A sulfide oxidation-induced acid rock slope spray-seeding ecological restoration method

Abstract

The present application relates to the technical field of spray seeding, and discloses a rock slope spray seeding ecological restoration method for acidification caused by sulfide oxidation, which comprises the following steps: cleaning and leveling the acidic bedrock area; spraying a microbial inhibitor on the surface of the bedrock slope first, and then spraying a mixture of phosphate powder and calcium carbonate powder or spraying the mixture of the microbial inhibitor, the phosphate powder and the calcium carbonate powder to form a neutralization layer; mixing limestone powder and straw particles and then spraying the mixture on the surface of the neutralization layer as a slow-release layer; and spraying guest soil on the surface of the slow-release layer, wherein the guest soil is mixed with herbaceous plant seeds. The present application adopts a composite structure of the neutralization layer and the slow-release layer as a buffer layer, can effectively block and neutralize the acid and alkaline substances released by the bedrock, provides a stable pH environment for the guest soil, can maintain an effective buffering effect for more than one year through one-time paving, and covers the key period of plant root penetration. In addition, the present application selects low-cost materials and a small amount of microbial inhibitor, thereby reducing the engineering cost and being suitable for large-scale popularization and application.

Description

Technical Field

[0001] This invention relates to the field of hydroseeding technology, specifically to a hydroseeding ecological restoration method for rock slopes affected by sulfide oxidation and acidification. Background Technology

[0002] Rock strata rich in reducing sulfides such as pyrite (FeS2) are widely distributed in my country. These sulfide-rich strata, exposed to the atmosphere due to tectonic movements or human engineering activities, readily generate acidic water and expansive sulfates under the hydrochemical action of dissolved oxygen. The rapid changes in the composition, structure, and texture of the rock strata caused by acidic water not only occur within the strata themselves, causing rock damage and soil acidification, but also promote the corrosion of building materials in adjacent rock strata and contact structures. This results in significant ecological and slope protection failure problems. Exposed rock slopes are generally classified into three weathering types: unweathered, semi-weathered, and completely weathered. The acidity of the soil on rock slopes is usually mainly related to the content of sulfide minerals, primarily pyrite, dispersed in the semi-weathered or unweathered black shale within the slope. Atmospheric precipitation or surface water containing dissolved oxygen enters the slope through the pores of the geological mass and undergoes chemical reactions to produce acidic water. This acidic water easily dissolves other constituent minerals or cementation materials within the slope, leading to the destruction of the rock mass structure and the deterioration of the overall mechanical strength of the slope. Therefore, the ecological restoration of acidic bedrock slopes is currently a key focus.

[0003] Hydroseeding, as a highly efficient method for slope ecological restoration, is widely used for vegetation restoration in exposed rock areas such as abandoned mine sites and highway / railway slopes. This technology creates an artificial growth substrate to provide plants with an initial growth environment, thus quickly achieving green coverage of exposed surfaces. However, in practical applications, especially in areas with acidic bedrock, the success rate of vegetation restoration is often unsatisfactory. The core reason is that the acidity or alkalinity of the bedrock continuously affects the chemical environment of the hydroseeding soil through weathering and leaching. Plants are highly sensitive to pH levels during germination and early growth stages; an overly acidic environment severely affects their physiological metabolic processes, leading to seed failure, seedling death, and other problems, rendering the initial restoration efforts futile.

[0004] Currently, the industry lacks sufficient understanding of the impact of bedrock acidity on hydroseeding and lacks targeted technical measures. In some remediation projects, pH regulators may be directly added to the topsoil, but this method has significant drawbacks: first, the regulating effect is short-lived and cannot withstand the continuous release of acid from the bedrock; second, uneven mixing of the regulator and topsoil can easily cause excessive local pH fluctuations; and third, for large-scale remediation projects, the cost is high and economical. Therefore, there is an urgent need for a technical solution that can effectively and stably regulate the pH of the topsoil at a reasonable cost to address the adverse effects of acidic bedrock on hydroseeding vegetation remediation. Summary of the Invention

[0005] In view of this, the present invention provides an ecological restoration technology for acidified rock slopes by hydroseeding, which solves the problems of existing acid bedrock hydroseeding that does not fully consider the geochemical characteristics of the bedrock, especially the continuous impact of pH environment on the topsoil, only focuses on the adjustment of the initial pH of the topsoil, and lacks a long-term stabilization mechanism, resulting in a series of problems such as high cost, poor stability and inability to actively adjust pH value.

[0006] To achieve the above objectives, this invention provides a method for ecological restoration of rock slopes affected by sulfide oxidation and acidification through hydroseeding, comprising the following steps:

[0007] S1. Clean and level the bedrock slopes (such as quartzite) containing sulfides with a pH < 5.5;

[0008] S2. First, spray the mixed solution of microbial inhibitor and water onto the surface of the bedrock slope, and then spray a mixture of 15-30wt% phosphate powder and 70-85wt% calcium carbonate powder onto the surface of the bedrock slope to form a neutralization layer.

[0009] Alternatively, a mixture of 3-5 wt% microbial inhibitor, 15-30 wt% phosphate powder, and 70-85 wt% calcium carbonate powder can be sprayed onto the surface of the bedrock slope to form a neutralizing layer.

[0010] S3. Spray a mixture of 25-35 wt% limestone powder and 65-75 wt% straw pellets onto the surface of the neutralization layer to form a slow-release layer.

[0011] S4. Spray topsoil onto the surface of the slow-release layer. The topsoil contains seeds of local suitable herbaceous plants.

[0012] As a further preferred technical solution of the present invention, when cleaning and leveling the bedrock slope, the surface cracks and pits of the bedrock slope are filled with the slow-release layer mixture prepared in step S3.

[0013] As a further preferred technical solution of the present invention, step S2 involves using a drone or manual spraying of a microbial inhibitor solution onto the surface of the bedrock slope.

[0014] As a further preferred technical solution of the present invention, in step S2, the microbial inhibitor is prepared into a solution with water at a concentration of 6~8 mg / L.

[0015] As a further preferred technical solution of the present invention, when the microbial inhibitor is sprayed, a mixture is formed by 25wt% phosphate powder and 75wt% calcium carbonate powder; when the microbial inhibitor is mixed and sprayed, a mixture is formed by 5wt% microbial inhibitor, 20wt% phosphate powder and 75wt% calcium carbonate powder.

[0016] As a further preferred technical solution of the present invention, step S3 consists of a mixture of 30 wt% medium limestone powder and 70 wt% straw particles.

[0017] As a further preferred embodiment of the present invention, the thickness of the neutralizing layer is 1-3 cm and the thickness of the sustained-release layer is 3-5 cm.

[0018] As a further preferred technical solution of the present invention, the length of the straw pellets is 1-3cm, and the straw is crop straw such as wheat straw and corn straw.

[0019] As a further preferred embodiment of the present invention, the phosphate powder is selected from calcium phosphate commonly used in agricultural fertilizers; the microbial inhibitor is selected from sodium dodecyl sulfate (SDS) or sodium benzoate.

[0020] As a further preferred technical solution of the present invention, after spraying the neutralizing layer and the slow-release layer, compaction treatment is performed.

[0021] The mechanism of this invention is as follows: Sulfides (such as pyrite FeS2) in acidic bedrock undergo oxidation reactions in the presence of water and oxygen, producing acidic substances such as sulfuric acid. A neutralization layer is applied to the surface of the acidic bedrock slope. Calcium carbonate powder acts as a rapid acid neutralizer, quickly neutralizing the acid produced by oxidation. Furthermore, the calcium sulfate formed by the reaction of calcium carbonate and sulfuric acid (CaCO3 + H2SO4 = CaSO4 + CO2↑ + H2O) is insoluble in water and gradually precipitates on the rock surface or in pores, forming a dense calcium sulfate crystalline film. This film prevents sulfides from contacting oxygen and water, thus controlling acid production. Microbial oxidation of sulfide minerals is ten times faster than normal oxidation. Pre-spraying a microbial inhibitor solution utilizes microbial inactivation agents to inhibit the biological oxidation process of sulfides. The addition of phosphates forms insoluble phosphate minerals with iron ions, thereby reducing the oxidation of pyrite by iron ions and forming a coating on the pyrite surface to further inhibit its oxidation. The straw fiber structure in the slow-release layer provides support, preventing concentrated settlement of limestone powder during laying and subsequent spraying, and ensuring the uniformity of the buffer layer (neutralization layer + slow-release layer). The slow-release layer also isolates the neutralization layer from the topsoil layer, ensuring that the added microbial inhibitors do not affect the microorganisms in the topsoil layer, thus maximizing the effectiveness of the microbial inhibitors.

[0022] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0023] 1) This invention uses “microbial inhibition + phosphate + limestone powder” as the neutralization layer material and “limestone powder + straw” as the slow-release layer material. In the repair of acidic bedrock edge waves, the synergistic mechanism of each component ensures the stability and durability of the pH adjustment effect, and maintains the pH value of the imported soil within the range suitable for early plant growth for a long time.

[0024] 2) The present invention uses a neutralization layer + slow release layer composite structure as a buffer layer at the bottom of the topsoil layer, which can effectively block and neutralize the acidic and alkaline substances released by the bedrock, provide a stable pH environment for the topsoil, and maintain an effective buffering effect for more than 1 year after one laying, covering the critical period of plant rooting.

[0025] 3) This invention uses low-cost materials (limestone powder, straw, phosphate) and a small amount of microbial inhibitors, which reduces engineering costs and is suitable for large-scale promotion and application.

[0026] 4) The ecological restoration method of this invention, through regular monitoring after spraying, stabilizes the pH value of the imported soil between 6.2 and 6.8. After 3 months, the seed germination rate can reach more than 85%, the seedlings grow vigorously, and the vegetation coverage is significantly improved compared with traditional imported soil spraying. Moreover, after 1 year (12 months), the pH value of the imported soil is still maintained above 6.0, the plant roots have penetrated into the buffer layer and begun to extend into the bedrock fissures, and the vegetation community tends to be stable. Detailed Implementation

[0027] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0028] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art to which this invention pertains. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0029] All the following examples and comparative examples use bedrock slopes containing sulfides (pH=3.2, ±0.2) as the vegetation restoration targets, and the mixed materials (plant seeds, growth substrate, fertilizer, water-retaining agent, etc.) and processes for topsoil spraying are the same.

[0030] Comparative Example 1

[0031] Vegetation restoration was carried out using conventional hydroseeding techniques, as detailed below:

[0032] S1. Clean and level the bedrock slope containing sulfides;

[0033] S2. Apply the following topsoil spraying materials:

[0034] Mix 40wt% planting soil, 25wt% peat moss, 15wt% sheep manure, 13wt% straw powder, 2wt% water-retaining agent (polyacrylamide), and 5wt% binder (xanthan gum) evenly. Add plant seeds (alfalfa: tall ewe: ryegrass = 3:2:2) to prepare a topsoil spraying material with a moisture content of 15wt%. Finally, spray the topsoil onto the slope to form a topsoil spraying layer with a thickness of 8cm-10cm.

[0035] Example 1

[0036] This embodiment provides an ecological restoration method for acidic bedrock slopes with a pre-set neutralization buffer layer (neutralization layer + slow-release layer), as detailed below:

[0037] S1. Clean and level the bedrock slope containing sulfides;

[0038] S2. First, prepare a 7.5 mg / L aqueous solution of the microbial inhibitor sodium dodecyl sulfate (SDS) and spray it on the bedrock slope; then, mix 20% calcium phosphate powder and 80% calcium carbonate powder evenly according to the mass percentage, spray and compact it to obtain a neutral layer with a thickness of 3 cm.

[0039] S3. Mix 30% limestone powder and 70% wheat straw granules (1-3cm in length) evenly by mass percentage, then spray the mixture onto the surface of the neutralization layer and compact it to obtain a slow-release layer with a thickness of 5cm.

[0040] S4. Spray topsoil onto the surface of the slow-release layer, following the same procedure as step S2 in Comparative Example 1.

[0041] Example 2

[0042] The process steps in this embodiment are the same as those in Example 1, except that the microbial inhibitor used is sodium benzoate and the concentration of the prepared solution is 10.0 mg / L.

[0043] Example 3

[0044] The process steps in this embodiment are the same as those in Embodiment 1, except that the microbial inhibitor sodium dodecyl sulfate (SDS) used is a solid powder, and 20% phosphate powder, 5% microbial inhibitor and 75% calcium carbonate powder are mixed evenly according to the mass percentage to form a neutralization layer.

[0045] Comparative Example 2

[0046] As a control experiment for Example 1, the only difference from Example 1 is that step S2 is omitted, that is, only a 5cm slow-release layer is set before topsoil spraying.

[0047] Comparative Example 3

[0048] As a control experiment for Example 1, the only difference from Example 1 is that the ratio in the neutralization layer was adjusted, that is, 5 wt% calcium phosphate powder and 95 wt% calcium carbonate powder were mixed evenly before spraying.

[0049] Comparative Example 4

[0050] As a control experiment for Example 1, the only difference from Example 1 is that phosphate was omitted in the neutralization layer, i.e., 100 wt% calcium carbonate powder was sprayed.

[0051] Comparative Example 5

[0052] As a control experiment of Example 1, the only difference from Example 1 is that the aqueous solution of microbial inhibitor (SDS) was omitted from the neutralization layer, that is, only a mixture of 20 wt% phosphate powder and 80 wt% calcium carbonate powder was sprayed to form the neutralization layer.

[0053] Tables 1 and 2 show the changes in soil pH and vegetation cover of Examples 1-3 and Comparative Examples 1-5 with different formulations of neutralizing and slow-release layers, respectively. The data were recorded from the day after the topsoil was sprayed to the 12th month.

[0054] Table 1: Statistics of pH values ​​differing between the examples and comparative examples in different months.

[0055]

[0056] The vegetation index was calculated using a UAV's multispectral lens by scanning the vertical projection area of ​​different blocks. The flight altitude was set to 60cm, flight speed to be within a certain range, and overlap to be greater than 80% front-to-back and 70% left-to-right. The vegetation cover was calculated using the Modified Soil Vegetation Index (MSAVI), with the following formula:

[0057]

[0058] NIR represents the near-infrared band, RED represents the red band, and L is the soil regulating factor.

[0059] Changes in vegetation cover over different time periods reflect, to some extent, the germination of plant seeds and the growth of vegetation. This demonstrates the impact of different formulations and comparative proportions on plant growth.

[0060] Table 2: Statistical table of vegetation index (MSAVI) at different times for the examples and comparative examples

[0061]

[0062] Based on the experimental data in Tables 1 and 2, and through comparative analysis of Examples 1, 2, and 3 with Comparative Examples 1 to 5, it was found that the method proposed in this invention plays an important role in maintaining stable pH values ​​in the topsoil and promoting plant growth. Compared to Example 1, Example 2 changed the inhibitor, and the inhibitor in Example 3 was mixed with other neutralizing materials and sprayed, with slightly worse effects than Example 1. After adjusting the proportions of the neutralizing layer materials in each comparative example, compared to Example 1, the plants showed a significant decrease in growth index after about 7 days, and the pH values ​​were significantly lower than in Example 1. This indicates that the neutralizing layer, through the synergistic mechanism of its components, ensures the stability and durability of pH regulation in the repair of acidic bedrock edge waves. Moreover, the data shows that the method of this invention can quickly regulate the pH value of acidic bedrock slopes in a short period of time, creating stable environmental conditions for plant germination. During subsequent monitoring, the pH value of Example 1 remained stable above 6.0, while the comparative examples showed that the pH value could not quickly rise above 6.0 or exhibited significant acidification in the later stages. In summary, the method of this invention can provide a stable acid-base environment throughout the entire plant growth process.

[0063] While specific embodiments of the present invention have been described above, those skilled in the art should understand that these are merely illustrative examples, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is defined only by the appended claims.

Claims

1. A method for ecological restoration of rock slopes affected by sulfide oxidation and acidification through hydroseeding, characterized in that, Includes the following steps: S1. Clean and level the bedrock slope containing sulfides with a pH < 5.5; S2. First, spray the mixed solution of microbial inhibitor and water onto the surface of the bedrock slope, and then spray a mixture of 15-30 wt% phosphate powder and 70-85 wt% calcium carbonate powder onto the surface of the bedrock slope to form a neutralization layer. Alternatively, a mixture of 3-5 wt% microbial inhibitor, 15-30 wt% phosphate powder, and 70-85 wt% calcium carbonate powder can be sprayed onto the surface of the bedrock slope to form a neutralizing layer. S3. Spray a mixture of 25-35 wt% limestone powder and 65-75 wt% straw pellets onto the surface of the neutralization layer to form a slow-release layer. S4. Spray topsoil on the surface of the slow-release layer. The topsoil contains herbaceous plant seeds. The neutralizing layer has a thickness of 1-3 cm, and the slow-release layer has a thickness of 3-5 cm; the straw particles have a length of 1-3 cm; after spraying the neutralizing layer and the slow-release layer, compaction is performed.

2. The method for ecological restoration of rock slopes affected by sulfide oxidation and acidification according to claim 1, characterized in that, When cleaning and leveling the bedrock slope, the surface cracks and pits of the bedrock slope are filled with the slow-release mixture prepared in step S3.

3. The method for ecological restoration of rock slopes affected by sulfide oxidation and acidification according to claim 1, characterized in that, Microbial inhibitor solutions are sprayed onto the surface of bedrock slopes using drones or manual labor.

4. The method for ecological restoration of rock slopes affected by sulfide oxidation and acidification according to claim 1, characterized in that, The microbial inhibitor was prepared into a solution with water at a concentration of 6-8 mg / L.

5. The method for ecological restoration of rock slopes affected by sulfide oxidation and acidification according to claim 1, characterized in that, When the microbial inhibitor is sprayed, a mixture of 25 wt% phosphate powder and 75 wt% calcium carbonate powder is formed; when the microbial inhibitor is mixed and sprayed, a mixture of 5 wt% microbial inhibitor, 20 wt% phosphate powder and 75 wt% calcium carbonate powder is formed.

6. The method for ecological restoration of rock slopes affected by sulfide oxidation and acidification according to claim 1, characterized in that, The slow-release layer mixture consists of 30 wt% medium limestone powder and 70 wt% straw pellets.

7. The method for ecological restoration of rock slopes affected by sulfide oxidation and acidification according to claim 1, characterized in that, The phosphate powder is selected from calcium phosphate; the microbial inhibitor is selected from sodium dodecyl sulfate or sodium benzoate.

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