Changes in the forms of metal occurrence in bottom sediment under conditions of artificial hypolimnetic aeration of Rybnik Reservoir, Southern Poland

The content of metals in carbonates, sulfides, exchangeable, adsorbed and organically bound forms was determined in bottom sediment by means of a sequential chemical extraction method after Rudd et al. Cadmium, nickel and copper was found mainly in the forms of sulfides (Cd > 40%, Ni > 30%, Cu > 70%), chromium and zinc in the fraction of carbonates and sulfides. Manganese was attributed to an organically bound form (25%), carbonates and sulfides. Iron had a very small contribution of the exchangeable and adsorbed forms (<1%); sulfides contributed the most (40-45%). Lead was found mainly in the fraction of carbonates (about 35%) at all sites. Aeration of the hypolimnetic water caused only slight changes in the forms of metal occurrence in the bottom sediment.