Ratio of the concentration of anthraquinone to anthracene in coastal marine sediments

The ratio of the concentration of the oxidation product anthraquinone to th at of its parent polycyclic aromatic hydrocarbon anthracene is reported for several coastal marine sediments. The ratio ranges from 0.317 in a highly contaminated industrialized harbor to 2.81 in a remote, less contaminated s ite. We hypothesize that differences in this ratio result from the input so urce of PAHs, with input from atmospheric deposition at remote sites result ing in a predominance of anthraquinone (ratio > 1), and direct discharge to highly contaminated industrialized harbors resulting in a predominance of anthracene (ratio < 1). To support this hypothesis, the fate of anthracene in the marine environment was investigated with respect to conversion to it s oxidation product, anthraquinone. Once associated with sediments, anthrac ene is believed to be relatively persistent; however, it can potentially be subjected to oxidation via biological (microbial degradation) and chemical (chemical oxidation and photooxidation) processes. An assessment of the ex tent of oxidation of anthracene associated with sediments was conducted bot h under conditions simulating those found in the marine environment and und er rigorous conditions by exposure to UV radiation. Results of this study s how that while anthracene associated with marine sediments does not readily undergo oxidation to anthraquinone under conditions normally encountered i n the marine environment, under extreme conditions anthracene is photooxidi zed by exposure to UV radiation. The extent of oxidation is influenced by s ediment characteristics such as percent organic carbon, humic acid content and sediment surface area. The relative stability of anthracene under norma l conditions may help to validate the use of the anthraquinone to anthracen e ratio in marine sediments as an environmental marker of contaminant sourc e. (C) 1999 Elsevier Science Ltd. All rights reserved.