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I~ <br />~r <br /> <br /> <br /> <br /> <br /> <br /> <br />IJ <br />^ <br />1 <br /> <br />^ <br /> <br /> <br />- 4 - <br />Carbonates commonly involved in the neutralization prociess <br />include calcite (CaC03) and dolomite (CaMg(C03)p), and infrequent~y, side- <br />rite (FeC03). The dissolution of carbonates in strong acid is a pseudo - <br />first order reaction and; therefore, rates of dissolution are proportional <br />to the surface area exposed to acid (34). <br />The rate of release of acidity from pyrite oxidation, ar~d alka- <br />linity from carbonate dissolution, may be quite different and could affect <br />the generation of acid mine drainage. Geidel (29) suggests that the <br />release of alkalinity is limited to a maximum value by the partial pressure <br />of carbon dioxide while the build up of acidity is not constrained. <br />Several methods have been developed to predict the formation of <br />acid mine drainage despite an incomplete understanding of the initial step. <br />These include both static tests, which examine the balance between acid <br />producing materials (sulphides) and acid consuming materials icarbonates), <br />and kinetic tests which attempt to model the acid producing and consuming <br />reactions over time. A summary of tests routinely used to predict acid <br />mine drainage formation are shown in Table I. In general, static tests are <br />used more frequently due to their simplicity and low cost. Results from <br />the static tests are easy to interpret but may not be representatiwe of <br />natural reactions. Failure to account for different acid producin~al and <br />consuming reaction rates are suggested as a major drawback to Lhe lase of <br />these methods (24). Kinetic metfiods, on the other hand, may present a more <br />realistic model of natural reactions but are expensive, and resultsc may be <br />difficult to interpret. <br />In this paper, two techniques are compared, acid/base accounting <br />(static) and humidity cells (kinetic). The acid/base accounting ar~d B.C. <br />Research - initial test, are the most widely used methods to predict acid <br />mine drainage in both coal and hard rock mining in the United States and <br />Canada. <br />The humidity cell was developed in the United States for predict- <br />ing AMD formation in coal bearing rocks. In this study, we used the <br />r method to predict the formation of AMD for rock samples from hard rock - <br />1 <br /> <br />