Assessment of cleanup needs of oiled sandy beaches: lessons from the Prestige oil spill.

Surveys of the oiled sandy beaches along the northern Atlantic coast of Spain, 2-5 years after the Prestige oil spill of November 2002, have provided new evidence regarding buried fuel and its behavior. The persistence and depth of burial of oil, and the capacity of the beach for natural regeneration, depend on beach morphodynamics, which drive a sequence of physicochemical processes that reduce subsurface tar balls to highly divided oil forms while also allowing appreciable weathering despite burial. These findings prompted reassessment of current spill evaluation strategies. A protocol is proposed that combines the modeling of beach morphodynamics, an environmentally friendly coring survey, and well-calibrated hydrocarbon analysis.

Geological characterization of the Prestige sinking area.

The tanker Prestige sank off NW Iberia on the 19th November 2002. The stern and bow of the Prestige wreck are located on the southwestern edge of the Galicia Bank, at 3565 m and 3830 m water depths, respectively. This bank is a structural high controlled by major faults with predominant N-S, NNE-SSW, and NNW-SEE trends. It is characterized by moderate to low seismic activity. The faults have controlled the local depositional architecture, deforming, fracturing, relocating and distributing sediments since the Valangian (early Cretaceous). The Prestige sinking area corresponds to an asymmetric half-graben structure with a N-S trend, which conditions the present-day morphology. The faulted flank outcrops and its activity and erosion have favoured the occurrence of mass-movements (slumps, slump debris, mass-flows and turbidity currents), building valleys and depositional lobes. Nearsurface sediments comprise mostly terrigenous and biogenous turbiditic muds and sands with a minor presence of hemipelagic muds, except on the fault scarp where pelagites predominate. Potential geological hazards resulting from tectonic and sedimentary processes affect almost the entire Prestige sinking area.