Karst carbon sink pot experiment device and measuring method based on high-resolution water chemistry online monitoring

Abstract

The application discloses a karst carbon sink potting simulation device based on high-resolution water chemistry online monitoring and a measuring and calculating method. ‑ The application discloses a karst carbon sink potting simulation device based on high-resolution water chemistry online monitoring and a measuring and calculating method. ‑ The application discloses a karst carbon sink potting simulation device based on high-resolution water chemistry online monitoring and a measuring and calculating method. 2‑ The application discloses a karst carbon sink potting simulation device based on high-resolution water chemistry online monitoring and a measuring and calculating method. The application can realize automatic control of rainfall, high-resolution continuous flow measurement, carbon sink monitoring integration capable of accurately excluding exogenous acid interference, and solves the technical problems of low time resolution and interference of impurity ions under a complex fertilization background in the traditional method.

Description

Technical Field

[0001] This invention belongs to the field of environmental geology and agricultural ecological carbon sink monitoring technology, specifically relating to a potted plant simulation device and method for karst carbon sink based on high-resolution online hydrochemical monitoring. Background Technology

[0002] Exploring the mechanisms by which fertilizer reduction and the application of different soil amendments (such as biochar and organic fertilizer) enhance soil productivity and carbon sequestration capacity in karst areas is of great significance. Currently, the main methods for assessing karst carbon sequestration intensity are hydrochemical runoff and dissolution specimen methods. However, existing pot simulation and monitoring techniques have significant shortcomings: First, traditional experiments rely heavily on natural rainfall, making it impossible to control rainfall variables; second, the hydrochemical runoff method relies on manual collection of leachate for testing or on-site titration, which is time-consuming, labor-intensive, and has extremely low temporal resolution, making it difficult to capture dynamic runoff generation and transient changes in ion concentration during rainfall; third, with the application of fertilizers and amendments, leachate contains a large number of exogenous acid ions (such as nitrate and sulfate ions), and these impurity ions severely interfere with the analysis of conductivity and bicarbonate (HCO3-) concentrations. - The linear relationship between precipitation and flow rate leads to severe distortion in the assessment of karst carbon sink flux. Therefore, there is an urgent need for an integrated carbon sink monitoring device and method that can automatically control rainfall, perform high-resolution continuous flow measurement, and accurately eliminate interference from exogenous acids. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a potted carbon sink simulation device and calculation method based on high-resolution online hydrochemical monitoring. This device achieves integrated carbon sink monitoring with automatic rainfall control, high-resolution continuous flow measurement, and accurate elimination of exogenous acid interference, thus solving the technical problems of low time resolution and susceptibility to interference from impurity ions under complex fertilization conditions in traditional methods.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: The high-resolution online monitoring device for karst carbon sink potted plant simulation of karst water chemistry provided by the present invention includes, from top to bottom, a simulated rainfall unit, a potted plant container unit, a high-resolution flow measurement unit, a water collection and sensing unit, and a support frame. The simulated rainfall unit consists of a water storage tank, a water supply pump, a PWM controller, and sprinkler heads. The PWM controller provides rainfall input with controllable intensity and duration. The inlet of the water supply pump is connected to the outlet of the water storage tank. Several sprinkler heads are installed on the outlet pipe of the water supply pump and are evenly distributed along the pipe. The water supply pump is linked to the PWM controller, and the pump speed is controlled by PWM (Pulse Width Modulation) technology. A fine-tuning valve is installed at the outlet of the water supply pump.

[0005] The main body of the potted plant container unit is a potted plant bucket, which is located on a support frame. Inside the bucket, from bottom to top, are layers of carbonate rock blocks, a buffer filter layer, and a soil layer. An overflow outlet is located on the lower side wall of the bucket at a certain distance from the bottom, and this overflow outlet is connected to an outlet pipe for the leachate to flow out. The carbonate rock block layer serves as a rock reaction layer. During operation, due to the raised overflow outlet design, a saturated water-rock reaction zone (permafrost layer) is maintained within this layer at a constant water level.

[0006] The high-resolution flow measurement unit is a miniature tipping bucket flow meter or a titration flow meter, which is installed at the lower outlet of the outflow pipe and is used to record the dynamic flow rate Q(t) of the leachate in real time at high frequency.

[0007] The water collection sensing unit consists of a gas-liquid sealed water collection bottle, an integrated pH and temperature probe, and a carbon dioxide sensor for measuring the partial pressure of dissolved CO2 (pCO2) in water. The water collection bottle consists of a bottle body and a sealing cap, which is tightly connected to the end of the outflow pipe through the sealing cap. It is used to collect the leachate flowing through the flow meter. A liquid guide port is provided on the upper side wall of the water collection bottle. The measuring ends of the integrated pH and temperature probe and the carbon dioxide sensor are inserted into the water collection bottle through the sealing cap, and the other ends are tightly fixed to the sealing cap. They are connected to the data acquisition unit in the data acquisition box through cables.

[0008] Furthermore, the carbonate rock block layer is 5 cm to 15 cm thick and is composed of carbonate rock fragments (including but not limited to limestone or dolomite fragments) with a particle size between 0.5 cm and 2 cm. This layer is designed to provide a solid-phase dissolution medium, simulating the soil-rock interface reaction environment of a karst area in the field.

[0009] The buffer layer is a buffer filter; The soil layer is the experimental soil, and different soils are selected according to different experimental purposes. The thickness is 20 cm to 40 cm. The surface layer of the soil layer is mixed with soil conditioners to be evaluated (such as biochar, organic fertilizer or pig manure) to evaluate the impact of different soil conditioners on carbon sequestration, and to explore the mechanism of fertilizer reduction and application of different soil conditioners (such as biochar, organic fertilizer, etc.) on improving soil productivity and carbon sequestration capacity in karst areas.

[0010] Furthermore, the overflow outlet of the potted planter is 5-10 cm from the bottom of the pot, creating a saturated reaction zone (water-rock reaction zone, or stagnant water layer) at the bottom of the pot through elevated overflow, overcoming the shortcomings of traditional direct-flow potted planters where the flow rate is too fast and the reaction time is too short. This design promotes the full dissolution of the CO2-rich solution infiltrating the soil layer and the gravel layer, effectively increasing the background HCO3 content of the leachate. -Concentration greatly amplified the carbon sequestration differences between treatment groups with different amendments (such as pig manure and purified fertilizer), ensuring the reliability of the experimental conclusions.

[0011] Furthermore, the main body of the potted planter is a cylindrical potted planter made of high-strength corrosion-resistant material (such as PVC), with a preferred diameter of 20 cm to 40 cm and a preferred height of 40 cm to 60 cm.

[0012] Furthermore, a microporous anti-clogging filter screen is built into the inlet of the outlet pipe.

[0013] Furthermore, the carbon dioxide sensor is equipped with a waterproof and breathable membrane for measuring the partial pressure of dissolved carbon dioxide. This ensures that, even when the device is completely submerged in water for an extended period, only dissolved CO2 gas molecules in the water are allowed to penetrate the membrane pores and enter the optical measurement chamber, thereby accurately determining the pCO2(t) of the leachate.

[0014] Furthermore, the integrated pH and temperature probe uses an industrial-grade composite glass electrode with automatic temperature compensation.

[0015] Furthermore, the data acquisition box is fixed on the bracket.

[0016] Furthermore, the data acquisition device is connected to a computer terminal to transmit data to the computer terminal for data analysis and processing.

[0017] Preferably, the data acquisition device is an industrial-grade gateway recorder with a 4G wireless communication module. This recorder has multiple independent RS485 signal interfaces and analog acquisition interfaces, supporting the Modbus-RTU protocol. Specifically, physical optocoupler isolation technology is used between the interfaces to effectively shield the signal interference of CO2 sensor power supply leakage current to the high-impedance pH electrode in the same water body. After inserting a mobile communication card, the terminal can synchronously upload the high-frequency acquired raw data to the cloud monitoring software platform.

[0018] The method for calculating karst carbon sinks based on high-resolution online hydrochemical monitoring provided by this invention, using the aforementioned device of this invention, includes the following steps: Step S1 (Rainfall Induction and Runoff Monitoring): The simulated rainfall unit is turned on, and the rainfall intensity and duration are set by the PWM controller. The CO2-enriched leachate seeps down through the pot container unit, and after fully reacting in the water-retaining layer, it flows out from the outlet pipe. The instantaneous runoff Q(t) is recorded in real time by the high-resolution flow measurement unit. Step S2 (High-frequency acquisition of water chemical parameters): The underwater carbon dioxide sensor, pH and temperature integrated probe in the water collection sensing unit synchronously collect the carbon dioxide partial pressure pCO2(t), pH(t) and temperature T(t) of the leachate in real time at high frequency (e.g. every 15 minutes), and transmit the data to the data acquisition unit. Step S3 (Temperature Compensation): Based on the real-time temperature T t Using empirical chemical thermodynamic algorithms for carbonates (Formulas 1 and 2), the first-order ionization constant (equilibrium constant) K1(t) of carbonate and the Henry's constant K of carbon dioxide at the current time t and temperature are dynamically calculated. H (t); K1 and K H Kelvin temperature T k The function is calculated as follows: (Formula 1), Where A, B, and C are thermodynamic constants, which are -14.0184, 2385.73, and 0.015264, respectively; (Formula 2), Where A, B, C, D, and E are thermodynamic constants of -356.3094, -0.06091964, 21834.37, 126.8339, and -1684915, respectively; K1 and K H The units are all mol / L.

[0019] Step S4 (Bicarbonate Concentration Anti-interference Inversion): Based on the thermodynamic equilibrium equation Formula 3, calculate in real time, shield against external acid ion interference, obtain the instantaneous concentration, and get the anti-interference instantaneous concentration of bicarbonate in the leachate [HCO3-]. - ] t ; (Formula 3), Among them, 10 -pH The hydrogen ion concentration in the leachate [H] + ], pCO 2（t） This represents the instantaneous partial pressure of dissolved carbon dioxide.

[0020] Step S5 (Calculation of time integral of karst carbon sink): The [HCO3] obtained in step S4 - ] t Multiply the flow rate Q(t) obtained in step S1 to obtain the instantaneous yield of the karst carbon sink, perform time integration calculation on the entire cycle of a single rainfall event, output high-resolution karst carbon sink amount, and plot the dynamic coordinated change curve of flow rate and karst carbon sink amount (carbon sink intensity).

[0021] Furthermore, in the above method, Formula 3 is based on a combination of the following two fundamental equilibrium equations: Henry's Law equilibrium of carbon dioxide in water: (Formula 4), H2CO3 * (aq) represents the combined total concentration of "free carbonic acid + hydrated carbon dioxide" dissolved in water; Equilibrium constant K H (Henry constant): (Formula 5), × (Formula 6), First-order ionization equilibrium of carbonic acid:

[0022] Equilibrium constant K1: (Formula 8), Substituting formula 6 into formula 8 and rearranging, we get: (Formula 9), = (Formula 10), (Formula 11), Due to [H] + ]=10 -pH Finally obtained (Formula 3).

[0023] The above-mentioned technical solutions of the present invention can also be automatically processed and calculated by embedding the empirical algorithm of the chemical thermodynamics of carbonate water containing the above-mentioned calculation formula proposed in the present invention in a cloud platform or local microprocessor.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. Completely Eliminate External Interference: Addressing the issue of high concentrations of sulfate and nitrate ions in soil leachate under the background of reduced chemical fertilizer use and combined application of organic fertilizers, this invention abandons traditional methods of measuring conductivity or manual titration sampling. Instead, it innovatively constructs a water collection and sensing environment to acquire pCO2, pH, and temperature of the leachate in real-time on-site. Utilizing the principle of chemical thermodynamic equilibrium of carbonate rock water, it inversely calculates HCO3. - Concentration, thereby completely eliminating large amounts of NO3 in the soil. - and SO4 2-The interference from non-carbonate ions is completely shielded from the interference of impurity ions from a physicochemical perspective, greatly improving data accuracy.

[0025] 2. Extremely high temporal resolution: It has achieved a leap from "collecting one bottle of water and measuring one average value during a single rainfall event" to "minute-level dynamic flow generation and continuous change curve of ion concentration", which truly reveals the dynamic mechanism of karst carbon sink in the process of rainfall leaching.

[0026] 3. High degree of automation and low cost: The cumbersome process of sending samples back to the laboratory for ion chromatography analysis is transformed into an automated process that uses low-cost physical sensors for in-situ edge computing, which greatly reduces the human and material costs of long-term monitoring. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the karst carbon sink potted plant simulation device described in Example 1.

[0028] Figure 2 for Figure 1 Schematic diagram of the probe arrangement inside the CIMC water sensing unit.

[0029] Figure 3 for Figure 1 Schematic diagram of the arrangement of simulated rainfall units.

[0030] Figure 1-3 The components are: 1. Rain sprinkler head; 2. Potted container; 3. Test soil and amendment; 4. Buffer filter; 5. Carbonate rock block; 6. Outlet pipe; 7. Flow meter; 8. Liquid inlet; 9. Water collection bottle; 10. pH electrode; 11. CO2 sensor; 12. Data acquisition box; 13. Support frame; 14. Leachate; 15. Waterproof and breathable membrane; 16. Cable; 17. Fine-tuning valve; 18. Water supply pump; 19. PWM controller; 20. Water storage tank.

[0031] Figure 4 The data is Q(t), which is the high-frequency real-time collected flow rate per unit area in Example 2.

[0032] Figure 5 Figures a, b, and c in Example 2 show high-frequency data acquisition data for pCO2(t), pH(t), and temperature T(t), respectively.

[0033] Figure 6 For Example 2, the high-frequency K1(a) and K are calculated based on temperature. H Value (b).

[0034] Figure 7 The real-time [HCO3] inversion of Example 2 - ]concentration.

[0035] Figure 8 This is a dynamic correlation diagram showing the real-time flow rate Q(t) and karst carbon sink (F) under a single rainfall event in Example 2. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0037] Example 1: A potted plant simulation device for karst carbon sinks based on high-resolution online hydrochemical monitoring like Figures 1 to 3 As shown, this embodiment provides a karst carbon sink potted plant simulation device based on high-resolution online hydrochemical monitoring, which includes a simulated rainfall unit, a potted plant container unit, a high-resolution flow measurement unit, a water collection and sensing unit, and a support frame arranged sequentially from top to bottom; The simulated rainfall unit consists of a water tank, a water pump, a PWM controller, and sprinkler heads, providing rainfall input with controllable intensity and duration. The inlet of the water pump is connected to the outlet of the water tank. Several sprinkler heads are arranged on the outlet pipe of the water pump and evenly distributed along the pipe. A fine-tuning valve is installed at the outlet of the water pump. The water pump is linked to the PWM controller, and the pump speed is controlled by PWM (Pulse Width Modulation) technology. This unit provides simulated rainfall with precise controllable intensity and duration to eliminate random interference from natural rainfall. Multiple sprinkler heads are evenly distributed about 50cm above the soil layer in the pot, and the sprinkler heads are full-cone micro-mist nozzles. The rainfall intensity is preferably adjusted from 5 mm / h to 150 mm / h by the PWM controller to ensure that the rainfall distribution uniformity is greater than 90% and to avoid excessive water droplet kinetic energy damaging the soil surface structure. The potted plant container unit includes a potted plant bucket, which is located on a support frame. The bucket is filled with a layer of carbonate rock blocks, a buffer layer, and a soil layer from bottom to top. An overflow port is provided on the lower side wall of the bucket. The overflow port is connected to an outlet pipe for the leaching liquid to flow out. A microporous anti-clogging filter screen is built into the inlet of the outlet pipe.

[0038] The main body of the potted planter is a cylindrical potted planter made of high-strength corrosion-resistant material (such as PVC), with a diameter of 30cm and a height of 50cm.

[0039] Carbonate rock block layer: laid at the bottom of the bucket, with a thickness of 5 cm to 15 cm (preferably 10 cm in this embodiment), composed of carbonate rock fragments (including but not limited to limestone or dolomite fragments) with a particle size between 0.5 cm and 2 cm. This layer is intended to provide a solid-phase dissolution medium to simulate the soil-rock interface reaction environment in karst areas in the field.

[0040] Buffer layer: A buffer filter is installed above the rock reaction layer.

[0041] Soil layer: The test specimens were filled with 20 cm to 40 cm thick test soil, and the surface layer was mixed with soil conditioner organic fertilizer to be evaluated.

[0042] The leaching solution of this invention is not discharged directly from the bottom as in the traditional method. Instead, an overflow outlet is provided on the lower side wall of the potting container, with the outlet positioned 5cm to 10cm above the bottom of the container. This design ensures that the rock reaction layer at the bottom of the potting plant maintains a saturated water-rock reaction zone (stagnant water layer) with a constant water level. An external conduit and anti-clogging filter are connected to the outlet.

[0043] Traditional industrial flow meters are unsuitable for the low flow rate and intermittent dripping characteristics of potted plant leachate. In this embodiment, a miniature tipping bucket flow meter (or photoelectric titration flow meter) is preferably used as the flow measurement unit, positioned directly below the outlet pipe. Its single-tip measurement volume accuracy is preferably 0.1 mL to 0.2 mL, with a measurement range covering 0 to 100 mL / min. This miniature flow meter can accurately capture the instantaneous flow rate Q(t) from the initial rainfall phase to the steady-state phase with extremely high resolution, and transmits the pulse signal to the data acquisition and processing terminal in real time, recording the dynamic flow rate Q(t) of the leachate at high frequency in real time.

[0044] The water collection sensing unit consists of a gas-liquid sealed water collection bottle, an integrated pH and temperature probe, a carbon dioxide sensor for measuring the partial pressure of dissolved CO2 (pCO2) in water, and a temperature sensor. The water collection bottle comprises a bottle body and a sealing cap, which is tightly connected to the outflow pipe via the sealing cap. It is used to collect the leachate flowing through the flow meter. A liquid guide port is provided on the upper side wall of the water collection bottle to drain excess water when the leachate level reaches the guide port, ensuring real-time replacement of the leachate. It can also be used to collect the drained leachate for further testing of macro- and micro-elements or isotopes. The measuring ends of the integrated pH and temperature probe and the carbon dioxide sensor are inserted into the water collection bottle through the sealing cap, and the other ends are tightly fixed to the sealing cap. They are connected to the data acquisition unit in the data acquisition box via cables. The carbon dioxide (pCO2) sensor has a waterproof and breathable membrane for measuring the partial pressure of dissolved carbon dioxide. The data acquisition box is fixed on a bracket.

[0045] Underwater dissolved carbon dioxide (pCO2) sensor: This sensor employs non-dispersive infrared (NDIR) analysis, with a measurement range of 0–20,000 ppmv and an output of 0–5V analog signal. Its unique design features a PTFE (polytetrafluoroethylene) waterproof and breathable membrane component surrounding the sensor probe. This ensures that even when fully submerged in water for extended periods, only dissolved CO2 gas molecules in the water are allowed to penetrate the membrane pores and enter the optical measurement chamber, thus accurately determining the pCO2(t) of the leachate.

[0046] pH and temperature integrated probe: It adopts an industrial-grade composite glass electrode with automatic temperature compensation function, outputs signals through RS485 interface, and has a pH measurement range of 0.00~14.00 with an accuracy of ±0.01; and a temperature measurement range of -20℃ to 80℃ with an accuracy of ±0.5℃.

[0047] Data acquisition device configuration: An industrial-grade data acquisition unit with a 4G wireless communication module is used. This unit features multiple independent RS485 signal interfaces and analog acquisition interfaces, supporting the Modbus-RTU protocol. Notably, physical optocoupler isolation technology is employed between the interfaces to effectively shield the signal interference from CO2 sensor power supply leakage current to the high-impedance pH electrode in the same water body. With a mobile communication SIM card inserted, the raw data acquired at high frequency can be synchronously uploaded to a cloud-based monitoring software platform.

[0048] Example 2: High-resolution online calculation method for karst carbon sinks based on the above-mentioned device In conjunction with the apparatus in Example 1, this example provides a method for calculating karst carbon sinks based on hydrochemical thermodynamic equilibrium inversion. This method can completely eliminate the interference of exogenous acid ions (such as sulfate, nitrate, and chloride ions) on carbon sink monitoring caused by the application of reduced-volume fertilizers and organic amendments. Specifically, it includes the following steps: Step S1 (System Initialization and Rainfall Simulation): The simulated rainfall unit is activated, and the target rainfall intensity (e.g., 30 mm / h) and duration are set. After the leachate infiltrates through the potted container unit and undergoes water-rock interaction, the rainwater flows through the soil layer and passes through a 10 cm thick layer of carbonate rock blocks, resulting in sufficient water-rock interaction. Due to the presence of the overflow outlet on the side wall (5-10 cm from the bottom), the infiltrated water forms a saturated reaction zone at the bottom, effectively prolonging the multiphase contact time of air-water-soil-rock, and allowing for sufficient carbonate dissolution reaction. Subsequently, the fully reacted, high-concentration leachate overflows from the side wall, and the dynamic flow rate Q(t) is recorded in real time by a miniature tipping bucket flow meter, converting the pulses into flow rate data per unit area (e.g., L / km²). 2 • 15min), such as Figure 4.

[0049] Step S2 (High-frequency acquisition of water chemical parameters): The leachate flows into the water collection sensing unit, and the data acquisition and processing terminal simultaneously collects data at a set frequency (e.g., 15 minutes / time) from the integrated underwater pH and temperature probe, as well as the real-time carbon dioxide partial pressure (pCO2(t), pH(t), and temperature (T(t)) from the carbon dioxide (pCO2) sensor. Figure 5 .

[0050] Step S3 (Dynamic Temperature Compensation for Thermodynamic Constants): Based on the real-time temperature T(t), the first-order ionization constant of carbonate K1(t) and the Henry's constant of carbon dioxide K at the current water temperature are dynamically calculated. H (t). K1 and K H Kelvin temperature T k The function is calculated as follows: (Formula 1), Where A, B, and C are thermodynamic constants with values ​​of -14.0184, 2385.73, and 0.015264, respectively.

[0051] (Formula 2), Where A, B, C, D, and E are thermodynamic constants with values ​​of -356.3094, -0.06091964, 21834.37, 126.8339, and -1684915, respectively.

[0052] K1 and K H The units are all mol / L, the calculation results are as follows Figure 6 .

[0053] Step S4 (Bicarbonate concentration anti-interference inversion): Without the need for water sample collection for titration or chromatographic analysis, the true instantaneous concentration of bicarbonate ions [HCO3] in the leachate can be calculated in real time using the carbonate thermodynamic equilibrium equation (Formula 3). - ]t: (Formula 3), Among them, [HCO3] - The unit is mol / L, pCO2 is atm (standard atmosphere). Note that if the sensor output is ppmv (parts per million by volume), unit conversion is required: 1 atm = 10 6ppmv. Therefore, pCO2(atm) = pCO2(ppmv) / 10 6 .

[0054] This calculation process relies solely on characteristic parameters of carbonate thermodynamic equilibrium, completely shielding SO4 from complex fertilizer backgrounds from a physicochemical perspective. 2- and NO3 - The resulting conductivity artifact interference affects the real-time [HCO3] inversion. - Concentration such as Figure 7 .

[0055] Formula 3 is based on a combination of the following two fundamental equilibrium equations: Henry's Law equilibrium of carbon dioxide in water: (Formula 4), Equilibrium constant K H (Henry constant): (Formula 5), × (Formula 6), First-order ionization equilibrium of carbonic acid:

[0056] Equilibrium constant K1: (Formula 8), Substituting formula 6 into formula 8 and rearranging, we get: (Formula 9), = (Formula 10), (Formula 11), Due to [H] + ]=10 -pH Finally obtained (Formula 3).

[0057] Step S5 (High-resolution karst carbon sink integration): The instantaneous concentration [HCO3] obtained from step S4 is used for inversion. - The instantaneous intensity of the carbonate rock karst carbon sink is obtained by multiplying the instantaneous flow rate Q(t) obtained in step S1.

[0058] (Formula 12), According to Equation 12, the dissolution equation of carbonate rocks, for every 1 mol of CO2 consumed, 2 mol of HCO3 will be produced. - Based on this, the karst carbon sink (F) calculated using hydrochemistry-runoff can be expressed as: F(t) = 0.5 × [HCO3] - ](t)×Q / A(t)×44 (Formula 13). Where A is the base area of ​​the potted planter, in km². 2 44 represents the molecular weight of CO2. By performing time integration calculations on the entire process of a single rainfall event, a high-precision online output of the total karst carbon sink amount for the rainfall event is obtained, and a dynamic correlation curve between flow rate and karst carbon sink amount is plotted, such as... Figure 8 .

[0059] Experiments have shown that the device and method of the present invention achieve significantly better results than the prior art: Completely solves the flow rate problem: The "saturated reaction zone" designed with a 5-10 cm elevated overflow outlet completely overcomes the shortcomings of traditional straight-through potted plants, such as excessively fast flow rates and short reaction times. This design promotes the thorough dissolution of the CO2-rich solution infiltrating the soil layer and the gravel layer, effectively increasing the background HCO3 content of the leachate. - Concentration greatly amplified the carbon sequestration differences between different soil conditioner treatment groups (such as pig manure and purified fertilizer), ensuring the reliability of the experimental conclusions.

[0060] Interference resistance and high resolution: Under the condition that the conductivity is distorted due to the application of a large amount of chemical fertilizer, the NDIR-pCO2 probe with waterproof and breathable membrane and real-time pH inversion are used to successfully eliminate the interference of impurity ions and realize minute-level, automated and high-precision monitoring of carbon sink kinetic processes.

Claims

1. A potted plant simulation device for karst carbon sinks based on high-resolution online hydrochemical monitoring, characterized in that, It includes, from top to bottom, a simulated rainfall unit, a potted plant container unit, a high-resolution flow measurement unit, a water collection and sensing unit, and a support frame; The simulated rainfall unit consists of a water storage tank, a water supply pump, a PWM controller, and sprinkler heads. The PWM controller provides rainfall input with controllable intensity and duration. The inlet of the water supply pump is connected to the outlet of the water storage tank. Several sprinkler heads are installed on the outlet pipe of the water supply pump and are evenly distributed along the pipe. The water supply pump is linked to the PWM controller. A fine-tuning valve is installed at the outlet of the water supply pump. The main body of the potted plant container unit is a potted plant bucket, which is located on a support frame. The bucket is filled with a layer of carbonate rock blocks, a buffer filter screen layer, and a soil layer from bottom to top. An overflow port is provided on the lower side wall of the bucket at a certain distance from the bottom of the bucket. The overflow port is connected to an outlet pipe for the leaching liquid to flow out. The high-resolution flow measurement unit is a miniature tipping bucket flow meter or a titration flow meter, which is installed at the lower outlet of the outflow pipe and is used to record the dynamic flow rate Q(t) of the leachate in real time at high frequency. The water collection sensing unit consists of a gas-liquid sealed water collection bottle, an integrated pH and temperature probe, and a carbon dioxide sensor for measuring the partial pressure of dissolved CO2 in the water. The water collection bottle is composed of a bottle body and a sealing cap, and is tightly connected to the end of the outflow pipe through the sealing cap. It is used to collect the leachate flowing through the flow meter. A liquid guide port is provided on the upper side wall of the water collection bottle. The measuring ends of the integrated pH and temperature probe and the carbon dioxide sensor are inserted into the water collection bottle through the sealing cap, and the other ends are tightly fixed to the sealing cap. They are connected to the data acquisition unit in the data acquisition box through cables.

2. The apparatus according to claim 1, characterized in that, The carbonate rock layer is 5 cm to 15 cm thick and is composed of carbonate rock fragments with a particle size of 0.5 cm to 2 cm. The buffer layer is a buffer filter. The soil layer is experimental soil, and different soils are selected according to different experimental purposes. The thickness is 20 cm to 40 cm. The surface of the soil layer is mixed with soil conditioner to be evaluated.

3. The apparatus according to claim 1, characterized in that, The overflow outlet of the potted planter is 5-10cm from the bottom of the potted planter.

4. The apparatus according to claim 1, characterized in that, The main body of the potted planter is a cylindrical potted planter made of high-strength and corrosion-resistant material, with a diameter of 20 cm to 40 cm and a height of 40 cm to 60 cm.

5. The apparatus according to claim 1, characterized in that, The inlet of the outlet pipe has a built-in microporous anti-clogging filter.

6. The apparatus according to claim 1, characterized in that, The carbon dioxide sensor has a waterproof and breathable membrane.

7. The apparatus according to claim 1, characterized in that, The integrated pH and temperature probe uses an industrial-grade composite glass electrode with automatic temperature compensation.

8. The apparatus according to claim 1, characterized in that, The data acquisition box is fixed on the bracket.

9. The apparatus according to claim 1, characterized in that, The data acquisition device is an industrial-grade gateway recorder with a 4G wireless communication module.

10. A method for calculating karst carbon sinks based on high-resolution online hydrochemical monitoring, characterized in that, Using the apparatus according to any one of claims 1 to 9 includes the following steps: Step S1, Rainfall Induction and Runoff Monitoring: The simulated rainfall unit is turned on, and the rainfall intensity and duration are set by the PWM controller. The CO2-enriched leachate seeps down through the potted container unit, and after fully reacting in the water-retaining layer, it flows out from the outlet pipe. The instantaneous runoff Q(t) is recorded in real time by the high-resolution flow measurement unit. Step S2, High-frequency acquisition of water chemical parameters: The underwater carbon dioxide sensor and the integrated pH and temperature probe in the water collection sensing unit collect the carbon dioxide partial pressure pCO2(t), pH(t), and temperature T(t) of the leachate in real time at high frequency and synchronously, and transmit the data to the data acquisition unit. Step S3, Temperature Compensation: Based on the real-time temperature T t Using an empirical algorithm based on the chemical thermodynamics of carbonates, the first-order ionization constant K1(t) of carbonates and the Henry's constant K of carbon dioxide at the current time t and temperature are dynamically calculated. H (t); K1 and K H Kelvin temperature T k The function is calculated as follows: (Official 1), Where A, B, and C are thermodynamic constants, which are -14.0184, 2385.73, and 0.015264, respectively; (Official 2), Where A, B, C, D, and E are thermodynamic constants of -356.3094, -0.06091964, 21834.37, 126.8339, and -1684915, respectively; K1 and K H The units are all mol / L; Step S4, Interference-resistant inversion of bicarbonate concentration: Based on the thermodynamic equilibrium equation (Formula 3), calculate in real time, shield against external acid ion interference, obtain the instantaneous concentration, and get the interference-resistant instantaneous concentration of bicarbonate in the leaching solution [HCO3-]. - ] t ; (Official 3), Among them, 10 -pH The hydrogen ion concentration in the leachate [H] + ], pCO 2（t） This refers to the instantaneous partial pressure of dissolved carbon dioxide. Step S5, Time Integral Calculation of Karst Carbon Sequestration: The [HCO3] obtained in step S4... - ] t Multiply the flow rate Q(t) obtained in step S1 to obtain the instantaneous yield of the karst carbon sink, perform time integration calculation over the entire cycle of a single rainfall event, output high-resolution karst carbon sink volume, and plot the dynamic synergistic change curve of flow rate and karst carbon sink volume.

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