CN113772804B - Groundwater pollution monitoring natural attenuation restoration prediction method, system and device - Google Patents
Groundwater pollution monitoring natural attenuation restoration prediction method, system and device Download PDFInfo
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Abstract
The invention provides a method, a system and a device for nature attenuation repair prediction in underground water pollution monitoring, wherein the system comprises the following steps: the standard establishing module is used for establishing an MNA conceptual model of the polluted site and determining a monitoring target and an MNA control standard of the polluted site; the on-site monitoring network determines a monitoring position, a monitoring object, a monitoring index and a monitoring frequency based on the conceptual model so as to realize on-site monitoring of a polluted site; the evaluation module is used for evaluating the feasibility of the MNA repair technology through an indoor simulation test and field monitoring; if not, strengthening natural attenuation is carried out; and if the MNA is feasible, outputting a final MNA validity evaluation result. The method and the device realize effective prediction of groundwater pollution monitoring natural attenuation restoration, are simple to execute, can realize accurate prediction of medium and long periods, and greatly reduce time cost of evaluation.
Description
Technical Field
The invention belongs to the field of environmental remediation, and particularly relates to a method, a system and a device for monitoring and predicting natural attenuation remediation of underground water pollution.
Background
The Monitored Natural Attenuation (MNA) is a restoration method that reduces the concentration, total amount, toxicity, mobility and the like of pollutants in soil and underground water to acceptable risk levels within a reasonable time range according to the natural attenuation effects of physics, chemistry, biology and the like naturally occurring in a polluted site by implementing a planned monitoring strategy. Compared with other 'active' restoration technologies (physical, chemical or biological restoration), the method has the advantages of small interference on the underground environment, relatively low restoration cost and the like due to monitoring of natural attenuation, and is widely adopted, particularly for restoration of underground water pollution.
The natural attenuation process of pollutants in underground water comprises the following steps: firstly, carrying out solute physical migration process on underground water pollutants; the process of physical and chemical conversion of underground water pollutant; ③ the transformation process of the microbial degradation. The MNA needs to carry out long-term tracking and monitoring of natural attenuation effects so as to ensure that the natural attenuation effects of pollutants are consistent with the prediction. In the process, the evaluation basis for proving the technical feasibility and effectiveness of MNA comprises the following steps: (1) reduction of pollutant mass; (2) changes in geochemical indices (electron acceptor donors, characteristic products, alkalinity, etc.) characterizing microbial degradation; (3) change of microbial degradation flora. The 3 aspects can provide direct or powerful evidence for natural attenuation of pollutants independently or jointly, the evidence is mainly obtained by means of methods such as pollutant mass calculation, geochemical index analysis, stable isotope analysis, microbial molecular technology and the like at present, but the methods are trend analysis based on current data and lack scientific prediction of long-term repair effect, so that numerical simulation is very important for guiding MNA development.
At present, in the field of environmental remediation, water pollution conditions are usually judged according to certain measured key indexes, and an effective water environment remediation monitoring method is not formed.
Disclosure of Invention
In view of this, the present invention specifically provides the following technical solutions:
in one aspect, the invention provides a method for natural attenuation restoration and prediction in underground water pollution monitoring, which comprises the following steps:
s1, establishing an MNA conceptual model of the polluted site, and determining a monitoring target and an MNA control standard of the polluted site;
s2, constructing a field monitoring network based on the conceptual model, and carrying out field monitoring on the polluted site; the establishment of the monitoring network at least determines the monitoring position, the monitoring object, the monitoring index, the monitoring frequency and the like in the field monitoring of the polluted site so as to facilitate the acquisition of the subsequent actual measurement data and the trend judgment based on the acquired data;
s3, evaluating the feasibility of MNA repair technology through indoor simulation tests and field monitoring; if not, Enhanced Natural Attenuation (ENA) can be performed, if possible, go to step S4;
and S4, evaluating the effectiveness of the MNA.
Preferably, in S3, the feasibility of MNA repair technology is evaluated, including technical feasibility evaluation;
the technical feasibility assessment mode comprises the following steps: trend prediction based on presence data, or numerical simulation prediction.
Preferably, the numerical simulation prediction further comprises:
s31, constructing a three-dimensional geological model, carrying out mesh subdivision, and setting boundary conditions;
s32, setting relevant parameters of the geochemistry; the geochemical-related parameters may include, for example, permeability coefficient, porosity, temperature, pressure, water chemistry concentration, and the like;
s33, carrying out numerical simulation operation; the numerical simulation comprises: solute transport simulation, biodegradation simulation, and the like; in addition, during simulation operation, correction can be performed based on actual data, including correction for parameters in simulation;
s34, predicting the MNA effect; in the numerical simulation process, when the simulated particle concentration is smaller than a set target value, the requirement is considered to be met, and the recorded simulation time is used as the restoration effect prediction standard reaching time. Based on the prediction, whether the MNA meets the standard can be evaluated, so that the MNA is comprehensively guided to be developed.
Preferably, in S33, the solute transport simulation is performed by:
based on solute conservation, simulations were performed for a certain solute:
wherein the content of the first and second substances,
is the number of moles of ions in grid n at time k, V n Is the volume of the grid, A nm Is the contact area between the grids n and m,
is the flux of solute between the two grids,
in order to be a source and a sink,
is an ion adsorption term and is characterized in that,
is expressed as:
wherein ρ S Is the density of the pore medium, S l Is the liquid phase saturation, K d Is the ion linear distribution coefficient (ion content in solid phase/ion content in liquid phase), and phi is the porosity.
Preferably, in S33, the biodegradation simulation is performed by:
wherein, lambda is degradation coefficient (1/s), delta t is time step length,
is the number of moles of ions in the grid n at time k, V n Is the volume of the grid, A nm Is the contact area between the grids n and m,
is the flux of solute between the two grids,
is a source and sink item;
the degradation coefficient lambda is estimated as follows:
preferably, in S3, the feasibility of MNA repair technology is evaluated, and economic feasibility evaluation is also included; the economic feasibility assessment is based on time cost of contaminated site development and utilization, as well as cost, to determine whether monitoring natural attenuation techniques will achieve a contaminated remediation within a controllable remediation time or within an acceptable risk level.
Preferably, in S3, the feasibility of MNA repair technology is evaluated, and human health and environmental risk feasibility evaluations are also included. The assessment of human health and environmental risk comprises auditing site basic data, identifying all concerned pollutants and hazard effects thereof in the site, wherein the concerned pollutants and hazard effects of the concerned pollutants have potential risks to sensitive receptors such as people, surface water, drinking water source sites, ecological protection areas and the like, analyzing human health and environmental risk assessment areas, and determining assessment ranges and objects. And according to the current situation of the groundwater pollution and the simulation and prediction result, the evaluation area comprises the area where the groundwater pollution plume is located and the area potentially influenced by the pollution plume. And obtaining a risk evaluation result by adopting a related risk evaluation model, and demonstrating and monitoring the human health and the environmental risk feasibility of the natural attenuation technology.
Preferably, the trend prediction based on the presence data includes:
collecting primary evidence, intermediate evidence and high-grade evidence of a polluted site, and proving the situation of a natural attenuation process, thereby carrying out MNA technical feasibility evaluation;
the primary evidence comprises pollution change characteristics and pollution plume change trends;
the intermediate evidence comprises geochemical data including electron acceptor or donor data, characteristic product data, alkalinity data, and the like;
the high-level evidence includes quantitative microbiological analysis data, isotopic analysis data, and the like.
In addition, the invention also provides a system for monitoring, naturally attenuating, repairing and predicting the pollution of underground water, which comprises:
the standard establishing module is used for establishing an MNA conceptual model of the polluted site and determining a monitoring target and an MNA control standard of the polluted site;
the on-site monitoring network determines a monitoring position, a monitoring object, a monitoring index and a monitoring frequency based on the conceptual model so as to realize on-site monitoring of a polluted site;
the evaluation module is used for evaluating the feasibility of the MNA repair technology through an indoor simulation test and field monitoring; if not, the natural attenuation can be strengthened; and if the MNA is feasible, outputting a final MNA validity evaluation result.
Preferably, in the evaluation module, the feasibility of MNA repair technology is evaluated, including technical feasibility evaluation;
the technical feasibility assessment mode comprises the following steps: trend prediction based on current data, or numerical simulation prediction;
the numerical simulation prediction is realized by the following modes:
s31, constructing a three-dimensional geological model, carrying out mesh subdivision, and setting boundary conditions;
s32, setting relevant parameters of the geochemistry;
s33, carrying out numerical simulation operation; the numerical simulation comprises: solute transport simulation, biodegradation simulation, and the like;
s34, predicting the MNA effect; in the numerical simulation process, when the simulated particle concentration is smaller than a set target value, the requirement is considered to be met, and the recorded simulation time is used as the restoration effect prediction standard reaching time.
In addition, the invention also provides a device for monitoring, naturally attenuating, repairing and predicting the pollution of the underground water, which comprises a memory, a processor and a computer program which is stored in the memory and can run on the processor, wherein the processor realizes the steps of the method for monitoring, naturally attenuating, repairing and predicting the pollution of the underground water or carries the system for monitoring, naturally attenuating, repairing and predicting the pollution of the underground water when executing the computer program.
Compared with the prior art, the technical scheme of the invention realizes effective prediction of natural attenuation restoration aiming at groundwater pollution monitoring, is simple to execute, can be combined with measured values of a pollution site to carry out prediction correction, can realize accurate prediction of medium and long periods, guides and optimizes restoration implementation, realizes graded restoration of pollution according to prediction results, and greatly reduces time and economic cost aiming at natural attenuation restoration of groundwater pollution.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a flow chart of a method for monitoring natural attenuation according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a numerical simulation process according to an embodiment of the present invention;
FIG. 3 is a three-dimensional geological and grid subdivision of a study area according to an embodiment of the present invention;
FIG. 4 is a graph of a degradation factor simulation according to an embodiment of the present invention;
FIG. 5 is a graph showing the distribution of the concentration of volatile phenol in example 100 days;
FIG. 6 is a graph showing a distribution of volatile phenol concentration for 200 days in the example of the present invention;
FIG. 7 is a chart showing the 384-day volatile phenol concentration profile of example of the present invention;
FIG. 8 is a graph showing the distribution of the concentration of volatile phenol in 800 days according to example of the present invention;
FIG. 9 is a graph showing a graph of the concentration of volatile phenol in example 1000 days;
FIG. 10 is a graph showing the distribution of the volatile phenol concentration for 1200 days in the example of the present invention;
FIG. 11 is a graph showing the distribution of the volatile phenol concentration for 1500 days in the example of the present invention;
FIG. 12 is a graph showing the change in the concentration of volatile phenol at the observation points of the mild and moderate contamination zones in the example of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be understood that the described embodiments are only some embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be appreciated by those of skill in the art that the following specific examples or embodiments are a series of presently preferred arrangements of the invention to further explain the principles of the invention, and that such arrangements may be used in conjunction or association with one another, unless it is expressly stated that some or all of the specific examples or embodiments are not in association or association with other examples or embodiments. Meanwhile, the following specific examples or embodiments are only provided as an optimized arrangement mode and are not to be understood as limiting the protection scope of the present invention.
Example 1
In a specific embodiment, shown in fig. 2 and fig. 1, the invention provides a method for monitoring natural attenuation remediation of underground water pollution, and simulation and effect prediction are performed in combination with a numerical simulation mode.
The invention is realized by the following technical method:
firstly, establishing an MNA conceptual model of a polluted site, and primarily determining a monitoring target and an MNA control standard of the site;
the MNA conceptual model is defined as a concept model of the polluted site, which comprises all data and information related to the polluted site, such as basic information of the site, geological and hydrogeological conditions, pollution sources, history, distribution, degree, migration paths, possible pollution exposure media, paths and potential pollution receptors, and sets monitoring targets and MNA control standards of the polluted site based on the concept model of the polluted site. The MNA control standard is a risk control target of a polluted site.
Secondly, constructing a field monitoring network according to the MNA conceptual model, wherein the field monitoring network comprises monitoring positions, monitoring objects, monitoring indexes, monitoring frequency and the like; subsequently, the feasibility of MNA repair technology is evaluated through indoor simulation experiments and field monitoring, and if the MNA repair technology is not feasible, Enhanced Natural Attenuation (ENA) can be performed; finally, the effectiveness of the MNA was evaluated and rated.
The MNA feasibility assessment comprises technical feasibility assessment, economic feasibility assessment and human health and environmental risk feasibility assessment.
1. Assessment of technical feasibility
The evaluation basis for confirming the technical feasibility and effectiveness of MNA comprises the following steps: (1) reduction of pollutant mass; (2) changes in geochemical indices (electron acceptor donors, characteristic products, alkalinity, etc.) characterizing microbial degradation; (3) change of microbial degradation flora. The 3 aspects can provide direct or strong evidence for natural attenuation of pollutants individually or jointly, and the evidence is mainly obtained by means of pollutant mass calculation, geochemical index analysis, stable isotope analysis, microbial molecular technology and the like at present.
The evaluation of the feasibility and the effectiveness of the MNA can be carried out by analyzing and evaluating the trend through the current data and judging and evaluating the trend change by collecting the different types of data, and the evidence can be divided into 3 stages of primary evidence, intermediate evidence and advanced evidence: the primary evidence comprises evaluation of pollution change characteristics and pollution plume change trends, and can directly indicate that natural attenuation occurs; the intermediate evidence consists of geochemical data and can indirectly indicate that the natural attenuation process occurs in the field; advanced evidence, involving quantitative analysis of microorganisms and isotopic analysis, can serve as strong, auxiliary evidence to demonstrate that natural decay processes are occurring.
In addition to the above trend analysis and evaluation based on the current data, in a more preferred embodiment, the technical feasibility prediction can be performed by using a numerical simulation prediction method, and the main flow is as shown in fig. 2. Firstly, a three-dimensional geological model is constructed, a grid is subdivided, boundary conditions are set, then relevant parameters (such as permeability coefficient, porosity, temperature, pressure, water chemical component concentration and the like) of a geological and chemical system are set, then the model is operated, actual data are utilized for correction, finally, MNA effect is predicted and analyzed, and MNA is comprehensively guided to be developed.
(1) Solute transport simulation
The solution based on the integral finite difference can be expressed for a certain solute conservation as:
wherein
Is the number of moles of ions in the grid n at time k, V n Is the volume of the grid, A nm Is the contact area between the grids n and m,
is the flux of solute between the two grids,
in order to be a source and a sink,
is an ion adsorption term expressed as:
ρ S is the density of the pore medium, S l Is the liquid phase saturation, K d Is the ion linear distribution coefficient (ion content in solid phase/ion content in liquid phase), and phi is the porosity.
(2) Biodegradation simulation
In the natural attenuation process, biodegradation reaction mainly occurs, and the biodegradation process adopts the following simulation mode:
where λ is the degradation coefficient (1/s) and Δ t is the time step. The degradation coefficient lambda is an important parameter, and the estimation method comprises the following steps:
(3) iterative solution
In the simulation process, when the simulated ion concentration is smaller than a set target value, the simulation time is recorded and judged as the restoration effect prediction standard reaching time, and the simulation result is considered to be in line with the requirement.
2. Economic feasibility assessment
The economic feasibility of the monitoring natural attenuation technology can be evaluated only by comprehensively knowing the cost composition of the implementation of the monitoring natural attenuation technology. The main cost items of the monitoring natural attenuation technology comprise long-term monitoring system operation and maintenance cost, sample detection cost, information collection cost, test result research and analysis cost, potential land cost of a monitoring attenuation repair site and the like.
When economic feasibility is evaluated, time cost of development and utilization of a polluted site needs to be fully analyzed, and whether pollution restoration can reach the standard or be controlled within an acceptable risk level of a development and utilization land or not by a natural attenuation technology is monitored within controllable restoration time.
3. Human health and environmental risk feasibility assessment
The human health and the environmental risk can be accepted as the final target of implementing the monitoring natural attenuation technology, and the evaluation project of quality control in the whole process of repair design, construction and acceptance inspection is required. And auditing site basic data, identifying all concerned pollutants with potential risks to sensitive receptors such as people, surface water, drinking water source sites, ecological protection areas and the like in the site and the hazard effects thereof, analyzing body health and environmental risk assessment areas, and determining assessment ranges and objects. According to the current situation of groundwater pollution and the result of simulation and prediction, the health risk assessment area should include the area where groundwater pollution plume is located and the area potentially affected by the pollution plume. And obtaining a risk evaluation result by adopting a relevant risk evaluation model, and demonstrating and monitoring the human health and the environmental risk feasibility of the natural attenuation technology. The risk assessment model can adopt a mature model in the prior art to perform assessment calculation, and details are not repeated here.
In another specific embodiment, the technical solution of the present invention can also be implemented by a system, and the present invention further provides a system for natural attenuation restoration prediction in groundwater pollution monitoring, the system including:
the standard establishing module is used for establishing an MNA conceptual model of the polluted site and determining a monitoring target and an MNA control standard of the polluted site;
the on-site monitoring network determines a monitoring position, a monitoring object, a monitoring index and a monitoring frequency based on the conceptual model so as to realize on-site monitoring of a polluted site;
the evaluation module is used for evaluating the feasibility of the MNA repair technology through an indoor simulation test and field monitoring; if not, the natural attenuation can be strengthened; and if the result is feasible, outputting a final MNA validity evaluation result.
It should be noted here that, the module arrangement of the system described above can be appropriately adjusted or subdivided by those skilled in the art according to the requirements on the platform or hardware architecture carried by the system, and these adjustments or repartitions do not affect the implementation of the original basic functions, and the adjustment or sufficient partitioning manner of the module should also be considered to fall within the protection scope of the present application.
In order to further realize the basic functions of the system, in the evaluation module, the feasibility of MNA repair technology is evaluated, including technical feasibility evaluation;
the technical feasibility assessment mode comprises the following steps: trend prediction based on current data, or numerical simulation prediction;
the numerical simulation prediction is realized by the following modes:
s31, constructing a three-dimensional geological model, carrying out mesh subdivision, and setting boundary conditions;
s32, setting relevant parameters of the geochemistry;
s33, carrying out numerical simulation operation; the numerical simulation comprises: solute transport simulation and biodegradation simulation;
s34, predicting the MNA effect; in the numerical simulation process, when the simulated particle concentration is smaller than a set target value, the requirement is considered to be met, and the recorded simulation time is used as the restoration effect prediction standard reaching time.
In the technical feasibility prediction by a numerical simulation mode, the main simulation mode comprises the following steps:
(1) solute transport simulation
The solution based on the integral finite difference can be expressed for a certain solute conservation as:
wherein
Is the number of moles of ions in the grid n at time k, V n Is the volume of the grid, A nm Is the contact area between the grids n and m,
is the flux of solute between the two grids,
in order to be a source and a sink,
is an ion adsorption term expressed as:
ρ S is the density of the pore medium, S l Is the liquid phase saturation, K d Is the ion linear distribution coefficient (ion content in solid phase/ion content in liquid phase), and phi is the porosity.
(2) Biodegradation simulation
In the natural attenuation process, biodegradation reaction mainly occurs, and the biodegradation process adopts the following simulation mode:
where λ is the degradation coefficient (1/s) and Δ t is the time step. The degradation coefficient lambda is an important parameter, and the estimation method comprises the following steps:
(3) iterative solution
In the simulation process, when the simulated ion concentration is smaller than a set target value, the simulation time is recorded and judged as the restoration effect prediction standard reaching time, and the simulation result is considered to be in line with the requirement.
Through the technical feasibility prediction, the natural attenuation restoration effect of underground water pollution can be evaluated based on the collected historical data and the like, and basic model parameters related in numerical simulation are corrected by combining part of synchronous data collected on the spot, so that a more accurate prediction result is obtained.
In addition, in a further embodiment, the feasibility assessment of the MNA further comprises economic feasibility assessment, human health and environmental risk feasibility assessment.
In another embodiment, the technical solution of the present invention may also be implemented by a groundwater pollution monitoring natural attenuation restoration prediction apparatus, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the groundwater pollution monitoring natural attenuation restoration prediction method described above when executing the computer program, or is equipped with a groundwater pollution monitoring natural attenuation restoration prediction system described above.
Example 2
In this example, the specific implementation of the inventive protocol will be described in conjunction with a field trial example of the inventive protocol. Taking an example of volatile phenol pollution of underground water of a certain place in North China as an example, the feasibility evaluation of the monitoring natural attenuation technology is carried out by using numerical simulation aiming at a moderate pollution area (the volatile phenol concentration is more than or equal to 0.5mg/L) and a light pollution area (the volatile phenol concentration is more than or equal to 0.002mg/L), and the model correction is carried out by combining sampling analysis of 18 underground water monitoring wells, so that the technical route of repair is optimized.
1. Three-dimensional geological model construction and boundary condition setting
A three-dimensional geological model with the length of 100m, the width of 80m and the thickness of 50m is established according to a research area. The requirements of the area, the calculation efficiency and the precision of the research area are comprehensively considered, the simulation adopts an irregular splitting method, and the three-dimensional geological model is spatially dispersed into 16800 grids and 54349 connections, as shown in fig. 3.
According to the condition of a region of interest, setting a class boundary with a fixed water head on the southeast side of the region of interest, namely the upstream of the ground water flow direction; and the downstream of the groundwater flow direction, namely the northwest direction, is also set as a type of boundary with a fixed water head; on the east and west sides of the study area, two types of boundaries with zero flux were set, due to approximately parallel ground water flow direction; at the bottom of the model, because the model is positioned below a confined aquifer and mainly comprises fine sand and lacks corresponding hydrogeological parameters, a water-resisting boundary with zero flux is set in the simulation process; at the top of the model, due to the lack of evaporation rainfall data and the short simulation time, the data are ignored in the simulation process. In order to obtain an underground water flow field with a fixed flow rate, the pressure was set to 2.0 atmospheres at the time of setting the boundary conditions on the south-east side, according to the difference in elevation of the underground water level on the south-east and north-west sides, and was kept constant.
2. Geological and chemical system parameter settings
The first layer in the research area is mainly a silt aquifer, and the permeability is 5.97 multiplied by 10 -14 m 2 An average porosity of about 0.42 and a permeability of 5.97X 10 in the horizontal and vertical directions, respectively -14 m 2 And 1.66X 10 -14 m 2 。
In the simulation process, the temperature change is not involved, so the simulation process is kept constant. The temperature of the entire study area was set to 20.0 ℃ based on the study area data. The initial pressure of the other areas except for the boundary conditions was set to 1.0 atmosphere.
The chemical initial components of moderately polluted water and slightly polluted water are set as shown in the table 1 through the detection and analysis of underground water samples.
TABLE 1 initial Water chemistry (mol/L)
| Chemical ions | Moderate pollution | Slight pollution |
| H + | 1.0×10 -7 | 1.0×10 -7.5 |
| Cl - | 9.66×10 -4 | 0.00845 |
| Ca 2+ | 0.0043 | 0.0059 |
| Mg 2+ | 0.00405 | 0.0043 |
| Na + | 0.0075 | 0.00826 |
| K + | 1.2×10 -4 | 4.9×10 -4 |
| HCO 3 - | 0.0172 | 0.0158 |
| Volatile phenols | 5.36×10 -6 | 6.9×10 -8 |
3. Model operation and correction
In order to describe the biodegradation process of the volatile phenol, the biodegradation coefficients are mainly used for comprehensive generalization in the simulation process, and the actual measured value and the empirical value of the site are used for correction, as shown in fig. 4. In the simulation, 6 different degradation coefficients were set, i.e., λ 1 ═ 10.0e-8s -1 ,λ2＝8.0e-8s -1 ,λ3＝5.0e-8s -1 ,λ4＝4.0e-8s -1 ,λ5＝3.5e-8s -1 ,λ6＝3.0e-8s -1 . The field measured values show that the volatile phenol concentration is 0.065mg/L in 12-month and 8-month of 2020, and the volatile phenol concentration is reduced to 0.023mg/L (2.44mol/L) in 03-month and 01-month of 2021 for about 82 days. When the degradation coefficient is 3.5e-8s -1 Time, the volatile phenol concentration at 82 days was simulatedThe fitting with the measured value is good, so that the degradation coefficient in the later simulation process adopts 3.5e-8s -1 And (6) performing prediction.
4. Analysis of simulation results
With reference to fig. 5 to 11, the simulation time is set to 10 years, it takes 113.09 seconds, and the simulation results are shown in fig. 5 to 11 after 54 iterations.
When the operation is carried out for 1500 days, the concentration of volatile phenol in the pollution plume is completely reduced to 2.13 multiplied by 10 -8 mol/L (0.002mg/L) or less.
A monitoring point is selected in the medium pollution area and the light pollution area respectively, and the degradation condition of volatile phenol is observed, as shown in figure 12.
The predicted results in FIG. 12 show that the concentration of volatile phenol in groundwater in a moderately contaminated area can be reduced to the standard value of 2.13X 10 after about 3.2 years -8 mol/L (less than 0.002mg/L), while the lightly contaminated zone may fall below the standard after about 2.3 years.
Because the progress requirement of the area is that the repair reaches the standard within 3 years, the simulation evaluation analysis is combined, the repair technical route is optimized to be a slightly polluted area and the natural attenuation repair is adopted, and other active repair measures are adopted to strengthen the repair in a moderately polluted area.
It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above may be implemented by a computer program, which may be stored in a computer readable storage medium and executed by a computer to implement the processes of the embodiments of the methods described above. The storage medium may be a magnetic disk, an optical disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), or the like.
The above description is only for the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (5)
1. A groundwater pollution monitoring natural attenuation restoration prediction method is characterized by comprising the following steps:
s1, establishing an MNA conceptual model of the polluted site, and determining a monitoring target and an MNA control standard of the polluted site;
s2, constructing a field monitoring network based on the conceptual model, and carrying out field monitoring on the polluted site;
s3, evaluating the feasibility of MNA repair technology through indoor simulation tests and field monitoring; if not, strengthening natural attenuation is carried out, if feasible, turning to step S4;
s4, evaluating the effectiveness of MNA;
in the step S3, assessing the feasibility of the MNA repair technology, including technical feasibility assessment;
the technical feasibility assessment mode comprises the following steps: performing numerical simulation prediction;
the numerical simulation prediction further comprises:
s31, constructing a three-dimensional geological model, carrying out mesh subdivision, and setting boundary conditions;
s32, setting relevant parameters of the geochemistry;
s33, carrying out numerical simulation operation; the numerical simulation comprises: solute transport simulation and biodegradation simulation;
s34, predicting the MNA effect; in the numerical simulation process, when the simulated particle concentration is smaller than a set target value, the requirement is considered to be met, and the recorded simulation time is used as the restoration effect prediction standard reaching time;
in S33, the solute transport simulation is performed by:
based on solute conservation, simulations were performed for a certain solute:
wherein the content of the first and second substances,
is the number of moles of ions in the grid n at time k, V n Is the volume of the grid, A nm Is the contact area between the grids n and m,
is the flux of solute between the two grids,
in order to be a source and a sink,
is an ion adsorption term and is characterized in that,
is expressed as:
wherein ρ s Is the density of the pore medium, S l Is the liquid phase saturation, K d Is the ion linear distribution coefficient, phi is the porosity;
in S33, the biodegradation simulation is performed by:
wherein, lambda is degradation coefficient (1/s), delta t is time step length,
is the number of moles of ions in the grid n at time k, V n Is the volume of the grid, A nm Is the contact area between the grids n and m,
is the flux of solute between the two grids,
is a source and sink item;
the degradation coefficient lambda is estimated as follows:
2. the method of claim 1, wherein in S3, assessing the feasibility of MNA repair techniques further comprises an economic feasibility assessment; the economic feasibility assessment is based on the time cost and the expense cost of the development and utilization of the polluted site, and whether the pollution can be repaired to reach the standard or be within an acceptable risk level by monitoring the natural attenuation technology in a controllable repairing time is judged.
3. The method of claim 1, wherein in S3, the feasibility of MNA repair techniques is evaluated, and the feasibility evaluation of human health and environmental risk is further included.
4. An apparatus for performing the groundwater pollution monitoring natural decay remediation prediction method of claim 1, the apparatus comprising:
the standard establishing module is used for establishing an MNA conceptual model of the polluted site and determining a monitoring target and an MNA control standard of the polluted site;
the on-site monitoring network determines a monitoring position, a monitoring object, a monitoring index and a monitoring frequency based on the conceptual model so as to realize on-site monitoring of a polluted site;
the evaluation module is used for evaluating the feasibility of the MNA repair technology through an indoor simulation test and field monitoring; if not, strengthening natural attenuation is carried out; and if the MNA is feasible, outputting a final MNA validity evaluation result.
5. A groundwater contamination monitoring natural attenuation remediation prediction device, the device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: the processor, when executing the computer program, realizes the steps of the groundwater pollution monitoring natural attenuation remediation prediction method according to any one of claims 1 to 3.
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