An emergency groundwater source origin analysis method combining isotope dating and hydrochemistry

Abstract

The application provides an emergency groundwater source origin analysis method combining isotope dating and water chemistry, comprising the following steps: determining the groundwater recharge, runoff and discharge conditions of a research area according to the regional hydrogeological conditions, setting sampling points in the research area, obtaining the water chemistry ion data, hydrogen and oxygen stable isotope data and radioactive isotope data of the groundwater in the research area, obtaining the basic characteristics of the water chemistry of the regional groundwater, ion spatial distribution, main control ion and source and water-rock reaction path based on the water chemistry ion data, obtaining the groundwater recharge source information and water body age information based on the hydrogen and oxygen stable isotope data and the radioactive isotope data, coupling the information obtained based on the water chemistry ion data, the hydrogen and oxygen stable isotope data and the radioactive isotope data, integrally analyzing the groundwater water chemistry genesis and evolution law of the emergency water source, and generating a tracing conclusion. The application provides a reference basis for the management and water taking of the emergency water source.

Description

Technical Field

[0001] This invention relates to the fields of environmental science and hydrogeology, and in particular to an emergency groundwater source source analysis method based on isotope dating and hydrochemical combination. Background Technology

[0002] With the rapid development of my country's social economy and the acceleration of urbanization, water scarcity and uneven distribution have become key factors restricting people's livelihoods and sustainable economic development. Rainfall distribution in my country is extremely uneven in time and space, with most areas experiencing abundant rainfall in summer and scarce rainfall in winter. This poses a severe challenge to the single water supply method relying primarily on surface water during the dry season. At the same time, surface water bodies are susceptible to sudden pollution events and extreme weather events, such as the Songhua River pollution in 2005, the severe drought in Chongqing in 2006, and the severe meteorological drought in Jiangxi Province in 2022. These events have all seriously threatened regional water supply security, even damaging existing water supply systems and reducing their capacity, directly affecting the basic water security for urban residents.

[0003] Against this backdrop, the construction of emergency groundwater sources has become a key measure to enhance water supply resilience. However, the core of their scientific site selection and management relies on the accurate analysis of groundwater sources and hydrogeochemical characteristics. Traditional assessment methods have limitations in this regard, and there is an urgent need for a new technology that can quickly and accurately trace groundwater sources and determine their characteristics to support the scientific delineation and safety assessment of emergency water sources. Summary of the Invention

[0004] This invention provides a method for source apportionment of emergency groundwater using a combination of isotope dating and hydrochemistry, comprising: S1. Based on the regional hydrogeological conditions, determine the groundwater recharge, runoff, and discharge conditions in the study area; the regional hydrogeological conditions are obtained through data collection and field investigation. S2. Set up sampling points in the study area to obtain hydrochemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data of groundwater in the study area. S3. Based on hydrochemical ion data, obtain the basic hydrochemical characteristics of regional groundwater, spatial distribution of ions, main controlling ions and their sources, and water-rock reaction pathways; S4. Obtain information on groundwater recharge sources and water body age based on hydrogen and oxygen stable isotope data and radioactive isotope data; S5. By combining information from hydrochemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data, an integrated analysis of the hydrochemical formation and evolution of groundwater in emergency water sources is conducted to generate source tracing conclusions.

[0005] Furthermore, the regional hydrogeological conditions mentioned in step S1 include: regional aquifer system structure, groundwater recharge, runoff and discharge conditions, type and distribution of surface water bodies, geological structure and topography, hydrogeochemical background, and impact of human activities.

[0006] Furthermore, the water chemical ion data mentioned in step S2 includes Ca 2+ K + Na + Mg 2+ HCO3 - SO4 2- NO3 - Cl - F - pH value, redox potential, total dissolved solids, total hardness, total alkalinity, conductivity, and ion ratio are any one or a combination of at least two of these parameters.

[0007] Furthermore, the stable hydrogen and oxygen isotopes mentioned in step S2 are deuterium and oxygen-18.

[0008] Furthermore, the radioactive isotopes mentioned in step S2 are tritium and krypton-85.

[0009] Furthermore, step S3, which involves acquiring the basic hydrochemical characteristics, spatial distribution characteristics of ions, main controlling ions and their sources, and water-rock reaction pathways of regional groundwater based on hydrochemical ion data, includes: The hydrochemical ionic composition of groundwater was determined by statistical analysis of hydrochemical data using SPSS software. The Nemerow composite index method was used to quantitatively assess groundwater quality. Piper triline plots and the Shukalev classification method were used to determine the hydrochemical type of groundwater; The spatial distribution characteristics of groundwater ions were obtained using the Kriging interpolation method, and the potential spatial range of pollution in the study area was preliminarily determined. The sources of dominant ions in groundwater and the water-rock reaction pathways were determined using hydrochemical graphical methods and groundwater chemical inverse simulation. The hydrochemical graphical methods included Gibbs diagrams, Gaillardet endmember diagrams, and ion proportioning coefficient methods.

[0010] Furthermore, the ion content ratio relationships in the ion ratio coefficient method include: the ratio of the total concentration of sodium ions plus potassium ions to the concentration of chloride ions; the ratio of the total concentration of calcium ions plus magnesium ions to the total concentration of bicarbonate ions plus sulfate ions; the ratio of the total concentration of calcium ions plus magnesium ions to the concentration of bicarbonate ions; the ratio of the result of the concentration ratio of magnesium ions to calcium ions to the concentration of bicarbonate ions; the ratio of the total concentration of calcium ions plus magnesium ions minus sulfate ions minus bicarbonate ions to the total concentration of sodium ions plus potassium ions minus chloride ions; and the ratio of the result of sulfate ions to calcium ions to the result of the result of nitrate ions to calcium ions.

[0011] Furthermore, the process of obtaining groundwater recharge source information and water body age information based on hydrogen and oxygen stable isotope data and radioactive isotope data in step S4 includes: Hydrogen and oxygen isotope analysis maps of unconfined and confined water samples in the study area were drawn. The sources of groundwater recharge were determined by referring to global and local atmospheric precipitation lines. Information on recharge sources was also determined by deuterium surplus. The age of groundwater in the study area was calculated using krypton and tritium isotopes, and the spatial distribution of groundwater age in the study area was obtained by combining the analysis.

[0012] Furthermore, the information obtained in step S5, which involves coupling water chemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data, to conduct an integrated analysis of the hydrochemical formation and evolution of groundwater in emergency water source areas, includes: The source of groundwater recharge and evaporation history in the study area were determined by hydrogen and oxygen stable isotope data, which served as the initial boundary conditions for hydrochemical evolution. Determining the age of groundwater using radioactive isotope data provides a timescale constraint for the evolution of water chemistry. Geochemical simulations and inverse calculations were performed based on water chemical ion data under the initial boundary conditions and time scale constraints to quantify the water-rock interaction process. By cross-validating and analyzing the information obtained from the three types of data, the complete chemical evolution path of groundwater from recharge to discharge in the study area was obtained.

[0013] Furthermore, the source tracing conclusions mentioned in step S5 include the groundwater source quality in the study area, the main controlling ions and sources of groundwater, the scope and type of groundwater pollution, the sources of groundwater recharge, the age distribution of groundwater, and the direction of groundwater runoff.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1) It overcomes the limitations and ambiguities of traditional single-technology methods. By coupling water chemistry, hydrogen and oxygen stable isotope and radioactive isotope data, it can achieve rapid and accurate source tracing in the event of a sudden water crisis, thereby improving emergency response capabilities.

[0015] 2) Reveal the entire process of water chemical evolution to support the scientific diagnosis and prediction of emergency water sources.

[0016] 3) Provides multi-dimensional decision support and optimizes the whole life cycle management of water sources. Attached Figure Description

[0017] Figure 1 A flowchart illustrating an emergency groundwater source analysis method combining isotope dating and hydrochemistry, provided as an embodiment of the present invention.

[0018] Figure 2 A distribution diagram of sampling point locations provided for embodiments of the present invention.

[0019] Figure 3 Piper diagram of water chemistry types in the study area provided for embodiments of the present invention.

[0020] Figure 4 Spatial distribution map of groundwater chemistry in the study area provided for embodiments of the present invention.

[0021] Figure 5 Spatial distribution map of the hydrochemical properties of confined water in the study area provided for embodiments of the present invention.

[0022] Figure 6 Correlation diagram of groundwater chemical indicators in the study area provided for embodiments of the present invention.

[0023] Figure 7 Correlation diagram of hydrochemical indicators of confined water in the study area provided for embodiments of the present invention.

[0024] Figure 8 Gibbs diagram of groundwater chemistry in the study area provided for embodiments of the present invention.

[0025] Figure 9 Gaillardet endmember diagram of groundwater chemistry in the study area provided for embodiments of the present invention.

[0026] Figure 10 A graph showing the proportion of ions in the groundwater of the study area provided for an embodiment of the present invention.

[0027] Figure 11 The chlor-alkali index diagram of the study area provided for embodiments of the present invention.

[0028] Figure 12 (Ca) provided for the embodiments of the present invention 2+ +Mg 2+ )-(HCO3) - +SO4 2- ) and (Na + +K + )-Cl- Change diagram.

[0029] Figure 13 The reverse simulation path diagram provided for embodiments of the present invention.

[0030] Figure 14 NO3 in groundwater provided in the embodiments of the present invention - / Ca 2+ With SO4 2- / Ca 2+ Relative relationship diagram.

[0031] Figure 15 This is a hydrogen and oxygen isotope analysis diagram provided in an embodiment of the present invention.

[0032] Figure 16 Groundwater provided for embodiments of the present invention 85 Schematic diagram for calculating groundwater age using Kr.

[0033] Figure 17 The tritium input curve of atmospheric precipitation in Xinyu area is provided for the embodiments of the present invention.

[0034] Figure 18 A groundwater age distribution map of the study area provided for an embodiment of the present invention.

[0035] Figure 19 A conceptual model of groundwater hydrochemical evolution provided for embodiments of the present invention. Detailed Implementation

[0036] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in 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 this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0037] Example 1 Please see Figure 1 , Figure 1 A flowchart illustrating the steps of an emergency groundwater source apportionment method combining isotopic dating and hydrochemistry, provided in an embodiment of the present invention.

[0038] This invention provides a method for source apportionment of emergency groundwater using a combination of isotope dating and hydrochemistry, comprising: S1. Based on the regional hydrogeological conditions, determine the groundwater recharge, runoff, and discharge conditions in the study area; the regional hydrogeological conditions are obtained through data collection and field investigation. S2. Set up sampling points in the study area to obtain hydrochemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data of groundwater in the study area. S3. Based on hydrochemical ion data, obtain the basic hydrochemical characteristics of regional groundwater, spatial distribution of ions, main controlling ions and their sources, and water-rock reaction pathways; S4. Obtain information on groundwater recharge sources and water body age based on hydrogen and oxygen stable isotope data and radioactive isotope data; S5. By combining information from hydrochemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data, an integrated analysis of the hydrochemical formation and evolution of groundwater in emergency water sources is conducted to generate source tracing conclusions.

[0039] Application Example 1 This application example uses the method described in Example 1 to perform source analysis on groundwater in the study area, which is the Ma Hong groundwater emergency water source in the northeast of Xinyu City, Jiangxi Province.

[0040] 1. Determination of the recharge-runoff-discharge relationship in the study area Data collection and field investigation were conducted in the study area to analyze the geographical location, aquifer system structure, groundwater recharge, runoff and discharge conditions, surface water types and distribution, geological structure and topography, hydrogeochemical background, and the impact of human activities, revealing the recharge-runoff-discharge relationship of groundwater in the study area.

[0041] 2. Sampling point setup Based on the hydrogeological conditions of the study area, sampling points were scientifically deployed at different hydrogeological units (such as recharge zones, runoff zones, and discharge zones), different depths (shallow wells and confined wells), and downstream of potential pollution sources. The sampling point distribution map is shown below. Figure 2 As shown.

[0042] Sampling work was mainly carried out using exploration wells and domestic pumping wells in the study area. Among them, the domestic pumping wells were relatively shallow and mainly represented unconfined aquifers; the exploration wells and some pumping wells were relatively deep and were used to collect deep confined water.

[0043] Before sampling water from the deep well, the well was cleaned. Sample collection began when the extracted water was free of particulate matter and colorless. Before sampling, a 500ml polyethylene plastic sampling bottle was rinsed three times with the water sample. The bottle was then filled with the water sample, and the opening was quickly sealed with sealing film. A label was affixed, and the sampling number was recorded for determination of anions, cations, tritium isotopes, and stable hydrogen and oxygen isotopes. The water sample was degassed using a water flow vacuum degasser. Gas was collected through the exhaust pipe. An aluminum vacuum bag was placed in a basin containing the water sample, with the water level above the bag's inlet. When the gas reached two-thirds of the bag's capacity, the cap was tightened underwater, and the sampling number was recorded for determination.85 Kr isotopes. Simultaneously, the surrounding environment of the sampling points was observed and recorded to facilitate later analysis.

[0044] In this application example, a total of 26 sets of anion and cation water samples were collected, including 7 sets of unconfined water samples and 19 sets of confined water samples; at the same time, 9 tritium isotope water samples, 1 krypton isotope water sample, and 26 stable hydrogen and oxygen isotope water samples were collected.

[0045] This water sample testing included the determination of routine hydrochemical indicators, stable isotopes of hydrogen and oxygen, tritium isotopes, krypton isotopes, and anions and cations in the groundwater samples. Specifically, the anion and cation contents of the groundwater samples were sent to the 240 Research Institute of Nuclear Industry for testing; the stable isotopes of hydrogen and oxygen and tritium isotopes were sent to the Third Institute of Oceanography, Ministry of Natural Resources for testing; the krypton isotopes were sent to the University of Science and Technology of China for testing; and the remaining indicators were measured on-site. pH was measured using a Hach portable pH meter (HACH, HQ11D, USA), and temperature, ORP, TDS, and conductivity were measured using a portable water quality analyzer (Eureka, Manta, USA).

[0046] 3. Data Validation and Analysis Methods 3.1 Verification of the accuracy of water sample data Before conducting the research, to ensure the reliability of the research conclusions, the accuracy of the collected water sample data was verified. First, the accuracy of all collected groundwater sample data was verified using the anion-cation balance test method, based on formulas (1) and (2): (1) Where: m a Indicates the molar concentration of cations; m c Z represents the molar concentration of the anion; Z represents the charge number of the ion.

[0047] Based on formula (1), the formula for testing the ion charge balance of groundwater in this application example is shown in formula (2): (2) Meanwhile, the charge balance error E (%) of each groundwater sample is calculated according to formula (3) to further evaluate the data quality. The formula is as follows: (3) In the formula, Nc represents the cation milliequivalent concentration and Na represents the anion milliequivalent concentration.

[0048] In a preferred embodiment of this application example, the sum of the products of the molar concentration of cations and the number of charges in the water sample is calculated according to formula (2) as 0.12, and the sum of the products of the molar concentration of anions and the number of charges is also 0.12, indicating that the ion charge in the water sample has reached equilibrium. At the same time, the charge balance error of all water samples is calculated according to formula (3) as less than 5%, and the average error is only 0.4%, indicating that the water quality test results are reliable and the data can be used for subsequent analysis.

[0049] 3.2 Data Analysis Methods This application example employs different analytical methods to analyze the acquired data. Excel is used for preliminary processing of the measured data from unconfined and confined water, followed by statistical analysis using SPSS 26 software. Origin 2021 is used to generate key maps such as Piper triline plots, Gibbs plots, Gaillardet endmember plots, and ion proportion plots. PHREEQC software is used to simulate and calculate the mineral saturation index in groundwater, and Suffer software is used to generate spatial distribution maps of hydrochemical indicators.

[0050] 4. Analysis of basic chemical characteristics of groundwater By sampling, detecting, and analyzing the chemical ionic composition of water and the quality of groundwater, the basic characteristics of groundwater are determined, and its feasibility as a water source is preliminarily assessed.

[0051] 4.1 Analysis of the chemical ionic composition of water This application example uses SPSS software to perform statistical analysis on the hydrochemical data of unconfined and confined water in the study area. The statistical results of the hydrochemical data of unconfined and confined water are shown in Table 1 and Table 2, respectively.

[0052] Table 1. Statistical Analysis of Shallow Chemical Characteristics in the Study Area Table 2. Statistical Analysis of Chemical Characteristics of Confined Water in the Study Area (1) Statistical characteristics of diving chemistry Table 1 presents the statistical characteristics of the groundwater chemistry in the study area. As shown in Table 1, the groundwater in the study area is generally weakly acidic, with pH values ​​ranging from 5.74 to 7.62, and an average of 6.90. The average total hardness (TH) is 136.78 mg / L, falling into the category of soft water. The average total dissolved solids (TDS) is 176.37 mg / L, indicating low mineralization. In terms of ionic composition, the dominant groundwater chemistry type is HCO3-. - and Ca 2+ The dominant component is HCO3. -The content is 12.50 - 259.00 mg / L, for Ca 2+ is 9.33 - 84.90 mg / L. The order of average cation concentration is Ca 2+ > K + > Na + > Mg 2+ ; the order of average anion concentration is HCO 3- > SO4 2- > NO3 - > Cl - > F - . In addition, the spatial variability characteristics of each index show that the variation coefficient of pH value is only 10%, belonging to weak variability, indicating that it is relatively evenly distributed in the study area. While the variation coefficient of K + is as high as 177%, showing strong variability, reflecting its extremely uneven spatial distribution in the study area. The remaining indexes all belong to medium variation degree (10% < Cv < 100%). The standard deviation represents the deviation degree of each water sample value from the mean value. The standard deviations of HCO3 - , TH and TDS in phreatic water samples are relatively large, indicating that the local concentration significantly deviates from the mean value. The reason may be that the outcropping of limestone in some areas leads to an increase in the content of HCO3 - in phreatic water.

[0053] (2) Chemical statistical characteristics of confined water Table 2 is the analysis table of chemical statistical characteristics of confined water in the study area. It can be seen from Table 2 that the confined water in the study area is generally weakly alkaline, with the pH value ranging from 6.24 to 8.10 and the mean value being 7.22, higher than that of phreatic water. The mean value of total dissolved solids (TDS) is 241.54 mg / L, belonging to low salinity water. The mean value of total hardness (TH) is 215.76 mg / L, belonging to the category of medium hard water. Its value range is relatively wide, and soft water to hard water types can be seen in local areas. The overall hardness is slightly higher than that of phreatic water. The chemical composition of confined water is mainly HCO3 - (110.00 - 362.00 mg / L) and Ca 2+ (39.40 - 108.00 mg / L), and the concentration variation ranges of the two are relatively large. The order of average cation concentration is Ca 2+ >Mg 2+ >Na + >K + , and the order of average anion concentration is HCO3 - >SO4 2- >Cl - >NO3 - >F - . From the perspective of spatial variability, the variation coefficient of pH value is only 6%, belonging to weak variability, reflecting its most uniform distribution in the region. Ca 2+ , HCO3- The coefficients of variation for TDS and TH are similar (25%–28%), exhibiting moderate variability and relatively consistent distribution. + Mg 2+ and SO4 2- The coefficients of variation all exceeded 100%, indicating strong variability and suggesting that these components are spatially highly unevenly distributed. This may be related to the fact that many sampling points are located in karst areas. Under these conditions, HCO3... - With Ca 2+ The content remains relatively stable.

[0054] The above preliminary analysis of the chemical statistical characteristics of unconfined and confined water indicates that: ① The overall quality of the groundwater in the study area is excellent, characterized by weak acidity, softness, and low mineralization, thus possessing the basic conditions to serve as an emergency or backup water source; K + Exhibiting strong variability and NO3 - The detection of these substances reflects the potential impact of human activities on localized diving areas.

[0055] ② The confined aquifer exhibits characteristics of "weakly alkaline, low mineralization, and medium-hard water," with an extremely low pH coefficient of variation (6%), indicating good sealing properties and making it an ideal source of drinking water and emergency water. K + Mg 2+ and SO4 2- The strong variability in certain areas suggests that these regions may be related to karst zones and pose a certain potential risk of pollution.

[0056] 4.2 Groundwater Quality Analysis To further analyze the feasibility of using groundwater as a water source in the study area, the Nemerow Comprehensive Index method was used to quantitatively assess the groundwater quality of the Mahong emergency water source area. The comprehensive score (F) of the water samples at the sampling points was calculated using formulas (4) and (5). According to the national standard for groundwater quality (GB / T 14848—2017), the relative quality of the groundwater was determined by the comprehensive score. The groundwater quality classification table is shown in Table 3.

[0057] (4) (5) In the formula: F represents the comprehensive score; F imax Indicates the evaluation factor water quality level and F i The maximum value among the determined individual score values; F represents the score value of each individual component. i The average value; n represents the number of terms.

[0058] Table 3 Groundwater Quality Classification Table The groundwater quality in the study area was classified according to the groundwater quality classification table. The groundwater quality in the study area is shown in Table 4.

[0059] Table 4. Groundwater Quality Status in the Study Area The groundwater quality status table of the study area shows that the water quality at most points of the confined aquifer meets or exceeds Class III standards, and the overall water quality is better than that of unconfined aquifers. It is preliminarily determined that the confined aquifer can be used as an emergency backup water source.

[0060] 4.3 Analysis of Groundwater Hydrochemical Types (1) Piper's three-line diagram This application example uses Piper tri-line diagrams to identify control units of water body hydrochemical components and preliminarily determine the hydrochemical type of groundwater. Figure 3 Piper triline diagram of water chemistry types in the study area.

[0061] from Figure 3 As can be seen, the water sample points in the phreatic layer are closer to Ca in the cation triangle diagram. 2+ end, where Ca 2+ The terminal cation accounts for 60%–80% of the total cation equivalent, Mg 2+ The terminal proportion is 20%–40%; the anion is mainly HCO3-. 3- The majority (50%–80%) of the water's chemical composition is calcium. This indicates that the chemical composition of submerged water is mainly influenced by calcium. 2+ With HCO3 - The water chemistry is controlled to be of the HCO3-Ca type. The Ca cations in the pressurized water are... 2+ The proportion of end-stage Mg was 60%–95%, and most water samples contained Mg. 2+ The proportion is less than 30%, (Na) + +K + The overall proportion was less than 20%; most confined water samples contained less HCO3. - The ions account for more than 80% of the total anion milligram equivalents. This indicates that Ca... 2+ With HCO3 - It is also a dominant factor in the chemical evolution of confined water, and its hydrochemical type is also HCO3-Ca.

[0062] (2) Shukalev classification The Shukalev classification method was used to further determine the hydrochemical types of groundwater in the study area, and the results are shown in Table 5. As can be seen from the table, there are two types of hydrochemical types in the unconfined aquifers: HCO3+SO4-Ca and HCO3-Ca, accounting for 29% and 71% respectively, with HCO3-Ca being the dominant type. There are also two types of hydrochemical types in the confined aquifers: HCO3-Ca+Mg and HCO3-Ca, with HCO3-Ca accounting for the largest proportion at 89%. These results are consistent with those obtained using the Piper triline diagram method, indicating that the hydrochemical type of groundwater in the aquifer system of the study area is mainly HCO3-Ca.

[0063] Table 5 Groundwater Hydrochemical Types The above results indicate that: All groundwater in the study area is of the HCO3-Ca type, indicating that water quality formation throughout the region is controlled by a unified hydrogeochemical process dominated by the weathering and dissolution of carbonate rocks. The highly consistent HCO3-Ca water type suggests that the groundwater has not been subject to significant anthropogenic pollution, and its quality is primarily controlled by the natural geological background, confirming the reliability of this area as an emergency water source.

[0064] 5. Analysis of the spatial distribution characteristics of groundwater ions The Kriging interpolation method in Suffer software was used to interpolate the ion concentrations of water samples from unconfined and confined water sources. At the same time, data from points with large interpolation deviations were reasonably corrected to generate contour maps of hydrochemical indicators for unconfined and confined water sources, thereby obtaining the spatial distribution characteristics of groundwater ions.

[0065] (1) Spatial distribution of various hydrochemical indicators of groundwater Spatial distribution of various hydrochemical indicators of diving water Figure 4 As shown, the overall distribution pattern of groundwater hydrochemical indicators is "low in the middle and high in the north and south," indicating that the central Gutang area may be a concentrated runoff or discharge area for groundwater, where water flows converge and accelerate. Specifically, Na... + Cl - With SO4 2- The high-value and low-value areas of Na+ are roughly the same. The high-value area is concentrated in the northwestern region from Shenanli to Tushan, the medium-value area is located in Duijia and Shilong, and the low-value area is near Zhoujia in the southeast. Because Na+... + Cl - With SO4 2- It is a typical indicator of domestic sewage, agricultural and industrial pollution, suggesting that the unconfined aquifer in the northwest may have been significantly affected by human activities. 2+ Mg 2+ With HCO3- The spatial distribution trend of ions is generally consistent, showing a high concentration at the periphery and a low concentration in the center, with Mg being the most abundant. 2+ The high-value area is located further north, concentrated near Lian'gang; Ca 2+ and HCO3 - The high-value ion areas are located in the south, near Yuanjia, suggesting that there may be different lithological or hydrochemical environments in the north and south. In addition, the high-value TDS areas are mainly distributed in the northern Liangang, western Tushan and Baizitang areas, while the area near Gutang is a low-value area. The spatial distribution patterns of pH and total hardness are similar, both showing a high value in the south and a low value in the central Gutang area.

[0066] (2) Spatial distribution of various hydrochemical indicators of confined water The spatial distribution of various hydrochemical indicators of confined water in the study area is as follows: Figure 5 As shown, the spatial distribution pattern of hydrochemical parameters in confined water differs significantly from that in unconfined water. K + Na + and Cl - Overall, the northern and southern parts are low-value areas, while the central area near the pithead is a high-value area, though the high-value area is relatively small; Ca 2+ HCO3 - The spatial distribution characteristics of TDS and TH are similar. The high-value area is located near Tushan in the northwest, the medium-value area is distributed from Mahong Township to Jianjia Village, and the low-value area is located in the southeast. The lowest value appears near Shanggang in the central part. The distribution of the four indicators consistently reflects the Ca 2+ With HCO3 - The dominant contribution to TDS and TH indicates that the groundwater chemical background is uniformly dominated by the dissolution of carbonate rocks (calcite, dolomite); Mg 2+ and SO4 2- The high-value area is relatively small, concentrated in the west, while the rest of the area is mainly low-value. pH values ​​show a pattern of high in the central region, gradually decreasing towards the edges, with the western region exhibiting a lower pH. Overall, various hydrochemical indicators of the confined water are generally higher in the northwest, with Ca... 2+ Mg 2+ SO4 2- HCO3 - TDS and pH gradually decrease along the direction of groundwater runoff from the recharge area to the discharge area, presenting a classic geochemical evolution model of groundwater from the recharge area (northwest) to the discharge area (southeast), indicating that confined aquifers are mainly controlled by natural processes; while K + Na + Cl - The pH values ​​show a distribution pattern of high in the middle and low around the edges, indicating that there may be a locally closed hydrogeochemical environment (such as water sequestration, ion exchange, or a specific reducing environment) inside the confined aquifer.

[0067] Preliminary analysis of the spatial distribution characteristics of groundwater ions indicates that: ① The unconfined aquifer in the northwest may have been significantly affected by human activities and is not suitable as a direct source of drinking water.

[0068] ② Confined water is controlled by natural processes, and there may be water formation and ion exchange processes inside.

[0069] ③ Ca 2+ and HCO3 - These are the main ions in submerged and pressurized water; 6. Analysis of the chemical origins and evolution of water To determine the main ion sources, hydrochemical formation, and evolution of groundwater, this application example uses correlation analysis of hydrochemical indicators to preliminarily identify the dominant ions and their possible sources; Gibbs diagrams and Gaillardet endmember diagrams are used to analyze the control mechanisms of hydrochemical formation; and the main ion source information is determined through ion content ratio analysis, chlor-alkali index analysis, and reverse simulation of groundwater chemistry, thus exploring the hydrochemical formation and evolution of groundwater.

[0070] 6.1 Dominant Ions in Groundwater and Their Possible Sources This application example uses hydrochemical correlation coefficient analysis to preliminarily infer the dominant ions and possible sources of groundwater in each aquifer.

[0071] (1) Correlation analysis of diving The hydrochemical correlation coefficient analysis diagram of the groundwater in the study area is shown in the figure below. Figure 6 As shown, from Figure 6 It can be seen from Cl - with Na + Ions, SO4 2- With K + Na + Ions, HCO3 - With Ca 2+ Mg 2+ All ions showed extremely significant correlations, from which it can be inferred that Na + With Cl - HCO3 - With Ca² + and Mg 2+ The shared origin indicates that the weathering and dissolution of sulfate minerals such as rock salt and gypsum, as well as carbonate rocks, have influenced the hydrochemical composition of groundwater. TDS and K... + SO4² - and NO3 - All major ions except Cl showed extremely significant correlations, with Cl being the most significantly correlated. - The correlation coefficient was the highest (0.94). Combined with the geological background of high content in regional rock salt and carbonate rocks, it is inferred that Na...+ Ca 2 + Mg² + HCO3 - and Cl - These are the five dominant ions that determine the chemical type of diving.

[0072] (2) Correlation coefficient analysis of confined water The correlation coefficient analysis diagram of hydrochemical parameters of confined water in the study area is shown in the figure below. Figure 7 As shown, from Figure 7 It can be seen from Cl - Only with Na + A significant correlation was observed (correlation coefficient 0.69), but the correlation was weaker than that of unconfined groundwater, suggesting that the influence of rock salt on the chemical composition of groundwater decreased during the transition from unconfined to confined water; SO4² - With Mg² + A highly significant correlation was found (0.74) between HCO3 and HCO3. - With Ca 2+ It also showed a highly significant correlation (0.86) with Mg². + The correlation was significant (0.50), suggesting that the dissolution of sulfate and carbonate minerals is the main source of the chemical composition of pressurized water.

[0073] In addition, Na + With Ca² + The negative correlation indicates that the two ions are from different sources, suggesting the existence of alternating cation adsorption, i.e., Na+. + Ca is adsorbed onto the mineral surface. 2+ Released into water, leading to Ca 2+ Concentration increases. TDS and Ca 2+ Mg² + K + Na + SO4² - and HCO3 - All six ions were significantly correlated, with HCO3- being the most significantly correlated. - The highest correlation (0.80) indicates that these six ions collectively control the chemical composition of pressurized water.

[0074] The above results preliminarily indicate that: ① The chemical type of the diving water mainly consists of Na + Ca 2+ Mg 2+ HCO3 - and Cl - Five ions control, and TDS and Cl - Highly correlated; ② Confined water is subject to Ca 2+ Mg 2+ K+ Na + SO4 2- HCO3 - Six ions work together to control TDS and HCO3. - The correlation is the strongest, reflecting that carbonate weathering is dominant in confined water; ③ Cation exchange occurs in pressurized water; ④ The weathering and dissolution of rock salt, gypsum, and carbonate minerals are the main processes controlling the chemical composition of water. From groundwater to confined water, the effect of rock salt weakens while the effect of sulfate and carbonate increases.

[0075] 6.2 Factors Controlling Groundwater Hydrochemical Formation The controlling factors of groundwater formation were determined based on Gibbs diagrams and Gaillardet endmember diagrams.

[0076] (1) Gibbs diagram Analysis of TDS and Na + / (Na + +Ca² + ) and Cl - / (Cl - +HCO3 - Based on the ratio relationships, Gibbs diagrams were plotted to identify three main hydrochemical control mechanisms: evaporation concentration, rock weathering, and atmospheric precipitation. Gibbs diagrams for unconfined and confined water are shown below. Figure 8 (a) and Figure 8 (b). From Figure 8 As can be seen, both unconfined and confined groundwater sampling points in the study area are concentrated in the central-left region. + / (Na + +Ca² + ) and Cl - / (Cl - +HCO3 - The ratios were all below 0.5, indicating that the groundwater chemistry in the study area was mainly a product of the interaction between water and rocks, with rock weathering being the primary controlling factor for the groundwater's chemical composition. This characteristic is consistent with the fact that the western part of the study area has high terrain, dense vegetation, thick overburden, and a thick vadose zone, providing favorable conditions for water-rock interaction.

[0077] (2) Gaillardet endmember graph analysis Through Ca² + / Na + Mg² + / Na + and HCO3 - / Na + Analysis of the ratio relationships further clarifies the controlling mechanism of water chemical formation. Mg² + / Na + and Ca² + / Na + The ratio relationship is shown in Figure 9 (a), HCO3 - / Na + With Ca² + / Na + The ratio relationship is shown in Figure 9 (b).

[0078] from Figure 9 As can be seen from the data, groundwater samples from the study area are mainly distributed between two control endmembers: silicate and carbonate rocks. This indicates that the hydrochemical composition of groundwater in the study area is controlled by the combined weathering and dissolution of silicates and carbonates. Water samples from the unconfined aquifer are closer to the silicate rock endmembers, reflecting the significant contribution of silicate weathering to the unconfined aquifer. The distribution of confined water samples shows a spatial pattern: samples from the recharge area are concentrated in the carbonate rock endmembers, indicating that the confined water in this area is mainly controlled by carbonate rock weathering; some runoff and discharge area samples are shifted towards the silicate rock endmembers, reflecting enhanced silicate weathering. Considering the geological background conditions of the study area in this application example, the area contains a large amount of limestone, consistent with the mineral influencing factors shown in the endmember map.

[0079] The above results indicate that: ① The chemical composition of groundwater in the study area is controlled by rock weathering, that is, the chemical composition of groundwater is jointly controlled by the weathering and dissolution of silicate rocks and carbonate rocks.

[0080] ② The submerged water is affected by the combined weathering of silicates and carbonates, with metasilicate weathering.

[0081] ③ Confined water is mainly weathered by carbonates, and this weathering varies with the runoff path. In the recharge area, confined water is almost entirely controlled by carbonate weathering, while as the water flows towards the runoff and discharge areas, the contribution of silicate weathering increases relatively.

[0082] 6.3 Determination of the main ion sources in groundwater Determining Na in groundwater by ion content ratio + K + Ca 2+ Mg 2+ SO4 2- The main ion sources are...

[0083] (1) Na + With K + source Through (Na) + +K + ) ions and Cl - Ion concentration ratio analysis of Na in groundwater + K +The source of the ions, plotting γ(Na) + +K + ) / γ(Cl - Ion proportion coefficient diagram, such as Figure 10 As shown in (a). From Figure 10 As can be seen in (a), the water sample points in the study area are distributed on both sides of the 1:1 line. The water sample points located below the 1:1 line indicate that the Na content in the water sample is high. + K + It mainly comes from the dissolution of rock salt, or may have involved cation exchange, which lowered the Na content. + K + Concentration; water samples distributed above the 1:1 line indicate Na + K + In addition to the dissolution of rock salt, there is also the dissolution of silicate rocks.

[0084] (2) Ca 2+ Mg 2+ SO4 2- source Through (Ca) 2+ +Mg 2+ ) and (HCO3) - +SO4 2- The milligram equivalent ratio of calcium in groundwater is used to determine the calcium content. 2+ and Mg 2+ Main source, (Ca 2+ +Mg 2+ ) and (HCO3) - +SO4 2- The ion ratio coefficient diagram is shown below. Figure 10 As shown in (b). From Figure 10 As can be seen in (b), the water sampling points located above the 1:1 line indicate that the dissolution of carbonate rocks was caused by Ca in the groundwater. 2+ and Mg 2+ The main source; the point located below the 1:1 line indicates that the dissolution of silicate rocks and evaporites is due to Ca in groundwater. 2+ and Mg 2+ The main source. As can be seen from the figure, most water samples from unconfined and confined water in the study area are mainly distributed above the 1:1 line, indicating that the dissolution of carbonate rocks into Ca is the primary source. This is because most water samples from the unconfined and confined water in the study area are mainly distributed above the 1:1 line, indicating that the carbonate rocks dissolve into Ca. 2+ and Mg 2+ The main source is silicate or evaporite, with a few located in the subsurface area reflecting localized silicate or evaporite sources.

[0085] Further comparison of γ (Ca) 2+ +Mg 2+ ) and γ (HCO3) - The ratio relationship Figure 10 (c) It was found that most water sampling points were located above the 1:1 line, indicating that there was excess Ca in the groundwater of the study area.2+ and Mg 2+ It is made of SO4 2- To balance this out, but with a small overall shift, namely the SO4 produced by the dissolution of gypsum or other sulfate minerals. 2- and Ca 2+ The deviations were relatively small. Most of the deviations were observed in samples from confined aquifer recharge areas, reflecting a weakening of the role of sulfate minerals in the runoff process of confined aquifers.

[0086] To further identify the main mineral components involved in the dissolution of carbonate rocks, such as Figure 10 As shown in (d), based on γ(Mg) 2+ ) / γ(Ca 2+ ) and γ (HCO3) - The ratio of calcite to dolomite is used to determine the composition of the solution. A ratio of 0 indicates that calcite is the dominant solvent, 1 indicates that dolomite is the dominant solvent, and 0.5 indicates that both solvents work together.

[0087] from Figure 10 As can be seen from (d), the water samples in the study area are mainly distributed below 0.5, indicating that calcite is the main dissolved mineral; only one point is located on the 0.5 line, reflecting that the area is affected by both calcite and dolomite.

[0088] The above results indicate that: ① The dissolution of salt and silicate rocks is caused by Na+ in groundwater. + and K + The main source of ions; ② The dissolution of carbonate rocks such as calcite is Ca 2+ Mg 2+ HCO3 - The main source; ③ The dissolution of gypsum or other sulfate rocks is SO4. 2- The main source.

[0089] 6.4 Determination of the chemical origins and evolutionary pathways of water The hydrochemical evolution path of groundwater is controlled by its flow environment and genetic background. By analyzing cation exchange and performing reverse simulation of groundwater chemistry, combined with regional geological and chemical mechanisms, the hydrochemical genesis of unconfined and confined water in the study area is systematically identified, and the hydrochemical evolution path is determined.

[0090] (1) Cation exchange Using the chlor-alkali index and γ[(Ca 2+ +Mg 2+ )-(HCO3 - +SO4 2- )] and γ[(Na + +K + )-Cl - The relationship between K in unconfined and confined water in the study area + Na+ With Ca² + Mg² + The ion exchange process between them was analyzed. The chlor-alkali index includes two parameters, CAI-1 and CAI-2, and their calculation formulas are given in formulas (6) and (7), respectively: (6) (7) When both CAI-1 and CAI-2 are less than 0, it indicates that the Ca²⁺ in the groundwater is low. + Mg² + With Na in aqueous medium + K + A positive ion exchange occurs; when both are greater than 0, it indicates that Na+ in the groundwater... + K + With Ca² in the medium + Mg² + Reverse ion exchange occurs.

[0091] ① Analysis of ion exchange Figure 11 To obtain the chlor-alkali index map of groundwater in the study area, from... Figure 11 As can be seen, the CAI values ​​of both unconfined and confined water in the study area are distributed in both positive and negative ranges. In confined water, negative values ​​account for 53% and positive values ​​for 47%; in unconfined water, positive values ​​account for 57% and negative values ​​for 43%, indicating that both types of water bodies exhibit positive and negative exchange reactions. Spatially, the recharge and discharge areas of confined water are predominantly negative, while the runoff area is predominantly positive, reflecting the changing direction of ion exchange under different hydrogeochemical environments.

[0092] ② Cation exchange strength assessment Figure 12 For γ[(Ca² + +Mg² + )-(SO4² - +HCO3 - )] and γ[(Na + +K + )-Cl - [Change graph] If the sample spots are distributed along the -1:1 line, it indicates significant cation exchange. From Figure 12 As can be seen from the figure, the confined water sample is basically distributed along the line, indicating that strong ion exchange occurs during its migration; the unconfined sample deviates slightly from the line, indicating that its exchange is weaker than that of the confined water.

[0093] The above results indicate that: Cation exchange is prevalent in both unconfined and confined water within the study area. Forward exchange occurs in both the recharge and discharge zones of the confined water. The Ca²⁺ in the water...+ Mg² + It is adsorbed by the medium, and the Na in the medium + K + It is released into the water. The reverse exchange occurs in the runoff zone of confined water. During this process, the Na+ in the water... + K + Adsorbed, while Ca² + Mg² + Released.

[0094] (2) Reverse simulation of groundwater chemistry By using inverse chemical simulation of groundwater, possible groundwater flow paths can be obtained and quantitatively described. ① Select simulation path The groundwater flow direction in the study area is from northwest to southeast. In a preferred embodiment of this application, the simulation path is located in a confined aquifer. Along the groundwater flow direction, three paths, CY13 to CY12, are selected for simulation, namely path 1, path 2, and path 3. (See attached diagram). Figure 13 .

[0095] ② Determination of possible mineral phases Based on the hydrogeological conditions, dissolution equilibrium analysis, and hydrochemical data of the study area, the main mineral phases involved in water-rock interactions were identified as calcite, dolomite, fluorite, gypsum, rock salt, and potash. Combined with the cation exchange analysis results, ion-exchange phases NaX and CaX2 were added to the simulation. The possible reaction equations for each mineral phase are shown below.

[0096] ③ Simulation calculation of water-rock interaction conversion Phreeqc software was used to perform reverse geochemical simulations on three typical pathways. The ionic composition and determined mineral facies of water samples from the starting points of each pathway were used as inputs to obtain multiple solutions for mineral migration. The most reasonable solution was selected based on hydrogeological conditions. The simulation results are summarized in Table 6, with reference to the reverse simulation pathway diagram (…). Figure 13 ) Analyze the path.

[0097] Table 6. Transfer volume of each mineral item along different routes In pathway 1, calcite, fluorite, and potassium salt precipitate, with precipitation amounts of 179.60 × 10⁻⁶. -5 mmol / L, 0.12×10 -5 mmol / L and 0.13×10 -5 mmol / L; dolomite, gypsum, and rock salt dissolved, with dissolution amounts of 10.66 × 10 mmol / L, respectively. -5 mmol / L, 9.27×10 -5 mmol / L and 21.90×10-5 mmol / L. This process is dominated by calcite precipitation, leading to HCO3- - With Ca 2+ The concentrations decreased by 193 mg / L and 64 mg / L, respectively. This was accompanied by Na... + –Ca 2+ Exchange reaction, Na+ in water + Reduced by 13.68 × 10 - 5 mmol / L, correspondingly increased by 6.84×10 -5 mmol / L Ca 2+ .

[0098] In path 2, calcite, dolomite, fluorite, and potassium salt dissolved, with dissolution amounts of 133.90 × 10⁻⁶. -5 mmol / L, 3.83×10 -5 mmol / L, 0.05×10 -5 mmol / L and 0.08×10 -5 mmol / L; gypsum and rock salt precipitated, with precipitation amounts of 3.12 × 10 mmol / L. -5 mmol / L and 13.05×10 -5 mmol / L. This pathway is mainly based on calcite dissolution, HCO3 - With Ca 2+ The concentrations increased by 163 mg / L and 39 mg / L, respectively. Cation exchange resulted in a 29.37 × 10⁻⁶ concentration. -5 mmol / L Ca 2+ Adsorbed, while releasing 58.74 × 10⁻⁶. -5 mmol / L Na + Entering the water body.

[0099] In pathway 3, calcite, rock salt, and potassium salt dissolve, with dissolution amounts of 1.19 × 10⁻⁶. -5 mmol / L, 3.00×10 -5 mmol / L and 0.10×10 -5 mmol / L; dolomite, fluorite, and gypsum precipitated, with precipitation amounts of 14.20 × 10 mmol / L. - 5 mmol / L, 0.01×10 -5 mmol / L and 11.51×10 -5 mmol / L. Na+ occurs during this process. + –Ca 2+ Exchange, Na in water + Reduced by 51.22 × 10 -5 mmol / L, Ca 2+The corresponding increase is 25.61 × 10 -5 mmol / L.

[0100] Two of the three pathways show reverse cation exchange, and the selected pathways are located in the confined water runoff area, which is consistent with the conclusion obtained from the previous chlor-alkali index analysis that "reverse exchange is the main feature in the runoff area".

[0101] The above results indicate that: ① Along different pathways, the dissolution or precipitation of calcite is the most dominant process controlling the evolution of hydrochemistry (precipitation in pathway 1: 179.60, dissolution in pathway 2: 133.90, values ​​much higher than other minerals). Although other minerals (such as gypsum and rock salt) are also sources of ions, their contribution rates are relatively small.

[0102] ② It was jointly confirmed that reverse cation exchange (Na+) is prevalent in confined water runoff areas. + When it enters the water, Ca 2+ (Being adsorbed).

[0103] ③ The simulation of the three pathways reveals three different hydrochemical evolution patterns. Pathway 1 is dominated by calcite precipitation, leading to water decalcification and softening; Pathway 2 is dominated by calcite dissolution, resulting in increased calcium and hardness in the water; and Pathway 3 features weak mineral reactions and is dominated by cation exchange. Based on these different hydrochemical evolution pathways (i.e., different "geochemical units"), the area is divided into zones. If the emergency extraction well is located in an area similar to Pathway 1, the risk of scaling during extraction is extremely high, requiring preventative measures. If located in an area similar to Pathway 2, the water quality will be relatively stable, but hardness and TDS may slowly increase.

[0104] 6.5 Analysis of the Impact of Human Activities To identify the impact of human activities on the chemical composition of groundwater, SO4 was used. 2- / Ca 2+ With NO3 - / Ca 2+ The ratio serves as an indicator. Among them, SO4 2- / Ca 2+ An increase in the ratio usually reflects the impact of industrial and mining activities on water bodies, while NO3... - / Ca 2+ An increase in the ratio mainly indicates agricultural activities or the input of domestic sewage.

[0105] Depend on Figure 14 The chemical ratios of groundwater in the study area shown indicate that SO4 in the confined water samples... 2- / Ca 2+ The generally high ratios indicate that they are influenced to some extent by industrial and mining activities; some groundwater samples showed higher levels of NO3. - / Ca 2+The ratio reflects the localized impact of agricultural activities and domestic sewage on groundwater in the area.

[0106] The above results indicate that: ① There may be localized and concentrated pollution input points from industrial and mining enterprises in the recharge area or runoff path of confined water. ② The groundwater may be affected by non-point source pollution from agricultural activities and domestic sewage.

[0107] ③ In selecting emergency water sources, for confined water systems, priority should be given to investigating industrial and mining enterprises upstream of their recharge and runoff areas to determine SO4 levels. 2- The specific source of the elevation should be identified, and the presence of other associated pollutants such as heavy metals should be assessed to cut off the pollution source. Diving should focus on whether nitrate levels exceed the standard, and non-point source pollution should be controlled by designating protected areas.

[0108] 7. Analysis of groundwater recharge sources and age 7.1 Determination of Groundwater Recharge Sources This application example analyzes 26 hydrogen and oxygen stable isotope water samples from the study area to determine the source of groundwater recharge in the study area. The hydrogen and oxygen isotope analysis diagram is shown below. Figure 15 As shown.

[0109] from Figure 15 As can be seen, the δD values ​​of the groundwater in the study area range from -37.9‰ to -23.4‰, with an average value of -30.4‰; δ¹ 8 The O value ranges from -5.4‰ to -3.8‰, with an average of -4.5‰. The δD value of confined water ranges from -43.2‰ to -29.7‰, with an average of -36.9‰; δ¹ 8 O values ​​ranged from -5.9‰ to -4.2‰, with an average of -5.2‰. All sample points fell near the global and local precipitation lines, indicating that groundwater is primarily replenished by atmospheric precipitation. The slope of the local precipitation line was 8.28, higher than the global precipitation line, reflecting relatively weak evaporation in the region.

[0110] Deuterium surplus can be used to indicate the intensity of evaporation experienced by a water body, and its expression is shown in Equation 8. The deuterium surplus of typical global atmospheric precipitation is approximately 10‰. In this study, the deuterium surplus values ​​of unconfined groundwater ranged from 2.28‰ to 7.31‰, with an average of 5.45‰; the deuterium surplus values ​​of confined groundwater ranged from 1.61‰ to 6.98‰, with an average of 4.70‰. The deuterium surplus of both types of water bodies is below 10‰, indicating that the groundwater in the study area is still affected by evaporation to some extent during recharge, and that confined groundwater may have a longer runoff path or more intense water-rock interaction.

[0111] (8) The above results indicate that: ① The groundwater recharge source is mainly atmospheric precipitation, and the groundwater in the study area is a product of the "modern water cycle", rather than ancient sealed water or other special sources.

[0112] ② The confined water recharge environment may be relatively high or low in temperature (such as precipitation during cold seasons or recharge at high altitudes).

[0113] 7.2 Groundwater Age Determination This application example uses krypton and tritium isotopes to determine the age of groundwater and studies the age distribution of groundwater in the study area.

[0114] (1) Krypton isotope dating of groundwater age Krypton-85 is a radioactive isotope of krypton with a half-life of 10.76 years. It exists in the atmosphere. 85 The natural sources of Kr are primarily cosmic rays and stable isotopes. 86 Spallation reactions between Kr; while its anthropogenic sources are mainly human nuclear activities such as nuclear testing and nuclear fuel reprocessing. Since the 1940s, atmospheric... 85 The concentration of Kr increases significantly due to anthropogenic release, making it an ideal tracer for groundwater dating within the range of 2–50 years.

[0115] This application example uses data from the North China region, corrected by Yang Guomin. 85 The Kr atmospheric input curve was used as a reference. Based on the sample collection time and... 85 The Kr half-life is used to calculate the initial concentration at the time of recharge, and the concentration decay curve is plotted. The time corresponding to the intersection of this curve and the atmospheric input curve is the year of groundwater recharge.

[0116] This study collected a set of confined water samples for testing. 85 Kr analysis. Using the above method, based on... 85 The Kr decay formula is used to inversely deduce the initial concentration, and the replenishment time is determined by intersecting it with the atmospheric concentration curve. The results are as follows: Figure 16 As shown in the figure, the age of the groundwater sample was calculated to be approximately 9 years, which is considered relatively young groundwater.

[0117] (2) Tritium isotope dating of groundwater age ① Groundwater tritium isotope values Table 7 shows the tritium values ​​collected from eight pressurized water samples in the study area for this application example. The table shows that the tritium values ​​ranged from 1.95 to 7.71 TU, with an average of 3.8 TU.

[0118] Table 7 Measured tritium values ​​in the study area ② Methods for determining the age of groundwater This application example uses the exponential-piston flow combination model (EPM) to calculate the groundwater age. The age distribution function of the EPM model is shown in formula (9): In the formula: τm represents the average residence time (average age) of groundwater; η represents the ratio of the volume of flowing water to the volume of exponential water in the system. When η=0, the model is an exponential model. The larger η is, the greater the proportion of piston-flow water.

[0119] When using EPM to calculate groundwater age, long-term atmospheric precipitation tritium concentration data are required. Since Xinyu City lacks relevant monitoring data, it is necessary to reconstruct the historical atmospheric precipitation tritium concentrations for this region.

[0120] The method used in this application to reconstruct the historical tritium concentration in atmospheric precipitation in Xinyu City is as follows: Based on tritium concentration data for my country and neighboring countries released by the International Atomic Energy Agency (IAEA), the Wuhan monitoring station, which is geographically close to Xinyu City and has similar precipitation conditions, was selected as a reference station to obtain its measured tritium concentration sequence. Reference factor analysis was used to extend and reconstruct the Wuhan station data to construct the atmospheric tritium concentration sequence for the Xinyu area, providing reliable input for subsequent groundwater age calculations.

[0121] The tritium concentration in atmospheric precipitation calculated by factor analysis takes into account factors such as latitude effect, continental effect and rainfall. The influencing factors cp(t,1) and cp(t,2) of the Northern and Southern Hemispheres are extracted. The annual average tritium concentration in atmospheric precipitation at any station in the world is a linear combination of these two common factors. The mathematical equation is shown in formula (10): (10) In the formula: c p (t) represents the annual average concentration of tritium in atmospheric precipitation; b represents the constant term; f1 and f2 represent the common factor c. p (t, 1), c p The regression coefficients of (t, 2); ε represents the random error.

[0122] Common factor c in the formula p (t, 1), c p The specific values ​​of (t, 2) are shown in Table 8. The parameters b, f1, and f2 are solved using the least-multiply-two method.

[0123] Table 8 Standardized common factors for predicted tritium concentration in precipitation. The indirect parameter-finding method was used to reconstruct the tritium value of atmospheric precipitation at Wuhan station. First, Hong Kong and Ottawa stations, which have relatively abundant measured tritium data and are geographically distant, were selected as reference stations. Based on the measured annual average tritium value of atmospheric precipitation at these stations from 1960 to 2005, i.e., c... p(t), using the least-multiply-two method to inversely calculate parameters b, f1, and f2, the annual mean atmospheric precipitation tritium value recovery models for Hong Kong and Ottawa stations are obtained, and the results are as follows: Hong Kong Station: Ottawa Station: Among them, R2=0.82 for Hong Kong station and R2=0.99 for Ottawa station; the parameters of the two stations were interpolated using the latitudinal relationship to obtain the parameter values ​​of Wuhan station, and substituted into equation 3.13 to obtain the tritium value of atmospheric precipitation at Wuhan station from 1960 to 2005. The calculation results are shown in Table 9.

[0124] Wuhan Station: Table 9. Factor analysis method for reconstructing tritium values ​​of atmospheric precipitation at Wuhan station. Tritium values ​​from atmospheric precipitation in Xinyu were restored from 1960 to 2005. Linear correlation equations were established between measured tritium values ​​from the Ottawa station for 1953–1959 and 2006–2021 and the restored annual tritium values. These equations were then substituted into the Ottawa station tritium values ​​to obtain the tritium values ​​from atmospheric precipitation in Xinyu. The average of the previous five years was used for 2022–2024 to calculate the historical tritium values ​​from atmospheric precipitation in the Xinyu area. The restored historical tritium values ​​were corrected by weighting atmospheric precipitation, and the correction coefficient was determined. α The calculation formula is shown in Formula (11). The average annual precipitation in Xinyu from 1953 to 2024 was 1247.4 mm. The corresponding calculation results are shown in Table 10. The annual curves of tritium concentration in atmospheric precipitation in Xinyu area are also plotted. Figure 17 As shown.

[0125] (11) In the formula: α i P represents the correction factor; i This represents the annual atmospheric precipitation in Xinyu from 1953 to 2024, in mm.

[0126] Table 10 Results of Tritium Value Recovery and Correction in Atmospheric Precipitation in Xinyu Area This application example uses TracerLPM (Tracer Lump Parameter Model) to calculate groundwater age. The EPM model is selected for fitting, different age ranges are set, parameters are adjusted, and the optimal solution for tritium age is sought. In this fitting example, η is set to 2. The model is used to calculate the relationship curve between tritium output concentration and average residence time of groundwater in the sampling year, obtaining multiple solutions for the tritium age of the sample. 85By comparing the Kr isotope calculation results, the age of groundwater was confirmed. The calculation results are shown in Table 11.

[0127] Table 11. Tritium Age of Groundwater 7.3 Calculation of Groundwater Age pass 3 H, 85 Kr was used as a tracer to calculate groundwater age and to plot the spatial distribution of groundwater age. Figure 18 As shown, comprehensive calculations show that the age of groundwater ranges from 8 to 25 years. The groundwater age is smaller in the west, and increases from west to east.

[0128] The above results indicate that the groundwater recharge area is located in the west and has the youngest water age; the groundwater flow direction is generally from west to east, and the discharge area is likely located in the east. To protect the water source, priority must be given to protecting its upstream recharge area. Therefore, the western region is the core area requiring key protection.

[0129] 8. Determination of the chemical evolution pathway of groundwater in the study area Based on comprehensive information on regional hydrogeological conditions, hydrochemical and evolutionary patterns, as well as groundwater recharge sources and age, a conceptual model of regional groundwater hydrochemical evolution is obtained, such as... Figure 19 As shown.

[0130] from Figure 19 As can be seen, the groundwater in the study area is mainly recharged by rainfall infiltration. Based on the lithological distribution characteristics, the sandstone of the Shuibei Formation in the northwest receives rainfall infiltration, forming bedrock fissure water that flows from northwest to southeast. During the flow, it comes into contact with the Maokou Formation limestone and laterally recharges the limestone karst aquifer. During the flow, the groundwater interacts with carbonate and silicate rocks in the aquifer. In the recharge runoff area of ​​the study area, the weathering and dissolution of carbonate rocks such as calcite and dolomite enriches the groundwater with Ca. 2+ HCO3 - Based on the reverse simulation in path 1 above, cation exchange also occurs during groundwater recharge runoff, leading to an increase in the amount of Na in the water. + Ion reduction. As groundwater flows into the discharge zone, the dissolution intensity of silicate rocks increases, releasing Na+ into the groundwater. + K + Ions, along with alternating cations, cause the Ca in the discharge zone water to... 2+ The content decreased. Carbonate minerals are widely distributed in the study area and are the main controlling factor in groundwater hydrochemistry. HCO3 - Ca 2+成为 The main ions in the groundwater form groundwater of the HCO3-Ca type.

[0131] 9. Water source status assessment and management (1) Emergency water source tracing information ① The groundwater in the study area is weakly acidic and has low mineralization, falling into the category of hard water. The average cation concentrations in the area are in the order of Ca. 2+ >K + Na + >Mg 2+ The anion sequence is HCO3- - SO4 2- NO3 - >Cl - >F - Confined water is weakly alkaline, low-mineralized, medium-hard water, with cations in the order Ca2+. 2+ >Mg 2+ Na + >K + The anion sequence is HCO3- - SO4 2- >Cl - NO3 - >F - .

[0132] ② Piper tri-line plot analysis shows that the groundwater chemistry in the entire area belongs to the HCO3–Ca type. Water quality assessment results based on the Nemerow composite index method further indicate that the overall quality of confined aquifers is better than that of unconfined aquifers, with most sampling points meeting or exceeding Class III standards, thus satisfying drinking water quality requirements.

[0133] ③ The spatial distribution characteristics of groundwater ions indicate that unconfined aquifers in the northwest may have been significantly affected by human activities and are not suitable as direct drinking water sources. Confined aquifers are controlled by natural processes and may contain water formation and ion exchange processes.

[0134] ④ Gibbs plot and Gaillardet endmember plot show that the chemical composition of groundwater in the study area is controlled by rock weathering. Unconfined groundwater is affected by the weathering of both silicates and carbonates, with metasilicate weathering. Confined water is mainly weathered by carbonates. In the recharge area, it is almost entirely controlled by carbonate weathering. However, as the water flows towards the runoff and discharge areas, the contribution of silicate weathering increases relatively.

[0135] ⑤ The ion ratio relationship indicates that the dissolution of salt rocks and silicate rocks is caused by Na+ in groundwater. + and K + The main source of ions, such as the dissolution of calcite and other carbonate rocks, is Ca. 2+ Mg 2+ HCO3 - The main source of SO4 is the dissolution of gypsum or other sulfate rocks. 2- The main source.

[0136] ⑥ The analysis of the impact of human activities indicates that there may be localized and concentrated pollution input points from industrial and mining enterprises in the recharge area or runoff path of confined water; and that groundwater may be affected by non-point source pollution from agricultural activities and domestic sewage.

[0137] ⑦ Hydrogen and oxygen isotope data indicate that both groundwater and confined water samples are located near global and local precipitation lines, with atmospheric precipitation infiltration being the primary recharge source. Deuterium surpluses are generally lower than the global average, reflecting higher humidity in the recharge areas and relatively weaker evaporation.

[0138] ⑧ Through ³H and 85 Kr joint dating determined that the age of groundwater ranged from 8 to 25 years, with a spatial trend of gradually increasing age from west to east, indicating that the overall flow direction of groundwater is from west to east, with the western part being the recent recharge zone and the eastern part being the relatively stagnant zone.

[0139] (2) Guidance on the management of emergency water sources Based on known source tracing information of emergency water sources, an assessment of the status of water sources is conducted to provide guidance for the planning and management of emergency water sources.

[0140] ① Selection of water source Groundwater formation in the study area is dominated by a unified natural background of carbonate rock weathering and dissolution, resulting in overall stable water quality. All groundwater levels generally meet drinking water quality standards and are suitable as a water source. Furthermore, confined aquifers exhibit good sealing properties and are minimally affected by surface pollution. Therefore, confined aquifers should be identified as the core emergency extraction target. Unconfined aquifers can be used as temporary water sources, but adequate emergency response measures are necessary.

[0141] ② Precise delineation of protected areas Based on the spatial distribution characteristics of groundwater ions, the analysis of the impact of human activities, and the sources and age distribution of groundwater recharge, it is shown that the groundwater in the study area is recharged by atmospheric precipitation, and the water flows from west to east. It is determined that the western part of the study area is the groundwater recharge area, while the eastern part is the discharge or stagnant area, and the system belongs to an "active modern water cycle system". At the same time, the western recharge area may be affected by modern human activities (pollution), so the western area must be strictly managed as the highest level of water source conservation and protection area.

[0142] ③ Monitoring network deployment Monitoring wells should be deployed based on the groundwater chemical evolution pathways and pollution information in the study area, arranged from west to east, to effectively monitor water quality and water level dynamics. In the youngest western region, NO3 should be the primary focus of monitoring. - Modern pollution indicators such as TDS and hardness are important; in the east, more attention should be paid to the stability of background indicators such as TDS and hardness.

[0143] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

Claims

1. A method for source apportionment of emergency groundwater using a combination of isotopic dating and hydrochemistry, characterized in that, include: S1. Based on the regional hydrogeological conditions, determine the groundwater recharge, runoff, and discharge conditions in the study area; the regional hydrogeological conditions are obtained through data collection and field investigation. S2. Set up sampling points in the study area to obtain hydrochemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data of groundwater in the study area. S3. Based on hydrochemical ion data, obtain the basic hydrochemical characteristics of regional groundwater, spatial distribution of ions, main controlling ions and their sources, and water-rock reaction pathways; S4. Obtain information on groundwater recharge sources and water body age based on hydrogen and oxygen stable isotope data and radioactive isotope data; S5. By combining information from hydrochemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data, an integrated analysis of the hydrochemical formation and evolution of groundwater in emergency water sources is conducted to generate source tracing conclusions.

2. The method according to claim 1, characterized in that, The regional hydrogeological conditions mentioned in step S1 include: regional aquifer system structure, groundwater recharge, runoff and discharge conditions, types and distribution of surface water bodies, geological structure and topography, hydrogeochemical background, and impacts of human activities.

3. The method according to claim 1, characterized in that, The water chemical ion data mentioned in step S2 includes Ca 2+ K + Na + Mg 2+ HCO3 - SO4 2- NO3 - Cl - F - pH value, redox potential, total dissolved solids, total hardness, total alkalinity, conductivity, and ion ratio are any one or a combination of at least two of these parameters.

4. The method according to claim 1, characterized in that, The stable isotopes of hydrogen and oxygen mentioned in step S2 are deuterium and oxygen-18.

5. The method according to claim 1, characterized in that, The radioactive isotopes mentioned in step S2 are tritium and krypton-85.

6. The method according to claim 1, characterized in that, Step S3, which involves acquiring the basic hydrochemical characteristics, spatial distribution characteristics of ions, main controlling ions and their sources, and water-rock reaction pathways of regional groundwater based on hydrochemical ion data, includes: The hydrochemical ionic composition of groundwater was determined by statistical analysis of hydrochemical data using SPSS software. The Nemerow composite index method was used to quantitatively assess groundwater quality. Piper triline plots and the Shukalev classification method were used to determine the hydrochemical type of groundwater; The spatial distribution characteristics of groundwater ions were obtained using the Kriging interpolation method, and the spatial extent of pollution in the study area was preliminarily determined. The sources of dominant ions in groundwater and the water-rock reaction pathways were determined using hydrochemical graphical methods and groundwater chemical inverse simulation. The hydrochemical graphical methods included Gibbs diagrams, Gaillardet endmember diagrams, and ion proportioning coefficient methods.

7. The method according to claim 6, characterized in that, The ion ratio coefficient method includes the following ion content ratios: the ratio of the total concentration of sodium ions plus potassium ions to the concentration of chloride ions; the ratio of the total concentration of calcium ions plus magnesium ions to the total concentration of bicarbonate ions plus sulfate ions; the ratio of the total concentration of calcium ions plus magnesium ions to the concentration of bicarbonate ions; the ratio of the magnesium ion to calcium ion concentration to the bicarbonate concentration; the ratio of the total concentration of calcium ions plus magnesium ions minus sulfate ions minus bicarbonate ions to the total concentration of sodium ions plus potassium ions minus chloride ions; and the ratio of sulfate ions to calcium ions to nitrate ions to calcium ions.

8. The method according to claim 1, characterized in that, The process of obtaining groundwater recharge source information and water body age information based on hydrogen and oxygen stable isotope data and radioactive isotope data in step S4 includes: Hydrogen and oxygen isotope analysis maps of unconfined and confined water samples in the study area were drawn. The sources of groundwater recharge were determined by referring to global and local atmospheric precipitation lines. Information on recharge sources was also determined by deuterium surplus. The age of groundwater in the study area was calculated using krypton and tritium isotopes, and the spatial distribution of groundwater age in the study area was obtained by combining the analysis.

9. The method according to claim 1, characterized in that, The information obtained in step S5, which involves coupling water chemical ion data, hydrogen and oxygen stable isotope data, and radioactive isotope data, to conduct an integrated analysis of the hydrochemical origins and evolution of groundwater in emergency water sources, includes: The source of groundwater recharge and evaporation history in the study area were determined by hydrogen and oxygen stable isotope data, which served as the initial boundary conditions for hydrochemical evolution. Determining the age of groundwater using radioactive isotope data provides a timescale constraint for the evolution of water chemistry. Geochemical simulations and inverse calculations were performed based on water chemical ion data under the initial boundary conditions and time scale constraints to quantify the water-rock interaction process. By cross-validating and analyzing the information obtained from the three types of data, the complete chemical evolution path of groundwater from recharge to discharge in the study area was obtained.

10. The method according to claim 1, characterized in that, The source tracing conclusions mentioned in step S5 include the groundwater source quality in the study area, the main controlling ions and sources of groundwater, the scope and type of groundwater pollution, the sources of groundwater recharge, the age distribution of groundwater, and the direction of groundwater runoff.

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