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Chapter 15
Pollution from Petroleum Hydrocarbons
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Hydrocarbons consist of many different
chemical mixtures both natural & refined.
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They are complex enough that each oil is distinctive
& can be traced to its origin.
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Oil is about 80% carbon, 10-15% hydrogen with
the rest mostly sulfur & oxygen & traces of nitrogen, lead, mercury,
vanadium, iron & other elements.
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Input to aquatic systems--about 15% of the
total is from natural sources, and about 30% is from municipal
& industrial wastewater discharges.
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River channels receive about 23% of the total
discharged into water bodies. Ports & harbors receive about 47.6 %.
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Urban runoff & sewer outflows go to both
& account for about 56% of total discharges. It is estimated that 2-10
million tons of oil are discharged into water bodies each year.(Table 15.1)
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In Table 15.2 note that 47.1 % came from unclassified
souces. Also note that 15.97 million gallons do not weigh 2-10 tons. One
gallon of oil will cover about 4 acres of water under stable conditions,
though the weight of the oil is also a factor.
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Oil is particularly hard to clean up because
it does not evaporate easily (25 to 50% at best)
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dispersion is slow & partial, emulsification
of heavier oil slows dispersion even more, photo-oxidation is minor.
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About 200 species decompose oil. Several bacteria
may be particularly helpful, but they use up oxygen. It is estimated that
it takes 320,000 gallons of water to provide oxygen to decompose 1 gallon
of oil.
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More significant than the few large spills
are the many day-to-day spills & discharges. Sublethal effects occur
at levels as low as 1 ppb.
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Cleaning & rehabilitation of waterfowl
has little ecological value.
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A few measures that would help are;
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NPDES permitting of stormwater discharge
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storage tanks of impervious material
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response contingency plans with drills
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fines for poorly tuned & leaky engines
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Double-hauled tankers are now required by
certain dates
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fines have been raised.
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