Method for planting crops on heavy metal polluted land around sulfide ore collecting area

Abstract

The invention provides a method for planting crops on a heavy metal polluted land around a sulfide ore collecting area, which comprises the following steps of: leveling the heavy metal polluted land, sampling and detecting a soil profile, and determining the pollution depth; digging holes or furrowing according to crop planting requirements, wherein crops comprise arbors or shrubs; mixing biomass charcoal with sandy soil, and filling the holes or ditches with the mixture; digging planting holes or furrows at the positions of the holes or furrows at intervals; waste wood, spacing layers, fertilizers and mixed soil are laid at the bottoms of the planting holes or ditches; crops are planted, then landfill and fixation are conducted through mixed soil, and water-soluble fertilizer containing amino acid and / or mineral source humic acid are / is adopted for thorough watering; laying grass shielding cloth, and planting heavy metal hyperaccumulation plants among crop rows. According to the method, vegetation of the heavy metal polluted land around the sulfide ore collecting area can be recovered, green value-added benefits are generated, a large amount of earth-rock engineering and water and soil loss are avoided, the structure and fertility of soil and the diversity of microorganisms are improved, and the vegetation coverage rate is increased.

Description

Technical Field

[0001] The present invention relates to the field of heavy metal pollution control around mining areas or the technical field of green value-added utilization of economic crops cultivated on abandoned land, and in particular to a method for planting crops on heavy metal contaminated land around sulfide mining areas. Background Art

[0002] During the natural weathering and long-term (some mining areas have existed for hundreds of years) mining, mineral processing, transportation, etc., minerals in metal sulfide ore clusters release a large amount of heavy metal ions, such as lead, zinc, copper, cadmium, mercury, arsenic, etc., resulting in heavy metal content in the soil around the mining area far exceeding the background value. For example, in some large sulfide mining areas, the cadmium, lead, and zinc content in the soil may be several times or even dozens of times the local soil background value. Long-term mining activities have caused the continuous accumulation of heavy metals in the soil, the degree of pollution has continued to increase, and ecological pollution cases have emerged in an endless stream. For example, in recent years, the non-biologically necessary elements cadmium and lead produced in the process of mineral resource mining have serious hazards, resulting in poisonous rice and other events that constantly remind people that environmental protection is urgent. The government has taken action to divide the polluted land into safe control land, which has caused the abandonment of the land to a certain extent.

[0003] Heavy metal pollution can change the physical, chemical and biological properties of soil. For example, heavy metals can combine with organic matter, clay minerals, etc. in the soil, reducing soil fertility and air permeability; they can have a toxic effect on the microbial community in the soil, affecting the biological activity and ecological function of the soil, leading to a decline in soil quality, affecting the growth of vegetation and agricultural production; and they may threaten human health through the food chain. Crops grown in soil contaminated by heavy metals will absorb heavy metals in the soil. When people eat these crops, the heavy metals will enter the human body. Long-term accumulation may lead to various diseases, such as cancer, neurological diseases, etc.; they can affect the balance and stability of the soil ecosystem and destroy biodiversity.

[0004] At present, the remediation technologies for heavy metal pollution in soil at home and abroad include engineering measures (soil import, soil replacement, soil turning, deep plowing, topsoil removal, etc.), physical and chemical measures (heat treatment, vitrification, electric remediation, chemical solidification (passivation), soil leaching, etc.), ecological agricultural measures (agronomy, ecological factor regulation, etc.) and biological measures (plant remediation, animal remediation, microbial remediation). These technologies all have limitations. So far, there is no remediation technology that can be widely promoted, highly applicable, safe and economical. Physical and chemical passivation measures have a small remediation area, high cost, and limited passivation life. They cannot fundamentally eliminate heavy metals in the soil, and there is a risk of secondary pollution and leakage. Ecological agriculture and biological measures are both emerging, green, and pilot remediation technologies. Although the remediation time is long, their advantages such as in-situ remediation, low investment and maintenance costs, based on natural ecological processes, low probability of secondary pollution, and economic added value output make them the current research and practice hotspots.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for planting crops on heavy metal contaminated land around sulfide mining areas. The method can generate green value-added benefits for abandoned or controlled land contaminated by heavy metals around sulfide mining areas, avoid a large amount of earthwork and soil erosion, improve the soil structure, fertility and microbial diversity, and increase vegetation coverage.

[0007] The present invention provides a method for planting crops on heavy metal-contaminated land around a sulfide mining area, comprising the following steps:

[0008] S1. After leveling the land contaminated by heavy metals (such as Cd, Pb, As), take samples of the soil profile and determine the depth of contamination. The depth of contamination is generally less than 1 meter. Once the depth of contamination is too deep, it will affect the normal growth of crops.

[0009] Preferably, in step S1, during the sampling and detection of the soil profile, the number of profiles is set to maintain an average of 1 / 1000m 2 , the profile depth is between 1.4-2m, and the sampling test interval is between 0.1-0.2m.

[0010] Preferably, in step S1, the contamination depth is determined by the following method:

[0011] (I) The maximum depth at which the total content of various heavy metals detected is greater than the risk screening value (refer to the "Soil Environmental Quality Agricultural Land Soil Pollution Risk Control Standard (Trial)");

[0012] (II) The ratio of the secondary phase to the primary phase (BSP) is greater than 2;

[0013] The ratio of secondary phase to primary phase (BSP) = heavy metal content (or mass fraction) in secondary phase (Msec) / heavy metal content (or mass fraction) in primary phase (Mprim). Heavy metals can be divided into seven forms according to their different occurrence forms in the soil: water-soluble, ion-exchange, carbonate-bound, humic acid-bound, iron-manganese-bound, strongly organic-bound and residual. Metals in the residual state refer to metals existing in the crystal lattice of primary minerals, which are called primary geochemical phases. Metals in water-soluble, ion-exchange, carbonate-bound, humic acid-bound, iron-manganese-bound and strongly organic-bound states are metals released after weathering of primary minerals, and participate in various ecological, hydrological, biological, geological and geochemical processes such as adsorption, exchange, precipitation, chelation and absorption in the surface environment, collectively referred to as secondary geochemical phases.

[0014] Regardless of the type of heavy metal content or ratio that triggers a single trigger, it is considered to be the depth of pollution. Due to the mining of sulfide polymetallic mines and the smelting of surrounding chemical plants, the heavy metals in the pollution-controlled land around the mining area are all external inputs such as atmospheric deposition. Soil pollution has no inheritance from geological factors such as bedrock and structure. The depth of pollution is often 0.6-1m, and the depth of pollution is ultimately determined based on profile testing.

[0015] Preferably, the location of the polluted land is more than 5 km away from the pollution source. If the location is too close to the pollution source, the crops will be affected by atmospheric deposition, which is not conducive to crop growth.

[0016] S2. Digging holes or trenches according to crop planting requirements, wherein the crops include one or more trees or shrubs.

[0017] Since shrubs and trees have a higher metal tolerance than herbs, in the present invention, blueberries and loquats are planted after improvement, or inedible cotton is planted, and the crops grow well.

[0018] Preferably, in step S2, the blueberry plant spacing is 1-1.5m*row spacing is 2-2.5m, the loquat plant spacing is 3-3.5m*row spacing is 4-5m, and the cotton row spacing is 0.7-1m; holes are dug for blueberries and loquats at 0.5m*0.5m*((H-(0.1-0.2)))m, where H is the pollution depth determined by detection; and furrows are dug for cotton at 0.3m*0.4m (not less than 1 / 2 of the pollution depth).

[0019] S3. Mix the biochar with the sand and soil dug out of the hole or trench, and fill the hole or trench, preferably 0.1-0.3m above the ground relative to the ridge.

[0020] Preferably, in step S3, the biochar is formed by drying one or more of abandoned rapeseed, wheat, corn stalks, or coconut shells under natural conditions to reduce the moisture content to less than 10%, and carbonizing at a temperature of 300-800° C. in a relative lack of oxygen. Specifically, different carbonization temperatures can be selected according to the pH value suitable for crop growth to form biochar with different pH values.

[0021] Preferably, in step S3, the mass ratio of the biochar to the sand is (1-2):(5-10).

[0022] Optionally, if planting blueberries or loquats, dig drainage ditches every 3-4 rows. The width of the drainage ditch should be 0.3-0.5m and the depth should be 0.3-0.4m. This is not necessary for planting cotton.

[0023] S4. At regular intervals, dig planting holes or planting trenches at the locations of the holes or trenches.

[0024] Preferably, in step S4, the interval is 4-8 months, more preferably about 6 months from the planting or cultivation period.

[0025] Preferably, the planting hole or planting trench is dug to (0.3-0.4)*(0.3-0.4)*(h(original digging depth)-(0.1-0.2m))(blueberry, loquat), or the trench is dug to be 0.3m wide*0.4m deep(cotton).

[0026] S5. The bottom of the planting hole or planting ditch is covered with discarded wood, a spacer layer, fertilizer and mixed soil dug out of the planting hole or planting ditch in sequence; the fertilizer has a suitable pH value according to the crop requirements.

[0027] Preferably, in step S5, the spacer layer is made of fermented straw to ensure some space underneath.

[0028] Preferably, in step S5, the fertilizer and mixed soil layer is laid with a thickness of about 0.2 m.

[0029] Preferably, in step S5, the fertilizer is one or more of woody peat (organic matter content>70%), phosphate rock powder / potash feldspar calcined activated material, rapeseed cake and straw fermentation.

[0030] Preferably, the mass ratio of the woody peat, phosphate rock powder / potash feldspar calcined activated material, rapeseed cake, straw fermentation product and mixed soil is (20-40):(1-5):(5-10):(5-10):(50-70).

[0031] Preferably, the straw fermentation product is made of rapeseed, wheat, rice and other straws, which are crushed into pieces less than 5 cm in size, mixed with a certain amount of livestock manure, and wetted and piled for fermentation for 2-3 months, wherein the straw is turned over every 2-3 weeks and humidified.

[0032] Preferably, in step S5, the waste wood has a length of less than 10 cm, a diameter of less than 5 cm, and a paving layer thickness of 0.1-0.2 m.

[0033] S6. Plant the crops, fill and fix them with mixed soil, and irrigate them thoroughly with water-soluble fertilizers containing amino acids and / or mineral humic acid.

[0034] Preferably, in step S6, 2-year-old blueberries and loquats with soil balls are selected for planting, and then they are fixed with mixed soil for filling, and then irrigated with water-soluble fertilizer containing multiple amino acids diluted 800-1000 times or mineral humic acid; cotton is planted in the improved ditch, and the planting depth in the improved ditch should be maintained between 3-5 cm.

[0035] S7. Lay turf cloth and plant heavy metal hyperaccumulators between crop rows.

[0036] Preferably, black grass cloth is laid around the tree row, and Cd hyperaccumulator Sedum sutchuenensis is planted between the crop rows. The land with a width of 60 cm in the middle of the crop row is loosened, and the mixture of herbal peat and compound fertilizer is evenly spread in a ratio of 5:1, mixed evenly, and the mixing depth is about 10 cm. The film is covered, and Sedum sutchuenensis is planted in rows with a spacing of 15 cm. The Sedum sutchuenensis needs to be harmlessly disposed of in the later stage.

[0037] The present invention has at least the following beneficial effects:

[0038] (1) The present invention performs targeted improvement according to the depth of contaminated soil. The first layer of biochar is mixed to passivate heavy metals, reduce the occurrence forms of heavy metals in water-soluble, ionic and other active states, and the formation of biochar at different temperatures can appropriately maintain or increase the pH value, which can be more suitable for the growth environment of economic crops.

[0039] (2) The waste wood laid at the bottom of the planting hole or ditch of the present invention facilitates the roots to entangle and pile up, relatively solidifies the soil in the hole, fixes the root system, prevents soil erosion in sandy land, forms larger gullies, improves the material layer to provide fertility, increases soil organic matter, improves the soil microenvironment, and matches the pH value suitable for economic crops.

[0040] (3) The trees or shrubs selected by the present invention, such as blueberry, loquat, and cotton, are crops with high economic value, and are less prone to heavy metal accumulation in their fruit parts compared to rice and wheat. In the case of cotton, it is not edible and cannot enter the human food chain.

[0041] (4) The materials involved in the present invention are all readily available materials or waste materials in the market, which is conducive to the comprehensive utilization of waste resources; moreover, no complex chemical reactions are produced, mixing is simple, the mass ratio is relatively wide and easy to operate, no secondary pollution is produced to the soil, and the heavy metals in the soil can be passivated and are not easy to migrate.

[0042] (5) The present invention can generate green value-added benefits for abandoned or controlled land around mining areas, avoid a large amount of earthwork and soil erosion, improve the structure, fertility and microbial diversity of the soil, increase vegetation coverage, and have economic and tourism leisure value to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0044] Figure 1 This is the spatial distribution diagram of the heavy metal Cd, As, and Pb contents in three sections (types) of the test field for safe utilization of the present invention.

[0045] Figure 2 This is the BSP-profile depth diagram of heavy metals Cd, As, and Pb in three profiles (types) of the test field for safe utilization of the present invention.

[0046] Figure 3 It is a schematic cross-sectional view of the planting hole for economic crops (blueberry, loquat) of the present invention.

[0047] Figure 4 This is a demonstration test field for planting blueberries and loquats in the wild according to the present invention.

[0048] Figure 5 The blueberries of the present invention are grown two years later (fruiting).

[0049] Figure 6 The loquats of the present invention were planted two years later.

[0050] Explanation of the accompanying reference numerals: 1. Waste wood layer; 2. Spacer layer; 3. Fertilizer and mixed soil layer; 4. Transplanted seedlings with soil balls; 5. Blueberry; 6. Grass cover; 7. Sedum sedum; 8. Drainage ditch; 9. Loquat. DETAILED DESCRIPTION

[0051] It should be noted that the following detailed descriptions are illustrative and are intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present application belongs.

[0052] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0053] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0054] Example 1

[0055] This embodiment takes the planting of blueberries as an example to provide a method for planting crops on heavy metal contaminated land around sulfide mining areas, including the following steps:

[0056] (1) The test field for safe land use is 2 mu of polluted farmland around a sulfide polymetallic mining area in Hengyang City, Hunan Province. According to atmospheric deposition data before and after 2022, the atmospheric deposition sediments of Cd, As, and Pb in areas 5 km away from the chemical plant dropped sharply. Therefore, the test field was selected 5 km away from the chemical plant. If it was selected too close, the heavy metal content in the fruits of cash crops would be easily affected by atmospheric deposition.

[0057] Three 2m deep soil profiles HNPM01, HNPM02 and HNPM03 were collected, and a soil sample was taken every 20cm, a total of 30 soil samples were taken, and the soil heavy metal forms were analyzed. The results showed that the soil pH in the test area was 4.90-6.61, and the pH gradually increased with the increase in depth. Among the heavy metals in the soil, only Cd and As within 100cm exceeded the standard. The Cd form was mainly in the water-soluble and ion-exchange state, which was easy to migrate. The As form was mainly in the residual state and humic acid-bound state, which was difficult to migrate and be used by organisms, and was relatively safe for the environment. For details, see Figure 1 . According to the comparison of BSP values, ( Figure 2 ): Cd is severely polluted, Pb is severely polluted in soils above 60-80cm, the rest are lightly to moderately polluted, and As is non-polluted. It can be seen that heavy metals are all enriched in the soil surface and are not inherited. It can be determined that the depth of heavy metal pollution is within 80cm.

[0058] (2) The holes should be dug according to the blueberry plant spacing of 1.5m and row spacing of 2m, with the specifications of 0.5m*0.5m*0.6m.

[0059] (3) In October and November of the same year, the mixture of discarded rape and corn stalks was dried under natural conditions to reduce its moisture content to less than 10%, and carbonized at 300°C-400°C in a relatively hypoxic environment to form biochar (biochar is slightly acidic to ensure that the pH value of the mixed soil does not increase). The biochar was mixed with the contaminated sandy soil dug out of the hole at a mass ratio of 1:5, and then filled into the hole and raised 0.2m above the ground relative to the ridge. Drainage ditches 8 were dug every 3 rows, with a width of 0.3m and a depth of 0.4m.

[0060] (4) In mid-April of the following year, dig a new planting hole of 0.4m*0.4m*0.5m at the original location.

[0061] (5) The bottom of the hole is covered with waste wood with a length of less than 10 cm and a diameter of less than 5 cm. The waste wood layer 1 is approximately 0.2 m thick. Some straw fermentation material is sprinkled on top to ensure some space underneath. Then, woody peat (organic content > 70%): phosphate rock powder: rapeseed cake: straw fermentation material (crushed rapeseed, rice and other straw into pieces less than 5 cm, mixed with a certain amount of livestock manure, wetted and piled for fermentation for 2-3 months, turned over every 2-3 weeks and humidified): mixed soil with a mass ratio of 40:5:6:6:60 to form a fertilizer and mixed soil layer 3 with an approximate thickness of about 0.2 m (the cross section of the planting hole is as follows: Figure 3 shown).

[0062] (6) Select 2-year-old blueberry transplant seedlings with soil balls, interplant three varieties of blueberries, Lexi, O'Neill and Mist, and then use the original mixed soil mixed with a small amount of sulfur powder to fill and fix, and then irrigate with water-soluble fertilizer containing multiple amino acids diluted 800 times. The survival rate of blueberries is 100%, and they grow well. In the second year, they have already borne fruit, with an average of about 300g of fruit per plant, and the heavy metal content of the fruit does not exceed the standard. In the future, the heavy metal content of blueberries needs to be monitored every year. (The blueberries in the experimental field are only used for experimental testing and are not put on the market).

[0063] (7) Black turf cloth 6 is laid around the tree rows, and hyperaccumulative plants such as Sedum serrata 7, ramie, etc. can be appropriately planted between the tree rows.

[0064] Comparison Example

[0065] This control example is basically the same as Example 1, except that steps (2) and (3) are not performed, and the woody peat in step (5) is removed, that is, the material that passivates heavy metals is removed.

[0066] The blueberries of Example 1 and the control example were grown for two years, and the fruits of the second year were tested. The testing company was: Biomérieux Testing Technology (Guangzhou) Co., Ltd.

[0067] In July this year, three different varieties of fresh blueberries of Example 1 were picked, 2 samples of each variety, a total of 6 samples, and 2 control samples of Control Example 1 were picked. The test results show that the heavy metal content of the 6 samples of Example 1 is As: 0.0269-0.0423 mg / kg; Cd: 0.011-0.0155 mg / kg; Pb: 0.0939-0.192 mg / kg, which are all lower than the limit values ​​of pollutants in fruits in the national food safety standards (As: 0.05 mg / kg; Cd: 0.05 mg / kg; Pb: 0.2 mg / kg). The heavy metal contents of the two control samples of the control example are As: 0.0456~0.125mg / kg; Cd: 0.014~0.0157mg / kg; Pb: 0.208~0.302mg / kg; Cd does not exceed the standard, As and Pb are also very rarely exceeded, and others such as Cu, Hg, and Zn do not exceed the standard, and most are below the detection limit. It can be seen that the blueberry fruit itself has a low accumulation capacity for heavy metals, especially cadmium. If the soil is properly passivated, the heavy metal content of blueberries is lower than the limit value in the relevant national food safety standards. In addition, there is no difference between the detection values ​​of vitamins, anthocyanins, fructose, glucose and other nutrients in blueberries and those on the market.

[0068] Blueberries are sweet and sour, rich in nutrients, and can prevent brain nerve aging, protect eyesight, strengthen the heart, fight cancer, soften blood vessels, and enhance human immune function. As a small berry tree species with high economic value and broad development prospects, it ranks first among the 15 global health foods listed by British authoritative nutritionists, and was listed as one of the five major health foods for humans by the Food and Agriculture Organization of the United Nations in 2017. It is known as the "king of berries". Economic benefit calculation: After two years of experiments, the cost of blueberry planting is about 30,000 to 40,000 yuan per mu. In the future, the annual agronomic management, pesticides and fertilizers, and some additions of improved repair materials will cost about 20,000 yuan per mu. Blueberries are calculated based on 250 plants per mu. In the peak fruiting period, one plant produces 5 kilograms of fruit, 1,250 kilograms per mu. The wholesale price of blueberries is 30 yuan per kilogram, and the income per mu is 37,500 yuan, including a cost of 20,000 yuan per mu and a net income of 17,500 yuan per mu. The calculated income is considerable. If blueberries meet food safety standards after long-term testing and evaluation, they can be promoted on a large scale.

[0069] Example 2

[0070] This embodiment takes loquat planting as an example to provide a method for planting crops on heavy metal contaminated land around sulfide mining areas, comprising the following steps:

[0071] (1) The steps are the same as those in Example 1 and will not be repeated here.

[0072] (2) Dig holes according to the loquat plant spacing of 3m and row spacing of 4m, with a specification of 0.5m*0.5m*0.6m.

[0073] (3) In October and November of the same year, a mixture of discarded rape and corn stalks was dried under natural conditions to reduce its moisture content to less than 10%. In a relatively oxygen-deficient environment, the mixture was carbonized at 700°C-800°C to form biochar (biochar is alkaline). The biochar was mixed with the contaminated sand from the holes at a mass ratio of 1:4, and then filled into the holes and raised 0.2m above the ground relative to the ridges. Drainage ditches were dug every two rows, with a width of 0.3m and a depth of 0.4m.

[0074] (4) In mid-April of the following year, dig a new planting hole of 0.4m*0.4m*0.5m at the original location.

[0075] (5) The bottom of the hole is covered with waste wood with a length of less than 10 cm and a diameter of less than 5 cm. The waste wood layer 1 is approximately 0.2 m thick. Some straw fermentation material is sprinkled on top to ensure some space below. Then, woody peat (organic content > 70%): potassium feldspar calcined activated material (alkaline, which can appropriately increase the pH by about 0.5-1): rapeseed cake: straw fermentation (crushed rape, rice and other straw into less than 5 cm, mixed with a certain amount of livestock manure, wetted and piled for fermentation for 2-3 months, turned over every 2-3 weeks, and humidified): mixed soil with a mass ratio of 30:5:6:10:70 to form a fertilizer and mixed soil layer 3 with an approximate thickness of about 0.2 m.

[0076] (6) Select 2-year-old loquat seedlings with soil balls and transplant them 4, then fill them with the original mixed soil for fixation, and then water them thoroughly with water-soluble fertilizer containing multiple amino acids diluted 800 times. The survival rate of loquats was 100%, and they grew well. No heavy metals were found to hinder their healthy growth, and no fruit was produced during the test year.

[0077] (7) Black tarpaulin was laid around the tree rows, and Cd hyperaccumulator Sedum sutchuenensis was planted between the tree rows. The 60 cm wide land between the tree rows was loosened, and a mixture of herbaceous peat and compound fertilizer was evenly spread in the mixture at a mass ratio of 5:1. The mixture was mixed to a depth of about 10 cm, and then covered with film. Sedum sutchuenensis was planted in rows with a spacing of 15 cm. Sedum sutchuenensis needs to be disposed of harmlessly in the later stage.

[0078] The actual scene of the test field is as follows Figure 4 As shown, Figure 5 This is blueberry 5 (fruiting) after two years of planting. Figure 6 This is loquat 9 two years after planting.

[0079] In summary, the present invention plants economic crops such as blueberries and loquats on heavy metal-contaminated land around sulfide mining areas. After long-term monitoring, the heavy metal content in blueberries and loquats does not exceed the standard, which meets the food safety standards. By interplanting some hyperaccumulative plants, this utilization method can generate green value-added benefits for abandoned or controlled land around the mining area. It avoids a large amount of earthwork and soil erosion, improves the structure, fertility and microbial diversity of the soil, increases the vegetation coverage rate, and has economic and tourism leisure value to a certain extent.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for planting crops on heavy metal-contaminated land around sulfide mining areas, characterized in that: The steps include: S1. After leveling the heavy metal contaminated land, conduct soil profile sampling and testing to determine the contamination depth, which is less than 1 meter; S2. digging holes or trenches according to crop planting requirements, wherein the crops include one or more trees or shrubs; S3, mixing the biochar with the sand and soil dug out of the hole or trench, and filling the hole or trench; S4. After a certain period of time, dig a planting hole or planting trench at the location of the hole or trench; S5. Spread waste wood, a spacer layer, fertilizer, and mixed soil from the planting hole or planting ditch in sequence at the bottom of the planting hole or planting ditch; the fertilizer has a suitable pH value according to the crop requirements; S6, planting crops, and then filling and fixing them with mixed soil, and watering them thoroughly with water-soluble fertilizer containing amino acids and / or mineral humic acid; S7. Lay turf cloth and plant heavy metal hyperaccumulators between crop rows.

2. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S1, during the sampling and detection of the soil profile, the average number of profiles is set to maintain 1 / 1000m 2 , the profile depth is between 1.4-2m, and the sampling test interval is between 0.1-0.2m.

3. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S1, the contamination depth is determined by the following method: (I) The maximum depth at which the total content of each type of heavy metal detected is greater than the risk screening value; (II) The ratio of the secondary phase to the primary phase is greater than 2; The pollution depth is determined when a single trigger is reached, either the heavy metal content or the difference between the secondary phase and the primary phase.

4. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: The crops include: one or more of blueberry, loquat or cotton.

5. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S3, the biochar is made of one or more of discarded rape, wheat, corn stalks or coconut shells, and is dried under natural conditions to reduce its moisture content to below 10%, and is carbonized at 300-800°C in a relatively oxygen-deficient environment.

6. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S3, the mass ratio of the biochar to the sand is (1-2):(5-10).

7. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S4, the interval is 4-8 months.

8. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S5, the spacer layer is made of fermented straw; the fertilizer is made of one or more of woody peat, phosphate rock powder / potash feldspar calcined activated material, rapeseed cake and fermented straw.

9. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S5, the waste wood has a length of less than 10 cm, a diameter of less than 5 cm, and a paving layer thickness of 0.1-0.2 m.

10. The method for planting crops on heavy metal contaminated land around sulfide ore concentration areas according to claim 1, characterized in that: In step S7, the heavy metal hyperaccumulator plants include: one or more of Sedum serrata or Ramie.

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