CN104550210A - Method for continuously remediating soil cadmium contamination by using chelating agent EDDS and ramie - Google Patents

Abstract

The invention belongs to the technical field of soil pollution control, and specifically relates to a method for continuously repairing soil heavy metal pollution by chelating agent EDDS and ramie, comprising the following steps: implanting ramie into the soil to be repaired; Add the biodegradable chelating agent EDDS, and the application rate is 75-300kg/mu; every 30 days, use the EDDS solution with a concentration of 0.005-0.015mol/L to irrigate once, and irrigate normally in the rest of the time; regularly harvest the stems of the ramie above ground stems and leaves, and the underground part remains in the soil to continue to reproduce and grow. Compared with the prior art, the repairing method of the present invention has better repairing effect, is more environmentally friendly, is convenient to operate, has certain economic benefits, and has broad promotion prospects.

Description

A method for continuous remediation of soil cadmium pollution by chelating agent EDDS and ramie

technical field

The invention belongs to the technical field of soil pollution control, and in particular relates to a method for continuously repairing soil heavy metal pollution with chelating agent EDDS and ramie.

Background technique

The destruction of soil ecological functions and agricultural products caused by heavy metal pollution in soil have attracted increasing public attention. Heavy metals not only directly poison soil organisms and plants, destroy soil structure, but can also migrate and transform through the food chain, endangering human health. In recent years, there have been many major heavy metal pollution incidents in my country, which have seriously threatened the lives and health of the people. Soil heavy metal pollution is closely related to the safety of agricultural products, and is related to the atmospheric environment and water environment through the soil atmosphere and soil-water interface. Therefore, how to repair heavy metal-contaminated soil and ensure the safety of agricultural products is an important environmental issue at present. Carrying out the research on remediation technology of heavy metal pollution in soil is of great significance to promote the quality and safety of agricultural products and protect the lives and health of the general public.

The remediation and treatment of heavy metal-contaminated soil is currently mainly carried out around solidification and activation removal, mainly through physical, chemical and biological methods to cut off the migration of heavy metals to the food chain. The physical engineering treatment method (leaching method or alien soil method, etc.) is a relatively classic soil heavy metal pollution control measure. It has the advantages of thoroughness and stability, but it has a large amount of engineering, high investment costs, damage to the soil structure, and causes Soil fertility is reduced, and the replaced dirty soil must be stacked or disposed of. Chemical remediation is to use chemical reagents, chemical reactions or chemical principles to reduce the mobility and bioavailability of heavy metals in soil, reduce or even remove heavy metals in soil, so as to achieve soil governance and restoration. Chemical restoration mainly includes leaching, rinsing extraction, curing, electrochemical methods, and application of modifiers. The advantage of the chemical remediation method is that it is simple and easy to implement, but it only changes the existing form of heavy metals in the soil, and the metal elements remain in the soil, which is easy to reactivate and harm plants.

Phytoremediation is simple, low cost, and does not damage the ecological environment of the soil, has good economic and ecological benefits, and has broad application prospects. However, the remediation efficiency of plants to heavy metals is limited, and the limiting factors affecting the uptake and remediation efficiency of heavy metal-contaminated soils by plants mainly include: low solubility of heavy metals in soil, poor migration ability, and low transport efficiency of heavy metals from plant roots to shoots, and heavy metals in soil Most of them are difficult to be absorbed by plants. The addition of phytoremediation agents can increase the bioavailability of heavy metals and promote the absorption of heavy metals by plants; and the application of phytoremediation agents can also enhance the tolerance of plants to heavy metals and improve the ability of plants to repair heavy metal soils. The currently studied phytoremediation agents include organic chelating agents, acid-base regulators, microbial agents and organic wastes.

Chelating agents can increase the solubility of metal ions but reduce the activity of ions. Surfactants can solubilize and increase the flow of trace heavy metal cations. After combining with heavy metals, they can significantly improve the dissolution of heavy metals in soil. Applying chelating agents and surfactants to the soil can improve the absorption and enrichment of metals by plants, and improve the efficiency of phytoremediation. Even conventional plants may be used for phytoremediation of soil. Adding organic chelating agents to improve the absorption of heavy metals in the soil by plants may have two mechanisms: one is to activate heavy metal ions in the soil and improve their bioavailability; the other is to promote the absorption of heavy metals by plants and their transfer to the aboveground. The total content of heavy metals in the soil is high, but their bioavailability is usually low, and the amount that plants can take up is limited, even if the hyperaccumulator plants with strong transport capacity are often the same. The addition of chelating agents can promote the desorption and dissolution of heavy metal ions and improve their bioavailability. Chelating agents and heavy metals form chelates that can be absorbed by plants, thereby reducing the toxicity of heavy metals to plants and facilitating the absorption and enrichment of heavy metals by plants.

At present, commonly used chelating agents and surfactants are EDTA (ethylenediaminetetraacetic acid), HEDTA (hydroxyethylethylenediaminetriacetic acid), DTPA (diethyltriaminepentaacetic acid), EGTA (ethylene glycol diethyl ether di amine tetraacetic acid), NTA (nitrilotriacetic acid), EDDHA (ethylenediamine di-o-phenylacetic acid), CyDTA (cyclohexanediamine tetraacetic acid), etc. EDTA and DTPA are more widely used. Chelating agents currently used in plant extraction research are mainly non-biodegradable chelating agents represented by EDTA. Many studies have shown that EDTA, HEDTA, DTPA, EGTA, EDDHA, HEIDA, NTA, etc. can increase the bioavailability of heavy metals such as cadmium, arsenic, lead, and copper. Although there are existing technologies for soil remediation using chelating agent EDTA and plants, the above-mentioned complexing agents represented by EDTA are non-degradable complexing agents, and a large amount of application is likely to cause secondary pollution to surface water. At present, EDTA, NTA The problem of environmental pollution has been concerned, and the use of EDTA in cleaning agents has been banned in Europe. In municipal wastewater systems, EDTA can chelate heavy metal ions, posing a potential threat to drinking water supplies. In addition, Germany restricts the use of EDTA in printing and writing paper, and the European Union explicitly prohibits the use of EDTA in the bleaching process of carbon paper.

Therefore, the development and selection of suitable environment-friendly chelating agents and the selection of suitable remediation plants are of great significance for the popularization and application of phytoremediation of soil heavy metal pollution.

Contents of the invention

The purpose of the embodiments of the present invention is to address the defects of the above-mentioned prior art, and provide a method for continuously remediating soil cadmium (Cd) pollution with better effect and more environment-friendly chelating agent EDDS and ramie.

The technical scheme that the present invention takes in order to realize the above object is:

A kind of method that chelating agent EDDS and ramie repair soil cadmium pollution continuously, comprises the following steps:

Plant ramie into the soil to be repaired;

After the ramie survives, apply the biodegradable chelating agent EDDS to the soil at an application rate of 75-300kg/mu;

Every 30 days, irrigate once with EDDS solution with a concentration of 0.005-0.015mol/L, and irrigate normally for the rest of the time;

The stalks and leaves of the aboveground part of ramie are harvested regularly, and the underground part is left in the soil to continue to breed and grow.

Further, in the method for continuously remediating soil cadmium pollution by the aforementioned chelating agent EDDS and ramie, the ramie to be implanted is a cultivated ramie seedling with a height of 35-45 cm.

Further, in the method for continuously remediating soil cadmium pollution by the aforementioned chelating agent EDDS and ramie, NaOH is used to adjust the pH value of the EDDS solution to be the same as the pH value of the soil to be remediated.

Furthermore, in the aforementioned method of continuously remediating soil cadmium pollution with the chelating agent EDDS and ramie, the stems and leaves of the aerial part of ramie are harvested 2 to 3 times a year.

Further, the aforementioned method of chelating agent EDDS and ramie to continuously remediate soil cadmium pollution, the ramie implanted in the soil, after every 2-3 years, all the underground parts are harvested, and then new ramie seedlings are reimplanted until the soil cadmium pollution is repaired complete.

Further, the aforementioned chelating agent EDDS and ramie continuously repair soil cadmium pollution method, the concentration of the EDDS solution is 0.009mol/L.

Further, the aforementioned chelating agent EDDS and ramie continuously repair soil cadmium-polluted method, the amount of EDDS applied to the soil to be repaired is 225kg/mu.

Further, the method for continuously remediating soil cadmium pollution by the aforementioned chelating agent EDDS and ramie, the application method of the chelating agent EDDS is:

Spread evenly or furrow;

Alternatively, the chelating agent EDDS is dissolved in water, and applied once or divided into 2-3 times on average into the soil to be repaired along with watering.

Further, the aforementioned method of chelating agent EDDS and ramie to continuously remediate soil cadmium pollution, before the ramie is planted, apply base fertilizer to the soil to be repaired, the base fertilizer is (NH ₄ ) ₂ SO ₄ , KH ₂ PO ₄ , K ₂ SO ₄ .

Further, the method for continuously repairing soil cadmium pollution by the aforementioned chelating agent EDDS and ramie, the application amount of the base fertilizer is: (NH ₄ ) ₂ SO ₄ : 45kg/mu, KH ₂ PO ₄ : 30kg/mu, K ₂ SO ₄ : 45kg/mu.

Compared with the prior art, the soil cadmium pollution remediation method of the present invention has the following beneficial effects:

1, the biodegradable chelating agent EDDS (ethylenediamine disuccinic acid) that selects in the restoration method of the present invention, is to obtain from a kind of actinomycetes isolation at first, is a kind of natural substance; Compared with EDTA, its biological The toxicity, including the toxicity to plants and soil microorganisms, is lower than EDTA, while EDDS is biodegradable, and its half-life is between 3.8 and 7.5 days depending on the application amount, while the minimum half-life of EDTA is 36 days. Therefore, the environmental pollution risk of EDDS is much smaller than that of EDTA, so it is more environmentally friendly.

2, the ramie selected in the repair method of the present invention has the following advantages: 1, as the repair plant ramie is a kind of non-edible perennial economic crop that can tolerate multiple heavy metals (such as Pb, Zn and Cd), it is widely distributed and adapts to Various soil conditions, easy to reproduce in a large area, can tolerate and absorb Pb, Zn and Cd at the same time, its aerial parts can be highly enriched in heavy metals such as Pb, Zn and Cd, and it is perennial, with well-developed root system, fast growth and high biomass; 2. Urticaceae ramie is a perennial herb. The bast fibers in its stems can be used as textile raw materials. It is an important fiber crop with very good economic value and considerable potential economic benefits. It is easy to popularize and apply; 3. Entering the food chain, it will not cause any potential heavy metal hazards to the human body; 4. Urticaceae ramie is a perennial herbaceous plant, which is a perennial plant. You can only harvest the stems and leaves of the aboveground part, and the underground part can continue to grow, thereby Achieve continuous soil remediation.

3. With EDDS as the chelating agent, and adopt the application concentration and application method disclosed in the invention, the content of the acid extractable state (weak acid extraction state, such as carbonate binding state) that heavy metals are easily absorbed by plants in the soil increases significantly, and the plant The content of oxidizable (organic) and residual (residue) forms which are difficult to utilize is significantly reduced. Irrigation with EDDS solution with a concentration of 0.005-0.015mol/L every 30 days can effectively match the growth cycle of ramie, replenish degraded EDDS, and significantly promote the continuous absorption of heavy metals activated by chelating agent EDDS in ramie roots. The content of heavy metals in ramie has increased, which greatly enhanced the ability of ramie to repair heavy metal-contaminated soil. At the same time, the content of heavy metals in the soil is significantly reduced, and EDDS is also biodegraded, reducing the risk of secondary pollution that may be caused by chelating agents and heavy metals. At the same time, compared with EDTA, the same concentration of EDDS caused less adverse stress to ramie.

4. In the restoration method disclosed in the present invention, the chelating agent EDDS does not need to be coated or processed by other complicated processes, and the method of adding by irrigation is more convenient.

5. For the restoration method disclosed in the present invention, the application concentration and application time of EDDS are the optimized concentrations obtained after many tests on the form of heavy metals in the soil. Reasonable configuration, selected within the range recommended by the restoration method disclosed in the present invention, has application value applicable to actual large-area soil restoration.

6. Compared with other physical and chemical restoration methods, the restoration method provided by the present invention is low in cost, environmentally friendly, simple in operation, and simple in follow-up treatment after restoration. Secondary pollution, while remediating without disrupting the soil ecosystem, helps to reduce the risk of soil quality degradation and reduced productivity.

Description of drawings

Fig. 1 is a comparison chart of the effect of EDDS on the form of soil cadmium;

Fig. 2 Comparison chart of cadmium content in various parts of ramie after restoration;

Figure 3 is a comparison chart of cadmium content in the soil after remediation;

Fig. 4 EDTA is processed and the malondialdehyde content contrast figure in the ramie leaf of EDDS processing;

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

The method that chelating agent EDDS of the present invention and ramie repair soil cadmium pollution continuously may further comprise the steps:

The ramie seedlings with a height of 35-45cm that have been cultivated are implanted in the soil to be repaired;

After the ramie survives, apply the biodegradable chelating agent EDDS to the soil, the application rate is 75-300kg/mu, the application method is uniform spreading or furrow application, and then the water is dissolved and washed into the soil, or the chelating agent is washed into the soil. EDDS is dissolved in water, once or divided into 2-3 times on average, and applied to the soil to be repaired with field irrigation;

Every 30 days, irrigate once with the EDDS solution of 0.005-0.015mol/L with a concentration, and carry out normal irrigation according to the needs of field ramie growth in the rest of the time, and the pH value of the EDDS solution can be adjusted to the pH value of the soil to be repaired with NaOH same or similar;

The stalks and leaves of the aboveground part of ramie can be harvested every 2-3 months, and the underground part is left in the soil to continue to breed and grow;

The ramie planted into the soil can be harvested together with the underground part after 2-3 years. If the soil needs to be repaired, new ramie seedlings can be replanted until the soil cadmium pollution is repaired.

Before the ramie is planted, base fertilizer can be applied to the soil to be repaired. The base fertilizer is (NH ₄ ) ₂ SO ₄ : 45kg/mu, KH ₂ PO ₄ : 30kg/mu, K ₂ SO ₄ : 45kg/mu.

The degradable chelating agent selected by the present invention is EDDS (ethylenediamine disuccinic acid), and its CAS number is 20846-91-7. Molecular formula: C10H16N2O8. Molecular weight: 292.24. Chinese synonyms are: N,N'-ethylenediamine disuccinic acid; N,N'-(1,2-ethanediyl)bispartic acid; N,N'-(1,2-ethanediyl) base) bis-aspartic acid. The English name is TRISODIUMETHYLENEDIAMINE DISUCCINATE. English synonyms: L-Asparticacid, N-1,2-ethanediylbis-; 2-[2-(1,2-dicarboxyethylamino)ethylamino]butanedioic acid; N,N'-ethylenediamine discuccinic acid; 1-Ethylenediaminedisuccinic acid; Aspartic acid, N,N'-ethylenedi-(7CI); Aspartic acid, N,N'-ethylenedi-,1,1-(8CI); N,N'-1,2-ethanediylbis-1-Aspartic acid; n,n' -1,2-ethanediylbis-l-aspartic acid.

EDDS has strong coordination ability, easy biodegradation, and strong chelating effect with transition metals. It was originally isolated from an actinomycete and is a natural substance. Compared with EDTA, its biological toxicity includes to plants The toxicity of EDDS and soil microorganisms is lower than that of EDTA, and it is biodegradable. The half-life of EDDS is between 3.8 and 7.5 days depending on the amount of application, while the minimum half-life of EDTA is 36 days. Therefore, the environmental risk of EDDS is very small compared with EDTA.

Select degradable EDDS as the chelating agent for phytoremediation soil, and adopt the application concentration and application method disclosed in the invention, the content of acid extractable state (weak acid extraction state, such as carbonate binding state) in the soil where heavy metals are easily absorbed by plants Significantly increased, while the oxidizable state (organic state) and residual state (residue state) content that is difficult for plants to use decreased significantly. Irrigation with EDDS solution with a concentration of 0.005-0.015mol/L every 30 days can effectively match the growth cycle of ramie, replenish degraded EDDS, and significantly promote the continuous absorption of heavy metals activated by chelating agent EDDS in ramie roots. The content of heavy metals in ramie has increased, which greatly enhanced the ability of ramie to repair heavy metal-contaminated soil. At the same time, the content of heavy metals in the soil is significantly reduced, and EDDS is also biodegraded, reducing the risk of secondary pollution that may be caused by chelating agents and heavy metals. At the same time, compared with EDTA, applying the same concentration of EDDS caused less adverse stress to ramie and had better affinity to ramie. At the same time, as a chelating agent, EDDS does not need to be coated or other complicated processes, and the method of adding irrigation is more convenient.

The ramie used in the restoration method provided by the invention has certain economic value, does not enter the food chain, has considerable potential economic benefits, and is easy to popularize and apply. Ramie was chosen as the restoration plant because ramie is a non-edible perennial economic crop that can tolerate a variety of heavy metals (such as Pb, Zn and Cd), and the shoots of ramie can be highly enriched in heavy metals such as Pb, Zn and Cd. It is a perennial herb of the genus Ramie of the family Urticaceae. The bast fibers in its stems can be used as textile raw materials and are important fiber crops. As a phytoremediation material, ramie has the following advantages: 1. It is widely distributed, adapts to various soil conditions, and can tolerate and absorb Pb, Zn and Cd at the same time; 2. It has great economic value and does not go through the food chain; 3. Urticaceae Ramie is a perennial herbaceous plant. It is a perennial plant. It can only harvest the stems and leaves of the aboveground part, and the underground part can continue to grow, so as to realize continuous soil restoration. Its root system is well developed, fast growing, and high in biomass; 4. Easy to reproduce in large areas.

Compared with other physical and chemical restoration methods, the restoration method provided by the present invention has low cost, environmental protection, simple operation, and simple follow-up treatment after restoration. Remediation without disrupting soil ecosystems helps reduce the risk of soil quality degradation and reduced productivity.

The present invention will be further described below by specific embodiment:

Example 1

The method for chelating agent EDDS of the present invention and ramie to continuously restore soil cadmium pollution may further comprise the steps:

Plant ramie into the soil to be repaired;

After the ramie survives, apply the biodegradable chelating agent EDDS to the soil at an application rate of 300kg/mu, and sprinkle it on the surface of the soil to be repaired at one time, and then immediately water it, dissolve it and wash it into the soil;

Every 30 days, irrigate once with the EDDS solution of 0.009mol/L with concentration, and carry out normal irrigation according to the needs of field ramie growth in the rest of the time;

The stalks and leaves of the aerial part of ramie can be harvested every 3 months, and the underground part can be left in the soil to continue to breed and grow;

Every time the ramie is planted into the soil, it can be harvested together with the underground part after 3 years. If it is necessary to continue to restore the soil, new ramie seedlings can be replanted until the soil cadmium pollution is repaired.

Example 2

The ramie seedling that the height that will cultivate is 40cm is implanted in the soil to be repaired;

After the ramie survives, apply the biodegradable chelating agent EDDS to the soil at an application rate of 150kg/acre, ditch it once and apply it to the surface of the soil to be repaired, and immediately irrigate it, dissolve it and wash it into the soil;

Every 30 days, the EDDS solution with a concentration of 0.015mol/L was irrigated once, and the rest of the time was normally irrigated according to the needs of field ramie growth. The pH value of the EDDS solution was adjusted to be the same as the pH value of the soil to be repaired with NaOH.

The stalks and leaves of the aerial part of ramie can be harvested every 2 months, and the underground part can be left in the soil to continue to breed and grow;

Every time the ramie is planted into the soil, it can be harvested together with the underground part after 2 years. If it is necessary to continue to repair the soil, new ramie seedlings can be replanted until the soil cadmium pollution is repaired.

Example 3

Apply base fertilizer to the soil to be repaired, the base fertilizer is (NH ₄ ) ₂ SO ₄ , KH ₂ PO ₄ , K ₂ SO ₄ , and the application can be determined according to the reasonable needs of the growth of ramie;

The ramie seedling that the height that will cultivate is 45cm, selects the good similar ramie of growing way to transplant, and implants in the soil to be repaired;

After the ramie survives, apply the biodegradable chelating agent EDDS to the soil again, the application rate is 75kg/mu, dissolve the chelating agent EDDS in water, and apply it to the soil to be repaired with the irrigation water at one time during irrigation;

Every 30 days, the EDDS solution with a concentration of 0.005mol/L was irrigated once, and the rest of the time was normally irrigated according to the needs of field ramie growth. The pH value of the EDDS solution was adjusted to be the same as the pH value of the soil to be repaired with NaOH.

The stalks and leaves of the aboveground part of ramie can be harvested every 2.5 months, and the underground part is left in the soil to continue to breed and grow;

Every time the ramie is planted into the soil, it can be harvested together with the underground part after two and a half years. If it is necessary to continue repairing the soil, new ramie seedlings can be replanted until the soil cadmium pollution is repaired.

Example 4

Apply base fertilizer to the soil to be repaired, the base fertilizer is (NH ₄ ) ₂ SO ₄ : 45kg/mu, KH ₂ PO ₄ : 30kg/mu, K ₂ SO ₄ : 45kg/mu;

With the ramie seedling that the height that cultivates is 35cm, select the good similar ramie of growing way to transplant, implant in the soil to be repaired;

After the ramie survives, apply the biodegradable chelating agent EDDS to the soil again, the application rate is 225kg/mu, dissolve the chelating agent EDDS in water, divide it into 2 times on average, and apply it in the soil to be repaired with the irrigation water ;

Every 30 days, use the EDDS solution irrigation of 0.010mol/L with concentration once, carry out normal irrigation according to the needs of field ramie growth in the rest of the time, the pH value of described EDDS solution is adjusted to be identical with the pH value of the soil to be repaired with NaOH;

The stalks and leaves of the aerial part of ramie can be harvested every 3 months, and the underground part can be left in the soil to continue to breed and grow;

Every time the ramie is planted into the soil, it can be harvested together with the underground part after two and a half years. If it is necessary to continue repairing the soil, new ramie seedlings can be replanted until the soil cadmium pollution is repaired.

Example 5

Apply base fertilizer to the soil to be repaired, the base fertilizer is (NH ₄ ) ₂ SO ₄ : 45kg/mu, KH ₂ PO ₄ : 30kg/mu, K ₂ SO ₄ : 45kg/mu;

The ramie seedling that the height that will cultivate is 30cm, selects the good similar ramie of growing way to transplant, and implants in the soil to be repaired;

After the ramie survives, apply the biodegradable chelating agent EDDS to the soil again, the application rate is 200kg/mu, dissolve the chelating agent EDDS in water, divide it into 3 times on average, and apply it in the soil to be repaired with the irrigation water ;

Every 30 days, use the EDDS solution irrigation that concentration is 0.009mol/L once, carry out normal irrigation according to the needs of field ramie growth in the rest of the time, the pH value of described EDDS solution is adjusted to be identical with the pH value of soil to be repaired with NaOH;

The stalks and leaves of the aboveground part of ramie can be harvested every 2.5 months, and the underground part is left in the soil to continue to breed and grow;

The ramie implanted into the soil can be harvested together with the underground part after 3 days. If it is necessary to continue to repair the soil, new ramie seedlings can be re-implanted until the soil cadmium pollution is repaired.

In order to further verify the remediation effect of the remediation method disclosed in the present invention on soil cadmium pollution, the inventor has conducted multiple verification implementations, and some experiments are described in detail as follows.

Experimental example 1: Effect experiment of EDDS on soil cadmium form

1. In this test, the soil polluted by heavy metals is selected, and the soil in the 0-20cm soil layer is taken.

The soil was collected from a farmland outside a zinc smelting plant. The basic properties and element contents of the soil were: cadmium 95.2mg kg-1, lead 241mg kg-1, nitrogen 1.32g/kg, phosphorus 1.12g/kg, potassium 17.56g/kg, pH7.8.

2. The effect of using biodegradable chelating agent EDDS on the morphology in soil.

After the soil samples were ground and sieved, 20.00g of cadmium-contaminated soil samples were weighed and placed in 50mL polyethylene plastic bottles with lids. EDDS was added to 20.00 g of contaminated soil samples at different application levels (CK, 1.5 mmol/kg soil, 3 mmol/kg soil, 6 mmol/kg soil, 9 mmol/kg soil), and the soil was cultivated at room temperature for 30 days. Humidity is around 70%. Then, the form and content of cadmium in the soil were determined by continuous extraction and leaching by BCR, and the influence of EDDS on various forms of cadmium was explored. The BCR method is a relatively new division method proposed by the European Community Bureau of Reference, which divides the form of cadmium into four types, namely: acid-soluble state (weak acid extraction state, such as carbonate-bound state), Reduction state (such as iron manganese oxide state), oxidizable state (such as organic state), residue state.

Referring to Fig. 1, EDDS is to the control figure of the action effect of soil cadmium form, the result shows: compared with contrast, after applying EDDS, the acid extractable state (weak acid extractable state, such as carbonate binding state) of heavy metals in the soil is easily absorbed by plants ) content increased significantly, while the oxidizable (organic) and residual (residual) content, which was difficult for plants to use, decreased significantly, and the effect was the best when the application rate of EDDS was 9 mmol/kg soil.

Experimental example 2: The effect of EDDS and ramie combined remediation of heavy metal polluted soil

1. In this test, the soil polluted by heavy metals is selected, and the soil in the 0-20cm soil layer is taken.

The soil was collected from a farmland outside a zinc smelting plant. The basic properties and element contents of the soil were: cadmium 95.2mg kg-1, lead 241mg kg-1, nitrogen 1.32g/kg, phosphorus 1.12g/kg, potassium 17.56g/kg, pH7.8.

2. Add base fertilizer (NH ₄ ) ₂ SO ₄ : 0.3g·kg-1, KH ₂ PO ₄ : 0.2g·kg-1, K ₂ SO ₄ : 0.3g·kg-1 to the polluted soil for potting soil ;

Select about 40cm of plant height, and the ramie that grows well and similarly is transplanted;

After the ramie survives, add 0.05%, 0.10%, 0.15%, and 0.20% of the biodegradable chelating agent EDDS to the soil;

Every 30 days, irrigate once with EDDS solution with a concentration of 0.009mol/L, and irrigate normally for the rest of the time;

At the maturity stage after 64 days of transplanting, the ramie plants were taken out and washed with tap water and distilled water, and the plant height, stem diameter and tiller number were measured, and then the roots, stems and leaves were separated to measure the biomass of each part, and after drying, the Fix the greens at 105°C for 30 minutes, then dry at 80°C to constant weight, and measure the heavy metal content in ramie roots, stems, and leaves after crushing;

After the soil was naturally air-dried, it was passed through a 0.15mm (100 mesh) nylon sieve, digested with aqua regia-perchloric acid-atomic absorption spectrometry, and the cadmium content of the soil samples was determined.

See Figure 2, the comparison chart of cadmium content in various parts of ramie after restoration. The results show that after repairing with this method, the cadmium content in each part of ramie roots, stems and leaves has increased significantly, and the root has the largest increase, when the application concentration is 0.15 % to 0.20%, it can reach 70%. When the application concentration is 0.05%, the content of cadmium in the aboveground part is reduced, but the content of cadmium in the soil is still significantly reduced, indicating that the overall bioaccumulation of the aboveground part is still increasing at this concentration. Cadmium absorption effect is better. The relationship of cadmium uptake in each part of ramie was: cadmium content in roots>weight cadmium content in stems>cadmium content in leaves.

See Figure 3, the comparison chart of cadmium content in the soil after remediation; compared with before remediation, after remediation by this method, the content of cadmium in the soil has been significantly reduced, respectively decreased by 38% to 40%, and the remediation effect has been very good withdraw.

Test example 3: Comparison of EDDS and EDTA application on ramie stress

The EDDS of this method is compared with the joint restoration method of EDTA and ramie at the same concentration. The specific experimental method is the same as the operation steps in Experimental Example 2. In terms of treatment, different concentrations of EDTA are added. Ten days before harvest, fresh leaves of ramie were collected, and the content of malondialdehyde (MDA) in the leaves was determined. Membrane lipid peroxidation often occurs because plant organs are aging or damaged under adversity. Malondialdehyde (MDA) is the final decomposition product of membrane lipid peroxidation, and its content can reflect the degree of adversity damage to plants. Experimental comparison found that at various concentrations of application, the content of malondialdehyde in ramie leaves was EDTA>EDDS, indicating that EDTA had greater adverse stress on ramie, and EDDS had less adverse stress on ramie itself. Plant ramie has a higher affinity. It has been verified that EDDS is more environmentally friendly than EDTA, and has greater promotion and use value.

In order to further verify the remediation effect of the remediation method disclosed in the embodiments of the present invention on soil cadmium pollution, the inventor has conducted several field verification implementations. In the field experiment, according to the specific method of Test Example 2, the application amount of EDDS, EDDS solution and base fertilizer was converted into field application amount. , converted into the amount per mu of the field, that is, the base fertilizer applied to the soil to be repaired is (NH ₄ ) ₂ SO ₄ : 45kg/mu, KH ₂ PO ₄ : 30kg/mu, K ₂ SO ₄ : 45kg/mu; Apply biodegradable chelating agent EDDS, the application rate is 75kg/mu, 150kg/mu, 225kg/mu, 300kg/mu. According to the specific operation steps of the test example 2, the field experiment was carried out. Finally, the ramie was harvested and soil was taken for determination. The results of the field experiment are not much different from those of the pot experiment. This method has an excellent effect on remediating soil cadmium pollution and is more environmentally friendly.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (10)

1. a method for chelating agent EDDS and ramie to continuously repair soil cadmium pollution, is characterized in that, may further comprise the steps: Plant ramie into the soil to be repaired; After the ramie survives, apply the biodegradable chelating agent EDDS to the soil at an application rate of 75-300kg/mu; Every 30 days, irrigate once with EDDS solution with a concentration of 0.005-0.015mol/L, and irrigate normally for the rest of the time; The stalks and leaves of the aboveground part of ramie are harvested regularly, and the underground part is left in the soil to continue to breed and grow. 2. the method for chelating agent EDDS according to claim 1 and ramie continuous repair soil cadmium pollution is characterized in that, The implanted ramie is a cultivated ramie seedling, and its height is 35-45cm. 3. the method for chelating agent EDDS according to claim 1 and ramie continuous repair soil cadmium pollution is characterized in that, The pH value of the EDDS solution is adjusted with NaOH to be the same as the pH value of the soil to be repaired. 4. the method for chelating agent EDDS according to claim 1 and ramie continuous restoration soil cadmium pollution is characterized in that, The stems and leaves of the aerial part of ramie are harvested 2 to 3 times a year. 5. the method for chelating agent EDDS according to claim 1 and ramie continuous restoration soil cadmium pollution is characterized in that, The ramie implanted in the soil shall be harvested together with the underground part after every 2-3 years, and then replanted with new ramie seedlings until the soil cadmium pollution is repaired. 6. the method for chelating agent EDDS according to claim 1 and ramie continuous repair soil cadmium pollution is characterized in that, The concentration of the EDDS solution is 0.009mol/L. 7. the method for chelating agent EDDS according to claim 1 and ramie continuous repair soil cadmium pollution is characterized in that, The amount of EDDS applied to the soil to be repaired is 225kg/mu. 8. the method for chelating agent EDDS according to claim 1 and ramie continuous remediation soil cadmium pollution is characterized in that, The application method of described chelating agent EDDS is: Spread evenly or furrow; Alternatively, the chelating agent EDDS is dissolved in water, and applied once or divided into 2-3 times on average into the soil to be repaired along with watering. 9. the method for chelating agent EDDS according to claim 1 and ramie continuous restoration of soil cadmium pollution, is characterized in that, Before the ramie is planted, a base fertilizer is applied to the soil to be repaired, and the base fertilizer is (NH ₄ ) ₂ SO ₄ , KH ₂ PO ₄ , K ₂ SO ₄ . 10. the method for chelating agent EDDS according to claim 8 and ramie continuous remediation soil cadmium pollution is characterized in that, The application rate of the base fertilizer is: (NH ₄ ) ₂ SO ₄ : 45kg/mu, KH ₂ PO ₄ : 30kg/mu, K ₂ SO ₄ : 45kg/mu.