Download Speciation of cadmium in seawater - Umwelt

Speciation of cadmium in seawater - a direct voltammetric approach
E. Helmers (1994)
Fres. Z. Anal. Chem. 350: 62-67
Distribution of Cd was investigated in surface waters of the Atlantic Ocean
over a wide geographical range as well as the water column. Surface water
sampling on board the research vessel Polarstern was performed from the bow
boom of the ship as well as with a snorkel system which allowed continuous
sample-taking. Two different Cd species could be differentiated in the
voltammograms. UV-irradiation experiments allowed the identification of an
inorganic and an organic Cd species, the latter caused by the association
between Cd and organic matter as e.g. humic substances (HS). Atlantic ocean
surface seawater normally contains between 2 and 4 ng organically complexed
Cd/kg and no detectable inorganic Cd. Some areas however showed readings of
up to 14 ng inorganic Cd/kg in addition. Water column samples exhibited an
enrichment of inorganic Cd by depth. Occurrence of inorganic Cd at the surface
could be related to specific oceanographical conditions. Together with
analytical results of trace metal contents in the particulate phases of surface
seawater, new aspects could be established about the biogeochemical cycling of
Cd in the sea.