Abstract:
Photo-oxidation is one of the important environmental weathering processes that changes the chemical composition of spilled oil. This study examines the effect of sunlight shined on the spilled oil, and reports toxicity of transformation products of native compounds in the oil mixture. The toxicity due to transformation products was experimentally determined using copepods as test organisms, and this was compared to the native hydrocarbons parent compounds. Photo generated transformation products of light jet oil was also determined. Our experiments show that the photo generated transformation products are more toxic to copepods at lethal and sub lethal endpoints. However, this change in the toxicity depends on exactly where the oxygen atom is added in the carbon backbone of the parent compound. This study highlights that the photo generated transformation products are environmentally relevant family of chemicals, which should not be ignored during risk assessment of oil spills in the environment. For millions of years animals are used as test objects for risk assessment aid, to compile with the regulatory authorities like REACH and US EPA. Using animals for toxicity assays is an ethical implication. In this study a new model is developed to see PDMS can be used as an alternative to animal testing and how much passive sampling phases resembles toxicity end points. For hydrocarbons, the model shows root mean square error (rmse) of
0.30 log unit when compared to the experimental values (n=46) reported in literature. Whereas previous model of critical membrane concentration returned higher rmse value (0.35 log unit) for same experimental dataset (n=46). Model for oxygenated hydrocarbons (OxHCs) transformation products which were formed in weathered oil samples due to photo oxidation, consisting of ketones, aldehydes, alcohols and acids, show higher rmse values indicating these chemicals have higher toxic mode of action than narcosis.
Key words: Photo oxidation, Transformation products, Hydrocarbons, Oxygenated hydrocarbons, jet oil, Bioassays, Polydimethylsiloxane
