Lead (Pb)
| Atomic number: |
82 |
| Atomic weight: |
207.2 |
| Average concentration in ocean: |
13 pmol/kg |
| Residence time: |
80 years |
Distribution in ocean
Dissolved Pb has a scavenged element vertical profile.
Concentrations are high at the surface due to atmospheric input and the
concentrations decrease with depth as dissolved Pb is sorbed on to sinking
particles and removed to the sediment (data). The
atmospheric input of lead is dominated by lead from industrial activities and
the entire ocean is contaminated with this lead. There is good news
however. Dissolved Pb concentrations often have a minimum
at the surface because the atmospheric input has decreased dramatically in the
past decade as leaded gasoline, one of the major atmospheric sources, is phased
out of usage.
Speciation
Lead is present as the +II ion as the PbCO30 ion.
Residence time
The lead residence time is difficult to estimate because fluxes through the
modern ocean are strongly perturbed by man. The pre-industrial lead cycle
was estimated to have an 80 year residence time in the deep-sea (Flegal and
Patterson, 1983).
Analysis
Lead is determined by mass spectrometry or graphite furnace atomic absorption
sperctrometry after preconcentration using an organic ligand.
References & Notes