Weathering of an Oil Spill

The polycyclic aromatic hydrocarbons in crude oil sensitize the photochemical formation of singlet oxygen (Section 5.2.2), which oxidizes the olefins present to cyclic dioxides and hydroperoxides:

O

These compounds can either rearrange directly [equation 6-1] or be cleaved photochemically to form hydroxyl radicals

OOH hv

OOH hv

that attack the other unsaturated molecules present:

alcohols, phenols, carbonyl compounds, and acids

The net result of these radical processes is the solubilization of the polycyclic aromatic hydrocarbons by conversion to phenols, alcohols, carbonyl compounds, and acids.

The breakup of the spill is slowed if it is washed up on the shore. Dispersal and degradation will continue if there is a strong wind and surf, but oil spills in quiet bays or lagoons may take 5-10 years to disperse in the absence of wave and wind action. The toxic effects on marine life likewise persist for 5-10 years in these environments.

The long-term effects of an oil spill are determined by the environment in which it occurs. Spills that never reach the shore have the least effect because most marine life tends to be near the land-sea interface, where food supplies are more abundant and fish travel to lay eggs and birds and amphibians raise their young. Thus a spill that remains at sea has less chance of damaging the eggs and rapidly developing young marine life, which are the organisms most susceptible to toxins of any sort.

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