Effect of soil depth on phytoremediation efficiency for petroleum contaminants

Biodegradation of organic contaminants in soil may be enhanced by the presence of vegetation. Evaluating the effect of soil depth on phytoremediation efficiency may provide researchers and regulators with a clearer understanding of contaminant clean-up. A column study with polycyclic aromatic hydrocarbons (PAHs) and diesel-contaminated soil was conducted over a 147-day period of switchgrass (Panicum virgatum) growth. Analysis of the contaminants and plant biomass was conducted along with microbial enumeration at three soil depths in 49-day intervals. Remediation proceeded rapidly near the surface of the soil (0-20 cm) for both vegetated and unvegetated columns, but the effect of vegetation relative to an unvegetated control only was significant in the lower soil depths. Contaminant dissipation in the 20-40 and 40-60 cm layers was not significantly different between vegetated and unvegetated soil.