THE USE OF AN OBJECTIVE INDEX FOR THE ASSESSMENT OF THE CONTAMINATIONOF SURFACE-WATER AND GROUNDWATER BY ACID-MINE DRAINAGE

Temporal and spatial comparisons of acid mine-drainage contaminated wa ters are difficult because of the complex physico-chemical nature of t he pollutant, and an objective index has been developed and evaluated for the assessment of such waters. The acid mine-drainage index is cal culated using a modified arithmetic weighted index utilizing seven par ameters which are most indicative of acid mine-drainage contamination, i.e. pH value, sulphate, iron, zinc, aluminium, copper and cadmium. W eighting is used to express the relative indicator value of each param eter. pH and sulphate are considered to be of greatest indicator value as they are unaffected by sorption processes, while sulphate is also unaffected by natural neutralization processes. The acid mine-drainage index, as proposed, is designed to detect and quantify contamination from acid mine drainage, and to help categorize samples, quantify impa ct and to monitor the recovery of receiving waters.