exudation
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tion, the complexes are destroyed with nitric acid and the metals back
extracted into double quartz-distilled water. The advantages of the method
are: (a) the salt matrix is removed, and (b) the elements are concentrated by
a factor of 50 or more.
exudation of organic matter (sometimes called excretion, -7excretory organs) the
escape of soluble organic compounds from all kinds of water plants (macrophytes, phytoplankton) during photosynthesis. Normally less than 5 % of the C
fIxed during photosynthesis is exudated, but higher fIgures have been
reported at high light intensities and at the end of phytoplankton blooms.
Some are probably artifacts. This fraction does not form an important contribution to the DOC (-7carbon, organic) pool in sea, because the compounds
concern small amounts of amino acids and larger amounts of short-chain
acids (e.g., glycolic acid), glycerol, carbohydrates and polysaccharides which
are rapidly assimilated by bacteria. Exudation may be passive as well as
active. Active exudation includes extracellular metabolites of algae, like
metal-chelating (-7chelation) compounds in metal-polluted waters, and antibacterial compounds.
Eotvos correction -7Coriolis force.