Effects of oil dispersants on photodegradation of parent and alkylated anthracene in seawater.

This study investigated effects of three model oil dispersants on photodegradation of two model PAHs (anthracene and 9,10-dimethyanthracene (9,10-DMA)) under simulated sunlight. All three dispersants, i.e. Corexit EC9500A, Corexit EC9527A and SPC 1000, promoted the photolysis rate of 9,10-DMA, following the order of Corexit EC9500A > Corexit EC9527A > SPC 1000. The photodegradation rate was well interpreted by a two-stage, first-order kinetic law with a faster initial photolysis rate in the presence of the dispersants. Span 80, Tween 85 and kerosene were found as the key dispersant components, of which Span 80 and Tween 85 promoted the photodegradation by boosting absorbance of solar irradiation while kerosene by dispersing more PAHs in the upper layer of the water column. Dissolved oxygen (DO) inhibited photolysis of anthracene regardless of dispersant resulting from quenching the excited states of the PAH, while DO facilitated photolysis of 9,10-DMA due to the formation singlet oxygen (