Combination of aquatic plant with phosphorus inactivation material to overcome high internal P loading in eutrophic urban lakes

Aquatic plants are typically used to reduce the sediment phosphorus (P) release from eutrophic urban lakes. However, aquatic plants do not necessarily function well to control P release from urban lakes with high internal sediment P loading. To identify an effective method, aquatic plants (Vallisneria spiralis) and lanthanum-modified clay (LMC) were combined or used individually to remediate sediment P of various concentrations (low, moderate, high, and extremely high levels). Our results showed that the combination can efficiently control the P concentration in water columns and pore water, and inhibited sediment P release regardless of internal P level. At low and moderate internal P levels, Vallisneria spiralis alone exerts a similar control effect on pore water P and P flux compared with the combination method. However, there was 51% less reduction of P flux in Vallisneria spiralis treatment compared with combination treatment at high or extremely high level. Aquatic plants can only efficiently reduce sediment mobile P proportion (6%–7%) at low and moderate level. By contrast, LMC efficiently reduced the sediment mobile P proportion (13%–21%) and concurrently increased inert P fractions (HCl–P) at all investigated sediment P levels. The combination of chemical and ecological methods integrated all the advantages and can overcome the impact of high sediment internal P loading. This novel remediation method offers high application prospects in eutrophic urban lakes affected by severe internal P pollution.