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

Abstract

The invention discloses an ozone vertical flux measurement system and method based on a relaxation vortex accumulation technology. The system is composed of a vortex related flux measurement system, a gas circuit module, a sampling gas circuit, a zero gas supplementing module, an ozone measurement system and a data acquisition and program control system. The three-dimensional wind speed is measured through the ultrasonic anemograph, a sampling path is controlled by combining the high-frequency three-way electromagnetic valve, and accurate sampling of rising and sinking airflow is achieved. An ultraviolet ozone analyzer is adopted to measure the ozone concentration, and automatic control and data processing are realized through a data acquisition and program control system. The system is low in cost and high in portability, is suitable for remote areas and environments with limited resources, and can still keep high-precision measurement under complex and changeable meteorological conditions.

Description

Technical Field

[0001] The present invention relates to the technical field of measurement, and particularly relates to an ozone vertical flux measurement system and method based on a relaxation vortex accumulation technique. Background Art

[0002] Ozone (O3) is the most important gaseous pollutant in the atmosphere, and has an important impact on regional air quality, human health, ecosystems, and climate change. Tropospheric O3 is mainly controlled by photochemical generation and consumption, and a small part comes from stratospheric input, and is cleared through the dry deposition process. Among them, the dry deposition process accounts for about 20% of the total loss of tropospheric O3 (Lelieveld and Dentener, 2000), directly affecting the global tropospheric O3 burden and its temporal and spatial variations. The O3 dry deposition process mainly occurs near the surface, directly affecting the distribution, variation, and lifetime of near-surface O3, and has an important impact on regional O3 pollution. At the same time, after O3 is deposited on the plant surface or absorbed by plants, it will directly damage the photosynthesis and respiration of plants, affect the growth of vegetation and crop yields, and further affect the regional and global carbon-water cycles. Therefore, the observation and research of O3 dry deposition have important theoretical and practical significance for the improvement of environmental air quality, agroforestry ecology, and climate impact assessment.

[0003] Accurately measuring the O3 vertical flux is crucial for quantifying the contribution of O3 dry deposition to regional O3 pollution and evaluating the ecological agricultural impact of O3 pollution. At present, the measurement of O3 vertical flux mainly uses the eddy covariance technique and the gradient method.

[0004] Eddy covariance technique is based on the statistical analysis of turbulence and transport. By synchronously measuring the pulsation signals of vertical wind speed and O3 concentration, and using the covariance between the two to calculate the vertical flux of O3. Compared with other flux measurement techniques, the eddy covariance technique has fewer basic assumptions, is more in line with theoretical and practical situations, and can directly measure the eddy flux of O3. On a relatively uniform underlying surface, the eddy covariance technique can effectively monitor the long-term and short-term variation characteristics of the vertical flux of O3. Measuring the vertical flux of O3 by the eddy covariance technique requires a vertical anemometer and an O3 sensor with fast response (10 - 20 Hz), and the response time and delay time of the instrument should be small. At the same time, to avoid the interference of the measuring instrument on atmospheric turbulence, the system requires that the volume of the sensor should be small. Usually, the eddy covariance technique uses an ultrasonic anemometer and an O3 sensor based on chemiluminescence method to synchronously measure the vertical wind speed and O3 concentration respectively, and the measurement time resolution is above 10 Hz to ensure accurate measurement of their rapid fluctuations in turbulence. Among them, the ultrasonic anemometer directly measures the vertical wind speed; while the O3 analyzer samples first and then measures, but requires a short sampling tube and a large sampling flow rate to reduce the delay time of the instrument. During the measurement process, a data collector is used to simultaneously collect the measurement data of the two instruments, and a special software or program is used to process the pulsation signals according to the covariance formula to calculate the vertical flux of O3, and the time resolution is usually 30 minutes.

[0005] The gradient method is based on the flux-gradient theory (K-theory). By measuring the O3 concentration at different heights and combining with the diffusion coefficient, the vertical flux of O3 can be calculated. Compared with the eddy covariance technique, the gradient method does not require a fast-response O3 sensor to measure the O3 concentration. Therefore, when a fast-response O3 analyzer is lacking, the gradient method is an effective alternative method for measuring the vertical flux of O3, and it can accurately obtain the long-term variation characteristics of the vertical flux of O3. The basic assumption of the gradient method is that turbulent transport is similar to molecular diffusion, that is, the turbulent transport flux follows Fick's law, and the vertical turbulent diffusion of O3 is proportional to the mean concentration gradient. Therefore, in actual field observations, first, the O3 concentration is measured at different heights to obtain the vertical concentration gradient of O3. The diffusion coefficient is usually converted from the vertical flux measured based on the eddy covariance technique. According to 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 usually requires continuous observation of the O3 concentration at multiple height layers. Assuming that the heat and O3 transport equations are similar, the O3 diffusion coefficient is calculated based on the Monin-Obukhov similarity theory. The modified Bowen ratio method only needs to measure the O3 concentration at two height layers, and the diffusion coefficient is replaced by the diffusion coefficients of alternative scalars such as H2O, CO2, and sensible heat. Therefore, the O3 vertical flux observation system based on the modified Bowen ratio method also needs to measure the vertical flux of the alternative scalar and measure the alternative scalar at the same height as O3. According to the measured gradient and flux of the alternative scalar, the diffusion coefficient of the alternative scalar is deduced, and the O3 diffusion coefficient is equal to the diffusion coefficient of the alternative scalar. Finally, based on the calculated diffusion coefficient and combined with the measured O3 concentration gradient, the O3 vertical flux is calculated using the formula.

[0006] Although there are currently relatively mature O3 vertical flux observation techniques, both the eddy covariance technique and the gradient method have certain defects and limitations, which restrict the current O3 vertical flux observation.

[0007] Eddy covariance technique mainly uses a fast-response chemiluminescence O3 analyzer to measure the pulsation value of O3 concentration online, so as to calculate the O3 vertical flux. The O3 analyzer based on chemiluminescence method is not only expensive itself, but also its daily measurement, maintenance and calibration require expensive gases and reagents, and the labor cost is high, which easily leads to discontinuous observation results. In addition, when measuring O3 fluctuations by chemiluminescence method, there are quite large sources of uncertainty. Different O3 sensors can cause measurement errors of up to 25% (Muller et al., 2009). The sensor separation, closed system and gas diffusion in the system pipeline of the O3 analyzer will all cause high-frequency loss (Foken et al., 2006; Massman and Lee, 2002; Oliphant et al., 2004; Villalobos, 1997; Wintjen et al., 2020), resulting in O3 flux loss. Secondly, the eddy covariance technique also requires a high degree of synchronization between the measurement signals of the ultrasonic anemometer and the O3 analyzer to reduce the error of vertical flux measurement, which has high requirements for the observation equipment.

[0008] Although the gradient method does not require a fast-response O3 analyzer, due to the overall small difference in O3 concentration at different heights, the gradient method has very high requirements for the accuracy of the O3 analyzer, requiring it to be in the range of 0.02 to 0.5% (Businger, 1986). The gradient method needs to sample and measure the O3 concentration at different heights, but the sources and sinks of O3 are non-uniform in different spaces or times, which will affect the proportional relationship between the O3 vertical gradient and the flux, resulting in O3 flux error. On the one hand, the O3 vertical gradient is affected by chemical reactions such as O3 and nitrogen oxides, and there is a large spatio-temporal variability, resulting in a certain error in the measured flux. On the other hand, the O3 concentration at different heights on non-uniform surfaces (such as tall crops or forests) is affected by many factors, and the basic assumptions between the O3 vertical flux and the gradient will not hold, making the gradient method inapplicable. The O3 diffusion coefficient is jointly affected by the actual wind field, atmospheric temperature stratification, etc. For example, temperature inversion will significantly inhibit the vertical diffusion of O3, making it difficult to accurately measure the O3 diffusion coefficient. Therefore, there is a large uncertainty in the O3 deposition flux measured by the gradient method under complex and variable atmospheric environmental conditions. Summary of the Invention

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

[0010] In a first aspect, an ozone vertical flux measurement system based on the relaxation vortex accumulation technique is provided. The system consists of 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, where:

[0011] The eddy covariance flux measurement system is used to measure three-dimensional wind speed, virtual temperature, CO2, and H2O concentrations. Specifically, it includes an ultrasonic anemometer, an open-path CO2 / H2O analyzer, and a data collector. The data collector sends the measurement data to the data acquisition and program control system in real time through 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, the normally closed end is connected to the zero gas pipe, and the outlet ends are the rising air flow and sinking air flow outlets respectively. This module is controlled by the program control system and will control the sampling path of the air flow according to the obtained real-time vertical wind speed direction. This module needs to be placed near the ultrasonic anemometer to ensure the consistency between the observed samples and the observations of the eddy covariance flux measurement system.

[0013] 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 rising and sinking air flows 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 sinking air flow sampling pipelines, and the front-end inlet pipe is close to the measurement center of the ultrasonic anemometer.

[0014] The zero gas replenishment module is connected to the gas path module and is used to generate zero gas through a zero gas generator when not sampling, and supplement the zero gas to the normally closed end of the gas path module through a bypass. Among them, the zero gas replenishment module includes an air compressor and a zero gas generator.

[0015] The ozone measurement system is used to measure the ozone concentrations in the rising and sinking air flows. The ozone measurement system includes two ultraviolet ozone analyzers, and the ozone analyzers are regularly calibrated at multiple points using an ozone calibrator.

[0016] 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.

[0017] Optionally, in the ozone measurement system, two ultraviolet ozone analyzers are used to measure the ozone concentrations in the rising and sinking air flow sampling pipelines respectively, and the ozone flux is expressed as:

[0018]

[0019] wherein, b is the vortex accumulation coefficient, and σ w is the standard deviation of the vertical wind speed; and are respectively the average ozone concentrations in the upward and downward airflows within a measurement period.

[0020] Optionally, during the operation of the system, the ultrasonic anemometer measures the vertical wind speed in real time. After receiving the wind speed data, the system control program immediately judges and sends commands to control the rapid switching of the electromagnetic valves in the gas path module; ambient air or zero air is collected in the two sampling pipelines according to the real-time w, and the mixed ozone concentration in the pipelines is measured online by two ultraviolet ozone analyzers; according to the actual ambient sample collection time, sampling flow rate, and ozone concentration, according to the formula:

[0021]

[0022] Integrate and calculate the average ozone concentration in the upward / downward airflows within 30 minutes. Among them, c i is the ozone mass concentration averaged per minute, flow i is the sampling flow rate averaged per minute, and t sample gas,i is the proportion of the total sampled gas time in the i-th minute; the actual ambient ozone concentration is the average of the ozone concentrations in the upward and downward airflows.

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

[0024]

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

[0026]

[0027] meeting the requirements for the gas to be in a turbulent state.

[0028] Optionally, the total uncertainty calculation formula of the system is:

[0029]

[0030] wherein, represents the total uncertainty calculation result, and δ b represents the uncertainty result of the vortex accumulation coefficient b, represents the instrument measurement uncertainty factor, Indicates the uncertainty results of ozone concentration difference measurement.

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

[0032] The data acquisition and program control system includes a control program and a data acquisition program. The control program controls the valve switching of the gas path module in real time according to the real-time vertical wind speed direction, and marks the sampling type as ascending pipeline sampling, descending pipeline sampling or non-sampling. The data acquisition program reads the real-time flow data of the mass flowmeter based on the RS-485 serial port and the MODBUS communication protocol, and finally calibrates and unifies all data times according to the PC time.

[0033] Optionally, the response switching time of the high-frequency three-way solenoid valve of the gas path module is less than 10 ms, and the normally open end of the gas path module is connected to the intake 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, open the normally open end sampling pipe of the ascending air flow valve to collect the sample gas; when the vertical wind speed is less than the negative threshold, open the normally open end sampling pipe of the descending air flow valve to collect the sample gas; when the vertical wind speed is within the threshold range, open the normally closed ends of the two valves to collect the zero gas.

[0034] Optionally, the front intake pipe of the sampling gas path uses a 1 / 8-inch diameter polytetrafluoroethylene tube, the ascending and descending air flow sampling pipelines use 1 / 4-inch diameter polytetrafluoroethylene tubes, and the sampling gas path is shaded from the eddy covariance flux tower to the indoor. The front intake pipe is 0.4 meters long, and the air inlet is near the center of the ultrasonic anemometer to reduce the horizontal distance of the measurement eddy center and reduce the high-frequency loss of the eddy flux. The flow rate in the intake pipeline of the sampling gas path is set to 2.65 SLPM to ensure that the gas is in a turbulent state and meets the Reynolds coefficient requirements of the gas turbulent state.

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

[0036] Second aspect, a method for measuring ozone vertical flux based on relaxation vortex accumulation technology, which is applied to the ozone vertical flux measurement system according to any one of the above first aspects. The method includes:

[0037] Start the eddy covariance flux measurement system, use an ultrasonic anemometer to measure the three-dimensional wind speed, use an open-path CO2 / H2O analyzer to measure virtual temperature, CO2 and H2O concentrations. The data collector collects and saves the measurement data at a time resolution of 10 Hz, and sends the data to the data acquisition and program control system in real time through the RS-485 serial communication method;

[0038] According to the real-time vertical wind speed direction, control the sampling paths of the upward and downward airflows through the gas path module; when the vertical wind speed is greater than the threshold, collect the upward airflow sample; when the vertical wind speed is less than the negative threshold, collect the downward airflow sample; when the vertical wind speed is within the threshold range, collect zero air;

[0039] Guide the samples of the upward and downward airflows into the ozone analyzer through the sampling gas path; the front intake pipe of the sampling gas path uses a 1 / 8-inch diameter polytetrafluoroethylene tube, and the sampling pipelines for the upward and downward airflows use 1 / 4-inch diameter polytetrafluoroethylene tubes, and the sampling gas path is shaded from the eddy covariance flux tower to the indoor area;

[0040] Use the ultraviolet ozone analyzer in the ozone measurement system to measure the ozone concentrations in the upward and downward airflows, and regularly calibrate the ozone analyzer at multiple points using an ozone calibrator to ensure the measurement accuracy;

[0041] The data acquisition and program control system controls the solenoid valve switching of the gas path module according to the real-time vertical wind speed, and marks the sampling type as upward pipeline sampling, downward pipeline sampling or non-sampling; the control program receives the high-frequency data of the ultrasonic anemometer through the RS-485 serial communication method, and controls the solenoid valve switching in the gas path module according to the relationship between the vertical wind speed and the preset threshold;

[0042] The data acquisition program reads the real-time flow data of the mass flowmeter based on the MODBUS communication protocol through the RS-485 serial port, and finally calibrates and unifies all data times according to the PC time;

[0043] Calculate the ozone vertical flux according to the average ozone concentrations, sampling flow rates and standard deviations of the vertical wind speeds in the collected upward and downward airflows.

[0044] The beneficial effects brought by the technical solutions provided in the embodiments of the present application at least include:

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

[0046] (2) The system of this application can accurately measure the 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 the 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 each module in real time, realizing automatic control and data processing. Through RS-485 serial communication and the MODBUS protocol, the system can efficiently synchronize and calibrate data, ensuring the accuracy and reliability of measurement results. Description of the Drawings

[0048] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings described below are only exemplary. For those of ordinary skill in the art, without creative efforts, other implementation drawings can also be obtained according to the provided drawings.

[0049] Figure 1 Design drawing of the ozone vertical flux measurement system provided by the embodiment of this application;

[0050] Figure 2 Schematic diagram of farmland O3 deposition flux, deposition rate and concentration change provided by the embodiment of this application. Detailed Embodiments

[0051] In order to make the purpose, technical solutions and advantages of this application clearer, the following further details this application in combination with the drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain this application and are not used to limit this application.

[0052] In the description of the present invention, the terms "include", "have" and any of their variations are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily limit to the clearly listed steps or units, but may also include other steps or units inherent to these processes, methods, products or devices that are not clearly listed, or steps or units added by further optimized solutions based on the concept of the present invention.

[0053] Due to the defects and deficiencies of the eddy covariance technique and the gradient method in measuring the O3 vertical flux, the observation of the O3 vertical flux is restricted. The present invention aims to design and develop an O3 vertical flux system based on the relaxed eddy accumulation technique, providing new technical support for the future observation of the O3 vertical flux and the research on O3 dry deposition.

[0054] The relaxed eddy accumulation technique overcomes the limitations of fast response gas analyzers. At the same time, it adopts the same physical principle as the eddy covariance technique without introducing other uncertainties. Therefore, in the absence of a fast response gas analyzer, the relaxed eddy accumulation technique is an effective alternative method for flux measurement compared to the eddy covariance technique. The relaxed eddy accumulation technique performs conditional sampling according to the direction of the real-time vertical wind speed, enabling accurate identification and processing of the airflow signal. Thus, it can accurately measure the gas vertical flux under complex and variable environmental conditions. Meanwhile, compared with the gradient method, the relaxed eddy accumulation technique only requires sampling at a single layer and is not affected by the gas vertical gradient. In addition, the overall cost of the relaxed eddy accumulation technique system is low, its portability is good, and the operation process and system construction are relatively simple. Currently, the relaxed eddy accumulation technique has been widely applied to the flux measurement of volatile organic pollutants, ammonia, aerosols, etc., but it has not been applied to the observation of the O3 vertical flux.

[0055] Therefore, the main objective of the present invention is to apply the relaxed eddy accumulation technique to the observation of the O3 vertical flux, build a new O3 flux observation system, and conduct a series of optimizations on its parameters and performance, providing a new means for the observation and research of O3 dry deposition.

[0056] Please refer to Figure 1 , which shows an ozone vertical flux measurement system based on the relaxed eddy accumulation technique provided by an embodiment of the present application. It is characterized in that the system consists of 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, and specifically includes an ultrasonic anemometer, an open-path CO2 / H2O analyzer, and a data collector. The data collector transmits the measurement data to the data acquisition and program control system in real time through RS-485 serial communication;

[0058] 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, the normally closed end is connected to the zero gas pipe, and the outlet ends are the rising airflow and the sinking airflow outlets respectively. This module is controlled by the program control system and controls the sampling path of the airflow according to the obtained real-time vertical wind speed direction. This module needs to be placed near the ultrasonic anemometer to ensure the consistency between the observed samples and the observation of the eddy covariance flux measurement system;

[0059] A sampling gas path, connected to the gas path module and the ozone measurement system, 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 upward and downward airflow sampling pipelines, and the front-end intake pipe is close to the measurement center of the ultrasonic anemometer;

[0060] A zero-air replenishment module, connected to the gas path module, 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 replenishment module includes an air compressor and a zero-air generator;

[0061] An ozone measurement system, 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] A data acquisition and program control system, 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 is composed of an ultrasonic anemometer, 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, as well as 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 anemometer 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 upflow and downflow outlets respectively. When w > -w0, the NO end of the upflow valve is opened to collect the sample gas, and the NC end of the downflow valve is opened to collect the zero gas; when -w0 < w < w0, the NC ends of the two valves are opened to collect the zero gas; when w < -w0, the NC end of the upflow valve is opened to collect the zero gas, and the NO end of the downflow valve is opened to collect the sample 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 upflow and downflow sampling pipes. The front-end inlet pipe is 0.4 m long, and the inlet is located near the center of the ultrasonic anemometer (4.5 m above the ground), as close as possible to the measurement center of the ultrasonic anemometer 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 polytetrafluoroethylene (Teflon) pipe, which is small in size to avoid interfering with the flow field of the sampling pipe; at the same time, under the same sampling flow rate, the linear flow velocity of the gas in the inlet pipe is increased to reduce the residence time of the sample gas between the front-end inlet pipe and the sampling valve. The upflow and downflow sampling pipes are both made of 1 / 4-inch Teflon pipes and are respectively connected to the two outlets of the gas path module, and then are divided into two paths (the sample gas pipe 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, and all are shaded to inhibit the O3-related photochemical reactions in the gas path.

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

[0074] (5) To ensure the stability of the air flow in the O3 analyzer and the sampling pipeline, the system is equipped with a zero gas make-up module, that is, when sampling stops at the sampling end, zero gas is collected in the sampling pipeline. The zero gas is generated by an air compressor and a zero gas generator. The zero gas generator can remove O3, NO, NO2, CO, VOCs, etc. from ambient air. Considering that the output flow rate of the zero gas generator is much higher than the sampling requirement of the system, a bypass is set on the zero gas make-up pipeline, and a needle valve is used to adjust its flow rate to ensure normal sampling of the system.

[0075] (6) The data acquisition and program control system mainly consists of two programs written in the Python language. One program receives high-frequency data sent by the data collector in real time through RS-485 and saves it. At the same time, according to the w direction, it controls the valve switching of the gas path module in real time through the module and marks the sampling type (sampling in the rising pipeline, sampling in the sinking pipeline, or no sampling). Another program reads the real-time flow rate of the mass flow meter (MFM) with a time resolution of 1 minute based on the MODBUS communication protocol through the RS-485 serial port and saves it. The two programs run synchronously and independently without interfering with each other. In addition, both O3 analyzers are connected to the PC, and the O3 content is obtained online through the Thermo iPort software. All data times are finally calibrated and unified according to the PC time.

[0076] During the operation of the system, the ultrasonic anemometer measures the vertical wind speed in real time. After 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 gas is collected in the two sampling pipelines according to the real-time w, and the mixed O3 concentration in the pipeline is measured online by two O3 analyzers. According to the actual sampling time of the environmental sample, the sampling flow rate, and the O3 concentration, the average O3 concentration in the rising / sinking air flow within 30 minutes is calculated by integration. The calculation formula is as follows:

[0077]

[0078] Integrate to calculate the average ozone concentration in the rising / sinking air flow within 30 minutes, where c i is the average ozone mass concentration per minute, flow i is the average sampling flow rate per minute, and tsample gas,i is the time proportion of the total sampled gas within the i-th minute; the actual ambient ozone concentration is the average of the ozone concentrations in the upward and downward airflows, as shown in the following formula:

[0079]

[0080] 3. Parameter Selection

[0081] (1) Vertical Wind Speed Threshold

[0082] The purpose of setting the vertical wind speed threshold (w0) is to avoid the adverse effects of weak turbulence conditions on flux measurement. Research shows that in most cases, the concentration difference of gases or particles with slower settling velocities in the upward and downward airflows is less than 0.1%, which requires a very high sensitivity of the instrument. Therefore, in the eddy covariance method or REA technology, using w0 is beneficial for the system to sample large eddies. The flux in large eddies is relatively large, so the gas concentration difference in the upward and downward airflows increases accordingly; at the same time, the eddy frequency spectrum in the sampled gas shifts to lower frequencies, but it does not cut off all high-frequency signals, only filtering samples with relatively small vertical displacements, and the impact on the flux is relatively small. On the other hand, using w0 for conditional sampling can extend the service life of the high-frequency solenoid valve, and at the same time avoid system sampling errors near w = 0 and corresponding flux measurement errors caused by the sensitivity limitation of the ultrasonic anemometer.

[0083] Although setting w0 is beneficial for flux measurement, the size of w0 needs to be carefully considered and determined. In the REA flux system, the increase in gas concentration difference will lead to an overestimation of the corresponding flux. According to the simulation data results, when w0 < 0.1 m / s -1 the ratio of the gas flux to the actual flux (without using w0) is close to 1; when 0.1 m / s -1 < w0 < 0.3 m / s -1 the gas flux will be slightly overestimated; when w0 > 0.3 m / s -1 the eddy flux will be significantly overestimated. The value of w0 can be set as a dynamic threshold according to σ w or set as a constant. In this application, to increase the O3 concentration difference in the upward and downward airflows and considering the difference in diurnal turbulence intensity, the REA - O3 flux system uses fixed w0 for conditional sampling in different time periods:

[0084] During the day (08:00 to 18:): w0 = 0.05 m / s -1 ;

[0085] At night (19:00 to 07:00 the next day): w0 = 0.01 m / s -1 .

[0086] (2) Eddy Accumulation Coefficient

[0087] The eddy accumulation coefficient (b) is determined by the joint frequency 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, there is a linear relationship between the gas vertical flux (F) and the eddy accumulation coefficient b. When b changes from 0.51 to 0.62, it causes a change of about 20% in F. Therefore, it is necessary to carefully select the value of b during observation to avoid large uncertainties in the REA flux value. In some observation experiments, b is set as a constant for flux value observation and calculation, and the typical value is 0.60. In actual observation, the range of b is usually 0.54 - 0.63, and it will change significantly in a short time. Therefore, usually the REA flux system uses a similar surrogate scalar to dynamically calibrate b to reduce the uncertainty it causes to F. The basic assumption is that there is similarity in the turbulent transport characteristics of different scalars, that is, the turbulent transport frequency density distribution functions of the surrogate and target scalars are highly similar, and the turbulent transport has similar transport efficiencies in eddies of different sizes and shapes. In the observation experiments of trace gas or particulate matter fluxes, usually the sensible heat flux or both the sensible heat flux and the CO2 flux are used as surrogate scalars to calibrate b.

[0088] The calculation method is as follows:

[0089]

[0090] where, and are the average values of the surrogate scalar in the updraft and downdraft respectively.

[0091] In the REA - O3 flux system, on the one hand, CO2 does not have any impact on the entire turbulent exchange process; on the other hand, part of O3 enters the plant body and is removed by sedimentation during the transportation and exchange process of CO2 and H2O in the leaves and plant tissues after the plant stomata open. Therefore, CO2 can be selected as the surrogate scalar for O3. When and are both close to 0, the obtained b will have an abnormally high error situation. Therefore, the value of b is first calibrated during the flux calculation process. The calibration steps include two steps: first, eliminate the abnormally high b; second, eliminate the b outside the daily mean ± 1 times the standard deviation, and perform daily linear interpolation on b.

[0092] (3) Sampling flow rate

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

[0094]

[0095] The Reynolds number of the gas in the pipe is

[0096]

[0097] meeting the requirement for the gas to be in a turbulent state.

[0098] (4) System response and delay time

[0099] The system response and delay time mainly include the residence time in the intake pipe in front of the valve, the valve response time, the program response time, and the residence time in the sampling pipe. The length of the 1 / 8-inch intake pipe is 0.4 m, and the flow velocity in the pipe is 22 m / s -1 , and the residence time t1 is: t1 = 0.4 ÷ 22.0 = 18 ms.

[0100] The valve response switching time t2 is less than 10 ms, partially offsetting the residence time of the sample gas from the intake to the valve; the program response time can be ignored. The length of the 1 / 4-inch sampling pipe is 10 m, the inner diameter is 3.17 mm, and the flow velocity in the pipe is:

[0101]

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

[0103] There are two particulate filters on the sampling pipe, and the dead volume of the filter is 50 mL. The residence time t4 in the filter is: t4 = 50 ÷ 1.02 × 2 = 5.9 s.

[0104] Therefore, the total time (T delay,1 ) for the sample gas to enter the rising or sinking sampling pipe from the system intake is less than `10 ms`, meeting the sampling switching requirement (10 Hz) for EC high-frequency data conditions. The total delay time from the intake to the O3 analyzer is T delay,2 = t1 + t2 + t3 + t4 ≈ 10 s, which is less than the time resolution (1 min) of the O3 concentration and flow rate data, so it meets the instrument measurement requirements.

[0105] 4. System Evaluation

[0106] The uncertainty in the flux measurement of the REA-O3 system consists of three aspects: b, σ w and the difference in O3 concentration between the upward and downward airflows. b, σ w The error of is mainly affected by the uncertainty in instrument measurement. Among them, the uncertainty in CO2 measurement is less than 1%, while the uncertainty in w is 0.5%. Therefore, the uncertainty of b (δ b ) should be expressed as:

[0107]

[0108] Where:

[0109]

[0110] Therefore:

[0111]

[0112] The uncertainty in the measurement of the O3 concentration difference between the upward and downward airflows mainly consists of three aspects: the uncertainty of the O3 analyzer itself, w0, and pipeline differences. The relative uncertainty (δw0) in the daytime flux caused by w0 is 13%, and δw0 at night is 10%; the uncertainty (δ tube ) caused by the difference in the system sampling pipeline is 2%. The precision of the O3 analyzer is 1 ppb, and the average O3 concentration during the observation period is 34.7 ppb. Therefore, the average δ instrument = 2.9%. The uncertainty in the measurement of the O3 concentration difference should be expressed as:

[0113] [[ID=B]]

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

[0115]

[0116] Where, represents the calculation result of the total uncertainty, δ b δ b represents the uncertainty result of the vortex accumulation coefficient b, represents the uncertainty factors in instrument measurement, represents the uncertainty result of the measurement of the ozone concentration difference. The total uncertainty in the measurement of the daytime O3 flux by the REA-O3 system is 14.1%, and the uncertainty at night is 11.3%.

[0117] As can be seen from the above, the present invention first applies the relaxation vortex accumulation technology to the observation of O3 vertical flux, and designs and builds a complete set of O3 vertical flux observation system (REA-O3 system). This system can measure the O3 vertical flux in combination with a conventional slow-response O3 analyzer. The system cost is relatively low, and the operation process and manual maintenance are relatively simple. In addition, this system has good portability and can be used to observe the O3 vertical flux in remote areas. Compared with the gradient method, the REA-O3 system can accurately measure the O3 vertical flux under variable environmental meteorological conditions and on relatively rough surfaces (such as the surface of taller crops), and the overall error is relatively small.

[0118] Such as Figure 2 shows the schematic diagram of the change of O3 deposition flux (a), deposition rate (v d , b) and concentration (c) of farmland O3 in this application.

[0119] In this embodiment, during the main crop growth season in 2023 (from February 13th to October 14th), the REA-O3 flux observation system was used to conduct observations on the O3 dry deposition on the surfaces of different crops (wheat and corn) at the agricultural meteorological field scientific observation and research station. The results are as Figure 2 shown. During the observation period, a total of 5,437 sets of effective O3 deposition data (deposition flux and deposition rate) were obtained, indicating the stability and reliability of the REA-O3 system in long-term observations. From February 13th to October 14th, 2023, the average farmland O3 deposition flux was -0.41 ± 0.88 μg m -2 s -1 . During the wheat growth season, the average O3 deposition rate was 0.29 ± 0.33 cm s -1 , the average value during the day was 0.40 ± 0.38 cm s -1 , and the average value at night was 0.17 ± 0.26 cm s -1 ; during the corn growth season, the average O3 deposition rate was 0.52 ± 0.81 cm s -1 , the average value during the day was 0.72 ± 0.91 cm s -1 , and the average value at night was 0.22 ± 0.51 cm s -1 . The O3 deposition rate observed on the wheat surface based on the new REA-O3 flux system in this application is similar to the O3 deposition rate value measured on the wheat surface at the Yucheng Station in Shandong by Zhu et al. (2015) based on the eddy covariance technique (during the day: 0.42 cm s -1 ; at night: 0.14 cm s -1 ); during the corn growth season, the O3 deposition rates during the day and at night are significantly higher than the observed values at the Yucheng Station (during the day: 0.29 cm s -1 ; at night: 0.09 cm s -1)(Zhu et al., 2014), but the overall mean value is similar to the mean value (0.5 cm s -1 ) observed by Lamaud et al. on the surface of Cordoba maize using the eddy covariance technique, indirectly indicating that the new REA-O3 flux system provides reliable ozone deposition observations. Whether on the surface of low crops (wheat) or high crops (maize), the REA-O3 flux observation system can stably and accurately measure the vertical ozone flux, indicating its wide applicability. The REA-O3 flux observation system can not only accurately observe the diurnal and seasonal variations of the vertical ozone flux in the farmland ecosystem, but also capture the rapid change process of the vertical ozone flux under complex and changeable environmental meteorological conditions. For example, during the rapid increase in soil moisture, the vertical ozone flux measured by this system shows a synchronous rapid upward process. Therefore, it can be seen that the ozone vertical flux measurement system designed and built based on the relaxation eddy accumulation technique in the present invention is reliable for measuring the vertical ozone flux and can stably and accurately measure it in long-term field observations.

[0120] The embodiments of the present application also provide an ozone vertical flux measurement method based on the relaxation eddy accumulation technique, which is applied to the above-mentioned ozone vertical flux measurement system. The method includes:

[0121] Start the eddy covariance flux measurement system, use an ultrasonic anemometer to measure the three-dimensional wind speed, use an open-path CO2 / H2O analyzer to measure the virtual temperature, CO2 and H2O concentrations. The data collector collects and stores the measurement data at a time resolution of 10 Hz and sends the data to the data acquisition and program control system in real time through the RS-485 serial communication method;

[0122] According to the real-time vertical wind direction, control the sampling paths of the upward and downward airflows through the gas path module. When the vertical wind speed is greater than the threshold, collect the upward airflow sample; when the vertical wind speed is less than the negative threshold, collect the downward airflow sample; when the vertical wind speed is within the threshold range, collect zero air;

[0123] Guide the samples of the upward and downward airflows into the ozone analyzer through the sampling gas path. The front intake pipe of the sampling gas path uses a 1 / 8-inch diameter polytetrafluoroethylene tube, and the sampling pipelines for the upward and downward airflows use 1 / 4-inch diameter polytetrafluoroethylene tubes, and the sampling gas path is shaded from the eddy covariance flux tower to the indoor area;

[0124] Use the ultraviolet ozone analyzer in the ozone measurement system to measure the ozone concentrations in the upward and downward airflows, and regularly calibrate the ozone analyzer at multiple points using an ozone calibrator to ensure the measurement accuracy;

[0125] The data acquisition and program control system controls the solenoid valve switching of the gas circuit module according to the real-time vertical wind speed, and marks the sampling type as ascending pipeline sampling, descending pipeline sampling or non-sampling. The control program receives the high-frequency data of the ultrasonic anemometer through the RS-485 serial communication method, and controls the solenoid valve switching in the gas circuit module according to the relationship between the vertical wind speed and the preset threshold value;

[0126] The data acquisition program reads the real-time flow data of the mass flowmeter through the RS-485 serial port based on the MODBUS communication protocol, and finally calibrates and unifies all data times according to the PC time;

[0127] Calculate the ozone vertical flux according to the average ozone concentration, sampling flow rate and standard deviation of the vertical wind speed in the ascending and descending airflows collected.

[0128] The technical features of the above embodiments can be combined arbitrarily. For the sake of concise description, 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, it should be considered as the scope described in this specification.

[0129] The above embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. An ozone vertical flux measurement system based on the relaxation vortex accumulation technology, characterized in that The system consists of 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, where: The eddy covariance flux measurement system is used to measure the three-dimensional wind speed, virtual temperature, CO2, and H2O concentration at 10 Hz. Specifically, it includes an ultrasonic anemometer, an open-path CO2 / H2O analyzer, and a data collector. The data collector sends the measurement data to the data acquisition and program control system in real time through 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 intake pipe, the normally closed end is connected to the zero gas pipe, and the outlet ends are the upward and downward air flow outlets respectively. This module is controlled by the program control system and will control the sampling path of the air flow according to the acquired real-time vertical wind speed direction. This module needs to be placed near the ultrasonic anemometer to ensure the consistency between the observed samples and the observations of the eddy covariance flux measurement system. 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 air flows of the gas path module into the ozone analyzer in the ozone measurement system. The sampling gas path includes a front intake pipe and upward and downward air flow sampling pipelines, and the nozzle of the front intake pipe is close to the measurement center of the ultrasonic anemometer. The zero gas replenishment module is connected to the gas path module and is used to generate zero gas through a zero gas generator when not sampling, and supplement zero gas to the normally closed end of the gas path module through a bypass. Among them, the zero gas replenishment module includes an air compressor and a zero gas generator. The ozone measurement system is used to measure the ozone concentration in the upward and downward air flows. The ozone measurement system includes two ultraviolet ozone analyzers, and the ozone analyzers are regularly calibrated at multiple points using an ozone calibrator. 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.

2. The ozone vertical flux measurement system according to claim 1, characterized in that In the ozone measurement system, the ozone concentrations in the sampling pipelines of the upward and downward airflows are measured by two ultraviolet ozone analyzers respectively, and the ozone flux is expressed as: where b is the vortex accumulation coefficient, and σ w is the standard deviation of the vertical wind speed; and are the average ozone concentrations in the updraft and downdraft during a measurement period, respectively.

3. The ozone vertical flux measurement system according to claim 1, wherein During the operation of the system, the ultrasonic anemometer measures the vertical wind speed in real time. After the system control program receives the wind speed data, it immediately judges and sends a command to control the rapid switching of the electromagnetic valves in the gas path module. The ambient air or zero gas is collected in the two sampling pipelines according to the real-time w, and the mixed ozone concentration in the pipelines is measured online by two ultraviolet ozone analyzers. According to the actual sampling time of the ambient samples, the sampling flow rate, and the ozone concentration, according to the formula: Integrate to calculate the average ozone concentration in the updraft / sinking airflow within 30 minutes, where c i is the ozone mass concentration averaged over 1 minute, and flow i is the sampling flow averaged over 1 minute, and t samplegas,i is the proportion of the total sampled gas time within the i-th minute; the actual ambient ozone concentration is the average of the ozone concentrations in the updraft and sinking airflow.

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 behind the valve to increase the front-end flow rate, ensuring that the intake air is in a turbulent state. The flow rates of the upward and downward sampling pipelines are set to 1.03 SLPM, and the flow rate in the 1 / 8-inch intake pipe at the front end is set to 2.65 SLPM. Then the flow velocity at the intake port of the 1 / 8-inch pipe with an inner diameter of 1.6 mm is: The Reynolds number of the gas in the pipe is Meeting the requirements for the gas to be in a turbulent state.

5. The ozone vertical flux measurement system according to claim 1, wherein, The total uncertainty calculation formula of the system is: Among them, represents the total uncertainty calculation result, δ b represents the uncertainty result of the vortex accumulation coefficient b, represents the uncertainty factors of instrument measurement, represents the uncertainty result of ozone concentration difference measurement.

6. The ozone vertical flux measurement system according to claim 1, wherein The time resolution of the eddy covariance flux measurement system is 10 Hz. The ultrasonic anemometer is used to measure the three-dimensional wind speed (u, v, w), and the open-path CO2 / H2O analyzer is used to measure the virtual temperature, CO2, and H2O concentrations. The data collector is used to collect and save the measurement data and send the data to the data acquisition and program control system in real time through the RS-485 serial communication method; The data acquisition and program control system includes a control program and a data acquisition program. The control program controls the valve switching of the gas path module in real time according to the real-time vertical wind speed direction and marks the sampling type as ascending pipeline sampling, descending pipeline sampling, or no sampling. The data acquisition program reads the real-time flow data of the mass flowmeter based on the RS-485 serial port and the MODBUS communication protocol and calibrates and unifies all data times according to the PC time finally.

7. The ozone vertical flux measurement system according to claim 1, characterized in that The response switching time of the high-frequency three-way solenoid valve of the gas path module is less than 10 ms, and the normally open end of the gas path module is connected to the intake 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, open the normally open end sampling pipe of the ascending air valve to collect the sample gas; when the vertical wind speed is less than the negative threshold, open the normally open end sampling pipe of the descending air valve to collect the sample gas; when the vertical wind speed is within the threshold range, open the normally closed ends of the two valves to collect the zero gas.

8. The ozone vertical flux measurement system according to claim 1, characterized in that The front intake pipe of the sampling gas path uses a 1 / 8-inch diameter polytetrafluoroethylene tube, and the ascending and descending air flow sampling pipelines use 1 / 4-inch diameter polytetrafluoroethylene tubes, and the sampling gas path is shaded from the eddy covariance flux tower to the indoor. The front intake pipe is 0.4 m long, and the air inlet is near the center of the ultrasonic anemometer to reduce the horizontal distance of the measurement eddy center and reduce the high-frequency loss of the eddy flux. The flow rate in the intake pipeline of the sampling gas path is set to 2.65 SLPM to ensure that the gas is in a turbulent state and meets the Reynolds number requirements of the gas turbulent state.

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 the fixed threshold in different time periods according to the difference in the diurnal turbulence intensity. The daytime threshold is 0.05 m / s, and the nighttime threshold is 0.01 m / s. The threshold setting module dynamically adjusts the vertical wind speed threshold according to the actual measurement environment and the change of the turbulence intensity to optimize the sampling efficiency and measurement accuracy of the system.

10. A method for measuring ozone vertical flux based on the cumulative technology of relaxation vortices, which is applied to the ozone vertical flux measurement system according to any one of claims 1-9, and is characterized in that, The method includes: Start the eddy covariance flux measurement system, use the ultrasonic anemometer to measure the three-dimensional wind speed, use the open-path CO2 / H2O analyzer to measure the virtual temperature, CO2, and H2O concentrations. The data collector collects and saves the measurement data at a time resolution of 10 Hz and sends the data to the data acquisition and program control system in real time through the RS-485 serial communication method; According to the real-time vertical wind speed direction, control the sampling paths of the ascending air flow and the descending air flow through the gas path module; when the vertical wind speed is greater than the threshold, collect the ascending air flow sample; when the vertical wind speed is less than the negative threshold, collect the descending air flow sample; when the vertical wind speed is within the threshold range, collect the zero gas; Samples of rising and sinking airflows are guided into the ozone analyzer through a sampling gas path; the front intake pipe of the sampling gas path is made of 1 / 8-inch diameter polytetrafluoroethylene (PTFE) tubing, and the rising and sinking airflow sampling tubing is made of 1 / 4-inch diameter PTFE tubing. The sampling gas path is shaded from the eddy covariance flux tower to the indoor area. The ultraviolet ozone analyzer in the ozone measurement system is used to measure the ozone concentration in the rising and sinking airflows. 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 solenoid valve switching of the gas path module according to the real-time vertical wind speed and marks the sampling type as rising pipeline sampling, sinking pipeline sampling, or no sampling. The control program receives the high-frequency data of the ultrasonic anemometer through RS-485 serial communication and controls the solenoid valve switching in the gas path module according to the relationship between the vertical wind speed and the preset threshold. The data acquisition program reads the real-time flow rate data of the mass flowmeter through the RS-485 serial port based on the MODBUS communication protocol, and finally calibrates and unifies all data times according to the PC time. The ozone vertical flux is calculated based on the average ozone concentration, sampling flow rate, and standard deviation of the vertical wind speed in the collected rising and sinking airflows.

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