Multiple reaction monitoring tool applied in the geochemical investigation of a mysterious oil spill in northeast Brazil

Abstract

In 2019, much of the northeastern coast of Brazil was impacted by a mysterious oil spill that caused an environmental disaster affecting 1009 beaches. Four samples were collected in the beaches between Sergipe and Pernambuco for geochemical characterization of the spilled oil and to compare with those main produced in Sergipe-Alagoas basin. Our approach in this evaluation was the use of a highly selective technique of sequential mass spectrometry by multiple reaction monitoring, to obtain the diagnostic ratios of hopanes and steranes biomarkers. Using these biomarkers ratios associated with multivariate statistical analysis, we found direct correlation between the spilled oil collected along the northeastern coast and no relationship between Sergipe-Alagoas basin crude oils was found. Furthermore, reported data for oils from Orinoco belt in Venezuelan basins were used for qualitative evaluation considering the indicative aspects suggested by the literature. Presence of highly specifi c biomarker 18α(H)-oleanane, and fi ve other important diagnostic ratios evidenced correlation between the spilled oil and Naricual formation crude oils. Besides, due to the oleanane index, Ayacucho's crude oil presented the strongest factor of correlation with the spilled oil found on the northeast coast of Brazil.

Synergy of Analytical Approaches Enables a Robust Assessment of the Brazil Mystery Oil Spill

“…Given the differences in GC-FID traces (Figure ), we performed additional compositional analysis to determine if our samples shared the same source as those of Lourenço et al (2020), Oliveira et al (2020), and Carregosa et al (2021). ,, Quantitative analysis of diagnostic ratios supported the qualitative differences observed in GC-FID and GC×GC-FID chromatograms from Lourenço et al (2020), Oliveira et al (2020), and Carregosa et al (2021) (Figure ). ,, A comparison of overlapping diagnostic ratios in the aforementioned studies is listed in Table S4. An expanded list of ratios from GC×GC-FID revealed that our 12 samples were similar and had relative standard deviations of less than 10% for all but the oleanane/hopane (O/H) ratio, which had a relative standard deviation of 15%.…”

“…Map of Brazilian coastline with locations of reported oiling (red line) and field samples from this study (yellow circle), de Oliveira et al, 2020 (green circles), Lourenço et al, 2020 (purple circles), and Carregosa et al, 2021 (blue circles) . See Figure S1 and Table S1 for additional details on the locations and analyses performed on each sample in this study.…”

“…Fourteen samples were collected from September to October 2019 on beaches spanning ∼200 km along the northeast State of Ceará in Brazil. The collection locations for each sample are listed in Table S1 and shown in Figures and S1 along with the local currents, shipwrecks, area of oiling, natural seeps, and locations of other samples collected following the Brazil mystery oil spill. ,, These locations were easily accessed from land and near populated areas. The samples were collected above the high-tide line, initially stored in precleaned aluminum foil-lined envelopes prior to being transferred to glass jars in the laboratory, and then refrigerated until sample analysis.…”

“…Initial geochemical analyses of oil samples by gas chromatography with flame ionization detection (GC-FID) and mass spectrometry (GC-MS) indicated a common source. , In addition, the spilled oil appeared to be crude oil or heavy fuel oil, with the origin consistent with a Venezuelan crude oil . Evaluation of hopane and sterane biomarkers present in the mystery oil by GC with triple-quadruple MS (GC-QQQ-MS) supported these findings and suggested the oil was most strongly correlated with the oil from the Venezuelan Eastern basin . Despite these efforts, the specific identity of the source of the spill remains a mystery with several hypotheses offered. , The proposed sources include several wrecks in the region, particularly vessels sunk during World War II, an extraction platform (e.g., presalt or postsalt oil fields), or natural oil seeps (Figure ).…”

The most extensive oil spill registered in tropical oceans (Brazil): the balance sheet of a disaster

“…The original hypotheses regarding the origin of this mysterious oil spill were as follows: (1) It came from natural sources (e.g., asphalt seep sites) in Brazil or Africa; (2) the oil spilled from platforms in Brazil or Africa; (3) the oil spilled (intentionally or not) from ships in transit off the Brazilian coast; and (4) the oil came from shipwrecks (recent or old) (Escobar 2019;Soares et al 2020a, b). Geochemical and biomarker analyses of sedimentary basins indicated that the oil originated from Venezuelan sedimentary oil basins (e.g., Ayacucho oil, from Naricual Formation in Venezeluan Eastern basin); therefore, hypotheses 1 and 2 were discarded (Lourenço et al 2020;Oliveira et al 2020;Carregosa et al 2021;Zacharias et al 2021a, b). Currently, hypotheses 3 and 4 remain with ongoing and intense debate.…”