TY - JOUR

T1 - Oxidative release of chromium from Archean ultramafic rocks, its transport and environmental impact – A Cr isotope perspective on the Sukinda valley ore district (Orissa, India)

AU - Paulukat, Cora Stefanie

AU - Døssing, Lasse Nørbye

AU - Mondal, Sisir K.

AU - Vögelin, Andrea Regula

AU - Frei, Robert

PY - 2015

Y1 - 2015

N2 - This study investigates Cr isotope fractionation during soil formation from Archean (3.1–3.3 Ga) ultramafic rocks in a chromite mining area in the southern Singhbhum Craton (Orissa, India). The Cr-isotope signatures of two studied weathering profiles, range from non-fractionated mantle values to negatively fractionated values as low as δ53Cr = −1.29 ± 0.04‰. Local surface waters are isotopically heavy relative to the soils. This supports the hypothesis that during oxidative weathering isotopically heavy Cr(VI) is leached from the soils to runoff.The impact of mining pollution is observed downstream from the mine where surface water Cr concentrations are significantly increased, accompanied by a shift to less positive δ53Cr values relative to upstream unpolluted surface water. A microbial mat sample indicates that microbes have the potential to reduce and immobilize Cr(VI), which could be a factor in controlling the hazardous impact of Cr(VI) on health and environment.The positive Cr isotope signatures of the Brahmani estuary and coastal seawater collected from the Bay of Bengal further indicate that the positively fractionated Cr isotope signal from the catchment area is preserved during its transport to the sea. Isotopically lighter Cr(VI) downstream from the mine is probably back-reduced to Cr(III) during riverine transport leading to similar Cr-isotope values in the estuary as observed upstream from the mine.

AB - This study investigates Cr isotope fractionation during soil formation from Archean (3.1–3.3 Ga) ultramafic rocks in a chromite mining area in the southern Singhbhum Craton (Orissa, India). The Cr-isotope signatures of two studied weathering profiles, range from non-fractionated mantle values to negatively fractionated values as low as δ53Cr = −1.29 ± 0.04‰. Local surface waters are isotopically heavy relative to the soils. This supports the hypothesis that during oxidative weathering isotopically heavy Cr(VI) is leached from the soils to runoff.The impact of mining pollution is observed downstream from the mine where surface water Cr concentrations are significantly increased, accompanied by a shift to less positive δ53Cr values relative to upstream unpolluted surface water. A microbial mat sample indicates that microbes have the potential to reduce and immobilize Cr(VI), which could be a factor in controlling the hazardous impact of Cr(VI) on health and environment.The positive Cr isotope signatures of the Brahmani estuary and coastal seawater collected from the Bay of Bengal further indicate that the positively fractionated Cr isotope signal from the catchment area is preserved during its transport to the sea. Isotopically lighter Cr(VI) downstream from the mine is probably back-reduced to Cr(III) during riverine transport leading to similar Cr-isotope values in the estuary as observed upstream from the mine.

U2 - 10.1016/j.apgeochem.2015.04.016

DO - 10.1016/j.apgeochem.2015.04.016

M3 - Journal article

VL - 59

SP - 125

EP - 138

JO - Applied Geochemistry

JF - Applied Geochemistry

SN - 0883-2927

ER -