Seasonal variations of heavy metals in water, sediment, and organs of Vossia cuspidata (Roxb.) Griff. in River Nile ecosystem: implication for phytoremediation.

The present study aimed at investigating (1) the seasonal concentrations of heavy metals in different organs of Vossia cuspidata (Roxb.) Griff. in its main natural habitats in the River Nile ecosystem in Cairo, Egypt, (2) the bioaccumulation and translocation of heavy metals in the organs of V. cuspidata and its potentials as a phytostabilizer, and (3) the seasonal changes in the dry matter (DM) biomass of the organs. Two river islands were selected for seasonal sampling of water, sediment, and plant organs in eighteen randomly distributed quadrates (0.5 × 0.5 m each) during the period from February 2018 to January 2019. The total annual mean DM biomass was ≈ 18.7 ton ha. The aboveground organs had significant seasonal variations in DM biomass (p < 0.05). The belowground DM biomass represents 23% of the aboveground DM biomass. Belowground organs had the highest DM biomass values in winter for the roots (23.85 g DM m, 4.75% from the total DM) and spring for the rhizomes (108.96 g DM m, 37.3% from the total DM). Regardless of the heavy metals concentrations in water and sediment, V. cuspidata can accumulate Fe, Mn, Ni, and Pb at high levels. There was a statistically significant interaction between the effects of seasons and organs on the concentrations of Mn, Ni, and Pb at p < 0.001. The root was the main accumulating organ for the analyzed elements in the present study. Vossia cuspidata can transfer low concentrations of the analyzed metals from belowground to aboveground organs. We recommend V. cuspidata as a potential phytostabilizer to Fe, Zn, Mn, Cu, Ni, and Pb from the mainstream of River Nile.