Plant intercropping method for realizing cadmium-polluted soil remediation and safe planting

Abstract

The invention discloses a plant intercropping method for realizing cadmium-polluted soil remediation and safe planting, the method innovatively constructs a three-dimensional synergistic remediation system of hyperaccumulator-low accumulation crop-barrier plant, through scientific configuration of sedum alfredii hance, low-cadmium rice and vetiver grass, and in combination with biochar soil improvement and EDTA activation technologies, the cadmium-polluted soil remediation and safe planting can be realized, and the cadmium-polluted soil remediation and safe planting can be realized. And the double effects of repairing and producing at the same time are achieved. The key technology comprises the following steps: 1) establishing a plant intercropping mode with a row ratio of 1: 3; 2) developing a root system ecological niche separation technology; and (3) optimizing an accurate application scheme of the activating agent. The implementation effect shows that the soil cadmium removal rate reaches 58.7% / year, the rice cadmium content is smaller than or equal to 0.1 mg / kg, the remediation cost is only 1 / 4 of that of chemical remediation, and the farmland economic output keeps 85% or above of the conventional level. The method is suitable for medium-light cadmium-polluted farmland (1-3mg / kg) with the pH value of 4.5-8.0, has the characteristics of simplicity and convenience in operation, environmental friendliness, remarkable benefits and the like, and provides an innovative solution for heavy metal pollution treatment of the farmland.

Description

Technical Field

[0001] The present invention belongs to the technical field of agricultural environmental engineering and soil remediation, and particularly relates to a method for synchronously realizing the remediation of cadmium-polluted soil and the safe production of agricultural products through a specific plant intercropping system. Background Art

[0002] Defects of the prior art:

[0003] Physical / chemical remediation methods: For example, soil replacement (CN105170628A) costs up to 800 - 1200 yuan per ton and damages the soil ecology;

[0004] Single-plant remediation (CN102660399B): The remediation period requires 3 - 5 years, during which the land has no economic output;

[0005] Traditional intercropping patterns (CN104255987A): Do not consider the transfer risk of heavy metals between crops and pose potential food safety hazards.

[0006] Scientific problems:

[0007] How to synergistically solve the three major contradictions of the efficient remediation (removal rate > 50%) of cadmium-polluted soil, its safe utilization (crop compliance rate of 100%), and economic sustainability (yield loss < 15%). Summary of the Invention

[0008] The technical problem to be solved by the present invention is to provide a plant intercropping method for realizing the remediation of cadmium-polluted soil and safe planting. The core of the present invention lies in constructing a "extraction - isolation - control" trinity plant intercropping system.

[0009] The present invention is achieved through the following scheme: A plant intercropping method for realizing the remediation of cadmium-polluted soil and safe planting, comprising the following steps:

[0010] (a) Planting cadmium hyperaccumulator plants, low-accumulation crops, and barrier plants according to a preset spatial layout;

[0011] (b) Applying heavy metal activators during the critical growth period of low-accumulation crops;

[0012] (c) Differentially harvesting and processing each plant component.

[0013] The hyperaccumulator plant is Sedum plumbizincicola or Sedum alfredii, and its planting density is 8 - 12 plants / m 2 , and the root system is concentrated in the soil layer of 0 - 15 cm.

[0014] The low-accumulation crop is Amaranthus hypochondriacus or the red rice variety "Zhongzao 39", and its row ratio with the hyperaccumulator plant is 2:1 to 4:1, and the overlapping rate of the root ecological niche between the two is < 30%.

[0015] The barrier plants form a closed strip-shaped barrier along the edge of the field block, with a bandwidth of 40 - 60 cm and a planting density of 20 - 30 plants / m 2 .

[0016] The heavy metal activator is a citric acid or EDTA solution at 0.2 - 0.8 mmol / kg, and is applied 15 - 20 days before the flowering of the low-accumulation crops.

[0017] It also includes adding 0.5 - 1.0% of alkaline biochar (pH > 8.0, particle size < 2 mm) to the soil before planting.

[0018] After the hyperaccumulator plants are harvested, they are disposed of as hazardous waste, and when the cadmium content is > 100 mg / kg, they are treated by co-incineration in a cement kiln.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. Significant synergistic effect

[0021] Through the scientific configuration of hyperaccumulator plants, low-accumulation crops and barrier plants, a high degree of coordination between pollution remediation and agricultural production is achieved. It can not only effectively remove cadmium pollution in the soil, but also ensure the safety and quality of agricultural products, enabling the farmland during the remediation period to still maintain good economic output.

[0022] 2. Excellent ecological safety

[0023] The pure phytoremediation technology is adopted to avoid the risk of secondary pollution caused by chemical remediation. The barrier plant system effectively controls the migration and diffusion of heavy metals and protects the surrounding ecological environment. The entire remediation process does not damage the ecological structure and function of the soil.

[0024] 3. Strong sustainability

[0025] The established phytoremediation system has the characteristics of self-maintenance and continuous improvement, and the remediation effect improves with the increase of planting years. The supporting agronomic measures are simple and easy to implement, facilitating long-term popularization and application.

[0026] 4. Outstanding economic benefits

[0027] Compared with traditional remediation technologies, the present invention significantly reduces the treatment cost. At the same time, the economic output of the farmland is maintained through intercropping, achieving the unity of environmental benefits and economic benefits.

[0028] 5. Wide adaptability

[0029] For different pollution degrees and soil types, precise remediation can be achieved by adjusting the plant combination and planting parameters, and it shows good applicability in various agricultural ecological regions.

[0030] 6. Technical integration and innovation

[0031] For the first time, the technologies of plant extraction, barrier passivation and safe utilization are organically integrated to form a complete technical system for the treatment of heavy metal pollution in farmland, providing an innovative solution for similar problems. Detailed implementation manners

[0032] The present invention will be further described below, but the protection scope of the present invention is not limited to the described content.

[0033] For clarity, not all features of the actual embodiments are described. In the following description, well-known functions and structures are not described in detail because they would obscure the present invention with unnecessary details. It should be considered that in the development of any actual embodiment, a large number of implementation details must be made to achieve the specific goals of the developer, for example, changing from one embodiment to another according to the relevant system or commercial limitations. In addition, it should be considered that such development work may be complex and time-consuming, but it is only routine work for those skilled in the art.

[0034] Example 1: Remediation of moderately cadmium-polluted paddy fields (southern double-cropping rice area)

[0035] 1. Base overview

[0036] The paddy field soil around a certain mining area in Jiangxi Province is acidic (pH 5.8), and the total cadmium content reaches 1.62 mg / kg, exceeding the standard limit for agricultural land. The local original single-season rice was planted, and the cadmium in the rice exceeded the standard seriously, resulting in losses to farmers' income.

[0037] 2. Implementation method

[0038] In early April in spring, the soil was deeply plowed and 400 kg of bamboo charcoal-based biochar was evenly mixed per mu. In early May, Sedum alfredii seedlings were transplanted at a density of 10 plants per square meter, intercropped with the low-cadmium rice variety "Zhenxiangyou Yusi Miao" in a row ratio of 1:3, and the row spacing of the rice was kept at 25 cm. Vetiveria zizanioides was densely planted in double rows around the ridge, with a plant spacing of 20 cm. In mid-July during the full tillering stage of the rice, a 0.3 mmol / L EDTA solution was sprayed on the leaf surface.

[0039] 3. Remediation effect

[0040] After one growing season, the total cadmium content in the soil decreased from 1.62 mg / kg to 0.97 mg / kg, with a decrease rate of 40.1%. The cadmium content in the harvested rice was 0.12 mg / kg, fully meeting the food safety standards. The cadmium enrichment amount in the above-ground part of Sedum alfredii reached 368 mg / kg (dry weight), and the cadmium extraction amount per mu reached 58 grams. The vetiveria zizanioides on the ridge formed an effective barrier zone, and the cadmium concentration in the surrounding irrigation water decreased by 65%.

[0041] Example 2: Remediation of slightly cadmium-polluted dry land (North China Plain)

[0042] 1. Base overview

[0043] The farmland soil in a sewage irrigation area in Hebei Province is slightly alkaline (pH 7.2), and the total cadmium content of 0.86 mg / kg is close to the risk screening value. Winter wheat is mainly planted in this plot, and there is a slight risk of cadmium pollution.

[0044] 2. Implementation method

[0045] Before sowing in autumn, deeply plow the soil by 30 cm, and apply 800 kg of humic acid modified biochar per mu. Sow Sedum plumbizincicola and low-cadmium wheat "Zhongmai 895" in drill rows with a row ratio of 4:1. The row spacing of Sedum is 30 cm, and the wheat uses the wide-width sowing technique. Plant a 1-meter-wide Elsholtzia splendens isolation belt at the edge of the field. In April of the following year, at the jointing stage of wheat, apply 0.2 mmol / kg citric acid solution through the drip irrigation system.

[0046] 3. Remediation effect

[0047] After two seasons of crop rotation, the available cadmium content in the soil decreased from 0.31 mg / kg to 0.14 mg / kg. The cadmium content in wheat grains was 0.06 mg / kg, which was better than the national standard limit. Sedum plumbizincicola extracted 8.7 grams of cadmium per mu, and its root exudates increased the rhizosphere pH value of wheat by 0.8 units, effectively inhibiting the transfer of cadmium to grains. The cumulative biomass of the plants in the isolation belt reached 2.3 tons per mu, and the cadmium content in the leaves reached 45 mg / kg.

[0048] Example 3: Remediation of severely cadmium-polluted vegetable fields (suburban facility agriculture)

[0049] 1. Base overview

[0050] The total cadmium in the soil of the greenhouse around an electronic waste dismantling area in Hunan Province is as high as 4.35 mg / kg, which is severely polluted, and the traditional planting mode can no longer guarantee the safety of agricultural products.

[0051] 2. Implementation method

[0052] Adopt a high-density remediation strategy, plant 15 plants of Sedum alfredii per square meter, and intercropping with fast-growing Amaranthus hypochondriacus (growth period of 60 days). Vetiveria zizanioides is densely planted on both sides of the drainage ditch in the greenhouse to form a three-dimensional barrier system. Alternately spray a mixed solution of 0.5 mmol / L EDTA and 0.1% surfactant (TW-80) every week. Implement zoning and staged harvesting. Harvest the above-ground parts of Amaranthus hypochondriacus after 60 days of growth, and harvest Sedum alfredii every 3 months.

[0053] 3. Remediation effect

[0054] After 3 months of remediation, the total cadmium in the soil decreased by 27.1%, and the cumulative decrease reached 53.8% after 6 months. The cadmium content in the stems and leaves of Amaranthus hypochondriacus was always lower than the feed safety standard (0.5 mg / kg), enabling resource utilization. The cadmium accumulation per plant of Sedum alfredii increased with the growth cycle and reached 3.72 mg / plant at 6 months. The barrier system effectively prevented cadmium from leaking out with irrigation water, and the cadmium concentration in the surrounding water bodies was controlled below 0.005 mg / L.

[0055] Although the technical solutions of the present invention have been described in detail and enumerated, it should be understood that for those skilled in the art, making modifications to the above embodiments or adopting equivalent alternative solutions are obvious to those skilled in the art. These modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection required by the present invention.

Claims

1. A method for intercropping plants to achieve the remediation of cadmium-polluted soil and safe planting, characterized in that, Including the following steps: (a) Planting cadmium hyperaccumulator plants, low-accumulation crops and barrier plants according to a preset spatial layout; (b) Applying heavy metal activators during the critical growth period of low-accumulation crops; (c) Differentially harvesting and processing each plant component.

2. The intercropping method of plants for cadmium-contaminated soil remediation and safe planting according to claim 1, characterized in that, The hyperaccumulator plants are Sedum plumbizincicola or Sedum alfredii, and their planting density is 8-12 plants / m 2 , and the roots are concentrated in the soil layer of 0-15 cm.

3. The intercropping method of plants for cadmium-polluted soil remediation and safe planting according to claim 1, characterized in that The low-accumulation crop is Amaranthus hypochondriacus or the red rice variety "Zhongzao 39", and the row ratio between it and the hyperaccumulator plant is 2:1 to 4:1, and the root niche overlap rate between the two is <30%.

4. A method for intercropping plants to achieve the remediation of cadmium - polluted soil and safe planting according to claim 1, characterized in that, The barrier plants form a closed strip-shaped barrier along the edge of the field block, with a strip width of 40 - 60 cm and a planting density of 20 - 30 plants / m 2 .

5. The intercropping method of plants for cadmium-polluted soil remediation and safe planting according to claim 1, characterized in that, The heavy metal activator is a citric acid or EDTA solution with a concentration of 0.2 - 0.8 mmol / kg, and it is applied 15 - 20 days before the low-accumulation crop blooms.

6. A method for intercropping plants to achieve the remediation of cadmium-polluted soil and safe planting according to claim 1, characterized in that It also includes adding 0.5 - 1.0% of alkaline biochar (pH > 8.0, particle size < 2 mm) to the soil before planting.

7. A method for intercropping plants for cadmium-polluted soil remediation and safe planting according to claim 1, characterized in that, After the hyperaccumulator plant is harvested, it is disposed of as hazardous waste, and when its cadmium content > 100 mg / kg, it is treated by co-incineration in a cement kiln.