Determining\nMarine\nBiodegradation Kinetics of Chemicals\nDischarged from Offshore Oil PlatformsWhole Mixture Testing\nat High Dilutions Increases Environmental Relevance

Offshore\noil platforms discharge enormous volumes of\nproduced water\nthat contain mixtures of petrochemicals and production chemicals.\nIt is crucial to avoid the discharge of particularly those chemicals\nthat are persistent in the marine environment. This study aims to\n(1) develop a biodegradation testing approach for discharged chemicals\nby native marine microorganism, (2) determine how dilution affects\nbiodegradation, and (3) determine biodegradation kinetics for many\ndischarged chemicals at low and noninhibitory concentrations. Produced\nwater from an offshore oil platform was diluted in the ratio of 1:20,\n1:60, and 1:200 in seawater from the same location and incubated for\n60 days at 10 °C. Automated solid-phase microextraction GC-MS\nwas used as a sensitive analytical technique, and chemical-specific\nprimary degradation was determined based on peak area ratios between\nbiotic test systems and abiotic controls. Biodegradation was inhibited\nat lower dilutions, consistent with ecotoxicity tests. Biodegradation\nkinetics were determined at the highest dilution for 139 chemicals\n(43 tentatively identified), and 6 chemicals were found persistent\n(half-life >60 days). Nontargeted analysis by liquid chromatography-high-resolution\nMS was demonstrated as a proof-of-principle for a comprehensive assessment.\nBiodegradation testing of chemicals in discharges provides the possibility\nto assess hundreds of chemicals at once and find the persistent ones.