Unit:
Κατεύθυνση Χημεία και Τεχνολογία ΠεριβάλλοντοςLibrary of the School of Science
Author:
Ανδριώτη Αμαρυλλίς
Supervisors info:
Εμμανουήλ Δασενάκης Καθηγητής
Original Title:
Μελέτη της γεωχημείας του Cr σε δείγματα υπερβασικών πετρωμάτων και διερεύνηση της κινητικότητας του Cr(VI)
Translated title:
Study of the geochemistry of Cr in ultramafic rocks and investigation of the mobility of Cr(VI)
Summary:
The presence of geogenic Cr(VI) in the groundwater of areas with abundant
exposures of ultramafic rocks is a well recognised environmental problem.
Considering the widespread occurrence of ultramafic rocks in Greece, the aim of
this thesis is the investigation of the mechanisms that could lead to
groundwater contamination by Cr(VI). Under this scope, rock samples were
collected from a weathering sequence; the samples analyzed included
serpentinised peridotites, overlying soil and laterites. The mineralogical and
chemical composition of the samples was consistent with the weathering
processes, namely laterization. Hexavalent chromium was detected in all of the
samples and its concentration increased along the toposequence. Ophiolite
samples consisted mostly of exchangeable forms, while in the soil and laterite
samples, insoluble forms of Cr(VI) were more abundant. Batch experiments of
the samples showed that the release rate and the concentration of Cr(VI) were
higher in the slightly acidic pH (6), rather than in the slightly alkaline pH
(8.5). Cr(VI) was generated in the ophiolite sample, through oxidation of
Cr(III) by the manganese oxides that are abundant in the sample. The genesis of
hexavalent chromium from ultramafic rocks is an ongoing process and could lead
to the severe degradation of the groundwater quality.
Keywords:
Chromium, Hexavalent chromium, Ultranafic rocks, Geogenic Cr(VI), Natural enrichment
Number of index pages:
13-16, 110-111
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