Gadolinium (Gd)

Atomic number:	64
Atomic weight:	157.25
Average concentration in ocean:	5.7 pmol/kg
Residence time:	450 - 1100 years

Distribution in ocean
Gd has a modified, nutrient-like profile similar to that of copper. Concentrations are low at the surface and increase with depth nearly continuously (data).

Speciation
The rare earth elements are present in seawater in the +III oxidation state, except Ce, which can also be oxidized to the +IV state. Complexation with carbonate ion dominates the speciation of REE's, e.g., LaCO₃⁺.

Residence time
The residence time was estimated from the Y and Ho residence times and the ratio of the particulate fraction of the metals (Alibo and Nozaki, 1999). This assumes reversible scavenging onto sinking particles.

Analysis
Rare earth elements are determined by mass spectrometry. The measurements shown here were determined using Inductively Coupled Plasms-Mass Spectrometry in shore based laboratories.

References