tify the oil quality from which a certain tar ball derives, by analyzing the vanadiumnickel percentage.
Little is known about the fate of petroleum hydrocarbons in the metabolism of animals, and whether animals play a role in petroleum degradation. Marine animals
living in oil-polluted seawater exhibit a higher concentration of certain enzymes, the
mixed function oxydases (MFO) and this seems to be an indication that the animal
organism reacts on contact with petroleum hydrocarbons.
f) Mechanical Reduction: Clumps of tar as big as peas are floating on all the seas.
They have different origins. Tarry residue is scraped off the walls of a tanker when it
is cleaned. This residue is flushed out at sea. Clumps of tar are also left over when oil
ages that has been floating on the surface of the sea. The volatile components disappear through evaporation, dissolution, emulsification, and microbiological degradation, and those components remain which are difficult to attack. If water samples
are studied more carefully, minute particles, 20-80 J.Lm in size, and which have the
same composition as the clumps of tar on the surface can be found floating in the
water, even at depths of 100 m. It seems that clumps of tar decompose on the surface, fmally turning into fine particles (Morris et al. 1976).
g) Sinking: Floating clumps of tar often form the substratum for sedentary marine
animal life, for goose barnacles (Lepas) and other barnacles, for example. The calcareous parts of these animals can reduce the buyocancy of tar to the extent that the
clumps sink. When other organisms with calcareous or siliceous solid parts also settle
on clumps of tar, the specific gravity can become heavier than the seawater. In the
aging process, some kinds of heavy oils attain a corresponding density.
Apparently, it is more common for fresh oil to reach the bottom of the ocean than
was previously assumed. When drops of oil are dispersed in seawater, they are absorbed
just like other floating particles into the inte5tines of filter-feeding plankton animals.
Together with other indigestible materials, they appear regularly in the fecal pellets
of copepod plankton. Even if they consist of up to 7% oil, these balls of excrement
have a heavier specific gravity than seawater and sink to the bottom (Conover 1971).
They are absorbed by filtering bottom animals.
There is a remarkable affinity of oil to particles suspended in the seawater, and oilseston-compounds form which may be heavy enough to sink to the sea bottom
(Boesch et al. 1974). It is still an open question whether the final fate of oil released
with an oil accident is microbiological degradation, or incorporation into the sediment. Deep sea sediments contain about 1 mg/kg or 50 mg/m 2 in hydrocarbons; this
amount is comparable to the amounts of oil estimated in the water column or drifting
at the sea surface as tar balls (Butler et al. 1977).
h) Beaching: Floating clumps of tar and fairly large amounts of oil collect on the
beaches when an oil slick is driven up on the coast by the wind. Oil can then easily get
worked into the sediment. Penetration into the interstitial system between grains of
sediment is particularly intensive when dispersant chemicals are used. Oil is persistent
when it is buried so deeply in the sediment that it no longer has any contact with the
oxygen-containing surface stratum. It is persistent because bacterial biodegrading
77
Little is known about the fate of petroleum hydrocarbons in the metabolism of animals, and whether animals play a role in petroleum degradation. Marine animals
living in oil-polluted seawater exhibit a higher concentration of certain enzymes, the
mixed function oxydases (MFO) and this seems to be an indication that the animal
organism reacts on contact with petroleum hydrocarbons.
f) Mechanical Reduction: Clumps of tar as big as peas are floating on all the seas.
They have different origins. Tarry residue is scraped off the walls of a tanker when it
is cleaned. This residue is flushed out at sea. Clumps of tar are also left over when oil
ages that has been floating on the surface of the sea. The volatile components disappear through evaporation, dissolution, emulsification, and microbiological degradation, and those components remain which are difficult to attack. If water samples
are studied more carefully, minute particles, 20-80 J.Lm in size, and which have the
same composition as the clumps of tar on the surface can be found floating in the
water, even at depths of 100 m. It seems that clumps of tar decompose on the surface, fmally turning into fine particles (Morris et al. 1976).
g) Sinking: Floating clumps of tar often form the substratum for sedentary marine
animal life, for goose barnacles (Lepas) and other barnacles, for example. The calcareous parts of these animals can reduce the buyocancy of tar to the extent that the
clumps sink. When other organisms with calcareous or siliceous solid parts also settle
on clumps of tar, the specific gravity can become heavier than the seawater. In the
aging process, some kinds of heavy oils attain a corresponding density.
Apparently, it is more common for fresh oil to reach the bottom of the ocean than
was previously assumed. When drops of oil are dispersed in seawater, they are absorbed
just like other floating particles into the inte5tines of filter-feeding plankton animals.
Together with other indigestible materials, they appear regularly in the fecal pellets
of copepod plankton. Even if they consist of up to 7% oil, these balls of excrement
have a heavier specific gravity than seawater and sink to the bottom (Conover 1971).
They are absorbed by filtering bottom animals.
There is a remarkable affinity of oil to particles suspended in the seawater, and oilseston-compounds form which may be heavy enough to sink to the sea bottom
(Boesch et al. 1974). It is still an open question whether the final fate of oil released
with an oil accident is microbiological degradation, or incorporation into the sediment. Deep sea sediments contain about 1 mg/kg or 50 mg/m 2 in hydrocarbons; this
amount is comparable to the amounts of oil estimated in the water column or drifting
at the sea surface as tar balls (Butler et al. 1977).
h) Beaching: Floating clumps of tar and fairly large amounts of oil collect on the
beaches when an oil slick is driven up on the coast by the wind. Oil can then easily get
worked into the sediment. Penetration into the interstitial system between grains of
sediment is particularly intensive when dispersant chemicals are used. Oil is persistent
when it is buried so deeply in the sediment that it no longer has any contact with the
oxygen-containing surface stratum. It is persistent because bacterial biodegrading
77