Gschwend%20thesis.pdf

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those at room temperature. On the other hand, many volatiles will be lost
even with evaporation at room temperatur~ and, therefore, comparison to this
sample may underestimate the volatile fraction of the DOC. Thus, it is
difficult to judge the accuracy of Vityuk's result.
Armstrong and Boalch (1960) measured the UV absorption ,of several sea-
water distillates. They found an absorbance maximum (10 em cell) of O. 17 at
-1
ZlO nm . Assuming a fairly high extinction coefficient of 10,000, a con-
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centration of distilled absorbing material of 2 x 10 M or approximately
200 l.:g/kg (for MW 100) can be calculated. Returning this to the original
seawater (1/10 distilled over), the figure reduces to ZO l.g/kg. The au-
thors made DOC determinations on the distillates obtained from seawater with
excess NaOH added and found ZO-50 ii'gC/kg seawater. They also reported the
presence of sulfur in the distillates at approximately 1-4 l. gS/kg seawater.
These data tell us little about volatiles undetected by UV absorbance (must
be less than ca. 50 l.'gC/kgseawater), and unfortunately the UV method will
include those compounds which codistill with water but are not "stripable."
Recent work by MacKinnon (pers. comm.) has shown that on the order of L-LO
l.gC/kg seawater may be purged' with prolonged bubbling from seawater (at 60oC)
and trapped on Tenax. This volatile fraction estimate is based on procedures
most closely resembling those of this thesis. Therefore, this is the most
relevant estimate of the volatile fraction which is the subject of this
thesis.
Qualitative Information on the Volatile Fraction in Seawater
There is very little information available concerning the structures
of volatile compounds occurring in seawater.
Giger (1977) has recently reviewed "the inventory of organic gases and
volatiles" in the marine environment. He notes that methane is the only