Seasonal changes in the concentration of some trace elements in macrophyte shoots

Seasonal changes in the concentrations of trace elements (Ni, Cu, Pb, Zn, Cr and As) were analysed in shoots of macrophytes Myriophyllum spicatum, Najas marina, Potamogetoncrispus, Potamogeton lucens, Potamogeton nodosus, Potamogeton pectinatus and Nuphar lutea taken from lake Velenjsko jezero (Slovenia), an artificial lake resulting from mining activity. Lake lies in the vicinity of the Šoštanj Thermal Power Plant, from which fly ash slurry was transported by pipeline and emptied into Velenjsko jezero until 1983. The degree of concentration of elements in plant’s shoots varied according to the species of plant and the time of the season. The average concentrations of non-essential elements (Ni, Cr, Pb and As) in stems and leaves were the highest in Myriophyllum spicatum and the lowest in Nuphar lutea. Concentration of two essential elements Cu and Zn were the highest in the shoots of Potamogeton lucens and Potamogeton crispus respectively. Element concentration showed seasonal variation. For essential elements Zn and Cu there was a clear concentration decline from May to September in almost all macrophyte shoots, while non-essential elements remained at the same level or decreased through the season.