Evaluation of dissipation mechanisms for benzo[a]pyrene in the rhizosphere of tall fescue

Although polycyclic aromatic hydrocarbons are common contaminants in soil and are potentially carcinogenic and mutagenic, little is known about their fate in the soil/root environment. The impact of tall rescue (Festuca arundinacea Schreber) on chemical and biological transformations of benzo[a]pyrene in soil was investigated in a greenhouse experiment in which ¹⁴C-benzo[a]pyrene was added to soil and placed in sealed chambers with and without plants. The distribution of ¹⁴C in soil, plant tissue, and CO₂ was quantified. Dissipation due to mineralization and volatilization accounted for <2% of the total ¹⁴C added in both planted and unplanted chambers and was greater in the presence of plants. Plant uptake of ¹⁴C was <0.12%. Residual benzo[a]pyrene was lower in soil with plants (44%) than in the absence of plants (53%). The majority of the ¹⁴C label was associated with the soil matrix. The presence of plants enhance the degradation of highly adsorbed, recalcitrant benzo[a]pyrene in soil.