Influence of biochar and fulvic acid on the ryegrass-based phytoremediation of sediments contaminated with multiple heavy metals

Utilizing hyperaccumulators for the removal of heavy metals in sediment is a promising and environment-friendly bioremediation method. However, the efficiency of phytoremediation for multiple heavy metals contaminated sediments needs to be further improved. In this study, a 30-day incubation experiment was conducted to explore the potential role of BC and FA in assisting the hyperaccumulator, ryegrass (Lolium perenne L.), to extract cadmium (Cd), zinc (Zn) and lead (Pb) from sediments. The results of BCR (Community Bureau of Reference) analysis showed that BC and FA increased the proportions of bioavailable Cd and Zn, while decreased the bioavailability of Pb in the contaminated sediments. Metal accumulation results revealed that BC and FA were selective in facilitating the extraction of heavy metals from sediments by ryegrass in the presence of multiple heavy metals. Compared to CK, the co-treatment of BC and FA promoted the extraction efficiency by ryegrass for Cd and Zn from the sediment, with their contents in roots and stems increased by 50.7% and 143.6% for Cd, and 70.2% and 29.9% for Zn, respectively. In contrast, the Pb content in ryegrass roots and stems decreased by 59.9% and 62.1%, respectively. These results indicated that BC and FA increased Cd and Zn accumulation in ryegrass was due to the increased bioavailable Cd and Zn, and the decreased Pb accumulation in ryegrass was due to the decreased bioavailable Pb, and revealed the potential of BC and FA in assisting phytoremediation of ryegrass on heavy metals in sediments.