Robert J. Fiocco
Summit, New Jersey U.S.A.
AEA Technology, Culham, Oxfordshire U. K.
Introduction: The purpose of any oil spill response is to minimise
the damage that could be caused by the spill. Dispersants are one of
the limited number of practical responses that are available to respond
to oil spills at sea.
When oil is spilled at sea, a small proportion will be naturally dispersed
by the mixing action caused by waves. This process can be slow and proceed
to only a limited extent for most situations. Dispersants are used to
accelerate the removal of oil from the surface of the sea by greatly
enhancing the rate of natural dispersion of oil and thus prevent it
from coming ashore. Dispersed oil will also be more rapidly biodegraded
by naturally occurring microorganisms. The rationale for dispersant
use is that dispersed oil is likely to have less overall environmental
impact than oil that persists on the surface of the sea, drifts and
eventually contaminates the shoreline.
The development of modern dispersants began after the Torrey Canyon
oil spill in 1967. Many lessons have been learned since that spill,
and consequently the modern dispersants and application techniques in
use today have become an effective way of responding to an oil spill.
For example, the dispersant response to the Sea Empress spill
in 1996 demonstrated that dispersants can be very effective and prevent
a much greater amount of environmental damage from being caused (6).
This chapter describes the chemistry and physics of dispersants, planning
and decision-making considerations, and finally their practical application
and operational use in oil spill response.
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