CN108872199A - The rapid detection method of soil magnesium elements based on conllinear double-pulse laser induced breakdown spectrum - Google Patents
The rapid detection method of soil magnesium elements based on conllinear double-pulse laser induced breakdown spectrum Download PDFInfo
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Abstract
The invention discloses a kind of rapid detection methods of soil magnesium elements based on conllinear double-pulse laser induced breakdown spectrum, including：Contain the soil sample of N number of magnesium density than mixed method preparation by multiple standards soil and its two-by-two etc.；Then the instrument parameter of dipulse LIBS system is optimized, and acquires the LIBS spectral line of soil tabletting sample；To spectroscopic data after pretreatment, select Mg I 277.98nm, Mg I 280.22nm, Mg I 285.21nm, Mg I 518.36nm, the signal at Mg I 552.84nm as input value, magnesium elements concentration is as output valve in sample, the Multivariable regressive analysis model of soil sample content of magnesium prediction is established, predicts coefficient of determination R2Reach 0.922.The present invention realizes the quick detection of magnesium in soil constituent content, has the features such as easy to operate, at low cost；Simultaneously because the signal enhancing effect of conllinear dipulse, the detection accuracy of this method is higher, can provide reference to develop portable soil magnesium element content detecting instrument.
Description
Technical field
The present invention relates to soil nutrient elements detection techniques more particularly to a kind of induced with laser based on conllinear dipulse to hit
Wear the rapid detection method of the soil magnesium elements of spectrum.
Background technique
Soil nutrient elements are able to reflect the fertility of soil, influence crop yield and quality.Wherein, magnesium elements can promote to make
The synthesis of object Determination of Chlorophyll and protein.The too low growth and development that will affect crop of soil content of magnesium, too high levels will cause money
Source waste causes soil nutrient distribution unbalance.Therefore, to the quantitative detection of magnesium in soil element for plant growth and soil matter
Amount monitoring has great significance.Currently, the method that predominantly detects of magnesium in soil element has an atomic absorption method, inductive coupling etc. from
Daughter mass spectrography, the chemical detection methods such as inductively coupled plasma atomic emission spectrometry, although these methods examine accuracy
Height, but need to consume chemical reagent and resolution processing is carried out to sample, height is required to the professional degree of operator, detection process is multiple
It is miscellaneous, the period is longer, cannot achieve the efficient, accurate of soil magnesium elements, real-time detection.
Laser induced breakdown spectrograph (Laser-Induced Breakdown Spectroscopy, LIBS) utilizes pulse
Laser ablation sample generates the specific spectral signal of plasma emission, passes through the light for the plasma emission that spectrometer obtains
The analysis of element composition and content in sample may be implemented in spectrum.But the problem of the higher always LIBS technology of Element detection limit.
Therefore, LIBS Signal Enhanced Technology becomes the focus of domestic and foreign scholars.LIBS signal enhancing skill based on conllinear dipulse
Art is that current effect is preferable, using more one of Signal Enhanced Technology.Using conllinear double-pulse laser induced breakdown spectrum skill
Art can fast and accurately obtain soil content of magnesium, be conducive to plant growth and Soil quality monitoring.
Summary of the invention
The invention discloses a kind of rapid detection method of soil nutrient elements, realizes and lured based on conllinear double-pulse laser
Quick detection of the breakdown spectral to soil magnesium elements is led, there is the features such as easy to operate, testing cost is low, and accuracy is high.
The specific technical solution of the present invention is as follows：
A kind of rapid detection method of the soil magnesium elements based on conllinear double-pulse laser induced breakdown spectrum, including step
Suddenly：
1) soil sample containing magnesium of N number of gradient is made, and press sheet compression is made, magnesium elements concentration is denoted as Y in sample；
2) using the LIBS spectroscopic data X of double-pulse laser acquisition soil sample containing magnesium；
3) magnesium elements pair are found out in conjunction with wavelength and the one-to-one relationship of element according to LIBS spectroscopic data X data and curves
The wavelength answered；
4) LIBS spectroscopic data X is pre-processed, pretreated data be X1, extracted in X1 in step 3)
The corresponding spectroscopic data X2 of magnesium elements wavelength；Gained spectroscopic data (X2, Y) is pressed 2 using X-Y co-occurrence matrix method:1 ratio is drawn
It is divided into modeling collection and forecast set；
5) respectively to model the X2 concentrated as input, Y is to export, establish in soil sample magnesium elements concentration with it is corresponding
The multivariate linear regression analysis model of LIBS the intensity of spectral line：
Y=-0.0006X1-0.0007X2+0.006X3-0.0016X4+0.0034X5+2.8904
Wherein, Y is the actual content of magnesium elements in sample, and X1, X2, X3, X4, X5 are respectively corresponding with magnesium elements
The signal strength of 277.98nm, 280.22nm, 285.21nm, 518.36nm, 552.84nm；
The Quantitative Analysis Model that X2 in forecast set is brought into foundation obtains the prediction concentrations of magnesium elements in sample.
In step 1), it is mixed with the soil sample containing magnesium using weight such as different soils, magnesium in soil element
Concentration is respectively：15.48mg·g-1、15.66mg·g-1、6.96mg·g-1、11.94mg·g-1、11.22mg·g-1、
16.50mg·g-1。
In the technical program, six kinds of soil of preparation soil sample containing magnesium are respectively Inner Mongol Hangjin Rear Banner saline-alkali soil
(GBW07447), Zhejiang Province Xiangshan East Sea Tidal Flat Sediments (GBW7452), Yangjiang city's South Beach deposit
(GBW7453), Shaanxi Province's Luochuan Loess (GBW7454), Anhui Wu He Sediments from Huaihe River (GBW7455), Jiangsu Province Zhangjiagang are clear
River deposit (GBW7456).
In step 1), soil sample containing magnesium is made to the rectangular press sheet compression of equal-specification, every tablet quality is 0.5g, each
Gradient prepares 3 tabletting samples.
In step 2), the parameter of laser induced breakdown spectrograph is optimized, obtained optimized parameter is：First beam
Laser energy is 25mJ；Second beam laser energy is 75mJ；Optical maser wavelength is 532nm；Delay time is 6us；The time of integration is
10us, pulse spacing 1.2us.Under the conditions of optimized parameter, the average signal-to-noise ratio of 5 spectral line single pulse signals of magnesium elements in sample
(ratio of signal and noise) is minimum to have reached 59.16, and the average signal-to-noise ratio of dipulse signal is minimum to have reached 113.71, signal
It can obviously be distinguished with noise.
In step 4), noise reduction process is carried out using small wave converting method, small echo odd function is db4, and the number of plies is set as 3.
In step 4), sample is divided using SPXY method.First all samples are all regarded as when specific method
Modeling collects candidate samples, is then collected using two farthest vectors of the method choice Euclidean distance of iteration to modeling is entered, until
Select required number of samples.Its range formula is as follows：
Wherein, dxy(m, n) is Euclidean distance, dx(m, n) is spectrum intervals, dy(m, n) is physicochemical property characteristic distance.
The present invention uses SPXY method when sample divides, while considering the spectral signature and physicochemical property feature of sample,
The predictive ability of model can be improved.
In step 5), according to the characteristic wavelength that U.S.'s NIST atomic spectra database and pilot system are demarcated, for building
The characteristic spectral line of the magnesium elements of formwork erection type is：Mg I 277.98nm,Mg I 280.22nm,Mg I 285.21nm,Mg I
518.36nm、Mg I 552.84nm。
Compared with the existing technology, the invention has the advantages that：
(1) quantitative detection of soil magnesium elements is realized.
(2) detection of soil magnesium elements is carried out using the LIBS technology based on conllinear dipulse, there is easy to operate, cost
The features such as low, quickly, efficiently and accurately.It is complicated effectively to overcome traditional detection method program, higher cost is big etc. to sample broke
Disadvantage.
(3) representative magnesium elements wavelength has been selected, the exploitation of portable sensor instrument is conducive to.
Detailed description of the invention
Fig. 1 is the Multivariable regressive analysis model prediction result of soil sample magnesium elements concentration.
Specific embodiment
Below with reference to specific implementation case and Detailed description of the invention, the invention will be further described.
A kind of rapid detection method of the soil magnesium elements based on conllinear double-pulse laser induced breakdown spectrum, including：
(1) sample preparation.The pedotheque purchase that this research uses is in the standard soil sample of the China Measures Institute, and six kinds
Soil is respectively Inner Mongol Hangjin Rear Banner saline-alkali soil (GBW07447), Zhejiang Province Xiangshan East Sea Tidal Flat Sediments (GBW7452), wide
East saves Yangjiang City South Beach deposit (GBW7453), Shaanxi Province's Luochuan Loess (GBW7454), Anhui Wu He Sediments from Huaihe River
(GBW7455), Jiangsu Province Zhangjiagang Chengjiang deposit (GBW7456).It is more dense in order to be obtained using existing six kinds of soil
Gradient is spent, is mixed to get the magnesium elements soil-like containing 21 concentration gradients two-by-two using six kinds and six kinds of pedotheque equivalent
This.The concentration of magnesium elements is respectively in 6 kinds of standard soil samples：15.48mg·g-1、15.66mg·g-1、6.96mg·g-1、
11.94mg·g-1、11.22mg·g-1、16.50mg·g-1.Being fabricated to specification using tablet press machine (10MPa pressure continues 30s) is
10mm × 10mm × 2mm square sample, every tablet quality are 0.5g.Each concentration prepares 3 samples, and 63 soil pressures are obtained
Piece sample is for testing.
(2) the LIBS spectral signal of collecting sample.Laboratory apparatus preheating 30min is reached into stable state before experiment.
According to the first beam laser energy 25mJ, the second beam laser energy 75mJ, optical maser wavelength 532nm, delay time 6us, the time of integration
10us, the pulse spacing, 1.2us was configured instrument parameter.Sample is placed in displacement platform, adjustment programme sets displacement platform
Movement routine, open laser, recall two beam laser, guarantee to hit laser under the conditions of the impact position of two beam laser is consistent
The different points of 16 originally that draw a design, each point accumulation 5 spectral signals of acquisition.
(3) according to original LIBS spectroscopic data (X) curve, in conjunction with U.S.'s NIST atomic spectra database and pilot system mark
Fixed characteristic wavelength, the main feature spectral line for finding out magnesium elements are：Mg I277.98nm,Mg I 280.22nm,Mg I
285.21nm、Mg I 518.36nm、Mg I 552.84nm。
(4) wavelet transformation noise reduction carried out to original LIBS spectroscopic data (X), be averaging pretreatment, process is pretreated
Data are denoted as X1, extracted in X1 with 3) in the corresponding spectroscopic data of magnesium elements wavelength, be denoted as X2.Using SPXY method according to
2:1 ratio divides sample, obtains modeling collection 42, sample, 21, forecast set sample.
(5) multiple regression is established according to the content of magnesium elements in the peak strength of magnesium elements spectral line in modeling collection X2 and sample
Analysis model：
Y=-0.0006X1-0.0007X2+0.006X3-0.0016X4+0.0034X5+2.8904
Wherein, Y is the actual content of magnesium elements in sample, X1、X2、X3、X4、X5It is respectively corresponding with magnesium elements
The signal strength of 277.98nm, 280.22nm, 285.21nm, 518.36nm, 552.84nm.
Bring the peak strength of magnesium elements spectral line in forecast set into magnesium elements concentration that regression analysis model is predicted, such as
Shown in Fig. 1.The result shows that magnesium element content and corresponding conllinear dipulse LIBS the intensity of spectral line linear dependence are preferable, prediction
The fitting coefficient of determination R of collection2Reach 0.922.The above results show that method of the invention can be realized the quick of magnesium in soil
Quantitative detection can provide reference for plant growth and Soil quality monitoring, have a good application prospect.
Claims (7)
1. a kind of rapid detection method of the soil magnesium elements based on conllinear double-pulse laser induced breakdown spectrum, feature exist
In, including step：
1) soil sample containing magnesium of N number of gradient is made, and press sheet compression is made, magnesium elements concentration is denoted as Y in sample；
2) using the LIBS spectroscopic data X of double-pulse laser acquisition soil sample containing magnesium；
3) it is corresponding that magnesium elements are found out in conjunction with wavelength and the one-to-one relationship of element according to LIBS spectroscopic data X data and curves
Wavelength；
4) LIBS spectroscopic data X is pre-processed, pretreated data are X1, are extracted in X1 and magnesium member in step 3)
The corresponding spectroscopic data X2 of plain wavelength；Gained spectroscopic data (X2, Y) is pressed 2 using X-Y co-occurrence matrix method:1 ratio cut partition is
Modeling collection and forecast set；
5) respectively to model the X2 concentrated as input, Y is output, establishes magnesium elements concentration in soil sample and composes with corresponding LIBS
The multivariate linear regression analysis model of line intensity：
Y=-0.0006X1-0.0007X2+0.006X3-0.0016X4+0.0034X5+2.8904
Wherein, Y is the actual content of magnesium elements in sample, X1、X2、X3、X4、X5277.98nm respectively corresponding with magnesium elements,
The signal strength of 280.22nm, 285.21nm, 518.36nm, 552.84nm；
The Quantitative Analysis Model that X2 in forecast set is brought into foundation obtains the prediction concentrations of magnesium elements in sample.
2. the quick detection side of the soil magnesium elements as described in claim 1 based on conllinear double-pulse laser induced breakdown spectrum
Method, which is characterized in that in step 1), be mixed with the soil sample containing magnesium, magnesium in soil using weight such as different soils
The concentration of element is respectively：15.48mg·g-1、15.66mg·g-1、6.96mg·g-1、11.94mg·g-1、11.22mg·g-1、16.50mg·g-1。
3. the quick detection side of the soil magnesium elements as claimed in claim 2 based on conllinear double-pulse laser induced breakdown spectrum
Method, which is characterized in that in step 1), soil sample containing magnesium is made to the rectangular press sheet compression of equal-specification, every tablet quality is
0.5g, each gradient prepare 3 tabletting samples.
4. the quick detection side of the soil magnesium elements as described in claim 1 based on conllinear double-pulse laser induced breakdown spectrum
Method, which is characterized in that in step 2), the parameter of laser induced breakdown spectrograph is optimized, obtained optimized parameter is：
First beam laser energy is 25mJ；Second beam laser energy is 75mJ；Optical maser wavelength is 532nm；Delay time is 6us；Integral
Time is 10us, pulse spacing 1.2us.
5. the quick detection side of the soil magnesium elements as described in claim 1 based on conllinear double-pulse laser induced breakdown spectrum
Method, which is characterized in that in step 4), noise reduction process is carried out using small wave converting method, small echo odd function is db4, and the number of plies is set
It is 3.
6. the quick detection side of the soil magnesium elements as described in claim 1 based on conllinear double-pulse laser induced breakdown spectrum
Method, which is characterized in that in step 4), when being divided using X-Y co-occurrence matrix method to sample, by all soil-likes containing magnesium
This all regards modeling collection candidate samples as, is then modeled using two farthest vectors of the method choice Euclidean distance of iteration to entering
Collection, until selecting required number of samples；Its range formula is as follows：
Wherein, dxy(m, n) is Euclidean distance, dx(m, n) is spectrum intervals, dy(m, n) is physicochemical property characteristic distance.
7. the quick detection side of the soil magnesium elements as described in claim 1 based on conllinear double-pulse laser induced breakdown spectrum
Method, which is characterized in that in step 5), according to the characteristic wavelength that U.S.'s NIST atomic spectra database and pilot system are demarcated,
The characteristic spectral line of magnesium elements for establishing model is：Mg I 277.98nm,Mg I 280.22nm,Mg I 285.21nm,Mg
I 518.36nm、Mg I 552.84nm。
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