Vertical distributions of Sb(III) and Sb(V) in Pavin Lake, France

Vertical profiles of dissolved total inorganic antimony (ΣSb), Sb(V) and Sb(III) have been determined in Pavin Lake, a small meromictic lake in France. A slight depletion of Sb(V) in the surface water is observed. The concentration is about 0.1 nM at the surface and it is about 0.35 nM at depths in the oxic water column of the mixolimnion. In contrast, an enrichment of Sb(III) at the surface is observed. The concentration is about 0.1 nM at the surface and it is undetectable at depths. Both Sb(V), thermodynamically stable species, and Sb(III), thermodynamically unstable species, are equally important species at the surface. At the depths, on the other hand, Sb(V) is the only detectable species in accordance with the thermodynamic prediction. A possible perturbation induced by biological activity is suggested. In the anoxic waters of the monimolimnion, only ΣSb has been determined. The concentration is low, less than 0.06 nM. Precipitation of antimony sulfide is suggested.