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the tailings. Clearly, all other factors being equal, if the ANP exceeds the AGP, net acid <br />generation by the tailings will not occur. These tests are called static test procedures. <br />There are several factors associated with these tests which must be considbred in order to <br />interpret the data obtained correctly: <br />1. Total sulfur is determined by the Leto furnace technique. This linvolves heating <br />the tailings, volatilizing all the sulfur as sulfur dioxide, and collection and <br />measurement of this gas. However, all sulfur species present in the tailings will <br />be volatilized. This includes sulfate, organically-bound sulfur $nd non-reactive <br />sulfide species, none of which will generate acid by air oxid~tion. The total <br />sulfur-based determination of acid generation potential is conservative and will <br />over-estimate the actual AGP of the tailings. <br />2. The acid neutralization potential is determined by taking a given mass of the <br />• tailings, adding acid of known concentration (by titration), and (determining the <br />ability of the material to neutralize this acid. The test protocdl gives a rather <br />limited time exposure of the acid to the material. Hence relatively slow acid <br />neutralizing reactions, such as aluminosilicate decomposition, aqe not accounted <br />for by the test. The results are likely conservative and somewhat underestimate <br />the actual acid neutralizing potential. <br />3. As noted above, offsetting the AGP and the AI3P (sometimes Called acidJbase <br />accounting), assumes "all other factors are equal" in the neu[tai~zation process. <br />However, chemical reactions and the liberation of chemical species to take part <br />in reactions are time dependent (i.e., they aze kinetically determmined). <br />From the foregoing description, it is apparent that tailings materials may be nodacid generating <br />if they contain nonreactive sulfur species, yet appear to be acid generating on the basis of static <br />testing. Therefore, kinetic testing is used as the second phase of assessment for 8cid generation. <br />13 <br />