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.
Levasseur
S
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.
Birck
JL
Allegre
CJ