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Vt <br /> r <br /> sITASCA: <br /> Denver, Inc. <br /> sufficiently oxidizing conditions, such as in the presence of atmospheric oxygen, dissolved <br /> oxygen, or ferric iron. In contrast, carbonate minerals are more soluble, and the dissolution of <br /> carbonate minerals can occur regardless of oxidation state. If the system is not oxidizing, <br /> carbonate minerals may still dissolve and neutralization capacity will still be consumed, though <br /> sulfide oxidation may not occur. Furthermore, solubility controls may limit dissolved <br /> concentrations under some geochemical reaction environments. For example, gypsum and <br /> anhydrite (calcium sulfate minerals) are likely to precipitate from solution at the concentrations <br /> measured in deep groundwater at the Project (CC&V 2015). Any limits on solute release related <br /> to solubility constraints are not addressed in ABA testing. <br /> Regarding the third factor contributing to ABA uncertainty, ABA assumes that all sulfur minerals <br /> (or only sulfide minerals in some cases) contribute acidity in a manner similar to pyrite. In reality, <br /> some sulfide minerals such as sphalerite and galena may not generate acidity. Some soluble- <br /> sulfate minerals, such as gypsum and anhydrite, and insoluble-sulfate minerals, such as barite, <br /> do not release acidity at all.Therefore,the assumption that sulfate minerals release acidity in the <br /> same manner as pyrite is likely incorrect in the presence of sulfate minerals such as gypsum and <br /> barite. As described above, some studies elect to consider only the sulfide minerals when <br /> evaluating AGP in order to prevent false positives for AGP that can result from these types of <br /> sulfate minerals. However, acid-sulfate minerals such as alunite and jarosite may also contribute <br /> acidity,though they are relatively insoluble and thus typically generate acidity at rates lower than <br /> pyrite. In contrast, acid-sulfate salts dissolve nearly instantly upon being exposed to water and <br /> thus generate acidity at faster rates than pyrite. <br /> Regarding the fourth factor contributing to ABA uncertainty,carbonate neutralization is assumed <br /> to be fully efficient in the ANP calculation.This includes the assumption that 1 mole of carbonate <br /> neutralizes 2 moles of acidity, as shown in Equation 3.2. This is generally the case in acidic <br /> solutions because dissolved carbonate tends to form carbonic acid (H2CO3) under acidic <br /> conditions. However, under circumneutral conditions,the dissolved carbonate will primarilyform <br /> 15 <br />