Treatment method for weathering crust eluviation type rare earth mining area overwater landscape slope polluted soil

Abstract

The invention discloses a treatment method for polluted soil of a water landscape slope in a weathering crust eluviation type rare earth mining area, and belongs to the field of treatment and regeneration of polluted soil. The method comprises the following steps: constructing a recyclable barrier system for pollutants in slope rainfall runoff of weathering crust eluviation type rare earth mining area soil, a strong reduction treatment system for polluted soil, a bionic transpiration system, and a system for combined application of strong reduction treatment and bionic transpiration and valuable substance recovery. According to the method, both symptoms and root causes of the polluted soil of the weathering crust eluviation type rare earth mining area overwater landscape slope are treated, soil pollution is treated, the treated soil is prevented from being polluted again by adjacent environmental pollutants, valuable pollutants in the adjacent environment can be recycled, water flowing, evaporation and leakage of the overwater landscape slope are effectively controlled, and the water quality of the overwater landscape slope is improved. The soil environment condition beneficial to improvement and treatment of the polluted soil of the overwater landscape sloping field is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of contaminated soil treatment and regeneration, and in particular relates to a method for treating contaminated soil on a water landscape slope in a weathering crust leaching type rare earth mining area. Background Art

[0002] Weathering crust elution type rare earth ore is an important mineral resource, containing a large number of medium and heavy rare earths. At present, the polluted soil in weathering crust elution type rare earth mining areas is seriously degraded, acidified, and has a low organic matter content. There are many types of pollutants, including pollutants from the rare earth mines themselves, such as rare earths, heavy metals, aluminum ions, etc.; there are also pollutants from rare earth leaching agents, such as ammonium sulfate leaching causing ammonium nitrogen, sulfate, and nitrate pollution. On the other hand, the migration of pollutants in contaminated soil usually causes pollution of adjacent water bodies.

[0003] For the treatment of contaminated soil in leaching rare earth mining areas, chemical or biological remediation methods are currently usually used, and the treatment is carried out according to the classification of pollutants. For example, chemical remediation methods can be used to stabilize heavy metal ions and rare earth ions in contaminated soil, where the stabilization reagents for soil heavy metal ions include clay minerals, lime materials, biochar, organic high-sulfur stabilizers, etc., and the stabilization reagents for soil rare earth ions include clay minerals, phosphates, etc.; or calcium chloride, potassium chloride, sodium chloride, sodium carbonate, potassium carbonate, magnesium sulfate, aluminum sulfate, iron sulfate, citric acid, saponin and saponin are used to elute rare earth or ammonia nitrogen in the soil, and then recover rare earth or ammonium nitrogen; or plant remediation methods are used to plant heavy metal or rare earth hyperaccumulator plants on contaminated soil, and use the aboveground parts of plants to extract and recover heavy metals or rare earths in the soil; or plants are used to absorb nitrogen and sulfur in the soil to reduce nitrogen and sulfur pollutants in the contaminated soil. Bionic trees with transpiration are occasionally used to treat heavy metal contaminated soil, but the method is immature, especially the bionic wood of bionic trees is prone to air embolism and cannot sustain bionic transpiration. However, these soil remediation methods have the following problems: 1. They are only suitable for improving soil fertility or treating one or a class of pollutants, and are often powerless against other soil degradation factors, and even lead to further enhancement of the effects of other soil degradation factors; 2. Chemical remediation methods will cause the passivated pollutants to dissolve again, causing secondary pollution; and biological remediation methods are subject to various restrictive conditions for the growth of plants and soil microorganisms, such as temperature, humidity, nutrients, water, redox, sunlight, etc.; Bionic trees are only suitable for treating some soil heavy metal pollution, are prone to air embolism and cannot sustain bionic transpiration, and cannot sustainably treat contaminated soil; these soil remediation methods consume a lot of labor and energy. There are also the following unique problems for the remediation of contaminated soil on water landscape slopes: 1. The pollutants contained in the contaminated soil at a higher level adjacent to the water landscape slopes will migrate and contaminate the soil on the water landscape slopes; 2. The slope and soil properties of the water landscape slopes affect the migration and transformation of soil substances, which indirectly has an adverse impact on the remediation of contaminated soil on the water landscape slopes. In addition, weathering crust leaching rare earth mines are mostly hilly and mountainous areas, and it is difficult to implement strong reduction on this type of soil. On the one hand, this type of soil has a slope, and on the other hand, this type of soil is mostly sandy soil, and it is difficult for water to remain in the soil, and it is not easy to form the flooding conditions required to maintain the strong reduction state of the soil, which makes it difficult to use strong reduction technology to treat this type of contaminated soil. Summary of the invention

[0004] Purpose of the invention: In order to solve the above technical problems, the present invention provides a method for treating polluted soil on water landscape slopes in weathering crust leaching rare earth mining areas, which achieves the following purposes: 1. Treat multiple pollutants in the polluted soil at the same time, while stabilizing the heavy metals in the soil, recover the rare earth and ammonium nitrogen in the soil, and reduce the sulfate and nitrate content of the soil; and improve the soil, reduce the acidity of the soil, and increase the organic matter content of the soil. 2. Compared with conventional chemical remediation technology, it is not easy to cause secondary pollution of certain pollutants; compared with conventional biological remediation technology, it is not limited by biological habitat conditions, and it also overcomes the problem that the bionic tree itself is prone to air embolism and cannot continue to bionic transpiration and treat polluted soil. 3. Save energy, save labor, have a short cycle, low cost, high efficiency, and simple management of polluted soil treatment. 4. Take measures to prevent pollutants from the adjacent environment from polluting the soil on the water landscape slope again; take measures to control the flow and leakage of water on the water landscape slope to achieve environmental conditions of a strong reduction state of soil that is beneficial to the improvement and treatment of polluted soil on the water landscape slope.

[0005] The present invention also provides the application of the method for treating polluted soil on water landscape slopes in weathering crust elution type rare earth mining areas in the treatment and regeneration of polluted soil on water landscape slopes in weathering crust elution type rare earth mining areas.

[0006] Technical solution: To achieve the above-mentioned purpose, the method for treating polluted soil on water landscape slopes in weathering crust leaching type rare earth mining areas described in the present invention includes a recoverable barrier system for pollutants in slope rainfall runoff, a strong reduction treatment system for polluted soil, a bionic transpiration system, a combined application of strong reduction treatment and bionic transpiration, and a valuable substance recovery system;

[0007] The specific steps include:

[0008] S1. Construct a recyclable barrier system for pollutants in the slope rainfall runoff of the contaminated soil of the water landscape slope in the weathering crust leaching type rare earth mining area, which is used to block the pollutants that are transferred into the runoff in the form of water-soluble or particulate matter due to the scouring of the contaminated soil on the slope;

[0009] S2. Construct a strong reduction treatment system for soil contaminated by weathering crust leaching rare earth mining areas, transform the water landscape slopes to be treated into gentle slope terraces, and carry out strong reduction treatment on the contaminated soil;

[0010] S3. Constructing a bionic transpiration system, implanting a bionic tree that can perform bionic transpiration in the contaminated soil treated with strong reduction in step S2;

[0011] S4. Build a greenhouse above the strongly reduced contaminated soil and the bionic tree, implement the combined application of soil strong reduction and bionic transpiration and recovery of valuable substances, and recover rare earth and ammonium nitrogen from the leaves of the bionic tree.

[0012] Furthermore, in step S1, the method for constructing a recoverable barrier system for pollutants in the slope rainfall runoff of polluted soil in the water landscape slope of the weathering crust leaching type rare earth mining area is:

[0013] (1) digging a ridgeless earth pit in the left and right directions at the upper edge of the horizontal height of the water landscape slope of the weathered crust eluvial rare earth mining area to be treated, as the boundary between the upstream polluted slope of the slope rainfall runoff and the downstream slope to be treated; the horizontal height is set according to the conditions of the polluted slope to be treated, and if necessary, a number of repeated ridgeless earth pit units are set to ensure that the ridgeless earth pit or ridgeless earth pit unit is dug in the left and right directions along the contour line, with a rectangular cross-section, a depth of 0.75-1.5m, and a width of 2.1-2.9m; wherein the set horizontal height refers to the upper horizontal edge of the polluted slope to be treated after it is determined; the ridgeless earth pit is dug in the left and right directions along the contour line;

[0014] (2) Adsorption bags are piled on one side of the soil pit without ridges connected to the polluted slope upstream of the slope runoff. The width of the adsorption bags is 1.6-2.4m. The middle part of the upper part of the adsorption bag pile is parallel to the slope surface in the horizontal direction to leave a left and right ditch. The top plane of the tail of the adsorption bag pile is 0.25-0.5m higher than the top plane of the head of the adsorption bag pile. The head of the adsorption bag pile is connected to the polluted slope upstream of the slope runoff.

[0015] (3) There is a 0.5-0.8m gap between the tail of the adsorption bag stack in the pit without ridges and the downstream slope to be treated. Montmorillonite or uncontaminated guest soil is filled in to form a recoverable barrier system for pollutants in slope rainfall runoff with a depth of 0.2-0.4m. The lower edge of the left and right drainage ditches are connected to one side of the downstream slope to be treated. The downstream slope to be treated is the slope to be treated downstream of the slope rainfall runoff.

[0016] Furthermore, in step (2), part of the adsorption bags are adsorption bags filled with anion exchange resin, and the other part are adsorption bags filled with cation exchange resin. The adsorption bags are stacked in order so that when the slope rainfall runoff flows through the adsorption bags, it first contacts only the adsorption bags filled with anion exchange resin to perform anion exchange; after the slope rainfall runoff flows through the adsorption bags filled with anion exchange resin, it contacts the adsorption bags filled with cation exchange resin to perform cation exchange.

[0017] Furthermore, in step S2, the method for constructing a strong reduction treatment system for polluted soil on a water landscape slope in a weathering crust leaching type rare earth mining area is:

[0018] (4) At the lower edge of the left-right drainage ditch at the lower edge of the recoverable barrier system for pollutants in the slope rainfall runoff, and at the contaminated soil on the slope of the downstream slope to be treated that borders the drainage ditch, dig and build ridges at the same horizontal height; along the slope direction of the downstream slope to be treated, set the horizontal height according to the conditions of the slope to be treated, and dig a number of drainage ditches or multiple drainage ditch units. The drainage ditches are left-right, forming a drainage ditch with a width of 0.4-0.6m and a depth of 0.2-0.4m. After the drainage ditch is filled with montmorillonite or uncontaminated foreign soil, ridges are respectively built at the contaminated soil on the slope surface of the downstream slope to be treated that borders the two sides of the drainage ditch; between the lower edge ridge of each horizontal drainage ditch and the upper edge ridge of the next horizontal drainage ditch, a ridge pit is dug, and above each ridge pit and the unit formed by the ridges on both sides, an underlay soil impermeable membrane is integrally laid, and then the contaminated soil dug out of the ridge pit is backfilled onto the underlay impermeable membrane above the ridge pit, and the land is leveled;

[0019] (5) Add easily degradable organic materials to the leveled backfill contaminated soil and mix well, flood the soil, and lay a top film for soil strong reduction treatment on top of the unit formed by the pit between each ridge and the ridges on both sides to construct a strong reduction treatment system for the backfill contaminated soil, and then carry out strong reduction treatment.

[0020] Furthermore, in step (4), the depth of the pit between the ridges is 0.75-1.5m, and the width is 1.3-2.6m; the height of the ridge is 0.4-0.6m, and the width is 0.3-0.4m; the cycle of the strong reduction treatment in step (5) is 2-4 weeks, and small holes for planting bionic trees are arranged at equal distances on the upper film of the ridge and the pit between the ridges, with a hole diameter of 5-10cm and a center spacing of 30-50cm.

[0021] Furthermore, the method of implanting the bionic tree for performing bionic transpiration in step S3 comprises the following steps:

[0022] (6) Assemble the bionic xylem and its hard shell of the bionic tree rhizome and the bionic phloem and its hard shell of the bionic tree rhizome into a bionic tree rhizome; assemble the bionic xylem and its hard shell of the bionic tree leaf and the bionic xylem and its hard shell of the bionic tree leaf into a bionic tree leaf; the bionic phloem and its hard shell of the bionic tree rhizome and the bionic xylem and its hard shell of the bionic tree leaf are provided with a connection part, a horizontal connection part is provided in the bionic tree rhizome, and a vertical connection part is provided in the bionic tree leaf to maintain connectivity; the connection part is provided with a one-way valve controlled by a hinge, so that when each bionic xylem is short of water, the bionic phloem can replenish water to avoid embolism of the bionic xylem; a float with a scale indicating the water level is inserted into the upper opening of the bionic phloem of the bionic tree leaf to display the water level of the upper edge of the bionic phloem;

[0023] (7) When the contaminated soil is backfilled onto the bottom soil impermeable membrane of the pit between ridges in step (4) of constructing the strong reduction treatment system for contaminated soil, the assembled bionic tree rhizomes are buried in the soil, and then flooded and covered with an upper membrane, and the upper end of the bionic tree rhizomes passes through the planting holes set on the upper membrane; then the gap between the upper membrane and the bionic tree rhizomes is closed to prevent gas from escaping;

[0024] (8) Connect the assembled bionic leaf blades to the assembled bionic tree roots.

[0025] Furthermore, the bionic xylem of the bionic leaf is arranged above the space surrounded by the edge of the bionic phloem of the bionic leaf; a hole is arranged in the center of the bionic phloem of the bionic leaf, and the bionic xylem of the bionic tree rhizome passes through the bionic phloem of the bionic leaf through the hole and is directly connected to the bionic xylem of the bionic leaf;

[0026] The diameter of the bionic tree leaf is 20-40cm, the diameter of the bionic tree rhizome is 3-8cm, and the height of the bionic tree rhizome is 20-40cm; the hard shells of the bionic tree leaf and rhizome are both made of plastic, and are divided into a bionic xylem space and a bionic phloem space, which are filled with bionic xylem and bionic phloem materials respectively;

[0027] The bionic xylem and bionic phloem materials can be the same or different, such as filter paper, gauze, etc., with capillary pores, and can produce capillary action; a water level indicator float can be inserted into the upper opening of the bionic phloem of the bionic leaf, which is a scaled float indicating the water level;

[0028] The float has a diameter of 1 cm and is made of foam plastic. The float is connected to a wooden pole with a diameter of 0.5 cm. The wooden pole has scales that can display the water level of the upper edge of the bionic phloem of the bionic leaf.

[0029] On the hard shell on one side of the bionic xylem of the bionic tree rhizome, a water inlet is arranged every 5-10 cm to allow soil solution to enter the bionic xylem of the bionic tree rhizome; the bionic xylem of the bionic tree leaf and its hard shell are opened upward to the air to perform transpiration;

[0030] A series of connection parts are arranged every 5-10 cm along the vertical direction between the bionic xylem and the bionic phloem of the bionic tree leaf; a series of connection parts are arranged every 5-10 cm along the horizontal direction between the bionic xylem and the bionic phloem of the bionic tree rhizome; the bionic phloem is provided with a part for placing a scaled float indicating the water level, and the bionic phloem and the hard shell of the bionic tree leaf are provided with a part for injecting water from the outside;

[0031] The connecting parts of the bionic xylem and bionic phloem of the bionic tree leaves, as well as the connecting parts of the bionic xylem and bionic phloem of the bionic tree roots, are all tubular connections with a length of 0.5-1 cm and a diameter of 0.5-1 cm. A one-way valve is provided in the tubular connection. The one-way valve is fixed and controlled by a hinge so that the opening angle of the one-way valve is less than 30°. The one-way valve opens when the bionic xylem cannot effectively obtain water from the soil and the water pressure is too high. At this time, water flows from the bionic phloem to the bionic xylem to replenish water and prevent the formation of bionic xylem embolism.

[0032] Furthermore, the bionic xylem of the bionic tree rhizome is directly connected to the bionic xylem of the bionic tree leaf. During transpiration, the capillary force pulls the soil solution into the bionic xylem of the bionic tree rhizome and then into the bionic xylem of the bionic tree leaf. The bionic phloem of the bionic tree rhizome is directly connected to the bionic phloem of the bionic tree leaf. The water injected into the bionic phloem of the bionic tree leaf can enter the bionic phloem of the bionic tree rhizome due to gravity. At the same time, the connection parts between the bionic xylem and the bionic phloem of the bionic tree leaf and the connection parts between the bionic xylem and the bionic phloem of the bionic tree rhizome are all tubular connections, and a one-way valve is arranged in the tubular connection. When the bionic xylem of the bionic tree leaf loses excessive water, the water injected into the bionic phloem of the bionic tree leaf can flow to the bionic xylem of the bionic tree leaf through the one-way valve in one direction, thereby avoiding the embolism phenomenon that may be caused by excessive water loss of the bionic xylem of the bionic tree leaf during bionic transpiration; and the water in the bionic phloem of the bionic tree rhizome can flow to the bionic xylem of the bionic tree rhizome through the one-way valve in one direction when the bionic xylem of the bionic tree rhizome loses excessive water, thereby avoiding the embolism phenomenon that may be caused by excessive water loss of the bionic xylem of the bionic tree rhizome during bionic transpiration.

[0033] Furthermore, in step S4, the greenhouse is a simple greenhouse with fresh air exchange windows; the implementation of the combined application of soil strong reduction and bionic transpiration and valuable material recovery, and recovery of rare earth and ammonium nitrogen from bionic tree leaves, includes the following steps:

[0034] (9) A simple greenhouse with fresh air exchange windows is built above the strongly reduced contaminated soil and bionic trees. The fresh air exchange windows heat the gas entering the greenhouse through a sensible heat exchange system and recover the condensed water in the greenhouse exhaust gas to a high-level water storage tank;

[0035] (10) Rare earth ions and ammonium nitrogen in the soil solution enter the leaves of the bionic tree from the bionic tree roots and leaves in the bionic xylem, and are concentrated as the water evaporates; the rare earth ions and ammonium nitrogen in the bionic tree leaves are washed with EDTA solution in a high-level water tank and recovered;

[0036] (11) After the treatment of the contaminated soil excavated from the pits between ridges on the water landscape slope of the weathering crust elution type rare earth mining area is completed, the above-mentioned recyclable barrier system shall be maintained; the simple greenhouse, the upper covering film and the lower anti-seepage film shall be removed, and the treated soil in the original pits between ridges shall be piled from the upper and lower edges of the horizontal height of the original pits between ridges to the midline of the horizontal height to form a new soil ridge; the untreated soil of the original soil ridge of the water landscape slope of the above-mentioned rare earth mining area shall be excavated to form a new pit between ridges; in the new pit between ridges, the soil shall be treated by the same strong reduction and bionic transpiration scheme.

[0037] Furthermore, the water landscape slope in the weathering crust elution type rare earth mining area is a water landscape slope with a slope less than 25°, and the gentle slope terrace is a gentle slope terrace with a slope less than 10°.

[0038] The method for treating polluted soil on water landscape slopes in weathering crust elution type rare earth mining areas of the present invention is applied in treating and regenerating polluted soil on water landscape slopes in weathering crust elution type rare earth mining areas.

[0039] Preferably, the method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope includes the following steps:

[0040] S1. Based on the characteristics that weathering crust leaching type rare earth mines are mostly water landscape slopes, a recyclable barrier system for pollutants in slope rainfall runoff of the slope soil to be treated was constructed. While blocking pollution, ion exchange resin was used to achieve the special function of valuable material recovery;

[0041] S2. Based on the characteristics that weathering crust elution type rare earth mines are mostly water landscape slopes, a strong reduction treatment system for slope contaminated soil was constructed for the first time, and the water landscape slopes in the rare earth mining area to be treated were transformed into gentle slope terraces, and the contaminated soil was subjected to strong reduction treatment;

[0042] S3. Constructing a bionic transpiration system, implanting a bionic tree that can perform bionic transpiration in the contaminated soil treated with strong reduction in step S2, achieving the special role of directly recovering valuable substances under strong reduction conditions;

[0043] S4. A greenhouse is set up above the strongly reduced contaminated soil and the bionic tree to implement soil strong reduction and bionic transpiration, and to recover rare earth and ammonium nitrogen from the leaves of the bionic tree, and to implement the combined application of strong reduction treatment and bionic transpiration and the recovery of valuable substances. Among them, the elements in the rare earth refer to the 14 lanthanide elements except promethium, namely La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y.

[0044] Preferably, one part of the adsorption bag is filled with anion exchange resin (styrene-based strong base anion exchange resin [Purolite A520E]), and the other part is filled with cation exchange resin (AG50W-X8 ion exchange resin). The upper film and the lower anti-seepage film are made of polyethylene film, wherein the anti-seepage film is under water and the upper film is to isolate the air.

[0045] Furthermore, in the treatment method, ionic pollutants in the slope rainfall runoff penetrate into the adsorption bag, and are adsorbed on the anion or cation exchange resin in the adsorption bag through an anion exchange adsorption or cation adsorption process, and are subsequently desorbed to recover rare earth, nitrogen and sulfur, and the ion exchange resin is regenerated; particulate pollutants in the slope rainfall runoff are deposited in the left and right ditches parallel to the slope in the horizontal direction at the middle part of the upper part of the adsorption bag stack, and after a sufficient amount of sediment is collected and stored, it is placed in the treatment system of the present invention that combines strong reduction treatment and bionic transpiration technology, and is treated according to the method of the present invention.

[0046] Among them, the slope rainfall runoff is the runoff flowing from the higher level of the slope to the lower level, carrying pollutants such as rare earths, heavy metals, nitrogen, and sulfur; the gentle slope terraces are terraces that have been transformed and are equipped with earth ridges and drainage ditches, and have a slope less than the original slope. The bionic transpiration is carried out by the bionic tree under sunlight. The bionic xylem of the bionic tree contains rich vertical capillary structures, and the bionic leaf leaves of the bionic tree contain rich horizontal capillary structures. The valuable substances are mainly rare earth elements.

[0047] The present invention constructs a strong reduction treatment system to effectively reduce the sulfate and nitrate pollution levels in the polluted soil of the water landscape in the weathering crust leaching type rare earth mining area, effectively reduce the toxicity of hexavalent chromium in the soil, so that the heavy metals in the polluted soil are effectively passivated and their biological effectiveness is reduced; the tetravalent cerium in the soil is converted into trivalent cerium that is easy to migrate, so as to effectively reduce the soil acidity and the soil aluminum ion concentration, and improve the physical and chemical properties of the soil.

[0048] Among them, the bionic tree leaves undergo bionic transpiration and lose water under light conditions, pulling the soil solution into the bionic tree rhizomes, and transporting it upward to the bionic xylem of the bionic tree leaves through capillary action and along the bionic xylem of the bionic rhizomes. The bionic phloem is always filled with water and connected to the bionic xylem, using a one-way valve to avoid the possible bionic embolism of the bionic xylem during bionic transpiration. The soil solution containing pollutants such as rare earths and ammonium nitrogen is continuously migrated out of the contaminated soil and into the bionic tree leaves under the bionic transpiration of the bionic tree.

[0049] The invention discloses a method for treating soil contaminated by weathering crust leaching rare earth mining areas on water landscape slopes, comprising a recoverable barrier system for pollutants in slope rainfall runoff, a strong reduction treatment system for contaminated soil, a bionic transpiration system, and a combined application of strong reduction treatment and bionic transpiration technology and a valuable substance recovery system.

[0050] Invention mechanism:

[0051] 1. A recyclable barrier system for pollutants in slope rainfall runoff. The design principle of the invention is based on:

[0052] 1-1. Ionic pollutants in the slope rainfall runoff penetrate into the adsorption bag, and through the anion exchange adsorption or cation adsorption process, they are adsorbed on the anion or cation exchange resin in the adsorption bag, thereby solidifying the ionic pollutants and preventing them from re-polluting the treated soil; this is a common method for soil pollution control. However, the subsequent targeted desorption and recovery of rare earths, nitrogen, and sulfur in the present invention is not a conventional operation of soil solidification technology. The present invention effectively realizes the recovery of valuable substances such as rare earths on rare earth contaminated soil and realizes the regeneration of ion exchange resins.

[0053] 1-2. In the present invention, particulate pollutants in rainfall runoff on slopes are deposited in the horizontal ditch parallel to the slope in the middle part of the upper part of the adsorption bag stack. After sufficient sediment is collected and stored, it is placed in the treatment system of the present invention that combines strong reduction treatment with bionic transpiration technology to recover valuable substances such as rare earths. This is not a conventional operation of soil pollution control technology, and it can effectively realize the recovery of valuable substances such as rare earths on rare earth contaminated soil.

[0054] 2. The strong reduction treatment technology scheme for contaminated soil in weathering crust leaching type rare earth mining areas in the present invention is based on the design principle of:

[0055] 2-1. Strong reduction treatment of soil is usually carried out on horizontal plots. It is difficult to flood slopes, and water on slopes is easy to form runoff loss; at the same time, sandy soil is difficult to retain water and is not easy to form flooding conditions. Weathering crust elution type rare earth mines are mostly hilly and mountainous. It is difficult to implement strong reduction of this type of soil because the soil has a slope, and the water required for strong reduction of soil to maintain a flooded state is difficult to retain in the soil. At the same time, the soil is mostly sandy soil, which is not easy to retain water. The design of the present invention uses a method similar to terraces to solve the problem of runoff loss of soil moisture on slopes; at the same time, the method of laying an impermeable membrane solves the problem of water leakage in sandy soil, and effectively realizes strong reduction of soil. Usually, the contaminated soil in rare earth mining areas belongs to sandy loam, and the soil in rare earth mining areas has a certain slope, which makes it difficult to maintain a flooded state and difficult to achieve strong reduction treatment of soil; the technical solution of the present invention adopts measures such as transformation into terraces, ridge building, and laying an impermeable membrane, which can effectively maintain soil water storage and achieve strong reduction treatment of soil.

[0056] 2-2. The redox potential of the soil can be as low as -200mV, and the system can effectively reduce tetravalent cerium (Ce(IV)+e→Ce 3+ ,1.72V), hexavalent chromium (Cr(VI)+3e→Cr 3+ ,1.33V), pentavalent arsenic (As(V)+2e→As(III),0.56V). For soil treated by strong reduction, if the selected organic material has a high sulfur content, it can be converted into a large amount of sulfur ions through reduction, which form precipitation with heavy metal ions in the soil, thus stabilizing the heavy metals in the soil. Usually, heavy metal ions are soft acids, which are easy to coordinate with sulfur ions, which are soft bases, to form precipitation. In this way, for heavy metal ions and rare earth ions, the strong reduction system shows obvious differences in results: soft acid heavy metal ions form precipitation with sulfur ions, are stabilized and treated in the soil; rare earth ions and Cr 3+ It is a hard acid and is not easy to coordinate with the sulfide ion which is a soft base. It is not solidified in the soil and still maintains its effectiveness. It is easy to migrate out of the contaminated soil and be recovered. Different from the existing soil pollution control, the present invention only recovers some specific valuable substances in the soil of the mining area; on rare earth contaminated soil, it effectively realizes the recovery of valuable substances such as rare earth, effectively solidifies heavy metals, and realizes the separation of rare earth from heavy metals.

[0057] 3. The bionic transpiration of the bionic tree in the present invention is based on the following principles:

[0058] 3-1. The bionic transpiration of the bionic tree uses solar energy to cause the evaporation of water from the leaves of the bionic tree to generate negative water potential; the method is often used to obtain water and substances in the soil solution. The difficulty of the existing technology is that part or all of the bionic xylem will produce air embolism due to water loss, making it difficult to maintain bionic transpiration continuously; the present invention uses bionic phloem to effectively replenish water to the bionic xylem to avoid embolism and achieve continuous bionic transpiration.

[0059] 3-2. In a conventional bionic tree, the solution in the bionic leaf part is recovered by gravity. In this way, if the bionic transpiration is intense, the water potential of the solution in the bionic leaf is relatively negative and difficult to recover; if the bionic transpiration is not intense, the soil solution is difficult to be lifted to the bionic leaf. In the present invention, a simple greenhouse equipped with a fresh air exchange window is set up above the strongly reduced soil and the bionic tree. The fresh air exchange window heats up the gas entering the greenhouse through sensible heat exchange, and recovers the condensed water in the greenhouse exhaust gas to a high-level water tank. The water in the high-level water tank is regularly made into an EDTA solution of a certain concentration, which is used to rinse the rare earths and ammonium nitrogen in the bionic tree leaves and recover them. This can effectively realize the combined treatment of the strong reduction treatment of the polluted soil on the water landscape slope in the weathering crust leaching type rare earth mining area and the bionic transpiration technology.

[0060] The method for treating polluted soil on water landscape slopes in weathering crust leaching type rare earth mining areas by combined application of strong reduction treatment and bionic transpiration technology can simultaneously treat the pollution of rare earth, heavy metals, nitrogen and sulfur in polluted soil on water landscape slopes in weathering crust leaching type rare earth mining areas, recover rare earth and ammonium nitrogen therein, and improve the soil; compared with conventional chemical remediation technology, the method is not easy to cause secondary pollution of certain pollutants; compared with conventional biological remediation technology, the method is not limited by biological habitat conditions, and also overcomes the problem that the bionic tree itself is prone to air embolism and cannot continue bionic transpiration and treat polluted soil; it realizes the use of solar energy to save energy, short cycle and save labor, low cost, high efficiency and simple management of polluted soil treatment.

[0061] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0062] 1. The treatment method of the present invention achieves both symptomatic and root-cause treatment of soil contamination on water landscape slopes in weathering crust leaching rare earth mining areas. It not only treats soil pollution and improves soil, but also prevents the treated soil from being re-contaminated by pollutants from the adjacent environment, and can also recover valuable pollutants in the adjacent environment. The method of the present invention can effectively control the flow, evaporation and leakage of water on water landscape slopes, implement strong soil reduction, and help achieve soil environmental conditions that are beneficial to the improvement and treatment of contaminated soil on water landscape slopes.

[0063] 2. The treatment method of the present invention simultaneously treats multiple pollutants in contaminated soil, stabilizes soil heavy metals, recovers rare earths and ammonium nitrogen in the soil, and reduces the sulfate and nitrate content in the soil; in addition, it also improves the soil, reduces soil acidity, and increases soil organic matter content.

[0064] 3. The treatment method of the present invention avoids the secondary pollution of certain pollutants that may be caused by soil chemical remediation technology, such as removing rare earth elements from the soil; avoids the demanding habitat of soil biological remediation technology, such as temperature, humidity, nutrients, water, redox, sunlight, etc.; makes the bionic tree suitable for treating the coexistence of multiple pollutants in the contaminated soil in rare earth mining areas, and avoids air embolism in the bionic tree and the inability to continue bionic transpiration and treat contaminated soil.

[0065] 4. The treatment method of the present invention realizes the treatment and regeneration of contaminated soil by utilizing solar energy to save energy and labor, with a short cycle, low cost, high efficiency and simple management. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1A three-dimensional structural diagram of a weathering crust elution-type rare earth mine and a small watershed provided in an embodiment of the present invention, wherein: 1-the top of the mine mountain; 2-the hillside; 3-the implementation area of ​​the barrier and recovery system; 4-the implementation area of ​​the strong reduction treatment and bionic transpiration combined management; 5-the water landscape slope; 6-the riverbed; 7-the river water.

[0067] Figure 2 A structural diagram of a recoverable barrier system for pollutants in slope rainfall runoff constructed for an embodiment of the present invention, wherein: 8 - mine at the upper edge of the recoverable barrier system; 9 - runoff flowing downward from the top of the mine mountain; 10 - adsorption bags filled with anion exchange resin; 11 - adsorption bags filled with cation exchange resin; 12 - drainage ditches; 13 - montmorillonite or uncontaminated guest soil; 14 - a water landscape slope area where strong reduction treatment and bionic transpiration combined treatment are implemented.

[0068] Figure 3 Schematic diagram of soil strong reduction treatment constructed for an embodiment of the present invention, wherein: 12-drainage ditch; 13-montmorillonite or uncontaminated guest soil; 15-gentle slope one-step terrace; 16-upper covering film; 17-lower soil anti-seepage film; 18-earth ridge; 19-earth pit between ridges; 20-backfill contaminated soil; 21-soil-water interface; 22-flooding.

[0069] Figure 4 Schematic diagram of a bionic tree constructed according to an embodiment of the present invention, wherein: 23-bionic leaf; 24-the connecting part between the bionic leaf and the bionic tree rhizome; 25-bionic tree rhizome; 26-bionic phloem of the bionic leaf; 27-bionic xylem of the bionic leaf; 28-bionic phloem of the bionic tree rhizome; 29-bionic xylem of the bionic tree rhizome; 30-bionic xylem hard shell of the bionic tree rhizome; 31-bionic xylem hard shell of the bionic leaf; 32-bionic phloem hard shell of the bionic tree rhizome; 33-bionic phloem hard shell of the bionic leaf.

[0070] Figure 5 A top view of a bionic tree constructed according to an embodiment of the present invention, wherein: 24 - the connection between the bionic tree leaf and the bionic tree rhizome; 26 - the bionic phloem of the bionic tree leaf; 27 - the bionic xylem of the bionic tree leaf; 31 - the bionic xylem hard shell of the bionic tree leaf; 33 - the bionic phloem hard shell of the bionic tree leaf.

[0071] Figure 6A cross-sectional view of a bionic tree constructed according to an embodiment of the present invention, wherein: 21-soil-water interface; 24-connection between bionic tree leaf and bionic tree rhizome; 26-bionic phloem of bionic tree leaf; 27-bionic xylem of bionic tree leaf; 28-bionic phloem of bionic tree rhizome; 29-bionic xylem of bionic tree rhizome; 30-bionic xylem hard shell of bionic tree rhizome; 31-bionic xylem hard shell of bionic tree leaf; 32-bionic phloem hard shell of bionic tree rhizome; 33-bionic phloem hard shell of bionic tree leaf; 34-a graduated float indicating water level; 35-connection between bionic xylem and bionic phloem of bionic tree leaf; 36-connection between bionic xylem and bionic phloem of bionic tree rhizome; 37-soil solution.

[0072] Figure 7 Schematic diagram of the connection part between the bionic xylem and the bionic phloem constructed for the embodiment of the present invention, wherein: 26-bionic phloem of the bionic tree leaf; 27-bionic xylem of the bionic tree leaf; 28-bionic phloem of the bionic tree rhizome; 29-bionic xylem of the bionic tree rhizome; 35-the connection part between the bionic xylem of the bionic tree leaf and the bionic phloem; 36-the connection part between the bionic xylem of the bionic tree rhizome and the bionic phloem; 38-one-way valve; 39-hinge.

[0073] Figure 8 The present invention is a schematic diagram of a combined treatment system of strong reduction treatment and bionic transpiration for polluted soil on a water landscape slope in a weathering crust leaching type rare earth mining area according to an embodiment of the present invention; wherein: 16 - upper covering film; 17 - lower soil anti-seepage film; 18 - earth ridge; 20 - backfill contaminated soil; 21 - soil-water interface; 22 - flooding; 23 - bionic tree leaves; 25 - bionic tree rhizomes; 40 - simple greenhouse; 41 - greenhouse covering film.

[0074] Fig. 9 This is a schematic diagram of implanting a bionic tree in the strong reduction treated upper covering film according to an embodiment of the present invention, wherein: 16 - upper covering film; 25 - rhizome of the bionic tree; 42 - planting hole; 43 - sealing tape.

[0075] Fig.10 This is a schematic diagram of a greenhouse according to an embodiment of the present invention, wherein: 23-bionic leaf blades; 44-ventilation system; 45-exhaust system; 46-air intake system; 47-condensed water; 48-sensible heat exchange system; 49-high-level water tank; 50-EDTA solution; 51-water pipe; 52-concentrated solution recovery system. DETAILED DESCRIPTION

[0076] The present invention is further described below in conjunction with embodiments and drawings.

[0077] Example 1

[0078] The present embodiment provides a treatment system for contaminated soil on water landscape slopes in weathering crust leaching rare earth mining areas by combined application of strong reduction treatment and bionic transpiration technology, including construction of a recoverable barrier system for pollutants in slope rainfall runoff, a strong reduction treatment system for contaminated soil, a bionic transpiration system, a combined application of strong reduction treatment and bionic transpiration technology, and a valuable substance recovery system.

[0079] Among them, the water landscape slopes in the weathering crust elution type rare earth mining area, such as Figure 1 As shown in the figure, the three-dimensional structure diagram of the weathering crust elution type rare earth mine and small watershed, the mountain from top to bottom are: mine mountain top 1, hillside 2, water landscape slope 5, riverbed 6, river water 7. Water landscape slope 5 is a water landscape slope with a slope of less than 25°, including the barrier and recovery system implementation area 3 and the strong reduction treatment and bionic transpiration joint management implementation area 4. The barrier and recovery system implementation area 3 is transformed into a barrier system space for the recovery of pollutants in the slope rainfall runoff, and the strong reduction treatment and bionic transpiration joint management implementation area 4 is transformed into a gentle slope terrace space with an angle of less than 10°, to isolate and recover pollutants carried by the slope rainfall runoff from the mine 8 on the upper edge of the recyclable barrier system ( Figure 2 ).

[0080] like Figure 2 As shown, a ridgeless earth pit with a depth of 0.75-1.5m is dug horizontally parallel to the slope surface in the left and right directions. The upper edge of the ridgeless earth pit is connected to the upstream slope of the slope rainfall runoff, serving as the boundary between the upstream polluted slope of the slope rainfall runoff and the downstream slope of the slope rainfall runoff (the downstream slope to be treated). Several layers of adsorption bags 11 filled with cation exchange resin (AG50W-X8 ion exchange resin) are stacked in order at the bottom of the ridgeless earth pit, and adsorption bags 10 filled with anion exchange resin (styrene-based strong base anion exchange resin [PuroliteA520E]) are stacked above the several layers of adsorption bags 11 filled with cation exchange resin and on the front end surface. The adsorption bags 10 filled with anion exchange resin are closer to the upstream polluted slope of the slope rainfall runoff. The runoff 9 flowing downward from the top of the mine mountain flows through the adsorption bag, and first contacts only the adsorption bag 10 filled with anion exchange resin to perform anion exchange; after the runoff flows through the adsorption bag 10 filled with anion exchange resin, it contacts the adsorption bag 11 filled with cation exchange resin to perform cation exchange.

[0081] Among them, the top plane of the adsorption bag stacking tail is higher than the top plane of the adsorption bag stacking head to control the flow rate of water in the up-down direction, and the head of the adsorption bag 10 filled with anion exchange resin is connected to the polluted slope upstream of the slope rainfall runoff. There is a 0.5-0.8m gap between the tail of the adsorption bag 11 filled with cation exchange resin stacked in the pit without ridges and the downstream slope to be treated, and a certain amount of montmorillonite or uncontaminated guest soil 13 is filled to form a horizontal drainage ditch 12 parallel to the left and right of the slope. The drainage ditch 12 can recover the lower edge pollutants in the barrier system and is connected to one side of the water landscape slope area 14 where the strong reduction treatment and bionic transpiration combined treatment of the downstream slope to be treated are implemented.

[0082] like Figure 3 The figure shows the implementation area 4 of the combined treatment of strong reduction treatment and bionic transpiration constructed by the present invention. The strong reduction treatment system of contaminated soil includes a gentle slope one-step terrace 15 transformed from a water landscape slope. The upper edge of the gentle slope one-step terrace 15 is adjacent to the drainage ditch 12, and the drainage ditch 12 is filled with montmorillonite or uncontaminated guest soil 13.

[0083] The first-level terrace 15 of the gentle slope is provided with drainage ditches 12 at several set levels along the slope surface, and earth ridges 18 are respectively provided on both sides of the drainage ditches 12. Between the earth ridge 18 at the lower edge of the drainage ditch 12 constructed at each level and the earth ridge 18 at the upper edge of the drainage ditch 12 constructed at the next level, an earth pit 19 is dug between the earth ridges 18 at the lower edge and the earth ridges 18 at the upper edge of the drainage ditch 12 constructed at the next level. The pits 19 between ridges and the ridges 18 on both sides are paved with lower soil impermeable membranes 17, and then the contaminated soil 20 (i.e. the excavated soil) is backfilled on the lower soil impermeable membrane 17, the land is leveled, and easily degradable organic materials (crop straw, organic fertilizers that have been fermented to a certain extent, or one or more green manures) are added and mixed, and then flooded 22 is covered to form a soil-water interface 21, and finally an upper covering film 16 for soil strong reduction treatment is covered above the unit formed by each pit 19 between ridges and the ridges 18 on both sides to form a soil strong reduction treatment system.

[0084] The bionic transpiration system is located in the strong reduction treatment and bionic transpiration combined treatment implementation area 4, and is set above the strong reduction treatment system of contaminated soil, such as Figure 4 , Figure 5As shown, the bionic tree is composed of bionic leaf blades 23, the connecting parts 24 between the bionic leaf blades and the bionic tree rhizomes, and the bionic tree rhizomes 25. The bionic leaf blades 23 are composed of the bionic phloem 26 of the bionic leaf blades, the bionic xylem 27 of the bionic leaf blades, the bionic xylem hard shell 31 of the bionic leaf blades, and the bionic phloem hard shell 33 of the bionic leaf blades; the bionic tree rhizomes are composed of the bionic phloem 28 of the bionic tree rhizomes, the bionic xylem 29 of the bionic tree rhizomes, the bionic xylem hard shell 30 of the bionic tree rhizomes, and the bionic phloem hard shell 32 of the bionic tree rhizomes. The bionic xylem of the bionic tree is used to transport water upward, and is composed of the bionic xylem 29 of the bionic tree rhizome directly connected with the bionic xylem 27 of the bionic tree leaf; the bionic phloem of the bionic tree is used to prevent the formation of xylem embolism, and is composed of the bionic phloem 28 of the bionic tree rhizome directly connected with the bionic phloem 26 of the bionic tree leaf.

[0085] like Figure 5 , Figure 6 As shown, the bionic xylem 27 of the bionic leaf is arranged above the space surrounded by the edge of the bionic phloem 26 of the bionic leaf; a hole is provided in the center of the bionic phloem 26 of the bionic leaf, and the bionic xylem 29 of the bionic tree rhizome passes through the bionic phloem 26 of the bionic leaf through the hole and is directly connected to the bionic xylem 27 of the bionic leaf.

[0086] The diameter of the bionic tree leaf 23 is 20-40cm, the diameter of the bionic tree rhizome 25 is 3-8cm, and the height of the bionic tree rhizome 25 is 20-40cm; the bionic xylem hard shell 31 of the bionic tree leaf, the bionic phloem hard shell 33 of the bionic tree leaf, the bionic xylem hard shell 30 of the bionic tree rhizome, and the bionic phloem hard shell 32 of the bionic tree rhizome are all made of plastic, divided into bionic xylem space and bionic phloem space, which are filled with bionic xylem and bionic phloem materials respectively; the bionic xylem and bionic phloem materials can be the same or different, such as filter paper, gauze, etc., with capillary pores, and can produce capillary action. A scaled float 34 indicating water level is inserted into the upper opening of the bionic phloem 26 of the bionic tree leaf. The scaled float 34 indicating water level is made of foam plastic and is spherical with a diameter of 1 cm. The scaled float 34 indicating water level is connected to a wooden pole with a diameter of 0.5 cm. The wooden pole has scales on it, which can show the upper edge of the water level of the bionic phloem 26 of the bionic tree leaf. On one side of the bionic xylem hard shell 30 of the bionic tree rhizome, a water inlet is set every 5-10 cm to allow soil solution to enter the bionic xylem 29 of the bionic tree rhizome; the bionic xylem 27 of the bionic tree leaf and the bionic xylem hard shell 31 of the bionic tree leaf are opened upward to the air for transpiration, and at the same time, the bionic phloem 26 of the bionic tree leaf and the bionic phloem hard shell 33 of the bionic tree leaf are set with a position where water can be added from the outside.

[0087] Between the bionic xylem 27 of the bionic tree leaf and the bionic phloem 26 of the bionic tree leaf, a series of connection parts 35 between the bionic xylem and the bionic phloem of the bionic tree leaf are arranged every 5-10 cm along the vertical direction; between the bionic xylem 29 of the bionic tree rhizome and the bionic phloem 26 of the bionic tree leaf, a series of connection parts 36 between the bionic xylem and the bionic phloem of the bionic tree rhizome are arranged every 5-10 cm along the horizontal direction.

[0088] The connection part 35 between the bionic xylem and the bionic phloem of the bionic tree leaf, and the connection part 36 between the bionic xylem and the bionic phloem of the bionic tree rhizome are both tubular connections with a length of 0.5 cm and a diameter of 0.5 cm. Figure 7 As shown, a one-way valve 38 is provided in the tubular connection, and the one-way valve 38 is fixed and controlled by a hinge 39 so that the opening angle of the one-way valve 38 is less than 30°. The one-way valve 38 is opened when the bionic xylem 29 of the bionic tree root cannot effectively obtain water from the soil and the water pressure is too high. At this time, water flows from the bionic phloem to the bionic xylem to replenish water and prevent the formation of bionic xylem embolism.

[0089] The bionic tree leaf 23 undergoes bionic transpiration under light conditions, and the water loss pulls the soil solution 37 into the bionic xylem 29 of the bionic tree rhizome, and is transported upward from the bionic tree rhizome 25 along the bionic xylem 29 of the bionic tree rhizome to the bionic tree leaf 23. The bionic phloem is always filled with water and connected to the bionic xylem, thereby avoiding the embolism phenomenon that may be caused by excessive water loss in the bionic xylem during bionic transpiration. Under the bionic transpiration, the soil solution containing pollutants such as rare earth and ammonium nitrogen is continuously migrated out of the contaminated soil, into the bionic tree rhizome, and then to the bionic tree leaf.

[0090] Specifically, the bionic xylem 29 of the bionic tree rhizome is directly connected to the bionic xylem 27 of the bionic tree leaf. The bionic xylem 27 of the bionic tree leaf undergoes bionic transpiration under light conditions, and water is lost. The capillary force pulls the water in the bionic xylem 29 of the bionic tree rhizome into the bionic xylem 27 of the bionic tree leaf, and at the same time pulls the soil solution 37 into the bionic xylem 29 of the bionic tree rhizome. The bionic phloem 26 of the bionic tree leaf is always filled with water. Since the bionic phloem 28 of the bionic tree rhizome is directly connected to the bionic phloem 26 of the bionic tree leaf, the water injected into the bionic phloem 26 of the bionic tree leaf can enter the bionic phloem 28 of the bionic tree rhizome due to gravity. Through the connection part 35 of the bionic xylem and the bionic phloem of the bionic tree leaf, which is controlled by the one-way valve 38, when the bionic xylem 27 of the bionic tree leaf loses excessive water, the water retained in the bionic phloem 26 of the bionic tree leaf flows unidirectionally from the bionic phloem 26 of the bionic tree leaf to the bionic xylem 27 of the bionic tree leaf, thereby avoiding the embolism phenomenon that may be caused by excessive water loss of the bionic xylem 27 of the bionic tree leaf during bionic transpiration; the connection part 36 of the bionic xylem and the bionic phloem of the bionic tree rhizome is controlled by the one-way valve 38. When the bionic xylem 29 of the bionic tree rhizome loses excessive water, the water that enters the bionic phloem 28 of the bionic tree rhizome due to gravity flows unidirectionally to the bionic xylem 29 of the bionic tree rhizome, thereby avoiding the embolism phenomenon that may be caused by excessive water loss of the bionic xylem 29 of the bionic tree rhizome during bionic transpiration.

[0091] The bionic tree rhizome 25 is buried in the soil when the soil is backfilled to the soil pit 19 between the ridges, and then flooded and covered with film to form a strong reduction system. Figure 8 , Fig. 9 As shown, after the strong reduction system arranges the bionic tree rhizome 25 and the bionic tree leaf 23, a simple greenhouse 40 and a greenhouse covering film 41 are built thereon. After the bionic tree rhizome 25 is buried, its upper end passes through the planting hole 42 on the upper covering film 16. The hole diameter of the planting hole 42 is 5-10 cm, and the hole center spacing is 30-50 cm. They are arranged on the upper covering film 16 at equal distances. After the upper end of the bionic tree rhizome 25 passes through the upper covering film 16, the gap between the planting hole 42 and the bionic tree rhizome 25 is sealed with a sealing tape 43 to prevent gas from escaping from under the covering film.

[0092] The combined application of strong reduction treatment and bionic transpiration technology and the valuable material recovery system include: a simple greenhouse 40 with fresh air exchange windows and a greenhouse film 41 are set up above the strong reduction treated soil and the bionic tree. Fig.10As shown, the fresh air exchange window includes a ventilation system 44, an exhaust system 45, an intake system 46, condensed water 47 and a sensible heat exchange system 48. The sensible heat exchange system 48 heats up the gas entering the simple greenhouse 40, and recovers the condensed water 47 in the exhaust gas of the simple greenhouse 40 to a high-level water tank 49. The water in the high-level water tank 49 is regularly made into a 10-30mM EDTA solution 50, which is used to rinse the rare earth and ammonium nitrogen in the bionic leaf 23, and then recovered through the concentrated solution recovery system 52 after passing through the water pipe 51.

[0093] After the treatment of the contaminated soil excavated from the pits between ridges of the water landscape slope in the rare earth mining area is completed, the above-mentioned recyclable barrier system is maintained; the simple greenhouse 40, the upper covering film 16 and the lower soil anti-seepage film 17 are removed, and the treated soil in the original pits between ridges 19 is piled from the upper and lower edges of the horizontal height of the original pits between ridges to the midline of the horizontal height to form a new soil ridge; the untreated soil of the original soil ridge of the water landscape slope in the rare earth mining area is excavated to form a new pit between ridges; in the new pit between ridges, the soil is treated by the same strong reduction and bionic transpiration scheme.

[0094] Example 2

[0095] like Figure 1-10 Based on the treatment system of the combined application of strong reduction treatment and bionic transpiration technology for the contaminated soil on the water landscape slope of the weathering crust leaching type rare earth mining area in Example 1, a treatment method of the combined application of strong reduction treatment and bionic transpiration technology for the contaminated soil on the water landscape slope of the weathering crust leaching type rare earth mining area is provided, comprising the following steps:

[0096] S1. Construct a recoverable barrier system for pollutants in the slope rainfall runoff of the water landscape slope soil in the weathering crust leaching type rare earth mining area.

[0097] (1) A non-ridged earth pit of a certain depth is dug in the left and right directions at a set horizontal height to serve as the boundary between the upstream polluted slope of the slope runoff and the downstream slope to be treated; the non-ridged earth pit is dug in the left and right directions along the contour line, with a rectangular cross-section, a depth of 0.75-1.5m, and a width of 2.1-2.9m.

[0098] (2) The ridgeless earth pit is connected to the upstream slope of the slope runoff. Several layers of adsorption bags 10 filled with anion exchange resin and adsorption bags 11 filled with cation exchange resin are stacked in order in the ridgeless earth pit. The stacking width of the adsorption bags 10 filled with anion exchange resin and the adsorption bags 11 filled with cation exchange resin is 1.6-2.4m. The top plane of the adsorption bag stacking tail is 0.25-0.5m higher than the top plane of the adsorption bag stacking head to control the flow rate of water in the up and down directions. The head of the adsorption bag 10 filled with anion exchange resin is connected to the upstream polluted slope of the slope runoff. There is a gap of about 0.5-0.8m between the tail of the adsorption bag 11 filled with cation exchange resin in the ridgeless earth pit and the downstream slope to be treated. A certain amount of montmorillonite or uncontaminated guest soil is filled to form a drainage ditch 12 with a depth of about 0.2-0.4m, which is connected to the downstream slope to be treated as a whole.

[0099] One part of the adsorption bag is an adsorption bag 10 filled with anion exchange resin, which can block sulfate, nitrate and the like in the slope rainfall runoff; the other part is an adsorption bag 11 filled with cation exchange resin, which can block cations such as rare earth, heavy metals, and ammonium in the slope rainfall runoff. The adsorption bags are stacked in order, and when the slope rainfall runoff (i.e., the runoff 9 flowing down from the top of the mine mountain) flows through the adsorption bags, it first contacts only the adsorption bag 10 filled with anion exchange resin to exchange anions; after the slope rainfall runoff flows through the adsorption bag filled with anion exchange resin, it contacts the adsorption bag 11 filled with cation exchange resin to exchange cations.

[0100] (3) In the recoverable barrier system for pollutants in slope rainfall runoff, ionic pollutants in slope rainfall runoff infiltrate the adsorption bag, and are adsorbed on the anion or cation exchange resin in the adsorption bag through the anion exchange adsorption and cation adsorption processes, and then desorbed to recover rare earth, nitrogen, and sulfur, and regenerate the ion exchange resin. The particulate pollutants in the slope rainfall runoff are deposited in the left and right ditches in the middle of the upper part of the adsorption bag stack parallel to the slope in the horizontal direction. After collecting and storing a sufficient amount of sediment, they are placed in the treatment system of the present invention that combines strong reduction treatment and bionic transpiration technology, and treated according to the method of the present invention.

[0101] S2. Construct a strong reduction treatment system for contaminated soil on water landscape slopes in weathering crust leaching type rare earth mining areas, transform the water landscape slopes in the rare earth mining areas to be treated into gentle slope terraces, and perform strong reduction treatment on the soil.

[0102] (4) At the soil of the water landscape slope to be treated that is adjacent to the drainage ditch 12 at the lower edge of the pollutant recoverable barrier zone, the soil is excavated at the same horizontal height to form a soil ridge 18; then, at several set horizontal heights along the slope direction of the water landscape slope, a drainage ditch 12 with a width of about 0.5m and a depth of 0.2-0.4m is excavated in the left and right directions, and soil ridges 18 are respectively built on both sides of the drainage ditch 12; between the soil ridge 18 at the lower edge of the drainage ditch 12 at each horizontal height and the soil ridge 18 at the upper edge of the drainage ditch 12 at the next horizontal height, a soil pit 19 of a certain depth is excavated, and a bottom-laying soil impermeable membrane 17 is laid in the soil pit 19 between the two soil ridges 18 after excavation, and then the contaminated soil 20 is backfilled into the bottom-laying soil impermeable membrane 17 to level the land.

[0103] The depth of the pit 19 between the ridges is 0.75-1.5m, the width is 1.3-2.6m, and the height of the ridge 18 is 0.4-0.6m, and the width is 0.3-0.4m. After the strong soil reduction system is constructed, the strong reduction treatment is carried out for 2-4 weeks to effectively reduce the sulfate and nitrate pollution levels in the water landscape polluted soil of the weathering crust leaching type rare earth mining area, and effectively reduce the toxicity of hexavalent chromium in the soil; the heavy metals in the polluted soil are effectively passivated, and their biological effectiveness is reduced; the tetravalent cerium in the soil is converted into trivalent cerium that is easy to migrate. Effectively reduce soil acidity, soil aluminum ion concentration, and improve soil physical and chemical properties.

[0104] (5) Add an appropriate amount of easily degradable organic materials to the leveled contaminated soil and mix well, then perform flooding 22 to form a soil-water interface 21, and finally cover with an upper film 16 for soil strong reduction treatment to form a soil strong reduction treatment system.

[0105] S3. Construct a bionic transpiration system, and plant bionic trees that can perform bionic transpiration in the contaminated soil treated with the above-mentioned strong reduction treatment.

[0106] (6) The bionic xylem 29 of the bionic tree rhizome and the bionic xylem hard shell 30 of the bionic tree rhizome, the bionic phloem 28 of the bionic tree rhizome and the bionic phloem hard shell 32 of the bionic tree rhizome are assembled into the bionic tree rhizome 25; the bionic xylem 27 of the bionic tree leaf and the bionic xylem hard shell 31 of the bionic tree leaf, the bionic phloem 26 of the bionic tree leaf and the bionic phloem hard shell 33 of the bionic tree leaf are assembled into the bionic leaf leaf 23. A hole is provided in the center of the bionic phloem 26 of the bionic tree leaf, and the bionic xylem 29 of the bionic tree rhizome passes through the bionic phloem 26 of the bionic tree leaf through the hole to directly connect with the bionic xylem 27 of the bionic tree leaf. A connection part is provided between the bionic phloem and the bionic xylem. A connection part 36 between the bionic xylem of the bionic tree rhizome and the bionic phloem is provided in the horizontal direction of the bionic tree rhizome 25, and a connection part 35 between the bionic xylem of the bionic tree leaf and the bionic phloem is provided in the vertical direction of the bionic tree leaf 23 to maintain the connection. Both connection parts are provided with a one-way valve 38 controlled by a hinge 39, so that when the bionic xylem lacks water, the bionic phloem can be used to replenish water to avoid embolism of the bionic xylem. A scaled float 34 indicating the water level is inserted into the upper opening of the bionic phloem 26 of the bionic tree leaf to display the upper edge of the water level of the bionic phloem.

[0107] (7) When the backfilled contaminated soil 20 is backfilled onto the bottom soil impermeable membrane 17 of the inter-ridge pit 19, the bionic tree rhizome 25 is buried in the soil, the organic materials are mixed, and then flooding and film covering are performed. The upper end of the bionic tree rhizome 25 passes through the planting hole 42 on the upper film 16; then the gap between the upper film 16 and the bionic tree rhizome 25 is sealed with a sealing tape 43 to prevent gas from escaping from under the upper film 16. Planting holes 42 for planting bionic trees are arranged at equal distances on the upper film 16, with a hole diameter of 5-10 cm and a center distance of 30-50 cm.

[0108] (8) Connect the bionic leaf blades to the bionic root of the bionic tree.

[0109] The bionic tree structure includes a bionic tree leaf 23 and a bionic tree rhizome 25. The bionic xylem 27 of the bionic tree leaf undergoes bionic transpiration and water loss under light conditions, pulling the aqueous solution in the bionic xylem 29 of the bionic tree rhizome up to the bionic tree leaf 23 for replenishment, thereby pulling the soil solution into the bionic xylem 29 of the bionic tree rhizome. The bionic phloem 26 of the bionic tree leaf and the bionic phloem 28 of the bionic tree rhizome are a whole, always keeping full of water, and maintaining communication with the bionic xylem 27 of the bionic tree leaf, and the bionic phloem 28 of the bionic tree rhizome also maintains communication with the bionic xylem 29 of the bionic tree rhizome; water can be replenished from the bionic phloem to the bionic xylem through the one-way valve 38, thereby avoiding the embolism of the bionic xylem and the bionic phloem during the bionic transpiration. The soil solution containing pollutants such as rare earth and ammonium nitrogen is continuously migrated out of the polluted soil under the bionic transpiration of the bionic tree, enters the bionic xylem 29 of the bionic tree rhizome, and then to the bionic xylem 27 of the bionic tree leaves.

[0110] S4. Implement the combined application of strong reduction treatment and bionic transpiration technology and recovery of valuable substances. Build a simple greenhouse equipped with fresh air exchange windows above the strongly reduced soil and bionic trees, implement soil strong reduction and bionic transpiration, and recover rare earth and ammonium nitrogen from bionic tree leaves.

[0111] (9) A simple greenhouse 40 with a fresh air exchange window is arranged above the strongly reduced soil and the bionic tree. The fresh air exchange window is composed of a ventilation system 44, an exhaust system 45 and an intake system 46. The fresh air exchange window heats the gas entering the simple greenhouse 40 through a sensible heat exchange system 48, and recovers condensed water 47 in the exhaust gas of the greenhouse to a high-level water tank 49.

[0112] (10) The water in the high-level water tank 49 is regularly made into an EDTA solution 50 of a certain concentration to wash the rare earth and ammonium nitrogen in the bionic leaf leaves 23 and recover them.

[0113] (11) After the treatment of the backfill contaminated soil 20 excavated from the pits 19 between ridges of the water landscape slope in the rare earth mining area is completed, the above-mentioned recyclable barrier system is maintained; the simple greenhouse 40, the upper covering film 16, and the lower soil waterproofing film 17 are removed, and the treated backfill contaminated soil 20 in the original pits 19 between ridges is piled from the upper and lower edges of the horizontal height of the original pits between ridges to the midline of the horizontal height to form a new soil ridge; the untreated soil of the original ridge 18 of the water landscape slope in the rare earth mining area is excavated to form a new pit between ridges; in the new pit between ridges, the soil is treated by the same strong reduction and bionic transpiration scheme.

[0114] After 6 months of treatment by the treatment method of the present invention, the physical and chemical properties of the polluted soil on the water landscape slope of the weathering crust leaching type rare earth mining area changed as follows: the soil pH value increased from 4.54-5.09 to 5.51-6.86, and the organic matter content increased from 0.32-0.44% to 1.66-1.91%. The soil ammonium nitrogen decreased from 51.3-167.4 mg / kg to 10.6-25.2 mg / kg, the nitrate nitrogen decreased from 20.1-40.4 mg / kg to <10 mg / kg, and the sulfate ion decreased from 20.2-105.8 mg / kg to 9.5-14.3 mg / kg. The rare earth element content decreased from 699.6-942.4 mg / kg to 298.4-439.1 mg / kg. The content of biologically effective heavy metals was determined by leaching using the soil environmental quality standard method: pure water was adjusted to pH 5.8-6.3 with hydrochloric acid as the leaching agent, soil sample (g) and leaching agent (mL) were mixed at a solid-liquid ratio of 1:10, and the mixed solution was above 500mL; the sample bottle was placed on an oscillator at room temperature 20°C and pressure 101.325kPa, and oscillated continuously for 6 hours at 200 times / min and an amplitude of 4-5cm to leach the pollutants. The Pb content in the soil elution solution increased from 1.06 to 2.04. -6.13mg / L to <0.01mg / L, Cd content from 0.02-0.09mg / L to <0.01mg / L, As content from 0.44-1.21mg / L to <0.01mg / L; soil hexavalent chromium content (determined by diphenylcarbazide method) from 141.8-1027.2mg / kg to <0.5mg / kg, heavy metal dissolution in the soil after treatment is low; the above shows that soil pollutants will not cause secondary pollution to water bodies. At the same time, the recovery rate of soil rare earth elements is 83.3-87.6%, and the recovery rate of ammonium nitrogen is greater than 53.2-66.5%.

Claims

1. A method for treating soil contaminated by weathering crust leaching rare earth mining areas on water landscape slopes, characterized in that: The treatment method includes a recoverable barrier system for pollutants in slope rainfall runoff, a strong reduction treatment system for contaminated soil, a bionic transpiration system, a combined application of strong reduction treatment and bionic transpiration, and a valuable substance recovery system; The specific steps include: S1. Construct a recyclable barrier system for pollutants in slope rainfall runoff to block pollutants that are transferred into the runoff in water-soluble or particle form due to scouring of slope polluted soil; S2. Construct a strong reduction treatment system for contaminated soil, transform the water landscape slope in the rare earth mining area to be treated into gentle slope terraces, and carry out strong reduction treatment on the contaminated soil; S3. Constructing a bionic transpiration system, implanting a bionic tree for bionic transpiration in the contaminated soil treated with strong reduction in step S2; S4. Build a greenhouse above the strongly reduced contaminated soil and the bionic tree, implement the combined application of soil strong reduction and bionic transpiration and recovery of valuable substances, and recover rare earth and ammonium nitrogen from the leaves of the bionic tree.

2. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 1, characterized in that: The method for constructing a recyclable barrier system for pollutants in slope rainfall runoff in step S1 is: (1) digging a non-ridged soil pit in the left and right directions at the upper edge of the horizontal height of the water landscape slope of the weathered crust eluvial rare earth mining area to be treated, as a boundary between the upstream polluted slope of the slope rainfall runoff and the downstream slope to be treated; the non-ridged soil pit is dug in the left and right directions along the contour line; (2) The adsorption bags are piled on one side of the soil pit without ridges connected to the polluted slope upstream of the slope runoff. The middle part of the upper part of the adsorption bag pile leaves a left-right ditch parallel to the slope in the horizontal direction. The top plane of the tail of the adsorption bag pile is higher than the top plane of the head of the adsorption bag pile. The head of the adsorption bag pile is connected to the polluted slope upstream of the slope runoff. (3) There is a gap between the tail of the adsorption bag stack in the pit without ridge and the downstream slope to be treated. Montmorillonite or uncontaminated guest soil is filled in to form a recoverable barrier system for pollutants in the slope rainfall runoff. The lower edge of the drainage ditch is connected to the downstream slope to be treated.

3. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 2 is characterized in that: The adsorption bags in step (2) are adsorption bags filled with anion exchange resin and adsorption bags filled with cation exchange resin. The adsorption bags are stacked in sequence so that the slope rainfall runoff flows through the adsorption bags and first contacts only the adsorption bags filled with anion exchange resin and then contacts the adsorption bags filled with cation exchange resin.

4. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 2, characterized in that: The method for constructing a strong reduction treatment system for contaminated soil in step S2 is: (4) At the lower edge of the left-right drainage ditch at the lower edge of the recoverable barrier system for pollutants in the slope rainfall runoff, dig and build ridges at the contaminated soil on the slope of the downstream slope to be treated that borders the drainage ditch; then, dig a number of left-right drainage ditches along the slope of the downstream slope to be treated, fill the drainage ditches with montmorillonite or uncontaminated guest soil, and then build ridges at the contaminated soil on the slope of the downstream slope to be treated that borders both sides of the drainage ditch; dig inter-ridge pits between the lower edge ridge of each drainage ditch and the upper edge ridge of the next drainage ditch, and lay an underlay soil impermeable membrane on top of each inter-ridge pit and the unit formed by the ridges on both sides, and then backfill the contaminated soil in the excavated inter-ridge pits onto the underlay soil impermeable membrane above the inter-ridge pits, and level the land; (5) Add easily degradable organic materials to the leveled backfill contaminated soil and mix well, flood it with water, and lay a covering film on top of the unit formed by the earth pit between each ridge and the earth ridges on both sides to construct a strong reduction treatment system for the backfill contaminated soil, and then carry out strong reduction treatment.

5. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 4 is characterized in that: The drainage ditch in step (4) is 0.4-0.6m wide and 0.2-0.4m deep; the pit between ridges is 0.75-1.5m deep and 1.3-2.6m wide; The height of the earth ridge is 0.4-0.6m, and the width is 0.3-0.4m. The cycle of the strong reduction treatment in step (5) is 2-4 weeks. Small holes for planting bionic trees are arranged at equal distances on the upper film of the earth ridge and the earth pit between the ridges, with a hole diameter of 5-10cm and a center spacing of 30-50cm.

6. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 4, characterized in that: The method of implanting a bionic tree for performing bionic transpiration in step S3 comprises the following steps: (6) Assemble the bionic xylem and its hard shell of the bionic tree rhizome, and the bionic phloem and its hard shell of the bionic tree rhizome into a bionic tree rhizome; assemble the bionic xylem and its hard shell of the bionic tree leaf, and the bionic phloem and its hard shell of the bionic tree leaf into a bionic leaf; set a horizontal connection part on the bionic tree rhizome, and set a vertical connection part on the bionic tree leaf to keep them connected; set a one-way valve controlled by a hinge at the connection part, and when each bionic xylem is short of water, the bionic phloem will replenish water to avoid embolism of the bionic xylem; insert a scaled float indicating the water level into the upper opening of the bionic phloem of the bionic leaf to display the water level of the upper edge of the bionic phloem; (7) When the contaminated soil is backfilled onto the bottom soil impermeable membrane of the pit between ridges in step (4) of constructing the strong reduction treatment system for contaminated soil, the assembled bionic tree rhizomes are buried in the soil, and then flooded and covered with an upper membrane, and the upper end of the bionic tree rhizomes passes through the planting holes set on the upper membrane; then the gap between the upper membrane and the bionic tree rhizomes is closed to prevent gas from escaping; (8) Connect the assembled bionic leaf blades to the assembled bionic tree roots.

7. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 6, characterized in that: The bionic xylem of the bionic tree leaf is arranged above the space surrounded by the edge of the bionic phloem of the bionic tree leaf; a hole is arranged in the center of the bionic phloem of the bionic tree leaf, and the bionic xylem of the bionic tree rhizome passes through the bionic phloem of the bionic tree leaf through the hole and is directly connected with the bionic xylem of the bionic tree leaf; the diameter of the bionic tree leaf is 20-40cm, the diameter of the bionic tree rhizome is 3-8cm, and the height of the bionic tree rhizome is 20-40cm; the hard shells of the bionic tree leaf and the bionic tree rhizome are both made of plastic, and are divided into a bionic xylem space and a bionic phloem space; On the outer shell of one side of the bionic xylem of the bionic tree rhizome, a water inlet is arranged every 5-10 cm to allow the soil solution to enter the bionic xylem of the bionic tree rhizome; the bionic xylem of the bionic tree leaf is opened upward to the air to perform transpiration; A series of connection parts are arranged between the bionic xylem and the bionic phloem of the bionic tree leaf at intervals of 5-10 cm along the vertical direction; a series of connection parts are arranged between the bionic xylem and the bionic phloem of the bionic tree root at intervals of 5-10 cm along the horizontal direction; The connecting parts of the bionic xylem and the bionic phloem of the bionic tree leaf, as well as the connecting parts of the bionic xylem and the bionic phloem of the bionic tree rhizome, are all tubular connections with a length of 0.5-1 cm and a diameter of 0.5-1 cm. A one-way valve is provided in the tubular connection, and the one-way valve is fixed and controlled by a hinge. The one-way valve opens when the bionic xylem cannot effectively obtain water from the soil and the water pressure is too high. At this time, water flows from the bionic phloem to the bionic xylem to replenish water and prevent the formation of bionic xylem embolism.

8. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 1, characterized in that: In step S4, the greenhouse is a simple greenhouse with fresh air exchange windows; the method of implementing the combined application of soil strong reduction and bionic transpiration and valuable material recovery, and recovering rare earth and ammonium nitrogen from bionic tree leaves, comprises the following steps: (9) A simple greenhouse with fresh air exchange windows is built above the strongly reduced contaminated soil and bionic trees. The fresh air exchange windows heat the gas entering the simple greenhouse through a sensible heat exchange system and recover the condensed water in the exhaust gas of the simple greenhouse to a high-level water tank; (10) Rare earth ions and ammonium nitrogen in the soil solution enter the bionic tree leaves from the roots and stems, and are concentrated as the water evaporates; the rare earth ions and ammonium nitrogen in the bionic tree leaves are eluted with EDTA solution in a high-level water tank and recovered; (11) After the treatment of the contaminated soil excavated from the pits between ridges in the water landscape slope of the weathering crust leaching type rare earth mining area is completed, the recyclable barrier system shall be maintained; the simple greenhouse shall be removed, the upper film shall be covered, and the anti-seepage film shall be laid below, and the treated soil in the original pits between ridges shall be piled from the upper and lower edges of the horizontal height of the original pits between ridges to the midline of the horizontal height to form a new ridge; The untreated soil of the original earth ridges of the water landscape slope in the rare earth mining area is dug out to form new pits between ridges; in the new pits between ridges, the same strong reduction and bionic transpiration methods are continued to be used to treat the soil.

9. The method for treating soil contaminated by weathering crust leaching type rare earth mining area water landscape slope according to claim 1, characterized in that: The water landscape slope in the weathering crust elution type rare earth mining area is a water landscape slope with a slope of less than 25°, and the gentle slope terrace is a gentle slope terrace with a slope of less than 10°.

10. An application of the method for treating soil contaminated by weathering crust elution type rare earth mining area water landscape slope land according to claim 1 in treating and regenerating soil contaminated by weathering crust elution type rare earth mining area water landscape slope land.

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