Effects of phenanthrene and its nitrogen-heterocyclic analogues aged in soil on the earthworm Eisenia fetida

Major sources of homocyclic polycyclic aromatic hydrocarbons (PAHs) and N-containing analogues (N-PAHs) are found in the environment after being discharged through petrogenic, pyrogenic and biogenic activities. Using a health index tool and the OECD guideline 207, the ecotoxicity of phenanthrene and its nitrogen-containing analogues to the earthworm Eisenia fetida were assessed in agricultural soil at different times after spiking. The effects were measured over a 21 d exposure period (over time), during which earthworms' general health condition, mortality and biomass were assessed. The LC50 and EC50 (based on weight loss) ranged from 400-500 mg kg−1 dry soil and 1.2-500 mg kg−1 dry soil, respectively. The N-PAHs were more toxic to E. fetida and over time more available in soil than the homocyclic-phenanthrene analogue. Benzo[h]quinoline (B[h]Q) was the most toxic and persistent of the chemicals. Furthermore, the observed physical damages to the earthworms showed that N-PAHs, especially B[h]Q, may have cellular autolytic impact on E. fetida. These findings offer new insight on the toxicity of aromatics in soil which might be useful in risk assessment of contaminated sites.