Safe utilization method for arable land polluted by arsenic and cadmium

Abstract

The invention discloses a safe utilization method for arable land polluted by arsenic and cadmium in a combined mode, and belongs to the technical field of soil remediation. The method comprises the following steps: carrying out soil sampling detection on the arsenic-cadmium combined polluted cultivated land and judging the arsenic-cadmium pollution grade; preparing a targeted composite passivator according to the pH value of the soil, applying the targeted composite passivator into the plough layer soil in a layered manner, and regulating and controlling the microenvironment to obtain passivated plough layer soil; after a compound microbial agent and decomposed organic fertilizer are mixed and applied to the passivated plough layer soil, pioneer plants are interplanted in a differentiated mode, a nutritional agent is sprayed, cutting is conducted, and a planting substrate is obtained; crop seeds are planted on a planting substrate after being subjected to stress resistance pretreatment, and growth regulation and control are performed through silicon fertilizer spraying and leaf surface resistance and control. According to the method, a targeted passivation, microorganism and plant synergy and crop stress resistance regulation and control integrated technology is adopted, the bioavailability of arsenic and cadmium is synchronously reduced, the problem that a single remediation technology is poor in effect is solved, it is guaranteed that cultivated land is safely utilized, agricultural products meet the GB 2762-2022 standard, and practicability is high.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, specifically to a method for the safe utilization of arable land contaminated with arsenic and cadmium. Background Technology

[0002] With the irrational use of industrial production, mineral development, and agricultural inputs, the problem of combined arsenic and cadmium pollution in arable land is becoming increasingly prominent. Arsenic and cadmium have strong mobility and bioaccumulation, easily entering the food chain through the soil-crop system. This not only leads to reduced crop yields and quality but also endangers human health, severely restricting the safe use of polluted arable land.

[0003] Current remediation technologies for arsenic and cadmium combined pollution mainly include passivation remediation, phytoremediation, and combined remediation, but they have obvious limitations: single passivating agents lack targeting and are difficult to simultaneously achieve arsenic and cadmium solidification effects; pioneer plants are mostly planted alone, which has poor adaptability to combined pollution and low remediation efficiency; existing technologies lack an integrated design for the entire process from pollution diagnosis to crop planting, and the synergistic effect of each link is insufficient, resulting in the risk of heavy metal contamination in crops after remediation.

[0004] Therefore, there is an urgent need to develop an integrated technical solution with strong targeting and good synergistic effect to simultaneously reduce the bioavailability of arsenic and cadmium, and ensure the safe use of polluted farmland and the compliance of agricultural product quality standards. Summary of the Invention

[0005] The purpose of this invention is to provide a safe utilization method for arable land contaminated by arsenic and cadmium, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A method for the safe utilization of arable land contaminated with arsenic and cadmium includes the following steps:

[0008] S1. Sampling and testing of soil in arsenic-cadmium co-contaminated farmland, and determining the arsenic-cadmium pollution level of the farmland based on the soil test results;

[0009] S2. Based on the soil pH value of the arsenic-cadmium co-contaminated farmland, a targeted composite passivating agent is prepared. The targeted composite passivating agent is applied in layers to the topsoil of the arsenic-cadmium co-contaminated farmland and mixed evenly. At the same time, the microenvironment of the topsoil is regulated to obtain passivated topsoil.

[0010] S3. After mixing the compound microbial agent and decomposed organic fertilizer and applying it to the passivated topsoil, pioneer plants are intercropped according to the different levels of arsenic and cadmium pollution. Nutrients are sprayed on the pioneer plants regularly and they are mowed to obtain the planting base.

[0011] S4. After stress-resistant pretreatment, crop seeds are planted on a planting base, and the growth of the crop seeds is regulated by silicon fertilizer spraying and foliar control measures to obtain agricultural products.

[0012] Preferably, the soil testing results include soil cadmium content. Soil arsenic content and soil pH value; the arsenic and cadmium pollution levels include mild pollution, moderate pollution, and severe pollution, wherein mild pollution is: ≤40mg / kg and ≤0.3mg / kg, moderate pollution is defined as: as well as There is 40mg / kg < ≤60mg / kg and 0.3< The heavily polluted area is defined as any of the following conditions: ≤0.6 mg / kg. >60mg / kg and >0.6mg / kg.

[0013] Preferably, the method for soil sampling and testing is as follows:

[0014] Sampling points were evenly distributed throughout the arsenic and cadmium-contaminated farmland using a grid-based sampling method, with each sampling point spaced no more than 50m apart. Stainless steel soil augers were used to collect soil samples from the 0-20cm topsoil layer at each sampling point. Five subsamples were collected from each sampling point using a five-point mixing method. After merging, 1kg of mixed sample was retained using the quartering method and placed in a clean polyethylene sealed bag labeled with the sampling point information.

[0015] The mixed samples were placed in a clean and ventilated environment to air dry naturally. After removing impurities, they were ground with an agate mortar and pestle and passed through a 20-mesh nylon sieve and a 100-mesh nylon sieve, respectively, to obtain 20-mesh and 100-mesh soil samples. The arsenic content of the 100-mesh soil samples was determined by the method of "Determination of Total Arsenic in Soil - Silver Diethyldithiocarbamate Spectrophotometry" (GB / T 17134-1997), and the cadmium content was determined by the method of "Determination of Total Cadmium in Soil - Graphite Furnace Atomic Absorption Spectrophotometry" (GB / T 17141-1997). The pH value of the 20-mesh soil samples was determined by the method of "Determination of Soil pH Value - Potentiometric Method" (NY / T 1121.2-2006). The average value of the soil cadmium content, soil arsenic content, and soil pH value of all sampling points was taken as the soil test result.

[0016] Preferably, when the soil pH is < 6, the targeted composite passivating agent comprises, by weight: 120-150 parts hydroxyapatite, 60-80 parts dolomite powder, 25-30 parts bamboo charcoal-based biochar, and 6-8 parts nano-zero-valent iron, wherein the nano-zero-valent iron has a particle size of 50-100 nm and a purity ≥ 99%;

[0017] When the soil pH is ≥6, the targeted composite passivating agent comprises, by weight, 100-120 parts steel slag powder, 40-50 parts bone char, 15-20 parts montmorillonite, and 12-15 parts humic acid.

[0018] Preferably, the method for configuring the targeted composite passivating agent is as follows:

[0019] (1). Preparation of targeted composite passivating agent when soil pH < 6:

[0020] Hydroxyapatite with a purity ≥95% was selected, crushed to a particle size ≤2mm by a jaw crusher, and then pulverized to 100-200 mesh by a pulverizer to obtain hydroxyapatite powder. At the same time, dolomite powder was purified, passed through a 150-mesh sieve, and dried to a moisture content ≤3% to obtain dried dolomite powder. Bamboo charcoal-based biochar was activated at 800-900℃ for 2-3 hours, then crushed and passed through a 200-mesh sieve to obtain bamboo charcoal-based biochar powder. Hydroxyapatite powder, dried dolomite powder, bamboo charcoal-based biochar powder, and nano-zero-valent iron were weighed according to weight and added to a twin-screw mixer. The mixing speed of the twin-screw mixer was controlled at 40-50 r / min, and the mixture was continuously mixed for 25-30 minutes to obtain a targeted composite passivating agent.

[0021] (2). Preparation of targeted composite passivating agent when soil pH ≥ 6:

[0022] After removing iron from steel slag powder by magnetic separation, it is crushed to 150-200 mesh, washed with water to remove soluble salts, and then dried to obtain spare steel slag powder with a moisture content ≤3%. At the same time, bone char is carbonized at 600-700℃ for 3-4 hours, crushed and passed through a 200-mesh sieve to obtain bone char powder. Montmorillonite and humic acid are pulverized and passed through a 200-mesh sieve respectively to obtain montmorillonite powder and spare humic acid. The spare steel slag powder, bone char powder, montmorillonite powder and spare humic acid are weighed according to the weight parts. The spare steel slag powder and montmorillonite powder are put into a plow-type mixer and premixed for 10 minutes at a mixing speed of 35-45 r / min. Then, bone char powder and spare humic acid are added and the mixing is continued for 20-25 minutes to obtain a targeted composite passivating agent.

[0023] Preferably, the layered application method is as follows: the targeted composite passivating agent and fine soil are premixed at a mass ratio of 25:1 using a twin-shaft spiral mixer to obtain premixed passivating material. The premixed passivating material is then applied to the bottom of the furrow through a furrow opener and covered with soil. The application rate of the premixed passivating material is 80-100 kg / mu. The targeted composite passivating agent is then granulated into granular targeted composite passivating agent with a particle size of 2-5 mm. The granular targeted composite passivating agent is then evenly spread on the surface. The application rate of the granular targeted composite passivating agent is 30-40 kg / mu. Subsequently, a rotary tiller is used to perform shallow and deep tillage in sequence.

[0024] The trencher opens trenches with a depth of 12-15cm and a width of 15-20cm. The shallow spiral is 8-10cm deep, and the deep spiral is 18-22cm deep.

[0025] Preferably, the method for regulating the microenvironment is as follows: the soil pH of the topsoil is stabilized at 6.5-7.2 by supplementing with sulfur powder and dolomite powder, wherein the sulfur powder is used to reduce soil acidity and the dolomite powder is used to increase soil alkalinity. The moisture content of the topsoil is maintained at 60%-70% of field capacity by drip irrigation system, and the topsoil is shallowly tilled to a depth of 5-8 cm once every 2 weeks for 4 weeks.

[0026] Preferably, the compound microbial agent is composed of Lactobacillus acidophilus, Pseudomonas aeruginosa, and Bacillus megaterium in a mass ratio of 3:2:1, and the total number of viable bacteria in the compound microbial agent is ≥1×10⁻⁶. 8 CFU / g; the organic matter content of the decomposed organic fertilizer is ≥45% and the heavy metal content meets the NY 525-2021 standard. The decomposed organic fertilizer and the compound microbial agent are mixed at a mass ratio of 100:1 to obtain a compound microbial fertilizer mixture. The application rate of the compound microbial fertilizer mixture is 1.5-2.5t / mu.

[0027] Preferably, the differentiated intercropping is as follows: ryegrass and centipede grass are intercropped in lightly polluted arsenic-cadmium co-polluted farmland, with a planting ratio of 2:1 for ryegrass and centipede grass; alfalfa and sedum are intercropped in moderately polluted arsenic-cadmium co-polluted farmland, with a planting ratio of 1:1 for alfalfa and sedum; and centipede grass and mineral-bearing sedum are intercropped in heavily polluted arsenic-cadmium co-polluted farmland, with a planting ratio of 1:2 for centipede grass and mineral-bearing sedum.

[0028] Preferably, the nutrient is a mixed aqueous solution of 0.2% potassium dihydrogen phosphate, 0.1% urea and 0.05% EDTA-calcium, and the nutrient is applied at a rate of 50-60 L / mu, sprayed once each for the seedling and vigorous growth stages of the pioneer plants; the mowing is carried out every 25 days, leaving 5-10 cm of the root of the pioneer plants during mowing, and the above-ground parts of the mowed pioneer plants are sealed and transported to the hazardous waste treatment site.

[0029] Preferably, the terminating condition for the mowing is that after two consecutive mowings, 3-5 representative sampling points are randomly selected in the planting area of ​​the pioneer plants using the five-point sampling method. Three above-ground parts of the pioneer plants are collected at each sampling point. After removing impurities, the above-ground parts of the pioneer plants are mixed and crushed. The total arsenic content is detected using the "Determination of Total Arsenic and Inorganic Arsenic in Food" (GB / T 5009.11-2024), and the total cadmium content is detected using the "Determination of Cadmium in Food" (GB / T 5009.15-2023). If the total arsenic content of the above-ground parts of the pioneer plants is ≤30mg / kg and the total cadmium content is ≤5mg / kg, then the mowing is stopped, the entire pioneer plant is removed, and the planting substrate is obtained.

[0030] Preferably, the stress-resistant pretreatment involves soaking crop seeds in a 50 mg / L nano-silica solution for 2 hours, then removing and drying them before soaking them in a 100 mg / L salicylic acid solution for 8-12 hours, and finally removing and drying them for later use.

[0031] Preferably, the spray solution for the silicon fertilizer application is a 0.3% sodium silicate solution, and the application rate is 60L / mu, applied once each during the jointing stage and the booting stage of the crop; the foliar inhibition is achieved by spraying a foliar inhibition compound solution at an application rate of 50L / mu onto the crop during the booting stage, and the foliar inhibition compound solution is a mixed aqueous solution of 0.1% humic acid and 0.05% EDTA-zinc.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. Overcoming the limitations of single passivating agents lacking targeting, a composite passivating agent formula is customized for soil pH differences. Combined with a layered application process, it achieves simultaneous solidification of arsenic and cadmium at different depths in the topsoil, solving the problem that traditional passivation technology cannot simultaneously address the solidification effect of two pollutants, and significantly improving the targeting and stability of passivation.

[0034] 2. Innovative differentiated intercropping model: Matching shallow-rooted and deep-rooted pioneer plant combinations according to pollution level, combined with the synergistic effect of compound microbial agents, to replace the traditional single planting scheme, significantly improving the remediation efficiency and adaptability of compound polluted soil, and enhancing the effect of heavy metal enrichment and removal.

[0035] 3. Construct an integrated technology system encompassing pollution diagnosis, targeted passivation, microbial-plant synergistic remediation, and crop stress resistance regulation. This system overcomes the shortcomings of traditional technologies where each step is fragmented, and forms a closed-loop management system through precise connection of each step. This reduces the risk of heavy metal contamination in agricultural products from the source, and promotes the synergistic advancement of safe utilization of polluted arable land and crop production. Attached Figure Description

[0036] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a flowchart of the method steps of the present invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0039] A method for the safe utilization of arable land contaminated with arsenic and cadmium includes the following steps:

[0040] S1. Sampling and testing of soil in arsenic-cadmium co-contaminated farmland, and determining the arsenic-cadmium pollution level of the farmland based on the soil test results;

[0041] S2. Based on the soil pH value of the arsenic-cadmium co-contaminated farmland, a targeted composite passivating agent is prepared. The targeted composite passivating agent is applied in layers to the topsoil of the arsenic-cadmium co-contaminated farmland and mixed evenly. At the same time, the microenvironment of the topsoil is regulated to obtain passivated topsoil.

[0042] S3. After mixing the compound microbial agent and decomposed organic fertilizer and applying it to the passivated topsoil, pioneer plants are intercropped according to the different levels of arsenic and cadmium pollution. Nutrients are sprayed on the pioneer plants regularly and they are mowed to obtain the planting base.

[0043] S4. After stress-resistant pretreatment, crop seeds are planted on a planting base, and the growth of the crop seeds is regulated by silicon fertilizer spraying and foliar control measures to obtain agricultural products.

[0044] Furthermore, the working principle of the present invention will be illustrated below through embodiments:

[0045] Example 1: Select a lightly polluted arsenic-cadmium co-contaminated farmland with a soil pH value <6, and divide the arsenic-cadmium co-contaminated farmland into four equal-area areas, denoted as A1, A2, A3 and A4 respectively.

[0046] Step 1: Select hydroxyapatite with a purity ≥95%, crush it to a particle size ≤2mm using a jaw crusher, and then pulverize it to 100-200 mesh using a pulverizer to obtain hydroxyapatite powder; remove impurities from dolomite powder, pass it through a 150-mesh sieve, and dry it to a moisture content ≤3% to obtain dried dolomite powder; activate bamboo charcoal-based biochar at 800-900℃ for 2-3 hours, then crush it and pass it through a 200-mesh sieve to obtain bamboo charcoal-based biochar powder; weigh 120 parts by weight of hydroxyapatite powder. 60 parts of dried dolomite powder, 25 parts of bamboo charcoal-based biochar powder, and 6 parts of nano-zero-valent iron were added to a biaxial spiral mixer. The mixing speed of the biaxial spiral mixer was controlled at 40-50 r / min, and the mixture was continuously mixed for 25-30 minutes to obtain the targeted composite passivating agent A1. Similarly, 150 parts by weight of hydroxyapatite powder, 80 parts by weight of dried dolomite powder, 30 parts by weight of bamboo charcoal-based biochar powder, and 8 parts by weight of nano-zero-valent iron were weighed and added to the biaxial spiral mixer to maintain the targeted composite preparation of A1. The target composite passivating agent A2 was obtained by mixing under the same mixing conditions as the passivating agent. 135 parts by weight of hydroxyapatite powder, 70 parts by weight of dried dolomite powder, 28 parts by weight of bamboo charcoal-based biochar powder, and 7 parts by weight of nano-zero-valent iron were weighed and added to a biaxial spiral mixer and mixed under the same mixing conditions as the preparation of the target composite passivating agent A1 to obtain the target composite passivating agent A3. The target composite passivating agents A1, A2, and A3 were then premixed with fine soil at a mass ratio of 25:1 to obtain A... 1. Premixed passivating materials A2 and A3 are applied to the bottom of the furrow at a rate of 80 kg / mu using a furrow opener, followed by soil covering. Then, the targeted composite passivating agent of A1, A2 and A3 is granulated and evenly spread on the corresponding surface of A1, A2 and A3 at a rate of 30 kg / mu. The mixture is then mixed by shallow and deep rotary tillage, and the microenvironmental conditions of the topsoil of A1, A2 and A3 are kept the same for 4 weeks to obtain the passivated topsoil of A1, A2 and A3.

[0047] Step 2: Mix the compound microbial inoculant with well-rotted organic fertilizer at a ratio of 100:1 to obtain a compound microbial fertilizer mixture. Apply 1.5t / mu to the passivated topsoil of A1, A2, and A3 respectively, and intercrop them at a differentiated ratio of ryegrass: centipede grass = 2:1. When the pioneer plants ryegrass and centipede grass enter the seedling and vigorous growth stages, spray 50L / mu of nutrient solution on each. After the pioneer plants enter the stable growth stage, mow them every 25 days, leaving 5cm of roots. After mowing, seal the above-ground parts and transport them to the hazardous waste treatment site. Continue mowing until the total arsenic and cadmium content of the above-ground parts of the pioneer plants meets the requirements. Stop mowing and remove the entire plant to obtain the planting base of A1, A2, and A3.

[0048] Step 3: Select plump rice seeds, soak them in 50 mg / L nano-silica solution for 2 hours, remove and dry them, then soak them in 100 mg / L salicylic acid solution for 8 hours, and dry them again for later use. Sow the pretreated rice seeds on planting bases of A1, A2 and A3 respectively, and spray them with 0.3% sodium silicate solution at 60 L / mu at the jointing stage and the booting stage. At the same time, spray the foliar inhibitory compound solution at 50 L / mu at the booting stage, and maintain the same water and fertilizer conditions during the growth regulation period until harvest.

[0049] Example 2: A moderately polluted arsenic-cadmium contaminated farmland with the same soil pH value as that in Example 1 was selected. This arsenic-cadmium contaminated farmland was divided into four equal-area areas, denoted as B1, B2, B3 and B4 respectively.

[0050] Step 1: Prepare targeted composite passivating agents B1, B2, and B3 in the same manner as preparing targeted composite passivating agents A1, A2, and A3 in Step 1 of Example 1. Premix the targeted composite passivating agents B1, B2, and B3 with fine soil at a mass ratio of 25:1 to obtain premixed passivated materials of B1, B2, and B3. Apply 90 kg / mu of B1, B2, and B3 to the bottom of the furrow using a furrow opener and cover with soil. Then, granulate the targeted composite passivating agents B1, B2, and B3 and evenly spread 35 kg / mu of the corresponding B1, B2, and B3 on the soil surface. Then, use a rotary tiller to mix them evenly with shallow and deep rotation, and keep the microenvironmental conditions of the topsoil of B1, B2, and B3 the same for 4 weeks to obtain the passivated topsoil of B1, B2, and B3.

[0051] Step 2: Mix the compound microbial inoculant with well-rotted organic fertilizer at a ratio of 100:1 to obtain a compound microbial fertilizer mixture. Apply 2t / mu of the passivated topsoil of B1, B2, and B3 respectively, and intercrop them at a ratio of 1:1 for alfalfa and sedum. When the pioneer plants alfalfa and sedum enter the seedling and vigorous growth stages, spray 50L / mu of nutrient solution on each. After the pioneer plants enter the stable growth stage, mow them every 25 days, leaving 5cm of roots. After mowing, seal the above-ground parts and transport them to the hazardous waste treatment site. Continue mowing until the total arsenic and cadmium content of the above-ground parts of the pioneer plants meets the requirements. Stop mowing and remove the entire plant to obtain the planting base of B1, B2, and B3.

[0052] Step 3: Select plump rice seeds, soak them in 50 mg / L nano-silica solution for 2 hours, remove and dry them, then soak them in 100 mg / L salicylic acid solution for 8 hours, and dry them again for later use. Sow the pretreated rice seeds on planting bases of B1, B2 and B3 respectively, and spray them with 0.3% sodium silicate solution at 60 L / mu at the jointing stage and the booting stage. At the same time, spray the foliar inhibitory compound solution at 50 L / mu at the booting stage, and maintain the same water and fertilizer conditions during the growth regulation period until harvest.

[0053] Example 3: A heavily polluted arsenic-cadmium contaminated farmland with the same soil pH value as that in Example 1 was selected. The farmland was divided into four equal-area areas, denoted as C1, C2, C3 and C4 respectively.

[0054] Step 1: Prepare targeted composite passivating agents C1, C2, and C3 in the same manner as preparing targeted composite passivating agents A1, A2, and A3 in Step 1 of Example 1. Premix the targeted composite passivating agents C1, C2, and C3 with fine soil at a mass ratio of 25:1 to obtain premixed passivated materials of C1, C2, and C3. Apply C1, C2, and C3 at a rate of 100 kg / mu to the bottom of the furrow using a furrow opener and then cover with soil. Subsequently, granulate the targeted composite passivating agents of C1, C2, and C3 and evenly spread them on the corresponding C1, C2, and C3 surfaces at a rate of 40 kg / mu. Then, use a rotary tiller to mix them evenly with shallow and deep rotation, and maintain the same microenvironmental conditions for the topsoil of C1, C2, and C3 for 4 weeks to obtain passivated topsoil of C1, C2, and C3.

[0055] Step 2: Mix the compound microbial inoculant with well-rotted organic fertilizer at a ratio of 100:1 to obtain a compound microbial fertilizer mixture. Apply 2.5t / mu to the passivated topsoil of C1, C2, and C3 respectively, and intercrop them at a differentiated ratio of Centipede Grass and Sedum sarmentosum = 1:2. When the pioneer plants Centipede Grass and Sedum sarmentosum enter the seedling and vigorous growth stages, spray 50L / mu of nutrient solution on each. After the pioneer plants enter the stable growth period, mow them every 25 days, leaving 5cm of roots. After mowing, seal the above-ground parts and transport them to the hazardous waste treatment site. Continue mowing until the total arsenic and cadmium content of the above-ground parts of the pioneer plants meets the requirements. Stop mowing and remove the entire plant to obtain the planting base of C1, C2, and C3.

[0056] Step 3: Select plump rice seeds, soak them in 50 mg / L nano-silica solution for 2 hours, remove and dry them, then soak them in 100 mg / L salicylic acid solution for 8 hours, and dry them again for later use. Sow the pretreated rice seeds on planting bases of C1, C2 and C3 respectively, and spray them with 0.3% sodium silicate solution at 60 L / mu at the jointing stage and the booting stage. At the same time, spray the foliar inhibitory compound solution at 50 L / mu at the booting stage, and maintain the same water and fertilizer conditions during the growth regulation period until harvest.

[0057] Example 4: Select a lightly polluted arsenic-cadmium co-contaminated farmland with a soil pH value ≥ 6, and divide the arsenic-cadmium co-contaminated farmland into four equal-area areas, denoted as F1, F2, F3 and F4 respectively.

[0058] Step 1: After magnetic separation to remove iron from the steel slag powder, crush it to 150-200 mesh, wash it with water to remove soluble salts, and then dry it to obtain steel slag powder with a moisture content ≤3%. Simultaneously, carbonize the bone char at 600-700℃ for 3-4 hours, then crush it and pass it through a 200-mesh sieve to obtain bone char powder. Crush the montmorillonite and humic acid and pass them separately through a 200-mesh sieve to obtain montmorillonite powder and humic acid for later use. Weigh out 100 parts of the steel slag powder, 40 parts of the bone char powder, and montmorillonite powder according to the following weight proportions. 15 parts of montmorillonite powder and 12 parts of prepared humic acid were added to a plow-type mixer and premixed for 10 minutes at a mixing speed of 35-45 r / min. Then, bone char powder and prepared humic acid were added and mixed for another 20-25 minutes to obtain the targeted composite passivating agent for F1. Similarly, 120 parts by weight of prepared steel slag powder, 50 parts by weight of bone char powder, 20 parts by weight of montmorillonite powder, and 15 parts by weight of prepared humic acid were used to prepare the targeted composite passivating agent for F1. The same mixing conditions were used to prepare the targeted composite passivating agent F2. Then, 110 parts by weight of steel slag powder, 45 parts by weight of bone char powder, 18 parts by weight of montmorillonite powder, and 13 parts by weight of humic acid were mixed under the same conditions as those used to prepare the targeted composite passivating agent F1 to obtain the targeted composite passivating agent F3. Finally, the targeted composite passivating agents F1, F2, and F3 were premixed with fine soil at a mass ratio of 25:1 to obtain the premixes of F1, F2, and F3. The passivated materials were applied to the bottom of the furrow at a rate of 80 kg / mu for F1, F2, and F3 using a furrow opener and then covered with soil. Subsequently, the targeted composite passivating agents for F1, F2, and F3 were granulated and evenly spread on the surface of the corresponding F1, F2, and F3 at a rate of 30 kg / mu. The mixture was then mixed by shallow and deep rotary tillage, and the microenvironmental conditions of the topsoil of F1, F2, and F3 were kept the same for 4 weeks to obtain the passivated topsoil of F1, F2, and F3.

[0059] Step 2: Mix the compound microbial inoculant with well-rotted organic fertilizer at a ratio of 100:1 to obtain a compound microbial fertilizer mixture. Apply 1.5t / mu to the passivated topsoil of F1, F2, and F3 respectively, and intercrop them at a differentiated ratio of ryegrass: centipede grass = 2:1. When the pioneer plants ryegrass and centipede grass enter the seedling and vigorous growth stages, spray 50L / mu of nutrient solution on each. After the pioneer plants enter the stable growth stage, mow them every 25 days, leaving 5cm of roots. After mowing, seal the above-ground parts and transport them to the hazardous waste treatment site. Continue mowing until the total arsenic and cadmium content of the above-ground parts of the pioneer plants meets the requirements. Stop mowing and remove the entire plant to obtain the planting base of F1, F2, and F3.

[0060] Step 3: Select plump rice seeds, soak them in 50 mg / L nano-silica solution for 2 hours, remove and dry them, then soak them in 100 mg / L salicylic acid solution for 8 hours, and dry them again for later use. Sow the pretreated rice seeds on the planting base of F1, F2 and F3 respectively, and spray them with 0.3% sodium silicate solution at 60 L / mu at the jointing stage and the booting stage. At the same time, spray the foliar inhibitory compound solution at 50 L / mu at the booting stage, and maintain the same water and fertilizer conditions during the growth regulation period until the harvest.

[0061] Example 5: Select a moderately polluted arsenic-cadmium co-contaminated farmland with the same soil pH value as that in Example 4, and divide the arsenic-cadmium co-contaminated farmland into four equal-area areas, denoted as E1, E2, E3 and E4 respectively.

[0062] Step 1: Prepare targeted composite passivating agents E1, E2, and E3 in the same manner as preparing targeted composite passivating agents F1, F2, and F3 in Step 1 of Example 1. Premix the targeted composite passivating agents E1, E2, and E3 with fine soil at a mass ratio of 25:1 to obtain premixed passivated materials of E1, E2, and E3. Apply 90 kg / mu of E1, E2, and E3 to the bottom of the furrow using a furrow opener and cover with soil. Then, granulate the targeted composite passivating agents of E1, E2, and E3 and evenly spread 35 kg / mu on the corresponding E1, E2, and E3 soil surfaces. Then, use a rotary tiller for shallow and deep mixing and maintain the same microenvironmental conditions for the topsoil of E1, E2, and E3 for 4 weeks to obtain passivated topsoil of E1, E2, and E3.

[0063] Step 2: Mix the compound microbial inoculant with well-rotted organic fertilizer at a ratio of 100:1 to obtain a compound microbial fertilizer mixture. Apply 2t / mu to the passivated topsoil of E1, E2, and E3 respectively, and intercrop them at a ratio of 1:1 for alfalfa and sedum. When the pioneer plants alfalfa and sedum enter the seedling and vigorous growth stages, spray 50L / mu of nutrient solution on each. After the pioneer plants enter the stable growth stage, mow them every 25 days, leaving 5cm of roots. After mowing, seal the above-ground parts and transport them to the hazardous waste treatment site. Continue mowing until the total arsenic and cadmium content of the above-ground parts of the pioneer plants meets the requirements. Stop mowing and remove the entire plant, as well as the planting base of E1, E2, and E3.

[0064] Step 3: Select plump rice seeds, soak them in 50 mg / L nano-silica solution for 2 hours, remove and dry them, then soak them in 100 mg / L salicylic acid solution for 8 hours, and dry them again for later use. Sow the pretreated rice seeds on planting bases of E1, E2 and E3 respectively, and spray them with 0.3% sodium silicate solution at 60 L / mu at the jointing stage and the booting stage. At the same time, spray the foliar inhibitory compound solution at 50 L / mu at the booting stage, and maintain the same water and fertilizer conditions during the growth regulation period until harvest.

[0065] Example 6: A heavily polluted arsenic-cadmium contaminated farmland with the same soil pH value as that in Example 4 was selected. The farmland was divided into four equal-area areas, denoted as G1, G2, G3 and G4 respectively.

[0066] Step 1: Prepare targeted composite passivating agents G1, G2, and G3 in the same manner as preparing targeted composite passivating agents F1, F2, and F3 in Step 1 of Example 1. Premix the targeted composite passivating agents G1, G2, and G3 with fine soil at a mass ratio of 25:1 to obtain premixed passivated materials of G1, G2, and G3. Apply G1, G2, and G3 at 100 kg / mu to the bottom of the furrow using a furrow opener and cover with soil. Then, granulate the targeted composite passivating agents G1, G2, and G3 and evenly spread them on the corresponding surface of G1, G2, and G3 at 40 kg / mu. Mix them thoroughly using a rotary tiller with shallow and deep rotation, and maintain the same microenvironmental conditions for the topsoil of G1, G2, and G3 for 4 weeks to obtain passivated topsoil of G1, G2, and G3.

[0067] Step 2: Mix the compound microbial inoculant with well-rotted organic fertilizer at a ratio of 100:1 to obtain a compound microbial fertilizer mixture. Apply 2.5t / mu to the passivated topsoil of G1, G2, and G3 respectively, and intercrop them at a differentiated ratio of Centipede Grass and Sedum sarmentosum = 1:2. When the pioneer plants Centipede Grass and Sedum sarmentosum enter the seedling and vigorous growth stages, spray 50L / mu of nutrient solution on each. After the pioneer plants enter the stable growth period, mow them every 25 days, leaving 5cm of roots. After mowing, seal the above-ground parts and transport them to the hazardous waste treatment site. Continue mowing until the total arsenic and cadmium content of the above-ground parts of the pioneer plants meets the requirements. Stop mowing and remove the entire plant to obtain the planting base of G1, G2, and G3.

[0068] Step 3: Select plump rice seeds, soak them in 50 mg / L nano-silica solution for 2 hours, remove and dry them, then soak them in 100 mg / L salicylic acid solution for 8 hours, and dry them again for later use. Sow the pretreated rice seeds on planting bases of G1, G2 and G3 respectively, and spray them with 0.3% sodium silicate solution at 60 L / mu at the jointing stage and the booting stage. At the same time, spray the foliar inhibitory compound solution at 50 L / mu at the booting stage, and maintain the same water and fertilizer conditions during the growth regulation period until harvest.

[0069] Rice harvested from the above six examples was used as a control. Simultaneously, the same rice seeds were cultivated in fields A4, B4, C4, F4, E4, and G4 using the existing method described in CN116637925A, and the harvested rice was used as a control. The inorganic arsenic and cadmium content in the rice was determined, and the specific results are shown in the table below:

[0070] Group Pollution level Soil pH Inorganic arsenic content in rice (mg / kg) Cadmium content in rice (mg / kg) Compliant with GB 2762-2022 standard Conclusions compared with the same group of embodiments A1 Mild ＜6 0.08 0.06 yes Optimal A2 Mild ＜6 0.07 0.05 yes Optimal A3 Mild ＜6 0.07 0.05 yes Optimal A4 Mild ＜6 0.18 0.17 yes Meets standards B1 moderate ＜6 0.12 0.10 yes Optimal B2 moderate ＜6 0.11 0.09 yes Optimal B3 moderate ＜6 0.10 0.08 yes Optimal B4 moderate ＜6 0.23 0.18 Inorganic arsenic exceeded the standard Exceeding the standard for a single item C1 Severe ＜6 0.16 0.15 yes Optimal C2 Severe ＜6 0.15 0.14 yes Optimal C3 Severe ＜6 0.14 0.13 yes Optimal C4 Severe ＜6 0.28 0.25 Exceeding the standard in both items Exceeding the standard in both items F1 Mild ≥6 0.09 0.07 yes Optimal F2 Mild ≥6 0.08 0.06 yes Optimal F3 Mild ≥6 0.08 0.06 yes Optimal F4 Mild ≥6 0.19 0.18 yes Meets standards E1 moderate ≥6 0.13 0.11 yes Optimal E2 moderate ≥6 0.12 0.10 yes Optimal E3 moderate ≥6 0.11 0.09 yes Optimal E4 moderate ≥6 0.19 0.23 Excessive cadmium Exceeding the standard for a single item G1 Severe ≥6 0.17 0.16 yes Optimal G2 Severe ≥6 0.16 0.15 yes Optimal G3 Severe ≥6 0.15 0.14 yes Optimal G4 Severe ≥6 0.21 0.24 Exceeding the standard in both items Exceeding the standard in both items

[0071] As shown in the table above, although the mildly polluted control examples A4 and F4 both meet the GB 2762-2022 standard, the inorganic arsenic and cadmium content in the rice reaches 0.18-0.19 mg / kg and 0.17-0.18 mg / kg, respectively, which is significantly higher than the 0.07-0.09 mg / kg and 0.05-0.07 mg / kg of the same group of examples. The moderately polluted control examples B4 and E4 show single-item exceedances of inorganic arsenic and cadmium by 0.23 mg / kg, respectively, and the content of the compliant indicators is also higher than that of the same group of examples. The heavily polluted control examples C4 and G4 both exceed the standards for two items, namely inorganic arsenic 0.21-0.28 mg / kg and cadmium 0.24-0.25 mg / kg. However, even in heavily polluted farmland, the embodiments of the present invention can still strictly control the two indicators within the standard limits. In summary, all comparative examples, regardless of whether they met the standards, had higher heavy metal content than the embodiments of the present invention in the same group. Moreover, the higher the pollution level, the more significant the gap between the prior art and the present invention. This fully demonstrates that the integrated technical solution of the present invention has outstanding technical progress in reducing the accumulation of heavy metals in agricultural products, ensuring the safe use of arable land, and ensuring the quality and safety of agricultural products.

[0072] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; modifications to the technical solutions described in the foregoing embodiments, or equivalent substitutions of some of the technical features, do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for the safe utilization of arable land contaminated with arsenic and cadmium, characterized in that, Includes the following steps: S1. Sampling and testing of soil in arsenic-cadmium co-contaminated farmland, and determining the arsenic-cadmium pollution level of the farmland based on the soil test results; S2. Based on the soil pH value of the arsenic-cadmium co-contaminated farmland, a targeted composite passivating agent is prepared. The targeted composite passivating agent is applied in layers to the topsoil of the arsenic-cadmium co-contaminated farmland and mixed evenly. At the same time, the microenvironment of the topsoil is regulated to obtain passivated topsoil. S3. After mixing the compound microbial agent and decomposed organic fertilizer and applying it to the passivated topsoil, pioneer plants are intercropped according to the different levels of arsenic and cadmium pollution. Nutrients are sprayed on the pioneer plants regularly and they are mowed to obtain the planting base. S4. After pre-treatment to resist stress, crop seeds are planted on a planting base, and the growth of the crop seeds is regulated by silicon fertilizer spraying and foliar control measures to obtain agricultural products.

2. The method for safe utilization of arable land contaminated with arsenic and cadmium as described in claim 1, characterized in that, The soil testing results include soil cadmium content. Soil arsenic content and soil pH value; the arsenic and cadmium pollution levels include mild pollution, moderate pollution, and severe pollution, wherein mild pollution is: ≤40mg / kg and ≤0.3mg / kg, moderate pollution is defined as: as well as There is 40mg / kg < ≤60mg / kg and 0.3< The heavily polluted area is defined as any of the following conditions: ≤0.6 mg / kg. >60mg / kg and >0.6mg / kg.

3. The method for safe utilization of arable land contaminated with arsenic and cadmium as described in claim 2, characterized in that, When the soil pH is <6, the targeted composite passivating agent comprises, by weight: 120-150 parts of hydroxyapatite, 60-80 parts of dolomite powder, 25-30 parts of bamboo charcoal-based biochar, and 6-8 parts of nano-zero-valent iron. When the soil pH is ≥6, the targeted composite passivating agent comprises, by weight, 100-120 parts steel slag powder, 40-50 parts bone char, 15-20 parts montmorillonite, and 12-15 parts humic acid.

4. The method for safe utilization of arable land contaminated with arsenic and cadmium as described in claim 3, characterized in that, The layered application method is as follows: the targeted composite passivating agent and fine soil are premixed at a mass ratio of 25:1 using a twin-shaft spiral mixer to obtain premixed passivating material. The premixed passivating material is then applied to the bottom of the trench through a furrow opener and covered with soil. The targeted composite passivating agent is then granulated into granular targeted composite passivating agent with a particle size of 2-5mm. The granular targeted composite passivating agent is then evenly spread on the surface, followed by shallow and deep tillage using a rotary tiller. The trencher opens trenches with a depth of 12-15cm and a width of 15-20cm. The shallow spiral is 8-10cm deep, and the deep spiral is 18-22cm deep.

5. The method for safe utilization of arable land contaminated with arsenic and cadmium as described in claim 4, characterized in that, The microenvironment regulation method is as follows: the soil pH of the topsoil is stabilized at 6.5-7.2 by supplementing with sulfur powder and dolomite powder, and the soil moisture content of the topsoil is maintained at 60%-70% of field capacity by drip irrigation system. The topsoil is also shallowly tilled to a depth of 5-8cm once every 2 weeks for 4 weeks.

6. The method for safe utilization of arable land contaminated with arsenic and cadmium as described in claim 1, characterized in that, The compound microbial agent is composed of Lactobacillus acidophilus, Pseudomonas, and Bacillus megaterium in a mass ratio of 3:2:1, and the total number of viable bacteria in the compound microbial agent is ≥1×10⁻⁶. 8 CFU / g; the organic matter content of the decomposed organic fertilizer is ≥45% and the heavy metal content meets the NY 525-2021 standard. The decomposed organic fertilizer and the compound microbial agent are mixed at a mass ratio of 100:1 to obtain a compound microbial fertilizer mixture. The application rate of the compound microbial fertilizer mixture is 1.5-2.5t / mu.

7. The method for safe utilization of arable land contaminated with arsenic and cadmium as described in claim 6, characterized in that, The differentiated intercropping is as follows: For lightly polluted arsenic-cadmium co-contaminated farmland, ryegrass and centipede grass are intercropped, with a planting ratio of 2:1; for moderately polluted arsenic-cadmium co-contaminated farmland, alfalfa and sedum are intercropped, with a planting ratio of 1:1; and for heavily polluted arsenic-cadmium co-contaminated farmland, centipede grass and mineral-bearing sedum are intercropped, with a planting ratio of 1:

2.

8. The method for safe utilization of arable land contaminated with arsenic and cadmium as described in claim 7, characterized in that, The nutrient solution is a mixed aqueous solution of 0.2% potassium dihydrogen phosphate, 0.1% urea and 0.05% EDTA-calcium, and is applied at a rate of 50-60 L / mu, sprayed once each for the seedling and vigorous growth stages of the pioneer plants; the mowing is carried out once every 25 days, and the mowing is stopped when, after two consecutive mowings, the total arsenic content of the aboveground parts of the pioneer plants is ≤30 mg / kg and the total cadmium content is ≤5 mg / kg.

9. A method for the safe utilization of arable land contaminated with arsenic and cadmium as described in claim 8, characterized in that, The stress-resistance pretreatment involves soaking crop seeds in a 50 mg / L nano-silica solution for 2 hours, then removing and drying them before soaking them in a 100 mg / L salicylic acid solution for 8-12 hours, and finally removing and drying them for later use.

10. A method for the safe utilization of arable land contaminated with arsenic and cadmium as described in claim 9, characterized in that, The spray solution for the silicon fertilizer application is a 0.3% sodium silicate solution, and the application rate is 60L / mu. The foliar inhibition is achieved by spraying a foliar inhibition compound solution on crops in the booting stage at an application rate of 50L / mu. The foliar inhibition compound solution is a mixed aqueous solution of 0.1% humic acid and 0.05% EDTA-zinc.

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