SHORELINE CLEANSING BY INTERACTIONS BETWEEN OIL AND FINE MINERAL PARTICLES

ABSTRACT Interactions of fine mineral particles with oil stranded on shorelines following spills has been shown to be an important natural cleansing process, capable of accelerating oil removal in most environments, and particularly in low energy environments where wave action and abrasion are negligible. This process involves formation of solids-stabilized oil-in-water emulsions by flocculation of micron-sized mineral fines with oil droplets in the presence of water containing ions (such as sea water). Once flocculated, the oil droplets do not coalesce, and the oil no longer adheres strongly to shoreline sediments, facilitating its removal and dispersion by waves and tidal currents. The importance of the flocculation process to the rate of oil removal from sediments, the conditions needed for the process to occur, and the properties of the resulting floe have been studied in detail for the Exxon Valdez spill. Its potential role in shoreline cleansing also has been studied for other recent spills: Metula (1974, Chile), Arrow (1970, Nova Scotia), BIOS test spill (1981, Cape Hatt, Northwest Territories), Nosac Forest (1993, Tacoma, Washington), and Fred Bouchard (1993, Tampa, Florida). This paper summarizes the various laboratory and field studies and discusses the findings within the contexts of natural shoreline cleansing, and the use of certain treatment techniques.