Phytoremediation and bacterial community dynamics of diesel- and heavy metal-contaminated soil: Long-term monitoring on a pilot scale

The objective of this study was to investigate the long-term phytoremediation characteristics and the bacterial community structure in diesel- and heavy metals-contaminated soil on a pilot scale. Soil was contaminated with diesel, Cu, Pb, and Cd. Festuca arundinacea (tall fescue) seedlings were cultivated in the co-contaminated soil, and the phytoremediation performance was monitored for 571 days. The maximum total petroleum hydrocarbon (TPH) removal rate was 62.6%, with residual TPHs remaining at the end of the experiment. Of the three heavy metals, Cd had the highest uptake efficiency in tall fescue, with a bioconcentration factor of 0.58. In the bacterial community, the most dominant bacterial genera exhibited either petroleum hydrocarbon biodegradability or heavy-metal tolerance. Correlation analysis revealed that ambient temperature did not significantly affect phytoremediation performance, while soil pH and organic content had significant effects on pollutant concentrations in the soil. The results of this study, obtained from the long-term monitoring of phytoremediation on a pilot scale, provide useful information on pollutant behavior and bacterial community dynamics that can be employed in the development of phytoremediation strategies for soils co-contaminated with diesel and heavy metals.