ABSTRACT
Depths . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369 10.3.4 The DeepSpill Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
10.4 Effects of Emulsion Properties on Oil Spill Countermeasures . . . . . . . . . . . . . . . . . . . . . . . . 373 10.4.1 Slick Lifetime . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373 10.4.2 Mechanical Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 374 10.4.3 Use of Chemical Dispersants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 377
10.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
When oils are spilt at sea different weathering processes alter the properties of the oil as a function of time and weather conditions. Evaporation of volatiles, water-in-oil emulsification (w/o emulsions), and natural dispersion (o/w emulsions) are important weathering processes taking place when oil is spilled at sea. The emulsification of water in the oil contributes to a change in properties of the spilled oil and increases the total volume of pollutant. The natural dispersion contributes to a removal of the oil from the sea surface into the water column. The behavior of spilled crude oils and refined oil products depends on the ambient conditions (e.g., temperature, sea-state, currents) and on the chemical composition of the oil. Large variations in oil properties cause them to behave differently when spilled at sea. The Gullfaks crude spilled at the Braer incident in the Shetlands has a low content of waxes and asphaltenes, which are important compounds for stabilizing water-in-oil (w/o) emulsions formed on the sea surface. This, combined with heavy sea state, resulted in consequences that were much less severe than might have been expected (1). Almost all of the 84,000 tons of the spilled Gullfaks crude oil was naturally dispersed into the water column as o/w-emulsions (2). In the Amoco Cadiz and the Metula spills,
persistent “chocolate mousse” has contaminated the shorelines for years after the initial spill (3,4). Knowledge about weathering behavior of crude oils and fuel oils is therefore of importance for environmental risk assessment of a spill, for contingency planning, response analysis, net environmental benefit analysis (NEBA), and for rapid and right decision making in the case of an oil spill.
