CN111515236B - In-situ reduction remediation method for cadmium-polluted farmland - Google Patents
In-situ reduction remediation method for cadmium-polluted farmland Download PDFInfo
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- CN111515236B CN111515236B CN202010338628.8A CN202010338628A CN111515236B CN 111515236 B CN111515236 B CN 111515236B CN 202010338628 A CN202010338628 A CN 202010338628A CN 111515236 B CN111515236 B CN 111515236B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/02—Extraction using liquids, e.g. washing, leaching, flotation
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/08—Reclamation of contaminated soil chemically
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/10—Reclamation of contaminated soil microbiologically, biologically or by using enzymes
- B09C1/105—Reclamation of contaminated soil microbiologically, biologically or by using enzymes using fungi or plants
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A40/00—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production
- Y02A40/10—Adaptation technologies in agriculture, forestry, livestock or agroalimentary production in agriculture
- Y02A40/22—Improving land use; Improving water use or availability; Controlling erosion
Abstract
The invention relates to an in-situ reduction remediation method for a cadmium-polluted farmland, which comprises the steps of ploughing the farmland to be remedied, introducing an eluent solution into the farmland, uniformly mixing ploughed soil and the eluent solution, standing for layering, putting an ecological floating plate into the farmland, taking out the ecological floating plate after 15-30 days, and realizing in-situ removal of cadmium in the cadmium-polluted farmland. The method can efficiently reduce and restore Cd polluted farmland in situ, and has the advantages of simple process flow, low cost and environmental friendliness.
Description
Technical Field
The invention relates to an in-situ decrement remediation method for cadmium-polluted farmland, belonging to the technical field of soil pollution remediation for environmental protection.
Background
At present, the general condition of farmland soil environment in China is great, and according to the results of the soil pollution condition survey bulletin published by the environmental protection department and the national soil resources department in 2014, more than 12% of 18.26 hundred million acres of cultivated land area in China is polluted by heavy metal, the total point standard exceeding rate is 16.1%, and the cadmium (Cd) polluted point standard exceeding rate reaches 7%. Cd pollution is mainly caused by industrial sewage discharge, mineral development and unreasonable use of chemical fertilizers and pesticides. Cd pollution not only causes the yield reduction of farmland grains, but also damages the renal function of a human body and hinders the growth of bones after long-term eating of the grains with Cd exceeding the standard, thereby causing pain diseases. Therefore, in order to ensure the quality of agricultural products and the production safety of grains, the method is very important for repairing and controlling the soil of the farmland cultivated layer polluted by Cd.
At present, the method for restoring Cd polluted soil mainly comprises physical restoration, chemical restoration and biological restoration, wherein the physical restoration comprises methods of soil dressing, soil replacement, surface soil removal, deep ploughing and soil turning, heat treatment, electric restoration, solidification vitrification and the like; chemical repair refers to methods such as passivation, leaching and the like; the biological method comprises animal repair, plant repair and microbial repair. The physical method is mostly used in industrial soil, has large engineering quantity, high energy consumption and large soil structure destruction, and is rarely used in farmland soil. The leaching method is to put leacheate into the soil, then recycle the leacheate, treat the leacheate to obtain Cd, and achieve the purpose of reducing the amount of the Cd in the soil; the in-situ passivation method is to add a passivating agent into farmland soil and reduce the solubility, the mobility and the biological toxicity of Cd through chemical reaction. The leaching method can cause the change of soil types and the reduction of soil fertility, and the generated leaching waste water is a great problem to be treated. The passivation method changes the existing form of Cd, but does not eradicate the Cd from the soil, and needs to prevent Cd activation and increase the biological risk of Cd. The biological method is a method which is applied to farmland soil more frequently, is widely used due to simplicity, practicability and high treatment efficiency, but has the advantages of long simple bioremediation period, slow treatment effect, great influence by soil environment and artificial conditions, limited tolerance of organisms to Cd and certain limitation.
The method is characterized in that Cd in farmland soil is simply leached, and then the Cd in leacheate is adsorbed, so that in actual application, the leacheate is easy to damage the soil structure, and meanwhile, the problem of high economic cost exists. The patent CN109807165A provides a heavy metal leaching and reduction method for cadmium-polluted soil, which comprises the steps of compounding an artificially synthesized chelating agent EDTA, a natural organic acid chelating agent and a surfactant NP-10 (nonionic surfactant) according to a certain mass ratio, adding water to dissolve and dilute the mixture into a soil heavy metal leaching agent, adsorbing Cd in a solution through metal minerals, and generating NP (nonylphenol polyoxyethylene ether) along with the decomposition of microorganisms after the surfactant enters the soil, thereby influencing the endocrine system of the organisms and causing long-term harm. The patent CN103706629A discloses a method for removing cadmium in polluted soil by washing watermelon peel, which comprises the steps of leaching watermelon peel powder with KCl solution to prepare watermelon peel washing liquid, and then shaking and washing the Cd polluted soil in farmland with the washing liquid. However, the patent does not treat subsequent leachate, so that secondary pollution is easily caused, meanwhile, the leaching efficiency is low, the pH value of the soil needs to be adjusted during leaching, the soil structure is easily damaged, and the economic cost is increased. Patent CN108311538A discloses a leaching treatment method for heavy metal contaminated soil, which is used for leaching soil for multiple times, has strong destructiveness on the soil structure, and needs to backfill the treated soil, and the method has the advantages of large engineering quantity, high economic cost and low treatment efficiency. The patent CN109877147A discloses a method for leaching and repairing cadmium-contaminated soil, wherein an amino acid-hydrochloric acid ionic liquid aqueous solution is used as a leaching agent, the method leaches the soil through amino acid, the treatment efficiency is high, the harm to the soil is small, but the leaching solution needs to be reprocessed, and the economic cost is increased. Patent CN106216379A discloses a comprehensive leaching and repairing method for heavy metal contaminated soil, which comprises the steps of scattering solid materials, introducing water, turning over to leach out heavy metals and transferring the heavy metals into leaching water, and removing the heavy metals by biochar microorganisms. The concentration of the leacheate is uneven when solid materials are scattered, turned over and leached, the comprehensive leaching process is complex and tedious, the occupied area is large, the field cultivation area is limited, and the method is difficult to popularize and implement.
In the field of soil Cd remediation, the remediation technology taking biochar as a material is widely applied. Patent CN107716532A discloses a method for studying the influence of biochar on the properties and the form of cadmium-contaminated soil. In the method, biochar is added into soil to reduce the bioavailability of Cd, but Cd which is changed into a ferro-manganese oxide combined state from an exchange state is easy to activate under the action of soil microorganisms, and the long-acting stability of Cd is poor. Patent CN110180887A discloses duckweed biochar for curing/stabilizing soil heavy metal Pb and Cd combined pollution and a using method thereof. The method takes plants in the eutrophic river as biochar, prepares ecological duckweed, and puts the duckweed into soil for maintenance, is simple and easy to implement, has low economic cost, but has low efficiency, only stabilizes a small part of effective Cd in the soil, and does not achieve the purpose of Cd reduction. The patent CN105665435A discloses a remediation agent for treating cadmium-contaminated soil and application thereof, and the invention changes the existence form of Cd in the soil, so that the leaching rate of the Cd in the soil is reduced, but the total amount of the Cd is not reduced, and certain environmental risk exists.
The hyper-enriched plant is widely applied to soil remediation due to the high accumulation and tolerance of the hyper-enriched plant to heavy metals, and has the advantages of no secondary pollution, low cost and the like. Patent CN107695088A discloses a method for restoring As and Cd combined polluted farmland soil by utilizing a hyper-enriched plant biomass charcoal combined system. The method utilizes hyper-enrichment plants and a modifier to restore the soil Cd; but the repair efficiency is low, the repair cycle is long, the repair process is complex, and the treatment cost is increased. Patent CN107999535A discloses a method for restoring cadmium-polluted soil by using herbaceous plants, patent CN108114977A discloses a method for quickly restoring cadmium-polluted cultivated land by using super-enriched plants and energy plants for crop rotation planting, and patent CN109127695A discloses a phytorestoration method for heavy metal Cd-polluted soil. The above patents have low mass transfer efficiency, low Cd reduction efficiency, complex operation and higher cost. Therefore, a Cd reduction method which does not cause secondary pollution, is environment-friendly, and has high and lasting treatment efficiency is urgently needed.
Disclosure of Invention
Aiming at the defects of the prior art, the invention discloses an in-situ reduction remediation method for a cadmium-polluted farmland, which is used for realizing the rapid and efficient remediation of the cadmium-polluted farmland.
In order to solve the technical problems, the technical scheme of the invention is as follows:
an in-situ reduction remediation method for a cadmium-polluted farmland comprises the steps of ploughing the farmland to be remediated, introducing an eluent solution into the farmland, uniformly mixing ploughed soil and the eluent solution, standing for layering, putting an ecological floating plate into the farmland, taking out the ecological floating plate after 15-30 days, and realizing in-situ removal of cadmium in the cadmium-polluted farmland;
wherein the concentration of ferric chloride in the eluent solution is 1-10mM, and the concentration of citric acid is 1-5 mM; standing and layering, wherein the water covering height in the farmland is 8-12 cm; the ecological floating plate is provided with a planting groove, the wall of the planting groove is provided with a plurality of through holes, a mixed matrix consisting of biochar and clay is filled in the planting groove, and cadmium-enriched plants are planted on the mixed matrix; the throwing density of the ecological floating plate is 1-5/m2。
Further, during the plowing treatment, the plowing depth of the soil in the field to be restored is 15-30 cm.
Further, the concentration of ferric chloride in the eluent solution is 3-7mM, and the concentration of citric acid is 2-4 mM.
And further, standing for 12-48h to realize layering, namely layering the eluent solution and the soil.
Further, the volume ratio of the biochar to the clay in the mixed matrix is 1-2: 1.
Further, in the mixed matrix, the particle sizes of biochar and clay are both greater than 0.15 mm, preferably, the biochar is derived from one or more of rice straw, corn straw and sesame straw, and the clay comprises one or more of attapulgite, kaolin and montmorillonite.
Furthermore, the throwing density of the ecological floating plate is 2-3/m2。
Further, the cadmium-enriched plant is one or more of Potentilla tormentosa, Viola Baoshanensis, Picris japonica, houttuynia cordata, Thalasia alata, red mula leaves, Brassica juncea, Artemisia selengensis and Solanum nigrum.
Further, the content of Cd in the soil of the farmland to be restored is 0.6-5 mg/kg.
The method can effectively solve the problems existing in the related methods in the prior art, for example, in the restoring process of the farmland soil Cd, the biological effectiveness of the Cd can be reduced by the passivation technology, but the stability and the timeliness are limited, and the problem of the farmland soil Cd pollution can not be fundamentally solved; in the leaching technology, the conventional leaching agent causes secondary pollution to soil, and the generated leaching wastewater needs to be treated again, so that the treatment steps and the cost are increased; when Cd is restored in farmland soil by planting Cd-enriched plants, secondary pollution to the soil is avoided, but the growth cycle of the plants is long, and the restoration efficiency is low.
Compared with the prior art, the in-situ reduction remediation method for the cadmium-polluted farmland, provided by the invention, adopts a physical-chemical-plant combined remediation technology, firstly, a chemical leaching method is adopted, the Cd in the soil is activated by the ferric chloride and citric acid composite leaching agent, and the nitrogen, phosphorus and potassium in the soil are activated and can be used as nutrient substances for the subsequent plant growth; putting the ecological floating plate into leacheate, and adsorbing part of activated Cd in the biochar and clay matrix by a physical adsorption method; and finally, enriching Cd in the leacheate and the matrix in the plant body through a Cd enrichment plant, and finally realizing the in-situ removal of the Cd-polluted farmland soil. Through the application of a physical-chemical-plant combined remediation method, the Cd in the farmland polluted soil can be reduced in situ in a short time by promoting the Cd in the farmland polluted soil.
In the invention, the ecological floating plate is put into the eluent solution, and the ecological floating plate floats on the field eluent solution. The biochar and the clay matrix in the ecological floating plate have double functions, can be used as an adsorbent to adsorb Cd in leaching water, and can also be used as a nutrient matrix for Cd enrichment plant growth, wherein the biochar contains 5-37% of easily-decomposed carbon components, nutrient elements on the biochar are leached out under the action of an eluent, can be preferentially utilized by Cd enrichment plant roots, and can promote the growth of Cd hyperaccumulation plants. The biochar and the clay matrix have huge specific surface areas, and can effectively adsorb Cd in the leaching water, so that the removal rate of the Cd in the leaching water is higher.
Wherein, the raw material of the biochar is one or more of rice straw, corn straw and sesame straw, which are agricultural and forestry waste, and the agricultural and forestry waste is recycled; the clay mineral comprises one or more of attapulgite, kaolinite and montmorillonite, and has low economic cost and good adsorption effect.
According to the invention, the Cd-enriched plant in the ecological floating plate can absorb Cd in the biochar and the clay matrix through the root system and can also directly absorb Cd in the leaching water, and compared with the method for directly planting the Cd-enriched plant in a farmland, the Cd-enriched plant in the invention has higher mass transfer efficiency, so that the Cd-enriched plant in the invention has stronger absorption effect on Cd.
In order to further ensure the restoration effect, the Cd-enriched plant is a hyper-enriched plant which is in the vegetative growth period, grows rapidly and is in the period of vigorous metabolism.
According to the invention, the volume ratio of the biochar to the clay in the planting tank is 1:1-2:1, and the applicant finds that if the ratio is lower than 1:1, the biochar is reduced, the clay can wrap the biochar, and the Cd adsorption efficiency of the biochar is influenced, and if the ratio is higher than 2:1, the clay ratio is reduced, the holding capacity of the substrate to the adsorbed Cd is weakened, so that the Cd enrichment efficiency of the hyper-enriched plants is weakened.
According to the invention, the net is laid in the planting groove for containing the matrix, so that the matrix can be effectively prevented from being diffused into the leacheate.
In addition, the plowing depth of the soil is 15-30cm, the root group depth of the farmland plants is generally within 30cm, the Cd is absorbed by root systems to cause crop pollution, and when the Cd is within 30cm of the soil depth, the Cd absorption capacity of the root systems of the farmland plants in the range is strong, and the environmental risk is high; when the concentration of Cd exceeds 30cm, the contact probability of farmland plant roots to Cd is low, the absorption capacity to Cd is weak, and the environmental risk is low. Therefore, when the plowing depth is 15-30cm, the economic cost can be reduced under the condition that crops are not affected by Cd.
The eluting agent is a mixed solution of ferric chloride and citric acid, wherein the concentration of the ferric chloride is 1-10mM, the concentration of the citric acid is 1-5mM, and the problem of poor eluting effect of a single eluting agent can be solved by the ferric chloride and citric acid composite eluting agent. The ferric chloride can activate the Cd in the soil to transfer the Cd from the soil to the leacheate, and the citric acid serving as a chemical complexing agent and a soil acidifying agent can cooperate with the ferric chloride to activate the Cd in the soil, so that the bioavailability of the Cd in the soil is improved, and the leaching efficiency of the leacheate on the Cd in the soil is improved.
The citric acid in the eluent can provide nutrients for Cd-enriched plants, so that the eluent can be used as a 'liquid culture medium' to promote the growth of the Cd-enriched plants, the elution efficiency of the Cd in the soil can be effectively improved through the composite eluent of the ferric chloride and the citric acid, the growth of the Cd-enriched plants in the ecological floating plates can be promoted, and the absorption of the Cd-enriched plants by the Cd-enriched plants is improved.
According to the invention, the retention time of the ecological floating plate in the leaching wastewater is 15-30 days, and Cd-enriched plants grow on the ecological floating plate and are put into the leaching water along with the floating plate, so that compared with other plant restoration technologies, the method provided by the invention has the advantages of simple steps and convenience in operation, and greatly improves the working efficiency.
In the invention, the Cd-enriched plant is one or more of Potentilla tormentosa, Viola baoshanensis, Picris japonica, houttuynia cordata, Thalasia repens, red mula leaves, Indian mustard, Artemisia selengensis and Solanum nigrum, and the hyper-enriched plant can enrich Cd exceeding 100mg/kg in the plant body, has strong absorption capacity and tolerance capacity on Cd, can directly absorb Cd in a matrix and a water body, has higher restoration efficiency than other common plants, and has strong tolerance on the environment, thereby having stronger applicability.
The main mechanism of the invention for in-situ reduction and restoration of Cd polluted farmland comprises: the leaching agent, the biochar and the clay can provide nutrient substances for Cd hyperaccumulation plants, promote the growth of the plants and further promote the enrichment of Cd in leaching wastewater and matrix by the plants. The method has the advantages of efficient reduction and restoration of Cd polluted farmland in situ, simple process flow, low cost and environmental friendliness.
In general, compared with the prior art, the above technical solution contemplated by the present invention can achieve the following beneficial effects:
(1) according to the invention, a physical-chemical-plant combined remediation technology is utilized, Cd in soil is eluted by an eluent, then the Cd in the elution wastewater is enriched by biochar and clay, and finally the Cd in the elution water and the Cd in a matrix are enriched in a plant body by a Cd enrichment plant. The mixed matrix can release nutrient substances to promote plant growth while absorbing Cd, and has double effects on Cd reduction. Therefore, the method can realize the in-situ remediation of the Cd farmland polluted soil, and can effectively reduce the total amount of Cd in the farmland soil in a short time.
(2) According to the invention, the leaching efficiency of the Cd-polluted soil can be obviously improved in the process of ploughing and leaching Cd-polluted farmland. The ecological floating plate is directly placed in leaching wastewater (namely farmland covering water), Cd in the leaching wastewater can be absorbed, and the wastewater after treatment can be directly discharged after the Cd in the leaching wastewater is fully absorbed on the biochar and clay matrix and is absorbed by the Cd-enriched plant Jing. The invention does not need to further treat the leaching wastewater, simplifies the repair process, reduces the economic cost and can carry out large-area popularization test.
(3) According to the invention, the Cd hyperaccumulator grows on the ecological floating plate, indirectly absorbs Cd in farmland soil, can migrate along with the ecological floating plate, and can be taken out when the Cd in leaching wastewater is fully absorbed by the matrix in the ecological floating plate, so that the restoration time is obviously shortened, and the restoration efficiency is improved.
(4) The raw materials of the biochar are rice straw, corn straw, sesame straw and other agricultural and forestry wastes, so that the resources are fully utilized, and compared with the biochar made of other materials, the biochar has low environmental risk.
(5) The eluting agent used in the invention is a compound eluting agent of ferric chloride and citric acid, has high eluting efficiency, no secondary pollution, environmental protection and cleanness.
Drawings
FIG. 1 is a flow chart of an in-situ reduction remediation method for cadmium-contaminated farmland according to the invention.
FIG. 2 is a schematic view of a cross-sectional structure of a farmland in an in-situ decrement remediation process of the present invention.
FIG. 3 is a top plan view of an agricultural field in an in situ abatement remediation process of the invention.
Fig. 4 is a schematic structural view of an ecological floating plate of the present invention.
Fig. 5 is a top view of an ecological floating plate of the present invention.
FIG. 6 is a cross-sectional view of a mixed substrate and cadmium-enriched plant in a planting tank of the present invention.
FIG. 7 is a diagram showing the effect of removing Cd from the leaching wastewater.
FIG. 8 is a graph showing the adsorption effect of Cd in leaching wastewater by different biochar and clay ratios in a planting tank matrix.
FIG. 9 is a graph showing the efficiency of Cd enrichment in leach wastewater and substrates from Viola baoshanensis.
Wherein, 1-cadmium enrichment plants, 2-floating plates, 3-planting grooves, 4-farmlands, 5-ground, 6-water inlet pipes, 7-water outlet pipes and 8-mixed substrates.
Detailed Description
The following description describes alternative embodiments of the invention to teach one of ordinary skill in the art how to make and use the invention. Some conventional aspects have been simplified or omitted for the purpose of teaching the present invention. Those skilled in the art will appreciate that variations or substitutions from these embodiments will fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention.
Example 1
1000 g of farmland Cd-polluted soil is taken, wherein the Cd content is 1.64mg/kg, and the effective state Cd content is 0.63 mg/kg. Using 8 mMFeCl respectively38mM citric acid, and compound eluting agent (FeCl)3(5 mM) + citric acid (3 mM)) as eluent and deionized water as blank for soil contaminationAnd (3) soil leaching, namely placing the polluted soil into a beaker, wherein the coverage height of the leaching solution is 5cm, leaching for 12 h, and the leaching rate of Cd (1.64 mg/kg) in the soil is shown in Table 1.
TABLE 1 elution Effect of different eluents on Cd in effective state and total Cd in soil
As can be seen from Table 1, the eluent mainly acts on the effective Cd in the soil, and the compound eluent FeCl3+ citric acid has the best rinsing effect. Using FeCl3The leaching rate of (5 mM) + citric acid (3 mM) for leaching the soil to the total Cd reaches 13.1 percent, which is far higher than the expected value, and the leaching rate of the compound leaching agent to the effective Cd in the soil reaches 34.3 percent, so that FeCl is selected3+ citric acid compound eluent.
Example 2
Preparing eluent solution (FeCl)3(5 mM) + citric acid (3 mM)), introducing an eluent solution into the field through a water inlet pipe 6 to continue plowing while plowing and smashing the farmland soil to be repaired, so that heavy metal Cd in the soil is leached and dissolved out and is transferred into the eluent; standing for 24 h to allow the field leaching wastewater to stand for layering, wherein the depth of the farmland middle-covering water is 10 cm; placing the ecological floating plate into the leaching wastewater (the placing density is 3/m)2) The floating plate is utilized to float on the leaching wastewater, the wastewater is taken out after being placed for 30 days, and the leaching wastewater can be discharged through the water outlet pipe 7. And (3) determining the leaching rate of Cd in the soil, the removal rate of Cd in the leaching water and the enrichment rate of Cd in the Cd enrichment plant.
The content of Cd in the eluting effluent is 0.22mg/L and the elution rate of the effective Cd in the soil reaches 34.3% as measured by an atomic absorption spectrometer, and the reduction effect of the Cd in the eluting effluent is shown in FIG. 6 after the ecological floating plate is repaired, so that the removal rate of the Cd in the eluting effluent can reach 90.1%. As shown in fig. 7, the adsorption efficiency of Cd in biochar and clay is 77.2%. As shown in fig. 9, the plant uptake of Cd in the wash water and the substrate can reach 11.7%.
In this embodiment, as shown in FIG. 3The ecological floating plate comprises a floating plate 2 and planting grooves 3, the planting grooves 3 are arranged on the floating plate 2, the bottoms and the side edges of the planting grooves are made into inverse round platforms by nylon nets, through holes with the diameter of 5mm are formed in the walls of the planting grooves, the diameter of the upper bottom is 30cm, the diameter of the lower bottom is 20cm, and the height is 10 cm; the grid size of the nylon net is 0.05 mm; the volume ratio of the sesame straw biochar to the attapulgite in the planting groove is 2:1, wherein the volume of the sesame straw biochar is 14 dm3The volume of the attapulgite is 7dm3The floating plate is connected to the upper end of the planting groove, the planting groove penetrates through the floating plate, the side length of the floating plate is 50cm, and the thickness of the floating plate is 5 cm. Transplanting cadmium-enriched plant 1 (Viola baoshanensis) in the growth vigorous stage into a planting groove of an ecological floating plate.
Through the analysis and the experiment, the in-situ reduction remediation method for the cadmium-polluted farmland can rapidly solve the remediation problem of the Cd-polluted farmland in a large area through a physical-chemical-combined remediation technology, improve the phytoremediation efficiency and the current situation of low cycle length, and solve the problems of difficult treatment, complex process and the like of the generated leaching wastewater in the chemical leaching actual remediation process of the Cd-polluted farmland. And (3) adopting a leaching agent with a certain concentration and turning over to transfer the Cd into the leaching water in a short time, and then putting the ecological floating plate device into the leaching water to adsorb and enrich the Cd in a short time and then move the floating plate away, so that the purpose of restoring Cd pollution farmland decrement in situ is achieved.
Example 3
Example 2 was repeated with the only difference that: in the embodiment, the volume ratio of the sesame straw biochar to the attapulgite in the planting groove is controlled to be 1: 5.
As shown in fig. 8, as the proportion of the clay in the planting groove matrix increases, a large amount of clay is adsorbed on the surface of the biochar, which hinders the adsorption effect of the biochar in the mixed matrix on Cd, and thus the adsorption efficiency of the planting groove matrix on Cd becomes poor.
Example 4
Example 2 was repeated with the only difference that: in the embodiment, the volume ratio of the sesame straw biochar to the attapulgite in the planting groove is controlled to be 5: 1.
As shown in fig. 8, as the proportion of the biochar in the planting groove matrix increases, the gelation of the clay matrix is obviously weakened, so that the adsorption effect of the mixed matrix on Cd is enhanced firstly and then reduced, and the fixing capacity of the planting groove matrix on Cd is deteriorated.
The foregoing examples are set forth to illustrate the present invention more clearly and are not to be construed as limiting the scope of the invention, which is defined in the appended claims to which the invention pertains, as modified in all equivalent forms, by those skilled in the art after reading the present invention.
Claims (8)
1. An in-situ reduction remediation method for a cadmium-polluted farmland is characterized in that the farmland to be remediated is plowed, meanwhile, an eluent solution is introduced into the farmland, so that plowed soil and the eluent solution are uniformly mixed, then the farmland is placed statically for layering, an ecological floating plate is put into the farmland, and after 15-30 days, the ecological floating plate is taken out, so that in-situ removal of cadmium in the cadmium-polluted farmland is realized;
wherein the concentration of ferric chloride in the eluent solution is 3-7mM, and the concentration of citric acid is 2-4 mM; standing and layering, wherein the water covering height in the farmland is 8-12 cm; the ecological floating plate is provided with a planting groove, the wall of the planting groove is provided with a plurality of through holes, a mixed matrix consisting of biochar and clay is filled in the planting groove, and cadmium-enriched plants are planted on the mixed matrix; the throwing density of the ecological floating plate is 1-5/m2；
The volume ratio of the biochar to the clay in the mixed matrix is 1-2: 1.
2. The in-situ reduction remediation method according to claim 1, wherein the depth of plowing the soil in the field to be remediated during plowing is 15 to 30 cm.
3. The in-situ reduction repair method according to claim 1, wherein the delamination is achieved by standing for 12-48 h.
4. The in-situ reduction remediation method of claim 1, wherein the particle size of biochar and clay in the mixed matrix is both > 0.15 mm, the biochar is derived from one or more of rice straw, corn straw and sesame straw, and the clay comprises one or more of attapulgite, kaolin and montmorillonite.
5. The in-situ decrement repair method as defined in claim 1, wherein the inner wall of the planting groove is provided with a net with a mesh size of 0.05-0.08 mm; the size of the through holes is larger than the mesh size of the net, and the size of the through holes is 3-8 mm.
6. The in-situ decrement repair method as defined in claim 1, wherein the ecological floating plate is thrown at a density of 2-3/m2。
7. The in situ decrement repair method according to any one of claims 1 to 6, wherein the cadmium-rich plant is one or more of Potentilla tormentosa, Viola hirsuta, Sonchus oleracea, houttuynia cordata, Thalasia repens, red mulled leaf mustard, Sinapis albo-marginata, Artemisia selengensis and Solanum nigrum.
8. The in-situ reduction remediation method according to any one of claims 1 to 6, wherein the Cd content in the soil of the farmland to be remediated is from 0.6 to 5 mg/kg.
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| CN103357655A (en) * | 2013-07-15 | 2013-10-23 | 南京农业大学 | Composite chemical leaching method for remediation of heavy metal contaminated soil |
| CN104259192A (en) * | 2014-09-24 | 2015-01-07 | 长江水利委员会长江科学院 | Ecological water conservancy restoration system and method for heavy metal polluted farmland soil |
| CN107138511A (en) * | 2017-05-11 | 2017-09-08 | 南京大学 | A kind of method of renovation of heavy metal polluted soil with combined |
| CN110899317A (en) * | 2019-12-25 | 2020-03-24 | 中国电建集团中南勘测设计研究院有限公司 | Cadmium-polluted farmland soil remediation method based on magnetic biochar |
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| CN103357655A (en) * | 2013-07-15 | 2013-10-23 | 南京农业大学 | Composite chemical leaching method for remediation of heavy metal contaminated soil |
| CN104259192A (en) * | 2014-09-24 | 2015-01-07 | 长江水利委员会长江科学院 | Ecological water conservancy restoration system and method for heavy metal polluted farmland soil |
| CN107138511A (en) * | 2017-05-11 | 2017-09-08 | 南京大学 | A kind of method of renovation of heavy metal polluted soil with combined |
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