CN112964742B - EDXRF soil potassium and phosphorus content detection system and method - Google Patents
EDXRF soil potassium and phosphorus content detection system and method Download PDFInfo
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Abstract
The invention discloses an EDXRF soil potassium and phosphorus content detection system and method. The EDXRF soil potassium and phosphorus content detection method comprises the steps of original spectrogram acquisition, baseline deduction, filtering processing, linear interpolation, local weighted regression smoothing, peak value fitting and the like. The method and the system can realize rapid and semi-quantitative analysis among different soil matrixes and realize rapid and quantitative analysis in similar soil matrix samples. The method has good applicability to fertilizer efficiency detection of large-area cultivated land.
Description
Technical Field
The invention relates to the technical field of detection, in particular to an EDXRF soil potassium and phosphorus content detection system and method.
Background
The crops need various nutrients for growth, and K (potassium) element and P (phosphorus) element are two of the elements with large use amount and large content change. In modern agriculture, before soil cultivation, targeted fertilization is required, and different crops, different current soil situations and different climates all have great influence on fertilization types and fertilization amounts. If the content of K, P element in the soil is high and the fertility is lost slowly, no fertilizer or little fertilizer is needed. Otherwise, a large amount of supplement is needed to ensure that the nutrient supply of the crops is good. The cultivated land area in China reaches 18 hundred million mu, and cultivated species are abundant. Soil nutrients are evaluated before modern agriculture is planted, and the contents of K and P are contained in the soil nutrients.
The soil detection method applied to the agricultural scene needs to meet the three characteristics of high speed, accuracy and low cost. Current K, P element measurements are dominated by laboratory chemistry methods. In foreign studies, researchers have described an automated method to determine P and K in specific soil extracts. Researchers use a special light intensity threshold value method to qualitatively judge the content of the soil K, P to be detected. Some researchers have better processed soil N, P, K using image recognition in combination with neural networks. The national standard determination method is mainly referred by domestic researchers, and some researchers adopt the national standard method, the sodium hydroxide fusion-flame photometry is used for total potassium measurement, the sodium hydroxide fusion-alkali molybdenum antimony scandium colorimetry is used for total phosphorus measurement, and the result is more accurate; researchers measure K, P two elements by using one digestion solution with perchloric acid, hydrochloric acid and hydrofluoric acid in a special proportion, and the effect is good. Researchers have used visible and near infrared spectroscopy for measuring the content of K and P with high accuracy. Researchers use the near infrared spectrum and the least square support vector machine to measure the content of K and P, and the accuracy is high. Researchers use the LED light source and the optical fiber sensor to measure soil K, P, and the result is accurate. Researchers use an inductively coupled plasma spectroscopy method to measure the K, P content in the fertilizer, and the result is more accurate.
The chemical method in the method has high measurement accuracy, but has slow speed, very complex flow and higher requirement on metering personnel.
Disclosure of Invention
Therefore, the invention provides an EDXRF soil potassium and phosphorus content detection system and method, and aims to solve the problems that the existing detection method is slow in speed, very complex in process and high in requirement on measuring personnel.
In order to achieve the above purpose, the invention provides the following technical scheme:
the invention provides an EDXRF soil potassium and phosphorus content detection method, which comprises the following steps:
a, acquiring a plurality of standard sample original spectrograms of a plurality of standard soil samples and a measurement sample original spectrogram of a soil sample to be measured by an EDXRF soil potassium and phosphorus content detection system;
b, carrying out baseline deduction on the standard sample spectrogram and the measured sample spectrogram to obtain a standard sample net spectrogram and a measured sample net spectrogram;
c, filtering the pure spectrogram of the standard sample and the pure spectrogram of the measured sample to obtain a filter spectrogram of the standard sample and a filter spectrogram of the measured sample;
d, performing linear interpolation on the standard sample filtering spectrogram and the measured sample filtering spectrogram to obtain a standard sample interpolation spectrogram and a measured sample interpolation spectrogram;
e, performing local weighted regression smoothing on the standard sample interpolation spectrogram and the measured sample interpolation spectrogram to obtain a standard sample weighted spectrogram and a measured sample weighted spectrogram;
f, performing peak value fitting on the standard sample weighted spectrogram and the measured sample weighted spectrogram to obtain a standard sample fitting spectrogram and a measured sample fitting spectrogram;
step g, calculating potassium element peak areas in a standard sample fitting spectrogram and a measurement sample fitting spectrogram, obtaining a potassium element quantitative analysis vector coefficient according to the potassium element peak areas of the standard sample fitting spectrogram, and calculating the potassium element content of the measurement sample according to the potassium element quantitative analysis vector coefficient and the potassium element peak areas of the measurement sample fitting spectrogram;
and h, calculating the peak areas of the phosphorus elements in the standard sample fitting spectrogram and the measured sample fitting spectrogram, obtaining a quantitative analysis vector coefficient of the phosphorus elements according to the peak areas of the phosphorus elements in the standard sample fitting spectrogram, and calculating the content of the phosphorus elements in the measured sample according to the quantitative analysis vector coefficient of the phosphorus elements and the peak areas of the phosphorus elements in the measured sample fitting spectrogram.
Further, the step a specifically includes: respectively manufacturing a plurality of standard soil samples and soil samples to be detected into sample cups with consistent dryness, consistency and area thickness, covering a Mylar film above the sample cups as a detection window, irradiating X rays to the detection window, and detecting the X rays through a detection head to obtain an original spectrogram of the standard sample and an original spectrogram of the measured sample.
Further, in step b, the baseline subtraction is performed by a second-order decaying exponential function fitting method.
Further, the filtering process is performed by analyzing a power spectrum window function formula as follows:
further, the step g comprises the following steps:
step g 1: and deducting the calcium interference area in the potassium peak area according to the proportional coefficient, and obtaining the content of the potassium according to the potassium peak area.
Further, the step g1 includes: the integrated potassium area is calculated by the integrated potassium area formula:
K * ＝Ag measuring +K Measuring +10Ag Comprises ；
Wherein Ag is Measuring Is the corresponding peak of Ag element after fittingIntegral area, K Measuring The integrated area of the corresponding peak of K element after fitting, Ag Comprises In order to test the content of the Ag element in the soil sample, 10 is an empirical coefficient;
the integrated calcium area is calculated by the integrated calcium area formula:
Ca*＝Ca measuring -Sn Measuring -0.2k*；
Wherein Ca Measuring Is the integral area of the corresponding peak of Ca element after fitting, Sn Measuring The integral area of the peak corresponding to the fitted Sn element is represented by K, K is the comprehensive K area obtained by the formula, 0.2 is an empirical coefficient, and the product represents K of the K element β Interference caused by wires;
constructing a linear equation set according to the comprehensive potassium area and the comprehensive calcium area of the fitting spectrogram of the standard sample and the potassium content in the standard sample, and obtaining a quantitative potassium analysis vector coefficient according to the linear equation set;
and multiplying the potassium element quantitative analysis vector coefficient serving as the column vector by the comprehensive potassium area, the comprehensive calcium area and the row vector consisting of 1 of the fitting spectrogram of the measurement sample to obtain the content of the potassium element in the measurement sample.
Further, step g 2: and (4) deducting the peak area of the zirconium element in the peak area of the phosphorus element, and obtaining the content of the phosphorus element according to the peak area of the phosphorus element.
Further, the step g2 includes:
deducting the peak area of a zirconium element in the peak area of a phosphorus element of a fitting spectrogram of a standard sample, constructing a linear equation set according to the peak area of the phosphorus element, the peak area of the zirconium element and the content of the phosphorus element in the standard sample, and obtaining a quantitative analysis vector coefficient of the phosphorus element according to the linear equation set;
and obtaining the content of the phosphorus element in the measurement sample according to the product of the quantitative analysis vector coefficient of the phosphorus element as a column vector and a row vector formed by the peak area of the phosphorus element in the measurement sample, the peak area of the zirconium element and 1.
The invention has the following advantages:
the method and the system can realize rapid and semi-quantitative analysis among different soil matrixes and realize rapid and quantitative analysis in similar soil matrix samples. The method has good applicability to fertilizer efficiency detection of large-area cultivated land.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary and that other implementation drawings may be derived from the provided drawings by those of ordinary skill in the art without inventive effort.
The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so that those skilled in the art can understand and read the present invention, and do not limit the conditions for implementing the present invention, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the functions and purposes of the present invention, should still fall within the scope of the present invention.
FIG. 1 is a schematic structural diagram of an EDXRF soil potassium and phosphorus content detection system provided by the invention;
FIG. 2 is a schematic diagram of an excitation source according to the present invention;
FIG. 3 is a schematic structural diagram of an X-ray filtering collimator provided by the present invention;
FIG. 4 is a schematic structural diagram of a controller provided in the present invention;
FIG. 5 is a schematic diagram of the high-low voltage power supply and peripheral devices provided by the present invention;
FIG. 6 is a spectrum of a sample obtained from the test of example 7 of the present invention;
FIG. 7 is a baseline-subtracted spectrum obtained from the test of example 7 provided in the present invention;
FIG. 8 is a graph of a filtered spectrum obtained from the test of example 7 provided by the present invention;
FIG. 9 is a graph of the weighted regression smoothed spectrum obtained from the test of example 7 provided by the present invention;
FIG. 10 is a spectrum of a test of example 7 according to the present invention after peak fitting
In the figure:
1. an excitation source; 2. an X-ray filtering collimator; 3. a detector; 4. a controller; 5. high and low voltage power supplies and peripheral devices; 6. a computer; 7. a sample stage;
101. an X-ray tube; 102. a power source; 103. a high voltage anode; 104. a target material; 105. a filament; 106. a high voltage cathode; 107. a high voltage monitoring meter; 108. a filament current monitoring meter; 109. an aluminum alloy radiation shielding head; 110. x-rays; 111. a beryllium window; 112. an electron beam;
201. a filter; 202. an X-ray collimating aperture; 203. a circular fixing sheet; 204. a motor; 205. a gear; 206. a filter;
401. a differentiating circuit; 402. a hold sampling circuit; 403. an analog-to-digital converter; 404. a level matching circuit; 405. a removable storage medium; 406. a main control chip; 407. a non-volatile memory; 408. a power management module; 409. a type-c interface; 410. a Bluetooth module; 411. a WiFi module;
501. a direct current power supply; 502. a high voltage conversion module; 503. a power supply chip; 504. a power isolation mechanism; 505. an X-ray tube power output module; 506. an X-ray tube signal input module; 507. a detector power supply; 508. a controller power supply output module; 509. a control signal input module; 510. and a voltage reduction power supply.
Detailed Description
The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
As shown in fig. 1, the present embodiment provides an EDXRF soil potassium and phosphorus content detection system, which is characterized in that the EDXRF soil potassium and phosphorus content detection system includes an excitation source 1, an X-ray filter collimator 2, a detector 3, a controller 4, a high-low voltage power supply and peripheral devices 5, a computer 6 and a sample stage 7; the excitation source 1 is connected with the high-low voltage power supply and peripheral devices 5 and emits X rays towards the sample stage 7, the X ray filtering collimator 2 is arranged between the excitation source 1 and the sample stage 7 to realize the collimation and filtering of the X rays, the high-low voltage power supply and peripheral devices 5 are connected with the controller 4, the controller 4 is connected with the detector 3 and the computer 6, and the detector 3 faces the sample stage 7 to detect the X rays from the sample stage 7.
In the embodiment, an excitation source 1 emits X-rays to a sample stage 7, the X-rays are filtered and collimated by an X-ray filtering collimator 2 and then enter a soil sample on the sample stage 7, the X-rays are reflected by the soil sample and then detected by a detector 3, and then the X-rays are transmitted to a computer 6 through a controller 4 for processing. The controller simultaneously sends control signals to the high-low voltage power supply and peripheral devices 5 and the detector 3, and the control signals of the high-low voltage power supply and peripheral devices 5 are sent to the excitation source 1 to emit X rays. The system of the embodiment can realize rapid and semi-quantitative analysis among different soil matrixes and realize rapid and quantitative analysis in similar soil matrix samples. The method has good applicability to fertilizer efficiency detection of large-area cultivated land.
Example 2
As shown in fig. 2, the excitation source 1 includes an X-ray tube 101, a power source 102, a high voltage anode 103, a target 104, a filament 105, a high voltage cathode 106, and an aluminum alloy ray shielding head 109, the power source 102 is disposed at a tail end of the X-ray tube 101, an X-ray outlet is disposed at a head end of the X-ray tube 101, the high voltage anode 103, the target 104, and the high voltage cathode 106 are sequentially disposed between the X-ray outlet and the power source 102, two filaments 105 are disposed in the high voltage cathode 106, the two filaments 105 are respectively disposed in the X-ray tube 101 at two sides of the X-ray outlet to emit an electron beam 112 toward the target 104, a positive electrode of the power source 102 is connected to the high voltage anode 103, a negative electrode of the power source 102 is connected to the high voltage cathode 106, the aluminum alloy ray shielding head 109 is disposed at an outer side of the X-ray tube 101 and is provided with a beryllium window 110 through which the X-ray 111 is emitted from the X-ray outlet, the power supply 102 is provided with a control interface.
This example provides a specific embodiment of an excitation source 1. When the X-ray tube is used specifically, power is supplied to the high-voltage anode 103 and the high-voltage cathode 106 of the X-ray tube 101 through the power supply 10, the filament 105 of the high-voltage cathode 106 emits high-speed electrons to the target 104 of the high-voltage anode 103, the target 104 is bombarded by the electrons, the high-speed electrons reach the target surface, the movement is suddenly stopped, a small part of kinetic energy of the high-speed electrons is converted into radiation energy and is emitted in the form of X-rays, and then the radiation energy is output outwards through the beryllium window 110 of the aluminum alloy ray shielding head 109. The excitation source 1 is arranged in a compact manner and has stable emission of X-rays.
Example 3
As shown in fig. 2, the EDXRF soil potassium and phosphorus content detection system further includes a high voltage monitoring meter 107 and a filament current monitoring meter 108, the high voltage monitoring meter 107 is connected to the power supply 102, the high voltage anode 103 and the high voltage cathode 106, and the filament current monitoring meter 108 is connected to the power supply 102 and the filament 105.
In the embodiment, the current and voltage conditions inside the excitation source 1 are monitored by the high voltage monitoring meter 107 and the filament current monitoring meter 108, so that the instrument is prevented from being burnt out due to excessive current and voltage.
Example 4
As shown in fig. 3, X-ray filtering collimator 2 includes filter 201 and the X-ray collimating aperture 202 of control X-ray export size, filter 201 includes circular stationary blade 203, six filters 206, motor 204 and gear 205, set up six windows along the circumference interval in the circular stationary blade 203, six filters 206 set up respectively in six windows, circular stationary blade 203 periphery is provided with the meshing tooth, gear 205 cover is established in motor 204 pivot periphery, gear 205 rotates with the meshing tooth meshing in order to drive circular stationary blade 203, X-ray collimating aperture 202 is located the light-emitting direction of a window, the material of six filters 206 is Al, Cu, Ti, Ag, AlCu and mylar (blank) respectively.
The present embodiment provides a specific form of a filtering collimator. The filtering collimator has a filtering function and a collimating function, and solves the problem of unmatched original level spectrums. According to the needs of different measurements, can set up different filters, for the switching between the filters, can drive the rotation that gear 205 drove circular stationary blade 203 through motor 204, and then drive the switching of six filters, it need not to explain, circular stationary blade 203 has the pivot, for example, the filter locks in the light window sub-window of circular stationary blade 203 with screw thread buckle is tight, add the tungsten alloy packing ring and prevent wearing and tearing, adopt 12 pages of sub-meshing piece spiral control on the other hand, how much of emergent X-ray volume is relied on in the collimation of X-ray, this embodiment is applied to the collimator with the diaphragm. The aperture is a device for controlling the quantity of light rays which penetrate through the lens and enter the photosensitive surface in the machine body, and can also be arranged in the X-ray emergent direction to control the quantity of emergent X-rays, for example, the size of a collimation outlet can be controlled by utilizing a transmission mechanism according to the angle of phase difference between the laminated layers to determine the collimation direction and the divergence angle. The X-ray filtering collimator 2 of the embodiment has less X-ray clutter for collimation and filtering and high imaging efficiency.
Example 5
As shown in fig. 4, the controller 4 includes a first circuit board, a differential circuit 401, a holding and sampling circuit 402, an analog-to-digital converter 403, a level matching circuit 404, a removable storage medium 405, a main control chip 406, a non-volatile memory 407, a power management module 408, a type-c interface 409, a bluetooth module 410 and a WiFi module 411, the differential circuit 401, the holding and sampling circuit 402, the analog-to-digital converter 403, the level matching circuit 404, the removable storage medium 405, the main control chip 406, the non-volatile memory 407, the power management module 408, the type-c interface 409, the bluetooth module 410 and the WiFi module 411 are disposed on the first circuit board, the differential circuit 401, the holding and sampling circuit 402, the analog-to-digital converter 403 and the level matching circuit 404 are sequentially connected, and the main control chip 406 is connected to the non-volatile memory 407, the power management module 408, the type-c interface 409, the WiFi module 411 and the level matching circuit 404, The bluetooth module 410 and the WiFi module 411, the main control chip 406 is connected with the controller 4, the high-low voltage power supply and peripheral device 5, and the computer 6.
The present embodiment provides a specific structure of the controller. The controller can send the X-ray of the detector 3 to the computer, and can also control the detector 3 and the excitation source 1 to amplify, shape, sample, convert, record and send the electric pulse. The differential circuit can convert a rectangular wave into a sharp pulse wave, the holding and sampling circuit can track or hold a level value of an input analog signal, the analog-to-digital converter refers to an electronic element for converting the analog signal into a digital signal, the level matching circuit realizes that the levels of front and back two-stage input and output of the circuit are the same or similar, a mobile storage medium can copy and take away data, such as a U disk or a hard disk, a nonvolatile memory (EMMC) is a memory for preventing the stored data from disappearing after the current is turned off, and the power management module effectively distributes power to different components of the system. The modules of the embodiment can adopt the existing modules and can be integrated together.
And the detector part is responsible for converting the rays into step-up voltage signals. In this example, VITUS H3040 mm, KETEK, Germany, was used 2 The SDD detector is matched with a front-end amplifier of an integrated front-end ASIC chip, and has the resolution of minimum 129eV, the peak-to-back ratio of more than 15000 and the counting rate of 2000 kcps. Under the condition of good cooling, the peak forming time is as small as 1us, and an 8um beryllium window is configured, so that the detection sensitivity is improved to the maximum extent, and the stray wave interference is reduced.
Example 6
As shown in fig. 5, the high-voltage and low-voltage power supply and peripheral device 5 includes a second circuit board, a dc power supply 501, a high-voltage conversion module 502, a power chip 503, a power isolation mechanism 504, an X-ray tube power output module 505, an X-ray tube signal input module 506, a detector power 507, a controller power output module 508, a control signal input module 509, and a step-down power supply 510, where the dc power supply 501, the high-voltage conversion module 502, the power chip 503, the power isolation mechanism 504, the X-ray tube power output module 505, the X-ray tube signal input module 506, the detector power 507, the controller power output module 508, the control signal input module 509, and the step-down power supply 510 are disposed on the second circuit board, the dc power supply 501 is connected to the high-voltage conversion module 502, the high-voltage conversion module 502 is connected to the power chip 503, and the power chip 503 is connected to the X-ray tube power output module 505, the step-down power supply 510, The power isolation mechanism 504 is used for isolating the direct current power supply 501, the step-down power supply 510, the detector power supply 507, the X-ray tube power supply output module 505 and the controller power supply output module 508.
The high and low voltage power supply and peripherals 5 of this embodiment are used to deliver power to the controller 4, excitation source 1 and detector 3 by converting external high voltage power to low voltage power and then distributing the power by communicating with the controller 4, excitation source 1 and detector, and power isolation mechanism 504 is used to isolate the power supplies from each other. Specifically, the power supply is powered by a DC-DC power supply, the total power is designed to be DC-DC 12V30W, and the configuration circuit supplies power supplies in different ranges of modulus 1.8V, digital 3.3V, direct current 12V, analog +/-5V, direct current-168V high-voltage small power and the like to the respective areas.
Example 7
The present embodiment provides a detection method using the inventive system.
(1) Experimental Material
4 national standard soil samples GSS-2, GSS-3, GSS-14 and GSS-21. Table 1 shows the K, P contents of two elements in four national standards of soil.
(2) Laboratory apparatus
The EDXRF soil potassium and phosphorus content detection system has the structure shown in figure 1. The device comprises an excitation source 1, an X-ray filtering collimator 2, a detector 3, a controller 4, a high-low voltage power supply and peripheral devices 5, a computer 6 and a sample stage 7.
The X-ray filtering collimator adopts 6 position variable filters including Al, Cu, Ti, Ag, AlCu and Mylar film (blank). The optical filter is locked in the variable light window by a thread buckle, and a tungsten alloy gasket is added to prevent abrasion. The 12-leaf meshing sheet is adopted for spiral control, and the size of the collimation outlet is controlled by a transmission mechanism according to the angle of the phase difference between the laminated layers, so that the collimation direction and the divergence angle are determined.
The detector is VITUS H3040 mm KETEK Germany 2 SDD detector using integrated front-end ASIC chipFront end amplifier, detector with minimum resolution of 129eV and peak to back ratio of more than 15000, count rate of 2000 kcps. Under the condition of good cooling, the peak forming time is as small as 1us, and an 8um beryllium window is configured, so that the detection sensitivity is improved to the maximum extent, and the stray wave interference is reduced.
The power supply is powered by a DC-DC power supply, the total power is designed to be DC-DC 12V30W, and the configuration circuit supplies power supplies in different ranges of 1.8V modulus, 3.3V digital, 12V DC, 5V analog, 168V high-voltage low power and the like to respective areas. The basic configuration parameters for the experimental measurements are shown in table 2.
(3) Spectrogram range selection
The tube voltage of the X-ray tube is 50kV, the soil elements are various, the fluorescence spectrum range is quite large, and the distribution is from 1.5keV to 40 keV. In this embodiment, the analysis of the content of potassium and phosphorus elements starts from K-series spectral lines of two elements, and the spectral line distribution and the possible influence range are between 1.7keV and 4keV, so the analysis and operation processing is emphasized on the spectral lines in this region.
(4) National standard soil measurement
And respectively manufacturing the national standard soil samples into sample cups with consistent dryness, consistency and area and thickness, and covering a Maillard film on the sample cups to serve as a detection window. The detection head is accurately aligned, compaction measurement is carried out, the single measurement time is 180 seconds, and the measured spectral line is shown in figure 6.
(5) Baseline subtraction
The XRF spectrum of soil has a definite trend, which is composed of the combination of various elements in soil, such as Si, Al, etc., and is generally in a steady state. The spectral lines can thus be processed by a baseline subtraction method to yield a net spectral line, thereby reducing the interference of the relevant elements. Determining a base line by a multi-point calibration fitting line mode, selecting 20 base line positioning points after multiple tests, and fitting by using a second-order attenuation exponential function (ExpDec 2). The parameters are shown in table 3. The baseline subtraction of the measured lines for the four soil samples is shown in FIG. 7.
(6) Window filtering
Considering that the corresponding elements of the wave band are rich in types, the energy value is consistent, 18 elements are contained in the soil, each element generates a plurality of spectral lines such as K series and L series, and the total number of the spectral lines exceeds 60. Elemental or compound analysis allows full spectral analysis, but it is clearly impractical to analyze over 60 lines with significant overlap in such complex mixtures, and can only be processed and analyzed specifically.
To obtain spectral lines with less interference, filtering is performed on the spectral lines. Through a large number of experiments, the content of the P element is mainly influenced by K of Zr (zirconium) element positioned at the right side of the potassium element α Line interference, L in which K is mainly represented by Ag (silver) on the left β Line, right side L of Sn (tin) element α Wire and K of Ca (calcium) element with large content α Line interference. Therefore, for the distribution range of the element characteristic spectral lines, considering that the spectral line distribution is mostly a Gaussian curve, the formula (1) is a formula for selecting an analysis energy window function.
The resulting window filter pattern and filter effect are shown in fig. 8.
After filtering by adopting the filter, K except Zr element α L of wire, Ag element β Wire, L of Sn element α K of thread, Ca element α There will be some very low level of stray line interference outside the line.
(7) Linear interpolation
Since the spectral peaks of the selected region are generally composed of a few points or even one point. Abnormal peak and correlation coefficient R can appear when the spectral line with too few points is subjected to multimodal fitting 2 Too low a phenomenon. The curve to be fitted is therefore linearly interpolated prior to fitting. The area of the peak intensity peak of the image after interpolation and the area of the peak intensity peak before interpolation do not have any change, but the calculation resolution is higher.
(8) Locally weighted regression smoothing
Subsequently, a gaussian function is used to perform peak fitting solution. The peak of the gaussian function is a smooth curve, but the peak of the spectral line is not generally a smooth curve due to interference of the remaining low-content elemental clutter lines after filtering and the limitation of the resolution of the probe. Such a curve will interfere with the fitting result when fitting. Therefore, the local weighted regression method is used for smoothing the spectral line, and the curve smoothing particle size span value is 0.01. Fig. 9 shows the spectral lines after local weighted regression smoothing, and it can be seen that smoothing with good effect is achieved under the condition that the peak positions of the spectral lines have no great change.
(9) Peak fitting
Peak fitting needs to accurately identify spectral lines and interference, and some spectral lines need to be accurately identified due to the phenomenon of red shift or blue shift of 40eV caused by spectral line scattering and the like. In the fitting process, the fitting boundary needs to be limited, the error between the fitting peak position and the actual peak position is ensured to be less than 0.01keV, the half-height width and the area deviation range are allowed to be adaptive, the fitting direction is upward fitting, and the weight value is not matched. Figure 10 is a comparison of the peaks and combined lines after fitting. GSS-2 correlation coefficient R after fitting 2 0.9959, GSS-3 correlation coefficient R 2 0.9940, GSS-14 correlation coefficient R 2 0.9768, GSS-21 correlation coefficient R 2 Is 0.9964. 4 the spectral curves of the soil samples realize extremely accurate fitting matching.
(10) Product calculation and element value solution
After peak fitting, the spectral line of each soil sample is divided into superposition of 6 small single-peak Gaussian curves, and the peak area of each peak represents the element content at the position. The integral calculation was performed according to the area of the single peak, and the peak areas of 6 peaks were obtained.
L of Ag element whose K element is mainly left β Line, L of Sn element on right side α Wire and K of Ca element with large content α Line interference. After peak fitting decoupling, interference of Sn element and Ag element is basically eliminated, but the variation range of Ca element is large, and the influence is large. Therefore, the interference caused by Ca element needs to be deducted from the peak area of K element according to a certain proportionality coefficient. According to a large number of experiments, interference factors are removed, and the comprehensive potassium area K and the comprehensive calcium area Ca are obtained.
The integrated potassium area formula:
K*＝Ag measuring +K Side survey +10Ag Comprises # (2)
Wherein Ag is Measuring The integral area of the corresponding peak of the fitted Ag element, K Measuring The integrated area of the corresponding peak of K element after fitting, Ag Comprises For testing the content of Ag element in the soil sample, 10 is an empirical coefficient.
The comprehensive calcium area formula is as follows:
Ca*＝Ca measuring -Sn Measuring -0.2k*# (3)
Wherein Ca Measuring Is the integral area of the corresponding peak of Ca element after fitting, Sn Measuring The integral area of the peak corresponding to the fitted Sn element is calculated, K is the comprehensive K area calculated by the formula, 0.2 is an empirical coefficient, and the product represents the K of the K element β Interference caused by wires (K of K element) β K of wire and Ca element α The lines substantially overlap). Table 4 shows the measured data and the calculated integrated area data.
And obtaining a linear equation set according to the comprehensive potassium area, the comprehensive calcium area and the element content information of the three kinds of soil, namely GSS-2, GSS-3 and GSS-21. The following is a linear system of equations in matrix form.
Obtaining by solution:
the product of vector formula (5) and vector formed by K, Ca and 1 corresponding to GSS-14 soil is used to calculate that the content of K element in GSS-14 soil is 28315.33, and the error is 15.1%
The content of the P element is mainly influenced by K of Zr (zirconium) element positioned at the right side of the K element α Line interference. The Zr element content in various soils is stable in the elemental analysis and calculation. Therefore, the calculation was performed by removing the peak area of the Zr element by a scaling factor using the entire area of the local region. Table 5 is a table of measurement data, local integral total area data.
Formula (6) is represented by the total area, Zr Measuring Constant ofItem 1 and P Comprises The system of linear equations is formed as follows:
obtaining by solution:
p of soil using vector formula (7) and GSS-14 Measuring 、Zr Measuring And the vector formed by the 1 is multiplied to obtain that the content of the GSS-14 soil P element is 915.72, and the error is 25.4%. The error is large, and the calculation mode is replaced. Using P Measuring ，Zr Measuring And P Comprises To form a system of linear equations:
obtaining by solution:
using the vector equations (9) and P Measuring 、Zr Side survey And the vector formed by the step 1 is multiplied to obtain that the content of the soil P element of the GSS-14 is 904.50, the error is 23.9 percent, and the accuracy is improved to a certain extent compared with the method.
As can be seen from the above, the quantitative analysis vector coefficients of K, P two elements are obtained by using three national standard soil samples of GSS-2, GSS-3 and GSS-21 and carrying out data processing such as baseline deduction, filtering, interpolation, smoothing, fitting and the like. And predicting the K, P element content of the national standard soil GSS-14 according to the quantitative analysis vector coefficient. The error of K element is 15.1%, and the error of P element is 23.9%. In the soil EDXRF detection method, rapid and semi-quantitative analysis can be realized among different soil matrixes, and rapid and quantitative analysis can be realized in similar soil matrix samples. The method has good applicability to fertilizer efficiency detection of large-area cultivated land.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Table 1: K. p element content meter
Table 2: measurement parameter table
Table 3: second order decay exponential function parameter table
Table 4: element-related measurement and integrated area data sheet
Table 5: p element measured value and local integral area data table
Claims (8)
1. The EDXRF soil potassium and phosphorus content detection method is characterized by comprising the following steps:
a, acquiring a plurality of standard sample original spectrograms of a plurality of standard soil samples and a measurement sample original spectrogram of a soil sample to be measured by an EDXRF soil potassium and phosphorus content detection system;
b, carrying out baseline deduction on the standard sample spectrogram and the measured sample spectrogram to obtain a standard sample net spectrogram and a measured sample net spectrogram;
c, filtering the pure spectrogram of the standard sample and the pure spectrogram of the measured sample to obtain a filter spectrogram of the standard sample and a filter spectrogram of the measured sample;
d, performing linear interpolation on the standard sample filtering spectrogram and the measured sample filtering spectrogram to obtain a standard sample interpolation spectrogram and a measured sample interpolation spectrogram;
e, performing local weighted regression smoothing on the standard sample interpolation spectrogram and the measured sample interpolation spectrogram to obtain a standard sample weighted spectrogram and a measured sample weighted spectrogram;
f, performing peak value fitting on the standard sample weighted spectrogram and the measured sample weighted spectrogram to obtain a standard sample fitting spectrogram and a measured sample fitting spectrogram;
step g, calculating potassium element peak areas in a standard sample fitting spectrogram and a measurement sample fitting spectrogram, obtaining a potassium element quantitative analysis vector coefficient according to the potassium element peak areas of the standard sample fitting spectrogram, and calculating the potassium element content of the measurement sample according to the potassium element quantitative analysis vector coefficient and the potassium element peak areas of the measurement sample fitting spectrogram;
step h, calculating the peak areas of phosphorus elements in a standard sample fitting spectrogram and a measured sample fitting spectrogram, obtaining a phosphorus element quantitative analysis vector coefficient according to the peak areas of the phosphorus elements in the standard sample fitting spectrogram, and calculating the content of the phosphorus elements in the measured sample according to the peak areas of the phosphorus elements in the phosphorus element quantitative analysis vector coefficient and the measured sample fitting spectrogram;
the step g specifically comprises:
the integrated potassium area is calculated by the integrated potassium area formula:
K * ＝Ag measuring +K Measuring +10Ag Comprises ；
Wherein Ag is Measuring The integral area of the corresponding peak of the fitted Ag element, K Measuring The integrated area of the corresponding peak of K element after fitting, Ag Comprises 10 is an empirical coefficient for testing the content of Ag element in the soil sample;
the integrated calcium area is calculated by the integrated calcium area formula:
Ca*＝Ca side survey -Sn Measuring -0.2k*；
Wherein Ca Side survey Is the integral area of the corresponding peak of Ca element after fitting, Sn Measuring The integral area of the peak corresponding to the fitted Sn element is represented by K, K is the comprehensive K area obtained by the formula, 0.2 is an empirical coefficient, and the product represents K of the K element β Interference caused by wires;
constructing a linear equation set according to the comprehensive potassium area and the comprehensive calcium area of the fitting spectrogram of the standard sample and the potassium content in the standard sample, and obtaining a quantitative potassium analysis vector coefficient according to the linear equation set;
and multiplying the potassium element quantitative analysis vector coefficient serving as the column vector by the comprehensive potassium area, the comprehensive calcium area and the row vector consisting of 1 of the fitting spectrogram of the measurement sample to obtain the content of the potassium element in the measurement sample.
2. The EDXRF soil potassium and phosphorus content detection method as recited in claim 1, wherein said step a specifically comprises: respectively manufacturing a plurality of standard soil samples and soil samples to be detected into sample cups with consistent dryness, consistency and area thickness, covering a Mylar film above the sample cups as a detection window, irradiating X rays to the detection window, and detecting the X rays through a detection head to obtain an original spectrogram of the standard sample and an original spectrogram of the measured sample.
3. The EDXRF soil potassium and phosphorus content detection method as claimed in claim 1, wherein in step b, the baseline subtraction is performed by a second order decay exponential function fitting method.
4. The EDXRF soil potassium and phosphorus content detection method according to claim 1, wherein the filtering is performed by an analysis energy spectrum window function formula as follows:
5. the method for detecting the content of potassium and phosphorus in EDXRF soil according to claim 1, wherein the steps of g 2: and (4) deducting the peak area of the zirconium element in the peak area of the phosphorus element, and obtaining the content of the phosphorus element according to the peak area of the phosphorus element.
6. The EDXRF soil potassium and phosphorus content detection method as claimed in claim 5, wherein said step g2 includes:
deducting the peak area of a zirconium element in the peak area of a phosphorus element of a fitting spectrogram of a standard sample, constructing a linear equation set according to the peak area of the phosphorus element, the peak area of the zirconium element and the content of the phosphorus element in the standard sample, and obtaining a quantitative analysis vector coefficient of the phosphorus element according to the linear equation set;
and obtaining the content of the phosphorus element in the measurement sample according to the product of the quantitative analysis vector coefficient of the phosphorus element as a column vector and a row vector formed by the peak area of the phosphorus element in the measurement sample, the peak area of the zirconium element and 1.
7. The EDXRF soil potassium and phosphorus content detection method as claimed in claim 1, characterized in that, the EDXRF soil potassium and phosphorus content detection system comprises an excitation source (1), an X-ray filtering collimator (2), a detector (3), a controller (4), a high-low voltage power supply and peripheral devices (5), a computer (6) and a sample stage (7); the excitation source (1) is connected with the high-low voltage power supply and peripheral devices (5) and emits X rays towards the sample stage (7), the X ray filtering collimator (2) is arranged between the excitation source (1) and the sample stage (7) to achieve collimation and filtering of the X rays, the high-low voltage power supply and peripheral devices (5) are connected with the controller (4), the controller (4) is connected with the detector (3) and the computer (6), and the detector (3) faces the sample stage (7) to detect the X rays from the sample stage (7).
8. The EDXRF soil potassium and phosphorus content detection method according to claim 7, characterized in that said excitation source (1) comprises an X-ray tube (101), a power supply (102), a high voltage anode (103), a target (104), a filament (105), a high voltage cathode (106), and an aluminum alloy ray shielding head (109), said power supply (102) is disposed at the tail end of said X-ray tube (101), the head end of said X-ray tube (101) is provided with an X-ray outlet, said high voltage anode (103), target (104) and high voltage cathode (106) are sequentially disposed between the X-ray outlet and the power supply (102), two said filaments (105) are disposed in said high voltage cathode (106), and two said filaments (105) are respectively disposed in the X-ray tube (101) at two sides of said X-ray outlet to emit electron beams (112) to said target (104), the positive electrode of said power supply (102) is connected to said high voltage anode (103), the cathode of the power supply (102) is connected with the high-voltage cathode (106), the aluminum alloy ray shielding head (109) is arranged on the outer side of the X-ray tube (101) and is provided with a beryllium window (110) for emitting X-rays (111) through an X-ray outlet, and the power supply (102) is provided with a control interface; the EDXRF soil potassium and phosphorus content detection system further comprises a high-voltage monitoring meter (107) and a filament current monitoring meter (108), wherein the high-voltage monitoring meter (107) is connected with the power supply (102), the high-voltage anode (103) and the high-voltage cathode (106), and the filament current monitoring meter (108) is connected with the power supply (102) and the filament (105); the X-ray filtering collimator (2) comprises an optical filter (201) and an X-ray collimating aperture (202) for controlling the size of an X-ray outlet, wherein the optical filter (201) comprises a circular fixing sheet (203), six filter sheets (206), a motor (204) and a gear (205), six windows are formed in the circular fixing sheet (203) along the circumferential interval, the six filter sheets (206) are respectively arranged in the six windows, meshing teeth are arranged on the periphery of the circular fixing sheet (203), the gear (205) is sleeved on the periphery of a rotating shaft of the motor (204), the gear (205) is meshed with the meshing teeth to drive the circular fixing sheet (203) to rotate, the X-ray collimating aperture (202) is located in the light-emitting direction of one window, and the six filter sheets (206) are respectively made of Al, Cu, Ti, Ag, AlCu and Mylar films; the controller (4) comprises a first circuit board, a differential circuit (401), a holding and sampling circuit (402), an analog-to-digital converter (403), a level matching circuit (404), a mobile storage medium (405), a main control chip (406), a nonvolatile memory (407), a power management module (408), a type-c interface (409), a Bluetooth module (410) and a WiFi module (411), wherein the differential circuit (401), the holding and sampling circuit (402), the analog-to-digital converter (403), the level matching circuit (404), the mobile storage medium (405), the main control chip (406), the nonvolatile memory (407), the power management module (408), the type-c interface (409), the Bluetooth module (410) and the WiFi module (411) are arranged on the first circuit board, and the differential circuit (401), the holding and sampling circuit (402), the analog-to-digital converter (403) and the WiFi module (411) are arranged on the first circuit board, The level matching circuit (404) is connected in sequence, the main control chip (406) is connected with a nonvolatile memory (407), a power management module (408), a type-c interface (409), a Bluetooth module (410) and a WiFi module (411), and the main control chip (406) is connected with the controller (4), the high-low voltage power supply and peripheral devices (5) and the computer (6); the high-low voltage power supply and peripheral device (5) comprises a second circuit board, a direct current power supply (501), a high-voltage conversion module (502), a power chip (503), a power isolation mechanism (504), an X-ray tube power output module (505), an X-ray tube signal input module (506), a detector power supply (507), a controller power output module (508), a control signal input module (509) and a voltage reduction power supply (510), wherein the direct current power supply (501), the high-voltage conversion module (502), the power chip (503), the power isolation mechanism (504), the X-ray tube power output module (505), the X-ray tube signal input module (506), the detector power supply (507), the controller power output module (508), the control signal input module (509) and the voltage reduction power supply (510) are arranged on the second circuit board, and the direct current power supply (501) is connected with the high-voltage conversion module (502), the high-voltage conversion module (502) is connected with the power supply chip (503), the power supply chip (503) is connected with the X-ray tube power supply output module (505), the X-ray tube signal input module (506), the detector power supply (507), the controller power supply output module (508), the control signal input module (509) and the voltage reduction power supply (510), and the power supply isolation mechanism (504) isolates the direct current power supply (501), the voltage reduction power supply (510), the detector power supply (507), the X-ray tube power supply output module (505) and the controller power supply output module (508).
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