Vol. 53 - Alaska Resources Library and Information Services

2.3 Discussion
The analytical results presented here and in Boehm (1982) considerably
increase our knowledge of the differential fate and behavior of chemically dispersed and
surface oil. Furthermore, the transport of oil to the benthos, its route of transport to
benthic organisms (oil acquisition), and the species-specific chemical nature of biotal oil
depuration are revealed in the wealth of data obtained in this study. We will discuss some
of the most important observations and trends here as they pertain to the behavior of oil
in the experiments, and to specific important transport paths and biotal impacts.
The quantities of oil driven into the water column as a result of chemical
dispersion are far greater than those that result from transport of untreated surface oil
into the water column. Concentrations of chemically dispersed oil in the water column
ranged from 1 to greater than 50 ppm (~100 ppm) during the dispersed oil discharge and
for as long as twelve hours after discharge ceased at some points in Bay 9. Differential
movement of oil released at different points along the diffuser resulted in direct
northward movement of oil at greater depths of release (10 m) and initial southerly
movement of oil at shallower depths followed by subsequent reversal of direction and
"reinvasion" of Bays 9 and 10 four hours after formal oil/dispersant discharge ceased. The
dispersed oil plume formed a very stable layer of oil in the water column for perhaps 6-13
hours after dispersal. Dispersed oil droplets carried by strong shore currents were
advected for considerable distances without a significant change in the composition of the
oil. Whether this occurred due to the stability of the small (~10 µm) oil droplets, thus
retarding fractionation (i.e., dissolution or evaporation), or whether particulate and
dissolved parcels of oil traveled coherently due to strong advection (0.5 knot currents), is
difficult to ascertain. Results of large volume water samplings which were taken outside
of these concentrated plumes and after the passage of the highest concentrations
indicated that a physical-chemical fractionation of hydrocarbon compounds did occur. It
is, however, quite significant that fresh oil with its full suite of low molecular weight
saturated and aromatic components persisted as a coherent plume for considerable periods
of time (6-13 hours), apparently cut off from evaporative loss from either the dissolved
state or by advection to the surface. Indeed, confirmation of this coherent oil layer was
made by fluorescence profiling and by discrete sampling, sometimes indicating a tenfold
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