The determination of barium and strontium directly from sea water by isotope dilution mass spectrometry proves to be an efficient, precise, and virtual blank free procedure. Results for an eastern Pacific profile confirm a regularly increasing barium concentration from 5 to 23 ,clg/kg at 2500 m, but strontium concentrations appear to be nearly homogeneous below 50 m at 7.6 f 0.1 I;lg/kg with a single low value for the surface water. Results for a western Mediterranean profile show uniform concentrations for both barium and strontium, similar to the Atlantic. There appears to be a nearly conservative strontium-to-salinity ratio of 0.218 i 0.002 for sea waters below mixed surface zones. The barium salinity ratio for the Mediterranean and Atlantic is (0.30 f 0.01) X lo3 but the integrated Pacific profile shows a ratio almost twice as great
