Cyanide ion concentration in the effluent from two gold mines in Zimbabwe and in a stream receiving effluent from one of the goldmines

Abstract

Abstract Cyanide ion levels were measured in the effluent from two gold mines in Zimbabwe where the gold is extracted by the cyanide process, and at points along a stream receiving effluent from one of the Mines. Cyanide ion levels in the mine effluent were 2.1 x 10‐1g/L and 2.6 g/l at the two Mines. The levels in the stream were much lower at 2.6 x 10‐6g/L and <2.6 x 10‐7g/L about 500 meters and 1 km below the point were effluent enters the stream. The plot of log [CN‐] vs sampling point shows a rapid drop in cyanide concentration along the stream. Possible processes leading to the drop in levels of CN in the stream are discussed.