Chemistry Reference
In-Depth Information
off by suitable machines. In some cases, surfactants are used to emulsify the oil, and
this emulsion sinks to the bottom slowly.
However, no two oil spills are the same because of the variation in oil types, loca-
tions, and weather conditions involved. However, broadly speaking, there are four
main methods of response.
1. Leave the oil alone so that it breaks down by natural means. If there is no
possibility of the oil polluting coastal regions or marine industries, the best
method is to leave it to disperse by natural means. A combination of wind,
sun, current, and wave action will rapidly disperse and evaporate most oils.
Light oils will disperse more quickly than heavy oils.
2. Contain the spill with booms and collect it from the water surface using
skimmer equipment. Spilt oil floats on water and initially forms a slick that
is a few millimeters thick. There are various types of booms that can be
used either to surround and isolate a slick or to block the passage of a slick
to vulnerable areas such as the intake of a desalination plant, fish farm
pens, or other sensitive locations. Boom types vary from inflatable neo-
prene tubes to solid but buoyant material. Most rise up about a meter above
the waterline. Some are designed to sit flush on tidal flats, while others are
applicable to deeper water and have skirts that hang down about a meter
below the waterline. Skimmers float across the top of the slick contained
within the boom and suck or scoop the oil into storage tanks on nearby ves-
sels or on the shore. However, booms and skimmers are less effective when
deployed in high winds and high seas.
3. Use dispersants to break up the oil and speed its natural biodegradation.
Dispersants act by reducing the surface tension that inhibits oil and water
from mixing. Small droplets of oil are then formed, which helps promote
rapid dilution of the oil by water movements. The formation of droplets also
increases the oil surface area, thus increasing its exposure to natural evapo-
ration and bacterial action. Dispersants are most effective when used within
an hour or two of the initial spill. However, they are not appropriate for all
oils and all locations. Successful dispersion of oil through the water column
can affect marine organisms such as deep-water corals and sea grass. It can
also cause oil to be temporarily accumulated by subtidal seafood. Decisions
on whether or not to use dispersants to combat an oil spill must be made in
each individual case. The decision will take into account the time since the
spill, the weather conditions, the particular environment involved, and the
type of oil that has been spilt.
4. Introduce biological agents to the spill to hasten biodegradation. Most of
the components of oil washed up along a shoreline can be broken down by
bacteria and other microorganisms into harmless substances such as fatty
acids and carbon dioxide. This action is called biodegradation.
Oil spill technology is very advanced and can operate under very divergent condi-
tions (from the cold seawaters to the tropic seas). The biggest difference arises from
the oil, which may contain varying amounts of heavy components (such as tar).
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