A method for monitoring and analyzing groundwater environment sampling

Abstract

The application belongs to the technical field of water body sampling, and specifically discloses a groundwater environment sampling, monitoring and analyzing method. The well washing process is theoretically divided into a first stage and a second stage through the comparison between the cumulative pumping volume and the well water volume, and then the water temperature change is used for replacement start identification in different stages, and the zeroing of the conductivity response stiffness is used for replacement completion identification. The differences in the response characteristics of various parameters in different stages of the well washing process are fully utilized, the accuracy and timeliness of well washing standard judgment are improved, and after the well washing reaches the standard, the verification nodes are set at intervals within the preset sampling constraint time length, and the sampling is paused at each verification node. The current water quality is compared with the reference parameter value recorded when the well washing reaches the standard, the water body state in the sampling process can be continuously verified whether it drifts, and the risk of data scrap due to the change of the sampling condition is reduced to a certain extent.

Description

Technical Field

[0001] This invention belongs to the field of water sampling technology, and specifically discloses a method for sampling, monitoring and analyzing groundwater environment. Background Technology

[0002] Groundwater sampling is an essential part of groundwater environmental monitoring. Because groundwater resides in the pores or fissures of aquifers, the water quality inside the wellbore, under long-term stagnant conditions, differs from that of the surrounding aquifers and cannot represent the true water quality of the target aquifer. Therefore, before formal sampling, a well-washing operation is necessary to drain the stagnant, aged water from the wellbore, allowing fresh water from the surrounding aquifers to enter and fully exchange with the water.

[0003] In practice, well washing typically involves continuously pumping water from the monitoring well using a pump. Once the water temperature, pH value, conductivity, and other parameters of the pumped water reach stable standards, samples are taken to obtain representative water samples.

[0004] Existing technologies already have relevant technical solutions. For example, the invention patent with authorization announcement number CN112362399B proposes an intelligent groundwater low-speed well washing sampling system and method. This solution uses an airbag pump in conjunction with an air pump to achieve no contact between air and water samples throughout the sampling process. A water quality monitor is set at the outlet, and water sample parameters are measured in real time using pH sensors, conductivity sensors, and turbidity sensors. Before the parameters meet the standards, the water sample is discharged from the wastewater outlet, and after the standards are met, it is collected from the water sample outlet. This realizes the quantitative judgment of well washing effect and the automatic control of water sample collection conditions.

[0005] While the above scheme achieves real-time monitoring and automatic determination of well washing parameters, it performs a unified standard determination on all parameters acquired in real time during the well washing process at the same time segment. Since the source and occurrence state of the water body are dynamically changing during the well washing process, this change causes the response time of each parameter to water exchange to be different. Performing standard determination on multiple parameters at a unified time segment can easily lead to a lag or deviation in the determination of well washing standard, which is not conducive to the representativeness of subsequent water sample collection.

[0006] Furthermore, if the water condition in the well changes during the sample collection process after the well has been cleaned to meet the standards, the existing scheme lacks corresponding monitoring methods to verify the validity of the collected samples. Summary of the Invention

[0007] This invention proposes a groundwater environment sampling, monitoring and analysis method, which aims to overcome the above-mentioned shortcomings of the existing technology, realize the phased compliance judgment based on the differentiated response characteristics of each parameter during the well washing process, and continuously verify the water body status during the sampling process, so as to enhance the effectiveness and reliability of sample collection.

[0008] The technical solution adopted by the present invention to solve the technical problem is: a groundwater environment sampling, monitoring and analysis method, including the following steps: obtaining the water volume of the monitoring well, recording the total amount of water pumped out of the well by the pumping equipment after the well washing is started as the cumulative pumping volume, and theoretically dividing the well washing process into the first stage and the second stage based on the comparison between the cumulative pumping volume and the water volume of the well.

[0009] In the first stage, water temperature readings are collected and the water temperature at adjacent times is compared one by one. When the difference between adjacent water temperatures continues to increase, the second stage begins.

[0010] In the second stage, conductivity is collected, and the ratio of the change in conductivity to the change in the cumulative pumping volume is used as the replacement response rate. The trend of the replacement response rate is used to identify whether the replacement completion condition is met. After the replacement completion condition is met, pH readings are collected, and the deviation of the pH reading from the initial pH value is used to determine whether the well washing meets the standard.

[0011] When the well washing meets the standards, record the water temperature, pH, and conductivity readings as benchmark parameter values.

[0012] After sampling is started, multiple verification nodes are set at intervals within the preset sampling constraint time. At each verification node, sampling is paused and the water temperature, pH, conductivity and benchmark parameter values ​​are read and compared. Whether to stop sampling is determined according to the type of deviation parameter.

[0013] Combining all the above technical solutions, the positive effects of this invention are as follows: 1. This invention theoretically divides the well-washing process into a first stage and a second stage by comparing the cumulative pumping volume with the well water volume. In the first stage, water temperature readings are collected, and the continuous increase in the temperature difference between adjacent water sources is used as the trigger condition for entering the second stage. In the second stage, conductivity and pH are used together as the basis for judging whether the well-washing meets the standards. Specifically, the changing trend of the ratio of the change in conductivity to the change in the cumulative pumping volume is used to identify the replacement completion condition. After the replacement completion condition is met, the deviation of the pH reading from the initial pH value is used to determine whether the well-washing meets the standards. Thus, water temperature, conductivity, and pH are used to make judgments at different stages of the well-washing process, accurately identifying the replacement initiation and replacement completion in the well-washing process, and improving the accuracy and timeliness of judging whether the well-washing meets the standards.

[0014] 2. After the well washing meets the standards, the present invention sets verification nodes at intervals within a preset sampling constraint period and pauses sampling at each verification node. The current water temperature, pH, and conductivity readings are compared with the baseline parameter values ​​recorded when the well washing meets the standards. This can continuously verify whether the water state has drifted during the sampling process, avoid sample failure due to changes in the water during the sampling period, and reduce the risk of data failure due to changes in sampling conditions to a certain extent. Attached Figure Description

[0015] The present invention will be further described with reference to the accompanying drawings, but the embodiments in the drawings do not constitute any limitation on the present invention. For those skilled in the art, other drawings can be obtained based on the following drawings without creative effort.

[0016] Figure 1 This is a diagram illustrating the implementation steps of the method of the present invention.

[0017] Figure 2 This is a schematic diagram of water quality parameter collection at each stage in this invention.

[0018] Figure 3 This is a flowchart illustrating the process of determining whether well washing meets the standards in this invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] Figure 1 This is a flowchart of a groundwater environment sampling, monitoring and analysis method according to an embodiment of this application. The specific steps are as follows: S1. Obtain the water volume of the monitoring well. After the well washing is started, record the total amount of water pumped out of the well by the pumping equipment as the cumulative pumping volume. The well washing process is theoretically divided into the first stage and the second stage based on the comparison between the cumulative pumping volume and the water volume of the well.

[0021] After a monitoring well is completed, the water inside the wellbore has developed a water quality difference from the water in the surrounding aquifer under long-term static conditions. If the water sample is taken directly without well washing, the water sample will reflect the water quality of the water stagnant inside the wellbore rather than the true water quality of the target aquifer. Well washing, by continuously pumping water, pumps the stagnant water inside the wellbore to the surface, forcing fresh water from the surrounding aquifer to seep into and replenish the wellbore.

[0022] To determine whether well washing is complete, it is necessary to monitor the water quality parameters of the extracted water during the washing process. However, if water quality parameters are tested at the very beginning of well washing, the initial extracted water mainly consists of water already stored in the well, and the water quality parameters at this stage reflect the characteristics of the water remaining in the well, making it difficult to determine whether fresh water from the outside has entered the well. Therefore, this invention theoretically divides the well washing process into stages to reveal the replacement progress, providing a time-series reference for subsequent water quality parameter testing and well washing compliance assessment.

[0023] Considering that the cumulative pumping volume of the monitoring well is an objectively measurable progress indicator during the well washing process, and the well body water volume is the total space that the monitoring well casing and filter media can hold water, the magnitude of the cumulative pumping volume relative to the well body water volume can reflect the proportion of the water volume pumped out during well washing to the total water storage space of the well casing, and can be used as a theoretical reference benchmark for the well washing process. However, considering that the fresh water from the outside begins to seep into the well casing under the negative pressure of pumping, the actual replacement start time may be earlier than the time when the cumulative pumping volume reaches the well body water volume. Therefore, the water temperature change signal described below is used as the basis for judging the actual replacement start, and the comparison relationship between the cumulative pumping volume and the well body water volume is used as a theoretical boundary reference. The two are combined to realize the stage division of the washing process.

[0024] Based on the above-mentioned stage division criteria, it is first necessary to obtain the water volume of the monitoring well. However, after the monitoring well is completed, the water stored inside the well pipe and the water stored in the pores of the filter layer together constitute the total amount of water that can be pumped out. However, the water in the pores of the filter layer is located in an invisible underground area and its volume cannot be obtained by direct measurement at the wellhead. It can only be calculated based on the well structure parameters and the pore characteristics of the filter layer.

[0025] After a well is completed, its completion file records parameters such as the inner diameter of the well casing, the water level inside the well casing, the borehole diameter, the outer diameter of the well casing, the filter media filling height in the aquifer section, and the effective porosity of the filter media. The water volume in the well can be calculated using these parameters.

[0026] In one specific embodiment, the process of obtaining the water volume of the monitoring well using monitoring well parameters is as follows: First, obtain the water storage volume of the well casing: The water storage volume of the well casing refers to the volume occupied by the water column in the internal space of the well casing. Extract the inner diameter of the well casing from the well completion file, calculate the cross-sectional area of ​​the well casing based on the inner diameter, and use the product of the cross-sectional area of ​​the well casing and the water height inside the well casing as the water storage volume of the well casing. The water height inside the well casing is the height from the static water level to the bottom of the well in the static stable state after well completion. This part of the volume represents the amount of water stored in the cavity inside the well casing, that is, the space where the water was first extracted in the initial stage of well flushing.

[0027] Secondly, the volume of the annular space is obtained: During the well completion process, the borehole diameter is larger than the well casing outer diameter, and the annular gap between them is filled with filter media. The borehole diameter and well casing outer diameter recorded in the well completion file are read. The borehole cross-sectional area is calculated based on the borehole diameter, and the well casing outer cross-sectional area is calculated based on the well casing outer diameter. The volume of the annular space is obtained by subtracting the well casing outer cross-sectional area from the borehole cross-sectional area and multiplying the result by the filter media filling height of the aquifer section. This volume represents the total space occupied by the filter media filling area.

[0028] Next, the pore volume of the filter media is obtained: the filter media filling the annular space itself has pores, and the water is contained within these pores rather than occupying the volume of the filter media particles themselves. Therefore, multiplying the volume of the annular space by the effective porosity of the filter media yields the effective volume of water that can be contained within the filter media pores. This volume represents the actual water storage space in the filter media layer. The effective porosity of the filter media can be obtained from the well completion record, which records the material, particle size distribution, and corresponding effective porosity measurement value of the filter media used during well completion. If it is not recorded in the well completion record, it can be determined by referring to relevant technical manuals based on the filter media material and particle size distribution.

[0029] Finally, the well volume is determined: the total amount of water that can be extracted from the monitoring well includes both the water stored in the cavity inside the well pipe and the water stored in the pores of the filter layer. Therefore, the sum of the water storage volume in the well pipe and the pore volume of the filter layer is taken as the well volume of the monitoring well. This well volume is the water storage capacity of the monitoring well in a static state, and serves as a fixed benchmark for the theoretical stage division during the well washing process.

[0030] Since the cross-sections of the well casing, borehole, and outer wall of the well casing are all circular, their respective cross-sectional areas can be obtained by converting their corresponding diameters to radii and substituting them into the formula. Therefore, the expression for calculating the cross-sectional area based on the inner diameter in the above operation is: ,in represents the inner diameter, It represents pi (π).

[0031] Furthermore, after obtaining the water volume of the monitoring well, the total amount of water pumped out of the well by the pumping equipment during the well washing process needs to be recorded simultaneously as the cumulative pumping volume. The specific method is as follows: when the well washing is started before sampling, the start time is used as the starting point for measuring the cumulative pumping volume.

[0032] Throughout the well washing process, the water flow rate read by the water metering device installed at the outlet of the pumping equipment is accumulated, and the accumulated value is used as the cumulative pumping volume. The cumulative pumping volume is stored in association with the reading time.

[0033] The purpose of well flushing is to allow fresh water from the surrounding aquifer to enter the wellbore and replace it. This needs to be determined by water quality parameters. However, during well flushing, the water quality parameters are relatively stable when fresh water from the surrounding aquifer has not yet entered the wellbore. Therefore, it is not very meaningful to conduct comprehensive testing of each parameter at this time.

[0034] This embodiment uses the comparison between the cumulative pumping volume and the well water volume as the theoretical boundary for dividing the well washing process into stages. When the cumulative pumping volume is less than the well water volume, theoretically, the fresh water from the outside has not fully entered the well, which is the initial stage of well washing, and is called the first stage.

[0035] When the cumulative pumping volume reaches or exceeds the well volume, theoretically the original water stored in the well has been replaced, and fresh water from the outside should occupy the well, which is recorded as the second stage.

[0036] It should be clarified that the water quality parameters mentioned above do not refer to the various indicators that are collected after well washing and sent to the laboratory for testing. Instead, they refer to the on-site water quality indicators that can be read in real time at the outlet of the pumping equipment through a detection probe. These mainly include water temperature, pH value, and conductivity. These indicators can reflect the basic characteristics of the water source and can be obtained at the outlet through a detection probe.

[0037] S2. In the first stage, water temperature readings are collected and the water temperature at adjacent times is compared one by one. When the difference between adjacent water temperatures continues to increase, the second stage is entered.

[0038] See Figure 2 After the well washing process is divided into stages, since the division is based on the theoretical comparison between the cumulative pumping volume and the well water volume, the fresh water from the outer aquifer may enter the well before the cumulative pumping volume reaches the well water volume. If the water quality parameter detection is started after the first stage is completed, the initial signal of parameter changes when the outer water enters early may be missed, resulting in a delay in the start of the second stage.

[0039] To address the aforementioned issues, this invention considers the varying response characteristics of different water quality parameters to the influx of external water into the wellbore. Specifically, the water temperature signal reflects the mixing trend between the wellbore's stored water and the surrounding water in the initial stage of well washing, and its changes can be used to determine whether replacement has commenced. Changes in conductivity directly correlate with the degree of reduction in the chemical composition differences between the water within the wellbore and the surrounding aquifer, while changes in pH reflect the shift in acid-base balance. Both serve as the basis for determining whether well washing has met standards. Therefore, water temperature is used as a priori indicator parameter, and water temperature changes are continuously monitored in the first stage to indicate whether to proceed to the second stage.

[0040] Before using water temperature for the first stage of judgment, the validity of the water temperature signal is pre-evaluated: the water temperature of the static water in the well before the well washing is started is read as the initial value of the well water temperature, and the known temperature data of the aquifer outside the area where the monitoring well is located is read as the reference value of the surrounding water temperature, and the two are compared.

[0041] If the difference between the two can be detected by the detection probe, the water temperature signal is deemed valid, and the determination is made using water temperature changes in the first stage.

[0042] If the difference between the two cannot be recognized by the detection probe, the water temperature signal is deemed invalid, and the first stage of water temperature determination is skipped. Instead, the cumulative pumping volume reaches the well water volume as the trigger condition for entering the second stage.

[0043] In one specific embodiment, the first stage of the process is as follows: the inlet of the pumping equipment is placed at a fixed depth in the middle of the screen tube inside the well, and a detection probe is set at the outlet of the pumping equipment. The detection probe has real-time detection functions for water temperature, conductivity and pH value. The minimum resolution of each parameter can be read from the manufacturer's technical specifications of the detection probe, which is used to determine whether the parameter change reaches the level that the probe can detect.

[0044] In the first stage, the detection probe is used to continuously collect water temperature readings at equal time intervals, and the absolute value of the difference between the current water temperature reading and the previous water temperature reading is calculated as the current adjacent water temperature difference.

[0045] In the early stage of well washing, the extracted water mainly consists of the original water stored in the well. The water source is singular, and the temperature difference between adjacent waters is at a low level. The current adjacent water temperature difference is compared with the previous adjacent water temperature difference. If the current adjacent water temperature difference is greater than the previous adjacent water temperature difference, it indicates that the temperature change range is expanding, which means that water of different temperatures from the surrounding aquifer is entering the well and mixing with the well water. At this time, a difference expansion event is recorded.

[0046] When the difference widening event occurs within three consecutive monitoring cycles, it indicates that the temperature difference between adjacent water bodies is continuously increasing, suggesting that fresh water from the outside is entering the well and dominating the temperature change. Even if the cumulative pumping volume has not reached the well volume at this time, it means that the actual start of replacement is earlier than the theoretical water volume boundary, and the second stage is entered ahead of schedule.

[0047] If the cumulative pumping volume increases to be greater than or equal to the well volume but the water temperature difference does not continue to expand, it indicates that the water temperature difference between the surrounding aquifer and the well water is insufficient as a valid signal. If we continue to wait for the water temperature to change, it may cause unnecessary time consumption. Therefore, the first stage ends and the second stage begins, in which the conductivity parameters of the subsequent stage continue to identify and determine the compliance of the well washing process.

[0048] S3. In the second stage, the conductivity is collected, and the ratio of the change in conductivity to the change in the cumulative pumping volume is used as the replacement response rate. The trend of the replacement response rate is used to identify whether the replacement completion condition is met. After the replacement completion condition is met, the pH reading is collected, and the deviation of the pH reading from the initial pH value is used to determine whether the well washing meets the standard.

[0049] After the first stage is completed, it has been confirmed that fresh water from the outside is continuously entering the well, and the replacement process has started. At this time, conductivity and pH can be used to detect the replacement process to determine whether the well washing meets the standards.

[0050] In this embodiment, the detection order is set first for conductivity and then for pH. This is because conductivity reflects the concentration of total dissolved ions in the water and is sensitive to changes in the mixing ratio of the two water sources. It can continuously indicate the degree of reduction in the chemical composition difference between the water inside the well and the surrounding aquifer during the replacement process. pH, on the other hand, is controlled by the water's buffering system, and its changes usually only become apparent after the replacement has progressed to a certain extent, making it more suitable as the final confirmation indicator for replacement completion. Therefore, conductivity is used first to determine whether replacement has progressed, and then pH is used to verify whether replacement is complete, forming a progressive confirmation relationship.

[0051] See Figure 3 As one possible implementation of the present invention, S3 includes the following:

[0052] S31. Determination of the substitution response rate.

[0053] The rate of change of electrical conductivity during the displacement process is not constant. It changes most rapidly in the initial mixing stage when the peripheral water first enters the wellbore, and the rate of change gradually slows down as displacement progresses. To characterize this rate of change, the displacement response rate is introduced as a quantitative indicator.

[0054] In the second stage, the conductivity readings are continuously collected at equal time intervals using the detection probes installed at the outlet of the pumping equipment, and the cumulative pumping volume at each time point is recorded.

[0055] The second stage timeline is divided into multiple monitoring windows in chronological order, with no overlap between the monitoring windows. Each monitoring window has a preset length; for example, the preset length of the monitoring window can cover at least 5 consecutive conductivity readings.

[0056] For each monitoring window, the change in conductivity between the start and end points of the window, as well as the change in cumulative pumping volume between the start and end points of the same window, are recorded.

[0057] The displacement response rate of the monitoring window is defined as the ratio between the change in conductivity and the change in cumulative pumping volume, with dimensions in μS·cm. -1 ·L -1 (When conductivity is expressed in μS / cm and cumulative pumping volume is expressed in L).

[0058] Under relatively stable pumping rates, the change in displacement response rate mainly reflects the change in conductivity. Its physical meaning is the change in conductivity caused by pumping out a unit volume of water, that is, the sensitivity of water quality to continued pumping during the displacement process. The larger the ratio, the more sensitive the conductivity is to the change in pumping rate at the current stage, and the difference in chemical composition between the peripheral water and the well water is being rapidly reduced. When the ratio approaches zero, it indicates that continued pumping no longer causes a change in conductivity.

[0059] In order to ensure that the calculated displacement response rate has a sufficient signal-to-noise ratio, the cumulative change in pumping volume in the above displacement response rate calculation shall not be less than the volume corresponding to the minimum resolution of the water metering device.

[0060] It should be noted that the displacement response rate is not a conversion of conductivity into an absolute value of total dissolved solids, but rather a relative characterization of the rate of change in conductivity during the displacement process. During well washing, the change in the ionic composition of the water within the wellbore mainly comes from the mixing of the wellbore's stored water and the fresh water from the surrounding aquifer. The ionic compositions of the two water bodies are relatively stable, and the impact of changes in the ionic composition ratio during mixing on conductivity is within a controllable range. Therefore, the displacement response rate can be used to characterize the degree of displacement advancement.

[0061] S32, Replacement completed and identification completed.

[0062] As the monitoring window progresses along the time axis, the displacement response rates calculated for each monitoring window are arranged in chronological order to form a displacement response rate sequence.

[0063] The trajectory of the displacement response rate depends on the degree of conductivity difference between the surrounding aquifer water and the well water, and there are two scenarios:

[0064] Scenario 1: Large difference in conductivity.

[0065] When there is a large difference in conductivity between the water in the surrounding aquifer and the water in the well, the water in the surrounding aquifer begins to mix with the water in the well in the early stage of replacement, the rate of change of conductivity gradually increases, and the replacement response rate rises from a low value; in the middle stage of replacement, the change of conductivity is the most drastic, and the replacement response rate reaches its peak; in the later stage of replacement, as the water in the well gradually approaches the water quality of the surrounding aquifer, the rate of change of conductivity gradually slows down, and the replacement response rate falls back from its peak value.

[0066] For scenario one, the following method is used to identify the conditions for completion of the permutation: compare the permutation response rates of adjacent windows in the permutation response rate sequence one by one, and mark the turning point in the adjacent comparison where the permutation response rate changes from the previous window being smaller than the next window to the previous window being larger than the next window, as the peak position of the permutation response rate.

[0067] After the peak position, the displacement response rate is continuously compared with that of adjacent windows. When the displacement response rate is less than a preset zero threshold in multiple consecutive windows, the displacement response rate is determined to have met the condition for completion of displacement. The preset zero threshold is determined by the ratio of the conductivity resolution of the detection probe to the resolution of the water metering device. For example, in a typical groundwater well flushing scenario, the initial value of the displacement response rate is usually between 0.1 and 10 μS·cm. -1 ·L -1Within the range, it gradually decreases as the replacement process progresses, reaching a minimum of 0.01 μS·cm. -1 ·L -1 The following conditions can be used to determine that the displacement response rate meets the conditions for displacement completion.

[0068] Scenario 2: Small difference in conductivity.

[0069] When the difference in electrical conductivity between the water in the surrounding aquifer and the water in the well is small, the electrical conductivity changes slowly from the beginning of the replacement process, and the replacement response rate will not rise or reach a peak, but will always remain at a low level.

[0070] For scenario two, the replacement completion condition is identified as follows: If no peak position appears in the replacement response rate sequence, sufficient water replacement is used as the criterion for replacement completion. This can avoid unnecessary well washing time extension caused by waiting for the conductivity change to narrow further, while ensuring the representativeness of the sample. Specifically, when the cumulative pumping volume reaches a preset multiple of the well water volume, it is determined that the replacement completion condition has been met.

[0071] The above-mentioned preset multiple is preferably 3 times, based on the fact that in conventional well washing practice, the volume of water discharged from the well is usually required to reach 3 to 5 times the volume of water in the well body in order to be considered as sufficient replacement.

[0072] S33, pH deviation verification.

[0073] Once the replacement conditions are met, it indicates that, from the perspective of ion concentration, the total dissolved solids in the wellbore water have approached the level of the surrounding aquifer. However, conductivity alone is insufficient to confirm whether the acid-base balance has also migrated synchronously; therefore, independent verification of the acid-base balance is required.

[0074] pH, as an indicator of the acid-base balance of a water body, is controlled by the water's buffering system. At the start of well flushing, the pH value reflects the acid-base characteristics of the water stored in the well. As fresh water from the surrounding aquifer enters the well and gradually replaces the existing water, the acid-base balance of the mixed water shifts. If the replacement is complete, the acid-base balance of the water within the well should have shifted from the initial characteristics of the well's stored water to those of the surrounding aquifer. Therefore, by using the initial pH value recorded at the start of well flushing as a reference, monitoring the deviation of the pH from the initial value can determine whether the acid-base balance shift has been completed.

[0075] The specific verification process is as follows: pH readings are continuously collected using a detection probe installed at the outlet of the pumping equipment.

[0076] Using the initial pH value recorded at the start of well washing as a reference, the pH reading at each moment is compared with the initial pH value successively. The difference between the current pH reading and the initial pH value is calculated, and the sign of the difference is recorded as the direction of deviation. The difference is used to quantify the degree of pH deviation from the initial value; the larger the difference, the more obvious the acid-base balance shift. The sign is used to confirm the direction of deviation. If the sign of the deviation direction remains consistent at each moment, it indicates that the pH is continuously shifting from the initial value in a single direction. The combination of both is used to determine whether the pH has deviated from the initial value.

[0077] When the pH deviation exceeds the upper limit of the normal fluctuation range at multiple sampling times, and the positive and negative signs of the deviation direction remain consistent at each time, it is determined that the pH has deviated, that is, the acid-base balance of the water in the well has migrated from the initial well water storage characteristics to the characteristics of the surrounding aquifer, and the well washing meets the standard. Otherwise, it indicates that the pH has not completed the migration, and subsequent readings should be collected and monitored until the above conditions are met.

[0078] The above-mentioned normal fluctuation range can be determined in the following way: pH readings are collected at equal time intervals from the end of the first stage to the beginning of the second stage. The maximum and minimum values ​​of pH readings during this period are recorded. The difference between the two values ​​is taken as the natural fluctuation range of pH in the state where no migration has occurred. The set multiple of the natural fluctuation range is preferably 2 times as the boundary of the normal fluctuation range.

[0079] S4. When the well washing meets the standards, record the water temperature, pH, and conductivity readings as benchmark parameter values.

[0080] Once the well washing is deemed successful, it indicates that the water quality in the monitoring well has approached the actual water quality state of the surrounding aquifer, meeting the conditions for water sampling. At this point, the water temperature, pH, and conductivity readings at the moment the standard is met are recorded as baseline parameter values. These baseline parameter values ​​record the water quality state in the well at the time the well washing is successful and serve as a reference for determining whether the water quality has changed during the sampling period.

[0081] S5. After sampling starts, multiple verification nodes are set at intervals within the preset sampling constraint time. At each verification node, sampling is paused and the water temperature, pH, conductivity and benchmark parameter values ​​are read and compared. The type of deviation parameter determines whether to stop sampling.

[0082] Although the water quality inside the wellbore after well washing is close to the true water quality of the surrounding aquifer, changes in water quality due to external factors during sampling will affect the representativeness of the samples. Therefore, a sampling constraint period is usually set after well washing to require sampling to be completed within this period, in order to reduce the risk of changes in water quality. However, this period is only a standard time constraint and does not mean that the water quality will necessarily remain unchanged within this period.

[0083] To this end, the present invention sets multiple verification nodes at intervals within the sampling constraint period, and verifies the water status in real time at each verification node to confirm whether the water in the well during the sampling period is still consistent with the water quality when the well was washed to meet the standard.

[0084] It should be noted that water temperature changes reflect the thermal state of the water body, and a single deviation from the baseline value does not necessarily indicate a substantial change in the water composition. However, changes in conductivity and pH directly reflect the ion concentration and acid-base balance of the water body; deviations from the baseline value indicate a genuine change in the water composition. Therefore, this invention makes differentiated judgments at the verification node based on the type of deviation parameter: sampling is immediately stopped when conductivity or pH deviates, while sampling continues after recording when water temperature deviates alone, for further confirmation at the next verification node.

[0085] The specific verification process is operated according to the following example:

[0086] First, configure the verification node.

[0087] The preset sampling constraint duration is divided into multiple intervals, and a verification node is set at the boundary of each interval. The verification nodes are evenly distributed along the sampling time axis. After sampling starts, the verification nodes arrive sequentially according to the progress order of the sampling time axis.

[0088] In one specific embodiment, the sampling constraint duration is set to 2 hours, which is divided into four intervals. Verification nodes are set at the first quarter, the second quarter, and the third quarter, respectively. That is, a verification node is set at the 30-minute, 60-minute, and 90-minute positions along the sampling time axis.

[0089] Secondly, the comparison at the verification node.

[0090] After sampling starts, the time consumed by sampling is continuously recorded. Sampling is paused when the time consumed by sampling reaches the current verification node position.

[0091] In the paused state, the current water temperature, pH, and conductivity readings are read and compared with the water temperature, pH, and conductivity baseline values ​​recorded when the well was washed to meet the standards. The deviation values ​​of each parameter are calculated. The deviation values ​​reflect the degree of deviation between the water state in the well when sampling reaches the current verification node and the water state when the well was washed to meet the standards. The larger the deviation, the higher the degree of deviation of the sampling conditions from the effective state.

[0092] Next, the results of the comparison are determined.

[0093] If the pH or conductivity deviation exceeds the minimum resolution of the detection probe, it indicates that the chemical composition of the water in the well has changed during the sampling period, the sampling conditions have failed, triggering a stop sampling signal, and the sampling is immediately terminated.

[0094] If the pH deviation and conductivity deviation do not exceed the minimum resolution of the detection probe, but the water temperature deviation exceeds the minimum resolution of the detection probe, then the water temperature deviation alone is insufficient to determine that the water state has undergone a substantial change, and further confirmation is required from the next verification node.

[0095] At the next verification node, if the pH deviation or conductivity deviation exceeds the minimum resolution of the detection probe, it is determined that the water state has changed, triggering a stop acquisition signal and terminating the sampling.

[0096] If the pH deviation and conductivity deviation at the next calibration node do not exceed the minimum resolution of the detection probe, continue sampling until the next calibration node or all samples are collected.

[0097] The minimum resolution of the detection probe refers to the minimum change in reading that the probe can identify and output. When the actual change in the parameter is less than this resolution, the probe outputs a constant reading. When the actual change in the parameter reaches or exceeds the resolution, the probe outputs a recognizable change in reading.

[0098] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0099] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0100] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0101] Finally, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for sampling, monitoring, and analyzing groundwater environment, characterized in that, include: The water volume in the monitoring well is obtained. After the well washing is started, the total amount of water pumped out of the well by the pumping equipment is recorded as the cumulative pumping volume. The well washing process is theoretically divided into the first stage and the second stage based on the comparison between the cumulative pumping volume and the water volume in the well. In the first stage, water temperature readings are collected and the water temperature at adjacent times is compared one by one. When the difference between adjacent water temperatures continues to increase, the second stage is initiated. In the second stage, conductivity is collected, and the ratio of the change in conductivity to the change in cumulative pumping volume is used as the replacement response rate. The trend of the replacement response rate is used to identify whether the replacement completion condition is met. After the replacement completion condition is met, pH reading is collected, and the deviation of the pH reading from the initial pH value is used to determine whether the well washing meets the standard. When the well washing meets the standards, record the water temperature, pH, and conductivity readings as baseline parameter values; After sampling is started, multiple verification nodes are set at intervals within the preset sampling constraint time. At each verification node, sampling is paused and the water temperature, pH, conductivity and benchmark parameter values ​​are read and compared. Whether to stop sampling is determined according to the type of deviation parameter.

2. The groundwater environment sampling, monitoring, and analysis method as described in claim 1, characterized in that: The process of obtaining the water volume in the monitoring well is as follows: The well pipe inner diameter and the water height inside the well pipe are extracted from the well completion records of the monitoring wells. The product of the well pipe cross-sectional area and the water height inside the well pipe is used as the water storage volume of the well pipe. The borehole diameter and well casing outer diameter recorded in the well completion file are read to calculate the cross-sectional area of ​​the borehole and the outer cross-sectional area of ​​the well casing, respectively. The volume of the annular space is obtained by subtracting the outer cross-sectional area of ​​the well casing from the cross-sectional area of ​​the borehole and multiplying it by the filling height of the filter material in the aquifer section. The product of the annular space volume and the effective porosity of the filter media is taken as the pore volume of the filter media. The sum of the water storage volume in the well casing and the pore volume of the filter material is used as the water volume in the monitoring well.

3. The groundwater environment sampling, monitoring, and analysis method as described in claim 1, characterized in that: The process of recording the total amount of water pumped out of the well by the pumping equipment as the cumulative pumping volume after the well washing is started is as follows: The starting point for measuring the cumulative pumping volume is the time when well washing starts. During the entire well washing process, the water flow rate read by the water metering device at the outlet of the pumping equipment is accumulated, and the accumulated value is used as the cumulative pumping volume.

4. The groundwater environment sampling, monitoring, and analysis method as described in claim 1, characterized in that: The well-washing process is theoretically divided into a first stage and a second stage, as described below: During the well cleaning process, the current cumulative pumping volume is continuously compared with the water volume in the well. When the cumulative pumping volume is less than the well volume, well washing is in the first stage. When the cumulative pumping volume increases to be greater than or equal to the well volume, well washing enters the second stage.

5. The groundwater environment sampling, monitoring, and analysis method as described in claim 4, characterized in that: The process of entering the second stage when the temperature difference between adjacent waters continues to increase is as follows: The inlet of the pumping equipment is placed at a fixed depth in the middle of the screen pipe inside the well, and a detection probe is installed at the outlet of the pumping equipment. Before using water temperature for the first stage of judgment, the water temperature of the static water in the well before the well washing is started is read as the initial value of the well water temperature, and the known temperature data of the aquifer outside the area where the monitoring well is located is obtained as the reference value of the surrounding water temperature. The two are then compared. If the difference between the two can be identified by the detection probe, then in the first stage, the detection probe is used to continuously collect water temperature readings at equal time intervals, and the absolute value of the difference between the current water temperature reading and the previous water temperature reading is calculated as the current adjacent water temperature difference. Compare the current adjacent water temperature difference with the previous adjacent water temperature difference. If the current adjacent water temperature difference is greater than the previous adjacent water temperature difference, record a difference amplification event. When the difference widening event occurs within three consecutive monitoring periods, the first stage ends and the second stage begins. If the cumulative pumping volume increases to a level greater than or equal to the well volume without a continuous increase in the water temperature difference, then the first stage ends and the second stage begins. If the difference between the two is not detected by the detection probe, the first stage of water temperature determination is skipped, and the cumulative pumping volume reaches the well water volume as the trigger condition for entering the second stage.

6. The groundwater environment sampling, monitoring, and analysis method as described in claim 1, characterized in that: The displacement response rate is determined as follows: After entering the second stage, the conductivity readings are continuously collected at equal time intervals using the detection probe set at the outlet of the pumping equipment, and the cumulative pumping volume at each time moment is recorded. The second phase timeline is divided into multiple monitoring windows in chronological order, with no overlap between the monitoring windows; For each monitoring window, the change in conductivity between the start and end points of the window, as well as the change in cumulative pumping volume between the start and end points of the same window, are recorded. The displacement response rate of the monitoring window is the ratio between the change in conductivity and the change in cumulative pumping volume.

7. The groundwater environment sampling, monitoring, and analysis method as described in claim 6, characterized in that: The process of identifying whether the conditions for completion of the permutation are met is as follows: The displacement response rates calculated from each monitoring window are arranged in chronological order to form a displacement response rate sequence. In the permutation response rate sequence, the permutation response rates of adjacent windows are compared one after another, and the turning point where the permutation response rate changes from the previous window being smaller than the next window to the previous window being larger than the next window is marked as the peak position. If a peak position exists, the permutation response rate of adjacent windows is compared sequentially after the peak position. When the permutation response rate is less than the preset zero threshold in multiple consecutive windows, it is determined that the permutation completion condition has been met. If no peak position appears in the replacement response rate sequence, the replacement completion condition is determined when the cumulative pumping volume reaches a preset multiple of the well water volume.

8. The groundwater environment sampling, monitoring and analysis method as described in claim 1, characterized in that: The process for determining whether well washing meets the standards is as follows: After the replacement conditions are met, pH readings are continuously collected using a detection probe installed at the outlet of the pumping equipment. Using the initial pH value recorded at the start of well washing as a reference, the pH reading at each moment is compared with the initial pH value one by one, the difference between the current pH reading and the initial pH value is calculated, and the sign of the difference is recorded as the direction of deviation. When the pH deviation exceeds the upper limit of the normal fluctuation range at multiple sampling times, and the positive and negative signs of the deviation direction remain consistent at each time, the well washing is deemed to have met the standard. Otherwise, sampling and monitoring of subsequent readings will continue until the above conditions are met.

9. The groundwater environment sampling, monitoring, and analysis method as described in claim 1, characterized in that: The process of setting up multiple verification nodes is as follows: The preset sampling constraint duration is divided into multiple intervals, and a verification node is set at the boundary of each interval. After sampling is initiated, each verification node arrives sequentially according to the progress order of the sampling timeline.

10. A groundwater environment sampling, monitoring, and analysis method as described in claim 9, characterized in that: The process of determining whether to stop the data acquisition based on the type of deviation parameter is as follows: After sampling starts, the time consumed by sampling is continuously recorded. When the time consumed by sampling reaches the current verification node position, the sampling operation is paused. In the paused state, read the current water temperature, pH and conductivity readings, and compare them with the water temperature reference value, pH reference value and conductivity reference value recorded when the well washing meets the standard, and calculate the deviation value of each parameter; If the pH deviation or conductivity deviation exceeds the minimum resolution of the detection probe, a stop acquisition signal is triggered, and sampling is terminated. If the pH deviation and conductivity deviation do not exceed the minimum resolution of the detection probe, but the water temperature deviation exceeds the minimum resolution of the detection probe, then sampling continues. If the pH deviation or conductivity deviation exceeds the minimum resolution of the detection probe at the next calibration node, a stop acquisition signal is triggered, and sampling is terminated. If the pH deviation and conductivity deviation at the next calibration node do not exceed the minimum resolution of the detection probe, continue sampling until the next calibration node or all samples are collected.

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