Ecological curing agent for side slope and method for applying ecological curing agent to ecological restoration of mine side slope

Abstract

The invention provides a side slope ecological curing agent and a method for ecological restoration of a mine side slope, the side slope ecological curing agent is generated through hydrolysis and mineralization reaction of a biological enzyme catalyst and a biological cementing agent, is used for enhancing the stability of a plant growing substrate on the side slope, and can release inorganic elements and organic carbon required by plant growth, so that the ecological curing agent has a good application prospect. Moreover, the ecological curing agent can passivate heavy metals in the tailing sand and promote safe ecological utilization of the tailing sand. Wherein the vegetation substrate comprises tailing sand, fine-grained soil, organic fibers and a reinforcing microbial agent, the tailing sand is supplemented through the fine-grained soil, so that the fine-grained soil and the tailing sand have better grain composition, the water and fertilizer retention effect of the vegetation substrate is enhanced, and the organic fibers can enhance the long-term effect of the ecological curing agent on slope curing of the vegetation substrate; a certain amount of organic carbon is provided by slow-release decay, and the salt tolerance of the plant to the solidified vegetation matrix can be improved by the enhanced microbial inoculum.

Description

Technical Field

[0001] The invention belongs to the technical field of slope ecological restoration, and in particular relates to a slope ecological curing agent and a method for using the same for ecological restoration of mine slopes. Background Art

[0002] With the rapid development of the economy and society, China's infrastructure construction has accelerated. The implementation of transportation, water conservancy, mining, and power projects has brought many negative impacts on the ecological environment. The most prominent of these is the destruction of local vegetation, which has formed a large number of exposed slopes. These exposed slopes not only affect the ecological landscape, but some also pose geological disaster risks, increasing the intensity of soil erosion, landslides, and mud-rock flows. They also cause ecological disasters such as local climate deterioration and disruption of the food chain. The construction of construction projects has caused the exposed slopes to have loose soil and poor water retention, affecting the safety and stability of the main greening projects. Therefore, ecological restoration and consolidation of these exposed slopes are very necessary.

[0003] At present, vegetation concrete is usually used for ecological restoration of slopes, but most of the vegetation concrete is in the research and development test stage. Vegetation concrete requires the use of special cementitious materials; it also needs to provide the space, nutrients and water necessary for plant growth; and it needs to have sufficient durability and operability for vegetation replanting. In the existing technology, ordinary silicate cement is used as the cementitious material for the preparation of vegetation concrete. During the hydration process of vegetation concrete, strong alkaline hydration products such as calcium hydroxide will be produced, creating a strong alkaline environment, which has an adverse effect on the environment for plant growth and is not conducive to the early germination of plants and the long-term growth in the later period, resulting in the situation where plants do not germinate or the growth rate in the following year is low. At the same time, carbon emissions will also be increased during the preparation of cement, causing environmental pollution.

[0004] Therefore, how to provide a slope ecological solidifier that solidifies the vegetation matrix through biological enzyme catalysts and biological binders, provides nutrients for plant growth, and evenly sprays it on the exposed slopes through spraying to achieve ecological restoration of the slopes is a technical problem that technical personnel in this field urgently need to solve. Summary of the Invention

[0005] The purpose of the present invention is to provide a slope ecological curing agent and a method for using the same for mine slope ecological restoration, so as to solve at least one of the above technical problems.

[0006] To achieve the above-mentioned purpose, the first aspect of the present invention provides a slope ecological solidifier, which includes a biological enzyme catalyst and a biological binder, and is used to solidify a vegetation matrix; wherein the phosphate hydrolysis activity in the biological enzyme catalyst is greater than 20,000 U; the vegetation matrix includes tailings sand, fine-grained soil, organic fiber and enhancing bacterial agent, and the mass ratio of the tailings sand, the fine-grained soil, the organic fiber, the enhancing bacterial agent and the biological binder is 10:6:0.5:0.05:(0.8-1).

[0007] In the first aspect, the bio-enzyme catalyst comprises at least one of phytase, phosphatase and Aspergillus niger.

[0008] In the first aspect, the biocementing agent comprises magnesium glycerophosphate, ammonium salt and alkaline supplement; the mass ratio of the magnesium glycerophosphate, the ammonium salt and the alkaline supplement is (2.5-2.7):1:(0.15-0.2).

[0009] In the first aspect, the ammonium salt includes at least one of ammonium chloride, ammonium acetate, and ammonium sulfate.

[0010] In the first aspect, the alkaline supplement includes at least one of magnesium oxide, calcium oxide, steel slag and carbide slag, and the content of calcium oxide or magnesium oxide in the steel slag and the carbide slag is not less than 30%.

[0011] In the first aspect, the alkaline supplement has a particle size of less than 200 mesh.

[0012] In the first aspect, the enhancing bacterial agent is a biological fertilizer containing Pseudomonas and Bacillus subtilis; the effective bacterial count in the enhancing bacterial agent is ≥ 200 million CFU / g.

[0013] In the first aspect, the organic fiber comprises at least one of corn straw, rice straw, and wheat straw; and the length of the organic fiber is 1 to 2 cm.

[0014] The second aspect of the present invention provides a method for using the slope ecological curing agent as described in the first aspect for ecological restoration of mine slopes, the method comprising: mixing tailings sand, fine-grained soil, organic fiber and reinforcing bacterial agent in a mass ratio of 10:6:0.5:0.05 to obtain a vegetation matrix; mixing the vegetation matrix and the biological binder, wherein the mass ratio of the vegetation matrix to the biological binder is 16.55:(0.8-1) to obtain a mixture; adding a biological enzyme catalyst to water and mixing evenly to obtain a catalytic liquid; adding the catalytic liquid to the mixture and mixing evenly, wherein the liquid-solid ratio of the catalytic liquid to the mixture is (3-4):10 to obtain a slope ecological restoration spraying substrate; and evenly spraying the slope ecological restoration spraying substrate on the exposed slope to be repaired, with a spraying amount of 200-280 kg / m 2 , forming a base layer; spraying plant seeds on the base layer to form a seed layer to complete the ecological restoration of the exposed slope.

[0015] In the second aspect, the base layer is sprayed at least three times, and the thickness of each spraying is 5-10 cm.

[0016] Beneficial effects: The present invention provides a slope ecological solidifying agent comprising a bio-enzyme catalyst and a bio-binder, which are used to solidify the vegetation matrix, provide nutrients for plant growth, and passivate heavy metals. The vegetation matrix comprises tailings sand, fine-grained soil, organic fiber, and an enhancing bacterial agent. The bio-binder is catalytically hydrolyzed by the bio-enzyme catalyst to generate a cementing product that can release elements required for plant production, and the cementing product can passivate heavy metal pollutants in the tailings sand or mines. At the same time, the tailings sand is supplemented by fine-grained soil, so that the fine-grained soil and tailings sand have a better particle grading, thereby reducing the porosity of the vegetation matrix, enhancing the water and fertilizer retention effect of the vegetation matrix, and the strength after solidification. The application of organic fiber can further enhance the tensile and shear strength of the vegetation matrix and enhance the stability of the vegetation matrix on the slope surface. The application of the enhancing bacterial agent is salt-tolerant nitrogen-fixing bacteria and root-based growth-promoting bacteria, which can reduce the salt content of the vegetation matrix and improve the habitat of the vegetation matrix to enhance plant adaptability. The present invention also uses spraying equipment to evenly spray the slope ecological restoration spray base material after the ecological curing agent solidifies the vegetation matrix on the slope to be repaired to form a base layer, promote the growth of plant seeds, and achieve green ecological restoration of the slope.

[0017] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0019] Figure 1 The present invention is a flow chart of a method for using a slope ecological curing agent in the present invention for ecological restoration of mine slopes. DETAILED DESCRIPTION

[0020] The present invention will be described in detail below in conjunction with specific embodiments and examples, and the advantages and various effects of the present invention will be more clearly presented. It should be understood by those skilled in the art that these specific embodiments and examples are for illustrating the present invention, rather than for limiting the present invention.

[0021] Throughout this specification, unless otherwise specified, the terms used herein should be understood as having the same meaning as commonly used in the art. Therefore, unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In the event of any conflict, the present specification shall take precedence.

[0022] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or obtained through existing methods.

[0023] The present invention provides a slope ecological solidifier, which includes a bio-enzyme catalyst and a bio-binder, and is used to solidify a vegetation matrix; wherein the phosphate hydrolysis activity in the bio-enzyme catalyst is greater than 20,000 U; the vegetation matrix includes tailings sand, fine-grained soil, organic fiber and a reinforcing bacterial agent, and the mass ratio of the tailings sand, the fine-grained soil, the organic fiber, the reinforcing bacterial agent and the bio-binder is 10:6:0.5:0.05:(0.8-1).

[0024] Specifically, the present invention provides a slope ecological solidifying agent including a bio-enzyme catalyst and a bio-binder, which is used to solidify the vegetation matrix and provide nutrients for plant growth, wherein the vegetation matrix includes tailings sand, fine-grained soil, organic fiber and reinforcing bacteria. The bio-enzyme catalyst catalyzes the hydrolysis of the bio-binder to generate a cementing product that can release elements required for plant production. At the same time, the tailings sand is supplemented by fine-grained soil, so that the fine-grained soil and tailings sand have a better particle grading, thereby reducing the porosity of the vegetation matrix, enhancing the water and fertilizer retention effect of the vegetation matrix, and the strength after solidification. Furthermore, the application of organic fibers can enhance the tensile and shear strength of the vegetation matrix and enhance the stability of the vegetation matrix on the slope surface. The application of reinforcing bacteria such as salt-tolerant nitrogen-fixing bacteria and root-based growth-promoting bacteria can reduce the salinity of the vegetation matrix and improve the habitat of the vegetation matrix to enhance plant adaptability.

[0025] In some possible embodiments, the biological enzyme catalyst includes at least one of phytase, phosphatase and Aspergillus niger.

[0026] In some possible embodiments, the biocementing agent includes magnesium glycerophosphate, ammonium salt and alkaline supplement; the mass ratio of the magnesium glycerophosphate, the ammonium salt and the alkaline supplement is (2.5-2.7):1:(0.15-0.2).

[0027] Those skilled in the art can understand that the bio-enzyme catalyst can catalyze the degradation of phosphate bonds to form magnesium hydrogen phosphate cement and small molecule organic matter glycerol required for plant / microorganism growth. Furthermore, the magnesium hydrogen phosphate cement reacts with ammonium salt to generate adhesive products such as magnesium ammonium phosphate and acid with slow-release fertilizer effect. As the reaction proceeds, the acid gradually increases and the pH value in the reaction site gradually decreases, thereby inhibiting the formation of magnesium ammonium phosphate. In order to promote the formation of magnesium ammonium phosphate, an alkaline supplement is added to the reaction site to adjust the pH value to generate a large amount of magnesium ammonium phosphate, which can slowly release the components required for plant growth.

[0028] Magnesium glycerophosphate and ammonium salts are the raw materials for the adhesive cementing product. The alkaline supplement neutralizes the acid generated by the reaction, maintaining a neutral environment and promoting plant growth. Furthermore, when the alkaline supplement is added in high amounts, the reaction system becomes alkaline, which inhibits the activity of the bio-enzyme catalyst. Furthermore, when the pH value of the reaction system exceeds 9, the ammonium ions in the ammonium salts escape as ammonia gas, causing ammonia and nitrogen loss and reducing the nutritional content of the slope bio-curing agent.

[0029] In some possible embodiments, the ammonium salt includes at least one of ammonium chloride, ammonium acetate, and ammonium sulfate.

[0030] In some possible embodiments, the alkaline supplement includes at least one of magnesium oxide, calcium oxide, steel slag and carbide slag, and the content of calcium oxide or magnesium oxide in the steel slag and the carbide slag is not less than 30%.

[0031] In some possible embodiments, the particle size of the alkaline supplement is less than 200 mesh.

[0032] Those skilled in the art will understand that controlling the particle size of the alkaline supplement to less than 200 mesh is to maintain a high specific surface area to increase the amount and rate of alkalinity release, and to maintain the content of calcium oxide or magnesium oxide in carbide slag or steel slag to be no less than 30%, in order to increase the alkali equivalent to enhance the curing performance of the slope ecological curing agent.

[0033] In some possible embodiments, the enhancing bacterial agent is a biological fertilizer containing Pseudomonas and Bacillus subtilis; the effective bacterial count in the enhancing bacterial agent is ≥ 200 million CFU / g.

[0034] In some possible embodiments, the organic fiber comprises at least one of corn straw, rice straw, and wheat straw; and the length of the organic fiber is 1 to 2 cm.

[0035] Those skilled in the art can understand that applying organic fibers can further enhance the tensile and shear strength of the planting matrix and enhance the stability of the planting matrix on the slope surface; the applied enhancing bacterial agents are salt-tolerant nitrogen-fixing bacteria and root-based growth-promoting bacteria, which can reduce the salt content of the planting matrix and improve the habitat of the planting matrix to enhance plant adaptability.

[0036] Based on a general inventive concept, please refer to Figure 1 The second aspect of the present invention provides a method for using the slope ecological curing agent as described in the first aspect for mine slope ecological restoration, the method comprising: (1) Tailings sand, fine-grained soil, organic fiber and enhancing bacterial agent were mixed evenly in a mass ratio of 10:6:0.5:0.05 to obtain a planting matrix; (2) mixing the plant matrix and the biocement, wherein the mass ratio of the plant matrix to the biocement is 16.55:(0.8-1), to obtain a mixture; (3) Adding a bio-enzyme catalyst to water and mixing it evenly to obtain a catalytic liquid; (4) adding a catalytic liquid to the mixture and mixing them uniformly, wherein the liquid-to-solid ratio of the catalytic liquid to the mixture is (3-4):10, to obtain a slope ecological restoration spraying substrate; (5) Spray the slope ecological restoration spray base material evenly on the exposed slope to be repaired, with a spraying volume of 200-280 kg / m 2 , forming the basal layer; (6) Spraying plant seeds on the base layer to form a seed layer to complete the ecological restoration of the exposed slope.

[0037] In combination with the second aspect of the present application, the base layer is sprayed no less than three times, and the thickness of each spraying is 5-10 cm.

[0038] Specifically, the present invention provides a method for using a slope ecological solidifier for ecological restoration of mine slopes. First, tailings sand, fine-grained soil, organic fiber and reinforcing bacterial agent are evenly mixed to obtain a vegetation matrix, and then the vegetation matrix and biological binder are evenly mixed to obtain a mixture with excellent particle grading and capable of providing nutrients for plant seeds; secondly, a biological enzyme catalyst is added to water to regulate biological activity to obtain a catalytic liquid, and the catalytic liquid and the mixture are evenly mixed to obtain a slope ecological restoration spray base material suitable for spraying; then, the slope ecological restoration spray base material is evenly sprayed on the exposed slope to be repaired through a spraying equipment to form a base layer, and the spraying thickness and number of spraying times are selected according to actual conditions to improve the soil structure of the slope; finally, plant seeds are sprayed on the base layer, and the nutrients released by the base layer are used to promote plant growth and store water for plant growth. The plants after growth can further fix the soil structure, thereby realizing green ecological restoration of the slope.

[0039] The present application will be further described below in conjunction with specific examples. It should be understood that these examples are intended to illustrate the present application only and are not intended to limit the scope of the present application. The experimental methods in the following examples where specific conditions are not specified are usually measured in accordance with national standards. If there are no corresponding national standards, then the methods are carried out in accordance with general international standards, conventional conditions, or according to the conditions recommended by the manufacturer.

[0040] Example In this example, lead-zinc tailings are selected as exposed slopes for ecological restoration. The specific steps are as follows: (1) Tailings sand, fine-grained soil, organic fiber, and enhancing microbial agent were mixed evenly in a mass ratio of 10:6:0.5:0.05 to obtain a planting matrix; the fine-grained soil was silt from the mining area, and the organic fiber was 2 cm thick wheat straw; (2) The plant matrix and the bio-binder are mixed uniformly in a ratio of 16.55:1 to obtain a mixture; wherein the bio-binder is obtained by mixing magnesium glycerophosphate, ammonium acetate and carbide slag in a mass ratio of 2.5:1:0.15, and the calcium oxide content in the carbide slag is 35%, and the particle size is less than 200 mesh; (3) Add phytase to water and adjust the phosphate hydrolysis activity to be greater than 20,000 U, mix well, and obtain a catalytic liquid; (4) The catalytic liquid and the mixture are evenly mixed at a liquid-to-solid ratio of 3:10 to obtain a slope ecological restoration spraying base material; (5) Use spraying equipment to evenly spray the slope ecological restoration spray base material on the exposed slope to be repaired, with a spraying volume of 280kg / m 2 , forming the basal layer; (6) Continue to spray plant seeds on the base layer to form a seed layer to complete the ecological restoration of the exposed slope.

[0041] According to the test, the strength of the base layer formed in this embodiment was 480KPa after 1 day, the vegetation rate was 89% after 30 days, and the bioavailability of heavy metals Pb / Zn / Cd in the tailings sand was reduced by more than 90% (determined according to HJ804-2016).

[0042] Comparative Example 1 In this comparative example, no carbide slag was added to the biocement, and the remaining steps were the same as in the embodiment. According to the test, the strength of the base layer formed in this comparative example was 320KPa after 1 day, and the vegetation rate was 73% after 30 days.

[0043] Comparative Example 2 In this comparative example, no fine-grained soil was added to the vegetation matrix, and the remaining steps were the same as in the embodiment. The test showed that the strength of the base layer formed in this comparative example was 312 KPa after 1 day, and the vegetation rate was 67% after 30 days.

[0044] Comparative Example 3 In this comparative example, the phosphate hydrolysis activity of phytase was 5000 U, and the remaining steps were the same as those in the embodiment. The test showed that the strength of the substrate formed in this comparative example was 304 KPa after 1 day, and the vegetation rate was 72% after 30 days.

[0045] Comparative Example 4 In this comparative example, no enhancing microbial agent was added, and the remaining steps were the same as in the example. The test showed that the strength of the base layer formed in this comparative example was 452 KPa after 1 day, and the vegetation rate was 71% after 30 days.

[0046] It can be seen from the above test results that in Comparative Example 1, since acetic acid generated by the neutralization reaction of carbide slag was not added, the yield of the generated magnesium ammonium phosphate cementation product was reduced, thereby weakening the nitrogen fixation ability and the loss of free nitrogen affecting plant growth; in Comparative Example 2, since fine-grained soil was not added and the particle size of the tailings sand was large, the tailings sand was easily settled in the vegetation matrix, resulting in poor uniformity of the prepared slope ecological restoration spraying substrate, affecting the subsequent spraying effect; in addition, the lack of fine-grained soil resulted in poor particle grading of the vegetation matrix, affecting the product The cementation effect results in poor water and fertilizer retention capacity, thereby reducing the vegetation rate; in Comparative Example 3, the hydrolysis activity of phytase is low, which reduces the decomposition rate of magnesium glycerol phosphate and the generation rate of magnesium ammonium phosphate cementation products. In the subsequent spraying process, the slope ecological restoration spraying substrate is not easy to adhere to the exposed slope, thereby destroying the structure of the vegetation matrix, resulting in reduced strength of the matrix layer and a decrease in the vegetation rate. In Comparative Example 4, no enhancing bacterial agent was added, so that the salt stress of the solidified vegetation matrix to the plants was stronger than that in the embodiment, and the plant growth rate decreased.

[0047] In summary, compared with the prior art, the present invention has the following advantages: (1) The present invention uses a biological binder and a biological enzyme catalyst to prepare a neutral magnesium ammonium phosphate material with adhesion, slow-release fertilizer effect and pollutant solidification function, thereby improving the slope soil structure and achieving slope ecological restoration.

[0048] (2) This invention uses tailings sand and fine-grained soil to adjust the optimal particle size distribution, optimize the slope vegetation matrix structure, water-air-heat transport capacity, and water storage capacity, promote plant growth, and use organic solid waste to prepare fibers to further enhance the stability of the vegetation structure after curing with an ecological curing agent. This promotes the resource utilization of tailings sand and agricultural and forestry waste.

[0049] (3) The present invention utilizes salt-tolerant nitrogen-fixing bacteria and root growth-promoting bacteria to improve the habitat of the plant substrate, which can alleviate the impact of high salinity on ecological slopes on plant stress.

[0050] Finally, it should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements, but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0051] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0052] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A slope ecological curing agent, characterized in that: The slope ecological solidifier includes a biological enzyme catalyst and a biological binder, which are used to solidify the vegetation matrix; wherein, the phosphate hydrolysis activity in the biological enzyme catalyst is greater than 20,000 U; the vegetation matrix includes tailings sand, fine-grained soil, organic fiber and reinforcing bacterial agent, and the mass ratio of the tailings sand, the fine-grained soil, the organic fiber, the reinforcing bacterial agent and the biological binder is 10:6:0.5:0.05:(0.8-1).

2. The slope ecological curing agent according to claim 1, characterized in that: The biological enzyme catalyst includes at least one of phytase, phosphatase and Aspergillus niger.

3. The slope ecological curing agent according to claim 1, characterized in that: The biocementing agent comprises magnesium glycerophosphate, ammonium salt and alkaline supplement; the mass ratio of the magnesium glycerophosphate, the ammonium salt and the alkaline supplement is (2.5-2.7):1:(0.15-0.2).

4. The slope ecological curing agent according to claim 3, characterized in that: The ammonium salt includes at least one of ammonium chloride, ammonium acetate and ammonium sulfate.

5. The slope ecological curing agent according to claim 3, characterized in that: The alkaline supplement includes at least one of magnesium oxide, calcium oxide, steel slag and carbide slag, and the content of calcium oxide or magnesium oxide in the steel slag and the carbide slag is not less than 30%.

6. The slope ecological curing agent according to claim 3, characterized in that: The particle size of the alkaline supplement is less than 200 mesh.

7. The slope ecological curing agent according to claim 1, characterized in that: The enhancing bacterial agent is a biological fertilizer containing Pseudomonas and Bacillus subtilis; the effective bacterial count in the enhancing bacterial agent is ≥ 200 million CFU / g.

8. The slope ecological curing agent according to claim 1, characterized in that: The organic fiber comprises at least one of corn straw, rice straw, and wheat straw; and the length of the organic fiber is 1 to 2 cm.

9. A method for using the slope ecological curing agent according to any one of claims 1 to 8 for mine slope ecological restoration, characterized in that: The method comprises: Tailings sand, fine-grained soil, organic fiber and enhancing bacterial agent are mixed evenly in a mass ratio of 10:6:0.5:0.05 to obtain a planting matrix; Mixing the plant matrix and the biocement, wherein the mass ratio of the plant matrix to the biocement is 16.55:(0.8-1), to obtain a mixture; Adding a biological enzyme catalyst to water and mixing uniformly to obtain a catalytic liquid; Adding a catalytic liquid to the mixture and mixing them evenly, wherein the liquid-to-solid ratio of the catalytic liquid to the mixture is (3-4):10, to obtain a slope ecological restoration spraying substrate; The slope ecological restoration spray base material is evenly sprayed on the exposed slope to be repaired, with a spraying rate of 200-280 kg / m 2 , forming the basal layer; Plant seeds are sprayed on the base layer to form a seed layer to complete the ecological restoration of the exposed slope.

10. The method for using the slope ecological curing agent for mine slope ecological restoration according to claim 9, characterized in that: The base layer is sprayed at least three times, and the thickness of each spraying is 5-10 cm.

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