Possibility of Using Energy Crops for Phytoremediation of Heavy Metals Contaminated Land—A Three-Year Experience

Abstract

Heavy metal soil contamination is a worldwide problem. The affected sites could be either sites of a former industrial activity or arable land located in their vicinity. The presence of heavy metals in excessive quantities renders these sites idle or underused due to contamination and lack of efficient ways to remediate. Phytoremediation driven energy crops production may be a promising alternative for the management of these sites. A four year field experiment has been established on heavy metal (HM) contaminated sites located in Bytom, Upper Silesia Industrial Region, Southern Poland (arable land) and Leipzig, Germany (post-industrial site). The objective for this experiment was to distinguished energy crop species optimal with respect to both: energy crop yield and phytoremediation potential. The testing involves the following pre-selected plant species: miscanthus (Miscanthus x giganteus), virginia mallow (Sida hermaphrodita), cordgrass (Spartina pectinata), and switchgrass (Panicum virgatum). The experimental trials were established in May 2014. Both sites were treated as follows: (i) K—Control, no treatment; (ii) NPK—NPK standard fertilization, applied to the soil before the experiment; (iii) INC—Commercial microbial inoculum Emfarma Plus®, ProBiotics Poland. The presented data were collected after the third growing season; heavy metal uptake for each of the species and experimental options were determined. Levels of the bioavailable content of heavy metals in the soil seem to be the main factor responsible for the differences in the metal uptake by the plants. Plant species cultivated at the German site were characterized by low metal concentration in shoots, except P. virgatum which accumulated a high amount of zinc, even if the bioavailability of this metal in soil was low. The highest lead uptake was observed for M. x giganteus and P. virgatum, while the highest cadmium content was found for S. hermaphrodita grown on a contaminated arable soil in Bytom. Cultivation of energy crops on HM contaminated areas could be a solution for remediating these sites while increasing their economic value.