Online observation method of carbon dioxide flux at the water-air interface in estuaries / bays

Abstract

The present invention discloses an online observation method for carbon dioxide flux at the water-air interface in estuaries / bays. The method comprises: setting n acoustic tomography stations on both sides of the water's shoreline; setting m data collection stations in the water; the acoustic tomography stations set on both sides of the water's shoreline calculate the average sound velocity between the two stations by using the average propagation time of the acoustic signal; inverting the average temperature of the water area using an empirical formula for the sound velocity; measuring relevant data such as the carbon dioxide mole fraction in the surface water at the data collection stations set in the water area, and calculating and processing the carbon dioxide flux at the water-air interface at the stations; using the water temperature data inverted by the acoustic tomography system to calculate the carbon dioxide flux at the water's interface at locations in the water area where no data collection stations are located; and integrating the carbon dioxide exchange rate per unit time at the water-air interface in the observed water area based on the area of ​​the water area. The present invention enables real-time online observation of carbon dioxide flux at the water-air interface at a regional scale.

Description

Technical Field

[0001] The present invention relates to the technical field of online observation of carbon flux at a water-air interface, and in particular to an online observation method of carbon dioxide flux at a water-air interface in an estuary / bay area. Background Art

[0002] Since the Industrial Revolution, human activities have emitted large amounts of carbon dioxide (CO2), exacerbating climate change and threatening human survival and sustainable development. The Chinese government has announced a goal to peak CO2 emissions by 2030 and achieve carbon neutrality by 2060. CO2 emissions from rivers and their estuaries are considered a crucial component of the global carbon cycle. Studies as early as 2005 showed that estuaries globally emit approximately 0.34 GtC of CO2 into the atmosphere annually, roughly equivalent to 43% of the global river carbon output (~0.8 GtC) annually. However, whether estuaries are a source or sink of atmospheric CO2 remains controversial. This is primarily due to the fact that current estimates of global estuarine CO2 fluxes are based on very limited datasets, and that biogeochemical processes in estuaries are significantly more influenced by nearby human activities and climate change than by other factors. Therefore, it is imperative to establish an online observation system for CO2 fluxes at the water-air interface in estuaries and bays.

[0003] Chinese scientists have proposed a variety of negative emissions (active carbon sink enhancement) schemes to achieve carbon neutrality, including a coordinated land-sea carbon dioxide emission reduction and carbon sink enhancement project. The online carbon dioxide flux observation system at the water-air interface can dynamically identify the source and sink states in estuaries and bays, providing a macroscopic quantitative basis for land-sea carbon dioxide emission reduction and carbon sink enhancement projects. It also offers key technical support for the study of biogeochemical processes in estuaries and bays.

[0004] Current systems for measuring carbon dioxide flux at the water-air interface generally cannot achieve real-time, online observations at a regional scale. For example, observation systems mounted on buoy platforms can measure carbon dioxide flux at a single point over a long period of time, but cannot simultaneously monitor the flux of carbon dioxide across an entire region. Remote sensing technology can monitor carbon dioxide flux in a specific area, but cannot provide continuous observations over long periods of time. Therefore, a method for real-time, online observations of carbon dioxide flux at the water-air interface at a regional scale is needed. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to propose an online observation method for the carbon dioxide flux at the water-air interface in estuary / bay areas, which can observe the carbon dioxide flux at the water-air interface at a regional scale in real time.

[0006] According to one aspect of the present invention, a method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area is provided, comprising: setting n (n≥2) acoustic tomography stations on the shorelines on both sides of a water area; setting m (m≥1) data collection stations in the water area; two acoustic tomography stations can mutually transmit and receive acoustic signals, and the average sound velocity between the two stations is calculated by the average propagation time of the acoustic signals, and then the average temperature of the water area is inverted by the empirical formula of the sound velocity; the data collection stations set in the water area measure relevant data such as the carbon dioxide mole fraction in the surface water, and calculate and process the carbon dioxide flux at the water-air interface; using the water temperature data of the acoustic tomography system to calculate the carbon dioxide flux at the water-air interface at other stations in the water area; and integrating the carbon dioxide exchange amount at the water-air interface per unit time in the observed water area based on the area of ​​the water area.

[0007] In the above technical scheme, the present invention can meet the long-term real-time observation needs of carbon dioxide flux at the water-air interface in most estuary / bay areas. It has the advantages of low observation cost, strong scalability, and convenient observation. It is suitable for the investigation of carbon sources / sinks in larger water areas, and provides important data support for coordinated land and sea emission reduction and sink enhancement projects and ecological environment research and protection.

[0008] In some embodiments, the average propagation time is expressed as follows:

[0009]

[0010] Among them, T AB T is the propagation time when the acoustic signal transmitted by acoustic tomography station A is received by acoustic tomography station B, BA It is the propagation time when the acoustic signal transmitted by acoustic tomography station B is received by acoustic tomography station A.

[0011] In some embodiments, the average speed of sound is calculated as follows:

[0012] The straight-line distance between two acoustic tomography stations is L

[0013] The average speed of sound between two points:

[0014]

[0015] in, is the average propagation time.

[0016] Based on the cross-correlation algorithm, T aB and T BA The calculation method is:

[0017]

[0018] In the above formula, x(n) is the received signal, N is the data length of the transmitted signal y(n), and m is the offset of the transmitted signal along the x-axis. The offset range must at least meet the requirements for the received signal and the transmitted signal to separate, overlap, and then separate again.

[0019] When the nth acoustic tomography station transmits and the n+1th acoustic tomography station receives the acoustic signal, the time of signal transmission is taken as 0. According to the properties of the cross-correlation function, if the cross-correlation function R xy (m) The offset m0 of the maximum correlation peak is obtained + , then the propagation time is:

[0020]

[0021] Where, f s is the sampling rate, and similarly,

[0022]

[0023] The cross-correlation algorithm has high temporal resolution and reliability. For example, if the sampling rate fs is 1200000 Sa / s, the temporal resolution is as high as 0.83 μs, and the reliability of determining the signal arrival time by using the maximum correlation peak is relatively high.

[0024] In some embodiments, the average temperature between two points is calculated by averaging the speed of sound as follows:

[0025] The temperature can be calculated using the NRL II sound velocity empirical formula proposed by Del Grosso:

[0026] C S,T,P = 0,, +ΔC T +ΔC P +ΔC S +ΔC STP

[0027] Among them, C 0,, =1402.392, indicating that S = 0‰, T = 0℃ and P = 0kg / cm 2 The speed of sound at ΔC T , ΔC P , ΔC S , ΔC STP Respectively represent the effects of temperature, pressure, and salinity on the speed of sound, as well as the combined effects of the three on the speed of sound, C S,T,P is the average speed of sound, that is

[0028] In some embodiments, according to the NRL II sound speed empirical formula, the ΔC T , ΔC P , ΔCS , ΔC STP The calculation formula is as follows:

[0029] ΔC T =5.01109398873×T-0.0550946843×T 2 +0.00022153596924×T 3

[0030] ΔC P =0.15605925×P+0.0000244998×P 2 -0.8839233251×10 -8 ×P 3

[0031] ΔC S =1.32952290781×S+0.000128955756844×S 2

[0032] ΔC STP =-0.0127562783426×T×S+0.0063519163389×T×P+0.265484716608×10 -7 ×T 2 ×P 2 -0.159349479045×10 -5 ×T×P 2 +0.522116437235×10 -9 ×T×P 3 -0.438031096213×10 -6 ×T 3 ×P-0.161674495909×10 -8 ×S 2 ×P 2 +0.96840315641×10 -4 ×T 2 ×S+0.485639620015×10 -5 ×T×S 2 ×P-0.340597039004×T×S×P

[0033] The unit of T is ℃, the unit of S is ‰, and the unit of P is kg / cm 2 When the salinity S and pressure P are known, the relationship between the average temperature and the average speed of sound can be obtained from this empirical formula, and the average temperature can be calculated based on the average speed of sound.

[0034] In fresh water, the following empirical formula for sound velocity can be used to invert the temperature:

[0035]

[0036] in, is the average speed of sound, T is the temperature in °C, and 0≤T≤100°C; P is the pressure in bar, and 0<P≤200bar. From this formula, we can obtain the relationship between the average speed of sound and the average temperature in fresh water, and then calculate the average temperature based on the average speed of sound.

[0037] In some embodiments, the average temperature inverted by the acoustic tomography system, the carbon dioxide flux at the water-air interface at each station, and the water area are used to calculate the real-time carbon dioxide exchange rate at the water-air interface per unit time in the water area.

[0038] Specifically include:

[0039] The data collection station measures the carbon dioxide mole fraction and other related data in the surface water. The water-air interface carbon dioxide flux at the data collection station is calculated based on the measured data. The water-air interface carbon dioxide flux at the water area without data collection station is calculated by the average water temperature inverted by the acoustic tomography system. Finally, the water-air interface carbon dioxide exchange rate per unit time in the region is calculated based on the water-air interface carbon dioxide flux at different stations. The calculation method is as follows:

[0040]

[0041] Among them, pCO2 Eq is the carbon dioxide partial pressure in the water-gas balance in the automatic carbon dioxide partial pressure measuring device, xCO2 is the carbon dioxide mole fraction in the surface water measured by the automatic carbon dioxide partial pressure measuring device, P baro is the atmospheric pressure on the water surface, P H2O is the saturated water vapor pressure in the water-gas balance.

[0042]

[0043] Among them, pCO2 surf is the carbon dioxide partial pressure of surface water, ST is the surface water temperature, t eq is the temperature in the water-gas balance.

[0044]

[0045] Among them, S c is the Schmidt number, t surf is the surface water temperature in degrees Celsius (℃).

[0046]

[0047] Where s is the solubility of carbon dioxide in water, is the dimensionless Bunsen coefficient, T is the Kelvin temperature in K, and S represents the salinity in ‰.

[0048]

[0049] Among them, k w is the water-gas exchange rate of carbon dioxide, U 10 It is the wind speed at 10 m above sea level, in m / s.

[0050]

[0051] Where F is the carbon dioxide flux at the water-air interface at the data collection station, pCO2 surf is the partial pressure of carbon dioxide in surface water, pCO2 air is the partial pressure of carbon dioxide in the atmosphere.

[0052] When calculating the carbon dioxide flux at the water-air interface in waters without data collection stations, the (pCO2 surf -pCO2 air ) and U 10 , recalculate k using the water temperature inverted by the acoustic tomography system w and s, and then calculate the water-air interface carbon dioxide flux at other stations.

[0053]

[0054] Among them, F total is the carbon dioxide exchange capacity at the water-air interface per unit time, F is the carbon dioxide flux at the water-air interface, and A is the area of ​​the observation area.

[0055] In some embodiments, the regional water-air interface carbon dioxide exchange rate per unit time is calculated by averaging the calculated water-air interface carbon dioxide fluxes at all stations, and the calculation method is as follows:

[0056] F total =F aver ×A

[0057] Among them, F total is the carbon dioxide exchange capacity of the water-air interface per unit time in the observation area, F aver is the ensemble average of the carbon dioxide flux at the water-air interface of all stations in the observation area, and A is the area of ​​the observation area.

[0058] In the above technical scheme, the present invention realizes high-resolution real-time observation of carbon dioxide flux at the water-air interface on a regional scale, thereby providing observation data support for the carbon source / sink distribution in the estuary / bay area, providing observation truth for the research on biogeochemical processes in the estuary / bay and the development of related models, and providing basic technical support for the coordinated land and sea emission reduction and carbon sink enhancement project, which is of great significance to the development of related disciplines.

[0059] According to another aspect of the present invention, a system for evaluating carbon dioxide exchange at the water-air interface in an estuary / bay region is provided, which is applied to the above-mentioned method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay region, comprising: a first calculation module, a second calculation module, and a third calculation module connected in sequence;

[0060] The first calculation module, the acoustic tomography system inverts the average water temperature of the water area;

[0061] The second calculation module calculates the carbon dioxide flux at the water-air interface at the data collection station based on the relevant data measured at the station. The water temperature data inverted by the acoustic tomography system is then used to calculate the carbon dioxide flux at the water-air interface at other stations in the water area.

[0062] The third calculation module calculates the real-time carbon dioxide flux per unit time at the water-air interface in the water area.

[0063] The above technical solution can meet the needs of long-term real-time observation of carbon dioxide flux at the water-air interface in most estuary / bay areas. It has the advantages of low observation cost, strong scalability, and convenient observation. It is suitable for the investigation of carbon sources / sinks in larger water areas, and provides important data support for coordinated land and sea emission reduction and carbon sink enhancement projects and ecological environment research and protection.

[0064] According to another aspect of the present invention, a buoy collection unit is provided, which is applied to the above-mentioned method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area, comprising: an automatic measuring device for carbon dioxide partial pressure at the water-air interface, a small weather station, a GPS positioning system, a control computer and a power supply device; wherein the automatic measuring device for carbon dioxide partial pressure at the water-air interface, the small weather station and the GPS positioning system are respectively connected to the control computer; the control computer includes a wireless transmission module for data transmission; and the power supply device is connected to the automatic measuring device for carbon dioxide partial pressure at the water-air interface, the small weather station, the GPS positioning system and the control computer.

[0065] In this technical solution, an automatic water-air interface carbon dioxide partial pressure measurement device integrated on a buoy and a small weather station, combined with an acoustic tomography system covering the entire region, enables high-resolution, real-time observation of carbon dioxide fluxes at the water-air interface on a regional scale. This provides observational data support for carbon source / sink distribution in estuaries / bays, provides observational truth for research on biogeochemical processes in estuaries / bays and the development of related models, and provides fundamental technical support for coordinated land-sea emission reduction and carbon sink enhancement projects, thus having important implications for the development of related disciplines. This invention is a novel ecosystem observation technology based on an acoustic tomography system, offering advantages such as high observation accuracy, wide spatial coverage, low cost, high resolution, and the ability to observe carbon over a long period of time in real time. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0067] Figure 1 is a schematic diagram of a method flow in an embodiment of the present invention;

[0068] Figure 2 is a system schematic diagram of an embodiment of the present invention;

[0069] Figure 3 This is a schematic structural diagram of a buoy acquisition unit provided by an embodiment of the present invention;

[0070] Figure 4 Schematic diagram of the structure of each acoustic tomography station provided in an embodiment of the present invention;

[0071] Figure 5 It is a schematic structural diagram of a system for evaluating carbon dioxide exchange at the water-air interface in an estuary / bay area provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0072] The present invention will be described in further detail below with reference to the accompanying drawings and examples. It is particularly noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Similarly, the following examples are only some embodiments of the present invention and are not intended to be exhaustive. All other embodiments obtained by those of ordinary skill in the art without creative effort are intended to fall within the scope of protection of the present invention.

[0073] The present invention provides an online observation method for the carbon dioxide flux at the water-air interface in an estuary / bay area, which can observe the carbon dioxide flux at the water-air interface at a regional scale in real time online. Based on acoustic tomography stations and data acquisition stations, real-time, online, continuous and high-resolution observation of the carbon dioxide flux at the water-air interface at a regional scale is achieved. Specifically, the present invention uses an automatic water-air interface carbon dioxide partial pressure measurement device integrated on a buoy and a small meteorological station, combined with an acoustic tomography system covering the entire area, to achieve high-resolution real-time observation of the carbon dioxide flux at the water-air interface at a regional scale, thereby providing observation data support for the carbon source / sink distribution in the estuary / bay area, providing observation truth values ​​for the study of biogeochemical processes in the estuary / bay and the development of related models, and providing basic technical support for the coordinated land-sea emission reduction and sink enhancement project, which is of great significance to the development of related disciplines. The present invention is a new ecosystem observation technology based on an acoustic tomography system, which has the advantages of high observation accuracy, large spatial coverage, low cost, high resolution and long-term real-time observation.

[0074] The present invention provides an online observation method for carbon dioxide flux at the water-air interface at the estuary / bay regional scale. Please refer to the following procedures: Figure 1 , as follows:

[0075] S1. Set n (n≥2) acoustic tomography stations on both sides of the water area; set m (m≥1) data collection stations in the water area;

[0076] In this embodiment, reference Figure 2 , including the buoy system (data collection station, the same below), the acoustic tomography system (acoustic tomography station, the same below) and the ground control observation station. The following is a detailed introduction to each part:

[0077] The buoy system includes an automatic measuring device for the carbon dioxide partial pressure at the water-air interface, a small weather station, a GPS positioning system, a control computer and a power supply device.

[0078] Furthermore, one or more buoy systems may be placed according to the specific observation area.

[0079] like Figure 3 As shown, the automatic measuring device for the partial pressure of carbon dioxide at the water-air interface, the small weather station and the GPS positioning system are directly connected to the control computer respectively; the control computer receives the observation data collected by the automatic measuring device for the partial pressure of carbon dioxide at the water-air interface, the small weather station and the GPS positioning system, processes the observation data, and then wirelessly transmits the observation data to the ground control observation station; the control computer controls the automatic measuring device for the partial pressure of carbon dioxide at the water-air interface, the small weather station, the GPS positioning system and the power supply device, and saves the data at the same time.

[0080] In the present invention, various devices carried in the buoy system must be waterproof and moisture-proofed to ensure the long-term stable operation of various instruments and equipment.

[0081] Specifically, the automatic measuring device for the carbon dioxide partial pressure at the water-gas interface based on the water-gas balance principle is used to measure the molar fraction of carbon dioxide (xCO2) in surface water and transmit data such as the surface water temperature, the saturated water vapor pressure and temperature in the water-gas balance to the control computer.

[0082] A small weather station is used to measure the temperature, air pressure, true wind speed, true wind direction and saturated water vapor pressure at 10m above sea level and transmit the data to the control computer.

[0083] The GPS positioning system is used to measure the coordinate data of the buoy in the earth coordinate system, and is used to convert the data measured by the automatic measurement device of the carbon dioxide partial pressure at the water-air interface and the small weather station into the earth coordinate system, and then transmit it to the control computer.

[0084] A control computer is used to control the automatic measuring device for the partial pressure of carbon dioxide at the water-air interface, a small weather station, a GPS positioning system and a power supply device; to control the addition of standard gas to the automatic measuring device for the partial pressure of carbon dioxide at the water-air interface; to store data of each buoy subsystem; to control the power supply of each buoy subsystem; and to provide a wireless connection to a ground control observation station.

[0085] The power supply device supplies power to the control computer, the automatic measurement device of carbon dioxide partial pressure at the water-air interface, the GPS positioning system and the small weather station. To ensure the long-term operation of the buoy, a solar power supply system is selected.

[0086] The acoustic tomography system includes: a main control cabinet unit, a power amplifier unit, and a signal transmitting and receiving unit.

[0087] n (n≥2) acoustic tomography systems are deployed on the shore of the measurement area for real-time, online, continuous and high-resolution measurement of the average surface water temperature in the area.

[0088] Furthermore, the number of acoustic tomography systems can be adjusted according to the size of the carbon dioxide flux observation area at the specific water-air interface and the temperature measurement accuracy.

[0089] like Figure 4 As shown, each acoustic tomography system includes a main control cabinet unit, a power amplifier unit, and a signal transmitting and receiving unit. The acoustic signal is generated by the main control cabinet unit, amplified by the power amplifier unit, and transmitted by the transmitting transducer in the signal transmitting and receiving unit. The signals transmitted from other acoustic tomography sites are received by the hydrophone in the signal transmitting and receiving unit, analyzed and processed, and temperature inverted in the main control cabinet unit, and the temperature data is saved and uploaded in real time.

[0090] In the present invention, the power supply of the acoustic tomography system is not limited to a certain power supply mode. When conditions permit, it can be powered by commercial electricity, and under field conditions, it can be powered by solar energy.

[0091] Specifically, the main control cabinet unit includes: an industrial computer module, a GPS module, a data acquisition module, an amplification and filtering module, and a remote communication module.

[0092] The industrial computer module is equipped with an acoustic tomography software program, which is used to modulate and generate acoustic signals and process data in real time, thereby obtaining temperature data of the observation area in real time;

[0093] The GPS module is used for high-precision positioning and timing, and for distance measurement and time synchronization between acoustic tomography sites;

[0094] The data acquisition module is used for conversion between digital signals and analog signals and signal acquisition;

[0095] The amplification and filtering module amplifies and filters the received signal;

[0096] The remote communication module is connected to the network using a wireless network and is used to transmit the regional temperature data inverted by the acoustic tomography system to a ground control observation station in real time for carbon flux calculation.

[0097] The power amplification unit is used to amplify the transmission signal generated by the industrial computer so that it can be received by another acoustic tomography station;

[0098] The signal transmitting and receiving unit is used to transmit the acoustic signal amplified by the power amplifying unit and receive signals sent from other acoustic tomography sites.

[0099] S2, two acoustic tomography stations receive and transmit acoustic signals from each other and calculate the average propagation time;

[0100] Assume that any two sites of the acoustic tomography system are A and B, and the two sites transmit and receive sound waves. The acoustic tomography program is used to calculate the propagation time T of the sound signal when site A transmits and site B receives. AB And the propagation time T of the acoustic signal when station B transmits and station A receives BA , and then calculate the average propagation time of the acoustic signal between sites A and B:

[0101]

[0102] S3, the acoustic tomography system uses the empirical formula for the speed of sound to calculate the average water temperature;

[0103] Calculate the average sound speed between two points based on the average propagation time, and then calculate the average temperature between the two points using the average sound speed;

[0104] The GPS modules at sites A and B can calculate the distance L between the two sites, and thus the average speed of sound between the two sites:

[0105]

[0106] The average surface temperature in the bay area can then be calculated using the NRLⅡ sound velocity empirical formula proposed by Del Grosso:

[0107] C S,T,P =C 0,0,0 +ΔC t +ΔC P +ΔC S +ΔC StP (3)

[0108] Among them, C 0,, =1402.392, ΔAC T , ΔAC P , ΔAC S , ΔAC StP They represent the effects of temperature (T), pressure (P), and salinity (S) on the speed of sound, as well as their combined effects on the speed of sound. S,, is the average speed of sound

[0109] in:

[0110] ΔC t =5.01109398873×T-0.0550946843×T 2 +0.00022153596924×T 3

[0111] ΔC P =0.15605925×P+0.0000244998×P 2 -0.8839233251×10 -8 ×P 3

[0112] ΔC S =1.32952290781×S+0.000128955756844×S 2

[0113] ΔC STP =-0.0127562783426×T×S+0.0063519163389×T×P

[0114] +0.265484716608×10 -7 ×T 2 ×P 2-0.159349479045×10 -5

[0115] ×T×P 2 +0.522116437235×10 -9 ×T×P 3 -0.438031096213

[0116] ×10 -6 ×T 3 ×P-0.161674495909×10 -8 ×S 2 ×P 2

[0117] +0.96840315641×10 -4 ×T 2 ×S+0.485639620015×10 -5 ×T

[0118] ×S 2 ×P-0.340597039004×T×S×P

[0119] In the estuary area, the following sound velocity empirical formula can be used to invert the surface water temperature ST:

[0120] C=1402.7+4.88×ST-0.0482×ST 2 +0.000135×ST 3 +(0.159+

[0121] 0.00028×ST+0.0000024×ST 2 )×P(4)

[0122] The temperature T is in °C, and 0≤T≤100°C; the temperature P is in bar, and 0<P≤200 bar.

[0123] The ground-based observation station is wirelessly connected to the buoy system and the acoustic tomography system, receiving observation data transmitted by them and enabling wireless control of the systems. The ground-based observation station is a computer device comprising memory, a processor, and a display. The observation data is numerically calculated by the ground-based observation station to produce a high-resolution, real-time distribution of carbon dioxide flux at the regional water-air interface and the real-time regional carbon dioxide exchange rate per unit time at the water-air interface. The data is stored and displayed on the display.

[0124] S4. Calculate the carbon dioxide flux at the water-air interface based on the relevant data of the data collection station;

[0125] The data collection station measures relevant data in the water area and transmits it to the ground control observation station to calculate the carbon dioxide flux at the water-air interface;

[0126] The numerical calculation of the ground control observation station is mainly based on the following formula:

[0127]

[0128] Among them, pCO2 Eq is the carbon dioxide partial pressure in the water-gas balance in the automatic carbon dioxide partial pressure measuring device at the water-gas interface, xCO2 is the carbon dioxide mole fraction in the surface water measured by the automatic carbon dioxide partial pressure measuring device, and P baro is the atmospheric pressure on the water surface, P H2O is the saturated water vapor pressure in the water-gas balance.

[0129]

[0130] Among them, pCO2 surf is the carbon dioxide partial pressure of surface water, ST is the surface water temperature, t eq is the temperature in the water-gas balance.

[0131] The carbon dioxide partial pressure (pCO2) in the water vapor balance is calculated by formula 6. Eq ) to obtain the partial pressure of carbon dioxide in surface seawater (pCO2 surf ).

[0132]

[0133] Where F is the carbon dioxide flux at the water-air interface, k w is the water-gas exchange rate of carbon dioxide, s is the solubility of carbon dioxide in water, pCO2 air is the partial pressure of carbon dioxide in the atmosphere.

[0134]

[0135] Among them, xCO2 air is the mole fraction of carbon dioxide in the atmosphere, P 10 is the atmospheric pressure 10 m above sea level, P H2O surf is the saturated water vapor pressure at surface water temperature.

[0136] In formula 7

[0137] Among them, U 10 is the wind speed at 10 m above sea level in m / s, and Sc is the Schmidt number.

[0138]

[0139] Where s is the solubility of carbon dioxide in surface water, is the dimensionless Bunsen coefficient, T is the Kelvin temperature in K, and S is the salinity in ‰.

[0140]

[0141] Among them, t surf is the surface water temperature in degrees Celsius (℃).

[0142] S5. The ground control observation station calculates the real-time carbon dioxide exchange rate per unit time at the water-air interface in the water area.

[0143] Furthermore, after receiving the water temperature data inverted by the acoustic tomography system, the ground control observation station can calculate the carbon dioxide flux at the water-air interface in the observation area where there is no buoy system based on the relevant data transmitted by the buoy system.

[0144] When calculating the carbon dioxide flux at the water-air interface in waters without a buoy system, the (pCO2 surf -pCO2 air ) and U 10 , recalculate k using the water temperature inverted by the acoustic tomography system w and s, and then calculate the water-air interface carbon dioxide flux at other stations.

[0145] S5. Calculate the real-time carbon dioxide flux per unit time at the water-air interface in the water area;

[0146] According to the area of ​​the observation area and the carbon dioxide flux at the water-air interface, the real-time carbon dioxide exchange rate at the water-air interface per unit time is calculated;

[0147]

[0148] Among them, F total is the amount of carbon dioxide exchange at the water-air interface per unit time in the observation area, and A is the area of ​​the observation area.

[0149] Embodiments of the present invention also provide another method for evaluating the water-air interface carbon dioxide exchange rate. The ground control observation station averages the water-air interface carbon dioxide fluxes at all stations in the observation area. The water-air interface carbon dioxide exchange rate per unit time in the observation area is then calculated using the water area according to Equation 10.

[0150] F total = F aver × A (10)

[0151] Among them, F averis the ensemble average of the carbon dioxide flux at the water-air interface of all stations in the observation area, and A is the water area.

[0152] The embodiment of the present invention also provides a system for evaluating the carbon dioxide exchange rate at the water-air interface in an estuary / bay area. Figure 5 Shown, including:

[0153] The first calculation module is used to obtain regional surface water temperature data measured by the acoustic tomography system. For details, see the relevant descriptions of S2 and S3 in the above embodiment.

[0154] The second calculation module is used to obtain relevant data from the buoy system used to calculate the water-air interface carbon dioxide flux at the data collection station, and calculate the water-air interface carbon dioxide flux at the data collection station. Water temperature data inverted by the acoustic tomography system is obtained and combined with relevant data from the buoy system to calculate the water-air interface carbon dioxide flux at each station in the observation area. For details, see the description of S4 in the above embodiment.

[0155] The third calculation module is used to calculate the water-air interface carbon dioxide exchange rate per unit time in the region based on the water area of ​​the observation region and the water-air interface carbon dioxide flux. For details, see the relevant description of S5 in the above embodiment.

[0156] The above descriptions are only some embodiments of the present invention and do not limit the scope of protection of the present invention. Any equivalent device or equivalent process transformation made by using the contents of the description and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for online observation of carbon dioxide flux at the water-air interface in estuaries / bays, characterized in that: include: n acoustic tomography stations are set up on the shorelines on both sides of the water area, n≥2; m data collection stations are set up in the water area, m≥1; The acoustic tomography stations on both sides of the shoreline receive and transmit acoustic signals to each other. The average sound velocity between the two stations is calculated by the average propagation time of the acoustic signal in the water area, and then the average water temperature is inverted using the empirical formula of sound velocity. The data collection station mainly measures parameters related to the mole fraction of carbon dioxide in surface water, and calculates the carbon dioxide flux at the water-air interface at the station; The carbon dioxide flux at the water-air interface in the water area without data collection stations is calculated by averaging the water temperature, and then the real-time carbon dioxide exchange rate per unit time at the water-air interface is calculated. The carbon dioxide flux at the water-air interface at the data collection station is calculated based on the relevant parameters of the carbon dioxide mole fraction in the surface water measured by the data collection station, and the carbon dioxide flux at the water-air interface in the water area without data collection station is calculated based on the average water temperature inverted by the acoustic tomography system, specifically including: The data collection station measures the mole fraction of carbon dioxide in the surface water, and the water-air interface carbon dioxide flux at the data collection station is calculated based on the measured data. The water-air interface carbon dioxide flux in the water area without data collection station is calculated by the average water temperature inverted by the acoustic tomography system. The calculation method is as follows: Among them, pCO2 Eq is the carbon dioxide partial pressure in the water vapor balance of the carbon dioxide partial pressure automatic measuring device, xCO2 is the carbon dioxide mole fraction in the surface water measured by the carbon dioxide partial pressure automatic measuring device, P baro is the atmospheric pressure on the water surface, P H2O is the saturated water vapor pressure in the water-gas balance; Among them, pCO2 surf is the carbon dioxide partial pressure of surface water, ST is the surface water temperature, t eq is the temperature in the water-gas balance; Among them, S c is the Schmidt number, t surf is the surface water temperature in degrees Celsius, ℃; Where s is the solubility of carbon dioxide in water, is the dimensionless Bunsen coefficient, T is the Kelvin temperature in K, and S represents the salinity in ‰; Among them, k w is the water-gas exchange rate of carbon dioxide, U 10 is the wind speed at 10 m above sea level, in m / s; Where F is the carbon dioxide flux at the water-air interface, pCO2 surf is the partial pressure of carbon dioxide in surface water, pCO2 air is the partial pressure of carbon dioxide in the atmosphere; When calculating the carbon dioxide flux at the water-air interface in waters without data collection stations, the pCO2 of the adjacent data collection stations is used. surf -pCO2 air and U 10 , recalculate k using the water temperature inverted by the acoustic tomography system w and s, and then calculate the carbon dioxide flux at the water-air interface at other stations; The carbon dioxide exchange rate at the water-air interface per unit time in the water area is calculated by calculating the carbon dioxide flux at the water-air interface at different stations. The calculation method is as follows: in, is the carbon dioxide exchange capacity of the water-air interface per unit time in the water area, F is the carbon dioxide flux of the water-air interface at different stations in the water area, including those with and without data collection stations, and A is the area of ​​the observed water area.

2. The method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area according to claim 1, characterized in that: The average propagation time is expressed as follows: in, is the propagation time of the acoustic signal transmitted by acoustic tomography station A and received by acoustic tomography station B, The propagation time of the acoustic signal transmitted by acoustic tomography station B and received by acoustic tomography station A; Based on the cross-correlation algorithm, and The calculation method is: In the above formula, To receive the signal, To transmit a signal The data length is m, and the offset of the transmitted signal along the x-axis direction is 1, and the offset range must at least satisfy the requirement that the received signal and the transmitted signal are separated, overlapped, and then separated again; When two acoustic tomography stations send and receive sound signals to each other, the time of signal transmission is taken as 0. According to the properties of the cross-correlation function, if the cross-correlation function Get the offset of the maximum correlation peak , then the propagation time is: Where, is the sampling rate, and similarly, 。 3. The method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area according to claim 1, characterized in that: The average speed of sound is calculated as follows: The straight-line distance between two acoustic tomography stations is L The average speed of sound between two points: in, is the average propagation time.

4. The method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area according to claim 1, characterized in that: The average temperature between two points is calculated by the average speed of sound as follows: The temperature can be calculated using the NRL II sound velocity empirical formula proposed by Del Grosso: in, , indicating that at S=0‰, T=0℃ and P=0kg / The speed of sound, Respectively represent the effects of temperature, pressure, and salinity on the speed of sound, as well as the combined effects of the three on the speed of sound. is the average speed of sound, that is .

5. The method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area according to claim 4, characterized in that: According to the NRL II sound speed empirical formula, the The calculation formula is as follows: Among them, the unit of T is ℃, the unit of S is ‰, and the unit of P is kg / When the salinity S and pressure P are known, the relationship between the average temperature and the average speed of sound is obtained from this empirical formula, and then the average temperature is calculated based on the average speed of sound; The following empirical formula for the speed of sound in fresh water is used to invert the temperature: in, is the average speed of sound, T is the temperature in °C, with 0≤T≤100 °C; P is the pressure in bar, with 0<P≤200 bar; the relationship between the average temperature and the average temperature in fresh water is obtained from this formula, and then the average temperature is calculated based on the average speed of sound.

6. The method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area according to claim 1, characterized in that: The carbon dioxide exchange rate per unit time at the water-air interface of the water area is calculated by the average value of the carbon dioxide flux at the water-air interface at all stations in the water area. The calculation method is as follows: in, is the amount of carbon dioxide exchange at the water-air interface per unit time in the water area, is the average carbon dioxide flux at the water-air interface of all stations in the water area, and A is the area of ​​the water area.

7. A system for evaluating carbon dioxide exchange at the water-air interface in an estuary / bay region, applied to the online observation method for carbon dioxide flux at the water-air interface in an estuary / bay region according to any one of claims 1 to 6, characterized in that: include: A first computing module, a second computing module, and a third computing module connected in sequence; The first calculation module, the acoustic tomography system inverts the average water temperature of the water area; The second calculation module calculates the carbon dioxide flux at the water-air interface at the data collection station based on the relevant data measured at the station; and then uses the water temperature data inverted by the acoustic tomography system to calculate the carbon dioxide flux at the water-air interface at other stations in the water area; The third calculation module calculates the real-time carbon dioxide flux per unit time at the water-air interface in the water area.

8. A buoy data acquisition unit, used as a data acquisition station in the method for online observation of carbon dioxide flux at the water-air interface in an estuary / bay area according to any one of claims 1 to 6, characterized in that: include: An automatic measuring device for the partial pressure of carbon dioxide at the water-air interface, a small weather station, a GPS positioning system, a control computer and a power supply device; wherein the automatic measuring device for the partial pressure of carbon dioxide at the water-air interface, the small weather station and the GPS positioning system are respectively connected to the control computer; the control computer includes a wireless transmission module for data transmission; the power supply device is connected to the automatic measuring device for the partial pressure of carbon dioxide at the water-air interface, the small weather station, the GPS positioning system and the control computer.

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