Polycyclic aromatic hydrocarbons (PAHs) dissipation from a contaminated technosol composed of dredged sediments with Miscanthus x giganteus and Trifolium repens L. in mono- and co-culture

Purpose Dredged sediments from waterways are often contaminated due to human activities. We tested an original remediation method consisting of mixing dredged contaminated sediments with contaminated soil to create a technosol and establish a phytoremediation technique. The objective was to determine if the Miscanthus x giganteus (MxG) and white clover co-culture could improve the PAH dissipation compared with monoculture. Materials and methods MxG and white clover were tested in mono- and co-culture on a technosol composed of sediments and soil in mesocosm during 263 days (a life cycle of MxG until its senescence). PAHs measurements and ecotoxicity and genotoxicity tests were performed at the beginning (T-0) and the end (T-F) of the phytoremediation experiment. Results and discussion PAH removal varied according to the planting patterns and the PAHs involved, but overall, the presence of vegetation significantly induced dissipation of total PAHs in the technosol. After 263 days of culture, 26.24% of the total 16 priority PAHs were removed with white clover monoculture, 29.27% with co-culture, and 31.65% with MxG monoculture. Moreover, after 263 days of culture, the index of additive cancer risk (IACR) values were 4.26 for the non-planted technosol, 3.43 for MxG monoculture, 3.31 for white clover monoculture, and 3.43 for co-culture. The different planting patterns improved the decrease of the IACR values in the technosol compared with the non-planted technosol, even if it remained above the reference value. Furthermore, co-culture significantly enhanced the dissipation of pyrene and anthracene and decreased the technosol ecotoxicity in contrary to MxG monoculture. Conclusion The present study showed the possibility to remediate dredged sediments after mixing them with soil, thus opening a new way to clean up contaminated excavated sediments. The presence of vegetation significantly promoted the dissipation of the total 16 priority PAHs and improved the decrease of the IACR values. Co-culture was more efficient for the dissipation of specific PAH, such as pyrene and anthracene, compared with MxG monoculture. Moreover, the co-culture improved the decrease of the technosol ecotoxicity contrarily to other planting patterns.