Gschwend%20thesis.pdf

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Potentially, this fraction includes many normal, branched ,and cyclic
alkanes, alkenes, aromatics, aldehydes, ketones, esters, ethers, halogenated
hydrocarbons, and thioethers. Consequently, one would expect a diverse
group of organic compounds to be included. This diversity holds substantial
information concerning sources, transformations,and sinks of the specific
compounds, as well as of the more general organic fraction. This fraction
does not include organic aompounds of boiling point lower than about ioooc
or of water solubility greater than about 1 gm/kg (~ 0.01 M). Therefore,
this fraction is a subset of the total volatile fraction.
Estimates of. the Size of the Total Volatile Fraction
Motivated by the desire to measure accurately the dissolved organic
carbon (DOC) in seawat~r, a few workers have attempted to estimate the size
of the total volatile fraction. Duursma (1961) reported that less than 10%
of the DOC, or about 0.1 mg/kg, was volatile. This conclusion was based on
an experiment in which he used acetic acid as a model volatile compound.
Vityuk (reported in Skopintsev, 1966) also attempted to measure the
total volatile fraction. He dried one set of seawater samples at 600C for
routine dry-combustion analysis and a parallel set at room temperature with
a dessicant. He found an average 18% lower value for the 600C dried samples,
indicating that the volatiles make up 15% of the DOC (or about 0.3 mg/kg) *.
However, if some of the organic matter autoxidizes during evaporation of the
seawater, more oxidation will certainly occur at the elevated temperature.
This would also reduce the DOC values of samples dried at600C relative to
* Russian workers, using dry-combustion methods, typically find 2 mgC/kg
seawater, about twice the value found by Canadian and American investigators,
who rely chiefly on wet-combustion analyses.
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