ABSTRACT
According to Intergovernmental Maritime Consultative Organization protocols (MARPOL 73/78), clean ballast water (producing no surface sheen and/or containing less than 15 parts per million total oil) from crude oil cargo tanks of tankers can be discharged into coastal waters. As part of an assessment of the potential impact of clean ballast water discharges on Red Sea coral reefs, we have determined the hydrocarbon composition of clean ballast water from crude oil cargo tanks and have determined its rate of dilution following discharge to coastal waters at Yanbu, Kingdom of Saudi Arabia.
In 52 clean ballast water samples from 10 crude oil tankers, total petroleum hydrocarbon concentrations, measured by gas chromatography, ranged from 0.09 to 11 milligrams/liter (ppm). In most cases, the dominant hydrocarbons in the samples were Cll through C20 n-paraffins. Up to 58 micrograms/liter (ppb) total naphthalenes and 744 μg/l benzene, toluene, and ethylbenzene combined were detected in some samples. Clean ballast water was diluted rapidly upon discharge to the ocean. Dilutions of 100-fold or greater were observed within 10 to 20 meters of the discharge and dilutions of 500 to 1,000-fold were measured 1,500 to 2,000 meters downcurrent and within two to four hours of the discharge. Based on these results, it is predicted that discharge of clean ballast water to the coastal waters of the Red Sea in compliance with MARPOL 73/78 rules will have little or no adverse impact on coral reefs of the area.
