title: Origin of hexavalent chromium in groundwater: The example of Sarigkiol Basin, Northern Greece.
abstract: Hexavalent chromium constitutes a serious deterioration factor for the groundwater quality of several regions around the world. High concentrations of this contaminant have been also reported in the groundwater of the Sarigkiol hydrological basin (near Kozani city, NW Greece). Specific interest was paid to this particular study area due to the co-existence here of two important factors both expected to contribute to Cr(VI) presence and groundwater pollution; namely the area's exposed ophiolitic rocks and its substantial fly ash deposits originating from the local lignite burning power plant. Accordingly, detailed geochemical, mineralogical, hydro-chemical, geophysical and hydrogeological studies were performed on the rocks, soils, sediments and water resources of this basin. Cr(VI) concentrations varied in the different aquifers, with the highest concentration (up to 120μgL-1) recorded in the groundwater of the unconfined porous aquifer situated near the temporary fly ash disposal site. Recharge of the porous aquifer is related mainly to precipitation infiltration and occasional surface run-off. Nevertheless, a hydraulic connection between the porous and neighboring karst aquifers could not be delineated. Therefore, the presence of Cr(VI) in the groundwater of this area is thought to originate from both the ophiolitic rock weathering products in the soils, and the local leaching of Cr(VI) from the diffused fly ash located in the area surrounding the lignite power plant. This conclusion was corroborated by factor analysis, and the strongly positively fractionated Cr isotopes (δ53Cr up to 0.83‰) recorded in groundwater, an ash leachate, and the bulk fly ash. An anthropogenic source of Cr(VI) that possibly influences groundwater quality is especially apparent in the eastern part of the Sarigkiol basin.
authors.affiliation: Aristotle University of Thessaloniki, School of Geology, Lab. of Engineering Geology and Hydrogeology, 54124 Thessaloniki, Greece.
authors.forename: N
authors.initials: N
authors.lastname: Kazakis
authors.affiliation: Aristotle University of Thessaloniki, School of Geology, Dept. of Mineralogy, Petrology and Economic Geology, 54124 Thessaloniki, Greece. Electronic address: kantira@geo.auth.gr.
authors.forename: N
authors.initials: N
authors.lastname: Kantiranis
authors.affiliation: Aristotle University of Thessaloniki, Department of Chemical Engineering, 54124 Thessaloniki, Greece.
authors.forename: K
authors.initials: K
authors.lastname: Kalaitzidou
authors.affiliation: Aristotle University of Thessaloniki, Department of Chemical Engineering, 54124 Thessaloniki, Greece.
authors.forename: E
authors.initials: E
authors.lastname: Kaprara
authors.affiliation: Aristotle University of Thessaloniki, Department of Chemical Engineering, 54124 Thessaloniki, Greece.
authors.forename: M
authors.initials: M
authors.lastname: Mitrakas
authors.affiliation: University of Copenhagen, Department of Geoscience and Natural Resource Management Nord CEE, Denmark.
authors.forename: R
authors.initials: R
authors.lastname: Frei
authors.affiliation: Aristotle University of Thessaloniki, School of Geology, Applied Geophysics Lab., 54124 Thessaloniki, Greece.
authors.forename: G
authors.initials: G
authors.lastname: Vargemezis
authors.affiliation: Aristotle University of Thessaloniki, School of Geology, Applied Geophysics Lab., 54124 Thessaloniki, Greece.
authors.forename: P
authors.initials: P
authors.lastname: Tsourlos
authors.affiliation: Aristotle University of Thessaloniki, Department of Chemistry, Lab. of General and Inorganic Chemical Technology, 54124 Thessaloniki, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Zouboulis
authors.affiliation: Aristotle University of Thessaloniki, School of Geology, Dept. of Mineralogy, Petrology and Economic Geology, 54124 Thessaloniki, Greece.
authors.forename: A
authors.initials: A
authors.lastname: Filippidis
keywords: Chromium isotopes; Cr(VI) presence; Dispersion of fly ash; Electric resistivity tomography; Factor analysis; Ophiolitic rocks