Effects on lead bioavailability and plant uptake during the bioremediation of soil PAHs

Bioremediation has been used extensively to remove organic pollutants. However, soil contamination with polyaromatic hydrocarbons is always accompanied by metals. Changes in metal behaviour were assessed prior and subsequent to fungal bioremediation of phenanthrene contaminated soil. Lead bioavailable concentrations were assessed by Diffusive Gradients in Thin-films (DGT), and metal uptake to plants was quantified. DGT-concentrations were found to significantly increase (α 0.05, β 0.001) after the addition of fungi in the presence of plants: <0.2 μg l^-1 before bioremediation and approximately 1.4-1.7 μg 1^-1 after fungal addition. Nevertheless, while DGT responded immediately to uptake, plant uptake does not start immediately. Pb uptake was fairly low for 9 days after fungal addition before increasing rapidly over the last 6 days. Pb was not translocated. The results indicate that fungal bioremediation reduces organic contaminants significantly while it simultaneously increases bioavailable metal concentrations and plant uptake, as a side effect of the decontamination process.