A method for calculating the various forms and total amount of chloride ions in soil

Abstract

The present invention discloses a method for calculating the various forms and total amount of chloride ions in soil, including: S1, pouring a quantitative soil sample and an ammonium carbonate solution into a centrifuge tube according to a solid-liquid ratio, centrifugally separating after oscillation, filtering, obtaining a filtrate and a filter residue, and diluting the filtrate to obtain an ion exchange state test liquid of soil chlorine; S2, secondary processing of the filter residue to obtain a secondary filter residue, mixing a mixed solution of nitric acid, hydrogen peroxide, and ammonium bifluoride with the secondary filter residue and then performing microwave digestion, and diluting the digested liquid after cooling to obtain a strong ion binding state test liquid of soil chlorine; S3, calculating the ion exchange state amount and the strong ion binding state amount of soil chlorine by ICP-MS; S4, summing to obtain the total amount of chloride ions in the soil. The calculation method has the technical effects of high sensitivity, low detection limit, high detection efficiency and stability, and can fully reflect the form distribution and content of effective chloride ions in the soil.

Description

Technical Field

[0001] The invention belongs to the field of soil chloride ion content detection, and in particular relates to a method for calculating various forms and total amount of chloride ions in soil. Background Art

[0002] Most of the chlorine in the soil exists in the form of water-soluble salts such as sodium chloride, magnesium chloride and calcium chloride, and a small part exists in the form of water-insoluble salts such as silver chloride and lead chloride or organic binding. The determination of chloride ions in soil generally includes three methods: silver nitrate titration, ion chromatography and powder tablet-X-ray fluorescence spectrometry. The sample pretreatment of silver nitrate titration and ion chromatography is to manually extract chloride ions in the soil at room temperature with neutral water and then conduct detection. This method belongs to the partial extraction method of chlorine in soil. This method not only has a large sampling volume and many manual operations, but also has low determination results for soil samples containing water-insoluble salts such as lead chloride and silver chloride and complex soil samples with more humus that are difficult to extract with neutral water, and the reproducibility of the determination results of low-content chloride ions is poor. The cleanliness requirements of the sample solution of ion chromatography are high. For soil sample solutions with complex matrix components, if the impurities are not separated by a pretreatment column, the anion exchange column is difficult to clean after being contaminated, and even serious problems such as the exchange column being scrapped may occur. Therefore, ion chromatography is rarely used for the determination of chlorine in soil. Powder tableting-X-ray fluorescence spectrometry belongs to the full-quantity analysis method. This method has high requirements for the homogeneity of the preparation of soil tablets. However, soil types vary greatly in nature, and it is difficult for the matrix components of the soil samples to be tested and the standard substances to be completely consistent, resulting in poor stability and accuracy of the measurement results. In summary, the determination of chloride ion content in soil in the prior art has technical problems such as large sampling volume, more manual operations, low detection efficiency, poor stability and accuracy of measurement results, poor reproducibility of measurement results for low-content chloride ions, and inability to fully reflect the morphological distribution of effective chloride ions in the soil. Summary of the invention

[0003] In order to at least solve the technical problems in the above-mentioned background technology that the determination of chloride ion content in soil has the characteristics of large sampling volume, more manual operations, low detection efficiency, poor stability and accuracy of the determination results, poor reproducibility of the determination results of low-content chloride ions, and inability to fully reflect the form distribution of effective chloride ions in the soil, the present invention provides a method for calculating the various forms and total amount of chloride ions in soil. The method divides the chloride ions in the soil into the ion exchange state of soil chlorine and the strong ion binding state of soil chlorine, and uses an inductively coupled plasma mass spectrometer to respectively calculate the ion exchange state amount of soil chlorine and the strong ion binding state amount of soil chlorine, thereby reducing manual operations, effectively improving the sensitivity of the detection method and reducing the detection limit of the method, and detecting The method has the technical effects of high efficiency and stability, accurate determination of low-content chlorine by inductively coupled plasma mass spectrometry, and complete reflection of the morphological distribution and content of effective chlorine ions in the soil; the method uses ammonium carbonate solution to extract the ion exchange state of soil chlorine, which has the technical effect of reflecting the actual extractable natural effective amount of chloride ions in the soil to the greatest extent, and is helpful in helping to understand the actual effective state of exchangeable and extractable chloride ions in the soil and the characteristics of their occurrence, migration, and transformation; the method uses a mixed solution of nitric acid, hydrogen peroxide, and ammonium bifluoride to extract the strongly ion-bound state of soil chlorine, which is beneficial to the thorough digestion of soil components and mineral silicon and plant silicon in the components, improving the recovery rate of the method, and improving the accuracy of the measurement results.

[0004] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0005] The present invention provides a method for calculating various forms and total amount of chloride ions in soil, comprising the following steps:

[0006] S1, pouring the quantitative soil sample and the ammonium carbonate solution into a centrifuge tube according to the solid-liquid ratio, shaking and centrifuging, filtering, obtaining a filtrate and a filter residue, and diluting the filtrate to obtain a soil chlorine ion exchange state test solution;

[0007] S2, performing secondary processing on the filter residue to obtain a secondary filter residue, mixing a mixed solution of nitric acid, hydrogen peroxide and ammonium bifluoride with the secondary filter residue and performing microwave digestion, and diluting the digested liquid after cooling to obtain a test solution of soil chlorine in a strongly ion-bound state;

[0008] S3, passing the soil chlorine ion exchange state test liquid and the soil chlorine strong ion binding state test liquid into an inductively coupled plasma mass spectrometer through a refrigeration device for quantitative analysis to obtain the soil chlorine ion exchange state amount and the soil chlorine strong ion binding state amount;

[0009] S4, obtaining the total amount of chloride ions in the soil according to the ion exchange state of the soil chlorine and the strong ion binding state of the soil chlorine.

[0010] According to one embodiment of the present invention: in step S1, the centrifuge tube is a stoppered centrifuge tube; the device used for oscillation is a constant temperature oscillator; the device used for centrifugal separation is a centrifuge; and the device used for filtration is a membrane filter.

[0011] According to an embodiment of the present invention: the particle size of the soil sample is 2 mm; the mass of the soil sample is 2 to 5 g; the concentration of the ammonium carbonate solution is 0.05 to 0.15 mol / L; the solid-liquid ratio is: soil sample (g): ammonium carbonate solution (mL) is 1:5; the oscillation conditions are: temperature 10 to 40°C, time 30 to 60 min, and oscillation frequency 180 r / min; the centrifugal separation conditions are: speed 4000 r / min, time 5 min; the pore size of the filter membrane in the membrane filter is 0.45 μm; the method for diluting the filtrate is: take 0.5 to 5 mL of filtrate into a 10 to 100 mL volumetric flask, dilute to the scale with pure water, and the dilution multiple is 2 to 200 times.

[0012] According to one embodiment of the present invention: the concentration of the ammonium carbonate solution is 0.1 mol / L; the oscillation conditions are: temperature 25±2°C, time 45 min; the ammonium carbonate is high-grade pure ammonium carbonate, ω((NH4)2CO3) content ≥98%; the pure water is high-purity water with a resistivity of more than 18 MΩ·cm.

[0013] According to one embodiment of the present invention: in step S2, the equipment used for the microwave digestion is a microwave digestion instrument with a power of 1200W; the conditions for the secondary processing are: adding pure water to the filter residue, stirring evenly, centrifuging on a centrifuge, discarding the aqueous phase, leaving the filter residue, and after the filter residue is naturally air-dried, grinding it with a ball mill and passing it through a 0.149mm aperture sieve; the conditions for the centrifugal separation are: a speed of 4000r / min, a time of 5min; the sampling mass of the secondary filter residue is 0.1-0.2g; the method for diluting the digested liquid is: transferring the digested liquid to a 50mL volumetric flask and diluting it to the scale with pure water.

[0014] According to one embodiment of the present invention: the volume of the mixed solution is 7 mL, the ratio is: nitric acid: hydrogen peroxide: ammonium bifluoride (volume ratio) = 5:1:1, and the molar concentration of the ammonium bifluoride solution is 5.26 mol / L; the conditions of the microwave digestion are: process 1: 120°C, heating for 10 min, maintaining for 8 min; process 2: 200°C, heating for 15 min, maintaining for 10 min; the nitric acid is high-grade pure concentrated nitric acid, with an ω (HNO3) content of 68.0-70.0%, the hydrogen peroxide is high-grade pure hydrogen peroxide, with an ω (H2O2) content of ≥30%; the ammonium bifluoride is high-grade pure ammonium bifluoride, with an ω (NH4HF2) content of ≥99.99%; the pure water is high-purity water with a resistivity of more than 18 MΩ·cm.

[0015] According to an embodiment of the present invention: in step S3, the refrigeration device is a Peltier semiconductor refrigeration device; the detection conditions of the inductively coupled plasma mass spectrometer are: the monitoring mass number is 35 Cl, the test mode is kinetic energy discrimination mode (KED), the RF transmission power is 1550W, the sampling depth is 10-15mm, the internal standard element is Sc (0.50mg / L), the helium flow rate is 3.5-5.0mL / min, the collision cell inlet voltage: -70V, the collision cell outlet voltage: -160V, the internal standard addition method is three-way, the nebulizing gas flow rate is 1.1mL / min, the cooling gas flow rate is 14mL / min, the auxiliary gas flow rate is 0.85mL / min, the Peltier semiconductor refrigeration device injection temperature is 3°C, the nebulizer is a polytetrafluoroethylene concentric nebulizer, the nebulizer chamber is a polytetrafluoroethylene cyclonic nebulizer, and the center tube is a sapphire center tube.

[0016] According to an embodiment of the present invention: the sampling depth is 12 mm; the helium flow rate is 4.3 mL / min.

[0017] According to an embodiment of the present invention: the atomizing gas, the cooling gas and the auxiliary gas are all argon.

[0018] According to an embodiment of the present invention: in step S4, the total amount of chloride ions in the soil is the sum of the ion exchange state of soil chlorine and the strongly ion bound state of soil chlorine.

[0019] The technical scheme of the present invention divides the chloride ions in the soil into the ion exchange state of soil chlorine and the strong ion binding state of soil chlorine, and respectively calculates the ion exchange state amount of soil chlorine and the strong ion binding state amount of soil chlorine by using an inductively coupled plasma mass spectrometer, thereby reducing manual operation, effectively improving the sensitivity of the detection method and reducing the detection limit of the method, having high detection efficiency and stability, realizing accurate determination of low-content chlorine by inductively coupled plasma mass spectrometry, and being able to fully reflect the morphological distribution and content of effective chloride ions in the soil; by using an ammonium carbonate solution to extract the ion exchange state of soil chlorine, the technical effect of reflecting the actual extractable natural effective amount of chloride ions in the soil to the greatest extent is achieved, which is helpful for helping to understand the actual effective state of exchangeable and extractable chloride ions in the soil and the occurrence, migration and transformation characteristics; by using a mixed solution of nitric acid, hydrogen peroxide and ammonium bifluoride to extract the strong ion binding state of soil chlorine, the technical effect of being conducive to thoroughly digesting the soil components and the mineral silicon and plant silicon in the components, improving the recovery rate of the method, and improving the accuracy of the determination results is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1A flow chart of a method for calculating various forms and total amount of chloride ions in soil according to the present invention;

[0021] Figure 2 The standard curve of Example 1 of a method for calculating various forms and total amount of chloride ions in soil of the present invention;

[0022] Figure 3 The standard curve of Example 2 of a method for calculating various forms and total amount of chloride ions in soil of the present invention;

[0023] Figure 4 The standard curve of Example 3 of a method for calculating various forms and total amount of chloride ions in soil of the present invention;

[0024] Figure 5 This is the standard curve of Example 4 of a method for calculating various forms and total amount of chloride ions in soil of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be described clearly and completely below in conjunction with the drawings in the specification. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] Please refer to Figure 1 The present invention provides a method for calculating the various forms and total amount of chloride ions in soil, comprising the following steps:

[0027] S1, pouring the quantitative soil sample and the ammonium carbonate solution into a centrifuge tube according to the solid-liquid ratio, shaking and centrifuging, filtering, obtaining a filtrate and a filter residue, and diluting the filtrate to obtain a soil chlorine ion exchange state test solution;

[0028] S2, performing secondary processing on the filter residue to obtain a secondary filter residue, mixing a mixed solution of nitric acid, hydrogen peroxide, and ammonium bifluoride with the secondary filter residue and performing microwave digestion, and diluting the digested liquid after cooling to obtain a test solution of soil chlorine in a strongly ion-bound state;

[0029] S3, passing the soil chlorine ion exchange state test liquid and the soil chlorine strong ion binding state test liquid into an inductively coupled plasma mass spectrometer through a refrigeration device for quantitative analysis to obtain the soil chlorine ion exchange state amount and the soil chlorine strong ion binding state amount;

[0030] S4. According to the ion exchange state of soil chlorine and the strong ion binding state of soil chlorine, the total amount of chloride ions in the soil is obtained.

[0031] The principle of step S1 is: the alkaline ammonium carbonate solution extracts the ion exchange state of soil chlorine. After extraction, in addition to the water-soluble chloride ions such as sodium chloride, magnesium chloride and calcium chloride, the chloride ions in other water-insoluble silver chloride and lead chloride are easily subjected to the following reactions and enter the extract:

[0032]

[0033] AgCl+2NH3·H2O=Ag(NH3)2Cl+2H2O

[0034] PbCl2+2NH3·H2O=Pb(OH)2↓+2NH4Cl

[0035] The results showed that ammonium carbonate solution, as an ion exchange extractant for soil chloride, can extract soluble and insoluble effective chloride ions, which is more helpful for calculating the total amount of chloride ions in the soil and for evaluating the lack and pollution of chloride ions in environmental soil.

[0036] The principle of step S2 is: by adding a nitric acid-hydrogen peroxide-ammonium bifluoride mixed solution to the secondary filter residue and performing digestion in a closed microwave manner, at a certain microwave digestion temperature, adding nitric acid and hydrogen peroxide is beneficial to digesting soil mineral components and humus in the soil, adding ammonium bifluoride, which is safer to use than hydrofluoric acid, is beneficial to digesting the silicon dioxide components in soil minerals and soil humus, and digesting the chloride ions trapped by the silicon component to a greater extent, so that the strong ion binding state of soil chlorine in the sample is more completely digested, so as to calculate the total amount of chloride ions in the soil.

[0037] The principle of step S3 is: using an inductively coupled plasma mass spectrometer with high sensitivity, high detection efficiency and low background count to measure chlorine with a mass number of 35, there may be the following problems: first, the ionization energy of chlorine is high, resulting in a low ionization degree of chlorine after passing through the plasma; second, 16 O+ 19 F and 12 C+ 23 That pair 35 Cl has strong polyatomic ion interference, which may reduce the sensitivity of the method. Therefore, the present invention mainly adopts the following three measures to solve the above problems:

[0038] (1) The ionization degree of chlorine atoms can be increased by appropriately increasing the sampling depth and prolonging the ionization time of chlorine in the plasma.

[0039] (2) The temperature of the atomization chamber is controlled at 3°C ​​by a Peltier semiconductor refrigeration device to remove large particle aerosols, solvents and water vapor in the atomization gas that are not fully atomized, thereby reducing the oxygen atoms produced by the decomposition of water vapor and improving the stability of the excitation source.

[0040] (3) By using the kinetic energy discrimination mode (KED) detection to control the helium flow, the 16 O+ 19 F and 12 C+ 23 The interference of Na on chlorine with mass number 35 fully improves the sensitivity of the method.

[0041] The technical scheme of the present invention has the technical effects of reducing manual operation, effectively improving the sensitivity of the detection method and reducing the detection limit of the method, realizing accurate determination of low-content chlorine by inductively coupled plasma mass spectrometry, high detection efficiency and stability, and being able to fully reflect the morphological distribution and content of effective chlorine ions in the soil; extracting the ion exchange state of soil chlorine with ammonium carbonate solution has the technical effect of reflecting the actual extractable natural effective amount of chloride ions in the soil to the greatest extent, which is helpful to help understand the actual effective state of exchangeable and extractable chloride ions in the soil and the occurrence, migration and transformation characteristics; extracting the strongly ion-bound state of soil chlorine with a mixed solution of nitric acid, hydrogen peroxide and ammonium bifluoride has the technical effect of being conducive to thoroughly digesting soil components and mineral silicon and plant silicon in the components, improving the recovery rate of the method and improving the accuracy of the determination results.

[0042] According to one embodiment of the present invention, in step S1, the centrifuge tube is a stoppered centrifuge tube; the device used for oscillation is a constant temperature oscillator; the device used for centrifugal separation is a centrifuge; and the device used for filtration is a membrane filter. The above devices are all commonly used in testing laboratories and have the technical effect of being easy to operate and low in cost.

[0043] According to one embodiment of the present invention, the particle size of the soil sample is 2 mm; the mass of the soil sample is 2 to 5 g; the concentration of the ammonium carbonate solution is 0.05 to 0.15 mol / L; the solid-liquid ratio is: soil sample (g): ammonium carbonate solution (mL) is 1:5; the oscillation conditions are: temperature 10 to 40°C, time 30 to 60 min, and oscillation frequency 180 r / min; the centrifugal separation conditions are: speed 4000 r / min, time 5 min; the pore size of the filter membrane in the membrane filter is 0.45 μm; the method of diluting the filtrate is: take 0.5 to 5 mL of filtrate into a 10 to 100 mL volumetric flask, dilute to volume with pure water, and the dilution multiple is 2 to 200 times.

[0044] According to one embodiment of the present invention, the concentration of the ammonium carbonate solution is 0.1 mol / L; the oscillation conditions are: temperature 25±2°C, time 45 min; the ammonium carbonate is high-grade pure ammonium carbonate, and the ω((NH4)2CO3) content is ≥98%; and the pure water is high-purity water with a resistivity of more than 18 MΩ·cm.

[0045] According to one embodiment of the present invention, in step S2, the equipment used for the above-mentioned microwave digestion is a microwave digestion instrument with a power of 1200W; the conditions for secondary processing are: adding pure water to the filter residue, stirring evenly, centrifuging on a centrifuge, discarding the aqueous phase, leaving the filter residue, and after the filter residue is naturally air-dried, grinding it with a ball mill and passing it through a 0.149mm aperture sieve; the conditions for centrifugal separation are: speed 4000r / min, time 5min; the sampling mass of the secondary filter residue is 0.1~0.2g; the method for diluting the digested liquid is: transferring the digested liquid to a 50mL volumetric flask and making up to volume with pure water.

[0046] According to one embodiment of the present invention, the volume of the mixed solution is 7 mL, and the ratio is: nitric acid: hydrogen peroxide: ammonium bifluoride (volume ratio) = 5:1:1, and the molar concentration of the ammonium bifluoride solution is 5.26 mol / L; the conditions for microwave digestion are: process 1: 120° C., heating for 10 min, and maintaining for 8 min; process 2: 200° C., heating for 15 min, and maintaining for 10 min; the nitric acid is high-grade pure concentrated nitric acid, with an ω (HNO3) content of 68.0-70.0%, the hydrogen peroxide is high-grade pure hydrogen peroxide, with an ω (H2O2) content of ≥30%; the ammonium bifluoride is high-grade pure ammonium bifluoride, with an ω (NH4HF2) content of ≥99.99%; and the pure water is high-purity water with a resistivity of more than 18 MΩ·cm.

[0047] According to one embodiment of the present invention, in step S3, the refrigeration device is a Peltier semiconductor refrigeration device; the detection conditions of the inductively coupled plasma mass spectrometer are: the monitoring mass number is 35 Cl, the test mode is kinetic energy discrimination mode (KED), the RF transmission power is 1550W, the sampling depth is 10-15mm, the internal standard element is Sc (0.50mg / L), the helium flow rate is 3.5-5.0mL / min, the collision cell inlet voltage: -70V, the collision cell outlet voltage: -160V, the internal standard addition method is three-way, the nebulizing gas flow rate is 1.1mL / min, the cooling gas flow rate is 14mL / min, the auxiliary gas flow rate is 0.85mL / min, the Peltier semiconductor refrigeration device injection temperature is 3°C, the nebulizer is a polytetrafluoroethylene concentric nebulizer, the nebulizer chamber is a polytetrafluoroethylene cyclonic nebulizer, and the center tube is a sapphire center tube.

[0048] According to one embodiment of the present invention, the sampling depth is 12 mm; the helium flow rate is 4.3 mL / min.

[0049] According to one embodiment of the present invention, the atomizing gas, cooling gas and auxiliary gas are all argon.

[0050] According to one embodiment of the present invention, in step S4, the total amount of chloride ions in the soil is the sum of the ion exchange state of soil chlorine and the strong ion binding state of soil chlorine. That is:

[0051] Total amount of chloride ions in soil (mg / kg) = ion exchange state of soil chloride (mg / kg) + strong ion binding state of soil chloride (mg / kg)

[0052] The specific implementation of the present invention is:

[0053] Embodiment 1:

[0054] The method for determining the ion exchange state of soil chlorine, the strongly ion-bound state of soil chlorine and the total amount of chlorine ions in the soil comprises the following steps:

[0055] (1) Preparation of soil chlorine ion exchange test solution for sample and sample blank:

[0056] Quantitatively weigh 5.00 g of the uniformly prepared soil sample that passes through a 2 mm sieve hole into a stoppered centrifuge tube, quantitatively add 25 mL of 0.1 mol / L ammonium carbonate solution, tighten the stopper of the centrifuge tube and place it in a 25±2°C constant temperature oscillator (full name: constant temperature culture shaker, manufacturer: Shanghai Yiheng Scientific Instrument Co., Ltd., model: THZ-100B), oscillate at a frequency of 180 r / min for 45 min, remove it, put the centrifuge tube into a centrifuge (full name: multi-tube rack automatic balance centrifuge, manufacturer: Shanghai Lu Xiangyi Centrifuge Instrument Co., Ltd., model: TDZ5-WS), centrifuge at a speed of 4000 r / min for 5 min, take it out, open the centrifuge tube, filter the solution through a 0.45 μm filter membrane, obtain the filtrate and the residue, take 1 mL of the supernatant into a 100 mL volumetric flask respectively, shake well, and obtain the ion exchange state test solution of soil chlorine. The remaining filtrate is discarded, leaving the residue.

[0057] A sample blank was prepared according to the above-mentioned soil chlorine ion exchange state test solution sample processing steps to obtain a soil chlorine ion exchange state sample blank test solution.

[0058] (2) Preparation of soil chlorine strong ion binding state test solution for sample and sample blank

[0059] Add an appropriate amount of pure water to the filter residue in the above (1), stir evenly, centrifuge and separate on a centrifuge, discard the aqueous phase, leave the residue, air-dry the residue naturally, and grind it in a ball mill (full name: planetary gear ball mill, manufacturer: Nanjing Nanda Instrument Co., Ltd., model: QM-3SP4) until it all passes through a 0.149 mm aperture sieve, and prepare a uniform secondary filter residue. Quantitatively weigh 0.1 g of the secondary filter residue into a microwave digestion tank, add a mixed digestion solution of nitric acid-hydrogen peroxide-ammonium bifluoride, cover and tighten, put into a microwave digester, and digest according to the program set by the microwave digester (full name: high-throughput closed microwave digester, manufacturer: CEM Company, USA, instrument model: Mars6). After the digestion is completed, cool to room temperature, transfer the digestion solution to a 50 mL volumetric flask, dilute to the scale with pure water, shake well, and obtain the strongly ion-bound state test solution of soil chlorine; wherein, the microwave digestion program is as follows: power 1200 W, process 1: 120 ° C, temperature rise 15 min, hold 8 min; process 2: 200 ° C, temperature rise 15 min, hold 10 min.

[0060] The strongly ion-bound sample blank of soil chlorine was prepared according to the above steps to obtain the strongly ion-bound sample blank test solution of soil chlorine.

[0061] (3) Prepare standard solution and draw standard working curve:

[0062] Prepare standard solution: dilute 100 μg / mL chlorine standard solution (national standard sample GNM-SCL-002-2013) step by step into a series of standard solutions of 1.00 μg / L, 2.50 μg / L, 5.00 μg / L, 10.0 μg / L, 25.0 μg / L, 50.0 μg / L, 100 μg / L, and 250 μg / L for use; the medium is pure water.

[0063] Draw the standard working curve ( Figure 2 ): Use pure water 0.00 (blank solution), 1.00, 2.50, 5.00, 10.0, 25.0, 50.0, 100, 250μg / L chlorine series standard solutions and 0.50mg / L 45The Sc internal standard solution (medium is 2% nitric acid solution) was mixed in a three-way manner, and its mass-to-charge ratio count value (cps) was determined on an inductively coupled plasma mass spectrometer (model: iCAP RQ ICP-MS, manufacturer: Thermo Scientific) under the following test conditions: the monitoring mass number is 35 chlorine; the test mode is the kinetic energy discrimination mode (KED); the RF transmission power is 1550W; the sampling depth is 12mm; the helium flow rate is 4.3mL / min; the collision cell inlet voltage is -70V; the collision cell outlet voltage is -160V; the nebulizing gas (Ar) flow rate is 1.1mL / min; the cooling gas (Ar) flow rate is 14mL / min; the auxiliary gas (Ar) flow rate is 0.85mL / min; the Peltier semiconductor refrigeration injection temperature is 3°C; the nebulizer is a polytetrafluoroethylene concentric nebulizer; the nebulizer chamber is a polytetrafluoroethylene cyclonic nebulizer; and the center tube is a sapphire center tube.

[0064] (4) Sample and sample blank determination:

[0065] The sample solution and blank solution in (1) and (2) were respectively measured on an inductively coupled plasma mass spectrometer (same as above), and the test conditions were the same as (3).

[0066] (5) Calculate the total amount of chloride ions in the soil:

[0067] Total amount of chloride ions in soil (mg / kg) = ion exchange state of soil chloride (mg / kg) + strong ion binding state of soil chloride (mg / kg)

[0068] (6) Results Analysis

[0069] After testing and calculation: the ion exchange state of soil chlorine in the soil sample is 42.3 mg / kg, the strong ion binding state of soil chlorine is 25.5 mg / kg, and the total amount of chloride ions in the soil is 67.8 mg / kg.

[0070] Embodiment 2:

[0071] The analytical method for the ion exchange state of soil chlorine, the strongly ion-bound state of soil chlorine and the total amount of chloride ions in the soil in this embodiment is different from that in Example 1 in that: three types of soil samples in the A region of Henan Province are selected and prepared uniformly: Sample 1: acidic soil (pH 4.9), Sample 2: neutral soil (pH 7.03), Sample 3: alkaline soil (pH 8.61), and 6 samples of each are taken in parallel for measurement to observe the reproducibility of the results of this calculation method. The results are shown in Tables 1, 2 and 3:

[0072] Table 1: Ion exchange state test data of chlorine in different types of soil

[0073]

[0074] Table 2: Detection data of strong ion binding state of chlorine in different types of soil

[0075]

[0076]

[0077] Table 3: Detection data of total chloride ion in different types of soil

[0078]

[0079] It can be seen from Table 1, Table 2 and Table 3 that the analytical method of Example 1 is also suitable for the determination of the ion exchange state of chlorine in acidic, neutral and alkaline soils, the strongly ion-bound state of chlorine in soils and the total amount of chloride ions in soils, and the reproducibility of the measurement results meets the standards.

[0080] Example 3 (Comparative Example 1)

[0081] At present, there is no standard basis for the morphological classification and detection of chlorine ion exchange state, soil chlorine strong ion binding state and total chloride ion in soil in my country. Now we refer to the quantitative detection method of total chlorine in "Analysis Method of Regional Geochemical Samples Part 10: Determination of Chlorine and Bromine Powder Tablet-X-ray Fluorescence Spectrometry" (DZ / T 0279.10-2016) to conduct a method comparison test.

[0082] During the determination, the soil component analysis standard reference samples GBW07981, GBW07539, and GBW07544 were divided into two groups. One group was determined according to the method of Example 1, and the other group was determined according to the method in Reference Comparative Example 1. The determination results are shown in Table 4 below.

[0083] The method for determining the chlorine content in this comparative example 1 comprises the following steps:

[0084] (1) Sample preparation

[0085] Quantitatively weigh 4 g of the sample and evenly put it into a low-pressure polyethylene plastic ring, place it on a press (full name: sample press, manufacturer: Beijing Zhonghe Chuangye Technology Development Co., Ltd., instrument model: ZHY-601B), increase the pressure to 10 MPa, stay for 5 seconds, and take it out after decompression.

[0086] (2) Preparation of standard series specimens

[0087] The soil component analysis standard materials GBW07401 to GBW07408, GBW07446 to GBW07453 were selected as the standard to draw the standard curve. A standard series of specimens were prepared according to (1).

[0088] (3) Sample measurement

[0089] The tube excitation voltage of the X-ray fluorescence instrument (full name: X-ray fluorescence instrument, manufacturer: Japan Rigaku Co., Ltd., instrument model: ZSXPrimus IV) was selected to be 50KV, 50mA, 30mm diameter of the sample fabric cover, coarse collimator, and vacuum optical path. The measurement conditions of chlorine element are: element: ClKα; crystal: Ge; spectral line 92.73 (2θ / (°)); background: 94.90 (2θ / (°)); spectral line measurement time: 40s; background measurement time: 40s; detector: F-PC; PHA: 10~35; attenuator: 1.

[0090] The one-point method is used to deduct the background. The calculation formula for deducting the background is:

[0091] I N =I P —I B

[0092] Where: I N —Analysis line intensity after background subtraction; I P — spectral line intensity; I B —Background intensity.

[0093] The fluorescence intensity of the chlorine element analysis line in all standard series test pieces and the test sample pieces is determined within one startup time, and the chlorine element content in the sample pieces is calculated by computer software.

[0094] Table 4: Results of two analytical methods

[0095]

[0096] As can be seen from Table 4: the error range of the total amount of chlorine in the soil component analysis standard reference samples GBW07981, GBW07539, and GBW07544 determined in this embodiment is between -2.14 and 1.28%, which is better than the error range of -3.21 to 11.2% in Example 3 (Comparative Example 1), indicating that Example 1 can meet the requirements for the determination of the total amount of chloride ions in soil. Compared with Comparative Example 1, the prepared solution to be tested in Example 1 is sealed and placed with a stopper, eliminating the problem of increased measurement results in Comparative Example 1 due to increased measurement times, extended vacuuming time, and extended sample placement time, indicating that Example 1 is more adaptable to the determination of the total amount of chloride ions in soil.

[0097] Example 4 (Comparative Example 2)

[0098] Since there is no basis for the ion exchange state detection method of chlorine in my country, the determination results of water-soluble chlorine in the soil effective state component analysis standard materials GBW07412a (Liaoning brown soil, pH 6.80), GBW07458 (Heilongjiang black soil, pH 6.14), and GBW07459 (Xinjiang gray calcium soil, pH 8.61) determined by "Analysis of Water-Soluble Salts in Forest Soils" (LY / T 1251-1999) are referred to, and compared with the measurement results of this embodiment.

[0099] The method for determining the value of water-soluble chloride ions in this comparative example 2 comprises the following steps:

[0100] (1) Preparation of sample solution

[0101] Accurately weigh 50.0g of air-dried soil sample that has passed through a 2mm sieve, put it into a dry 500mL conical flask, accurately add 250mL of carbon dioxide-free pure water using a measuring cylinder, stopper it, shake it for 3 minutes, and filter it with filter paper to obtain the clear solution to be tested.

[0102] (2) Sample measurement

[0103] Use a pipette to draw 25.00mL of the leachate into a 150mL conical flask, adjust the pH value to about 7 with sodium bicarbonate solution, add 5 drops of 50g / L potassium chromate indicator, use a 25mL burette to add 0.04mol / L silver nitrate standard solution, and shake as you add until the brick-red precipitate no longer disappears. Record the milliliters of silver nitrate used and quantitatively calculate the chloride ion content.

[0104] Table 5: Comparison of chlorine ion exchange test results and water-soluble chlorine value results (mg / kg)

[0105] Standard substances GBW07412a GBW07458 GBW07459 Example 1 27.4 21.6 50.3 Water solubility rating 20±5 16±4 49±12 ratio / % 1.37 1.35 1.03

[0106] As can be seen from Table 5, the ion exchange state determination values ​​of soil chlorine in GBW07412a and GBW07458 are more than 1.3 times higher than the determination results of water-soluble chloride ions, indicating that the method of using water to extract water-soluble chloride ions in soil samples does not take into account the increase in exchangeable chloride ions caused by the soil environment with the rise and fall of groundwater levels, fertilization management, water diversion and irrigation, pH value changes, etc., that is, it is not completely a true reaction of effective chloride ions in the soil. The determination value of the method in Example 1 of GBW07459 is close to the water-soluble determination result, indicating that the chloride ions in the Xinjiang gray-calcium soil samples are basically completely present in a water-soluble ionic state. For this type of sample, both the method in Example 1 and the water-soluble salt extraction method can be used.

[0107] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0108] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for calculating the various forms and total amount of chloride ions in soil, characterized in that: The following steps are involved: S1, pouring the quantitative soil sample and the ammonium carbonate solution into a centrifuge tube according to the solid-liquid ratio, shaking and centrifuging, filtering, obtaining a filtrate and a filter residue, and diluting the filtrate to obtain a soil chlorine ion exchange state test solution; the solid-liquid ratio is: soil sample (g): ammonium carbonate solution (mL) is 1:5; S2, performing secondary processing on the filter residue to obtain a secondary filter residue, mixing a mixed solution of nitric acid, hydrogen peroxide and ammonium bifluoride with the secondary filter residue and performing microwave digestion, and diluting the digested liquid after cooling to obtain a test solution of soil chlorine in a strongly ion-bound state; S3, passing the soil chlorine ion exchange state test liquid and the soil chlorine strong ion binding state test liquid into an inductively coupled plasma mass spectrometer through a refrigeration device for quantitative analysis to obtain the soil chlorine ion exchange state amount and the soil chlorine strong ion binding state amount; S4, obtaining the total amount of chloride ions in the soil according to the ion exchange state of the soil chlorine and the strong ion binding state of the soil chlorine.

2. The method for calculating the various forms and total amount of chloride ions in soil according to claim 1, characterized in that: In step S1, the centrifuge tube is a stoppered centrifuge tube; the device used for oscillation is a constant temperature oscillator; the device used for centrifugal separation is a centrifuge; and the device used for filtration is a membrane filter.

3. The method for calculating the various forms and total amount of chloride ions in soil according to claim 2, characterized in that: The particle size of the soil sample is 2 mm; the mass of the soil sample is 2 to 5 g; the concentration of the ammonium carbonate solution is 0.05 to 0.15 mol / L; the oscillation conditions are: temperature 10 to 40° C., time 30 to 60 min, and oscillation frequency 180 r / min; the centrifugal separation conditions are: speed 4000 r / min, time 5 min; the pore size of the filter membrane in the membrane filter is 0.45 μm; the filtrate dilution method is: take 0.5 to 5 mL of filtrate into a 10 to 100 mL volumetric flask, dilute to the scale with pure water, and the dilution multiple is 2 to 200 times.

4. The method for calculating the various forms and total amount of chloride ions in soil according to claim 3, characterized in that: The concentration of the ammonium carbonate solution is 0.1 mol / L; the oscillation conditions are: temperature 25±2°C, time 45 min; the ammonium carbonate is high-grade pure ammonium carbonate, with a ω((NH4)2CO3) content of ≥98%; and the pure water is high-purity water with a resistivity of more than 18 MΩ·cm.

5. The method for calculating the various forms and total amount of chloride ions in soil according to claim 1, characterized in that: In step S2, the equipment used for the microwave digestion is a microwave digestion instrument with a power of 1200W; the conditions for the secondary processing are: adding pure water to the filter residue, stirring evenly, centrifuging on a centrifuge, discarding the aqueous phase, leaving the filter residue, and after the filter residue is naturally air-dried, grinding it with a ball mill and passing it through a 0.149mm aperture sieve; the conditions for the centrifugal separation are: a speed of 4000r / min, a time of 5min; the sampling mass of the secondary filter residue is 0.1-0.2g; the method for diluting the digested liquid is: transferring the digested liquid to a 50mL volumetric flask and diluting it to the scale with pure water.

6. The method for calculating the various forms and total amount of chloride ions in soil according to claim 5, characterized in that: The volume of the mixed solution is 7 mL, and the ratio is: nitric acid: hydrogen peroxide: ammonium bifluoride (volume ratio) = 5:1:1, and the molar concentration of the ammonium bifluoride solution is 5.26 mol / L; the conditions of the microwave digestion are: process 1: 120° C., heating for 10 min, and maintaining for 8 min; process 2: 200° C., heating for 15 min, and maintaining for 10 min; the nitric acid is high-grade pure concentrated nitric acid, and the ω (HNO3) content is 68.0-70.0%, the hydrogen peroxide is high-grade pure hydrogen peroxide, and the ω (H2O2) content is ≥30%; the ammonium bifluoride is high-grade pure ammonium bifluoride, and the ω (NH4HF2) content is ≥99.99%; the pure water is high-purity water with a resistivity of more than 18 MΩ·cm.

7. The method for calculating the various forms and total amount of chloride ions in soil according to claim 1, characterized in that: In step S3, the refrigeration device is a Peltier semiconductor refrigeration device; the detection conditions of the inductively coupled plasma mass spectrometer are: the monitoring mass number is 35 Cl, the test mode is kinetic energy discrimination mode (KED), the RF transmission power is 1550W, the sampling depth is 10-15mm, the internal standard element is Sc, 0.50mg / L, the helium flow rate is 3.5-5.0mL / min, the collision cell inlet voltage: -70V, the collision cell outlet voltage: -160V, the internal standard addition method is three-way, the nebulizing gas flow rate is 1.1mL / min, the cooling gas flow rate is 14mL / min, the auxiliary gas flow rate is 0.85mL / min, the Peltier semiconductor refrigeration device injection temperature is 3°C, the nebulizer is a polytetrafluoroethylene concentric nebulizer, the nebulizer chamber is a polytetrafluoroethylene cyclonic nebulizer, and the center tube is a sapphire center tube.

8. The method for calculating the various forms and total amount of chloride ions in soil according to claim 7, characterized in that: The sampling depth is 12 mm; the helium flow rate is 4.3 mL / min.

9. The method for calculating the various forms and total amount of chloride ions in soil according to claim 7, characterized in that: The atomizing gas, cooling gas and auxiliary gas are all argon.

10. The method for calculating the various forms and total amount of chloride ions in soil according to claim 1, characterized in that: In step S4, the total amount of chloride ions in the soil is the sum of the ion exchange state of soil chlorine and the strongly ion bound state of soil chlorine.

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