Chromium speciation, mobility, and Cr(VI) retention–release processes in ultramafic rocks and Fe–Ni lateritic deposits of Greece

• Published in: Environmental geochemistry and health Vol. 44; no. 8; pp. 2815 - 2834
• Main Authors: Botsou, Fotini, Koutsopoulou, Eleni, Andrioti, Amaryllis, Dassenakis, Manos, Scoullos, Michael, Karageorgis, Aristomenis P.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.08.2022; Springer Nature B.V
• Subjects: adsorption; Aquatic environment; Chemical precipitation; Chromium; Contamination; Earth and Environmental Science; Environment; Environmental Chemistry; Environmental Health; Geochemistry; Geographical distribution; Greece; Hexavalent chromium; Iron; Laterites; Leaching; Manganese; Mineralogy; Mobility; Original Paper; Oxidation; Oxides; pH effects; Public Health; Retention; Rocks; serpentinite; Soil; Soil contamination; Soil Science & Conservation; Soils; Speciation; Terrestrial Pollution; Trivalent chromium; Ultramafic materials; Ultramafic rocks; Water pollution; Weathering; Greece; Serpentinites; Fe–Ni laterite deposit; Cr(III) oxidation; Mn oxides; Geochemical fractionation; Geogenic Cr(VI); Speciation
• ISSN: 0269-4042; 1573-2983; 1573-2983
• DOI: 10.1007/s10653-021-01078-8

Water contamination by geogenic hexavalent chromium is an emerging issue in areas developed on ultramafic rocks and their weathering products. In this study, samples of serpentinites, soil, and laterites were collected and analyzed for the levels of Cr species, distribution into phases of different mobility, mineralogy, Cr oxidation capacity, and leaching of Cr(VI). Total chromium (2176–21,929 mg kg −1 ) was mainly found in Cr spinels (~ 50% wt as Cr 2 O 3 ) and Fe (hydr)oxides (2.5% wt). Total Cr(VI) contents (0.49–11.5 mg kg −1 ) increased from the serpentinites to the soil and lateritic deposit, i.e., during the advanced stages of weathering, which were accompanied by increased Cr mobility. Batch experiments of 500-h duration showed that Cr(VI) released in water at rates of 0.25–1.20 nM h –1 . Rates were higher in water of pH 5.7 rather than pH 8.5, because more Cr(VI) was formed during the experimental period. Asbolane-type Mn oxides and Mn-bearing crystalline Fe oxides were responsible for Cr(III) oxidation. Most of the generated Cr(VI) (52–79% of total Cr(VI)) remained solid-bound by adsorption and/or precipitation processes. Because all samples had a self-capacity to oxidize Cr(III), it seems that retention processes will ultimately define the extent of geogenic Cr(VI) contamination of aquatic systems.