WO2014094381A1

WO2014094381A1 - Method and system for quickly measuring nitrogen distribution on soil surface

Info

Publication number: WO2014094381A1
Application number: PCT/CN2013/070978
Authority: WO
Inventors: 赵春江; 董大明; 郑文刚; 赵贤德; 矫雷子; 鲍锋; 吴文彪
Original assignee: 北京农业信息技术研究中心
Priority date: 2012-12-20
Filing date: 2013-01-25
Publication date: 2014-06-26
Also published as: CN103076309A; CN103076309B

Abstract

A method and system for quickly measuring nitrogen distribution on a soil surface, the system comprising: an enclosed negative pressure cabin (8), an analysis device (5), a two-dimensional movable sample platform(12), a laser excitation device, and an atomic spectrum collection device; the analysis device (5) controls the motion of the two-dimensional movable sample platform (12); the laser excitation device and the atomic spectrum collection device are used to excite and collect the trace atomic emission spectrum on a soil surface, and analyze the nitrogen content at the irradiated position on the soil surface; the analysis device (5) is used to control the load, employ a calibrated and quantitative regression algorithm to calculate the nitrogen content at different irradiated positions on the soil surface, and automatically plot the nitrogen distribution. The method and system can obtain the distribution plot of organic nitrogen, available nitrogen components, and nitrogen element on the surface of a soil sample, thus effectively eliminating the effect of air-borne nitrogen on a measurement result.

Description

Method and system for rapidly measuring nitrogen element distribution on soil surface

Technical field

The invention relates to the field of earth exploration technology, in particular to a method and a system for rapidly measuring the distribution of nitrogen elements on a soil surface.

Background technique

The rapid measurement of some elements in the soil is of great significance. On the one hand, the determination of elemental content in soil is inseparable from research on resource exploration and archaeology. Fast and accurate determination can provide powerful tools for geological change and element migration law research. On the other hand, the determination of nutrients such as nitrogen is important for the development and utilization of soil nutrients. Soil nutrients are an important source of crop nutrition. Measuring nitrogen in farmland soils helps guide scientific fertilization. Therefore, it is of great scientific value and application value to rapidly measure the nitrogen on the soil surface and obtain the distribution image of nitrogen on the soil surface.

In traditional methods, the measurement of nitrogen in soil is more complicated. After the soil is ground, it is pretreated in the laboratory by calcination, and then measured by chromatography, atomic absorption, and the like. A method for measuring elements in soil based on the principle of laser induced breakdown spectroscopy is disclosed in the prior art. The patent proposes a probe that can be applied in the field and the probe can be inserted into the soil. A laser is built in the probe, and the surface of the soil to be tested is excited to a plasma state in the measurement, and the plasma signal is collected by the optical fiber in the probe, sent to the spectrometer for spectrometry, and then analyzed by a stoichiometry method such as partial least squares. The content of each element. This background art has the following differences with respect to this patent:

(1) The background art can only analyze the components of a certain position of the substance to be tested, and cannot present the distribution image of nitrogen on the surface of the soil;

(2) The background technology analyzes the content of various elements in the soil, but the content of some elements is insufficient for the study of soil composition, and more attention is paid to the existence form of the elements. (3) Nitrogen in the air has a certain degree of influence on the measurement. The background art does not consider the problem of the reduction of nitrogen in the air, and it is difficult to accurately measure the nitrogen.

Summary of the invention

(1) Technical problems to be solved

The technical problem to be solved by the present invention is to provide a rapid measurement method and system for the distribution of nitrogen elements on the soil surface, thereby obtaining a distribution image of organic nitrogen and available nitrogen on the surface of the sheet-like soil to be tested.

(2) Technical plan

In order to solve the above technical problems, the present invention provides an aspect of the present invention to provide a rapid measurement system for nitrogen content distribution on a soil surface, including: a sealed negative pressure chamber and an analysis device, and a two-dimensional motion sample stage disposed in a sealed negative pressure chamber, laser excitation Device and atomic spectrum collection device;

The analyzing device controls a motion state of the two-dimensional motion sample stage, and the two-dimensional motion table performs synchronous control with a laser excitation device and an atomic spectrum collection device;

The laser excitation device and the atomic spectrum collection device are used to excite and acquire a trace atomic emission spectrum of the soil surface, and analyze the nitrogen content of the irradiated position on the soil surface;

The analysis device is used for carrying control, calibration and quantitative regression algorithms to calculate the nitrogen content of the soil surface irradiated at different locations, and automatically maps the nitrogen distribution.

Further, one end of the sealed negative pressure chamber is provided with a negative pressure type inlet, and the soil sample is placed into the sealed negative pressure chamber through the inlet.

Further, the utility model further comprises an air pump, wherein the air pump is used for extracting gas in the cabin to form a negative pressure environment; the sealed negative pressure tank body is provided with a gas nozzle, and an internal pressure of about 20%-50% atmospheric pressure is formed under the pumping of the air pump. condition.

Further, the two-dimensional motion sample stage is linked with the laser excitation device, and the two-dimensional motion sample stage is provided with a trigger module. After the laser excitation, the trigger module issues a command to control the two-dimensional motion table to perform two-dimensional motion.

Further, the two-dimensional motion sample stage is connected to a horizontal axis stepping motor and a vertical axis stepping motor, and the horizontal axis stepping motor and the vertical axis stepping motor are controlled by a pulse signal, and the horizontal axis stepping motor and the vertical axis step The motor is driven by a screw to drive the two-dimensional motion sample table for two-dimensional motion.

Further, the laser emitting device comprises two sets of lasers having different wavelengths, wherein one set of lasers has a wavelength of 532 nm and the other set of lasers has a wavelength of 1064 nm; and the wavelength of 532 nm is used to excite all nitrogen in the soil; The laser with a wavelength of 1064 nm is used to excite the available nitrogen in the soil; the laser emitted by the two lasers is focused to the same position by the transmission and reflection of the beam splitter;

The laser excitation device is composed of a laser, a focusing mirror, a fiber coupler, an exiting fiber, and a beam splitter.

Further, the atomic spectrum collecting device is configured to acquire a spectrum of the excited plasma state signal, and the plasma state light signal is collected by an optical fiber forming a 45° inclination angle with the sample stage, and the concave grating and the area array charge coupled component are used. The collected light is wavelength separated to obtain a high resolution spectrum in the 720-770 nm band.

Further, the analysis device consists of two FPGAs in parallel processing system, which is responsible for calculation of available nitrogen in soil samples, calculation of organic nitrogen, analysis of delay time between laser excitation and spectral collection, and analysis of nitrogen distribution in samples. Features.

Further, the two-dimensional motion sample stage is provided with a fastening structure to fine tune its own height.

In another aspect, the present invention also provides a rapid measurement method for nitrogen element distribution on a soil surface, the method comprising the steps of:

S1. The soil sample is placed into the sealed negative pressure chamber through the inlet;

S2. The 532nm and 1064nm lasers of the laser excitation device sequentially hit the surface of the soil sample to be tested;

S3. After the laser striking, the optical fiber sequentially collects the plasma optical signals generated after the two hits, and transmits them to the atomic spectrum collecting system;

S4. The atomic emission spectrum acquires the atomic emission spectrum, and the available nitrogen and organic nitrogen content of the excited position are obtained by calculation of the analytical device;

S5. Under the trigger of the analyzer signal, the two-dimensional motion table soil moves the sample at a slight distance to measure the nitrogen content at another position;

S6. After repeating the above process, after the preset area scanning is completed, the analyzing device draws a distribution map of available nitrogen and organic nitrogen on the basis of obtaining the nitrogen content of each pixel position.

(3) Beneficial effects

The method and system for rapidly measuring the distribution of nitrogen elements on the soil surface provided by the embodiments of the present invention make up for the deficiencies of the comparative technology, and have the following advantages:

(1) obtaining organic nitrogen and available nitrogen components on the soil surface;

(2) obtaining a distribution image of nitrogen on the surface of the soil sample;

(3) It can effectively eliminate the influence of nitrogen in the air on the measurement results.

DRAWINGS

1 is a structural block diagram of a rapid measurement system for nitrogen distribution of soil surface according to an embodiment of the present invention;

2 is a flow chart of a method for rapidly measuring the distribution of nitrogen elements on the soil surface according to an embodiment of the present invention.

Among them: 1: air pump; 2: 532 nm laser; 3: high resolution spectroscopic system; 4: stepper motor controller, 5: analysis device, 6: horizontal axis stepper motor; 7: vertical axis stepper motor 8: negative pressure cabin; 9: gas nozzle; 10: optical fiber; 11: stepper motor drive system; 12: two-dimensional motion sample stage; 14: sample clamping device; 15: sample injection channel; Sample port; 17: 1064 nm laser; 18: beam splitter.

detailed description

The specific embodiments of the present invention are further described in detail below with reference to the drawings and embodiments. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.

As shown in FIG. 1 , the rapid measurement system for the distribution of nitrogen elements on the soil surface provided by the embodiments of the present invention includes:

The utility model comprises: a sealed negative pressure chamber and an analysis device, a two-dimensional motion sample stage disposed in the sealed negative pressure chamber, a laser excitation device and an atomic spectrum collecting device;

An analysis device controls a motion state of the two-dimensional motion sample stage, and the two-dimensional motion sample stage is synchronously controlled with a laser excitation device and an atomic spectrum collection device;

Specifically, the negative pressure chamber 8 is a rectangular parallelepiped of 60 cm*50 cm*50 cm, and the material is alloy aluminum. The cabin is airtight. When the system is in operation, the air pump 1 draws the inside of the cabin through the air nozzle 9 installed at one end of the cabin, and exhausts it outward until the interior forms about 20%-50% atmospheric pressure (controlled by the air pump working time). At this point, the effect of nitrogen in the air on the measurement results is negligible.

The inlet 16 is a circular hole having a diameter of 5 cm. A flexible sheet of plastic is placed in front of the hole as a shield to ensure that no outside air enters the chamber, further confirming that the measurement results are not affected by outside air.

At the time of measurement, the occlusion was opened by hand, and a soil sample (within a sphere of 5 cm diameter) was pressed into the injection port 16. Due to the negative pressure state in the chamber, the soil sample can smoothly enter the sample injection channel 15 and reach the two-dimensional motion sample stage 12, which is fixed by the sample holding device 14.

The two-dimensional motion sample stage 12 is 80 mm * 80 mm of steel material * 10 mm flat plate, soil sample is fixed on the two-dimensional motion sample stage 12. The two-dimensional motion sample stage 12 is connected with a horizontal axis stepping motor 6 and a vertical axis stepping motor 7, and the horizontal axis stepping motor and the vertical axis stepping motor are respectively connected to the two-dimensional motion sample stage 12 through two lead screws to drive the sample. The table moves in two axial directions. The horizontal axis stepping motor 6 and the vertical axis stepping motor 7 are all controlled by a pulse signal, and the control program is run in the analysis and calculation system, and the control command and the pulse signal are issued in real time according to the operating state of the system. The stepping motor is connected to the stepping motor controller 4, the two-dimensional motion sample stage 12 is linked with the laser excitation device, and the two-dimensional motion sample stage is provided with a trigger module. After the laser excitation, the trigger module issues a command to control the two-dimensional motion table for two-dimensional operation. motion.

In the embodiment, the laser emitting device comprises two sets of lasers with different wavelengths, wherein one set of lasers 2 has a wavelength of 532 nm and the other set of lasers 17 has a wavelength of 1064 nm; and the wavelength of 532 nm is used to excite all nitrogen elements in the soil. The laser with a wavelength of 1064 nm is used to excite the available nitrogen in the soil; the exit beams of the two lasers are respectively struck by the transmission and reflection on the surface of the beam splitter 18 to the same position of the sample; the laser excitation device is composed of a laser and a focusing mirror. , fiber coupler, outgoing fiber, beam splitter.

Among them, the laser is a Qd laser of Nd:YAG, and the two sets of lasers use their respective temperature control systems to control the temperature of the substrate at 20 °C. The two sets of lasers are perpendicular to each other, and the two outgoing laser beams are passed through a transflective beam splitter, thereby achieving coaxiality of the two laser light paths. By sequentially controlling the two lasers, the beams exiting the two lasers will be sequentially focused and struck at the same location in the sample.

This embodiment uses a quartz fiber 10 at a 45 degree angle to the sample stage 12 to collect optical signals. In the present embodiment, the time interval of the laser excitation device and the atomic spectrum collection device is set to 4 microseconds. The high-resolution spectroscopic system 3 used in the embodiment is a concave grating structure, and a 511-unit linear array CCD detector is applied. The detector material is silicon with an acquisition band of 300-1100 nm and a resolution of 0.5 nm. The integration time is 1ms.

The two-dimensional motion sample stage 12 is provided with a fastening structure to fine-tune its own height (step by 100 micrometers), thereby solving the problem of inconsistent focus point height caused by different sample thicknesses.

The analysis device 5 is composed of two FPGAs and a parallel processing system, and is responsible for the calculation of the available nitrogen in the soil sample, the calculation of the organic nitrogen, the delay time analysis between the laser excitation and the spectral collection, and the analysis of the nitrogen distribution spectrum in the sample.

When the sample is clamped on the sample stage, press the system start button and the system starts working. Two stepper motors first drive the sample stage to zero. Under the control of the analytical device, the 532 nm laser first hits the soil sample zero and acquires the spectrum. After 2ms, the 1064nm laser hits the soil sample at the same location and acquires the spectrum. Next, the horizontal axis stepping motor drives the sample stage to move to the next position and repeats the above process. After the 100 points of the first line are tested. The longitudinal stepper motor drives the sample stage to move to the next row and repeats the above process until it is condensed into 100*100 points for testing and data acquisition.

After the above process is completed, the analysis device calculates total nitrogen and available nitrogen in the soil sample based on the obtained spectral data. The distribution of total nitrogen and available nitrogen on the surface of soil samples was plotted with nitrogen concentration as brightness.

As shown in FIG. 2, an embodiment of the present invention provides a rapid measurement method for nitrogen element distribution on a soil surface, wherein the method includes the following steps:

The above is only a preferred embodiment of the present invention, and it should be noted that those skilled in the art can make several improvements and substitutions without departing from the technical principles of the present invention. It should also be considered as the scope of protection of the present invention.

Industrial applicability

The method and system for rapidly measuring the distribution of nitrogen elements on the soil surface provided by the invention make up for the deficiency of the comparative technology, and obtain the organic nitrogen and available nitrogen components on the soil surface; the distribution image of the surface nitrogen of the soil sample can be obtained; the air can be effectively eliminated The effect of nitrogen on the measurement results.

Claims

Claims

A rapid measurement system for the distribution of nitrogen elements on a soil surface, comprising: a sealed negative pressure chamber and an analysis device, and a two-dimensional motion sample stage, a laser excitation device, and an atomic spectrum collection disposed in the sealed negative pressure chamber Device

The analyzing device controls a motion state of the two-dimensional motion sample stage, and the two-dimensional motion sample stage is synchronously controlled with a laser excitation device and an atomic spectrum collection device;

The laser excitation device and the atomic spectrum collection device are used to excite and acquire a trace atomic emission spectrum of the soil surface, and analyze the nitrogen content of the irradiated position on the soil surface;

The analysis device is used for carrying control, calibration and quantitative regression algorithms to calculate the nitrogen content of the soil surface irradiated at different locations, and automatically maps the nitrogen distribution.

2. The rapid measurement system for nitrogen content distribution on soil surface according to claim 1, wherein one end of the sealed negative pressure chamber is provided with a negative pressure type inlet, and the soil sample is placed through the inlet. Into the closed negative pressure chamber.

3. The rapid measurement system for nitrogen content distribution on a soil surface according to claim 1, further comprising an air pump for extracting gas in the cabin to form a negative pressure environment; and said sealed negative pressure chamber A gas nozzle is provided to form an internal gas pressure condition of about 20%-50% atmospheric pressure under the pumping of the air pump.

4. The rapid measurement system for nitrogen content distribution on a soil surface according to claim 1, wherein the two-dimensional motion sample stage is linked with a laser excitation device, and the two-dimensional motion sample stage is provided with a trigger module. The trigger module issues an instruction to control the two-dimensional motion sample stage for two-dimensional motion.

A rapid measurement system for nitrogen content distribution on a soil surface according to claim 4, wherein said two-dimensional motion sample stage is connected to a horizontal axis stepping motor and a vertical axis stepping motor, a horizontal axis stepping motor and a longitudinal The axis stepping motor is controlled by a pulse signal, and the horizontal axis stepping motor and the vertical axis stepping motor are respectively driven by a screw to drive the two-dimensional motion sample stage for two-dimensional motion.

6. The rapid measurement system for nitrogen content distribution on a soil surface according to claim 1, wherein the laser emitting device comprises two sets of lasers having different wavelengths, wherein one set of lasers has a wavelength of 532 nm and the other set of laser wavelengths. It is 1064 nm; the laser with a wavelength of 532 nm is used to excite all nitrogen in the soil; the laser with a wavelength of 1064 nm is used to excite the available nitrogen in the soil; the laser emitted by the two lasers is focused by the transmission and reflection of the beam splitter. To the same location;

The laser excitation device is composed of a laser, a focusing mirror, a fiber coupler, an exiting fiber, and a beam splitter.

7. The rapid measurement system for nitrogen content distribution on a soil surface according to claim 1, wherein the atomic spectrum collecting device is configured to acquire a spectrum of the excited plasma state signal, and the plasma state light signal passes through a two-dimensional image. The moving sample stage forms an optical fiber with a 45° inclination angle for collection, and the collected light is wavelength-separated by a concave grating and an area array charge coupled device to obtain a high-resolution spectrum in the 720-770 nm band.

8. The rapid measurement system for nitrogen content distribution on a soil surface according to claim 1, wherein the analysis device comprises a parallel processing system composed of two FPGAs, and is responsible for calculation of available nitrogen in the soil sample, calculation of organic nitrogen, The function of delay time analysis control between laser excitation and spectral collection, and nitrogen distribution map analysis in samples.

9. A rapid measurement system for nitrogen content distribution on a soil surface according to claim 1, wherein said two-dimensional motion sample stage is provided with a fastening structure to fine tune its own height.

10. A method of rapidly measuring nitrogen content distribution on a soil surface according to any one of claims 1-9, characterized in that the method comprises the steps of:

S1. The soil sample is placed into the sealed negative pressure chamber through the inlet;

S2. The 532nm and 1064nm lasers of the laser excitation device sequentially hit the surface of the soil sample to be tested;

S3. After the laser striking, the optical fiber sequentially collects the plasma optical signals generated after the two hits, and transmits them to the atomic spectrum collecting system;

S4. The atomic emission spectrum acquires the atomic emission spectrum, and the available nitrogen and organic nitrogen content of the excited position are obtained by calculation of the analytical device;

S5. Under the trigger of the analyzer signal, the soil of the two-dimensional motion sample table moves the sample at a slight distance to measure the nitrogen content at another position;

S6. After repeating the above process, after the preset area scanning is completed, the analyzing device draws a distribution map of available nitrogen and organic nitrogen on the basis of obtaining the nitrogen content of each pixel position.