Analysis method for step-by-step continuous extraction of silicon form in soil

Abstract

The invention is applicable to the technical field of soil detection, and particularly provides an analysis method for gradually and continuously extracting a silicon form in soil, which adopts a step-by-step continuous extraction method and sequentially adopts an acetic acid-sodium acetate solution, hydrogen peroxide, an acetic acid-sodium acetate solution, a hydroxylamine hydrochloride solution and a sodium hydroxide solution as extracting agents. The method comprises the following steps: fully oscillating with a soil sample to extract different forms of silicon, and determining the silicon content by using a silicon molybdenum blue colorimetric method, so that the content of the silicon in each form, including effective silicon, organic combined silicon, iron and manganese oxide combined silicon and amorphous silicon, in the soil can be rapidly detected. And the content of amorphous silicon in the soil can be obtained. The soil silicon form analysis method is simplified, the detection efficiency is improved, and a theoretical basis is provided for knowing the soil silicon supply capacity and evaluating the silicon nutrition effect in the soil.

Description

Technical Field

[0001] The invention belongs to the technical field of soil detection, and in particular relates to an analysis method for extracting silicon forms in soil step by step and continuously. Background Art

[0002] Silicon is one of the most abundant elements in the soil and is also a mineral element necessary for crop growth. Silicon can not only increase crop yield and improve crop quality, but also effectively improve plants' resistance to heavy metal pollution and crop photosynthesis.

[0003] Soil silicon deficiency has become one of the important factors affecting sustainable agricultural production, but there are few reports on the morphology of soil labile silicon pools.

[0004] In the relevant technology, silicon in the soil includes organic silicon and inorganic silicon. The content of soil organic silicon is much lower than that of inorganic silicon. Inorganic silicon includes extractable silicon and crystalline silicon. Crystalline silicon is a form of silicon that is difficult for plants to use. Therefore, the research on soil extractable silicon, such as effective silicon, organically bound silicon, iron-manganese oxide-bound silicon, amorphous silicon, etc., is of great significance to plant silicon nutrition.

[0005] At present, the analysis of extractable silicon in soil mainly adopts the method of separate extraction. The traditional analysis method of extracted silicon is costly and inefficient, and most of them focus on the extraction of a single form of silicon, which is not conducive to the comprehensive quantification of the labile silicon pool in soil. Summary of the invention

[0006] The purpose of the embodiment of the present invention is to provide an analytical method for step-by-step continuous extraction of silicon forms in soil, aiming to solve the technical problem that the existing analytical methods focus more on the extraction of a single form of silicon, which is not conducive to the comprehensive quantification of the unstable silicon pool in the soil. The detection method of the present invention can extract and detect the content of different forms of silicon in the soil, including effective silicon, organically bound silicon, iron-manganese oxide-bound silicon, amorphous silicon and non-crystalline silicon.

[0007] To achieve the above object, the present invention provides the following technical solutions.

[0008] An embodiment of the present invention provides a method for analyzing silicon forms in soil by continuous step-by-step extraction, comprising the following steps: Step S1: After mixing the soil sample to be tested with acetic acid-sodium acetate buffer, first oscillation and solid-liquid separation are performed in sequence to obtain a first extract and a first residual soil; after mixing the first extract, water and molybdenum blue color developer, absorbance measurement is performed, and the content of effective silicon is obtained according to the obtained absorbance value A and a predetermined standard curve; Step S2: mixing the first residual soil with 30% H2O2, heating in a water bath, then evaporating to near dryness, cooling, adding acetic acid-sodium acetate buffer, performing a second oscillation, and solid-liquid separation in sequence to obtain a second extract and a second residual soil; mixing the second extract, water, and a molybdenum blue color developer, and then measuring the absorbance, and obtaining the content of organically bound silicon according to the obtained absorbance value B and a predetermined standard curve; Step S3: after mixing the second residual soil with the hydroxylamine hydrochloride solution, performing a third oscillation in sequence, and performing solid-liquid separation to obtain a third leachate and a third residual soil; after mixing the third leachate, water, and a molybdenum blue color developer, performing absorbance measurement, and obtaining the content of silicon bound to iron-manganese oxides according to the obtained absorbance value C and a predetermined standard curve; Step S4: after mixing the third residual soil with the sodium hydroxide solution, sequentially performing a fourth oscillation and solid-liquid separation to obtain a fourth leachate and a fourth residual soil; after mixing the fourth leachate, water, and a molybdenum blue color developer, performing absorbance measurement, and obtaining the content of amorphous silicon according to the obtained absorbance value D and a predetermined standard curve; Step S5: Adding the contents of the effective silicon, organically bound silicon, iron-manganese oxide bound silicon and amorphous silicon to obtain the content of non-crystalline silicon.

[0009] As a further limitation of a preferred embodiment of the present invention, the concentration of the acetic acid-sodium acetate buffer in step S1 and step S2 is 1 mol / L, and the pH is 4.0.

[0010] As a further limitation of a preferred embodiment of the present invention, in step S2, the temperature during the water bath heating process is maintained at 90°C.

[0011] As a further limitation of a preferred embodiment of the present invention, in step S3, the concentration of the hydroxylamine hydrochloride solution is 0.5 mol / L and is prepared and used immediately; and the solution is kept away from light during the third oscillation.

[0012] As a further limitation of a preferred embodiment of the present invention, in step S4, the concentration of the sodium hydroxide solution is 0.5 mol / L; and before the fourth oscillation, the third residual soil and the sodium hydroxide mixture are first placed in an ultrasonic water bath at 60° C. for 1 hour.

[0013] As a further limitation of a preferred embodiment of the present invention, in steps S1 to S4, the time of the first oscillation, the second oscillation, the third oscillation, and the fourth oscillation are all controlled to be 20 hours, the rotation speed is 200 rpm, and the temperature is 25-30°C; the centrifugal rate is 4000 rpm, and the centrifugal time is 20 minutes.

[0014] As a further limitation of a preferred embodiment of the present invention, in steps S1-S4, the molybdenum blue developer includes a sulfuric acid solution, an ammonium molybdate solution, an oxalic acid solution and an ammonium ferrous sulfate solution; the sulfuric acid solution and the first sulfuric acid solution and the second sulfuric acid solution, wherein the first sulfuric acid solution is prepared by slowly adding 16.6 mL of concentrated sulfuric acid to water and diluting to 1 L; the second sulfuric acid solution is prepared by slowly adding 166 mL of concentrated sulfuric acid to water and diluting to 1 L after cooling; The ammonium molybdate solution is prepared by dissolving 50g of ammonium molybdate in 1L of water; The oxalic acid solution is prepared by dissolving 50g of oxalic acid in 1L of water; The ammonium ferrous sulfate solution is prepared by dissolving 5 g of ammonium ferrous sulfate in 100 mL of the second sulfuric acid solution.

[0015] Furthermore, in step S1, the volume ratio of the first leachate, water, sulfuric acid solution, ammonium molybdate solution, oxalic acid solution and ammonium ferrous sulfate is 1:2:1:1:1:1; the first leachate, water, sulfuric acid solution and ammonium molybdate solution are mixed and allowed to stand for 10 minutes, and then the oxalic acid solution and the ammonium ferrous sulfate solution are added, and then allowed to stand for 30 minutes, and then the absorbance is measured; the wavelength of the absorbance measurement is 700nm.

[0016] Compared with the prior art, the advantages of the analytical method for extracting silicon forms in soil step by step and continuously in the present invention are: First, the present invention adopts a step-by-step continuous extraction method, using acetic acid-sodium acetate solution, hydrogen peroxide and acetic acid-sodium acetate solution, hydroxylamine hydrochloride solution and sodium hydroxide solution as extractants in sequence, and fully shaking with the soil sample to extract different forms of silicon, and using the silicon molybdenum blue colorimetry to determine the silicon content, which can quickly detect the content of various forms of silicon in the soil, including effective silicon, organically bound silicon, iron-manganese oxide-bound silicon and amorphous silicon. The present invention can obtain the content of non-crystalline silicon in the soil by calculating the sum of the contents of the four forms of silicon; Second, the present invention uses the provided detection kit to analyze silicon morphology, which is simple to operate and realizes the convenient separation and accurate quantitative analysis of different forms of silicon in the soil. The analysis cost is low, the detection efficiency is effectively improved, and it has the prospect of large-scale application.

[0017] In summary, the present invention simplifies the analysis method of soil silicon forms, improves detection efficiency, and provides a theoretical basis for understanding the silicon supply capacity of soil and evaluating the nutritional effect of silicon in soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention.

[0019] Figure 1 It is a schematic diagram of a process of a method for analyzing silicon forms in soil by continuous step-by-step extraction according to the present invention; Figure 2 This is a statistical diagram of silicon content in the form of effective silicon in the soil according to the embodiment of the present disclosure; Figure 3 This is a statistical graph of silicon content in the form of organically bound silicon in the soil according to the embodiments of the present disclosure; Figure 4 This is a statistical graph of silicon content in the form of iron-manganese oxide-bound silicon in the soil according to the embodiment of the present disclosure; Figure 5 This is a statistical graph of silicon content in the form of amorphous silicon in the soil according to the embodiment of the present disclosure; Figure 6 This is a statistical diagram of silicon content in the amorphous silicon form of the soil in the embodiment of the present disclosure; Figure 7 This is a soil silicon morphology distribution diagram in the embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0021] In addition, the methods, equipment and reagents used in the present disclosure are conventional methods, equipment and reagents in the technical field unless otherwise specified. The technical terms or scientific terms used in the present disclosure have the usual meanings that can be understood by persons with ordinary skills in the technical field to which the present disclosure belongs.

[0022] The specific implementation of the method for analyzing silicon forms in soil by step-by-step continuous extraction of the present invention is described in detail below in conjunction with specific embodiments.

[0023] Example 1 Please refer to Figure 1 In an embodiment of the present invention, a method for analyzing silicon forms in soil by continuous step-by-step extraction is provided, and the method comprises the following steps: Step S1: After mixing the soil sample to be tested with acetic acid-sodium acetate buffer, first oscillation and solid-liquid separation are performed in sequence to obtain a first extract and a first residual soil; after mixing the first extract, water and molybdenum blue color developer, absorbance measurement is performed, and the content of effective silicon is obtained according to the obtained absorbance value A and a predetermined standard curve; In step S1 of the present invention, in the step of measuring absorbance after mixing the first extract, water and molybdenum blue color developer, the water used is ultrapure water; where water is used below, ultrapure water is preferably used unless otherwise specified.

[0024] In an optional embodiment of step S1, the naturally air-dried soil sample to be tested is passed through a 100-mesh sieve, mixed with acetic acid-sodium acetate buffer, mediated by a mediator, placed in an air bath constant temperature oscillator, and subjected to the first oscillation (horizontal oscillation) in sequence. After oscillation for 20 hours, the sample is placed in a centrifuge, centrifuged at 4000 rpm for 20 minutes, poured into a prepared syringe, and filtered through a 0.45 μm filter membrane to obtain a first extract and a first residual soil, and the extract is stored in a refrigerator at 4°C; the first extract, ultrapure water and molybdenum blue color developer are mixed, mediated by a mediator, and allowed to stand for 30 minutes before using an ultraviolet spectrophotometer to measure the absorbance, and the absorbance value A is substituted into the absorbance value A to calculate the content of effective silicon according to the measured absorbance value A and a predetermined standard curve; Step S2: mixing the first residual soil with 30% H2O2, heating in a water bath, then evaporating to near dryness, cooling, adding acetic acid-sodium acetate buffer, performing a second oscillation, and solid-liquid separation in sequence to obtain a second extract and a second residual soil; mixing the second extract, water, and a molybdenum blue color developer, and then measuring the absorbance, and obtaining the content of organically bound silicon according to the obtained absorbance value B and a predetermined standard curve; In step S2 of the embodiment of the present invention, the temperature is maintained at 90° C. during the water bath heating process.

[0025] Wherein, in an optional embodiment of step S2, the first residual soil is mixed with 30% H2O2, mediated by a mediator, heated in a water bath at a specific temperature, then evaporated to near dryness, cooled, added with acetic acid-sodium acetate buffer, mediated by a mediator, placed in an air bath constant temperature oscillator, and subjected to a second oscillation (horizontal oscillation) in sequence, oscillated for 20 hours, placed in a centrifuge, centrifuged at 4000 rpm for 20 minutes, poured into a prepared syringe, filtered through a 0.45 μm filter membrane, and a second extract and a second residual soil are obtained, and the extract is stored in a refrigerator at 4°C; the second extract, ultrapure water and molybdenum blue color developer are mixed, mediated by a mediator, left to stand for 30 minutes, and then the absorbance is measured by a UV spectrophotometer, and the content of organically bound silicon is calculated by substituting the measured absorbance value B and a predetermined standard curve into the absorbance value B; Step S3: after mixing the second residual soil with the hydroxylamine hydrochloride solution, performing a third oscillation in sequence, and performing solid-liquid separation to obtain a third leachate and a third residual soil; after mixing the third leachate, water, and a molybdenum blue color developer, performing absorbance measurement, and obtaining the content of silicon bound to iron-manganese oxides according to the obtained absorbance value C and a predetermined standard curve; In an optional embodiment of step S3, the second residual soil is mixed with a hydroxylamine hydrochloride solution, mediated by a mediator, and then placed in an air bath constant temperature oscillator, and a third oscillation (horizontal oscillation) is performed in sequence. After oscillation for 20 hours, the mixture is placed in a centrifuge, centrifuged at 4000 rpm for 20 minutes, poured into a prepared syringe, and filtered through a 0.45 μm filter membrane to obtain a third extract and a third residual soil, and the extract is stored in a refrigerator at 4° C.; the third extract, ultrapure water and molybdenum blue color developer are mixed, mediated by a mediator, and then allowed to stand for 30 minutes before using an ultraviolet spectrophotometer to measure absorbance, and the content of silicon bound to iron and manganese oxides is calculated by substituting the absorbance value C measured and a predetermined standard curve into the absorbance value C; Step S4: after mixing the third residual soil with the sodium hydroxide solution, sequentially performing a fourth oscillation and solid-liquid separation to obtain a fourth leachate and a fourth residual soil; after mixing the fourth leachate, water, and a molybdenum blue color developer, performing absorbance measurement, and obtaining the content of amorphous silicon according to the obtained absorbance value D and a predetermined standard curve; In an optional embodiment of step S4, the third residual soil is mixed with a sodium hydroxide solution, mediated by a mediator, and then ultrasonically treated at a specific temperature, followed by a fourth oscillation (horizontal oscillation). After oscillation for 20 hours, the mixture is placed in a centrifuge and centrifuged at 4000 rpm for 20 minutes. The mixture is poured into a prepared syringe and filtered through a 0.45 μm filter membrane to obtain a fourth extract and a fourth residual soil. The fourth extract, ultrapure water and molybdenum blue color developer are mixed, mediated by a mediator, and allowed to stand for 30 minutes before absorbance measurement using an ultraviolet spectrophotometer. The amorphous silicon content is calculated by substituting the absorbance value D measured and a predetermined standard curve into the absorbance value D.

[0026] Step S5: Adding the contents of the effective silicon, organically bound silicon, iron-manganese oxide bound silicon and amorphous silicon to obtain the content of non-crystalline silicon.

[0027] Preferably, the analysis method of the embodiment of the present disclosure further includes the steps of drying and sieving the soil sample in sequence before the soil sample is mixed with the acetic acid-sodium acetate buffer; wherein: the drying method is natural air drying; the natural air drying time is one week; the sieving screen is 100 mesh.

[0028] Furthermore, in an embodiment of the present invention, in step S1, the first oscillation mode is air bath constant temperature oscillation, the oscillation temperature is 25°C-30°C, the oscillation time is 20h, and the oscillation frequency is 200rpm; the solid-liquid separation method is centrifugal separation, using a centrifuge, centrifuged at 4000rpm for 20min.

[0029] In the present invention, in step S1, the amount of the soil sample to be tested and the acetic acid-sodium acetate buffer solution is 1.0000 g:10 mL; the concentration of the acetic acid-sodium acetate buffer solution is 1 mol / L, and the pH is 4.0.

[0030] In steps S1 to S4 of the present invention, the molybdenum blue developer comprises a sulfuric acid solution, an oxalic acid solution, an ammonium molybdate solution and an ammonium ferrous sulfate solution; Further, the molybdenum blue developer includes a sulfuric acid solution, an ammonium molybdate solution, an oxalic acid solution and an ammonium ferrous sulfate solution; the sulfuric acid solution includes a first sulfuric acid solution and a second sulfuric acid solution; wherein the first sulfuric acid solution is prepared by slowly adding 16.6 mL of concentrated sulfuric acid to water and diluting to 1 L; the second sulfuric acid solution is prepared by slowly adding 166 mL of concentrated sulfuric acid to water and diluting to 1 L after cooling; The ammonium molybdate solution is prepared by dissolving 50g of ammonium molybdate in 1L of water; The oxalic acid solution is prepared by dissolving 50g of oxalic acid in 1L of water; The ammonium ferrous sulfate solution is prepared by dissolving 5 g of ammonium ferrous sulfate in 100 mL of the second sulfuric acid solution.

[0031] Furthermore, in step S1, the volume ratio of the first leachate, water, sulfuric acid solution (the first sulfuric acid solution and the second sulfuric acid solution are prepared in equal proportions), ammonium molybdate solution, oxalic acid solution and ammonium ferrous sulfate is 1:2:1:1:1:1; the first leachate, water, sulfuric acid solution and ammonium molybdate solution are mixed and allowed to stand for 10 minutes, and then the oxalic acid solution and the ammonium ferrous sulfate solution are added, and then allowed to stand for 30 minutes, and then the absorbance is measured; preferably, in this embodiment, the wavelength of the absorbance measurement is 700 nm.

[0032] In step S2 of the present invention, the dosage of the first residual soil and acetic acid-sodium acetate buffer is 1.0000 g:20 mL; the concentration of the acetic acid-sodium acetate buffer is 1 mol / L, and the pH is 4.0.

[0033] In step S2 of the present invention, the second oscillation and solid-liquid separation method are the same as the first oscillation and solid-liquid separation method in step S1, which will not be repeated here; similarly, the second extract is measured in the same manner as the first extract, which will not be repeated here.

[0034] In addition, in step S3 of the present invention, the dosage of the second residual soil and the hydroxylamine hydrochloride solution is 1.0000 g:10 mL; and the concentration of the hydroxylamine hydrochloride solution is 0.5 mol / L.

[0035] In step S3 of the present invention, the third oscillation needs to be protected from light; the solid-liquid separation method in step S3 is the same as the solid-liquid separation method in step S1, which will not be repeated here; the determination method of the third extract is the same as that of the first extract, which will not be repeated here.

[0036] In step S3, the present invention mixes the third residual soil with a sodium hydroxide solution, performs ultrasound at 60° C. for 1 hour, and then sequentially performs a fourth oscillation and centrifugation to obtain a fourth extract and a fourth residual soil.

[0037] Furthermore, in step S4 of the present invention, the third residual soil and the sodium hydroxide mixture are first placed in an ultrasonic water bath at 60° C. for 1 hour before the fourth oscillation; and the solid-liquid separation method of step S4 is the same as that of step S1, which will not be repeated here.

[0038] In step S4 of the present invention, the dosage of the third residual soil and the sodium hydroxide solution is 1.0000 g: 20 mL; the concentration of the sodium hydroxide is 0.5 mol / L; in addition, the determination method of the fourth extract is the same as that of the first extract, which will not be repeated here.

[0039] Finally, in step S5 of the present invention, the content of the effective silicon obtained in step S1, the organically bound silicon obtained in step S2, the iron-manganese oxide-bound silicon obtained in step S3 and the amorphous silicon obtained in step S4 are added together to obtain the content of the non-crystalline silicon.

[0040] Please refer to Figure 2-Figure 7 , the present invention Figure 2-Figure 6 The statistical graph of soil silicon content in different forms obtained by the analysis method of the present invention is shown; Figure 7 The soil silicon form distribution diagram obtained by the analysis method of the present invention is shown; in the figure, CK represents the control, GS represents the silicon fertilizer application treatment in Gansu, KE represents the silicon fertilizer application treatment in Kenya, IM represents the silicon fertilizer application treatment in Inner Mongolia, LS represents the liquid silicon fertilizer application treatment, and IM+LS represents the combined application treatment of silicon fertilizer and liquid silicon fertilizer in Inner Mongolia; the purpose of the year comparison of the present invention is to verify the stability and reliability of the method.

[0041] It can be seen that the present invention adopts a step-by-step continuous extraction method, and adopts acetic acid-sodium acetate solution, hydrogen peroxide and acetic acid-sodium acetate solution, hydroxylamine hydrochloride solution and sodium hydroxide solution as extractants in sequence, and fully shakes the soil sample to extract different forms of silicon, and uses the silicon molybdenum blue colorimetry to determine the silicon content. It can quickly detect the content of various forms of silicon in the soil, including effective silicon, organically bound silicon, iron-manganese oxide-bound silicon and amorphous silicon. The present invention can obtain the content of non-crystalline silicon in the soil by calculating the sum of the contents of the four forms of silicon.

[0042] Example 2 An analysis method for step-by-step continuous extraction of silicon forms in soil provided by an embodiment of the present invention is implemented using a detection kit, wherein the detection kit includes acetic acid-sodium acetate buffer, 30% H2O2, hydroxylamine hydrochloride reagent, sodium hydroxide solution and molybdenum blue color developer, wherein the molybdenum blue color developer includes sulfuric acid solution, oxalic acid solution, ammonium molybdate solution and ammonium ferrous sulfate solution; The 30% H2O2 in the test kit indicates a hydrogen peroxide solution with a mass fraction of 30%; The pH of the acetic acid-sodium acetate buffer in the test kit is 4.0; The hydroxylamine hydrochloride reagent in the detection kit must be prepared and used immediately.

[0043] The following describes the step-by-step continuous extraction analysis method of silicon forms in soil according to the present invention in combination with the reagent usage process of the detection kit: The use of the detection kit of the present invention requires the use of the following multiple reagents: Reagent 1: 1 mol / L acetic acid-sodium acetate (pH 4.0) buffer: 49.2 mL glacial acetic acid, 14 g sodium acetate, adjust pH to 4.0 with 1 mol / L NaOH, and make up to 1 L; Reagent 2: 30% H2O2; Reagent 3: 0.5 mol / L hydroxylamine hydrochloride solution (prepared using 25% CH3COOH): weigh 34.745 g of hydroxylamine hydrochloride and dissolve it in 25% acetic acid; 25% acetic acid (acetic acid) is prepared by absorbing 25 mL of acetic acid (100%) and diluting to 1 L; Reagent 4: 0.5 mol / L sodium hydroxide solution: weigh 20 g of sodium hydroxide and dissolve it in 1 L of water; Reagent 5: 0.6 mol / L sulfuric acid solution (1 / 2H2SO4): Slowly add 16.6 mL of concentrated sulfuric acid into 800 mL of water, and adjust the volume to 1 L after cooling; Reagent 6: 6 mol / L sulfuric acid solution (1 / 2H2SO4): Slowly add 166 mL of concentrated sulfuric acid into 800 mL of water, and adjust the volume to 1 L after cooling; Reagent 7: 50g / L ammonium molybdate solution: weigh 50g ammonium molybdate [(NH4)6Mo7O 24 ·4H2O, analytical grade] dissolved in water and made up to 1L; Reagent 8: 50g / L oxalic acid solution: weigh 50g oxalic acid [H2C2O4·2H2O, analytical grade] and dissolve it in water to make up to 1L; Reagent 9: Ammonium ferrous sulfate solution: weigh 5 g of ammonium ferrous sulfate [(NH4)2SO4·FeSO4·4H2O, analytical grade] and dissolve it in 100 mL of reagent 6. Prepare as needed; Reagent 10: Molybdenum blue color developer: Add reagent 5, reagent 7, reagent 8, and reagent 9 in equal proportions and prepare as needed; Silicon standard solution: 100 mg / L silicon dioxide standard solution in water: purchased from the market.

[0044] Specifically, the step-by-step continuous extraction and analysis method of silicon forms in soil of the present invention comprises the following steps: Weigh 1.0000g of air-dried soil that has passed through a 100-mesh sieve, place it in a 50mL centrifuge tube, add 10mL of reagent 1, and oscillate at a constant temperature of 30°C for 20h. After the oscillation, centrifuge at 4000rpm for 20min. Take the extract as the first extract. Take 1mL of the first extract, add 2mL of deionized water, and then add 4mL of reagent 10 (molybdenum blue color developer). Shake well and let it stand for 30min. Measure the absorbance colorimetrically at a wavelength of 700nm. Add 5 mL of reagent 2 to the residual soil in the previous step, heat at 85°C for 1 h, then add another 5 mL of reagent 2, continue heating at 85°C for 1 h, evaporate to near dryness, cool, add 20 mL of reagent 1, oscillate at 30°C for 20 h, centrifuge at 4000 rpm for 20 min after the oscillation, take the extract as the second extract, take 1 mL of the second extract, add 2 mL of deionized water, add 4 mL of reagent 10 (molybdenum blue color developer), shake well and let stand for 30 min, and measure the absorbance colorimetrically at a wavelength of 700 nm; Add 10 mL of reagent three to the residual soil in the previous step, shake at a constant temperature of 30°C in the dark for 20 hours, centrifuge at 4000 rpm for 20 minutes after the shaking, take the extract as the third extract, take 1 mL of the third extract, add 2 mL of deionized water, add 4 mL of reagent ten (molybdenum blue color developer), shake well and let stand for 30 minutes, and measure the absorbance colorimetrically at a wavelength of 700 nm; Add 20 mL of reagent 4 to the residual soil in the previous step, ultrasonicate at 60°C for 1 h, then oscillate at a constant temperature of 30°C for 20 h. After the oscillation, centrifuge at 4000 rpm for 20 min. Take the extract as the fourth extract. Take 0.1 mL of the fourth extract, add 2.9 mL of deionized water, add 4 mL of reagent 10 (molybdenum blue color developer), shake well and let stand for 30 min. Measure the absorbance colorimetrically at a wavelength of 700 nm. The content of non-crystalline silicon is obtained by adding the contents of the four forms of silicon (effective silicon, organically bound silicon, iron-manganese oxide-bound silicon, and amorphous silicon).

[0045] The present invention adopts the provided detection kit to analyze the silicon form, which is simple to operate, realizes the convenient separation and accurate quantitative analysis of different forms of silicon in soil, has low analysis cost, effectively improves the detection efficiency, and has the prospect of large-scale application.

[0046] In summary, the present invention simplifies the analysis method of soil silicon forms, improves detection efficiency, and provides a theoretical basis for understanding the silicon supply capacity of soil and evaluating the nutritional effect of silicon in soil.

[0047] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily realized. Therefore, without departing from the general concept defined by the claims and equivalent scope, the present invention is not limited to the specific details and the illustrations shown and described here.

Claims

1. A method for analyzing silicon forms in soil by continuous step-by-step extraction, characterized in that: The following steps are involved: Step S1: After mixing the soil sample to be tested with acetic acid-sodium acetate buffer, first oscillation and solid-liquid separation are performed in sequence to obtain a first extract and a first residual soil; after mixing the first extract, water and molybdenum blue color developer, absorbance measurement is performed, and the content of effective silicon is obtained according to the obtained absorbance value A and a predetermined standard curve; Step S2: mixing the first residual soil with 30% H2O2, heating in a water bath, then evaporating to near dryness, cooling, adding acetic acid-sodium acetate buffer, performing a second oscillation, and solid-liquid separation in sequence to obtain a second extract and a second residual soil; mixing the second extract, water, and a molybdenum blue color developer, and then measuring the absorbance, and obtaining the content of organically bound silicon according to the obtained absorbance value B and a predetermined standard curve; Step S3: after mixing the second residual soil with the hydroxylamine hydrochloride solution, performing a third oscillation in sequence, and performing solid-liquid separation to obtain a third leachate and a third residual soil; after mixing the third leachate, water, and a molybdenum blue color developer, performing absorbance measurement, and obtaining the content of silicon bound to iron-manganese oxides according to the obtained absorbance value C and a predetermined standard curve; Step S4: after mixing the third residual soil with the sodium hydroxide solution, sequentially performing a fourth oscillation and solid-liquid separation to obtain a fourth leachate and a fourth residual soil; after mixing the fourth leachate, water, and a molybdenum blue color developer, performing absorbance measurement, and obtaining the content of amorphous silicon according to the obtained absorbance value D and a predetermined standard curve; Step S5: Adding the contents of the effective silicon, organically bound silicon, iron-manganese oxide bound silicon and amorphous silicon to obtain the content of non-crystalline silicon.

2. The method for analyzing silicon forms in soil by step-by-step continuous extraction according to claim 1, characterized in that: The concentration of the acetic acid-sodium acetate buffer in step S1 and step S2 is 1 mol / L, and the pH is 4.

0.

3. The method for analyzing silicon forms in soil by step-by-step continuous extraction according to claim 2, characterized in that: In step S2, the temperature during the water bath heating process is maintained at 90°C.

4. The method for analyzing silicon forms in soil by step-by-step continuous extraction according to claim 3, characterized in that: In step S3, the concentration of the hydroxylamine hydrochloride solution is 0.5 mol / L and it is prepared and used immediately; and the solution is kept away from light during the third oscillation.

5. The method for analyzing silicon forms in soil by step-by-step continuous extraction according to claim 4, characterized in that: In step S4, the concentration of the sodium hydroxide solution is 0.5 mol / L; before the fourth oscillation, the third residual soil and the sodium hydroxide mixture must be ultrasonically bathed at 60° C. for 1 hour.

6. The method for analyzing silicon forms in soil by step-by-step continuous extraction according to claim 5, characterized in that: In step S1 to step S4, the time of the first oscillation, the second oscillation, the third oscillation and the fourth oscillation are all controlled to be 20 hours, the rotation speed is 200 rpm, the temperature is 25-30°C; the centrifugal speed is 4000 rpm, and the centrifugal time is 20 minutes.

7. The method for analyzing silicon forms in soil by step-by-step continuous extraction according to claim 6, characterized in that: In step S1-step S4, the molybdenum blue developer includes sulfuric acid solution, ammonium molybdate solution, oxalic acid solution and ammonium ferrous sulfate solution; The sulfuric acid solution includes a first sulfuric acid solution and a second sulfuric acid solution, wherein the first sulfuric acid solution is prepared by slowly adding 16.6 mL of concentrated sulfuric acid into water and diluting to 1 L; the second sulfuric acid solution is prepared by slowly adding 166 mL of concentrated sulfuric acid into water and diluting to 1 L after cooling; The ammonium molybdate solution is prepared by dissolving 50g of ammonium molybdate in 1L of water; The oxalic acid solution is prepared by dissolving 50g of oxalic acid in 1L of water; The ammonium ferrous sulfate solution is prepared by dissolving 5 g of ammonium ferrous sulfate in 100 mL of the second sulfuric acid solution.

8. The method for analyzing silicon forms in soil by step-by-step continuous extraction according to claim 7, characterized in that: In step S1, the volume ratio of the first leachate, water, sulfuric acid solution, ammonium molybdate solution, oxalic acid solution and ammonium ferrous sulfate is 1:2:1:1:1:1; the first leachate, water, sulfuric acid solution and ammonium molybdate solution are mixed and allowed to stand for 10 minutes, and then the oxalic acid solution and the ammonium ferrous sulfate solution are added, and then allowed to stand for 30 minutes, and then the absorbance is measured; The wavelength of the absorbance measurement is 700 nm.

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