11.SHORELINE CLEANUP BY ACCELERATION OF CLAY-OIL FLOCCULATION PROCESSES
During the cleanup operations following the Sea Empress oil spill, it was observed that the oil emulsion did not adhere strongly to the shoreline and that fine mineral particles present in the surf waters interacted with oil to form clay-oil floes. In an attempt to enhance clay-oil flocculation, Amroth beach was subjected to repeated “surf washing”: the oiled cobbles from the high water mark were moved down to the intertidal zone using an excavator at low tide. After 4 days of treatment, most of the oil emulsion was removed from the cobbles. We estimate that the majority of the oil was removed as clay-oil flocs and that the remainder was released from the cobbles as a broken surface slick. Microscopic and chemical analysis of samples of flocs and oiled sediments showed that energy imparted to the surf zone resulted in clay-oil flocculation, which increased biodegradation rates of the residual oil. Surf washing increased the availability of fine mineral particles, which (1) minimized the contact of oil directly with the substrate, thereby reducing the adhesion of oil to the shoreline, and (2) prevented the recoalescence of oil droplets, thereby promoting the dispersion of oil within the surf zone.