Study of the Characteristics of Floating and Sunken Oil in Seawater Exposed to Long Term Weathering

ABSTRACT

How the oil spill compositions change in the weathering process is an important topic for marine environment protection. In this study, long-term weathering simulation tests were conducted for 2 kinds of crude oils from the platforms of different blocks in Bohai Sea and 2 kinds of heavy marine fuel oils. Both floating oils and oils sunken in the seawater were analyzed. Gas chromatography (GC) results showed that light components (<C17) within floating oils underwent complete weathering, while sunken oils can maintain a little (such as C16). Fluorescence spectra revealed that polycyclic aromatic hydrocarbons experienced the same degree of weathering in floating and sunken oils, and fuel oils lost their fluorescent characteristics in contrast with the crude oils. The vanadium content in fuel oils decreased significantly after weathering, but still about one order of magnitude higher than those in the crude oils. A method is proposed here for judging whether the oil sampled has sunken to the sea floor before floating up as the basis for further identification of its sources.

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