Toxic chromium release from nickel mining sediments in surface waters, New Caledonia

Mining sediments are excavated from nickel ore exploitation in New Caledonia. In those sediments, chromium (Cr) occurs as Cr(III), but Cr(III) can be oxidized to the toxic Cr(VI) under oxic conditions, for instance in overlying water. Here, we aimed to determine whether mining sediments could releas...

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Bibliographic Details
Published inEnvironmental chemistry letters
Main Authors Gunkel-Grillon, Peggy, Laporte-Magoni, Christine, Le Mestre, Monika, Bazire, Nicolas
Format Journal Article
LanguageEnglish
Published Springer Verlag 04.07.2014
Subjects
Analytical chemistry
Chemical Sciences
Environmental Sciences
Mining sediments
Surface water
Chromium
Ophiolitic substrate
Ni mines
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Summary:Mining sediments are excavated from nickel ore exploitation in New Caledonia. In those sediments, chromium (Cr) occurs as Cr(III), but Cr(III) can be oxidized to the toxic Cr(VI) under oxic conditions, for instance in overlying water. Here, we aimed to determine whether mining sediments could release available Cr(VI) in surface waters. Water samples were collected in a mine and in the village downstream, and then were analysed for Cr. Batch leaching experiments were performed on mining sediments in order to determine their exchangeable and their water-soluble Cr content as a function of pH. Results show that mine waters contain high concentrations of total dissolved Cr, of up to 0.73 mg/L. Moreover, Cr(VI) concentration in village waters increases with the rainfall rate upto 0.34 mg/L. Cr is released from sediments solely as Cr(VI). Desorption of chromate complexes is the main process involved in Cr release. We conclude that drainage of sediments mobilized by opencast Ni mines is a source of toxic Cr(VI) for surface waters.
ISSN:1610-3653
1610-3661
DOI:10.1007/s10311-014-0475-1