A comprehensive soil remediation method based on blue-green spatial pattern optimization

Abstract

The application discloses a kind of based on blue-green space pattern optimization comprehensive soil remediation method, belong to soil remediation field, especially relate to wetland soil, the remediation method is as follows: (1) the water level of wetland is reduced to lowest point and exposes wetland soil, so that wetland bed is in water unsaturated state;(2) in wetland soil, water floating purification particles are scattered, then covered with thin soil, and plants are planted;(3) after treatment time is greater than 30 days, water can be added or stored, and water floating purification particles are removed from the water surface, and the remediation is completed.The application solves the problem of wetland soil remediation difficulty, helps to improve the ecological benefits of blue-green space, and promotes regional sustainable development.

Description

Technical Field

[0001] This invention relates to the field of wetland soil remediation technology, and in particular to a comprehensive soil remediation method based on the optimization of blue-green spatial patterns. Background Technology

[0002] Blue-green space refers to the natural or semi-natural spatial system composed of various open spaces such as water bodies, wetlands, and green spaces within the national land area. "Blue space" includes natural and artificial water bodies such as wetlands, rivers, lakes, reservoirs, and coastal areas; "green space" includes predominantly vegetated areas such as woodlands, grasslands, parks, and farmland. Blue-green spaces play a vital role in climate regulation, environmental improvement, and recreation. Rapid urbanization has exacerbated the evolution of the blue-green ecological pattern, leading to a series of problems such as environmental pollution, the heat island effect, soil erosion, and urban flooding. As urbanization enters a stage of high-quality development, optimizing the blue-green spatial pattern and enhancing its efficiency have become key factors for sustainable urban development.

[0003] Wetlands, as an important component of blue-green spaces, play a vital role in maintaining biodiversity and environmental health. They not only purify water, absorb carbon dioxide, and provide recreational value, but also play a crucial role in regulating stormwater runoff in the hydrological cycle. Land use change, habitat fragmentation, and unscientific riverbank construction have led to a reduction in wetland area and a decline in its functions. Urban wetlands, in particular, face heavy metal pollution in soil and water. Soil provides essential ecosystem services such as nutrient cycling, soil and water conservation, and carbon storage, serving as a crucial carrier of multiple ecosystem services in blue-green spaces. The challenges of wetland soil remediation lie in its complex community structure, high soil moisture content, and the need to protect biodiversity. Conventional soil remediation methods are difficult to apply to wetland soil remediation; therefore, there is an urgent need for a wetland soil remediation method that addresses the difficulties of remediating wetland soil, thereby improving land use efficiency and ecosystem service functions in blue-green spaces. Summary of the Invention

[0004] Therefore, the purpose of this invention is to provide a comprehensive wetland soil remediation method based on the optimization of blue-green space patterns, which can solve the soil remediation problem of natural or semi-natural wetlands in blue-green spaces and help improve the ecosystem service functions of urban blue-green spaces.

[0005] A comprehensive soil remediation method based on blue-green spatial pattern optimization, the remediation method is as follows:

[0006] (1) Lower the wetland water level to the lowest point to expose the wetland soil, so that the wetland bed is in an unsaturated state.

[0007] (2) Spread water-floating purification particles in the wetland soil, then cover with a thin layer of soil and plant plants;

[0008] (3) After the treatment time is greater than 30 days, water can be added or stored, and the floating purification particles can be removed from the water surface to complete the repair.

[0009] The difficulty in remediating wetland soil compared to terrestrial soil lies in its high water content and the difficulty in removing heavy metals after they have accumulated. Therefore, this invention innovates a water-floating purification particle to remediate wetlands based on phytoremediation, solving the problem of heavy metal pollution in wetland soil and ensuring that cities can solve environmental problems while maintaining a balanced blue-green ecological pattern.

[0010] In the initial remediation process, it is essential to ensure a low water level at the remediation site, exposing the wetland soil. The water-floating purification particles are then scattered into the mud, followed by a thin layer of soil to prevent wetland animals from consuming them and posing a danger. The particles' own weight and the pressure of the soil allow them to settle into the wetland soil for remediation. Landscape plants can then be planted in the wetland mud. After a period of remediation, the biodegradable components of the water-floating purification particles will decompose, reducing their weight. They will then float to the surface due to buoyancy. After removal, the particles are used for the next round of remediation based on the actual situation.

[0011] Furthermore, the remediation method described in this invention is suitable for soil remediation of artificial wetlands, river wetlands, lake wetlands, and marsh wetlands, and is especially suitable for small wetlands, or may also have a certain effect on the remediation of other open water areas in blue-green spaces or lakes and tidal flats with thick silt.

[0012] Furthermore, the plants planted during the restoration process are selected from one or more of the following: reed, cogon grass, herbs, water pepper, pickerelweed, and calamus. The selected plants are suitable for aquatic life and possess a certain ability to accumulate heavy metals, and can also be used for wetland landscaping.

[0013] Furthermore, the water flotation purification particles used in the remediation method include the following raw materials:

[0014] Expandable polystyrene, fiber, sodium alginate, xanthate, sodium pyrophosphate, sodium molybdate, vermiculite powder, calcium chloride, ethyl acetate, polyacrylamide.

[0015] Furthermore, the method for preparing the water flotation purification particles is as follows:

[0016] (1) Mix vermiculite powder with ethyl acetate and heat to 150-180℃. Then remove the vermiculite and mix it with expandable polystyrene. Heat the expandable polystyrene with steam at 100℃ until it expands to 20-30 times its original size. Then add sodium molybdate and xanthate and stir evenly. Let stand for 15-20 hours to obtain a polystyrene mixture.

[0017] (2) Mix sodium alginate with water to make a 2-5 wt% sodium alginate solution, add fiber and sodium pyrophosphate, mix evenly, and then add to make a 1 wt% polyacrylamide aqueous solution. Heat to 80-90℃, then keep warm and stir for 1-2 hours to obtain the glue solution for later use.

[0018] (3) Mix the polystyrene mixture after standing with the adhesive solution evenly, spray with 8wt% calcium chloride solution heated to 60℃ under constant temperature of 60-70℃, cure for 1-2 hours and then cool to obtain water-floating purification particles.

[0019] Expandable polystyrene containing a foaming agent produces lightweight and stable foam, but it has a low capacity to remove heavy metal ions. Therefore, this invention utilizes it as a base material to modify it and prepare a water-floating particle. Vermiculite itself is a functional material with certain adsorption properties. Therefore, adding vermiculite and calcium alginate gel to polystyrene can not only increase the particle weight but also further improve the adsorption of heavy metal ions. However, vermiculite is difficult to load onto the molded polystyrene foam and is easily separated. Therefore, by soaking vermiculite in ethyl acetate solution and treating it at high temperature, the composite performance of vermiculite and expandable polystyrene is improved. Furthermore, the pores of vermiculite are modified to change the interlayer molecular structure, promoting the opening of the interlayer structure under steam conditions, allowing sodium molybdate and xanthate to adhere. After static reaction, sodium molybdate and xanthate are stably grafted and fixed onto the polystyrene mixture.

[0020] Sodium alginate transforms into a gel under the influence of calcium ions. The frequent activity of microorganisms and benthic animals in wetland soil leads to the rapid depletion of calcium ions, causing premature gel decomposition. Therefore, this invention crosslinks a portion of sodium alginate ions with polyacrylamide hydrogel. Since the crosslinking process consumes some carboxyl hydroxyl groups, reducing metal complexation, biodegradable fibers and sodium pyrophosphate are added during the complexation process. When reconstructing the gel's network structure, sodium pyrophosphate and fibers are crosslinked internally, increasing the ability to remove heavy metals and enhancing gel strength, while preventing the release of heavy metal ions after the decomposition of calcium alginate. The settled polystyrene mixture is then mixed with the adhesive solution and sprayed with a calcium ion solution for curing, promoting adhesive hardening and foam maturation to form solid water-floating purification particles, facilitating transportation, storage, and use.

[0021] Furthermore, the mass ratio of the vermiculite powder to expandable polystyrene is (0.8-1):1.

[0022] Furthermore, the mass ratio of the vermiculite powder to sodium molybdate and xanthate is 1:(0.3-0.5):(0.5-0.8).

[0023] Furthermore, the mass ratio of sodium alginate to polyacrylamide and sodium pyrophosphate is 1:(0.5-1):(0.1-0.2); the mass ratio of expandable polystyrene to sodium alginate is (3-5):1.

[0024] Furthermore, the fiber includes one or both of plant fiber and seaweed fiber. Preferably, the amount of fiber added does not exceed 30% of the mass of sodium alginate.

[0025] Furthermore, the particle size of the water flotation purification particles is 0.5-10cm.

[0026] Beneficial effects:

[0027] The comprehensive soil remediation method disclosed in this invention is applicable to the remediation of wetland ecosystems with high water content within blue-green spaces, particularly for the in-situ treatment of heavy metals in wetland soils. The method is convenient and simple to operate, and has a high capacity for removing heavy metals. Combined with phytoremediation, it maintains wetland community stability while creating a beautiful landscape. The water-floating purification particles are suitable for wetland soil remediation under both acidic and alkaline conditions, offering broad applicability and rapid treatment speed. This remediation method is of great significance in creating urban blue-green spaces and provides positive assistance for the ecological restoration of artificial water bodies. Attached Figure Description

[0028] Figure 1 Images of the restored wetlands;

[0029] Figure 2 Images of wetlands in an unsaturated water state;

[0030] Figure 3 Images taken during the wetland soil remediation process. Detailed Implementation

[0031] The present invention will now be described in detail with reference to specific embodiments and accompanying drawings:

[0032] Example 1:

[0033] Weigh the raw materials according to the following proportions:

[0034] 500g expandable polystyrene granules, 30g bamboo fiber, 100g sodium alginate, 200g xanthate, 10g sodium pyrophosphate, 120g sodium molybdate, 400g vermiculite powder (passed through a 20-25 mesh sieve), 150g calcium chloride, 50g polyacrylamide, and an appropriate amount of ethyl acetate.

[0035] (1) Soak vermiculite powder in ethyl acetate, ensuring the ethyl acetate completely covers the vermiculite, heat to 150°C, then remove the vermiculite powder, dry it, and mix it with expandable polystyrene. Under steam conditions at 100°C, expandable polystyrene swells to 20 times its original size, then add sodium molybdate and xanthate, stir until homogeneous, and let stand at room temperature for 15 hours to obtain a polystyrene mixture.

[0036] (2) Sodium alginate is mixed with water to make a 2wt% sodium alginate solution. Bamboo fiber and sodium pyrophosphate are added and mixed evenly. Then, a 1wt% polyacrylamide aqueous solution is added and heated to 80°C. After stirring for 1 hour, the adhesive solution is obtained for later use.

[0037] (3) Mix the polystyrene mixture after standing with the adhesive solution evenly, spray with 8wt% calcium chloride solution heated to 60℃ under constant temperature conditions, cure for 1 hour and then cool to obtain water-floating purification particles.

[0038] Example 2:

[0039] Weigh the raw materials according to the following proportions:

[0040] 500g expandable polystyrene granules, 30g bamboo fiber, 100g sodium alginate, 300g xanthate, 15g sodium pyrophosphate, 200g sodium molybdate, 500g vermiculite powder (passed through a 20-25 mesh sieve), 160g calcium chloride, 60g polyacrylamide, and an appropriate amount of ethyl acetate.

[0041] (1) Soak vermiculite powder in ethyl acetate, ensuring the ethyl acetate completely covers the vermiculite, heat to 160°C, then remove the vermiculite powder, dry it, and mix it with expandable polystyrene. Under steam conditions at 100°C, expandable polystyrene swells to 20 times its original size. Then, add sodium molybdate and xanthate, stir until homogeneous, and let stand at room temperature for 18 hours to obtain a polystyrene mixture.

[0042] (2) Sodium alginate is mixed with water to make a 3wt% sodium alginate solution. Bamboo fiber and sodium pyrophosphate are added and mixed evenly. Then, a 1wt% polyacrylamide aqueous solution is prepared. The solution is heated to 90°C and then kept warm and stirred for 1.5 hours to obtain the adhesive solution for later use.

[0043] (3) Mix the polystyrene mixture after standing with the adhesive solution evenly, spray with 8wt% calcium chloride solution heated to 60℃ under constant temperature of 65℃, cure for 1.5h and then cool to obtain water-floating purification particles.

[0044] Example 3:

[0045] Weigh the raw materials according to the following proportions:

[0046] 500g expandable polystyrene, 40g bamboo fiber, 150g sodium alginate, 270g xanthate, 30g sodium pyrophosphate, 180g sodium molybdate, 450g vermiculite powder (passed through a 20-25 mesh sieve), 300g calcium chloride, 150g polyacrylamide, and an appropriate amount of ethyl acetate.

[0047] (1) Soak vermiculite powder in ethyl acetate, ensuring the ethyl acetate completely covers the vermiculite, heat to 180°C, then remove the vermiculite powder, dry it, and mix it with expandable polystyrene. Under steam conditions at 100°C, the expandable polystyrene swells to 30 times its original size. After this process, add sodium molybdate and xanthate, stir until homogeneous, and let stand at room temperature for 20 hours to obtain a polystyrene mixture.

[0048] (2) Sodium alginate is mixed with water to make a 5wt% sodium alginate solution. Bamboo fiber and sodium pyrophosphate are added and mixed evenly. Then, a 1wt% polyacrylamide aqueous solution is prepared. The solution is heated to 85°C and then kept warm and stirred for 2 hours to obtain the adhesive solution for later use.

[0049] (3) Mix the polystyrene mixture after standing with the adhesive solution evenly, spray with 8wt% calcium chloride solution heated to 60℃ under constant temperature of 70℃, and cool after curing for 2 hours to obtain water-floating purification particles.

[0050] Comparative Example 1:

[0051] This comparative example is compared with Example 1. The difference between the two examples is that the vermiculite was not treated during the preparation of this comparative example. The vermiculite was directly mixed with expandable polystyrene, swollen under steam conditions, and then sodium molybdate and xanthate were added to obtain a polystyrene mixture. The subsequent preparation method was the same.

[0052] Comparative Example 2:

[0053] This comparative example is compared with Example 1. The difference between Example 1 and Example 1 is that the sodium alginate was not treated. Instead, the polystyrene mixture was directly mixed with the sodium alginate solution and bamboo fiber. The specific preparation method is as follows:

[0054] Sodium alginate was mixed with water to prepare a 2wt% sodium alginate solution. Bamboo fiber was added and stirred until a paste was obtained for later use. The polystyrene mixture that had been left to stand was mixed with the paste until a paste was obtained. The paste was then sprayed with an 8wt% calcium chloride solution heated to 60℃ under a constant temperature of 60℃. After curing for 1 hour, the paste was cooled to obtain water-floating purification particles.

[0055] Comparative Example 3:

[0056] This comparative example is compared with Example 1. The difference between Example 1 and Example 1 is that only polystyrene foam balls capable of adsorbing heavy metal ions are prepared. The specific preparation method is as follows:

[0057] Expandable polystyrene was swelled 20 times its original size under steam at 100°C and then added to TP260 exchange resin. The mixture was then cured at 60°C for 1 hour and cooled to obtain water-floated purification particles.

[0058] Comparative Example 4:

[0059] This comparative example is compared with Example 1. The difference between Example 1 and Example 1 is that calcium alginate particles are directly added. The specific preparation method is as follows:

[0060] (1) Soak vermiculite powder in ethyl acetate, ensuring the ethyl acetate completely covers the vermiculite, heat to 150°C, then remove the vermiculite powder, dry it, and mix it with expandable polystyrene. After swelling to 20 times its original size under steam at 100°C, add sodium molybdate and xanthate, stir until homogeneous, and let stand at room temperature for 15 hours to obtain a polystyrene mixture.

[0061] (2) Sodium alginate is mixed with water to make a 2wt% sodium alginate solution. Bamboo fiber and sodium pyrophosphate are added and mixed evenly. Then, a 1wt% polyacrylamide aqueous solution is prepared. The solution is heated to 80°C and then kept warm and stirred for 1 hour to obtain a glue solution. The glue solution is added dropwise to an 8wt% calcium chloride solution to make calcium alginate granules.

[0062] (3) Mix the polystyrene mixture after standing with calcium alginate particles evenly, cure at a constant temperature of 60℃ for 1 hour, and obtain water-floating purification particles after cooling.

[0063] Comparative Example 5:

[0064] This comparative example is compared with Example 1. The only difference between this example and Example 1 is that sodium molybdate and xanthate were not added. After the expandable polystyrene swelled to 20 times its original size, it was directly left to stand at room temperature for 15 hours to obtain a polystyrene mixture. The subsequent preparation method is the same.

[0065] Comparative Example 6:

[0066] This comparative example is compared with Example 1. The only difference between this example and Example 1 is that sodium pyrophosphate was not added; the rest of the preparation process is the same.

[0067] experiment:

[0068] In Example 1 and Comparative Examples 1-6, water-floated purification particles with a particle size of approximately 3 cm were prepared. These water-floated purification particles were then used in a laboratory experiment to simulate heavy metal removal. The specific experimental procedure is as follows:

[0069] 1. Lead nitrate, zinc sulfate, and copper sulfate were used as pollution sources, and a small amount of water was added to prepare a simulated solution.

[0070] 2. Clay and river sand are mixed at a mass ratio of 1:0.5, then excess water is added. After standing overnight, the water is removed, and the simulated liquid is added and mixed evenly with the silt to simulate wetland soil in an unsaturated state. The soil thickness in the simulation experiment is 20cm.

[0071] 3. The initial concentrations of lead, zinc, and copper ions in the simulated wetland soil were all 80 mg / kg.

[0072] 4. Adjust the pH of wetland soil to 4, 7 and 10 to simulate the removal of heavy metal ions under acidic, normal and alkaline conditions;

[0073] 5. The water flotation purification particles prepared in Examples 1-6 and Comparative Examples 1-6 were prepared at a ratio of 500 g / m³. 3 The heavy metal content was added to the test chamber in the specified proportion, covered with a 2cm layer of sand, and left to stand for 50 days. The heavy metal content in the test chamber was then measured after 50 days. The data obtained are shown in Table 1.

[0074] Table 1 (mg / kg)

[0075]

[0076] Analysis of the data in Table 1 shows that:

[0077] 1. Compared with Comparative Example 1, Example 1 focuses on the treatment of vermiculite. The role of vermiculite is not only to increase the weight and utilize its adsorption properties, but also to open up the interlayer structure after the vermiculite is modified and expanded, stabilize sodium molybdate and xanthate to prevent them from falling off, thereby improving the adsorption of heavy metal ions, minimizing the content of heavy metal ions in the mud, and preventing the back osmosis of adsorbed heavy metal ions.

[0078] 2. Compared with Comparative Example 2, Example 1 is different in that sodium alginate was not cross-linked with polyacrylamide and sodium pyrophosphate, which caused the microorganisms in the mud to consume calcium ions in advance, resulting in gel failure. The water flotation purification particles separated from the mud under the action of buoyancy, and the heavy metal ion adsorption capacity was reduced, resulting in a higher heavy metal content in the mud.

[0079] 3. Compared with Comparative Example 3, Example 1 directly uses resin adsorption. Resin adsorption of heavy metal ions also has a good effect. However, because the resin becomes heavy after absorbing water, the particles do not float and settle in the soil, making it difficult to clean. At the same time, resin adsorption is more effective for alkaline wetland soils but less effective for acidic soils, which results in a narrow range of applications.

[0080] 4. Compared with Comparative Example 4, Example 1 shows that the direct addition of calcium alginate particles will cause the calcium alginate particles to separate from the polystyrene foam, and the calcium alginate will partially fall off, thereby reducing the heavy metal adsorption capacity.

[0081] 5. Compared with Comparative Example 5, Example 1 did not add sodium molybdate and xanthate, and Comparative Example 6 did not add sodium pyrophosphate. Their adsorption performance decreased, and the water flotation purification particles of Comparative Example 5 had a lower degree of buoyancy. This may be because sodium molybdate reacts not only with heavy metal ions in the water but also with calcium ions in calcium chloride, forming a microfilm-like structure on the surface of the water flotation purification particles while generating calcium alginate gel, which can prevent wetland soil from entering the particle interior.

[0082] Example 4:

[0083] The water-floating purification particles prepared in Example 1 were used for the remediation of constructed wetlands, as shown in the figure. The remediation operation is as follows:

[0084] (1) Drain or pump out the water in the wetland to lower the water level to the lowest point, so that the wetland bed is in an unsaturated state and the soil in the wetland water area that needs to be restored is exposed.

[0085] (2) Apply water-floating purification granules to the wetland soil at a rate of 400-500 g / m³. 2 Then cover it with a thin layer of soil, about 0.5-1cm thick, and you can plant calamus on the floating bed as a landscape plant;

[0086] (3) The treatment time is greater than 30 days, preferably 50 days. Then, the artificial wetland is filled with water until the water level reaches the original level. The floating purification particles are removed from the water surface, and the repair is completed.

[0087] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention. Technical aspects, shapes, and structures not described in detail in this invention are all well-known technologies.

Claims

1. A comprehensive soil remediation method based on blue-green spatial pattern optimization, characterized in that, The repair method is as follows: (1) the water level of wetland is lowered to the lowest point to expose the wetland soil, so that the wetland bed is in a water unsaturated state; (2) water floating purification particles are applied in the wetland soil, and then thin soil is covered, and plants are planted; (3) the treatment time is greater than 30 days, then water is added or stored, and the water floating purification particles are removed from the water surface, and the repair is completed; The water floating purification particles used in the repair method include the following raw materials: Expandable polystyrene, fiber, sodium alginate, xanthate, sodium pyrophosphate, sodium molybdate, vermiculite powder, calcium chloride, ethyl acetate, polyacrylamide; The preparation method of the water floating purification particles is as follows: (1) the vermiculite powder is mixed with ethyl acetate, heated to 150-180℃, then the vermiculite is taken out, mixed with expandable polystyrene, and heated with 100℃ steam until the expandable polystyrene expands to 20-30 times, then sodium molybdate and xanthate are added and stirred uniformly, and the mixture is left to stand for 15-20h to obtain a polystyrene mixture; (2) sodium alginate is mixed with water to prepare a 2-5wt% sodium alginate solution, fiber and sodium pyrophosphate are added, mixed uniformly, and then a 1wt% polyacrylamide aqueous solution is added, heated to 80-90℃, then stirred for 1-2h, and a glue solution is obtained for standby; (3) the polystyrene mixture after standing is mixed with the glue solution, and 8wt% calcium chloride solution heated to 60℃ is sprayed under constant temperature conditions of 60-70℃, and the water floating purification particles are obtained after solidification for 1-2h and cooling; The mass ratio of vermiculite powder to expandable polystyrene is (0.8-1):1; The mass ratio of vermiculite powder to sodium molybdate and xanthate is 1:(0.3-0.5):(0.5-0.8); The mass ratio of sodium alginate to polyacrylamide and sodium pyrophosphate is 1:(0.5-1):(0.1-0.2); The mass ratio of expandable polystyrene to sodium alginate is (3-5):

1.

2. The method according to claim 1, wherein, The repair method is suitable for soil repair of artificial wetlands, river wetlands, lake wetlands and marsh wetlands.

3. The method according to claim 2, wherein, The plants planted in the repair process are selected from one or more of arundo donax, thatch, mint, knotweed, swordfish grass and alocasia.

4. The method according to claim 3, wherein, The fiber includes one or both of plant fiber and seaweed fiber.

5. The method according to claim 4, wherein, The particle size of the water floating purification particles is 0.5-10cm.

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