A method for obtaining the groundwater pollution status of a landfill in a plain terrain

Abstract

The present invention relates to a method for obtaining the groundwater pollution status of a landfill in a plain terrain, comprising the following steps: obtaining the possible leakage areas around the landfill, and obtaining the pollutant concentrations at multiple set positions in the leakage areas through drilling; performing geophysical exploration using geophysical exploration methods, identifying the suspected polluted areas according to the geophysical exploration parameters obtained from the geophysical exploration, and establishing a quantitative relationship between the geophysical exploration parameters and the pollutant concentrations based on the pollutant concentrations at multiple set positions and the corresponding geophysical exploration parameters; determining the geophysical exploration parameter threshold according to the critical pollutant concentration and the said quantitative relationship; identifying the suspected polluted areas according to the geophysical exploration parameter threshold to determine the scope of the polluted areas. Drilling is carried out at the determined polluted areas to obtain pollutant information. The construction period of the method of the present invention is short, and it is convenient and fast.

Description

Technical Field

[0001] The present invention relates to the technical field of contaminated site investigation, and particularly relates to a method for obtaining the groundwater pollution status of a landfill in a plain terrain. Background Art

[0002] The statements herein only provide background art related to the present invention and do not necessarily constitute prior art.

[0003] Groundwater is an important part of the water resource system. In recent years, with the continuous development of society, more and more people have begun to pay attention to the ecological security problems and environmental health risks brought by groundwater pollution.

[0004] The main way to deal with domestic waste is landfill. There are problems such as landfill body landslides, landfill gas leakage, and leachate leakage in landfills, which will cause varying degrees of pollution to the soil and water underground in the landfill site and its surrounding areas. Because groundwater pollution has characteristics such as being difficult to detect and difficult to repair, and the polluted groundwater will endanger human health when used as a drinking water source, it is urgent to investigate landfills and evaluate the pollution risks they pose to the groundwater environment.

[0005] At present, the preliminary investigation of landfills mainly relies on traditional drilling methods. This method requires drilling at multiple points. Due to its non - continuity in space, it is easy to miss leakage areas during point layout, and it is impossible to comprehensively understand the current situation of groundwater pollution in landfills. Summary of the Invention

[0006] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for obtaining the groundwater pollution status of a landfill in a plain terrain to solve the problems existing in the above - mentioned technology.

[0007] To achieve the above - mentioned purpose, the present invention adopts the following technical solutions

[0008] An embodiment of the present invention provides a method for obtaining the groundwater pollution status of a landfill in a plain terrain, including the following steps:

[0009] Obtain the possible leakage areas around the landfill, and obtain the pollutant concentrations at multiple set positions in the leakage areas through drilling;

[0010] Use geophysical exploration methods for geophysical prospecting, identify suspected pollution areas according to the geophysical prospecting parameters obtained from the geophysical prospecting, and establish a quantitative relationship between the geophysical prospecting parameters and the pollutant concentrations based on the pollutant concentrations at multiple set positions and the corresponding geophysical prospecting parameters;

[0011] Determine the geophysical prospecting parameter threshold according to the critical pollutant concentration and the above - mentioned quantitative relationship;

[0012] Identify the suspected contaminated areas based on the geophysical exploration parameter thresholds to determine the scope of the contaminated areas.

[0013] Conduct borehole drilling at the determined contaminated areas to obtain pollutant information.

[0014] Optionally, the method for identifying the suspected contaminated areas includes the following steps:

[0015] Conduct geophysical exploration according to the determined geophysical exploration method to obtain the original geophysical exploration parameter data;

[0016] Perform data processing and inversion interpretation on the original geophysical exploration parameter data;

[0017] Determine the suspected contaminated areas according to the inversion results.

[0018] Optionally, after inversion of the processed original data, a geophysical exploration parameter profile is obtained. Determine the pollution leakage location and the spread range of the pollution plume according to the numerical values and trends of the resistivity and polarization rate abnormal areas on the geophysical exploration parameter profile, and then identify the suspected contaminated areas.

[0019] Optionally, the geophysical exploration method combines the high-density resistivity method and the induced polarization method.

[0020] Optionally, arrange multiple borehole points in the areas around the landfill where leakage may occur, and obtain pollutant concentration information after drilling.

[0021] Optionally, at the same borehole point, drill holes to obtain pollutant concentration information at different depths.

[0022] Optionally, when conducting geophysical exploration, arrange survey lines around the landfill in the direction perpendicular to the groundwater flow direction and in the direction parallel to the groundwater flow direction.

[0023] Optionally, the groundwater flow direction is obtained by drilling at the borehole points in the areas where leakage may occur.

[0024] Optionally, in the suspected contaminated areas, the areas determined according to the comparison results between the geophysical exploration parameters obtained by geophysical exploration and the geophysical exploration parameter thresholds are the contaminated areas.

[0025] Optionally, determine the borehole positions according to the geophysical exploration inversion profile within the determined contaminated area range, and conduct drilling at the borehole positions to obtain the pollutant concentration to verify the contaminated area identification results.

[0026] Advantages of the present invention:

[0027] The method of the present invention identifies a suspected contaminated area by using geophysical exploration methods, and then combines initial borehole drilling to establish a quantitative relationship between the geophysical exploration parameters of the geophysical exploration method and the pollutant concentration. According to the obtained quantitative relationship and the critical pollutant concentration set for the landfill, a threshold value of the geophysical exploration parameters is obtained. Furthermore, the suspected contaminated area can be delineated by the geophysical exploration parameters of the suspected contaminated area to obtain the contaminated area, realizing the identification of the contaminated area. It can convert the judgment of the pollution status by the pollutant concentration into the judgment of the pollution status by the geophysical exploration parameters, making the location of the borehole layout more targeted, improving the defect of easily missing the leakage area. Moreover, since the suspected contaminated area is identified for the entire area, it is convenient to understand the groundwater pollution status of the landfill as a whole. And only the borehole layout and drilling are carried out at the determined contaminated area location to obtain pollutant information, improving the accuracy of the preliminary pollution survey and enabling the comprehensive and rapid acquisition of the groundwater environment status of the landfill. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The specification drawings forming a part of the present application are used to provide a further understanding of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute a limitation to the present application.

[0029] Figure 1 It is a schematic flow chart of the method of Embodiment 1 of the present invention;

[0030] Figure 2 It is a schematic diagram of the survey line distribution of Embodiment 1 of the present invention; DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] Embodiment 1

[0032] This embodiment provides a method for obtaining the groundwater pollution status of a landfill in a plain terrain, as Figure 1 shown, including the following steps:

[0033] Step 1: Obtain the possible leakage areas around the landfill and obtain the pollutant concentrations at multiple set positions in the leakage areas through drilling.

[0034] Specifically, the possible leakage areas are determined according to the first-phase site environmental investigation recorded in the Technical Guidelines for Site Environmental Investigation HJ25.1-2014, and the relevant data are obtained through on-site investigation. The on-site investigation includes data collection, on-site inspection, and personnel interviews.

[0035] Specifically, when collecting landfill data, it is necessary to prioritize ensuring the collection of basic data and then try to collect auxiliary data as much as possible. After that, the collected data should be sorted and analyzed to clarify the basic geology, hydrogeology, and groundwater environment supervision of the landfill. The on-site inspection should verify the accuracy of the collected data, focus on inspecting the landfill leachate treatment area and environmentally sensitive areas, and determine whether geophysical exploration can be carried out according to the topography and geomorphology.

[0036] In this embodiment, the basic data collected includes the groundwater quality status (such as turbidity, pH, total coliforms, nitrates), the types of landfilled materials, the treatment methods of leachate, the designed storage capacity of the landfill, the anti-seepage situation, etc. The auxiliary data includes the types of pollutants, the construction situation of environmental protection facilities, and the main exploited horizons of water wells.

[0037] The on-site inspection method is to identify abnormal odors through observation or use on-site rapid detection equipment to identify the exceeding standard situation of various ionic components in the groundwater environment of the site.

[0038] The method for determining the possibly leaking areas can adopt the existing methods and will not be described in detail here.

[0039] Set up preset boreholes in the possibly leaking areas around the landfill obtained in the above steps. The positions and quantities of the boreholes can be set according to the actual situation.

[0040] Drill through the boreholes to obtain the groundwater flow direction and pollutant concentration information of the landfill.

[0041] Step 2: Use geophysical exploration methods for geophysical prospecting, identify the suspected contaminated areas according to the geophysical prospecting parameters obtained from the geophysical prospecting, and establish a quantitative relationship between the geophysical prospecting parameters and the pollutant concentrations based on the pollutant concentrations and the corresponding geophysical prospecting parameters at multiple preset positions.

[0042] In the plain area, there is no large topographic undulation, the change of the stratigraphic sedimentary environment is relatively simple, and there is no sudden change in the groundwater flow velocity and direction. It is suitable to use geophysical methods for preliminary exploration to master the basic information of the groundwater environment.

[0043] Specifically, the geophysical exploration method in this embodiment adopts a method combining the high-density resistivity method and the induced polarization method.

[0044] For the adopted geophysical exploration method, a unified wiring method is adopted: when wiring, try to avoid hardened roads, and the detection electrodes directly contact the soil.

[0045] The specific wiring principles are as follows:

[0046] Set the short axis direction of the landfill as the width direction with the maximum distance being x, and the long axis direction as the length direction with the maximum distance being y. If x or y ≤ 60m, taking x ≤ 60m as an example, the layout of the survey lines is determined by the following formula:

[0047]

[0048] In the formula: L i - Survey line; x i - Distance from the survey line to the landfill. If both x and y are less than 60m, then the smaller value of the two is used as the standard for arranging the layout of the survey lines.

[0049] Under the condition that the site space and terrain permit, arrange 3 survey lines perpendicular to the groundwater flow direction in the downstream of the groundwater flow direction of the landfill, which are L 1 、L 2 and L 3 respectively, to monitor the distribution and diffusion of the pollution plume; arrange 1 survey line parallel to the groundwater flow direction on each side of the landfill, which are L 4 and L 5 respectively, to monitor the leakage of pollutants; arrange 1 survey line L 6 perpendicular to the groundwater flow direction in the upstream of the groundwater flow direction of the landfill as the upstream control survey line to obtain the background value of the geophysical exploration parameters.

[0050] If x, y > 60m, then the layout position of the survey lines is determined by the following formula:

[0051]

[0052] Among them, the flow direction of the groundwater is determined according to the drilling information in step 1.

[0053] In this embodiment, the maximum distance in the width direction is 50m, and the maximum distance in the length direction is 80m, which conforms to the first wiring situation. As Figure 2 shown, that is, at the position close to the landfill in the downstream of the groundwater flow, at 25m and 25 - 42m, arrange 1 survey line perpendicular to the groundwater flow direction respectively, which are L 1 、L 2 and L 3 respectively, to monitor the distribution and diffusion of the pollution plume; arrange 1 survey line parallel to the groundwater flow direction at 25 - 42m from the landfill on each side of the landfill, which are L 4 and L 5 respectively, to monitor the leakage of pollutants; arrange 1 horizontal survey line L 6 perpendicular to the groundwater flow direction at 25 - 42m in the upstream of the groundwater flow direction of the landfill as the upstream control survey line to obtain the background value of the geophysical exploration parameters, that is, the background value corresponding to the resistivity parameter or the background value corresponding to the polarization rate parameter.

[0054] In this embodiment, it is necessary to determine whether the arranged survey line is within the range of 5-10 m around the borehole in Step 1. If it is not within this range, a survey line needs to be arranged within the range of 5-10 m around the borehole in Step 1 to collect data relationships, facilitating the subsequent establishment of a quantitative relationship between geophysical parameters and pollutant concentrations.

[0055] For the above two wiring situations, if the pollution plume spreads significantly in four directions and geophysical signal anomalies occur, such as the resistivity being significantly lower than its corresponding background value or the polarization rate being significantly higher than its corresponding background value, the geophysical survey lines should be appropriately increased and densified.

[0056] When conducting geophysical exploration, existing instrument and equipment can be used. Generally, high-density resistivity and induced polarization data are measured synchronously with the existing instrument and equipment, and the distribution of pollutants is interpreted using resistivity and polarization rate as parameters. The main working steps are as follows: Electrodes are arranged along the survey line at a fixed pole pitch and kept in a fixed position. The electrodes are connected to the measuring instrument through an electrode conversion switch. Non-polarizable electrodes are arranged at a parallel position 0.5 m away from the electrodes to collect induced polarization signals. The electrodes are switched using the electrode conversion switch to complete the geophysical exploration work of the landfill. After one survey line is measured, the entire electrode array is moved to conduct the measurement of the next survey line until all survey lines are completely measured.

[0057] This embodiment is illustrated by taking the acquisition of the quantitative relationship between resistivity and pollutant concentration as an example, that is, the geophysical parameter uses resistivity:

[0058] Specifically, the resistivity corresponding to different boreholes at different depths in Step 1 is obtained, and a quantitative relationship between resistivity and pollutant concentration is established.

[0059] A quantitative relationship between resistivity parameters and pollutant concentration can be constructed using a fitting formula. Using the linear fitting formula y = ax + b, where a is the slope and b is the intercept. Let the dependent variable be resistivity ρ and the independent variable be pollutant concentration c. Then the relationship between resistivity parameters and pollution concentration is ρ = ac + b. According to the relationship between the resistivity at different depths of the boreholes and the pollutant concentration obtained, and the relationship between the resistivity and pollutant concentration at different boreholes, the fitting formula is determined.

[0060] According to the results of geophysical exploration, the suspected pollution area is determined. The specific steps are as follows:

[0061] First, the original data in the instrument needs to be input into the calculation software, and the data is sorted and converted into a file format that can be processed by the computer. When sorting the data, a series of data processing operations such as inspection, manual removal of bad points, and terrain correction need to be carried out. Then, the processed data is stored and inverted and interpreted using the electrical method inversion software to obtain the geophysical parameter profile. All areas with large changes in resistivity and polarizability on the profile are regarded as the pollution leakage locations, and the suspected pollution areas are initially identified.

[0062] The method for determining the pollution leakage location is to compare the resistivity or polarizability with the background value of the resistivity or polarizability. When the resistivity at a certain location is significantly lower than the corresponding background value of the resistivity (or the polarizability is higher than the corresponding background value of the polarizability), then this location is determined as the pollution leakage location, and the area within 50m around it is the suspected pollution area.

[0063] Step 3: According to the pollutant concentration, the on-site remediation target value, and the quantitative relationship between the pollutant concentration and the resistivity value determined in Step 2, determine the resistivity value corresponding to the critical pollutant concentration, that is, the resistivity threshold.

[0064] Step 4: Compare the resistivity in the suspected pollution area with the resistivity threshold. When the resistivity in the set area within the suspected pollution area is lower than the resistivity threshold, then this set area can be determined as the polluted area. By analogy, the polluted areas are delineated within the suspected pollution area.

[0065] Step 5: Conduct sampling and drilling in the polluted area to obtain pollutant information, complete the preliminary investigation of the groundwater pollution status of the landfill, and be able to verify the identified polluted areas.

[0066] The sampling and drilling mentioned above are as follows: The sampling positions are determined by the geophysical inversion profile of the delineated polluted area, and are mainly arranged in the abnormal electrical signal areas where the resistivity or polarizability profile fluctuates significantly, so as to verify the geophysical exploration results and obtain more pollutant information.

[0067] In this embodiment, the drilling depth is determined by the geophysical inversion profile, generally based on exposing the shallow groundwater aquifer without penetrating its confining floor. For different types of groundwater, different numbers of monitoring points should be arranged: 5 - 7 monitoring points are arranged for pore water, at least 4 monitoring points are arranged for karst water, and at least 5 - 6 monitoring points are arranged for fissure water.

[0068] Using the method of this embodiment, a complete method for obtaining the groundwater pollution status of a landfill in a plain terrain is designed, providing data and reference for subsequent detailed investigations and improving the efficiency of the preliminary investigation of the groundwater environment status of the landfill. The geophysical exploration method is combined to identify the suspected polluted area to guide the determination of the subsequent layout position, quantity, and drilling depth. The accuracy of the preliminary pollution survey is improved, the number of layout points is effectively reduced, and the groundwater environment status of the landfill can be comprehensively and quickly obtained.

[0069] Although the specific embodiments of the present invention are described above in conjunction with the accompanying drawings, it is not a limitation on the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, various modifications or deformations that can be made by those skilled in the art without creative labor are still within the protection scope of the present invention.

Claims

1. A method for obtaining the groundwater pollution status of a landfill in a plain terrain, characterized in that, it includes the following steps: Obtain the possible leakage areas around the landfill, and obtain the pollutant concentrations at multiple set positions in the leakage areas through drilling; Use geophysical exploration methods for geophysical exploration, identify the suspected pollution areas according to the geophysical parameters obtained from the geophysical exploration, and establish a quantitative relationship between the geophysical parameters and the pollutant concentrations based on the pollutant concentrations at multiple set positions and the corresponding geophysical parameters; Determine the geophysical parameter threshold according to the critical pollutant concentration and the said quantitative relationship; Identify the suspected pollution areas according to the geophysical parameter threshold, and determine the scope of the pollution areas; Conduct point drilling in the determined pollution areas to obtain pollutant information; Among them, the identification method of the suspected pollution areas includes the following steps: Conduct geophysical exploration according to the determined geophysical exploration method to obtain the original geophysical parameter data; Perform data processing and inversion interpretation on the original geophysical parameter data; Determine the suspected pollution areas according to the inversion results; After inversion of the processed original data, obtain a geophysical parameter profile diagram, and determine the pollution leakage location and the pollution plume diffusion range according to the numerical magnitudes and trends of the resistivity and polarization rate abnormal areas on the geophysical parameter profile diagram, and then identify the suspected pollution areas.

2. A method for obtaining the groundwater pollution status of a landfill in a plain terrain as described in claim 1, characterized in that, the geophysical exploration method combines the high-density resistivity method and the induced polarization method.

3. A method for obtaining the groundwater pollution status of a landfill in a plain terrain as described in claim 1, characterized in that, Arrange multiple drilling points in the areas around the landfill where leakage may occur, and obtain pollutant concentration information after drilling.

4. A method for obtaining the groundwater pollution status of a landfill in a plain terrain as described in claim 3, characterized in that, At the same drilling point, drill to obtain pollutant concentration information at different depths.

5. A method for obtaining the groundwater pollution status of a landfill in a plain terrain as described in claim 1, characterized in that, When conducting geophysical exploration, survey lines are arranged around the landfill in the direction perpendicular to the groundwater flow direction and in the direction parallel to the groundwater flow direction.

6. A method for obtaining the groundwater pollution status of a landfill in a plain terrain as described in claim 5, characterized in that, The groundwater flow direction is obtained through drilling at the drilling points in the areas where leakage may occur.

7. A method for obtaining the groundwater pollution status of a landfill in a plain terrain as described in claim 1, characterized in that, In the suspected pollution areas, the areas determined according to the comparison results of the geophysical parameters obtained from the geophysical exploration and the geophysical parameter threshold are the pollution areas.

8. A method for obtaining the groundwater pollution status of a landfill in a plain terrain as described in claim 1, characterized in that, Determine the point positions according to the geophysical inversion profile of the geophysical exploration within the determined pollution area scope, and conduct drilling at the point positions to obtain the pollutant concentration to verify the pollution area identification result.

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