dissolved samples. However, filtration becomes important for coastal waters, and certainly for scavenged-type elements in any place, since particle
association could easily exceed dissolved concentration. Various types of membrane filters with different pore sizes, generally in the range B1–0.04 mm,
have been used, and, therefore, the so-called ‘dissolved’ concentration includes different amounts of
colloidal form.
Furthermore, ionic species of many trace elements
form complexes with ligands in sea water. Table 1
lists the most probable inorganic species as deduced
from thermodynamics. Recently, complexation of
heavy metals (e.g., Fe, Zn, Cu, and Co) with organic
ligands which occur at nanomolar concentration
levels in the surface water has been investigated (see
Transition Metals and Heavy Metal Speciation).
These organic complexes are particularly important
for understanding the roles of trace elements in
plankton biology and metabolism. However, the
technologies to detect and separate these metal–organic complexes are not yet available.
Summary
The chemical constituents of sea water show a very
wide range in their concentration of more than 15
orders of magnitude, from chlorine (B0. 5 mol kg
À1 )
to the least abundant platinum group elements (e.g.,
IroB1 fmol kg
À1 ). The measurement of trace elements in sea water is extremely difficult for a long time
and was not achieved properly for most elements due
to large contamination problems in various stages of
sampling and analysis. It was only during the last
quarter of the twentieth century that those problems
were eventually overcome by current efforts of
chemical oceanographers. Since then, more and more
reliable data have accumulated and now the oceanic
distribution is known for almost all the elements.
Some of the trace metals, such as Al, and rare earth
elements (see Transition Metals and Heavy Metal
Speciation) serve as useful tracers of water masses in
describing hydrographic structures and patterns of
ocean circulation. Others, such as Fe, Si, and perhaps
Zn, have an essential role in phytoplankton growth
and hence affect the global carbon cycle through the
‘biological pump.’ Resemblance in the oceanic distribution between Cd and phosphorus, and between
Ba and alkalinity, provides a basis by which those
heavy metals can serve as useful proxies in reconstructing the paleo-oceanographic environment
from deep-sea sediment strata.
See also
Anthropogenic Trace Elements in the Ocean.
Conservative Elements. Conservative Elements.
Refractory Metals. Transition Metals and Heavy
Metal Speciation.
Further Reading
Nozaki Y (1997) A fresh look at element distribution in the
North Pacific Ocean. EOS Transactions, AGU 78: 221.
Li YH (1991) Distribution patterns of elements in the
ocean: a synthesis. Geochimica et Cosmochimica Acta
55: 3223--3240.
12 ELEMENTAL DISTRIBUTION: OVERVIEW
association could easily exceed dissolved concentration. Various types of membrane filters with different pore sizes, generally in the range B1–0.04 mm,
have been used, and, therefore, the so-called ‘dissolved’ concentration includes different amounts of
colloidal form.
Furthermore, ionic species of many trace elements
form complexes with ligands in sea water. Table 1
lists the most probable inorganic species as deduced
from thermodynamics. Recently, complexation of
heavy metals (e.g., Fe, Zn, Cu, and Co) with organic
ligands which occur at nanomolar concentration
levels in the surface water has been investigated (see
Transition Metals and Heavy Metal Speciation).
These organic complexes are particularly important
for understanding the roles of trace elements in
plankton biology and metabolism. However, the
technologies to detect and separate these metal–organic complexes are not yet available.
Summary
The chemical constituents of sea water show a very
wide range in their concentration of more than 15
orders of magnitude, from chlorine (B0. 5 mol kg
À1 )
to the least abundant platinum group elements (e.g.,
IroB1 fmol kg
À1 ). The measurement of trace elements in sea water is extremely difficult for a long time
and was not achieved properly for most elements due
to large contamination problems in various stages of
sampling and analysis. It was only during the last
quarter of the twentieth century that those problems
were eventually overcome by current efforts of
chemical oceanographers. Since then, more and more
reliable data have accumulated and now the oceanic
distribution is known for almost all the elements.
Some of the trace metals, such as Al, and rare earth
elements (see Transition Metals and Heavy Metal
Speciation) serve as useful tracers of water masses in
describing hydrographic structures and patterns of
ocean circulation. Others, such as Fe, Si, and perhaps
Zn, have an essential role in phytoplankton growth
and hence affect the global carbon cycle through the
‘biological pump.’ Resemblance in the oceanic distribution between Cd and phosphorus, and between
Ba and alkalinity, provides a basis by which those
heavy metals can serve as useful proxies in reconstructing the paleo-oceanographic environment
from deep-sea sediment strata.
See also
Anthropogenic Trace Elements in the Ocean.
Conservative Elements. Conservative Elements.
Refractory Metals. Transition Metals and Heavy
Metal Speciation.
Further Reading
Nozaki Y (1997) A fresh look at element distribution in the
North Pacific Ocean. EOS Transactions, AGU 78: 221.
Li YH (1991) Distribution patterns of elements in the
ocean: a synthesis. Geochimica et Cosmochimica Acta
55: 3223--3240.
12 ELEMENTAL DISTRIBUTION: OVERVIEW