Spatiotemporal response and phytopotential of Typha domingensis for management of aquatic metal pollution on the Central African Copperbelt

Abstract

Anthropogenically accelerated metal pollution of lotic systems draining mining landscapes remains a global concern due to its non-degradability and ecotoxic nature. Nevertheless, the efficacy of macrophytes as indicators and remediators of metal(loid) pollutants in aquatic ecosystems in mining regions is recognised globally. However, in the mineral-rich Central African Copperbelt (CACB), there is limited research on the effectiveness of macrophytes for mining pollution management. Therefore, this study investigated the phytopotential of Typha domingensis Pers. (Typhaceae), as a nature-based approach for managing aquatic metal(loid) pollution on the CACB. A total of 252 samples each for sediment and T. domingensis were collected monthly between May 2022 and April 2023 from seven streams in the Kansanshi sub-catchment of the CACB and analysed to evaluate the spatiotemporal variability of the phytoindication and phytoremediation potential of T. domingensis for As, Cu, Pb and Zn in stream sediments. Metal(loid)s in T. domingensis at 71% of the streams were predominantly accumulated in the below-ground biomass with mean concentrations of 3–6 mg/kg As, 9–259 mg/kg Cu, 25–36 mg/kg Pb and 38–69 mg/kg Zn. The BAF was above 1 for As (0.8–2.6), Pb (10.7–24.3) and Zn (1.4–4.3), indicating T. domingensis as an accumulator of these elements but an excluder for Cu (BAF < 1). Additionally, TF was above 1 for As (1.5–2.0), Pb (1.4–1.5) and Zn (1.0–2.0), indicating the macrophyte's extraction efficacy. For Cu (TF < 1), the limited translocation characterised T. domingensis as a potential metal phytostabiliser. Similar seasonal trends for BAF and TF for As, Cu, Pb and Zn were also observed. Therefore, the spatiotemporal response of T. domingensis as a phytoindicator and phytoremediator of metal contaminants in sediments should be considered in the nature-based management of CACB's aquatic ecosystems.