Post-fire soil remediation method

Abstract

The invention provides a post-fire soil remediation method. The post-fire soil remediation method comprises the following steps: step 1, fire soil diagnosis and pretreatment; 2, gradient pyrolysis biochar is prepared and applied; step 3, inoculating with a compound microbial agent; 4, nutrient regulation and plant combined remediation. According to the invention, through combined application of gradient pyrolysis biochar, cooperative regulation and control of soil acidity and alkalinity, heavy metals and organic pollutants after a fire disaster are realized, and meanwhile, the survival rate and colonization ability of functional microorganisms in a high-temperature environment are remarkably improved by adopting a carrier embedding technology. According to the method, the remediation period can be effectively shortened, the ecological function of the soil is remarkably restored, the remediation cost is greatly reduced by using localized materials, and the problems that in a traditional remediation technology, adaptability is poor, efficiency is low, and cost is high are solved on the whole.

Description

Technical Field

[0001] The present invention relates to the field of environmental pollution remediation technology, and more particularly to a method for post-fire soil remediation. Specifically, it relates to a synergistic remediation technology combining biochar modification with functional microbial inoculation, suitable for restoring the ecological function of soil in forests, farmlands, and other areas after fires. Background Art

[0002] Currently, post-fire soils often face problems such as organic matter loss, nutrient imbalance, microbial community disruption, and toxic accumulation. Traditional remediation methods, such as soil replacement, are costly, while the sole application of chemical fertilizers can easily lead to secondary pollution. Biochar, due to its pore structure and adsorption capacity, is used for soil improvement, but its targeted degradation of specific post-fire pollutants is limited. Existing microbial remediation technologies often overlook the inhibitory effect of the high temperature residual environment in post-fire soils on bacterial activity.

[0003] Therefore, there is an urgent need for an efficient, low-cost and adaptable post-fire soil remediation method. Summary of the Invention

[0004] In view of this, in order to solve the problems existing in the technical background, the present invention proposes a method for soil remediation after fire. The specific technical solution is as follows:

[0005] A method for soil remediation after fire, comprising the following steps:

[0006] Step 1: Fire soil diagnosis and pretreatment;

[0007] Step 2: Gradient pyrolysis biochar preparation and application;

[0008] Step 3: Inoculation of composite microbial agents;

[0009] Step 4: Nutrient regulation and plant restoration.

[0010] Furthermore, in step 1, remediation units were defined within the fire area, and soil samples were collected from the 0-20 cm surface layer to measure pH, organic carbon content, and polycyclic aromatic hydrocarbon concentrations. The soil was classified into three levels based on the degree of contamination: mild, moderate, and severe. Mechanical tillage was used to break up the soil crust to a depth of 15 cm, and any unburned debris larger than 5 cm in diameter was removed.

[0011] Furthermore, in the second step, localized shrub branches in the fire area are used as raw materials, and oxygen-limited pyrolysis is performed at 300°C, 500°C and 700°C to prepare biochar at low, medium and high temperature ranges. The three types of biochar are mixed at a mass ratio of 1:2:1 in the lightly polluted area, and at a mass ratio of 1:1:2 in the moderate and heavy pollution areas. The mixed biochar is heated at a rate of 3-5 kg / m 2Spread the application amount evenly on the soil surface and mix it with the top 15cm soil using a rotary tiller.

[0012] Furthermore, in step 3, a composite bacterial agent containing thermostable amyloliquefaciens, Pseudomonas aeruginosa and Azotobacter chrysogenum is prepared, and the ratio of the number of live bacteria of the three bacteria is 5:3:2. The bacterial agent is embedded in a sodium alginate-bentonite composite carrier with a carrier particle size of 0.5-1 mm. 8 The inoculum amount of CFU / g was applied together with biochar, or in furrow application within 7 days after biochar application.

[0013] Furthermore, in step 4, a slow-release organic-inorganic compound fertilizer is applied, combined with 2 kg / m of calcium humate. 2 Select ryegrass, alfalfa and local pioneer shrubs for intercropping, with a planting density of 30-50 herbaceous plants / m 2 , 1-2 woody plants / 5m 2 The implementation period is 12-18 months, during which soil respiration intensity and enzyme activity changes are monitored monthly.

[0014] Furthermore, the remediation method also includes evaluation and adjustment of remediation effectiveness. Soil samples are collected 90 days after remediation to measure microbial diversity, PAH degradation rate, and cation exchange capacity. When PAH residues exceed the initial value by 20%, additional inoculation with the specialized degrading strain Sphingomonas is performed. When available phosphorus levels fall below 10 mg / kg, additional calcium dihydrogen phosphate slow-release granules are applied.

[0015] The above technical solution has the following beneficial effects:

[0016] This method achieves synergistic regulation of soil pH, heavy metals, and organic pollutants after fires through the combined application of gradient pyrolysis biochar. Simultaneously, the use of carrier-encapsulated technology significantly enhances the survival rate and colonization capacity of functional microorganisms in high-temperature environments. This method effectively shortens the remediation cycle, significantly restores soil ecological functions, and significantly reduces remediation costs through the use of localized materials. Overall, it addresses the challenges of poor adaptability, low efficiency, and high costs associated with traditional remediation technologies. DETAILED DESCRIPTION

[0017] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0018] Example 1, a post-fire soil remediation method, comprising the following steps: Step 1: fire soil diagnosis and pretreatment; Step 2: gradient pyrolysis biochar preparation and application; Step 3: composite microbial inoculation; Step 4: nutrient regulation and plant combined remediation.

[0019] In step 1, remediation units were defined within the fire area, and soil samples were collected from the 0-20 cm surface layer to measure pH, organic carbon content, and polycyclic aromatic hydrocarbon concentrations. The soil was classified into three levels based on the degree of contamination: mild, moderate, and severe. Mechanical tillage was used to break up the soil crust to a depth of 15 cm, and any unburned debris larger than 5 cm in diameter was removed.

[0020] In the second step, localized shrub branches in the fire area are used as raw materials, and low, medium and high temperature range biochars are prepared by pyrolysis at 300℃, 500℃ and 700℃ respectively. The three types of biochars are mixed in a mass ratio of 1:2:1 in the lightly polluted area, and in a mass ratio of 1:1:2 in the moderate and heavy pollution areas. The mixed biochar is heated at a rate of 3-5kg / m 2 Spread the application amount evenly on the soil surface and mix it with the top 15cm soil using a rotary tiller.

[0021] In step 3, a composite bacterial agent containing thermostable amyloliquefaciens, Pseudomonas aeruginosa and Azotobacter chrysogenum is prepared, and the ratio of the number of live bacteria of the three bacteria is 5:3:2. The bacterial agent is embedded in a sodium alginate-bentonite composite carrier with a carrier particle size of 0.5-1mm. 8 The inoculum amount of CFU / g was applied together with biochar, or in furrow application within 7 days after biochar application.

[0022] In the step 4, a slow-release organic-inorganic compound fertilizer is applied, and 2 kg / m2 of calcium humate is added. 2 Select ryegrass, alfalfa and local pioneer shrubs for intercropping, with a planting density of 30-50 herbaceous plants / m 2 , 1-2 woody plants / 5m 2 The implementation period is 12-18 months, during which soil respiration intensity and enzyme activity changes are monitored monthly.

[0023] Remediation measures also include evaluation and adjustment of remediation effectiveness. Soil samples were collected 90 days after remediation to measure microbial diversity, PAH degradation rate, and cation exchange capacity. When PAH residues exceeded 20% of the initial value, a supplemental inoculation with the specialized degrading strain Sphingomonas was performed. When available phosphorus levels fell below 10 mg / kg, sustained-release calcium dihydrogen phosphate granules were applied.

[0024] Example 2, based on Example 1, targets a slightly contaminated area after a pine forest fire. During restoration, a deep tiller is first used to plow the soil to a depth of 15 cm to remove unburned pine needle debris from the surface. Using locally collected Chinese pine branches as raw materials, biochar was prepared at 300°C, 500°C, and 700°C, respectively. The mixture was mixed in a ratio of 1:2:1 and then heated to 3 kg / m 2 The application amount is rotary tilled into the soil. The composite microbial agent is composed of thermostable Bacillus amyloliquefaciens (5×10 8 CFU / g), Pseudomonas aeruginosa (3×10 8 CFU / g) and brown ball nitrogen-fixing bacteria (2×10 8 CFU / g), which was embedded in a 0.8 mm sodium alginate-bentonite carrier and then applied simultaneously with biochar.

[0025] The restoration plant of choice is alfalfa (40 plants / m 2 ) and local Chinese pine seedlings (1 plant / 5m 2 ) intercropping, combined with humic acid calcium 2kg / m 2 And slow-release compound fertilizer (N-P2O5-K2O=15-10-10) 1.5kg / m 2 Tests six months after restoration showed that the degradation rate of polycyclic aromatic hydrocarbons in the soil reached 78%, the microbial Shannon index increased by 2.3 times, and the alfalfa biomass reached 85% of that in the unaffected area.

[0026] Example 3, based on Example 1, applies an enhanced remediation strategy to a heavily polluted fire area (polycyclic aromatic hydrocarbons > 200 mg / kg, cadmium 5.2 mg / kg) surrounding a chemical plant. After tillage, 700°C high-temperature biochar (50%) is applied to preferentially adsorb heavy metals. The mixing ratio is adjusted to 1:1:2 (low:medium:high). The inoculum dose is increased to 1.5×10 9 CFU / g, and Sphingomonas (1×10 8 CFU / g) and specifically degraded polycyclic aromatic hydrocarbons.

[0027] A phased fertilization program was adopted: initial application of calcium dihydrogen phosphate slow-release granules (0.5 kg / m 2 ) to activate microbial activity, and after 60 days, add 3kg / m3 of humic acid calcium 2 The plant combination is ryegrass (50 plants / m 2 ) and heavy metal hyperaccumulator Sedum alfredii (20 plants / m 2 ), the shrub layer selected pollution-resistant paper mulberry (2 plants / 5m 2Twelve months after restoration, the degradation rate of polycyclic aromatic hydrocarbons (PAHs) reached 91%, the available cadmium content decreased by 62%, and soil dehydrogenase activity recovered to 70% of pre-disaster levels. Through periodic monitoring and adjustments, and secondary enhancement with the inoculation of Pseudomonas aeruginosa during the mid-term restoration phase, the soil's ecological functions ultimately met industrial land standards.

[0028] The above examples demonstrate that this method, through its modular design of biochar gradient combination, targeted inoculation of functional microorganisms, and phytoremediation, can be flexibly adapted to fire-affected soils of varying contamination levels and types. It demonstrates significant synergistic removal of heavy metals and organic matter in highly contaminated environments, particularly in highly contaminated areas. Dynamic monitoring and parameter adjustment mechanisms during the remediation process further ensure the adaptability and stability of the technology.

[0029] This method achieves synergistic regulation of soil pH, heavy metals, and organic pollutants after fires through the combined application of gradient pyrolysis biochar. Simultaneously, the use of carrier-encapsulated technology significantly enhances the survival rate and colonization capacity of functional microorganisms in high-temperature environments. This method effectively shortens the remediation cycle, significantly restores soil ecological functions, and significantly reduces remediation costs through the use of localized materials. Overall, it addresses the challenges of poor adaptability, low efficiency, and high costs associated with traditional remediation technologies.

[0030] The above describes the basic principles and main features of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions only illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the invention to be protected. The scope of protection of the invention is defined by the attached claims and their equivalents.

Claims

1. A method for soil remediation after fire, characterized in that: The following steps are involved: Step 1: Fire soil diagnosis and pretreatment; Step 2: Gradient pyrolysis biochar preparation and application; Step 3: Inoculation of composite microbial agents; Step 4: Nutrient regulation and plant restoration.

2. A post-fire soil remediation method according to claim 1, characterized in that: In step one, remediation units were defined within the fire area. Topsoil samples were collected from the 0-20 cm layer and measured for pH, organic carbon content, and polycyclic aromatic hydrocarbon concentrations. The soil was then classified as mild, moderate, or severe based on the degree of contamination. Mechanical tillage was used to break up the soil crust to a depth of 15 cm, removing any unburned debris larger than 5 cm in diameter.

3. The post-fire soil remediation method according to claim 1, characterized in that: In the second step, localized shrub branches in the fire area are used as raw materials, and low, medium and high temperature range biochars are prepared by pyrolysis at 300℃, 500℃ and 700℃ respectively. The three types of biochars are mixed in a mass ratio of 1:2:1 in the lightly polluted area, and in a mass ratio of 1:1:2 in the moderate and heavy pollution areas. The mixed biochar is heated at a rate of 3-5kg / m 2 Spread the application amount evenly on the soil surface and mix it with the top 15cm soil using a rotary tiller.

4. A post-fire soil remediation method according to claim 1, characterized in that: In the step 3, a composite bacterial agent containing thermostable amyloliquefaciens, Pseudomonas aeruginosa and Azotobacter chrysogenum is prepared, the ratio of the number of live bacteria of the three bacteria is 5:3:2, the bacterial agent is embedded in a sodium alginate-bentonite composite carrier, the carrier particle size is 0.5-1mm, and the mixture is heated to 1000 ℃. 8 The inoculum amount of CFU / g was applied together with biochar, or in furrow application within 7 days after biochar application.

5. The method for soil remediation after fire according to claim 1, characterized in that: In the step 4, a slow-release organic-inorganic compound fertilizer is applied, and 2 kg / m2 of calcium humate is added. 2 , select ryegrass, alfalfa and local pioneer shrubs for intercropping, with a planting density of 30-50 herbaceous plants / m 2 , 1-2 woody plants / 5m 2 The implementation period is 12-18 months, during which soil respiration intensity and enzyme activity changes are monitored monthly.

6. A post-fire soil remediation method according to claim 1, characterized in that: The remediation method also includes remediation effect evaluation and adjustment. Soil samples are collected 90 days after remediation to measure the microbial diversity index, polycyclic aromatic hydrocarbon degradation rate and cation exchange capacity. When the residual polycyclic aromatic hydrocarbons are 20% higher than the initial value, the specialized degradation strain Sphingomonas is supplemented by inoculation; when the available phosphorus content is lower than 10 mg / kg, calcium dihydrogen phosphate slow-release granules are added.