Vue aérienne de la côte Nord de la Grande Terre – Nouvelle Calédonie
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L’article “Mobility of Ni, Co, and Mn in ultramafic mining soils of New Caledonia, assessed by kinetic EDTA extractions.” par Pasquet, C.; Monna, F.; van Oort, F.; Gunkel-Grillon, P.; Laporte-Magoni, C.; Losno, R.; Chateau, C. vient d’être publié dans Environmental Monitoring and Assessment. 2018, 190, 638.
Camille Pasquet (email: pasquet.camille@hotmail.fr) a étudié dans le cadre de sa thèse les capacités de mobilisation du nickel du cobalt et du manganèse dans les sols ultramafiques de Nouvelle Calédonie. Deux séries de sols ont été prélevées: des sols nus dans les mines de nickel en exploitation, et des sols forestiers, soit aux abords des mines, soit en zones éloignées des exploitations. Afin d’estimer la mobilité maximale des métaux, des extractions cinétiques à l’EDTA ont été appliquées. Les métaux dans les sols forestiers apparaissent plus facilement extractibles, mais les sols miniers représentent une plus grande menace du fait de leurs fortes teneurs en métaux, et de leur capacité a être remobilisé par le ruissellement ou l’érosion éolienne.
Abstract: The aim of this study was to determine the mobilization capability of Ni, Co, and Mn contained in New Caledonian ultramafic soils. Two series of soils
were sampled: bare-surface mining soils in a Ni-mining context (n = 10), and forest soils, either in the vicinity of mine-working areas (n = 3) or far away from any known mining activity (n = 2).We focused on the < 100 μm soil fraction, because of its sensitivity to wind erosion, and its possible dissemination toward urbanized areas. In order to assess maximum potential metal mobility, EDTA kinetic extractions were performed over 24 h. Extraction curves were modeled as the sum of two first order reactions. The first EDTA extracted pool corresponds to “quickly” released metals, while the second pool corresponds to “slowly” released metals. The remaining fraction is the EDTA non-extractable pool. Extractable Ni, Co, and Mn were always low in relation to total concentrations (< 5% for Ni, and 5–35% for Co and Mn). The extraction rate of the less labile pool was significantly higher for forest soils than for mining soils, whatever the metal. Despite the greater extractability potential in forest surface soils, mining soils represent a bigger environmental risk, because of their high metal content and, above all, because of their predisposition to surface runoff and eolian deflation.