Ecological restoration method for waste alum mine land

Abstract

The invention discloses an ecological restoration method for waste alum mine land. The ecological restoration method comprises the following steps: (1) soil improvement; (2) suitable plant species are selected, vetiver grass is planted in herbaceous species, neoleucaena leucocephala and broussonetia papyrifera are planted in arbor species, and lespedeza speciosa is planted in shrub species; (3) firstly adopting grass planting belts to fix the soil, selecting vetiver grass seedlings for planting, and planting one grass belt every 10 meters along the contour line to fix the soil; and planting arbors, shrubs and other herbaceous plants among the planting belts. The invention has the following advantages: 1, degraded soil can be repaired and improved, soil functions are recovered, and further degradation of land is prevented; 2, the living environment of other species is locally improved, and water and soil loss is prevented; and 3, the water storage function of the waste land is improved, and the underground root system and the overground stem leaves have mechanical reinforcement, anchoring and supporting effects and obvious water and soil conservation and ecological slope protection functions of intercepting rainfall, inhibiting surface runoff, weakening splash erosion and the like.

Description

Technical Field

[0001] The invention belongs to the ecological field, and in particular relates to an ecological restoration method for abandoned alum mines. Background Art

[0002] With the rapid development of industry, the scale of human exploitation of mineral resources is expanding. However, due to backward production technology, improper disposal of solid waste and tailings generated during mining, and open-air storage, these abandoned lands not only occupy a large amount of land resources, but also destroy the landscape and pollute the surrounding environment. How to effectively manage such abandoned land, make full use of mining land resources, restore and rebuild forest vegetation, and improve the ecological environment of mining areas are important topics in forestry ecological engineering and land management. In terms of the improvement and management of contaminated soil, physical and chemical methods such as imported soil method, lime improvement method, leaching method, adsorption fixation method, biological reduction method, etc. have been used internationally. Although these methods have certain theoretical significance, they are difficult to promote on a large scale. The phytoremediation technology developed in recent years has the characteristics of safety and low cost, and has become a hot spot for research and development.

[0003] The soil properties of alum mine slag land are mainly sandy soil with too high sand content. It is breathable and water-permeable, but not easy to retain water, and the soil temperature fluctuates greatly. In addition, the surface area ratio of the sand is small, the ability to absorb effective nutrients is poor, and the fertilizer retention capacity is small. However, it is easy to cultivate and plants can easily take root. However, the continuous high temperature in summer can easily cause plants to die from lack of water and drought.

[0004] By testing the chemical properties of the mine wasteland, we have preliminarily come to the following conclusions: The pH value of the slag soil is 4.20-4.29, which is strongly acidic and only suitable for the growth of some acidic plants; the organic matter content is 0-0.47g.kg-1, and it is extremely difficult to ensure the organic nutrition required for normal plant growth. The N content is extremely low, only 0-0.003g.kg-1, while the P, K, and Ca contents are much higher than those in the control area, which can meet the needs of plant growth and do not pose a hazard. The S content is significantly higher than that in the control area, and other metal elements and heavy metal elements do not exceed the standard. Therefore, when introducing species, the main considerations are acid-resistant plants, and legumes that can naturally fix N and are tolerant to S.

[0005] The cost of using physical, chemical or biological methods to repair abandoned mining areas is high, and even in economically developed areas, large-scale restoration is difficult. The restoration of the abandoned alum mine in Cangnan can only find a high-efficiency, low-investment, no secondary pollution, no damage to the original ecological environment, and simple and convenient management. Many scholars believe that the metabolic process of plants can transform, mineralize or take away pollutants, and the cost is low, and the ecological and economic benefits are considerable (Wang Qingren et al., 2001; Wang Youbao et al., 2004; Luo Yongming, 1999; Chaney et al., 1999; Heaton et al. 1998). Based on the actual situation, it is feasible to use plants to carry out ecological restoration of the abandoned alum mine in Cangnan.

[0006] Although the Cangnan alum mine is located in an area with superior climatic conditions, which is conducive to plant growth and development, the formation and succession of plant communities are affected by a combination of environmental factors. In the special site conditions of abandoned land, soil conditions have become the main influencing factors (Shu Wensheng et al., 1997; Liu Qi et al., 1998; Lan Chongyu et al., 1996). On the slag land, the soil texture is mainly sandy soil. Although it has good ventilation and tax evaporation performance and a large permeability coefficient, it has a small water storage capacity and strong evaporation and water loss. The capillaries of sandy soil are coarse, and the height of capillary water rise is small. When the water level is low, it cannot rely on groundwater to moisten the surface through capillary rise, so it has weak drought resistance; the organic matter content is low and the N content is low, which hinders the absorption of nutrients by plants. However, the slag soil has very low N but rich P, which is conducive to the growth of N-fixing plants. The toxic effect of heavy metal element S affects the normal function of plants and aggravates the barrenness of the soil; the soil pH value is low and the acidity is too strong, which seriously restricts the normal growth of plants. The physical and chemical properties of this type of abandoned land, especially the chemical properties, seriously restrict the survival of these plants. To repair this type of land, the first thing to do is to improve the substrate to improve the ability to retain water and fertilizer, and then add fertilizer to make up for the lack of nutrients, and plant resistant plants that are suitable for acidic soils and can avoid heavy metal poisoning. In theory, it is possible to improve highly acidic soils, but it is very difficult in actual operation. While reducing soil acidity, it may lead to excessive amounts of other elements and produce new poisoning. Therefore, the best way to control soil acidity is to select tolerant plants, supplemented by necessary management measures, and carry out in-situ restoration of plant organisms.

[0007] The Wenzhou Alum Mine in Zhejiang Province is located in Fanshan Town, Cangnan County, Zhejiang Province. It is the only manufacturer of potassium alum in the world. The total area of ​​the mining area is k㎡. The total proven reserves of alum stone are 167 million tons, accounting for 76% of the world's reserves, and the annual output accounts for 70% of the country's total output. Cangnan is therefore known as the world's alum capital. The mining of the alum mine began during the Hongwu period of the Ming Dynasty, and has a history of more than 600 years. Long-term mining has caused serious damage to the local natural ecosystem. Alum slag has accumulated into mountains in the mining area. The slag yard mainly includes two areas, Jilongshan Niupitan and Fengshuhu yard. The vegetation has seriously degraded, which has weakened or lost its corresponding ecological functions, and has led to land degradation, environmental pollution, and destruction of animal and plant habitats. Bioremediation of degraded ecosystems has been recognized as a low-cost and high-ecological-efficiency restoration method. Selecting appropriate plant species to repair the damaged environment can not only absorb, transform or enrich pollutants, reduce or prevent their spread, but also shorten the time it takes to rebuild the ecosystem. Summary of the invention

[0008] The above technical purpose of the present invention is achieved through the following technical scheme: a method for ecological restoration of abandoned alum mines.

[0009] A method for ecological restoration of alum mine wasteland comprises the following steps:

[0010] (1) Soil improvement

[0011] The soil in the slag land was improved using water retaining agent, lime, yellow mud and organic fertilizer.

[0012] (2) Selecting suitable plant species

[0013] Vetiver is planted as herbaceous plants, New Leucaena leucaena and Broussonetia chinensis are planted as trees, and Lespedeza bicolor is planted as shrubs.

[0014] Among the woody plants, Lespedeza bicolor, Leucaena leucophylla and Broussonetia papyrifera have strong adaptability to the environment of the abandoned alum mine. Among the herbaceous plants, Vetiver is the most suitable and can be used as a pioneer species for environmental restoration. Indigofera dasyphylla, Duckbill grass, Imperata cylindrica and Sisal hemp have the effect of enriching potassium, and Indigofera dasyphylla also has the effect of enriching aluminum.

[0015] (3) Mixed planting of trees, shrubs and grasses

[0016] Since the abandoned alum mines are all waste slag and the soil is very loose, we first planted grass belts to stabilize the soil. Vetiver seedlings were selected for planting. A grass belt was planted every 10 meters along the contour line to stabilize the soil. Trees, shrubs and other herbaceous plants were planted between each planting belt. In terms of planting density, a dense planting method was adopted, with a tree planting density of 1m×1m, a shrub planting density of 0.5×0.5m, and a herb planting density of 1m 2 Plant 20 plants.

[0017] Furthermore, the soil improvement in step (1) is specifically a water retaining agent: yellow mud: lime ratio of 2:100:1.

[0018] Furthermore, in step (3), the herbs and trees are planted by seedling planting, and the shrub Lespedeza bicolor is sown by seeds.

[0019] Furthermore, in step (3), seedlings with soil balls or container seedlings are selected as much as possible, and the seedlings should not be too large. One-year-old seedlings are selected as much as possible for trees and shrubs.

[0020] Furthermore, container seedlings are preferably used in step (3) because the soil in the alum mine wasteland has poor water retention and container seedlings are good at retaining water, thereby improving the survival rate.

[0021] In summary, the present invention has the following beneficial effects: 1. The use of lime, water retaining agent and yellow mud can make it more suitable for plant growth and ecosystem health, appropriately improve the growth of plants, and by improving the soil, repair and improve degraded soil, restore soil function and prevent further degradation of the land; 2. Lespedeza serrata, Leucaena leucophylla, Broussonetia papyrifera and Vetiver are pioneer species that can be introduced into the abandoned alum mine site at the earliest. The soil N content of the abandoned alum mine site is extremely low, and although the P content is high, its existing form is difficult to be absorbed and utilized by plants under acidic conditions, and the soil environment is poor. Leguminosae plants have biological nitrogen fixation and can effectively fix N2 in the atmosphere to increase the accumulation of nitrogen in the soil, which is not only beneficial to the growth of leguminous plants themselves, but also beneficial to the release of other nutrients (such as P) in the soil, and ultimately plays a role in locally improving the living environment of other species. Vetiver of the Gramineae family has a developed and fine root system, has a strong absorption function and prevents soil and water loss, so it can grow well under poor site conditions. 3. The planting of vetiver hedges reduces the soil loss on a 15-degree slope to only 1.13 t / ha, which is only 0.06% of the soil loss when no grass is planted, and intercepts 99.4% of the soil loss. The restoration method provided by the present invention increases the water storage function of the rock slope, which originally had almost zero water storage function, to about 26 kg / ㎡. The dry weight of the aboveground and underground biomass is 657.16 g / ㎡ and 254.82 g / ㎡ respectively; the average litter biomass is 148.82 g / ㎡, playing an important role in fixing CO2. At the same time, the underground root system and the aboveground stems and leaves have mechanical reinforcement, anchoring, and support effects, as well as obvious soil and water conservation and ecological slope protection functions such as intercepting rainfall, inhibiting surface runoff, and weakening splash erosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is the survival rate in the soil improvement experiment in the embodiment;

[0023] Figure 2 is the seedling height in the soil improvement experiment in the embodiment;

[0024] Figure 3 is the total leaf area in the soil improvement experiment in the embodiment;

[0025] Figure 4 This is a schematic diagram of the mixed planting of trees, shrubs and grasses according to the arrangement in step (3) of the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments:

[0027] (1) Soil improvement

[0028] Orthogonal test of water retainer, lime and yellow mud was used. The test was divided into three factors: water retainer, lime and yellow mud, among which water retainer had three levels (0, 5g, 10g), yellow mud had two levels (0, 250g, 500g), and lime had three levels (0, 5g, 10g). L9 (34) orthogonal table was used for design. One month after planting, the survival rate, seedling height and total leaf area were investigated.

[0029] Table 1 Experimental design table

[0030] Processing number deal with 1 A1B1C1 2 A1B2C2 3 A1B3C3 4 A2B1C2 5 A2B2C3 6 A2B3C1 7 A3B1C3 8 A3B2C1 9 A3B3C2

[0031] Table 2 Index table

[0032]

[0033]

[0034] The P value of the model is less than 0.05, indicating that there is a statistically significant relationship between the variables in the model and the response variable, which means that the data is statistically significant. Figure 1 , Figure 2 , Figure 3 It can be verified that 10g of water-retaining agent, 500g of yellow mud and 5g of lime have the best survival rate, seedling height and total leaf area.

[0035] (2) Screening of suitable plant species

[0036] Through the investigation of natural settlement plants in the alum mine wasteland, 18 species of plants were identified, including 15 woody plants and 3 herbaceous plants, and tested for ecological restoration species. Through a comprehensive analysis of survival rate, growth adaptability, and physiological adaptability, among the woody plants, Lespedeza bicolor, Leucaena leucophylla and Broussonetia papyrifera have strong adaptability to the environment of the alum mine wasteland. Among the herbaceous plants, Vetiver zephyranthes is the most suitable and can be used as a pioneer species for environmental restoration. As can be seen from Table 3 below, the highest growth is Lespedeza bicolor, reaching 8.43cm; followed by Juniper, reaching 6.18cm; the height growth of Pittosporum tobira, Coral Tree and Leucaena leucophylla is also obvious, above 2cm, while Huashan alum has no height growth. The ground diameter growth of all species is not obvious: Juniper, which has the largest growth, has increased by 3.51mm, and other species are very small, about 1mm, or even smaller; there is no increase in honeysuckle. The crown width growth varies greatly among different species, and the difference is significant. In Table 4, the tree with the largest crown width growth is Lespedeza bicolor, which grows to 24.5 cm, followed by Broussonetia papyrifera, Alum of Huashanica and Leucaena leucophylla, which are all above 10 cm; while Nerium oleander and Pinus cypress grow less than 1 cm. Although the growth characteristics of the species themselves may lead to differences in growth, the growth traits of some species with similar growth characteristics are still quite different, such as the crown width growth of Alum of Huashanica, a deciduous small tree, is 16.56 cm, while that of Alum of Huashanica is 9.55 cm.

[0037] Therefore, among the woody plants proposed in the present invention, Lespedeza bicolor, Leucaena leucophylla and Broussonetia papyrifera have strong adaptability to the environment of abandoned alum mines, and among the herbaceous plants, Vetiver zizyphus is the most suitable and can be used as pioneer species for environmental restoration.

[0038] Table 3 Comparison of the growth of 15 woody plants on abandoned alum mines

[0039] Tab.2Comparison of growth among 15woody

[0040] species on alum mining tailings

[0041]

[0042] Table 4 Analysis of variance of physiological traits of tested plants

[0043] Tab.3 Variance analysis for physiological character between experimental plants

[0044]

[0045] (3) Mixed planting of trees, shrubs and grasses

[0046] refer to Figure 4 Planting method: Since the abandoned alum mine is full of waste slag and the soil is very loose, we first plant grass belts to fix the soil and plant seedlings. A grass belt is planted every 10 meters along the contour line to fix the soil;

[0047] Between each planting belt, new Leucaena leucaena, Broussonetia papyrifera, Lespedeza chinensis, and Vetiver are planted. New Leucaena leucaena and Broussonetia papyrifera are selected as seedlings with soil balls or container seedlings, and trees and shrubs are selected as one-year-old seedlings. Lespedeza chinensis shrubs are planted from seeds.

[0048] In terms of planting density, the method of close planting is adopted, with a planting density of 1m×1m for trees, 0.5×0.5m for shrubs, and 1m for herbs. 2 Plant 20 plants.

[0049] This specific embodiment is merely an explanation of the present invention and is not a limitation of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by the patent law.

Claims

1. A method for ecological restoration of abandoned alum mines, characterized in that: The following steps are involved: (1) Soil improvement Use water retaining agent, lime, yellow mud and organic fertilizer to improve the soil of slag land; (2) Selecting suitable plant species Vetiver is planted as herb, Leucaena leucaena and Broussonetia sylvestris are planted as tree, and Lespedeza serrata is planted as shrub; (3) Mixed planting of trees, shrubs and grasses First, grass strips are used to stabilize the soil. Vetiver seedlings are selected for planting. A grass strip is planted every 10 meters along the contour line to stabilize the soil. Trees, shrubs and other herbaceous plants are planted between each planting strip. The planting density is densely planted. The planting density of trees is 1m×1m, that of shrubs is 0.5×0.5m, and that of herbs is 1m 2 Plant 20 plants.

2. The method for ecological restoration of a waste alum mine according to claim 1, characterized in that: The soil improvement in step (1) is specifically a water retaining agent: yellow mud: lime ratio of 2:100:

1.

3. The method for ecological restoration of alum mine wasteland according to claim 1, characterized in that: In the step (3), the herbs and trees are planted by seedling planting, and the shrub Lespedeza bicolor is sown by seeds.

4. The method for ecological restoration of alum mine wasteland according to claim 1, characterized in that: In the step (3), the seedlings are selected to be seedlings with soil balls or container seedlings, and the trees and shrubs are one-year-old seedlings.

5. The method for ecological restoration of alum mine wasteland according to claim 1, characterized in that: In the step (3), container seedlings are used.

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