Published online by Cambridge University Press: 15 February 2009
The concentrations of the Al, Co, Cr, Cu, Pb, Sn, Ni, and Zn trace metals were monitored in Lake Ipê (Brazil) during twohydrological sub-periods : June - December 1999 (low water period, LW), and January - April 2000 (high water period, HW).A detailed study of the physical and chemical state of the metals was performed through the MINTEQA2 computer programusing 15 abiotic parameters. An increase in concentration of many trace metals in July 1999 was due to the sudden entry ofallochthonous matter. The seasonal study showed that the metal concentrations in the lake were governed by the hydrologicalregime of the Paran· River (HW), and by the occurrence of occasional flood pulses and rainfall (LW).