Abstract
The hydrogeochemical processes and natural background levels (NBLs) of chromium in the ultramafic environment of Vermio Mountain, Western Macedonia, Greece, were studied. Seventy groundwater samples were collected from 15 natural springs between 2014–2020, and an extensive set of physical and chemical parameters were determined. The ultramafic-dominated environment of western Vermio Mt. favors elevated groundwater concentrations of dissolved magnesium (Mg2+), silicon (Si), nickel (Ni), and Cr in natural spring waters. Chromium was the principal environmental parameter that exhibited a wide range of concentrations, from 0.5 to 131.5 μg/L, systematically exceeding the permissible limit of 50 μg/L for drinking water. Statistical evaluation of hydrogeological, hydrochemical, and hydrological data highlighted the water-ultramafic rock process as the predominant contributor of Cr in groundwater. The NBL assessment for Cr and Cr(VI) was successfully applied to the typical ultramafic-dominated spring “Potistis” that satisfied all the methodology criteria. The NBLs of Cr and Cr(VI) were defined at 130 μg/L and 100 μg/L, respectively, revealing that a natural ultramafic-dominated environment exhibits the geochemical potential to contribute very high concentrations of geogenic Cr to groundwater. The holistic methodology, proposed herein, could be implemented in any catchment scale to assess geogenic and anthropogenic Cr-sources that degrade groundwater quality.
Highlights
Natural background levels (NBLs) are defined as “the concentration of a substance or the value of an indicator in a body of groundwater corresponding to no, or only very minor, anthropogenic alterations to undisturbed conditions” according to the Groundwater Daughter Directive (GDD) (Directive 2006/118/electrical conductivity (EC)) [1]
The need to separate natural background levels (NBLs) from the anthropogenic impacts is frequently satisfied through statistical and pre-selection (PS) methods [10]. Such methods were applied within the EU-Specific Targeted Research Project BRIDGE (Background cRiteria for the iDentification of Groundwater thrEsholds), the objective of which was to develop a comprehensive methodology to evaluate threshold values (TVs) and NBLs of various qualitative parameters in the groundwater resources [11]
We study the geochemical fingerprint of the water–ultramafic rock interaction process in the western Vermio Mt., Western Macedonia, Greece, and determine the NBLs of Cr in groundwater from natural springs
Summary
Natural background levels (NBLs) are defined as “the concentration of a substance or the value of an indicator in a body of groundwater corresponding to no, or only very minor, anthropogenic alterations to undisturbed conditions” according to the Groundwater Daughter Directive (GDD) (Directive 2006/118/EC) [1]. The need to separate NBLs from the anthropogenic impacts (e.g., urbanization, industrialization, agricultural activity) is frequently satisfied through statistical and pre-selection (PS) methods [10]. Such methods were applied within the EU-Specific Targeted Research Project BRIDGE (Background cRiteria for the iDentification of Groundwater thrEsholds), the objective of which was to develop a comprehensive methodology to evaluate threshold values (TVs) and NBLs of various qualitative parameters in the groundwater resources [11]. The challenging assessment of NBLs in an environment in which the prevailing geochemical conditions favor the occurrence and mobilization of naturally occurring chemical elements could provide essential information regarding the controversial geogenic and anthropogenic inputs in a complex environmental setting.
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