Polycyclic Aromatic Hydrocarbons (PAHs) and Bis(2-ethylhexyl) Phthalate (BEHP) in the Soil of Teff-Acacia decurrens-Charcoal Production System in Northern Ethiopia

Abstract

The current study is aimed at investigating the level of polycyclic aromatic hydrocarbons (PAHs) and bis(2-ethylhexyl) phthalate (BEHP), which pose a potential risk to human health, in soil samples collected from a teff-Acacia decurrerns-charcoal production system (TACP system) in northern Ethiopia. Soil samples were collected from the TACP system and from an adjacent teff monocropping system (TM system) from 0 to 20 cm soil depth. Individual PAHs and total concentrations of PAHs and BEHP generally exhibited no significant variation between the TM and the TACP systems over three rotations. In the land-use systems, the mean concentration of PAHs decreased in the order phenanthrene > fluorene > pyrene > chrysene. Fluorene (22.84–24.69 ng g−1 dry soil), pyrene (21.99 ng g−1), and chrysene (21.79 ng g−1) were detected in the TACP system only, suggesting that they were from charcoal production. The maximum concentration of BEHP recorded in the soil samples was 104.00 µg g−1, which could be attributed to the polyethylene (PE) bags used for planting the Acacia decurrens seedlings of the TACP system. In soil samples, the sum of all PAHs analyzed ranged from not detected (ND) to 170.69 ng g−1, which is below the limits of prevention established by European regulations for soils (3000 ng g−1) and previous studies. Carcinogenic equivalent (BaP-TEQ) and mutagenic equivalent (BaP-MEQ) concentrations calculated for the individual PAHs in the land-use systems ranged from ND to 0.374 ng g−1 and from ND to 0.218 ng g−1, respectively, which is far below many international safety standards. Our results indicate that the charcoal production and the use of the charcoal residues as soil amendment in the TACP system is safe concerning soil contamination by PAHs and BEHP and the risk of cancer and mutation.