Method for testing oxidizable organic carbon content and carbon stable isotope
Patent Information
- Application Number
- CN202611241782.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-08-17
- Publication Date
- 2026-10-30
AI Technical Summary
[0005]本发明的目的是为了解决现有测试易氧化有机碳（LOC）方法高锰酸钾溶液的用量大且仅能测试易氧化有机碳（LOC）含量的技术问题，提供了一种易氧化有机碳（LOC）含量及碳稳定同位素测试方法
[0025]1.土壤样品用量少，仅为传统方法样量的10%；
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Figure CN123008967A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a method for testing the content of easily oxidizable organic carbon (LOC) and carbon stable isotopes, belonging to the field of testing and analysis technology. Background Technology
[0002] Easily oxidizable organic carbon (LOC) in soil refers to the portion of organic carbon that is readily utilized by microorganisms and plants and is chemically active. Unlike other stable organic carbons, it is characterized by high solubility, high mobility, easy decomposition, and easy oxidation and mineralization. Due to its high availability to plant roots and soil microorganisms in its form and distribution location, it plays a crucial role in the soil ecosystem. Active organic carbon in soil is not a single compound, but a mixture of various easily decomposed and transformed organic substances. Its main sources include plant residues (such as fallen leaves and roots), fungal hyphae, microbial cells and their metabolic products (such as polysaccharides and organic acids). These substances together constitute a dynamically changing organic carbon pool that can be rapidly decomposed and utilized by soil microorganisms.
[0003] Easily oxidizable organic carbon carbon stable isotopes (LOC- 13 C) Soil plays a vital role in scientific research, for example: studying the dissolution, adsorption, release, and migration of soil nutrients, affecting plant nutrient uptake; as a major energy source for microorganisms, regulating their growth and metabolism, and studying how it affects the decomposition rate of organic matter; studying the adsorption, desorption, and bioavailability of heavy metals and organic pollutants in soil; studying how it affects soil structure formation and stability during soil formation; and due to its easy decomposition, the turnover of active organic carbon is closely related to carbon dioxide emissions, studying its impact on the global carbon cycle. Because of its significant impact on soil fertility, environmental protection, and climate change, it has become an important research topic in soil science, environmental science, and ecology in recent years.
[0004] Currently, easily oxidizable organic carbon (LOC) is usually determined using the potassium permanganate oxidation method. The soil sample to be tested is weighed and then transferred to a 50ml capped plastic centrifuge tube, with no soil sample added as a blank. 25ml of potassium permanganate solution with a concentration of 333mmol / L is added to the centrifuge tube, shaken for 1 hour, centrifuged, the supernatant is diluted, and the absorbance is measured using a spectrophotometer. The soil active organic carbon content is calculated by subtracting the concentration of the potassium permanganate solution after oxidation of active organic carbon from the concentration of the blank potassium permanganate. This method has many shortcomings: (1) The traditional method is to measure the absorbance of the solution with a spectrophotometer for quantification. The potassium permanganate solution is unstable, and the storage time of the sample to be tested will directly affect the accuracy of the measurement results; (2) It is difficult to ensure that the potassium permanganate solution added to the blank and the sample is highly consistent, which will also cause a large error in the test results; (3) This method can only test the LOC content in the soil and cannot provide the soil active organic carbon content. 13 Stable isotope values of carbon. Summary of the Invention
[0005] The purpose of this invention is to solve the technical problems of existing methods for testing easily oxidizable organic carbon (LOC) that require a large amount of potassium permanganate solution and can only test the content of easily oxidizable organic carbon (LOC), and to provide a method for testing the content of easily oxidizable organic carbon (LOC) and carbon stable isotopes.
[0006] The methods for testing the content of easily oxidizable organic carbon and carbon stable isotopes are as follows:
[0007] I. Sample Pretreatment; Soil samples containing easily oxidizable organic carbon (LOC) are pretreated;
[0008] II. Sample Weighing and Oxidation: Weigh 0.5 mg - 1.5 mg of pretreated soil sample containing easily oxidizable organic carbon (LOC) and place it in a 12 mL Labco headspace sampler (manufactured by Tianjin Oujie Technology Co., Ltd.). Add a magnetic rotor, then add 2 mL of 333 mmol / L potassium permanganate solution. Tighten the cap and stir the sample at 25°C for 1 hour. After the reaction is complete, centrifuge at 4000 r / min for 5 minutes to obtain the sample vial for testing (at this point, the easily oxidizable organic carbon (LOC) is oxidized to CO2 gas by potassium permanganate and sealed in the headspace sampler).
[0009] III. Establishing a standard curve and verifying precision:
[0010] Different weights of glucose were measured using a multi-purpose online sample preparation device coupled with a stable isotope ratio mass spectrometer. A linear regression equation was established between the absolute amount of easily oxidizable organic carbon (LOC) and the peak area of CO2. The test results were subjected to linear regression, and the equation was y = 0.0065x, with a correlation coefficient R. 2Given a value of 0.9988, plot the standard curve of the absolute amount of easily oxidizable organic carbon (LOC) and the peak area of CO2. In the equation y=0.0065x, y represents the absolute amount of easily oxidizable organic carbon (LOC) and x represents the peak area of CO2.
[0011] Glucose was selected as the reference material for carbon stable isotope testing. Five parallel determinations were performed, with a standard deviation of 0.11, and the curve verification results were satisfactory.
[0012] IV. Measurement: The gas in the sample vial was measured using a multi-purpose online sample preparation device coupled with a stable isotope ratio mass spectrometer to obtain the CO2 peak area and the stable isotope ratio of easily oxidizable organic carbons (LOC-). 13 C);
[0013] V. Calculation of Results: Stable Isotope Ratio of Easily Oxidizable Organic Carbons (LOC-) 13 C), using glucose for single-point correction, the formulas for calculating the content of easily oxidizable organic carbon (LOC) (LOC%) and the absolute amount of easily oxidizable organic carbon (LOC) are as follows:
[0014] y=0.0065x Formula 1
[0015] In Formula 1, y represents the absolute amount of easily oxidizable organic carbon (LOC), and x represents the peak area of CO2.
[0016] Easily oxidizable organic carbon (LOC) content (%) = A * 0.0065 / m * 100% (Formula 2)
[0017] In Formula 2, A represents the CO2 peak area, and m represents the sample weight.
[0018] The sample pretreatment described in step one is as follows: the collected soil samples are air-dried naturally, ground, and passed through an 80-mesh sieve.
[0019] Step 2: Weigh a soil sample containing 1 mg of carbon.
[0020] The stable isotope ratio mass spectrometer system described in step three is model Delta V Advantage.
[0021] The stable isotope mass spectrometer is an analytical instrument that was put into use on September 17, 2019. It is primarily used in the fields of earth sciences, hydraulic engineering, and environmental and resource science and technology. This instrument measures carbon (δ¹⁸O₂) by... 13 C), hydrogen (δD), oxygen (δ) 18 O), nitrogen (δ 15 N), sulfur (δ) 34 S isotope ratios are used to analyze the cycle of biogenic elements in water-soil-biological systems, supporting research on carbon and nitrogen balance, water use efficiency, and material turnover rate.
[0022] In the field of automation technology for trace gas analysis, in 2023, Tan Yang's team at the Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences, developed an automated sample introduction system for a gas pre-concentration device of a stable isotope mass spectrometer. This system integrates pre-concentration, purification, and automated sample introduction testing for trace gas samples such as N2O, CO2, and CH4, reducing the impact of human operation and improving the detection accuracy and efficiency of stable isotopes of carbon, nitrogen, and oxygen in trace gases.
[0023] To improve work efficiency and promote environmental friendliness, this invention proposes a novel method to address the problems of traditional methods, automating sample testing, freeing up significant human resources, reducing human error, improving data accuracy, and enabling simultaneous determination of carbon stable isotope values. This invention provides a method for determining the content of easily oxidizable organic carbon (LOC) and carbon stable isotopes in soil.
[0024] The specific advantages of this invention, a method for determining the content of readily oxidizable organic carbon (LOC) and carbon stable isotopes in soil, are as follows:
[0025] 1. The amount of soil sample used is small, only 10% of that used in traditional methods;
[0026] 2. The amount of potassium permanganate solution used is reduced by 90%, which greatly reduces the use and emissions of chemical reagents, making it relatively green and environmentally friendly;
[0027] 3. The LOC content of soil samples can be directly calculated by testing the CO2 produced by the oxidation of easily oxidizable organic carbon (LOC) by potassium permanganate solution. Both the testing precision and accuracy are higher than those of traditional methods.
[0028] 4. The method for determining easily oxidizable organic carbon (LOC) of the present invention can simultaneously provide the LOC content in soil and 13 Stable isotope values of carbon. Attached Figure Description
[0029] Figure 1 It is a standard curve of sample peak area and absolute amount of easily oxidizable organic carbon (LOC). Detailed Implementation
[0030] The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.
[0031] Specific Implementation Method 1: The method for testing the content of easily oxidizable organic carbon and carbon stable isotopes in this implementation method is as follows:
[0032] I. Sample Pretreatment; Soil samples containing easily oxidizable organic carbon (LOC) are pretreated;
[0033] II. Sample Weighing and Oxidation: Weigh 0.5 mg - 1.5 mg of pretreated soil sample containing easily oxidizable organic carbon (LOC) and place it in a 12 mL Labco headspace sampler (manufactured by Tianjin Oujie Technology Co., Ltd.). Add a magnetic rotor, then add 2 mL of 333 mmol / L potassium permanganate solution. Tighten the cap and stir the sample at 25°C for 1 hour. After the reaction is complete, centrifuge at 4000 r / min for 5 minutes to obtain the sample vial for testing (at this point, the easily oxidizable organic carbon (LOC) is oxidized to CO2 gas by potassium permanganate and sealed in the headspace sampler).
[0034] III. Establishing a standard curve and verifying precision:
[0035] Different weights of glucose were measured using a multi-purpose online sample preparation device coupled with a stable isotope ratio mass spectrometer. A linear regression equation was established between the absolute amount of easily oxidizable organic carbon (LOC) and the peak area of CO2. The test results were subjected to linear regression, and the equation was y = 0.0065x, with a correlation coefficient R. 2 Given a value of 0.9988, plot the standard curve of the absolute amount of easily oxidizable organic carbon (LOC) and the peak area of CO2. In the equation y=0.0065x, y represents the absolute amount of easily oxidizable organic carbon (LOC) and x represents the peak area of CO2.
[0036] Glucose was selected as the reference material for carbon stable isotope testing. Five parallel determinations were performed, with a standard deviation of 0.11, and the curve verification results were satisfactory.
[0037] IV. Measurement: The gas in the sample vial was measured using a multi-purpose online sample preparation device coupled with a stable isotope ratio mass spectrometer to obtain the CO2 peak area and the stable isotope ratio of easily oxidizable organic carbons (LOC-). 13 C);
[0038] V. Calculation of Results: Stable Isotope Ratio of Easily Oxidizable Organic Carbons (LOC-) 13 C), using glucose for single-point correction, the formulas for calculating the content of easily oxidizable organic carbon (LOC) (LOC%) and the absolute amount of easily oxidizable organic carbon (LOC) are as follows:
[0039] y=0.0065x Formula 1
[0040] In Formula 1, y represents the absolute amount of easily oxidizable organic carbon (LOC), and x represents the peak area of CO2.
[0041] Easily oxidizable organic carbon (LOC) content (%) = A * 0.0065 / m * 100% (Formula 2)
[0042] In Formula 2, A represents the CO2 peak area, and m represents the sample weight.
[0043] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the sample pretreatment in step one is as follows: The collected soil sample is air-dried naturally, ground, and passed through an 80-mesh sieve. Everything else is the same as in Specific Implementation Method One.
[0044] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that step 2 involves weighing a soil sample containing 1 mg of carbon. Everything else is the same as in Specific Implementation Method 1 or 2.
[0045] Specific Implementation Method Four: This implementation method differs from one of Specific Implementation Methods One to Three in that the stable isotope ratio mass spectrometer system described in step three is model Delta V Advantage. Everything else is the same as in one of Specific Implementation Methods One to Three.
[0046] The following experiments were used to verify the effectiveness of the invention:
[0047] Experiment 1:
[0048] The methods for testing the content of easily oxidizable organic carbon and carbon stable isotopes are as follows:
[0049] I. Sample Pretreatment; Soil samples containing easily oxidizable organic carbon (LOC) are pretreated;
[0050] II. Sample Weighing and Oxidation: Weigh 0.5 mg - 1.5 mg of pretreated soil sample containing easily oxidizable organic carbon (LOC) and place it in a 12 mL Labco headspace sampler (manufactured by Tianjin Oujie Technology Co., Ltd.). Add a magnetic rotor, then add 2 mL of 333 mmol / L potassium permanganate solution. Tighten the cap and stir the sample at 25°C for 1 hour. After the reaction is complete, centrifuge at 4000 r / min for 5 minutes to obtain the sample vial for testing (at this point, the easily oxidizable organic carbon (LOC) is oxidized to CO2 gas by potassium permanganate and sealed in the headspace sampler).
[0051] III. Establishing a standard curve and verifying precision:
[0052] Different weights of glucose were measured using a multi-purpose online sample preparation device coupled with a stable isotope ratio mass spectrometer. A linear regression equation was established between the absolute amount of easily oxidizable organic carbon (LOC) and the peak area of CO2. The test results were subjected to linear regression, and the equation was y = 0.0065x, with a correlation coefficient R. 2 Given a value of 0.9988, plot the standard curve of the absolute amount of easily oxidizable organic carbon (LOC) and the peak area of CO2. In the equation y=0.0065x, y represents the absolute amount of easily oxidizable organic carbon (LOC) and x represents the peak area of CO2.
[0053] The test process and results are as follows:
[0054] After weighing different weights of glucose and following the procedure in step two, the absolute amount of easily oxidizable organic carbon (LOC) (y) and the peak area of CO2 (x) were measured. The results were then subjected to linear regression, yielding the equation y = 0.0065x, with a correlation coefficient R0. 2 It is 0.9988.
[0055] Table 1
[0056]
[0057] The standard curve of sample peak area and absolute amount of easily oxidizable organic carbon (LOC) is as follows: Figure 1 .
[0058] Glucose was selected as the reference material for carbon stable isotope testing. Five parallel determinations were performed, with a standard deviation of 0.11, and the curve verification results were satisfactory.
[0059] Table 2 Stable carbon isotopes of easily oxidizable organic carbons (δ¹²) 13 C) Statistical results of the measurement results
[0060]
[0061] IV. Measurement: The gas in the sample vial to be tested was measured using a multi-purpose online sample preparation device-stable isotope ratio mass spectrometer system to obtain the CO2 peak area and the carbon stable isotope ratio of easily oxidizable organic carbon.
[0062] V. Calculation of Results: The stable isotope ratio of easily oxidizable organic carbon was corrected using glucose at a single point. The formulas for calculating the content and absolute amount of easily oxidizable organic carbon are as follows:
[0063] y=0.0065x Formula 1
[0064] In Formula 1, y represents the absolute amount of easily oxidizable organic carbon, and x represents the peak area of CO2.
[0065] Easily oxidizable organic carbon content = A * 0.0065 / m * 100% (Formula 2)
[0066] In Formula 2, A represents the CO2 peak area, and m represents the sample weight.
[0067] The results of the test for easily oxidizable organic carbon (LOC) content in four soil types (standard soil sample (standard number IVA33802176), forest soil, Yunnan red soil, and Sichuan yellow-brown soil) are shown in the table below. 13 The standard deviations for C and LOC (%) tests were 0.10, 0.04; 0.12, 0.05; 0.07, 0.05; and 0.05, 0.03, respectively.
[0068] Table 3
[0069]
Claims
1. A method for testing the content of easily oxidizable organic carbon and carbon stable isotopes, characterized in that... The methods for testing the content of easily oxidizable organic carbon and carbon stable isotopes are as follows: I. Sample pretreatment; Pretreatment of soil samples containing easily oxidizable organic carbon; II. Sample weighing and oxidation: Weigh 0.5 mg - 1.5 mg of pretreated soil sample containing easily oxidizable organic carbon, place it in a 12 mL Labco headspace vial, add a magnetic rotor, then add 2 mL of 333 mmol / L potassium permanganate solution, tighten the cap, and stir the reaction at 25℃ for 1 hour. After the reaction is complete, centrifuge at 4000 r / min for 5 minutes to obtain the sample vial for testing. III. Establishing a standard curve and verifying precision: Different weights of glucose were measured using a multi-purpose online sample preparation device coupled with a stable isotope ratio mass spectrometer. A linear regression equation was established between the absolute amount of easily oxidizable organic carbon and the peak area of CO2. The test results were subjected to linear regression, and the equation was y = 0.0065x, with a correlation coefficient R. 2 Given a value of 0.9988, plot the standard curve of the absolute amount of easily oxidizable organic carbon and the peak area of CO2. In the equation y=0.0065x, y represents the absolute amount of easily oxidizable organic carbon and x represents the peak area of CO2. Glucose was selected as the reference material for carbon stable isotope testing. Five parallel determinations were performed, with a standard deviation of 0.11, and the curve verification results were satisfactory. IV. Measurement: The gas in the sample vial to be tested was measured using a multi-purpose online sample preparation device-stable isotope ratio mass spectrometer system to obtain the CO2 peak area and the carbon stable isotope ratio of easily oxidizable organic carbon. V. Calculation of Results: The stable isotope ratio of easily oxidizable organic carbon was corrected using glucose at a single point. The formulas for calculating the content and absolute amount of easily oxidizable organic carbon are as follows: y=0.0065x Formula 1 In Formula 1, y represents the absolute amount of easily oxidizable organic carbon, and x represents the peak area of CO2. Easily oxidizable organic carbon content = A * 0.0065 / m * 100% (Formula 2) In Formula 2, A represents the CO2 peak area, and m represents the sample weight.
2. The method for testing the content of easily oxidizable organic carbon and carbon stable isotopes according to claim 1, characterized in that... The sample pretreatment described in step one is as follows: the collected soil samples are air-dried naturally, ground, and passed through an 80-mesh sieve.
3. The method for testing the content of easily oxidizable organic carbon and carbon stable isotopes according to claim 1, characterized in that... Step 2: Weigh a soil sample containing 1 mg of carbon.
4. The method for testing the content of easily oxidizable organic carbon and carbon stable isotopes according to claim 1, characterized in that... The stable isotope ratio mass spectrometer system described in step three is model Delta V Advantage.