Method for measuring content of available boron in soil

Abstract

The invention discloses a method for determining the content of effective boron in soil, and belongs to the technical field of determination of effective state components in soil. An aluminum nitrate solution with a certain concentration is adopted as an extracting agent and is suitable for soil samples with different pH values, water-soluble fluorine in the soil is preferentially complexed with aluminum to generate an aluminum hexafluoride complex during water-bath heating extraction, so that fluorine is difficult to react with water-soluble boron (effective boron) in the soil, volatilization of generated boron trifluoride is avoided, and the quality of the soil is improved. The situation that the effective boron measurement result in the soil is low and inaccurate is avoided. The effective boron in the soil is directly determined by the filtrate through the inductively coupled plasma emission spectrometry, and a standard solution is selected to establish a standard working curve, so that the method for rapidly determining the effective boron content in the soil through the inductively coupled plasma emission spectrometry is realized. Sample treatment operation is simple and safe, and detection efficiency is high; the detection limit is 0.006 mg / kg, the adding standard recovery rate is 98.00%-105.00%, and the method has the advantages of being high in anti-interference capacity, wide in linear range and high in accuracy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soil effective component determination, and particularly relates to a method for determining the content of effective boron in soil. BACKGROUND

[0002] Boron is one of the trace elements necessary for the growth and development of crops and most plants, which can not only promote the vegetative growth of crops, but also plays a key role in the normal development of reproductive organs. Boron deficiency in crops will affect the differentiation and elongation of root tip meristem of crops, and will also affect the flowering and fruiting of crops, thereby affecting the yield and quality of crops. However, the content of effective boron in soil is very low, and the abundance and deficiency limits of boron content in crops are very narrow. Therefore, relevant personnel need to master the soil effective boron determination method and grasp the content of soil effective boron in time, so as to scientifically and reasonably supply boron elements, which is also one of the key technologies to improve the yield and quality of crops.

[0003] At present, the determination of the content of effective boron in soil often adopts spectrophotometry, including curcumin spectrophotometry and azomethine-H spectrophotometry. Both of the two methods are to directly boil the soil sample and then add curcumin or azomethine-H for spectrophotometric determination. The curcumin spectrophotometry is complex in operation and requires strict control of the sample reaction process, so it is less used in actual test. The azomethine-H spectrophotometry is simple and fast in operation, suitable for determination of multiple samples and determination of samples with high content of effective boron, and the method is widely used. However, the sensitivity of the method is low, and factors such as color development temperature and light can easily interfere with the test results. In addition, the pretreatment method for the determination of effective boron is to use direct boiling method, and the boiling time and boiling temperature are not easy to control, which often causes large deviation of the results. Moreover, the quartz glass required for direct boiling is expensive and has high cost. Some studies have optimized the pretreatment process of effective boron determination, such as boiling water bath extraction method and microwave extraction method. The boiling water bath extraction method has low cost, is easy to control and has high efficiency, and is generally considered to be suitable for the pretreatment process of effective boron test. However, there are many studies on the extraction time and extraction method of the boiling water bath extraction method, and the conclusions are not uniform. During the water immersion process, fluorine in soil also dissolves synchronously and is easy to react with boron to generate volatile boron trifluoride, which leads to low effective boron determination value and affects the determination accuracy. SUMMARY

[0004] The present application aims to provide a method for determining the content of effective boron in soil, which solves the problems of low precision and low determination result of the direct boiling method and boiling water bath extraction method for the determination of effective boron in soil.

[0005] To solve the above technical problems, the present application adopts the following technical scheme: a method for determining the content of effective boron in soil, characterized by comprising the following steps: a) Weigh an air-dried soil sample and place it in a capped polyethylene plastic bottle. Add 0.1–0.5 g / L aluminum nitrate solution as an extractant, tighten the cap, and gently shake the polyethylene plastic bottle to disperse the soil. Place the bottle in a water bath and maintain a gentle boil at 85–95°C for 12–15 minutes. Remove the polyethylene plastic bottle and allow it to cool. Open the cap and separate the solid and liquid components of the sample solution in the polyethylene plastic bottle. Collect the filtrate in a plastic cup to obtain the test solution. Perform a blank test at the same time. b) Preparation of standard solutions: Pipette boron standard solution and dilute to volume with 0.1-0.5 g / L aluminum nitrate solution to prepare a series of boron-containing standard solutions, and prepare blank solutions at the same time; c) Select a hydrofluoric acid resistant injection system and use inductively coupled plasma atomic emission spectrometry to sequentially determine the blank solution and the standard series working solutions of step b). Plot the mass concentration of boron in the standard series working solutions as the abscissa and the emission intensity value of boron as the ordinate to obtain the standard working curve for determining available boron in soil. d) The boron response values ​​in the test solution and blank solution of the sample in step a) were determined by inductively coupled plasma atomic emission spectrometry, and the available boron content in the soil sample was calculated according to the standard working curve.

[0006] A further technical solution is that the air-dried soil samples in step a) include acidic soil with pH < 6.5, neutral soil with pH 6.5 ≤ pH ≤ 7.5, and alkaline soil with pH > 7.5.

[0007] A further technical solution is that the aluminum nitrate in step a) is GR grade aluminum nitrate nonahydrate; the aluminum nitrate solution is prepared with boron-free water, and the pH of the aluminum nitrate solution is 4.25-4.50.

[0008] A further technical solution is that in step a), the air-dried soil sample is soil that has passed through a 2 mm pore size nylon sieve, and the amount of aluminum nitrate solution added is 18-20 mL / 10 g soil sample.

[0009] A further technical solution is that in step b), the concentrations of the boron-containing standard series solutions are 0.05 mg / L, 0.10 mg / L, 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L, respectively, and the concentration of the boron standard solution is 10 mg / L.

[0010] A further technical solution is that the instrument operating parameters for the inductively coupled plasma atomic emission spectrometry in steps c) to e) are as follows: measurement wavelength 249.773 nm; high-frequency emission power 1150 W; plasma gas flow rate 12 L / min; auxiliary gas flow rate 0.5 L / min; nebulizing gas flow rate 0.7 L / min; observation height 15 mm; peristaltic pump speed 110 r / min.

[0011] A further technical solution includes step e) determining the available boron content in soil national standard materials ASA-10a-CZ, GBW07412a, and GBW07416a according to the methods in steps a) to d) and comparing it with their certified values.

[0012] Working mechanism: Using a certain concentration of aluminum nitrate solution as an extractant, suitable for soil samples with different pH values, during water bath heating and extraction, water-soluble fluoride in the soil preferentially complexes with aluminum to form aluminum hexafluorophosphate complex, making it difficult for fluoride to react with water-soluble boron (available boron) in the soil, avoiding the volatilization of boron trifluoride, and avoiding the occurrence of low and inaccurate results in the determination of available boron in the soil.

[0013] A standard working curve was established using standard solutions. The standard series solutions were then diluted with aluminum nitrate solution to eliminate the matrix mismatch problem and further improve the accuracy and stability of the determination.

[0014] Compared with existing technologies, the beneficial effects of this invention are: it provides a simple and rapid method for testing available boron in soil using aluminum nitrate extraction via water bath heating and inductively coupled plasma atomic emission spectrometry (ICP-AES). By extracting soil samples with aluminum nitrate solution and heating them in a water bath, within a certain temperature and time range, water-soluble boron (available boron) in the soil does not react with water-soluble fluoride in the soil, and no boron trifluoride volatilization is generated. A standard working curve is established using a series of standard solutions diluted with aluminum nitrate solution. Inductively coupled plasma atomic emission spectrometry (ICP-AES) is then used to rapidly determine the available boron content in the soil. This method features minimal matrix effect, simple and safe sample pretreatment, and solves the problem of inaccurate results from extraction methods such as direct boiling and boiling water bath extraction. Furthermore, this method significantly improves work efficiency and reduces energy consumption, showing promising application prospects and substantial economic benefits.

[0015] The detection limit of the above method is 0.006 mg / kg, the relative standard deviation is less than 6.2%, and the spiked recovery rate is 98.00%–105.00%. It has the characteristics of strong anti-interference ability, wide linear range, high precision, high accuracy, and good stability. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0017] A method for determining available boron content in soil by water bath heating aluminum nitrate extraction-inductively coupled plasma atomic emission spectrometry (ICP-AES): Equipment and instruments used: Avio 200 full-spectrum direct-reading plasma emission spectrometer with echelle grating; two-dimensional array (CCD) detector; hydrofluoric acid resistant sample introduction system; HH-S6 digital display constant temperature water bath.

[0018] The instrument's operating parameters are as follows: measurement wavelength 249.773 nm; high-frequency emission power 1150 W; plasma gas flow rate 12 L / min; auxiliary gas flow rate 0.5 L / min; nebulizing gas flow rate 0.7 L / min; observation height 15 mm; peristaltic pump speed 110 r / min.

[0019] The specific steps are as follows: a) Accurately weigh 10.00 g of air-dried soil sample that has passed through a 2 mm nylon sieve into a 150 mL capped polyethylene plastic bottle. Add 20.0 mL of 0.1 g / L aluminum nitrate solution (pH 4.50). Tighten the cap and gently shake the polyethylene plastic bottle to disperse the soil. Place the bottle in a water bath and maintain a gentle boil at 85 ℃ for 12 min (time accurately). Remove the polyethylene plastic bottle and let it cool. Open the cap and pour the test solution from the polyethylene plastic bottle onto filter paper. Collect the filtrate in a plastic cup (discard if the filtrate is initially turbid) to obtain the test solution. Perform a blank test at the same time. b) Preparation of standard solutions: Accurately pipette 0.00 mL, 0.50 mL, 1.00 mL, 2.00 mL, 5.00 mL, and 10.00 mL of 10 mg / L boron standard solution into 100 mL volumetric flasks, and dilute to volume with 0.1 g / L aluminum nitrate solution as the extraction solvent to obtain a series of standard solutions containing boron of 0.00 mg / L, 0.05 mg / L, 0.10 mg / L, 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L. A blank solution is also prepared. c) Using a hydrofluoric acid-resistant injection system, inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to sequentially determine the blank solution and the standard series working solutions from step b). The mass concentration of boron in the standard series working solutions was plotted on the x-axis, and the emission intensity of boron on the y-axis to obtain a standard working curve for determining available boron in soil. The linear regression equation and linear correlation coefficient are shown in Table 1. Under optimal instrument operating conditions, the blank solution was continuously measured 10 times, and the detection limits for each element were calculated using a factor of 3. The results are shown in Table 1. Table 1 shows that the correlation coefficients are all above 0.9998, indicating high correlation, high reliability, low detection limits, and high precision.

[0020] Table 1. Linear range, linear regression equation, correlation coefficient, and detection limit of the calibration curve. d) The boron content in the soil sample was calculated by inductively coupled plasma atomic emission spectrometry (ICP-AES) of the sample test solution and blank solution in step a). The available boron in soil samples ASA-6b-CZ (pH 6.53, available boron 0.13 mg / kg, water-soluble fluoride 2.0 mg / kg) and ASA-9a-CZ (pH 8.35, available boron 0.43 mg / kg, water-soluble fluoride 6.6 mg / kg) was determined using the above method. Precision and recovery tests were conducted, and the results are shown in Table 2. As can be seen from Table 2, the relative standard deviation (RSD, n=11) of the determination results is less than 5.6%, and the recovery rate is 98.00% to 100.00%, both of which meet the requirements for analytical testing.

[0021] Table 2. Results of Precision and Recovery Tests e) The available boron content in soil national standard materials ASA-10a-CZ (pH 8.80, available boron 0.47 mg / kg, water-soluble fluoride 8.5 mg / kg), GBW07412a (pH 6.80, available boron 0.42 mg / kg, water-soluble fluoride 5.1 mg / kg), and GBW07416a (pH 4.71, available boron 0.17 mg / kg, water-soluble fluoride 0.75 mg / kg) was determined according to steps a) to d) and compared with their certified values. The results are shown in Table 3. It can be seen that the measured available boron values ​​are basically consistent with the certified values, further proving that the method has high reliability and high precision.

[0022] Table 3. Results of available boron determination using national standard materials for soil (mg / kg) Example 2 A method for determining available boron content in soil by water bath heating aluminum nitrate extraction-inductively coupled plasma atomic emission spectrometry (ICP-AES): Equipment and instruments used: Avio 200 full-spectrum direct-reading plasma emission spectrometer with echelle grating; two-dimensional array (CCD) detector; hydrofluoric acid resistant sample introduction system; HH-S6 digital display constant temperature water bath.

[0023] The instrument's operating parameters are as follows: measurement wavelength 249.773 nm; high-frequency emission power 1150 W; plasma gas flow rate 12 L / min; auxiliary gas flow rate 0.5 L / min; nebulizing gas flow rate 0.7 L / min; observation height 15 mm; peristaltic pump speed 110 r / min.

[0024] The specific steps are as follows: a) Accurately weigh 10.00 g of air-dried soil sample that has passed through a 2 mm nylon sieve into a 150 mL capped polyethylene plastic bottle. Add 20.0 mL of 0.2 g / L aluminum nitrate solution (pH=4.40), tighten the cap, gently shake the polyethylene plastic bottle to disperse the soil, fix it in a water bath and keep it at 90 ℃ for 12 min (accurate timing). Remove the polyethylene plastic bottle and let it cool. Open the cap and pour the test solution in the polyethylene plastic bottle onto filter paper in one go. Collect the filtrate in a plastic cup (discard if the filtrate is initially turbid) to obtain the test solution. At the same time, perform a blank test. b) Preparation of standard solutions: Accurately pipette 0.00 mL, 0.50 mL, 1.00 mL, 2.00 mL, 5.00 mL, and 10.00 mL of 10 mg / L boron standard solution into 100 mL volumetric flasks, and dilute to volume with 0.2 g / L aluminum nitrate solution as the extraction solvent to obtain a series of standard solutions containing boron of 0.00 mg / L, 0.05 mg / L, 0.10 mg / L, 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L. A blank solution is also prepared. c) Using a hydrofluoric acid-resistant injection system, inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to sequentially determine the blank solution and the standard series working solutions from step b). The mass concentration of boron in the standard series working solutions was plotted on the x-axis, and the emission intensity of boron on the y-axis to obtain a standard working curve for determining available boron in soil. The linear regression equation and linear correlation coefficient are shown in Table 4. Under optimal instrument operating conditions, the blank solution was continuously measured 10 times. The detection limits for each element in the method were calculated using three times the standard deviation, and the results are shown in Table 4. Table 4 shows that the correlation coefficients are all above 0.9998, indicating high correlation, high reliability, low detection limits, and high precision.

[0025] Table 4. Linear range, linear regression equation, correlation coefficient, and detection limit of the calibration curve. d) The boron content in the soil sample was calculated by inductively coupled plasma atomic emission spectrometry (ICP-AES) of the sample test solution and blank solution in step a). The above method was used to determine the available boron in soil samples ASA-6b-CZ (pH 6.53, available boron 0.13 mg / kg, water-soluble fluoride 2.0 mg / kg) and ASA-9a-CZ (pH 8.35, available boron 0.43 mg / kg, water-soluble fluoride 6.6 mg / kg). Precision and recovery tests were performed, and the results are shown in Table 5. As can be seen from Table 5, the relative standard deviation (RSD, n=11) of the determination results is less than 6.0%, and the recovery rate is 98.00% to 101.00%, both of which meet the requirements for analytical testing.

[0026] Table 5. Results of Precision and Recovery Tests e) Determine the available boron content in the national standard soil reference materials ASA-10a-CZ (pH 8.80, available boron 0.47 mg / kg, water-soluble fluoride 8.5 mg / kg), GBW07412a (pH 6.80, available boron 0.42 mg / kg, water-soluble fluoride 5.1 mg / kg), and GBW07416a (pH 4.71, available boron 0.17 mg / kg, water-soluble fluoride 0.75 mg / kg) according to the methods in steps a) to d), and compare them with their certified values. The results are shown in Table 6. It can be seen that the measured available boron values ​​are basically consistent with the certified values, further proving that the method has high reliability and high precision.

[0027] Table 6. Results of available boron determination using national standard materials for soil (mg / kg) Example 3 A method for determining available boron content in soil by water bath heating aluminum nitrate extraction-inductively coupled plasma atomic emission spectrometry (ICP-AES): Equipment and instruments used: Avio 200 full-spectrum direct-reading plasma emission spectrometer with echelle grating; two-dimensional array (CCD) detector; hydrofluoric acid resistant sample introduction system; HH-S6 digital display constant temperature water bath.

[0028] The instrument's operating parameters are as follows: measurement wavelength 249.773 nm; high-frequency emission power 1150 W; plasma gas flow rate 12 L / min; auxiliary gas flow rate 0.5 L / min; nebulizing gas flow rate 0.7 L / min; observation height 15 mm; peristaltic pump speed 110 r / min.

[0029] The specific steps are as follows: a) Accurately weigh 10.00 g of air-dried soil sample that has passed through a 2 mm nylon sieve into a 150 mL capped polyethylene plastic bottle. Add 20.0 mL of 0.5 g / L aluminum nitrate solution (pH=4.25), tighten the cap, gently shake the polyethylene plastic bottle to disperse the soil, fix it in a water bath and keep it at 95 ℃ for 12 min (accurate timing). Remove the polyethylene plastic bottle and let it cool. Open the cap and pour the test solution in the polyethylene plastic bottle onto filter paper in one go. Collect the filtrate in a plastic cup (discard if the filtrate is initially turbid) to obtain the test solution. At the same time, perform a blank test. b) Preparation of standard solutions: Accurately pipette 0.00 mL, 0.50 mL, 1.00 mL, 2.00 mL, 5.00 mL, and 10.00 mL of 10 mg / L boron standard solution into 100 mL volumetric flasks, and dilute to volume with 0.2 g / L aluminum nitrate solution as the extraction solvent to obtain a series of standard solutions containing boron of 0.00 mg / L, 0.05 mg / L, 0.10 mg / L, 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L. A blank solution is also prepared. c) Using a hydrofluoric acid-resistant injection system, inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to sequentially determine the blank solution and the standard series working solutions from step b). The mass concentration of boron in the standard series working solutions was plotted on the x-axis, and the emission intensity of boron on the y-axis to obtain the standard working curve for determining available boron in soil. The linear regression equation and linear correlation coefficient are shown in Table 7. Under optimal instrument operating conditions, the blank solution was continuously measured 10 times. The detection limits for each element in the method were calculated using three times the standard deviation. The results are shown in Table 7. Table 7 shows that the correlation coefficients are all above 0.9998, indicating high correlation, high reliability, low detection limits, and high precision.

[0030] Table 7. Linear range, linear regression equation, correlation coefficient, and detection limit of the calibration curve. d) The boron content in the soil sample was calculated by inductively coupled plasma atomic emission spectrometry (ICP-AES) of the sample test solution and blank solution in step a). The above method was used to determine the available boron in soil samples ASA-6b-CZ (pH 6.53, available boron 0.13 mg / kg, water-soluble fluoride 2.0 mg / kg) and ASA-9a-CZ (pH 8.35, available boron 0.43 mg / kg, water-soluble fluoride 6.6 mg / kg). Precision and recovery tests were performed, and the results are shown in Table 8. As can be seen from Table 8, the relative standard deviation (RSD, n=11) of the determination results is less than 6.2%, and the recovery rate is 99.00% to 105.00%, both of which meet the requirements of analytical testing.

[0031] Table 8. Results of Precision and Recovery Tests e) Determine the available boron content in soil national standard materials ASA-10a-CZ (pH 8.80, available boron 0.47 mg / kg, water-soluble fluoride 8.5 mg / kg), GBW07412a (pH 6.80, available boron 0.42 mg / kg, water-soluble fluoride 5.1 mg / kg), and GBW07416a (pH 4.71, available boron 0.17 mg / kg, water-soluble fluoride 0.75 mg / kg) according to steps a) to d), and compare them with their certified values. The results are shown in Table 9. It can be seen that the measured available boron values ​​are basically consistent with the certified values, further proving that the method has high reliability and high precision.

[0032] Table 9. Results of available boron determination in soil national standard materials (mg / kg) Example 4 To further verify, aluminum nitrate concentrations of 0.1, 0.2, and 0.5 g / L were selected. 10.00 g each of air-dried soil standard materials GBW(E)070333, GBW(E)070337, and GBW(E)070339, which passed through a 2 mm nylon sieve, were accurately weighed and placed in 150 mL capped polyethylene plastic bottles. 20.0 mL of 0.1 g / L, 0.2 g / L, and 0.5 g / L aluminum nitrate solutions were added respectively. The caps were tightened, and the polyethylene plastic bottles were gently shaken to disperse the soil. The bottles were then placed in a water bath and kept at 90 ℃ for 12 minutes (accurate timing). After cooling, the caps were opened, and the pH value of the effective boron solution after extraction was measured using a pH meter. The experimental results are shown in Table 10. As shown in Table 10, selecting aluminum nitrate concentrations of 0.1, 0.2, and 0.5 g / L as the extraction agent can satisfy the accurate determination of available boron in acidic, neutral, and alkaline soils with pH values ​​ranging from 4.0 to 9.0.

[0033] Table 10. pH values ​​of available boron solution after leaching with aluminum nitrate solution of different concentrations To further compare with the method of this invention, the traditional industry standard for determining available boron in soil (NY / T 1121.8-2006) was first used, employing boiling water extraction and determining boron in the extract under weakly acidic conditions using the methylimine-H colorimetric method. Three national soil standard materials, GBW07459, ASA-1b-CZ, and ASA-8a-CZ, were selected for comparative experiments using the industry standard and this invention. The experimental results are shown in Table 11. Table 11 shows that the determination of available boron in soil using the GBW07459 and ASA-8a-CZ soil standard materials according to NY / T1121.8-2006 resulted in a larger error, while the method of this invention yielded more accurate results. This is because GBW07459 and ASA-8a-CZ have higher contents of water-soluble fluoride and available boron in alkaline soils, leading to the volatilization of boron trifluoride and resulting in lower measured values. Using this method, the accuracy of available boron determination is high because the influence of pH and fluoride on the determination results is considered.

[0034] Table 11 Comparison of Effective Boron Determination Results by Analytical Methods To further verify the accuracy of the determination method of the present invention under different concentrations of aluminum nitrate solution, soil standard samples GBW07459, ASA-1b-CZ, and ASA-8a-CZ were extracted with aluminum nitrate concentrations of 0.05, 0.08, 0.1, 0.2, 0.5, 0.55, and 0.6 g / L. The experimental results are shown in Table 12. Table 12 shows that using aluminum nitrate concentrations of 0.1, 0.2, and 0.5 g / L to extract soil standard samples GBW07459, ASA-1b-CZ, and ASA-8a-CZ resulted in more accurate determinations of available boron in the soil.

[0035] Table 12 Comparison of available boron determination results from aluminum nitrate leaching at different concentrations Although the invention has been described herein with reference to several illustrative embodiments, it should be understood that many other modifications and implementations can be devised by those skilled in the art, which will fall within the scope and spirit of the principles disclosed herein. More specifically, various modifications and improvements can be made to the components or layouts within the scope of the disclosure and claims. Besides modifications and improvements to the components or layouts, other uses will be apparent to those skilled in the art.

Claims

1. A method for determining the available boron content in soil, characterized in that: Includes the following steps: Weigh out an air-dried soil sample and place it in a capped polyethylene plastic bottle. Add 0.1–0.5 g / L aluminum nitrate solution as an extractant, tighten the cap, and gently shake the polyethylene plastic bottle to disperse the soil. Place the bottle in a water bath and maintain a gentle boil at 85–95 °C for 12–15 min. Remove the polyethylene plastic bottle and allow it to cool. Open the cap and separate the solid and liquid components of the sample solution in the polyethylene plastic bottle. Collect the filtrate in a plastic cup to obtain the test solution. Perform a blank test simultaneously. Preparation of standard solutions: Pipette boron standard solution and dilute to volume with 0.1-0.5 g / L aluminum nitrate solution to prepare a series of boron-containing standard solutions, and prepare blank solutions at the same time; A hydrofluoric acid-resistant injection system was selected, and inductively coupled plasma atomic emission spectrometry was used to sequentially determine the blank solution and the standard series working solutions of step b). The mass concentration of boron in the standard series working solutions was used as the abscissa, and the emission intensity value of boron was used as the ordinate to obtain the standard working curve for determining available boron in soil. d) The boron response values ​​in the test solution and blank solution of the sample in step a) were determined by inductively coupled plasma atomic emission spectrometry, and the available boron content in the soil sample was calculated according to the standard working curve.

2. The method for determining the available boron content in soil according to claim 1, characterized in that: The air-dried soil samples in step a) include acidic soil with pH < 6.5, neutral soil with pH 6.5 ≤ pH ≤ 7.5, and alkaline soil with pH > 7.

5.

3. The method for determining the available boron content in soil according to claim 1, characterized in that: The aluminum nitrate in step a) is GR grade aluminum nitrate nonahydrate; the aluminum nitrate solution is prepared with boron-free water and the pH of the aluminum nitrate solution is 4.25 to 4.

50.

4. The method for determining the available boron content in soil according to claim 1, characterized in that: In step a), the air-dried soil sample is soil that has passed through a 2 mm nylon sieve, and the amount of aluminum nitrate solution added is 18-20 mL / 10 g soil sample.

5. The method for determining the available boron content in soil according to claim 1, characterized in that: In step b), the concentrations of the boron-containing standard series solutions are 0.05 mg / L, 0.10 mg / L, 0.20 mg / L, 0.50 mg / L, and 1.00 mg / L, respectively, and the concentration of the boron standard solution is 10 mg / L.

6. The method for determining the available boron content in soil according to claim 1, characterized in that: The instrument operating parameters for inductively coupled plasma atomic emission spectrometry in steps c) to e) are as follows: measurement wavelength 249.773 nm; high-frequency emission power 1150 W; plasma gas flow rate 12 L / min; auxiliary gas flow rate 0.5 L / min; nebulizing gas flow rate 0.7 L / min; observation height 15 mm; peristaltic pump speed 110 r / min.

7. The method for determining the available boron content in soil according to claim 1, characterized in that: It also includes step e) determining the available boron content in soil national standard materials ASA-10a-CZ, GBW07412a, and GBW07416a according to the methods in steps a) to d) and comparing it with their certified values.

Images