Layered in-situ sampling and dynamic monitoring method for shallow underground water

Abstract

The invention discloses a shallow groundwater layered in-situ sampling and dynamic monitoring method, which comprises the following steps of: collecting data for determining the thickness of a sand layer, a lithologic structure, a water level annual change rule and diameter filling drainage characteristics; then determining the layer number and depth of a monitoring well, laying the monitoring well, and dynamically monitoring the water level of the well bottom day by day through a Levlogger Edge water level and temperature automatic recorder and a CS901 underground water flow velocity and flow direction instrument in the monitoring well, wherein the Levlogger Edge water level and temperature automatic recorder and the CS901 underground water flow velocity and flow direction instrument are used for monitoring the water level of the well bottom day by day; collecting a sample, and testing the sample; wherein the number of well spacing layers is based on the principle of uniformly dividing the thickness of a water-containing sand layer; monitoring wells with different depths are arranged according to the distribution characteristics of pollutants and a native geological environment discontinuous water-resisting layer in the stratum, and the water quality characteristics of different layers of shallow underground water are obtained through analysis by taking the principle that the depth of the central monitoring well is deepest and the depth is gradually shallower from the central monitoring well to the outside; and further comprehensive evaluation, prediction and analysis of underground water quality evolution are facilitated.

Description

Technical Field

[0001] The invention relates to the technical field of groundwater sampling, and in particular to a shallow groundwater stratified in-situ sampling and dynamic monitoring method. Background Art

[0002] In most plains of my country, there are thick sand layers of shallow groundwater, especially in the Huanghuaihai Plain. At present, due to the pressure of groundwater extraction and the significant increase in rainfall in the north, the water level of shallow groundwater in a large area has stopped falling and rebounded. The rising water level has caused changes in the groundwater environment. There may be a large number of pollutants in the aeration zone. As a result, the impact of the rising water level on the groundwater quality is unclear. Summary of the invention

[0003] The purpose of the present invention is to provide a shallow groundwater stratification in-situ sampling and dynamic monitoring method, which is conducive to the comprehensive evaluation, prediction and analysis of groundwater quality evolution, so as to solve the shortcomings of the prior art.

[0004] To achieve the above object, the present invention provides the following technical solutions:

[0005] A shallow groundwater stratification in-situ sampling and dynamic monitoring method comprises the following steps:

[0006] S1: Data collection: Collect relevant hydrogeological data for the target area, determine the thickness of the sand layer, lithology structure and annual variation of water level, and the characteristics of drainage and recharge;

[0007] S2: Determine the number and depth of monitoring wells: The number of wells is based on the principle of evenly dividing the thickness of the water-bearing sand layer; the depth of the wells is based on the distribution characteristics of pollutants and discontinuous impermeable layers in the original geological environment. Monitoring wells of different depths are arranged, with the center monitoring well being the deepest and the depth gradually becoming shallower as it goes outwards;

[0008] S3: Laying out monitoring wells: Use a car drill to drill continuously at a rate of one meter per foot in the target area until the designed hole depth is reached. Use a straight-pushing drill bit in the shallow layer. After reaching the water level, use mud wall impact drilling to drill a hole and place the monitoring well. Set a Levelogger Edge water level and temperature automatic recorder and a CS901 groundwater velocity and direction meter inside the monitoring well. Fill the bottom of the well with gravel, fill the wellhead section with clay to fix the well pipe, and then use a submersible pump to wash the well until the well water is clear.

[0009] S4: The bottom water level is dynamically monitored once a day through the Levelogger Edge water level and temperature automatic recorder and the CS901 groundwater velocity and direction meter;

[0010] S5: Collect samples: first extract groundwater from the outermost monitoring well, and stop pumping after the first layer of groundwater is drained, that is, when the water level in the deepest part of the well is 0, the water level automatic recorder shows that the water level is 0. Collect groundwater samples after the water level recovers to 1-3m. Drain the second layer of groundwater in the same way, collect groundwater samples after the water level recovers to a certain level, and collect groundwater samples in turn until the end for testing.

[0011] S6: Sample testing: On-site testing of redox sensitive indicators, and sending samples to the laboratory for routine testing and toxic and harmful testing. Through analysis, the water quality characteristics of different layers of shallow groundwater are obtained, and further comprehensive evaluation of the evolution of groundwater quality is carried out.

[0012] Furthermore, the layout method of the monitoring well layers in S2 is as follows:

[0013] The thickness of the sand layer is less than 20cm, and the number of layers is 1-2; the thickness of the sand layer is 20-50cm, and the number of layers is 2-4; the thickness of the sand layer is greater than 50cm, and the number of layers is 3-5.

[0014] Furthermore, in S3, the lithological characteristics of the original soil samples taken out during the drilling process are analyzed, recorded, and corresponding soil samples and groundwater samples are obtained.

[0015] Furthermore, the specific structural features of the monitoring well include a monitoring well protective cover, a PVC well pipe, gauze, a stainless steel filter, a water filter pipe, a buried depth of the water level in the monitoring well, a steel wire rope, a Levelogger Edge water level and temperature automatic recorder, and a CS901 groundwater flow rate and direction meter; the PVC well pipe adopts a 10 cm aperture to form the well wall, a monitoring well protective cover is arranged at the pipe mouth of the PVC well pipe, a steel wire rope is wound around the monitoring well protective cover, and the lower ends of the steel wire ropes are respectively suspended with a LeveloggerEdge water level and temperature automatic recorder and a CS901 groundwater flow rate and direction meter located in the PVC well pipe; an electric drill is used to drill a hole in the lower part of the PVC well pipe to form a water filter pipe, and the outside of the water filter pipe is wrapped with two layers of 70-mesh gauze, a stainless steel filter is arranged at the bottom of the PVC well pipe, the stainless steel filter is located at the bottom of the well, and the outside of the stainless steel filter is wrapped with gauze.

[0016] Furthermore, the number of monitoring wells and their depths in S2 are determined based on the empirical formula of influence radius, as follows:

[0017] 1. For submersible wells:

[0018] a. For a complete submerged well, the impact radius is calculated using the Kusakin empirical formula:

[0019]

[0020] Where: K: permeability coefficient of aquifer (m / d); H: thickness of phreatic aquifer m; S: well water level drawdown m;

[0021] b. Submersible incomplete well, impact radius

[0022] 2. For pressurized water wells:

[0023] a. For single-hole pumping of stable flow complete-hole confined water, the influence radius R is calculated using the Girardt empirical formula:

[0024]

[0025] Where: R is the influence radius of the pumping well, m; k is the permeability coefficient, m / d; S is the drawdown of the pumping test, m; M is the thickness of the aquifer, m; r is the radius of the pumping well, m; Q is the water yield of the pumping well, m 3 / d;

[0026] b. For the stable flow, the complete bore confined water belt is pumped from two observation holes. The calculation formula for the influence radius R is calculated using the Qiu Buyi formula:

[0027]

[0028] Where: r1 and r2 are the distances from observation hole 1 and observation hole 2 to the main hole, m; S1 and S2 are the water level drops of observation hole 1 and observation hole 2, m;

[0029] After determining the impact radius, identify the deepest well in the center, and then arrange shallow wells in each circle in sequence, with the depth of the wells gradually becoming shallower from the center to the outside.

[0030] Furthermore, the redox sensitive indicators in S6 include total iron, ferrous iron, ammonium, sulfite, and sulfide; the routine laboratory detection indicators include potassium, sodium, calcium, magnesium, chloride, sulfate, carbonate, bicarbonate, nitrate, total dissolved solids, total hardness, total acidity and Ph; the toxic and harmful detection indicators include mercury, cadmium, chromium, lead and sulfide, cyanide, fluoride, arsenic, and selenium.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The shallow groundwater stratified in-situ sampling and dynamic monitoring method of the present invention comprises collecting data, determining the number of layers and depth of monitoring wells, laying monitoring wells, and dynamically monitoring the bottom water level of the well once a day through the Levelogger Edge water level temperature automatic recorder and the CS901 groundwater flow velocity and direction meter inside the monitoring well; then collecting samples, and then testing the samples, and obtaining the water quality characteristics of different layers of shallow groundwater through analysis, which is conducive to further comprehensive evaluation, prediction and analysis of the evolution of groundwater quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a plan view of the monitoring well arrangement of the present invention;

[0034] Figure 2 It is an elevation view of the monitoring well arrangement of the present invention;

[0035] Figure 3 It is a schematic diagram of the monitoring well structure of the present invention.

[0036] In the figure: 201, monitoring well protection cover; 202, PVC well pipe; 203, gauze; 204, stainless steel filter screen; 205, water filter pipe; 206, monitoring well water level burial depth; 207, wire rope; 208, Levelogger Edge water level and temperature automatic recorder; 209, CS901 groundwater flow velocity and direction meter. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only 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.

[0038] like Figure 1-3 As shown, an embodiment of the present invention provides a shallow groundwater stratification in-situ sampling and dynamic monitoring method, comprising the following steps:

[0039] S1: Data collection: Collect relevant hydrogeological data for the target area. If the data is insufficient, it is necessary to supplement the drilling data to understand the thickness and lithology characteristics of the shallow groundwater-bearing sand layer in the area, which is used to determine the thickness of the sand layer, lithology structure and annual variation of water level, and to supplement the drainage characteristics:

[0040] S2: Design the number of wells and their depth: Understand the distribution characteristics of pollutants, original geological environment (high iron, manganese, arsenic and other heavy metals), discontinuous impermeable layers in the stratum, and lay out monitoring wells of different depths. The principle of laying out the number of monitoring wells is to evenly divide the thickness of the water-bearing sand layer, and comprehensively consider other influencing factors. The center monitoring well is the deepest, and the depth becomes shallower as it goes outwards;

[0041] S3: Lay out monitoring wells: Lay out monitoring wells according to the designed monitoring well deployment, such as Figure 1-2As shown, a car drill is used to drill continuously at a rate of one meter per foot until the designed hole depth is reached. A straight-pushing drill bit is used for the shallow layer, and a mud wall impact drill is used to drill a hole after the water level reaches the water level. The well wall uses a PVC well pipe 202 with a pore size of 10 cm, and the lower water filter pipe 205 is drilled through the entire pipe with an electric drill. The water filter pipe 205 is wrapped with two layers of 70-mesh gauze 203, and the water filter pipe 205 is arranged at the bottom of the PVC well pipe 202. The bottom of the well is filled with gravel, and the wellhead section is filled with clay to fix the PVC well pipe 202. The mouth of the PVC well pipe 202 is protected by a monitoring well protective cover 201. No sealing ring is placed on the monitoring well protective cover 201 so that the well can communicate with the atmosphere without foreign matter falling into and clogging the wellbore. A waterproof stainless steel filter screen 204 is added to the bottom of the well and wrapped with gauze 203 to prevent mud and sand from entering the PVC well pipe 202 and clogging the monitoring well. After the well is completed, a submersible pump is placed underground to wash the well until the well water is clear. During the drilling process, the lithological characteristics of the original soil samples taken out are analyzed, records are kept, and corresponding soil samples and groundwater samples are obtained.

[0042] S4: Placement of dynamic monitoring instruments: Dynamic monitoring includes dynamic water level monitoring and flow velocity and direction monitoring. The dynamic water level monitoring adopts the Levelogger Edge water level and temperature automatic recorder 208 for monitoring; the flow velocity and direction monitoring adopts the CS901 groundwater flow velocity and direction meter 209 for monitoring. The Levelogger Edge water level and temperature automatic recorder 208 and the CS901 groundwater flow velocity and direction meter 209 are connected to the monitoring well protective cover 201 by the wire rope 207. The instruments are set to monitor once a day.

[0043] S5: Scenario description: Collect data, find out the thickness of the sand layer, determine the number of well layers and the depth of each monitoring well. According to the depth of the pumping well and the soil structure where the pumping well is located, the influence radius of the monitoring well is calculated according to the empirical formula of the influence radius. The empirical formula of the influence radius is calculated according to the following empirical formula:

[0044] (1)Diving well

[0045] ① For a complete submersible well, the impact radius is calculated using the Kusakin empirical formula.

[0046]

[0047] Where K: permeability coefficient of aquifer (m / d); H: thickness of phreatic aquifer (m);

[0048] ② Submersible incomplete well, impact radius

[0049] Where S: well water level drawdown, m; H: phreatic aquifer thickness, m; K: aquifer permeability coefficient (m / d);

[0050] (2) Pressure water well

[0051] ① For single-hole pumping of stable flow complete-hole confined water, the influence radius R is calculated using the Girardt empirical formula:

[0052]

[0053] Where: R is the influence radius of the pumping well, m; k is the permeability coefficient, m / d; S is the drawdown of the pumping test, m; M is the thickness of the aquifer, m; r is the radius of the pumping well, m; Q is the water yield of the pumping well, m 3 / d.

[0054] ② The calculation formula for the pumping influence radius R of the two observation holes in the stable flow complete hole pressure water belt is calculated using the Qiu Buyi formula:

[0055]

[0056] Where: r1 and r2 are the distances from observation hole 1 and observation hole 2 to the main hole, m; S1 and S2 are the water level drawdowns of observation hole 1 and observation hole 2, m.

[0057] After determining the impact radius, determine the deepest well in the center, and then arrange the shallow wells in each circle in sequence, with the depth of the wells gradually becoming shallower from the center to the outside.

[0058] After the layout of each monitoring well is completed and samples are collected, the Levelogger Edge water level temperature automatic recorder 208 and the CS901 groundwater velocity and direction meter 209 are installed. First, the groundwater in the outermost monitoring well is extracted. After the first layer of groundwater is drained, that is, the water level in the deepest part of the well is displayed as 0, the water is pumped out, and after the water level recovers to a certain level (1-3m), the groundwater sample is collected for detection.

[0059] For the second layer of water samples, drain the second layer of groundwater in the same way, and collect groundwater samples after the water level recovers to a certain level. Collect groundwater samples from each layer in turn until the end.

[0060] S6: On-site testing of redox sensitive indicators and sending samples to the laboratory for routine testing and toxic and harmful testing. Through analysis, the water quality characteristics of different layers of shallow groundwater are obtained, and a comprehensive evaluation of the evolution of groundwater quality is further conducted.

[0061] In summary, the present invention provides a shallow groundwater stratification in-situ sampling and dynamic monitoring method, which mainly includes:

[0062] 1. Principles for the depth layout of monitoring wells:

[0063] Collect relevant hydrogeological data for the target area. If the data is insufficient, it is necessary to supplement the drilling data to understand the thickness and lithology of the shallow groundwater sand layer in the area. It is used to determine the interannual variation of sand layer thickness, lithology structure and water level, and to supplement the drainage characteristics. Understand the distribution characteristics of pollutants, original geological environment (heavy metals such as high iron, manganese and arsenic), and discontinuous impermeable layers in the stratum, and lay out monitoring wells of different depths. The length of the flower pipes is 1-2m extending upward from the bottom. The principle of monitoring well layout is mainly to evenly divide the thickness of the water-bearing sand layer, and comprehensively consider other influencing factors, as shown in Table 1:

[0064] Table 1 Monitoring well layout principles

[0065]

[0066] Note: The specific number of layers can be increased based on site characteristics and monitoring purposes.

[0067] 2. Monitoring well distribution and sampling plan:

[0068] Based on the stratified characteristics, sampling wells are arranged with the aim of extracting the outermost (shallow) groundwater, lowering the regional groundwater level, and maintaining the water level at the first bottom plate depth; collecting the second layer of groundwater and maintaining the second layer of groundwater level; and so on to collect the fourth, fifth, and sixth layers.

[0069] Among them, the first layer has the largest scope, and the number of wells is determined according to the richness of groundwater, the yield of a single well, and the relative position of the center point to other wells. After the drainage water level stabilizes and the water level recovers to a certain level (1-3m), groundwater samples are collected for testing.

[0070] The second layer of water samples is arranged inside the first layer. After the first layer of groundwater is drained, the second layer of groundwater is drained in the same way. After the water level recovers to a certain level, groundwater samples are collected.

[0071] And so on, collect groundwater samples from the third and fourth layers.

[0072] The specific drainage plan is to drain water into ditches 200m away from the study area; water samples are collected after the water level stabilizes for field and laboratory tests.

[0073] 3. Sample testing:

[0074] ① On-site testing, redox sensitive indicators: total iron, ferrous iron, ammonium ion, sulfite, sulfide, etc.

[0075] ② Routine laboratory tests: potassium, sodium, calcium, magnesium, chloride (as Cl - ), sulfate (as SO4 2- ), carbonate, bicarbonate, nitrate (as NO -), total dissolved solids, total hardness (as CaCO3), total acidity (as CaCO3) and pH, etc.

[0076] ③Toxic and harmful testing: mercury, cadmium, chromium, lead and sulfide, cyanide, fluoride, arsenic, selenium, etc.

[0077] 4. Dynamic monitoring:

[0078] ① Dynamic monitoring of groundwater level: The dynamics of groundwater level are monitored by a fully automatic water level and temperature recorder. The automatic recorder is placed in the monitoring well and is set to monitor the changes in groundwater level once a day.

[0079] ② Flow velocity and direction monitoring: The groundwater flow velocity and direction monitoring uses the CS901 groundwater flow velocity and direction meter 209. This intelligent measuring instrument can measure the underground seepage flow velocity, flow direction and vertical flow velocity and flow direction in a single well under the natural flow field. Set the CS901 groundwater flow velocity and direction meter 209 to monitor the borehole once a day.

[0080] ③ Water quality analysis: According to the dynamic changes of groundwater level, complete 1-2 phases in a complete hydrological year.

[0081] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for in-situ sampling and dynamic monitoring of shallow groundwater layers, characterized in that: The following steps are involved: S1: Data collection: Collect relevant hydrogeological data for the target area, determine the thickness of the sand layer, lithology structure and annual variation of water level, and the characteristics of drainage and recharge; S2: Determine the number and depth of monitoring wells: The number of wells is based on the principle of evenly dividing the thickness of the water-bearing sand layer; the depth of the wells is based on the distribution characteristics of pollutants and discontinuous impermeable layers in the original geological environment. Monitoring wells of different depths are arranged, with the center monitoring well being the deepest and the depth gradually becoming shallower as it goes outwards; S3: Laying out monitoring wells: In the target area, a car drill is used to drill continuously at a rate of one meter per foot until the designed hole depth is reached. A straight-pushing drill is used in the shallow layer. After the water level is reached, a mud wall impact drill is used to drill a hole and place the monitoring well. A Levelogger Edge water level and temperature automatic recorder (208) and a CS901 groundwater velocity and direction meter (209) are installed inside the monitoring well. Gravel is filled at the bottom of the well, and clay is filled at the wellhead section to fix the well pipe. A submersible pump is then placed underground to wash the well until the well water is clear. S4: The bottom water level is dynamically monitored once a day by using the Levelogger Edge water level and temperature automatic recorder (208) and the CS901 groundwater velocity and direction meter (209); S5: Collect samples: first extract groundwater from the outermost monitoring well, and stop pumping after the first layer of groundwater is drained, that is, when the water level in the deepest part of the well is 0, the water level automatic recorder shows that the water level is 0. Collect groundwater samples after the water level recovers to 1-3m. Drain the second layer of groundwater in the same way, collect groundwater samples after the water level recovers to a certain level, and collect groundwater samples in turn until the end for testing. S6: Sample testing: On-site testing of redox sensitive indicators, and sending samples to the laboratory for routine testing and toxic and harmful testing. Through analysis, the water quality characteristics of different layers of shallow groundwater are obtained, and further comprehensive evaluation of the evolution of groundwater quality is carried out.

2. A shallow groundwater stratification in-situ sampling and dynamic monitoring method as claimed in claim 1, characterized in that: The layout method of monitoring well layers in S2 is as follows: The thickness of the sand layer is less than 20cm, and the number of layers is 1-2; the thickness of the sand layer is 20-50cm, and the number of layers is 2-4; the thickness of the sand layer is greater than 50cm, and the number of layers is 3-5.

3. A shallow groundwater stratification in-situ sampling and dynamic monitoring method as claimed in claim 1, characterized in that: In S3, during the drilling process, the lithological characteristics of the original soil samples taken out were analyzed and recorded, and the corresponding soil samples and groundwater samples were obtained.

4. A shallow groundwater stratification in-situ sampling and dynamic monitoring method as claimed in claim 1, characterized in that: The specific structural features of the monitoring well include a monitoring well protective cover (201), a PVC well pipe (202), gauze (203), a stainless steel filter (204), a water filter pipe (205), a buried depth of the water level in the monitoring well (206), a steel wire rope (207), a Levelogger Edge water level and temperature automatic recorder (208) and a CS901 groundwater velocity and direction meter (209); the PVC well pipe (202) uses a 10 cm aperture to form a well wall, a monitoring well protective cover (201) is arranged at the pipe mouth of the PVC well pipe (202), a steel wire rope (207) is wound around the monitoring well protective cover (201), and the lower end of the steel wire rope (207) is suspended from a Levelogger Edge located in the PVC well pipe (202). Edge water level temperature automatic recorder (208) and CS901 groundwater flow velocity and direction meter (209); the lower part of the PVC well pipe (202) is drilled with an electric drill to form a water filter pipe (205), the outside of the water filter pipe (205) is wrapped with two layers of 70 mesh gauze (203), and a stainless steel filter net (204) is arranged at the bottom of the PVC well pipe (202), the stainless steel filter net (204) is located at the bottom of the well, and the outside of the stainless steel filter net (204) is wrapped with gauze (203).

5. A shallow groundwater stratification in-situ sampling and dynamic monitoring method as claimed in claim 1, characterized in that: The number of monitoring wells and their depths in S2 are determined based on the empirical formula for the influence radius, as follows:

1. For submersible wells: a. For a complete submerged well, the impact radius is calculated using the Kusakin empirical formula: Where: K: permeability coefficient of aquifer (m / d); H: thickness of phreatic aquifer m; S: well water level drawdown m; b. Submersible incomplete well, impact radius 2. For pressurized water wells: a. For single-hole pumping of stable flow complete-hole confined water, the influence radius R is calculated using the Girardt empirical formula: Where: R is the influence radius of the pumping well, m; k is the permeability coefficient, m / d; S is the drawdown of the pumping test, m; M is the thickness of the aquifer, m; r is the radius of the pumping well, m; Q is the water yield of the pumping well, m 3 / d; b. For the stable flow, the complete bore confined water belt is pumped from two observation holes. The calculation formula for the influence radius R is calculated using the Qiu Buyi formula: Where: r1 and r2 are the distances from observation hole 1 and observation hole 2 to the main hole, m; S1 and S2 are the water level drawdowns of observation hole 1 and observation hole 2, m; After determining the impact radius, identify the deepest well in the center, and then arrange shallow wells in each circle in sequence, with the depth of the wells gradually becoming shallower from the center to the outside.

6. A shallow groundwater stratification in-situ sampling and dynamic monitoring method as claimed in claim 1, characterized in that: The redox sensitive indicators in S6 include total iron, ferrous iron, ammonium, sulfite, and sulfide; routine laboratory detection indicators include potassium, sodium, calcium, magnesium, chloride, sulfate, carbonate, bicarbonate, nitrate, total dissolved solids, total hardness, total acidity and Ph; toxic and harmful detection indicators include mercury, cadmium, chromium, lead and sulfide, cyanide, fluoride, arsenic, and selenium.

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