Barium (Ba)

Atomic number:	56
Atomic weight:	137.33
Average concentration in ocean:	109 nmol/kg
Residence time:	10,000 years

Distribution in ocean
Ba has a nutrient-like vertical profile with moderately depleted concentrations found at the surface and values increasing to a deep maximum (data).

Speciation
Barium is present in seawater as the Ba²⁺ ion.

Residence time
The residence time was determined from the global river input of barium and the impacts of estuarine sources of dissolved barium (Chan et al., 1976).

Analysis
Barium may be determined by inductively coupled plasma mass spectrometry or graphite furnace atomic absorption spectrophotometry with appropriate matrix modifiers.

References