Occurrence and Distribution of Polycyclic Aromatic Hydrocarbons and Nitrogen-Containing Polycyclic Aromatic Hydrocarbon Analogues in Soils from the Niger Delta, Nigeria

Anyanwu, I.N. and Semple, K.T. (2022) Occurrence and Distribution of Polycyclic Aromatic Hydrocarbons and Nitrogen-Containing Polycyclic Aromatic Hydrocarbon Analogues in Soils from the Niger Delta, Nigeria. Polycyclic Aromatic Compounds, 42 (9). pp. 6290-6302. ISSN 1040-6638

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]Peq) 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.