Encyclopedia of Environmental Science and Engineering, Volume I and II

OIL SPILLAGE INTO WATER—TREATMENT 807

effi cient and logistically simple method for eliminating oil

under certain conditions. As a backup for mechanical cleanup

techniques, in-situ burning can provide a useful means of elim-

inating large quantities of oil quickly, while avoiding the need

for recovered oil storage containers. Anyone considering the

use of burning should be sure that all regulatory controls have

been satisfi ed, that the ignition and burning operations can be

carried out safety, and that the temporary reductions in local air

quality represent the lower of all other environmental impacts

should the spilled oil not be burned.”

TREATMENT OF THE SURFACE OIL

Chemical Treatment of Surface Oil Should Be

Considered as an Alternate Solution

It is generally agreed, as indicated above, that situations can

arise where the spill cannot be contained and recovered because

sea conditions, weather state, and so on, are beyond the cur-

rent operating capability of containment devices. There are

also instances wherein the logistics of containment and recov-

ery equipment, that is, containment boom availability and/or

deployment time and effort, could indicate chemical treatment

as the most practical and expedient handling technique. When

physical recovery of the oil pollutant is impractical, there are,

in effect, two courses of action possible. In one case, the oil

may be permitted to remain as intact cohesive slick on the

surface of the water and possibly reach shore. The alternate

course is to “treat” this surface oil—such treatment essentially

directed toward the removal of the oil from the water surface

and the enhancement of its ultimate removal from the environ-

ment. This many be accomplished by chemical dispersion.

The Ecological and Economic Damage Caused by an

Untreated Oil Spill Can Be Extensive

The damage resulting from an untreated oil spill is both visu-

ally apparent and extensive. It encompasses both biological

as well as property damage. The potential damage may be

summarized as follows:

Marine fowl, particularly diving birds, are particularly

vulnerable to an oil spill. As reported by Nelson-Smith,^13

sea birds are most obvious victims of an oil spill due to

“mechanical damage.” The oil penetrates and clogs the

plumage which the bird depends upon for waterproofi ng and

heat insulation. For example, a duck with oil-impregnated

plumage is under the same stress at a moderate temperature

of  59 F as a normal bird would be under a more severe

temperature condition at −4F. Some statistics regarding bird

damage have been cited by McCaull.^14 More than 25,000

birds, mostly guillemots and razorbills, were killed after the

Torrey Canyon grounding. The guillemot casualties equaled

the entire breeding stock between the Isle of Wright and

Cardigan Bay. Bird losses in the Santa Barbara spill, accord-

ing to the state Department of Fish and Game, totaled 3500.

Shore contamination by beached oil represents biologi-

cal, as well as property damage. The tendency of oil to cling

to shore surfaces, such as beach sand, sea walls, and the resul-

tant property damage, are well established. This is perhaps

the most apparent and widely publicized damaging aspect as

attested by lawsuits on the part of tourist interests, property

owners, etc. There is also, in a biological sense, a physical

smothering effect on some attached, intertidal organisms

such as mussels and barnacles. The effects of untreated oil

coming ashore is well illustrated by Blumer et al.^15 regarding

a No. 2 diesel fuel spill from the barge Florida in Buzzards

Bay, Massachusetts in September 1969. Oil was incorpo-

rated into the bottom sediment to at least 10 meters of water

depth, testifying to the wetting effect of untreated oil in

this instance, the oil was physically dispersed by the heavy

seas but retained its adhesive characteristics. Therefore, it

is deduced that the oil droplets probably came into contact

with and wetted and upswept, suspended particulates which

later settled again to the bottom. Other spill instances depict-

ing the importance of this aspect that of the incorporation of

oil into the sediment-have been reported by Murphy.^16 In the

Buzzards Bay and several other spill incidents of distillate

fuels cited by Murphy, there has been a signifi cant kill of all

marine life in the area since these highly aromatic products

are known to be much more toxic than whole crude oil.

Persistent tarry agglomerates are formed as the spilled oil

weathers at sea. There has been increasing attention directed

to the presence of tar-like globules ranging up to 10 cm in

diameter in the open sea. As reported by Baker^17 during the

voyage of Thor Heyerdahl’s papyrus boat, Ra, during fi ve

separate days, they sailed through masses of these agglomer-

ates whose age could be substantiated by the growth of goose

barnacles adhering to them. There have been other inci-

dents reported recently by the International Oceanographic

Foundation^18 and a well documented survey was made by

the research craft, R.V. Atlantis, as reported by Horn et al.^19

In this latter investigation, tarry agglomerates were present

in 75% of over 700 hauls with a surface skimming (neuston)

net in the Mediterranean Sea and eastern North Atlantic. The

amount of tar in some areas was estimated at 0.5 milliliter in

volume per square meter of sea surface.

The Behavior of Spilled Oil at Sea

Before consideration of the mechanism of dispersing oil and

its associated effects, an understanding of the behavior of

spilled oil at sea will be useful. When a volume of oil is

spilled onto the surface of water, the oil has a driving force

to fi lm out or spread-in essence, a spreading pressure usually

expressed as a Spreading Coeffi cient. This Spreading S o/w ,

is readily quantifi ed and is determined by a balance of the

surface tension forces as follows.

So/w gg gw o/w o,

(1)

wherein:

S o/w is the spreading coeffi cient for oil on water

ergs/cm^2 or dynes/cm

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