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OrgUlrÙ- Ger,,'hemilir.l. 1978. Vol. i. pp. 93 to 107. Pergamon rres~;. 1 ,.inied in Great Britain
Volatile organic compounds in coastal seawater*
RENE P. SCHWARZENBACH,t¡ RICHARD H. BROMUND,~
PHILIP M. GSCHWENDt and OLIVER C. ZAFIRIOUt-
(Received 12 January 1978; accepted in revised form 2 March 1978)
Abstract- T~e occurren~. and temporal variations of a variety of low to medium polarity organic
compounds in the volatility range bracketed by n-heptane and n-octadecane have been studied in
seawater from a station in Vineyard Sound, Massachusetts, and from a tidal creek in Sippewisset
Marsh, Massachusetts. The closed-loop vapoR phase stripping method of Grob and Zürcher (J. Chromatogr.,
v. i i 7, p. 285-294), high resolution glass capilary gas chromatography, and gas chromatographymass
spectrometry were used. Approximately 50 compounds were found at ~ 2 ng/kg; most were recovered
at less t?an 10 ng/kg, while the 20 ng/kg level was only rarely exceded by a few components.
The total material recovered was 0.2-1.0 pg organic carbon equivalent/kg seawater. The major compound
c~asses fo~nd were normal alkanes, ~ikenes, aromatic and alkylaromatic hydrocarbons, n-aldehydes,
dimethyldisulfide and. dim~thyltrisulfr,Je, and a .few halogenated hydrocarbons. The preliminary
results suggest that bot~ biogenic and anthropogenic sources were represented. Also, air-sea gas
exchange and other physical processes may be important non-biological sinks.
INTRODUcrON
SEAWATER contains an extremely complex, diverse,
and largely unidentified mixture of organic compounds.
Historically most studies of seawater organic
matter have focused on such properties of the mixture
as its concentration and distribution (Skopintsev,
1966,1971; Menzel and Ryther, 1970;.Menzel, 1974;
Williams, 1971; Riley, 1970; Wangersky, 1972, 1976;
among others), its size distribution (Sheldon et al.,
1972; Sharp, 1973; Ogura, 1974), or qualitative
properties such as cSI3C (Wiliams, 1968; Wiliams
and Gordon, 1970), absorption spectrum (Mattson et
ai" 1974), or biodegradabilty (Barber, 1968; Ogura,
1970, 1972; Zsolnay, 1975). Only a minor portion of
the organic matter in seawater has been characterized
structurally, principally as. amino acids and sugars
and their biopolymers, urea, fatty acids and alcohols
and their esters, sterols, hydrocarbons, parially char-
. acterized pigments, and vitamins (Wagner, 1969).
Recently, efforts have been made to obtain the molecular
composition of some compound classes in sea-
.:iwater for numerous individual samples in order to
characterize the marine environment in terms of the
individual organic structures present and their spatio- .
temporal variabilty (e.g. Brooks and Sackett, 1973;
Lee and Bada, 1975; Gagosian, 1976). These studies
have obtained information regarding the sources,
transport, transformations, and sinks of organic
mattèr in the water column.
.. Woods Hole Oceanographic Institution Contribution
No. 4079. .
t Department of Chemistry, Woods Hole Oceanographic
Institution, Woods Hole, MA 02543, U.S.A.
t Present address: EA WAG, 8600 Dübendorf, Switzerland.
§ Department of Chemistry, The College of W00ster.
Wooster, OH; Visiting Investigator, Woods Hole Oreano-
graphic Institution (1977).
.. To whom correspondence should be addressed.
93
Thus far methodological diffculties have prevented
the application of this molecular approach to seawater
organic compounds over a structural range
broader than individual compound classes. The analytical
task of determining these compound groups
routinely has been arduous enough to make wider
coverage by simultaneous use of several methods pro- .
hibitively diffcult.
In this paper we report the preliminary results of
analyses of volatile organic compounds (VC) in
coastal seawater samples. The compounds fallng into
the VC class constitute a little-investigated group of
compoUnds in seawater, which are too volatile to be
handled by conventional extraètion techniques, yet
not volatile enough to be determined by procedures
designed for the determination of very light organic
compounds, such as C1-C4 hydrocarbons (Swinnerton
and Linnenbom, 1967; Brooks and Sackett, 1973).
We used the closed-loop vapor phase stripping
method of Grob and Zürcher (1976), in conjunction
with glas capilary gas chromatography (GC) and
combined gas chromatography-mass spectrometry
(GC-MS), for the rapid and routine recovery, separation,
identification, and quantification of this chemically
diverse group of marine organic compounds.
The method consists of removing those compounds
with appreciable vapor pressure over seawater from
a sample by purging it with a large volume of gas
as finely divided bubbles, followed by adsorbing the
compounds in the gas stream onto a charcoal trap.
Subsequent extraction from charcoal and high performance
GC and GC-MS analyses characterize and
quantify the volatile compounds. The method was
originally developed for drinking water quality assessment
and the study of pollutants in lakes and rivers
(K. Grob and G. Grob, 1974). We have applied the
method to studying volatile compounds at the nglkg .
leveL.