102
Marine Sediments
4.4
Organics
4.4.7
Aliphatic Hydrocarbons
Gas chromatography. Gas chromatography has also been used to distinguish between
fossil fuels added to sediments through oil pollution and those hydrocarbons present
in low concentrations as natural biogenic products (Blumer and Sass [289]; Farrington and Quinn [290]).
Walker et al. [291] studied profIles of hydrocarbons in sediment according to depth
in sediment cores collected at Baltimore harbour in Chesapeake Bay, Maryland. Gas
liquid chromatography was used to detect hydrocarbons present at different depths in
the sediment, while low resolution mass spectrometry was employed to measure
concentrations of paraffins, cycloparaffins, aromatics and polynuclear aromatics.
Their data show that the concentrations of total and saturated hydrocarbons decreased with increased depth, and it was noted that identification and quantification of
hydrocarbons in oil-contaminated sediments is required if the fate of these compounds in dredge spills is to be determined.
May et al. [292] have described a gas chromatographic method for analysing
hydrocarbons in marine sediments and sea water which is sensitive at the submicrogram per kilogram level. Dynamic head space sampling for volatile hydrocarbon
components, followed by coupled-column liquid chromatography for analysing the
non-volatile components, requires minimal sample handling, thus reducing the risk
of sample component loss and / or sample contamination. The volatile components
are concentrated on a Tenax gas chromatographic precolumn and determined by gas
chromatography or gas chromatography-mass spectrometry.
Brown et al. [293] have described a gas chromatography-mass spectrometry technique for fingerprinting petrogenic hydrocarbons. The technique identified and quantified n-alkanes, the isoprenoids pristane and phytane, pentacyclic triterpanes, the
unresolved complex mixture, and total hydrocarbon content. Results obtained using
sediments preserved with chloroform during sediment trap collection were compared
with those for unpreserved anoxic sediments and anoxic bottom surface sediment.
Petrogenic hydrocarbons were detected at all stations, concentrations decreasing with
increasing distance from an urban area. Carbon preference index values increased
along the transect, indicating a greater dominance of biogenic hydrocarbons further
out in the archipelago. The compositions of preserved and unpreserved anoxic samples were very similar. These results indicated that the sediment trap technique was a
useful method of collecting and preserving material for fingerprinting petro genic hydrocarbons.
Mark [294] has described an infrared method for the determination of the oil
content of marine sediments. He showed that the magnitude of the CH 2 stretching
band at 2 925 cm- I , normally used to determine oil in a sediment, is enhanced when
biological matter is also present. The concentration of this material can generally be
estimated from the magnitude of the protein-NH band at 1 650 cm- I with the use of a
calculated correction to the total absorption at 2925 cm- I , but the oil must contribute
Marine Sediments
4.4
Organics
4.4.7
Aliphatic Hydrocarbons
Gas chromatography. Gas chromatography has also been used to distinguish between
fossil fuels added to sediments through oil pollution and those hydrocarbons present
in low concentrations as natural biogenic products (Blumer and Sass [289]; Farrington and Quinn [290]).
Walker et al. [291] studied profIles of hydrocarbons in sediment according to depth
in sediment cores collected at Baltimore harbour in Chesapeake Bay, Maryland. Gas
liquid chromatography was used to detect hydrocarbons present at different depths in
the sediment, while low resolution mass spectrometry was employed to measure
concentrations of paraffins, cycloparaffins, aromatics and polynuclear aromatics.
Their data show that the concentrations of total and saturated hydrocarbons decreased with increased depth, and it was noted that identification and quantification of
hydrocarbons in oil-contaminated sediments is required if the fate of these compounds in dredge spills is to be determined.
May et al. [292] have described a gas chromatographic method for analysing
hydrocarbons in marine sediments and sea water which is sensitive at the submicrogram per kilogram level. Dynamic head space sampling for volatile hydrocarbon
components, followed by coupled-column liquid chromatography for analysing the
non-volatile components, requires minimal sample handling, thus reducing the risk
of sample component loss and / or sample contamination. The volatile components
are concentrated on a Tenax gas chromatographic precolumn and determined by gas
chromatography or gas chromatography-mass spectrometry.
Brown et al. [293] have described a gas chromatography-mass spectrometry technique for fingerprinting petrogenic hydrocarbons. The technique identified and quantified n-alkanes, the isoprenoids pristane and phytane, pentacyclic triterpanes, the
unresolved complex mixture, and total hydrocarbon content. Results obtained using
sediments preserved with chloroform during sediment trap collection were compared
with those for unpreserved anoxic sediments and anoxic bottom surface sediment.
Petrogenic hydrocarbons were detected at all stations, concentrations decreasing with
increasing distance from an urban area. Carbon preference index values increased
along the transect, indicating a greater dominance of biogenic hydrocarbons further
out in the archipelago. The compositions of preserved and unpreserved anoxic samples were very similar. These results indicated that the sediment trap technique was a
useful method of collecting and preserving material for fingerprinting petro genic hydrocarbons.
Mark [294] has described an infrared method for the determination of the oil
content of marine sediments. He showed that the magnitude of the CH 2 stretching
band at 2 925 cm- I , normally used to determine oil in a sediment, is enhanced when
biological matter is also present. The concentration of this material can generally be
estimated from the magnitude of the protein-NH band at 1 650 cm- I with the use of a
calculated correction to the total absorption at 2925 cm- I , but the oil must contribute