Impact of Cyanide Utilization in Mining on the Environment

Abstract

Cyanide (CN ) is a toxic species that is found predominantly in industrial effluents generated by metallurgical operations. Cyanide’s strong affinity for metals makes it favorable as an agent for metal finishing and treatment and also as a lixiviate for metal leaching, particularly gold. These technologies are environmentally sound but require safeguards to prevent accidental spills from contaminating soils as well as surface and ground waters. In this work, total cyanide, sodium, cadmium, iron, zinc and copper concentrations were determined in soil, cassava, hand dug wells and pipe-borne water from Bibiani, a gold mining town in the Western Region of Ghana. Total cyanide levels in soil ranged from 6.04 to 26.17 mg/kg and in water, from 2.17 to 7.83 mg/L. Total cyanide concentrations in raw cassava ranged from 82.45 to 142.91 mg/kg fresh weight. The cooked cassava had cyanide concentrations ranging from 6.79 to 24.91 mg/kg and the cassava peels, 360.05 to 509.51 mg/kg. Sodium concentrations ranged from 998.1 to 1794.7 mg/kg in the soil, 25.94 to 29.92 mg/L in the water and 114.7 to 159.6 mg/kg in cassava. The concentration of iron in the soil ranged from 77.88 to 302.08 mg/kg whilst in water and cassava, iron was below detection limit. Copper concentrations ranged from 12.4 mg/kg to 115.4 mg/kg in soil, 4.6 to 6.0 mg/kg in cassava and below detection in water. The zinc concentrations ranged from 24.1 to 170.3 and 7.6 to 11.6 mg/kg, in soil and cassava respectively. Zinc was below detection in most of the water samples and cadmium was generally low in all the samples. The pH of the soil, water and cassava ranged from 3.88 to 6.95, 3.14 to 7.44 and 5.42 to 5.60 respectively. The moisture content of the soil ranged between 2.47 and 35.40% and that of cassava, 56.08 to 56.87 %. Electrical conductivity and total dissolved solids of water ranged from 34 to 155.5 μS/cm and 31 to 89 mg/L respectively. The results showed a correlation between the metal and cyanide concentrations in all the samples.