High resolution field vocs flux online monitoring system and method

Abstract

The application discloses a kind of high-resolution site VOCs transmission flux on-line monitoring system and method, the system includes: solar power supply system;Monitoring well, monitoring well includes multiple sampling tubes and connecting pipe, each sampling tube includes gas permeable passive sampling probe and the gas guide pipe that is communicated with gas permeable passive sampling probe;Online detection system, online detection system is connected with solar power supply system, and online detection system includes multi-channel electromagnetic valve, multi-channel electromagnetic valve has multiple independent gas inlet pipes, and multiple gas inlet pipes are communicated with the gas permeable passive sampling probe of different depth in monitoring well by gas guide pipe respectively;And data processing terminal, it is connected with online detection system by data transmission system, and data processing terminal is used to receive pollutant concentration detection data, and based on received pollutant concentration detection data, each monitoring section pollutant transmission flux and pollutant attenuation coefficient are calculated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of site pollution risk assessment, and particularly relates to a high-resolution site VOCs transmission flux online monitoring system and method. BACKGROUND

[0002] Generally, the groundwater of enterprise land engaged in industrial production is polluted to a certain extent, and volatile organic compounds (VOCs) are one of the main pollutants. With the upgrading and adjustment of industrial structure, before such enterprise land is used as residential land for redevelopment and construction, soil and groundwater sampling is needed to find out the spatial distribution of pollution, combined with land use planning for risk assessment, and corresponding treatment and risk control measures are carried out to ensure the safety of the land.

[0003] Traditional site pollution investigation mainly collects soil or groundwater samples and sends them to the laboratory for target pollutant concentration detection. Due to the cost of sampling and detection, only a limited number of samples can be detected, so traditional pollution investigation is a discrete investigation, and the sample detection results can only represent the pollution status of the corresponding sample position at the sampling time, and cannot represent the spatial and temporal variation of pollution in the actual site over time. In recent years, online monitoring technology and equipment for groundwater have been developed, but they mainly target conventional water chemical indicators such as dissolved oxygen content, pH, and conductivity in groundwater. The online monitoring technology and equipment for volatile organic pollutants in groundwater are mainly based on the traditional groundwater sampling and detection technology, which focuses on miniaturizing the detection laboratory located in a remote place and setting it on site. Its main idea is to set a sampling pump in the monitoring well and install a small modular detection device such as purge and trap-gas chromatography-mass spectrometer near the ground of the monitoring well. Through the central control system, the sampling pump in the monitoring well is started regularly to transport the groundwater sample in the monitoring well to the ground for quantitative detection of target pollutant concentration by purge and trap-gas chromatography-mass spectrometer. This kind of equipment is relatively complex, and the manufacturing and operation and maintenance cost is high, which is difficult to popularize and apply in actual projects. Because the traditional groundwater online monitoring technology usually serves only one monitoring well with one set of online monitoring equipment, when the target site has a large area of groundwater pollution, thick aquifer, and strong spatial heterogeneity of water-bearing medium, in order to achieve fine characterization of pollution, the number of monitoring wells and the number of online monitoring equipment need to be increased, and the overall construction and operation cost is usually difficult to bear.

[0004] In addition, the traditional pollution risk assessment is mainly based on the concentration of a single discrete sample to calculate the risk, but the site soil and groundwater pollution usually has strong heterogeneity, and the risk is usually overestimated or underestimated only according to the detection concentration of a single discrete sample. On the basis of the detection concentration of a single discrete sample, the spatial variation characteristics of the sample concentration and hydrogeological conditions are fused to calculate the transport flux of the pollutants at the key section, so as to further quantitatively evaluate the pollution risk, which has gradually become a mainstream method in the world and is one of the development trends of the site soil and groundwater pollution risk assessment methodology. SUMMARY

[0005] The purpose of the present application is to provide a high-resolution site VOCs transport flux online monitoring system and method to solve the problems raised in the background art.

[0006] To achieve the above-mentioned purpose, the present application provides a high-resolution site VOCs transport flux online monitoring system, comprising: a solar power supply system; a monitoring well, the monitoring well comprising a plurality of sampling pipes and a connecting pipe, each sampling pipe comprising a gas-permeable passive sampling probe and a gas guide pipe in communication with the gas-permeable passive sampling probe; an online detection system, the online detection system being connected with the solar power supply system, the online detection system comprising a multi-channel electromagnetic valve, the multi-channel electromagnetic valve having a plurality of independent gas inlet pipes, the plurality of gas inlet pipes being respectively in communication with the gas-permeable passive sampling probes at different depths in the monitoring well through the gas guide pipes; and a data processing terminal, the data processing terminal being connected with the online detection system through a data transmission system, the data processing terminal being used for receiving pollutant concentration detection data and calculating pollutant transport flux and pollutant attenuation coefficient of each monitoring section based on the received pollutant concentration detection data.

[0007] In a preferred embodiment, the online detection system further comprises a gas outlet pipe, a low-flow pneumatic diaphragm pump, an integrated detector and a pressure compensation pipe, the gas outlet pipe being connected with one end of the multi-channel electromagnetic valve and one end of the low-flow pneumatic diaphragm pump respectively, the other end of the low-flow pneumatic diaphragm pump being connected with the integrated detector, the integrated detector comprising a front-end pretreatment module for removing water vapor, a photoionization detector module with an ionization potential not less than 10.6 eV, and a detection signal wireless transmission module, and the pressure compensation pipe being connected with the multi-channel electromagnetic valve.

[0008] In a preferred embodiment, the sampling pipe further comprises a water guide screen pipe, a connector and a communication pipe, the gas guide pipe being connected with the communication pipe through a quick connector in a gas-tight manner, the communication pipe being fixed with the connector in a gas-tight manner through screwing or welding, one end of the connector being connected with the water guide screen pipe in a gas-tight manner, and the other end of the connector being connected with the connecting pipe in a gas-tight manner through screwing or a flexible pipe clamp.

[0009] In a preferred embodiment, the air-permeable passive sampling probe comprises an air-permeable inert organic polymeric membrane with a thickness of about 0.1-0.5 mm and a hollow porous rigid support, the air-permeable inert organic polymeric membrane being uniformly loaded on the outer surface of the porous rigid support so that the gaseous volatile organic pollutants can pass through the air-permeable inert organic polymeric membrane into the inner cavity of the porous rigid support, and the liquid water is blocked from entering the inner cavity.

[0010] In a preferred embodiment, the porous rigid support is a stainless steel mesh made by a roll-plate process, the stainless steel mesh having an opening rate of more than 95%, the porous rigid support having an outer diameter of 2.5 cm, an inner diameter of 2.0 cm, and a height of 20 cm, the bottom end being sealed, and the top end being airtightly connected to the gas guide tube through a quick connector.

[0011] In a preferred embodiment, the solar power supply system comprises a solar panel mounting stand, a solar panel, and a power transmission line, the solar power supply system supplying power to the online detection system through the power transmission line.

[0012] In a preferred embodiment, the data processing terminal comprises:

[0013] a start-stop function module for starting or stopping the operation of the online detection system;

[0014] a running mode setting module for setting the running mode of the online detection system;

[0015] a calibration curve function module for target pollutants quantitative concentration values and detection signals, which can automatically convert the target pollutant concentration signals detected by the online detection system at different monitoring positions of the monitoring wells and transmitted out through the data transmission system into the corresponding target pollutant quantitative concentration values at the monitoring positions, and perform data display;

[0016] a matrix concentration automatic correction algorithm module, for example, when the air-permeable passive sampling probe at the monitoring position is located in the groundwater aquifer, the matrix concentration automatic correction algorithm module of the data processing terminal corrects the test results by using Formula 1 to convert the gas phase concentration C g into the pollutant concentration C w in the groundwater at the position of the air-permeable passive sampling probe.

[0017] C w =C g / k Formula 1

[0018] In Formula 1, C w is the pollutant concentration in the groundwater at the position of the air-permeable passive sampling probe, and the unit is mg / L; C gThe target pollutant concentration signal detected by the online detection system at the position of the air-permeable passive sampling probe is calibrated by the target pollutant quantitative concentration value and the calibration curve function module of the detection signal of the data processing terminal, and the calibrated target pollutant concentration is mg / L; k is the Henry constant of the target pollutant in the same temperature equilibrium state as the position of the air-permeable passive sampling probe, which is dimensionless.

[0019] In a preferred embodiment, the data processing terminal further comprises: a pollutant transport flux calculation function module for each monitoring section, which is used to combine the groundwater flow rate of the monitoring area and the area of the monitoring section to automatically calculate the pollutant transport flux of each monitoring section in real time, and perform data display; the target pollutant transport flux of the groundwater monitoring section is calculated by using the algorithm of formula 2 to calculate the horizontal transport flux of the pollutant along the groundwater flow direction:

[0020]

[0021] In formula 2, F h is the transport flux of the target pollutant at a certain groundwater monitoring section perpendicular to the groundwater flow direction, and the unit is mg / (m 2 ×d); C wij is the target pollutant concentration in the groundwater at the position of the air-permeable passive sampling probe of the i-th row and the j-th column of a certain groundwater monitoring section, and the unit is mg / L, which is obtained by calculation according to formula 1; v is the groundwater flow rate of the monitoring section, and the unit is m / d, which is calculated according to the groundwater hydraulic gradient of the monitoring area and the permeability coefficient of the groundwater aquifer medium; A ij is the monitoring area represented by the air-permeable passive sampling probe of the i-th row and the j-th column of a certain monitoring section, and the unit is m 2 , which is calculated by dividing the total area of the monitoring section by the total number of air-permeable passive sampling probes arranged in the monitoring section.

[0022] The application also provides a method for online monitoring of pollutant transport flux by using the above-mentioned high-resolution field VOCs transport flux online monitoring system, which comprises the following steps:

[0023] Step 1: determining the monitoring section and the number and position of the monitoring points on each monitoring section in combination with the groundwater flow direction and the horizontal distribution characteristics of the pollutants in the field;

[0024] Step 2: calculating the number of sampling pipes to be installed at each monitoring point according to the thickness of the target monitoring layer of the groundwater in the field, and the vertical distance between adjacent two sampling pipes is not more than 2 meters, and the number of sampling pipes at each monitoring point is determined according to the vertical distribution characteristics of the pollutants in the field;

[0025] Step three, drill at each monitoring point according to the specification, form a well hole, assemble the monitoring well on site, vertically install the assembled monitoring well in the well hole of each monitoring point, and make the monitoring well located in the center of the well hole;

[0026] Step four, fill clean quartz sand filter material between the outer wall of the sampling pipe in the monitoring well and the well hole wall, and fill clean bentonite between the outer wall of the connecting pipe in the monitoring well and the well hole wall;

[0027] Step five, the other end of the gas guide pipe connected with the gas permeability passive sampling probe at different depths is airtightly connected with the gas inlet pipe in the online detection system through a quick connector;

[0028] Step six, install a solar power supply system, and connect the solar power supply system with the online detection system;

[0029] Step seven, start the solar power supply system to supply power for the online detection system, start the online detection system, and start the data processing terminal, and set the start-stop mode of the low-flow-rate pneumatic diaphragm pump in the data processing terminal;

[0030] Step eight, collect not less than 5 groundwater samples with different concentrations in the monitoring area, and detect them by using the detection methods of HJ1019-2019 and HJ639-2012 technical specifications and the online detection system, establish a calibration curve between the concentration signal of the online detection system and the concentration value of the target pollutant detected by the detection method of the technical specification, and input the calibration curve into the target pollutant quantitative concentration value and detection signal calibration curve function module in the data processing terminal;

[0031] Step nine, start the target pollutant quantitative concentration value and detection signal calibration curve function module of the data processing terminal, calibrate the received monitoring point pollutant concentration signal transmitted by the online detection system to the concentration value of the target pollutant, and start the matrix concentration automatic correction algorithm module of the data processing terminal to correct the concentration, and calculate the concentration of the target pollutant in the groundwater of the corresponding monitoring point;

[0032] Step ten, start the monitoring section pollutant transmission flux calculation function module of the data processing terminal, calculate the transmission flux of the target pollutant of each monitoring section, and display it in the data processing terminal.

[0033] In a preferred embodiment, the low-flow-rate pneumatic diaphragm pump is set to be started once a month, or is determined and dynamically adjusted according to the groundwater flow rate and the concentration change trend of the monitoring area, and the flow rate of the low-flow-rate pneumatic diaphragm pump is 10 mL / min.

[0034] Compared with the prior art, the beneficial effects of the present application are:

[0035] 1. The present application can divide the quantitative online detection of volatile organic pollutants in groundwater into two steps, the gaseous pollutants in the cavity of the air permeability passive sampling probe at the monitoring point under the balanced state are collected and transported to the photoionization detector by the low flow rate pneumatic diaphragm pump in the online detection system arranged on the ground for online detection of the total amount of pollutants, and the concentration signal is transmitted to the data processing terminal, the quantitative concentration value of the target pollutant in the data processing terminal and the calibration curve function module of the detection signal can use the standard curve between the concentration signal of the total amount of pollutants and the concentration value of each specific pollutant established in advance to calibrate the concentration of each specific pollutant, and the concentration of the target pollutant in the groundwater at the monitoring point is inverted by using the balanced distribution model. The system of the present application avoids the defects that the traditional groundwater online monitoring technology usually needs to use purge-trapping-gas chromatography-mass spectrometer combination for quantitative detection of the concentration of the target pollutant, resulting in complex detection system and high construction and operation and maintenance cost.

[0036] 2. The present application uses the balance algorithm between gas-liquid phases of pollutants to convert the online monitoring of groundwater into the concentration test of gaseous pollutants under the balanced state, and then inverts the concentration value of the corresponding pollutant in the groundwater at the monitoring point by testing the concentration of volatile organic pollutants in the gas phase under the balanced state, which avoids the shortcomings of the traditional groundwater online monitoring system, i.e. the need to set a groundwater sampling pump in the groundwater monitoring well, resulting in complex system construction, high operation and maintenance cost, and inability to realize deep pollutant concentration monitoring of the groundwater aquifer in the same groundwater monitoring well.

[0037] 3. The present application develops a pollutant transmission flux algorithm in the data processing terminal, calculates the transmission flux of the target pollutant of each monitoring section by fusing the site hydrogeological condition information and the spatial distribution information of the pollutant concentration of the monitoring section, and is used for quantitative evaluation of the risk of the pollutant, which to some extent overcomes the defects of overestimation or underestimation of the actual risk caused by the use of traditional groundwater discrete concentration data for evaluation, and has important significance for improving the current groundwater pollution investigation and risk evaluation technical method system. BRIEF DESCRIPTION OF DRAWINGS

[0038] Figure 1 It is a schematic diagram of the elevation structure of the system of the present application.

[0039] Figure 2 It is a schematic diagram of the structure of the solar power supply system of the present application.

[0040] Figure 3 It is a schematic diagram of the structure of the online detection system of the present application.

[0041] Figure 4 It is a schematic diagram of the structure of the monitoring well of the present application.

[0042] Figure 5 It is a schematic diagram of the structure of the sampling tube of the present application.

[0043] Figure 6 Figure 1 is a sectional view of the air permeable passive sampling probe of the present application.

[0044] Figure 7 Figure 2 is a schematic diagram of the monitoring sections of the groundwater pollution area in the field of the present application and the arrangement of the monitoring points on each monitoring section.

[0045] Figure 8 Figure 3 is a schematic diagram of the setting of one of the monitoring points of the first monitoring section of the present application.

[0046] Figure 9 Figure 4 is a calibration curve between the concentration signal of the online detection system and the target pollutant concentration value measured by the detection method of the technical specification of the present application.

[0047] Explanation of the main reference signs:

[0048] 1 - solar power supply system, 11 - solar panel mounting stand, 12 - solar panel, 13 - power transmission line, 2 - online detection system, 21 - air inlet pipe, 22 - six-way valve, 23 - air outlet pipe, 24 - low-flow pneumatic diaphragm pump, 25 - integrated detector, 26 - pressure compensation pipe, 3 - monitoring well, 31 - connecting pipe, 32 - sampling pipe, 321 - air permeable passive sampling probe, 322 - water guide pipe, 323 - air guide pipe, 324 - connector, 325 - communication pipe, 4 - data transmission system, 5 - data processing terminal, 6 - groundwater pollution area, 7 - first monitoring section, 8 - second monitoring section, 9 - third monitoring section. DETAILED DESCRIPTION

[0049] The technical solutions in the embodiments of the present application will be described clearly and completely below. All other embodiments obtained by the person of ordinary skill in the art without making creative efforts belong to the scope of protection of the present application.

[0050] Embodiment 1

[0051] As Figures 1-5As shown, the high-resolution field VOCs transmission flux online monitoring system of the preferred embodiment of the present application comprises: a solar power supply system 1, an online detection system 2, a monitoring well 3, a data transmission system 4 and a data processing terminal 5. Among them, the solar power supply system 1, the online detection system 2 and the data transmission system 4 are installed on the ground near the monitoring point, the monitoring well 3 is installed below the ground of the monitoring point, a set of solar power supply system can supply power for multiple sets of online detection system 2 and data transmission system 4, or only for a set of online detection system 2 and data transmission system 4, a set of online detection system 2 and data transmission system 4 can serve one monitoring well 3, or can serve multiple monitoring wells 3 at the same time. The data processing terminal 5 is installed in the central control room, which can be set in the monitoring site or in the office of the relevant staff. Usually, one data processing terminal can control multiple sets of online detection system 2. The monitoring well 3 comprises multiple sampling pipes 32 and connecting pipes 31, each sampling pipe 32 comprises a gas-permeable passive sampling probe 321 and a gas guide pipe 323 connected with the gas-permeable passive sampling probe 321. The online detection system 2 is connected with the solar power supply system 1, and the online detection system 2 comprises a multi-channel electromagnetic valve 22, which has multiple independent gas inlet pipes 21, and the multiple gas inlet pipes 21 are respectively connected with the gas-permeable passive sampling probes 321 at different depths in the monitoring well 3 through the gas guide pipes 323. The data processing terminal 5 is connected with the online detection system 2 through the data transmission system 4, and the data processing terminal 5 is used for receiving pollutant concentration detection data and calculating pollutant transmission flux and pollutant attenuation coefficient of each monitoring section based on the received pollutant concentration detection data.

[0052] Further, the sampling pipe 32 further comprises a water guide screen pipe 322, a connector 324 and a communication pipe 325, the gas-permeable passive sampling probe 321 is arranged in the water guide screen pipe 322, the gas guide pipe 323 is connected with the communication pipe 325 in a gas-tight manner through a quick connector, the communication pipe 325 is fixed with the connector 324 in a threaded or welded manner and the interface is sealed, one end of the connector 324 is connected with the water guide screen pipe 322 in a gas-tight manner, and the other end is connected with the connecting pipe 31 in a gas-tight manner through a threaded or flexible pipe clamp. The connection mode of the connector 324 with the water guide screen pipe 322 and the connecting pipe 31 is preferably threaded connection, and welding or other modes can also be selected.

[0053] Further, the online detection system 2 further comprises an outlet pipe 23, a low-flow pneumatic diaphragm pump 24, and an integrated detector 25. The outlet pipe 23 is connected to the multi-channel electromagnetic valve 22 at one end and to the low-flow pneumatic diaphragm pump 24 at the other end. The low-flow pneumatic diaphragm pump 24 is connected to the integrated detector 25 at the other end. The integrated detector 25 comprises a front-end pre-processing module for removing water vapor, a photoionization detector module with an ionization potential of not less than 10.6 eV, and a wireless transmission module for detection signals. The integrated detector 25 is used to receive the gas sample discharged from the outlet pipe of the low-flow pneumatic diaphragm pump 24 and detect the total amount of VOCs in the gas, and transmit the concentration signal to the data processing terminal 5.

[0054] Further, the online detection system 2 further comprises a pressure compensation pipe 26 connected to the multi-channel electromagnetic valve 22. During the detection process, the low-flow pneumatic diaphragm pump 24 will extract a certain volume of gas, causing a certain negative pressure in the air permeability passive sampling probe 321 and the connecting pipe 325. If the pressure compensation pipe is not started to restore the system pressure, the balance will be broken. On the one hand, if there are places in the pipeline that are not well connected, external air will enter the pipeline through these places, causing inaccurate test results. At the same time, maintaining a negative pressure will break the balance and affect the accuracy of the final test results. The connecting pipes between all components inside the online detection system 2 are Teflon or stainless steel pipes, and all components are made of inert materials.

[0055] Further, the air permeability passive sampling probe 321 comprises an air-permeable inert organic polymer membrane 3211 and a hollow porous rigid support 3212. The air-permeable inert organic polymer membrane 3211 has a thickness of about 0.1-0.5 mm and is uniformly loaded on the outer surface of the porous rigid support 3212, so that gaseous volatile organic pollutants can pass through the air-permeable inert organic polymer membrane 3211 and enter the inner cavity 3213 of the porous rigid support 3212, but liquid water cannot enter the inner cavity 3213. The porous rigid support 3212 is a stainless steel mesh made by coiling process. The opening rate of the stainless steel mesh is greater than 95%. The outer diameter of the porous rigid support 3212 is 2.5 cm, the inner diameter is 2.0 cm, and the height is 20 cm. The bottom end is sealed, and the top end is airtightly connected to the gas guide pipe 323 through a quick connector.

[0056] Further, the solar power supply system 1 comprises a solar panel mounting column 11, a solar panel 12, and a power transmission line 13. The solar power supply system 1 supplies power to the online detection system 2 through the power transmission line 13.

[0057] Further, the data processing terminal 5 comprises a start-stop function module, a running mode setting module, a target pollutant quantitative concentration value and detection signal calibration curve function module, a matrix concentration automatic correction algorithm module, and a pollutant transmission flux calculation function module for each monitoring section. Specifically:

[0058] The start-stop function module is used to start or stop the online detection system 2;

[0059] The running mode setting module is used to set the running mode of the online detection system 2;

[0060] The target pollutant quantitative concentration value and detection signal calibration curve function module can automatically convert the target pollutant concentration signal detected by the online detection system 2 at different monitoring positions of each monitoring well and transmitted out through the data transmission system 4 into the target pollutant quantitative concentration value at the corresponding monitoring position, and perform data display;

[0061] The matrix concentration automatic correction algorithm module, such as the air-permeable passive sampling probe 321 located in the underground water aquifer, will use formula 1 to correct the test results, and convert the gas phase concentration C g into the pollutant concentration C w in the underground water at the position of the air-permeable passive sampling probe 321.

[0062] C w =C g / k formula 1

[0063] In formula 1, C w is the pollutant concentration in the underground water at the position of the air-permeable passive sampling probe 321, with the unit of mg / L; C g is the target pollutant concentration signal detected by the online detection system 2 at the position of the air-permeable passive sampling probe 321 after calibration by the target pollutant quantitative concentration value and detection signal calibration curve function module of the data processing terminal 5, with the unit of mg / L; k is the Henry constant of the target pollutant under the same temperature equilibrium state at the position of the air-permeable passive sampling probe 321, dimensionless.

[0064] The pollutant transport flux calculation function module is used to automatically calculate the pollutant transport flux of each monitoring section in real time in combination with the underground water flow rate of the monitoring area and the area of the monitoring section, and perform data display. The target pollutant transport flux of the underground water monitoring section is calculated by using the algorithm of formula 2 to calculate the transport flux of the target pollutant in the horizontal direction along the flow direction of the underground water:

[0065]

[0066] In formula 2, F h is the transport flux of the target pollutant at a certain underground water monitoring section perpendicular to the flow direction of the underground water, with the unit of mg / (m 2 ×d); C wijThe concentration of the target pollutant in the groundwater at the position of the air permeability passive sampling probe 321 in the i-th row and j-th column of the monitoring section is calculated by formula 1, and the unit is mg / L; v is the groundwater flow rate of the monitoring section, and the unit is m / d, which is calculated according to the groundwater hydraulic gradient and the permeability coefficient of the groundwater aquifer medium in the monitoring area; A ij The monitoring area represented by the air permeability passive sampling probe 321 in the i-th row and j-th column of the monitoring section is calculated by formula 2, and the unit is m 2 The total area of the monitoring section is divided by the total number of air permeability passive sampling probes 321 arranged in the monitoring section to obtain the total number of air permeability passive sampling probes 321 arranged in the monitoring section.

[0067] Example 2

[0068] The application also provides a method for monitoring the transmission flux of pollutants on-line by using the high-resolution field VOCs transmission flux on-line monitoring system, which comprises the following steps:

[0069] Step one, according to the groundwater flow direction and the horizontal distribution characteristics of pollutants, the monitoring section is selected at different positions along the groundwater flow direction in the field, and the number and position of the monitoring points on each monitoring section are calculated and determined according to the relevant technical specification requirements;

[0070] Step two, according to the thickness of the target monitoring layer of the groundwater in the field, the number of sampling pipes 32 required to be installed at each monitoring point is calculated, the vertical distance between the adjacent two sampling pipes 32 is not more than 2 meters, and the number of sampling pipes 32 at each monitoring point is determined according to the vertical distribution characteristics of pollutants in the field;

[0071] Step three, drilling is carried out at each monitoring point position according to the specification to form a well hole, and a monitoring well 3 is assembled on site, the assembled monitoring well 3 is vertically installed in the well hole at each monitoring point, and it is ensured that the monitoring well 3 is located in the center of the well hole;

[0072] Step four, clean quartz sand filter material is filled between the outer wall of the sampling pipe 32 in the monitoring well 3 and the well hole wall, and clean bentonite is filled between the outer wall of the connecting pipe 31 in the monitoring well 3 and the well hole wall;

[0073] Step five, the other end of the air guide pipe 323 connected with the air permeability passive sampling probe 321 at different depths is connected with the air inlet pipe 21 in the on-line detection system 2 through a quick connector, and the corresponding sampling probe 321 installation depth of the corresponding pipeline is marked;

[0074] Step six, install the solar power supply system 1, and connect the solar power supply system 1 with the on-line detection system 2 according to the specification;

[0075] Step seven, start the solar power supply system 1 to supply power for the online detection system 2, start the online detection system 2, and start the data processing terminal 5, set the start-stop mode of the low-flow pneumatic diaphragm pump 24 in the data processing terminal 5, which can be set to start once a month, or can be determined and dynamically adjusted according to the change trend of the groundwater flow rate and the pollutant concentration in the monitoring area, and the flow rate of the low-flow pneumatic diaphragm pump 24 is 10 mL / min;

[0076] Step eight, collect not less than 5 groundwater samples with different concentrations in the monitoring area, and use the detection methods of HJ1019-2019 and HJ639-2012 technical specifications and the online detection system 2 to detect, establish the calibration curve between the concentration signal of the online detection system and the target pollutant concentration value measured by the detection method of the technical specification, and input the calibration curve into the target pollutant quantitative concentration value and detection signal calibration curve function module in the data processing terminal 5;

[0077] Step nine, start the target pollutant quantitative concentration value and detection signal calibration curve function module of the data processing terminal 5, calibrate the received monitoring point pollutant concentration signal transmitted by the online detection system 2 to the concentration value of the target pollutant, and start the matrix concentration automatic correction algorithm module of the data processing terminal 5 to correct the concentration, and calculate the concentration of the target pollutant in the groundwater at the corresponding monitoring point;

[0078] Step ten, start the monitoring section pollutant transport flux calculation function module of the data processing terminal 5, calculate the transport flux of the target pollutant of each monitoring section, and display it in the data processing terminal 5.

[0079] Example 3

[0080] In a specific embodiment, the method for monitoring the transport flux of pollutants online by using the above-mentioned high-resolution field volatile organic pollutant transport flux online monitoring system comprises the following steps:

[0081] Step one, according to the groundwater flow direction and the distribution characteristics of the pollutants, three monitoring sections are arranged at different positions in the groundwater pollution area 6 in the field along the groundwater flow direction, which are the first monitoring section 7, the second monitoring section 8, and the third monitoring section 9. The width of the first monitoring section 7 and the third monitoring section 9 is 150 meters, the width of the second monitoring section 8 is 200 meters, and the distance between the adjacent two monitoring sections is 100 meters. According to the requirements of the relevant technical specifications, 5 monitoring points are arranged on each monitoring section, the horizontal distance between the monitoring points of the first monitoring section 7 and the third monitoring section 9 is 30 meters, and the horizontal distance between the monitoring points of the second section 8 is 40 meters. The arrangement of the monitoring sections in the field and the monitoring points on each monitoring section is shown in Figure 7 .

[0082] Step two, according to the thickness of the site target monitoring layer, calculate the number of sampling tubes 32 needed to be installed at each monitoring point, the vertical distance between adjacent two sampling tubes 32 is not more than 2 meters. According to the vertical distribution characteristics of pollutants in the site, the number of sampling tubes 32 at each monitoring point is determined to be 4. Taking the first monitoring section 7 as an example, the vertical distance between the centers of the passive sampling probes at the same monitoring point of the monitoring section is 2 meters, that is, the vertical distance between the centers of the passive sampling probes 321a and 321b, 321b and 321c, and 321c and 321d is 2 meters respectively. The setting of the monitoring point of the monitoring section 7 is shown in FIG. 2. Figure 8

[0083] Step three, drill at each monitoring point according to the specification to form a well hole, assemble the monitoring well 3 on site, and vertically install the assembled monitoring well 3 in the well hole at each monitoring point to ensure that the monitoring well 3 is located at the center of the well hole.

[0084] Step four, fill clean quartz sand filter material between the outer wall of the sampling tube 32 in the monitoring well 3 and the well hole wall, and fill clean bentonite between the outer wall of the connecting tube 31 in the monitoring well 3 and the well hole wall.

[0085] Step five, gas-tightly connect the other end of the gas guide tube 323 connected with the different depth air permeable passive sampling probe 321 to the gas inlet tube 21 in the online detection system 2 through a quick connector, and mark the corresponding sampling probe 321 installation depth of the corresponding pipeline.

[0086] Step six, install the solar power supply system 1, and connect the solar power supply system 1 with the online detection system 2 according to the specification.

[0087] Step seven, start the solar power supply system 1 to supply power to the online detection system 2, start the online detection system 2, and start the data processing terminal 5. Set the start-stop mode of the low-flow pneumatic diaphragm pump 24 in the data processing terminal 5, which can be set to start once a month, or can be determined and dynamically adjusted according to the groundwater flow rate and pollutant concentration change trend in the monitoring area. The flow rate of the low-flow pneumatic diaphragm pump 24 is 10 mL / min.

[0088] Step eight, collect not less than 5 groundwater samples with different concentrations in the monitoring area, and detect them by using the detection methods of HJ1019-2019 and HJ639-2012 technical specifications and the online detection system 2. Establish the calibration curve between the concentration signal of the online detection system and the target pollutant concentration value measured by the detection method of the technical specification, as shown in FIG. 3, and input the calibration curve into the target pollutant quantitative concentration value and detection signal calibration curve function module in the data processing terminal 5. Figure 9

[0089] ​​Step nine, start the calibration curve function module of the target pollutant quantitative concentration value and the detection signal of the data processing terminal 5, calibrate the received monitoring point pollutant concentration signal transmitted by the online detection system 2 to the concentration value of the target pollutant, and start the matrix concentration automatic correction algorithm module of the data processing terminal 5 to correct the concentration, calculate the concentration of the target pollutant in the underground water of the corresponding monitoring point, and the result is shown in Table 1.

[0090] Step ten, start the monitoring section pollutant transmission flux calculation function module of the data processing terminal 5, calculate the transmission flux of the target pollutant of each monitoring section, and display the result on the data processing terminal 5, which is shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094]

[0095] Although the embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-resolution field VOCs transport flux online monitoring system, characterized in that: The utility model relates to a solar power supply system (1); Monitoring well (3), the monitoring well (3) includes a plurality of sampling tubes (32) and connecting pipe (31), each sampling tube (32) includes the air permeability passive sampling probe (321) and the air guide pipe (323) that communicates with air permeability passive sampling probe (321); Online detection system (2) is connected with solar power supply system (1), and online detection system (2) includes multichannel electromagnetic valve (22), multichannel electromagnetic valve (22) has a plurality of independent air inlet pipe (21), and a plurality of air inlet pipe (21) are communicated with the air permeability passive sampling probe (321) of different depth in monitoring well (3) through air guide pipe (323) respectively;And Data processing terminal (5) is connected with online detection system (2) through data transmission system (4), and data processing terminal (5) is used to receive pollutant concentration detection data, and each monitoring section pollutant transport flux and pollutant attenuation coefficient are calculated based on the received pollutant concentration detection data; Wherein, the data processing terminal (5) includes: Start-stop function module, it is used to start or stop online detection system (2) work; Running mode setting module, it is used to set the running mode of online detection system (2); Target pollutant quantitative concentration value and detection signal's calibration curve function module, it can automatically convert the target pollutant concentration signal of each monitoring well different monitoring position by online detection system (2) detection and through data transmission system (4) export into corresponding monitoring position target pollutant quantitative concentration value, and carries out data display; The data processing terminal (5) further includes: The matrix concentration automatic correction algorithm module, such as the air permeability passive sampling probe (321) of the monitoring point is located in the groundwater aquifer, and the matrix concentration automatic correction algorithm module of the data processing terminal (5) will correct the test results by formula (1), and the calibrated target pollutant concentration C g is converted into the pollutant concentration in the groundwater at the position of the corresponding air permeability passive sampling probe (321) C w ; Formula (1); Cp is the concentration of the target pollutant in the groundwater at the location of the air permeable passive sampling probe (321) in mg / L. C w Cp is the concentration of the target pollutant in the groundwater at the location of the air permeable passive sampling probe (321) in mg / L. C g Cp is the concentration of the target pollutant in the groundwater at the location of the air permeable passive sampling probe (321) in mg / L. k Cp is the concentration of the target pollutant in the groundwater at the location of the air permeable passive sampling probe (321) in mg / L. Each monitoring section pollutant transport flux calculation function module, it is used to combine monitoring area groundwater velocity and monitoring section area, and each monitoring section pollutant transport flux is calculated in real time automatically, and data display, groundwater monitoring section target pollutant transport flux, the horizontal direction transmission flux of pollutant along groundwater flow direction is calculated using the algorithm of formula (2): Online detection system (2) further includes air outlet pipe (23), low flow rate air-driven diaphragm pump (24), integrated detector (25) and pressure compensation pipe (26), and one end of air outlet pipe (23) is connected with multichannel electromagnetic valve (22), low flow rate air-driven diaphragm pump (24) respectively, the other end of low flow rate air-driven diaphragm pump (24) is connected integrated detector (25), and integrated detector (25) includes the front end pretreatment module of water vapor, the photoionization detector module of ionization potential not less than 10.6 eV and detection signal wireless transmission module, and pressure compensation pipe (26) is connected with multichannel electromagnetic valve (22). Formula (2); In formula (2), The transport flux of a target pollutant at a groundwater monitoring section perpendicular to the groundwater flow direction is expressed in mg / (m³). 2 ×d); For a certain groundwater monitoring section i Line number j The concentration of the target pollutant in the groundwater at the location of the passive sampling probe (321) of the column is in mg / L and is calculated by formula (1); The groundwater flow velocity at the monitoring section is measured in m / d and is calculated based on the hydraulic gradient of the groundwater in the monitoring area and the permeability coefficient of the groundwater aquifer medium. For a certain monitoring section i Line number j The monitoring area represented by the air permeability passive sampling probe (321) in the column, in m². 2 The area is calculated by dividing the total area of ​​the monitoring section by the total number of air permeability passive sampling probes (321) set in the monitoring section.

2. The high-resolution field VOCs transfer flux online monitoring system according to claim 1, characterized in that: ​ 3. The high-resolution field VOCs transfer flux online monitoring system according to claim 1, characterized in that: The sampling tube (32) further comprises a water guide screen pipe (322), a connector (324) and a communication pipe (325), the air guide pipe (323) is connected with the communication pipe (325) through a quick connector in an air-tight manner, the communication pipe (325) is fixed with the connector (324) in a threaded or welded manner and is sealed, one end of the connector (324) is connected with the water guide screen pipe (322) in an air-tight manner, and the other end is connected with the connecting pipe (31) in an air-tight manner through a threaded or flexible pipe clamp.

4. The high-resolution field VOCs transfer flux online monitoring system according to claim 3, characterized in that: The air-permeable passive sampling probe (321) comprises an air-permeable inert organic polymer film (3211) and a hollow porous rigid support (3212), the air-permeable inert organic polymer film (3211) has a thickness of 0.1-0.5 mm and is uniformly loaded on the outer surface of the porous rigid support (3212) so that gaseous volatile organic pollutants can pass through the air-permeable inert organic polymer film (3211) into the inner cavity (3213) of the porous rigid support (3212) and liquid water is blocked from entering the inner cavity (3213).

5. The high-resolution field VOCs transfer flux online monitoring system according to claim 4, characterized in that: The porous rigid support (3212) is a stainless steel mesh made by a plate rolling process, the opening rate of the stainless steel mesh is greater than 95%, the outer diameter of the porous rigid support (3212) is 2.5 cm, the inner diameter is 2.0 cm, the height is 20 cm, the bottom end is sealed, and the top end is connected with the air guide pipe (323) in an air-tight manner through a quick connector.

6. The high-resolution field VOCs transfer flux online monitoring system according to claim 1, characterized in that: The solar power supply system (1) comprises a solar panel mounting stand (11), a solar panel (12) and a power transmission line (13), and the solar power supply system (1) supplies power to the online detection system (2) through the power transmission line (13).

7. A method for online monitoring using the high-resolution field VOCs transport flux online monitoring system according to any one of claims 1-6, characterized in that: The method comprises the following steps: Step one, determine the monitoring section and the number and position of monitoring points on each monitoring section according to the underground water flow direction and the horizontal distribution characteristics of pollutants; Step two, calculate the number of sampling tubes (32) to be installed at each monitoring point according to the thickness of the target monitoring layer of the site underground water, the vertical distance between adjacent two sampling tubes (32) is not more than 2 meters, and the number of sampling tubes (32) at each monitoring point is determined according to the vertical distribution characteristics of pollutants in the site; Step three, drill at each monitoring point according to the specification to form a well hole, assemble the monitoring well (3) on site, vertically install the assembled monitoring well (3) in the well hole at each monitoring point, and make the monitoring well (3) located in the center of the well hole; Step four, fill clean quartz sand filter material between the outer wall of the sampling tube (32) in the monitoring well (3) and the well hole wall, and fill clean bentonite between the outer wall of the connecting pipe (31) in the monitoring well (3) and the well hole wall; Step five, connect the other end of the air guide pipe (323) connected with the air-permeable passive sampling probe (321) at different depths with the air inlet pipe (21) in the online detection system (2) through a quick connector in an air-tight manner; Step six, install the solar power supply system (1) and connect the solar power supply system (1) with the online detection system (2). Step seven, start the solar power supply system (1) for the online detection system (2) power supply, start the online detection system (2), and start the data processing terminal (5), set the start-stop mode of the low flow rate pneumatic diaphragm pump (24) in the data processing terminal (5); Step eight, collect no less than 5 different concentrations of groundwater samples in the monitoring area, and detect them by using the detection methods of HJ1019-2019 and HJ639-2012 technical specifications and the online detection system (2), establish the calibration curve between the concentration signal of the online detection system and the target pollutant concentration value measured by the detection method of the technical specification, and input the calibration curve into the target pollutant quantitative concentration value and detection signal calibration curve function module in the data processing terminal (5); Step nine, start the target pollutant quantitative concentration value and detection signal calibration curve function module of the data processing terminal (5), calibrate the received monitoring point pollutant concentration signal transmitted by the online detection system (2) to the concentration value of the target pollutant, and start the matrix concentration automatic correction algorithm module of the data processing terminal (5) to correct the concentration, calculate the concentration of the target pollutant in the corresponding monitoring point of the groundwater; Step ten, start the monitoring section pollutant transmission flux calculation function module of the data processing terminal (5), calculate the transmission flux of the target pollutant of each monitoring section, and display it in the data processing terminal (5).

8. The method of claim 7, wherein: The low flow rate pneumatic diaphragm pump (24) is set to start once a month, or is determined and dynamically adjusted according to the monitoring area groundwater flow rate and pollutant concentration change trend, and the flow rate of the low flow rate pneumatic diaphragm pump (24) is 10 mL / min.

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