A method for crop planting on heavy metal-polluted land around a sulfide ore concentration area

Abstract

The present invention provides a method for planting crops on heavy metal-polluted land around a sulfide ore concentration area, which comprises the following steps: after leveling the heavy metal-polluted land, soil profile sampling and detection are carried out to determine the pollution depth; digging holes or trenches according to the crop planting requirements, and the crops include arbors or shrubs; mixing biochar with sandy soil and filling it into the holes or trenches; after a period of time, digging open the planting holes or trenches at the positions of the holes or trenches; laying waste wood, an intermediate layer, fertilizer and mixed soil at the bottom of the planting holes or trenches; planting crops, and then filling and fixing them with mixed soil, and thoroughly watering them with an amino acid water-soluble fertilizer and / or a mineral source humic acid; laying a weed-proof cloth, and planting heavy metal hyperaccumulator plants between the crop rows. The present invention can restore the vegetation of the heavy metal-polluted land around the sulfide ore concentration area, generate green value-added benefits, avoid a large amount of earthwork and soil erosion, improve the soil structure, fertility and microbial diversity, and increase the vegetation coverage rate.

Description

Technical Field

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

[0002] During the natural weathering of minerals in sulfide ore concentration areas and the long-term (some mining areas have existed for hundreds of years) processes of mining, ore dressing, transportation, etc., a large amount of heavy metal ions, such as lead, zinc, copper, cadmium, mercury, arsenic, etc., are released, resulting in the heavy metal content in the soil around the mining areas far exceeding the background value. For example, in some large sulfide mining areas, the cadmium, lead, and zinc contents in the soil may be several times or even dozens of times the local soil background value.

[0003] Heavy metal pollution will change the physical, chemical, and biological properties of the soil. For example, heavy metals will combine with organic matter, clay minerals, etc. in the soil, reducing the soil fertility and air permeability; have a toxic effect on the microbial community in the soil, affecting the biological activity and ecological function of the soil, resulting in a decline in soil quality, affecting the growth of vegetation and agricultural production; and may pose a threat to human health through the food chain.

[0004] At present, the remediation technologies for soil heavy metal pollution at home and abroad include engineering measures (such as soil replacement, soil turning, deep plowing, removing topsoil, etc.), physical and chemical measures (such as heat treatment, vitrification, electrokinetic remediation, chemical solidification (passivation), soil washing, etc.), ecological agriculture measures (such as agronomy, ecological factor regulation, etc.) and biological measures (such as phytoremediation, animal remediation, microbial remediation). These technologies all have limitations. So far, there has not been a remediation technology that can be widely promoted, has high applicability, and good safety and economy. Physical and chemical passivation measures have a small remediation area, high cost, limited passivation years, cannot fundamentally eliminate soil heavy metals, and have risks of secondary pollution and leakage. Ecological agriculture and biological measures are all emerging, green, and pilot-type remediation technologies. Although the remediation time is long, their advantages of in-situ remediation, low investment and maintenance costs, based on natural ecological processes, low probability of secondary pollution, and the ability to generate economic added value make them the current research and practice hotspots.

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

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

[0007] The present invention provides a method for growing crops on heavy metal - polluted land around a sulfide ore concentration area, comprising the following steps:

[0008] S1. After leveling the heavy metal (such as Cd, Pb, As) - polluted land, sampling and detecting the soil profile to determine the pollution depth. The pollution depth is generally less than 1 m. Once the pollution depth is too deep, it will affect the normal growth of crops.

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

[0010] Preferably, in step S1, the following method is used to determine the pollution depth:

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

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

[0013] The ratio of secondary phase to primary phase (BSP)= the content (or mass fraction) of heavy metals in the secondary phase (Msec) / the content (or mass fraction) of heavy metals in the primary phase (Mprim). Heavy metals can be divided into 7 forms according to their different occurrence forms in the soil: water - soluble state, ion - exchange state, carbonate - bound state, humic - acid - bound state, iron - manganese - bound state, strong organic - bound state, and residual state. The metals in the residual state refer to the metals existing in the lattice of primary minerals, called the primary geochemical phase. While the metals in the water - soluble state, ion - exchange state, carbonate - bound state, humic - acid - bound state, iron - manganese - bound state, and strong organic - bound state are the metals released after the 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 the secondary geochemical phase.

[0014] If any single trigger of the heavy metal content or ratio is met, it is determined as the pollution depth. Due to the mining of sulfide polymetallic mines and the smelting in surrounding chemical plants, the heavy metals in the polluted land under control around the mining area are all exogenous inputs such as atmospheric deposition. The soil pollution has no inheritance of geological factors such as bedrock and tectonics, and the pollution depth is often between 0.6 - 1 m. Finally, the pollution depth is determined according to the profile detection.

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

[0016] S2. Dig holes or trenches according to the planting requirements of crops, where the crops include one or more of trees or shrubs.

[0017] Since the metal tolerance of shrubs and trees is greater than that of herbs, in this invention, blueberries and loquats are selected for planting after improvement, or non-edible cotton is planted, and the growth of the crops is good.

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

[0019] S3. Mix the biochar with the sandy soil dug out from the holes or trenches, and fill the holes or trenches, preferably 0.1 - 0.3 m higher than the ridges.

[0020] Preferably, in step S3, the biochar is formed by drying one or more of the waste rape, wheat, corn straws, or coconut shells under natural conditions to reduce the water content to less than 10%, and then carbonizing at a relatively anoxic condition with a temperature of 300 - 800 °C. Specifically, different carbonization temperatures can be selected according to the suitable pH value for the growth of the crops to form biochars with different pH values.

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

[0022] Optionally, if planting blueberries or loquats, about 3 - 4 rows of drainage ditches need to be dug, with the width of the drainage ditches being 0.3 - 0.5 m and the depth being 0.3 - 0.4 m. For cotton planting, it is not required.

[0023] S4. After a certain period of time, dig open the planting holes or planting trenches at the positions of the holes or trenches.

[0024] Preferably, in step S4, the certain period of time is 4 - 8 months, and more preferably about 6 months after planting or sowing.

[0025] Preferably, the planting holes or planting trenches are dug with a size of (0.3 - 0.4) * (0.3 - 0.4) * (h (original digging depth) - (0.1 - 0.2 m)) (for blueberries and loquats), or the trench is dug with a width of 0.3 m and a depth of 0.4 m (for cotton).

[0026] S5. Lay waste wood, spacer layer, fertilizer, and the mixed soil dug out from the opened planting holes or planting trenches at the bottom of the planting holes or planting trenches in sequence; the fertilizer is selected according to the suitable pH value for the crops.

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

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

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

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

[0031] Preferably, the straw fermented product is obtained by crushing straws such as rape, wheat, and rice to less than 5 cm, mixing with a certain amount of livestock manure, wetting, piling up, and fermenting for 2 - 3 months, turning it over every 2 - 3 weeks and humidifying it.

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

[0033] S6. Plant crops, then bury and fix them with mixed soil, and pour thoroughly with amino acid water-soluble fertilizer and / or mineral source humic acid.

[0034] Preferably, in step S6, select blueberries and loquats with a 2-year-old tree age and soil balls for planting. After burying and fixing them with mixed soil, pour thoroughly with amino acid water-soluble fertilizer or mineral source humic acid diluted 800 - 1000 times; for cotton, use the planting method, and the planting depth in the improved ditch should be kept between 3 - 5 cm.

[0035] S7. Lay a weed mat and plant heavy metal hyperaccumulator plants between the crop rows.

[0036] Preferably, lay a black weed mat around the tree rows, and plant Sedum plumbizincicola, a Cd hyperaccumulator plant, between the crop rows. Loosen the soil in the middle 60 cm wide land between the crop rows, evenly spread and mix it according to the mass ratio of herbaceous peat to compound fertilizer of 5:1, and the mixing depth is about 10 cm. Cover with a film, plant Sedum plumbizincicola at a spacing of 15 cm in rows, and the Sedum plumbizincicola needs to be harmlessly treated later.

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

[0038] (1) The present invention conducts directional improvement according to the depth of contaminated soil. In the first pass, biochar is mixed to passivate heavy metals, reducing the occurrence forms of mobile heavy metals such as water-soluble and ionic states. Biochar formed at different temperatures can appropriately maintain or slightly increase the pH value, making it more suitable for the growth environment of cash crops.

[0039] (2) The waste wood laid at the bottom of the planting holes or trenches in the present invention facilitates the roots to wind into piles, relatively solidifying the improved soil in the holes, fixing the roots, preventing soil erosion in sandy land, forming larger gullies, and the improved material layer provides fertility, improves soil organic matter, improves the soil microenvironment, and matches the appropriate acidity and alkalinity for cash crops.

[0040] (3) The selected arbors or shrubs such as blueberries, loquats, and cotton in the present invention are crops with high economic value. Compared with rice and wheat, heavy metal enrichment is not likely to occur in the fruit part; if it is cotton, it is not edible and cannot enter the human food chain.

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

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

[0043] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

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

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

[0046] Figure 3 It is the schematic diagram of the planting hole profile of the cash crops (blueberries, loquats) of the present invention.

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

[0048] Figure 5 This is the blueberry (bearing fruit) after two years of planting in the present invention.

[0049] Figure 6 This is the loquat after two years of planting in the present invention.

[0050] Explanation of reference numerals in the drawings: 1. Abandoned wood layer; 2. Spacer layer; 3. Fertilizer and mixed soil layer; 4. Transplanting seedlings with soil balls; 5. Blueberry; 6. Weed mat; 7. Sedum plumbizincicola; 8. Drainage ditch; 9. Loquat. Detailed implementation manners

[0051] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0052] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary implementation manners 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, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0053] Next, the technical solutions of the present invention will be described clearly and completely in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0054] Embodiment 1

[0055] Taking the planting of blueberries as an example, this embodiment provides a method for planting crops on heavy metal polluted land around sulfide ore concentration areas, including the following steps:

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

[0057] Collect three soil profiles HNPM01, HNPM02, and HNPM03 with a depth of 2m. Take a soil sample every 20cm, for a total of 30 soil samples, and analyze the forms of soil heavy metals. The results show that the soil pH in this test area is 4.90 - 6.61, and the pH gradually increases with the increase in depth. Only Cd and As within 100cm of the soil exceed the standard. The form of Cd is mainly water-soluble and ion-exchangeable, and it is easy to migrate. The form of As is mainly residual and humic acid-bound, which is relatively difficult to migrate and be utilized by organisms, and is 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 the soil above 60 - 80cm, and the rest is mildly to moderately polluted. As is non-polluted. It can be seen that heavy metals are all concentrated in the soil surface layer and there is no inheritance. It can be determined that the depth of heavy metal pollution is within 80cm.

[0058] (2) Dig holes according to the plant spacing of blueberries of 1.5m * row spacing of 2m, with the specification of 0.5m * 0.5m * 0.6m.

[0059] (3) In October - November of the current year, use the mixture of waste rapeseed and corn straw to dry in natural conditions to reduce the water content to less than 10%. Carbonize it at a relatively low oxygen level and a temperature of 300℃ - 400℃ to form biochar (biochar is a bit more acidic to ensure that the pH value of the mixed soil does not increase). After mixing the prepared biochar with the polluted sandy soil dug out of the holes at a mass ratio of 1:5, fill the holes and form ridges 0.2m higher than the ground. Dig drainage ditches 8 every 3 rows, with the drainage ditch width of 0.3m and the depth of 0.4m.

[0060] (4) In mid-April of the following year, re-dig planting holes with a specification of 0.4m * 0.4m * 0.5m at the original hole positions.

[0061] (5) Lay waste wood with a length < 10cm and a diameter of less than 5cm at the bottom of the hole. The waste wood layer 1 has a thickness of approximately 0.2m. Sprinkle some straw fermentation products as the spacer layer 2 on it to ensure some gaps below. Then lay woody peat (organic matter content > 70%): rock phosphate: rapeseed cake: straw fermentation products (crush rapeseed, rice and other straws to less than 5cm, mix with a certain amount of livestock manure, humidify and stack for fermentation for 2 - 3 months, and turn it over every 2 - 3 weeks and humidify): the mixture of mixed soil in a mass ratio of 40:5:6:6:60 to form a fertilizer and mixed soil layer 3, with a thickness of approximately 0.2m (the planting hole profile is as Figure 3 shown).

[0062] (6) Select 4 blueberry transplant seedlings with a 2-year-old tree age and a ball of soil. Interplant blueberries of three varieties, namely, Lexi, O'Neal, and Mist. Then mix a small amount of sulfur powder with the original mixed soil, fill and fix it, and thoroughly water it with a water-soluble fertilizer containing multiple amino acids diluted 800 times. The survival rate of blueberries is 100%, the growth is good, and fruits have been borne in the second year. The average fruit yield per plant is about 300 g, and the heavy metals in the fruits do not exceed the standard. In the future, it is necessary to monitor the heavy metal content of blueberry fruits every year. (The blueberry fruits in the experimental field are only used for experimental detection and are not put on the market).

[0063] (7) Lay a black grass cover cloth 6 around the tree rows, and appropriate hyperaccumulator plants, such as Sedum plumbizincicola 7, ramie, etc., can be planted in the intervals between the tree rows.

[0064] Control example

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

[0066] After two years of growth of the blueberries in Example 1 and the control example, the fruits in the second year were tested by: bioMérieux Detection Technology (Guangzhou) Co., Ltd.

[0067] In July this year, 6 fresh blueberry samples of three different varieties in Example 1 were picked, with 2 samples for each variety, and 2 control samples of the control example 1 were picked. The test results show that the heavy metal contents of the 6 samples in Example 1 are as follows: As: 0.0269 - 0.0423 mg / kg; Cd: 0.011 - 0.0155 mg / kg; Pb: 0.0939 - 0.192 mg / kg, all of which are lower than the pollutant limit values for fruits in the relevant 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 2 control samples in the control example are as follows: As: 0.0456 - 0.125 mg / kg; Cd: 0.014 - 0.0157 mg / kg; Pb: 0.208 - 0.302 mg / kg; Cd does not exceed the standard, and only a very small number of As and Pb exceed the standard. Others such as Cu, Hg, and Zn do not exceed the standard, and most are lower than the detection limit. It can be seen that the blueberry fruits themselves have a low ability to accumulate heavy metals, especially a low ability to accumulate cadmium. If the soil is properly passivated, the heavy metal content of blueberry fruits is lower than the limit values in the relevant national food safety standards. In addition, the test values of nutrients such as vitamins, anthocyanins, fructose, and glucose in blueberries have no difference from those of blueberries 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) Lay waste wood with a length < 10 cm and a diameter of less than 5 cm at the bottom of the hole. The waste wood layer 1 has a thickness of approximately 0.2 m. Sprinkle some straw fermentation product spacer layer 2 on it to ensure some voids below. Then lay woody peat (organic matter content > 70%): potassium feldspar calcined activation material (alkaline, which can appropriately increase the pH by about 0.5 - 1): rapeseed cake: straw fermentation product (crush straw such as rape and rice to less than 5 cm, mix with a certain amount of livestock manure, humidify and stack for fermentation for 2 - 3 months, turning it over every 2 - 3 weeks and humidifying): a mixture of soil with a mass ratio of 30:5:6:10:70 to form a fertilizer and mixed soil layer 3 with a thickness of approximately 0.2 m.

[0076] (6) Select loquat transplant seedlings with a 2-year-old tree age and soil balls. After landfilling and fixing with the original mixed soil, pour thoroughly with a water-soluble fertilizer containing multiple amino acids diluted 800 times. The survival rate of loquats is 100%, the growth is good, no heavy metals are found to hinder their healthy growth, and no fruits are borne during the test year.

[0077] (7) Lay black grass-covering cloth around the tree rows, and plant Sedum plumbizincicola, a hyperaccumulator of Cd, in the intervals between the tree rows. Loosen the soil in the 60-cm-wide land in the middle of the tree rows, evenly sprinkle a mixture of herbaceous peat and compound fertilizer according to the mass ratio of 5:1, mix well, with a mixing depth of about 10 cm, cover with a film, and plant Sedum plumbizincicola at a spacing of 15 cm in rows. Sedum plumbizincicola needs to be harmlessly disposed of later.

[0078] The actual picture of this experimental field is as Figure 4 shown, Figure 5 for blueberries 5 (bearing fruits) after two years of planting, Figure 6 and for loquats 9 after two years of this planting.

[0079] In summary, the present invention plants economic crops such as blueberries and loquats on heavy metal-polluted land around sulfide ore concentration areas. After long-term monitoring, the heavy metal content in blueberries and loquat fruits does not exceed the standard and meets the food safety standards. Interplanting some hyperaccumulator plants in this way can enable the abandoned or controlled land around the mining area to generate green value-added benefits. It avoids a large amount of earthwork and soil erosion, improves the soil structure, fertility and microbial diversity, increases the vegetation coverage rate, and has economic and tourism and leisure values 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, not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions 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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