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The hydrogeochemistry of geothermal fluids provides insight into the occurrence, formation, and circulation of geothermal resources. We collected 13 geothermal water (> 34 °C) and 11 common groundwater samples (< 20 °C) from the Qingdong coal mine in China. The geothermal water samples had higher TDS, Ca2+, and SO42− contents, by 1.22-, 1.28-, and 1.25-fold, respectively. The hydrochemical facies of the geothermal water samples was 92% SO4·Cl–Ca.Mg and 8% SO4·Cl–Na, whereas the common groundwater samples was 73% SO4·Cl–Ca.Mg and 27% SO4·Cl–Na. Moreover, hydrogen and oxygen isotopic analysis revealed that atmospheric precipitation and water–rock interaction were the sources of the geothermal water. The chemical composition of the geothermal water is dominated by ion-exchange interactions and the dissolution of carbonates and silicates. Overall, geothermal water in the study area is characterized by optimal hydrodynamic conditions and more intense ion-exchange interactions than common groundwater. Moreover, the formation of geothermal water is controlled by hydrogeological and structural conditions, and by the infiltration of atmospheric precipitation, heating by deep circulation, and transportation by water-conducting faults (F11) to shallow coal strata. These results will facilitate the development of geothermal resources and the construction of green ecological mines, which will provide considerable economic and social benefits. [ABSTRACT FROM AUTHOR]

The Panama coastal aquifer system is an important water resource in the southeast coast of Sri Lanka that provides adequate supplies of water for agriculture and domestic uses. One of the biggest threats to these fragile aquifers is the sea water intrusion. In this study, recharging mechanism and geochemical evaluation of groundwater in the coastal sandy aquifer of Panama were evaluated using chemical and stable isotope techniques. Thirty groundwater samples were collected and analyzed for their major ion concentrations and stable isotope ratios of oxygen (O/O) and hydrogen (D/H). All studied samples showed a ranking of major anions in the order Cl> HCO> SO> N-NO while cations showed a decreasing order of abundance with Na> Ca> Mg> K. Dominant groundwater hydrogeochemical types were Na-Cl and mixed Ca-Mg-Cl. Results of saturation index calculations indicate that the investigated groundwater body was mostly saturated with respect to calcite, dolomite and gypsum. In addition, stable isotope and geochemical data suggest that fresh groundwater in the aquifer is recharged mainly by local precipitation with slight modification from evaporation and saline water intrusions. Isotope data suggest that mixing of salt water with freshwater occurs in aquifers which are located towards the lagoon. Since the communities in the study area depend entirely on groundwater, an understanding of the hydrogeochemical characteristics of the aquifer system is extremely important for the better water resource management in the region. [ABSTRACT FROM AUTHOR]