Soil erosion modulus measurement method based on high purity germanium gamma spectrometer

Abstract

The present invention provides a soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer, which includes: obtaining a number of standard nuclide sample boxes based on soil standard material samples corresponding to different nuclides; obtaining detection efficiency equations of curves of detection efficiency varying with the height of standard nuclide samples for different nuclides; selecting optimal time nuclides to obtain the optimal measurement time equation of the curve of optimal measurement time varying with nuclide content; obtaining the nuclide content to be measured for the soil to be measured; and obtaining the erosion modulus of the soil to be measured based on the nuclide content to be measured. The present invention obtains the optimal measurement time equations under different contents and the detection efficiency equations under different heights by means of linear fitting and polynomial fitting of curves, combined with statistical methods, which effectively solves the problem of low efficiency of radionuclide measurement due to soil sampling limit, improves measurement efficiency, shortens measurement time, and has practical application significance.

Description

Technical Field

[0001] The invention belongs to the technical field of soil erosion measurement, in particular to a soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer. Background Art

[0002] Land degradation is one of the main obstacles to the sustainable development of human society, and soil erosion is the main cause of land resource degradation and even complete destruction. Quantitative estimation of soil erosion is the basis for the rational allocation of soil and water conservation measures and the effective guidance of soil and water conservation planning. In the past few decades, radionuclide tracer technology has been widely used in the quantitative estimation of soil erosion and sediment deposition. It can be used to calculate the soil erosion and sediment deposition rates at any point in space, thereby obtaining the spatial distribution characteristics of soil erosion and sediment deposition in different scales such as slopes, small watersheds or regions. As the only method to obtain spatial distribution characteristics, radionuclide tracer technology makes up for the shortcomings of traditional soil erosion measurement methods.

[0003] High purity germanium (HPGe) gamma spectrometer is a new type of semiconductor detector that has been rapidly developed in recent decades. It can be used to measure the content of radionuclides that release gamma rays in soil, sediment, plants or water. In the gamma energy spectrum measurement and analysis, HPGe detectors have the advantages of high energy resolution, wide linear range, fast response time, excellent temperature characteristics and resistance to neutron irradiation damage. Therefore, high purity germanium (HPGe) gamma spectrometers are widely used in the analysis of low background gamma radionuclides and content, and are an important means of environmental radiation measurement. High purity germanium gamma spectrometers are available in N type, P type and well type, and the mass range of testable samples ranges from a few grams to hundreds of grams. Due to the limitation of field sampling of soil or water samples, the sample amount ranges from a few grams to hundreds of grams. At this time, the measurement efficiency and measurement time of the instrument will be greatly different. Therefore, in order to solve the problem of low measurement efficiency caused by the limitation of soil sampling amount, it is urgent and necessary to seek a soil erosion modulus measurement method based on high purity germanium gamma spectrometer to improve measurement efficiency and shorten measurement time. Summary of the invention

[0004] In view of the defects in the above-mentioned prior art, the present invention proposes a soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer. The method includes obtaining a number of standard nuclide sample boxes based on soil standard material samples corresponding to different nuclides; obtaining the detection efficiency equation of the curve of the detection efficiency changing with the height of the standard nuclide sample for different nuclides; selecting the optimal time nuclide to obtain the optimal measurement time equation of the curve of the optimal measurement time changing with the content; obtaining the content of the nuclide to be measured for the soil to be measured; and obtaining the erosion modulus of the soil to be measured based on the content of the nuclide to be measured. The present invention uses linear fitting and polynomial fitting of the curve, combined with statistical methods, to obtain the optimal measurement time equation under different contents and the detection efficiency equation under different heights, which effectively solves the problem of low efficiency of radioactive nuclide measurement due to soil sampling limit, thereby improving measurement efficiency and shortening measurement time.

[0005] The present invention provides a soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer, which comprises the following steps:

[0006] S1. Based on soil standard material samples corresponding to different nuclides, obtain several standard nuclide sample boxes;

[0007] S11. For m different nuclides, prepare several soil standard material samples corresponding to each nuclide;

[0008] S12, setting n standard nuclide sample heights, for m nuclides, respectively loading soil standard material samples of corresponding nuclides into n sample boxes according to the n standard nuclide sample heights, to obtain m×n standard nuclide sample boxes;

[0009] S2. For different nuclides, respectively obtain the detection efficiency equation of the curve of detection efficiency changing with the height of the standard nuclide sample;

[0010] S21. Based on a high-purity germanium gamma spectrometer, m×n standard nuclide sample boxes are measured and calculated to obtain the detection efficiency corresponding to the m nuclides at the n standard nuclide sample heights;

[0011] S22, for each of the m nuclides, perform quadratic polynomial fitting on all the detection efficiencies obtained at the n standard nuclide sample heights, and obtain detection efficiency equations for curves showing the change of detection efficiency of each nuclide with the standard nuclide sample height;

[0012] S3, selecting the optimal measurement time nuclide, and obtaining the optimal measurement time equation of the curve of the optimal measurement time varying with the nuclide content;

[0013] S31, selecting any one of the m nuclides as the optimal time nuclide, and preparing soil standard materials corresponding to the optimal time nuclide at k different contents;

[0014] S32, measuring the net peak area count rate of the soil standard substances corresponding to the k contents respectively based on a high purity germanium gamma spectrometer;

[0015] S33, based on the net peak area count rates measured at k contents, respectively calculating the optimal measurement time corresponding to the k contents;

[0016] S34, fitting the optimal measurement time corresponding to k contents with a power function equation to obtain an optimal measurement time equation for a curve of the optimal measurement time of the optimal time nuclide versus the nuclide content;

[0017] S4. Obtaining the nuclide content to be tested for the soil to be tested;

[0018] S5. Based on the nuclide content to be measured, the soil erosion modulus to be measured is obtained;

[0019] S51. Based on the nuclide content to be measured, calculate the nuclide content A(t) per unit area of ​​the soil to be measured:

[0020] A(t)=A×M / S (1)

[0021] Where A represents the nuclide content to be tested; M represents the total mass of the soil to be tested; S represents the sampling area;

[0022] S52. Based on the nuclide content per unit area of ​​the soil to be tested, the erosion modulus R of the soil to be tested is obtained:

[0023]

[0024] Where A(t) represents the content of the nuclide per unit area of ​​soil in the sampling year of the soil sample; t represents the sampling year of the soil sample; Γ represents the loss rate of the newly deposited nuclide before it is mixed into the tillage layer; I(t) represents the deposition of the nuclide from the beginning year of the deposition of the nuclide to the sampling year t; P represents the soil particle correction factor, that is, the ratio of the activity of the nuclide in the sedimentary soil to that in the erosion-migrated soil; R represents the annual soil erosion modulus; d m represents the accumulated mass depth of the cultivated layer soil; λ represents the decay constant of the nuclide.

[0025] Further, step S4 specifically includes the following steps:

[0026] S41, after air-drying, grinding and sieving the soil to be tested, the soil to be tested is placed in a sample box to obtain a soil sample box to be tested, and the height of the soil sample to be tested is recorded;

[0027] S42, using a high-purity germanium gamma spectrometer, after measuring the soil sample box to be tested for a second set time, obtaining an initial net peak area count rate and a nuclide type, and calculating an initial content of the nuclide to be tested of the corresponding nuclide type based on the initial net peak area count rate;

[0028] S43, substituting the initial content of the nuclide to be measured into the optimal measurement time equation in step S34 to obtain the optimal measurement time of the soil to be measured;

[0029] S44, based on a high-purity germanium gamma spectrometer, after measuring the optimal measurement time of the soil to be tested in the soil sample box to be tested, obtain the net peak area count rate of the soil to be tested;

[0030] S45, substituting the height of the soil sample to be tested into the detection efficiency equation corresponding to the nuclide type in step S22 to obtain the detection efficiency of the soil to be tested;

[0031] S46. Based on the detection efficiency of the soil to be tested and the net peak area counting rate of the soil to be tested, the content A of the nuclide to be tested in the soil to be tested is calculated.

[0032] Preferably, the detection efficiency ε in step S21 is expressed as:

[0033]

[0034] Among them, a s Indicates the net peak area count rate of gamma rays with energy E at the time of measurement; A 0 represents the activity of the nuclide at the time of preparation; Δt represents the time between the preparation time and the measurement time; e represents a natural constant;

[0035] The optimal measurement duration N in step S33 is expressed as:

[0036]

[0037] Among them, g represents the cutoff measurement time; α represents the set probability; f represents the degree of freedom; K represents the data accuracy; μ represents the average value of several contents of the optimal time nuclide obtained based on all the net peak area counting rates; σ represents the standard deviation of several contents of the optimal time nuclide obtained based on all the net peak area counting rates.

[0038] Preferably, the nuclide content A to be detected in step S46 is expressed as:

[0039]

[0040] Wherein, w represents the mass of the soil to be tested in the soil sample box; T represents the measurement time of the nuclide to be tested; A s Indicates the net peak area count rate of the soil to be tested; F 1represents the decay correction factor for the soil under test during the measurement period and F t It represents the gamma ray self-absorption correction coefficient of the soil to be tested relative to the calibration source.

[0041] Preferably, the standard deviation σ of the contents of the optimal time nuclides obtained based on all the net peak area count rates in step S33 is expressed as:

[0042]

[0043] Wherein, h represents the total number of measurements at the first set time interval; x i represents the content of the optimal time nuclide obtained based on the net peak area count rate obtained in the i-th measurement; It represents the average value of the n-time content of the optimal time nuclide obtained based on the net peak area count rate obtained by n measurements.

[0044] Preferably, the net peak area count rate in step S32 is measured once at a first set time interval.

[0045] Preferably, the sampling area in step S51 is a sampling drilling area or a square sampling device area.

[0046] Preferably, in step S12, soil standard material samples of m nuclides can be mixed together to obtain a mixed soil standard material sample, and the mixed soil standard material samples containing m nuclides are respectively loaded into n sample boxes according to the heights of the n standard nuclides samples to obtain n standard nuclide sample boxes.

[0047] Compared with the prior art, the technical effects of the present invention are:

[0048] 1. The present invention proposes a soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer. The optimal measurement time equation of the curve of the optimal measurement time varying with the nuclide content is obtained by means of linear fitting, and then the net peak area counting rate of the soil to be tested is obtained based on the high-purity germanium gamma spectrometer; the detection efficiency equation of the curve of the detection efficiency varying with the height of the standard nuclide sample is obtained by means of polynomial fitting, and then the detection efficiency of the soil to be tested is obtained; and the estimated value of the soil erosion modulus to be tested is obtained by combining the net peak area counting rate of the soil to be tested and the detection efficiency of the soil to be tested.

[0049] 2. The present invention proposes a soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer. To address the problem of low efficiency in radionuclide measurement due to limited soil sampling, standard nuclide samples are prepared by combining soil standard material samples, and a number of statistical data are obtained with the help of statistical methods. The soil erosion modulus measurement is effectively completed, the measurement efficiency is improved, and the measurement time is shortened, which has important practical application significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Other features, objects and advantages of the present application will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings.

[0051] Figure 1 It is a flow chart of the soil erosion modulus measurement method based on high-purity germanium gamma spectrometer of the present invention;

[0052] Figure 2 is a curve fitting diagram showing the change of detection efficiency of different nuclides with the height of the standard nuclide sample in a specific embodiment of the present invention;

[0053] Figure 3a is a schematic diagram of a large cylindrical sample box in a specific embodiment of the present invention;

[0054] Figure 3b is a schematic diagram of a small cylindrical sample box in a specific embodiment of the present invention;

[0055] Figure 3c is a schematic diagram of a test tube-shaped sample box in a specific embodiment of the present invention;

[0056] Figure 4a-4c This is a physical picture of different types of samples in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0057] The present application will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the relevant invention, rather than to limit the invention. It should also be noted that, for ease of description, only the parts related to the relevant invention are shown in the accompanying drawings.

[0058] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0059] Figure 1 The present invention shows a soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer, which comprises the following steps:

[0060] S1. Based on the soil standard material samples corresponding to different nuclides, obtain several standard nuclide sample boxes.

[0061] S11. For m different nuclides, prepare several soil standard material samples corresponding to each nuclide.

[0062] S12, setting n standard nuclide sample heights, for m nuclides, respectively loading soil standard material samples of corresponding nuclides into n sample boxes according to the n standard nuclide sample heights, to obtain m×n standard nuclide sample boxes. In addition, preferably, soil standard material samples of m nuclides can also be mixed together to obtain a mixed soil standard material sample, and mixed soil standard material samples containing m nuclides are respectively loaded into n sample boxes according to the n standard nuclide sample heights, to obtain n standard nuclide sample boxes.

[0063] S2. For different nuclides, the detection efficiency equations of the curves showing the change of detection efficiency with the height of the standard nuclide sample are obtained respectively.

[0064] S21. Based on the high-purity germanium gamma spectrometer, m×n standard nuclide sample boxes are measured and calculated respectively to obtain the detection efficiency corresponding to the m nuclides at the n standard nuclide sample heights; the detection efficiency ε is expressed as:

[0065]

[0066] Among them, a s It represents the net peak area count rate of gamma rays with energy E at the time of measurement; P represents the emission probability of gamma rays; A 0 represents the activity of the nuclide at the time of preparation; λ represents the decay constant of the nuclide; Δt represents the time between the preparation time and the measurement time; e represents the natural constant.

[0067] S22. For each of the m nuclides, all the detection efficiencies obtained at the n standard nuclide sample heights are fitted with a quadratic polynomial to obtain detection efficiency equations for curves showing how the detection efficiency of each nuclide changes with the standard nuclide sample height.

[0068] S3. Select the optimal measurement time nuclide and obtain the optimal measurement time equation of the curve of the optimal measurement time varying with the nuclide content.

[0069] S31. Select any one of the m nuclides as the optimal duration nuclide, and prepare soil standard materials corresponding to the optimal duration nuclide at k different contents.

[0070] S32. For each of the soil standard substances corresponding to the k contents, the net peak area count rate is measured based on a high-purity germanium gamma spectrometer, and the net peak area count rate is measured once at a first set time interval.

[0071] S33, based on the net peak area count rates measured at k contents, the optimal measurement time N corresponding to the k contents is calculated respectively; the optimal measurement time N is expressed as:

[0072]

[0073] Wherein, g represents the cut-off measurement time; α represents the set probability; f represents the degree of freedom; K represents the data accuracy; μ represents the average value of several contents of the optimal time nuclide obtained based on all net peak area count rates; σ represents the standard deviation of several contents of the optimal time nuclide obtained based on all net peak area count rates and is expressed as:

[0074]

[0075] Wherein, h represents the total number of measurements at the first set time interval; x i represents the content of the optimal time nuclide obtained based on the net peak area count rate obtained in the i-th measurement; It represents the average value of the n-time content of the optimal time nuclide obtained based on the net peak area count rate obtained by n measurements.

[0076] S34, fitting the optimal measurement time corresponding to k contents with a power function equation to obtain an optimal measurement time equation for a curve of the optimal measurement time of the optimal time nuclide versus the nuclide content.

[0077] S4. Obtain the nuclide content of the soil to be tested.

[0078] S41. After air-drying, grinding and sieving the soil to be tested, the soil to be tested is placed in a sample box to obtain a soil sample box to be tested, and the height of the soil sample to be tested is recorded.

[0079] S42. Based on the high-purity germanium gamma spectrometer, after measuring the soil sample box to be tested for a second set time, an initial net peak area count rate and nuclide type are obtained, and the initial content of the nuclide to be tested of the corresponding nuclide type is calculated based on the initial net peak area count rate.

[0080] S43, substituting the initial content of the nuclide to be measured into the optimal measurement time equation in step S34 to obtain the optimal measurement time of the soil to be measured.

[0081] S44. Based on a high-purity germanium gamma spectrometer, after measuring the optimal measurement time of the soil to be tested in the soil sample box, the net peak area count rate of the soil to be tested is obtained.

[0082] S45, substituting the height of the soil sample to be tested into the detection efficiency equation of the corresponding nuclide type in step S22 to obtain the detection efficiency of the soil to be tested.

[0083] S46. Based on the detection efficiency of the soil to be tested and the net peak area counting rate of the soil to be tested, the content of the nuclide to be tested in the soil to be tested is calculated; the content of the nuclide to be tested A is expressed as:

[0084]

[0085] Wherein, w represents the mass of the soil to be tested in the soil sample box; T represents the measurement time of the nuclide to be tested; A s Indicates the net peak area count rate of the soil to be tested; F 1 represents the decay correction factor for the soil under test during the measurement period and F t It represents the gamma ray self-absorption correction coefficient of the soil to be tested relative to the calibration source.

[0086] S5. Based on the nuclide content to be measured, the soil erosion modulus to be measured is obtained.

[0087] S51. Based on the nuclide content to be measured, calculate the nuclide content A(t) per unit area of ​​the soil to be measured:

[0088] A(t)=A×M / S (1)

[0089] Where M is the total mass of the soil to be tested after air drying, grinding and sieving; S is the sampling area. The sampling area is the area of ​​the sampling drill or the area of ​​the square sampling device.

[0090] S52. Based on the nuclide content per unit area of ​​the soil to be tested, the erosion modulus R of the soil to be tested is obtained:

[0091]

[0092] Among them, A(t) represents the content of the nuclide to be measured per unit area of ​​soil in the sampling year of the soil sample; t represents the sampling year of the soil sample; Γ represents the loss rate of the newly deposited nuclide to be measured before it is mixed into the tillage layer; I(t) represents the amount of the nuclide to be measured from the beginning year of the deposition of the nuclide to the sampling year t; P represents the soil particle correction factor, that is, the ratio of the activity of the nuclide to be measured in the sedimentary soil to that in the erosion-migrated soil, which is generally greater than 1.0 because 137 Cs is easily adsorbed on the surface of soil particles that are easy to migrate and have a small particle size; R represents the annual soil erosion modulus; d m represents the accumulated mass depth of the cultivated layer soil; λ represents the decay constant of the nuclide.

[0093] In one embodiment, the radionuclide 137 Cs as an example, the soil particle correction factor P is generally greater than 1.0 because 137 Cs is easily adsorbed on the surface of soil particles that are easy to migrate and have small particle sizes.

[0094] The following is a description of soil standard material samples or soil sample boxes. Figure 3a As shown, the large cylindrical sample box 1 contains the sample 2. Figure 3b The small and medium cylindrical sample box 3 contains the sample 2. Figure 3c The sample 2 is accommodated in the test tube-shaped sample box 4 . Figure 3aThe soil standard material is loaded into the large cylindrical sample box 1 at different heights, and the instrument detection efficiency of different heights and different nuclides is calculated. Sample 2 is loaded into the large cylindrical sample box 1, and the sample height is measured according to the amount of sample 2 in the large cylindrical sample box 1, and the nuclide content of the sample is calculated using the detection efficiency at the corresponding height. Figure 3b The small cylindrical sample box 3 is used as a middle box and can have the same bottom area and different heights as the large cylindrical sample box 1. The soil standard material is loaded at different heights, and the instrument detection efficiency of different heights and different nuclides is calculated. The sample 2 is loaded into the small cylindrical sample box 3, and the sample height is measured according to the amount of sample 2 in the small cylindrical sample box 3, and the sample nuclide content is calculated using the detection efficiency at the corresponding height. Figure 3c The small and medium cylindrical sample boxes 3 are small centrifuge cups. The soil standard materials are loaded at different heights, and the instrument detection efficiency of different heights and different nuclides is calculated. The samples are loaded into the small cylindrical sample box 3, and the sample height is measured according to the sample amount in the small cylindrical sample box 3. The sample nuclide content is calculated using the detection efficiency at the corresponding height.

[0095] At the same time, in a specific application example, Figure 4a A large cylindrical sample box 1, such as a Sample box; Figure 4b A small cylindrical sample box 3, for example Sample box, Figure 4c It is a small centrifuge cup, for example, a small cylindrical sample box 3 with a capacity of 7 ml.

[0096] In a specific embodiment, a P-type high purity germanium gamma spectrometer and Cylindrical sample boxes, such as Figure 2 , Figure 3a and Figure 4a The standard nuclide sample height and detection efficiency corresponding to different nuclides are shown in Table 1.

[0097]

[0098]

[0099] Table 1

[0100] For each nuclide, the curve of detection efficiency changing with the height of the standard nuclide sample is as follows: Figure 2 As shown, different nuclides correspond to different curves, and the fitting detection efficiency equations are:

[0101] Radionuclides 238 U(63.29Kev) 210 Pb (46.62Kev): ε = 0.00004h 2 -0.0045h+0.1844 (7)

[0102] Radionuclides 210 Pb (46.62Kev): ε = 0.00004h 2 -0.0049h+0.1709 (8)

[0103] Radionuclides 226 Ra(609.32Kev):ε=0.00001h 2 -0.0017h+0.0886 (9)

[0104] Radionuclides 137 Cs (661.66Kev): ε = 0.00001h 2 -0.0017h+0.0886 (10)

[0105] Radionuclides 232 Th(911.07Kev):ε=0.000007h 2 -0.001h+0.0548 (11)

[0106] Radionuclides 40 K(1460.75Kev):ε=0.000005h 2 -0.0007h+0.0403 (12)

[0107] Among them, ε represents the detection efficiency, which is dimensionless; h represents the height of the standard nuclide sample, in mm.

[0108] In a specific embodiment, a P-type high purity germanium gamma spectrometer is used. 137 Take the calculation of the optimal measurement time of Cs as an example, the sample number and the nuclide in the sample 137 The content of Cs is shown in Table 2. Each sample was put into a P-type high-purity germanium gamma spectrometer for measurement. The measurement time ensured that the uncertainty of the net peak area count was less than 5%. The first set time during measurement was 1 hour, that is, the data was saved every 1 hour. 137 Descriptive statistical analysis of Cs activity and calculation of the optimal measurement time, sample 137 The statistical data of Cs activity are shown in Table 3, and the optimal measurement time with an allowable error of 5% and 10% at confidence levels of 90%, 95% and 99% is shown in Table 4.

[0109]

[0110] Table 2

[0111]

[0112]

[0113]

[0114] Table 3

[0115]

[0116] Table 4

[0117] Based on the comprehensive consideration of measurement time and accuracy, it is recommended to take the optimal measurement time with an allowable error of 5% at a confidence level of 90%. The optimal measurement time equation obtained by fitting is:

[0118] T n =18.537·A n -0.834 (13)

[0119] Among them, T n Indicates the time the sample is tested, in hours; A n Indicates the activity of soil samples in Bq / kg.

[0120] In a specific embodiment, soil samples at different depths of 0-5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm and 25-30 cm were collected from the surface of cultivated land in the black soil region of Northeast China as an example, and the nuclides were measured based on a high-purity germanium gamma spectrometer. 137 Cs, thus high-precision tracer measurement of soil erosion modulus. A 6.5 cm high sample box was used to complete the sample loading. The sample did not fill the sample box. The nuclide was calculated according to formula (10) 137 The detection efficiency of Cs at different sample heights. The optimal measurement time for each sample is calculated according to formula (13). When the optimal measurement time is completed, the measurement is stopped and the sample counting results are saved. The nuclide of each sample is calculated according to formula (5). 137 The activity of Cs is calculated by formula (1), and the area activity of each sample is accumulated to obtain the area activity of the sampling point 137 Cs area activity, soil erosion modulus calculated according to formula (2) is 31.9t / (h·m 2 The results of the sampling height and soil erosion modulus calculation process are shown in Table 5.

[0121]

[0122]

[0123] Table 5

[0124] The soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer proposed in the present invention obtains an optimal measurement time equation of a curve in which the optimal measurement time varies with the nuclide content by means of linear fitting, and then obtains the net peak area count rate of the soil to be measured based on the high-purity germanium gamma spectrometer; obtains a detection efficiency equation of a curve in which the detection efficiency varies with the height of a standard nuclide sample by means of polynomial fitting, and then obtains the detection efficiency of the soil to be measured; combines the net peak area count rate of the soil to be measured and the detection efficiency of the soil to be measured to obtain an estimated value of the erosion modulus of the soil to be measured; in view of the problem of low radionuclide measurement efficiency due to soil sampling quantity limitation, standard nuclide samples are prepared by combining soil standard material samples, and a number of statistical data are obtained by means of statistical methods, so as to effectively complete the measurement of the soil erosion modulus, improve the measurement efficiency, and shorten the measurement time, which has practical application significance.

[0125] Finally, it should be noted that the above embodiments are only intended to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A soil erosion modulus measurement method based on a high-purity germanium gamma spectrometer, characterized in that: It includes the following steps: S1. Based on soil standard material samples corresponding to different nuclides, obtain several standard nuclide sample boxes; S11. For m different nuclides, prepare several soil standard material samples corresponding to each nuclide; S12, setting n standard nuclide sample heights, for m nuclides, respectively loading soil standard material samples of corresponding nuclides into n sample boxes according to the n standard nuclide sample heights, to obtain m×n standard nuclide sample boxes; S2. For different nuclides, respectively obtain the detection efficiency equation of the curve of detection efficiency changing with the height of the standard nuclide sample; S21. Based on a high-purity germanium gamma spectrometer, m×n standard nuclide sample boxes are measured and calculated to obtain the detection efficiency corresponding to the m nuclides at the n standard nuclide sample heights; S22, for each of the m nuclides, perform quadratic polynomial fitting on all the detection efficiencies obtained at the n standard nuclide sample heights, and obtain detection efficiency equations for curves showing the change of detection efficiency of each nuclide with the standard nuclide sample height; S3, selecting the optimal measurement time nuclide, and obtaining the optimal measurement time equation of the curve of the optimal measurement time varying with the nuclide content; S31, selecting any one of the m nuclides as the optimal time nuclide, and preparing soil standard materials corresponding to the optimal time nuclide at k different contents; S32, measuring the net peak area count rate of the soil standard substances corresponding to the k contents respectively based on a high purity germanium gamma spectrometer; S33, based on the net peak area count rates measured at the k contents, respectively calculating the optimal measurement time corresponding to the k contents; S34, fitting the optimal measurement time corresponding to k contents with a power function equation to obtain an optimal measurement time equation for a curve of the optimal measurement time of the optimal time nuclide versus the nuclide content; S4. Obtaining the nuclide content to be tested for the soil to be tested; S5. Based on the nuclide content to be measured, the soil erosion modulus to be measured is obtained; S51. Based on the nuclide content to be measured, calculate the nuclide content A(t) per unit area of ​​the soil to be measured: A(t)=A×M / S (1) Where A represents the nuclide content to be tested; M represents the total mass of the soil to be tested; S represents the sampling area; S52. Based on the nuclide content per unit area of ​​the soil to be tested, the erosion modulus R of the soil to be tested is obtained: Where A(t) represents the content of the nuclide per unit area of ​​soil in the sampling year of the soil sample; t represents the sampling year of the soil sample; Γ represents the loss rate of the newly deposited nuclide before it is mixed into the tillage layer; I(t) represents the deposition of the nuclide from the beginning year of the deposition of the nuclide to the sampling year t; P represents the soil particle correction factor, that is, the ratio of the activity of the nuclide in the sedimentary soil to that in the erosion-migrated soil; R represents the annual soil erosion modulus; d m represents the accumulated mass depth of the cultivated layer soil; λ represents the decay constant of the nuclide; The detection efficiency ε in step S21 is expressed as: Among them, a s represents the net peak area count rate of gamma rays with energy E at the measurement time; A0 represents the activity of the nuclide at the preparation time; Δt represents the time between the preparation time and the measurement time; e represents the natural constant, and λ represents the decay constant of the nuclide; The optimal measurement duration N in step S33 is expressed as: Among them, g represents the cutoff measurement time; α represents the set probability; f represents the degree of freedom; K represents the data accuracy; μ represents the average value of several contents of the optimal time nuclide obtained based on all the net peak area counting rates; σ represents the standard deviation of several contents of the optimal time nuclide obtained based on all the net peak area counting rates.

2. The soil erosion modulus measurement method based on high purity germanium gamma spectrometer according to claim 1 is characterized in that: Step S4 specifically includes the following steps: S41, after air-drying, grinding and sieving the soil to be tested, the soil is placed in a sample box to obtain a soil sample box to be tested, and the height of the soil sample to be tested is recorded; S42, using a high-purity germanium gamma spectrometer, after measuring the soil sample box to be tested for a second set time, obtaining an initial net peak area count rate and a nuclide type, and calculating an initial content of the nuclide to be tested of the corresponding nuclide type based on the initial net peak area count rate; S43, substituting the initial content of the nuclide to be measured into the optimal measurement time equation in step S34 to obtain the optimal measurement time of the soil to be measured; S44, based on a high-purity germanium gamma spectrometer, after measuring the optimal measurement time of the soil to be tested in the soil sample box to be tested, obtain the net peak area count rate of the soil to be tested; S45, substituting the height of the soil sample to be tested into the detection efficiency equation corresponding to the nuclide type in step S22 to obtain the detection efficiency of the soil to be tested; S46. Based on the detection efficiency of the soil to be tested and the net peak area counting rate of the soil to be tested, the content A of the nuclide to be tested in the soil to be tested is calculated.

3. The soil erosion modulus measurement method based on high purity germanium gamma spectrometer according to claim 2 is characterized in that: The nuclide content A to be measured in step S46 is expressed as: Wherein, w represents the mass of the soil to be tested in the soil sample box; T represents the measurement time of the nuclide to be tested; A s Indicates the net peak area count rate of the soil to be tested; F h represents the decay correction factor for the soil under test during the measurement period and F t It represents the gamma ray self-absorption correction coefficient of the soil to be tested relative to the calibration source.

4. The soil erosion modulus measurement method based on high purity germanium gamma spectrometer according to claim 3 is characterized in that: The standard deviation σ of the contents of the optimal time nuclides obtained based on all the net peak area count rates in step S33 is expressed as: Wherein, h represents the total number of measurements at the first set time interval; x i represents the content of the optimal time nuclide obtained based on the net peak area count rate obtained in the i-th measurement; It represents the average value of the h-time content of the optimal time nuclide obtained based on the net peak area counting rate obtained by h measurements.

5. The soil erosion modulus measurement method based on high purity germanium gamma spectrometer according to claim 1 is characterized in that: In step S32, the net peak area count rate is measured once at a first set time interval.

6. The soil erosion modulus measurement method based on high purity germanium gamma spectrometer according to claim 1 is characterized in that: The sampling area in step S51 is the sampling drill area or the square sampling device area.

7. The soil erosion modulus measurement method based on high purity germanium gamma spectrometer according to claim 1 is characterized in that: In step S12, soil standard material samples of m nuclides can be mixed together to obtain a mixed soil standard material sample, and the mixed soil standard material samples containing m nuclides are respectively loaded into n sample boxes according to the heights of the n standard nuclides samples to obtain n standard nuclide sample boxes.

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