Advances in acid drainage prediction using the net acid generating (NAG) test

A three year research project to evaluate and develop the net acid generating (NAG) test for identification and characterization of acid-forming mine rock and wastes is described. Samples from 17 mine sites from eight mining companies were tested. The 119 samples include process residues and rejects, waste rock, and ore. Samples were subjected to the following test procedures: pH and electrical conductivity tests, acid neutralizing capacity, total sulphur, net acid producing potential (NAPP), static and kinetic NAG tests, mineralogical study, and column leaching test work. The kinetics of the NAG test for predicting the exposure period required for development of acid conditions (field lag) under natural weathering is described. The results show that NAG test is simple, inexpensive, and suitable for field use. It is a separate test of acid generating potential, however, and not an alternative to NAPP. 9 refs., 7 figs., 2 tabs., 1 app.