Phytoremediation of Metals and Nutrients by Aquatic Macrophytes in an Urban Semiarid River (Mossoro, Brazil)

Abstract Urban expansion and riverbank anthropogenic pressures have intensified the elemental loading of urban rivers, a problem that is exacerbated in semiarid regions where low flows, long residence times, and evaporation favor solute concentration and changes in aqueous speciation. Here, we quantified nutrients and trace metals and assessed macrophyte bioaccumulation and translocation in the urban reach of the Apodi-Mossoró River. Water and plant tissues of Nymphaea alba and Eichhornia crassipes were collected in eight campaigns across six sites during dry and rainy seasons. The elemental suite comprised N, P, Na, K, Ca, Mg, Cu, Zn, Fe, Mn, Cd, Cr, Ni, and Pb. Descriptive statistics and multivariate analyses evidenced element-specific patterns driven by spatial gradients and climatic seasonality that influence metal mobility and bioavailability. Phytoremediation performance was species dependent: Nymphaea alba displayed higher bioaccumulation and translocation for Pb (16,669.64) and Cu (9.32), whereas Eichhornia crassipes showed greater accumulation and translocation for Cr (11,291.96) and Ni (23.23). Overall, the contrasting uptake and internal partitioning of trace metals, together with seasonal variability in nutrient concentrations, support the use of Nymphaea alba and Eichhornia crassipes as complementary biomonitors and as candidate species for phytoremediation of metal and nutrient contamination in urban semiarid rivers.