Weathering impacts on petroleum biomarker, aromatic, and polar compounds in the spilled oil at the northeast coast of Brazil over time

After the wide oil spill reached the northeast of Brazil, the resurgence of oil was recorded and to evaluate this oil in detail, two samples collected in the state of Pernambuco in 2019 and 2021 were submitted to multiple analytical techniques. For both, we have found similar saturated biomarkers and triaromatic steroid ratios, implying that they are from the same spilled source. The n-alkanes, isoprenoids, and cycloalkanes were almost completely degraded due to evaporation, photooxidation, and/or biodegradation processes. The preferential loss of less alkylated PAHs than the more alkylated ones suggests that biodegradation was the most active process. This hypothesis is reinforced by the formation of mono and dicarboxylic acids assessed by GC × GC-TOFMS and ESI(−) FT-ICR MS high-resolution techniques. Furthermore, based on the ESI(−) FT-ICR MS results, three new ratios were proposed to evaluate the progress of the biodegradation process over time: Ox>2/O, SOx/SO, and SOx/N. [Display omitted] •Spilled oils were found on Pernambuco beaches in 2019 and 2021.•Biomarker parameters suggested the same source for both spilled oils.•Weathering processes were responsible for chemical compositional changes.•GC × GC-TOFMS and ESI(−) ICR- FT MS results suggested biodegradation as main process.•New ratios using Ox, SOx, and N1 classes to evaluate biodegradation extension.