Compost reinforced laccase-based remediation method for soil polluted by persistent organic matters

Abstract

The invention discloses a compost reinforced laccase-based remediation method for soil polluted by persistent organic matters. According to the soil remediation method, compost and laccase are added into the soil polluted by the persistent organic matter, the synergistic effect of the compost and the laccase is achieved, and therefore the soil remediation efficiency and effect are remarkably improved. The compost not only provides rich organic matters and nutrient substances for the soil and promotes the growth and activity of soil microorganisms, but also enhances the water-retaining property, air permeability and fertilizer-retaining capacity of the soil and provides a good active environment for laccase. Meanwhile, substances such as humic acid in the compost can interact with the laccase, so that the stability and activity of the laccase are improved, and the laccase can more effectively catalyze and oxidize persistent organic pollutants in the soil. The synergistic effect not only accelerates the degradation process of pollutants, but also improves the thoroughness of repair and reduces the risk of possible secondary pollution.

Description

Technical Field

[0001] The invention belongs to the technical field of soil restoration contaminated by persistent organic matter, and specifically relates to a soil restoration method contaminated by persistent organic matter based on composting enhanced laccase. Background Art

[0002] With the development of social economy, various pollutants generated in the process of human industrial or agricultural production enter the soil environment through different pathways, eventually exceeding the self-purification capacity of the soil, causing changes in soil quality and function. In addition, soil is also a source of nutrition for agricultural products and some organisms. Pollutants will be transmitted and migrated through the food chain, eventually endangering the survival and development of humans and other organisms. Organic pollutants in the soil, such as nitrogen heterocyclic compounds (NHCs), polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs), are valued by environmental workers because of their toxicity, difficulty in degradation, and resistance to metabolic destruction, as well as their carcinogenic, teratogenic and mutagenic properties.

[0003] NHCs are organic compounds with heterocyclic structures containing nitrogen atoms in their molecules. They are a type of difficult-to-degrade organic matter with a wide range of pollution and high toxicity. They are widely present in soil and wastewater. Common NHCs mainly include pyrrole, indole, pyridine, quinoline, isoquinoline and their derivatives. Due to their difficulty in biodegradation, conventional biological treatment systems often fail to achieve satisfactory treatment results. PAHs are volatile hydrocarbons produced by incomplete combustion of organic matter. The rapid development of modern industry and agriculture has caused most of PAHs to eventually accumulate in soil and groundwater through atmospheric wet deposition, sewage irrigation and other channels, leading to serious soil and groundwater pollution. They are important environmental and food pollutants. PCBs are a class of artificially synthesized chlorinated aromatic hydrocarbon persistent organic pollutants. They are highly hydrophobic compounds with high lipophilicity, bioaccumulation, chemical stability and semi-volatility. They are easy to circulate in the environment. The main circulation process involves the volatilization and diffusion of PCBs from contaminated sites into the atmosphere, long-distance transportation through the atmosphere and entering the soil and water environment through dry and wet deposition. Therefore, studying the remediation technology of persistent organic matter in soil is in line with the current needs of soil pollution remediation and has important practical significance.

[0004] In recent years, soil pollution remediation has attracted more and more attention. Enzyme remediation technology directly uses the degradation ability of a certain exogenous microbial enzyme to purify contaminated soil. Compared with traditional physical and chemical methods, enzyme remediation technology has the advantages of high efficiency, environmental friendliness, no secondary pollution and easy operation. Direct use of enzymes for pollution remediation has more advantages than microbial treatment and plant treatment. For example, enzymes do not have high requirements for nutrients and other conditions in the environment; enzymes can degrade some specific pollutants. However, enzyme remediation technology also has some limitations: enzymes may be degraded by soil proteases; enzymes may be unstable and easily inactivated; enzymes may be degraded by soil proteases and unstable and easily inactivated.

[0005] Laccase is a glycoprotein that uses molecular oxygen to catalyze the oxidation of various phenolic and non-phenolic compounds through a free radical catalytic reaction mechanism. By inserting a mediator, laccase can be enabled to catalyze the oxidation of non-phenolic substances. Studies on mediators have shown that the common structural feature of N-OH exists in most non-natural mediators, and it is N-OH that can generate free radicals under the action of laccase, and then attack macromolecular substrates or non-phenolic substrates through the generated free radicals. Studies have shown that laccase has a good treatment effect on the remediation of NHCs, PAHs, and PCBs contaminated soils, but there are also some problems, such as expensive mediators, poor stability, and incomplete treatment.

[0006] Compost is an organic fertilizer made by composting various plant residues (crop straw, weeds, leaves, peat, garbage and other wastes, etc.) or human and animal feces and urine as the main raw materials. It is rich in nutrients, has a long and stable fertilizer effect, and is conducive to the formation of soil solid particle structure. At the same time, compost is rich in humic acid, which is an important source of compost fertility. Humic acid is a macromolecular organic substance widely present in nature. Its molecular structure is very complex and contains various functional groups, mainly oxygen-containing acidic functional groups, including carboxyl and phenolic hydroxyl groups on aromatic and aliphatic compounds. There are also a certain number of free radicals on the humic acid molecule, which are physiologically active. Humic acid has a strong binding ability with enzymes, and the interaction between them has a protective effect on the activity and stability of enzymes. In view of the nature of compost, the use of compost to repair contaminated soil has been reported. However, at present, a large number of studies are focused on the treatment of heavy metals, and there are few reports on the use of composting to treat organic pollution. Current research uses composting to treat polycyclic aromatic hydrocarbons-contaminated soil and pentachlorophenol-contaminated soil, but both have problems such as long treatment cycles and incomplete degradation, and there is also the possibility that intermediate products will continue to contaminate the soil. Summary of the invention

[0007] The object of the present disclosure is to provide a method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase, which can solve at least part of the above technical problems.

[0008] A first aspect of the disclosed embodiments provides a method for remediating soil contaminated by persistent organic matter based on composting-enhanced laccase, the soil remediation method comprising:

[0009] Adding compost to the soil to be remediated that is contaminated by persistent organic matter to obtain contaminated soil with added compost;

[0010] Adding laccase to the contaminated soil to which compost has been added to obtain soil being repaired;

[0011] After the soil being repaired is stirred evenly, it is kept in the air for several days, thereby repairing the soil contaminated by persistent organic matter.

[0012] Optionally, before the soil being repaired is stirred evenly, the moisture content of the soil being repaired needs to be adjusted to 35-40%.

[0013] Optionally, the amount of compost added is 5.5-18 wt % of the soil contaminated by persistent organic matter to be remediated.

[0014] Optionally, 400-500 U of laccase is added to each kg of the contaminated soil added to the compost.

[0015] Optionally, the time of being kept in the air is 3 to 7 days.

[0016] Optionally, the laccase comprises a laccase secreted by a white rot fungus.

[0017] Optionally, the enzyme activity of the laccase is 3-4 U / mL.

[0018] Optionally, the persistent organic matter includes at least one of nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

[0019] Optionally, the compost includes at least one of garden waste compost, livestock manure compost, and sludge compost.

[0020] The main technical effects achieved by the embodiments of the present disclosure are as follows: the present invention adopts laccase to repair soil contaminated by persistent organic matter, and can quickly degrade pollutants within a few days with high efficiency; the characteristics of laccase determine that the final products of pollutants will be H2O and CO2, which is environmentally friendly and will not cause secondary pollution; the present invention uses compost, which can not only increase the soil's ability to retain water, heat, air, and fertilizer, and to a certain extent improve the soil's fertility and quickly restore the soil's agricultural function, but also increase the number and activity of soil microorganisms, and significantly increase the activity of the original laccase in the soil, so that pollutants are more completely degraded; at the same time, the humic acid in the compost provides sufficient free radicals for laccase to degrade persistent organic matter, and the presence of hydroxyl groups on its molecular structure also makes humic acid a mediator for laccase to degrade non-phenolic persistent organic matter; the interaction between humic acid and laccase can also protect the stability and activity of the enzyme, slow down the rate of decrease in laccase activity, greatly increase the action time of laccase, and significantly improve the repair effect of soil contaminated by persistent organic matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The present invention is a schematic flow chart of a method for remediating soil contaminated by persistent organic matter based on composting-enhanced laccase in one embodiment of the present invention. DETAILED DESCRIPTION

[0022] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The modes described in the following exemplary embodiments do not represent all modes consistent with the present disclosure. Instead, they are merely examples of devices consistent with some aspects of the present disclosure as detailed in the appended claims.

[0023] The terms used in the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The words "first", "second" and similar words used in the present disclosure specification and claims do not indicate any order, quantity or importance, but are only used to distinguish different components. Similarly, similar words such as "one" or "one" do not indicate a quantitative limitation, but indicate that there is at least one, and if only "one" is referred to, it will be separately described. "Multiple" or "several" means two or more. Unless otherwise specified, similar words such as "front", "rear", "lower" and / or "upper" are only for the convenience of explanation, and are not limited to one position or one spatial orientation. Similar words such as "include" or "comprise" mean that the elements or objects appearing in front of "include" or "comprise" cover the elements or objects listed after "include" or "comprise" and their equivalents, and do not exclude other elements or objects. "Connected" or "connected" and similar words are not limited to physical or mechanical connections, and may include electrical connections, whether direct or indirect. The singular forms of "a", "an", "the" and "the" used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0024] like Figure 1 As shown, the first aspect of the embodiment of the present disclosure provides a method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase, the soil remediation method comprising:

[0025] Adding compost to the soil to be remediated that is contaminated by persistent organic matter to obtain contaminated soil with added compost;

[0026] Adding laccase to the contaminated soil to which compost has been added, thereby obtaining the soil being repaired;

[0027] After the soil being repaired is stirred evenly, it is kept in the air for several days, thereby repairing the soil contaminated by persistent organic matter.

[0028] The soil remediation method in the disclosed embodiment achieves the synergistic effect of compost and laccase in the soil contaminated by persistent organic matter, thereby significantly improving the efficiency and effect of soil remediation. Compost not only provides rich organic matter and nutrients to the soil, promotes the growth and activity of soil microorganisms, but also enhances the water retention, air permeability and fertilizer retention capacity of the soil, and provides a good active environment for laccase. At the same time, substances such as humic acid in the compost can interact with laccase, improve the stability and activity of laccase, and enable laccase to more effectively catalyze and oxidize persistent organic pollutants in the soil. This synergistic effect not only accelerates the degradation process of pollutants, but also improves the thoroughness of remediation and reduces the possible risk of secondary pollution. In addition, the steps of stirring and keeping in the air for several days ensure that the pollutants in the soil are fully in contact with the compost and laccase, further promoting the degradation of pollutants and achieving rapid recovery of the soil environment.

[0029] As an optional embodiment, the persistent organic matter in the present disclosure includes at least one of nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons and polychlorinated biphenyls; and the compost is organic fertilizer that has been decontaminated, air-dried and crushed; the compost includes at least one of garden waste compost, livestock manure compost and sludge compost.

[0030] As an optional implementation, before the soil being repaired is stirred evenly, the moisture content of the soil being repaired needs to be adjusted to 35-40%. The purpose of adjusting the moisture content of the soil being repaired to 35-40% is to ensure that the microorganisms and enzyme activities in the soil reach the optimal state. The appropriate moisture content can ensure the oxygen supply in the soil, promote microbial metabolism and enzyme reactions, and thus improve the effect of soil repair.

[0031] As an optional implementation, the amount of compost added is 5.5-18wt% of the soil contaminated by persistent organic matter to be remediated. The purpose of adding 5.5-18wt% of compost is to provide sufficient organic matter and microbial activity to promote the degradation of pollutants without damaging the soil structure. This ratio range is based on experimental data and the optimization results of soil remediation effects, aiming to achieve the best balance between cost-effectiveness and remediation effects.

[0032] As an optional embodiment, 400-500U of laccase is added to each Kg of contaminated soil added to the compost. The purpose of adding 400-500U of laccase to each Kg of contaminated soil added to the compost is to ensure that the pollutants in the soil can be effectively degraded. The amount of laccase added is determined based on experiments, which can ensure the remediation effect while avoiding the cost increase caused by excessive laccase.

[0033] As an optional embodiment, the time of keeping in the air is 3 to 7 days. Keeping in the air for 3 to 7 days is to provide enough time for microorganisms and enzymes in the soil to degrade pollutants. This time range is determined based on the degradation rate of pollutants and the actual needs of soil remediation, aiming to achieve rapid and effective soil remediation.

[0034] As an optional embodiment, laccase includes laccase secreted by white rot fungi. The laccase secreted by white rot fungi is used because this type of laccase has a strong oxidizing ability and can effectively degrade a variety of persistent organic pollutants. The laccase secreted by white rot fungi has been proven to be highly efficient and environmentally friendly in environmental remediation. Of course, in other embodiments, laccase can also include laccase secreted by other fungi, and the present disclosure is not limited to this.

[0035] As an optional embodiment, the enzyme activity of laccase is 3-4 U / mL. The enzyme activity of laccase is 3-4 U / mL to ensure sufficient activity to catalyze the oxidation reaction of pollutants. This activity level can ensure the catalytic efficiency of laccase in the soil remediation process, thereby improving the remediation effect.

[0036] It should be noted that the following multiple examples are also listed in the embodiments of the present disclosure for verification:

[0037] Example 1

[0038] A method for repairing soil contaminated by persistent organic matter based on compost-enhanced laccase. Compost is added to the soil contaminated by persistent organic matter to be repaired, and the amount of compost added is 5.5-14wt% of the soil contaminated by persistent organic matter to be repaired, to obtain contaminated soil with added compost; then 400-460U of laccase is added to each kg of contaminated soil with added compost to obtain soil being repaired; then the moisture content of the soil being repaired is adjusted to 35-38%, stirred evenly, and kept in the air for 3-5 days, and the soil contaminated by persistent organic matter is repaired.

[0039] Persistent organic matter is polycyclic aromatic hydrocarbons.

[0040] Example 2

[0041] A method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase. This example is the same as Example 1 except that the persistent organic matter is a mixture of nitrogen heterocyclic compounds and polychlorinated biphenyls.

[0042] Example 3

[0043] A method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase. This example is the same as Example 1 except that the persistent organic matter is a mixture of nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

[0044] Example 4

[0045] A method for repairing soil contaminated by persistent organic matter based on compost-enhanced laccase. Compost is added to the soil contaminated by persistent organic matter to be repaired, and the amount of compost added is 8-16wt% of the soil contaminated by persistent organic matter to be repaired, to obtain contaminated soil with added compost; then 440-480U of laccase is added to each kg of contaminated soil with added compost to obtain soil being repaired; then the moisture content of the soil being repaired is adjusted to 36-39%, stirred evenly, and kept in the air for 4-6 days, and the soil contaminated by persistent organic matter is repaired.

[0046] Persistent organic matter is nitrogen heterocyclic compounds.

[0047] Example 5

[0048] A method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase. This example is the same as Example 4 except that the persistent organic matter is a mixture of polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

[0049] Example 6

[0050] A method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase. This example is the same as Example 4 except that the persistent organic matter is a mixture of nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

[0051] Example 7

[0052] A method for repairing soil contaminated by persistent organic matter based on compost-enhanced laccase. Compost is added to the soil contaminated by persistent organic matter to be repaired, and the amount of the compost added is 10-18wt% of the soil contaminated by persistent organic matter to be repaired, to obtain contaminated soil with the addition of compost; then 460-500U of laccase is added to each kg of the contaminated soil with the addition of compost to obtain the soil being repaired; then the moisture content of the soil being repaired is adjusted to 37-40%, stirred evenly, and kept in the air for 5-7 days, and the soil contaminated by persistent organic matter is repaired.

[0053] The persistent organic substances are polychlorinated biphenyls.

[0054] Example 8

[0055] A method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase. This example is the same as Example 7 except that the persistent organic matter is a mixture of nitrogen heterocyclic compounds and polycyclic aromatic hydrocarbons.

[0056] Example 9

[0057] A method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase. This example is the same as Example 7 except that the persistent organic matter is a mixture of nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

[0058] The above specific implementation has the following advantages:

[0059] (1) This specific embodiment uses laccase to repair soil contaminated by persistent organic matter, which can quickly degrade pollutants within a few days with high efficiency; the characteristics of laccase determine that the final products of pollutants will be H2O and CO2, which is environmentally friendly and will not cause secondary pollution.

[0060] (2) The use of compost in this specific embodiment can not only increase the soil's ability to retain water, heat, air, and fertilizer, improve the soil's fertility to a certain extent, and quickly restore the soil's agricultural function, but also increase the number and activity of soil microorganisms and significantly increase the activity of the original laccase in the soil, thereby more completely degrading pollutants.

[0061] (3) This specific embodiment uses compost, in which humic acid provides sufficient free radicals for laccase to degrade persistent organic matter, and the presence of hydroxyl groups in its molecular structure also makes humic acid a mediator for laccase to degrade non-phenolic persistent organic matter. The interaction between humic acid and laccase can also protect the stability and activity of the enzyme, slow down the rate of laccase activity decline, greatly increase the action time of laccase, and significantly improve the remediation effect of soil contaminated by persistent organic matter.

[0062] The implementation scheme of the repair method in the present invention is shown in the table below.

[0063] plan Composting amount (%) Laccase amount (U) Moisture content (%) Holding time (d) Pollutants 1 5.5～14 400～460 35～38 3～5 PAHs 2 8～16 440～480 36～39 4～6 Nitrogen heterocycle 3 10～18 460～500 37～40 5～7 PCBs

[0064] Therefore, this specific implementation has the characteristics of short repair period and good repair effect.

[0065] The above are only preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the scope of protection of the present disclosure.

Claims

1. A method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase, characterized in that: The soil remediation method comprises: Adding compost to the soil to be remediated that is contaminated by persistent organic matter to obtain contaminated soil with added compost; Adding laccase to the contaminated soil to which compost has been added to obtain soil being repaired; After the soil being repaired is stirred evenly, it is kept in the air for several days, thereby repairing the soil contaminated by persistent organic matter.

2. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: Before the soil being repaired is stirred evenly, the moisture content of the soil being repaired needs to be adjusted to 35-40%.

3. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: The amount of the compost added is 5.5-18 wt % of the soil to be repaired that is contaminated by persistent organic matter.

4. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: 400-500 U of laccase is added to each kg of the contaminated soil added to the compost.

5. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: The time kept in the air is 3 to 7 days.

6. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: The laccase includes laccase secreted by white rot fungi.

7. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: The enzyme activity of the laccase is 3-4 U / mL.

8. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: The persistent organic matter includes at least one of nitrogen heterocyclic compounds, polycyclic aromatic hydrocarbons and polychlorinated biphenyls.

9. The method for remediating soil contaminated by persistent organic matter based on composting enhanced laccase according to claim 1, characterized in that: The compost includes at least one of garden waste compost, livestock manure compost and sludge compost.

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