Boron (B)

Atomic number: 5
Atomic weight: 10.811
Average concentration in ocean: 416 µmol/kg
Residence time: 9,600,000 years

Distribution in ocean
Boron is the 10th most abundant element dissolved in seawater and it has a conservative vertical profile.   Concentrations are nearly constant throughout the water column and they are similar in the Atlantic and Pacific Oceans (data).

Speciation
Boron is present in seawater as the borate ion (B(OH)4-) and undissociated boric acid (B(OH)30).

Residence time
The boron residence time is from Tracers in the Sea (Broecker, W. S. and Peng, T.-H., 1982.  Eldigo Press, Palisades, NY).  It was calculated from the global average river input.

Analysis
Boron is determined by mannitol titration after removing carbon dioxide.

References