The silica supersaturated waters of northern Evia and eastern central Greece

Abstract

Abstract:The area of north Evia and eastern central Greece is characterized by strong geomorphological contrast and is built up mainly of consolidated rocks. Unconsolidated young sediments of Pleistocene to Holocene age cover the valley and basin¯ats, forming the most productive aquifers in this area. However, two more types of aquifers can be distinguished within the consolidated rock area. The ®rst one is associated with karsti®ed limestones and the second with strongly tectonized ultrama®c rocks. The schist±chert formation, with intercalations of shales and cherts, seals the ultrama®c masses underneath.Surface and spring waters associated with ultrama®c rocks in north Evia and eastern central Greece were studied. Two types of water can be distinguished: (1) high Mg 2 and SiO 2 , bicarbonate as the dominant anion, pH 7 . 4±9 . 2, temperature 9 . 5±16 . 3 8C, low TDS (total dissolved solutes) (459±1037 mg/l), found both in peridotite and serpentinite areas, classi®ed as Mg±HCO 3 type; (2) high Ca 2 , low Mg 2 and SiO 2 , hydroxyl ion as the major anion, pH 11 . 2, temperature 28 8C, very low TDS (122 mg/l), found in peridotite areas, classi®ed as Ca±OH type. The studied waters are highly supersaturated with respect to quartz, amorphous silica, brucite and most low temperature magnesium silicates (antigorite, sepiolite, talc, etc.). These waters show relatively narrow SiO 2 concentration ranges and a trend parallel to the amorphous silica saturation surface. The silica supersaturated waters have the potential to precipitate silica and consequently could aect the people of the local communities that use it as drinking water, causing health problems (kidney stones).

A conceptual hydrogeological model of ophiolitic aquifers (serpentinised peridotite): The test example of Mt. Prinzera (Northern Italy)

“…Figure traced the possible evolution from a Ca‐HCO 3 , typical of surface water, to hyperalkaline passing through the Mg‐HCO 3 composition. This chemical evolution from HCO 3 − to OH − waters commonly occur in other peridotite aquifer worldwide (e.g., Barnes & O'Neil ; Cardace et al, ; Miller et al, ; Marques et al, ; Neal & Shand, ; Pawson, ; Stamatis & Gartzos, ), which was conventionally sorted by major ion chemistry into type I and type II waters, respectively (Neal & Stanger, ; ). Locally, it is the product of low‐temperature reaction between meteoric water and ultramafic rocks, which is firstly accompanied by Mg‐enrichment and then followed by Mg‐decrease as consequence of the precipitation of Mg‐bearing clay minerals (kaolinite, montmorillonite, saponite, and vermiculite) and serpentine, as supported by reaction‐path modeling (Boschetti & Toscani, ; Boschetti et al, ).…”

Groundwater quality assessment in Oropos–Kalamos basin, Attica, Greece

“…Interactions among water-rock-sediment-soil and the mineral composition of the aquifer materials through which water moves play an important role in groundwater chemistry variation and groundwater quality variation. Furthermore, groundwater quality is often degraded by anthropogenic activities (Arumugam and Elangovan 2009;Espinosa et al 2009;Fehdi et al 2009;Kelepertsis et al 2006;Lambrakis 2006;Stamatis and Gartzos 1999;Skeppstrom and Olofsson 2007;Simsek 2008;Liou et al 2009). …”

Assessment of water quality in the Messolonghi–Etoliko and Neochorio region (West Greece) using hydrochemical and statistical analysis methods

“…Furthermore, since water resources management has become increasingly important for sustainable development of these regions it is necessary to assess the suitability of water for agricultural use or human consumption. The quality of water is controlled by natural and anthropogenic factors that include geological structure and mineralogy of the watersheds and aquifers, the residence time, the reactions that take place within the aquifer as well as the type of land uses (Alexakis 2008;Appelo and Postma 2005;Bathrellos et al 2007;Hajizadeh Namaghi et al 2011;Kelepertsis et al 2001;Lambrakis 2006;Palma et al 2010;Saeedi et al 2010;Stamatis and Gartzos 1999;Stamatis et al 2006;Suthar et al 2010). The interaction of natural and anthropogenic factors leads to various water types.…”