Floating planting plate and phytoremediation method for cadmium contaminated farmland under waterlogging condition

Abstract

The application provides a floating planting disc and a phytoremediation method for cadmium-polluted farmland under waterlogging conditions, and relates to the technical field of cadmium pollution, and comprises a floating disc body, a cutting, cutting and planting, land preparation, floating planting management and the like. A plurality of planting holes are formed on the floating disc body and arranged in a matrix. A plurality of horizontal channels and vertical channels are arranged in the floating planting disc, the horizontal channels and the vertical channels are arranged in a vertical staggered manner, and are communicated or connected with the planting holes, and the horizontal channels and the vertical channels are located in the same cross section. The cutting is a mother plant of Sedum plumbizincicola or Sedum southeast, and at least has one growth point. The cutting is planted by cutting, the base of the cutting is soaked with a rooting agent, and the cutting is taken out and dried in the shade. The target remediation field is prepared, and the water layer height of the field is adjusted. The floating planting management is performed, and urea is sprayed every mu at 1 month and 3 months after floating planting. The floating planting time is combined with the seasonality of rice production, the cutting is performed in October-November, and the floating planting is removed in April or May of the next year.

Description

Technical Field

[0001] This invention relates to the technical field of cadmium pollution, and more specifically, to a floating planting tray and a phytoremediation method for cadmium-contaminated farmland under flooded conditions. Background Technology

[0002] With industrial development, cadmium pollution has become increasingly prominent, and its potential threat to human health has drawn global attention. Phytoremediation technology has gained significant attention due to its cost-effectiveness and environmental friendliness, and the extraction and removal of cadmium using hyperaccumulating plants has received widespread interest worldwide. As the proportion of primary industry in my country's economic output gradually decreases, the area of ​​fallow farmland continues to expand, and the rapid expansion of shrimp-rice farming has also led to an increase in the area of ​​waterlogged fallow farmland, especially in the rice-producing areas of the middle and lower reaches of the Yangtze River where many fallow farmlands are flooded. Due to current technological limitations, existing physical remediation and chemical extraction methods are largely unsuitable for remediation of cadmium-contaminated flooded farmland.

[0003] Existing phytoremediation technologies still face several challenges: First, limited by seedling technology, the industrialized seedling production of remediation plants is not yet mature, resulting in high seedling prices. Second, low remediation efficiency frequently occurs due to low yields or death of hyperaccumulating plants, and the labor costs required for cultivation measures such as water and fertilizer management and pest and weed control are high, necessitating further improvement in cultivation techniques. Third, weed control is difficult during phytoremediation, as weed infestations not only reduce the remediation effect but also cause frequent weed infestations in subsequent crops. Fourth, like most plants, most cadmium hyperaccumulating plants are not tolerant of waterlogging, and flooded farmland is unsuitable for their growth, making it difficult for remediation plants to survive in flooded fields, thus hindering the implementation of phytoremediation technologies in flooded areas. Summary of the Invention

[0004] The purpose of this invention is to provide a phytoremediation method for cadmium-contaminated farmland under flooded conditions. By setting up floating planting trays and a matching planting remediation method, the survival rate of cadmium-accumulating plants and the remediation effect can be improved.

[0005] This invention is achieved through the following technical solution: it includes a floating disc body, on which a plurality of planting holes are formed, the planting holes being arranged in a matrix;

[0006] The floating planting tray has several horizontal and vertical channels arranged perpendicularly to each other and connected to the planting holes. The horizontal and vertical channels are located on the same cross section.

[0007] To better realize the present invention, the distance between adjacent planting holes is further 8.5-9.0 cm;

[0008] The diameter of the transverse channel and the longitudinal channel is 0.5 to 0.8 cm.

[0009] To better realize the present invention, the planting hole is further shaped as a cuboid, with the top surface of the planting hole being square, the side length being 2.0-2.5cm and the height being 4.5-5.5cm. The square hole contains more substrate and the moisture is evenly distributed, which can ensure that the roots of the planted plants develop more fully. The bottom of the planting hole is also connected to a hole with a diameter of 0.5-0.8cm, which makes it easier for the plant to extend out of the floating plate and sink into the soil to be repaired.

[0010] Inserting cuttings into the planting hole can promote plant growth and increase the survival rate of the plants.

[0011] A phytoremediation method for cadmium-contaminated farmland under flooded conditions.

[0012] The following steps are included:

[0013] The polluted farmland was plowed, leveled, irrigated, and the water level was adjusted. Slow-release fertilizer was also applied as base fertilizer.

[0014] The aforementioned floating planting trays are placed in farmland, and the floating planting trays are planted with plants used to remove cadmium pollution, mainly Sedum aizoon or Sedum sarmentosum.

[0015] Fertilizer should be applied regularly during the restoration process.

[0016] This invention uses Sedum sarmentosum or Sedum aizoon to plant on a floating planting tray. During use, there is no need for multiple transplanting, saving labor costs. The restoration method is simple, highly operable, and has excellent restoration effect.

[0017] To better realize the present invention, further,

[0018] The specific steps for planting plants in the floating planting tray are as follows:

[0019] Fill the planting holes on the floating planting tray with the substrate;

[0020] Cut the lower end of the cutting into a horseshoe shape, soak the base of the cutting in a solution, and then remove the cutting and air dry it in a cool, ventilated place.

[0021] After treatment, the cuttings are planted by inserting them into the substrate to a depth of 0.8–1.5 cm. The substrate is then moistened with water.

[0022] This invention inserts cuttings into a substrate, enabling the cuttings to root quickly and significantly improving the survival rate compared to directly inserting them into farmland.

[0023] To better realize the present invention, further,

[0024] Soak the base of the cuttings in a solution, which may be a NAA solution with a concentration of 0.5–10.0 mg / L or an IBA solution with a concentration of 2.0–10.0 mg / L, for 30–60 minutes.

[0025] To better realize the present invention, further,

[0026] The floating planting process involves placing floating planting trays with plants in polluted farmland in November of the current year, fertilizing them regularly during the planting process, and removing them in April or May of the following year, repeating this process sequentially.

[0027] To better realize the present invention, further,

[0028] The water level in the farmland is 3.0 to 6.0 cm.

[0029] The optimal water level in the selected farmland is 5cm. After the floating planting trays are placed in the farmland, as the plants grow, their roots emerge through the holes at the bottom of the planting holes and extend into the farmland. Through the absorption of cadmium by the roots, the cadmium in the polluted farmland can be remediated. In addition, this water level facilitates integrated water and fertilizer management during cultivation.

[0030] To better realize the present invention, further,

[0031] During the placement of floating planting trays in farmland, multiple floating planting trays are arranged neatly side by side, with adjacent floating planting trays close together.

[0032] Floating planting trays are placed close together and neatly in flooded farmland. The main purpose of this is to ensure that the floating planting trays can fully cover the farmland and avoid incomplete restoration due to incomplete coverage. In addition, the close arrangement can effectively prevent weed growth.

[0033] To better realize the present invention, the plant is further selected as Sedum sarmentosum or Sedum dasycarpus.

[0034] Sedum sarcodactylum and Sedum aizoon are hyperaccumulators of cadmium and zinc, possessing advantages such as large biomass, wide distribution, multiple harvests, and tolerance to poor soil and drought. Actual remediation trials have shown that repeated planting does not affect the cadmium extraction efficiency of Sedum sarcodactylum, and the cadmium extraction efficiency is even higher in farmland with high pollution levels and fertile soil. This invention selects Sedum sarcodactylum and Sedum aizoon, whose plants prefer shade, dislike strong light but are cold-resistant, making them more suitable for planting in autumn, winter, and spring. During the trials, their remediation efficiency was high, making them suitable for remediating flooded and polluted farmland.

[0035] This invention selects Sedum plants for the remediation of cadmium pollution in flooded farmland. The floating planting tray can improve the survival rate of plants, ensure remediation efficiency, and avoid secondary pollution problems caused by the death of hyperaccumulating plants.

[0036] The beneficial effects of this invention are:

[0037] Firstly, in the floating planting technology of Sedum aizoon or Sedum sarmentosum for remediating Cd-contaminated farmland in flooded areas, the seedlings can be directly transplanted to the target remediation field after being inserted into the floating planting tray, eliminating the need for re-transplanting and saving labor costs. Secondly, the plants root quickly and have a high survival rate when inserted into the substrate. Thirdly, the water level in the target remediation field is suitable, allowing the roots to directly penetrate the farmland through the holes at the bottom of the planting pits to absorb Cd as the plants grow. Fourthly, the suitable water level in the target remediation field facilitates integrated water and fertilizer management during cultivation. Fifthly, the Sedum aizoon planted in the floating planting tray of this invention has a high survival rate, ensuring remediation efficiency while avoiding secondary pollution caused by the death of hyperaccumulating plants. Sixthly, during the remediation process, the floating planting tray covers the entire field, effectively preventing weed growth. Seventhly, the floating planting tray of this invention is recyclable, saving remediation costs. Eighthly, the remediation process is simple and highly operable. Attached Figure Description

[0038] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the present invention will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 A schematic diagram of the top surface structure of the floating planting tray provided by the present invention;

[0040] Figure 2 A schematic diagram of the bottom structure of the floating planting tray provided by the present invention;

[0041] Figure 3 A three-dimensional structural diagram of the floating planting tray provided by the present invention;

[0042] Figure 4 A first cross-sectional schematic diagram of the floating planting tray provided by the present invention;

[0043] Figure 5 This is a second cross-sectional schematic diagram of the floating planting tray provided by the present invention;

[0044] Figure 6 This is a cross-sectional schematic diagram of the floating planting technology used in this invention to remediate flooded Cd-contaminated farmland.

[0045] Icons: 100-Floating planting tray, 101-Floating tray body, 102-Planting hole, 103-Horizontal channel, 104-Vertical channel, 105-Plant, 106-Water layer, 107-Soil. Detailed Implementation

[0046] The technical solutions of the present invention will now be described with reference to the accompanying drawings.

[0047] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0048] This invention provides a method for phytoremediation of cadmium-contaminated farmland under flooded conditions using floating planting trays. Existing technologies for phytoremediation suffer from limitations in seedling cultivation, resulting in high seedling prices. Furthermore, the remediation process is inefficient and difficult to control pests and diseases. In addition, most cadmium-accumulating plants are not tolerant of waterlogging, making survival difficult in flooded fields. To address these technical problems, this invention redesigns a dedicated remediation device and a corresponding remediation method, thereby improving the survival rate of remediated plants and ensuring remediation effectiveness. Moreover, it facilitates integrated water and fertilizer management and effectively prevents weed growth.

[0049] like Figures 1-6 As shown, the repair device provided by the present invention is a floating planting tray. The floating tray is made of polystyrene foam and has a length of approximately 62.0–68.0 cm, a width of 32.0–34.0 cm, and a height of 5.0–6.0 cm. Several planting holes are provided on the floating planting tray, arranged in a matrix. The distance between adjacent planting holes is approximately 8.5–9.0 cm. In this embodiment, 6 planting holes are provided on the long side of the floating tray and 3 planting holes are provided on the short side, for a total of 18 planting holes. Preferably, the planting holes are cuboids. In practice, it is preferable that the top surface of the planting hole is square, with a side length of 2.0–2.5 cm and a height of 4.5–5.5 cm. The bottom of the planting hole is also connected to a hole with a diameter of 0.5–0.8 cm.

[0050] In addition to planting holes, the floating planting tray also has ventilation channels. These channels include longitudinal and transverse channels on the same cross-section, which are arranged perpendicularly to each other and connected to the planting holes to facilitate root aeration and promote plant growth.

[0051] This invention also provides a repair method:

[0052] The farmland to be repaired should be plowed and leveled, and the water level should be adjusted and base fertilizer should be applied. Specifically, the farmland can be plowed and leveled first, most of the small pits and mounds should be leveled, and weeds should be knocked down or removed to make the field surface as flat as possible and free of large weeds. At the same time, slow-release fertilizer should be applied. The water level of the field should be 3.0 to 6.0 cm. For fields with waterlogging or no surface water or low water level, appropriate flood irrigation can be used to adjust the water level to an appropriate height.

[0053] Floating planting trays filled with plants are placed one after another in the farmland, with adjacent floating planting trays tightly connected to reduce gaps and thus reduce the growth of weeds and other substances.

[0054] The floating planting time is for cuttings to be taken in October or November of the current year, and removed in April or May of the following year.

[0055] One month and three months after placing the floating planting trays, spray 10-15 catties of urea per mu of farmland. You can also apply fertilizer as needed based on the plant growth.

[0056] Example 1

[0057] The polluted farmland was tilled, leveled, and weeds were removed. The water level in the farmland was adjusted to 5 cm. Floating planting trays were placed in the farmland in October and November of this year. The floating planting trays contained plants used to remove cadmium pollution, and the selected plant was Sedum sarmentosum.

[0058] Fertilizer was applied regularly during the restoration process, and the floating planting trays were removed in May of the following year.

[0059] The specific structure of the floating planting tray is as follows: the tray body is 66cm long, 33cm wide, and 5.5cm high. The floating planting tray has 18 planting holes, 6 on the long side and 3 on the short side. The planting holes are cuboid in shape, specifically with a square top surface, a side length of 2.5cm, and a height of 5.0cm. The diameter of the hole at the bottom of the planting hole is 0.5cm. The distance between two adjacent planting holes is 8.8cm. In addition, the longitudinal and transverse channels of the floating planting tray are perpendicular to each other and connected to the planting holes. The diameter of both the longitudinal and transverse channels is 0.7cm.

[0060] Place the plants into the floating planting tray, and follow the specific steps:

[0061] Fill the floating planting tray with the substrate in its natural state, without pressing it down. Scrape the surface of the substrate on the floating planting tray to level it, and gently tap the floating planting tray to compact the substrate.

[0062] For propagation by cuttings, select *Sedum morganianum* as the mother plant and take cuttings with at least one growth point. The cuttings should be (8.0–12.0) cm long, with the lower end cut into a horseshoe shape. Soak the base of the cuttings in a solution of NAA (0.5–10.0 mg / L) or IBA (2.0–10.0 mg / L) for 30–60 minutes. After soaking, remove the cuttings and air dry them in a cool, well-ventilated place for 1–2 days, until a light-colored scab forms at the cut end, before planting. When planting, first use a small stick to poke holes about 1.5 cm deep in the substrate, place the base of the cutting into the hole, and then fill the hole with substrate. The depth of insertion of the cutting into the substrate should be 0.8–1.5 cm.

[0063] Spray water to moisten the substrate in the pre-planted floating planting trays, and then place them one by one into the flooded field to be restored. The floating planting trays planted on the same day are floated and placed on the same day, arranged neatly, with adjacent floating planting trays tightly connected.

[0064] During the planting and restoration process, apply 10-15 catties of urea per mu in the first and third months after the planters are placed in the floating planting trays.

[0065] Example 2

[0066] The polluted farmland was plowed, leveled, and weeds were removed. The water level in the farmland was adjusted to 5 cm.

[0067] Ordinary floating trays containing plants designed to remove cadmium contamination were placed in farmland during October and November of the current year; fertilization was carried out regularly during the remediation process, and the floating trays were removed in May of the following year.

[0068] The structure of this ordinary floating tray is 66cm long, 33cm wide, and 5.5cm high. Each tray has 200 holes, 20 on the long side and 10 on the short side. 32 plants are planted evenly in each tray, with the spacing between plants as consistent as possible. Only the holes with plants are filled with substrate, and the remaining holes are left unfilled. When filling the substrate, insert it into the floating tray in its natural state without pressing it down. Scrape the substrate on the surface of the floating tray and gently tap the tray to compact the substrate.

[0069] Propagation by cuttings. Select *Sedum morganianum* as the mother plant and take cuttings with at least one growth point. The cuttings should be 8.0–15.0 cm long, with the lower end cut into a horseshoe shape. Soak the base of the cuttings in a solution of NAA (0.5–10.0 mg / L) or IBA (2.0–10.0 mg / L) for 30–60 minutes. After soaking, remove the cuttings and air dry them in a cool, well-ventilated place for 1–2 days, until a light-colored scab forms at the cut end, before planting. First, use a small stick to poke holes about 1.5 cm deep in the substrate. Place the base of the cutting into the hole, then fill the hole with substrate, inserting the cutting into the substrate to a depth of 0.8–1.5 cm.

[0070] Spray water to moisten the substrate in the floating planting trays with the cuttings, and then place them one by one into the flooded field to be restored. The floating planting trays with cuttings planted on the same day are floated and placed neatly on the same day.

[0071] Floating planting management. Apply 10-15 catties of urea per mu (0.067 hectares) one month and three months after floating planting.

[0072] Example 3

[0073] For non-floating, direct cutting propagation, cuttings are directly planted in the target remediation field with a water level of 3.0–6.0 cm. Select *Sedum aizoon* as the mother plant and take cuttings with at least one growth point. The cuttings should be 8.0–15.0 cm long, with a horseshoe-shaped cut at the bottom. Soak the base of the cuttings in a solution of 0.5–10.0 mg / L NAA or 2.0–10.0 mg / L IBA for 30–60 minutes. After soaking, remove the cuttings and air-dry them in a well-ventilated, shady place for 1–2 days until a light-colored scab forms at the cut. Then proceed with the planting. First, use a small stick to poke holes about 1.5 cm deep in the field. Place the base of the cutting into the hole, then fill the hole with substrate, inserting the cutting into the substrate to a depth of 0.8–1.5 cm.

[0074] Example 4

[0075] The non-floating, rooted seedling transplanting method involves directly planting first- or second-grade Sedum sarmentosum seedlings with roots in the target remediation field where the water layer is 3.0 to 6.0 cm high.

[0076] Examples 1-4 were conducted in the same cadmium-contaminated farmland to be remediated, with a total cadmium content of 0.83 mg / kg and a pH of 4.9.

[0077] The experimental results are as follows:

[0078] Growth of Sedum sarmentosum associated with minerals in different embodiments

[0079]

[0080] Remediation effects of cadmium-contaminated farmland in different embodiments

[0081]

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A phytoremediation method for cadmium-contaminated farmland under flooded conditions, characterized in that, The following steps are included: The polluted farmland is plowed, leveled, irrigated, and the water level is adjusted to 3.0–6.0 cm. Slow-release fertilizer is also applied as base fertilizer. A floating planting tray is placed in the farmland. The floating planting tray includes a floating tray body and a number of planting holes are opened on the floating tray body. The planting holes are arranged in a matrix. The floating planting tray has several horizontal and vertical channels arranged perpendicularly to each other and connected to the planting holes. The horizontal and vertical channels are located on the same cross section. The distance between adjacent planting holes is 8.5 to 9.0 cm. The diameter of the horizontal and vertical channels is 0.5 to 0.8 cm. The floating planting tray contains plants used to remove cadmium pollution; the plants are Sedum sarmentosum or Sedum dasycarpus, and cuttings with at least one growth point are taken as cuttings. Fertilize regularly during the restoration process; The specific steps for planting plants in the floating planting tray are as follows: Fill the planting holes on the floating planting tray with the substrate; Cut the lower end of the cutting into a horseshoe shape, soak the base of the cutting in a solution, and then remove the cutting and air dry it in a cool, ventilated place. After treatment, the cuttings are planted by inserting them into the substrate to a depth of 0.8–1.5 cm. The substrate is then moistened with water after the cuttings are inserted. The floating planting process involves placing floating planting trays with plants in polluted farmland in November of the current year, fertilizing them regularly during the planting process, and removing them in April or May of the following year, repeating this process sequentially.

2. The phytoremediation method for cadmium-contaminated farmland under flooded conditions according to claim 1, characterized in that, The planting hole is rectangular in shape, with a square top surface having a side length of 2.0–2.5 cm and a height of 4.5–5.5 cm; the bottom of the planting hole is also connected to a hole with a diameter of 0.5–0.8 cm.

3. The phytoremediation method for cadmium-contaminated farmland under flooded conditions according to claim 1, characterized in that, Soak the base of the cuttings in a solution, which may be a NAA solution with a concentration of 0.5–10.0 mg / L or an IBA solution with a concentration of 2.0–10.0 mg / L, for 30–60 minutes.

4. The phytoremediation method for cadmium-contaminated farmland under flooded conditions according to claim 1, characterized in that, During the placement of floating planting trays in farmland, multiple floating planting trays are arranged neatly side by side, with adjacent floating planting trays close together.

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