Aquatic macrophytes in Ethiopian Rift Valley lakes; Their trace elements concentration and use as pollution indicators

Abstract

Trace elements (TEs) uptake from water and sediments to 10 aquatic macrophytes in the Ethiopia Rift Valley lakes Koka, Ziway and Awassa was investigated to evaluate pollution of these lakes. Concentrations of Cr, Co, Ni, Cu, Zn, As, Se, Cd, Pb and Mn have been determined in leaves of macrophytes, water and sediment, using ICP-MS (Inductively Coupled Plasma–Mass Spectrometry). Principal component analysis showed an existing variation in TEs concentration in leaves of aquatic macrophytes. High concentration of Mn (1.6×103 and 1.2×103mgkg−1 dw) was found in Aeschynomene elaphroxylon of Lake Ziway and Eichhornia crassipes of Lake Koka, respectively. Cr concentration in low molecular mass (LMM) fraction of water and total sediment (4.9μgL−1 and 95±4mgkg−1 dw, respectively) was higher in Lake Koka compared to lakes Ziway and Awassa. Some of the studied macrophytes can accumulate high level of trace elements concentration compared to the surrounding, showing their potential to be utilized as pollution indicators. Most TEs in macrophytes used as animal feed, such as Echinochloa stagnina (Retz.) P. Beauv, were sufficiently low.