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CONCLUSIONS
A number of specific conclusions concerning the levels of AMOCO
CADIZ petroleum hydrocarbons in various environmental compartments, the
changing chemistry of the hydrocarbon assemblages, and the persistence
of petroleum in these compartments are presented here.
1) Upon introduction into the environment, the oil weathered
rapidly with evaporation and biodegradation changing the oil's
chemistry markedly even prior to landfall.
2) Oil impacted a variety of intertidal sedimentary types and a
number of secondary impacts were noted at many stations.
3) Oil was buried in most sedimentary environments with burial
and/or penetration down to 15 cm in fine-grained sediments and
deeper (^20-30 cm) in sandy sediment.
4) Oil remained less biodegraded in sandy beach environments than
in fine-grained sediments in which heavily biodegraded oil was
characteristic.
5) The presence of UCM material, pentacyclic triterpanes, and
alkylated phenanthrene and dibenzothiophene compounds remain
as characteristic chemical features of AMOCO CADIZ oil in
sediments.
6) Less weathered oil appeared to be buried (10-20 cm) in finegrained
sediments as evidenced in samples taken one year after
the spill.
7) Offshore sediments were impacted after the shoreline impact,
probably through processes involving beaching, sorption on
intertidal sediments, and offshore transport of these sediments.
Samples taken after the spill in April 1978 do not
reveal AMOCO CADIZ oil, thus indicating a lag (weeks to
months) in offshore deposition.
8) Surface intertidal sediments taken in June 1981 show that
"normal" background inputs, both of biogenic and chronic
pollutant origins, have replaced AMOCO CADIZ oil as major
components of the hydrocarbon geochemistry. Only at the most
impacted stations at lie Grande marsh and within the sandy
beach sediment at AMC-4 (Portsall) do identifiable AMOCO
residues persist. At lie Grande the aromatic marker compounds
are absent, but hopanoid compounds (triterpanes) and a large
UCM persist.
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