Submerged macrophytes mediated remediation of molybdenum-contaminated sediments

Molybdenum (Mo) sourced mainly from artificial activities is an emerging environmental concern whose remediation is seldom reported. This study screened the Mo-enriched macrophyte Vallisneria natans (Lour.) Hara due to its high enrichment factor (10.25). Phytoremediation (V. natans) and microorganism-assisted phytoremediation (V. natans-Serratia marcescens A2) efficiency were compared. S. marcescens A2 improved phytoremediation in the early stage, however, it reduced the total Mo removal rate by 8.42%. Further experiments were conducted to investigate the environmental factors (light intensity and overlying water flow rate) on the phytoremediation by V. natans. The optimal phytoremediation performance was achieved under a high overlying water flow rate (0.022 cm·s^-1) with intense light (60 μmol·m^-2·s^-1) conditions. In addition, increasing the light intensity or flow rate increased the microbial communities' diversity in the sediment. Notably, the abundance of norank_f__Bacteroidetes_vadinHA17, related to Mo release in sediments, increased by 147.96% at optimal conditions. This study illustrated that the phytoremediation of Mo-contaminated sediments by V. natans is of practical potential.