Vol. 53 - Alaska Resources Library and Information Services

Oil did impact the sediments of Bays 9 and 10 immediately after the dispersed
oil spill where initially a significant amount of the sedimented oil (~20%) resided in the
surface floc. Sedimentation rates were estimated to be in the 2-10 mg/m 2 /day range.
Subsequently, the floc was tranported elsewhere, probably offshore, because floc from all
bays sampled in the second post-spill period (September 11) was free of any detectable oil.
Levels of oil in the sediments, however, remained elevated (1-5 ppm) in Bays 9 and 10 and
although this dosing is considerably less than a "massive" dosing, it will continue to affect
benthic biota for an unknown period of time. The overall sediment impact due to passage
of dispersed oil through Bays 9 and 10 was minimal, with less than 1 % of the discharged
oil probably residing in the sediment at any time.
Results from the initial sampling of sediments indicated that 80 % of the oil
detected in the top 0-3 cm was not associated with the floc. This is in contrast to results
from other spills (e.g., Boehm, Barak, Fiest and Elskus 1982; Boehm, Wait,
Fiest and Pilson 1982) and to experimental tank studies (Gearing et al., 1980)
in which most of the initially sediment-associated oil was in the floc layer.
What appears to be occurring in the BIOS dispersed oil spill is a low level,
direct and rapid penetration of dispersed oil into the bulk surface sediment,
presumably
a process mediated by the decrease of the oil's interfacial tension
due to chemical dispersion allowing for penetration of the solid interface
perhaps into interstitial waters. Indeed chemical results from polychaete
analyses in Bays 9 and 10 (Norstrom and Engelhardt, 1982) revealed an
initial uptake of an alkylated benzene and napthalene (i.e., water-soluble
fraction) enriched petroleum hydrocarbon assemblage in Bays 9 and 10 only,
perhaps associated with interstitial water penetration of fractions of the oil.
The Bay 7 "control" did receive 50-100 ppb of dispersed oil in the first few
days after the discharge. This quantity of oil was measured directly (Green et al., 1982)
and was monitored indirectly through hydrocarbon body burdens in filter-feeding bivalves
(i.e., Mya, Serripes). Direct sediment analyses and indirect evidence from deposit-feeding
animals (Macoma, Strongylocentrotus) indicate, however, that oil impact to Bay 7
sediments was quite minimal with only patchy low level inputs noted. The Bay 7
analytical results point to an important conclusion regarding application of UV/F and GC 2
techniques to the BIOS study. While background (by UV/F) levels of "oil equivalents" in
the sediments was ~0.5 ppm, many samples did exhibit post-spill oil levels of 1.0-1.5 ppm.
In this concentration, range levels were too low to unambiguously yield an oil/no oil
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