Phragmites australis and Scirpus holoschoenus for metal(loid)s polluted groundwater remediation: a wetland mesocosm study with different exposure regimes

Mitigation of pollutants is crucial for long-term sustainable management of groundwater and freshwater systems and ecosystem health. However, the potential of nature-based attenuation strategies, such as phytoremediation, in the presence of multi-element contamination and under changing exposure conditions, remains largely unexplored. This study aimed to comprehensively assess the potential of Phragmites australis and Scirpus holoschoenus for metal(loid) remediation in contaminated groundwater. The investigation involved both medium (4 L) static and large dynamic (65 L) mesocosms to simulate different exposure conditions, including abrupt (acute), and continuous (progressive and chronic), with a particular focus on reducing overall metal(loid) toxicity. Dynamic mesocosm results demonstrated that both macrophytes corrected water pH from 3.7 to 7.6, and significantly reduced Ni, Fe, and Cu, which initially exceeded the Flemish regulatory limits by up to 3182-fold. Additionally, P. australis exhibited superior bioenergy potential, with higher heating values (HHV) reaching up to 17.15 MJ kg⁻¹. Metal uptake followed a clear phytostabilization trend for Al, Cu, Fe, Ni, and Zn. Most notably, macrophytes assisted phytoremediation restored the HepG2 cell viability from 0% to over 75%, indicating an effective neutralization of polluted groundwater toxicity. In conclusion, this study demonstrated the potential of phytoremediation using P. australis and S. holoschoenus as sustainable strategy for contaminated water treatment, providing simultaneous benefits of metalloids removal, toxicity reduction, and the valorization of biomass for bioenergy applications. • Metal(loid)s polluted groundwater phytoremediation in different regimes was studied. • P. australis and S. holoschoenus performed phytostabilization of metal(loid)s. • Mesocosms neutralized water pH (3.7 to 7.6), promoting to metal immobilization. • Treated water restored the HepG2 cell viability, hence reducing health risk. • Both plants showed higher tolerance and biomass in chronic exposure.