Oil exposed to sunlight has been shown to produce oxygenated photoproducts, including aldehydes and ketones. Time-dependent studies have shown increasing concentrations of these photoproducts with irradiation time. However, the temperature dependence of these reactions has not been studied. Aldehyde and ketone photoproducts in the aqueous phase from irradiated oil on water were determined by electrospray ionization−tandem mass spectrometry (ESI−MS/MS) after derivatization with 2,4-dinitrophenylhydrazine (DNPH). Several oils from different wells were spread over pure water and exposed to simulated sunlight for 6 h (equivalent to 1.5 days of exposure to average Northern Gulf of Mexico sunlight) at different temperatures (12C, 25C, and 35C). The aqueous phase was collected after irradiation and derivatized with DNPH, which selectively reacts with aldehydes and ketones. Solid phase extraction with C18 cartridges was used to enrich the derivatized hydrazones before analysis by (-) ESI-MS/MS. The effect of temperature was complex, and the different oils showed different behavior with temperature. Total organic carbon (TOC) analysis of the aqueous phase demonstrated a distinct increase in photogenerated TOC with increasing temperature. These findings broaden our understanding of the photochemical product formation of oil spilled in aquatic systems and increase the applicability of laboratory results to a wider range of environmental conditions.

Temperature dependence of aldehyde and ketone photoproduct generation from crude oil-water systems under solar irradiation

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