Geochemical characterization of trace elements in thermomineral waters of Greece

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Trace elements have a fundamental role in natural and anthropogenic systems. In waters, theypresent a great variability of concentrations that mostly depends on the degree of gaswaterrockinteractions and geochemical conditions such as pH, temperature, redox and/or exchange reactions,etc. Even though, they are present in very low contents in hostrocks,elevated concentrations inground or surface waters may have a hazardous impact on human and animal health and thus, it isimportant to both quantify and try to understand their behaviour in natural systems.Here we present the results of about 300 cold and thermal mineral waters collected along theentire Hellenic territory. Physicochemical parameters (temperature, pH, electrical conductivityand Eh) were measured in situ, whilst samples were analysed by Ionic Chromatography (IC) andInductively Coupled Plasma Mass Spectrometry (ICPMS)for their major and trace elements’content. The great variability in hydrogeological settings justifies the wide range of temperatures(6.5 98°C) and pH (1.96 11.98).Total Dissolved Solids (TDS) values also covered a wide range,from 0.06 to 43 g/L. Based on the combination of pH, T and TDS, samples were subdivided into5 classes: i) thermal waters; ii) thermal waters affected by sea water contamination; iii) cold CO2richwaters; iv) hyperalkaline waters; and v) acidic waters.The great variability in chemical composition of the sampled waters is reflected in the large rangeof trace element contents (four to five orders of magnitude). Thermal waters affected by seawatercontamination show the strongest enrichments in Li (up to 17,600 μg/L), B (up to 38,200 μg/L),Sr (up to 80,000 μg/L) and Rb (up to 9230 μg/L), mostly deriving from waterrockinteraction.Cold CO2richwaters display elevated concentrations of Mn (up to 3970 μg/L), Ni (up to 111μg/L) and Fe (up to 218,000 μg/L), whilst at the water outflow an extensive precipitation of ironoxihydroxidesis observed. Hyperalkaline waters are generally strongly depleted in trace elementsdue to the precipitation of secondary minerals, however they are enriched in Al (up to 421 μg/L).Aluminium becomes soluble at extreme pH conditions and therefore also acidic waters presentenhanced concentrations (up to 100,000 μg/L). Acidic waters show also enrichments in Fe (upto 58,400 μg/L), Mn (up to 15,600 μg/L) and Ni (up to 101 μg/L).In some cases, the maximum contaminant levels (MCLs) fixed by the Directive 98/83/EC fordrinking water (and subsequent updates), are strongly exceeded in the under investigationwaters. Such elevated concentrations of harmful elements may create hazards to human healtheither via direct consumption of cold mineral waters or through mixing of highly mineralizedwaters evenin small proportions withshallow groundwater. For instance, As (MCL 10 μg/L)in the sampled waters reaches concentrations up to 1820 μg/L that derive from hightemperature waterrockinteraction within the hydrothermal circuit.
Original languageEnglish
Title of host publicationAbstract Volume 4a Conferenza A. Rittmann 12-14 Febbraio 2020
Number of pages1
Publication statusPublished - 2020

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