Method for polycyclic aromatic hydrocarbon contaminated soil bioremediation and soil carbon sequestration

Abstract

This invention relates to a method for enriching indigenous degrading microbial communities using biomass waste to enhance the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil and synergistically improve soil carbon sequestration. It belongs to the field of resource comprehensive utilization and ecological environmental protection and restoration technology. Using biomass waste and PAH-contaminated soil as enrichment culture media, a highly efficient PAH-degrading microbial community is enriched and cultivated by inoculating pioneer species, and a bio-enhancing agent is prepared. This bio-enhancing agent is then inoculated into PAH-contaminated soil to improve PAH degradation efficiency. Finally, vegetation restoration synergistically enhances soil carbon sequestration. This invention not only realizes the resource utilization of biomass waste but also significantly improves the carbon sequestration capacity of PAH-contaminated soil, which is of great significance for soil remediation and achieving the goal of "carbon neutrality," and has broad application prospects.

Description

Technical Field

[0001] This invention belongs to the field of ecological and environmental protection technology, and relates to a method for enriching indigenous degrading microbial communities using biomass waste, enhancing the remediation of polycyclic aromatic hydrocarbon-contaminated soil, and synergistically sequestering soil carbon. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are produced by the incomplete combustion of organic matter. Carcinogenic PAHs in soil primarily originate from the high-temperature incomplete combustion of coal. Vehicle exhaust emissions and oil spills also contribute to the accumulation of PAHs in soil. Under the combined effects of fossil fuel combustion, emissions from coal-fired power plants, and global atmospheric migration, PAHs gradually accumulate in soil. PAHs in the environment can exert carcinogenic, teratogenic, and mutagenic effects on human cells through respiratory, dermal, and digestive pathways.

[0003] In the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, commonly used technologies include physical, chemical, and biological remediation. Microbial remediation technology has the advantages of being economical, safe, and eco-friendly. Utilizing indigenous or exogenous microorganisms to degrade PAHs has gained widespread acceptance in the treatment of contaminated soil. Microbial remediation methods can be divided into biostimulation and bioenhancement based on their technical principles. Biostimulation involves artificially altering the growth conditions of microorganisms in the soil to stimulate the growth of in-situ PAH-degrading microorganisms, thereby improving their degradation efficiency. Bioenhancement involves adding highly efficient PAH-degrading microorganisms to the contaminated soil, thereby increasing the PAH degradation efficiency.

[0004] Adding highly efficient degrading microorganisms to contaminated soil is a common method to improve pollutant degradation efficiency. However, the effectiveness of bioaugmentation is often affected by environmental and biological factors, such as temperature, humidity, pH, and competition for ecological niches between the added microorganisms and existing soil microorganisms. Therefore, when screening for highly efficient degrading microorganisms, attention should be paid to improving their adaptability to the contaminated environment to enhance the bioaugmentation effect.

[0005] Polycyclic aromatic hydrocarbon (PAH) contamination in soil not only inhibits plant growth, but PAHs can also be absorbed by plants and transported to fruits and seeds, posing food safety risks. Biofortification can accelerate the remediation of PAH-contaminated soil, not only purifying the soil but also promoting plant growth and increasing soil organic matter content, thus improving soil carbon sequestration efficiency. Summary of the Invention

[0006] The purpose of this invention is to provide a method for enriching indigenous degrading microorganisms using biomass waste, enhancing the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, and synergistically improving soil carbon sequestration capacity. This method is simple to operate and has the functions of enhancing the remediation of contaminated soil and improving soil carbon sequestration.

[0007] To achieve the above objectives, the technical solution adopted by this invention is as follows: using biomass waste and polycyclic aromatic hydrocarbon (PAH) contaminated soil as enrichment culture medium, enriching and cultivating a highly efficient PAH-degrading bacterial community, and preparing it into a bio-enhancing bacterial agent, which is then inoculated into PAH-contaminated soil to improve the PAH degradation efficiency. Furthermore, vegetation restoration synergistically enhances the soil's carbon sequestration function. Its features include the following steps:

[0008] Enrichment culture of polycyclic aromatic hydrocarbon (PAH) degrading bacteria: Biomass waste (such as medicinal herb residue, sawdust, mushroom residue, etc.) is mixed with PAH-contaminated soil at a weight ratio of 10:1-2:1. Biogas slurry produced by fermenting livestock and poultry manure is added, and the moisture content of the material is adjusted to 50%-70% to obtain a solid enrichment culture medium. Trichoderma viride EBL13 and Rhodococcus sp. A17 are inoculated as pioneer strains for enriching PAH-degrading bacteria. The bacteria are co-cultured with naturally occurring microorganisms in PAH-contaminated soil and biomass waste at room temperature (15-35℃) for 5-15 days to enrich PAH-degrading bacteria.

[0009] Bioenhanced remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil: Add PAH-degrading microorganisms to PAH-contaminated soil at a weight ratio of 1%-10%, mix thoroughly, maintain soil moisture content at 15%-25%, and carry out bioenhanced remediation under natural environmental conditions; monitor the soil inoculated with PAH-degrading microorganisms, replenish water as needed to maintain soil moisture content between 15%-25%, and till the soil to ensure full contact between PAH-degrading microorganisms and contaminated soil until the PAH content in the soil is lower than the limit of the soil environmental quality standard.

[0010] The pioneer strains of polycyclic aromatic hydrocarbon degrading bacteria mentioned in the above technical solution were isolated and screened by the inventors from contaminated soil and deposited at the China General Microbiological Culture Collection Center (CGMCC). The accession number of Trichoderma viride EBL13 strain is CGMCC No. 8363, the accession date is October 18, 2013, and the accession address is No. 3, No. 1 Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences; the accession number of Rhodococcus sp. A17 strain is CGMCC No. 23725, the accession date is November 5, 2021, and the accession address is No. 1 Beichen West Road, Chaoyang District, Beijing, Institute of Microbiology, Chinese Academy of Sciences.

[0011] Vegetation restoration synergistic with soil carbon sequestration: Soils restored through the above-mentioned bio-enhanced methods are cultivated by planting native plants or crops. Plant roots grow in the soil or straw is returned to the field, increasing soil organic matter content, increasing soil carbon sequestration, and further improving the soil. Detailed Implementation

[0012] To better understand the technical content of the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0013] Example 1: Using medicinal herb residue to enrich polycyclic aromatic hydrocarbon (PAH) degrading bacteria for the remediation of PAH-contaminated soil.

[0014] Enrichment culture of polycyclic aromatic hydrocarbon (PAH) degrading bacteria: Traditional Chinese medicine residue and PAH-contaminated soil were mixed evenly at a weight ratio of 8:2. Biogas slurry produced from the fermentation of livestock and poultry manure was added, and the moisture content of the material was adjusted to 60% to obtain a solid enrichment medium. Trichoderma viride strain EBL13 and Rhodococcus sp. A17 were inoculated as pioneer strains for PAH degrading bacteria. The mixture was co-cultured with naturally occurring microorganisms in PAH-contaminated soil and biomass waste for 7 days at room temperature (25℃) to enrich the PAH-degrading bacteria.

[0015] Bioenhanced remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil: PAH-degrading microorganisms enriched with traditional Chinese medicine residue were added at a weight ratio of 5% to soil with a PAH content of 13.1 mg / kg. The mixture was thoroughly mixed, and the soil moisture content was maintained at approximately 20%. Bioenhanced remediation was carried out under natural environmental conditions. The soil inoculated with the PAH-degrading microorganisms was monitored, and water was replenished as needed. The soil was also tilled to ensure sufficient contact between the PAH-degrading microorganisms and the contaminated soil. Soil without PAH-degrading microorganisms served as a control. Soil samples were collected 35 days after remediation, and the PAH content was measured. The PAH content in the control group was 11.6 mg / kg, while the PAH content in the soil with added PAH-degrading microorganisms was 1.2 mg / kg, indicating that the PAH-degrading microorganisms significantly improved the PAH degradation efficiency in the soil.

[0016] Example 2: Using sawdust to enrich polycyclic aromatic hydrocarbon (PAH) degrading microorganisms for the remediation of PAH-contaminated soil.

[0017] Enrichment culture of polycyclic aromatic hydrocarbon (PAH) degrading bacteria: Sawdust and PAH-contaminated soil were mixed evenly at a weight ratio of 9:1. Biogas slurry produced from the fermentation of livestock and poultry manure was added, and the moisture content of the material was adjusted to 60% to obtain a solid enrichment medium. Trichoderma viride strain EBL13 and Rhodococcus sp. A17 were inoculated as pioneer strains of PAH degrading bacteria. The medium was co-cultured with naturally occurring microorganisms in PAH-contaminated soil and biomass waste at room temperature (25℃) for 10 days to enrich the PAH degrading bacteria.

[0018] Bioaugmented remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil: PAH-degrading microorganisms enriched with sawdust were added at a weight ratio of 3% to soil with a PAH content of 12.8 mg / kg. The mixture was thoroughly mixed, and the soil moisture content was maintained at approximately 20%. Bioaugmented remediation was carried out under natural environmental conditions. The soil inoculated with the PAH-degrading microorganisms was monitored, and water was replenished as needed. The soil was also tilled to ensure sufficient contact between the PAH-degrading microorganisms and the contaminated soil. Soil without PAH-degrading microorganisms served as a control. Soil samples were collected 35 days after remediation, and the PAH content was measured. The PAH content in the control group was 11.3 mg / kg, while the PAH content in the soil with added PAH-degrading microorganisms was 1.7 mg / kg, indicating that the PAH-degrading microorganisms significantly accelerated the degradation of PAHs in the soil.

[0019] Example 3: Using rice husks to enrich polycyclic aromatic hydrocarbon (PAH) degrading microorganisms for the remediation of PAH-contaminated soil

[0020] Enrichment culture of polycyclic aromatic hydrocarbon (PAH) degrading bacteria: Rice husks and PAH-contaminated soil were mixed evenly at a weight ratio of 7:3. Biogas slurry produced from the fermentation of livestock and poultry manure was added, and the moisture content of the material was adjusted to about 60% to obtain a solid enrichment culture medium. Trichoderma viride strain EBL13 and Rhodococcus sp. A17 were inoculated as pioneer strains of PAH degrading bacteria. The culture was co-cultured with naturally occurring microorganisms in PAH-contaminated soil and biomass waste at room temperature (25℃) for 15 days to enrich the PAH degrading bacteria.

[0021] Bioaugmented remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil: PAH-degrading bacteria enriched in rice husks were added at a weight ratio of 5% to soil with a PAH content of 12.3 mg / kg. The mixture was thoroughly mixed, and the soil moisture content was maintained at approximately 20%. Bioaugmented remediation was carried out under natural environmental conditions. The soil inoculated with the PAH-degrading bacteria was monitored, and water was replenished as needed. The soil was also tilled to ensure sufficient contact between the PAH-degrading bacteria and the contaminated soil. Soil without PAH-degrading bacteria served as a control. Soil samples were collected 50 days after remediation, and the PAH content was measured. The PAH content in the control group was 10.7 mg / kg, while the PAH content in the soil with added PAH-degrading bacteria was 0.8 mg / kg, indicating that the PAH-degrading bacteria significantly accelerated the degradation of PAHs in the soil.

[0022] Example 4: Sorghum planting in farmland after contaminated soil remediation synergistic with soil carbon sequestration

[0023] The contaminated soil remediated according to Example 1 was evenly dispersed in the topsoil of the remediated farmland. After thorough tillage using the cultivation method, sorghum was planted, and the plant roots were able to grow normally in the soil. Soil samples were taken before remediation and after sorghum harvest to determine the soil organic matter content. Sorghum growth was weak in the unremediated contaminated farmland, but grew well in the remediated farmland. Compared with the control, the organic matter content in the remediated farmland soil was significantly increased, and the carbon sequestration of the topsoil in the remediated contaminated farmland increased by an average of more than 3 tons of CO2 per acre.

[0024] Example 5: Planting corn in farmland after contaminated soil remediation to synergize with soil carbon sequestration

[0025] The contaminated soil remediated according to Example 2 was evenly dispersed in the topsoil of the remediated farmland. After thorough tillage using the cultivation method, corn was planted, and the plant roots were able to grow normally in the soil. Soil samples were taken before remediation and after corn harvest to determine the soil organic matter content. Sorghum grew weakly in the contaminated farmland without bio-enhanced remediation, but grew well in the bio-remediated farmland. Compared with the control, the organic matter content in the remediated farmland soil was significantly increased, and the carbon sequestration of the topsoil in the remediated contaminated farmland increased by an average of more than 2 tons of CO2 per acre.

[0026] The invention illustrates how different amounts and types of remediation microbial agents can be inoculated into contaminated soils with varying polycyclic aromatic hydrocarbon contents to effectively achieve the purpose of soil remediation. These methods will not be listed individually here.

Claims

1. A method for bioremediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil in synergistic with soil carbon sequestration, characterized in that, This method utilizes biomass waste to enrich indigenous degrading microbial communities, uses these microbial communities to enhance the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, and then uses vegetation restoration to synergistically improve the soil's carbon sequestration function.

2. The method for bioremediation and synergistic soil carbon sequestration of polycyclic aromatic hydrocarbon contaminated soil according to claim 1, characterized in that, The steps of enriching indigenous degrading microbial communities using biomass waste include: (1) Mix biomass waste (such as Chinese medicine residue, sawdust, mushroom residue, etc.) with polycyclic aromatic hydrocarbon contaminated soil in a weight ratio of 10:1-2:1, add biogas slurry produced by fermentation of livestock and poultry manure, adjust the moisture content of the material to 50%-70%, and obtain solid enrichment culture medium. (2) Inoculate Trichoderma viride strain EBL13 and Rhodococcus sp. A17 as pioneer strains for enriching polycyclic aromatic hydrocarbon (PAH) degrading bacteria. Co-culture with naturally occurring microorganisms in PAH-contaminated soil and biomass waste for 5-15 days at room temperature (15-35℃) to enrich PAH degrading bacteria.

3. The method for bioremediation and synergistic soil carbon sequestration of polycyclic aromatic hydrocarbon contaminated soil according to claims 1 and 2, characterized in that, Utilizing degrading microbial communities to enhance the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil includes the following steps: (1) Add polycyclic aromatic hydrocarbon degrading bacteria to the polycyclic aromatic hydrocarbon contaminated soil at a weight ratio of 1%-10%, mix evenly, maintain the soil moisture content at 15%-25%, and carry out bio-enhanced remediation under natural environmental conditions; (2) Monitor the soil inoculated with polycyclic aromatic hydrocarbon (PAH) degrading bacteria, replenish water in a timely manner to maintain the soil moisture content between 15% and 25%, and till the soil to ensure that the PAH degrading bacteria are in full contact with the contaminated soil until the PAH content in the soil is lower than the limit of the soil environmental quality standard.

4. The pioneer strain of the polycyclic aromatic hydrocarbon degrading bacteria according to claim 2, characterized in that, The pioneer strains were isolated and screened by the inventors from contaminated soil and deposited at the China General Microbiological Culture Collection Center (CGMCC). The accession number of Trichoderma viride strain EBL13 is CGMCC No. 8363, and the accession number of Rhodococcus sp. strain A17 is CGMCC No. 23725.

5. The method for bioremediation of polycyclic aromatic hydrocarbon contaminated soil and synergistic soil carbon sequestration according to claims 1 and 3, characterized in that, Enhancing soil carbon sequestration through vegetation restoration involves biologically reinforced soil by planting native plants or crops, allowing plant roots to grow in the soil or returning straw to the field, thereby increasing soil organic matter content, increasing soil carbon sequestration, and further improving the soil.