Ozone vertical flux measurement system and method based on relaxation vortex accumulation technique

Abstract

The application discloses an ozone vertical flux measuring system and method based on a relaxation vortex accumulation technique. The system is composed of an eddy correlation flux measuring system, an air path module, a sampling air path, a zero air supplement module, an ozone measuring system, and a data acquisition and program control system. The three-dimensional wind speed is measured by an ultrasonic anemometer, and the sampling path is controlled by a high-frequency three-way electromagnetic valve, so that the upward and downward air flows are accurately sampled. The ozone concentration is measured by an ultraviolet ozone analyzer, and the automatic control and data processing are realized through the data acquisition and program control system. The system has low cost and high portability, is suitable for remote areas and environments with limited resources, and can still maintain high-precision measurement under complex and changeable weather conditions.

Description

Technical Field

[0001] This invention relates to the field of measurement technology, and in particular to an ozone vertical flux measurement system and method based on relaxation vortex accumulation technology. Background Technology

[0002] Ozone (O3) is the most important gaseous pollutant in the atmosphere, significantly impacting regional air quality, human health, ecosystems, and climate change. Tropospheric O3 is primarily generated and depleted through photochemical reactions, with a smaller portion originating from stratospheric input and net removed via dry deposition. Dry deposition accounts for approximately 20% of total tropospheric O3 loss (Lelieveld and Dentener, 2000), directly influencing global tropospheric O3 load and its spatiotemporal variations. O3 dry deposition mainly occurs near the Earth's surface, directly affecting near-surface O3 distribution, variation, and lifetime, significantly impacting regional O3 pollution. Furthermore, O3 deposited on plant surfaces or absorbed by plants directly impairs photosynthesis and respiration, affecting vegetation growth and crop yields, and consequently impacting regional and global carbon cycles. Therefore, observational studies of O3 dry deposition are of significant theoretical and practical importance for improving ambient air quality, agricultural and forestry ecology, and assessing its impact on climate.

[0003] Accurate measurement of O3 vertical flux is crucial for quantifying the contribution of O3 dry deposition to regional O3 pollution and assessing the ecological and agricultural impacts of O3 pollution. Currently, the measurement of O3 vertical flux mainly employs eddy covariance techniques and gradient methods.

[0004] Eddy covariance (EC) is a statistical analysis based on turbulence and transport. It calculates the vertical O3 flux by simultaneously measuring the fluctuating signals of vertical wind speed and O3 concentration, and using their covariance. Compared to other flux measurement techniques, EC relies on fewer basic assumptions, better aligning with theory and reality, and allows for direct measurement of O3 eddy flux. On relatively homogeneous surfaces, EC can effectively monitor both long-term and short-term variations in O3 vertical flux. ECD requires fast-response (10-20 Hz) vertical anemometers and O3 sensors, with minimal response and latency. Furthermore, to avoid interference from atmospheric turbulence, the sensor size must be small. Typically, EC uses an ultrasonic anemometer and a chemiluminescence-based O3 sensor to simultaneously measure vertical wind speed and O3 concentration, with a time resolution of at least 10 Hz to ensure accurate measurement of their rapid fluctuations in turbulent conditions. The ultrasonic anemometer directly measures vertical wind speed, while the O3 analyzer samples first and then measures, requiring a short sampling tube and a large sampling flow rate to reduce instrument latency. During the measurement process, a data acquisition device simultaneously collects measurement data from both instruments, and specialized software or programs process the pulsating signals according to the covariance formula to calculate the vertical O3 flux, with a time resolution typically of 30 minutes.

[0005] The gradient method is based on flux-gradient theory (K-theory). It calculates the vertical flux of O3 by measuring the O3 concentration at different altitudes and combining this with the diffusion coefficient. Compared to eddy covariance techniques, the gradient method does not require a fast-response O3 sensor to measure O3 concentration. Therefore, when a fast-response O3 analyzer is unavailable, the gradient method is an effective alternative for measuring the vertical flux of O3, accurately obtaining its long-term variation characteristics. The basic assumption of the gradient method is that turbulent transport and molecular diffusion are similar, meaning that turbulent transport flux follows Fick's law, and the vertical turbulent diffusion of O3 is proportional to the average concentration gradient. Therefore, in actual field observations, the O3 concentration is first measured at different altitudes to obtain the vertical concentration gradient. The diffusion coefficient is usually derived from the vertical flux measured by eddy covariance techniques. Based on the calculation principle of the diffusion coefficient, the gradient method mainly includes two types: the aerodynamic gradient method and the modified Bowen ratio method. The aerodynamic gradient method typically requires continuous observation of O3 concentration at multiple altitude levels, assuming similarity between heat and O3 transport equations, and the O3 diffusion coefficient is calculated based on the Monin-Obukhov similarity theory. The improved Bowman's method, however, only requires measuring O3 concentration at two altitude levels, using diffusion coefficients for substitutes such as H2O, CO2, and sensible heat scalars for similarity substitution. Therefore, an O3 vertical flux observation system based on the improved Bowman's method also needs to measure the vertical flux of the substitute scalars and the substitute scalars at the same altitude as O3. Based on the measured gradient and flux of the substitute scalars, the diffusion coefficient of the substitute scalars is calculated, and the O3 diffusion coefficient is equal to the diffusion coefficient of the substitute scalars. Finally, based on the calculated diffusion coefficients and the measured O3 concentration gradient, the O3 vertical flux is calculated using a formula.

[0006] Although there are relatively mature O3 vertical flux observation technologies, eddy covariance techniques and gradient methods both have certain defects and limitations, which restricts the current observation of O3 vertical flux.

[0007] Eddy covariance techniques primarily employ fast-response chemiluminescence (CFR) O3 analyzers to measure the fluctuations in O3 concentration online, thereby calculating the vertical flux of O3. However, CFR-based O3 analyzers are not only expensive, but their daily measurement, maintenance, and calibration require costly gases and reagents, incurring high labor costs and potentially leading to discontinuous observations. Furthermore, the measurement of O3 fluctuations using CFR itself introduces significant uncertainties. Different O3 sensors can result in measurement errors as high as 25% (Mullere et al., 2009). Sensor separation, closed systems, and gas diffusion within the system piping of the O3 analyzer all contribute to high-frequency losses (Fokenetal., 2006; Massman and Lee, 2002; Oliphant et al., 2004; Villalobos, 1997; Wintjen et al., 2020), resulting in O3 flux loss. Secondly, eddy covariance technology also requires that the measurement signals of the ultrasonic anemometer and the O3 analyzer be highly synchronized in order to reduce the error in vertical flux measurement, which places high demands on the observation equipment.

[0008] Although the gradient method does not require a fast-response O3 analyzer, the relatively small overall difference in O3 concentration at different altitudes necessitates extremely high accuracy for measuring O3 vertical flux, requiring an accuracy within the range of 0.02 to 0.5% (Businger, 1986). The gradient method requires sampling and measuring O3 concentration at different altitudes, but the non-uniformity of O3 sources and sinks in different spaces or times affects the proportional relationship between the O3 vertical gradient and flux, leading to errors in O3 flux measurement. On one hand, the O3 vertical gradient is influenced by chemical reactions between O3 and nitrogen oxides, exhibiting significant spatiotemporal variability, thus causing errors in the measured flux. On the other hand, on non-uniform surfaces (such as tall crops or forests), O3 concentration at different altitudes is affected by multiple factors, rendering the fundamental assumptions about the relationship between O3 vertical flux and gradient invalid, thus making the gradient method unusable. The O3 diffusion coefficient is influenced by actual wind fields, atmospheric temperature stratification, etc. For example, temperature inversions significantly inhibit O3 diffusion in the vertical direction, making accurate measurement of the O3 diffusion coefficient difficult. Therefore, the O3 deposition flux measured by gradient under complex and variable atmospheric conditions has a large degree of uncertainty. Summary of the Invention

[0009] Based on this, the present application provides an ozone vertical flux measurement system and method based on relaxation vortex accumulation technology, which can solve the problems existing in the prior art and can accurately measure the observation of O3 dry deposition.

[0010] Firstly, an ozone vertical flux measurement system based on relaxed vortex accumulation technology is provided. The system comprises an vortex correlation flux measurement system, a gas path module, a sampling gas path, a zero-gas replenishment module, an ozone measurement system, and a data acquisition and program control system, wherein:

[0011] The eddy covariance flux measurement system is used to measure three-dimensional wind speed, virtual temperature, CO2 and H2O concentration. Specifically, it includes an ultrasonic anemometer, an open-circuit CO2 / H2O analyzer and a data acquisition unit. The data acquisition unit sends the measurement data to the data acquisition and program control system in real time via RS-485 serial communication.

[0012] The gas path module includes two high-frequency three-way solenoid valves. The normally open end of the high-frequency three-way solenoid valve is connected to the inlet pipe, and the normally closed end is connected to the zero gas pipe. The outlet ends are the rising airflow and the sinking airflow outlet, respectively. This module is controlled by the program control system, which controls the sampling path of the airflow according to the real-time vertical wind speed direction. This module needs to be placed near the ultrasonic anemometer to ensure the consistency between the observed sample and the observation of the eddy covariance flux measurement system.

[0013] The sampling gas path, connected to the gas path module and the ozone measurement system, is used to guide the sample of the rising and falling airflow of the gas path module into the ozone analyzer of the ozone measurement system. The sampling gas path includes a front-end inlet pipe and rising and falling airflow sampling pipes. The front-end inlet pipe is close to the measurement center of the ultrasonic anemometer.

[0014] A zero-air replenishment module, connected to the gas path module, is used to generate zero air through a zero-air generator when sampling is not performed, and replenishes the zero air by connecting to the normally closed terminal of the gas path module via a bypass; wherein, the zero-air replenishment module includes an air compressor and a zero-air generator;

[0015] An ozone measurement system is used to measure the ozone concentration in rising and falling air currents. The ozone measurement system includes two ultraviolet ozone analyzers, which are periodically calibrated at multiple points using an ozone calibrator.

[0016] A data acquisition and program control system is used to control the operation, data acquisition and processing of the entire system. The data acquisition and program control system includes a control program and a data acquisition program. The control program controls the switching of the solenoid valves of the gas path module according to the real-time vertical wind speed and marks the sampling type. The data acquisition program is used to receive and process data from the eddy covariance flux measurement system and the ozone measurement system.

[0017] Optionally, the ozone measurement system uses two ultraviolet ozone analyzers to measure the ozone concentration and ozone flux in the rising and falling airflow sampling pipes, respectively. Represented as:

[0018]

[0019] Where b is the vortex cumulative coefficient, σ w This represents the standard deviation of vertical wind speed. and These represent the average ozone concentrations in the rising and descending airflows over a single measurement period.

[0020] Optionally, during system operation, the ultrasonic anemometer measures the vertical wind speed in real time. Upon receiving the wind speed data, the system control program immediately determines and sends a command to control the rapid switching of the solenoid valves in the gas path module. Ambient air or zero-air is collected in the two sampling pipelines based on real-time data, and the mixed ozone concentration in the pipelines is measured online by two ultraviolet ozone analyzers. Based on the actual environmental sample collection time, sampling flow rate, and ozone concentration, the concentration is calculated according to the formula:

[0021]

[0022] The average ozone concentration in the rising / falling airflow over 30 minutes is calculated by integration, where c i The average ozone mass concentration over 1 minute, flow i The average sampling flow rate over 1 minute, t sample gas,i The time percentage of the total sampled air within the i-th minute; the actual ambient ozone concentration is the average ozone concentration in the rising and sinking airflows.

[0023] Optionally, in the sampling flow rate, the system sets a bypass in the sampling pipeline downstream of the valve to increase the front-end flow rate, ensuring that the intake air is in a turbulent state. The flow rates in the rising and sinking sampling pipelines are set to 1.03 SLPM, and the flow rate in the front 1 / 8 pipe intake is set to 2.65 SLPM. Then, the flow velocity at the 1 / 8 pipe intake port with an inner diameter of 1.6 mm is:

[0024]

[0025] The Reynolds coefficient of the gas inside the pipe is

[0026]

[0027] It meets the requirement that the gas is in a turbulent state.

[0028] Optionally, the total uncertainty of the system is calculated using the following formula:

[0029]

[0030] in, δ represents the result of the total uncertainty calculation. b This represents the uncertainty result of the vortex cumulative coefficient b. This indicates the uncertainty factor in instrument measurement. This indicates the uncertainty in the measurement of ozone concentration difference.

[0031] Optionally, the time resolution of the eddy covariance flux measurement system is 10 Hz, the ultrasonic anemometer is used to measure three-dimensional wind speed (u, v, w), the open-circuit CO2 / H2O analyzer is used to measure virtual temperature, CO2 and H2O concentration, and the data acquisition unit is used to collect and save the measurement data and send the data to the data acquisition and program control system in real time via RS-485 serial communication.

[0032] The data acquisition and program control system includes a control program and a data acquisition program. The control program controls the switching of the gas path module valves in real time according to the real-time vertical wind speed direction, and marks the sampling type as rising pipe sampling, sinking pipe sampling, or no sampling. The data acquisition program uses RS-485 serial port based on MODBUS communication protocol to read the real-time flow data of the mass flow meter, and finally calibrates and unifies all data time according to PC time.

[0033] Optionally, the response switching time of the high-frequency three-way solenoid valve of the gas path module is less than 10ms, and the normally open end of the gas path module is connected to the air inlet pipe, and the normally closed end is connected to the zero gas pipe; the gas path module controls the sampling path according to the real-time vertical wind speed direction: when the vertical wind speed is greater than the threshold, the normally open end of the rising airflow valve is opened to collect sample gas; when the vertical wind speed is less than the negative threshold, the normally open end of the sinking airflow valve is opened to collect sample gas; when the vertical wind speed is within the threshold range, the normally closed ends of both valves are opened to collect zero gas.

[0034] Optionally, the front-end inlet pipe of the sampling gas path is made of 1 / 8-inch diameter polytetrafluoroethylene (PTFE) pipe, and the rising and falling airflow sampling pipes are made of 1 / 4-inch diameter PTFE pipe. The sampling gas path extending from the eddy covariance flux tower into the room is shielded from light. The front-end inlet pipe is 0.4 meters long, and the inlet is located near the center of the ultrasonic anemometer to reduce the horizontal distance between the eddy centers and reduce the high-frequency loss of eddy flux. The flow rate in the inlet pipe of the sampling gas path is set to 2.65 SLPM to ensure that the gas is in a turbulent state and to meet the Reynolds coefficient requirements for the turbulent state of the gas.

[0035] Optionally, the system also includes a vertical wind speed threshold setting module, which is used to set fixed thresholds for different time periods according to the difference in turbulence intensity between day and night, with a daytime threshold of 0.05 m / s and a nighttime threshold of 0.01 m / s; the threshold setting module dynamically adjusts the vertical wind speed threshold according to the actual measurement environment and changes in turbulence intensity to optimize the sampling efficiency and measurement accuracy of the system.

[0036] Secondly, a method for measuring ozone vertical flux based on relaxation vortex accumulation technology, applied to any of the ozone vertical flux measurement systems described in the first aspect above, the method comprising:

[0037] The eddy covariance flux measurement system is started, the three-dimensional wind speed is measured using an ultrasonic anemometer, and the virtual temperature, CO2 and H2O concentration are measured using an open-circuit CO2 / H2O analyzer. The data acquisition unit collects and saves the measurement data with a time resolution of 10Hz, and sends the data to the data acquisition and program control system in real time via RS-485 serial communication.

[0038] Based on the real-time vertical wind speed direction, the sampling paths of rising and descending airflows are controlled by the air path module; when the vertical wind speed is greater than the threshold, rising airflow samples are collected; when the vertical wind speed is less than the negative threshold, descending airflow samples are collected; when the vertical wind speed is within the threshold range, zero air is collected.

[0039] The sample is guided into the ozone analyzer by the rising and falling airflow through the sampling gas path; the front inlet pipe of the sampling gas path is made of 1 / 8-inch diameter polytetrafluoroethylene (PTFE) pipe, and the rising and falling airflow sampling pipes are made of 1 / 4-inch diameter PTFE pipe. The sampling gas path is also shielded from light when it extends from the eddy covariance flux tower into the room.

[0040] The ozone concentration in rising and falling air currents is measured using an ultraviolet ozone analyzer in the ozone measurement system. The ozone analyzer is calibrated at multiple points regularly using an ozone calibrator to ensure measurement accuracy.

[0041] The data acquisition and program control system controls the switching of the solenoid valves in the air path module according to the real-time vertical wind speed, and marks the sampling type as rising pipe sampling, sinking pipe sampling, or no sampling; the control program receives high-frequency data from the ultrasonic anemometer via RS-485 serial communication, and controls the switching of the solenoid valves in the air path module according to the relationship between the vertical wind speed and the preset threshold.

[0042] The data acquisition program uses an RS-485 serial port based on the MODBUS communication protocol to read the real-time flow data of the mass flow meter, and finally calibrates and unifies all data time according to the PC time.

[0043] The ozone vertical flux is calculated based on the average ozone concentration in the collected rising and sinking airflows, the sampling flow rate, and the standard deviation of the vertical wind speed.

[0044] The beneficial effects of the technical solutions provided in this application include at least the following:

[0045] (1) This application employs relaxation vortex accumulation technology, combined with a conventional slow-response ozone analyzer, avoiding the use of expensive and high-maintenance fast-response chemiluminescence ozone analyzers. The overall system cost is significantly reduced, and the system is highly portable, making it suitable for use in remote areas or resource-limited environments.

[0046] (2) The system of this application can accurately measure ozone vertical flux under complex and variable environmental meteorological conditions. Through conditional sampling and vortex accumulation technology, the system can accurately identify and process airflow signals, and can accurately measure ozone vertical flux even on non-uniform surfaces (such as tall crops or forests).

[0047] (3) The data acquisition and program control system of this application can receive and process data from various modules in real time, realizing automated control and data processing. Through RS-485 serial communication and MODBUS protocol, the system can efficiently synchronize and calibrate data, ensuring the accuracy and reliability of measurement results. Attached Figure Description

[0048] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0049] Figure 1 Design diagram of the ozone vertical flux measurement system provided in the embodiments of this application;

[0050] Figure 2 This is a schematic diagram illustrating the changes in farmland O3 deposition flux, deposition rate, and concentration provided in the embodiments of this application. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0052] In the description of this invention, the terms “comprising,” “having,” and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units that are expressly listed, but may also include other steps or units that are not expressly listed but are inherent to these processes, methods, products, or apparatuses, or steps or units added based on further optimizations of the inventive concept.

[0053] Due to the limitations and shortcomings of eddy covariance techniques and gradient methods in measuring O3 vertical flux, O3 vertical flux observation is restricted. This invention aims to design and develop an O3 vertical flux system based on relaxed eddy accumulation technology, providing new technical support for future O3 vertical flux observation and O3 dry deposition research.

[0054] Relaxed vortex accumulation (EVI) technology overcomes the limitations of fast-response gas analyzers while employing the same physical principles as eddy covariance techniques, without introducing additional uncertainties. Therefore, in the absence of fast-response gas analyzers, EVI is an effective alternative to eddy covariance for flux measurement. EVI samples based on real-time vertical wind speed direction, enabling precise identification and processing of airflow signals, thus allowing for accurate measurement of vertical gas flux under complex and variable environmental conditions. Furthermore, compared to gradient methods, EVI only requires sampling at a single layer and is unaffected by vertical gas gradients. In addition, EVI offers low overall system cost, good portability, and relatively simple operation and system construction. Currently, EVI is widely used for flux measurement of volatile organic pollutants, ammonia, and aerosols, but has not yet been applied to O3 vertical flux observation.

[0055] Therefore, the main purpose of this invention is to apply the relaxation vortex accumulation technique to the observation of O3 vertical flux, build a new O3 flux observation system, and optimize its parameters and performance to provide a new means for the observation and research of O3 dry deposition.

[0056] Please refer to Figure 1 This application illustrates an ozone vertical flux measurement system based on relaxed vortex accumulation technology, characterized in that the system comprises an eddy covariance flux measurement system, a gas path module, a sampling gas path, a zero gas replenishment module, an ozone measurement system, and a data acquisition and program control system. The system may include:

[0057] The eddy covariance flux measurement system is used to measure three-dimensional wind speed, virtual temperature, CO2 and H2O concentration. Specifically, it includes an ultrasonic anemometer, an open-circuit CO2 / H2O analyzer and a data acquisition unit. The data acquisition unit sends the measurement data to the data acquisition and program control system in real time via RS-485 serial communication.

[0058] The gas path module includes two high-frequency three-way solenoid valves. The normally open end of each valve is connected to the inlet pipe, and the normally closed end is connected to the zero-air pipe. The outlet ends are for rising and descending airflow, respectively. This module is controlled by a programmable control system, which adjusts the airflow sampling path based on the acquired real-time vertical wind speed direction. This module must be placed near the ultrasonic anemometer to ensure consistency between the observed samples and the observations from the eddy covariance flux measurement system.

[0059] The sampling gas path is connected to the gas path module and the ozone measurement system, and is used to guide the samples of the upward and downward airflows of the gas path module into the ozone analyzer in the ozone measurement system. The sampling gas path includes a front-end intake pipe and the upward and downward airflow sampling pipelines, and the front-end intake pipe is close to the measurement center of the ultrasonic wind speed meter;

[0060] The zero-air supplement module is connected to the gas path module, and is used to generate zero air through a zero-air generator when not sampling, and supplement zero air to the normally closed end of the gas path module through a bypass; wherein, the zero-air supplement module includes an air compressor and a zero-air generator;

[0061] The ozone measurement system is used to measure the ozone concentration in the upward and downward airflows. The ozone measurement system includes two ultraviolet ozone analyzers, and the ozone analyzers are regularly calibrated at multiple points using an ozone calibrator;

[0062] The data acquisition and program control system is used to control the operation, data acquisition and processing of the entire system. The data acquisition and program control system includes a control program and a data acquisition program. The control program controls the solenoid valve switching of the gas path module according to the real-time vertical wind speed and marks the sampling type. The data acquisition program is used to receive and process the data from the eddy covariance flux measurement system and the ozone measurement system.

[0063] Based on the above system, the present invention designs and develops a new O3 vertical flux observation system (REA-O3) based on the relaxation eddy accumulation technology. The overall technical solution is as follows:

[0064] 1. Measurement principle

[0065] During the measurement process, the REA-O3 system performs conditional sampling at a constant flow rate according to the direction of the vertical wind speed (w). When w is greater than the vertical wind speed threshold (w0), the upward airflow sample is collected; when -w0 < w < w0, the system does not collect samples; when w < -w0, the downward airflow sample is collected. The samples enter the upward and downward sampling pipelines respectively, and the O3 concentrations in the two pipelines are measured by two O3 analyzers respectively. In the near-surface layer, the O3 flux is expressed as:

[0066]

[0067] where b is the eddy accumulation coefficient, and σ w is the standard deviation of the vertical wind speed; and are respectively the average values of the ozone concentrations in the upward and downward airflows within a measurement period.

[0068] 2. System design

[0069] The REA-O3 flux system mainly consists of six parts: an eddy covariance flux measurement system, a gas path module, a sampling gas path, a zero gas replenishment module, an O3 measurement system, and a data acquisition and program control system (abbreviated as the PC side).

[0070] (1) The eddy covariance flux measurement system consists of an ultrasonic wind speed sensor, an open-path CO2 / H2O analyzer, and a data collector, and is mainly used to measure three-dimensional wind speeds (u, v, w), ultrasonic virtual temperature (T s ), CO2 and H2O concentrations, and air temperature (T Air ), air pressure (P), etc. The time resolution is 10 Hz. The data is collected and saved by a CR1000, and at the same time, it is actively sent to the PC side of the REA-O3 system in real time through RS-485 serial communication.

[0071] (2) The gas path module is located beside the ultrasonic wind speed sensor and mainly consists of two high-frequency three-way solenoid valves made of inert materials. The normally open (NO) end of the solenoid valve is connected to the inlet pipe, the normally closed (NC) end is connected to the zero gas pipe, and the outlet ends are the rising air flow and sinking air flow outlets respectively. When w > -w0, the NO end of the rising air flow valve is opened to sample the gas, and the NC end of the sinking air flow valve is opened to sample the zero gas; when -w0 < w < w0, the NC ends of both valves are opened to sample the zero gas; when w < -w0, the NC end of the rising air flow valve is opened to sample the zero gas, and the NO end of the sinking air flow valve is opened to sample the gas.

[0072] (3) The system sampling gas path includes the inlet pipe at the front end of the gas path module, as well as the rising and sinking air flow sampling pipes. The front-end inlet pipe is 0.4 m long, and the inlet is near the center of the ultrasonic wind speed sensor (4.5 m above the ground), as close as possible to the measurement center of the ultrasonic wind speed sensor to reduce the horizontal distance of the measurement eddy center and reduce the high-frequency loss of the eddy flux. The front-end inlet pipe is made of 1 / 8-inch diameter polytetrafluoroethylene (Teflon) pipe, which is small in volume to avoid interfering with the flow field by the sampling pipe; at the same time, under the same sampling flow rate, the linear flow velocity of the air flow in the inlet pipe is increased to reduce the residence time of the sampled gas between the front-end inlet pipe and the sampling valve. Both the rising and sinking air flow sampling pipes are made of 1 / 4-inch Teflon pipe and are respectively connected to the two outlet ports of the gas path module, and then are divided into two paths (the sample gas path and the bypass). The sample gas pipe is 10 m long, and the tail end is connected to the O3 analyzer; the bypass is directly connected to the suction diaphragm pump to increase the gas flow velocity from the front-end inlet to the gas path module. The inertness of the Teflon pipe has been verified in a large number of experiments and is the best material for measuring reactive gases such as O3. The sampling gas path extends from the eddy covariance flux tower to the indoor area, and all are shaded to suppress the O3-related photoreaction in the gas path.

[0073] (4) The O3 measurement system uses two UV O3 analyzers to measure the O3 gas mixing ratio and sampling flow rate in the rising and sinking gas flow lines online. The O3 concentration in the rising and sinking gas flow lines is measured by a TE 49i O3 analyzer. During the observation period, the O3 analyzers are calibrated monthly at multiple points using an O3 calibrator. The standard gas generated by the TE 49i PS enters the flux system from the zero port, passes through the solenoid valve and the sampling line, and finally enters the O3 analyzer to calibrate the O3 analyzer and check the parallelism of the sampling line.

[0074] (5) To ensure stable airflow in the O3 analyzer and sampling pipeline, a zero-air replenishment module is installed in the system. This module collects zero air in the sampling pipeline when sampling stops at the sampling end. Zero air is generated by an air compressor and a zero-air generator. The zero-air generator removes O3, NO, NO2, CO, and VOCs from the ambient air. Considering that the output flow rate of the zero-air generator is much higher than the system's sampling requirements, a bypass is installed in the zero-air replenishment pipeline, and its flow rate is adjusted using a needle valve to ensure normal system sampling.

[0075] (6) The data acquisition and program control system mainly consists of two programs written in Python. One program receives and saves high-frequency data sent by the data acquisition unit in real time via RS-485. Simultaneously, based on the w-direction, it controls the switching of valves in the gas path module in real time and marks the sampling type (ascending pipe sampling, descending pipe sampling, or no sampling). The other program uses an RS-485 serial port based on the MODBUS communication protocol to read and save the real-time flow rate of the mass flow meter (MFM) at a 1-minute time resolution. The two programs run synchronously and independently without interference. Furthermore, both O3 analyzers are connected to a PC and acquire O3 content online via Thermo iPort software. All data times are ultimately calibrated and unified according to the PC time.

[0076] During system operation, the ultrasonic anemometer measures the vertical wind speed in real time. Upon receiving the wind speed data, the system control program immediately interprets the data and sends commands to control the rapid switching of the solenoid valves in the gas path module. Ambient air or zero-air samples are collected in both sampling pipelines in real time, and the mixed O3 concentration within the pipelines is measured online by two O3 analyzers. Based on the actual sampling time, sampling flow rate, and O3 concentration, the average O3 concentration in the rising / falling airflow over 30 minutes is calculated using the following formula:

[0077]

[0078] The average ozone concentration in the rising / falling airflow over 30 minutes is calculated by integration, where c i The average ozone mass concentration over 1 minute, flow i The average sampling flow rate over 1 minute, tsample gas,i The time percentage of the total sampled air within the i-th minute; the actual ambient ozone concentration is the average ozone concentration in both the rising and sinking airflows, as shown in the following formula:

[0079]

[0080] 3. Parameter Selection

[0081] (1) Vertical wind speed threshold

[0082] The purpose of setting a vertical wind speed threshold (w0) is to avoid the adverse effects of weak turbulence conditions on flux measurements. Studies have shown that in most cases, the concentration difference of slow-settling gases or particles in the rising and sinking airflows is less than 0.1%, requiring high instrument sensitivity. Therefore, in eddy covariance or REA techniques, using w0 is beneficial for the system to sample large eddies. Large eddies have relatively large fluxes, thus increasing the gas concentration difference between the rising and sinking airflows; simultaneously, the eddy frequency spectrum in the sample gas shifts to lower frequencies, but it does not cut off all high-frequency signals, only filtering samples with small vertical displacements, resulting in a relatively small impact on flux. On the other hand, using w0 for conditional sampling can extend the service life of high-frequency solenoid valves and avoid system sampling errors and corresponding flux measurement errors near w=0 caused by the sensitivity limitations of ultrasonic anemometers.

[0083] While setting w0 is beneficial for flux measurement, its magnitude needs careful consideration. In REA flux systems, increased gas concentration differences can lead to an overestimation of the corresponding flux. Simulation data shows that when w0 < 0.1 ms... -1 At that time, the ratio of gas flux to actual flux (without using w0) is close to 1; when 0.1 ms -1 <w0<0.3ms -1 At this time, the gas flux will be slightly overestimated; when w0 > 0.3ms -1 This will significantly overestimate the eddy flux. The value of w0 can be determined based on σ. w Set as a dynamic threshold or a constant. In this application, to increase the O3 concentration difference in the rising and falling airflows, and considering the difference in turbulence intensity between day and night, the REA-O3 flux system uses time-segmented fixed w0 for conditional sampling:

[0084] Daytime (08:00 to 18:00): w0 = 0.05ms -1 ;

[0085] Nighttime (19:00 to 07:00 the next day): w0 = 0.01ms -1 .

[0086] (2) Vortex cumulative coefficient

[0087] The vortex cumulative coefficient (b) is determined by the joint probability density (JPD) distribution function of vertical wind and gas turbulent motion. According to the ideal Gaussian joint probability distribution, the theoretical value of b is 0.627; according to the organized transport motion distribution, the theoretical value is 0.54. In the REA flux system, the vertical gas flux (F) and the vortex cumulative coefficient b have a linear relationship. When b changes from 0.51 to 0.62, it causes a change of approximately 20% in F. Therefore, the value of b should be carefully selected in observations to avoid causing significant uncertainty in the REA flux value. In some observational experiments, b is set as a constant for flux value observation and calculation, with a typical value of 0.60. In actual observations, the range of b is usually 0.54–0.63, and it changes significantly over a short period. Therefore, the REA flux system typically uses a similar surrogate scalar to dynamically calibrate b to reduce its uncertainty in F. The fundamental assumption is that different scalar turbulent transport characteristics are similar; that is, the turbulent transport frequency density distribution functions of the substitute and target scalars are highly similar, and turbulent transport has similar transport efficiencies in eddies of different sizes and shapes. In trace gas or particulate flux observation experiments, sensible thermal flux or both sensible thermal flux and CO2 flux are usually used as substitute scalars to calibrate b.

[0088] The calculation method is as follows:

[0089]

[0090] in, and These are the average values ​​of the substitution scalars in the rising and descending airflows, respectively.

[0091] In the REA-O3 flux system, CO2 has no impact on the overall turbulent exchange process; furthermore, some O3 enters the plant and is removed by sedimentation after the plant stomata open, following the transport and exchange of CO2 and H2O within the leaves and plant tissues. Therefore, CO2 can be used as a substitute scalar for O3. and When all values ​​are close to 0, the resulting value of b will contain abnormally high errors. Therefore, the value of b is first calibrated during the flux calculation process. The calibration process includes two steps: first, abnormally high values ​​of b are removed; second, values ​​of b that are not within ±1 standard deviation of the daily mean are removed, and daily linear interpolation of b is performed.

[0092] (3) Sampling flow rate

[0093] The gas in the inlet pipe upstream of the valve in the REA-O3 flux system should be in a turbulent state. However, due to the flow limiting device in the O3 analyzer itself, the inlet flow rate upstream of the O3 analyzer valve alone will not meet the requirements, and horizontal mixing of gas due to laminar flow is likely to occur in the inlet pipe. Therefore, a bypass is set in the sampling pipe downstream of the valve to increase the upstream flow rate and ensure that the inlet gas is in a turbulent state. In the REA-O3 flux system, the flow rate of the rising and sinking sampling pipes is set to 1.03 SLPM, and the flow rate in the upstream 1 / 8 tube inlet pipe is set to 2.65 SLPM. Therefore, the inlet velocity of the 1 / 8 tube (inner diameter of 1.6 mm) is:

[0094]

[0095] The Reynolds coefficient of the gas inside the pipe is

[0096]

[0097] It meets the requirement that the gas is in a turbulent state.

[0098] (4) System response and delay time

[0099] The system response and delay times mainly include the residence time in the inlet pipe before the valve, the valve response time, the program response time, and the residence time in the sampling pipeline. The 1 / 8 inlet pipe is 0.4m long, and the flow velocity inside the pipe is 22ms. -1 The dwell time t1 is: t1 = 0.4 ÷ 22.0 = 18 ms.

[0100] The valve response switching time t2 is less than 10ms, which partially offsets the residence time of the sample gas from the inlet to the valve; the program response time is negligible. The 1 / 4 sampling tube is 10m long with an inner diameter of 3.17mm, and the flow velocity inside the tube is:

[0101]

[0102] The dwell time t3 is: t3 = 10 ÷ 2.2 = 4.5s.

[0103] The sampling tube contains two particulate filter heads with a dead volume of 50 mL. The residence time t4 in the filter is: t4 = 50 ÷ 1.02 × 2 = 5.9 s.

[0104] Therefore, the total time (T) for the sample gas to travel from the system inlet to the rising or falling sampling tube is... delay,1 The time delay is less than 10ms, meeting the EC high-frequency data conditional sampling switching requirements (10Hz). The total delay time from the air inlet to the O3 analyzer is T. delay,2 = t1+t2+t3+t4≈10s, which is less than the time resolution (1min) of O3 concentration and flow rate data, thus meeting the instrument measurement requirements.

[0105] 4. System Evaluation

[0106] The uncertainty in flux measurement of the REA-O3 system includes three aspects: b, σ w And the O3 concentration difference in rising and sinking airflows. b, σ w The error is mainly affected by the instrument measurement uncertainty, where the uncertainty of CO2 measurement is less than 1%, while the uncertainty of w is 0.5%. Therefore, the uncertainty of b (δ) b It should be expressed as:

[0107]

[0108] in:

[0109]

[0110] therefore:

[0111]

[0112] The uncertainty in measuring the O3 concentration difference between rising and sinking airflows mainly includes three aspects: the uncertainty of the O3 analyzer itself, w0, and pipeline differences. w0 causes a relative uncertainty (δw0) of 13% for daytime flux and 10% for nighttime flux; the uncertainty caused by differences in the system sampling pipeline (δ... tube The O3 analyzer accuracy is 1 ppb, and the average O3 concentration during the observation period was 34.7 ppb, therefore the average δ... instrument =2.9%. Uncertainty in O3 concentration difference measurement. It should be expressed as:

[0113]

[0114] The formula for calculating the total uncertainty of the system is:

[0115]

[0116] in, δ represents the result of the total uncertainty calculation. b δ b This represents the uncertainty result of the vortex cumulative coefficient b. This indicates the uncertainty factor in instrument measurement. This indicates the uncertainty in the measurement of ozone concentration difference. The total uncertainty for daytime O3 flux measurement using the REA-O3 system is 14.1%, and the uncertainty for nighttime O3 flux measurement is 11.3%.

[0117] In summary, this invention is the first to apply the relaxed vortex accumulation technique to O3 vertical flux observation, designing and constructing a complete O3 vertical flux observation system (REA-O3 system). This system can be used in conjunction with conventional slow-response O3 analyzers to measure O3 vertical flux. The system cost is relatively low, and the operation and maintenance are relatively simple. Furthermore, the system is highly portable, enabling O3 vertical flux observation in remote areas. Compared to the gradient method, the REA-O3 system can accurately measure O3 vertical flux under varying environmental and meteorological conditions and on relatively rough surfaces (such as tall crop surfaces), with a relatively small overall error.

[0118] like Figure 2 The agricultural O3 settling flux (a) and settling rate (v) in this application are given. d Schematic diagram of changes in concentration (b) and (c).

[0119] In this embodiment, during the main crop growing season of 2023 (February 13 to October 14), the REA-O3 flux observation system was used at an agricultural meteorological field scientific observation and research station to observe the dry deposition of O3 on the surface of different crops (wheat and corn). The results are as follows: Figure 2 As shown in the figure. During the observation period, a total of 5437 sets of effective O3 deposition data (deposition flux and deposition rate) were obtained, demonstrating the stability and reliability of the REA-O3 system in long-term observation. Between February 13 and October 14, 2023, the average O3 deposition flux in farmland was -0.41 ± 0.88 μg m³. -2 s -1 During the wheat growing season, the average O3 deposition rate was 0.29 ± 0.33 cm / s. -1 The daytime average value is 0.40±0.38 cm s. -1 The nighttime average value was 0.17 ± 0.26 cm s. -1 The average O3 deposition rate during the maize growing season was 0.52 ± 0.81 cm / s. -1 The average daytime value was 0.72 ± 0.91 cm / s. -1 The nighttime average value was 0.22 ± 0.51 cm / s. -1 This application uses a novel REA-O3 flux system to observe O3 deposition rates on wheat surfaces, which are similar to those measured by Zhu et al. (2015) at the Yucheng station in Shandong Province using eddy covariance techniques (daytime: 0.42 cm / s). -1 Nighttime: 0.14 cm s -1 During the corn growing season, the daytime and nighttime O3 deposition rates were significantly higher than the values ​​observed at the Yucheng station (daytime: 0.29 cm / s). -1 Evening: 0.09cm s -1(Zhu et al., 2014), but the overall mean and the mean observed by Lamaudetal using eddy correlation technology on the surface of maize in Kodor (0.5 cm s) are different. -1 The similarity to other data indirectly indicates the reliability of the new REA-O3 flux system's O3 deposition observation results. Whether on low-crop (wheat) or high-crop (maize) surfaces, the REA-O3 flux observation system can stably and accurately measure ozone vertical flux, demonstrating its wide applicability. The REA-O3 flux observation system can not only accurately observe the diurnal and seasonal variations of ozone vertical flux in farmland ecosystems, but also capture rapid changes in ozone vertical flux under complex and variable environmental and meteorological conditions. For example, during a rapid increase in soil moisture, the ozone vertical flux measured by this system shows a synchronous and rapid increase. Therefore, it can be seen that the ozone vertical flux measurement system based on relaxation vortex accumulation technology designed and constructed in this invention is reliable for measuring ozone vertical flux and can provide long-term, stable, and accurate measurements in actual field observations.

[0120] This application also provides an ozone vertical flux measurement method based on relaxation vortex accumulation technology, applied to the above-mentioned ozone vertical flux measurement system, the method comprising:

[0121] The eddy covariance flux measurement system is started, the three-dimensional wind speed is measured using an ultrasonic anemometer, and the virtual temperature, CO2 and H2O concentration are measured using an open-circuit CO2 / H2O analyzer. The data acquisition unit collects and saves the measurement data with a time resolution of 10Hz, and sends the data to the data acquisition and program control system in real time via RS-485 serial communication.

[0122] Based on the real-time vertical wind speed direction, the sampling paths for rising and descending airflows are controlled via the air path module. When the vertical wind speed is greater than a threshold, rising airflow samples are collected; when the vertical wind speed is less than a negative threshold, descending airflow samples are collected; and when the vertical wind speed is within the threshold range, zero air is collected.

[0123] The sample is guided into the ozone analyzer by the rising and falling airflow through the sampling gas path. The inlet pipe at the front end of the sampling gas path is made of 1 / 8-inch diameter polytetrafluoroethylene (PTFE) tubing, and the rising and falling airflow sampling pipes are made of 1 / 4-inch diameter PTFE tubing. Furthermore, the sampling gas path extending from the eddy covariance flux tower to the indoor environment is protected from light.

[0124] The ozone concentration in rising and falling air currents is measured using an ultraviolet ozone analyzer in the ozone measurement system. The ozone analyzer is calibrated at multiple points regularly using an ozone calibrator to ensure measurement accuracy.

[0125] The data acquisition and program control system switches the solenoid valves of the air path module according to the real-time vertical wind speed and marks the sampling type as ascending pipe sampling, descending pipe sampling, or no sampling. The control program receives high-frequency data from the ultrasonic anemometer via RS-485 serial communication and controls the switching of the solenoid valves in the air path module according to the relationship between the vertical wind speed and a preset threshold.

[0126] The data acquisition program uses an RS-485 serial port based on the MODBUS communication protocol to read the real-time flow data of the mass flow meter, and finally calibrates and unifies all data time according to the PC time.

[0127] The ozone vertical flux is calculated based on the average ozone concentration in the collected rising and sinking airflows, the sampling flow rate, and the standard deviation of the vertical wind speed.

[0128] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0129] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A vertical ozone flux measurement system based on relaxation vortex accumulation technology, characterized in that, The system comprises an eddy covariance flux measurement system, a gas path module, a sampling gas path, a zero gas replenishment module, an ozone measurement system, and a data acquisition and program control system, wherein: The eddy covariance flux measurement system is used to measure three-dimensional wind speed, virtual temperature, CO2 and H2O concentration at 10 Hz. Specifically, it includes an ultrasonic anemometer, an open-circuit CO2 / H2O analyzer and a data acquisition unit. The data acquisition unit sends the measurement data to the data acquisition and program control system in real time via RS-485 serial communication. The gas path module includes two high-frequency three-way solenoid valves. The normally open end of the high-frequency three-way solenoid valve is connected to the inlet pipe, and the normally closed end is connected to the zero gas pipe. The outlet ends are the rising airflow and the sinking airflow outlet, respectively. This module is controlled by the program control system, which controls the sampling path of the airflow according to the real-time vertical wind speed direction. This module needs to be placed near the ultrasonic anemometer to ensure the consistency between the observed sample and the observation of the eddy covariance flux measurement system. The sampling gas path is connected to the gas path module and the ozone measurement system. It is used to guide the sample of the rising and falling airflow of the gas path module into the ozone analyzer in the ozone measurement system. The sampling gas path includes a front-end inlet pipe and rising and falling airflow sampling pipes. The inlet of the front-end inlet pipe is close to the measurement center of the ultrasonic anemometer. A zero-air replenishment module, connected to the gas path module, is used to generate zero air through a zero-air generator when sampling is not performed, and replenishes the zero air by connecting to the normally closed terminal of the gas path module via a bypass; wherein, the zero-air replenishment module includes an air compressor and a zero-air generator; An ozone measurement system is used to measure the ozone concentration in rising and falling air currents. The ozone measurement system includes two ultraviolet ozone analyzers, which are periodically calibrated at multiple points using an ozone calibrator. A data acquisition and program control system is used to control the operation, data acquisition and processing of the entire system. The data acquisition and program control system includes a control program and a data acquisition program. The control program controls the switching of the solenoid valves of the gas path module according to the real-time vertical wind speed and marks the sampling type. The data acquisition program is used to receive and process data from the eddy covariance flux measurement system and the ozone measurement system.

2. The ozone vertical flux measurement system according to claim 1, characterized in that, The ozone measurement system uses two ultraviolet ozone analyzers to measure the ozone concentration and ozone flux in the rising and falling airflow sampling pipes, respectively. Represented as: Where b is the vortex cumulative coefficient, σ w This represents the standard deviation of vertical wind speed. and These represent the average ozone concentrations in the rising and descending airflows over a single measurement period.

3. The ozone vertical flux measurement system according to claim 1, characterized in that, During system operation, the ultrasonic anemometer measures the vertical wind speed in real time. Upon receiving the wind speed data, the system control program immediately judges and sends commands to control the rapid switching of the solenoid valves in the gas path module. Ambient air or zero-air samples are collected in the two sampling pipelines based on real-time data, and the mixed ozone concentration within the pipelines is measured online by two ultraviolet ozone analyzers. Based on the actual environmental sample collection time, sampling flow rate, and ozone concentration, the formula is used: The average ozone concentration in the rising / falling airflow over 30 minutes is calculated by integration, where c i The average ozone mass concentration over 1 minute, flow i The average sampling flow rate over 1 minute, t samplegas,i The time percentage of the total sampled air within the i-th minute; the actual ambient ozone concentration is the average ozone concentration in the rising and sinking airflows.

4. The ozone vertical flux measurement system according to claim 1, characterized in that, In the sampling flow rate, the system sets a bypass in the sampling pipeline downstream of the valve to increase the front-end flow rate and ensure that the intake air is in a turbulent state. The flow rates in the rising and sinking sampling pipelines are set to 1.03 SLPM, and the flow rate in the front 1 / 8 pipe intake pipe is set to 2.65 SLPM. Then, the flow velocity at the 1 / 8 pipe intake port with an inner diameter of 1.6 mm is: The Reynolds coefficient of the gas inside the pipe is It meets the requirement that the gas is in a turbulent state.

5. The ozone vertical flux measurement system according to claim 1, characterized in that, The formula for calculating the total uncertainty of the system is: in, δ represents the result of the total uncertainty calculation. b This represents the uncertainty result of the vortex cumulative coefficient b. This indicates the uncertainty factor in instrument measurement. This indicates the uncertainty in the measurement of ozone concentration difference.

6. The ozone vertical flux measurement system according to claim 1, characterized in that, The time resolution of the eddy covariance flux measurement system is 10 Hz. The ultrasonic anemometer is used to measure three-dimensional wind speed (u, v, w). The open-circuit CO2 / H2O analyzer is used to measure virtual temperature, CO2 and H2O concentration. The data acquisition unit is used to collect and save the measurement data and send the data to the data acquisition and program control system in real time via RS-485 serial communication. The data acquisition and program control system includes a control program and a data acquisition program. The control program controls the switching of the gas path module valves in real time according to the real-time vertical wind speed direction, and marks the sampling type as rising pipe sampling, sinking pipe sampling, or no sampling. The data acquisition program uses RS-485 serial port based on MODBUS communication protocol to read the real-time flow data of the mass flow meter, and finally calibrates and unifies all data time according to PC time.

7. The ozone vertical flux measurement system according to claim 1, characterized in that, The high-frequency three-way solenoid valve of the gas path module has a response switching time of less than 10ms, and the normally open end of the gas path module is connected to the air inlet pipe, while the normally closed end is connected to the zero gas pipe. The gas path module controls the sampling path according to the real-time vertical wind speed direction: when the vertical wind speed is greater than the threshold, the normally open end of the rising airflow valve is opened to collect sample gas; when the vertical wind speed is less than the negative threshold, the normally open end of the sinking airflow valve is opened to collect sample gas; when the vertical wind speed is within the threshold range, the normally closed ends of both valves are opened to collect zero gas.

8. The ozone vertical flux measurement system according to claim 1, characterized in that, The front-end inlet pipe of the sampling gas path is made of 1 / 8-inch diameter polytetrafluoroethylene (PTFE) tubing, while the rising and falling airflow sampling pipes are made of 1 / 4-inch diameter PTFE tubing. The sampling gas path extending from the eddy covariance flux tower into the room is shielded from light. The front-end inlet pipe is 0.4 meters long, with the inlet located near the center of the ultrasonic anemometer to reduce the horizontal distance between the eddy centers and minimize high-frequency loss of the eddy flux. The flow rate within the inlet pipe of the sampling gas path is set to 2.65 SLPM to ensure the gas is in a turbulent state, meeting the Reynolds coefficient requirements for turbulent gas flow.

9. The ozone vertical flux measurement system according to claim 1, characterized in that, The system also includes a vertical wind speed threshold setting module, which is used to set fixed thresholds for different time periods based on the difference in turbulence intensity between day and night. The threshold is 0.05 m / s during the day and 0.01 m / s at night. The threshold setting module dynamically adjusts the vertical wind speed threshold according to the actual measurement environment and changes in turbulence intensity to optimize the sampling efficiency and measurement accuracy of the system.

10. A method for measuring ozone vertical flux based on relaxation vortex accumulation technology, applied to the ozone vertical flux measurement system as described in any one of claims 1-9, characterized in that, The method includes: The eddy covariance flux measurement system is started, the three-dimensional wind speed is measured using an ultrasonic anemometer, and the virtual temperature, CO2 and H2O concentration are measured using an open-circuit CO2 / H2O analyzer. The data acquisition unit collects and saves the measurement data with a time resolution of 10Hz, and sends the data to the data acquisition and program control system in real time via RS-485 serial communication. Based on the real-time vertical wind speed direction, the sampling paths of rising and descending airflows are controlled by the air path module; when the vertical wind speed is greater than the threshold, rising airflow samples are collected; when the vertical wind speed is less than the negative threshold, descending airflow samples are collected; when the vertical wind speed is within the threshold range, zero air is collected. The sample is guided into the ozone analyzer by the rising and falling airflow through the sampling gas path; the front inlet pipe of the sampling gas path is made of 1 / 8-inch diameter polytetrafluoroethylene (PTFE) pipe, and the rising and falling airflow sampling pipes are made of 1 / 4-inch diameter PTFE pipe. The sampling gas path is also shielded from light when it extends from the eddy covariance flux tower into the room. The ozone concentration in rising and falling air currents is measured using an ultraviolet ozone analyzer in the ozone measurement system. The ozone analyzer is calibrated at multiple points regularly using an ozone calibrator to ensure measurement accuracy. The data acquisition and program control system controls the switching of the solenoid valves in the air path module according to the real-time vertical wind speed, and marks the sampling type as rising pipe sampling, sinking pipe sampling, or no sampling; the control program receives high-frequency data from the ultrasonic anemometer via RS-485 serial communication, and controls the switching of the solenoid valves in the air path module according to the relationship between the vertical wind speed and the preset threshold. The data acquisition program uses an RS-485 serial port based on the MODBUS communication protocol to read the real-time flow data of the mass flow meter, and finally calibrates and unifies all data time according to the PC time. The ozone vertical flux is calculated based on the average ozone concentration in the collected rising and sinking airflows, the sampling flow rate, and the standard deviation of the vertical wind speed.

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