Gulf War oil spill, Saudi Arabian coast

In late January 1991 Iraqi forces began releasing crude oil into the Gulf from Kuwait's Sea Island terminal, from tankers and from other installations. Estimates of the volume range from the 11 million barrels first given by the Pentagon to the 2–6 million of researchers; according to Wikipedia the most likely figure is about 4 million barrels (480,000 m³). The slick reached 160 km by 68.

A 1993 UNESCO-sponsored study estimated that about half the oil evaporated, about one million barrels was recovered and 2–3 million came ashore, mostly in Saudi Arabia. About 30,000 grebes and cormorants died. The crude penetrated the sediments by 10 cm on average and up to nearly 50 cm, which greatly slowed its degradation (Linden and Husain 2002, cited by Wikipedia).

In 2002–2003 a survey of 1,679 sediment samples assessed the risk from 43 PAHs. High-risk samples were frequent in the 0–30 cm layer of tidal flats and in the 30–60 cm layer under heavily oiled halophytes and mangroves. North of Safaniya the sediments posed no risk, unlike those south of Tanajib: the shape and landscape of the coast decided where the oil stayed. The studies cited by Wikipedia agree that rocky shores and, for the most part, mangroves recovered, and that salt marshes recovered slowly.