Effects of Single, Binary and Quinary Mixtures of Phenanthrene and Its N-PAHs on Eisenia fetida in Soil

Anyanwu, Ihuoma N.; Clifford, Ojerime I.; Semple, K. T.

Effects of Single, Binary and Quinary Mixtures of Phenanthrene and Its N-PAHs on Eisenia fetida in Soil

2017

Anyanwu, Ihuoma N. | Clifford, Ojerime I. | Semple, K. T. (Kirk T.)

It is now acknowledged that aromatic hydrocarbons present in contaminated soils occur in mixtures. The effect of single, binary and quinary mixtures of phenanthrene and selected nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) were investigated on the survival, growth and behavioural index of earthworms (Eisenia fetida) over a 21-day incubation in soil. The results showed that the LC₅₀ values ranged from (not detected) ND–329.3 mg kg⁻¹ (single mixture), ND–219.8 mg kg⁻¹ (binary mixtures) to 148.4 mg kg⁻¹ (quinary mixture), while the EC₅₀ values (based on weight loss) ranged from 13.3–148.4 mg kg⁻¹ (single mixture), 63.8–148.4 mg kg⁻¹ (binary mixture) to 24.2 mg kg⁻¹ (quinary mixture). Greater impacts were recorded where N-PAHs are present with phenanthrene. Further, behavioural index of E. fetida was affected after 24-h exposure to N-PAH-amended soils. Among the N-PAHs however, benzo[h]quinoline recorded the greatest impact on the survival, growth and behavioural index of E. fetida in soil. Findings from this study showed that three ring-N-PAHs are more toxic than phenanthrene as expected from their physico-chemical properties. The binary and quinary mixtures of phenanthrene and N-PAHs in soil intensified toxicity, suggesting that PAHs-N-PAHs mixtures represent greater risk to soil biota.

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