RESUMO
In the present study, we applied forensic geochemistry to investigate the origin and fate of spilled oils like tarballs stranded at the beaches of Bahia, in northeastern Brazil, in September 2023, based on their fingerprints. Saturated and aromatic compounds were assessed by gas chromatography, and the oceanic surface circulation patterns were deciphered to determine the geographic origin of the spill. Contamination by petroleum represents an enormous threat to the unique, species-rich ecosystems of the study area. The geochemical fingerprint of the oil spilled in 2023 did not correlate with those of previous events, including the one in 2019, the one in early 2022 in Ceará, and an extensive spill across the Brazilian Northeast in late 2022. However, the fingerprint did correlate with crude oils produced by Middle Eastern countries, most likely Kuwait. The oil of the 2023 spill had a carbonate marine origin from early mature source rocks. These findings, together with the moderate weathering of the 2023 tarballs and the ocean circulation patterns at the time of the event, indicate that the oil was discharged close to the shore of Brazil, to the east or southeast of Salvador, by a tanker on an international route in the South Atlantic.
Assuntos
Poluição por Petróleo , Navios , Brasil , Monitoramento Ambiental , Petróleo , Poluentes Químicos da Água/análiseRESUMO
Since the 2019 oil spill on the northeastern coast of Brazil, oil materials have washed up on the beaches. A characteristic of the recent oil spill that began in late August was that some of the oiled material, such as tarballs, contained the goose barnacle species Lepas anatifera (Cirripedia, Lepadomorpha), which is well-known for its cosmopolitan distribution and wide occurrence in the oceans. The findings of this study provide information on the occurrence and contamination of petroleum hydrocarbons in animals adhered to the surfaces of tarballs sampled from beaches in the Brazilian states of Ceará and Rio Grande do Norte, between September and November 2022. The size of the barnacles varied from 0.122 to 2.20 cm, suggesting that the tarballs had been floating in the ocean for at least a month. All groups of L. anatifera collected from the tarballs had polycyclic aromatic hydrocarbons (PAHs) present (∑21PAHs from 476.33 to 3816.53 ng g-1). In comparison to high-molecular-weight PAHs, which are primarily from pyrolytic sources, low-molecular-weight PAHs, such as naphthalene and phenanthrene, which are mostly related to petrogenic sources, were shown to be more abundant. In addition, dibenzothiophene, which is exclusive of petrogenic origin, was found in all samples (30.74-537.76 ng g-1). The aliphatic hydrocarbons (AHs): n-alkanes, pristane, and phytane were also found and displayed petroleum characteristics. These results highlight the danger of increasing the absorption of petrogenic PAHs and AHs by organisms that use tarballs as substrates. L. anatifera is a crucial component of the food chain because many animals such as crabs, starfish, and gastropods consume it.