Major sources of iron to the world's oceans include
aeolian deposition, ¯uvial transport, hydrothermal
vents, continental shelf regeneration and upwelling
of Fe-enriched subsurface waters. In remote areas, the
ocean receives the majority of surface water iron from
atmospheric dusts, and the true impact of suspended
aerosols on trace element levels can only be made by
direct in-situ measurements. Attempts to map the
distribution and behaviour of iron in natural waters
have been hindered by its very low concentration and
ubiquitous sources of contamination in sampling
equipment, research vessels and laboratories. Furthermore,
the highly reactive characteristics of Fe species
have hampered the elucidation of accurate iron redox
models, and very little is known about the chemical
nature of iron associated with various operationally
de®ned fractions (e.g. labile, dissolved, colloidal,
organically bound, acid leachable, particulate). For
these reasons, coupled with the desire to evaluate the
effect iron limitation may have on phytoplankton
communities, there has been a demand for new analytical
methodologies which can provide rapid and
accurate iron determinations at pM levels on board
research vessels