Application of anaerobically digested sewage sludge in the phytoremediation of a weathered diesel contaminated soil

It has recently been proposed that the addition of organic matter may increase the phytoremediation of petroleum hydrocarbons (PHC) through the increased availability of nitrogen (N) and improvement of soil properties. The addition of biosolids to a soil contaminated with weathered diesel did not increase the extent of PHC degradation (i.e. residual PHC concentration), but it did increase the rate of degradation. Overall, vegetation establishment did not increase the rate or extent of PHC degradation, relative to that observed in non-amended, non-vegetated soils. Vegetation was, however, an important factor within the biosolids-amended treatments as was observed by an increase in the extent of degradation and a decrease in the concentration of biosolids-derived mineral N remaining in the soil. In general, the low-amendment rate of 13.348 biosolids kg-1 soil was the most successful treatment as determined by the increased PHC degradation rate, improved soil properties, and increased plant growth.