The remaining inputs are anthropogenic, except for an unknown fraction of the atmospheric deposition of hydrocarbons, which might have originated with emissions from terrestrial vegetation and from other natural sources. An estimate of the emission of petroleum hydrocarbons from natural submarine and coastal oil seeps is about 200–600 × 10 3 tonnes/year, or about 6–13% of the total petroleum input to the oceans. These biogenic hydrocarbons are an important component of the background concentration of hydrocarbons in the marine environment, but they are, of course, well dispersed and should not be considered to be an important source of marine pollution. In comparison to these anthropogenic inputs of petroleum to the oceans, the natural production of nonpetroleum hydrocarbons by marine plankton has been estimated at about 26 million tonnes/year, or about four to eight times the total input of petroleum hydrocarbons. e Koons (1984), best estimate, range in parentheses. d Baker (1983), best estimate, range in parentheses. b National Academy of Sciences (NAS) (1975d). The characteristics and ecological effects of terrestrial spills are described in more detail later in this chapter, in the context of oil spills in the Arctic.Ĭ Kornberg (1981). Because the spread of spilled oil is much more restricted on land than on water, terrestrial spills usually affect relatively localized areas (unless the spilled oil reaches a watercourse). However, because of the widespread use of spill sensors and mechanisms for shutting down sections of pipeline, individual events are usually much smaller than can potentially be spilled by oceanic supertankers or by blowouts of offshore platforms. The total quantity of oil spilled from pipelines is not well quantified in many parts of the world. They include faulty pumping equipment and pipe seam welds, earthquakes, sabotage, deliberate spillage as in the Gulf War, and sometimes hunters using aboveground pipelines for target practice. The causes of pipeline ruptures are diverse. Globally, in 1982 there were 64.5 thousand km of pipeline for the transportation of liquid petroleum and another 136 thousand km of natural gas pipeline ( Gilroy, 1983). However, the largest and most damaging pollution events usually involve spills of petroleum or heavy bunker fuel from disabled tankers or drill platforms at sea, from barges or ships on major inland waterways, or from blowouts of wells or broken pipelines on land.Ī spill on land can occur in many ways, but the largest events generally involve a pipeline rupture or a well blowout. Oil pollution can be caused by any spillage of crude oil or its refined products. Bill Freedman, in Environmental Ecology (Second Edition), 1995 Oil Spillage
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