The Kozi Brod (left tributary of the Biala Przemsza, east of Katowice) flows in a highly industrial coal-mining area dominated by the power plant of Siersza. Concentrations of the microelements nickel (Ni), chromium (Cr), cobalt (Co), zinc (Zn), manganese (Mn), lead (Pb), cadmium (Cd), copper (Cu),