Hydrogeochemistry and geogenic fluoride and boron groundwater problems in the Emscher Fm. (Münsterland region, Germany)

Die Sediment- und Grundwasserchemie des Emschermergels im Münsterland (NRW) wurde untersucht. Die Geochemie (Canorg- und Spyrit) wurde an 160 Gesteinsproben analysiert. Unterhalb einer geogenen Verwitterungszone wurden unverwitterte, pyrithaltige Gesteine vorgefunden. Die Grundwasserchemie des Emschermergels in Ostwestfalen wurde anhand von 580 Einzelanalysen aus Hausbrunnen, ergänzt durch weitere Literaturdaten, zusammengetragen und ausgewertet. Die Grundwässer weisen zum Teil hohe Fluorid- und Borkonzentrationen von jeweils bis zu 10 mg/l auf – regional liegen bis zu 30 % der Wässer über 1,5 mg/l Fluorid, und bis zu 50 % über 1 mg/l Bor – die räumliche Verteilung scheint vom Vorhandensein einer Quartärüberdeckung abzuhängen. Grundwässer mit hohen Fluoridkonzentrationen zeigen geringe Ca2+-Konzentrationen und umgekehrt, was auf eine Gleichgewichtseinstellung mit der Mineralphase Fluorit hindeutet. Grenzwertüberschreitende Gehalte treten fast ausnahmslos in Ionenaustauschwässern des Na-HCO3-(Cl)-Typs mit pH > 7,5 auf. Als wahrscheinlicher Hauptmobilisierungsmechanismus beider Kontaminanten erscheint die pH-gesteuerte Desorption von Mineraloberflächen. Die geologische Primärquelle ist unbekannt, eine nähere geochemisch-mineralogische Untersuchung des Emschermergels wäre wünschenswert.The hydrogeochemistry of the Cretaceous Emscher Fm. in northwest Germany was investigated, including analysis of 160 rock samples for carbon and sulfur content. Beneath a weathered zone, unweathered rocks containing pyrite were found. Groundwater data from the Emscher Fm. (580 analyses of house wells and additional literature data) were collected and evaluated. Some groundwater contains high fluoride and boron concentrations of up to 10 mg/l. Regionally, up to 30% of house wells show fluoride concentrations above 1.5 mg/l, and up to 50% above 1 mg/l boron. The spatial distribution depends on the presence of Quaternary cover sediments. Groundwater with high fluoride concentrations displays low Ca2+, and vice versa, indicating equilibrium with the mineral fluorite (CaF2). Concentrations above drinking water guidelines almost exclusively occur in ion exchange waters of the Na-HCO3 −(Cl) type with pH > 7.5. The main mobilization mechanism of both contaminants appears to be pH-triggered desorption from mineral surfaces

The Influence of Karst Aquifer Mineralogy and Geochemistry on Groundwater Characteristics: West Bank, Palestine

This work reports, for the first time, the mineralogical and geochemical characteristics of karst aquifers in the Central West Bank (CWB) catchment in Palestine. It provides an integrated study approach by correlating the geochemistry of the lithology and hydrochemical data of groundwater samples. Mineralogical analysis showed that all of the samples were dominantly composed of either calcite CaCO3 (5⁻100 wt. %) or dolomite CaMg(CO3)2 (4⁻100 wt. %), with minor amounts of quartz and feldspar, which is supported by the inorganic carbon content (9⁻13 wt. %) and hydrochemical composition of the spring water samples. The whole-rock geochemical data indicated that the samples have low contents of trace elements and transition metals. In contrast, the concentrations of alkaline earth elements (Mg, Ca, Sr, Ba) and Mn were high in the rock and groundwater samples. Generally, the trace elements of rock samples with concentrations >10 ppm included Sr (17⁻330 ppm), Mn (17⁻367 ppm), Ba (2⁻32 ppm), W (5⁻37 ppm), Cr (3⁻23 ppm), Zn (1.7⁻28 ppm), V (4⁻23 ppm), and Zr (1⁻22 ppm), while the concentrations of all the other trace elements was below 10 ppm. Ionic ratios and hierarchical cluster analysis (HCA) suggested that the chemical evolution of groundwater was mainly related to the geogenic (rock⁻water) interaction in the study area. This is clear in the alkaline earth elements (Mg, Ca, Sr, Ba) ratios, especially regarding the Sr values. The calcite rock samples had higher Sr (mean 160 ppm, n = 11) than those of the dolomite rocks (mean 76 ppm, n = 9)