Direct measurement of femtomoles of osmium and the 187Os/186Os ratio in seawater
Two depth profiles of the osmium concentration and the 187Os/186Os isotopic ratio in the Indian Ocean showed that the osmium concentration seems to be unaltered by chemical or biological processes occuring in seawater; accordingly, osmium is conservative. These data were obtained from an experimental method that eliminated the problems related to osmium preconcentration. This method led to a new evaluation of the concentration of osmium in seawater; the mean concentration of osmium and the 187Os/186Os ratio are equal to 10.86 +/- 0.07 picograms per kilogram and 8.80 +/- 0.07, respectively. The results suggest the existence of an organocomplex that dominates the speciation of osmium in seawater.
Laboratoire de Geochimie et Cosmochimie, Unite de Recherche Associee of CNRS 1758, Institut de Physique du Globe de Paris, Universite Paris 7, 4 place Jussieu, 75252 Paris Cedex 05, France.
S
Levasseur
JL
Birck
CJ
Allegre