Assessment of natural attenuation of volatile aromatic hydrocarbons in agricultural soil contaminated with diesel fuel

A diesel fuel spill was simulated on a 12-m2 plot of agricultural land, at a concentration of 1 L m−2 of soil. The natural attenuation of Volatile Aromatic Hydrocarbons (VAHs) was monitored at different soil depths over a period of 50 days. The natural attenuation of VAHs in the surface layer would be attributed to two processes, namely: volatilisation (mainly linked to the boiling point of each VAH, with t1/2 from 2 to 71 min for benzene and p-isopropyltoluene, respectively); and dissipation (related to the boiling point as well as the analyte–soil matrix interaction, with t1/2 from 2 to 169 h for benzene and p-isopropyltoluene, respectively). As expected, in the deeper layers, dissipation prevails over volatilisation. 50 days after the spill, only two VAHs were detected in the surface layer, at concentrations of 5–20 ng g−1, which had disappeared after 80 days of the spill.