Chapter 15

Pollution from Petroleum Hydrocarbons 

    •  Hydrocarbons consist of many different chemical mixtures both natural & refined.
      • They are complex enough that each oil is distinctive & can be traced to its origin.
      • Oil is about 80% carbon, 10-15% hydrogen with the rest mostly sulfur & oxygen & traces of nitrogen, lead, mercury, vanadium, iron & other elements.
    • Input to aquatic systems--about 15% of the total  is from natural sources, and  about 30% is from municipal & industrial wastewater discharges.
      • River channels receive about 23% of the total discharged into water bodies. Ports & harbors receive about 47.6 %. 
      • 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)
      • 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.
    • Oil is particularly hard to clean up because it does not evaporate easily (25 to 50% at best)
      • dispersion is slow & partial, emulsification of heavier oil slows dispersion even more, photo-oxidation is minor.
      • 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. 
    • 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. 

    • Cleaning & rehabilitation of waterfowl has little ecological value. 

    • A few measures that would help are;
      • NPDES permitting of stormwater discharge
      • storage tanks of impervious material
      • response contingency plans with drills 
      • fines for poorly tuned & leaky engines 
      • Double-hauled tankers are now required by certain dates 
      • fines have been raised.

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