A method, system and medium for real-time monitoring of in-situ seawater carbon dioxide partial pressure

Abstract

The application provides a kind of in situ seawater carbon dioxide partial pressure real-time monitoring method, system and medium, belong to marine environmental monitoring technical field, this method includes: from in situ seawater real-time acquisition high humidity equilibrium sample gas;From the sample gas, measured carbon dioxide humidity molar fraction, dew point temperature, sample gas pressure, gas phase temperature and in situ seawater temperature;Based on dew point temperature and sample gas pressure, water vapor molar fraction is obtained by inversion;Based on water vapor molar fraction, humidity compensation is carried out on carbon dioxide humidity molar fraction, to obtain dry gas carbon dioxide molar fraction;According to dry gas carbon dioxide molar fraction and sample gas pressure, gas phase carbon dioxide partial pressure is calculated;Based on gas phase temperature and in situ seawater temperature, temperature compensation is carried out on gas phase carbon dioxide partial pressure, to obtain in situ seawater carbon dioxide partial pressure, to realize real-time monitoring. This method does not need drying treatment, by accurately compensating the influence of water vapor interference and temperature difference, to realize real-time, accurate monitoring of in situ seawater carbon dioxide partial pressure.

Description

Technical Field

[0001] This invention belongs to the field of marine environmental monitoring technology, specifically relating to a method, system, and medium for real-time monitoring of in-situ seawater carbon dioxide partial pressure. Background Technology

[0002] partial pressure of carbon dioxide in seawater ( p CO2 is a core parameter for assessing carbon flux at the air-sea interface and the degree of ocean acidification, especially in marginal seas and estuaries, where the combined effects of tides, runoff, and biological activity contribute to its high concentration. p CO2 exhibits high-frequency and large-amplitude dynamic changes, posing higher demands on in-situ, real-time monitoring technologies. Currently, the mainstream monitoring method is based on a gas-liquid equilibrium membrane combined with a non-dispersive infrared detector. This method extracts the equilibrium gas from seawater through a breathable membrane for analysis. However, this method faces a key challenge in practical applications: since the equilibrium gas is a highly humid sample gas, water vapor significantly interferes with the infrared absorption of carbon dioxide. Existing technologies mostly employ chemical desiccants for dehumidification or corrections based on the saturated water vapor assumption. However, the former is difficult to adapt to long-term unattended marine environments, while the latter introduces systematic biases due to the inconsistency between the gas path temperature and the seawater temperature, leading to a decrease in measurement accuracy. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method, system, and medium for real-time monitoring of carbon dioxide partial pressure in in-situ seawater, thereby solving the aforementioned problems. This method, system, and medium can achieve real-time and accurate monitoring of carbon dioxide partial pressure in in-situ seawater by precisely compensating for the interference of water vapor and the effects of temperature differences without relying on drying treatment.

[0004] To address the aforementioned technical problems, this invention provides a method for real-time monitoring of in-situ seawater carbon dioxide partial pressure, comprising the following steps: High-humidity equilibrium gas samples were obtained in real time from in-situ seawater. Based on the high humidity equilibrium sample gas, the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature were obtained. Dew point inversion is performed based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction. Humidity compensation is performed based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry air carbon dioxide mole fraction. The partial pressure of carbon dioxide in the gas phase is obtained based on the mole fraction of carbon dioxide in the dry gas and the sample gas pressure. Temperature compensation is performed on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, so as to achieve real-time monitoring.

[0005] In the above scheme, a reliable basis for in-situ seawater carbon dioxide partial pressure measurement is provided by acquiring high-humidity equilibrium sample gas from in-situ seawater in real time. Simultaneously, the moisture mole fraction of carbon dioxide, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature are acquired to construct a multi-parameter system required for in-situ monitoring. The water vapor mole fraction is obtained by dew point inversion based on dew point temperature and sample gas pressure, providing an accurate basis for subsequent compensation processing. The dry gas carbon dioxide mole fraction is obtained through humidity compensation, thereby improving the accuracy of carbon dioxide mole fraction measurement. The gas phase carbon dioxide partial pressure is obtained by combining the dry gas carbon dioxide mole fraction and sample gas pressure, and then temperature compensation is used to eliminate the partial pressure deviation caused by the temperature difference between the gas and liquid phases, ultimately yielding the in-situ seawater carbon dioxide partial pressure. This scheme achieves real-time and accurate monitoring of in-situ seawater carbon dioxide partial pressure without relying on drying treatment, by accurately compensating for water vapor interference and temperature differences.

[0006] It should be noted that traditional methods typically assume that the water vapor in the sample gas is saturated and calculate the water vapor partial pressure based on seawater temperature. However, in actual membrane equilibrium and gas transport processes, gas temperature and seawater temperature are often inconsistent, and gas pressure varies with the environment and system operation. The gas water vapor is not strictly saturated, and this saturation assumption leads to significant systematic bias. The in-situ real-time monitoring method for seawater carbon dioxide partial pressure provided by this invention directly inverts the true water vapor partial pressure of the sample gas through dew point measurement, effectively avoiding errors introduced by the invalid saturation assumption and providing key technical support for accurate measurement of carbon dioxide partial pressure under high humidity conditions.

[0007] Furthermore, after obtaining the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high-humidity equilibrium sample gas, the method further includes: The dew point change rate is obtained based on the dew point temperature. The physical rationality is verified based on the dew point change rate. If the verification fails, the dew point temperature is marked as abnormal data, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0008] In the above scheme, after obtaining the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high humidity equilibrium sample gas, the dew point change rate is obtained based on the dew point temperature, and physical rationality is verified based on the dew point change rate. This allows for effective identification of the dew point temperature data. If the verification fails, the dew point temperature is marked as abnormal data, and a new high humidity equilibrium sample gas is obtained from the in-situ seawater to restart the real-time monitoring of carbon dioxide partial pressure in in-situ seawater. This avoids abnormal dew point temperature data from participating in subsequent dew point inversion, water vapor mole fraction acquisition, humidity compensation, temperature compensation, and in-situ seawater carbon dioxide partial pressure calculation processes, preventing abnormal data from interfering with the monitoring results, ensuring the accuracy of the calculation of each parameter and the final partial pressure result, and effectively improving the reliability and stability of real-time monitoring of carbon dioxide partial pressure in in-situ seawater.

[0009] Furthermore, the physical rationality verification based on the dew point change rate is performed. If the verification fails, the dew point temperature is marked as abnormal data. The abnormal data includes erroneous data, invalid data, and warning data, wherein: The dew point change rate is obtained based on the dew point temperature. If the dew point change rate is greater than or equal to a preset first change rate threshold, the dew point temperature is marked as erroneous data. If the dew point change rate is less than a preset first change rate threshold and greater than or equal to a preset second change rate threshold, then the dew point temperature is marked as invalid data. If the dew point change rate is less than a preset second change rate threshold and greater than or equal to a preset third change rate threshold, then the dew point temperature is marked as warning data.

[0010] In the above scheme, when performing physical rationality verification based on the dew point change rate, by setting preset first change rate threshold, preset second change rate threshold, and preset third change rate threshold, abnormal dew point temperature data can be finely classified and marked. When the dew point change rate is greater than or equal to the preset first change rate threshold, the dew point temperature is marked as erroneous data; when the dew point change rate is less than the preset first change rate threshold but greater than or equal to the preset second change rate threshold, it is marked as invalid data; when the dew point change rate is less than the preset second change rate threshold but greater than or equal to the preset third change rate threshold, it is marked as warning data. This allows for precise differentiation of dew point temperature data with different degrees of abnormality, preventing abnormal data from entering subsequent calculation processes and preventing it from interfering with monitoring results. This effectively improves the data discrimination accuracy and the accuracy and stability of monitoring results in real-time monitoring of in-situ seawater carbon dioxide partial pressure.

[0011] It should be noted that the preset first rate of change threshold is greater than the second rate of change threshold, and the second rate of change threshold is greater than the third rate of change threshold. Specific thresholds can be set according to sensor specifications, marine environmental change characteristics, and engineering experience to effectively identify abnormal operating conditions such as dew point jumps, sensor momentary interruptions, and dead volume effects.

[0012] Furthermore, the process of performing dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction includes: The partial pressure of water vapor is obtained by inverting the water vapor partial pressure based on the dew point temperature and the Magnus formula. The water vapor mole fraction is obtained based on the water vapor partial pressure, sample gas pressure, and Dalton's law of partial pressure.

[0013] In the above scheme, during the process of obtaining the water vapor mole fraction by dew point inversion based on the dew point temperature and sample gas pressure, the water vapor partial pressure is first inverted based on the dew point temperature and Magnus's formula to obtain the water vapor partial pressure, ensuring the accuracy and reliability of the water vapor partial pressure inversion result. Subsequently, the water vapor mole fraction is obtained based on the water vapor partial pressure, sample gas pressure, and Dalton's law of partial pressures, achieving accurate calculation of the water vapor mole fraction. This scheme, relying on standardized formulas and physical laws, can obtain a high-precision water vapor mole fraction based on measured dew point temperature and sample gas pressure, effectively improving the accuracy of basic parameter calculations. This provides reliable data for subsequent humidity compensation based on water vapor mole fraction and carbon dioxide moisture mole fraction, thereby ensuring the accuracy and stability of dry gas carbon dioxide mole fraction calculation and in-situ seawater carbon dioxide partial pressure monitoring results.

[0014] It should be noted that the Magnus formula is a commonly used approximate expression for saturated water vapor pressure in engineering, and its specific form is as follows: in The dew point temperature (°C) is used, and the calculated water vapor partial pressure is in kPa.

[0015] Furthermore, after obtaining the water vapor partial pressure by performing the water vapor partial pressure inversion based on the dew point temperature and the Magnus formula, the process further includes: The physical rationality of the water vapor partial pressure is verified. If the water vapor partial pressure is greater than or equal to the sample gas pressure, the water vapor partial pressure is marked as abnormal partial pressure data, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0016] In the above scheme, after obtaining the water vapor partial pressure through inversion based on dew point temperature and the Magnus formula, the physical rationality of the water vapor partial pressure is further verified. The numerical relationship between the water vapor partial pressure and the sample gas pressure is determined according to physical laws. If the water vapor partial pressure is greater than or equal to the sample gas pressure, it is marked as abnormal partial pressure data. Simultaneously, a high-humidity equilibrium sample gas is re-obtained from the in-situ seawater, and real-time monitoring of the carbon dioxide partial pressure in the in-situ seawater is resumed. This effectively identifies physically unreasonable water vapor partial pressure data, promptly blocks abnormal partial pressure data from participating in subsequent calculations, and avoids erroneous data caused by measurement anomalies affecting subsequent data processing. This ensures that the water vapor partial pressure data used for subsequent calculations is accurate and reasonable, providing a reliable data foundation for subsequent operations such as obtaining water vapor mole fraction and humidity compensation, thereby guaranteeing the accuracy and stability of the real-time monitoring results of the carbon dioxide partial pressure in the in-situ seawater.

[0017] Further, the step of performing humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry air carbon dioxide mole fraction includes: Error detection is performed based on the water vapor mole fraction. When an error is detected, the following steps are executed: Pressure compensation is performed based on the water vapor mole fraction, sample gas pressure, and preset calibration parameters to obtain the pressure-compensated moisture mole fraction. The pressure-compensated moisture mole fraction is used as the carbon dioxide moisture mole fraction to compensate for the moisture mole fraction and carbon dioxide moisture mole fraction, thus obtaining the dry gas carbon dioxide mole fraction.

[0018] In the above scheme, during the process of obtaining the dry gas carbon dioxide mole fraction through humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction, error detection is first performed based on the water vapor mole fraction. When an error is detected, a pressure compensation process is executed. Pressure compensation is performed based on the water vapor mole fraction, sample gas pressure, and preset calibration parameters to obtain the pressure-compensated moisture mole fraction. This pressure-compensated moisture mole fraction is then used as the carbon dioxide moisture mole fraction, and further humidity compensation is performed with the water vapor mole fraction to obtain the dry gas carbon dioxide mole fraction. This scheme can correct the carbon dioxide moisture mole fraction through pressure compensation after error identification, ensuring the accuracy and reliability of the parameters involved in humidity compensation, avoiding adverse effects of errors on the humidity compensation results, improving the calculation accuracy of the dry gas carbon dioxide mole fraction, and providing a precise data foundation for subsequent gas phase carbon dioxide partial pressure calculation and in-situ seawater carbon dioxide partial pressure monitoring, effectively improving the accuracy and reliability of monitoring results.

[0019] It should be noted that the error detection can be achieved through standard gas testing or real-time monitoring of the correlation between the carbon dioxide detector output and pressure changes. Preset calibration parameters are preferably obtained through experimental calibration. If the carbon dioxide detector itself has a pressure compensation function, this step can be skipped, but it is preferable to retain a bypass verification mechanism to automatically activate external pressure compensation when the detector's built-in compensation fails or drifts.

[0020] Furthermore, after temperature compensation is performed on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, the method further includes: The temperature difference is obtained based on the gas phase temperature and the in-situ seawater temperature; If the temperature difference exceeds a preset temperature difference threshold, the in-situ seawater carbon dioxide partial pressure is marked as temperature difference exceeding the limit, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0021] In the above scheme, after temperature compensation is performed on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, the temperature difference is further obtained based on the gas phase temperature and the in-situ seawater temperature, and the temperature difference is compared with a preset temperature difference threshold. If the temperature difference is greater than the preset temperature difference threshold, the partial pressure of carbon dioxide in the in-situ seawater is marked as exceeding the temperature difference limit, and a new high-humidity equilibrium sample gas is obtained from the in-situ seawater to restart the real-time monitoring of the partial pressure of carbon dioxide in the in-situ seawater. The above scheme can verify the rationality of the final monitoring data after temperature compensation, promptly identify abnormal situations where the difference between the gas phase temperature and the in-situ seawater temperature is too large, avoid the participation of temperature difference exceeding the limit data in subsequent data processing and result application, prevent abnormal temperature difference conditions from reducing the reliability of monitoring results, ensure that the obtained partial pressure of carbon dioxide in the in-situ seawater is accurate and effective, and further improve the overall accuracy and stability of real-time monitoring of the partial pressure of carbon dioxide in the in-situ seawater.

[0022] This invention also provides an in-situ real-time monitoring system for the partial pressure of carbon dioxide in seawater, comprising: The gas-liquid balance module is used to obtain high-humidity equilibrium sample gas from in-situ seawater in real time; The carbon dioxide monitoring module is used to obtain the moisture mole fraction of carbon dioxide based on the high humidity equilibrium sample gas. The dew point monitoring module is used to obtain the dew point temperature based on the high humidity equilibrium sample gas. The pressure monitoring module is used to obtain the sample gas pressure based on the high humidity equilibrium sample gas; The gas phase temperature monitoring module is used to obtain the gas phase temperature based on the high humidity equilibrium sample gas; The seawater temperature monitoring module is used to obtain the in-situ seawater temperature based on the high humidity equilibrium sample gas. The data processing module is used to perform dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction; to perform humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry gas carbon dioxide mole fraction; to obtain the gas phase carbon dioxide partial pressure based on the dry gas carbon dioxide mole fraction and sample gas pressure; to perform temperature compensation on the gas phase carbon dioxide partial pressure based on the gas phase temperature and in-situ seawater temperature to obtain the in-situ seawater carbon dioxide partial pressure, and output the real-time monitoring results.

[0023] The above scheme integrates a gas-liquid balance module, a carbon dioxide monitoring module, a dew point monitoring module, a pressure monitoring module, a gas phase temperature monitoring module, a seawater temperature monitoring module, and a data processing module to construct a collaborative in-situ seawater carbon dioxide partial pressure real-time monitoring system. The gas-liquid balance module can acquire high-humidity equilibrium sample gas from the in-situ seawater in real time. Each monitoring module simultaneously acquires carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature parameters based on the high-humidity equilibrium sample gas. The data processing module sequentially completes dew point inversion, humidity compensation, gas phase carbon dioxide partial pressure calculation, and temperature compensation, ultimately obtaining the in-situ seawater carbon dioxide partial pressure and outputting the real-time monitoring results. The modules have clear division of labor and close cooperation, enabling a complete operation from sample gas acquisition and parameter monitoring to data calculation and result output, ensuring a continuous and reliable monitoring process and achieving accurate and real-time monitoring of in-situ seawater carbon dioxide partial pressure.

[0024] Furthermore, the dew point monitoring module, after obtaining the dew point temperature based on the high humidity equilibrium sample gas, also includes: The dew point change rate is obtained based on the dew point temperature. The physical rationality is verified based on the dew point change rate. If the verification fails, the dew point temperature is marked as abnormal data, and the gas-liquid balance module is made to re-obtain high humidity balance sample gas from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0025] In the above scheme, after obtaining the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high humidity equilibrium sample gas, the dew point monitoring module obtains the dew point change rate based on the dew point temperature and performs physical rationality verification based on the dew point change rate, thereby achieving effective discrimination of the dew point temperature data. If the verification fails, the dew point temperature is marked as abnormal data, and a new high humidity equilibrium sample gas is obtained from the in-situ seawater to re-perform real-time monitoring of in-situ seawater carbon dioxide partial pressure. This avoids abnormal dew point temperature data from participating in subsequent dew point inversion, water vapor mole fraction acquisition, humidity compensation, temperature compensation, and in-situ seawater carbon dioxide partial pressure calculation processes, preventing abnormal data from interfering with the monitoring results, ensuring the accuracy of each parameter calculation and the final partial pressure result, and effectively improving the reliability and stability of real-time monitoring of in-situ seawater carbon dioxide partial pressure.

[0026] The present invention also provides a computer-readable storage medium, comprising: a stored computer program, which, when the computer program is running, controls the device where the computer-readable storage medium is located to perform the steps of the in-situ seawater carbon dioxide partial pressure real-time monitoring method of the present invention. Attached Figure Description

[0027] Figure 1 This is a schematic flowchart of an in-situ real-time monitoring method for carbon dioxide partial pressure in seawater according to an embodiment of the present invention; Figure 2 This is a schematic diagram of an in-situ real-time monitoring system architecture for seawater carbon dioxide partial pressure, provided as an embodiment of the present invention. Detailed Implementation

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0030] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0032] Please see Figure 1 This embodiment provides a method for real-time monitoring of in-situ seawater carbon dioxide partial pressure, including the following steps: Step S1: Obtain high-humidity equilibrium gas from in-situ seawater in real time; Step S2: Based on the high-humidity equilibrium sample gas, obtain the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature; Step S3: Perform dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction; Step S4: Perform humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry air carbon dioxide mole fraction; Step S5: Obtain the partial pressure of carbon dioxide in the gas phase based on the mole fraction of carbon dioxide in the dry gas and the sample gas pressure; Step S6: Perform temperature compensation on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, so as to achieve real-time monitoring.

[0033] In this embodiment, a reliable basis for in-situ seawater carbon dioxide partial pressure measurement is provided by acquiring high-humidity equilibrium sample gas from in-situ seawater in real time. Simultaneously, the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature are acquired, thus constructing a multivariate parameter system required for in-situ monitoring. Based on the dew point temperature and sample gas pressure, the water vapor mole fraction is obtained through dew point inversion, providing an accurate basis for subsequent compensation processing. The dry gas carbon dioxide mole fraction is obtained through humidity compensation, thereby improving the accuracy of carbon dioxide mole fraction measurement. The gas phase carbon dioxide partial pressure is obtained by combining the dry gas carbon dioxide mole fraction and sample gas pressure, and then temperature compensation is used to eliminate the partial pressure deviation caused by the temperature difference between the gas and liquid phases, finally obtaining the in-situ seawater carbon dioxide partial pressure. This embodiment achieves real-time and accurate monitoring of in-situ seawater carbon dioxide partial pressure without relying on drying treatment, by accurately compensating for water vapor interference and temperature differences.

[0034] In one embodiment, a method for real-time monitoring of in-situ seawater carbon dioxide partial pressure includes the following steps: First, high-humidity equilibrium sample gas is obtained in real time from in-situ seawater. Preferably, seawater is flowed through a gas-liquid equilibrium unit, using a Teflon tube as the equilibrium interface, so that the dissolved gases (including carbon dioxide and water vapor) in the liquid phase seawater can fully contact and reach equilibrium with the gas phase in the measurement pipeline, thereby outputting high-humidity equilibrium sample gas, providing a reliable basis for subsequent measurements.

[0035] Next, based on the high humidity equilibrium sample gas, several key parameters are simultaneously acquired, including: the mole fraction of carbon dioxide moisture in the sample gas, the dew point temperature of the sample gas, the pressure of the sample gas, the gas phase temperature of the sample gas, and the in-situ seawater temperature, thereby constructing a multi-parameter system required for in-situ monitoring.

[0036] Then, based on the obtained dew point temperature and sample gas pressure, dew point inversion is performed to calculate the partial pressure of water vapor in the sample gas, and further obtain the water vapor mole fraction.

[0037] It should be noted that this step directly inverts the actual water vapor partial pressure from the dew point temperature, rather than simply assuming the sample gas is in a saturated water vapor state, thus providing a more accurate basis for subsequent compensation. Based on the calculated water vapor mole fraction and the directly measured carbon dioxide wet mole fraction, humidity compensation is performed to remove the interference of water vapor on carbon dioxide measurement, obtaining the dry gas carbon dioxide mole fraction, thereby improving the accuracy of carbon dioxide mole fraction measurement.

[0038] Subsequently, pressure compensation and partial pressure conversion were performed based on the mole fraction of carbon dioxide in the dry gas and the sample gas pressure to obtain the partial pressure of carbon dioxide in the gas phase.

[0039] Finally, based on the difference between the sample gas phase temperature and the in-situ seawater temperature, temperature compensation is applied to the partial pressure of carbon dioxide in the gas phase to eliminate the partial pressure deviation caused by the temperature difference between the gas and liquid phases, thereby obtaining an accurate in-situ seawater carbon dioxide partial pressure and achieving real-time monitoring.

[0040] This embodiment effectively eliminates the influence of water vapor interference and temperature differences on the measurement results by combining the above-mentioned humidity compensation and temperature compensation, without relying on traditional drying equipment, and realizes real-time and accurate monitoring of in-situ seawater carbon dioxide partial pressure.

[0041] Furthermore, after obtaining the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high-humidity equilibrium sample gas, the method further includes: The dew point change rate is obtained based on the dew point temperature. The physical rationality is verified based on the dew point change rate. If the verification fails, the dew point temperature is marked as abnormal data, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0042] In this embodiment, after obtaining the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high humidity equilibrium sample gas, the dew point change rate is obtained based on the dew point temperature, and physical rationality is verified based on the dew point change rate. This allows for effective identification of the dew point temperature data. If the verification fails, the dew point temperature is marked as abnormal data, and a new high humidity equilibrium sample gas is obtained from the in-situ seawater to restart the real-time monitoring of carbon dioxide partial pressure in in-situ seawater. This avoids abnormal dew point temperature data from participating in subsequent dew point inversion, water vapor mole fraction acquisition, humidity compensation, temperature compensation, and in-situ seawater carbon dioxide partial pressure calculation processes, preventing abnormal data from interfering with the monitoring results, ensuring the accuracy of the parameter calculations and the final partial pressure results, and effectively improving the reliability and stability of real-time monitoring of carbon dioxide partial pressure in in-situ seawater.

[0043] Furthermore, the physical rationality verification based on the dew point change rate is performed. If the verification fails, the dew point temperature is marked as abnormal data. The abnormal data includes erroneous data, invalid data, and warning data, wherein: The dew point change rate is obtained based on the dew point temperature. If the dew point change rate is greater than or equal to a preset first change rate threshold, the dew point temperature is marked as erroneous data. If the dew point change rate is less than a preset first change rate threshold and greater than or equal to a preset second change rate threshold, then the dew point temperature is marked as invalid data. If the dew point change rate is less than a preset second change rate threshold and greater than or equal to a preset third change rate threshold, then the dew point temperature is marked as warning data.

[0044] In this embodiment, when performing physical rationality verification based on the dew point change rate, by setting preset first change rate threshold, preset second change rate threshold, and preset third change rate threshold, abnormal dew point temperature data can be finely classified and marked. When the dew point change rate is greater than or equal to the preset first change rate threshold, the dew point temperature is marked as erroneous data; when the dew point change rate is less than the preset first change rate threshold but greater than or equal to the preset second change rate threshold, it is marked as invalid data; when the dew point change rate is less than the preset second change rate threshold but greater than or equal to the preset third change rate threshold, it is marked as warning data. This allows for precise differentiation of dew point temperature data with different degrees of abnormality, preventing abnormal data from entering subsequent calculation processes and preventing it from interfering with monitoring results. This effectively improves the data discrimination accuracy and the accuracy and stability of the monitoring results in real-time monitoring of in-situ seawater carbon dioxide partial pressure.

[0045] It should be noted that the preset first rate of change threshold is greater than the second rate of change threshold, and the second rate of change threshold is greater than the third rate of change threshold.

[0046] Furthermore, the process of performing dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction includes: The partial pressure of water vapor is obtained by inverting the water vapor partial pressure based on the dew point temperature and the Magnus formula. The water vapor mole fraction is obtained based on the water vapor partial pressure, sample gas pressure, and Dalton's law of partial pressure.

[0047] In this embodiment, during the process of obtaining the water vapor mole fraction by dew point inversion based on the dew point temperature and sample gas pressure, the water vapor partial pressure is first inverted based on the dew point temperature and Magnus's formula to obtain the water vapor partial pressure, ensuring the accuracy and reliability of the water vapor partial pressure inversion result. Subsequently, the water vapor mole fraction is obtained based on the water vapor partial pressure, sample gas pressure, and Dalton's law of partial pressures, achieving accurate calculation of the water vapor mole fraction. This embodiment, relying on standardized formulas and physical laws, can obtain a high-precision water vapor mole fraction based on measured dew point temperature and sample gas pressure, effectively improving the accuracy of the calculation of basic parameters. This provides reliable data for subsequent humidity compensation based on water vapor mole fraction and carbon dioxide moisture mole fraction, thereby ensuring the accuracy and stability of the dry gas carbon dioxide mole fraction calculation and in-situ seawater carbon dioxide partial pressure monitoring results.

[0048] Furthermore, after obtaining the water vapor partial pressure by performing the water vapor partial pressure inversion based on the dew point temperature and the Magnus formula, the process further includes: The physical rationality of the water vapor partial pressure is verified. If the water vapor partial pressure is greater than or equal to the sample gas pressure, the water vapor partial pressure is marked as abnormal partial pressure data, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0049] In this embodiment, after obtaining the water vapor partial pressure through inversion based on dew point temperature and the Magnus equation, the physical rationality of the water vapor partial pressure is further verified. The numerical relationship between the water vapor partial pressure and the sample gas pressure is determined according to physical laws. If the water vapor partial pressure is greater than or equal to the sample gas pressure, it is marked as abnormal partial pressure data. Simultaneously, a high-humidity equilibrium sample gas is re-obtained from the in-situ seawater, and real-time monitoring of the carbon dioxide partial pressure in the in-situ seawater is resumed. This effectively identifies physically unreasonable water vapor partial pressure data, promptly blocks abnormal partial pressure data from participating in subsequent calculations, and avoids erroneous data caused by measurement anomalies affecting subsequent data processing. This ensures that the water vapor partial pressure data used for subsequent calculations is accurate and reasonable, providing a reliable data foundation for subsequent operations such as obtaining water vapor mole fraction and humidity compensation, thereby guaranteeing the accuracy and stability of the real-time monitoring results of the carbon dioxide partial pressure in the in-situ seawater.

[0050] Further, the step of performing humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry air carbon dioxide mole fraction includes: Error detection is performed based on the water vapor mole fraction. When an error is detected, the following steps are executed: Pressure compensation is performed based on the water vapor mole fraction, sample gas pressure, and preset calibration parameters to obtain the pressure-compensated moisture mole fraction. The pressure-compensated moisture mole fraction is used as the carbon dioxide moisture mole fraction to compensate for the moisture mole fraction and carbon dioxide moisture mole fraction, thus obtaining the dry gas carbon dioxide mole fraction.

[0051] In this embodiment, during the process of obtaining the dry gas carbon dioxide mole fraction through humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction, error detection is first performed based on the water vapor mole fraction. When an error is detected, a pressure compensation process is executed. Pressure compensation is performed based on the water vapor mole fraction, sample gas pressure, and preset calibration parameters to obtain the pressure-compensated moisture mole fraction. This pressure-compensated moisture mole fraction is then used as the carbon dioxide moisture mole fraction, and further humidity compensation is performed with the water vapor mole fraction to obtain the dry gas carbon dioxide mole fraction. This embodiment can correct the carbon dioxide moisture mole fraction through pressure compensation after error identification, ensuring the accuracy and reliability of the parameters involved in humidity compensation, avoiding adverse effects of errors on the humidity compensation results, improving the calculation accuracy of the dry gas carbon dioxide mole fraction, and providing a precise data foundation for subsequent gas phase carbon dioxide partial pressure calculation and in-situ seawater carbon dioxide partial pressure monitoring, effectively improving the accuracy and reliability of monitoring results.

[0052] Furthermore, after temperature compensation is performed on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, the method further includes: The temperature difference is obtained based on the gas phase temperature and the in-situ seawater temperature; If the temperature difference exceeds a preset temperature difference threshold, the in-situ seawater carbon dioxide partial pressure is marked as temperature difference exceeding the limit, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0053] In this embodiment, after temperature compensation is performed on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, the temperature difference is further obtained based on the gas phase temperature and the in-situ seawater temperature, and the temperature difference is compared with a preset temperature difference threshold. If the temperature difference is greater than the preset temperature difference threshold, the partial pressure of carbon dioxide in the in-situ seawater is marked as exceeding the temperature difference limit. At the same time, a high humidity equilibrium sample gas is re-obtained from the in-situ seawater, and real-time monitoring of the partial pressure of carbon dioxide in the in-situ seawater is carried out again. This embodiment can verify the rationality of the final monitoring data after temperature compensation, promptly identify abnormal situations where the difference between the gas phase temperature and the in-situ seawater temperature is too large, avoid the participation of temperature difference exceeding the limit data in subsequent data processing and result application, prevent abnormal temperature difference conditions from reducing the reliability of monitoring results, ensure that the obtained partial pressure of carbon dioxide in the in-situ seawater is accurate and effective, and further improve the overall accuracy and stability of real-time monitoring of the partial pressure of carbon dioxide in the in-situ seawater.

[0054] In one embodiment, firstly, a high-humidity equilibrium sample gas is obtained in real time from in-situ seawater. Preferably, by allowing seawater to flow through a gas-liquid equilibrium unit, using a Teflon tube as the equilibrium interface, the dissolved gases (including carbon dioxide and water vapor) in the liquid phase of the seawater are allowed to fully contact and reach equilibrium with the gas phase in the measurement pipeline, thereby outputting a high-humidity equilibrium sample gas, providing a reliable basis for subsequent measurements.

[0055] Next, several key parameters were simultaneously acquired based on the high-humidity equilibrium sample gas, specifically including: the mole fraction of carbon dioxide moisture in the sample gas ( ), sample gas dew point temperature ( Sample gas pressure (P), sample gas phase temperature ( ) and in-situ seawater temperature ( This allows for the construction of a multi-parameter system required for in-situ monitoring.

[0056] After obtaining the above parameters, a physical rationality check is first performed based on the dew point temperature. Specifically, the dew point change rate is obtained based on the dew point temperature, that is, the difference between the dew point temperature at the current moment and the dew point temperature at the previous moment. The dew point change rate is used for graded verification: if the dew point change rate is greater than or equal to a preset first change rate threshold (e.g., 0.083 / minute × ... If the dew point temperature is less than a preset first rate of change threshold and greater than or equal to a preset second rate of change threshold (e.g., 0.05 / minute × ...), then the dew point temperature is marked as erroneous data; if the dew point change rate is less than a preset first rate of change threshold and greater than or equal to a preset second rate of change threshold (e.g., 0.05 / minute × ... If the dew point change rate is less than a preset second change rate threshold and greater than or equal to a preset third change rate threshold (e.g., 0.0167 / minute × ...), it is marked as invalid data; If the value is 0, it is marked as warning data.

[0057] It should be noted that the preset first, second, and third rate of change thresholds decrease sequentially. By setting multiple threshold levels, abnormal dew point temperature data can be finely graded and marked, accurately distinguishing dew point temperature data of different degrees of abnormality. If the verification fails, i.e., the dew point data is marked as incorrect, invalid, or a warning, the dew point temperature is marked as abnormal data, and a new high humidity equilibrium sample gas is obtained from the in-situ seawater for re-monitoring. This avoids abnormal data from participating in subsequent calculation processes, ensuring the accuracy and stability of the monitoring results.

[0058] For the verified dew point temperature data, dew point inversion is performed based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction. Specifically, firstly, water vapor partial pressure is inverted based on the dew point temperature and the Magnus formula to obtain the water vapor partial pressure (…). Dew point is defined as the equivalent temperature at which saturation is achieved, therefore the partial pressure of water vapor is... Equal to the saturated vapor pressure corresponding to that dew point temperature ,satisfy: Calculated using an engineering approximation expression in Magnus form: All pressure units are in kPa.

[0059] It should be noted that this step directly inverts the actual water vapor partial pressure from the dew point temperature, rather than simply assuming that the sample gas is in a saturated water vapor state, thus providing a more accurate basis for subsequent compensation.

[0060] After obtaining the partial pressure of water vapor, the physical rationality of the water vapor partial pressure is further verified, and the numerical relationship between the water vapor partial pressure and the sample gas pressure is determined based on physical laws. To ensure numerical stability, constraints are added: If the partial pressure of water vapor is greater than or equal to the sample gas pressure ( If the dew point and pressure are inconsistent, it is considered that the discrepancy may be caused by abnormal dew point, abnormal pressure, or incorrect units. The partial pressure of water vapor is marked as abnormal partial pressure data. At the same time, a high humidity equilibrium sample gas is re-obtained from the in-situ seawater, and monitoring is carried out again to promptly prevent the abnormal partial pressure data from participating in the subsequent calculation process.

[0061] For the water vapor partial pressure that passes the verification, the water vapor mole fraction is obtained based on the water vapor partial pressure, sample gas pressure, and Dalton's law of partial pressure. ),satisfy: ,in The unit is ppm.

[0062] Simultaneously with obtaining the water vapor mole fraction, the measurement of the carbon dioxide moisture mole fraction is processed. First, error detection is performed based on the water vapor mole fraction to determine if there is a systematic error in the carbon dioxide detector that varies with pressure. When an error is detected (e.g., the flow rate fluctuation exceeds a threshold of 10% via a standard gas detector), a pressure compensation procedure is executed. Specifically, one or more standard gas concentrations are selected. At multiple pressure points The following calibration was performed to calculate the pressure sensitivity coefficient. ,satisfy: in To calibrate the reference pressure, at normal pressure =101.325 kPa.

[0063] During online measurement, pressure compensation is performed based on the water vapor mole fraction, sample gas pressure, and preset calibration parameters to obtain the pressure-compensated moisture mole fraction. : It should be noted that if the carbon dioxide detector itself has a built-in pressure compensation function and is working properly, this step can be skipped. However, it is recommended to retain the bypass calibration mechanism so that the external calibration is automatically activated when the detector's built-in compensation fails or drifts. Compensation is performed. In this embodiment, pressure compensation can be used to correct the carbon dioxide moisture mole fraction after the identification error, ensuring that the parameters involved in humidity compensation are accurate and reliable.

[0064] Subsequently, based on the water vapor mole fraction and carbon dioxide moisture mole fraction (after pressure compensation) Humidity compensation was performed to obtain the dry gas carbon dioxide mole fraction ( ),satisfy: At the same time, a safety lower limit is introduced, if the water vapor mole fraction If the value exceeds the preset maximum value (e.g., 950,000 ppm), an anomaly flag will be set directly to avoid calculation errors caused by the denominator being close to zero.

[0065] Based on the dry gas carbon dioxide mole fraction and sample gas pressure, pressure compensation and partial pressure conversion are performed to obtain the gas phase carbon dioxide partial pressure (…). ),satisfy: At normal pressure =101.325 kPa, The unit is μatm.

[0066] Finally, based on the sample gas phase temperature ( ) and in-situ seawater temperature ( The temperature compensation is applied to the partial pressure of carbon dioxide in the gas phase to eliminate the pressure deviation caused by the temperature difference between the gas and liquid phases, thereby obtaining an accurate in-situ partial pressure of carbon dioxide in seawater. Temperature compensation is achieved using the following formula: It should be noted that by combining the above-mentioned humidity compensation and temperature compensation, this embodiment effectively eliminates the influence of water vapor interference and temperature differences on the measurement results without relying on traditional drying equipment, and realizes real-time and accurate monitoring of in-situ seawater carbon dioxide partial pressure.

[0067] After obtaining the partial pressure of carbon dioxide in the in-situ seawater, the temperature difference ΔT is further obtained based on the gas phase temperature and the in-situ seawater temperature. The temperature difference is compared with a preset temperature difference threshold. If the temperature difference is greater than the preset temperature difference threshold (e.g., ΔT>3℃), the in-situ seawater carbon dioxide partial pressure is marked as exceeding the temperature difference limit, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater for monitoring.

[0068] This embodiment can verify the rationality of the final monitoring data after temperature compensation, promptly identify abnormal situations where the temperature difference between the gas phase and the in-situ seawater is too large, avoid the use of temperature difference exceeding the limit in subsequent data processing and result application, ensure that the obtained in-situ seawater carbon dioxide partial pressure data is accurate and effective, and further improve the overall accuracy and stability of real-time monitoring of in-situ seawater carbon dioxide partial pressure.

[0069] Please see Figure 2 This embodiment also provides an in-situ real-time monitoring system for seawater carbon dioxide partial pressure, including: The gas-liquid balance module is used to obtain high-humidity equilibrium sample gas from in-situ seawater in real time; The carbon dioxide monitoring module is used to obtain the moisture mole fraction of carbon dioxide based on the high humidity equilibrium sample gas. The dew point monitoring module is used to obtain the dew point temperature based on the high humidity equilibrium sample gas. The pressure monitoring module is used to obtain the sample gas pressure based on the high humidity equilibrium sample gas; The gas phase temperature monitoring module is used to obtain the gas phase temperature based on the high humidity equilibrium sample gas; The seawater temperature monitoring module is used to obtain the in-situ seawater temperature based on the high humidity equilibrium sample gas. The data processing module is used to perform dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction; to perform humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry gas carbon dioxide mole fraction; to obtain the gas phase carbon dioxide partial pressure based on the dry gas carbon dioxide mole fraction and sample gas pressure; to perform temperature compensation on the gas phase carbon dioxide partial pressure based on the gas phase temperature and in-situ seawater temperature to obtain the in-situ seawater carbon dioxide partial pressure, and output the real-time monitoring results.

[0070] In this embodiment, a collaborative in-situ real-time monitoring system for the partial pressure of carbon dioxide in seawater is constructed by integrating a gas-liquid balance module, a carbon dioxide monitoring module, a dew point monitoring module, a pressure monitoring module, a gas phase temperature monitoring module, a seawater temperature monitoring module, and a data processing module. The gas-liquid balance module acquires high-humidity equilibrium sample gas from the in-situ seawater in real time. Each monitoring module simultaneously acquires parameters such as the molar fraction of carbon dioxide moisture, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high-humidity equilibrium sample gas. The data processing module sequentially performs dew point inversion, humidity compensation, gas phase carbon dioxide partial pressure calculation, and temperature compensation, ultimately obtaining the in-situ seawater carbon dioxide partial pressure and outputting the real-time monitoring results. The modules have clear division of labor and close cooperation, enabling a complete workflow from sample gas acquisition and parameter monitoring to data calculation and result output, ensuring a consistent and reliable monitoring process and achieving accurate and real-time monitoring of the partial pressure of carbon dioxide in in-situ seawater.

[0071] In one specific embodiment, an in-situ real-time monitoring system for carbon dioxide partial pressure in seawater is provided for executing the aforementioned method for real-time monitoring of carbon dioxide partial pressure in seawater. The system includes a gas-liquid balance module, a carbon dioxide monitoring module, a dew point monitoring module, a pressure monitoring module, a gas phase temperature monitoring module, a seawater temperature monitoring module, a data processing module, and other auxiliary components. These modules work collaboratively to achieve fully automated monitoring from sample gas acquisition to data output.

[0072] Specifically, the gas-liquid balance module is used to acquire high-humidity equilibrium sample gas from in-situ seawater in real time. This module uses a Teflon tube as the gas-liquid balance interface, ensuring sufficient contact and equilibrium between the dissolved gases (including carbon dioxide and water vapor) in the liquid seawater and the gas phase in the measurement pipeline. The module includes an air pump to provide power for water-gas circulation, thus shortening the equilibrium response time; it also includes a filter to prevent salt spray and particulate matter that may be carried by the air pump outlet from entering the downstream pipeline, thus avoiding contamination.

[0073] It should be noted that Teflon materials have good hydrophobicity and air permeability, which can effectively promote the exchange of substances between the gas and liquid phases, thereby quickly obtaining equilibrium sample gas that represents the partial pressure of dissolved gases in seawater.

[0074] The carbon dioxide monitoring module is used to obtain the moisture mole fraction of carbon dioxide based on the high-humidity equilibrium sample gas. In this embodiment, a domestically produced single-channel non-dispersive infrared (NDIR) carbon dioxide detector is used, which has a constant temperature function for the light source, which can reduce the impact of ambient temperature changes on measurement stability. However, this detector does not have a water vapor absorption measurement channel, so its original output is the wet-based carbon dioxide concentration.

[0075] The dew point monitoring module is used to measure the dew point temperature of the high humidity equilibrium sample gas; The pressure monitoring module is used to measure the gas pressure of the high-humidity equilibrium sample gas in the carbon dioxide detector measurement chamber; The gas phase temperature monitoring module is used to measure the gas phase temperature inside the gas-liquid balance unit (in this embodiment, the temperature measured here is not the heat preservation temperature of the NDIR light source system, but the actual gas phase temperature participating in temperature compensation inside the balance film). The seawater temperature monitoring module is used to measure the external seawater temperature at the location of the gas-liquid balance unit, i.e., the in-situ seawater temperature.

[0076] The data processing module is connected to each of the aforementioned monitoring modules to receive the raw data collected by each module and perform a series of compensations and calculations. Specifically, the data processing module first performs dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction; then, it performs humidity compensation based on the water vapor mole fraction and the carbon dioxide moisture mole fraction to obtain the dry gas carbon dioxide mole fraction; next, it obtains the gas phase carbon dioxide partial pressure based on the dry gas carbon dioxide mole fraction and the sample gas pressure; finally, it performs temperature compensation on the gas phase carbon dioxide partial pressure based on the gas phase temperature and the in-situ seawater temperature to obtain the in-situ seawater carbon dioxide partial pressure and outputs the real-time monitoring results.

[0077] The data processing module described in this embodiment, by integrating the above-mentioned algorithm, can effectively eliminate the influence of water vapor interference and the temperature difference between the gas and liquid phases on the measurement results without relying on traditional drying devices, thereby achieving high-precision in-situ monitoring.

[0078] In addition, the system includes necessary auxiliary components, such as a watertight container to house all electronic components except the gas-liquid balance module, providing waterproofing and moisture protection; and cables to power the underwater observation system and connect to the power supply interface of the surface buoy, enabling electrical interconnection between the various modules. It is particularly noteworthy that the in-situ seawater carbon dioxide partial pressure real-time monitoring system provided in this embodiment eliminates components commonly found in traditional methods, such as gas drying devices, flow controllers, and solenoid valves. This not only simplifies the system structure and reduces power consumption but also minimizes measurement errors caused by desiccant failure or flow fluctuations, making the system more suitable for long-term, unattended in-situ monitoring applications.

[0079] Furthermore, the dew point monitoring module, after obtaining the dew point temperature based on the high humidity equilibrium sample gas, also includes: The dew point change rate is obtained based on the dew point temperature. The physical rationality is verified based on the dew point change rate. If the verification fails, the dew point temperature is marked as abnormal data, and the gas-liquid balance module is made to re-obtain high humidity balance sample gas from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

[0080] In this embodiment, after obtaining the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high humidity equilibrium sample gas, the dew point monitoring module obtains the dew point change rate based on the dew point temperature and performs physical rationality verification based on the dew point change rate, thereby achieving effective discrimination of the dew point temperature data. If the verification fails, the dew point temperature is marked as abnormal data, and a new high humidity equilibrium sample gas is obtained from the in-situ seawater to re-perform real-time monitoring of in-situ seawater carbon dioxide partial pressure. This avoids abnormal dew point temperature data from participating in subsequent dew point inversion, water vapor mole fraction acquisition, humidity compensation, temperature compensation, and in-situ seawater carbon dioxide partial pressure calculation processes, preventing abnormal data from interfering with the monitoring results, ensuring the accuracy of each parameter calculation and the final partial pressure result, and effectively improving the reliability and stability of real-time monitoring of in-situ seawater carbon dioxide partial pressure.

[0081] In one embodiment, a buoy-type in-situ real-time monitoring system for seawater carbon dioxide partial pressure is provided for performing the aforementioned monitoring method. The system includes a gas-liquid balance module, a carbon dioxide monitoring module, a dew point monitoring module, a pressure monitoring module, a gas phase temperature monitoring module, a seawater temperature monitoring module, a data processing module, and other auxiliary components. These modules work collaboratively to achieve fully automated monitoring from sample gas acquisition to data output.

[0082] Specifically, the gas-liquid balance module is used to obtain high-humidity equilibrium sample gas from in-situ seawater in real time. This module uses a Teflon tube as the gas-liquid balance interface, ensuring sufficient contact and equilibrium between the dissolved gases (including carbon dioxide and water vapor) in the liquid phase seawater and the gas phase in the measurement pipeline. A capsule filter (preferably with a filtration accuracy of 1-5 μm) is installed at the module inlet to prevent particulate matter from seawater from entering the pipeline; a micro-pump (preferably with a flow rate range of 100-1000 ml / min) is installed inside the module to provide power for water-gas circulation, thereby shortening the equilibrium response time and maintaining a stable sample gas flow rate.

[0083] It should be noted that Teflon materials have good hydrophobicity and air permeability, which can effectively promote the exchange of substances between the gas and liquid phases, thereby quickly obtaining equilibrium sample gas that represents the partial pressure of dissolved gases in seawater.

[0084] The carbon dioxide monitoring module is used to obtain the moisture mole fraction of carbon dioxide based on the high humidity equilibrium sample gas. In this embodiment, a single-channel non-dispersive infrared (NDIR) carbon dioxide detector (preferably with a range of 0-5000ppm) is used. The infrared light source and optical detection unit of the detector are set to a constant temperature operating state, and the constant temperature can be set, for example, to 40°C, to prevent temperature drift in carbon dioxide measurement caused by changes in ambient temperature.

[0085] It should be noted that the isothermal temperature described in this embodiment is different from the actual gas temperature of the sample gas in the gas pipeline and measurement chamber. The actual temperature of the sample gas is measured by an independent gas phase temperature sensor and participates in subsequent compensation calculations. Furthermore, the carbon dioxide detector does not have a water vapor absorption measurement channel; therefore, its original output is a wet-based carbon dioxide concentration, which needs to be corrected by subsequent humidity compensation.

[0086] The dew point monitoring module (preferably with a range of -60°C to 60°C) is used to measure the dew point temperature of the high humidity equilibrium sample gas. The pressure monitoring module (preferably with a range of 80-120 kPa) is used to measure the gas pressure of the high humidity equilibrium sample gas within the carbon dioxide detector measurement chamber. The gas phase temperature measurement module (preferably with a range of -50 to 50°C) is used to measure the gas phase temperature inside the gas-liquid equilibrium unit. The seawater temperature measurement module (preferably with a range of -50 to 50°C) is used to measure the external seawater temperature at the location of the gas-liquid equilibrium unit, i.e., the in-situ seawater temperature.

[0087] The data processing module is connected to each of the above monitoring modules and is used to receive the raw data collected by each module and perform a series of compensations and calculations.

[0088] In one application example, after acquiring the dew point temperature, the dew point monitoring module first obtains the dew point change rate based on the dew point temperature and performs a physical rationality check according to a preset threshold. If the check fails (e.g., the dew point jump exceeds a set limit), the dew point temperature is marked as abnormal data, and the gas-liquid balance module re-acquires a high-humidity equilibrium sample gas from the in-situ seawater to restart the monitoring process, avoiding abnormal data from contaminating subsequent calculation results. For dew point data that passes the check, the data processing module performs the following operations in sequence: dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction; humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry gas carbon dioxide mole fraction; gas phase carbon dioxide partial pressure based on the dry gas carbon dioxide mole fraction and sample gas pressure; temperature compensation based on the gas phase temperature and in-situ seawater temperature to obtain the in-situ seawater carbon dioxide partial pressure, and outputs the real-time monitoring results.

[0089] To more clearly illustrate the specific working process and data flow of the buoy-type in-situ seawater carbon dioxide partial pressure real-time monitoring system provided in this embodiment, a set of measured data is used as an example. In a certain test, the raw data acquired by each module are as follows: dew point temperature 19.987°C, gas pressure 103.555 kPa, gas phase temperature 26.5°C, seawater temperature 25.1°C, and the moisture carbon dioxide mole fraction output by the non-dispersive infrared carbon dioxide sensor is 559.284 ppm. Based on the above data, the data processing unit first obtained the water vapor partial pressure of 2.331 kPa by inverting the dew point temperature, and then calculated the water vapor mole fraction of 22507 ppm by combining it with the gas pressure. Subsequently, humidity compensation was performed to obtain the dry gas carbon dioxide mole fraction of 572.16 ppm. Next, pressure compensation and partial pressure conversion were performed by combining the gas pressure to obtain the gas phase carbon dioxide partial pressure of 584.8 µatm. Finally, temperature compensation was performed based on the difference between seawater temperature and gas phase temperature (ΔT = -1.4°C) to finally obtain the in-situ seawater carbon dioxide partial pressure of 546.7 µatm.

[0090] This embodiment effectively eliminates the influence of water vapor interference and the temperature difference between the gas and liquid phases on the measurement results by combining the above-mentioned humidity compensation and temperature compensation, without relying on traditional drying equipment, and realizes real-time and accurate monitoring of the partial pressure of carbon dioxide in in-situ seawater.

[0091] In addition, the system also includes necessary auxiliary components, such as a watertight tank (preferably made of PVC) to house all electronic components except for the gas-liquid balance module, which serves to prevent water and moisture damage; and cables (e.g., 12-24V, 3A specification) to power the underwater observation system and connect to the power supply interface of the surface buoy, enabling electrical interconnection between the various modules.

[0092] This embodiment eliminates components commonly found in traditional methods, such as gas drying devices, flow controllers, and solenoid valves. This not only simplifies the system structure and reduces power consumption, but also reduces measurement errors caused by desiccant failure or flow fluctuations, making the system more suitable for long-term, unattended buoy-type in-situ monitoring applications.

[0093] The modules integrated into the system equipment, if implemented as software functional units and sold or used as independent products, can be stored in a computer-readable storage medium. Based on this understanding, all or part of the processes in the above embodiments of the present invention can also be implemented by a computer program instructing related hardware. The computer program can be stored in a computer-readable storage medium, and when executed by a processor, it can implement the steps of the various method embodiments described above. The computer program includes computer program code, which can be in the form of source code, object code, executable files, or certain intermediate forms. The computer-readable medium can include: any entity or device capable of carrying the computer program code, recording media, USB flash drives, portable hard drives, magnetic disks, optical disks, computer memory, read-only memory (ROM), random access memory (RAM), electrical carrier signals, telecommunication signals, and software distribution media, etc.

[0094] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A method for real-time monitoring of in-situ seawater carbon dioxide partial pressure, characterized in that, Includes the following steps: High-humidity equilibrium gas samples were obtained in real time from in-situ seawater. Based on the high humidity equilibrium sample gas, the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature were obtained. Dew point inversion is performed based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction. Humidity compensation is performed based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry air carbon dioxide mole fraction. The partial pressure of carbon dioxide in the gas phase is obtained based on the mole fraction of carbon dioxide in the dry gas and the sample gas pressure. Temperature compensation is performed on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, so as to achieve real-time monitoring.

2. The method for real-time monitoring of in-situ seawater carbon dioxide partial pressure according to claim 1, characterized in that, After obtaining the carbon dioxide moisture mole fraction, dew point temperature, sample gas pressure, gas phase temperature, and in-situ seawater temperature based on the high humidity equilibrium sample gas, the method further includes: The dew point change rate is obtained based on the dew point temperature; The physical rationality is verified based on the dew point change rate. If the verification fails, the dew point temperature is marked as abnormal data, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

3. The method for real-time monitoring of in-situ seawater carbon dioxide partial pressure according to claim 2, characterized in that, The physical rationality verification based on the dew point change rate is performed. If the verification fails, the dew point temperature is marked as abnormal data. Abnormal data includes erroneous data, invalid data, and warning data, wherein: The dew point change rate is obtained based on the dew point temperature. If the dew point change rate is greater than or equal to a preset first change rate threshold, the dew point temperature is marked as erroneous data. If the dew point change rate is less than a preset first change rate threshold and greater than or equal to a preset second change rate threshold, then the dew point temperature is marked as invalid data. If the dew point change rate is less than a preset second change rate threshold and greater than or equal to a preset third change rate threshold, then the dew point temperature is marked as warning data.

4. The method for real-time monitoring of in-situ seawater carbon dioxide partial pressure according to claim 1, characterized in that, The process of dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction includes: The partial pressure of water vapor is obtained by inverting the water vapor partial pressure based on the dew point temperature and the Magnus formula. The water vapor mole fraction is obtained based on the water vapor partial pressure, sample gas pressure, and Dalton's law of partial pressure.

5. The method for real-time monitoring of in-situ seawater carbon dioxide partial pressure according to claim 4, characterized in that, After obtaining the water vapor partial pressure by performing water vapor partial pressure inversion based on the dew point temperature and the Magnus formula, the process further includes: The physical rationality of the water vapor partial pressure is verified. If the water vapor partial pressure is greater than or equal to the sample gas pressure, the water vapor partial pressure is marked as abnormal partial pressure data, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

6. The method for real-time monitoring of in-situ seawater carbon dioxide partial pressure according to claim 1, characterized in that, The process of obtaining the dry air carbon dioxide mole fraction by performing humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction includes: Error detection is performed based on the water vapor mole fraction. When an error is detected, the following steps are executed: Pressure compensation is performed based on the water vapor mole fraction, sample gas pressure, and preset calibration parameters to obtain the pressure-compensated moisture mole fraction. The pressure-compensated moisture mole fraction is used as the carbon dioxide moisture mole fraction to compensate for the moisture mole fraction and carbon dioxide moisture mole fraction, thus obtaining the dry gas carbon dioxide mole fraction.

7. The method for real-time monitoring of in-situ seawater carbon dioxide partial pressure according to claim 1, characterized in that, After temperature compensation is performed on the partial pressure of carbon dioxide in the gas phase based on the gas phase temperature and the in-situ seawater temperature to obtain the partial pressure of carbon dioxide in the in-situ seawater, the method further includes: The temperature difference is obtained based on the gas phase temperature and the in-situ seawater temperature; If the temperature difference exceeds a preset temperature difference threshold, the in-situ seawater carbon dioxide partial pressure is marked as temperature difference exceeding the limit, and a high humidity equilibrium sample gas is re-obtained from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

8. A real-time in-situ seawater carbon dioxide partial pressure monitoring system, characterized in that, include: The gas-liquid balance module is used to obtain high-humidity equilibrium sample gas from in-situ seawater in real time; The carbon dioxide monitoring module is used to obtain the moisture mole fraction of carbon dioxide based on the high humidity equilibrium sample gas. The dew point monitoring module is used to obtain the dew point temperature based on the high humidity equilibrium sample gas. The pressure monitoring module is used to obtain the sample gas pressure based on the high humidity equilibrium sample gas; The gas phase temperature monitoring module is used to obtain the gas phase temperature based on the high humidity equilibrium sample gas; The seawater temperature monitoring module is used to obtain the in-situ seawater temperature based on the high humidity equilibrium sample gas. The data processing module is used to perform dew point inversion based on the dew point temperature and sample gas pressure to obtain the water vapor mole fraction; to perform humidity compensation based on the water vapor mole fraction and carbon dioxide moisture mole fraction to obtain the dry gas carbon dioxide mole fraction; to obtain the gas phase carbon dioxide partial pressure based on the dry gas carbon dioxide mole fraction and sample gas pressure; to perform temperature compensation on the gas phase carbon dioxide partial pressure based on the gas phase temperature and in-situ seawater temperature to obtain the in-situ seawater carbon dioxide partial pressure, and output the real-time monitoring results.

9. The in-situ real-time monitoring system for carbon dioxide partial pressure in seawater according to claim 8, characterized in that, The dew point monitoring module, after obtaining the dew point temperature based on the high humidity equilibrium sample gas, further includes: The dew point change rate is obtained based on the dew point temperature; The physical rationality is verified based on the dew point change rate. If the verification fails, the dew point temperature is marked as abnormal data, and the gas-liquid balance module is made to re-obtain high humidity balance sample gas from the in-situ seawater to re-monitor the in-situ seawater carbon dioxide partial pressure in real time.

10. A computer-readable storage medium, characterized in that, include: A stored computer program, wherein, when the computer program is executed, it controls the device containing the computer-readable storage medium to perform a method for real-time monitoring of in-situ seawater carbon dioxide partial pressure as described in any one of claims 1-7.

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