ACID-BASE PROPERTIES OF A LIMED PYRITIC OVERBURDEN DURING SIMULATED WEATHERING

Surface-mine reclamation is often hindered by the formation of acid mi nesoil and acid mine drainage from FeS2 oxidation, Surface soils conta ining FeS2 are often treated with crushed limestone (predominately CaC O3) to prevent acid minesoil formation, The main objective of this stu dy was to evaluate the long-term effectiveness of liming pyritic mines oil to prevent the formation of acid minesoil and acid mine drainage, Pyritic minesoils that did not receive lime became acidic very rapidly and produced acidic leachate, Almost all of the FeS2 in this treatmen t oxidized during the first 200 d, The addition of lime at a rate of 2 5% of the theoretical acid-base account (ABA) significantly slowed FeS 2 oxidation, but rapid oxidation ensued after the added lime was neutr alized, Treatments receiving a liming hate of 50% ABA or greater remai ned neutral to alkaline throughout the study, Acid-base values and res idual FeS2-CO3 data, however, indicate that the lime was dissolving fr om the system faster than the FeS2 was oxidizing, and all the treatmen ts would eventually become acidic. The results indicate that the limin g of a pyritic overburden to an ABA of 125% is not a sustainable solut ion to preventing acid minesoil and acid mine drainage.