Ecological buffer zone system for controlling agricultural non-point source pollution of reservoir catchment area

Abstract

The invention discloses an ecological buffer zone system for controlling agricultural non-point source pollution in a reservoir catchment area, and belongs to the field of pollution treatment. An ecological buffer zone system for controlling agricultural non-point source pollution in a reservoir catchment area comprises an ecological filler area, a water storage area and a vegetation buffer area which are sequentially arranged along a slope, aquatic plants are planted in the water storage area, and the ecological filler area is close to a land area. The ecological filler area comprises a biochar doped in-situ soil layer, a ceramsite layer and a red soil layer which are sequentially arranged in the water permeation direction. The method has the advantage that the dual requirements of water and soil conservation and pollutant purification are met.

Description

Technical Field

[0001] This application relates to the field of pollution control, and particularly to an ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area. Background Art

[0002] The reservoir catchment area refers to the area within a certain range around the reservoir, and the precipitation or surface runoff within this area will eventually converge into the reservoir. Agricultural land is usually located around the reservoir. With the continuous expansion of agricultural activities, the phenomenon of pollutants such as pesticides and fertilizers flowing into the reservoir with surface water is becoming increasingly serious. As an important storage place for fresh water resources, the water quality of the reservoir directly affects the surrounding ecological system and the water use safety of nearby residents.

[0003] Therefore, an ecological buffer zone is generally set up in the reservoir catchment area. The ecological buffer zone is located at the junction of water and land, that is, the position climbing towards the shore slope, and is composed of trees and other vegetation, which absorb and purify the pollutants in the water body flowing from the land to the reservoir by using the vegetation.

[0004] However, a single vegetation buffer zone often has difficulty in meeting the dual requirements of soil and water conservation and pollutant purification, and it is difficult to achieve long-term and stable pollution control effects. Summary of the Invention

[0005] In order to meet the dual requirements of soil and water conservation and pollutant purification, this application provides an ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area.

[0006] The ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area provided by this application adopts the following technical solutions: An ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area includes an ecological filler area, a water storage area, and a vegetation buffer zone arranged in sequence along the slope. Aquatic plants are planted in the water storage area. The ecological filler area is close to the land area, and the ecological filler area includes a biochar-doped in-situ soil layer, a ceramsite layer, and a red soil layer arranged in sequence along the water infiltration direction.

[0007] By adopting the above technical scheme, in addition to setting up a vegetation buffer zone, an ecological filling zone and a water storage zone are set up. Surface water infiltrates into the water storage zone through the biochar-doped in-situ soil layer, ceramsite layer and laterite layer, thereby achieving preliminary treatment of pollutants. The use of in-situ soil can improve the adaptability of slope geology to the geology of the ecological filling zone, balance the risk of soil erosion with the structural stability of the ecological filling zone, and reduce soil erosion. Biochar-doped in-situ soil can intercept ammonia nitrogen pollutants. The ceramsite layer can further filter the infiltrated surface water and form a stable structural strength as the central support of the ecological filling zone to cope with the scenario of fast surface water infiltration in rainy days. The laterite layer has a good phosphorus removal effect, which further reduces the pollutant content of surface water. With the cooperation of biochar-doped in-situ soil layer, ceramsite layer and laterite layer, not only the purification effect is good, but also the duration is long, reducing the difficulty of maintenance and management of the water storage zone and the vegetation buffer zone.

[0008] After passing through the ecological filling area, surface water first stays in the water storage area, where it is further treated by the purification effect of aquatic plants, extending the water flow path to prevent the water from being discharged directly into the catchment area too early. When the water level in the water storage area is higher than the ground in the vegetation buffer zone, the water enters the vegetation buffer zone, blocking and purifying pollutants and particulate matter in the water, thereby achieving control of agricultural non-point source pollution in the catchment area.

[0009] Optionally, the aquatic plants are submerged plants, and the submerged plants include one or both of Duckweed and Hydrilla verticillata.

[0010] By adopting the above-mentioned technical solutions, emergent plants and submerged plants form a stable plant ecosystem, which reduces the entry of pollutants into vegetation buffer zones and water bodies in subsequent reservoir catchment areas through filtering, infiltration, retention, and sedimentation.

[0011] Optionally, the vegetation buffer zone includes emergent plants, and the emergent plants include one or more of water celery, lotus and wild rice stem.

[0012] By adopting the above technical solutions, a complex vegetation buffer zone is formed to strengthen the control of soil erosion and intercept pollutants.

[0013] Optionally, the ecological filler area further includes a permeable concrete layer, and the permeable concrete layer is arranged on the top of the ceramsite layer and the laterite layer, and on the side of the laterite layer away from the ceramsite layer.

[0014] By adopting the above technical solution, the permeable concrete layer serves as the structural frame of the ecological filler area, playing a role in stabilizing the ecological filler area. The permeable property of the permeable concrete enables surface water to smoothly penetrate through the ecological filler area. Moreover, the permeable concrete layer does not cover the biochar-doped in-situ soil layer, which helps the surface water to pass through the biochar-doped in-situ soil layer as much as possible before infiltrating into the next area, improving the purification effect on water bodies. At the same time, it is also convenient to regularly dig out the in-situ soil and replace it with new in-situ soil.

[0015] Optionally, the preparation method of the biochar-doped in-situ soil layer: Dig in-situ soil on the slope, add water to the in-situ soil to obtain a mixture. Separately, mix polyvinyl alcohol-acrylate emulsion and biochar and stir, then add it to the mixture and stir evenly. Then heat and dry it to a certain extent and then fill it into the corresponding position of the ecological filler area to form the biochar-doped in-situ soil layer.

[0016] By adopting the above technical solution, the polyvinyl alcohol-acrylate emulsion further crosslinks between the soil particles of the in-situ soil to form a three-dimensional structure to wrap and cement the soil particles, playing a role in soil reinforcement, improving the problem that the soil body is prone to loss after the in-situ soil is reset in the past. And under the long-term water infiltration effect, it can also help the stable combination of biochar and in-situ soil, reduce the phenomenon of biochar sinking in the in-situ soil layer, and keep the biochar evenly distributed. In addition, the polyvinyl alcohol-acrylate emulsion is doped in the in-situ soil layer, and the polyvinyl alcohol in it is biodegradable. After degradation, certain voids are formed, which helps the surface water to infiltrate in the in-situ soil layer and fully contact with the biochar, so as to balance the soil reinforcement effect and the pollutant purification effect.

[0017] Optionally, the preparation method of the polyvinyl alcohol-acrylate emulsion: Mix an emulsifier and water, heat, add methyl methacrylate, hydroxyethyl acrylate and polyvinyl alcohol, mix evenly and then add an initiator, and continue to react to obtain the polyvinyl alcohol-acrylate emulsion.

[0018] By adopting the above technical solution, with the preparation method of the seed emulsion, the polyvinyl alcohol is emulsified evenly in the acrylate system to form the polyvinyl alcohol-acrylate emulsion.

[0019] Optionally, the preparation method of the biochar: Take a biochar source, soak it in a polyethylene glycol solution, take it out, dry it and then calcine it to obtain the biochar.

[0020] By adopting the above technical solution, during the calcination process, polyethylene glycol plays a role in pore formation for the biochar source, increasing the porosity of the biochar, thereby improving the adsorption and purification effect on pollutants. At the same time, the biochar after pore formation can better contact with the polyvinyl alcohol-acrylate emulsion and is easier to crosslink, which helps the biochar to be evenly distributed.

[0021] Optionally, the preparation method of the red soil layer: Mix red soil and starch, roast at high temperature, and after cooling, fill it into the corresponding position of the ecological filler area to form the red soil layer.

[0022] By adopting the above technical solution, during the roasting process, the starch also plays a role in pore formation for the red soil, thereby improving the phosphorus adsorption capacity of the red soil.

[0023] In summary, the present application has the following beneficial effects: 1. In addition to setting up the vegetation buffer zone, the present application sets up the ecological filler area and the water storage area. The surface water penetrates through the biochar-doped in-situ soil layer, the ceramsite layer and the red soil layer into the water storage area, realizing the preliminary treatment of pollutants. Among them, the use of in-situ soil can improve the adaptability of the slope geology to the geology of the ecological filler area, balance the risk of soil erosion and the stable state of the structure of the ecological filler area, reduce soil erosion. The biochar-doped in-situ soil can intercept ammonia nitrogen pollutants. The ceramsite layer can further filter the infiltrating surface water and form a stable structural strength to support the middle part of the ecological filler area to cope with the scenario of fast infiltration speed of surface water on rainy days. The red soil layer has a good phosphorus removal effect, further reducing the pollutant content of the surface water. With the cooperation of the biochar-doped in-situ soil layer, the ceramsite layer and the red soil layer, not only the purification effect is good, but also the sustainable time is long, reducing the maintenance and management difficulty of the water storage area and the vegetation buffer zone.

[0024] 2. After the surface water passes through the ecological filler area, it first stays in the water storage area. Through the purification effect of aquatic plants, the water body is further treated, and the water flow path is extended to avoid the water body being directly discharged into the catchment area prematurely. After the water level in the water storage area is higher than the ground of the vegetation buffer zone, the water body enters the vegetation buffer zone to block and purify the pollutants and particulate matters in the water body, thereby realizing the control of agricultural non-point source pollution in the catchment area. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is the plan view structure diagram of the ecological buffer zone in Embodiment 1 of the present application.

[0026] Description of the reference numerals: 1. Ecological filler area; 11. Biochar-doped in-situ soil layer; 12. Ceramsite layer; 13. Red soil layer; 14. Permeable concrete layer; 2. Water storage area; 3. Vegetation buffer zone; 31. Emergent plants. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0027] The following is a further detailed description of the present application in combination with the attached Figure 1 Drawings.

[0028] Embodiment 1 An ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area, as Figure 1As shown, an ecological buffer zone system for controlling agricultural non-point source pollution in a reservoir catchment area includes an ecological filling area 1, a water storage area 2 and a vegetation buffer area 3 arranged in sequence along the slope. The ecological filling area 1 is close to the land, and the ecological filling area 1 includes a biochar-doped in-situ soil layer 11, a ceramsite layer 12 and a laterite layer 13 arranged in sequence along the water infiltration direction.

[0029] The ecological filling area 1 also includes a permeable concrete layer 14, which is arranged on the top of the expanded clay layer 12 and the laterite layer 13, and on the side of the laterite layer 13 away from the expanded clay layer 12. The permeable concrete layer 14 serves as a structural frame of the ecological filling area 1, and plays a role in stabilizing the ecological filling area 1. At the same time, the permeable performance of the permeable concrete itself enables surface water to penetrate smoothly through the ecological filling area 1.

[0030] When surface water passes through the ecological filling area 1, biochar doped with in-situ soil can intercept ammonia nitrogen pollutants, and the expanded clay layer 12 can further filter the infiltrated surface water and form a stable structural strength, serving as the middle support of the ecological filling area 1 to cope with the scenario of fast surface water infiltration in rainy days. The red soil layer 13 has a good phosphorus removal effect, which reduces the pollutant concentration before the surface water enters the water storage area 2, thereby reducing the difficulty of maintenance and management of the water storage area 2 and the vegetation buffer zone 3.

[0031] The biochar-doped in-situ soil layer 11 is filled with biochar-doped in-situ soil. The in-situ soil is dug out from the slope in the ecological buffer zone. The use of in-situ soil can improve the compatibility of the slope geology with the geology of the ecological filler area 1, balance the risk of soil erosion and the structural stability of the ecological filler area 1, and reduce soil erosion. The preparation method of the biochar-doped in-situ soil layer 11 is as follows: dig in-situ soil from the slope, add water to the in-situ soil to obtain a mixture with a water content of 30wt%, take polyvinyl alcohol-acrylate emulsion and mix with biochar, wherein the mass ratio of the mixture to the polyvinyl alcohol-acrylate emulsion is 1:0.08, and the mass ratio of the mixture to the biochar is 1:0.001, then add the polyvinyl alcohol-acrylate emulsion and the biochar mixture to the mixture and stir evenly, then heat to 70°C and dry until the water content of the mixture is 15wt%, and then fill the mixture to the corresponding position of the ecological filler area 1 to form the biochar-doped in-situ soil layer 11.

[0032] Among them, the preparation method of polyvinyl alcohol-acrylate emulsion: take dodecylphenol polyoxyethylene ether as an emulsifier and ammonium persulfate as an initiator, and further weigh methyl methacrylate, hydroxyethyl acrylate, polyvinyl alcohol (PVA-1788), dodecylphenol polyoxyethylene ether, ammonium persulfate and water according to a mass ratio of 1:2.5:0.2:0.3:0.05:7.

[0033] Dodecylphenol polyoxyethylene ether is mixed with water, heated to 85 °C, protected by nitrogen, and after emulsifying evenly, methyl methacrylate, hydroxyethyl acrylate and polyvinyl alcohol are added. After mixing evenly, an initiator is added, and the reaction continues for 3 h. After cooling, a polyvinyl alcohol-acrylate emulsion is obtained.

[0034] Preparation method of biochar: Take a biochar source, specifically coconut shell as the biochar source. Soak the coconut shell in a polyethylene glycol solution for 4 h. The polyethylene glycol solution is formed by dissolving polyethylene glycol 400 in water to form a 20 wt% solution. The mass ratio of the coconut shell to the polyethylene glycol solution is 1:3. Take out the coconut shell, dry it and then calcine it at 400 °C. After cooling, biochar is obtained.

[0035] The ceramsite layer 12 is filled with ceramsite, and the particle size of the ceramsite is 5 - 10 mm.

[0036] The red soil layer 13 is filled with red soil. Preparation method of the red soil layer 13: Take red soil and starch and mix them in a mass ratio of 1:0.02, calcine at 450 °C for 3 h, and after cooling, fill it into the corresponding position of the ecological filler area 1 to form the red soil layer 13.

[0037] Aquatic plants are planted in the water storage area 2. The aquatic plants include submerged plants, and the submerged plants include Ceratophyllum demersum and Hydrilla verticillata.

[0038] After the surface water passes through the ecological filler area 1, it first stays in the water storage area 2. Through the purification of the aquatic plants, the water body is further treated, and the flow path of the water body is extended, avoiding the direct discharge of the water body into the catchment area prematurely. After the water level in the water storage area 2 is higher than the ground of the vegetation buffer zone 3, the water body enters the vegetation buffer zone 3, blocking and purifying the pollutants and particulate matters in the water body, so as to achieve the control of agricultural non-point source pollution in the catchment area.

[0039] The vegetation buffer zone 3 includes emergent plants 31. The emergent plants 31 include Oenanthe javanica, Nelumbo nucifera and Zizania latifolia. The emergent plants 31 are planted in the water level fluctuation zone of the reservoir catchment area. The roots of the emergent plants 31 grow in the bottom mud, and the stems and leaves protrude above the water surface.

[0040] Example 2 The difference between this example and Example 1 is that in the preparation method of the biochar-doped in-situ soil layer, instead of adding the polyvinyl alcohol-acrylate emulsion, an equal amount of acrylate emulsion is added. Preparation method of the acrylate emulsion: Take dodecylphenol polyoxyethylene ether as an emulsifier and ammonium persulfate as an initiator. Further, methyl methacrylate, hydroxyethyl acrylate, dodecylphenol polyoxyethylene ether, ammonium persulfate and water are weighed according to a mass ratio of 1:2.5:0.3:0.05:7.

[0041] Dodecylphenol polyoxyethylene ether is mixed with water, heated to 85 °C, protected by nitrogen, and after emulsifying evenly, methyl methacrylate and 2-hydroxyethyl acrylate are added. After mixing evenly, an initiator is added, and the reaction continues for 3 h. After cooling, an acrylate emulsion is obtained.

[0042] Comparative Example 1 The difference between this comparative example and Example 1 is that the ecological buffer zone system includes a water storage area and a vegetation buffer zone arranged in sequence along the slope, and no ecological filler area is set.

[0043] Comparative Example 2 The difference between this comparative example and Example 1 is that the ecological filler area includes a biochar-doped red soil layer, a ceramsite layer, and a red soil layer arranged in sequence along the water infiltration direction. Preparation method of the biochar-doped red soil layer: Add water to the red soil to obtain a mixture with a water content of 30 wt%, and separately mix polyvinyl alcohol-acrylate emulsion and biochar. The mass ratio of the mixture to the polyvinyl alcohol-acrylate emulsion is 1:0.08, and the mass ratio of the mixture to the biochar is 1:0.001. Then add the mixture of polyvinyl alcohol-acrylate emulsion and biochar to the mixture and stir evenly. Then heat to 70 °C and dry until the water content of the mixture is 15 wt%. The mixture is then filled into the corresponding position of the ecological filler area to form a biochar-doped red soil layer.

[0044] Comparative Example 3 The difference between this comparative example and Example 1 is that the preparation method of the biochar-doped in-situ soil layer: Dig in-situ soil on the slope, add water to the in-situ soil to obtain a mixture with a water content of 30 wt%, add biochar, and the mass ratio of the mixture to the biochar is 1:0.001. Then heat to 70 °C and dry until the water content of the mixture is 15 wt%. The mixture is then filled into the corresponding position of the ecological filler area to form a biochar-doped in-situ soil layer.

[0045] Field treatment inspection Select a river bank slope in a certain place. The area near the river bank is arable land. Divide the slope into five areas with equal area. Each area is separated by impermeable concrete. First, conduct a one-year inspection of the pollutant release amount, and then layout the ecological buffer zone system according to this application. Among them, four areas are set with an ecological filler area, a water storage area, and a vegetation buffer zone according to Examples 1-2 and Comparative Examples 2-3, and the remaining one area is set with a water storage area and a vegetation buffer zone according to Comparative Example 1. The density of aquatic plants and vegetation in each area is the same.

[0046] After the ecological buffer zone system is laid out in the above five regions, a one-year inspection is carried out. The inspection content includes setting up pollutant detection equipment near the emergent plants in the vegetation buffer zone, collecting the pollutant release amount. The pollutant release amount detection includes the detection of the total ammonia nitrogen release amount and the total phosphorus release amount. The pollutant reduction amount is calculated by comparing with the pollutant release amount of the previous year. The results are shown in Table 1.

[0047] Table 1 Reduction amount of ammonia nitrogen release (t) Reduction amount of total phosphorus release (t) Example 1 0.225 0.097 Example 2 0.188 0.087 Comparative Example 1 0.085 0.022 Comparative Example 2 0.148 0.104 Comparative Example 3 0.121 0.074 Combined with Table 1, it can be seen that with the cooperation of the ecological filler area, the water storage area and the vegetation buffer zone, the reduction amount of ammonia nitrogen release and the reduction amount of total phosphorus release are obvious, while the buffer zone system without the ecological filler area has a poor ability to control pollution. In addition, for Comparative Example 2 and Comparative Example 3, after a one-year inspection, it is found that the soil near the ecological filler area is relatively soft and there is more loss, while the soil near the ecological filler area in Example 1 and Example 2 remains in good condition and has high stability.

[0048] This specific implementation manner is only an interpretation of the present application, and it does not limit the present application. Those skilled in the art can make modifications without creative contributions to this specific implementation manner according to needs after reading this specification, but as long as it is within the scope of the claims of the present application, it is protected by the patent law.

Claims

1. An ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area, characterized in that: The invention comprises an ecological filling area (1), a water storage area (2) and a vegetation buffer zone (3) which are sequentially arranged along a slope, wherein aquatic plants are planted in the water storage area (2), the ecological filling area (1) is close to land, and the ecological filling area (1) comprises a biochar-doped in-situ soil layer (11), a ceramsite layer (12) and a laterite layer (13) which are sequentially arranged along a water infiltration direction.

2. The ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area according to claim 1, wherein: The aquatic plants are submerged plants, and the submerged plants include one or both of Ceratophyllum demersum and Hydrilla verticillata.

3. The ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area according to claim 1, characterized in that: The vegetation buffer zone (3) comprises emergent plants (31), and the emergent plants (31) comprise one or more of water celery, lotus and wild rice stem.

4. An ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area according to claim 1, characterized in that: The ecological filler area (1) further comprises a permeable concrete layer (14), wherein the permeable concrete layer (14) is arranged on the top of the ceramsite layer (12) and the laterite layer (13), and on the side of the laterite layer (13) facing away from the ceramsite layer (12).

5. An ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area according to claim 1, characterized in that: The preparation method of the biochar-doped in-situ soil layer (11) comprises the following steps: excavating in-situ soil from a slope, adding water to the in-situ soil to obtain a mixture, mixing polyvinyl alcohol-acrylate emulsion with biochar, adding the mixture to the mixture and stirring evenly, then heating and drying to a certain degree and then filling the mixture to the corresponding position of the ecological filler area (1) to form the biochar-doped in-situ soil layer (11).

6. The ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area according to claim 5, characterized in that: The preparation method of the polyvinyl alcohol-acrylate emulsion comprises the following steps: mixing an emulsifier with water, heating, adding methyl methacrylate, hydroxyethyl acrylate and polyvinyl alcohol, mixing evenly, adding an initiator, and continuing the reaction to obtain the polyvinyl alcohol-acrylate emulsion.

7. An ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area according to claim 5, characterized in that: The method for preparing the biochar comprises the following steps: taking a biochar source, soaking the biochar source in a polyethylene glycol solution, taking the biochar source out, drying the biochar source, and then roasting the biochar source to obtain the biochar source.

8. The ecological buffer zone system for controlling agricultural non-point source pollution in the reservoir catchment area according to claim 1, characterized in that: The preparation method of the red soil layer (13) is as follows: red soil and starch are mixed, roasted at high temperature, and then filled into the corresponding position of the ecological filler area (1) after cooling, so as to form the red soil layer (13).

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