Soil and groundwater voc on-line monitoring device and method

Abstract

The application discloses a kind of soil and groundwater VOC online monitoring device and method, the device includes: groundwater VOC collection unit, the preset volume of groundwater collected in situ is heated to boiling, while VOC in groundwater volatilizes, liquid internal gas phase enters the process in the upper portion of liquid surface VOC is stripped off;Soil VOC collection unit, the soil is heated in the vadose zone soil VOC monitoring well periphery, and VOC in soil enters gas phase by thermal desorption;VOC online monitoring unit receives groundwater VOC and soil VOC transmitted by high-temperature heat tracing sampling tube and respectively carries out concentration detection.The device and method of the application can overcome the technical defects of insufficient detection accuracy caused by insufficient VOC volatilization during on-site sampling in petrochemical sites, and can simultaneously realize online monitoring and early warning of soil and groundwater VOC pollution in petrochemical sites.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of petrochemical site environmental protection technology, in particular to a soil and groundwater VOC online monitoring device and method. BACKGROUND

[0002] Petroleum, as the main component of global energy, plays a crucial role in the process of national economic development. However, oil leakage is inevitable during its exploitation, transportation, processing and storage, which seriously damages the soil and groundwater environment. VOC is a representative pollutant in petrochemical sites. VOC has certain toxicity and carcinogenic hazards. When the VOC content in the environment exceeds a certain amount, the human body will show intuitive phenomena such as memory loss, and even serious harm to the liver, nerves, brain, etc. Therefore, soil and groundwater VOC online monitoring and early warning are of great significance.

[0003] Currently, there are the following problems in soil and groundwater VOC monitoring:

[0004] 1) Soil and groundwater VOC pollution monitoring mainly relies on manual collection of soil and groundwater samples for detection, which has the problems of long cycle, high sampling operation requirements, high sample storage environment requirements, sample distortion, etc., and cannot timely discover pollution problems and respond quickly;

[0005] 2) The gas chromatograph used in the current groundwater VOC online monitoring system has high requirements for the experimental environment and high purchase and use costs;

[0006] 3) The existing site VOC online monitoring system cannot realize the synchronous online precise monitoring and early warning of groundwater and soil VOC pollution using the same set of monitoring system. If different monitoring equipment is used for groundwater and soil VOC, the site online monitoring cost is high, and it is difficult to promote and apply on a large scale;

[0007] 4) In the early stage of pollution, the concentration of volatile organic compounds in groundwater and soil is low. The existing system for monitoring VOC in the gas phase above the groundwater well and soil gas cannot accurately monitor and early warn due to the influence of factors such as the sealing property of the monitoring well, VOC concentration in the medium, temperature and volatility.

[0008] Chinese patent application CN110057396A discloses a soil and groundwater volatile organic compound (VOC) continuous monitoring system and early warning method. The system comprises a sensor integration unit, a data transmission unit and a data processing unit. The sensor integration unit is electrically connected with the data processing unit through the data transmission unit. The sensor integration unit comprises a float, a volatile gas detection sensor arranged at the top of the float and a water quality parameter sensor arranged at the bottom of the float. The monitoring system of the scheme can monitor online for a long time, improve the sampling and monitoring efficiency, and rely on the natural volatilization of VOC in the groundwater and soil at the ambient temperature to carry out monitoring and early warning. The ambient temperature of the groundwater and soil is not increased, the VOC volatilization is not sufficient, the VOC concentration in the gas phase cannot fully reflect the pollution condition of the groundwater and soil, the main pollution medium cannot be distinguished in the case of data anomaly, and the process is complex and the fault tolerance is low.

[0009] Therefore, there is an urgent need for a soil and groundwater VOC pollution online monitoring and early warning device for petrochemical sites, which has low cost, can achieve online monitoring and early warning of soil and groundwater VOC pollution of petrochemical sites at the same time, and can achieve high detection accuracy.

[0010] The information disclosed in this BACKGROUND section is only for the purpose of increasing the understanding of the general background of the application, and should not be regarded as acknowledging or implying in any form that this information constitutes prior art known to those of ordinary skill in the art. SUMMARY

[0011] The purpose of the present application is to provide a soil and groundwater VOC online monitoring device and method, which can overcome the technical defects of insufficient VOC volatilization leading to insufficient detection accuracy during on-site sampling of petrochemical sites, and can simultaneously achieve online monitoring and early warning of soil and groundwater VOC pollution of petrochemical sites.

[0012] To achieve the above-mentioned purpose, according to the first aspect of the present application, the present application provides a soil and groundwater VOC online monitoring device, comprising: a groundwater VOC collection unit, which heats the on-site collected groundwater of a preset volume to boiling, and blows off VOC in the process of the gas phase in the liquid entering the upper part of the liquid surface while VOC in the groundwater is volatilized; a soil VOC collection unit, which heats the soil around the vadose zone soil VOC monitoring well, and the VOC in the soil enters the gas phase through thermal desorption; and a VOC online monitoring unit, which receives the groundwater VOC and soil VOC transmitted through the high-temperature heat tracing sampling pipe and detects the concentration respectively.

[0013] Further, in the above technical solution, the groundwater VOC collection unit can further comprise: a groundwater sampler, which has a cylindrical hollow structure in the middle and a conical shape at the upper and lower ends, for collecting and heating the groundwater; and an elevator, which lowers or raises the groundwater sampler to a predetermined height.

[0014] Further, in the technical scheme, the underground water sampler can be provided with: a water level sensor, arranged on the inner wall of the underground water sampler, used for monitoring the underground water sampling water level; an underground water heater, arranged in the middle of the underground water sampler and below the sampling water level; and a one-way valve, arranged at the bottom of the underground water sampler, used for allowing the underground water to flow in one direction during sampling.

[0015] Further, in the technical scheme, the pipeline of the high-temperature heat tracing sampling pipe for transmitting the underground water VOC can be provided with: a first valve, used for controlling the gas emission in the underground water sampler before sampling and after underground water VOC monitoring; and a second valve, used for controlling the heated VOC gas to enter the VOC online monitoring unit during underground water VOC monitoring.

[0016] Further, in the technical scheme, the underground water sampler can be further provided with: a third valve, used for emptying the sampled underground water after underground water VOC monitoring.

[0017] Further, in the technical scheme, the soil VOC collection unit can include: a soil heater, used for heating the soil around the aeration zone soil VOC monitoring well; and a soil VOC sampling head, used for collecting the gas phase VOC desorbed after soil heating and transmitting the gas phase VOC to the VOC online monitoring unit through the high-temperature heat tracing sampling pipe.

[0018] Further, in the technical scheme, the online monitoring device can further include: a control unit, used for controlling the heating, sampling process of the underground water VOC collection unit and the soil VOC collection unit and transmitting the heated gas phase VOC to the VOC online monitoring unit.

[0019] Further, in the technical scheme, the online monitoring device can further include: a remote terminal, used for receiving the VOC concentration monitoring data from the VOC online monitoring unit, comparing and analyzing the data with the background value and outputting a preset level of early warning signal.

[0020] Further, in the technical scheme, the VOC online monitoring unit can adopt a PID gas detector.

[0021] According to the second aspect of the present application, the present application provides a soil and underground water VOC online monitoring method, including the following steps: A, heating the underground water of a preset volume collected on site in a monitoring target area to boiling, and blowing off the VOC in the process of entering the gas phase in the liquid into the upper part of the liquid surface while the VOC in the underground water is volatilized; B, heating the soil around the aeration zone soil VOC monitoring well in the monitoring target area, and allowing the VOC in the soil to enter the gas phase through thermal desorption; and C, transmitting the underground water VOC and the soil VOC through the high-temperature heat tracing sampling pipe and detecting the concentrations respectively.

[0022] Further, the technical scheme above, before step A, can further include: determining a background area upstream of the monitoring target area, and extracting a maximum value from continuous detection values of the groundwater VOC and the soil VOC of the background area as a background value.

[0023] Further, the technical scheme above, after step C, can further include: comparing and analyzing the groundwater and soil VOC concentration monitoring data of the monitoring target area with the corresponding background value, and outputting a preset level of early warning signal.

[0024] Compared with the prior art, the present application has the following beneficial effects:

[0025] 1) The present application can realize synchronous online precise monitoring and early warning of groundwater and soil VOC pollution using the same set of monitoring units;

[0026] 2) The groundwater sampler of the present application can take out the groundwater without disturbance, keep the sampling volume of the groundwater in the sampler fixed, and realize the consistency of the environment sampled at different time periods;

[0027] 3) Heating the groundwater in the sampler can accelerate the volatilization of VOC, and the process of gas phase entering the upper part of the liquid surface from the inside of the liquid plays a role in blowing off VOC, and the groundwater VOC in the gas phase is transmitted through the high-temperature heat tracing sampling pipe, which is convenient for the monitoring unit to monitor the concentration of groundwater VOC;

[0028] 4) The soil heater is arranged around the soil gas VOC online monitoring well, the VOC in the soil can be thermally desorbed and enter the gas phase in a high-temperature environment, and the soil VOC in the gas phase is transmitted through the high-temperature heat tracing sampling pipe, which is convenient for the monitoring unit to monitor the concentration of soil VOC;

[0029] 5) The remote terminal of the present application can output alarm information of different levels including emergency treatment plan according to different pollution data, which can ensure efficient disposal at the first time.

[0030] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application and can be implemented according to the content of the specification, at the same time, in order to make the above and other purposes, technical features and advantages of the present application more easy to understand, one or more preferred embodiments are listed as follows, and the details are described as follows with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 is a connection structure diagram of the soil and groundwater VOC online monitoring device of the present application.

[0032] Figure 2 is a schematic diagram of the internal structure of the groundwater sampler in the groundwater VOC collection unit of the present application.

[0033] Figure 3 is a schematic diagram of the cross-sectional structure of the upper port of the groundwater sampler of the present application.

[0034] Figure 4 is a schematic diagram of the flow process of the soil and groundwater VOC online monitoring method of the present application.

[0035] Main figure mark explanation:

[0036] 1 - groundwater monitoring well;

[0037] 2 - groundwater sampler; 21 - sampler shell; 22 - water level sensor; 23 - groundwater heater; 24 - one-way valve; 25 - third valve; 26 - groundwater sampling line; 27 - water level line;

[0038] 3 - sampler pipeline cluster; 30 - upper port of the sampler; 31 - VOC sampling pipe; 32 - line pipe;

[0039] 4 - ground; 5 - soil VOC monitoring well; 6 - soil VOC sampling head; 7 - soil heater; 8 - control line; 9 - high-temperature heat tracing sampling pipe; 10 - elevator support; 11 - elevator; 12 - VOC online monitoring unit; 13 - control unit; 14 - remote terminal; 15 - first valve; 16 - second valve. DETAILED DESCRIPTION

[0040] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments.

[0041] Unless otherwise clearly indicated, throughout the specification and claims, the term "comprise" or variations such as "comprises" or "comprising" will be understood to imply the inclusion of a stated element or group of elements but not the exclusion of any other element or group of elements.

[0042] In this document, spatially relative terms, such as "beneath", "below", "lower", "above", "upper", "on", "directly on", and the like, can be used to describe one element's or feature's relationship to another element or feature as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the figures. For example, if the device in the figures is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation of above and below. The device can be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative terms used herein interpreted accordingly.

[0043] In this document, the terms "first," "second," etc., are used to distinguish two different elements or parts, and are not used to define specific positions or relative relationships. In other words, in some embodiments, the terms "first," "second," etc., can also be used interchangeably.

[0044] This invention provides an online VOC monitoring device for soil and groundwater. The device includes a groundwater VOC acquisition unit, a soil VOC acquisition unit, and a VOC online monitoring unit 12. It may also include a control unit 13 and a remote terminal 14. The various components are described in detail below.

[0045] Groundwater VOC collection unit:

[0046] The groundwater VOC collection unit is used to heat a preset volume of groundwater collected on-site to boiling. Heating can accelerate the volatilization of VOCs in the groundwater, and at the same time, the process of the gas phase inside the liquid entering the upper part of the liquid surface can play the role of stripping away VOCs.

[0047] Furthermore, such as Figure 1 As shown, the groundwater VOC collection unit specifically includes a groundwater sampler 2 and a lift 11. The groundwater sampler 2 is installed in a groundwater monitoring well 1 below the ground surface 4. The diameter of the groundwater monitoring well 1 is preferably 80-200mm, taking into account the space required for the sampler's lifting and lowering. The groundwater sampler 2 has a cylindrical hollow structure in the middle and conical ends, used to collect and heat groundwater, minimizing disturbance to the groundwater during sampling. The diameter of the sampler is preferably 75-150mm. The lift 11 is fixed to the wellhead of the groundwater monitoring well 1 by a lift bracket 10. The lift 11 can lower the groundwater sampler 2 to a sampling point at a predetermined depth or raise it to a predetermined height near the wellhead.

[0048] Further as Figure 2As shown, the casing 21 of the underground water sampler 2 is provided with a water level sensor 22, an underground water heater 23 and a one-way valve 24. The water level sensor 22 is arranged on the inner wall of the underground water sampler 2 and used to monitor the underground water sampling level. When the sampled underground water reaches the position of the water level sensor 22, the control unit 13 controls the one-way valve 24 to close and stop sampling, so as to ensure that the volume of the sampled underground water is consistent each time and help improve the accuracy of measurement. The underground water heater 23 is arranged in the middle of the underground water sampler 2 and below the sampling level. The heater heating temperature range is preferably 50-260℃. After sampling is completed, the underground water sampler 2 is lifted to the vicinity of the well mouth under the action of the elevator 11. At this time, the underground water heater 23 starts to work and heats the sampled underground water to boiling, so that the VOC in the underground water is accelerated to volatilize, and the gas phase rising in the liquid can also strip the VOC. The arrangement of the underground water heater 23 in the underground water sampler 2 can more effectively obtain the gas phase VOC in the underground water and help improve the accuracy of monitoring. The present application can also increase the underground water aeration unit as needed to further increase the stripping effect. The one-way valve 24 is arranged at the bottom of the underground water sampler 2 and used to make the underground water flow in one direction during sampling. During sampling, the one-way valve 24 is in an open state. After the underground water VOC in the gas phase is obtained by heating, the underground water VOC needs to be sent to the VOC online monitoring unit 12 of the present application through the transmission pipeline.

[0049] Further as shown in Figure 1 , the present application adopts a high-temperature heat tracing sampling pipe 9 as the transmission pipeline, which can keep the underground water VOC in the high-temperature gas phase state at all times and facilitate the monitoring of the VOC online monitoring unit 12. The high-temperature heat tracing sampling pipe 9 for transmitting the underground water VOC is provided with a first valve 15 and a second valve 16. The first valve 15 is used to control the gas discharge in the underground water sampler before sampling and after underground water VOC monitoring. The second valve 16 is used to control the heated VOC gas to enter the VOC online monitoring unit during underground water VOC monitoring. Further as shown in Figure 2 , the underground water sampler 2 is provided with a third valve 25, which is used to empty the sampled underground water after underground water VOC monitoring and prepare for the next sampling.

[0050] Further as shown in Figure 1 , the underground water sampler 2 is connected with the VOC online monitoring unit 12 and the control unit 13 through the sampler pipeline cluster 3. Specifically, the pipeline cluster 3 has a VOC sampling pipe 31 leading to the VOC online monitoring unit 12, which communicates with the casing 21 of the underground water sampler 2. The pipeline cluster 3 also has a wire pipe 32 connected with the control unit 13, which can control the underground water heater 23 to work. Further as shown in Figure 2 , 3As shown, the cross-section of port 30 of the sampler illustrates the arrangement of the VOC sampling tube 31 and the conduit 32.

[0051] Soil VOC collection unit:

[0052] like Figure 1 As shown, this invention constructs vadose zone soil VOC monitoring wells 5 around a groundwater monitoring well 1. The soil VOC monitoring wells are located in the upper part of the saturated zone, and the tops of the monitoring wells are shielded. A soil VOC acquisition unit is used to heat the soil around the vadose zone soil VOC monitoring wells, allowing VOCs in the soil to enter the gas phase through thermal desorption. Specifically, the soil VOC acquisition unit includes a soil heater 7 and a soil VOC sampling head 6. The soil heater 7 is located around the soil VOC monitoring well 5 and heats the surrounding soil. The heaters are arranged around the monitoring well, preferably using four heaters. The control unit 13 controls the operation of the soil heater 7 via control lines. The heated soil undergoes thermal desorption, allowing the collection of gaseous VOCs. The soil VOC sampling head 6 collects the thermally desorbed gaseous VOCs from the heated soil and transmits them to the VOC online monitoring unit 12 via a high-temperature heated sampling pipe 9.

[0053] VOC online monitoring unit:

[0054] The VOC online monitoring unit 12 is used to receive groundwater VOC and soil VOC transmitted through the high-temperature heated sampling tube 9 and to detect the concentration of groundwater VOC and soil VOC respectively. Preferably, but not limitingly, the VOC online monitoring unit 12 uses a PID detector to detect the gas, with a measurement range of 0-50 ppm.

[0055] Control unit and remote terminal:

[0056] like Figure 1 As shown, the control unit 13 of this invention is used to control the heating and sampling processes of the groundwater VOC acquisition unit and the soil VOC acquisition unit, as well as to control the transmission of heated gaseous VOC to the VOC online monitoring unit. The remote terminal 14 of this invention is used to receive VOC concentration monitoring data from the VOC online monitoring unit 12, compare and analyze it with background values, and output a preset level of early warning signal. Specifically, this invention determines a background area in the monitoring site (i.e., the monitoring target area), which is set in an uncontaminated area upstream of the groundwater flow. Several sets of groundwater monitoring wells and soil monitoring wells are deployed in the background area to construct a soil and groundwater VOC online monitoring system, which operates continuously. The maximum value in the continuously running data is taken as the background value of the monitoring site. Comparative analysis is performed based on the background value, and multi-level early warnings can be output according to the comparison analysis results.

[0057] The present invention also provides a method for online monitoring of VOCs in soil and groundwater, which may include the following steps:

[0058] Step S101, determine the background area upstream of the monitoring target area, and extract the maximum value from the continuous detection values of the groundwater VOC and soil VOC in the background area as the background value.

[0059] Step S102, heat the groundwater of a preset volume collected on site in the monitoring target area to boiling, and blow off the VOC in the groundwater while the gas phase in the liquid enters the upper part of the liquid surface.

[0060] Specifically, during groundwater VOC monitoring, the control unit 13 controls the groundwater sampler 2 to descend, the first valve 15 is opened, the second valve 16 is closed, the groundwater enters the groundwater sampler 2 through the one-way valve 24, the gas discharged in the sampler is discharged through the first valve 15, the water level in the sampler reaches the preset water level line 27, and the water level sensor 22 sends a signal to the control unit 13, which can ensure the accuracy of the groundwater sampling depth. The control unit 13 sends an instruction to the elevator 11, and the groundwater sampler 2 stops and starts to rise, at which time the one-way valve 24 is automatically closed, and the groundwater sampler 2 rises. After the groundwater sampler 2 rises to the initial position, the second valve 16 is opened, the first valve 15 is closed, and the groundwater heater 23 in the sampler starts to work, the water sample in the sampler is heated to boiling, which accelerates the volatilization of VOC, and at the same time, the process of the gas phase entering the upper part of the liquid from the inside of the liquid plays a role in blowing off VOC.

[0061] Step S103, heat the soil around the vadose zone soil VOC monitoring well in the monitoring target area, and the VOC in the soil enters the gas phase through thermal desorption.

[0062] Specifically, the groundwater VOC in the gas phase enters the VOC online monitoring unit 12 through the high-temperature heat tracing sampling pipe 9 and the second valve 16, and the monitoring data is sent to the remote terminal 14; the soil VOC in the gas phase enters the VOC online monitoring unit 12 through the soil VOC sampling head 6 and the high-temperature heat tracing sampling pipe 9, and the monitoring data is sent to the remote terminal 14.

[0063] Step S104, transmit the groundwater VOC and soil VOC through the high-temperature heat tracing sampling pipe and detect the concentration respectively.

[0064] Specifically, the groundwater VOC in the gas phase enters the VOC online monitoring unit 12 through the high-temperature heat tracing sampling pipe 9 and the second valve 16, and the monitoring data is sent to the remote terminal 14; the soil VOC in the gas phase enters the VOC online monitoring unit 12 through the soil VOC sampling head 6 and the high-temperature heat tracing sampling pipe 9, and the monitoring data is sent to the remote terminal 14.

[0065] Step S105, compare and analyze the groundwater and soil VOC concentration monitoring data in the monitoring target area with the corresponding background value, and output a preset level of early warning signal.

[0066] Specifically, the remote terminal 14 can separate abnormal data by comparing the database, further judge the pollution data by abnormal data processing, once the pollution data is judged, directly output the alarm information, according to different pollution data, output different levels of alarm information, different levels of alarm information include different emergency treatment plan, can ensure that make efficient disposal in the first time.

[0067] For example, if the concentration value monitored by the monitoring site is 2 times the background value, a level III early warning can be output, corresponding to a level III emergency plan, that is, the monitoring site inspection personnel go to the monitoring point to check whether the sudden pollution occurs, if no pollution condition is found, the area is kept attention and the online monitoring frequency is increased; if the concentration value monitored by the monitoring site is 4 times the background value, a level II early warning can be output, that is, to go to the monitoring point to check whether the sudden pollution occurs, and collect groundwater and soil samples to send to the laboratory for detection, increase the online monitoring frequency, judge the pollution condition according to the detection condition, and organize personnel by the monitoring area environmental protection supervisor to carry out pollution investigation of the site and write the investigation report; if the concentration value monitored by the monitoring site is 6 times the background value, a level I early warning can be output, the monitoring site inspection personnel go to the monitoring point to check whether the sudden pollution occurs, collect groundwater and soil samples to send to the laboratory for detection, increase the online monitoring frequency, judge the pollution condition according to the detection condition, develop a site investigation plan, carry out site pollution condition investigation, and write a site investigation report.

[0068] The soil and groundwater VOC online monitoring device and method of the application can take out groundwater without disturbance, keep the sampling volume of groundwater in the sampler fixed, and realize the environmental consistency of sampling at different time periods; heating the groundwater in the sampler can accelerate the volatilization of VOC, and the process of gas phase entering the upper part of the liquid surface from the inside of the liquid plays a role in blowing off VOC; the thermal desorption technology is applied to online monitoring, the heater is arranged around the soil gas VOC online monitoring well, and the VOC in the soil is thermally desorbed and enters the gas phase under high temperature environment; the remote terminal can output alarm information of different levels including emergency treatment plan according to different pollution data, which can ensure efficient disposal in the first time.

[0069] Example 1

[0070] The background area is determined on the upstream unpolluted area of the groundwater flow in a certain petrochemical site, three groups of groundwater monitoring wells and soil monitoring wells are arranged in the background area, the soil and groundwater VOC online monitoring device is constructed, and continuous operation is performed for 30 days, the monitoring frequency is once every 5 days, and the maximum value in the continuous operation data is taken as the background value of the monitoring site, wherein the groundwater background value is 1.5 ppm, and the soil background value is 2 ppm.

[0071] The online monitoring device for VOC in soil and groundwater in the monitoring site is constructed, the background value of groundwater VOC is set to 1.5 ppm, the background value of soil VOC is set to 1 ppm, the monitoring frequency is 10 days once, and the continuous online operation monitoring is performed. The control unit controls the groundwater sampler to descend, the first valve is opened, the second valve is closed, the groundwater enters the groundwater sampler through the one-way valve, the gas in the sampler is discharged through the first valve, the water level in the sampler reaches the water level, the water level sensor transmits a signal to the control unit, the control unit sends an instruction to the elevator, the groundwater sampler stops and starts to rise, the one-way valve is automatically closed, after the groundwater sampler rises to the initial position, the second valve is opened, the first valve is closed, the heater in the groundwater sampler starts to work, the working temperature is set to 200 degrees Celsius, after a period of time, the water sample in the sampler boils, the VOC is fully volatilized, and the gas phase enters the upper part of the liquid surface from the inside of the liquid. The gas enters the VOC online monitoring unit through the high-temperature heat tracing sampling pipe and the second valve, and the monitoring data is sent to the remote terminal.

[0072] The groundwater monitoring well is constructed around the soil VOC monitoring well in the vadose zone, the heater is arranged around the soil VOC monitoring well, the control unit sends an instruction, the heater starts to work, the working temperature is set to 200 degrees Celsius, the VOC in the soil is thermally desorbed and enters the gas phase under the high-temperature environment, and the gas enters the VOC online monitoring unit through the high-temperature heat tracing sampling pipe.

[0073] After the groundwater VOC monitoring is completed, the control unit sends an instruction, the heater in the groundwater sampler stops working, the first valve is opened, the second valve is closed, the third valve of the groundwater sampler is opened, and the third valve is automatically closed after the water sample in the sampler is emptied. After the soil VOC monitoring is completed, the control unit sends an instruction, and the heater around the soil monitoring well stops working.

[0074] The remote terminal separates abnormal data by comparing the monitoring data with the background value, when the groundwater VOC in the monitoring data exceeds 3 ppm or the soil VOC exceeds 4 ppm, the remote terminal outputs a level III early warning, the monitoring site inspection personnel go to the monitoring point to investigate and find that there is no sudden pollution, the area is kept attention in the later period, and the online monitoring frequency is adjusted to 7 days once; when the groundwater VOC in the monitoring data exceeds 6 ppm or the soil VOC exceeds 8 ppm, the remote terminal outputs a level II early warning, the monitoring site inspection personnel go to the monitoring point to investigate and find that there is no leakage, and collect groundwater and soil samples to send to the laboratory for detection, the online monitoring frequency is adjusted to 7 days once, and the laboratory detection data of the groundwater and soil samples show that the site characteristic VOC pollutants are detected, but do not exceed the groundwater quality standard, and the personnel of the monitoring area environmental protection department organize the personnel to carry out pollution investigation on the site.

[0075] The foregoing description of specific exemplary embodiments of the application has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the application to the precise form disclosed, and various modifications and variations are possible in light of the above teachings. It is intended that the embodiments be limited only by the claims. A variety of changes and modifications can be suggested by the above description, and it is intended that the application encompass such changes and modifications as fall within the scope of the claims. Any simple modifications, equivalent changes, and modifications based on the above-described exemplary embodiments should fall within the protection scope of the application.

Claims

1. A soil and groundwater VOC on-line monitoring device, characterized in that, The device comprises: a groundwater VOC collection unit, which heats a preset volume of groundwater collected in situ to boiling, and blows off VOC in the groundwater while the gas phase inside the liquid enters the upper part of the liquid surface during the process of volatilization of VOC in the groundwater; the groundwater VOC collection unit comprises a groundwater sampler, the middle part of which is a columnar hollow structure and the upper and lower ends of which are conical, for collecting and heating groundwater; the groundwater sampler is provided with a water level sensor arranged on the inner wall of the groundwater sampler, for monitoring the groundwater sampling water level; a groundwater heater arranged in the middle part of the groundwater sampler below the sampling water level; and a one-way valve arranged at the bottom of the groundwater sampler, for allowing groundwater to flow in one direction during sampling; a soil VOC collection unit, which heats soil around the aeration zone soil VOC monitoring well, and causes VOC in the soil to enter the gas phase through thermal desorption; a VOC online monitoring unit, which receives the groundwater VOC and soil VOC transmitted through the high-temperature heat tracing sampling pipe and detects the concentrations of the two respectively.

2. The soil and groundwater VOC on-line monitoring device according to claim 1, characterized in that, The groundwater VOC collection unit further comprises: an elevator, which lowers or raises the groundwater sampler to a predetermined height.

3. The soil and groundwater VOC on-line monitoring device according to claim 1, characterized in that, The high-temperature heat tracing sampling pipe for transmitting groundwater VOC is provided with: a first valve, which is used to control the discharge of gas in the groundwater sampler before sampling and after monitoring of groundwater VOC; a second valve, which is used to control the entry of heated VOC gas into the VOC online monitoring unit during monitoring of groundwater VOC.

4. The soil and groundwater VOC on-line monitoring device according to claim 1, characterized in that, The groundwater sampler is further provided with: a third valve, which is used to empty the sampled groundwater after monitoring of groundwater VOC.

5. The soil and groundwater VOC on-line monitoring device according to claim 1, characterized in that, The soil VOC collection unit comprises: a soil heater, which heats soil around the aeration zone soil VOC monitoring well; a soil VOC sampling head, which collects the gas phase VOC desorbed by heating of soil and transmits the gas phase VOC to the VOC online monitoring unit through the high-temperature heat tracing sampling pipe.

6. The soil and groundwater VOC on-line monitoring device according to claim 1, characterized in that, The online monitoring device further comprises: a control unit, which is used to control the heating, sampling process of the groundwater VOC collection unit and soil VOC collection unit, and transmission of the gas phase VOC heated to the VOC online monitoring unit.

7. The soil and groundwater VOC on-line monitoring device according to claim 1, characterized in that, The online monitoring device further comprises: a remote terminal, which receives VOC concentration monitoring data from the VOC online monitoring unit, compares and analyzes the data with background values, and outputs a preset level of early warning signal.

8. The soil and groundwater VOC on-line monitoring device according to claim 1, characterized in that, The VOC online monitoring unit is a PID gas detector.

9. A method for on-line monitoring of soil and groundwater VOCs, characterized by, The device as claimed in any one of claims 1 to 8 comprises the following steps: A. heating a preset volume of groundwater collected in situ in a monitoring target area to boiling, and blowing off VOC in the groundwater while the gas phase inside the liquid enters the upper part of the liquid surface during the process of volatilization of VOC in the groundwater; B. heating soil around the aeration zone soil VOC monitoring well in the monitoring target area, and causing VOC in the soil to enter the gas phase through thermal desorption; C. transmitting groundwater VOC and soil VOC through a high-temperature heat tracing sampling pipe and detecting the concentrations of the two respectively.

10. The method of claim 9, wherein the soil and groundwater VOCs are monitored on-line. The step A is further preceded by: A background area is determined upstream of the monitoring target area, and a maximum value is extracted from continuous detection values of groundwater VOC and soil VOC in the background area as a background value.

11. The method of claim 10, wherein the soil and groundwater VOCs are monitored on-line. The step C further comprises: The groundwater and soil VOC concentration monitoring data of the monitoring target area are compared and analyzed with the corresponding background value, and a preset level of early warning signal is output.

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