Phytoremediation patterns of riparian macrophytes along a spatial pollution gradient: an integrated risk-performance...

Assessing the phytoremediation efficiency of riparian macrophytes in natural stream systems remains challenging because plant performance is often evaluated using metal concentrations alone, without considering biomass-driven removal or spatial contamination variability. This study evaluated four macrophytes (Typha latifolia, Phragmites australis, Lythrum salicaria, and Persicaria lapathifolia) along a pollution gradient in the Riva Stream. A novel Remediation Efficiency Index (REI) was developed to integrate contamination risk with plant performance and classify species into site-specific management zones. Five sites were sampled during the 2025 vegetation season, and water and aboveground plant biomass were analyzed using ICP-OES. Results revealed clear spatial patterns. Midstream sites represented key potentially toxic element hotspots. P. lapathifolia showed the highest Cu and Fe concentrations (184.6 and 465.3 mg kg^-1), while L. salicaria accumulated the highest Zn and Pb (119.5 and 2.83 mg kg^-1). P. australis dominated Cr uptake (10.3 mg kg^-1) and, due to its higher biomass (1145 g DW m^-2), achieved the greatest total metal removal. REI classification placed P. australis in the Sustainable Remediation zone, whereas the other species fell into Adaptive Management or High-Risk Intervention zones. These findings show that integrating biomass-driven removal with spatial contamination patterns can guide phytoremediation strategies in contaminated streams.