Toxicity and Bioaccumulation of Petroleum Mixtures with Alkyl PAHs in Earthworms

The toxicities of three oil products with boiling-point ranges representative of petroleum hydrocarbons were tested on earthworms (Eisenia fetida) to investigate the correlation between bioaccumulated concentrations of polycyclic aromatic hydrocarbons (PAHs) and toxicity. The toxicities to earthworms were in the sequence: kerosene > diesel > bunker-C. After 14 days, the LC50s of the soils contaminated with kerosene, diesel, and bunker-C were 1079, 9135, and 15,609 mg/kg, respectively. Analysis of the body residue concentrations of PAHs in the earthworms showed that the accumulation of alkyl PAHs predominated that of the 16 priority PAHs. Principal component analysis (PCA) identified 12 PAHs, including four alkylated naphthalenes, as the oil constituents that affected mortality in the kerosene-contaminated soil. For the diesel-contaminated soil, eight PAHs were identified, including dibenzothiophene. It was not clear which compounds affected mortality in the bunker-C soil. Across the three series, biota-to-soil accumulation factors (BSAFs) ranged from 10^-2.05 to 10^3.98, and generally increased as the hydrophobicity (K_ow) or molecular weight of the alkyl PAHs increased. The toxicity endpoints of each oil product can be used as reference values in the risk assessment of soils contaminated with petroleum, and individual PAHs screened out have implications for future toxicity assessment of petroleum hydrocarbons.