Method for reducing carbon emission reduction of wetland soil

Abstract

The invention discloses a method for reducing carbon emission reduction of wetland soil, which is based on an outdoor in-situ soil addition mode, and studies the influence of different reed and spartina alterniflora biochar additive amounts on the emission of three main greenhouse gases (CO2, CH4 and N2O) of the wetland soil to obtain the global warming potential of reducing the emission of the greenhouse gases of the soil by adding the biochar. And the method is a relatively effective carbon emission reduction technology aiming at the wetland.

Description

Technical Field

[0001] The present invention relates to the field of soil carbon emission reduction, and particularly relates to a method for reducing wetland soil carbon emission reduction. Background Art

[0002] The main greenhouse gases causing global warming, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), have been increasing in the atmosphere since the pre-industrial era and continue to increase due to human activities. Although the contents of CH4 and N2O in the atmosphere are small, their warming effects on the centennial scale are 34 times and 298 times that of CO2 respectively. CH4 is mainly produced by methanogens using simple substances such as H2, CO2, acetate and methyl compounds under anaerobic conditions, and the increase in its concentration contributes approximately 25% to global warming. N2O is mainly produced by the combined action of nitrification and denitrification by soil microorganisms, and its contribution to the global greenhouse effect accounts for about 6%. The climate change caused by these three greenhouse gases together accounts for more than 90% of anthropogenic emissions. In order to mitigate the impact of the greenhouse effect on the earth, it is urgent to reduce the concentration of greenhouse gases in the atmosphere. Although countries and organizations have been working hard to control emissions in the past 20 years, the concentration of CO2 in the earth's atmosphere has still been rising since the 1660s. The goal of most international organizations is to reduce the sources of greenhouse gases or offset these sources by sequestering carbon from the environment to limit the temperature rise within 2°C. To slow down the pace of climate change, it is imperative to take emission reduction measures for wetland greenhouse gases and suppress sources and increase sinks.

[0003] Biochar is a product of pyrolysis of biomass under partial or complete oxygen deficiency. Biochar applied to soil can change the physical and chemical properties of soil, such as conductivity, pH value, cation exchange capacity, nutrient cycling, porosity, bulk density and microbial community structure. Existing studies have shown that biochar has a multi-aromatic ring structure, exhibits high biochemical and thermal stability, is difficult to be utilized by microorganisms, can achieve long-term isolation of biomass carbon and the carbon cycle, and avoid the biomass carbon returning to the atmosphere in the form of CO2 again in the short term. And due to the physical and chemical properties of biochar such as high stability, porosity, strong adsorption, rich nutrient content, etc., it has great potential in soil improvement, carbon sequestration, greenhouse gas emission control, etc. The carbon sequestration effect of biochar is its most prominent effect in mitigating climate change.

[0004] The invention patent application with the publication number CN 112934951 A discloses a method for carbon emission reduction in wetland soil improved by biochar. Reed straw is rapidly pyrolyzed (600 °C) in a pyrolysis furnace to obtain reed and Spartina alterniflora biochar. Based on the indoor culture method, the effects of different addition doses of reed and Spartina alterniflora biochar on the emissions of three main greenhouse gases (CO2, CH4, and N2O) in the soil are verified. Based on the regular monitoring of the greenhouse gas emission rate during the cultivation period and the calculation of the cumulative emission flux, it is concluded that the addition of biochar reduces the global warming potential of greenhouse gas emissions in the soil, which is a relatively effective carbon emission reduction technology. Although this method can control the emissions of the three main greenhouse gases, its biochar addition method cannot well simulate the wetland environment. Summary of the Invention

[0005] To solve the deficiencies in the prior art, the present invention provides a method for reducing carbon emission in wetland soil, including the following steps:

[0006] (1) Collect reeds and Spartina alterniflora. After the reed and Spartina alterniflora biomass is dried, crushed, and sieved.

[0007] (2) Decompose and prepare biochar through a high-temperature pyrolysis furnace.

[0008] (3) Based on the outdoor in-situ soil addition method, study the effects of different addition doses of reed and Spartina alterniflora biochar on the emissions of three main greenhouse gases (CO2, CH4, and N2O) in wetland soil. The in-situ soil addition method is as follows: Directly dig out undisturbed soil blocks in the wild, transplant them into flowerpots together with the reeds, and apply reed / Spartina alterniflora biochar in three ratios (w / w) of low, medium, and high for soil improvement.

[0009] (4) Regularly monitor the greenhouse gas emission rate and calculate the cumulative emission flux.

[0010] Preferably, after the reed and Spartina alterniflora biomass is dried and crushed, it is screened through a 2 mm sieve.

[0011] Preferably in any of the above schemes, the heating rate of the high-temperature pyrolysis furnace is 10 °C / min, and the temperature is maintained at 600 °C for 30 min.

[0012] Preferably in any of the above schemes, the prepared biochar is ground to pass through a 0.25 mm sieve.

[0013] Preferably in any of the above schemes, the concentrations of CO2, CH4, and N2O are quantitatively measured by the chamber method.

[0014] Preferably in any of the above schemes, the outer diameter of the flowerpot is 55 cm, the inner diameter is 50 cm, and the height is 33 cm.

[0015] Preferably, in any of the above solutions, a gas chromatograph combined with a flame ionization detector and an electron capture detector is used to measure and calculate the emission rates of CO2, CH4, and N2O.

[0016] The calculation formulas for the greenhouse gas emissions of CO2, CH4, and N2O in the incubation experiment are as follows:

[0017]

[0018] In the formula, F represents the gas flow rate (mg m -2 h -1 );dc / dt is the change rate of the gas concentration during sampling; m is the molar mass of the gas to be measured; P is the pressure at the sampling point; T is the absolute temperature; V0, P0, and T0 are the molar volume, air pressure, and absolute temperature of the gas under standard conditions; and H is the height of the bottle cap above the soil or water surface.

[0019] The cumulative greenhouse gas emissions are calculated in units of CO2 equivalent using the global warming potential (GWP). Based on the currently obtained data within a 100-year time scale, the warming potential of N2O is 298 times that of CO2, and the warming potential of CH4 is 25 times that of CO2. The GWP calculation formula is as follows:

[0020] GWP = CO2 + 25 * CH4 + 298 * N2O

[0021] Beneficial effects:

[0022] In the present invention, based on the in-situ soil addition method outdoors, undisturbed soil blocks are directly dug in the wild and transplanted into flowerpots together with reeds. The reed / smooth cordgrass biochar is applied in three ratios (w / w) of low, medium, and high for soil improvement, which well simulates the outdoor wetland environment. The results show that the application of biochar significantly reduces the soil CO2 emissions. Biochar is prepared using reeds and smooth cordgrass plants widely distributed in wetland ecosystems. Through indoor incubation experiments, the emission characteristics of greenhouse gases (CO2, CH4, and N2O) in wetland soil under different addition doses are explored. It is found that the reed and smooth cordgrass biochar soil improvement technology can effectively reduce the global warming potential of wetlands, providing a basis for carbon emission reduction of wetland biochar soil improvement technology and scientific support for the relevant protection work and carbon sink function improvement of wetlands. Description of the Drawings

[0023] Figure 1 It is a technical roadmap for reducing carbon emissions in wetland soil of the present invention. Detailed Embodiments

[0024] The principles and spirit of the present invention will be described below with reference to several exemplary embodiments shown in the accompanying drawings. It should be understood that the description of these embodiments is only to enable those skilled in the art to better understand and then implement the present invention, rather than limiting the scope of the present invention in any way.

[0025] Example 1

[0026] Reeds widely distributed in wetland ecosystems and the important alien invasive species Spartina alterniflora were collected. After the reed and Spartina alterniflora biomass were dried and pulverized, they were screened through a 2 mm sieve, and then decomposed by a high-temperature pyrolysis furnace to prepare biochar. The heating rate of the pyrolysis furnace was 10 °C / min, and the temperature was maintained at 600 °C for 30 min. The carbon yields of reeds and Spartina alterniflora were 32.71% and 30.83% respectively. The prepared biochar was ground to pass through a 0.25 mm sieve and thoroughly homogenized for further analysis. The properties of the reed and Spartina alterniflora biochars prepared by the above method are shown in Table 1.

[0027] Table 1 Proximate analysis and elemental analysis of reed biochar (dry basis)

[0028]

[0029] Undisturbed soil blocks were directly dug in the field and transplanted into flower pots together with reeds. The flower pots had an outer diameter of 55 cm, an inner diameter of 50 cm, and a height of 33 cm. The concentrations of CO2, CH4, and N2O were quantitatively measured by the chamber method. Reed / Spartina alterniflora biochar was applied for soil improvement at three ratios (w / w) of low, medium, and high, and a total of 8 treatments were set: (1) 0%: (CK); (2) 1%: (P1 / S1); (3) 5%: (P2 / S2); (4) 10%: (P3 / S3). Each treatment included 3 replicates. During the experiment, water was supplemented every 1 - 2 weeks to keep the soil moist. Sampling was carried out on the 1st, 4th, 7th, 15th, 30th, 60th, and 90th days after the start of the experiment to measure the emission fluxes and cumulative emissions of CO2, CH4, and N2O. Two gas samples were collected at 2-hour intervals to determine the change rate (flux). Each time, 20 mL of gas samples were drawn through a plastic tube from the top of the chamber into a 60 mL airtight syringe. The greenhouse gas emission flux was calculated as the slope of the change in the concentration of the two gases over time. Within 2 weeks after gas collection, a gas chromatograph (Agilent 7890A, USA) combined with a flame ionization detector and an electron capture detector was used to measure and calculate the emission rates of CO2, CH4, and N2O.

[0030] The calculation formulas for the greenhouse gas emissions of CO2, CH4, and N2O in the incubation experiment are as follows:

[0031]

[0032] In the formula, F represents the gas flow rate (mg m -2 h -1 ); dc / dt is the change rate of gas concentration during sampling; m is the molar mass of the gas to be measured; P is the pressure at the sampling point; T is the absolute temperature; V0, P0, and T0 are the molar volume, air pressure, and absolute temperature of the gas under standard conditions; and H is the height of the bottle cap above the soil or water surface.

[0033] The cumulative greenhouse gas emissions are calculated in units of CO2 equivalent using the global warming potential (GWP). Based on the currently obtained data within a 100-year time scale, the warming potential of N2O is 298 times that of CO2, and the warming potential of CH4 is 25 times that of CO2. The GWP calculation formula is as follows:

[0034] GWP = CO2 + 25 * CH4 + 298 * N2O

[0035] The results show that the application of biochar significantly reduces soil CO2 emissions. The cumulative carbon dioxide emissions of the P1, P2, and P3 treatments during the incubation period increase sequentially with the increase in dose. The cumulative CO2 emissions of the soil improved with reed biochar are significantly lower than those of the control treatment group. The cumulative CO2 emissions of the S1, S2, and S3 treatments with Spartina alterniflora biochar increase sequentially. The cumulative CO2 emissions after the application of Spartina alterniflora biochar are significantly reduced compared with the control treatment, and the 1% addition dose of Spartina alterniflora biochar has the best CO2 emission reduction effect. Compared with the control, the soil cumulative CH4 fluxes of the P2 and P3 treatments increase significantly, while the change in the CH4 flux of the soil improved with Spartina alterniflora biochar does not reach a significant level.

[0036] The calculation results of the global warming potential show that: within the 90-day incubation period, low, medium, and high addition doses of reed biochar all have a relatively significant inhibitory effect on the comprehensive warming potential of the wetland, and the low dose addition has the best inhibitory effect. Spartina alterniflora biochar significantly reduces the comprehensive warming potential of the wetland.

[0037] In this article, specific examples are used to elaborate on the inventive concept in detail. The description of the above embodiments is only used to help understand the core idea of the present invention. It should be noted that for those of ordinary skill in the art of this technology, any obvious modifications, equivalent replacements, or other improvements made without departing from the inventive concept should be included within the protection scope of the present invention.

Claims

1. A method for reducing carbon emission in wetland soil, comprising the following steps: (1) Collect reed and Spartina alterniflora, and after drying and crushing the reed and Spartina alterniflora biomass, sieve it. (2) Decompose it through a high-temperature pyrolysis furnace to prepare biochar. (3) Based on the outdoor in-situ soil addition method, study the effects of different addition doses of reed and Spartina alterniflora biochar on the emissions of three main greenhouse gases (CO2, CH4, and N2O) in wetland soil. The in-situ soil addition method is as follows: directly dig out undisturbed soil blocks in the wild, transplant them together with reeds into flowerpots, and apply reed / Spartina alterniflora biochar in three proportions (w / w), low, medium, and high, for soil improvement. (4) Regularly monitor the greenhouse gas emission rate and calculate the cumulative emission flux.

2. The method for reducing wetland soil carbon emission reduction according to claim 1, wherein After drying and crushing the reed and Spartina alterniflora biomass, sieve it through a 2-mm sieve.

3. The method for reducing wetland soil carbon emission reduction as claimed in claim 1, wherein, The heating rate of the high-temperature pyrolysis furnace is 10 °C / min, and the temperature is maintained at 600 °C for 30 min.

4. The method for reducing wetland soil carbon emission reduction according to claim 1, characterized in that, Grind the prepared biochar to make it pass through a 0.25-mm sieve.

5. The method for reducing wetland soil carbon emission reduction according to claim 1, wherein Quantitatively determine the concentrations of CO2, CH4, and N2O by the chamber method.

6. The method for reducing wetland soil carbon emission reduction according to claim 1, wherein The outer diameter of the flowerpot is 55 cm, the inner diameter is 50 cm, and the height is 33 cm.

7. The method for reducing wetland soil carbon emission reduction according to claim 1, wherein Use a gas chromatograph combined with a flame ionization detector and an electron capture detector to measure and calculate the emission rates of CO2, CH4, and N2O.

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