Impact of nitrogen-polycyclic aromatic hydrocarbons on phenanthrene and benzo[a]pyrene mineralisation in soil

When aromatic hydrocarbons are present in contaminated soils, they often occur in mixtures. The impact of four different (3-ring) nitrogen-containing polycyclic aromatic hydrocarbons (N-PAHs) on C-12/14-phenanthrene and C-12/14-benzo[a]pyrene (B[a]P) mineralisation in soil was investigated over a 90 d incubation period. The results revealed that both C-12/14-phenanthrene and C-12/14-benzo[a]pyrene showed no significant mineralisation in soils amended with 10 mg kg(-1) and 100 mg kg(-1) N-PAHs (p > 0.05). However, increases in lag-phases and decreases in the rates and extents of mineralisation were observed, over time. Among the N-PAHs, benzo [h] quinoline impacted C-14-phenanthrene mineralisation with extended and diauxic lag phases. Furthermore,C-12/14-B[a]P and C-14-benzo[a]pyrene-nitrogen-containing polycyclic aromatic hydrocarbons (C-14-B[a]P-N-PAHs) amended soils showed extensive lag phases ( > 21 d); with some C-14-B [a]P-N-PAH mineralisation recording < 1% in both concentrations (10 mg kg(-1) and 100 mg kg(-1)), over time. This study suggests that the presence of N-PAHs in contaminated soil may impact the microbial degradation of polycyclic aromatic hydrocarbons (PAHs) and the impact was most likely the result of limited success in achieving absolute biodegradation of some PAHs in soil.