AEP combined remediation implementation method for in-situ treatment of heavily cadmium-polluted farmland

Abstract

The invention provides an AEP combined remediation implementation method for in-situ treatment of a heavily cadmium-polluted farmland, and belongs to the technical field of environmental treatment. The method comprises the following steps: firstly, investigating and analyzing cultivated land soil characteristics, and ensuring a plow pan permeability coefficient lt of a to-be-restored cultivated land; 10 <-6 > cm / s; then, micro-irrigation pipes are arranged in the field every two meters in the farming intermittent period, soil cadmium activation liquid is added into the field through the micro-irrigation pipes, and then the plough layer soil is evenly mixed at least twice with the help of a mini-tiller so that it can be guaranteed that plough layer soil cadmium can make full contact with the activation liquid; the soil cadmium activating solution comprises calcium chloride, ferric chloride and humic acid; within 24 hours after the uniform mixing operation, performing electric dialysis treatment on the activated cadmium in the soil pore solution by using an electric dialysis belt; and finally, after cadmium is removed through electric dialysis, passivating treatment is conducted on residual activated-state cadmium through a passivating agent. The activation release-electric dialysis-passivation conditioning combined remediation method is implemented in the intermission period of farming, the subsequent normal farming activity is not influenced, the rapid reduction of the soil cadmium content and the safe production of crops can be synchronously realized, and the method is particularly suitable for implementing large-scale severe cadmium pollution (the total cadmium content gt; 1.0 mg / kg), the farmland is rapidly treated and safely utilized, a farmland cadmium pollution remediation technical mode of'simultaneous treatment and production 'is assisted to be constructed, and the method has the outstanding technical advantages of high efficiency, economy, no secondary pollution and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of environmental governance, and particularly to an AEP combined remediation implementation method for in-situ remediation of severely cadmium-polluted farmland. Background Art

[0002] The cadmium content in farmland soil in industrially developed areas such as the Yangtze River Basin, the Pearl River Basin, and the Yellow River Basin is relatively high. Therefore, it is very necessary and urgent to repair and manage severely cadmium-polluted farmland.

[0003] The reduction and stabilization of soil cadmium are two key indicators for the successful remediation of severely cadmium-polluted farmland (total cadmium content > 1.0 mg / kg). The reduction remediation of severely cadmium-polluted farmland means significantly reducing the cadmium content in cultivated land soil and changing the soil cadmium pollution from severe to moderate or mild; the stabilization remediation means reducing the cadmium activity in cultivated land soil, effectively improving the stability of cadmium in the soil, and controlling the absorption of soil cadmium by crops to achieve the standard of cadmium content in crops.

[0004] However, in the current in-situ remediation of severely cadmium-polluted plough layer soil in the field, a single technology (such as passivation, leaching, electrokinetic remediation, phytoremediation, etc.) often fails to simultaneously meet the requirements of cadmium reduction and stabilization remediation of cultivated land soil. Therefore, providing an effective method for treating severely cadmium-polluted farmland to quickly repair the soil environment is a current research hotspot. Summary of the Invention

[0005] Based on this, the present invention provides an AEP combined remediation implementation method for in-situ remediation of severely cadmium-polluted farmland. This method uses a combined remediation technology that sequentially connects activated-release, electro-dialysis, and passivated-control for severely cadmium-polluted farmland. This remediation method can rapidly reduce the total amount of cadmium in the plough layer soil of farmland and ensure the safe production of crops, effectively supporting the long-term and safe utilization of severely cadmium-polluted farmland.

[0006] The present invention is specifically implemented by the following technical solutions:

[0007] An AEP combined remediation implementation method for in-situ remediation of severely cadmium-polluted farmland: includes the following steps:

[0008] The first step: Conduct an investigation and analysis of the characteristics of cultivated land soil to ensure that the permeability coefficient of the plough sole layer of the cultivated land to be remediated is < 10 -6 cm / s;

[0009] Step 2: During the farming intermission period, lay a micro-irrigation pipe every 2 meters in the field, use the micro-irrigation pipe to add the soil cadmium activation solution to the field, and then use a rotary tiller to mix the tillage layer soil at least 2 times to ensure that the cadmium in the tillage layer soil is in full contact with the activation solution; the soil cadmium activation solution includes calcium chloride, ferric chloride and humic acid;

[0010] Step 3: Within 24 hours after the mixing operation in Step 2, perform electrokinetic dialysis treatment on the activated cadmium in the soil pore solution using an electrokinetic dialysis belt; the discharged cadmium solution is handed over to the sewage treatment plant for centralized disposal.

[0011] Step 4: After electrokinetic dialysis to remove cadmium, use a passivator to passivate the remaining activated cadmium.

[0012] Preferably, the farming intermission period in Step 2 is at least 30 days before crop sowing or transplanting.

[0013] Preferably, in Step 2, the concentration of calcium chloride in the soil cadmium activation solution is 0.03 mol / L, the concentration of ferric chloride is 0.03 mol / L, and the concentration of humic acid is 1 wt%.

[0014] Preferably, in Step 2, the ratio of the dosage of the soil cadmium activation solution to the volume of the tillage layer soil is 1:5 to 1:3.

[0015] Preferably, in Step 2, the interval between the two mixing operations is 24 - 30 h.

[0016] Preferably, in Step 3, the electrokinetic dialysis treatment is to use a small trench digger to lay an electrokinetic dialysis belt vertically along the tillage layer soil body between every two micro-irrigation pipes; the vertical laying depth of the electrokinetic dialysis belt is the same as the tillage layer thickness, and the horizontal laying length can extend to 2 - 100 m; the distance between the two electrokinetic dialysis belts is 2.0 m, the applied voltage gradient is 2 V / cm, and the electrokinetic dialysis treatment is carried out in an intermittent electrokinetic mode.

[0017] More preferably, in Step 3, the operation duration of the electrokinetic dialysis treatment is 3 - 5 days.

[0018] Preferably, the passivator in Step 4 is calcium silicate fertilizer, quicklime or biochar.

[0019] More preferably, the dosage of the calcium silicate fertilizer is 300 - 900 kg / hm 2 , the dosage of the quicklime is 1500 - 2000 kg / hm 2 , and the dosage of the biochar is 1800 - 2250 kg / hm 2 .

[0020] Preferably, the passivation treatment in Step 4 is to perform plowing operation 1 - 2 times after applying the passivator, the plowing depth is 20 - 30 cm, and the passivation treatment lasts for 10 - 20 days.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] In the repair technology of the present invention, a soil activator is first added to the field to convert part of the stable cadmium in the soil into mobile cadmium, which is then released into the soil pore solution, i.e., activation and release are achieved. After the soil cadmium activation treatment, an electric dialysis belt arranged in the field is used to remove the activated cadmium in the soil pore solution from the soil mass, and at the same time, most of the activation liquid applied to the soil is discharged from the soil mass and recovered; after the cadmium is removed by electric dialysis, the soil cadmium pollution changes from severe to medium and mild, and then a passivator is used to passivate the remaining activated cadmium to reduce the availability of the residual cadmium in the soil and block the absorption of the residual cadmium by the subsequent planted crops, so as to achieve the stabilization treatment of the residual cadmium in the soil and the production of crops with qualified cadmium content.

[0023] The combined repair method of activation release - electric dialysis - passivation conditioning of the present invention is implemented during the farming intermission period, which does not affect subsequent normal farming activities, can simultaneously achieve rapid reduction of soil cadmium content and safe crop production, is especially suitable for the rapid treatment and safe utilization of large-scale severely cadmium-polluted (total cadmium content > 1.0 mg / kg) cultivated land, helps to construct a technical model for farmland cadmium pollution repair of "governing while producing", and has prominent technical advantages such as high efficiency, economy, and no secondary pollution. Description of the Drawings

[0024] Figure 1 It is a flow chart of the AEP combined repair implementation method for in-situ treatment of severely cadmium-polluted farmland of the present invention;

[0025] Figure 2 It is an electric dialysis belt, where 1 is a multi-functional electrode belt, 1-1 is a drainage groove, 1-2 is a metal wire, 2 is a conductive geotextile, and 3 is a drain pipe;

[0026] Figure 3 It is a schematic diagram of the layout of the electric dialysis belt in the field. Detailed Embodiments

[0027] The following further describes the preferred implementation embodiments of the present invention in conjunction with the embodiments.

[0028] Embodiment 1

[0029] An AEP combined repair implementation method for in-situ treatment of severely cadmium-polluted farmland, the specific steps are as follows:

[0030] The first step: Carry out an investigation and analysis of the soil characteristics of the cultivated land to ensure that the permeability coefficient of the plow sole layer of the cultivated land to be repaired is < 10 -6 cm / s to avoid the infiltration of the activation liquid into the groundwater through the plow sole layer in the subsequent implementation steps.

[0031] Step 2: During the farming intermission period (at least 30 days before crop sowing or transplanting), lay a micro-irrigation pipe every 2 meters in the field. Use the micro-irrigation pipe to add the soil cadmium activation solution to the field, and then use a rotary tiller to perform the mixing operation on the tillage layer soil twice. The interval between the two mixing operations is 24 hours to ensure full contact between the cadmium in the tillage layer soil and the activation solution. The soil cadmium activation solution contains 0.03 mol / L calcium chloride, 0.03 mol / L ferric chloride, and 1 wt% humic acid. The dosage ratio of the soil cadmium activation solution to the volume of the tillage layer soil is 1:5.

[0032] Step 3: Within 24 hours after the mixing operation in Step 2, perform electrokinetic dialysis treatment on the activated cadmium in the soil pore solution using an electrokinetic dialysis belt. Among them, for the electrokinetic dialysis treatment, use a small trencher to lay an electrokinetic dialysis belt vertically along the tillage layer soil body between every two micro-irrigation pipes. The vertical laying depth of the electrokinetic dialysis belt is the same as the tillage layer thickness, and the horizontal laying length can extend to 50 m. The distance between the two electrokinetic dialysis belts is 2.0 m, apply a voltage gradient of 2 V / cm, and perform electrokinetic dialysis treatment for 5 days using an intermittent electrokinetic mode.

[0033] Step 4: After electrokinetic dialysis to remove cadmium, use a passivator to passivate the remaining activated cadmium. The passivator is quicklime, and the usage amount of the quicklime is 2000 kg / hm 2 . The passivation treatment is to perform the plowing operation twice after applying the passivator, with a plowing depth of 25 cm, and the passivation treatment lasts for 15 days.

[0034] Example 2

[0035] An AEP combined remediation implementation method for in-situ treatment of severely cadmium-polluted farmland, the specific steps are as follows:

[0036] Step 1: Conduct an investigation and analysis of the cultivated land soil characteristics to ensure that the permeability coefficient of the plow sole layer of the cultivated land to be repaired is <10 -6 cm / s to prevent the activation solution from penetrating into the groundwater through the plow sole layer during subsequent implementation steps.

[0037] Step 2: During the farming intermission period (at least 30 days before crop sowing or transplanting), lay a micro-irrigation pipe every 2 meters in the field. Use the micro-irrigation pipe to add the soil cadmium activation solution to the field, and then use a rotary tiller to perform the mixing operation on the tillage layer soil twice. The interval between the two mixing operations is 24 hours to ensure full contact between the cadmium in the tillage layer soil and the activation solution. The soil cadmium activation solution contains 0.03 mol / L calcium chloride, 0.03 mol / L ferric chloride, and 1 wt% humic acid. The dosage ratio of the soil cadmium activation solution to the volume of the tillage layer soil is 1:4.

[0038] Step 3: Within 24 hours after the mixing operation in Step 2, electrokinetic dialysis treatment is carried out on the activated cadmium in the soil pore solution using an electrokinetic dialysis belt; for the electrokinetic dialysis treatment, a small trencher is used to vertically arrange an electrokinetic dialysis belt along the plough layer soil body between every two micro-irrigation pipes; the vertical arrangement depth of the electrokinetic dialysis belt is the same as the plough layer thickness, and the horizontal arrangement length can extend to 50 m; the distance between two electrokinetic dialysis belts is 2.0 m, the applied voltage gradient is 2 V / cm, and the electrokinetic dialysis treatment is carried out for 3 days using an intermittent electrokinetic mode;

[0039] Step 4: After the electrokinetic dialysis to remove cadmium, a passivating agent is used to passivate the remaining activated cadmium. The passivating agent is biochar, and the application rate of the biochar is 2200 kg / hm 2 . The passivation treatment is to carry out ploughing operation twice after applying the passivating agent, the ploughing depth is 25 cm, and the passivation treatment lasts for 15 days.

[0040] Example 3

[0041] An AEP combined remediation implementation method for in-situ treatment of severely cadmium-polluted farmland is as follows:

[0042] Step 1: Conduct an investigation and analysis of the cultivated land soil characteristics to ensure that the infiltration coefficient of the plough sole layer of the cultivated land to be remediated is <10 -6 cm / s to prevent the activated liquid from infiltrating into the groundwater through the plough sole layer in the subsequent implementation steps.

[0043] Step 2: During the farming interval period (at least 30 days before crop sowing or transplanting), a micro-irrigation pipe is arranged every 2 meters in the field, and the soil cadmium activation liquid is added to the field through the micro-irrigation pipe. Then, the tillage layer soil is mixed twice using a micro-tiller, and the interval between the two mixing operations is 30 h to ensure that the cadmium in the plough layer soil is fully contacted with the activation liquid; the soil cadmium activation liquid contains 0.03 mol / L calcium chloride, 0.03 mol / L ferric chloride and 1 wt% humic acid; the ratio of the application amount of the soil cadmium activation liquid to the volume of the plough layer soil is 1:3.

[0044] Step 3: Within 24 hours after the mixing operation in Step 2, electrokinetic dialysis treatment is carried out on the activated cadmium in the soil pore solution using an electrokinetic dialysis belt; for the electrokinetic dialysis treatment, a small trencher is used to vertically arrange an electrokinetic dialysis belt along the plough layer soil body between every two micro-irrigation pipes; the vertical arrangement depth of the electrokinetic dialysis belt is the same as the plough layer thickness, and the horizontal arrangement length can extend to 10 m; the distance between two electrokinetic dialysis belts is 2.0 m, the applied voltage gradient is 2 V / cm, and the electrokinetic dialysis treatment is carried out for 5 days using an intermittent electrokinetic mode;

[0045] Step 4: After removing cadmium by electro-dialysis, a passivator is used to passivate the remaining active cadmium. The passivator is biochar, and the application rate of the biochar is 2000 kg / hm 2 . The passivation treatment is to perform plowing operations twice after applying the passivator, with a plowing depth of 25 cm and a passivation treatment for 12 days.

[0046] Example 4

[0047] An AEP combined remediation implementation method for in-situ treatment of severely cadmium-polluted farmland is as follows:

[0048] Step 1: Conduct an investigation and analysis of the cultivated land soil properties to ensure that the permeability coefficient of the plow sole layer of the cultivated land to be remediated is <10 -6 cm / s to prevent the activation solution from penetrating into the plow sole layer and entering the groundwater during subsequent implementation steps.

[0049] Step 2: During the fallow period of farming (at least 30 days before crop sowing or transplanting), lay a micro-irrigation pipe every 2 meters in the field, use the micro-irrigation pipe to add a soil cadmium activation solution to the field, and then use a rotary tiller to perform a mixing operation on the tillage layer soil twice, with an interval of 28 h between the two mixing operations, to ensure that the cadmium in the plow layer soil is in full contact with the activation solution; the soil cadmium activation solution contains 0.03 mol / L calcium chloride, 0.03 mol / L ferric chloride, and 1 wt% humic acid; the application rate of the soil cadmium activation solution to the volume of the plow layer soil is 1:5.

[0050] Step 3: Within 24 h after the mixing operation in Step 2, electro-dialysis treatment is performed on the active cadmium in the soil pore solution using an electro-dialysis belt; in the electro-dialysis treatment, a small ditcher is used to lay an electro-dialysis belt vertically along the plow layer soil body between every two micro-irrigation pipes; the vertical laying depth of the electro-dialysis belt is the same as the thickness of the plow layer, and the horizontal laying length can extend to 20 m; the distance between the two electro-dialysis belts is 2.0 m, a voltage gradient of 2 V / cm is applied, and intermittent electro-mode is used for electro-dialysis treatment for 4 days;

[0051] Step 4: After removing cadmium by electro-dialysis, a passivator is used to passivate the remaining active cadmium. The passivator is calcium silicate fertilizer, and the application rate of the calcium silicate fertilizer is 600 kg / hm 2 . The passivation treatment is to perform plowing operations twice after applying the passivator, with a plowing depth of 25 cm and a passivation treatment for 20 days.

[0052] Example 5

[0053] An AEP combined remediation implementation method for in-situ treatment of severely cadmium-polluted farmland is as follows:

[0054] Step 1: Conduct an investigation and analysis of the characteristics of cultivated land soil to ensure that the permeability coefficient of the plow sole layer of the cultivated land to be repaired is < 10 -6 cm / s, to prevent the activation liquid from penetrating into the plow sole layer and entering the groundwater during subsequent implementation steps.

[0055] Step 2: During the farming interval period (at least 30 days before crop sowing or transplanting), lay a micro-irrigation pipe every 2 meters in the field. Use the micro-irrigation pipe to add the soil cadmium activation liquid to the field, and then use a rotary tiller to mix the soil in the plough layer 2 times. The interval between the two mixing operations is 25 h to ensure that the cadmium in the plough layer soil is fully contacted with the activation liquid; the soil cadmium activation liquid contains 0.03 mol / L calcium chloride, 0.03 mol / L ferric chloride and 1 wt% humic acid; the dosage ratio of the soil cadmium activation liquid to the volume of the plough layer soil is 1:4.

[0056] Step 3: Within 24 h after the mixing operation in Step 2, perform electrokinetic dialysis treatment on the activated cadmium in the soil pore solution using an electrokinetic dialysis belt; among them, for the electrokinetic dialysis treatment, use a small trench digger to lay an electrokinetic dialysis belt vertically along the plough layer soil body between every two micro-irrigation pipes; the vertical laying depth of the electrokinetic dialysis belt is the same as the thickness of the plough layer, and the horizontal laying length can extend to 30 m; the distance between the two electrokinetic dialysis belts is 2.0 m, apply a voltage gradient of 2 V / cm, and perform electrokinetic dialysis treatment for 5 days using an intermittent electrokinetic mode;

[0057] Step 4: After electrokinetic dialysis to remove cadmium, use a passivator to passivate the remaining activated cadmium. The passivator is calcium silicate fertilizer, and the usage amount of the calcium silicate fertilizer is 500 kg / hm 2 . The passivation treatment is to perform ploughing operation 2 times after applying the passivator, the ploughing depth is 25 cm, and the passivation treatment is carried out for 20 days.

[0058] Example 6

[0059] An AEP combined remediation implementation method for in-situ treatment of severely cadmium-polluted farmland, the specific steps are as follows:

[0060] Step 1: Conduct an investigation and analysis of the characteristics of cultivated land soil to ensure that the permeability coefficient of the plow sole layer of the cultivated land to be repaired is < 10 -6 cm / s, to prevent the activation liquid from penetrating into the plow sole layer and entering the groundwater during subsequent implementation steps.

[0061] Step 2: During the farming intermission period (at least 30 days before crop sowing or transplanting), lay a micro-irrigation pipe every 2 meters in the field. Use the micro-irrigation pipe to add soil cadmium activation solution to the field, and then use a rotary tiller to perform the mixing operation on the tillage layer soil twice. The interval between the two mixing operations is 24 hours to ensure that the cadmium in the tillage layer soil is fully in contact with the activation solution. The soil cadmium activation solution contains 0.03 mol / L calcium chloride, 0.03 mol / L ferric chloride, and 1 wt% humic acid. The dosage of the soil cadmium activation solution is in a ratio of 1:3 to the volume of the tillage layer soil.

[0062] Step 3: Within 24 hours after the mixing operation in Step 2, perform electrokinetic dialysis treatment on the activated cadmium in the soil pore solution using an electrokinetic dialysis belt. Among them, for the electrokinetic dialysis treatment, use a small trencher to lay an electrokinetic dialysis belt vertically along the tillage layer soil body between every two micro-irrigation pipes. The vertical laying depth of the electrokinetic dialysis belt is the same as the tillage layer thickness, and the horizontal laying length can extend to 60 m. The distance between the two electrokinetic dialysis belts is 2.0 m, apply a voltage gradient of 2 V / cm, and perform electrokinetic dialysis treatment for 4 days using an intermittent electrokinetic mode.

[0063] Step 4: After electrokinetic dialysis to remove cadmium, use a passivator to passivate the remaining activated cadmium. The passivator is quicklime, and the usage amount of the quicklime is 1500 kg / hm 2 . The passivation treatment is to perform the plowing operation twice after applying the passivator, with a plowing depth of 30 cm and a passivation treatment for 15 days.

[0064] Example 7

[0065] An AEP combined remediation implementation method for in-situ treatment of severely cadmium-polluted farmland is as follows:

[0066] Step 1: Conduct an investigation and analysis of the cultivated land soil characteristics to ensure that the permeability coefficient of the plow sole layer of the cultivated land to be repaired is 07×10 6 cm / s, the total cadmium in the soil is 1.36 mg / kg, and the available cadmium is 0.45 mg / kg.

[0067] Step 2: During the farming intermission period (at least 30 days before crop sowing or transplanting), lay a micro-irrigation pipe every 2 meters in the field. Use the micro-irrigation pipe to add soil cadmium activation solution to the field, and then use a rotary tiller to perform the mixing operation on the tillage layer soil twice. The interval between the two mixing operations is 24 hours to ensure that the cadmium in the tillage layer soil is fully in contact with the activation solution. The soil cadmium activation solution contains 0.03 mol / L calcium chloride, 0.03 mol / L ferric chloride, and 1 wt% humic acid. The dosage of the soil cadmium activation solution is in a ratio of 1:3 to the volume of the tillage layer soil.

[0068] Step 3: Within 24 hours after the mixing operation in Step 2, electro-dialysis treatment is carried out on the activated cadmium in the soil pore solution using an electric dialysis belt; for the electro-dialysis treatment, a small trench digger is used to vertically arrange an electric dialysis belt along the plough layer soil body between every two micro-irrigation pipes; the vertical arrangement depth of the electric dialysis belt is the same as the plough layer thickness, and the horizontal arrangement length can extend to 60 m; the distance between the two electric dialysis belts is 2.0 m, the applied voltage gradient is 2 V / cm, and the electro-dialysis treatment is carried out for 4 days in an intermittent electric mode;

[0069] Step 4: After the cadmium is removed by electro-dialysis, a passivating agent is used to passivate the remaining activated cadmium. The passivating agent is silicon-calcium fertilizer, quicklime and biochar. Among them, 500 kg / hm of silicon-calcium fertilizer 2 , 1600 kg / hm of quicklime 2 , and 2000 kg / hm of biochar 2 are used to passivate the remaining activated cadmium. The passivation treatment is to carry out one ploughing operation after applying the passivating agent, the ploughing depth is 30 cm, and the passivation treatment lasts for 15 days.

[0070] After the repair, the total cadmium content in the plough layer soil is reduced by about 34%, and the available cadmium content in the soil is reduced by 51%. Compared with the un-repaired farmland, the rice planted in the repaired farmland has no yield reduction and the cadmium content in the rice meets the standard.

[0071] The above-described embodiments are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

Claims

1. An AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland, characterized by: The following steps are involved: Step 1: Conduct soil property survey and analysis of cultivated land to ensure that the plow bottom permeability coefficient of the cultivated land to be restored is less than 10 -6 cm / s; Step 2: During the inter-cropping period, a micro-irrigation pipe is laid every 2 meters in the field, and soil cadmium activation solution is added to the field through the micro-irrigation pipe, and then the tillage layer soil is mixed at least twice with the help of a micro-tillage machine to ensure that the tillage layer soil cadmium is fully in contact with the activation solution; the soil cadmium activation solution includes calcium chloride, ferric chloride and humic acid; Step 3: Within 24 hours after the mixing operation in step 2, the activated cadmium in the soil pore solution is subjected to electrodialysis treatment using an electrodialysis belt; Step 4: After removing cadmium by electrodialysis, a passivating agent is used to passivate the remaining activated cadmium.

2. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 1 is characterized by: The second step of the crop break period is at least 30 days before crop sowing or transplanting.

3. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 1 is characterized by: In the second step, the concentration of calcium chloride in the soil cadmium activation solution is 0.03 mol / L, the concentration of ferric chloride is 0.03 mol / L, and the concentration of humic acid is 1 wt%.

4. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 1 is characterized by: In the second step, the ratio of the amount of soil cadmium activation solution added to the volume of the cultivated layer soil is 1:5 to 1:

3.

5. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 1 is characterized by: In the second step, the two mixing operations are separated by 24 to 30 hours.

6. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 1 is characterized by: The electric dialysis treatment in the third step is to use a small trenching machine to vertically lay an electric dialysis belt between every two micro-irrigation pipes along the tillage layer soil; the vertical laying depth of the electric dialysis belt is consistent with the thickness of the tillage layer, and the horizontal laying length can be extended to 2 to 100m; the spacing between the two electric dialysis belts is 2.0m, the applied voltage gradient is 2V / cm, and the intermittent electric mode is used for electric dialysis treatment.

7. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 6 is characterized by: The duration of the electric dialysis treatment in the third step is 3 to 5 days.

8. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 1, characterized in that: The fourth step passivation agent is silicon calcium fertilizer, quicklime or biochar.

9. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 8, characterized in that: The usage of the silicon calcium fertilizer is 300-900 kg / hm 2 The amount of quicklime used is 1500-2000 kg / hm2. 2 The amount of biochar used is 1800-2250 kg / hm 2 .

10. The AEP combined remediation implementation method for in-situ treatment of severely cadmium-contaminated farmland according to claim 1, characterized in that: The passivation treatment described in the fourth step is to apply the passivating agent and then perform ploughing operation 1 to 2 times, the ploughing depth is 20 to 30 cm, and the passivation treatment lasts 10 to 20 days.

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