Aerial reconnaissance is an essential element of effective response to marine oil spills. It is used for assessing the location and extent of oil contamination and verifying predictions of the movement and fate of oil slicks at sea. Aerial surveillance provides information facilitating deployment and control of operations at sea, the timely protection of sites along threatened coastlines and the preparation of resources for shoreline clean-up. Observation can be undertaken visually or by use of remote sensing systems.
Initial clean up responses to a spill at sea are often based upon the use of dispersant chemicals or the containment and recovery of oil using booms and skimmers. Whilst these techniques can be of use in the right circumstances, there are many difficulties associated with employing them effectively.
The type of oil and concerns over potential impacts of dispersed oil can preclude dispersant use. For example, they are not effective against many commonly transported oils which have a high viscosity, and soon become ineffective against lighter oils because natural weathering processes or the formation of water-in-oil emulsions greatly increases oil viscosity, often very quickly (a few hours to one to two days). The application of dispersant to treat large quantities of spilled oil also requires specialised equipment and extensive logistical support. Containment and recovery is limited by sea conditions and the relatively small oil encounter rate which the available systems can achieve.
Because of the logistical difficulties of picking up oil from the sea surface and storing it prior to final disposal on land, an alternative approach involves concentrating the oil in special fireproof booms and setting it alight. In practice, this technique is unlikely to be viable in most ship-source spills due to the difficulty of collecting and maintaining sufficient thickness of oil to burn.
Together, these factors usually mean that only a small fraction of a major spill can be dealt with at sea, and it is almost inevitable that oil will threaten coastal resources. Protective strategies are seldom employed to the extent possible and it will usually be necessary to mount a shoreline response operation. Priorities for protection and clean-up will need to be agreed and care must be taken to ensure that the techniques selected do not do more damage than the oil alone. The application of oil-degrading bacteria and nutrients to contaminated shorelines to enhance the process of natural degradation has generated considerable interest for more than two decades. However, it has so far not been demonstrated to be technologically feasible or beneficial for large-scale restoration projects.
The disposal of oil and debris may become a major problem both during and after a clean-up operation. Several disposal options are however available.