A soil moisture regulation and in-situ rhizosphere co2 dynamic capture system and method

Abstract

The application discloses a kind of soil humidity regulation and in situ rhizosphere CO2 dynamic capture system and method, the system includes: gas processing module, CO2 capture module, rhizosphere culture module, humidity regulation module and control module.Rhizosphere culture module contains soil and plant root system and carries out plant root system culture, its gas inlet is connected with gas processing module, its gas outlet is connected with CO2 capture module, it is also provided with outside communication gas port on it, first solenoid valve is arranged at its gas inlet.Humidity regulation module adjusts the humidity of soil in rhizosphere culture module.Control module includes first, second soil humidity sensors arranged in the inside and outside of rhizosphere culture module and programmable main control unit.The system of the application realizes the dynamic balance of rhizosphere microenvironment and natural soil humidity by integrating humidity regulation module and dynamic capture mechanism, while realizing continuous, accurate capture and quantitative analysis of rhizosphere CO2.

Description

Technical Field

[0001] This invention relates to a CO2 capture system, specifically to a soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system and method. Background Technology

[0002] Against the backdrop of global warming, CO2, as a major greenhouse gas, has profoundly impacted global climate and ecosystems due to changes in its atmospheric concentration. The carbon cycle in terrestrial ecosystems is a crucial link in regulating atmospheric CO2 concentration, and rhizosphere respiration, as a key process for material exchange between soil and atmospheric carbon pools, is vital for accurately monitoring rhizosphere CO2 release. This is essential for understanding the carbon budget of terrestrial ecosystems, assessing their carbon sink capacity, and predicting climate change trends.

[0003] However, the rhizosphere microhabitat in the field is complex and variable, significantly impacting the generation and transport of rhizosphere CO2. Traditional rhizosphere CO2 capture methods cannot meet the needs of current carbon cycle research.

[0004] Currently, devices for rhizosphere CO2 capture mainly have the following problems: First, the device covers and blocks natural rainfall, causing the cultivation environment to become disconnected from the external environment; Second, there is a lack of long-term, automated monitoring methods for the in-situ root systems of large tree species, resulting in a lot of manual intervention and low monitoring frequency.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of this disclosure, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system and method, which solves the problems of existing rhizosphere CO2 capture devices causing disconnection between the cultivation environment and the outside world due to the obstruction of natural precipitation, and the lack of long-term automated monitoring methods for the in-situ root systems of large tree species. By integrating a humidity regulation module and a dynamic capture mechanism, the invention achieves a dynamic balance between the rhizosphere microenvironment and natural soil moisture, while realizing continuous, accurate capture and quantitative analysis of rhizosphere CO2.

[0007] To achieve the above objectives, the present invention provides a soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system. This system comprises: a gas processing module for generating a CO2-free and dry airflow; a CO2 capture module for capturing rhizosphere respiration products carried by the carrier gas flow; a rhizosphere cultivation module for containing soil and plant roots and cultivating plant roots, its inlet connected to the gas processing module, its outlet connected to the CO2 capture module, and it also has an external communication port, with a first solenoid valve installed at the inlet; a humidity regulation module for regulating the soil humidity within the rhizosphere cultivation module; and a control... The control module includes a first soil moisture sensor disposed inside the rhizosphere culture module, a second soil moisture sensor disposed in the natural soil outside the rhizosphere culture module, and a programmable main control unit. The programmable main control unit is connected to the first soil moisture sensor, the second soil moisture sensor, a first solenoid valve, the second solenoid valve of the humidity control module, and a three-way solenoid valve, respectively. It acquires the numerical difference between the first soil moisture sensor and the second soil moisture sensor, and when the numerical difference meets the preset water replenishment conditions, it outputs a control signal to drive the second solenoid valve to open until the numerical difference returns to the balance range.

[0008] Preferably, the gas treatment module includes: an air pump connected in series; a first drying unit connected to the outlet of the air pump; a decarbonization unit connected to the outlet of the first drying unit; an air filter whose inlet is connected to the outlet of the decarbonization unit; and a needle valve whose inlet end is connected to the outlet of the air filter and whose outlet end is connected to the air inlet of the rhizosphere culture module.

[0009] More preferably, the first drying unit uses a first color-changing silica gel column; or / and, the decarbonization unit uses a soda lime column; or / and, the air filter uses a microporous membrane.

[0010] Preferably, the rhizosphere culture module includes: a sealed culture container, which is filled with experimental soil and contains plant roots to provide a natural environment for rhizosphere respiration; the sealed culture container has three air inlets, namely an air inlet, an air outlet, and an external air outlet, the air inlet being connected to the gas processing module, and the air outlet being connected to the CO2 capture module.

[0011] More preferably, one end of the sealed culture container is an air inlet and the other end is an air outlet. The air inlet of the sealed culture container is equipped with a first solenoid valve, and the air outlet of the sealed culture container is equipped with a three-way solenoid valve. One outlet of the three-way solenoid valve is connected to the inlet of the CO2 capture module through a hose, and the other outlet of the three-way solenoid valve is connected to the outside air; or / and, the sealed culture container is provided with an insertion port for inserting plant roots. The insertion port is provided with a removable silicone plug, and the silicone plug has a through hole for the plant roots to pass through.

[0012] Preferably, the CO2 capture module includes: a second drying unit and an absorption container containing an alkaline solution; wherein, the outlet of the rhizosphere culture module is connected to the second drying unit, the outlet of the second drying unit is connected to the absorption container, the second drying unit is used to prevent water vapor from entering the alkaline solution, and the absorption container is used to capture rhizosphere respiration products carried by the carrier gas flow.

[0013] More preferably, the second drying unit employs a second color-changing silica gel column.

[0014] Preferably, the humidity control module includes: a water storage container, a second solenoid valve, and a drip irrigation pipe installed within the rhizosphere culture module; wherein, the water storage container is located outside the rhizosphere culture module and is connected to the drip irrigation pipe, and the outlet of the water storage container is provided with a second solenoid valve for controlling the opening and closing of the drip irrigation.

[0015] Preferably, the programmable main control unit includes: a microcontroller, a wireless communication module, and a data storage unit; wherein, the wireless communication module is used to remotely receive control commands, and the remote communication module is connected to the microcontroller; the microcontroller is connected to the OLED display screen, the data storage unit, the first solenoid valve, the second solenoid valve, the three-way solenoid valve, the first soil moisture sensor, and the second soil moisture sensor via a bus; the programmable main control unit is housed inside a waterproof enclosure.

[0016] Preferably, the system further includes a solar photovoltaic panel and a battery, wherein the solar photovoltaic panel and the battery provide power.

[0017] The second objective of this invention is to provide a method for soil moisture regulation and in-situ rhizosphere CO2 dynamic capture, the method comprising: S1: System initialization, start the air pump to introduce CO2-free dry air into the rhizosphere culture module at a constant flow rate; S2: Data acquisition, using the programmable main control unit to periodically read the values ​​H from the first and second soil moisture sensors. in and H out ; S3: Differential feedback regulation, the programmable main control unit calculates the humidity difference ΔH = H out -H in If ΔH > δ, where δ is a preset threshold, then the second solenoid valve is activated to drip-irrigate the rhizosphere culture module until H... in ≥H out Close at any time; S4: Dynamic capture, the airflow carrying CO2 produced by rhizosphere respiration passes through the CO2 capture module, and the CO2 is chemically fixed by the alkaline absorption liquid; S5: Quantitative analysis. After the preset sampling period ends, the alkaline absorption liquid is taken out for analysis to calculate the total rhizosphere respiration during that period.

[0018] The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system and method of the present invention solves the problems of existing rhizosphere CO2 capture devices causing disconnection between the cultivation environment and the external environment due to obstruction of natural rainfall, and the lack of long-term automated monitoring methods for in-situ root systems of large tree species. It has the following advantages: (1) The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system of the present invention can eliminate the interference of humidity fluctuations on rhizosphere respiration by controlling the humidity of the rhizosphere microenvironment, accurately capture the CO2 in the rhizosphere, and provide reliable data support for in-depth research on rhizosphere physiological and ecological processes, the interaction between roots and soil microorganisms, and the response mechanism of the rhizosphere to global change. (2) The system of the present invention integrates a programmable main control unit and dual soil moisture sensors, realizing real-time monitoring and dynamic feedback adjustment of the humidity inside and outside the rhizosphere culture module. Through differential control logic, the rhizosphere soil moisture and the external natural soil moisture are kept in dynamic balance, maximizing the restoration of natural growth conditions and avoiding the microenvironment distortion problem caused by long-term coverage of traditional devices. (3) The present invention uses solar photovoltaic panels in conjunction with batteries for power supply, which significantly improves the system’s endurance and environmental adaptability in complex field environments, reduces dependence on external power sources, and is especially suitable for long-term observation experiments in remote areas. (4) The CO2 capture module of the present invention, through the combination design of the second drying unit and alkaline absorbent, not only effectively removes water vapor in the airflow to avoid affecting the absorption efficiency, but also achieves efficient CO2 capture through chemical fixation. Combined with subsequent analysis, the total amount of rhizosphere respiration can be accurately calculated, providing high-precision quantitative data for carbon cycle research. (5) The sealed culture container of the rhizosphere culture module of the present invention is designed with a three-way solenoid valve to connect with the outside world, which can flexibly switch between the collection state and the natural ventilation state, maintain gas exchange between the rhizosphere and the outside world during non-sampling periods, reduce the potential impact of long-term sealing on root activity, and the silicone plug structure facilitates the non-destructive implantation and sealing of plant roots, enhancing the applicability of the system to different plant types. (6) The wireless communication module in the control module of the present invention supports the reception and transmission of remote control commands, and works with the data storage unit to realize local data storage. The OLED display screen can display key parameters in real time, realizing the automation and intelligence of the monitoring process, greatly reducing manual intervention, improving the continuity and accuracy of monitoring data, and providing a stable and reliable technical platform for long-term ecological research. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system of the present invention.

[0020] Figure 2 This is a partial structural schematic diagram of the soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system of the present invention.

[0021] Figure 3 This is a schematic diagram of the internal structure of the soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system of the present invention.

[0022] Figure 4 This is a schematic diagram of the microcontroller used in this invention.

[0023] Figure 5 This is a circuit diagram of the two humidity sensors of the present invention.

[0024] Figure 6 This is a circuit diagram of the display screen of the present invention.

[0025] Figure 7 This is a circuit diagram of the 4G module of the present invention.

[0026] Figure 8 This is a circuit diagram showing the connection of the air pump of the present invention.

[0027] Figure 9 This is a circuit diagram of the SD card of the present invention.

[0028] Figure 10 This is a connection diagram of the extended circuit of the microcontroller of the present invention.

[0029] Figure 11 This is a circuit diagram of the filter circuit of the present invention.

[0030] Figure 12 This is the circuit diagram of the 16MHz crystal oscillator of the present invention.

[0031] Figure 13 This is a circuit diagram of the reset key of the present invention.

[0032] Figure 14 This is the circuit diagram of CH340G of the present invention.

[0033] Figure 15 This is the TYPEC circuit diagram of the present invention.

[0034] Figure 16 This is a circuit diagram of the 5V voltage regulator chip of the present invention.

[0035] Figure 17 This is a circuit diagram of the 3V voltage regulator chip of the present invention.

[0036] Figure 18 This is a circuit diagram of the tantalum capacitor of the present invention.

[0037] Figure 19 This is a circuit diagram of the self-resetting fuse of the present invention.

[0038] Figure 20 This is a circuit diagram of the relay module of the present invention.

[0039] Labels: 1. Waterproof box; 2. Solar photovoltaic panel; 3. Air filter; 4. Needle valve; 5. First solenoid valve; 6. Culture column; 7. Plant root system; 8. Silicone stopper; 9. Drip irrigation tube; 10. Three-way solenoid valve; 11. Water storage container; 12. First drying unit; 13. Decarbonization unit; 14. Second solenoid valve; 15. Second drying unit; 16. Empty bottle; 17. Absorption container; 18. Fixing clamp; 101. Air pump; 102. First soil moisture sensor; 103. Second soil moisture sensor; 104. Remote communication module; 105. Data storage unit; 106. Microcontroller; 107. OLED display screen. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] It should be noted that: Unless otherwise specified in the examples, conditions should be followed according to standard conditions or the manufacturer's recommendations. Instruments whose manufacturers are not specified are all commercially available products. Raw materials and reagents whose manufacturers are not specified are all commercially available goods or can be prepared using known methods.

[0042] In this invention, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are used only for simplicity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0043] The features mentioned in this invention can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification, provided that there is no contradiction in the combination of these features. Each feature disclosed in the specification can be replaced by any alternative feature that provides the same, equivalent, or similar purpose. Therefore, unless otherwise specified, the disclosed features are merely general examples of equivalent or similar features.

[0044] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. The terms "first," "second," "third," etc., and similar relational terms are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. Furthermore, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0045] A soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system is disclosed. The system comprises a gas processing module, a rhizosphere cultivation module, a CO2 capture module, a humidity regulation module, and a control module. The gas processing module generates a CO2-free and dry airflow. The rhizosphere cultivation module contains soil and plant roots for root cultivation. The air inlet of the rhizosphere cultivation module is connected to the gas processing module, and the air outlet is connected to the CO2 capture module. The CO2 capture module captures rhizosphere respiration products carried by the airflow. The humidity regulation module regulates the soil moisture within the rhizosphere cultivation module. The control module includes a first soil moisture sensor 102 disposed inside the rhizosphere cultivation module, a second soil moisture sensor 103 disposed in the natural soil outside the rhizosphere cultivation module, and a programmable main control unit. The programmable main control unit is connected to the first soil moisture sensor 102, the second soil moisture sensor 103 and the second solenoid valve 14 of the humidity adjustment module respectively. It obtains the numerical difference between the first soil moisture sensor 102 and the second soil moisture sensor 103, and when the numerical difference meets the preset water replenishment conditions, it outputs a control signal to drive the second solenoid valve 14 to open until the numerical difference returns to the balance range.

[0046] The aforementioned gas treatment module includes an air pump 101, a first drying unit 12, a decarbonization unit 13, and an air filter 3 connected in series. The outlet of the air pump 101 is connected to the inlet of the first drying unit 12 via a hose. The outlet of the first drying unit 12 is connected to the inlet of the decarbonization unit 13 via a hose. The outlet of the decarbonization unit 13 is connected to the inlet of the air filter 3 via a hose. The decarbonization unit 13 is used to remove background CO2 from the air.

[0047] Specifically, the decarbonation unit uses a soda lime column. Soda lime is a commonly used desiccant and gas purifier, mainly composed of sodium hydroxide (NaOH) and calcium hydroxide (Ca(OH)2), which can effectively absorb carbon dioxide. Sodium hydroxide reacts with carbon dioxide to produce sodium carbonate and water, and calcium hydroxide then reacts with sodium carbonate to produce calcium carbonate precipitate. Calcium hydroxide can also react with carbon dioxide to produce calcium carbonate precipitate.

[0048] Specifically, the first drying unit 12 uses a first color-changing silica gel column filled with silica gel desiccant. It displays different colors in the dry state and after absorption, making it easy to visually determine whether its drying capacity has failed. For example, in the dry state, it is a small blue sphere; after absorbing moisture, it turns pink. If the drying unit turns pink, the silica gel desiccant needs to be replaced to ensure the dryness of the air entering the decarbonization unit and prevent moisture from affecting the decarbonization efficiency of the soda lime.

[0049] Furthermore, the air filter 3 uses a microporous membrane to remove particulate matter from the gas, ensuring that the air entering the culture column 6 is clean.

[0050] Furthermore, a needle valve 4 is installed on the hose connecting the gas treatment module and the rhizosphere culture module. The function of the needle valve is to precisely adjust the airflow speed and provide stable airflow conditions for the accurate capture of rhizosphere CO2.

[0051] Specifically, the outlet of the air filter 3 is connected to the inlet of the needle valve 4 via a hose, and the outlet of the needle valve 4 is connected to the air inlet of the sealed culture container 6 of the rhizosphere culture module via a hose.

[0052] The rhizosphere culture module includes a sealed culture container 6, which is filled with experimental soil to accommodate plant roots 7, providing a natural environment for rhizosphere respiration. The sealed culture container 6 has three air inlets: an inlet, an outlet, and an external connection outlet. The inlet is connected to a gas processing module, and the outlet is connected to a CO2 capture module.

[0053] Specifically, the sealed culture container 6 can be a sealed culture column.

[0054] Furthermore, the sealed culture container 6 is provided with an insertion port for inserting plant roots 7. A silicone plug 8 is provided at the insertion port, and the silicone plug 8 has a through hole for the plant roots to pass through, which ensures the airtightness of the culture container without hindering the normal growth of the plant.

[0055] Furthermore, one end of the sealed culture container 6 is the air inlet, and the other end is the air outlet. The air inlet of the sealed culture container 6 is equipped with a first solenoid valve 5, and the air outlet of the sealed culture container 6 is equipped with a three-way solenoid valve 10. One outlet of the three-way solenoid valve 10 is connected to the inlet of the CO2 capture module through a hose, and the other outlet of the three-way solenoid valve 10 is connected to the outside air (i.e., the aforementioned outside air connection port).

[0056] The CO2 capture module described above includes a second drying unit 15 and an absorption container 17 containing an alkaline solution. The outlet of the rhizosphere culture module is connected to the second drying unit 15, and the outlet of the second drying unit 15 is connected to the absorption container 17 via a flexible hose. The second drying unit 15 prevents water vapor from entering the alkaline solution, and the absorption container 17 is used to capture rhizosphere respiration products carried by the carrier gas flow.

[0057] Specifically, one outlet of the three-way solenoid valve 10 at the vent of the sealed culture container 6 is connected to the inlet of the second drying unit 15 via a hose.

[0058] Specifically, the second drying unit 15 uses a second color-changing silica gel column filled with silica gel desiccant. It displays different colors in the dry state and after absorbing moisture, making it easy to visually determine whether its drying capacity has failed. For example, in the dry state, it is a small blue sphere; after absorbing moisture, it turns pink. If the drying unit turns pink, the silica gel desiccant needs to be replaced.

[0059] Furthermore, the CO2 capture module also includes an empty bottle 16 disposed between the second drying unit 15 and the absorption container 17 to prevent the alkaline solution in the absorption container 17 from being drawn back into the second drying unit 15.

[0060] Furthermore, the second drying unit 15, the empty bottle 16, and the absorption container 17, as well as the first drying unit 12 and the decarbonization unit 13, are fixed with a fixing clip 18. The integrated structure makes the device more convenient to carry.

[0061] The humidity control module includes a water storage container 11, a second solenoid valve 14, and a drip irrigation pipe 9 installed inside the sealed culture container 6. The water storage container 11 is located outside the sealed culture container 6 and is connected to the drip irrigation pipe 9. The second solenoid valve 14 is installed at the outlet of the water storage container 11 to control the opening and closing of the drip irrigation.

[0062] Specifically, the drip irrigation tube 9 is spirally installed inside the sealed culture container 6. Each spiral of the drip irrigation tube 9 has several drip irrigation holes evenly distributed, facing the experimental soil layer to ensure that water can penetrate evenly throughout the soil. The inlet of the drip irrigation tube 9 extends from a through-hole in the sealed culture container 6 and connects to the water storage container 11. A second solenoid valve 14 is installed at the outlet of the water storage container 11. The water storage container 11 controls the drip irrigation through the second solenoid valve 14, allowing the drip irrigation tube 9 to evenly deliver water into the sealed culture container 6.

[0063] For example, a 3cm thick bag of quartz sand (particle size 1-2cm) is laid on the surface and bottom of the experimental soil in the sealed culture container 6 to prevent clogging of the air inlet and outlet. The water storage container 11 can be filled with deionized water to reduce scale formation and lower the risk of clogging the drip irrigation pipe pores. The pores of the drip irrigation pipe are about 0.5mm, and water is mainly replenished by infiltration into the experimental soil.

[0064] Furthermore, the aforementioned programmable main control unit includes a microcontroller 106 (MCU), a wireless communication module 104, and a data storage unit 105. The wireless communication module is configured to support 4G or NB-IoT communication protocols for remotely receiving control commands. The remote communication module 104 supports remote online control and timing functions. The remote communication module 104 is connected to the microcontroller 106, which in turn is connected to a first soil moisture sensor 102 and a second soil moisture sensor 103. The first soil moisture sensor 102 is embedded inside the sealed culture container 6, while the second soil moisture sensor 103 is embedded parallel to the outside of the sealed culture container 6. These moisture sensors can better reflect the hydrological environment at the same horizontal level. The microcontroller 106 is connected to the OLED display 107, the data storage unit 105 (which may use an SD card module), the first solenoid valve 5, and the second solenoid valve 14 via a bus. The moisture sensors monitor soil moisture in real time, and the data is fed back to the microcontroller 106. The microcontroller 106 compares the difference between the first soil moisture sensor 102 and the second soil moisture sensor 103 to regulate the opening and closing of the second solenoid valve 14, thereby achieving soil moisture regulation. The humidity sensor first transmits data to the microcontroller 106, which then transmits it to the OLED display 107 and the data storage unit 105. The OLED display 107 displays soil moisture data in real time, and the data storage unit 105 stores the humidity data synchronously, enabling intelligent management. The programmable main control unit is housed inside the waterproof enclosure 1. The waterproof enclosure provides sealed protection for the system's critical electronic components, preventing short circuits and corrosion, and ensuring stable operation of the equipment in complex outdoor environments.

[0065] This invention eliminates the water stress error caused by the device blocking precipitation in field monitoring by using a humidity synchronization adjustment method based on dual sensors. The water replenishment condition of the second solenoid valve 14 adopts a hysteresis control algorithm. When the detection value of the first soil moisture sensor is lower than the detection value of the second soil moisture sensor and reaches a threshold, it is determined that the water replenishment condition is met. At this time, the second solenoid valve 14 is opened, so that the deionized water in the water storage container 11 can be accurately compensated through the drip irrigation pipe 9. When the detection value of the first soil moisture sensor rises back to the detection value of the second soil moisture sensor, it is determined that the water replenishment condition is stopped.

[0066] The hysteresis control algorithm of this invention is as follows: First, an internal soil moisture sensor (pin A0), an external soil moisture sensor (pin A1), and a solenoid valve control pin (pin 7) were defined. At the same time, a high threshold (difference between external and internal humidity of 5.0) and a low threshold (difference of 0.0, i.e., internal humidity is not lower than external humidity) for hysteresis control were set, and a water replenishment status flag variable was defined.

[0067] During the system initialization phase, serial communication at 9600 baud rate is enabled, the solenoid valve pin is configured to output mode and initialized to low level to close the solenoid valve, and a prompt message indicating that the initialization is complete is printed via the serial port. After entering the main loop, the system executes a detection process every 5 minutes. First, it reads the analog input values ​​of the two humidity sensors and converts them into corresponding humidity percentages (inner_humidity, outer_humidity), calculates the humidity difference ΔH between the two, and then executes hysteresis control logic: when not in a water replenishment state, if the humidity difference ΔH exceeds the high threshold (5.0), a water replenishment operation is triggered (the solenoid valve pin is set to high level to open the valve, the water replenishment state is marked as true, and the water replenishment start information is printed on the serial port); when in a water replenishment state, if the internal humidity is greater than or equal to the external humidity (i.e., the difference is lower than the low threshold 0.0), a water replenishment stop operation is triggered (the solenoid valve pin is set to low level to close the valve, the water replenishment state is marked as false, and the water replenishment stop information is printed on the serial port). In addition, a safety protection mechanism is set up. If the external humidity exceeds 90.0 and the system is in a water replenishment state, water replenishment will be forcibly stopped and a corresponding warning message will be printed on the serial port. After completing one detection process, a 5-minute delay is entered to wait for the next round of monitoring.

[0068] To prevent excessive water replenishment in the sealed culture container 6 due to extreme rainfall, which would prevent water from evaporating, the microcontroller 106 is programmed to stop the second solenoid valve 14 from working when the soil moisture data of the first soil moisture sensor 102 exceeds 90% of the preset value.

[0069] Specifically, the microcontroller 106 uses an ATMEGA328P-AU microcontroller, with the following structure: Figure 4 As shown. The ATMEGA328P-AU microcontroller is an 8-bit AVR microcontroller with 32KB of in-system programmable flash memory.

[0070] Furthermore, the system also includes: solar photovoltaic panels 2 and a battery. Powered by the solar photovoltaic panels and the battery, the main control unit automatically adjusts to enter a low-power sleep mode during non-data acquisition, non-water replenishment, and non-CO2 capture phases, reducing equipment energy consumption and extending its service life.

[0071] For example, at the hardware level, the ATMEGA328P-AU microcontroller supports a power-down low-power mode, which can shut down the clock signals of unnecessary modules, retaining only the power supply for timers and external interrupts. Simultaneously, the main control unit controls the wireless communication module, OLED display, and SD card module via the bus, cutting off their power supply during non-operational periods. The electronic control components of the gas processing module and humidity control module also cease operation during non-CO2 capture and non-water replenishment phases. At the software level, the system presets a soil moisture data acquisition cycle. When a data acquisition is completed and there is no water replenishment requirement (humidity difference ΔH ≤ preset threshold δ) and it is not in a CO2 capture state, a sleep process is triggered. Instructions cause the microcontroller to enter the power-down minimum power consumption mode, while saving key system parameters to the on-chip EEPROM to prevent data loss. During sleep, precise wake-up is achieved through timer interrupts (wake-up at preset cycles for data acquisition) and external interrupts (humidity surges, remote commands, and abnormal state triggers), ensuring continuous low power consumption during non-operational periods and rapid resumption of operation during operational periods without manual intervention.

[0072] For example, the circuit diagram of the system of the present invention is shown below. Figures 4-20 . Figure 4 The MCU (microcontroller unit, i.e., microcontroller 106) is the core control unit of the system, responsible for running user programs, processing sensor signals, communication interaction, etc. Its pins are connected to various functional modules to realize centralized control of the entire system. Figure 5 It consists of two independent dual-channel humidity detection circuits, which can simultaneously detect the humidity at two locations and output a humidity signal. Figure 6 This is an OLED display circuit used for local visualization of system status, displaying real-time humidity values, equipment operating modes, and fault prompts. Figure 7 It is a 4G module circuit used to enable communication between the device and the cloud / remote terminal, supporting remote data uploading and remote command reception to complete the Internet of Things (IoT) network. Figure 8 It provides external wiring for the pump and a power supply interface for external actuators, while suppressing power interference during pump operation. Figure 9 This is an SD card circuit used to enable SPI communication between the MCU and the TF card, and to locally store sensor data, system logs, and other information. Figure 10 For MCU expansion, it expands the USB interface, allowing connection of external USB devices (such as sensors and storage devices), or serves as a backup USB communication interface. Figure 11 This is a filtering circuit that filters the +5V power supply and the analog reference voltage (AREF) to remove voltage ripple and high-frequency interference, thereby improving the stability of the MCU power supply and the accuracy of analog sampling. Figure 12It is a 16MHz crystal oscillator, providing the operating clock for the ATMEGA328P (one of the standard clocks of the ATMEGA328P, which determines timing parameters such as system operating speed and serial port baud rate). Figure 13 The reset button enables "power-on reset + manual reset" for the MCU: when powered on, the circuit composed of C42+R46 automatically pulls the reset pin (RES) low, triggering MCU initialization; when the button is pressed, the RES pin is grounded, and the MCU is manually restarted (to resolve system abnormalities). Figure 14 The CH340G chip is used to implement protocol conversion between the "computer USB interface" and the "MCU serial port", supporting MCU program download and serial port debugging communication. Figure 15 Provides basic power supply for the Type-C interface, USB 2.0 data transfer, and is reversible. Figure 16 The circuit for the 5V voltage regulator chip stably converts the input voltage (VCC) into a 5V DC voltage, providing a stable power supply for subsequent electronic devices. Figure 17 The circuit for the 3V voltage regulator chip stably converts the input voltage (VCC) into a 3V DC voltage, providing a stable power supply for subsequent electronic devices. Figure 18 It is a tantalum capacitor circuit. Figure 19 These are self-resetting fuses, all of which are 5V power supply auxiliary protection modules used to optimize the stability and safety of 5V power supply and simplify status monitoring.

[0073] The energy storage and filtering circuit, combined with ceramic capacitors, is used to filter out high-frequency noise and voltage fluctuations at the power input, ensuring the power supply stability of subsequent circuits. Figure 19 This is a solenoid valve drive circuit that amplifies the current signal through a transistor to control the switching of the first and second solenoid valves, ensuring reliable valve operation. Figure 20 The power input interface circuit includes overcurrent protection and reverse connection protection modules to prevent damage to system components due to incorrect polarity or excessive current when an external power source is connected. These circuit modules work together to form the hardware foundation for stable system operation, ensuring the efficient implementation of functions such as humidity control, CO2 capture, data acquisition, and remote communication. Figure 20 This is a relay module used to achieve isolated control of high-voltage / high-current loads by the MCU, thereby improving system safety and anti-interference capabilities.

[0074] The method of using the soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system of the present invention is as follows: Before collection, the first solenoid valve 5 is opened, and the air pump 101 is turned on to continuously introduce clean, CO2-free air into the culture column 6 and exhaust it to the atmosphere through the exhaust port for 30 minutes to remove the residual background CO2 in the chamber.

[0075] During CO2 capture, the first solenoid valve 5 opens, and the air pump 101 pumps in air, which passes sequentially through the first drying unit 12, the decarbonization unit 13, and the air filter 3, forming CO2-free dry air that is then input into the sealed culture container 6. The three-way solenoid valve 10 opens the hose connected to the second drying unit 15, while closing the valve connecting to the outside air. During natural root growth cultivation, the three-way solenoid valve 10 opens the valve connecting to the outside air and closes the hose connected to the second drying unit 15, allowing real-time exchange between the inside of the culture column 6 and the atmospheric environment. Humidity regulation maintains consistent hydrology inside and outside the sealed culture container 6, ensuring the root physiological state remains natural.

[0076] The opening and closing of the three-way solenoid valve 10, the first solenoid valve 5, and the second solenoid valve 14 are controlled by the microcontroller 106. The acquisition time is set to 48 hours via the remote communication module 104, after which the system returns to its initial state.

[0077] During in-situ rhizosphere CO2 dynamic capture, data acquisition is performed by periodically reading the first soil moisture sensor 102 (H) using a programmable main control unit. in ) and the second soil moisture sensor 103 (H out The value of the soil moisture sensor; differential feedback adjustment, the programmable main control unit synchronously reads the real-time values ​​of the first and second soil moisture sensors according to a preset cycle, and the main control unit calculates the moisture difference ΔH = H. out - H in A preset humidity threshold δ is set. If ΔH > δ, it means that the soil humidity inside the culture container is lower than that of the external natural soil, meeting the water replenishment conditions. Then, a water replenishment command is triggered, and the second solenoid valve 14 is opened to drip-irrigate the sealed culture container 6 until H... in ≥H out When the system is closed, dynamic collection begins. The airflow carrying CO2 generated by rhizosphere respiration passes through the CO2 collection module, where the CO2 is chemically fixed by the alkaline absorbent. Through quantitative analysis, after the preset sampling cycle ends, the alkaline absorbent is taken out for titration analysis or total organic carbon analysis to calculate the total amount of rhizosphere respiration during that cycle.

[0078] The advantage of using differential feedback regulation is that it avoids frequent start-stop of the solenoid valve due to small fluctuations in humidity, improving equipment stability and water replenishment accuracy. The preset threshold δ can be set and modified according to the soil environment in the field. Soil texture directly affects water retention capacity and humidity fluctuation range, which is the primary basis for setting δ: Sandy soil has drastic humidity changes, so a larger δ setting (2~5%) can reduce the frequency of water replenishment, avoiding water waste and frequent equipment operation. At the same time, due to its poor water retention, a slightly larger difference between the rhizosphere and the natural soil is allowed before water replenishment, without affecting root growth. Soil humidity fluctuations are moderate, so a δ setting of (1.5~3%) balances "synchronization between the rhizosphere and the natural soil" and "equipment stability," making it suitable for most scientific research monitoring scenarios. Clay soil has small humidity fluctuations, so a smaller δ setting (1~2%) can ensure that the rhizosphere humidity keeps up with the natural soil in a timely manner, avoiding excessive dryness of the rhizosphere. Moreover, clay soil has strong water retention, and small amounts of water replenishment can achieve balance, so an excessively large δ value is not required. The system of this invention is applicable to forest, grassland, wetland, and farmland ecosystems, providing continuous monitoring support for carbon sink assessment and ecological management.

[0079] Furthermore, the system of this invention operates at low power consumption during long-term field monitoring. The main control unit has an automatic sleep mode to reduce energy consumption during non-data acquisition and water replenishment phases, and can achieve unattended operation with solar power. Humidity fluctuation data is displayed in real time on the OLED display screen 107 and simultaneously recorded to the data storage unit 105, providing a complete microenvironment monitoring sequence for subsequent scientific research and analysis.

[0080] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system, characterized in that, The system includes: A gas processing module for generating a CO2-free and dry gas stream; The CO2 capture module is used to capture rhizosphere respiration products carried by the carrier gas flow. The rhizosphere culture module is used to contain soil and plant roots and to cultivate plant roots. Its air inlet is connected to the gas treatment module, its air outlet is connected to the CO2 capture module, and it is also provided with an external air outlet. A first solenoid valve (5) is provided at its air inlet. A humidity control module for regulating the humidity of the soil within the rhizosphere culture module; and The control module includes a first soil moisture sensor (102) disposed inside the rhizosphere cultivation module, a second soil moisture sensor (103) disposed in the natural soil outside the rhizosphere cultivation module, and a programmable main control unit. The programmable main control unit is connected to the first soil moisture sensor (102), the second soil moisture sensor (103), the first solenoid valve (5), the second solenoid valve (14) of the humidity adjustment module, and the three-way solenoid valve (10), respectively. It obtains the numerical difference between the first soil moisture sensor (102) and the second soil moisture sensor (103), and when the numerical difference meets the preset water replenishment conditions, it outputs a control signal to drive the second solenoid valve (14) to open until the numerical difference returns to the balance range.

2. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 1, characterized in that, The gas processing module includes: Air pumps (101) connected in series. The first drying unit is connected to the outlet of the air pump (101); A decarbonization unit is connected to the outlet of the first drying unit; An air filter (3) has its inlet connected to the outlet of the decarbonization unit; as well as The needle valve (4) has its inlet end connected to the outlet of the air filter (3) and its outlet end connected to the air inlet of the rhizosphere culture module.

3. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 2, characterized in that, The first drying unit uses a first color-changing silica gel column; Or / and, the decarbonization unit is selected from a soda lime column; Or / and, the air filter (3) employs a microporous membrane.

4. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 1, characterized in that, The rhizosphere culture module includes: a sealed culture container (6), which is filled with experimental soil and contains plant roots (7) to provide a natural environment for rhizosphere respiration; the sealed culture container (6) is provided with three air ports, namely an air inlet, an air outlet and an external communication air port, the air inlet is connected to the gas processing module and the air outlet is connected to the CO2 capture module.

5. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 4, characterized in that, One end of the sealed culture container (6) is the air inlet and the other end is the air outlet. The air inlet of the sealed culture container (6) is equipped with a first solenoid valve (5), and the air outlet of the sealed culture container (6) is equipped with a three-way solenoid valve (10). One outlet of the three-way solenoid valve (10) is connected to the inlet of the CO2 capture module through a hose, and the other outlet of the three-way solenoid valve (10) is connected to the outside air. Or / and, the sealed culture container (6) is provided with an insertion port for inserting plant roots (7), and a removable silicone plug (8) is provided at the insertion port, and the silicone plug (8) has a through hole for the plant roots to pass through.

6. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 1, characterized in that, The CO2 capture module includes: a second drying unit (15) and an absorption container (17) containing an alkaline solution; wherein, the outlet of the rhizosphere culture module is connected to the second drying unit (15), the outlet of the second drying unit (15) is connected to the absorption container (17), the second drying unit (15) is used to prevent water vapor from entering the alkaline solution, and the absorption container (17) is used to capture the rhizosphere respiration products carried by the carrier gas flow; Or / and, the humidity control module includes: a water storage container (11), a second solenoid valve (14), and a drip irrigation pipe (9) arranged in the rhizosphere culture module; wherein, the water storage container (11) is located outside the rhizosphere culture module and is connected to the drip irrigation pipe (9), and the outlet of the water storage container (11) is provided with a second solenoid valve (14) for controlling the opening and closing of the drip irrigation.

7. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 6, characterized in that, The second drying unit (15) uses a second color-changing silica gel column.

8. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 1, characterized in that, The programmable main control unit includes: a microcontroller (106), a wireless communication module (104), and a data storage unit (105); wherein, the wireless communication module is used to remotely receive control commands, and the remote communication module (104) is connected to the microcontroller (106). The microcontroller (106) is connected to the OLED display (107), data storage unit (105), first solenoid valve (5), second solenoid valve (14), three-way solenoid valve (10), first soil moisture sensor (102) and second soil moisture sensor (103) via a bus. The programmable main control unit is housed inside the waterproof box (1).

9. The soil moisture regulation and in-situ rhizosphere CO2 dynamic capture system according to claim 1, characterized in that, The system also includes a solar photovoltaic panel (2) and a battery, which are powered by the solar photovoltaic panel (2) in conjunction with the battery.

10. A method for soil moisture regulation and in-situ rhizosphere CO2 dynamic capture, the method comprising: S1: System initialization, start the air pump to introduce CO2-free dry air into the rhizosphere culture module at a constant flow rate; S2: Data acquisition, using the programmable main control unit to periodically read the values ​​H from the first and second soil moisture sensors. in and H out ; S3: Differential feedback regulation, the programmable main control unit calculates the humidity difference ΔH = H out -H in If ΔH > δ, where δ is a preset threshold, then the second solenoid valve is activated to drip-irrigate the rhizosphere culture module until H... in ≥H out Close at any time; S4: Dynamic capture, the airflow carrying CO2 produced by rhizosphere respiration passes through the CO2 capture module, and the CO2 is chemically fixed by the alkaline absorption liquid; S5: Quantitative analysis. After the preset sampling period ends, the alkaline absorption liquid is taken out for analysis to calculate the total rhizosphere respiration during that period.

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