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adsorption <strong>of</strong> dispersant to sand surfaces, <strong>the</strong>reby reducing <strong>the</strong> sorption <strong>of</strong><br />

oil to <strong>the</strong> grains.<br />

In o<strong>the</strong>r words, repeated flushing by waves washing up a<br />

contaminated beach may pump PAHs deep into <strong>the</strong> sediment when<br />

dispersant is present. Natural dispersants—those produced by oildegrading<br />

bacteria—may support this effect when oil is present in <strong>the</strong> sand<br />

for longer time periods.<br />

Fur<strong>the</strong>rmore <strong>the</strong> continuous flushing by waves on an oilcontaminated<br />

beach may result in <strong>the</strong> release <strong>of</strong> PAHs from <strong>the</strong> sand back<br />

to <strong>the</strong> water. And after PAHs are released from <strong>the</strong> sediment, UV light can<br />

increase <strong>the</strong>ir degradation but also increase <strong>the</strong>ir toxicity to marine life by<br />

up to eightfold.<br />

As for what effects those long-lived PAHs have released back into <strong>the</strong><br />

water, <strong>the</strong> authors cite recent research findings:<br />

• Increased mortality in planktonic copepods exposed to<br />

dispersants with stronger effects on small-sized species.<br />

• In early life stages <strong>of</strong> Atlantic herring dispersed oil dramatically<br />

impaired fertilization success.<br />

• Grey mullet exposed to chemically dispersed oil showed both a<br />

higher bioconcentration <strong>of</strong> PAHs and a higher mortality than fish<br />

exposed to ei<strong>the</strong>r <strong>the</strong> water-soluble fraction <strong>of</strong> oil or <strong>the</strong> mechanically<br />

dispersed oil.<br />

Deepwater Horizon Response via Flickr

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