272
A. NELSON-SMITH
(Chipman and Galtsoff, 1949). During the “ Torrey Canyon ” affair
the French used “ craie de Champagne ”, which is ground calcium
carbonate treated with about 1 yo sodium stearate, apparently with
some success (Bone and Holme, 1968 ; Smith, 1968). Stearated whiting
has been advocated in Britain. Various absorbent waste materials such
as crushed cinders, brick-dust or pulverized fuel-ash can be rendered
hydrophobic but oleophilic by treatment with chloro-silane vapour a t
about 0.2% by weight (Anon., 1967a; Wardley Smith, 196813, c).
Wardley Smith also refers to a gypsum residue called “ Stucco ” which
is a by-product of the manufacture of phosphoric acid. It sets hard in
sea water and should thus bind the oil in a firm mass on the bottom.
Early attempts at applying these materials were made by spreading
the dry powder over the oil slick in about a 1 :1 ratio. After a pause,
the mixture was sunk by agitation with propellers or water-jets. This
is successful in harbours, for which most products were originally intended. The French, operating in Channel and Biscay waters, had to
withdraw naval vessels because chalk-dust carried by the wind was
ruining military equipment (Wyllie and Taylor, 1967). It has been
proposed more recently that hydrophobic sinking agents could be
applied as a slurry in water (see, for example, Holdsworth, 1968).
Another technical objection is that the nearest port at which a sufficient
quantity of the material could be loaded might be quite distant from
the slick. Stocks of the agent of choice might similarly be stored at a
distance from that port. The costs of transport, as well as of raw
materials and storage, could be minimized by a further suggestion from
Holdsworth that provision should be made for fitting suction-dredgers
with spray-booms. I n dealing with an off-shore spill, such a dredger
could be loaded with sand from the nearest shoal and her cargo could
be treated with a water-repellent agent while still wet in the hoppers and
then distributed through the spray-booms as a slurry while she steamed
through the floating oil.
Oil adsorbed onto inert particles is in a state favourable to bacterial
degradation and a sinking agent could even be seeded with the nutrients
likely to be limiting on the sea-bottom, or with oil-degrading bacteria
themselves (Anon., 1967a; Davies and Hughes, 1968). The fine droplets produced by dispersants may also be favourable to biodegradation,
but many emulsifiers are toxic to oil-degrading organisms as well as
to plankton in general. As neither sinking nor dispersing actually
destroys oil, methods which permit its collection and disposal seem
attractive. Natural materials such as straw (McKay, 1967 ; Roberts,
1967), pine-bark (Anon., 196810) or maritime vegetation (gorse and dune
grasses) have been used in emergencies by drawing them across the
A. NELSON-SMITH
(Chipman and Galtsoff, 1949). During the “ Torrey Canyon ” affair
the French used “ craie de Champagne ”, which is ground calcium
carbonate treated with about 1 yo sodium stearate, apparently with
some success (Bone and Holme, 1968 ; Smith, 1968). Stearated whiting
has been advocated in Britain. Various absorbent waste materials such
as crushed cinders, brick-dust or pulverized fuel-ash can be rendered
hydrophobic but oleophilic by treatment with chloro-silane vapour a t
about 0.2% by weight (Anon., 1967a; Wardley Smith, 196813, c).
Wardley Smith also refers to a gypsum residue called “ Stucco ” which
is a by-product of the manufacture of phosphoric acid. It sets hard in
sea water and should thus bind the oil in a firm mass on the bottom.
Early attempts at applying these materials were made by spreading
the dry powder over the oil slick in about a 1 :1 ratio. After a pause,
the mixture was sunk by agitation with propellers or water-jets. This
is successful in harbours, for which most products were originally intended. The French, operating in Channel and Biscay waters, had to
withdraw naval vessels because chalk-dust carried by the wind was
ruining military equipment (Wyllie and Taylor, 1967). It has been
proposed more recently that hydrophobic sinking agents could be
applied as a slurry in water (see, for example, Holdsworth, 1968).
Another technical objection is that the nearest port at which a sufficient
quantity of the material could be loaded might be quite distant from
the slick. Stocks of the agent of choice might similarly be stored at a
distance from that port. The costs of transport, as well as of raw
materials and storage, could be minimized by a further suggestion from
Holdsworth that provision should be made for fitting suction-dredgers
with spray-booms. I n dealing with an off-shore spill, such a dredger
could be loaded with sand from the nearest shoal and her cargo could
be treated with a water-repellent agent while still wet in the hoppers and
then distributed through the spray-booms as a slurry while she steamed
through the floating oil.
Oil adsorbed onto inert particles is in a state favourable to bacterial
degradation and a sinking agent could even be seeded with the nutrients
likely to be limiting on the sea-bottom, or with oil-degrading bacteria
themselves (Anon., 1967a; Davies and Hughes, 1968). The fine droplets produced by dispersants may also be favourable to biodegradation,
but many emulsifiers are toxic to oil-degrading organisms as well as
to plankton in general. As neither sinking nor dispersing actually
destroys oil, methods which permit its collection and disposal seem
attractive. Natural materials such as straw (McKay, 1967 ; Roberts,
1967), pine-bark (Anon., 196810) or maritime vegetation (gorse and dune
grasses) have been used in emergencies by drawing them across the