AN OBJECTIVE INDEX FOR THE ASSESSMENT OF THE CONTAMINATION OF SURFACE AND GROUND WATERS BY ACID MINE DRAINAGE

Abstract

Temporal and spatial comparisons of acid mine drainage (AMD) contaminated waters are difficult due to the complex physico-chemical nature of the pollutant. An objective index has been developed and evaluated for assessment of such waters. The acid mine drainage index (AMDI) is calculated using a modified arithmetic weighted index using seven parameters most indicative of AMD contamination. These are pH sulphate, iron, zinc, aluminium copper and cadmium. Weighting was used to express the relative indicator value of each parameter. The pH and sulphate were considered to be of greatest indicator value as they were unaffected by sorption processes, while sulphate was also unaffected by natural neutralization processes. The AMDI as proposed is designed to detect and quantify contamination from AMD and to help categorize samples, quantify impact to receiving waters and to monitor recovery. The AMDI is fully evaluated and discussed.