CN110899313A - Method for restoring mercury contaminated soil by combining chemical leaching and white clover - Google Patents
Method for restoring mercury contaminated soil by combining chemical leaching and white clover Download PDFInfo
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- CN110899313A CN110899313A CN201911310899.6A CN201911310899A CN110899313A CN 110899313 A CN110899313 A CN 110899313A CN 201911310899 A CN201911310899 A CN 201911310899A CN 110899313 A CN110899313 A CN 110899313A
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- soil
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- white clover
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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
- 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
Abstract
The method for restoring mercury-contaminated soil by combining chemical leaching and white clover can quickly remove mercury in soil, enhance the restoring effect of white clover on mercury in soil and play a role in quickly and efficiently restoring mercury-contaminated soil. Under the treatment of a proper amount of the chemical eluting agent, the removal rate of the soil mercury reaches 13.0-18.9%, the biomass of the overground part of the white clover plant is improved by 46.6-117.3%, the absorption amount of the soil mercury is improved by 29.8-280.8%, and the method for restoring the soil mercury by combining chemical eluting with the white clover has strong operability, is easy to popularize and has no secondary pollution.
Description
Technical Field
The invention belongs to a combined remediation technology of heavy metal contaminated soil, and particularly relates to a method for remediating mercury contaminated soil by combining chemical leaching and white clover.
Background
Mercury (Hg) is the only liquid heavy metal at room temperature, and is easily heated to form gaseous mercury, which is transported through the atmosphere to become a global pollutant. Mercury is extremely toxic, and can cause injuries such as slow movement, brain retardation, language disorder and the like of a human body and death of the human body due to long-term low-dose mercury exposure, so that the mercury is listed as a priority pollutant control by the international health organization. The artificial activities of garbage burning, coal burning, mercury ore smelting, sewage irrigation, sludge utilization, pesticide application, lamps and the like can generate mercury to pollute soil. After the cultivated land is polluted by mercury, the mercury is accumulated on the edible parts of the crops and enters the food chain, and the human health is directly threatened. Therefore, mercury contaminated soil remediation is imminent.
At present, the mercury polluted soil treatment and restoration technology mainly comprises a heat treatment technology, a soil-moving method, an in-situ passivation technology, a chemical leaching technology, a plant restoration technology and the like. The investment cost of the heat treatment technology is very high, the cost of the treatment equipment is expensive, and the heat treatment technology is not suitable for large-area use. The soil-access method is mostly applied to the remediation of the soil with small-area serious mercury pollution, is a pollution transfer method, and does not thoroughly eliminate the pollution. In situ passivation techniques merely slow the mobility of mercury in the soil, mercury is not substantially removed, and if conditions change, the immobilized mercury may be released again. The chemical leaching technology is simple to operate, low in cost and high in efficiency, and becomes the most widely applied technical means in remediation of the heavy metal contaminated soil. The technology for repairing heavy metal pollution by chemical leaching is established from 2001 to 2004 abroad and reaches the peak development period from 2010; the technology starts at home later, the technology is started in 2005, the technology is rapidly increased in 2010-2014, and the technology shows blowout type growth in 2015-2017. However, the key of the chemical leaching technology is to find a proper extracting agent to extract mercury in various forms without damaging the soil structure and generating secondary pollution. The phytoremediation technology utilizes plants to absorb and enrich mercury in soil so as to achieve the purpose of purifying the soil, and the method is green and environment-friendly and is more suitable for the requirement of environmental protection. However, mercury hyper-enrichment plants are not found internationally so far, and the general restoration plants have the problems of low mercury absorption efficiency and long restoration period, so that the requirement of quick and efficient soil restoration is difficult to meet. Therefore, each technology has the limitation, and the aim of quickly and efficiently restoring the mercury-polluted soil needs to be fulfilled by adopting the combined restoration of multiple technologies.
At present, the combined remediation technologies aiming at heavy metal contaminated soil treatment are few, for example, a patent (201410348538.1) discloses a chemical-biological combined remediation method for Cd contamination of soil, citric acid solution, β -cyclodextrin solution and rhamnolipid solution are compounded into leacheate, Cd hyperaccumulation plants of ryegrass and calendula officinalis are adopted for combined remediation, the remediation efficiency can reach more than 92%, and a patent (application number: 201610021402.9) discloses a method for remedying mercury contaminated soil by combining byproduct ammonium thiosulfate with calendula officinalis, wherein the method utilizes the calendula officinalis to enrich mercury in the soil, the ammonium thiosulfate can be used as a nitrogen fertilizer and a sulfur fertilizer to promote plant growth, and activates mercury in the mercury contaminated soil with the ammonium thiosulfate, so that mercury in the soil can be easily absorbed to the overground part by calendula officinalis root systems in a large amount.
Disclosure of Invention
The technical problem to be solved is as follows: the invention provides a method for restoring mercury-polluted soil by combining chemical leaching with white clover, which fully exerts the advantages of easy operation, no pollution and promotion of the growth of restoring plants of chemical leaching, aims to solve the problem of low restoring efficiency of mercury-polluted soil by a single restoring technology, and is a method for restoring mercury-polluted soil by combining chemical leaching with plants, and has high economical efficiency, strong operability and environmental friendliness.
The technical scheme is as follows: the method for restoring mercury contaminated soil by combining chemical leaching and white clover comprises the following steps:
step one, chemical leaching
A) Mechanically ploughing the mercury-polluted land, building a ridge, and covering a plastic film on the ridge;
B) uniformly spreading sodium thiosulfate solid on the surface of soil, wherein the application amount is 100-1000 kg/mu, mechanically ploughing to mix the sodium thiosulfate solid with the soil, draining water to submerge the soil, enabling the water depth to reach 8-12 cm, leaching the soil to be 10-20cm, and discharging leachate to a water collecting ditch after soaking for 8-12 h;
C) carrying out artificial ridging on the drained soil, airing for 1-2 days, after the water side on the ridge permeates into the water collecting channel, draining water for washing, and collecting the washed water in the water collecting channel;
E) adding 25 kg/mu to 250 kg/mu of precipitator sodium sulfide to precipitate mercury in leacheate in the water collecting ditch, and filtering to remove mercury precipitated by leaching;
step two, phytoremediation
F) After the soil to be repaired after chemical leaching is stabilized for 5-7 days in an open air environment, applying 500-1500 kg/mu of organic fertilizer as base fertilizer;
G) planting the white clover on the ridge surface of the washed soil to be repaired by adopting a drill planting mode, wherein the seeding quantity is 3.0-6.0 g/m2And harvesting the white clover 1 time every 3-4 months after sowing, and completing restoration.
Preferably, the ridge in the step A is 25cm high and 20cm wide.
Preferably, the water depth in the step B is 10cm, and the soil washing depth is 15 cm.
Preferably, in the step C, the width of the ridge surface is 1m, and the depth of the furrow is 5 cm.
Preferably, the sowing amount of white clover in the step G is 3.0G/m2。
The mercury content of the polluted soil is 25.25mg/kg, the pH value is 5.33, the dosage of the sodium thiosulfate is 1000 kg/mu, the repairing plant is white clover, and the seeding quantity of the white clover is 6.0g/m2。
Has the advantages that: under the treatment of proper dosage of the chemical eluting agent, the removal rate of the soil mercury reaches 13.0-18.9%, the biomass of the overground part of the white clover plant is improved by 46.6-117.3%, the absorption of the soil mercury is improved by 29.8-280.8%, and the method for restoring the soil mercury by combining chemical eluting with the white clover has strong operability, is easy to popularize and has no secondary pollution.
Detailed Description
Non-limiting examples of the invention are given below. The embodiment is implemented on the premise of the technical scheme of the invention, a detailed implementation mode and a detailed process are given, and conditions, methods and the like which are not noted are conventional treatment.
Example 1
The method comprises the steps of selecting certain farmland soil in a tin-free market as a repairing object, wherein the basic physicochemical property of the farmland soil is pH 5.78, the organic matter content is 37.9g/kg, the contents of total nitrogen, available phosphorus and available potassium are 1.79g/kg, 22.9mg/kg and 151.4mg/kg respectively, and the total Hg content is 1.85 mg/kg.
Aiming at the pollution condition of mercury in soil, the invention provides a chemical leaching-plant combined remediation method for mercury pollution of soil, which comprises the following specific remediation processes:
will be 300m2The field block is divided into test cells with the area of 5m multiplied by 10m, ridges with the height of 25cm and the width of 20cm are arranged between every two test cells, and plastic films are covered on the ridges to prevent side seepage; respectively applying 100 kg/mu and 200 kg/mu of sodium thiosulfate as leaching agents, uniformly spreading the sodium thiosulfate solids on the surface soil of a test cell, and mechanically ploughing to uniformly mix the agents with the soil; draining water to submerge the soil, keeping the water depth at about 10cm, and leaching the soilThe depth of the soil is about 15cm, and after soaking for 1 night, the leacheate is discharged into a water collecting ditch for anti-seepage treatment; carrying out artificial ridging on the soil after drainage, wherein the width of a ridge surface is about 1m, the depth of a ridge ditch is about 5cm, after airing for 1 day, after the water side on the ridge permeates into the ridge ditch, putting a small amount of water for washing, and collecting the washed water in a water collecting ditch; and adding 25 kg/mu of sodium sulfide to precipitate mercury in the leacheate.
After the washed soil to be repaired is stabilized for 5-7 days in the open air, 500 kg/mu of organic fertilizer is applied as base fertilizer, white clover is planted in a drilling mode, the variety of the white clover is the Rivendel of the technical center of Beijing Kelaowo grass industry, and the seeding amount is 3.0g/m2And harvesting the sown white clover for 1 time every 3-4 months.
From the processing results table 1, it can be seen that after the surface soil of a certain tin-free farmland is subjected to primary leaching, the treatment effect of the leaching agent of 100 kg/mu is obviously better than that of 200 kg/mu, after the leaching agent is subjected to leaching by using sodium thiosulfate of 100 kg/mu, the total mercury content in the soil is reduced from 1.85mg/kg to 1.50mg/kg, and the mercury removal rate reaches 18.9%; after being washed by 100 kg/mu of sodium thiosulfate, the annual biomass of the white clover planted in the soil is increased from 646.1 kg/mu to 1034.6 kg/mu by year (dry weight) compared with that of the control treatment (no washing treatment), and is increased by 60.9%; the mercury absorption per mu per year is improved from 190.8mg to 261mg, and the increase is 36.6%.
TABLE 1 chemical elution-Mercury removal from soil in certain farmland without tin by white clover
Example 2
The method comprises the following steps of selecting soil of a mercury-polluted farmland near a certain mining area in the copper-kernel city as a restoration object, wherein the soil has the following basic physicochemical properties: pH 5.33, Cation Exchange Capacity (CEC) 110.4mmol/kg, organic matter content 22.92g/kg, texture composition of sand 36.24%, powder 43.32%, and glutinous grain 20.44%. The total mercury content in 0-20cm surface soil is 25.25 mg/kg.
Aiming at the pollution condition of mercury in soil, the invention provides a chemical leaching-plant combined remediation method for mercury pollution of soil, which comprises the following specific remediation processes:
in an area of about 66m2Building ridges around the test cell, covering a plastic film, and preventing water from leaking to the side; uniformly spreading sodium thiosulfate solid on the surface soil of a cell according to the dosage of 1000 kg/mu, and turning the soil by a cultivator to fully mix the sodium thiosulfate solid into the soil; draining water into a test cell to enable the water depth to reach about 10cm and the soil leaching depth to be about 15 cm; soaking for 1 night, and draining water into a water collecting ditch for anti-seepage treatment; carrying out artificial ridging on the drained soil, wherein the width of a ridge surface is about 1m, the depth of a ridge ditch is about 5cm, airing for 1 day, putting a small amount of water for washing after the water side on the ridge permeates into the ditch, and collecting in a water collecting ditch; adding 250 kg/mu sodium sulfide to precipitate the dissolved mercury in the leacheate.
After the drenched soil to be repaired is stabilized in the open air for 5-7 days, 1000 kg/mu of organic fertilizer is applied as base fertilizer, white clover is planted on the ridge surface in a drilling mode, the white clover variety is the Riwendel, the Beijing Klowo grass technical center, and the seeding amount is 6.0g/m2And harvesting the sown white clover for 1 time every 3-4 months.
From the processing results shown in Table 2, after 3 times of rinsing, the mercury content in the surface soil of a certain mining area of the copper nut is reduced from 25.25mg/kg to 22.79, 22.11 and 21.49mg/kg, and the total removal rate after 3 times of rinsing is 14.9%. Annual biomass of white clover increased by 117.3% from 415.5 kg/acre per year (dry weight) to 902.8 tons/acre per year (dry weight) compared to the control treatment (no rinsing treatment); the mercury absorption amount per mu per year is increased from 403mg to 1534.8mg, and the increase is 280.8%.
TABLE 2 chemical elution-effect of white clover on removing mercury from soil in certain copper core area
Claims (6)
1. The method for restoring mercury contaminated soil by combining chemical leaching and white clover comprises the following steps:
step one, chemical leaching
A) Mechanically ploughing the mercury-polluted land, building a ridge, and covering a plastic film on the ridge;
B) uniformly spreading sodium thiosulfate solid on the surface of soil, wherein the application amount is 100 kg/mu-1000 kg/mu, mechanically ploughing to mix the sodium thiosulfate solid with the soil, draining water to submerge the soil, enabling the water depth to reach 8-12 cm, leaching the soil to be 10-20cm, and discharging leachate to a water collecting ditch after soaking for 8-12 h;
C) carrying out artificial ridging on the drained soil, airing for 1-2 days, after the water side on the ridge permeates into the water collecting channel, draining water for washing, and collecting the washed water in the water collecting channel;
E) adding 25 kg/mu to 250 kg/mu of precipitator sodium sulfide to precipitate mercury in leacheate in the water collecting ditch, and filtering to remove mercury precipitated by leaching;
step two, phytoremediation
F) After the soil to be repaired after chemical leaching is stabilized for 5-7 days in an open air environment, applying 500-1500 kg/mu of organic fertilizer as a base fertilizer;
G) planting the white clover on the ridge surface of the washed soil to be repaired by adopting a drill planting mode, wherein the seeding quantity is 3.0-6.0 g/m2And harvesting the white clover 1 time every 3-4 months after sowing, and completing restoration.
2. The method for remediating mercury contaminated soil using a combination of chemical leaching and white clover as defined in claim 1, wherein the ridge in step a is 25cm high and 20cm wide.
3. The method for remediating mercury contaminated soil using a combination of chemical leaching and white clover as defined in claim 1, wherein the water depth in step B is 10cm, and the leaching soil depth is 15 cm.
4. The method for remediating mercury contaminated soil by using the combination of chemical leaching and white clover as recited in claim 1, wherein in the step C, the width of the ridge surface is 1m, and the depth of the furrow is 5 cm.
5. The method for remediating mercury contaminated soil using a combination of chemical leaching and white clover as set forth in claim 1, wherein the seeding rate of white clover in step G is 3.0G/m2。
6. The method for remediating mercury contaminated soil using a combination of chemical leaching and white clover as claimed in claim 1, wherein the contaminated soil has a mercury content of 25.25mg/kg, a pH of 5.33, the sodium thiosulfate dosage is 1000 kg/acre, the remediating plant is white clover, and the seeding rate of white clover is 6.0g/m2。
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