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Understanding the hydrochemical evolution of surface water and groundwater is crucial for protecting regional ecological environments. Currently, there are few quantitative studies on the relative contributions of different processes to salinity enrichment of water bodies. In this study, sixty-seven water samples were collected for chemical, and isotopic analysis, along with simulation calculations. The results reveal distinct hydrochemical types of river water, phreatic water, lake water and hot spring water in the investigated area are Ca-Mg-HCO3, Na-Ca-HCO3, Na-SO4-HCO3 and Na-HCO3, respectively. Average temperature and depth of geothermal water storage are 196℃ and 1338 m, respectively. Average arsenic (As) content in hot spring water (298 μg/L) higher than that in lake water (39.2 μg/L), river water (9.59 μg/L) and phreatic water (4.02 μg/L). The ∑REEs content of river water in the study area is much higher than that of phreatic water and lake water. Result of δD and δ18O indicate that atmospheric precipitation is the source of recharge for all water bodies in the study area. Quantitative calculations indicate that evapo-concentration significantly enriches lake water salinity, contributing on average 90% of its salt content. In contrast, mineral dissolution contributes predominantly to the salinity of hot spring water (90.7%), phreatic water (65.8%), and river water (45.2%). Evapo-concentration emerges as the dominant mechanism for lake water salinity, while carbonate mineral dissolution primarily affects river water. Phreatic water and hot spring water are mainly controlled by the weathering and dissolution of silicate. The results can provide a theoretical basis for the study of the formation mechanism of water salinity in other regions with similar geological environment in the world. [ABSTRACT FROM AUTHOR]

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ObjectiveUnderground reservoirs in coal mines are capable of storing and purifying mine water. A deep understanding of the hydrochemical characteristics and formation mechanisms of water in underground reservoirs is identified as an important prerequisite for large-scale development of technologies for mine water treatment. MethodsThis study investigated the underground reservoirs in the Daliuta Coal Mine within the Shendong area by testing and analyzing their influent and effluent water samples. Using methods such as the ion ratio method, multivariate statistical analyses (e.g., correlation analysis and principal component analysis (PCA)), and the positive matrix factorization (PMF) model, this study delved into the hydrogeochemical characteristics and component sources of water in the underground reservoirs. Results and ConclusionsThe results of this study indicate that compared to the influent water of the underground reservoirs, the effluent water exhibits significantly reduced heavy metal indicators including suspended solids (SS), electrical conductivity (EC), total dissolved solids (TDS), Fe3+, and Mn2+. Furthermore, the Na+ and Cl− concentrations progressively increase while the Ca2+ and Mg2+ concentrations gradually decrease along the water flow direction. The hydrochemical type shifts from the Cl·SO4−Ca type of the influent water to the Cl·SO4−Na·Ca and Cl·SO4−Na types of the effluent water. The rocks collapsing in the underground reservoirs consist primarily of mudstones and sandstones. Their minerals comprise quartz, orthoclase, albite, illite, kaolinite, chlorite, gypsum, and pyrite. The principal hydrogeochemical processes the rocks experience include mineral dissolution (i.e., dissolution of halite, silicate, and gypsum), cation exchange, adsorption, precipitation, and mixing. The hydrochemical composition of water in the underground reservoirs is predominantly controlled by three factors: mineral dissolution and cation exchange (F1), the adsorption and precipitation of ions (F2), and the mixing of different water sources (F3), which contribute to 57.2%, 22.0%, and 20.8%, respectively, on average to the mass concentrations of ions in water bodies in the underground reservoirs. Specifically, F1 contributes 86.9%, 78.8%, 79.2%, 79.7%, 74.0%, and 74.8%, respectively, to the mass concentrations of Na+, K+, Ca2+, Cl−, \begin{document}${\mathrm{SO}}_4^{2-} $\end{document}, and \begin{document}${\mathrm{HCO}}_3^{-} $\end{document}; F2 contributes 83.9% and 70.3%, respectively, to the mass concentrations of Fe3+ and Mn2+, and F3 contributes 84.9% to the mass concentration of Mg2+. The results of this study provide theoretical support for a deep understanding of the water purification mechanisms for underground reservoirs in the coal mine. Additionally, these results offer technical guidance for optimizing the technologies for mine water treatment and achieving sustainable utilization of water resources.

In order to gain insight into the hydrochemical characteristics and formation mechanism of high fluoride groundwater in Zhuanlongwan Coal Mine, we conducted a comprehensive analysis of 48 samples including quaternary groundwater (QGW), sandstone groundwater (SGW), and mine water (MGW) using statistical analysis and hydrochemical methods. The findings demonstrate that the groundwater in Zhuanlongwan Coal Mine generally exhibits weak alkalinity, with predominant cations comprising of Ca2+ and Na+, and anions consisting of HCO3– and Cl–. The mean mass concentration of SO4 2–, Cl–, TDS, pH, and CO3 2– in groundwater follows the order of MGW>SGW>QGW, whereas HCO3– and F– exhibit the trend of SGW>MGW>QGW. Specifically, the average mass concentration of F– in QGW, SGW, and MGW is 0.76 mg/L, 4.55 mg/L, and 4.35 mg/L, respectively. Notably, most samples from SGW and MGW significantly exceed the permissible F−concentration threshold of 1.0 mg/L. The hydrochemical type of low fluoride (\begin{document}$\rho_{{\mathrm{F}}^{-}} $\end{document}1 mg/L) are mainly HCO3−Na (35.42%) and SO4·Cl−Na (45.83%). The dissolution of fluorinated minerals serves as the main source of F– in the high fluoride groundwater of Zhuanlongwan Coal Mine. Moreover, cation exchange, competitive adsorption, as well as the dissolution and precipitation of dolomite and calcite, are significant factors influencing the occurrence of high fluoride groundwater.

In recent years, mine water inrush accidents occurred several times in North China type coalfield during the mining process of the upper group of coal, and possessed great threat. Taking Dongtan Coal Mine as an example, statistical analysis, Piper trilinear diagram, Gibbs diagram, Chlorine-alkali index were used to analyze the hydrochemistry of the surface water and aquifers. The results show that the surface and groundwater in the research area is generally alkaline, rock weathering process is the main factor influencing the water quality, secondly is evaporation and precipitation, the atmospheric precipitation has little impact. The ion sources of aquifers are mainly silicate, evaporite and carbonate weathering and cation exchange. It is inferred that the hydraulic connection among Ordovician aquifer, surface water, Quaternary and the 14th limestone aquifers is close, Jurassic sandstone aquifer and No.3 coal roof sandstone aquifer have certain hydraulic connection. It is predicted that in the future, the first and the third mining areas will be affected by Ordovician water greater, then the fourteenth mining area, and the affection for the fourth mining areas is low. More attention must be paid to prevention in advance.

In order to grasp the groundwater chemistry characteristics and water quality in the Dingbian area, the collected 93 groundwater samples were used to assess the groundwater quality, water chemistry characteristics and human health risks caused by nitrate pollution by using WQI water quality index method, human health risk evaluation model, ion ratio method, Piper trilinear diagram and Gibbs model. The results show that the water chemistry in the study area is not significantly affected by nitrate contamination and it is mainly affected by evaporation and crystallization, dissolution and filtration and alternate cation adsorption. The groundwater quality in the study area is generally poor, which is mainly influenced by geological conditions and human activities, among which, NO-3 pollution is more serious. The water quality is gradually improved from south to north and from mountainous areas to plains. Nitrate pollution in groundwater can pose a threat to human health and children have a higher health risk due to nitrate production than adults. [ABSTRACT FROM AUTHOR]

Water-derived high iodine groundwater is a typical primary low-quality water, which poses a serious threat to drinking water safety. Taking the pore water in the central Taiyuan Basin as the research object, the characteristics of high iodine groundwater in the study area were analyzed by collecting 57 sets of groundwater samples in the study area, and the characteristics of high iodine groundwater in the study area were analyzed by comprehensively using the methods of Piper three-line diagram, correlation analysis and element ratio, and the enrichment process was discussed. The results show that the excessive iodine content in groundwater mainly occurs in the pore water of the alluvial plain, and the maximum I-mass concentration is 1128.0 μg/L; the horizontal zonation of high-iodine groundwater is obvious, and the I-mass concentration gradually increases along the groundwater flow direction; the vertical distribution is The characteristics show that with the increase of the burial depth of the water-bearing rock group, the average mass concentration of I- gradually decreases; the hydrochemical type of the high-iodine groundwater is mainly HCO3-Na type, and the groundwater components related to I- are Na+, TDS, Cl -, TOC, HCO-3, pH and ORP; alkaline weakly reducing sedimentary environment, rock weathering, groundwater runoff intensity, organic matter degradation, and competitive adsorption are the natural factors for iodine enrichment in pore water in Taiyuan Basin. Induced overcurrent recharge and stratigraphic mining are important external causes of iodine enrichment in pore water in the Taiyuan Basin. [ABSTRACT FROM AUTHOR]

The Yellow River in Inner Mongolia was selected as the study area in this study. In July (wet season) and October (dry season) of 2021, the acquisition of seasonal rivers, the Yellow River tributaries and precipitation, the Yellow River, Wuliangsuhai, Lake Hasuhai, Lake Daihai, an irrigation canal system, and underground water and sea water samples were collected to test the water chemical composition and hydrogen and oxygen isotopic values of different water types. Using the Piper triplot, Gibbs plot, ion ratio, and MixSIAR model methods, the evolution of water chemistry in the Mongolian section of the Yellow River Basin was analyzed, and the transformation relationship between precipitation, surface water, and groundwater was revealed. The results showed that both groundwater and surface water in the study area were slightly alkaline; the dominant anion in water was Cl - , and the dominant cation was Na + . The main hydrochemical types of surface water were Cl·SO 4 -Na·Mg and SO 4 ·HCO 3 -Na·Mg, whereas those of groundwater were Cl·SO 4 -Na·Mg and SO 4 ·HCO 3 -Na·Ca. Groundwater Ca 2+ and Mg 2+ were primarily derived from the dissolution of silicate and evaporite, and surface water Ca 2+ and Mg 2+ were primarily derived from carbonate karst dissolution and carbonate and sulfuric acid in water participating in the dissolution process of carbonate and sulfide minerals. Na + and Cl - in different water bodies were all affected by anthropogenic pollution sources. Owing to the seasonal effect, δ D and δ 18 O of surface water and groundwater were higher in the wet season than in the dry season. The results showed that surface water was affected by evaporative fractionation after receiving precipitation recharge, and the groundwater recharge sources were complex. The MixSIAR model revealed that surface water was the main recharge source of groundwater, accounting for 52.4%-62.2% of the total recharge, and atmospheric precipitation was the main recharge source of surface water, accounting for 85.4%-97.1% of the total recharge.