Device and method for detecting available nitrogen and phosphorus in soil

Abstract

The invention discloses a device and a method for detecting available nitrogen and phosphorus in soil, and aims to provide a set of economical, efficient, accurate and reliable soil nutrition detection scheme for agricultural production and environmental protection. The equipment comprises a man-machine interaction module, a system power supply module, a system control module, an absorbance detection module, a solution transfer module, an ultrasonic extraction module, an electrocatalytic digestion module, a reagent module and the like. The soil available nitrogen and phosphorus detection equipment can rapidly and accurately determine the content of available nitrogen and phosphorus in soil. The equipment has great application potential in the aspects of environmental protection and sustainable agricultural development, the function of rapidly detecting the content of available nitrogen and available phosphorus in soil on site is achieved, excessive use of fertilizer is avoided, the utilization efficiency of the fertilizer is improved, it is ensured that crops fully obtain essential nutrients, and the yield and quality are improved; meanwhile, sustainable development of agriculture is promoted, the ecological environment is protected, and long-term benefits are brought.

Description

Technical Field

[0001] The present invention relates to a soil detection device, and in particular to a soil effective nitrogen and phosphorus detection device and method. Background Art

[0002] Traditional methods for detecting effective nitrogen in soil mainly rely on complex laboratory chemical analysis techniques, such as the alkaline diffusion method recommended by the national standard. The principle is to treat soil samples with a strong alkaline solution (such as sodium hydroxide), convert ammonium nitrogen into ammonia, and then absorb the ammonia by acid solution through diffusion, and finally determine the ammonia content by standard acid titration or colorimetry. However, this method has some obvious limitations. It requires all effective nitrogen forms to be converted into ammonium nitrogen, and then converted into ammonia for detection. The operation steps are cumbersome and time-consuming. At the same time, the required devices and equipment are not easy to be miniaturized and integrated, and it is difficult to achieve rapid on-site detection. The samples can only be sent to the laboratory for analysis, which increases the detection cost and time, and may also introduce additional errors. In addition, the existing pre-treatment method only uses a strong alkaline solution to treat soil samples, which is not easy to integrate equipment and causes great damage to the environment.

[0003] In addition to the alkaline diffusion method, some other traditional chemical methods also have their own shortcomings. For example, the indophenol blue colorimetric method can only determine ammonium nitrogen in the soil, and cannot cover other effective nitrogen components such as nitrate nitrogen. The cadmium column reduction method and the stannous chloride colorimetric method are mainly used to determine nitrate nitrogen, and they also cannot fully reflect the content of effective nitrogen in the soil. The limitations of these methods make it difficult for them to meet the needs of modern agriculture for rapid and accurate soil effective nitrogen detection.

[0004] For soil available phosphorus, inductively coupled plasma emission spectrometry is a common detection method. This method uses inductively coupled plasma emission spectrometry technology to determine the content of available phosphorus in the soil. Although it has high accuracy and precision, it needs to be tested in the laboratory. The detection process is complicated and time-consuming, and it is difficult to achieve rapid on-site detection. In addition, there are sodium bicarbonate extraction-molybdenum antimony anti-spectrophotometry and ammonium fluoride-hydrochloric acid extraction-molybdenum antimony anti-spectrophotometry. Both detection methods are detection methods combined with molybdenum antimony anti-spectrophotometry. The disadvantage of both is that they cannot extract all available phosphorus. The detection effect may be better for suitable soils, but they cannot be applied to all types of soils.

[0005] Although modern instrumental analysis methods have improved detection efficiency and accuracy to a certain extent, there are still some problems. For example, continuous flow analyzer method, ion chromatography and near-infrared spectroscopy all require expensive large-scale instruments and professional operators, and still rely on laboratory environment and cannot perform real-time detection on site. The sample delivery cycle is long, and samples are prone to change during transportation and storage, which leads to increased errors in test results. In addition, near-infrared spectroscopy also requires the establishment of a large and reliable soil database and calibration model to accurately predict the effective nitrogen and phosphorus content in the soil, which is a huge challenge for different regions and different soil types.

[0006] Therefore, the development of a fast, accurate, convenient and low-cost on-site detection method and equipment for soil effective nitrogen and phosphorus is of great significance for guiding agricultural production, improving fertilizer utilization and protecting the ecological environment. Summary of the invention

[0007] Purpose of the invention: In view of the above problems, the present invention proposes a soil available nitrogen and phosphorus detection device and method, which can quickly, on-site and accurately detect the soil available nitrogen and phosphorus components.

[0008] Technical solution: The technical solution adopted by the present invention is a soil effective nitrogen and phosphorus detection device, including a detection box, the detection box body includes a system control module, a human-computer interaction module electrically connected to the system control module, an absorbance detection module, an ultrasonic extraction module and an electrocatalytic digestion module;

[0009] The system control module is used to control other modules to perform actions; it is also used to collect or receive detection data from the absorbance detection module and perform data processing, and the results of effective nitrogen and phosphorus concentrations obtained by processing are sent to the human-computer interaction module;

[0010] The solution transfer module is used for mixing and transferring the solution in the device;

[0011] The ultrasonic extraction module is used to extract nitrogen and phosphorus components in the soil sample to obtain an extract;

[0012] The electrocatalytic digestion module is used to catalytically oxidize nitrogen and phosphorus in the leaching solution, digest and oxidize nitrogen components in different forms into nitrate nitrogen, and digest and oxidize phosphorus components in different forms into positive pentavalent phosphorus;

[0013] The absorbance detection module is used to detect effective nitrogen and phosphorus in the extract after electrocatalytic digestion;

[0014] The human-computer interaction module is used for human-computer interaction and displaying the results of effective nitrogen and phosphorus detection;

[0015] A system power supply module is also included for supplying power to the device.

[0016] Preferably, the device further comprises a reagent box, wherein the reagent box body comprises a reagent module for storing reagents, wherein the reagents comprise an electrolyte solution, a quencher, and pure water.

[0017] Preferably, the solution transfer module uses multiple peristaltic pump modules connected to form an array.

[0018] The system control module includes two control boards, a main control board and a slave control board. The control contents of the main control board include: power control of the light source chip, back-end processing of the photodiode chip receiving signal, enable control of the slave control board, parameter modification of ultrasonic extraction, parameter modification of electrocatalytic digestion, parameter modification of absorbance test, and sending of test results; the control contents of the slave control board include: peristaltic pump module control.

[0019] The absorbance detection module includes a light source chip, a cuvette device, and a photodiode chip;

[0020] The light source chip sets the input current and input voltage of the light source through the system control module to provide a stable power supply to the light source; it performs closed-loop detection based on the photodiode chip at the back end and realizes self-checking by judging the detection error results;

[0021] Cuvette device, the cuvette is made of polytetrafluoroethylene and has quartz glass sheets on both sides;

[0022] Photodiode chip, during the spectrophotometric detection process, after the system control module turns on the light source, the light passes through the cuvette device and the liquid to be tested therein, and irradiates the photodiode in the photodiode chip, and the photodiode generates a detection signal.

[0023] The photodiode chip includes a photodiode with characteristic wavelengths of 230nm and 275nm or a spectrum chip including a wavelength band of 230nm and 275nm, a photodiode with a characteristic wavelength of 697nm or a spectrum chip including a wavelength band of 697nm.

[0024] The ultrasonic extraction module includes an ultrasonic transducer for generating high-frequency ultrasonic waves and an ultrasonic extraction tank; the ultrasonic transducer utilizes the synergistic effect of the cavitation effect, mechanical effect and thermal effect of high-frequency ultrasonic waves to ultrasonically crush the soil and extract the nitrogen and phosphorus components in the soil.

[0025] The electrocatalytic digestion module is used to: catalytically oxidize ammonium nitrogen, nitrate nitrogen and some insoluble organic nitrogen obtained after soil extraction, oxidize and digest other types of nitrogen including organic nitrogen and other inorganic nitrogen, and finally convert them into nitrate nitrogen and send them to the absorbance detection module for detection; catalytically oxidize all water-soluble phosphorus and some adsorbed phosphorus obtained after soil extraction, convert them into pentavalent phosphorus, oxidize and digest other types of phosphorus, and finally oxidize them into pentavalent phosphorus and send them to the absorbance detection module for detection. The other types of phosphorus include: slightly soluble inorganic phosphorus and easily mineralized organic phosphorus.

[0026] The electrocatalytic digestion module comprises an electrolytic cell, an electrocatalytic anode, and an electrocatalytic cathode; the electrolyte in the electrolytic cell comprises a sodium sulfate electrolyte solution, a sodium carbonate electrolyte solution, and pure water; the voltage between the electrocatalytic anode and the electrocatalytic cathode can be in the range of 0.1 to 32V, preferably in the range of 5V to 25V.

[0027] The present invention provides a soil available nitrogen and phosphorus detection method applied to the soil available nitrogen and phosphorus detection device, comprising the following steps:

[0028] Step 1, adding soil samples and pure water into the ultrasonic extraction module, the system control module opens the solution transfer module for mixing, and after mixing, extracts nitrogen and phosphorus components in the soil sample to obtain an extract;

[0029] Step 2: The solution transfer module transfers the leaching solution to the electrocatalytic digestion module, catalytically oxidizes the nitrogen and phosphorus in the leaching solution, digests and oxidizes the nitrogen components in different forms into nitrate nitrogen, and digests and oxidizes the phosphorus components in different forms into positive pentavalent phosphorus; after the digestion is completed, a quencher is added;

[0030] Step 3, add pure water to the cuvette of the absorbance detection module, perform absorbance detection at the characteristic wavelength, and obtain the blank value of the current detection; the solution transfer module transfers the extract to the absorbance detection module, performs absorbance detection at the characteristic wavelength, and obtains the detection value; the soil total phosphorus detection process is the same as the soil total nitrogen detection process, and each obtains the absorbance of the corresponding characteristic wavelength: the soil total nitrogen detection obtains the absorbance near the characteristic wavelengths of 230nm and 275nm; the soil total phosphorus detection obtains the absorbance near the characteristic wavelength of 697nm.

[0031] Step 4, the system control module collects or receives the blank value and the detection value of the absorbance detection module and performs data processing; the data processing includes: calculating the blank value and the detection value by Lambert-Beer law to obtain the results of effective nitrogen and phosphorus concentrations;

[0032] Step 5, the results of effective nitrogen and phosphorus concentrations are processed and sent to the human-computer interaction module; the human-computer interaction module displays the results of effective nitrogen and phosphorus concentrations.

[0033] Beneficial effects: The present invention has developed a new and efficient soil effective nitrogen and phosphorus detection device and method. Compared with the traditional alkaline hydrolysis method, this method is more time-saving and efficient, and avoids the use of strong acids and alkalis, and is more environmentally friendly. In addition, the present invention combines the electrocatalytic digestion pretreatment with the high-precision dual-wavelength spectrophotometry, without the use of a color developer, and cooperates with the independently developed high-stability light source chip and high-precision photodiode chip to achieve stable detection of absorbance and simplify the detection process. On the basis of achieving efficient and convenient pretreatment, high-precision detection of soil effective nitrogen and phosphorus concentrations is achieved, avoiding the relative error caused by laboratory testing of samples, and rapid on-site detection can be achieved. In summary, the present invention provides an innovative solution to replace the time-consuming and labor-intensive traditional soil effective nitrogen and phosphorus detection methods, which rely on professional personnel for operation, and chemical reagent pollution. The equipment is committed to achieving low-cost, high-precision, and on-site rapid detection of soil effective nitrogen and phosphorus content, providing convenient and accurate data support for agricultural production and environmental protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the composition structure of the soil available nitrogen and phosphorus detection device of the present invention;

[0035] Figure 2 It is an overall stereogram of the soil available nitrogen and phosphorus detection device of the present invention;

[0036] Figure 3 It is a schematic diagram of an explosion of the soil effective nitrogen and phosphorus detection device of the present invention;

[0037] Figure 4 It is a schematic diagram of the detection process of the soil available nitrogen and phosphorus detection device of the present invention;

[0038] Figure 5 It is a schematic diagram of the power-on, cleaning and resetting process of the soil available nitrogen and phosphorus detection device of the present invention;

[0039] Figure 6 It is a flow chart of the method for detecting effective nitrogen and phosphorus in soil according to the present invention;

[0040] Figure 7 It is a fitting curve of the detection results corresponding to different concentrations of available nitrogen detected by the present invention;

[0041] Figure 8 is a fitting curve of the detection results corresponding to different concentrations of available phosphorus detected by the present invention;

[0042] Fig. 9 It is a comparison diagram of the effects of the effective nitrogen pretreatment of different durations according to the present invention. DETAILED DESCRIPTION

[0043] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0044] Example 1

[0045] The soil effective nitrogen and phosphorus detection device of the present invention comprises a detection box, wherein the detection box body comprises a system control module 3, a human-computer interaction module 1 electrically connected to the system control module 3, an absorbance detection module 4, an ultrasonic extraction module 6 and an electrocatalytic digestion module 7;

[0046] The system control module 3 is used to control other modules to perform actions; it is also used to collect detection data of the absorbance detection module 4 and perform data processing, and the results of effective nitrogen and phosphorus detection obtained by processing are sent to the human-computer interaction module 1;

[0047] The ultrasonic extraction module 6 is used to extract nitrogen and phosphorus components in the soil sample to obtain an extract;

[0048] The electrocatalytic digestion module 7 is used to catalytically oxidize the nitrogen in the leaching solution, digest and oxidize the nitrogen components in different forms into nitrate nitrogen, and digest and oxidize the phosphorus components in different forms into positive pentavalent phosphorus;

[0049] The absorbance detection module 4 is used to detect effective nitrogen and phosphorus in the extract after electrocatalytic digestion;

[0050] The human-computer interaction module 1 is used for human-computer interaction and displaying the results of effective nitrogen and phosphorus detection;

[0051] It also includes a system power supply module 2 for supplying power to the device.

[0052] The device can also be optionally equipped with a reagent box, in which a reagent module 8 is included for storing reagents, and the reagents include an electrolyte solution, a quencher, and pure water.

[0053] In order to conveniently move the test liquid, a solution transfer module 5 may be added to the detection box body to mix and transfer the solution in the device.

[0054] See also Figure 1 , 2 , 3, are respectively the schematic diagram of the composition structure of the equipment, the overall stereogram and the exploded diagram:

[0055] Human-computer interaction module 1: It is set on the top of the device and is used for human-computer interaction to facilitate the user to operate and use the device;

[0056] System power supply module 2: set at the bottom of the device, used to provide energy to the device;

[0057] System control module 3: arranged at the lower part of the equipment, below the solution transfer module 5, for controlling all modules of the entire equipment and processing data;

[0058] Absorbance detection module 4: arranged in the middle and upper part of the equipment, in the upper part of the internal frame of the equipment, fixed in front of the ultrasonic extraction module and the electrolysis module, for final nitrate nitrogen detection;

[0059] Solution transfer module 5: It is located in the middle and upper part of the equipment and is used to transfer and transport all solutions in the equipment. Some of them also have the function of mixing solutions.

[0060] Ultrasonic extraction module 6: It is arranged in the middle of the equipment, on the left side of the electrocatalytic digestion module 7, and is used for extracting effective nitrogen and phosphorus from soil samples;

[0061] Electrocatalytic digestion module 7: It is arranged in the middle of the equipment, on the right side of the ultrasonic extraction module 6, and is used for catalytic oxidation of different types of nitrogen in the extracted solution, converting all nitrogen into a single type of nitrogen, and finally detecting nitrate nitrogen.

[0062] Reagent module 8: It is arranged in the reagent box and is used for storing reagents such as electrolyte solution, quencher, pure water, etc.

[0063] In this implementation case, the equipment is mainly divided into two boxes, the left box is the detection box, and the right box is the reagent box. The internal modules of the two boxes are introduced from left to right. The detection box is named from top to bottom, and the human-computer interaction module 1 is at the top, on the box after the entire detection box is opened. After opening the human-computer interaction module, you can see that the absorbance detection module 4 is in the form of a light-proof detection box, which is fixed above the solution transfer module 5. The ultrasonic extraction module 6 and the electrocatalytic digestion module 7 are fixed on the box and embedded in the middle of the solution transfer module 5. The system power supply module 2 and the system control module 3 are at the bottom of the box. The system control module 3 is below the peristaltic pump control module, and can be directly connected to the solution transfer module 5, and a via is reserved to directly connect the system power supply module 2. There is fixed cotton at the bottom of the reagent box, and eight 500mL round-bottom reagent bottles are embedded in the middle of the fixed cotton.

[0064] like Figure 3As shown, the human-machine interaction module 1 includes a human-machine interaction interface 11 and a display screen 12. The human-machine interaction interface is equipped with a hinge and can be opened upward. After opening it, operations such as electrode maintenance, equipment operation status inspection, and component replacement can be performed; the display screen is used for data display and equipment operation. After the equipment detection is completed, the data will be transmitted to the display screen under the control of the system control board and stored in the storage space of the display screen. The operations that can be performed by the display screen include: displaying data, storing data, setting parameters related to ultrasonic extraction, setting parameters related to electrocatalytic digestion, starting / pausing detection, shutting down the equipment, etc.

[0065] The system power supply module 2 contains multiple lithium batteries.

[0066] The system control module 3 mainly includes two system control boards. They are the main control board and the slave control board. The main control board includes a microprocessor. The model of the microprocessor can be MSP430 chip, AVR chip, ARM chip, STM32 chip or Arduino chip. The various parts on the slave control board are also controlled by the microcontroller on the main control board. The control parts included in the main control board include: precise power supply control of the light source chip, back-end processing of the photodiode chip receiving signal, enable control of the slave control board, modification of relevant parameters of ultrasonic extraction, modification of relevant parameters of electrocatalytic digestion, modification of relevant parameters of absorbance test, transmission of test results, etc. The main control board has a built-in voltage conversion circuit. The chip can be CD4000, LM7805, LM317, LM2596, TPS5430, which is used for voltage regulation and conversion. Built-in optocoupler relay control module, used to control the stable isolation of the front end and the back end, which can avoid the eddy current and crosstalk generated by the front end on the back end. The chip can be TLP240, TLP141, CPC1035, PS9303, used to control the device switch. The main control part of the slave control board is the control of the peristaltic pump module. The device switch control circuit of the built-in transistor and MOS tube, the transistor can be 2SD882, S8050, 2N5551, 2SC1623, MJD31C, and the MOS tube can be AO3401, 2N7002, AOD4184, IRF9540, NCE6050.

[0067] The absorbance detection module 4 mainly includes a light source chip 41 , a cuvette 42 , and a photodiode chip 43 .

[0068] Light source chip: The main control board can be used to set the light source input current and input voltage to provide a stable power supply to the light source. At the same time, closed-loop detection can be performed based on the photodiode chip at the back end, and self-checking can be achieved by judging the detection error results.

[0069] Cuvette device: The entire material of the cuvette is polytetrafluoroethylene (to achieve acid, alkali and high temperature resistance), the middle structure is hollow, and there are two quartz glass sheets on both sides (to meet the light transmittance of deep ultraviolet detection).

[0070] Photodiode chip: During spectrophotometry detection, after the control module turns on the light source, the light passes through the cuvette device and the liquid to be tested therein and irradiates the photodiode in the photodiode chip. The photodiode absorbs light of a specific wavelength and generates a photocurrent signal that is proportional to the light intensity.

[0071] The light source in the light source chip 41 is an independent LED light source of 230nm, 275nm and 697nm, or it can be a light source generated by white light passing through a filter of a specific band. The white light source can be a laser-driven white light source, a tritium lamp white light source, a tungsten lamp white light source, a xenon lamp white light source and a halogen tungsten lamp white light source.

[0072] The photodiode in the photodiode chip 43 can be a photodiode including characteristic wavelengths of 230nm and 275nm or a spectral chip including 230nm and 275nm bands (for effective nitrogen detection), a photodiode including a characteristic wavelength of 697nm or a spectral chip including a 697nm band (for effective phosphorus detection). The light intensity of the light at the corresponding wavelength can be detected by a photodiode or a spectral chip, and the effective nitrogen and effective phosphorus concentrations of the current detection solution can be calculated by the light intensity. A built-in high-precision operational amplifier performs IV amplification of the photocurrent signal, which can be OPA2277, ADA4625, SGM8551, AD711, JRC4558. A built-in secondary voltage signal amplification is used to amplify the voltage signal after the primary amplification to the voltage range available for the analog-to-digital conversion part, and to stabilize the voltage, which can be LM358, MCP6001, UA741, AD8422, TL064. The built-in ADC analog-to-digital conversion module is used to convert the stabilized voltage signal into digital form and transmit the converted AD value to the main control board for data processing. It can be XL1509, ADC0832, AD9833, PCM1794, or AD4111.

[0073] The solution transfer module 5 mainly includes a peristaltic pump module. The peristaltic pump motor in the peristaltic pump array module can be a DC electrode or a stepper motor. The working time of the DC electrode and the volume of the extracted liquid can be calculated by the peristaltic pump extraction efficiency. The extraction efficiency can be calculated by the extraction time and the liquid volume. After the extraction efficiency is obtained, the extraction time can be calculated by multiplying the extraction efficiency by the extraction time: assuming that the extraction time is T, the extraction efficiency is V, and the extraction liquid volume is S, then S=V×T. Therefore, before using a DC peristaltic pump, it is necessary to test its extraction efficiency. By timing and measuring the volume of the extracted liquid in the corresponding time, the corresponding extraction efficiency of a DC peristaltic pump can be calculated. The number of working pulses of the stepper motor is proportional to the volume of the extracted liquid. Therefore, the volume of liquid extracted for each working pulse number can be calculated based on the volume of liquid pumped by a certain number of pulses. Finally, a certain number of pulses can be applied according to the volume of liquid to be pumped to complete the precise volume of liquid: Assuming that the number of working pulses of the stepper motor is n, the volume of liquid extracted per unit pulse number is s, and the volume of extracted liquid is S, then S = n × s. Therefore, before using a stepper motor, it is necessary to test the volume of liquid extracted per unit pulse number. After sending a certain number of pulses, weigh the volume of liquid extracted to obtain the volume of liquid extracted per unit pulse number.

[0074] The ultrasonic leaching module 6 mainly includes an ultrasonic transducer 61 and an ultrasonic leaching tank 62 .

[0075] Ultrasonic transducer: The principle is to convert electrical signals into acoustic signals through various dielectrics with piezoelectric effect, and then use high-frequency ultrasonic signals to ultrasonically break the soil to extract effective nitrogen and phosphorus in the soil. Its morphology can be a conventional drum-shaped ultrasonic vibrator, or a columnar or long strip ultrasonic vibrator. The head of the ultrasonic vibrator can be pointed, round, square, etc.

[0076] Ultrasonic leaching tank: The ultrasonic leaching tank is about 160mm high, syringe-shaped, and made of polytetrafluoroethylene. The upper end is the liquid inlet, which is fixed by the upper cover; the lower end is the liquid outlet, which is responsible for discharging the liquid and performing the bubbling and mixing operation of the liquid.

[0077] In the process of extracting effective nitrogen and phosphorus from soil, the principle is to utilize the synergistic effect of ultrasonic cavitation, mechanical effect and thermal effect. Cavitation effect is the main mechanism of ultrasonic extraction. When ultrasonic waves propagate in liquid media, they will produce high-frequency compression and expansion cycles. In the expansion cycle, if the negative pressure of the sound wave is large enough, tiny bubbles, namely cavitation bubbles, will form in the liquid. These cavitation bubbles will quickly collapse in the subsequent compression cycle, generating local high temperature and high pressure and strong shock waves, as well as high-speed microjets. The vibration of ultrasonic waves will cause violent oscillations in the liquid medium, resulting in macroscopic turbulence and microscopic disturbances. This mechanical action is similar to stirring, which can accelerate the mass transfer of effective nitrogen and phosphorus between the solid-liquid interface and improve the extraction efficiency. At the same time, part of the energy of ultrasonic waves will be converted into heat energy, resulting in a slight increase in the temperature of the extraction system. A moderate temperature increase can increase the solubility and diffusion coefficient of effective nitrogen and phosphorus, which is conducive to the extraction of effective nitrogen and phosphorus.

[0078] The electrocatalytic digestion module 7 mainly includes an electrolytic cell 71 , an electrocatalytic anode 72 and an electrocatalytic cathode 73 .

[0079] Electrolytic cell: The electrolytic cell is about 160mm high, in the shape of a syringe, and made of polytetrafluoroethylene. The upper end is the liquid inlet, including sodium sulfate electrolyte solution, sodium carbonate electrolyte solution, pure water, etc., which is fixed by the upper cover; the lower end is the liquid outlet, which is responsible for discharging the liquid and bubbling and mixing the liquid.

[0080] Electrocatalytic anode: The electrocatalytic anode in the electrocatalytic electrode, the base material can be metal oxides such as titanium, tungsten, platinum, gold, silver, iron, copper, etc., and the surface can be coated with metal oxides such as iridium, ruthenium, lead, platinum, tin, etc.

[0081] Electrocatalytic cathode: The electrocatalytic cathode in the electrocatalytic electrode can be made of carbon or precious metal oxides such as ruthenium, iridium, platinum, or metal sulfides such as molybdenum and tungsten, as well as metal electrodes such as platinum, nickel, and stainless steel.

[0082] The electrocatalytic anode can be a pure ruthenium coating, a pure iridium coating, a ruthenium-iridium composite coating, an iridium-tantalum composite coating, or other metal oxide coatings. The electrocatalytic cathode can also be replaced, and can be replaced with a stainless steel sheet, a graphite sheet, or the like. The electrocatalytic digestion module is used to catalytically oxidize the ammonium nitrogen, nitrate nitrogen, and some insoluble organic nitrogen obtained after soil extraction, and other types of nitrogen including organic nitrogen and other inorganic nitrogen are oxidized and digested, and finally converted into nitrate nitrogen and sent to the absorbance detection module for detection; the electrocatalytic digestion module can be used to catalytically oxidize all water-soluble phosphorus and some adsorbed phosphorus obtained after soil extraction, and converted into pentavalent phosphorus, and other types of phosphorus (including: slightly soluble inorganic phosphorus and easily mineralized organic phosphorus) are oxidized and digested, and finally oxidized into pentavalent phosphorus and sent to the absorbance detection module for detection.

[0083] The reagent module 8 is a glass reagent bottle. The reagent bottle is placed in a reagent box with fixed cotton to ensure the stability and safety of the reagent. The reagent box and the detection box are two independent boxes. When the test is required, the peristaltic pump tube group of the detection box is taken out, and the peristaltic pump tube is inserted into the corresponding reagent bottle in sequence according to the number. After the end, it is necessary to check whether it corresponds, otherwise the test result will be inaccurate. When the reagent is exhausted and needs to be replaced or added, the bottle body can be directly inserted, and the original bottle cap does not need to be replaced, just tighten it and use it.

[0084] The human-computer interaction module 1 is mainly responsible for the control of the entire device and the display and storage of data. The system power supply module 2 is used for the energy drive of the entire device. The system control module 3 controls the operation of the entire device and the calculation and processing of data. The ultrasonic transducer 61 and the ultrasonic extraction tank 62 in the ultrasonic extraction module 6 are responsible for the extraction operation in the pre-treatment of the entire device. The electrolytic cell 71, the electrocatalytic anode 72 and the electrocatalytic cathode 73 in the electrocatalytic digestion module 7 perform the pre-treatment process of electrocatalytic digestion during the equipment detection process. The two modules jointly complete the pre-treatment process of the entire detection. The light source chip 41, the cuvette 42, and the photodiode chip 43 in the absorbance detection module 4 jointly realize the final detection of the equipment. The solution transfer module 5 realizes the liquid flow of the entire device. The reagent module 8 is responsible for the reagent reserve of the entire device.

[0085] See also Figure 4 The detection process of the soil available nitrogen and phosphorus detection device of the present invention is as follows:

[0086] 1. Before testing the effective nitrogen and phosphorus in the soil, soil samples should be prepared, including drying, grinding, sieving and weighing. After these processes, the weighed soil samples should be placed in an ultrasonic extraction tank and wait for testing to begin.

[0087] 2. After the equipment is powered on, press the start detection button on the display screen. The display screen sends a detection start command to the system control main board and waits for the automatic cleaning process to end. After receiving the command, the main system control board will proceed to the next step.

[0088] 3. The main system control board sends a start detection instruction to the slave system control board.

[0089] 4. Control the solution transfer module from the system board to add the extractant.

[0090] 5. The solution transfer module is used to add pure water.

[0091] 6. Control the solution transfer module from the system board to transfer the supernatant of the extraction solution.

[0092] 7. The solution transfer module adds the supernatant of the leaching solution to the electrocatalytic digestion tank.

[0093] 8. The solution transfer module performs the operation of adding the electrolyte solution to the electrocatalytic digestion cell.

[0094] 9. The solution transfer module performs the operation of adding pure water to the electrocatalytic digestion cell.

[0095] 10. Control the solution transfer module from the system board to transfer the electrolyzed solution.

[0096] 11. Control the light source chip from the system control board to turn on the light source.

[0097] 12. Control the photodiode chip from the system control board, initialize the light source and start receiving data.

[0098] 13. Receive data from the photodiode chip from the system control board and perform AD conversion on the data.

[0099] 14. The slave system control board sends the converted AD value of the data to the main system control board, which performs operations such as limiting, median filtering, noise reduction and smoothing.

[0100] 15. The main system control board sends the processed data to the display screen for display and stores it in the storage space of the human-computer interaction interface.

[0101] The working process of the soil available nitrogen and phosphorus detection device of the present invention is as follows:

[0102] 1. Press the power button to power on the entire device.

[0103] 2. Press the device power button to turn on the device.

[0104] 3. Enter the automatic cleaning mode to prevent power outages caused by abnormal conditions during the last operation of the device. The device first drains the liquid in the current cuvette, then drains the liquid in the electrolysis module, and finally drains the liquid in the ultrasonic leaching tank. The next step is in the opposite order. First, fill the ultrasonic leaching tank with pure water, turn on the ultrasonic transducer for ultrasonic cleaning, and drain the solution after the ultrasonic cleaning is completed. Then clean the electrolysis module, fill it with pure water, use a peristaltic pump for bubbling operation, and fully clean the electrolysis cell and electrodes. Finally, clean the cuvette, and the cleaning process is the same as the electrolysis module.

[0105] 4. The main system control board calls the slave system control board, and the slave system control board calls the peristaltic pump module in the peristaltic pump module to inject pure water into the cuvette. The main system control board calls the light source chip to turn on the light source, and at the same time calls the photodiode chip to run the absorbance detection module, perform a stability self-test, and obtain the absorbance of pure water at 230nm, 275nm and 697nm to check whether it is detected normally.

[0106] 5. After adding the specified number of grams of treated soil sample, click the detection start button on the display screen, and the command is sent from the display screen to the main system control panel.

[0107] 6. The main system control board calls the slave system control board, sends instructions to the solution transfer module, calls the peristaltic pump module to add pure water, and turns on the ultrasonic transducer for ultrasonic oscillation after adding to the specified amount.

[0108] 7. After the ultrasonic oscillation is completed, the peristaltic pump module is called from the system control board to absorb the supernatant, transfer it to the electrolysis module, and then fill the electrolyte solution. After the filling is completed, electrocatalytic digestion is carried out.

[0109] 8. When the electrocatalytic digestion is completed, add a quencher to eliminate OH - and CO 3 - After bubbling for 5 minutes, transfer the sample into a cuvette for nitrate nitrogen concentration detection.

[0110] 9. The main system control board calls the absorbance test module to perform absorbance detection. After completion, the data is transmitted to the slave system control board, and then the AD value is transmitted to the main system control board after AD conversion of the data.

[0111] 10. Finally, the main system control board processes the data, filters it, limits it, performs median and average composite filtering, and then sends it to the display screen for display and storage.

[0112] 11. The main system control module controls the entire system to repeat the cleaning process.

[0113] See also Figure 5 The power-on cleaning and resetting process of the present invention is as follows:

[0114] 1. After the entire device is powered on, click the Start Detection button on the display to automatically start the device cleaning process.

[0115] 2. First, drain the liquid in the cuvette into the waste liquid bucket, which may be caused by abnormal shutdown last time.

[0116] 3. The electrocatalytic digestion module discharges the waste liquid into the cuvette module.

[0117] 4. The cuvette discharges the waste liquid discharged from the electrocatalytic digestion module into the waste liquid bucket to prevent the solution from overflowing from the peristaltic pump port of the solution transfer module.

[0118] 5. The ultrasonic extraction module discharges waste liquid into the waste liquid barrel.

[0119] 6. Add pure water into the ultrasonic leaching tank and turn on the ultrasonic transducer to clean the leaching tank.

[0120] 7. Drain the waste liquid in the ultrasonic leaching tank.

[0121] 8. Add pure water into the electrocatalytic digestion cell and clean it by reverse bubbling with the help of the peristaltic pump of the solution transfer module.

[0122] 9. Drain the waste liquid from the electrocatalytic digestion tank.

[0123] 10. Drain the waste liquid from the electrocatalytic digestion cell into the waste liquid barrel.

[0124] 11. Add pure water into the cuvette and clean it by reverse bubbling with the help of the peristaltic pump of the solution transfer module.

[0125] 12. Drain the waste liquid in the cuvette into the waste liquid bucket.

[0126] Example 2

[0127] The invention discloses a method for detecting available nitrogen and phosphorus in soil.

[0128] See also Figure 6 The process of the soil available nitrogen and phosphorus detection equipment includes: pre-filling stage; soil extraction stage; electrocatalytic digestion stage; color development and colorimetry stage; data processing stage; cleaning stage. Here we take the soil total nitrogen detection process as an example:

[0129] (1) Pre-filling stage: In the process of soil total nitrogen detection, the reagents used include: electrolyte solution, buffer solution, pure water, supporting electrolyte, quencher, and a pump for extracting the extract. After the equipment is connected to the reagent box, the peristaltic pump pipeline of the peristaltic pump module needs to be pre-filled with solution. The capacity of each pipeline is 5mL, and the pumping rate of the DC motor peristaltic pump is 1mL / s. First, the program starts the solution transfer module 5, and pre-fills the remaining pumps except the extract extraction pump, and the pre-filling time is 6s. After the extraction is completed, the excess solution in the electrolytic cell, leaching cell and cuvette device is discharged, and then the pure water pump is turned on, and the transfer pump is turned on in the opposite direction for bubbling operation. The opening time is 10s to rinse the electrolytic cell, leaching cell and cuvette device. The pre-filling of the peristaltic pump with the extraction liquid is carried out after the soil extraction is completed. Assuming that the soil extraction stage has been completed, the peristaltic pump module in the solution transfer module 5 is controlled to open and the peristaltic pump with the extraction liquid is pre-filled. The opening time is 6s, and a pure water flushing operation is performed after the end.

[0130] (2) Soil extraction stage: After soil pretreatment (grinding, sieving, etc.) outside the detection equipment, a fixed gram soil sample is obtained and added to the supermarket electrolytic cell 62. The pure water pump is controlled to be turned on for 50 seconds, and the ultrasonic transducer 61 is turned on for ultrasonic extraction after the peristaltic pump is turned off, and the duration is 10 minutes. After the ultrasonic transducer is turned off, the extract extraction pump is turned on for pre-charging. After completion, it is turned on for 20 seconds to extract 20mL of extract into the electrocatalytic digestion cell 71 for electrocatalytic digestion.

[0131] (3) Electrocatalytic digestion stage: Turn on the peristaltic pumps of the electrolyte solution, supporting electrolyte, pure water, etc. and turn on the power supply for electrocatalytic digestion. After the digestion is completed, add the quencher for quenching. Turn on the peristaltic pump to transfer the pre-treated solution to the absorbance detection module 4 for detection.

[0132] (4) Color development and colorimetry stage: At the beginning, turn on the pure water pump, add pure water to the cuvette, and perform absorbance detection at 230nm and 275nm to obtain the blank value of the current detection. After the electrocatalytic digestion stage, test the liquid in the cuvette to obtain the absorbance of the pre-treated solution at 230nm and 275nm.

[0133] (5) Data processing stage: In the color development and colorimetry stage, the absorbance at 230nm and 275nm in different solutions is obtained through the photodiode chip 43, and the obtained data is the value after the operational amplifier and AD conversion. After data operations such as median filtering and mean filtering, the stable absorbance at different wavelengths is obtained. The final data included are: the absorbance at 230nm and 275nm corresponding to the pre-treated solution, and the absorbance value of pure water at 230nm and 275nm. The above 4 data are substituted into the model for calculation to obtain the final effective nitrogen concentration, and sent to the serial port screen for display and storage. The model is Lambert-Beer's law, the principle of which is that when a beam of monochromatic light passes through a uniform and non-scattering absorbing substance solution, the absorbance is proportional to the concentration of the absorbing substance and the optical path length.

[0134] A=ε·b·c

[0135] In the formula, ε is the molar absorptivity (or molar absorption coefficient), and the unit is usually L·mol-1·cm-1. It is a constant that depends on factors such as the nature of the absorbing substance, the wavelength of the incident light, and the solvent. The larger the ε value, the stronger the absorption ability of the substance at that wavelength; b is the optical path length, usually in cm. It refers to the distance the light beam passes through the solution of the absorbing substance; c is the concentration of the absorbing substance, usually in mol·L-1 (or M).

[0136] (6) Cleaning stage: drain all solutions, first open the discharge pumps of the absorbance detection module 4 and the ultrasonic extraction module 6, and then open the discharge pump of the electrocatalytic digestion tank 7. Open the pure water pump to add pure water, open the ultrasonic transducer 61 of the ultrasonic extraction module 6 for auxiliary cleaning, and open the discharge pumps of the absorbance detection module 4 and the electrocatalytic digestion tank 7 to perform bubbling operation in reverse for auxiliary cleaning. After 1 minute, turn off all pumps and transducers, turn on the discharge pumps of the absorbance detection module 4 and the ultrasonic extraction module 6, and turn on the discharge pump of the electrocatalytic digestion tank 7 after the absorbance detection module 4 is emptied. After emptying, turn off all pumps, and one-time detection is completed.

[0137] like Figure 7 The results shown in the figure are the results measured by the device. At a temperature of 25°C, the fitting curves of the detection results corresponding to different concentrations of effective nitrogen are obtained, and the following linear equation between absorbance and concentration is obtained: y = 0.08434*x + 0.11164, where R 2 The value is 0.998, the linearity is above 0.99, the sensitivity is high and the detection limit is low.

[0138] like Figure 8 The results shown in the figure are the results measured by the device. At a temperature of 25°C, the fitting curves of the detection results corresponding to different concentrations of available phosphorus are obtained. According to the data fitting, the following linear equation between absorbance and concentration is obtained: y=0.32*x+0.14, where the R^2 value is 0.99, indicating that the linear fitting effect is also very good. High sensitivity and low detection limit.

[0139] like Fig. 9 As shown in the figure, it is a comparison chart of the effects of different pre-treatment times before effective nitrogen detection. At a temperature of 25°C, the pre-treatment time has reached more than 95% in 25 minutes, with good results and high efficiency. The conversion rate of nitrate nitrogen to effective nitrogen is as high as more than 90%.

Claims

1. A soil available nitrogen and phosphorus detection device, characterized in that: The invention comprises a detection box, wherein the detection box body comprises a system control module (3), a human-machine interaction module (1) electrically connected to the system control module (3), an absorbance detection module (4), a solution transfer module (5), an ultrasonic extraction module (6) and an electrocatalytic digestion module (7); The system control module (3) is used to control other modules to perform actions; it is also used to collect or receive detection data from the absorbance detection module (4) and perform data processing, and the results of effective nitrogen and phosphorus concentrations obtained by the processing are sent to the human-computer interaction module (1); The solution transfer module (5) is used for mixing and transferring the solution in the device; The ultrasonic extraction module (6) is used to extract nitrogen and phosphorus components in the soil sample to obtain an extract; The electrocatalytic digestion module (7) is used to catalytically oxidize nitrogen and phosphorus in the leaching solution, digest and oxidize nitrogen components in different forms into nitrate nitrogen, and digest and oxidize phosphorus components in different forms into positive pentavalent phosphorus; The absorbance detection module (4) is used to detect effective nitrogen and phosphorus in the extract after electrocatalytic digestion; The human-computer interaction module (1) is used for human-computer interaction and displaying the results of effective nitrogen and phosphorus detection; It also includes a system power supply module (2) for supplying power to the device.

2. The soil available nitrogen and phosphorus detection device according to claim 1, characterized in that: It also includes a reagent box, wherein the reagent box body includes a reagent module (8) for storing reagents, wherein the reagents include an electrolyte solution, a quencher, and pure water.

3. The soil available nitrogen and phosphorus detection device according to claim 1, characterized in that: The solution transfer module (5) is formed by connecting a plurality of peristaltic pump modules to form an array.

4. The soil available nitrogen and phosphorus detection device according to claim 1, characterized in that: The system control module (3) includes two control boards, namely a main control board and a slave control board. The control content of the main control board includes: power supply control of the light source chip, back-end processing of the photodiode chip receiving signal, enable control of the slave control board, parameter modification of ultrasonic leaching, parameter modification of electrocatalytic digestion, parameter modification of absorbance test, and sending of test results; the control content of the slave control board includes: peristaltic pump module control.

5. The soil available nitrogen and phosphorus detection device according to claim 1, characterized in that: The absorbance detection module (4) comprises a light source chip (41), a cuvette device (42), and a photodiode chip (43); The light source chip sets the input current and input voltage of the light source through the system control module to provide a stable power supply to the light source; it performs closed-loop detection based on the photodiode chip at the back end and realizes self-checking by judging the detection error results; Cuvette device, the cuvette is made of polytetrafluoroethylene and has quartz glass sheets on both sides; Photodiode chip, during the spectrophotometric detection process, after the system control module turns on the light source, the light passes through the cuvette device and the liquid to be tested therein, and irradiates the photodiode in the photodiode chip, and the photodiode generates a detection signal.

6. The soil available nitrogen and phosphorus detection device according to claim 5, characterized in that: The photodiode chip (43) includes a photodiode with characteristic wavelengths of 230nm and 275nm or a spectrum chip with a wavelength band of 230nm and 275nm, and a photodiode with a characteristic wavelength of 697nm or a spectrum chip with a wavelength band of 697nm.

7. The soil available nitrogen and phosphorus detection device according to claim 1, characterized in that: The ultrasonic extraction module (6) comprises an ultrasonic transducer (61) for generating high-frequency ultrasonic waves, and an ultrasonic extraction tank (62); the ultrasonic transducer utilizes the synergistic effects of the cavitation effect, mechanical effect and thermal effect of the high-frequency ultrasonic waves to ultrasonically break the soil and extract the nitrogen and phosphorus components in the soil.

8. The soil available nitrogen and phosphorus detection device according to claim 1, characterized in that: The electrocatalytic digestion module is used to: catalytically oxidize ammonium nitrogen, nitrate nitrogen and some insoluble organic nitrogen obtained after soil extraction, oxidize and digest other types of nitrogen including organic nitrogen and other inorganic nitrogen, and finally convert them into nitrate nitrogen and send them to the absorbance detection module for detection; catalytically oxidize all water-soluble phosphorus and some adsorbed phosphorus obtained after soil extraction, convert them into pentavalent phosphorus, oxidize and digest other types of phosphorus, and finally oxidize them into pentavalent phosphorus and send them to the absorbance detection module for detection. The other types of phosphorus include: slightly soluble inorganic phosphorus and easily mineralized organic phosphorus.

9. The soil available nitrogen and phosphorus detection device according to claim 1, characterized in that: The electrocatalytic digestion module (7) comprises an electrolytic cell (71), an electrocatalytic anode (72), and an electrocatalytic cathode (73); the electrolyte in the electrolytic cell comprises a sodium sulfate electrolyte solution, a sodium carbonate electrolyte solution, and pure water; and the voltage between the electrocatalytic anode and the electrocatalytic cathode is in the range of 5V to 25V.

10. A method for detecting effective nitrogen and phosphorus in soil applied to the device for detecting effective nitrogen and phosphorus in soil according to claim 1, characterized in that: The following steps are involved: Step 1, a soil sample and pure water are added to an ultrasonic extraction module (6), and the system control module (3) opens a solution transfer module (5) for mixing, and after mixing, nitrogen and phosphorus components in the soil sample are extracted to obtain an extract; Step 2, the solution transfer module (5) transfers the leaching solution to the electrocatalytic digestion module (7), catalytically oxidizes the nitrogen and phosphorus in the leaching solution, digests and oxidizes the nitrogen components in different forms into nitrate nitrogen, and digests and oxidizes the phosphorus components in different forms into positive pentavalent phosphorus; after the digestion is completed, a quencher is added; Step 3, adding pure water to the cuvette of the absorbance detection module (4), performing absorbance detection at a characteristic wavelength, and obtaining a blank value of the current detection; the solution transfer module (5) transfers the extract to the absorbance detection module (4), performs absorbance detection at a characteristic wavelength, and obtains a detection value; Step 4, the system control module (3) collects or receives the blank value and the detection value of the absorbance detection module (4), and performs data processing; the data processing includes: calculating the blank value and the detection value by Lambert-Beer law to obtain the results of effective nitrogen and phosphorus concentrations; The soil total phosphorus detection process is the same as the soil total nitrogen detection process, and the absorbance at the corresponding characteristic wavelength is obtained for each: the soil total nitrogen detection obtains the absorbance at the characteristic wavelengths of 230nm and 275nm; the soil total phosphorus detection obtains the absorbance at the characteristic wavelength of 697nm. Step 5, the results of effective nitrogen and phosphorus concentrations are processed and sent to the human-computer interaction module (1); the human-computer interaction module (1) displays the results of effective nitrogen and phosphorus concentrations.

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