Environmental Implications of a Massive Oil Spill and

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Island offers a natural barrier to slicks from the north.  -


9. What natural processes would ~ect the spill?

Arabian cmde oil varies slightly from field to field, but once released into
the environment a number of processes would begin to change the oil's
characteristics dramatically. The most unportant of these processes would
be evaporation, formation of a water-in-oil emulsion, and sand fall. A
much smaller fraction of the oil would dissolve into the water column. In
combination, these processes would result in about half of the oil being
removed from the water surface over a period of a two to ten days.
During this period, the density of oil on the surface would increase from
an initial value of 0.87 to about 0.96 g/cm3.

Larger slicks would tend to disaggregate into small floating patches of oil
and tar balls. Along beaches, these patches of oil could accumulate, and in
areas of heavier accumulations, the patches would run together, mix with
sand, and form tar mats similar in consistency to softened asphalt
pavement.

Strong winds in the northem Gulf create sand storms that result in very
large sand deposition over coastal waters. These tend to be at an extreme
during the "shamal" period in spring, but high suspended particulate
concentrations are common throughout the year with typical air quality
standards exceeded -for a significant fraction of th~e time. These large sand
depositions would setde out on a surface oil slick, incieasing the density of
the oil such that it would sink. Oil reaching the bottom in this manner
would do so in a widely scattered form and, unlike the coastal
accumulations, not aggregate into tar mats. - During the Nowruz spill, large-
surface slicks did not appear to exist on the surface beyond about six
weeks, being removed by evaporation or sunk by sand deposition. Widely
scattered tar balls did continue to float for longer periods and occasionally
come ashore in isolated patches.


10. How toxic is Arabian crude oil and how does its toxicity vary over
time?

Acute toxicity to marine organisms is primarily a function of the
percentage of low molecular weight compounds in the oil. For most
Arabian crudes, this fraction generally represents 20-25% by weight of the


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