For most ISB applications, impacts would be very localized because of the small volumes of residues generated and their dispersal by currents. Background and Status of Knowledge Residues of oils burned in laboratory tests in the 1970s and 1980s floated, probably because of the small scale of those tests and the thinness of the burned oil. The 1991 Haven spill, in which large amounts of heated and burned oil residue sank, stimulated research into whether residue density affects whether a residue will float or sink. Thickness of the oil slick Residues from burns of thick crude oil slicks are more likely to sink than residues from burns of thin slicks of the same crude oils, because higher-molecular weight compounds concentrate in the residue as the burn progresses. Efficiency of the burn Factors affecting burn efficiency include original slick thickness, degree of emulsification and weathering, areal coverage of the flame, wind speed, and wave choppiness.
Emulsified oils can produce much thicker residues.
When burn residues sink, they do so only after cooling. Physical properties of burn residues depend on burn efficiency and oil type. Chemical analyses of burn residues show relative enrichment in metals and the higher-molecular weight PAHs, which have high chronic toxicity but are thought to have low bioavailability in the residue matrix. At the Honan Jade spill, burn residue sank in 2 hours and adversely affected nearby crab pens5. All residues, whether they floated or sank, could be ingested by fish, birds, mammals, and other organisms, and may also be a source for fouling of gills, feathers, fur, or baleen.