Abstract

Polycyclic aromatic hydrocarbons (PAHs) and the nitrogen heterocyclic analogues (N-PAHs) are known to co-exist in environmental samples. Despite the known toxicity in polluted soils, their distribution remains to be elucidated in specific regions. This study investigated the occurrence and distribution PAHs and N-PAHs in soils from the Niger Delta. Physico-chemical analysis shows that Niger Delta soils are calcic, low in cation-exchange capacity (CEC); with ƩPAHs and ƩN-PAHs ranges of 663.9–1,618,821.2 µg/kg and 488.2–3,510.3 µg/kg, respectively. The most abundant PAHs were 2,6-dimethyl-naphthalene and 4,7-phenanthroline. Petrogenic-PAHs dominated the crude oil spill sites; while, pyrogenic-PAHs were abundant in drilling and gas flaring sites. Oil spill sites recorded elevated levels of N-PAHs, with 3-rings and carcinogenic-N-PAHs showing dominance. Furthermore, ƩPAHs and ƩN-PAHs in the oil rich region exceeded the Alberta and Canadian soil quality guidelines and, are also higher than PAHs/N-PAHs studies in literature. Risk assessment based on Benzo[a]pyrene toxic equivalency (TEQ-B[a]P_eq) suggests high ecological risks. This is the first study on the occurrence and distribution of PAHs/N-PAHs in the area, and the data could serve a baseline purpose for risk assessment and remediation of contaminated sites.

摘要

众所周知，多环芳烃 (PAHs) 和氮杂环类似物 (N-PAHs) 共存于环境样品中。尽管已知污染土壤中的毒性，但它们在特定地区的分布仍有待阐明。本研究调查了尼日尔三角洲土壤中 PAHs 和 N-PAHs 的发生和分布情况。理化分析表明，尼日尔三角洲土壤是钙质的，阳离子交换能力（CEC）低；ƩPAHs 和ƩN-PAHs 范围分别为 663.9–1,618,821.2 µg/kg 和 488.2–3,510.3 µg/kg。最丰富的多环芳烃是 2,6-二甲基萘和 4,7-菲咯啉。石油-多环芳烃在原油泄漏现场占主导地位；而热解多环芳烃在钻井和天然气燃烧场所中含量丰富。溢油现场记录的 N-PAH 含量升高，3 环和致癌 N-PAHs 占主导地位。此外，富含石油地区的ƩPAHs 和ƩN-PAHs 超过了阿尔伯塔省和加拿大的土壤质量指南，并且也高于文献中的PAHs/N-PAHs 研究。基于苯并[a]芘毒性当量（TEQ-B[a]P）的风险评估_eq ) 表明生态风险较高。这是对该地区多环芳烃/多环芳烃的发生和分布的首次研究，该数据可以作为风险评估和污染场地修复的基线目的。