Coastal wetland restoration method based on vegetation-low flow barrier-dredged soil

Abstract

The application discloses a coastal wetland restoration method based on vegetation-flow barrier-dredged soil, which comprises the following steps: S1, establishing a flow barrier outside a recovery area; carrying out dehydration treatment on dredged soil; filling the dehydration-treated dredged soil along the inner edge of the flow barrier in the recovery area; cultivating salt marsh plants by using nutrient solution; and planting the salt marsh plants in the recovery area. The vegetation can play a role in sand capturing and siltation promoting, further increases the stability of the beach surface, forms a healthy ecological-geomorphic positive feedback effect, and can fix sediments after the vegetation is successfully planted. The dredged soil can also provide nutrients for the vegetation. In combination with local salt marsh vegetation customization, the flow barrier and plant planting can weaken the water power, the dredged soil lifting and the flow barrier setting can improve the survival rate of the plants, and the three are organically combined to interact with each other, reduce wave scouring, and improve the stability of the beach surface.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ecological restoration, and particularly relates to a coastal wetland restoration method based on vegetation-flow barrier-dredged soil. BACKGROUND

[0002] Coastal wetlands are important land and natural resources, playing a crucial role in maintaining ecological balance, protecting biodiversity, providing ecological services, regulating climate, and supporting sustainable development. Protecting and restoring coastal wetlands is a key environmental protection task, which helps to achieve sustainable management of oceans and coasts. However, factors such as sea level rise, changes in water and sediment in the watershed, extreme weather, and human activities interact to exacerbate the erosion and degradation of coastal wetlands, leading to a decrease in wetland area and destruction of the ecosystem structure. This reduces important ecological services such as biodiversity, water resource regulation, and coastal protection. Therefore, it is urgent to take environmentally friendly measures to protect and restore coastal wetlands, maintain ecological balance, and preserve the ecological service value of coastal wetlands.

[0003] Dredged soil refers to materials such as silt, sediment, and bottom mud removed from waterways, ports, or water bodies. Dredged soil can play an important role in the restoration of coastal wetlands. As a geomorphological optimization material for coastal wetlands, dredged soil can be used to raise the topographic height of the wetland, slow down the erosion of tidal waves, and improve the wetland's ability to resist floods and adapt to sea level rise. Dredged soil can also improve soil structure and water retention in wetlands.

[0004] Salt marsh plants are salt-tolerant and flood-tolerant plants that adapt to the environment of coastal wetlands, such as reeds, sea three-pronged rush, and alkali bush. Salt marsh plants are the main primary producers in estuarine and coastal ecosystems, and have high ecological and economic value. Planting salt marsh plants has significant advantages in improving sediment properties, capturing sand, protecting shores and beaches, and maintaining biodiversity.

[0005] Existing ecological geomorphological restoration methods propose a variety of wave-damping and flow-reducing measures. Chinese patent CN113431020A discloses a coastal shoal ecological beach cultivation method based on dredged soil. This method uses fill soil to fill the area to be restored on the eroded tidal beach into a coastal slope; wave-damping sandbags are placed on the low-tide beach, and salt marsh vegetation is transplanted and planted on the high-tide beach and the middle-tide beach to complete the protection of the eroded tidal beach. Most existing ecological geomorphological restoration methods use dredged soil to fully cover the restoration area. However, studies have shown that full coverage of the beach can have adverse effects on the original benthic biological groups.

[0006] At the same time, existing ecological geomorphological restoration methods using native salt marsh plants to restore wetland erosion are easily disturbed by waves, making it difficult to ensure the survival rate of salt marsh plants.

[0007] A self-organizing ecological wave-damping system disclosed in Chinese Patent Publication No. CN206570753U uses wooden piles as rigid wave-damping skeletons. However, the wave-damping skeletons in the above prior art need to be punched into the inner side of the flexible wave-damping plant belt unit along the embankment with multiple wooden piles and multiple willow piles, which is complicated to operate and cannot form a cooperative effect with the filled soil. SUMMARY

[0008] In view of the deficiencies of the prior art, the purpose of the present application is to provide a coastal wetland restoration method based on vegetation-flow-damping barrier-dredged soil, which can effectively alleviate the erosion trend of the coastal wetland, improve the stability of the coastal wetland topography, and conserve the ecological function of the coastal wetland.

[0009] The purpose of the present application is achieved by the following technical solutions:

[0010] The present application provides a coastal wetland restoration method based on vegetation-flow-damping barrier-dredged soil, comprising the following steps:

[0011] S1. Establishing a flow-damping barrier outside the restoration area;

[0012] S2. Dehydrating the dredged soil;

[0013] S3. Filling the dehydrated dredged soil along the inner edge of the flow-damping barrier in the restoration area;

[0014] S4. Cultivating salt marsh plants using nutrient solution;

[0015] S5. Planting salt marsh plants in the restoration area.

[0016] Preferably, the cadmium content of the channel dredged soil is less than 5.0 mg / kg, the mercury content is less than 2.0 mg / kg, the lead content is less than 250.0 mg / kg, the zinc content is less than 600 mg / kg, the copper content is less than 200.0 mg / kg, the chromium content is less than 270.0 mg / kg, and the arsenic content is less than 120.0 mg / kg.

[0017] Preferably, the water content of the dehydrated dredged soil in step S3 is not higher than 50%.

[0018] Preferably, the dredged soil filling in step S3 is only performed along the flow-damping barrier.

[0019] Preferably, the nutrient solution is prepared from raw materials comprising the following components and weight parts:

[0020]

[0021]

[0022] Preferably, the height of the dredged soil filled in step S3 is 5-20cm.

[0023] Preferably, the planting density of the salt marsh plants is not less than 5 plants / m 2 .

[0024] Preferably, the slow flow barrier comprises degradable biological material, and the degradable biological material comprises at least one of bamboo pieces and wooden stakes.

[0025] Preferably, between steps S1 and S2, the content of heavy metals in the channel dredged soil is determined, and the biological safety is evaluated.

[0026] Preferably, the slow flow barrier in step S1 is inserted into the ground to a depth of 40-60cm.

[0027] As another embodiment of the present application, the preparation method of the nutrient solution comprises: weighing a certain amount of sodium chloride, calcium nitrate tetrahydrate, potassium nitrate, ammonium nitrate, potassium dihydrogen phosphate, and magnesium sulfate according to the weight ratio, dissolving each in a proper amount of water, mixing, and adding water to the weight of water after mixing the components.

[0028] Compared with the conventional technology, the present application has the following beneficial effects:

[0029] 1. The use of channel dredged soil to increase the elevation of the beach surface can resourcefully utilize the channel dredged soil, weaken the scouring effect of wave power on the vegetation during the initial planting period, and increase the stability of the beach surface;

[0030] 2. The nutrient substances in the channel dredged soil can help to improve the survival rate of the vegetation and promote the growth of the vegetation;

[0031] 3. The use of general nutrient solution to cultivate salt marsh plants before the restoration of coastal wetlands can improve the plant traits and increase the survival rate of transplantation;

[0032] 4. After the vegetation grows stably, the vegetation can play a role in sand trapping and siltation promotion, further increasing the stability of the beach surface and forming a benign ecological-geomorphic positive feedback effect. After the successful planting of vegetation, the sediment can be fixed, and the dredged soil can provide nutrients for the vegetation. Combined with the customization of local salt marsh vegetation, the slow flow barrier and the planting of vegetation can weaken the water power, the dredged soil lifting and the slow flow barrier setting can improve the survival rate of the plants, and the organic combination of the three can interact to reduce wave scouring and improve the stability of the beach surface.

[0033] 5. Slow-flow barriers can help mitigate wave erosion and improve the survival rate of transplanted plants. Compared with existing technologies, the slow-flow barrier setup in this method is simpler and easier to implement. Only a single-layer fence is set up along the outer edge of the restoration area using biodegradable materials. Establishing slow-flow barriers on bare beaches is more targeted at early erosion embankments. After the slow-flow barrier is set up, dehydrated dredged soil is used to fill the inner edge of the barrier. Under the protection of the slow-flow barrier, the dredged soil is less likely to be lost, and the dredged soil has stronger stability after dehydration, thus providing support for the slow-flow barrier.

[0034] 6. This invention only fills the area within the wave-dissipating barrier with sediment, thus having a minimal impact on native benthic organisms. Attached Figure Description

[0035] Figure 1 This is a flowchart of the recovery method of the present invention.

[0036] Figure 2 This is a schematic diagram of the arrangement in Embodiments 1-2 of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0038] Figure 1 This is a flowchart of the recovery method of the present invention, by Figure 1 As can be seen, the repair technique of the present invention includes the following steps:

[0039] Step 1: Establish a flow-slowing barrier around the recovery zone;

[0040] Step 2: Determine the heavy metal content of the dredged soil in the waterway and assess its biosafety;

[0041] Step 3: Dewater the dredged soil;

[0042] Step 4: Fill the restoration area along the inner edge of the slow-flow barrier with dehydrated dredged soil;

[0043] Step 5: Cultivate salt marsh plants using nutrient solution;

[0044] Step Six: Plant salt marsh plants in the restoration area.

[0045] Example 1

[0046] The experimental site for this embodiment is a coastal wetland beach in the Yangtze River Estuary that is severely eroded, showing wetland degradation trends such as strong hydrodynamic disturbance, decreased beach elevation, and lack of vegetation.

[0047] The position of a suitable operation is selected as a recovery experimental area, and the area of the experimental area is 10 m x 10 m; a bamboo sheet with a length of 70 cm and a width of 5 cm is closely arranged on the sea side and the adjacent two sides of the experimental area to establish a wooden stake fence, and the wooden stake is inserted into the soil layer with a depth of 40 cm; the Yangtze River Estuary South Channel dredging soil is used, and the quality of the dredging soil meets the first class of marine sediment standards, and the heavy metal content is cadmium 3.5 mg / kg, mercury 1.2 mg / kg, lead 14.4 mg / kg, zinc 67.9 mg / kg, copper 20.4 mg / kg, chromium 76.3 mg / kg, and arsenic 4.8 mg / kg; the dredging soil is subjected to dewatering treatment, and the water content of the dewatered dredging soil is 35%; the dewatered dredging soil is filled in the recovery area along the inner edge of the slow flow barrier to form a soil dam with a width of 20 cm and a height of 5 cm at the bottom of the slow flow barrier, and the dredging soil filling is only performed along the slow flow barrier; the reed seedlings are cultivated using a nutrient solution to a height of more than 30 cm, and the nutrient solution is prepared from raw materials including the following components and weight parts: sodium chloride 8 parts, calcium nitrate tetrahydrate 1 part, potassium nitrate 0.5 part, ammonium nitrate 1.5 part, potassium dihydrogen phosphate 0.05 part, magnesium sulfate 1 part, and water 992 parts; the preparation method of the general nutrient solution is as follows: the sodium chloride, calcium nitrate tetrahydrate, potassium nitrate, ammonium nitrate, potassium dihydrogen phosphate, and magnesium sulfate are weighed according to the weight parts, and then dissolved in an appropriate amount of water, mixed, and then water is added to meet the weight parts of water; after the elevation of the experimental area is completed, the reeds are planted and cultivated in the experimental area, and the planting density is 5 plants / m 2 ; the arrangement schematic view is shown in Figure 2 .

[0048] After the construction of the coastal wetland recovery project by using the method, the beach elevation is successfully lifted, the growth of plants is promoted, and the erosion rate of the beach is slowed down.

[0049] Example 2

[0050] The present embodiment selects a suitable position of the work as a recovery experimental area, and the area of the experimental area is 10 m x 10 m; a bamboo sheet with a length of 90 cm and a width of 5 cm is closely arranged on the peripheral side of the experimental area close to the sea side and adjacent two sides to establish a bamboo fence, and the bamboo sheet is inserted into the soil layer with a depth of 60 cm; the Yangtze River estuary south channel dredging soil is used, and the quality of the dredging soil meets the first type of marine sediment standard, and the heavy metal content is cadmium 3.5 mg / kg, mercury 1.2 mg / kg, lead 14.4 mg / kg, zinc 67.9 mg / kg, copper 20.4 mg / kg, chromium 76.3 mg / kg, and arsenic 4.8 mg / kg; the dredging soil is subjected to dewatering treatment, and the water content of the dewatered dredging soil is 35%; the dewatered dredging soil is filled in the recovery area along the inner edge of the slow flow barrier to form a soil dam with a width of 30 cm and a height of 20 cm at the bottom of the slow flow barrier inner edge, and the dredging soil filling is only performed along the slow flow barrier; the sea rush seedlings are cultivated by using the nutrient solution until the height is more than 15 cm, and the nutrient solution is prepared from raw materials including the following components and weight parts: sodium chloride 3 parts, calcium nitrate tetrahydrate 2 parts, potassium nitrate 1 part, ammonium nitrate 0.8 part, potassium dihydrogen phosphate 0.1 part, magnesium sulfate 3 parts, and water 985 parts; the preparation method of the general nutrient solution is as follows: sodium chloride, calcium nitrate tetrahydrate, potassium nitrate, ammonium nitrate, potassium dihydrogen phosphate, and magnesium sulfate are weighed according to the weight parts, and then respectively dissolved in an appropriate amount of water, mixed, and then water is added to meet the weight parts of water; after the elevation of the experimental area is completed, the sea rush cultivated in the experimental area is planted, and the planting density is 20 plants / m 2 ; the arrangement schematic view is shown in Figure 2 .

[0051] After the method is used to build the coastal wetland recovery project, the beach elevation is successfully lifted, the growth of plants is promoted, and the erosion speed of the beach is slowed down.

[0052] Comparative Example 1

[0053] The difference between the present comparative example and example 1 is that the plant is not cultivated by using the nutrient solution, and the 30 cm high reed seedlings are directly planted in the dredging soil in the experimental area.

[0054] Comparative Example 2

[0055] The difference between the present comparative example and example 1 is that the dredging soil is not used to lift the elevation, but the reed seedlings cultivated by the nutrient solution are directly planted on the beach in the slow flow barrier.

[0056] Comparative Example 3

[0057] The difference between the present comparative example and example 1 is that the slow flow barrier is not established.

[0058] Comparative Example 4

[0059] The difference between the present comparative example and example 1 is that the dredged soil is used to raise the whole beach surface in the slow flow barrier.

[0060] Effect verification

[0061] The beach surface elevation is measured by RTK one month and one year after the repair implementation, and the beach erosion is calculated; one year after the repair implementation, the plants in the experimental area are sampled by the sampling method, and the biomass is measured after drying in the laboratory; one year after the repair implementation, the benthic organisms in the experimental area are sampled, and the biomass is calculated after treatment in the laboratory. The effect verification results are shown in Table 1.

[0062] Table 1 Effect verification results

[0063]

[0064] According to the results of examples 1-2 in Table 1, the coastal wetland ecological landscape repair method of the present application can also achieve good beach protection effect by using the native pioneer plant Scirpus mariqueter.

[0065] From the results of comparative examples 1-3, in comparative example 1, the plants are not cultivated with nutrient solution, although a certain beach protection effect is achieved, the plant growth is not as good as example 1, and the biomass is significantly lower than example 1; in comparative example 2, the elevation is not raised by using dredged soil, and the plants and slow flow measures alone cannot provide sufficient protection to the beach; in comparative example 3, the slow flow measures are not established, and the wave disturbance reduces the protection effect of the plants and dredged soil, and cannot reduce the beach scouring; in comparative example 4, the dredged soil is filled in the slow flow barrier inside and outside, forming a comprehensive coverage to the recovery area, affecting the survival of benthic organism groups, and reducing the benthic organism biomass.

[0066] It should be understood that the present application is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essential content of the present application. The embodiments of the present application and the features in the embodiments can be arbitrarily combined without conflict.

Claims

1. A method for the restoration of a coastal wetland based on a vegetation- slow flow barrier - dredged soil, characterized in that, The method comprises the following steps: S1, establishing a slow-flow barrier outside the recovery area; The slow-flow barrier is combined with the early-stage erosion scarp of the tidal flat to form the recovery area; The slow-flow barrier comprises degradable biological materials, which comprise at least one of bamboo pieces and wooden stakes; the bamboo pieces are closely arranged on the sea side and adjacent sides of the recovery area to establish a wooden stake fence; S2, performing dehydration treatment on the dredged soil; S3, filling the dehydration-treated dredged soil along the inner edge of the slow-flow barrier in the recovery area; The dredged soil is channel dredged soil; The method for filling the dredged soil in step S3 comprises forming a soil dam at the bottom of the inner edge of the slow-flow barrier, and the filling of the dredged soil is performed only along the inner edge of the slow-flow barrier; The width of the soil dam is 20-30 cm, and the height is 5-20 cm; S4, cultivating salt marsh plants using nutrient solution; S5, planting salt marsh plants in the recovery area.

2. The method of claim 1, wherein, The content of cadmium in the dredged soil is less than 5.0 mg / kg, the content of mercury is less than 2.0 mg / kg, the content of lead is less than 250.0 mg / kg, the content of zinc is less than 600 mg / kg, the content of copper is less than 200.0 mg / kg, the content of chromium is less than 270.0 mg / kg, and the content of arsenic is less than 120.0 mg / kg.

3. The method of claim 1, wherein, The water content of the dehydration-treated dredged soil in step S3 is not higher than 50%.

4. The method of claim 1, wherein, The nutrient solution is prepared from raw materials comprising the following components and weight parts: Sodium chloride 3-8 parts; Calcium nitrate tetrahydrate 1-2 parts; Potassium nitrate 0.5-1 part; Ammonium nitrate 0.8-1.5 parts; Potassium dihydrogen phosphate 0.05-0.1 part; Magnesium sulfate 1-3 parts; Water 985-992 parts.

5. The method of claim 1, wherein, The planting density of the salt marsh plant is not less than 5 plants per square meter 2 .

6. The method of claim 1, wherein, Between steps S1 and S2, the content of heavy metals in the channel dredged soil is determined, and the biological safety thereof is evaluated.

7. The method of claim 1, wherein, The insertion depth of the slow-flow barrier in step S1 into the ground is 40-60 cm.

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