Geochemical Investigation of Tar Balls Collected in a Brazilian Beach Using Biomarkers, Ni/V, δ13C Ratios and Ultra-High Resolution FT-ICR Mass Spectrometry

Representative tar balls collected in two distinct years (2012 and 2014) in a beach along the State of Bahia, northeastern Brazil, were geochemically characterized in order to identify correlations between them and investigate potential sources. Terpanes and steranes biomarkers (detected by gas chromatography coupled to mass spectrometry, GC-MS), carbon stable isotope ratio (δ13C), Ni and V ratios and polar compounds by Fourier transform ion cyclotron resonance mass spectrometry using electrospray ionization in negative mode (ESI(-) FT-ICR MS) were evaluated. Three Brazilian oil samples from distinct sources were assessed as possible spill sources, comparing their results with the tar ball samples. Using chemometric techniques, it was verified correlation between the two set of tar ball samples, suggesting same source. However, no correlation with the oil samples was observed, with different geochemical profile among them. The heteroatom class distribution displayed severe degradation levels for tar balls and its seems that photo-oxidation and biodegradation processes were further relevant. Tar ball samples show multiple classes, most oxygenated, and with one sample showing considerable relative abundance of N1 class, suggesting it is from a more recent oil spill. In brief, our results suggest that the region, with very sensitive ecosystem, is possibly subjected to frequent spills from the same source.于巴西东北部巴伊亚州沿岸海滩，分别于2012年与2014年采集的代表性焦油球（tar balls），经地球化学表征分析以明确两组样品间的关联并探究其潜在污染源。本研究针对多项指标开展系统性评估：采用气相色谱-质谱联用法（Gas Chromatography Coupled to Mass Spectrometry, GC-MS）检测萜烷（terpanes）与甾烷（steranes）生物标志物，分析碳稳定同位素比值（δ¹³C）、镍（Ni）与钒（V）元素比值，并通过电喷雾负离子模式傅里叶变换离子回旋共振质谱（Electrospray Ionization in Negative Mode (ESI(-) FT-ICR MS)）对极性化合物进行表征。选取3份来源各异的巴西原油样品作为潜在溢油污染源参照，将其检测结果与焦油球样品进行比对分析。经化学计量学（Chemometrics）技术分析，证实两组焦油球样品间存在显著相关性，表明二者源自同一污染源。但未发现焦油球样品与上述原油样品间存在关联，二者地球化学特征存在显著差异。焦油球的杂原子类别分布特征显示其经历了强烈降解作用，表明光氧化与生物降解过程对其成分演化起到了关键作用。焦油球样品包含多种杂原子类别，其中以含氧类为主；其中一份样品的N₁类化合物相对丰度较高，暗示其源自近期发生的溢油事件。综上，本研究结果表明，该区域拥有高度敏感的生态系统，可能频繁遭受同一污染源的溢油污染。