CN113319117A - Method for restoring heavy metal contaminated soil and organic-inorganic mixed conditioner adopted by method - Google Patents
Method for restoring heavy metal contaminated soil and organic-inorganic mixed conditioner adopted by method Download PDFInfo
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- CN113319117A CN113319117A CN202110634496.8A CN202110634496A CN113319117A CN 113319117 A CN113319117 A CN 113319117A CN 202110634496 A CN202110634496 A CN 202110634496A CN 113319117 A CN113319117 A CN 113319117A
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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
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- B09C1/10—Reclamation of contaminated soil microbiologically, biologically or by using enzymes
Abstract
The invention provides a method for repairing heavy metal contaminated soil and an organic-inorganic mixed conditioner adopted by the method, wherein the method for repairing the heavy metal contaminated soil comprises the following steps: before sowing, the organic soil conditioner and potassium sulfate are applied to the heavy metal polluted soil, and then sodium silicate and calcium magnesium phosphate fertilizer are applied. The invention combines an organic conditioner and an inorganic conditioner, and is applied by matching a plurality of conditioners to realize synergistic interaction so as to exert the maximum passivation effect. Firstly, the effective heavy metal in the soil is converted into a stable organic binding state and a stable sulfide binding state, and then the residual effective heavy metal is converted into a stable phosphate binding state, a stable silicate binding state and a metastable carbonate binding state and a stable hydroxide binding state, so that the long-term passivation of the effective heavy metal in the soil is facilitated, and the influence of cultivation and soil acid-base change on the effective heavy metal is reduced. The organic-inorganic mixed conditioner comprises 200-400 kg/mu of organic source soil conditioner, 20-40 kg/mu of potassium sulfate, 30-50 kg/mu of calcium magnesium phosphate fertilizer and 20-40 kg/mu of sodium silicate.
Description
Technical Field
The invention relates to the field of soil fertilizers, in particular to a method for repairing heavy metal contaminated soil and an organic-inorganic mixed conditioner adopted by the method.
Background
According to the investigation bulletin of the national soil pollution condition in 2014, the exceeding rate of the point position of the soil pollutant in the cultivated land is 19.4 percent, the pollution type is mainly inorganic type and secondly organic type, and the number of the exceeding point position of the inorganic pollutant accounts for 82.8 percent of the total exceeding point position. The inorganic pollutants are mainly cadmium, nickel, copper, arsenic, mercury and lead, wherein the standard exceeding rate of cadmium point position is the highest and reaches 7 percent, and the serious farmland production obstacle is caused by farmland pollution (particularly heavy metal cadmium). The excessive cadmium in the soil can cause serious obstacle to the production of cultivated land, on one hand, the excessive cadmium in the agricultural products can cause the heavy metal enrichment of plants, and the bone pain can be caused, and the body health can be seriously affected; on the other hand, the heavy metal in the soil exceeds the standard, which causes root poisoning, reduces the yield and reduces the benefit. The main reasons for the overproof heavy metal cadmium in cultivated land are as follows: the waste gas generated by metal smelting, coal-fired power generation, open-air garbage incineration and the like is settled, livestock and poultry manure with excessive heavy metal is greatly taken in, chemical fertilizer with excessive heavy metal (especially calcium superphosphate) is greatly taken in, irrigation water with excessive heavy metal and the like. In addition, a great amount of chemical fertilizers are used throughout the year, so that soil is acidified, heavy metals entering cultivated land are activated, and the production obstacle of the cultivated land is aggravated, so that the serious problem of grain safety is caused.
Based on the method, effective cadmium in acid soil is reduced for soil remediation, and the safety risk of agricultural products is reduced. In the prior art, minerals are mostly used as main raw materials to prepare a mineral source soil conditioner, and then the mineral source soil conditioner is applied to acid soil to reduce the effective cadmium in the soil. The mineral source soil conditioner can be applied singly and in large quantity, and can reduce the effective cadmium of the soil, but is easy to cause the following problems:
1. the mineral source soil conditioner is generally strong in alkalinity, is singly applied in a large amount, is easy to cause soil calcification and hardening, damages the physical and chemical properties of the soil, increases the volume weight of the soil, reduces the permeability of the soil, promotes the organic matters to be rapidly decomposed, reduces the crop yield and reduces the comprehensive benefit.
2. The mineral source soil conditioner contains high heavy metal, the total amount of soil cadmium is easily increased after long-term application of the mineral source soil conditioner in a large amount, and although the effective cadmium of the soil can be temporarily controlled during the application of the mineral source soil conditioner, once the soil conditioner is not used any more, the cadmium content of agricultural products is more than that before the mineral source soil conditioner is used.
3. The mineral source soil conditioner has high price and unit price, does not have the effects of improving soil organic matters and fertility, has no yield-increasing potential, and is not beneficial to large-area popularization and long-term use by farmers.
4. The mineral source soil conditioner mostly adopts the method of increasing the pH value to form cadmium hydroxide or cadmium carbonate precipitate so as to achieve the purpose of reducing the effective cadmium. However, the cadmium in the carbonate binding state and the cadmium in the hydroxide binding state are unstable and are easy to change along with organic acid secretion of a root system in soil cultivation and change of the pH value of the soil, the cadmium can form a free state again, and the risk that agricultural products exceed standards is increased.
5. The mineral source soil conditioner is singly used, the weight reducing mechanism is single, and the weight reducing effect is poor.
Therefore, it is necessary to develop a new soil conditioner or soil remediation method to solve the above problems.
Disclosure of Invention
The invention aims to provide a method for restoring soil polluted by heavy metal and an organic-inorganic mixed conditioner adopted by the method, wherein the restoring method is based on the stable condition of effective metal in different binding states, adopts the stepwise matched application of a plurality of conditioners, is beneficial to the long-term passivation of the effective heavy metal (especially the effective cadmium) in the soil, and reduces the influence of cultivation and soil acid-base change on the effective heavy metal in the soil.
In order to achieve the above object, the present invention provides, in a first aspect, a method for remediating heavy metal contaminated soil, comprising the steps of: before sowing, the organic soil conditioner and potassium sulfate are applied to the heavy metal contaminated soil, and then sodium silicate and calcium magnesium phosphate fertilizer are applied.
Different from the traditional soil remediation mode of singly using a mineral source soil conditioner or quicklime for conditioning, the soil conditioner disclosed by the invention combines an organic conditioner and an inorganic conditioner, the inorganic conditioner is matched by potassium sulfate, sodium silicate and a plurality of inorganic passivators of calcium-magnesium-phosphate fertilizer, and different conditioners are matched for application and synergistic interaction, so that the maximum passivation effect and the yield increasing effect of agricultural products are exerted. More importantly, the invention firstly applies the organic soil conditioner and the potassium sulfate to be fully combined with the effective heavy metal in the soil to respectively form an organic combined state and a sulfide combined state, the combined state does not change along with the change of the pH value of the soil and is relatively stable, and then sodium silicate and calcium magnesium phosphate fertilizer are used to further combine the residual effective heavy metal in the soil to form a relatively stable phosphate combined state and a silicate combined state, and a secondary stable carbonate combined state precipitate and a hydroxide combined state precipitate. The method converts the effective heavy metals in the soil into a stable organic binding state and a stable sulfide binding state, and then converts the residual effective heavy metals into a more stable phosphate binding state, a more stable silicate binding state and a less stable carbonate binding state and a more stable hydroxide binding state.
The invention provides an organic-inorganic mixed conditioner, which comprises 200-400 kg/mu of organic source soil conditioner, 20-40 kg/mu of potassium sulfate, 30-50 kg/mu of calcium magnesium phosphate fertilizer and 20-40 kg/mu of sodium silicate.
The organic-inorganic mixed conditioner disclosed by the invention is formed by combining an organic conditioner and an inorganic conditioner, the inorganic conditioner is formed by matching potassium sulfate, sodium silicate and various inorganic passivators of calcium magnesium phosphate fertilizer, and different conditioners are matched for application and synergistic interaction, so that the maximum passivation effect and the yield increasing effect of agricultural products are exerted. Specifically, the organic source soil conditioner contains a large amount of active functional groups which can form organic complexes with heavy metal ions and convert the organic complexes into stable organic binding states so as to reduce the effectiveness of the heavy metals; under the flooding environment, sulfate reducing bacteria in the soil perform anaerobic respiration to reduce potassium sulfate into hydrogen sulfide, the hydrogen sulfide is combined with free cadmium in the soil to form insoluble cadmium sulfide precipitate, the content of effective cadmium is reduced, meanwhile, the harm of the hydrogen sulfide to crops is avoided, and the added potassium element has positive promoting effects on crop yield increase and paddy field lodging resistance; the calcium magnesium phosphate fertilizer is an alkaline fertilizer, the pH value of soil can be increased, negative charges on the surface of soil particles can be increased by increasing the pH value, the adsorption capacity of the soil particles on heavy metal ions is further enhanced, the formation of hydroxide precipitates or carbonate combined precipitates in the soil by heavy metals is facilitated, phosphate radicals and free cadmium can generate precipitates, and the effectiveness of the cadmium is reduced; the sodium silicate contains silicate, forms insoluble cadmium silicate with cadmium, reduces the effectiveness of the cadmium, can supplement silicon element, strengthens cell walls and enhances the lodging resistance of crops.
Detailed Description
The method for restoring the heavy metal contaminated soil comprises the following steps: before sowing, the organic soil conditioner and potassium sulfate are applied to the heavy metal polluted soil, and then sodium silicate and calcium magnesium phosphate fertilizer are applied. The organic soil conditioner and the potassium sulfate are applied to the heavy metal contaminated soil before sowing, irrigation is carried out after rotary tillage, the water layer state of 3-5 cm is kept for 2-5 days, the water flooding environment is kept, anaerobic respiration of sulfate reducing bacteria is facilitated, the sulfate is reduced into hydrogen sulfide, and the hydrogen sulfide is combined with free cadmium in the soil to form insoluble cadmium sulfide precipitate. More specifically, the organic soil conditioner and potassium sulfate can be applied to the heavy metal contaminated soil 30 days before sowing, a cultivation layer of 15-20 cm is subjected to rotary tillage, then irrigation is carried out, and the water layer state of 3-5 cm is kept for 3 days, so that the effective heavy metal in the cultivation layer and the organic conditioner are fully combined to form a stable organic combination state. Applying sodium silicate and calcium magnesium phosphate fertilizer 10 days before sowing, and then carrying out rotary tillage on a 15-20 cm plough layer to further combine the effective heavy metals remained in the soil to form a phosphate combined state, a silicate combined state, a carbonate combined state and a hydroxide combined state precipitate. The pH value of the heavy metal contaminated soil is 4-7, the total cadmium content is 0.3-1 mg/kg, and the method is particularly suitable for cadmium remediation of acid soil.
The organic-inorganic mixed conditioner adopted for heavy metal contaminated soil remediation comprises 200-400 kg/mu of organic source soil conditioner, 20-40 kg/mu of potassium sulfate, 30-50 kg/mu of calcium magnesium phosphate fertilizer and 20-40 kg/mu of sodium silicate. Specifically, the content of the organic source soil conditioner can be, but is not limited to, 200 kg/mu, 225 kg/mu, 250 kg/mu, 275 kg/mu, 300 kg/mu, 325 kg/mu, 350 kg/mu, 375 kg/mu and 400 kg/mu, the content of potassium sulfate can be, but is not limited to, 20 kg/mu, 23 kg/mu, 25 kg/mu, 28 kg/mu, 30 kg/mu, 35 kg/mu, 38 kg/mu and 40 kg/mu, the content of calcium magnesium phosphate fertilizer can be, but is not limited to, 30 kg/mu, 33 kg/mu, 35 kg/mu, 38 kg/mu, 40 kg/mu, 45 kg/mu, 48 kg/mu and 50 kg/mu, the content of sodium silicate can be, but is not limited to, 20 kg/mu, 23 kg/mu, 25 kg/mu, 28 kg/mu, 40 kg/mu, 45 kg/mu, 25 kg/mu, 28 kg/mu, 30 kg/mu, or 30 kg/mu, 30 kg/mu, 35 kg/mu, 38 kg/mu and 40 kg/mu. The organic source soil conditioner is prepared by pretreating and screening kitchen waste serving as a raw material and fermenting the kitchen waste and microorganisms, the kitchen waste serving as the raw material can be changed into valuables, energy conservation and environmental protection are met, the kitchen waste is derived from food materials, the content of organic matters and humic acid in the kitchen waste is high, and the content of heavy metal is extremely low. Specifically, the kitchen waste is used as a raw material, is subjected to pretreatment, screening and other treatments, is mixed with microorganisms, and is fermented in a biochemical furnace at the temperature of 60-80 ℃ for 17-25 hours to form the organic source soil conditioner with the water content of less than 12%. The organic matter contains 75-85% of organic matter, 25-35% of humic acid and 20-30% of easily-oxidized organic matter, the water content is lower than 12%, the high-content organic matter and humic acid can quickly improve soil, improve soil organic matter, promote the formation of granular structures, solve the problem that the soil is easily hardened after quick acid adjustment, and improve the water and fertilizer retention capacity of the soil.
The method for remedying heavy metal contaminated soil and the organic-inorganic mixed conditioner used therein according to the present invention will be described in detail with reference to the following embodiments.
Example 1
The organic-inorganic mixed conditioner includes 375kg of organic source soil conditioner, 30kg of potassium sulfate, 40kg of calcium magnesium phosphate fertilizer and 30kg of sodium silicate. The organic source soil conditioner is prepared by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a biochemical furnace at 70 ℃ for 20 hours, wherein the organic source soil conditioner contains 80 wt.% of organic matters, the organic matters comprise 30 wt.% of humic acid and 25 wt.% of easily-oxidized organic matters, and the water content is lower than 12 wt.%.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying an organic soil conditioner and potassium sulfate 30 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, applying sodium silicate and calcium magnesium phosphate fertilizer 10 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
Example 2
The organic-inorganic mixed conditioner comprises 200kg of organic source soil conditioner, 30kg of potassium sulfate, 40kg of calcium magnesium phosphate fertilizer and 30kg of sodium silicate. The organic source soil conditioner is prepared by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a biochemical furnace at 70 ℃ for 20 hours, wherein the organic source soil conditioner contains 80 wt.% of organic matters, the organic matters comprise 30 wt.% of humic acid and 25 wt.% of easily-oxidized organic matters, and the water content is lower than 12 wt.%.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying an organic soil conditioner and potassium sulfate 30 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, applying sodium silicate and calcium magnesium phosphate fertilizer 10 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
Example 3
The organic-inorganic mixed conditioner comprises 300kg of organic source soil conditioner, 40kg of potassium sulfate, 45kg of calcium magnesium phosphate fertilizer and 40kg of sodium silicate. The organic source soil conditioner is prepared by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a biochemical furnace at 70 ℃ for 20 hours, wherein the organic source soil conditioner contains 80 wt.% of organic matters, the organic matters comprise 30 wt.% of humic acid and 25 wt.% of easily-oxidized organic matters, and the water content is lower than 12 wt.%.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying an organic soil conditioner and potassium sulfate 30 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, applying sodium silicate and calcium magnesium phosphate fertilizer 10 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
Example 4
The organic-inorganic mixed conditioner comprises 400kg of organic source soil conditioner, 20kg of potassium sulfate, 30kg of calcium magnesium phosphate fertilizer and 20kg of sodium silicate. The organic source soil conditioner is prepared by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a biochemical furnace at 70 ℃ for 20 hours, wherein the organic source soil conditioner contains 80 wt.% of organic matters, the organic matters comprise 30 wt.% of humic acid and 25 wt.% of easily-oxidized organic matters, and the water content is lower than 12 wt.%.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying an organic soil conditioner and potassium sulfate 30 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, applying sodium silicate and calcium magnesium phosphate fertilizer 10 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
Example 5
The organic-inorganic mixed conditioner includes 375kg of organic source soil conditioner, 30kg of potassium sulfate, 40kg of calcium magnesium phosphate fertilizer and 30kg of sodium silicate. The organic source soil conditioner is prepared by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture for 17 hours in a 75 ℃ biochemical furnace, wherein the organic source soil conditioner contains 75 wt.% of organic matters, the organic matters comprise 25 wt.% of humic acid and 20 wt.% of easily-oxidized organic matters, and the water content is lower than 12 wt.%.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying an organic soil conditioner and potassium sulfate 30 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, applying sodium silicate and calcium magnesium phosphate fertilizer 10 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
Comparative example 1
The organic-inorganic mixed conditioner includes 375kg of organic source soil conditioner, 30kg of potassium sulfate, 40kg of calcium magnesium phosphate fertilizer and 30kg of sodium silicate. The organic source soil conditioner is prepared by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a biochemical furnace at 70 ℃ for 20 hours, wherein the organic source soil conditioner contains 80 wt.% of organic matters, the organic matters comprise 30 wt.% of humic acid and 25 wt.% of easily-oxidized organic matters, and the water content is lower than 12 wt.%.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying sodium silicate and calcium magnesium phosphate fertilizer 30 days before sowing, then carrying out rotary tillage on a tillage layer of about 18cm, applying organic soil conditioner and potassium sulfate 10 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, and then carrying out crop planting after water is discharged.
Comparative example 2
The organic-inorganic mixed conditioner includes 375kg of organic source soil conditioner, 30kg of potassium sulfate, 40kg of calcium magnesium phosphate fertilizer and 30kg of sodium silicate. The organic source soil conditioner is prepared by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a biochemical furnace at 70 ℃ for 20 hours, wherein the organic source soil conditioner contains 80 wt.% of organic matters, the organic matters comprise 30 wt.% of humic acid and 25 wt.% of easily-oxidized organic matters, and the water content is lower than 12 wt.%.
Fertilizing soil of a certain crop planting base in 1 mu of Pengzhou city, applying an organic source soil conditioner, potassium sulfate, calcium magnesium phosphate fertilizer and sodium silicate 30 days before sowing, then carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, and then carrying out crop planting after water is discharged.
Comparative example 3
The organic-inorganic mixed conditioner comprises 375kg of organic source soil conditioner and 30kg of potassium sulfate, the organic source soil conditioner is obtained by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a 70 ℃ biochemical furnace for 20 hours, and the organic source soil conditioner comprises 80 wt% of organic matters, wherein the organic matters comprise 30 wt% of humic acid and 25 wt% of easily-oxidized organic matters, and the water content is lower than 12 wt%.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying an organic source soil conditioner and potassium sulfate 30 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, and then planting crops.
Comparative example 4
The inorganic conditioner comprises 40kg of calcium magnesium phosphate fertilizer and 30kg of sodium silicate.
Fertilizing soil of a certain crop planting base in 1 mu of Pengzhou city, applying a calcium magnesium phosphate fertilizer and sodium silicate 10 days before sowing, then carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
Comparative example 5
The soil conditioner is 375kg of organic source soil conditioner, the organic source soil conditioner is obtained by taking kitchen waste as a raw material, performing pretreatment, screening and other treatments, mixing the organic source soil conditioner with microorganisms, and fermenting the mixture in a biochemical furnace at 70 ℃ for 20 hours, and the organic source soil conditioner contains 80 wt% of organic matters, wherein the organic matters comprise 30 wt% of humic acid and 25 wt% of easily-oxidized organic matters, and the water content is lower than 12 wt%.
Fertilizing soil of a certain crop planting base in 1 mu of Pengzhou city, applying an organic source soil conditioner 30 days before sowing, then carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
Comparative example 6
The inorganic conditioner comprises 30kg of potassium sulfate, 40kg of calcium magnesium phosphate fertilizer and 30kg of sodium silicate.
Fertilizing soil of a certain crop planting base in Pengzhou city of 1 mu, applying potassium sulfate 30 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, then irrigating, keeping a water layer state of about 3cm for 3 days, applying sodium silicate and calcium magnesium phosphate fertilizer 10 days before sowing, carrying out rotary tillage on a tillage layer of about 18cm, and then carrying out crop planting.
The pH, cadmium content and organic matter content of the soils of examples 1 to 5 and comparative examples 1 to 6 before and after fertilization for 6 months were tested, and the soils at 3 different positions were each tested, and the test results are shown in Table 1.
As can be seen from the results in table 1, by using the remediation method of the present invention, namely, converting the available cadmium in the soil into a stable organic binding state and a sulfide binding state, and then converting the remaining available cadmium into a more stable phosphate binding state and silicate binding state, and a less stable carbonate binding state and hydroxide binding state, the available cadmium content in the soil can be effectively reduced for a long time, and the available cadmium content is reduced by more than 24.92% after 6 months of application. The organic-inorganic mixed conditioner is adopted to combine the organic conditioner with the inorganic conditioner, the inorganic conditioner is prepared by matching potassium sulfate, sodium silicate and various inorganic passivators of calcium magnesium phosphate fertilizer, and different conditioners are matched for application, so that the synergistic effect is realized, the cadmium effectiveness can be greatly reduced for a long time, the organic matter content in soil can be improved, the formation of a granular structure is promoted, the problem that the soil is easy to harden after rapid acid adjustment is solved, and the water and fertilizer retention capacity of the soil can be improved.
Comparative examples 1 and 2 although the same organic-inorganic hybrid conditioner as in example 1 was used, since the cadmium in the available state of comparative example 1 preferentially forms a large amount of precipitates in the phosphate-bound state, the silicate-bound state, the carbonate-bound state and the hydroxide-bound state, and the remaining cadmium in the available state reforms in the organic-bound state and the sulfide-bound state, and the precipitates in the phosphate-bound state, the silicate-bound state, the carbonate-bound state and the hydroxide-bound state are less stable than the precipitates in the organic-bound state and the sulfide-bound state, and particularly the precipitates in the carbonate-bound state and the hydroxide-bound state are susceptible to the organic acid secretion from the root system of soil cultivation and the change in the pH value of soil to reform the cadmium in the available state again, the effect of reducing the available cadmium in the soil is not good, and the effectiveness of cadmium cannot be reduced for a long period of time. Comparative example 2 in the fertilization, with one-time fertilization, cadmium in an effective state forms an organic binding state, a sulfide binding state, a phosphate binding state, a silicate binding state, a carbonate binding state and a hydroxide binding state simultaneously for precipitation, the 6 forms have a competitive relationship in the process, and calcium sulfide (slightly soluble) is formed by sulfide and calcium ions in calcium magnesium phosphate fertilizer, so that the content of the most stable organic binding state and sulfide binding state of cadmium in the comparative example 2 is less than that in the example 1. The conditioner adopted in the comparative examples 3 to 6 has single combination, single cadmium reduction mechanism and poor cadmium reduction effect.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention and not for limiting the protection scope of the present invention, and although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
TABLE 1 test results of pH, cadmium content and organic matter content of soil for examples 1 to 5 and comparative examples 1 to 6
Note: ck means before administration and T means 6 months after administration.
Claims (9)
1. The method for restoring the heavy metal contaminated soil is characterized by comprising the following steps: before sowing, the organic soil conditioner and potassium sulfate are applied to the heavy metal contaminated soil, and then sodium silicate and calcium magnesium phosphate fertilizer are applied.
2. The method for remediating heavy metal contaminated soil as claimed in claim 1, wherein the application of the organic soil conditioner and the potassium sulfate is carried out by applying the organic soil conditioner and the potassium sulfate to the heavy metal contaminated soil before sowing, irrigating water after rotary tillage, and keeping a water layer of 3-5 cm for 2-5 days.
3. The method for remediating heavy metal contaminated soil as claimed in claim 1, wherein the applying of the organic soil conditioner and the potassium sulfate is performed 30 days before sowing, and the organic soil conditioner and the potassium sulfate are applied to the heavy metal contaminated soil, and are subjected to rotary tillage for 15-20 cm of a plough layer, then are irrigated, and are kept in a 3-5 cm water layer state for 3 days.
4. The method for remediating heavy metal contaminated soil as claimed in claim 1, wherein the step of applying the sodium silicate and the calcium magnesium phosphate fertilizer comprises applying the sodium silicate and the calcium magnesium phosphate fertilizer 10 days before sowing and then carrying out rotary tillage on a 15-20 cm plough layer.
5. The method for remediating heavy metal contaminated soil as recited in claim 1, wherein the pH of the heavy metal contaminated soil is 4 to 7, and the total cadmium content is 0.3 to 1 mg/kg.
6. The organic-inorganic mixed conditioner used in the method for remediating heavy metal contaminated soil as recited in any one of claims 1 to 5, comprising 200 to 400 kg/mu of organic source soil conditioner, 20 to 40 kg/mu of potassium sulfate, 30 to 50 kg/mu of calcium magnesium phosphate fertilizer, and 20 to 40 kg/mu of sodium silicate.
7. The organic-inorganic mixed conditioner according to claim 6, wherein the organic source soil conditioner is obtained by pretreating and screening kitchen waste serving as a raw material and then fermenting the pretreated raw material with microorganisms.
8. The organic-inorganic hybrid conditioner according to claim 7, wherein the organic source soil conditioner and the microorganism are fermented in a biochemical furnace at 60 to 80 ℃ for 17 to 25 hours.
9. The organic-inorganic hybrid conditioner according to claim 7, wherein the organic source soil conditioner has a moisture content of less than 12 wt.%, and a composition comprising 75 to 85 wt.% of organic matter, wherein the organic matter comprises 25 to 35 wt.% of humic acid and 20 to 30 wt.% of easily oxidizable organic matter.
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