ABSTRACT
626Many of the most difficult and expensive environmental problems faced by mining companies result from Acid Rock Drainage (ARD). Sulphide minerals such as pyrite and pyrrhotite are commonly associated with many ore types, and it is the oxidation of these minerals and subsequent leaching of their acidic oxidation products including sulphuric acid, that leads to ARD. Discharge of acid solutions from mine workings is usually known as Acid Mine Drainage (AMD). As if generation of acid itself is not of sufficient concern, the potential for widespread and possibly far-reaching environmental damage is aggravated in many situations, by the presence of ‘heavy metals’ such as copper, arsenic, lead and zinc which may dissolve in acidic solutions, thereby becoming mobilized and, potentially, ‘bio-available’.
