Uranium (U)

Atomic number:	92
Atomic weight:	238.029
Average concentration in ocean:	13.4 nmol/kg
Residence time:	400,000 years

Distribution in ocean
Dissolved uranium has a conservative distribution in the ocean. Concentrations are relatively uniform vertically and horizontally and change only in proportion to salinity (data).

Speciation
Uranium is present as the uranyl carbonate ion (UO2(CO₃)₃^4-).

Residence time
The uranium residence time is calculated from the global average river input (3 to 6 x 10⁷ mol/yr; Palmer and Edmond, 1993).

Analysis
Uranium can be determined most accurately by mass spectrometry or, with less precision, by alpha counting.

References & Notes