A method for remediating heavy metal contaminated cultivated land

Abstract

The present invention provides a method for repairing heavy metal contaminated cultivated land, comprising: digging on the soil surface to form planting pits; laying a first barrier cloth on the bottom wall of the planting pits; laying planting soil on the upper surface of the first barrier cloth, and planting enrichment crops on the planting soil so that the root tips of the enrichment crops are immersed in the planting soil; laying a second barrier cloth on the upper surface of the planting soil, and a plurality of avoidance holes are formed in the second barrier cloth, and the stems of the enrichment crops pass through the avoidance holes; laying a second metal ion curing agent on the upper surface of the second barrier cloth first, and then laying rotation planting soil, and the leaves of the enrichment crops are located above the rotation planting soil. The first barrier cloth and the second barrier cloth play a role in blocking the transfer of heavy metal ions, so that the content of heavy metal ions in the planting soil is relatively fixed, and the root tips of the enrichment crops can fully absorb the heavy metal ions in the planting soil at a relatively close distance to them, playing a role in absorbing and fixing heavy metal ions.

Description

Technical Field

[0001] The present invention relates to the field of soil heavy metal treatment, and particularly to a method for repairing heavy metal-polluted cultivated land. Background Art

[0002] Heavy metals in cultivated land will be gradually absorbed as crops grow, and finally remain in the crops for subsequent processing into food. In some cultivated lands with relatively high heavy metal content, the crops produced there often pose significant food safety hazards as raw materials for food production.

[0003] In view of this situation, in some existing technologies, oil-producing crops such as soybeans (subsequently used as raw materials for industrial oil) are planted as plants for enriching heavy metal ions, so as to improve the heavy metal ion content in cultivated land. However, the roots of such crops are relatively deep, and their absorption of heavy metals mainly depends on the root tips. Therefore, only the deeper soil can be improved. The distance between the heavy metals in the near-surface soil and the root tips is relatively far, making it difficult to be absorbed, resulting in a still relatively high content. And if shallow-rooted edible crops such as wheat are planted, it will still cause a large amount of heavy metals to be absorbed by the wheat. Summary of the Invention

[0004] Based on this, in view of the problem that enrichment crops cannot effectively remove heavy metal ions in the shallow soil layer, it is necessary to provide a method for repairing heavy metal-polluted cultivated land.

[0005] The technical solution provided by the present invention is as follows:

[0006] To solve the above problems, the present invention provides a method for repairing heavy metal-polluted cultivated land.

[0007] A method for repairing heavy metal-polluted cultivated land includes:

[0008] Digging open the soil surface to form planting pits;

[0009] Laying a first barrier cloth on the bottom wall of the planting pit;

[0010] Laying planting soil on the upper surface of the first barrier cloth, and planting enrichment crops on the planting soil so that the root tips of the enrichment crops are immersed in the planting soil;

[0011] Laying a second barrier cloth on the upper surface of the planting soil. A number of avoidance holes are opened in the second barrier cloth, and the stems of the enrichment crops pass through the avoidance holes;

[0012] Laying a second heavy metal ion curing agent on the upper surface of the second barrier cloth first, and then laying rotation planting soil. The leaves of the enrichment crops are located above the rotation planting soil.

[0013] A first heavy metal ion curing agent is provided between the first barrier cloth and the planting soil in the present invention.

[0014] When harvesting the enriched crops of the present invention, the positions of the planting soil and the rotation planting soil are exchanged, and new enriched crops are replanted so that the root systems of the enriched crops are located in the rotation planting soil.

[0015] When harvesting the enriched crops of the present invention, first remove the rotation planting soil to expose the edge of the second barrier cloth, and then lift the entire second barrier cloth to recover and process the second metal ion curing agent.

[0016] After the present invention lifts the entire second barrier cloth, only remove the planting soil, lay the rotation planting soil on the first metal ion curing agent, and then successively replant enriched crops on the rotation planting soil, lay the second barrier cloth on the rotation planting soil, lay a new second metal ion curing agent on the second barrier cloth, and lay the planting soil on the second metal ion curing agent.

[0017] Before laying the rotation planting soil on the first metal ion curing agent, the present invention first lays a new layer of the first metal ion curing agent on the first barrier cloth.

[0018] The distance between the first barrier cloth and the second barrier cloth of the present invention is not greater than 20 cm.

[0019] The first barrier cloth of the present invention extends along the side wall of the planting pit to the second barrier cloth.

[0020] At least part of the second metal ion curing agent of the present invention is located at the edge of the avoidance hole.

[0021] The second metal ion curing agent of the present invention at least contains plant ash and calcium carbonate.

[0022] The beneficial effects of the present invention are as follows:

[0023] The first barrier cloth and the second barrier cloth play a role in blocking the transfer of heavy metal ions, making the heavy metal ion content in the planting soil relatively fixed. The root tips of the enriched crops can fully absorb the heavy metal ions in the planting soil that is relatively close to them, achieving the absorption and fixation of heavy metal ions. Subsequently, the planting soil from which heavy metal ions are removed can be exchanged with the rotation planting soil, so that the planting soil can be used for planting shallow-rooted crops. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is the first structural state corresponding to the heavy metal contaminated cultivated land remediation method in Embodiment 1 of the present invention;

[0025] Figure 2 It is the second structural state corresponding to the heavy metal contaminated cultivated land remediation method in Embodiment 1 of the present invention;

[0026] Figure 3It is the structural state three corresponding to the heavy metal contaminated cultivated land restoration method in Embodiment 1 of the present invention;

[0027] Figure 4 It is the structural state four corresponding to the heavy metal contaminated cultivated land restoration method in Embodiment 1 of the present invention;

[0028] Figure 5 It is the structural state five corresponding to the heavy metal contaminated cultivated land restoration method in Embodiment 1 of the present invention.

[0029] 1. Planting pit; 2. First barrier cloth; 3. First metal ion curing agent; 4. Enrichment crops; 5. Planting soil; 6. Second barrier cloth; 61. Avoidance hole; 7. Second metal ion curing agent; 8. Rotational planting soil. Detailed implementation manners

[0030] In order to make the above objects, features and advantages of the present invention more obvious and understandable, the following detailed description of the specific implementation manners of the present invention will be given with reference to the accompanying drawings. Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0031] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation of the present invention.

[0032] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "a plurality" means at least two, such as two, three, etc., unless otherwise specifically defined.

[0033] In the present invention, unless otherwise clearly defined and limited, terms such as "installed", "connected", "joined", "fixed", etc. shall be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components, unless otherwise clearly defined. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0034] In the present invention, unless otherwise clearly defined and limited, the first feature being "on" or "under" the second feature may be that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may be that the first feature is directly above or obliquely above the second feature, or merely indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or merely indicates that the first feature has a lower horizontal height than the second feature.

[0035] It should be noted that when an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are only for the purpose of illustration and do not represent the only implementation.

[0036] Embodiment:

[0037] This embodiment provides a method for repairing heavy metal contaminated cultivated land, including:

[0038] Step S1: Refer to Figure 1 , dig at the soil surface to form a planting pit 1. The shape and size of the planting pit 1 can be selected according to the specific types, planting densities, etc. of the enrichment crops 4 to be planted subsequently. For example, in this embodiment, it is generally a rectangular pit, and the enrichment crop 4 can be soybeans. The soil originally filled in the planting pit 1, a part of which is excavated in this step, is used as planting soil 5, and the other part is used as rotation planting soil 8 for later use. It can be understood that both the planting soil 5 and the rotation planting soil 8 contain heavy metal ions.

[0039] Step S2: Refer to Figure 2, on the basis of step S1, first, a first barrier cloth 2 is laid on the bottom wall of the planting pit 1, then a layer of first metal ion curing agent 3 is sprinkled on the upper surface of the first barrier cloth 2, and then the planting soil 5 is laid on the upper surface of the first metal ion curing agent 3.

[0040] The first barrier cloth 2 can prevent the heavy metal ions in the soil below the planting pit 1 from further transferring into the planting soil 5. The first barrier cloth 2 is made of a common material that can block the passage of ions. The soil is a relatively complex chemical environment. Although the first barrier cloth 2 is generally made of corrosion-resistant materials, after long-term contact with the soil, some damage may still occur, resulting in a decrease in the barrier effect of the first barrier cloth 2 on the heavy metal ions in the soil below the planting pit 1.

[0041] When the first barrier cloth 2 is damaged, during the transfer of heavy metal ions in the soil below the planting pit 1 to the planting soil 5 through the damaged part of the first barrier cloth 2, they need to contact the first metal ion curing agent 3 first, so they will also be fixed at the first metal ion curing agent 3 and cannot reach the planting soil 5.

[0042] Preferably, the first metal ion curing agent 3 contains at least plant ash and calcium carbonate. After the heavy metal ions react with the plant ash in the first metal ion curing agent 3, they can agglomerate and form lumps with calcium carbonate as the core, so as to fill the damaged position of the first barrier cloth 2. Moreover, the heavy metal ions actually reacted by the first metal ion curing agent 3 come not only from the soil below the planting pit 1 but also from the planting soil 5. Therefore, the size of the lumps formed after the reaction of the first metal ion curing agent 3 with the heavy metal ions is often larger, and generally larger than the size of the damaged part on the first barrier cloth 2. After the first metal ion curing agent 3 reacts fully, when the planting soil 5 is removed and the first barrier cloth 2 is lifted as a whole, the lumps formed by the first metal ion curing agent 3 fill the damaged position of the first barrier cloth 2 and will not fall off from the damaged part. Thus, the heavy metal ions fixed by the first metal ion curing agent 3 on the first barrier cloth 2 can be recycled as a whole.

[0043] It can be understood that during the process of the first metal ion curing agent 3 gradually fixing the heavy metal ions, the heavy metal content and concentration inside it gradually increase, the lumps formed by it become denser, and the water absorption capacity becomes weaker. The transfer of heavy metal ions in the soil is generally carried by water. Therefore, as the amount of heavy metal ions fixed by the first metal ion curing agent 3 increases, it becomes more difficult for the heavy metal ions in the soil below the planting pit 1 to transfer to the first metal ion curing agent 3 through the damaged position of the first barrier cloth 2. Correspondingly, the blocking method of the first metal ion curing agent 3 for the transfer of heavy metal ions from the soil below the planting pit 1 to the planting soil 5 gradually changes from chemical blocking to physical blocking.

[0044] It should be noted that the first metal ion curing agent 3 and the first barrier cloth 2 not only block the transfer of heavy metal ions from the soil below the planting pit 1 into the planting soil 5, but also block the transfer of heavy metal ions from the planting soil 5 to the soil below the planting pit 1.

[0045] Step S3: Refer to Figure 3 , plant the enrichment crop 4 on the planting soil 5 so that the root tips of the enrichment crop 4 are immersed in the planting soil 5. Then, lay a second barrier cloth 6 on the upper surface of the planting soil 5. A number of avoidance holes 61 are formed in the second barrier cloth 6. During the laying process of the second barrier cloth 6, the stems of the enrichment crop 4 are avoided through the avoidance holes 61, and finally the stems of the enrichment crop 4 pass through the avoidance holes 61.

[0046] The function of the enrichment crop 4 is to absorb the heavy metal ions in the planting soil 5 during the growth process of the roots, so that the heavy metal ions in the planting soil 5 are transferred and fixed in the enrichment crop 4. As long as the enrichment crop 4 is harvested, the removal of heavy metal ions from the planting soil 5 can be achieved. The specific operations after the enrichment crop 4 is planted on the planting soil 5 will be further described in the subsequent steps of this embodiment.

[0047] Step S4: Refer to Figure 4 , first lay a second metal ion curing agent 7 on the upper surface of the second barrier cloth 6. The composition of the second metal ion curing agent 7 is exactly the same as that of the first metal ion curing agent 3. In some other embodiments, it can also be different, but the second metal ion curing agent 7 needs to contain at least plant ash and calcium carbonate. Then, lay the rotation planting soil 8 on the surface of the second metal ion curing agent 7, and the leaves of the enrichment crop 4 are located above the rotation planting soil 8. If the enrichment crop 4 is still relatively short when laying the rotation planting soil 8, the top of the enrichment crop 4 can also be immersed in the rotation planting soil 8, and the leaves will only emerge above the rotation planting soil 8 after the enrichment crop 4 grows for a period of time.

[0048] Fertilization and irrigation are carried out on the soil surface, so nutrients and water are first supplemented into the rotation planting soil 8. Due to the existence of the avoidance holes 61, the nutrients and water in the rotation planting soil 8, as well as the heavy metal ions inside it, will gradually transfer into the planting soil 5. Of course, since the second metal ion curing agent 7 is located on the upper surface of the second barrier cloth 6, most of the heavy metal ions at the bottom of the rotation planting soil 8 will be fixed by the second metal ion curing agent 7, and correspondingly, the amount of heavy metal ions that can transfer from the rotation planting soil 8 to the planting soil 5 through the avoidance holes 61 is less.

[0049] Of course, if the size of the avoidance hole 61 is relatively large, there will still be a part of heavy metal ions transferred from the rotation planting soil 8 to the planting soil 5. Therefore, the second metal ion curing agent 7 is at least partially located at the edge of the avoidance hole 61, and the part of the second metal ion curing agent 7 in the avoidance hole 61 can cover the planting soil 5 during the spreading process. Similar to the first metal ion curing agent 3, as the reaction of the second metal ion curing agent 7 proceeds, it gradually agglomerates, and the agglomeration gradually increases. It can not only adhere to the part of the second barrier cloth 6 at the edge of the avoidance hole 61, but also gradually fill the avoidance hole 61, thus achieving the effect of blocking heavy metal ions. Of course, it will also block the transfer process of nutrients from the rotation planting soil 8 to the planting soil 5. However, it should be noted that the gradual agglomeration process of the second metal ion curing agent 7 is carried out synchronously with the growth of the enrichment crop 4. As the enrichment crop 4 gradually grows, the amount of nutrients it needs gradually decreases. Therefore, the agglomeration process of the second metal ion curing agent 7 will not affect the normal growth of the enrichment crop 4.

[0050] In this embodiment, the first barrier cloth 2 extends along the side wall of the planting pit 1 to the second barrier cloth 6, and the edge of the second barrier cloth 6 extends along the side wall of the planting pit 1 to the opening of the planting pit 1. Thus, the planting soil 5 is enclosed between the first barrier cloth 2 and the second barrier cloth 6. And under the combined action of the first metal ion curing agent 3 and the second metal ion curing agent 7, in terms of heavy metal ions, the space between the first barrier cloth 2 and the second barrier cloth 6 can be approximately regarded as a closed space, that is, the amount of heavy metal ions in the planting soil 5 is generally a fixed value.

[0051] For the enrichment crop 4, its roots are relatively deep, and its water absorption mainly depends on the root tips. Therefore, the absorption of heavy metals mainly relies on the root tips. The root tips of the enrichment crop 4 are located in the planting soil 5. Therefore, the heavy metal ions in the planting soil 5 are mainly absorbed and fixed by the enrichment crop 4. At the same time, both the whole planting soil 5 and the root tips of the enrichment crop 4 are relatively close and generally at the same horizontal height. Therefore, the enrichment crop 4 can absorb the heavy metal ions in the planting soil 5 more fully, thereby greatly reducing the concentration of heavy metal ions in the planting soil 5.

[0052] Therefore, after the enrichment crop 4 matures, the heavy metal ions in the planting soil 5 are generally cleared (most are absorbed by the enrichment crop 4, and a small amount reacts with the first metal ion solidifying agent 3 to be fixed). The enrichment crop 4 absorbs less heavy metal ions in the rotation planting soil 8, so there are still a large number of heavy metal ions in the rotation planting soil 8. When harvesting the enrichment crop 4, first remove the rotation planting soil 8, so that the second barrier cloth 6 is exposed at the edge of the opening of the planting pit 1. After the enrichment crop 4 loses the fixing effect of the rotation planting soil 8, its fixing force is mainly provided by the interaction between the planting soil 5 and the root tips of the enrichment crop 4. Preferably, the distance between the first barrier cloth 2 and the second barrier cloth 6 is not greater than 20 cm, that is, the thickness of the planting soil 5 is about 20 cm. The fastening force of the planting soil 5 on the root tips of the enrichment crop 4 is weak, and the enrichment crop 4 can be directly pulled out from the avoidance hole 61. When the enrichment crop 4 is pulled out from the avoidance hole 61, its stem or root system will be separated from the second metal ion solidifying agent 7, resulting in the loosening of the mass formed by the second metal ion solidifying agent 7. Since the second metal ion solidifying agent 7 will adhere to the edge of the avoidance hole 61 during the formation of the mass and the formed mass is large and difficult to directly fall from the avoidance hole 61, after the enrichment crop 4 is pulled out, the second barrier cloth 6 can be directly lifted, and the masses on the second barrier cloth 6 can be efficiently collected, so that the heavy metal ions in the masses are completely separated from the soil, reducing the heavy metal ions fixed in the soil and reducing the risk of the heavy metal ions becoming free again.

[0053] After the second barrier cloth 6 is taken out from the planting pit 1, the planting soil 5 can be removed from the first metal ion solidifying agent 3, and then the rotation planting soil 8 can be directly covered on the first metal ion solidifying agent 3. See Figure 5 , since the first metal ion solidifying agent 3 has formed a mass at this time, it can not only prevent the heavy metal ions below the planting pit 1 from moving into the rotation planting soil 8, but also prevent the nutrients in the rotation planting soil 8 from seeping down to the soil below the planting pit 1.

[0054] In some other embodiments, after the planting soil 5 is removed from the first metal ion curing agent 3, it can be processed according to the agglomerate state formed by the first metal ion curing agent 3. If there are some cracks in the agglomerate, some first metal ion curing agent 3 can be sprinkled again to form a supplement to fill the above-mentioned cracks, and then the rotational planting soil 8 is sprinkled, so as to ensure the blocking effect between the rotational planting soil 8 and the soil under the planting pit 1. If the agglomerate is already thick, the first barrier cloth 2 can be lifted first, so as to quickly collect and process the agglomerates formed by the first metal ion curing agent 3 on the first barrier cloth 2, and prevent these fixed heavy metal ions from returning to the soil again. Then the first barrier cloth 2 is re-laid on the bottom wall of the planting pit 1, and then a new first metal ion curing agent 3 is sprinkled on the upper surface of the first barrier cloth 2, and then the rotational planting soil 8 is covered on the new first metal ion curing agent 3.

[0055] After the rotational planting soil 8 is spread on the first metal ion curing agent 3, new enrichment crops 4 are planted on the rotational planting soil 8, and the root tips of the enrichment crops 4 are located in the rotational planting soil 8. Then a second barrier cloth 6 is laid on the upper surface of the rotational planting soil 8, so that the roots and stems of the new enrichment crops 4 pass through the avoidance holes 61. Then a new second metal ion curing agent 7 is sprinkled on the second barrier cloth 6, and finally the planting soil 5 after removing heavy metal ions is sprinkled on the second metal ion curing agent 7. Based on the blocking effect of the second metal ion curing agent 7 on heavy metal ions at the avoidance holes 61, shallow-rooted edible crops can be normally planted in the planting soil 5, so that the heavy metal content in the edible crops is within a controllable range. The enrichment crops 4 can fix and collect the heavy metal ions in the rotational planting soil 8, and the foregoing steps can be repeated in the subsequent process, so that the heavy metal ions in the rotational planting soil 8 can be removed with the harvest of the enrichment crops 4. By alternately changing the positions of the rotational planting soil 8 and the planting soil 5 in the subsequent process, both the rotational planting soil 8 and the planting soil 5 can be used for planting shallow-rooted crops and deep-rooted crops.

[0056] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0057] The above-described embodiments only represent several implementation manners of the present invention, and the description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A method for repairing heavy metal contaminated cultivated land, characterized in that, Including: Dig up the surface layer of the soil to form a planting pit; Lay a first barrier cloth on the bottom wall of the planting pit; Lay planting soil on the upper surface of the first barrier cloth. A first metal ion curing agent is provided between the first barrier cloth and the planting soil, and enrichment crops are planted on the planting soil so that the root tips of the enrichment crops are immersed in the planting soil; Lay a second barrier cloth on the upper surface of the planting soil. A number of avoidance holes are formed in the second barrier cloth, and the stems of the enrichment crops pass through the avoidance holes; Lay a second metal ion curing agent on the upper surface of the second barrier cloth first, and then lay rotation planting soil. The leaves of the enrichment crops are located above the rotation planting soil; When harvesting the enrichment crops, swap the positions of the planting soil and the rotation planting soil and replant new enrichment crops so that the roots of the enrichment crops are located in the rotation planting soil; When harvesting the enrichment crops, first remove the rotation planting soil to expose the edge of the second barrier cloth, and then lift the second barrier cloth as a whole to recycle the second metal ion curing agent; After lifting the second barrier cloth as a whole, only remove the planting soil, lay the rotation planting soil on the first metal ion curing agent, and then successively replant enrichment crops on the rotation planting soil, lay a second barrier cloth on the rotation planting soil, lay a new second metal ion curing agent on the second barrier cloth, and lay the planting soil on the second metal ion curing agent; Before laying the rotation planting soil on the first metal ion curing agent, lay a new layer of the first metal ion curing agent on the first barrier cloth.

2. The heavy metal contaminated cultivated land remediation method according to claim 1, wherein, The distance between the first barrier cloth and the second barrier cloth is not greater than 20 cm.

3. The heavy metal contaminated cultivated land remediation method according to claim 1, characterized in that, The first barrier cloth extends along the side wall of the planting pit to the second barrier cloth.

4. The heavy metal contaminated cultivated land remediation method according to claim 1, characterized in that, The second metal ion curing agent is at least partially located at the edge of the avoidance hole.

5. The heavy metal contaminated cultivated land restoration method according to claim 4, characterized in that, The second metal ion curing agent at least contains plant ash and calcium carbonate.

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