CN116879207A - Method for determining organic matters in soil - Google Patents
Method for determining organic matters in soil Download PDFInfo
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- CN116879207A CN116879207A CN202311010084.2A CN202311010084A CN116879207A CN 116879207 A CN116879207 A CN 116879207A CN 202311010084 A CN202311010084 A CN 202311010084A CN 116879207 A CN116879207 A CN 116879207A
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- 239000002689 soil Substances 0.000 title claims abstract description 157
- 238000000034 method Methods 0.000 title claims abstract description 67
- 239000005416 organic matter Substances 0.000 claims abstract description 48
- 239000000706 filtrate Substances 0.000 claims abstract description 40
- 238000002835 absorbance Methods 0.000 claims abstract description 34
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 32
- 229910017604 nitric acid Inorganic materials 0.000 claims description 32
- 239000012528 membrane Substances 0.000 claims description 12
- 238000001914 filtration Methods 0.000 claims description 7
- 239000000463 material Substances 0.000 claims description 7
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 239000012784 inorganic fiber Substances 0.000 claims description 5
- 238000007873 sieving Methods 0.000 claims description 5
- 239000011148 porous material Substances 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 3
- 238000012886 linear function Methods 0.000 claims description 2
- 238000012360 testing method Methods 0.000 abstract description 5
- 238000001514 detection method Methods 0.000 abstract 1
- KMUONIBRACKNSN-UHFFFAOYSA-N potassium dichromate Chemical compound [K+].[K+].[O-][Cr](=O)(=O)O[Cr]([O-])(=O)=O KMUONIBRACKNSN-UHFFFAOYSA-N 0.000 description 16
- 239000000243 solution Substances 0.000 description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 6
- 235000008733 Citrus aurantifolia Nutrition 0.000 description 6
- 235000011941 Tilia x europaea Nutrition 0.000 description 6
- 238000010304 firing Methods 0.000 description 6
- 239000004571 lime Substances 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 229910052799 carbon Inorganic materials 0.000 description 5
- 238000010438 heat treatment Methods 0.000 description 5
- 238000005259 measurement Methods 0.000 description 5
- 239000004033 plastic Substances 0.000 description 5
- 230000029087 digestion Effects 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 3
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 239000004016 soil organic matter Substances 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical group [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- 238000004497 NIR spectroscopy Methods 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 230000002378 acidificating effect Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
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- 239000000126 substance Substances 0.000 description 2
- 238000012546 transfer Methods 0.000 description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical group [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000007605 air drying Methods 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 231100000481 chemical toxicant Toxicity 0.000 description 1
- 239000002734 clay mineral Chemical group 0.000 description 1
- 238000009841 combustion method Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 230000035558 fertility Effects 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 239000003365 glass fiber Substances 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 230000000813 microbial effect Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000001320 near-infrared absorption spectroscopy Methods 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 238000002310 reflectometry Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005070 sampling Methods 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
- 238000004611 spectroscopical analysis Methods 0.000 description 1
- 239000012086 standard solution Substances 0.000 description 1
- 231100000331 toxic Toxicity 0.000 description 1
- 230000002588 toxic effect Effects 0.000 description 1
- 239000003440 toxic substance Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 230000004580 weight loss Effects 0.000 description 1
Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
- G01N21/31—Investigating relative effect of material at wavelengths characteristic of specific elements or molecules, e.g. atomic absorption spectrometry
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N1/00—Sampling; Preparing specimens for investigation
- G01N1/28—Preparing specimens for investigation including physical details of (bio-)chemical methods covered elsewhere, e.g. G01N33/50, C12Q
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- Biochemistry (AREA)
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Abstract
The invention discloses a method for measuring organic matters in soil. The method comprises the following steps: 1) Obtaining a plurality of scaled soil samples; 2) Establishing a standard curve by taking the organic matter content and the corresponding absorbance in each calibration soil sample filtrate as a horizontal coordinate and a vertical coordinate respectively; 3) Determination of the samples: selecting soil with the same type as the scaled soil as a soil sample to be measured; and reading out the organic matter content in the filtrate of the soil sample to be detected corresponding to the standard curve, and then calculating the organic matter content in the soil sample to be detected according to the specific formula. The method disclosed by the invention has the advantages that the required equipment is simple, the detection is faster, the test of each sample can be completed within about 40 minutes, the repeatability is good, and the cost is lower.
Description
Technical Field
The invention relates to a method for measuring organic matters, in particular to a method for measuring organic matters in soil.
Background
The soil organic matter is various organic matters generated by various animal and plant residues and microbial life activities, is taken as an important constituent part of soil, has extremely important effects on the formation of a soil structure, the improvement of quality, the improvement of volume weight and the improvement of fertility, and is a key for accurately and rapidly measuring the soil organic matter.
The method for measuring the organic matters in the soil comprises two main types of manual measurement and instrument measurement. Wherein the manual determination method mainly comprises a combustion method and a chemical oxidation method. The burning method is mainly divided into dry burning method and burning method, the dry burning method is to put soil in an electric furnace with temperature exceeding 900 ℃ and decompose samples to generate CO 2 Converting the total organic carbon value into a total organic carbon value by using a detector; the method can completely decompose soil organic matters, is simple and quick, but has high instrument and equipment requirements and high operation cost. The firing method is generally suitable for sandy soil, wherein the soil sample is subjected to moisture absorption and weighing at 105 ℃, then the soil sample is fired at 350-1000 ℃ for 2 hours, the organic matter content is calculated according to the mass lost after firing, the firing method is simple to operate and does not need to add chemical reagents, but the weight loss of carbonate, sulfide, clay mineral structure water and the like in the firing process is higher than that of a dry firing method, so that the application range of the organic matter content measured by the firing method is limited. The chemical oxidation method is mainly potassium dichromate oxidation method, under the acidic condition of sulfuric acid, using excessive potassium dichromate (K 2 Cr 2 O 7 ) To oxidize organic carbon in the soil, and the remaining potassium dichromate is treated with ferrous sulfate (FeSO 4 ) And (3) titrating a standard solution, and calculating the organic carbon content according to the consumed potassium dichromate. The method can eliminate the influence of carbonate on experimental results, but the method needs to be carried out under the heating of an oil bath, and has the problems of difficult control of temperature, low measurement speed, high pollution and the like.
The instrument measurement method mainly comprises a soil organic spectrometry and a near infrared spectrometry. According to the characteristic spectrum characteristics of soil, the soil organic spectrum measurement reflects the change condition of the reflectivity of organic matters in a specific wave band, and a related model is established so as to estimate the content of the organic matters; the near infrared spectroscopy mostly needs to pretreat the soil (such as drying, grinding, sieving and the like) to ensure that the particle size of the sample is small and uniform, the near infrared spectroscopy is selectively absorbed according to specific functional groups, a quantitative functional relation is established between the measured component content and the spectral absorbance (or the transformation thereof), and the characteristic index or the component content of the sample can be obtained according to the spectrum of an unknown sample by virtue of the relation. The two methods are quick, efficient and convenient testing methods, are suitable for large-scale quick determination, but parameter condition setting is ideal, is easily influenced by environmental factors, and has unsatisfactory accuracy of determination results.
At present, the most widely used method for determining soil organic matters is a potassium dichromate method, and in order to determine the soil organic matters more simply and rapidly, technicians perform various research improvements on the potassium dichromate method, wherein the improvements mainly comprise improvements on digestion methods: a glycerol bath method, a phosphoric acid bath method, an oven method, a microwave heating method, a temperature control electric furnace method, a graphite digestion furnace method (flat plate), a Kjeldahl nitrogen digestion furnace method and the like. However, the existing improved potassium dichromate oxidation methods still have the defects of poor temperature control precision, slow heat transfer rate, uneven heating of samples, multiple sample transfer in the test process and Ag consumption 2 SO 4 、HgSO 4 Expensive or toxic chemical reagents, high cost and high pollution.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the method for determining the organic matters in the soil, which has high accuracy, good repeatability and simple operation, according to the corresponding relation between the color of the acidic extracting solution of the soil and the organic matters.
The method for measuring organic matters in soil comprises the following steps:
1) Obtaining a plurality of scaled soil samples;
2) Establishing a standard curve:
2.1 Respectively reacting each calibration soil sample with nitric acid solution with the concentration of 0.43mol/L, filtering the obtained materials, collecting filtrate of each calibration soil sample, respectively measuring absorbance of each calibration soil sample at 540nm, and marking as Ai; then, the organic matter contents of the soil samples are measured respectively and marked as Pi, and then the organic matter contents in the soil samples are calculated according to the following formula (1) and marked as Ci:
Ci＝Pi×Mi/V (1)
wherein Ci is the organic matter content in each scaled soil sample, and the unit is; pi is the organic matter content in the filtrate of each scaled soil sample, and the unit is g/L; mi is the mass of each scaled soil sample in g; v is the volume of nitric acid added in L; wherein i represents the corresponding sample number;
in the step, the dosage of the nitric acid solution is calculated by adding 30mL of nitric acid solution into 0-10g of calibration soil sample;
2.2 Using the organic matter content and the absorbance corresponding to the organic matter content in the filtrate of each calibration soil sample as horizontal marks and vertical coordinates to establish a standard curve, and fitting to obtain a linear function shown in the following formula (2):
A＝aC+b (2)
wherein A is absorbance of a soil sample in a standard curve; a is the slope of a standard curve; c is the organic matter content in the soil sample, and the unit is mg/L; b is the intercept;
3) Determination of the samples:
3.1 Selecting soil of the same type as the scaled soil (the soil classification is performed according to the classification of soil class in China soil Classification and code (GB/T17296-2000)) to obtain a soil sample to be tested;
3.2 Reacting a soil sample to be detected with the mass of m with a nitric acid solution with the concentration of 0.43mol/L, filtering the obtained material, collecting filtrate of the soil sample to be detected, measuring the absorbance of the filtrate at 540nm, and marking the absorbance as A To be treated The method comprises the steps of carrying out a first treatment on the surface of the The consumption of the nitric acid solution is calculated by adding 30mL of the nitric acid solution into 0-10g of soil sample to be measured;
3.3 Reading out the organic matter content in the filtrate of the soil sample to be tested corresponding to the recorded absorbance according to the determined standard curve, or bringing the recorded absorbance into a formula (2) to obtain the filtrate of the soil sample to be tested corresponding to the absorbanceThe organic matter content is denoted as P To be treated ；
3.4 Calculating the organic matter content in the soil sample to be measured according to the following formula (3):
C to be treated ＝P To be treated ×M To be treated /V (3)
Wherein C is To be treated The unit is the organic matter content in the soil sample to be measured; p (P) To be treated The unit of the organic matter content in the filtrate of the soil sample to be detected is g/L; m is the mass of a soil sample to be detected, and the unit is g; v is the volume of nitric acid added in L.
In the method of the invention, the specific steps of obtaining the scaled soil sample or the soil sample to be measured comprise: drying soil sample (air-dried or naturally air-dried or oven-dried at 40deg.C), and sieving. Typically a sieve having a pore size of 2mm, and then collecting the undersize for subsequent steps.
In the method of the present invention, it is preferable to filter the material obtained by mixing the scaled soil sample or the soil sample to be measured with the nitric acid solution with a filter membrane having a pore size of 0.4 to 0.5. Mu.m, and it is more preferable to use a filter membrane having a pore size of 0.45. Mu.m. The filter membrane is preferably an inorganic fiber glass fiber filter membrane.
In the method according to the invention, the reaction time of the scaled soil sample or the soil sample to be measured with the nitric acid solution having a concentration of 0.43mol/L is usually 20 to 40 minutes, preferably 30 minutes.
In the method, a spectrophotometer is adopted to measure the absorbance of filtrate of a scaled soil sample or filtrate of a soil sample to be measured; and measuring the concentration content of organic matters in the filtrate of the scaled soil sample or the filtrate of the soil sample to be measured by adopting a TOC measuring instrument.
Compared with the prior art, the invention is characterized in that:
1. the method can be realized by only one set of sampling device, dosing device, spectrophotometer and TOC tester, and has simple equipment and relatively low cost; can be realized indoors and outdoors, and can realize the organic matter determination of different points of a large amount of similar soil.
2. The method provided by the invention is simple and easy to operate, high in precision, good in repeatability and quicker, and the test of each sample can be completed in about 40 minutes.
3. The method of the invention does not need to use toxic and expensive chemical reagents such as Hg, ag and the like, only needs nitric acid, and has low nitric acid concentration, less consumption, low cost and small influence on environment.
4. The method disclosed by the invention does not need the steps of heating, digestion and the like, is low in energy consumption and is more convenient for field operation.
5. The devices of the method are all mature products, can be directly purchased from the market, and are convenient and easy to obtain and easy to realize.
Drawings
FIG. 1 is a standard curve established in example 1 of the present invention, the abscissa is the organic content in g/L of the filtrate obtained by the reaction of the scaled soil with the nitric acid solution; the ordinate is absorbance;
FIG. 2 is a standard curve established in example 2 of the present invention, the abscissa is the organic content in g/L of the filtrate obtained by the reaction of the scaled soil with the nitric acid solution; the ordinate is absorbance.
Detailed Description
The present invention will be further described in detail with reference to the following examples to better understand the content of the present invention, but the present invention is not limited to the following examples.
When the method is used for measuring the organic matter content in soil, the following equipment and materials are preferably prepared:
1 branch of 50mL conical flask, 1 branch of 2mm soil sieve, 20 branches of tinfoil paper (used for airing soil samples), 20 branches of plastic centrifuge tube with volume of 100mL, one branch of 50mL PVC injector, 1 branch of 10mL injection filter, one branch of inorganic fiber filter membrane with aperture of 0.45 μm, one branch of portable visible light spectrophotometer (with cuvette), TOC tester, concentrated nitric acid (high grade pure) and 10 branches of 100mL PE bottle.
26.9mL of concentrated nitric acid was diluted to 1000mL to obtain a nitric acid solution with a concentration of 0.43 mol/L.
Example 1
1) Collecting soil black lime soil (Primary soil class) sample in Guangxi, placing on tinfoil paper, naturally air-drying (water content less than 5%), sieving with a sieve with aperture of 2mm, and collecting undersize; then respectively weighing 0.00g, 0.50g, 1.00g, 2.00g, 4.00g, 6.00g, 8.00g and 10.00g of soil samples as calibration soil samples, and respectively marking the calibration soil samples as a calibration soil sample 1, a calibration soil sample 2, a calibration soil sample 3, a calibration soil sample 4, a calibration soil sample 5, a calibration soil sample 6, a calibration soil sample 7 and a calibration soil sample 8;
2) Establishing a standard curve:
2.1 Placing the calibrated soil sample 1 into a plastic centrifuge tube with the volume of 100ml, adding 30ml of nitric acid solution with the concentration of 0.43mol/L into the plastic centrifuge tube, shaking the mixture evenly for 5min by hand, standing the mixture for reaction for 30min, filtering the mixture by using an injection filter (an inorganic fiber filter membrane with the filter membrane of 0.45 mu m), dividing the collected filtrate into two parts, wherein one part is used for measuring the organic matter content in the filtrate by using a TOC instrument, and recording the organic matter content; another aliquot was used to determine the absorbance of the filtrate at 540nm and recorded; repeating the above operations to obtain data for the remaining scaled soil filtrate samples 2-8, as shown in Table 1 below;
table 1 relationship between organic content of black lime filtrate and absorbance of sample.
| Each scaled soil sample number | Absorbance of light | Organic matter content (mg/L) in filtrate |
| 1 | 0.001 | 0 |
| 2 | 0.08 | 0.9 |
| 3 | 0.2 | 1.8 |
| 4 | 0.32 | 3.6 |
| 5 | 0.62 | 7.2 |
| 6 | 0.91 | 10.8 |
| 7 | 1.1 | 14.4 |
| 8 | 1.5 | 18 |
2.2 Using the organic matter content and the absorbance corresponding to the organic matter content in each calibration soil sample filtrate in table 1 as horizontal marks and vertical coordinates respectively to establish standard curves, as shown in fig. 1;
3) Determination of samples
3.1 Collecting the soil with the same type of the land, placing the soil on tinfoil paper, naturally airing, sieving with a sieve with the aperture of 2mm, and collecting undersize for later use; then weighing 3.0g of each of 6 groups as soil samples to be measured, and respectively marking the soil samples to be measured 1, 2, 3, 4, 5 and 6;
3.2 Placing the soil sample 1 to be detected into a plastic centrifuge tube with the volume of 100ml, adding 30ml of nitric acid solution with the concentration of 0.43mol/L into the plastic centrifuge tube, shaking the mixture evenly for 5min manually, standing the mixture for reaction for 30min, filtering the mixture by using an injection filter (an inorganic fiber filter membrane with the filter membrane of 0.45 mu m), collecting filtrate, measuring the absorbance of the filtrate at 540nm, and recording the absorbance; repeating the above operation to obtain data of the rest soil samples 2-6 to be tested, as shown in the following table 2;
3.3 Reading the organic matter content in the filtrate of the soil sample to be detected corresponding to the recorded absorbance according to the determined standard curve;
3.4 The organic matter content in each soil sample to be measured was calculated according to the following formula (3), and the results are shown in the following table 2:
C to be treated ＝P To be treated ×M To be treated /V (3)
Wherein C is To be treated The unit is the organic matter content in the soil sample to be measured; p (P) To be treated The unit of the organic matter content in the filtrate of the soil sample to be detected is g/L; m is the mass of a soil sample to be detected, and the unit is g; v is the volume of nitric acid added in L.
TABLE 2 correspondence between absorbance of soil sample to be measured and organic matter content of soil
| Number of soil sample to be measured | Absorbance of light | Corresponding filtrate concentration (g/L) | Organic matter content (%) |
| 1 | 0.30 | 3.44 | 3.44 |
| 2 | 0.45 | 5.32 | 5.32 |
| 3 | 0.21 | 2.32 | 2.32 |
| 4 | 0.22 | 2.44 | 2.44 |
| 5 | 0.65 | 7.82 | 7.82 |
| 6 | 0.29 | 3.32 | 3.32 |
Example 2
Collecting Guizhou brown lime soil as a calibration soil sample (the quality and parts of each sample are the same as those of the embodiment 1), performing analysis and test according to the method described in the embodiment 1, wherein the relation between the organic matter concentration value and the absorbance value of the obtained calibration soil sample filtrate is shown in a table 3, and further drawing a standard curve according to the method described in the embodiment 1, as shown in fig. 2;
table 3 relationship between organic content of brown lime filtrate and absorbance of sample.
| Each scaled soil sample number | Absorbance of light | Organic matter content (mg/L) in filtrate |
| 1 | 0.001 | 0 |
| 2 | 0.025 | 0.5 |
| 3 | 0.1 | 1 |
| 4 | 0.22 | 2 |
| 5 | 0.33 | 4 |
| 6 | 0.57 | 6 |
| 7 | 0.69 | 8 |
| 8 | 0.9 | 10 |
Samples 1 to 6 (each sample having the same mass as in example 1) were obtained in the procedure of example 1, the absorbance and the organic matter content of the filtrate obtained after the reaction of each sample with the nitric acid solution, and the organic matter content of each sample was calculated as shown in the following table 4:
TABLE 4 correspondence between absorbance of soil sample to be measured and organic matter content of soil
Example 3
The method provided by the invention is compared with the traditional determination method aiming at centralizing different soil types. The comparative results are shown in Table 5 below.
TABLE 5 comparison of the results of the method of the invention with other methods (in%)
| Soil type | The method of the invention | GB9834-1988 soil organic matter a) | TOC Instrument measurement b |
| Brown lime soil | 3.1 | 3 | 3.03 |
| Black lime soil | 4.9 | 4.5 | 4.88 |
| Yellow earth | 2.5 | 2.4 | 2.63 |
| Red soil | 2.9 | 2.6 | 2.98 |
a) GB9834-1988 is potassium dichromate (external heating method);
b) The model of the TOC total organic carbon analyzer is Shimadzu TOC-VCSH.
Claims (6)
1. A method for determining organic matter in soil, comprising the steps of:
1) Obtaining a plurality of scaled soil samples;
2) Establishing a standard curve:
2.1 Respectively reacting each calibration soil sample with nitric acid solution with the concentration of 0.43mol/L, filtering the obtained materials, collecting filtrate of each calibration soil sample, respectively measuring absorbance of each calibration soil sample at 540nm, and marking as Ai; then, the organic matter contents of the soil samples are measured respectively and marked as Pi, and then the organic matter contents in the soil samples are calculated according to the following formula (1) and marked as Ci:
Ci＝Pi×Mi/V (1)
wherein Ci is the organic matter content in each scaled soil sample, and the unit is; pi is the organic matter content in the filtrate of each scaled soil sample, and the unit is g/L; mi is the mass of each scaled soil sample in g; v is the volume of nitric acid added in L; wherein i represents the corresponding sample number;
in the step, the dosage of the nitric acid solution is calculated by adding 30mL of nitric acid solution into 0-10g of calibration soil sample;
2.2 Using the organic matter content and the absorbance corresponding to the organic matter content in the filtrate of each calibration soil sample as horizontal marks and vertical coordinates to establish a standard curve, and fitting to obtain a linear function shown in the following formula (2):
A＝aC+b (2)
wherein A is absorbance of a soil sample in a standard curve; a is the slope of a standard curve; c is the organic matter content in the soil sample, and the unit is mg/L; b is the intercept;
3) Determination of the samples:
3.1 Selecting soil of the same type as the scaled soil (the soil classification is performed according to the classification of soil class in China soil Classification and code (GB/T17296-2000)) to obtain a soil sample to be tested;
3.2 Reacting a soil sample to be detected with the mass of m with a nitric acid solution with the concentration of 0.43mol/L, filtering the obtained material, collecting filtrate of the soil sample to be detected, measuring the absorbance of the filtrate at 540nm, and marking the absorbance as A To be treated The method comprises the steps of carrying out a first treatment on the surface of the The consumption of the nitric acid solution is calculated by adding 30mL of the nitric acid solution into 0-10g of soil sample to be measured;
3.3 Reading out the organic matter content in the filtrate of the soil sample to be tested corresponding to the recorded absorbance according to the determined standard curve, or bringing the recorded absorbance into a formula (2), and obtaining the organic matter content in the filtrate of the soil sample to be tested corresponding to the absorbance, which is recorded as P To be treated ；
3.4 Calculating the organic matter content in the soil sample to be measured according to the following formula (3):
C to be treated ＝P To be treated ×M To be treated /V (3)
Wherein C is To be treated The unit is the organic matter content in the soil sample to be measured; p (P) To be treated Is soil to be measuredThe organic matter content in the soil sample filtrate is in g/L; m is the mass of a soil sample to be detected, and the unit is g; v is the volume of nitric acid added in L.
2. The method according to claim 1, characterized in that: the specific steps for obtaining the scaled soil sample or the soil sample to be measured comprise: drying the soil sample, and sieving to obtain the soil.
3. The method according to claim 1, characterized in that: filtering the material obtained by the reaction of the scaled soil sample or the soil sample to be tested and the nitric acid solution by using a filter membrane with the pore diameter of 0.4-0.5 mu m.
4. A method according to claim 3, characterized in that: the filter membrane is an inorganic fiber filter membrane.
5. The method according to any one of claims 1-4, wherein: the reaction time of the scaled soil sample or the soil sample to be measured and the nitric acid solution with the concentration of 0.43mol/L is 20-40min.
6. The method according to any one of claims 1-4, wherein: the reaction time of the scaled soil sample or the soil sample to be measured and the nitric acid solution with the concentration of 0.43mol/L is 30min.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311010084.2A CN116879207A (en) | 2023-08-11 | 2023-08-11 | Method for determining organic matters in soil |
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| CN118150556A (en) * | 2024-05-09 | 2024-06-07 | 中国地质调查局昆明自然资源综合调查中心 | Method for measuring mineralized carbon content in soil |
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