Hydrocarbon composition of oils spilt on the Brazilian coast in 2019 and 2022

The chemical composition of spilt oils from events that took place on the north-eastern coast of Brazil in 2019 and 2022 was investigated to better understand their sources, and post-spill processes. Oils from both events originated from different sources, based on their fingerprints, hydrocarbons composition and specific biomarkers, such as the C23 tricyclic terpane and oleanane. Despite the differences, the source rocks share similarities in paleoenvironments and depositional conditions and both oils suffered little weathering, mainly due to evaporation and dissolution. Our findings for 2019 spilt oil reinforce that it is a mixed product, enriched both in lighter n-alkanes and 25-norhopanes. Differently, the 2022 samples exhibited characteristics of a non-processed crude oil that originated from a paraffinic deposit in storage tanks. The molecular composition and diagnostic ratios reported for samples from these spill events help to establish baselines for ongoing monitoring of oil spills in marine ecosystems. [Display omitted] •Supports that the 2019 oil has characteristics of a mixed and Venezuelan oil.•2022 oil is a crude oil contaminated by heavy paraffins.•Oils spilt in 2019 and 2022 are from different sources.•Both source rocks share similarities in origin and depositional environment.•Geochemical ratios contribute with baselines for ongoing spilt oil monitoring.