The Molecular-Level Composition and Acute Toxicity of Photosolubilized Petrogenic Carbon.

Abstract

In order to examine the molecular-level composition and acute toxicity of petroleum-derived dissolved organic matter (DOMPD) produced via photo-oxidation, a heavy and light oil were irradiated over seawater with simulated sunlight. Increases in dissolved organic carbon (DOC) concentrations as a function of time were associated with changes in DOMPD composition and acute toxicity. Parallel factor analysis (PARAFAC) showed that the fluorescent dissolved organic matter (FDOM) composition produced from the heavy oil became more blue shifted over time, while the light oil produced a mixture of blue-shifted and red-shifted components similar to FDOM signatures. Ultrahigh resolution mass spectrometry reveals that the composition of the DOMPD produced from both the heavy and light oils was initially relatively reduced, with low O/C. With time, the composition of the DOMPD produced from the heavy oil shifted to unsaturated high oxygen compounds, while that produced from the light oil comprised a range of high O/C aliphatic, unsaturated, and aromatic compounds. Microtox assays suggest that the DOMPD initially produced is the most toxic (62% inhibition); however, after 24 hours, a rapid decrease in toxicity decreased linearly to 0% inhibition for the heavy and to 12% inhibition for the light DOMPD at extended exposure periods.