Device and method for measuring flux of CO2 and CH4 on water surface and calculating concentration of CO2 and CH4 in water

Abstract

The invention relates to a device and a method for measuring the flux of CO2 and CH4 on a water surface and calculating the concentration of CO2 and CH4 in water. The device comprises a static floating chamber, a gas inlet pipe, a gas outlet pipe, a foam plate, a drying bottle and a gas detector. The foam plate is arranged around the static floating chamber, the gas outlet pipe, the drying bottle and the gas inlet end of the gas detector are sequentially connected, and the gas outlet end of the gas detector is connected with the gas inlet pipe of the static floating chamber. A static floating chamber and foam plates around the static floating chamber are placed on the surface layer of the water surface of a water sample to be detected, the device is started to form a gas channel, a curve of CO2 and CH4 concentration data changing along with time is recorded, the flux of CO2 and CH4 on the water surface to be detected is obtained through curve fitting, and then the concentration of CO2 and CH4 in water is obtained through calculation. The measuring device is convenient to implement and low in cost, the measuring method is simple in calculation process and accurate in calculation result when used for calculating the concentration of CO2 and CH4 in water, the concentration of CO2 and CH4 in a water sample can be continuously monitored and analyzed for a long time, and theoretical data support is provided for subsequent treatment.

Description

Technical Field

[0001] The present invention relates to a nuclear radiation detection technology, in particular to a device and method for measuring the fluxes of CO2 and CH4 on the water surface and calculating the concentrations of CO2 and CH4 in water. Background Art

[0002] Carbon dioxide (CO2) and methane (CH4) in water bodies are important sources of greenhouse gases. The greenhouse effect of methane is 21 - 23 times that of carbon dioxide. The contributions of CO2 and CH4 to the global greenhouse effect are significant. Accurately measuring the concentrations of these two gases in water helps to study the carbon cycle and estimate the budget of global greenhouse gases, thereby better understanding and addressing climate change. Additionally, dissolved CO2 and CH4 in water can affect the acid-base balance and dissolved oxygen content of the water body, and further affect the living environment of aquatic organisms. Therefore, monitoring the concentrations of these two gases in water is also of great significance for evaluating the health status of water bodies, preventing water eutrophication and ecological disasters.

[0003] Common methods for measuring CO2 and CH4 include gas chromatography, mass spectrometry, and optical sensing technology measurement. Gas chromatography is one of the traditional methods for determining the concentration of dissolved gases in water. This method releases the gas in the water sample through a gas-liquid equilibrium device and then uses a gas chromatograph for separation and detection. It has high sensitivity and accuracy, but the operation process is relatively complex and requires professional equipment and technical personnel. Mass spectrometry analyzes the gas components in the sample through ionization, dispersion and other technologies. A dissolved methane detector in water based on mass spectrometry technology has been commercialized, with the characteristics of high sensitivity and high resolution, and can detect gas concentrations at trace levels. Optical sensing technologies include tunable diode laser absorption spectroscopy, off-axis integrated cavity output spectroscopy, etc., which measure the gas concentration by using the absorption characteristics of gas molecules for light of specific wavelengths, and have high sensitivity and high stability, and can achieve high detection accuracy in a relatively short average time. However, the above methods all require relatively high costs and complex data processing. Therefore, how to achieve simple and low-cost measurement of the concentrations of CO2 and CH4 in water is very important and necessary. Summary of the Invention

[0004] The object of the present invention is to overcome the above-mentioned deficiencies of the prior art and provide a device and method for measuring the fluxes of CO2 and CH4 on the water surface and calculating the concentrations of CO2 and CH4 in water.

[0005] The technical solution of the present invention is: a device for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water, including a static floating chamber, an intake pipe, an outlet pipe, a foam board, a drying bottle and a gas detector; the foam board is arranged around the static floating chamber and fixedly connected to the static floating chamber, a substance for drying gas is placed in the drying bottle, the intake pipe and the outlet pipe are respectively installed on the static floating chamber, the outlet pipe is connected to the intake end of the drying bottle through a hose, the outlet end of the drying bottle is connected to the intake end of the gas detector through a hose, and the outlet end of the gas detector is connected to the intake pipe of the static floating chamber through a hose.

[0006] A further technical solution of the present invention is: calcium chloride powder is placed in the drying bottle; the gas detector selects a JK40-M2-D detector.

[0007] Another technical solution of the present invention is: a method for applying the device for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water, including a measurement process and a calculation process, and the specific steps are as follows. I. Measurement process Place the static floating chamber and the surrounding foam board on the water surface of the water sample to be measured, start the pump of the gas detector, and the air containing CO2 and CH4 in the static floating chamber enters the drying bottle through the outlet pipe under the action of the pump for drying, and then enters the gas detector; during the measurement process, record the CO2 and CH4 concentration data measured by the gas detector to obtain the curves of the CO2 and CH4 concentration data changing with time.

[0008] II. Calculation process When the static floating chamber is statically placed on the water surface, the net precipitation amount of CO2 and CH4 released from the water to the air through the water-air interface is the CO2 and CH4 fluxes on the water surface. Since the water volume near the water surface is approximately infinite, it is assumed that the CO2 and CH4 concentrations in the water do not change when measuring the water surface fluxes. At this time, the gaseous CO2 and CH4 concentrations in the static floating chamber are calculated by the following expressions: (1) Where C(t) is the CO2 and CH4 concentration in the static floating chamber, with the unit of mol / m 3 ; S is the area of the water surface in the static floating chamber in contact with the air, with the unit of m 2 ; V is the gas path volume, including the volume of the static floating chamber, the volume of the gas in the drying bottle and the volume of the connecting hose, with the unit of m 3 ; C(H 2 O) is the CO2 and CH4 concentration in the water, with the unit of mol / m 3 ;A 1 is the rate of CO2 and CH4 in the air entering the water surface, with the unit of m / s; A 2 is the rate of CO2 and CH4 on the water surface entering the air, with the unit of m / s; λ l is the leakage coefficient, with the unit of m / s; C E is the concentration of CO2 and CH4 in the environment at the start of the measurement, with the unit of mol / m 3 .

[0009] When the static floating chamber is statically placed on the water surface, the calculation expression for the fluxes of CO2 and CH4 on the water surface is: (2) Let , combined with formula (2), transform the expression of formula (1) as follows: (3) Since at the start of the measurement, the concentrations of CO2 and CH4 C(0) are equal to the concentrations of CO2 and CH4 in the environment C E , substitute it into formula (3) and solve to get: (4) Use formula (4) to perform data fitting on the curves of the CO2 and CH4 concentration data measured by the gas detector over time to obtain the fluxes of CO2 and CH4 on the water surface F .

[0010] The calculation expression for the concentrations of CO2 and CH4 in the water obtained by transforming formula (2) is: (5) Under specific temperature measurement conditions, A 1 and A 2 are fixed values, obtained through theoretical calculation or experimental measurement; substitute A 1 、A 2 and the fluxes of CO2 and CH4 on the water surface obtained by fitting F into formula (5) to obtain the concentrations of CO2 and CH4 in the water.

[0011] The present invention has the following advantages compared with the prior art: 1. The measuring device provided by the present invention for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water has a simple and portable structure, is easy to operate, and has a lower cost compared with the existing measuring methods.

[0012] 2. By using the measuring method provided by the present invention to calculate the CO2 and CH4 concentrations in water, the calculation process is simple, the calculation results are accurate, and it can continuously monitor and analyze the CO2 and CH4 concentrations in water samples for a long time.

[0013] The detailed structure of the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. Description of the Drawings

[0014] Figure 1 It is a schematic structural diagram of the device for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water; Figure 2 It is a top view of the static floating chamber in the working state. Specific Embodiments

[0015] Example 1. As Figure 1-2 shown, the device for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water includes a static floating chamber 1, an intake pipe 2, an outlet pipe 3, a foam board 4, a drying bottle 5, and a gas detector 6. The foam board 4 is arranged around the static floating chamber 1 and fixedly connected to the static floating chamber 1, which can make the static floating chamber 1 float on the water surface to be measured. Substances for drying gases, such as calcium chloride powder, etc., are placed in the drying bottle 5. The gas detector 6 is selected as JK40 - M2 - D for detecting CO2 and CH4 gases. The intake pipe 2 and the outlet pipe 3 are respectively installed on the static floating chamber 1. The outlet pipe 3 is connected to the intake end of the drying bottle 5 through a hose. The outlet end of the drying bottle 5 is connected to the intake end of the gas detector 6 through a hose. The outlet end of the gas detector 6 is connected to the intake pipe 2 of the static floating chamber 1 through a hose.

[0016] Example 2. The method applied to the device for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water in Example 1 includes a measuring process and a calculating process, and the specific steps are as follows: I. Measuring Process Place the static floating chamber 1 and the surrounding foam board 4 on the surface layer of the water sample 7 to be measured. Start the pump of the gas detector 6. The air containing CO2 and CH4 in the static floating chamber 1 enters the drying bottle 5 through the outlet pipe 3 under the action of the pump for drying, and then enters the gas detector 6; during the measuring process, record the CO2 and CH4 concentration data measured by the gas detector 6 to obtain the curves of the CO2 and CH4 concentration data changing with time.

[0017] II. Calculating Process When the static floating chamber 1 is statically placed on the water surface, the net evolution amount of CO2 and CH4 in the water released into the air through the water-air interface is the flux of CO2 and CH4 on the water surface. Since the water volume near the water surface is approximately infinite, assuming that the concentrations of CO2 and CH4 in the water do not change when measuring the water surface flux, the concentrations of gaseous CO2 and CH4 in the static floating chamber 1 are calculated by the following expressions: (1) Wherein, C(t) is the concentration of CO2 and CH4 in the static floating chamber 1, with the unit of mol / m 3 ; S is the area of the water surface in the static floating chamber 1 in contact with the air, with the unit of m 2 ; V is the volume of the gas path, including the volume of the static floating chamber 1, the volume of the gas in the drying bottle and the volume of the connecting hose, with the unit of m 3 ; C(H 2 O) is the concentration of CO2 and CH4 in the water, with the unit of mol / m 3 ; A 1 is the rate of CO2 and CH4 in the air entering the water surface, with the unit of m / s; A 2 is the rate of CO2 and CH4 on the water surface entering the air, with the unit of m / s; λ l is the leakage coefficient, with the unit of m / s; C E is the concentration of CO2 and CH4 in the environment at the start of the measurement, with the unit of mol / m 3 .

[0018] When the static floating chamber 1 is statically placed on the water surface, the calculation expression of the flux of CO2 and CH4 on the water surface is: (2) Let , combined with formula (2), the expression of formula (1) is transformed as follows: (3) Since at the start of the measurement, the concentrations C(0) of CO2 and CH4 are equal to the concentrations of CO2 and CH4 in the environment C E , substituting it into formula (3) and solving, we get: (4) The curves of the CO2 and CH4 concentration data measured by the gas detector 6 changing with time are fitted with the formula (4) to obtain the fluxes of CO2 and CH4 on the water surface. F .

[0019] The calculation expressions for the concentrations of CO2 and CH4 in water are obtained by transforming the formula (2) as follows: (5) Under the specific temperature measurement conditions, A 1 and A 2 are constant values, which are obtained through theoretical calculation or experimental measurement. Substitute A 1 、A 2 and the fluxes of CO2 and CH4 on the water surface obtained by fitting F into the formula (5) to obtain the concentrations of CO2 and CH4 in water.

Claims

1. An apparatus for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water, characterized in that: It includes a static floating chamber, an intake pipe, an outlet pipe, a foam board, a drying bottle and a gas detector; the foam board is arranged around the static floating chamber and fixedly connected to the static floating chamber, a substance for drying gas is placed in the drying bottle, the intake pipe and the outlet pipe are respectively installed on the static floating chamber, the outlet pipe is connected to the intake end of the drying bottle through a hose, the outlet end of the drying bottle is connected to the intake end of the gas detector through a hose, and the outlet end of the gas detector is connected to the intake pipe of the static floating chamber through a hose.

2. The device for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water according to claim 1, wherein: Calcium chloride powder is placed in the drying bottle; the gas detector is the JK40-M2-D detector.

3. A method for applying the device for measuring the CO2 and CH4 fluxes on the water surface and calculating the CO2 and CH4 concentrations in water according to claim 1 or 2, characterized in that: It includes a measurement process and a calculation process, and the specific steps are as follows. I. Measurement process Place the static floating chamber and the surrounding foam board on the water surface of the water sample to be measured, start the pump of the gas detector, and the air containing CO2 and CH4 in the static floating chamber enters the drying bottle through the outlet pipe under the action of the pump for drying, and then enters the gas detector; during the measurement process, record the CO2 and CH4 concentration data measured by the gas detector to obtain the curves of the CO2 and CH4 concentration data changing with time. II. Calculation process When the static floating chamber is statically placed on the water surface, the net evolution amount of CO2 and CH4 released from the water to the air through the water-air interface is the flux of CO2 and CH4 on the water surface. Since the water volume near the water surface is approximately infinite, it is assumed that the CO2 and CH4 concentrations in the water do not change when measuring the water surface flux. At this time, the gaseous CO2 and CH4 concentrations in the static floating chamber are calculated by the following expressions: （1） Among them, C(t) is the static floating indoor CO2 and CH4 concentration, with the unit of mol / m 3 ; S is the area of the water surface in the static floating chamber in contact with the air, with the unit of m 2 ; V is the gas path volume, including the volume of the static floating chamber, the volume of the gas in the drying bottle and the volume of the connecting hose, with the unit of m 3 ; C(H 2 O) is the CO2 and CH4 concentration in water, with the unit of mol / m 3 ; A 1 is the rate of CO2 and CH4 in the air entering the water surface, with the unit of m / s; A 2 is the rate of CO2 and CH4 in the water surface entering the air, with the unit of m / s; λ l is the leakage coefficient, with the unit of m / s; C E is the CO2 and CH4 concentration in the environment at the start of the measurement, with the unit of mol / m 3 ; When the static floating chamber is statically placed on the water surface, the calculation expressions for the fluxes of CO2 and CH4 on the water surface are: （2） Let , combined with formula (2), transform the expression of formula (1) as follows: （3） Since at the start of the measurement, the CO2 and CH4 concentrations C(0) are equal to the CO2 and CH4 concentrations in the environment C E , substituting them into Equation (3) and solving gives: （4） The curves of the CO2 and CH4 concentration data measured by the gas detector changing with time are fitted with the formula (4) to obtain the fluxes of CO2 and CH4 on the water surface F ; The calculation expressions for the CO2 and CH4 concentrations in the water are obtained by transforming formula (2): （5） Under specific temperature measurement conditions, A 1 and A 2 are constant values, obtained through theoretical calculations or experimental measurements; substituting A 1 、A 2 and the fluxes of CO2 and CH4 on the water surface obtained by fitting F into Equation (5) yields the concentrations of CO2 and CH4 in water.

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