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2 Behavioral Models and the Resources at Risk
Pages 20-32

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From page 20...
... These models are descriptive, qualitative predictions of how oils with a density near or higher than the density of the receiving water might behave. The key factors that determine the behavior of spilled nonfloating oils are: water density, current speed, and the potential for interaction with sand.
From page 21...
... The density of oil relative to the receiving water is important only in determining whether the oil will initially float. Significant currents can keep heavier-than-water oil suspended in the water column.
From page 22...
... Evaporation of emulsified oils is slow, and, unless they interact with sediment, they will remain floating. When tar balls are eventually stranded, sometimes hundreds of kilometers away from the original spill site, the oil can still be relatively fresh and have a significant impact on the water surface and shoreline resources (see Box 2-1~.
From page 23...
... OlI ~ slinks 10 boMom Floating oil ~1 ~ . ~ - ~ ~ - ·- ~ ' ^ Suspanded Bar ~ # sand 23 FICURE 2-3c OiLto-~r density < 1.0; oU iniU~ly Bows but Saks ~~r mixing Dim sand ~ Am.
From page 24...
... . The distribution of sunken oil/sand tar mats was highly variable, ranging from thick, continuous deposits tens of meters long to small widely scattered tar balls.
From page 25...
... , response teams observed that floating oil sank by mixing with sand in nearshore waters, without coming into contact with intertidal sediments on the shoreline (Figure 2-3c)
From page 26...
... If the oil does accumulate on the bottom, the oil droplets recoalesce into pools of liquid oil that can be tens of centimeters thick. Evaporation and photo-oxidation of sunken oil are much slower than for floating oil slicks, and the oil tends to remain as a liquid on the bottom.
From page 27...
... For example, little or no oil accumulation on the bottom was observed after heavy-oil spills in the Columbia River (Kennedy and Baca, 1984) , the Mississippi River near Vicksburg (Weems et al., 1997)
From page 28...
... , our understanding of the behavior of these oils is based mostly on research conducted specifically with Orimulsion™, an emulsified fuel manufactured from bitumen produced in Venezuela. Laboratory and field experiments on emulsified oils have been conducted in Canada (Jokuty et al., 1995)
From page 29...
... Current flow Increased spreading over time/distance Deposition of bitumen/ sediment 29 FIGURE 2-4b Emulsified oil in freshwater; high currents; oil disperses and eventually sinks. Zone of high rates of particle contact and recoalescence into slicks Floating "tar" Adheres to suspended sediments Current flow Increased spreading to the point that recoalescence will not occur FIGURE 2-4c Emulsified oil in saltwater; high currents; oil initially disperses then coalesces into tarry slicks.
From page 30...
... These droplets are believed to have been formed as the still-buoyant oil became less viscous during the daytime heating of the water, allowing the oil to separate from the sand and droplets to break away from the submerged oil by wave action generated by the land-sea breezes. POTENTIAL EFFECTS OF NONFLOATING-OIL SPILLS When a floating oil is spilled, response teams typically have to recover oil slicks, clean up oil stranded on the shoreline, and recover and treat animals along the shoreline and in the water.
From page 31...
... Water Surface Less oil remains on the water surface. Oil tends to form fields of tar (-)
From page 32...
... Berman spill in Puerto Rico, divers observed dead fish, living fish with lesions and tumors, and many lethargic territorial fish in nearshore waters adjacent to the spill site (Vincente, 1994~. Mobile species may be able to move to uncontaminated areas, thus reducing their exposure.


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