[0032] The beneficial effects of this invention are as follows: Compared with the prior art, this invention is inspired by the existing physical desalination process and proposes a natural force driven negative pressure desalination device for saline-alkali soil. It utilizes the natural force of solar energy and soil water potential to dissolve, absorb, and recover the salt in the soil. This not only achieves soil desalination but also realizes the resource utilization of water and salt, effectively solving the problems of large engineering and investment, long construction period, soil salinization and secondary degradation in existing saline-alkali land improvement technologies. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of a natural force-driven negative pressure desalination device for saline-alkali soil.

[0034] Figure 2 This is a schematic diagram of the soil box structure;

[0035] Figure 3 This is a schematic diagram of the sealing cap structure;

[0036] Figure 4 This is a schematic diagram of a linear water source emitter.

[0037] Figure 5 This is a schematic diagram of the splitter structure;

[0038] Figure 6 This is a schematic diagram of a negative pressure filter structure;

[0039] Figure 7 These are real photos of microbial growth;

[0040] Figure 8 A graph showing data on the negative pressure absorption of saline solution.

[0041] Figure label:

[0042] 1. Mascherano bottle;

[0043] 1-1. Air inlet pipe; 1-2. Water supply valve; 1-3. Ruler; 1-4. Air outlet; 1-5. Water outlet valve 1.

[0044] 2. Earthen box;

[0045] 2-1 Sensor installation hole, 2-2 Sampling hole, 2-3 Sealing cap, 2-4 Saline-alkali soil, 2-5 Bottom hole plate, 2-31-1 Through hole, 2-31-2 Slot, 2-31-3 Boss, 2-32 O-ring, 2-33 Fastening screw;

[0046] 3. Linear water emitter;

[0047] 3-1. Pagoda connector; 3-2. Plug; 3-3. Micro-hole; 3-4. Inner liner; 3-5. Outer shell;

[0048] 4. Water distributor;

[0049] 4-1. Inlet valve; 4-2. Outlet valve 2;

[0050] 5. Negative pressure pump; 6. Water collector; 7. Electronic scale; 8. Control system.

[0051] 8-1. Control cabinet; 8-2. Transmission line; 8-3. Sensor; 8-4. Power cord;

[0052] 9-1, First water pipe; 9-2, Second water pipe; 9-3, Third water pipe; 9-4, Fourth water pipe;

[0053] 10. Photovoltaic systems;

[0054] 10-1. Photovoltaic panels; 10-2. Storage batteries;

[0055] Negative pressure filter 11;

[0056] Negative pressure interface 11-1, semi-permeable membrane 11-2 and water-permeable layer 11-3. Detailed Implementation

[0057] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0058] Example 1: As Figure 1-8 As shown, a natural force-driven negative pressure desalination system for saline-alkali soil includes a water supply system, a soil tank 2, and a negative pressure water absorption system. The soil tank 2 is a rectangular plexiglass container with an open top, used to store saline-alkali soil 2-4. The water supply system is located outside the soil tank 2, with one end of the water outlet inside the saline-alkali soil 2-4 in the soil tank 2, used to provide water at a constant pressure to the soil inside the soil tank 2. The water inlet of the negative pressure water absorption system is located inside the saline-alkali soil 2-4 in the soil tank 2, used to draw water out of the saline-alkali soil 2-4 to the outside of the soil. Utilizing the natural force of soil-water potential, the system dissolves, absorbs, and recovers the salt in the soil, achieving both soil desalination and resource utilization of water and salt. This effectively solves the problems of large engineering and investment, long construction period, soil salinization, and secondary degradation associated with existing saline-alkali land improvement technologies.

[0059] This invention utilizes fresh water (or slightly brackish water) to saturate and irrigate saline-alkali soil, causing the salt to dissolve in the soil water to form saline solution. Then, a negative pressure filter, water pipe, and negative pressure pump are used to transport the solution to an external water collector, thereby removing and collecting the salt from the soil. This invention can solve the problems of large engineering and investment, long construction period, soil salinization and secondary degradation in existing saline-alkali land improvement technologies.

[0060] The water supply system includes a Marshall bottle 1 and linear irrigators 3. The Marshall bottle 1 is equipped with an air inlet pipe 1-1, a water supply valve 1-2, a scale 1-3, an air outlet 1-4, and a water outlet valve 1-5. The water outlet valve 1-5 is connected to the inlet valve 4-1 of the distributor 4 via a first water supply pipe 9-1. Specifically, the water outlet valve 1-5 is connected to one end of the first water supply pipe 9-1, and the other end of the first water supply pipe 9-1 is connected to the inlet valve 4-1 of the distributor 4. The distributor 4 is installed on a soil box 2 and is connected to multiple linear irrigators 3 via multiple second water supply pipes 9-2. Four linear irrigators 3 are used. Figure 1 The four linear water source emitters, labeled 3A, 3B, 3C, and 3D, are arranged at intervals within the saline-alkali soil samples 2-4 in the soil tank 2. They are used to supply water to the saline-alkali soil. When using them, first open the Marshall bottle's water supply valve, add an appropriate amount of test water to the Marshall bottle, then close the valve and record the water level with a ruler. Adjust the lower end of the air outlet of the Marshall bottle's air inlet pipe to be flush with the upper surface of the soil sample. Open the first water outlet valve of the Marshall bottle and the inlet valve of the distributor; water flows from the Marshall bottle along the first water supply pipe into the distributor under constant pressure. Then, sequentially open the second of the four subdivided water outlet valves of the distributor, fine-tuning them to ensure the water flows evenly into the linear water source emitters. Observe the linear infiltration process, recording the trend of the wetting peak and the water level value on the ruler. During the linear infiltration process of the soil sample, attention should be paid to... Instructions: ① During the linear source infiltration process, the outlet valve 2 should be adjusted to a smaller opening to ensure a slow infiltration process and avoid excessive water velocity that could create preferential flow in the soil; ② Observe the water level scale in the Marble bottle. When the water level is low, promptly close the outlet valve 2 of the Marble bottle, record the scale water level value, open the replenishment valve of the Marble bottle to replenish water, record the scale water level value again after replenishment, and open the outlet valve of the Marble bottle to continue water supply; ③ When leakage occurs at the bottom of the soil tank, adjust the outlet valve 2 to reduce the infiltration volume; ④ When flowing water appears near a certain linear source irrigator on the soil sample surface, adjust the outlet valve 2 to balance the water supply of the four linear source irrigators and avoid excessive watering of a single irrigator; This water supply system can achieve a stable and uniform water supply to the soil in the soil tank.

[0061] After desalination is completed, a line source irrigation system can be used to connect to an oxygenation device to supplement oxygen in the soil. This involves connecting the water inlet of the distributor to the oxygenation device to create an oxygen-rich environment in the soil after desalination, promoting the reproduction and growth of bacteria and algae in the soil.

[0062] Specifically, the water distributor 4 has an inlet valve 4-1 installed at its inlet and multiple outlets equipped with outlet valves 4-2, namely outlet valves 4-2A, 4-2B, 4-2C, 4-2D and 4-2E as shown in the figure. The linear water emitters labeled 3A, 3B, 3C and 3D are respectively connected to outlet valves 4-2A, 4-2B, 4-2D and 4-2E. The water distributor can evenly distribute water to the four linear water emitters.

[0063] Specifically, the linear water emitter 3 includes a shell 3-5, a pagoda connector 3-1, a plug 3-2, micropores 3-3, and an inner liner 3-4. The shell 3-5 is a cylindrical structure open at both ends. The inlet of the pagoda connector 3-1 is connected to the second water supply pipe 9-2. The pagoda connector 3-1 and the plug 3-2 are fixedly connected to the upper and lower ends of the shell 3-5, respectively. The shell wall of the shell 3-5 is covered with multiple micropores 3-3 for water outlet. The inner liner 3-4 is a tubular structure open at both ends. The upper end is connected to the outlet of the pagoda connector 3-1 and maintains a gap with the shell 3-5, while the lower end is connected to... The inner end of the plug 3-2 maintains a gap. During use, water enters from the pagoda connector 3-1, flows through the interior of the liner 3-4, and then enters the gap between the lower end of the liner 3-4 and the plug 3-2, and then enters the gap between the liner 3-4 and the outer shell 3-5. Finally, it flows out from the micropores 3-3 of the outer shell 3-5. The linear water emitter 3 with this structure can slowly enter the saline-alkali soil, avoid impact, play a better buffering role, and the water seepage is relatively uniform, which is more conducive to testing accuracy and stability. The liner 3-4 is made of porous media, mainly to balance the water pressure of the multiple micropores 3-3 on the linear water emitter 3.

[0064] The negative pressure water suction system includes a negative pressure pump 5, a water collector 6, an electronic scale 7, and a negative pressure filter 11. The negative pressure filter 11 is placed in the middle of the saline-alkali soil 2-4. The linear water source emitters 3 are symmetrically arranged around the negative pressure filter 11. The water outlet at the top of the negative pressure filter 11 is connected to the water inlet of the negative pressure pump 5 through a third water supply pipe 9-3. The water outlet of the negative pressure pump 5 is connected to the water collector 6 through a fourth water supply pipe 9-4. The negative pressure pump 5 is installed on the ground or on the soil tank 2. The water collector 6 is installed on the electronic scale 7. This negative pressure water suction system can realize negative pressure suction of brine in saline-alkali soil and weigh it.

[0065] Specifically, the negative pressure filter 11 includes a negative pressure interface 11-1, a semi-permeable membrane 11-2, and a permeable layer 11-3. The permeable layer 11-3 is a barrel-shaped structure with an open top. The semi-permeable membrane 11-2 is placed inside the permeable layer 11-3, and the negative pressure interface 11-1 is connected to the top of the semi-permeable membrane 11-2. The negative pressure interface 11-1 is connected to the third water supply pipe 9-3, that is, one end of the negative pressure interface 11-1 is connected to the third water supply pipe 9-3, and the other end of the third water supply pipe 9-3 is connected to the inlet of the negative pressure pump 5. When the negative pressure pump provides negative pressure, the negative pressure filter can draw water that has permeated into the permeable layer in the saline-alkali soil to avoid clogging. The semi-permeable membrane 11-2 is made of a water-permeable but air-permeable process, that is, only water is allowed to pass through, while gas is prohibited from passing through. The permeable layer 11-3 is made of multiple layers of non-woven fabric or nylon fabric to facilitate the absorption of brine and prevent clogging.

[0066] Specifically, the soil box 2 has sensor installation holes 2-1 and sampling holes 2-2 on its four sides. The sensor installation holes 2-1 and sampling holes 2-2 are used to install the sensor 8-3 (soil temperature, humidity and conductivity sensor, i.e., a three-in-one sensor for temperature, humidity and moisture, model: RS-ECTH-N01) and to take soil samples, respectively. The sensor installation holes 2-1 and sampling holes 2-2 are detachably sealed with sealing caps 2-3. The bottom of the soil box 2 is designed with uniform small holes 2-5 (φ3mm) to facilitate the infiltration of soil for venting.

[0067] Specifically, the sealing cover 2-3 has a waist-shaped stepped structure, including a boss 2-31-3 and a closed end plate 2-31-1 located at one end of the boss 2-31-3. The boss 2-31-3 can be embedded with the sensor mounting hole 2-1 and the sampling hole 2-2. The closed end plate 2-31-1 can block the sensor mounting hole 2-1 and the sampling hole 2-2. The size of the closed end plate 2-31-1 is larger than that of the boss 2-31-3, and the closed end plate 2-31-1 is close to the boss 2-31. -3 is provided with an annular groove 2-31-2 around the perimeter. An O-ring 2-32 is installed in the groove 2-31-2. Before filling with soil, the sealing cap 2-3 should be used to seal all sampling holes 2-2 and sensor placement holes 2-1. The sealing process is as follows: first, install the O-ring 2-32 on the groove 2-31-2, then insert the boss 2-31-3 into the sampling holes 2-2 and sensor placement holes 2-1, and then use two fastening screws 2-33A and 2-33B to fix it to the soil box 2 through the two through holes 2-32-4A and 2-32-4B of the sealing cap 2-3. The sealing cap is convenient and quick to seal, simple to operate, and easy to install and remove.

[0068] Specifically, sensor 8-3 is connected to the controller via transmission line 8-2. The controller is installed in control cabinet 8-1. The controller is also connected to the negative pressure pump, Marshall bottle, and water distributor via transmission line 8-2. The controller is used to control the water supply and negative pressure absorption based on the sensor's detection signal. The controller is also connected to battery 10-2 via power line 8-4. Battery 10-2 is connected to photovoltaic panel 10-1. Battery 10-2 and photovoltaic panel 10-1 constitute photovoltaic system 10. Sensor 8-3, control cabinet 8-1, transmission line 8-2, and power line 8-4 constitute control system 8. The control system can automatically detect and control humidity in saline-alkali soil and use naturally driven photovoltaic power to save energy. Photovoltaic panel 10-1 provides charging energy for battery. Battery 10-2 is equipped with a charge and discharge protection device. Battery 10-2 is electrically connected to controller 8 to provide energy security for control system.

[0069] Example 2: A method for using a natural force-driven negative pressure desalination system for saline-alkali soil, the method comprising the following steps:

[0070] Step 1: Soil sample filling and sensor installation

[0071] First, lay qualitative filter paper at the bottom of the soil box and seal all sampling holes and sensor installation holes on the soil box with a sealing cap. After the saline soil sample is sieved through a 2mm sieve, it is loaded into the soil box according to the set bulk density, and evenly packed into the soil box in seven layers, each layer being 10cm thick, with the layers roughened. After the soil sample is filled, remove the seal of the sensor installation hole, insert the sensor horizontally into the sensor installation hole, and ensure that the sensor probe is fully inserted into the soil sample. After the sensor is installed, connect the sensor to the controller and set and test the communication between the sensor and the cloud data.

[0072] Step Two: Water Supply System Installation

[0073] Using a screwdriver, drill four bottom holes from the top surface of the soil sample downwards at the four corners of the soil sample surface. The four holes are axially symmetrical. Slowly insert four linear water emitters into the four bottom holes. Then connect the Mascher bottle, water distributor and linear water emitter using the first water supply pipe and the second water supply pipe.

[0074] Step 3: Installation of the negative pressure system

[0075] Using a screwdriver, make a bottom hole in the center of the soil sample from the top surface downwards. Slowly insert the negative pressure filter. Then, use the third and fourth water supply pipes to connect the pagoda head of the negative pressure filter, the negative pressure pump, and the water collector. Place the water collector on the electronic scale, set the electronic scale to tare, and finally connect the negative pressure pump and controller to test the negative pressure system.

[0076] Step 4: Linear infiltration into the soil

[0077] First, open the water supply valve of the Marble bottle, add an appropriate amount of test water to the Marble bottle, then close the water supply valve and record the water level value with a ruler. Adjust the lower end of the air outlet of the Marble bottle's air inlet pipe to be flush with the upper surface of the soil sample. Open the first water outlet valve of the Marble bottle and the water inlet valve of the distributor. Water flows from the Marble bottle into the distributor under constant pressure along the first water supply pipe. Open the second of the four subdivision water outlet valves of the distributor in sequence, and fine-tune the second of the four subdivision water outlet valves to make the water flow evenly into the linear source irrigation device. Observe the linear source infiltration process, record the trend of the wetting peak change and the water level value on the ruler. During the linear source infiltration process of the soil sample, the following should be noted: ① During the linear source infiltration process, the second water outlet valve should be adjusted to a smaller value. ① Ensure the opening of the valve is adjusted to allow for slow infiltration, preventing excessive water velocity from creating preferential flow in the soil; ② Observe the water level in the Marshall bottle. When the water level is low, promptly close the outlet valve of the Marshall bottle, record the water level value on the scale, open the water supply valve of the Marshall bottle to replenish water, record the water level value on the scale again after replenishment, and open the outlet valve of the Marshall bottle to continue water supply; ③ When leakage occurs at the bottom of the soil tank, adjust the outlet valve to reduce the amount of infiltrated water; ④ When flowing water appears near a certain linear irrigator on the soil sample surface, adjust the outlet valve to balance the water supply of the four linear irrigators and avoid excessive irrigation by a single irrigator;

[0078] Step 5: Negative pressure suction control

[0079] When water seeps out from the bottom of the soil tank, turn on the controller of the negative pressure system and adjust the controller parameters to a lower (15%-30%) flow rate to reduce soil infiltration. When the soil moisture sensor indicates that the soil is completely saturated, increase the controller parameters to increase the speed of the negative pressure pump, creating a negative pressure environment inside the negative pressure filter. Under the stress of water potential and negative pressure, the salt solution in the soil permeates through the permeable layer and semi-permeable membrane into the filter, and then enters the water collector through the third water supply pipe, the negative pressure pump, and the fourth water supply pipe. The mass of the water collector is recorded by an electronic scale. During use, it is important to ensure that the soil sample is saturated to promote the dissolution of salts in the soil sample. Therefore, when the moisture content of the soil sample changes, adjust the parameters of the linear irrigator and the negative pressure filter through the controller to coordinate the water supply intensity of the linear irrigator and the suction of the negative pressure pump.

[0080] Step Six: Stabilizing Desalination Control

[0081] Once the soil sample source infiltration and negative pressure absorption reach equilibrium, record the mass of the electronic scale. Start the stopwatch and record the stopwatch time once for each change in the displayed value of the electronic scale (e.g., 0.1 kg). When the cumulative change in the displayed value of the electronic scale reaches 0.9 kg, take a 50g water sample from the outlet of the fourth water pipe using a disposable cup and measure the conductivity value using a conductivity measuring device. This is recorded as a desalination process. If the conductivity of the day is... When the conductivity changes reach a very small set threshold for 7 consecutive times, the negative pressure pump is turned off, the soil is soaked, and the next set of desalination is carried out after 24 hours. The desalination process ends when the conductivity changes for 3 consecutive sets are very small.

[0082] Step 7: Data Processing

[0083] Calculate the mean value of desalination for each group. , upper deviation and lower deviation As in formula (1):

[0084] (1),

[0085] The measurement data were then fitted with non-uniform rational B-spline curves. For example, in formula (2):

[0086] (2),

[0087] In the formula, For node vectors, The vector called node i The vector of node p, The vector for node n+1, Control point The corresponding weighting factor, Indicates the first indivual Sub-B spline basis, The derivative of the B-spline basis functions. ≥0 and not all of them are 0. There are n+1 control points, forming a control polygon.

[0088] One example of a naturally force-driven negative pressure desalination device for saline-alkali soil and its usage method is described below. Figures 1 to 6 Design, processing, and assembly, in accordance with the described desalination method, Figure 1 Verification experiments were conducted using examples, and the results are as follows: Figure 8As shown, the soil was soaked from day 1 to day 5, during which some of the salts in the soil gradually dissolved. From day 5 to day 10, the dissolution of soil salts accelerated under the influence of negative pressure absorption, and the conductivity of the extract slowly increased. From day 10 to day 12, the soil salts dissolved rapidly, and the conductivity of the extract soared to a maximum of 53.39 ms / cm. From day 12 to day 25, the conductivity of the soil extract gradually decreased as the salt content in the soil decreased. From day 25 to day 35, the dissolution of soil salts slowed down, and the conductivity of the extract slowly decreased. After 35 days of absorption, the salt content of the extract decreased to 3.32 ms / cm, and the salt removal rate was 61.23%. The results show that after 15 days (days 10-25) of rapid absorption, most of the salt in the soil can be removed (about 52%), and after 35 days, more than 60% of the salt in the soil can be removed. According to the results, if the irrigation water quality is further changed to promote the dissolution of salt in the soil, the efficiency of salt removal is expected to be improved. This technology is feasible in theory and practice.

[0089] In addition, after desalination is completed, oxygen is replenished to the soil using the linear water source irrigator 3. Figure 7 After oxygenation, bacteria and algae grow rapidly at depths of 0 to 70 cm.

[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A natural force-driven negative pressure desalination system for saline-alkali soil, characterized in that, It includes a water supply system, a soil tank, and a negative pressure water suction system. The soil tank is a rectangular plexiglass container with an open top, used to store saline-alkali soil. The water supply system is located outside the soil tank with one end of the water outlet inside the saline-alkali soil in the soil tank, used to provide water at a constant pressure to the soil inside the soil tank. The water inlet of the negative pressure water suction system is located inside the saline-alkali soil in the soil tank, used to draw water out of the saline-alkali soil to the outside of the soil.

2. The natural force-driven negative pressure desalination system for saline-alkali soil according to claim 1, characterized in that, The water supply system includes a Marshall bottle and linear water emitters. The Marshall bottle is equipped with an air inlet pipe, a water supply valve, a scale, an air outlet, and a water outlet valve. The water outlet valve is connected to a water distributor through a first water supply pipe. The water distributor is installed on the soil tank and is connected to multiple linear water emitters through multiple second water supply pipes. The multiple linear water emitters are arranged at intervals in the saline-alkali soil inside the soil tank for supplying water to the saline-alkali soil.

3. The natural force-driven negative pressure desalination system for saline-alkali soil according to claim 2, characterized in that, The water distributor has an inlet valve installed at its inlet and multiple outlet valves installed at its outlets.

4. The natural force-driven negative pressure desalination system for saline-alkali soil according to claim 2, characterized in that, The linear water emitter includes a shell, a pagoda connector, a plug, micropores, and an inner liner. The shell is a cylindrical structure with open ends. The inlet of the pagoda connector is connected to the second water supply pipe. The pagoda connector and the plug are fixedly connected to the upper and lower ends of the shell, respectively. The shell wall is covered with multiple micropores. The inner liner is a tubular structure with open ends. The upper end is connected to the outlet of the pagoda connector and maintains a gap with the shell. The lower end maintains a gap with the inner end of the plug.

5. A natural force-driven negative pressure desalination system for saline-alkali soil according to claim 2, characterized in that, The negative pressure water intake system includes a negative pressure pump, a water collector, an electronic scale, and a negative pressure filter. The negative pressure filter is placed in the middle of the saline-alkali soil. Linear water emitters are symmetrically arranged around the negative pressure filter. The water outlet at the top of the negative pressure filter is connected to the negative pressure pump through a third water supply pipe. The negative pressure pump is connected to the water collector through a fourth water supply pipe. The water collector is installed on the electronic scale.

6. A natural force-driven negative pressure desalination system for saline-alkali soil according to claim 5, characterized in that, The negative pressure filter includes a negative pressure interface, a semi-permeable membrane, and a water-permeable layer. The water-permeable layer is a barrel-shaped structure with an open top. The semi-permeable membrane is placed inside the water-permeable layer, and the negative pressure interface is connected to the top of the semi-permeable membrane. The negative pressure interface is connected to the third water supply pipe.

7. A natural force-driven negative pressure desalination system for saline-alkali soil according to claim 2, characterized in that, The soil box has sensor installation holes and sampling holes on its four sides. The sensor installation holes and sampling holes are used to install sensors and to take soil samples, respectively. The sensor installation holes and sampling holes are detachable and sealed with sealing caps. The bottom of the soil box is designed with uniform small holes. The sensor is a three-in-one sensor for temperature, humidity and moisture.

8. A natural force-driven negative pressure desalination system for saline-alkali soil according to claim 7, characterized in that, The sensor is connected to the controller, which is also connected to the negative pressure pump, the Mascher bottle, and the water distributor. The controller is used to control the water supply and negative pressure intake based on the sensor's detection signals. The controller is connected to the battery, which is connected to the photovoltaic panel.

9. The method of using a natural force-driven negative pressure desalination system for saline-alkali soil according to claim 4, characterized in that, The usage method includes the following steps: Step 1: Soil sample filling and sensor installation First, lay qualitative filter paper at the bottom of the soil box and seal all sampling holes and sensor installation holes on the soil box with a sealing cap. After the saline soil sample is sieved through a 2mm sieve, it is loaded into the soil box according to the set bulk density, and evenly loaded into the soil box in seven layers, each layer being 10cm thick, with roughened between layers. After the soil sample is filled, remove the sealing piece of the sensor installation hole, insert the sensor horizontally into the sensor installation hole, and ensure that the sensor probe is fully inserted into the soil sample. After the sensor is installed, connect the sensor to the controller. Step Two: Water Supply System Installation Four bottom holes are drilled from the top surface of the soil sample downwards at the four corners of the soil sample surface. The four holes are axially symmetrical. Four linear water source emitters are slowly placed into the four bottom holes. Then, the first and second water supply pipes are used to connect the Mascher bottle, the water distributor and the linear water source emitters. Step 3: Installation of the negative pressure system Make a bottom hole from the top surface of the soil sample to the center of the soil sample, slowly put in the negative pressure filter, and then use the third and fourth water supply pipes to connect the pagoda head of the negative pressure filter, the negative pressure pump and the water collector. Place the water collector on the electronic scale, set the electronic scale to tare, and finally connect the negative pressure pump and the controller to test the negative pressure system. Step 4: Linear infiltration into the soil First, open the water supply valve of the Marshall bottle, add an appropriate amount of test water to the Marshall bottle, then close the water supply valve and record the water level value with a ruler. Adjust the lower end of the air outlet of the Marshall bottle's air inlet pipe to be flush with the upper surface of the soil sample. Open the first water outlet valve of the Marshall bottle and the water inlet valve of the distributor. Water flows from the Marshall bottle into the distributor under constant pressure along the first water delivery pipe. Then, open the second of the four subdivision water outlet valves of the distributor in sequence, and fine-tune the second of the four subdivision water outlet valves to make the water flow evenly into the linear source irrigation device. Observe the linear source infiltration process, record the trend of the wetting peak and the water level value on the ruler. Step 5: Negative pressure suction control When water seeps out from the bottom of the soil tank, turn on the controller of the negative pressure system and adjust the controller parameters to a lower flow rate. When the soil moisture sensor indicates that the soil is completely saturated, increase the controller parameters to increase the speed of the negative pressure pump, creating a negative pressure environment inside the negative pressure filter. Under the stress of water potential and negative pressure, the salt solution in the soil permeates through the permeable layer and semi-permeable membrane into the filter, and then enters the water collector through the third water supply pipe, the negative pressure pump, and the fourth water supply pipe. The mass of the water collector is recorded by an electronic scale. During use, it is important to ensure that the soil sample is saturated. When the moisture content of the soil sample changes, adjust the parameters of the linear irrigator and the negative pressure filter through the controller to coordinate the water supply intensity of the linear irrigator and the suction of the negative pressure pump. Step Six: Stabilizing Desalination Control Once the soil sample source infiltration and negative pressure absorption reach equilibrium, record the mass of the electronic scale. Start a stopwatch and record the stopwatch time each time the electronic scale reading changes by the set value. When the cumulative change in the electronic scale reading is complete, take a 50g water sample from the outlet of the fourth water pipe using a disposable cup and measure the conductivity using a conductivity measuring device. This is recorded as a desalination process. If the conductivity of the day is... When the set threshold is reached for 7 consecutive changes, the negative pressure pump is turned off and the soil is soaked. After 24 hours, the next set of desalination is carried out. The desalination process ends when the conductivity changes for 3 consecutive sets are very small. Step 7: Data Processing Calculate the mean value of desalination for each group. , upper deviation and lower deviation As in formula (1): （1）， The measurement data were then fitted with non-uniform rational B-spline curves. For example, in formula (2): （2）， In the formula, For node vectors, The vector called node i The vector of node p, The vector for node n+1, Control point The corresponding weighting factor, Indicates the first indivual Sub-B spline basis, The derivative of the B-spline basis functions. ≥0 and not all of them are 0. There are n+1 control points, forming a control polygon.

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