Desertified soil restoration method based on microorganism mineralization induction and moss-algae crust

Abstract

The invention discloses a desertified soil restoration method based on microorganism mineralization induction and moss-algae crust, which comprises the following steps: crushing soybeans, and dissolving the crushed soybeans in water to obtain a soybean urease crude extract; adding desert green algae and drought-enduring moss into the cementing liquid prepared from the travertine for later use; the algae crust cementing liquid is obtained; the method comprises the following steps: preparing a soybean urease crude extracting solution, uniformly mixing the soybean urease crude extracting solution with desertification soil needing to be recovered, adding a moss-algae crust cementing solution into the surface layer of the mixed desertification soil, and curing for a period of time to realize the solidification of the desertification soil and the moss-algae crust on the surface layer. On the basis of microorganism mineralization induced sand stabilization, the bryophyllum crust is further applied to the soil surface to enhance the compressive strength of the soil surface, so that the strength of the desertification soil can be effectively recovered, and meanwhile, the bryophyllum crust also enables the desertification soil to be covered by moss and algae again, and the nutrients and environment of the soil are recovered.

Description

Technical Field

[0001] This invention belongs to the field of desertification control and ecological environment, and in particular relates to a method for restoring sandy soil based on microbial mineralization induction and bryophyte crust formation. Background Technology

[0002] Climate change and human activities have exacerbated desertification, making soil desertification a serious social, economic, and environmental problem in many parts of the world. Depending on the driving factors and geographical environment, soil desertification may lead to increased bare soil, loss of soil productivity (such as nutrient loss, reduction of soil fine particles, and decreased water carrying capacity), increased soil salinity and toxicity, or changes in vegetation composition. Finding feasible ways to reverse desertification has become an urgent issue facing humanity in order to protect the environment and reduce the social and economic problems caused by soil desertification.

[0003] Currently, there are many studies on soil remediation in desertified areas, such as microbial induced calcium carbonate precipitation (MICP). This method involves culturing microorganisms to alter environmental conditions (such as pH and ion concentration), promoting the combination of calcium ions (Ca²⁺) and carbonate ions (CO₃²⁻) to form stable calcium carbonate crystals, thus fixing the soil. However, this method has stringent requirements for the culture environment, including precise control of temperature, pH, and nutrient concentration. This makes the culture process complex and prone to failure. Moreover, the entire reaction cycle of MICP is long, requiring a significant amount of time from microbial culture to the completion of calcium carbonate precipitation, resulting in low efficiency. For example, the method of artificially inoculating and cultivating desert algae on a large scale to form biological soil crusts can not only fix shifting sand, but also improve soil fertility and desert conditions, thus contributing to the restoration of desert ecosystems. However, biological soil crusts are formed by the preferential growth of algae, which fix the soil surface, followed by the growth of other cryptogams on top. In existing artificial soil crust fixation technologies, the newly inoculated desert algae have not yet formed an effective algal crust on the surface of sandy soil, resulting in a weak sand-fixing effect. Summary of the Invention

[0004] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0005] To achieve these objectives and other advantages of the present invention, a method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting is provided, comprising the following steps: Step 1: Roast soybeans, grind and sieve them to obtain soybean flour. Dissolve the soybean flour in water, stir and let it stand. Then centrifuge and filter to obtain crude soybean urease extract. Refrigerate for later use. Step 2: Isolate desert green algae from natural algal crusts, culture them in a culture medium to the required density for later use, and at the same time collect drought-resistant mosses, clean them, dry them in the shade, and crush them into powder for later use. Step 3: Dissolve travertine in hydrochloric acid, making sure there is a slight excess of travertine. Then centrifuge and filter the solution, take the supernatant and add urea to prepare a cementing solution. Then moisten the moss powder to restore its activity, and add the moss powder and desert green algae together to the cementing solution to obtain the moss-algae crust cementing solution. Step 4: First, spray the crude extract of soybean urease onto the surface of the sandy soil that needs to be restored. After the crude extract of soybean urease has penetrated into the sandy soil by gravity, spray the moss and algae crust cementing solution. Repeat the spraying several times. After a period of maintenance, the sandy soil can be solidified and the surface moss and algae crust can be formed.

[0006] Preferably, in step one, the soybean baking parameters are: baking at 40-50℃ for 6-8 hours, sieving with a mesh size of 100-150 mesh, soybean flour to water ratio of 60-100g:1L, stirring parameters: stirring at 300-400rpm for 30-40 minutes, standing at 4-5℃ for 2-4 hours, centrifugation parameters: centrifuging at 5000-6000rpm for 15-20 minutes at 4-5℃, and refrigeration temperature of 4-5℃.

[0007] Preferably, in step two, the desert green algae is one or more of the following: *Pseudocladophyta*, *Nostoc*, *Anabaena*, and *Oscillatoria*, and the culture conditions are BG11 as the culture medium at 120-150 μmol / m³. 2 Cultivate at a light intensity of ·s until the density reaches 1.2~1.5×10⁻⁶. 6 cells / mL.

[0008] Preferably, in step two, the moss is one or more of the following: *Bryophytum dentatum*, *Bryophytum longifolium*, *Bryophytum pubescens*, and *Bryophytum gracilistylus*, and the moss is pulverized to 1-3 mm.

[0009] Preferably, in step three, the calcium carbonate in the travertine is used as the standard, the ratio of travertine to hydrochloric acid is 1.05~1.1mol:2mol, after dissolution, water is added to dilute to a calcium ion concentration of 0.5~0.8mol / L, the centrifugation parameters are 4000~4500rpm for 5~10min, the ratio of urea to supernatant is 0.75~1mol:1L, and the ratio of moss powder, desert green algae and cementing solution is 20~40g:20~40g:1L.

[0010] Preferably, in step three, the specific method for moistening the moss powder to restore its activity is as follows: the moss powder is moistened by spraying water at 10~15℃ for 48~72h, during which the light intensity is 25~30μmol / m². 2•s, the light-dark cycle is 12 / 12h.

[0011] Preferably, in step four, when spraying the crude soybean urease extract and the moss-algal crust cementing solution, the concentration is 10-20 L of crude soybean urease extract per m³. 2 Sandy soil, 20-30L of moss and algae crust cementing solution / m 2 Spray the sandy soil repeatedly 10-20 times, using 1-2L each time. Cultivate at room temperature for 72-96 hours, supplementing with water every 24 hours for 10-20 minutes at a flow rate of 20-30 mL / m³. 2 •min, and apply diluted BG11 culture medium 1-2 times during this process.

[0012] The present invention has at least the following beneficial effects: By combining microbial mineralization induction and moss and algae crust formation, the present invention, based on microbial mineralization induction for sand fixation, also forms moss and algae crusts on the soil surface to enhance the compressive strength of the soil surface, which can effectively restore the strength of sandy soil. At the same time, the moss and algae crust formation also allows the sandy soil to be covered by moss and algae again, restoring soil nutrients and environment. Detailed Implementation

[0013] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0014] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0015] Example 1 A method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting includes the following steps: Step 1: Roast soybeans and then grind them through a 100-mesh sieve to obtain soybean flour. Dissolve 60g of soybean flour in 1L of water, stir at 300rpm for 30min, let stand at 4℃ for 2h, then centrifuge at 4℃ and 5000rpm for 15min, filter, and obtain crude soybean urease extract. Store at 4℃ for later use. Step 2: Isolate desert green algae (in this example, *Pseudocladophyta*) from natural algal crusts and culture them in BG11 medium at an illumination intensity of 120 μmol / m². 2 •s, cultured to 1.2×10 6 cells / mL, for later use. At the same time, drought-resistant moss (in this example, red moss was selected), cleaned and air-dried, and then crushed into 3mm powder for later use. Step 3: Dissolve 60g of travertine in 1L of 1mol / L hydrochloric acid, then dilute with water to a calcium ion concentration of 0.5mol / L. Centrifuge the solution at 4000rpm for 5min, filter to remove insoluble matter, take 1L of supernatant, add 0.75mol urea to prepare a cementing solution, and then spray the moss powder with water at 15℃ for 48h, during which the light intensity is 25μmol / m². 2 ·s, with a light / dark cycle of 12 / 12h, to moisten the moss powder and restore its activity. Then, 20g of the restored moss powder and 20g of pseudobranch algae were added to 1L of cementing solution to obtain moss-algae crust cementing solution. Step 4: Spray 10L of crude soybean urease extract onto a 1m wide area, using 1L of crude soybean urease extract per application and 2L of moss-algal crust cementing solution per application. 2 On the sandy soil requiring restoration, after the crude soybean urease extract has infiltrated into the sandy soil by gravity, 20L of bryophyll crust cementing solution is sprayed onto the sandy soil. This spraying is repeated 10 times. Then, the soil is cured at room temperature for 72 hours. During this period, water is sprayed every 24 hours for 20 minutes each time, with a water flow rate of 20mL / m². 2 By applying diluted BG11 culture solution once during the process, the sandy soil can be solidified and the surface moss and algae can form a crust.

[0016] Example 2 A method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting includes the following steps: Step 1: Roast soybeans and then grind them through a 100-mesh sieve to obtain soybean flour. Dissolve 80g of soybean flour in 1L of water, stir at 300rpm for 30min, let stand at 4℃ for 2h, then centrifuge at 4℃ and 5000rpm for 15min, filter, and obtain crude soybean urease extract. Store at 4℃ for later use. Step 2: Isolate desert green algae (Nostoc commune in this example) from natural algal crusts and culture them in BG11 medium at an illumination intensity of 120 μmol / m². 2 •s, cultured to 1.2×10 6 cells / mL, for later use. At the same time, drought-resistant moss (in this example, long-pointed leaf moss was selected), cleaned and air-dried, and then crushed into 3mm powder for later use. Step 3: Dissolve 60g of travertine in 1L of 1mol / L hydrochloric acid, then dilute with water to a calcium ion concentration of 0.5mol / L. Centrifuge the solution at 4000rpm for 5min, filter to remove insoluble matter, take 1L of supernatant, add 0.75mol urea to prepare a cementing solution, and then spray the moss powder with water at 15℃ for 48h, during which the light intensity is 25μmol / m². 2·s, with a light / dark cycle of 12 / 12h, to moisten the moss powder and restore its activity. Then, 30g of the restored moss and 30g of Nostoc coagulans were added to 1L of cementing solution to obtain moss-algal crust cementing solution. Step 4: Spray 10L of crude soybean urease extract onto a 1m wide area, using 1L of crude soybean urease extract per application and 2L of moss-algal crust cementing solution per application. 2 On the sandy soil requiring restoration, after the crude soybean urease extract has infiltrated into the sandy soil by gravity, 20L of bryophyll crust cementing solution is sprayed onto the sandy soil. This spraying is repeated 10 times. Then, the soil is cured at room temperature for 72 hours. During this period, water is sprayed every 24 hours for 20 minutes each time, with a water flow rate of 20mL / m². 2 By applying diluted BG11 culture solution once during the process, the sandy soil can be solidified and the surface moss and algae can form a crust.

[0017] Example 3 A method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting includes the following steps: Step 1: Roast soybeans and then grind them through a 100-mesh sieve to obtain soybean flour. Dissolve 100g of soybean flour in 1L of water, stir at 300rpm for 30min, let stand at 4℃ for 2h, then centrifuge at 4℃ and 5000rpm for 15min and filter to obtain crude soybean urease extract. Store at 4℃ for later use. Step 2: Isolate desert green algae (Anabaena in this example) from natural algal crusts and culture them in BG11 medium at an illumination intensity of 120 μmol / m². 2 •s, cultured to 1.2×10 6 cells / mL, for later use. At the same time, drought-resistant moss (in this example, moss purpurea was selected), was cleaned, dried in the shade, and pulverized into 3mm powder for later use. Step 3: Dissolve 60g of travertine in 1L of 1mol / L hydrochloric acid, then dilute with water to a calcium ion concentration of 0.5mol / L. Centrifuge the solution at 4000rpm for 5min, filter to remove insoluble matter, take 1L of supernatant, add 0.75mol urea to prepare a cementing solution, and then spray the moss powder with water at 15℃ for 48h, during which the light intensity is 25μmol / m². 2 ·s, with a light / dark cycle of 12 / 12h, to moisten the moss powder and restore its activity. Then, 40g of the restored moss and 40g of Anabaena were added to 1L of cementing solution to obtain moss and algae crust cementing solution. Step 4: Spray 10L of crude soybean urease extract onto a 1m wide area, using 1L of crude soybean urease extract per application and 2L of moss-algal crust cementing solution per application. 2On the sandy soil requiring restoration, after the crude soybean urease extract has infiltrated into the sandy soil by gravity, 20L of bryophyll crust cementing solution is sprayed onto the sandy soil. This spraying is repeated 10 times. Then, the soil is cured at room temperature for 72 hours. During this period, water is sprayed every 24 hours for 20 minutes each time, with a water flow rate of 20mL / m². 2 By applying diluted BG11 culture solution once during the process, the sandy soil can be solidified and the surface moss and algae can form a crust.

[0018] Comparative Example 1 This comparative example uses the existing technology that only uses urease to induce calcium carbonate precipitation for sand fixation: Step 1: Roast soybeans and then grind them through a 100-mesh sieve to obtain soybean flour. Dissolve 100g of soybean flour in 1L of water, stir at 300rpm for 30min, let stand at 4℃ for 2h, then centrifuge at 4℃ and 5000rpm for 15min and filter to obtain crude soybean urease extract. Store at 4℃ for later use. Step 2: Dissolve 0.5 mol calcium chloride and 0.75 mol urea in 1 L of water to prepare a cementing solution; Step 3: Spray 10L of crude soybean urease extract onto a 1m wide area, using 1L of crude soybean urease extract per application and 2L of cementing solution per application. 2 On the sandy soil requiring restoration, after the crude soybean urease extract has infiltrated into the sandy soil by gravity, 20L of cementing solution is sprayed onto the sandy soil. This spraying is repeated 10 times, followed by 72 hours of curing. During this period, water is sprayed every 24 hours for 20 minutes each time, at a flow rate of 20mL / m². 2 ·min.

[0019] Comparative Example 2 This comparative example uses the existing technology that only uses biological crusting for sand fixation: 10,000 L of *Micrococcus sheathingii* was cultured in a racetrack-style culture tank under natural light using simplified BG11 medium. When the biomass exceeded 0.2 g / L, precipitation was performed, and the supernatant was removed before collection to obtain 5,000 L of algal slurry. 1000 g of industrial-grade sodium alginate was dissolved in 100 L of water to prepare a 1% (w / w) viscous solution. The algal slurry and sodium alginate were mixed thoroughly and inoculated at an inoculum size of 2 g·DW / m³. 2 The dosage of sodium alginate is 1g / m 2 Within 15 days after inoculation, when the sand moisture content is below 20%, use micro-sprinkler irrigation, spraying once every 2 hours for 20 minutes each time, with a water flow rate of 30 mL / m³. 2 After 15 days, stop watering and allow the plant to grow naturally. During this process, apply diluted simplified BG11 culture medium once or twice as needed.

[0020] Comparative Example 3 This comparative example only uses cementing solution to solidify sandy soil: Step 1: Dissolve 0.5 mol calcium chloride and 0.75 mol urea in 1 L of water to prepare a cementing solution; Step 2: Add 4L of cementing solution to 5kg of sandy soil, mix well, and react at room temperature for 72 hours.

[0021] Mechanical property tests were conducted on sand cylinders with a diameter of 35 mm and a height of 80 mm from the solidified sand in Examples 1-3 and Comparative Examples 1-3, respectively. These tests included unconfined compression tests, shear tests, and splitting tests. Unsolidified sand was also taken using the same method for comparison. The test results are shown in Table 1.

[0022] The compressive strength of the sandy soil treated in the examples and comparative examples was tested, and the surface moss and algae coverage was calculated. The results are shown in Table 1.

[0023] Table 1 Unsolidified sand Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Unconfined compressive strength (MPa) 1.25 15.5 16.3 16.9 12.1 7.4 8.6 Shear strength (kPa) 133.2 3854.5 3895.6 3901.4 2812.65 2553.4 2666.4 Splitting strength (kPa) 8.0 1852.9 1866.2 1878.8 1355.2 1122.6 1256.3 Moss and algae coverage (%) 0 95.4% 96.7% 98.2% 0 89.4% 0 As can be seen from Table 1, this invention combines microbial mineralization induction and bryophyte crust formation. Based on microbial mineralization-induced sand fixation, bryophyte crust formation is also carried out on the soil surface to enhance the compressive strength of the soil surface, which can effectively restore the strength of sandy soil. At the same time, the bryophyte crust formation also allows the sandy soil to be covered by moss and algae again, restoring soil nutrients and environment.

[0024] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and examples shown and described herein.

Claims

1. A method for restoring desertified soil based on microbial mineralization induction and bryophyte crust formation, characterized in that, Includes the following steps: Step 1: Roast soybeans, grind and sieve them to obtain soybean flour. Dissolve the soybean flour in water, stir and let it stand. Then centrifuge and filter to obtain crude soybean urease extract. Refrigerate for later use. Step 2: Isolate desert green algae from natural algal crusts, culture them in a culture medium to the required density, and set them aside for later use. At the same time, collect drought-resistant mosses, clean them, dry them in the shade, and crush them into powder for later use. Step 3: Dissolve travertine in hydrochloric acid, then centrifuge and filter the solution. Take the supernatant and add urea to prepare a cementing solution. Then moisten the moss powder to restore its activity, and add the moss powder and desert green algae together to the cementing solution to obtain the moss-algae crust cementing solution. Step 4: First, spray the crude extract of soybean urease onto the surface of the sandy soil that needs to be restored. After the crude extract of soybean urease has penetrated into the sandy soil by gravity, spray the moss and algae crust cementing solution. Repeat the spraying several times. After a period of maintenance, the sandy soil can be solidified and the surface moss and algae crust can be formed.

2. The method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting as described in claim 1, characterized in that, In step one, the soybean baking parameters are: baking at 40-50℃ for 6-8 hours, sieving with a mesh size of 100-150, soybean flour to water ratio of 60-100g:1L, stirring parameters: stirring at 300-400rpm for 30-40 minutes, standing at 4-5℃ for 2-4 hours, centrifugation parameters: centrifuging at 5000-6000rpm for 15-20 minutes at 4-5℃, and refrigeration temperature of 4-5℃.

3. The method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting as described in claim 1, characterized in that, In step two, the desert green algae are one or more of the following: *Pseudocladophyta*, *Nostoc*, *Anabaena*, and *Oscillatoria*. The culture conditions are BG11 medium at 120–150 μmol / m³. 2 Cultivate at a light intensity of ·s until the density reaches 1.2~1.5×10⁻⁶. 6 cells / mL.

4. The method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting as described in claim 1, characterized in that, In step two, the moss is one or more of the following: *Bryophytum dentatum*, *Bryophytum longifolium*, *Bryophytum pubescens*, and *Bryophytum gracilistylus*. The moss is pulverized to 1-3 mm.

5. The method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting as described in claim 1, characterized in that, In step three, using calcium carbonate from travertine as the standard, the ratio of travertine to hydrochloric acid is 1.05~1.1 mol:2 mol. After dissolution, water is added to dilute to a calcium ion concentration of 0.5~0.8 mol / L. The centrifugation parameters are 4000~4500 rpm for 5~10 min. The ratio of urea to supernatant is 0.75~1 mol:1 L. The ratio of moss powder, desert green algae, and cementing solution is 20~40 g:20~40 g:1 L.

6. The method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting as described in claim 1, characterized in that, In step three, the specific method for restoring the activity of the moss powder by moistening it is as follows: the moss powder is moistened by spraying water at 10~15℃ for 48~72h, during which the light intensity is 25~30μmol / m². 2 •s, the light-dark cycle is 12 / 12h.

7. The method for restoring desertified soil based on microbial mineralization induction and bryophyte crusting as described in claim 1, characterized in that, In step four, when spraying the crude soybean urease extract and the moss-algal crust cementing solution, the concentration is 10-20 L of crude soybean urease extract per m³. 2 Sandy soil, 20-30L of moss and algae crust cementing solution / m 2 Spray the sandy soil repeatedly 10-20 times, using 1-2L each time. Cultivate at room temperature for 72-96 hours, supplementing with water every 24 hours for 10-20 minutes at a flow rate of 20-30 mL / m³. 2 •min, and apply diluted BG11 culture medium 1-2 times during this process.