Detection method of groundwater-soil coupled pollution in marine engineering sites under tidal action

Abstract

The present invention belongs to the technical field of pollution monitoring. The present invention is a method for detecting groundwater-soil coupled pollution in marine engineering sites under the action of tides, which includes: arranging groundwater monitoring stations at surrounding points, and automatically sampling and testing groundwater based on a time sequence, so as to obtain a detection data set. Based on the detection data set, the pollution source plant area is judged according to the water level change sequence and the time sequence of changes in pollutant concentration detected by the groundwater monitoring station, and the tidal law; and then the total amount of pollutants in the pollution source plant area is calculated by the fluid motion equation and the convection-diffusion equation. The pollution source plant area and the total amount of pollutants are output as the result of detecting groundwater-soil coupled pollution in the plant area. The present invention solves the water level change sequence, and then judges the pollution source plant area according to specific laws; and calculates the total amount of pollutants by combining the fluid motion equation and the convection-diffusion equation, providing a new solution to solve the method of detecting groundwater-soil coupled pollution in nearshore plant areas, and providing technical support for the investigation and control of groundwater pollution in plant areas.

Description

Technical Field

[0001] The invention belongs to the technical field of pollution monitoring, and in particular relates to a method for detecting underground water-soil coupled pollution in an ocean engineering site under tidal action. Background Art

[0002] With the rapid development of industry, the problem of groundwater pollution in factory areas has become increasingly serious, posing a huge threat to the environment and human health.

[0003] At present, in order to effectively control pollution problems, people are gradually increasing monitoring of factory areas, including but not limited to irregular spot checks and the establishment of permanent detection methods. Among them, erroneous emissions caused by illegal emissions or human errors have strong timeliness and concealment, making pollution monitoring very difficult. Furthermore, since groundwater pollution is also diffusible, and has a long impact period on surrounding areas, and has a coupling effect with the surrounding soil, it is not conducive to real-time monitoring. Therefore, in order to effectively monitor the pollution of groundwater and soil, it is proposed in the prior art that pollutants can be monitored for nearshore factory areas by utilizing the impact of tidal fluctuations on groundwater.

[0004] At present, the impact of tidal fluctuations on groundwater has been widely studied. This natural phenomenon can not only reveal the flow and storage characteristics of groundwater, but also reflect the interaction between groundwater, surface water and soil. However, there are still some technical problems to be solved in the application of this technology in pollution monitoring, such as:

[0005] 1. How to identify the pollution source plant (the plant that emits pollutants) through monitoring data;

[0006] 2. How to confirm the amount of pollutant emissions through monitoring.

[0007] In summary, it is also necessary to design a method based on tidal laws that can use groundwater to detect factory pollution, so as to investigate groundwater pollution affected by tides and provide a new solution for groundwater pollution monitoring and supervision in factory areas. Summary of the invention

[0008] In view of the problems existing in the prior art, the present invention provides a method for detecting underground water-soil coupled pollution in an ocean engineering site under tidal action to solve the above problems.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] The present invention provides a method for detecting underground water-soil coupled pollution in an ocean engineering site under tidal action, the steps comprising:

[0011] Groundwater monitoring stations were set up at points around multiple plant sites near the coast;

[0012] The groundwater monitoring station automatically samples and tests groundwater based on a time sequence, and forms a detection data set with the detection results, groundwater level and groundwater flow rate based on the sampling time;

[0013] Based on the detection data set of each point, the water level changes of the multiple plant areas are sorted to obtain a water level change sequence; the pollution source plant area is determined according to the water level change sequence and the time sequence of the change of pollutant concentration detected by the groundwater monitoring station, and the tidal law;

[0014] Based on the detection data sets of each point, the groundwater velocity field and the pollutant concentration field of the pollution source plant area are calculated by the fluid motion equation and the convection-diffusion equation, and the total amount of pollutants is calculated based on the groundwater velocity field and the pollutant concentration field;

[0015] The pollution source plant area and the total amount of pollutants are output as the result of detecting the coupled pollution of underground water and soil in the plant area.

[0016] Optionally, the groundwater monitoring station is equipped with a flow meter and a water level meter, and the groundwater monitoring station stores the sampled samples;

[0017] The groundwater monitoring stations take samples periodically, and the sampling time of each groundwater monitoring station is synchronized.

[0018] Optionally, the water level change sorting of the multiple plant areas includes:

[0019] Sorting the points in order of response of the groundwater level based on the tidal cycle;

[0020] According to the geographical location and order of each point, the tidal impact path is obtained by fitting;

[0021] The center point of each plant area is projected onto the tidal impact path to obtain the projection point of each plant area, and the water level change sequence is obtained based on the projection point and the direction of the tidal impact path.

[0022] Optionally, the fluid motion equation is the Navier-Stokes equation, and the equation formula is:

[0023] ;

[0024] In the formula, is the groundwater density, p is the groundwater pressure, v is the groundwater flow velocity, g is the acceleration due to gravity, is the dynamic viscosity of groundwater.

[0025] Optionally, it also includes: based on the discretized Navier-Stokes equations, through the time step The groundwater velocity field is obtained by iterative calculation, and the formula is:

[0026] ;

[0027] In the formula, n Represents the iteration number;

[0028] The time step discretization formula is: ;

[0029] In the formula, is the sampling time when the pollutant is detected at the point, is the time when the pollutant disappears for the first time after the pollutant is detected continuously at the point. N is a natural number greater than or equal to 2.

[0030] Optionally, the calculation formula for the groundwater velocity field is: ;

[0031] In the formula, for Time corresponds to spatial position The flow velocity at the point.

[0032] Optionally, the method further includes: calculating the groundwater flow rate during the pollution period based on the groundwater flow velocity field, and bringing the groundwater flow rate into the pollutant concentration field to solve for the total amount of pollutants.

[0033] Optionally, the convection-diffusion equation is established, and the formula is:

[0034] ;

[0035] In the formula, is the diffusion coefficient, is the pollutant concentration; is the source term of the equation, is the spatial coordinate of the point, is the sampling time.

[0036] Optionally, based on the discretization of the convection-diffusion equation, the time step The pollutant concentration field is obtained by iterative calculation, and the formula is:

[0037] ;

[0038] In the formula, n represents the iteration number, is the time when the pollutant disappears for the first time after the pollutant is detected continuously at the point. Corresponding to the spatial position When pollutants are detected at the point, the pollutant concentration is N is a natural number greater than or equal to 2.

[0039] Optionally, the time step discretization formula is: ;

[0040] In the formula, The sampling time for detecting the presence of pollutants at the point.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] The present invention solves the water level change sequence, and then determines the pollution source plant area according to the tidal law and the time sequence of pollutant concentration changes; combines the fluid motion equation and the convection-diffusion equation to calculate the total amount of pollutants, and then provides a new solution to the problem of groundwater-soil coupled pollution detection in nearshore plant areas, which can provide technical support for groundwater pollution investigation and control in plant areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0044] Figure 1 is a flow chart of the method of the present invention;

[0045] Figure 2 It is a scene illustration diagram in a specific embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0048] It should also be noted that the methods used in the present invention are all conventional methods unless otherwise specified; the raw materials and devices used are all conventional commercially available products unless otherwise specified.

[0049] The present invention provides a Figure 1 The detection method of groundwater-soil coupled pollution in marine engineering sites under tidal action is mainly used to investigate groundwater pollution in factories and enterprises affected by tidal action. It mainly investigates the source and status of groundwater pollution. Its main steps include:

[0050] Generally, in nearshore scenarios, there is rarely a single factory area. Usually, there are multiple factory areas in the form of development zones, and there may also be multiple enterprises in the factory area. Therefore, this embodiment needs to build the hardware conditions required for detection, that is, to deploy groundwater monitoring stations at points around multiple nearshore factory areas;

[0051] The groundwater monitoring station in this embodiment can adopt a conventional design, and add a water level meter and a flow meter in the water well to monitor the changes in groundwater level and flow rate. At the same time, the monitoring station is also equipped with a warehouse and a water storage container to seal the water sampled each time for later verification or traceability to retain evidence.

[0052] Therefore, the preset groundwater monitoring station automatically samples and tests groundwater based on time sequence, that is, sampling is performed at equal time intervals during the period of periodic sampling at the groundwater monitoring station, and the sampling time of each groundwater monitoring station is synchronized within the same tidal influence range, that is, sampling is performed at the same time. Afterwards, the corresponding test results, groundwater level and groundwater flow rate in a sampling time are combined and recorded, and the sampling time is attached to form the test data, and then the test data in a tidal cycle (including high tide-low tide) are merged to form the corresponding test data set.

[0053] Based on the detection data sets of the aforementioned various points, the water level changes of multiple plant areas are sorted. Specifically, the points are sorted in the order of response of the groundwater level based on the tidal cycle; Figure 2 As shown in the figure, it is assumed that there are three plant areas α, β, and γ, and a point is set up around each plant area and a groundwater monitoring station is installed. The three plant areas are all located in the same tidal range of groundwater. Experiments have shown that the rise and fall of tides will affect the change of groundwater levels, so the groundwater situation can be judged by the tides. However, due to the complexity of the distribution of groundwater in the stratigraphic structure, it is impossible to judge the distribution status based on the distance from the ocean. Therefore, it is necessary to first determine the order of groundwater flow through the three points to determine the flow pattern of groundwater between the three points under the action of tides.

[0054] Furthermore, before and after any tidal rise and fall, since the change of groundwater level is affected by the tide with a certain lag, automatic time-series sampling is performed at the same time point. At this time, three sets of flow velocity data of the same time period at different points will be obtained. These flow velocity data are 0 when there is no water flow, and the flow velocity will be displayed when there is water flow. If the groundwater level does not change with the tide at this time, it will always be 0; if the groundwater level changes with the tide at this time, the water level and speed of the point will begin to change. If there is a point where the flow velocity is not 0 and the water level rises during high tide, it means that this point is affected by high tide. Therefore, according to the order of the points affected by the tide, the ranking is obtained [plant area α, point 11], [plant area β, point 12], [plant area γ, point 13] (the front point represents the first point affected by the tide).

[0055] According to the geographical location and order of each point, the tidal impact path is obtained by fitting; specifically, the location of each point (such as longitude and latitude) is marked on the plane map, and multiple points on the plane map are fitted according to the specified above order through spline interpolation algorithm or polynomial fitting method to obtain a curve, that is, the tidal impact path. After that, the center point of each plant area is mapped to the tidal impact path, that is, the point on the curve closest to the center point is found. This point is the projection point of the center point on the curve, so as to obtain the mapping point of each plant area, and the water level change sequence is obtained based on the mapping point and the direction of the tidal impact path.

[0056] The water level change sequence obtained is combined with the time sequence of pollutant concentration changes detected by the groundwater monitoring station and the tidal law to determine the pollution source plant area; for example: assuming that Figure 2 As shown, when the tide changes, the pollution concentration of samples in the same time period is determined. It is known that the water level change sequence is [factory area α], [factory area β], [factory area γ]. If the pollution concentration change time of area α is later than that of area β, and the pollution concentration change time of area γ is earlier than that of area β, it can be judged that the pollution source comes from area γ; if the pollution concentration change time of area α is later than that of area β, and the pollution concentration change time of area γ is also later than that of area β, it can be judged that area β is a polluted area. By analogy, by comparing the relationship between the change time of pollutant concentration in water samples after a certain tidal rise and fall, the pollution source plant area can be judged.

[0057] Based on the detection data set of each point, the groundwater velocity field and pollutant concentration field of the pollution source plant area are calculated through the fluid motion equation and convection-diffusion equation, and the total amount of pollutants is calculated based on the groundwater velocity field and pollutant concentration field.

[0058] The location of a water intake point in the polluted area of ​​the factory is The measured groundwater flow velocity is v , the pollutant concentration is , the groundwater density is , the diffusion coefficient is ; is the sampling time, and At this sampling moment, pollutants are detected at the point, and the sampling moment when the pollutants disappear after the point is continuously detected is recorded as , and the time period during which the pollutant is detected is .

[0059] The above-mentioned plant area can invert the actual total flow and total pollution of groundwater through water samples obtained from the water sampling tank. Specifically, the fluid motion equation selected in this embodiment is the Navier-Stokes equation, and the formula is:

[0060] ;

[0061] In the formula, is the groundwater density, p is the groundwater pressure, v is the groundwater flow velocity, g is the acceleration due to gravity, is the dynamic viscosity of groundwater.

[0062] Thus, the velocity field is calculated by iteratively calculating the time step using the discretized Navier-Stokes equations. v . Let the time step be , then the above formula can be obtained as the iterative formula:

[0063] ;

[0064] In the formula, n Represents the iteration number; The force applied to the fluid is external, namely gravity.

[0065] In order to derive the flow velocity formula within the overall time, the time is discretized into N time steps, so the time step discretization formula is: ;

[0066] In the formula, is the sampling time when the pollutant is detected at the point, is the time when the pollutant disappears for the first time after the pollutant is detected continuously at the point. N is a natural number greater than or equal to 2.

[0067] Further, the above formula can be rearranged as:

[0068] ;

[0069] The overall flow rate can be expressed as the result after multiple iterations:

[0070] ,

[0071] In the formula, for Time corresponds to spatial position The flow velocity at the point.

[0072] Furthermore, the groundwater flow rate during the pollution period was calculated based on the groundwater velocity field. Q It is the volume flow rate of the entire water body passing through a certain cross section in a certain period of time. The flow rate can be obtained by integrating the velocity field, and the flow rate can be expressed as: ;

[0073] In the formula, i is the ordinal number of the point in the polluted area, n` is the unit normal vector of the boundary surface, dS is the area element on the boundary surface, is the area of ​​the boundary surface.

[0074] Substituting the above velocity field into the groundwater flow formula, we get: ;

[0075] In the formula, A. B is a replacement quantity used to represent the contents of the equation group.

[0076] The convection-diffusion equation describing the transport of pollutants is established, and the formula for its expansion calculation is: ;

[0077] In the formula, is the diffusion coefficient, is the pollutant concentration; is the source term of the equation, is the spatial coordinate of the point, is the sampling time.

[0078] Therefore, the fluid area corresponding to the point is discretized into grid points through a discretization method, and the discretized numerical integration formula is used for iterative calculation and solution.

[0079] Furthermore, the concentration field is calculated by iteratively calculating the time step using the discretized convection-diffusion equation. c for: ;

[0080] In the numerical solution, the discretization method is used, and the concentration c In time t 0The initial conditions are (corresponding to the spatial position Pollutant concentration when pollutants are detected at the point):

[0081] ;

[0082] After multiple time step iterations, the overall concentration is n Moment After multiple iterations, the expression is sorted into:

[0083] ;

[0084] Total amount of pollutants M is the total amount of pollutants in the entire water body within a certain period of time. The overall volume of the three-dimensional area of ​​pollution measurement is given as V , the pollution amount can be obtained by integrating the concentration field, the formula is:

[0085] ;

[0086] For a discretized grid, summing the concentrations over all grid cells yields:

[0087] ;

[0088] In the formula, j Represents the ordinal number of the discretized grid cell.

[0089] Substituting the previously obtained concentration relationship into the overall pollution amount formula, we can get the overall pollution amount formula as follows: ;

[0090] In the formula, E. F is a replacement quantity used to represent the contents of the equation group.

[0091] Therefore, the total amount of single pollutant emissions can be obtained through source tracing calculations. Combined with the aforementioned pollution source plant area, the pollution situation can be accurately and quickly obtained, and the pollution source plant area and the total amount of pollutants can be used as the output results of detecting the coupled pollution of groundwater and soil in the plant area and fed back to relevant departments.

[0092] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for detecting groundwater-soil coupled pollution in marine engineering areas under tidal action, characterized in that the steps include: Groundwater monitoring stations were set up at points around multiple plant sites near the coast; The groundwater monitoring station automatically samples and tests groundwater based on a time sequence, and forms a detection data set with the detection results, groundwater level and groundwater flow rate based on the sampling time; Based on the detection data set of each point, the water level changes of the multiple plant areas are sorted to obtain a water level change sequence; the pollution source plant area is determined according to the water level change sequence and the time sequence of the change of pollutant concentration detected by the groundwater monitoring station, and the tidal law; Based on the detection data sets of each point, the groundwater velocity field and the pollutant concentration field of the pollution source plant area are calculated by the fluid motion equation and the convection-diffusion equation, and the total amount of pollutants is calculated based on the groundwater velocity field and the pollutant concentration field; The fluid motion equation is the Navier-Stokes equation, and the equation formula is: ； In the formula, is the groundwater density, p is the groundwater pressure, v is the groundwater flow velocity, g is the acceleration due to gravity, is the dynamic viscosity of groundwater; The fluid motion equation is the Navier-Stokes equation, and the equation formula is: ； In the formula, is the groundwater density, p is the groundwater pressure, v is the groundwater flow velocity, g is the acceleration due to gravity, is the dynamic viscosity of groundwater; Also includes: Based on the discretized Navier-Stokes equations, the time step The groundwater velocity field is obtained by iterative calculation, and the formula is: ； In the formula, n Represents the iteration number; The time step discretization formula is: ； In the formula, is the sampling time when the pollutant is detected at the point, is the time when the pollutant disappears for the first time after the pollutant is detected continuously at the point. N is a natural number and is greater than or equal to 2; The calculation formula of the groundwater velocity field is: ； In the formula, for Time corresponds to spatial position The flow rate at the point; It also includes: calculating the groundwater flow rate during the pollution period based on the groundwater flow velocity field, and bringing the groundwater flow rate into the pollutant concentration field to solve and obtain the total amount of pollutants; The pollution source plant area and the total amount of pollutants are output as the result of detecting the coupled pollution of underground water and soil in the plant area.

2. The method for detecting underground water-soil coupled pollution in marine engineering areas under tidal action according to claim 1 is characterized in that: The groundwater monitoring station is equipped with a flow meter and a water level meter, and the groundwater monitoring station stores the samples taken; The groundwater monitoring stations take samples periodically, and the sampling time of each groundwater monitoring station is synchronized.

3. The method for detecting underground water-soil coupled pollution in marine engineering areas under tidal action according to claim 1 is characterized in that: The water level change sequencing of the multiple plant areas includes: Sorting the points in order of response of the groundwater level based on the tidal cycle; According to the geographical location and order of each point, the tidal impact path is obtained by fitting; The center point of each plant area is mapped onto the tidal impact path, and the mapping point of each plant area is obtained, and the water level change sequence is obtained based on the mapping point and the direction of the tidal impact path.

4. The method for detecting underground water-soil coupled pollution in marine engineering areas under tidal action according to claim 1 is characterized in that: The convection-diffusion equation is established as follows: ； In the formula, is the diffusion coefficient, is the pollutant concentration; is the source term of the equation, is the spatial coordinate of the point, is the sampling time.

5. The method for detecting underground water-soil coupled pollution in marine engineering areas under tidal action according to claim 4 is characterized in that: Based on the discretized convection-diffusion equation, the time step The pollutant concentration field is obtained by iterative calculation, and the formula is: ； In the formula, n represents the iteration number, is the time when the pollutant disappears for the first time after the pollutant is detected continuously at the point. Corresponding to the spatial position When pollutants are detected at the point, the pollutant concentration is N is a natural number greater than or equal to 2.

6. The method for detecting underground water-soil coupled pollution in marine engineering areas under tidal action according to claim 5 is characterized in that: The time step discretization formula is: ； In the formula, The sampling time for detecting the presence of pollutants at the point.

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