Incorporation of Organic Contaminants in Geochemical Samples and an Assessment of Potential Sources Samples: Examples from Geoscience Australia's Marine Survey S282

Organic geochemists are increasingly involved in multi-disciplinary collaborative studies but not often in the initial sample collection phase, so understanding the origin and source of contaminants derived from sample handling and containers is of vital importance as standard laboratory blanks cannot assess this contamination. A variety of organic contaminants was detected in different sediments collected during Geoscience Australia marine survey S282. These include fatty acid amides, chemical antioxidants such as butylated hydroxytoluene and octadecyl-3, 5-di-tert-butyl-4-hydroxyhydrocinnamate (Irganox 1076), plus the UV absorbers octabenzone and octyl methoxycinnamate. These compounds were introduced during sampling on board the research vessel or during subsequent handling. Solvent extraction of potential contamination sources identified two brands of plastic sampling bags as the main source for the fatty acid amides, butylated hydroxytoluene and Irganox 1076. Direct contact of samples with hands covered with sunscreen appears to have caused contamination by octabenzone and octyl methoxycinnamate. As the primary aim of the survey was to detect evidence for hydrocarbon seepage in the Arafura Sea, care was also taken to identify potential sources of hydrocarbons that might have been introduced during sampling and storage. Detailed examination of solvent extracts from plastic bags revealed the occurrence of several homologous series of branched alkanes with quaternary carbon atoms (BAQCs), as well as distributions of alkyl cyclohexanes and alkyl cyclopentanes with strong even over odd carbon predominance. These compounds were also found in sediment samples collected during the survey. Other potential sources of contamination used on board the ship, such as PVC core liners and lubricants, yielded hydrocarbons that could easily be mistaken for evidence of naturally occurring petroleum if care is not taken during interpretation.

有机地球化学家正日益深度参与多学科协作研究，但通常无法参与初始样品采集环节，因此明晰样品处理与容器引入的污染物来源与成因至关重要——这是因为标准实验室空白无法评估此类污染。在澳大利亚地球科学局（Geoscience Australia）S282海洋调查中采集的不同沉积物样品内，检测到多种有机污染物。此类污染物涵盖脂肪酸酰胺（fatty acid amides）、化学抗氧化剂（如丁基羟基甲苯（butylated hydroxytoluene）及十八烷基-3,5-二叔丁基-4-羟基氢化肉桂酸酯（Irganox 1076）），以及紫外线吸收剂奥克苯酮（octabenzone）和甲氧基肉桂酸辛酯（octyl methoxycinnamate）。上述化合物均在海洋科考船（research vessel）的采样作业或后续处理过程中引入。通过对潜在污染源开展溶剂萃取分析，查明两款塑料采样袋为脂肪酸酰胺、丁基羟基甲苯及Irganox 1076的主要污染源。样品与涂抹防晒霜的手部直接接触，被认为是造成奥克苯酮与甲氧基肉桂酸辛酯污染的诱因。鉴于本次调查的核心目标为检测阿拉弗拉海（Arafura Sea）的烃类渗漏（hydrocarbon seepage）证据，研究团队同时重点排查了采样与储存过程中可能引入的烃类潜在污染源。对塑料样品袋的溶剂萃取物进行详细解析后，检出多组带季碳原子的支链烷烃同系物（branched alkanes with quaternary carbon atoms, BAQCs），同时检测到烷基环己烷与烷基环戊烷的分布特征呈现显著的碳数偶数优于奇数的规律。此类化合物同样在本次调查采集的沉积物样品中被检出。船上使用的其他潜在污染源（如聚氯乙烯（PVC）岩心衬垫与润滑剂）也会释放烃类物质，若在数据解译过程中未加以谨慎甄别，此类烃类极易被误判为天然石油的存在证据。