TABLE OF CONTENTS Definition of the attribute. Oil (i.e., petroleum) slicks are barely visible at a concentration of about 25 gal/mi 2. At about 50 gal/mi 2, an oil film is about 3.0 10 6 in thick and is visible as a silvery sheen on the surface. Oil is destructive to aquatic life in the following ways:
Free oil and emulsions may coat and destroy algae and plankton.
Heavy coating may interfere with the natural processes of reaeration and photosynthesis.
Water-soluble fractions may exert a direct toxic action.
Settleable oil substances may coat the bottom, destroy benthic organisms, and interfere with spawning areas.
Activities that affect the attribute. Major activities responsible for oil pollution include bilge and ballast waters discharged from ships; oil refinery wastes; industrial plant wastes, such as oil, grease, and fats, and lubrication of machinery; gasoline filling stations; bulk stations; and accidental spills.
Sources of effects. Oil may reach natural waters by direct discharge or by surface runoff. Direct discharge may occur from bilge and ballast waters or by accidental spill from barges or tankers. Indirect oil release may occur from surface runoff or storm sewers or combined sewer overflows. In all cases, damage could be severe and long lasting. Water quality parameters affected by oil discharge are dissolved oxygen, general appearance, and taste and odor.
Variables to be measured; how variables are measured. Dissolved or emulsified oil or grease is extracted from water by intimate contact...
