API Publ 4689:2001 pdf download.Chemical Human Health Hazards Associated With Oil Spill Response
This section describes the environmental fate processes and provides a brief overview of some considerations that need to be included in discussions about potential exposure. The information found in this section is based on referenced literature (F ingas, 1994, 1995; GE SAMP, 1993; Koons and Jahns, 1992; Mielke, 1990; NRC, 1985, 1989). A more complete description of the environmental fate and effect processes are found in the Fate and Environmental Effects of Oil Spills in Freshwater Environments (API, 1999). ENVIRONMENTAL FATE Introduction When oil is released into the environment, numerous processes begin to affect the environmental fate of oil components and the chemical-physical properties of the oil. The composition and physical/chemical properties of crude oil and refined products are variable; therefore, no two crude or refined oils will behave exactly the same in the environment. In addition, meteorological and oceanographic conditions will affect the movement and weathering of oil. Spreading, drift, evaporation, dissolution, and dispersion are processes that begin immediately once oil is spilled. Figure 2-1 illustrates these processes. One process can occur at a greater relative magnitude than another process. For example, in the early phases of an oil spill, spreading occurs at a greater rate than oil drift. Dispersion of oil occurs at a greater magnitude than dissolution since only small amounts of oil components are soluble in water. Emulsification, sedimentation, biodegradation, and photooxidation can occur within the first day of a spill, but these processes are not as predominant as spreading, evaporation, and dispersion. Some of the fate processes, for example, evaporation, may be most relevant to human health exposure. Other processes, such as photooxidation and sedimentation, are not important determinants of human exposure. The major processes are discussed here to provide a general understanding of the environmental fate of spilled oil.
Oil composition, slick thickness, oil-water interfacial tension, and turbulence are factors affecting oil dispersion. Crude oils and other petroleum products contain nitrogen, sulfur, and oxygen- containing compounds that act as surface active agents (surfactants). Natural surfactants in petroleum tend to reduce the oil-water interfacial tension allowing the oil to disperse more readily. Turbulence enhances oil dispersion by increasing the interaction between the oil and water layers; therefore, dispersion is greater where there is high wave energy. Breaking waves may entrain fragments of the slick into the upper water column. The larger, more buoyant oil droplets may surface and coalesce with the slick, while smaller oil droplets are incorporated in the water column. .
API Publ 4689:2001 pdf download
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