Prediction
of Ecotoxicity of Heavy Crude Oil: Contribution
of Measured Components
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Abstract
A prediction
model for estimating the ecotoxicity of the water-accommodated
fraction (WAF) and water-soluble fraction (WSF) of heavy crude oil
is proposed. Iranian heavy crude oil (IHC), one of the major components
of the Hebei Spirit oil spill in Korea in 2007, was used as a model
crude oil for the preparation of the WAF and the WSF. Luminescence
inhibition of <i>Vibrio fischeri</i> was chosen as the model
ecotoxicity test for evaluating the baseline toxicity of aromatic
hydrocarbons in the IHC. The measured concentration of each chemical
species in WAF and WSF agreed well with the predicted soluble concentration
calculated using Raoult’s law from the measured amount in the
IHC. This indicates that the toxic potential of an oil mixture can
be evaluated from the dissolved concentration of each species, which
in turn, may be predicted from the composition of the crude or weathered
oils. In addition, the contribution of each species in the mixture
to the apparent luminescence inhibition by the WAF and the WSF was
assessed using a concentration-addition model. The relative contributions
of benzene, toluene, ethylbenzene, xylenes (BTEX), polycyclic aromatic
hydrocarbons (PAHs), and alkylated PAHs in luminescence inhibition
were estimated to be 76%, 2%, and 21%, respectively. It was further
identified that C3- and C4-naphthalenes were the most important aromatic
hydrocarbons responsible for baseline toxicity. This indicates that
alkylated PAHs would be the major components of oil-spill residue.
Further research is needed to evaluate the fate and ecotoxicity of
alkylated PAHs