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Wr1ITASCK <br /> Denver, Inc. <br /> all acidity being generated based on pyrite oxidation and the efficiency of neutralization reactions <br /> (at least in a closed system). It only partly addresses issues related to relative rates of reaction, <br /> and it does not address the loss of alkalinity in an open system or behavior under different <br /> geochemical environments. NAG tests were conducted on the WRCS Phase II samples. <br /> 3.2.1 Methods <br /> In a NAG test, hydrogen peroxide is added to a ground portion of the sample, and the mixture is <br /> allowed to react and then boiled to ensure that the oxidation reactions are completed. The pH <br /> of the sample after it has been oxidized with hydrogen peroxide is called the "NAG pH."The NAG <br /> pH is indicative of the combined effects of sulfide oxidation and acid neutralization bythe sample. <br /> As per MEND (2009), samples are classified as PAG if their NAG pH is less than 4.5 and may be <br /> non-PAG if their NAG pH is greater than or equal to 4.5. There are multiple variations of the NAG <br /> test, and in this study, the sequential NAG test was chosen because it is designed to address the <br /> common problem of incomplete sulfide oxidation. In a sequential NAG test, sulfate is measured <br /> in the hydrogen peroxide solution extract, and the procedure is repeated until the sulfate <br /> concentrations in the extract approach zero. <br /> As part of the NAG test, after the sample has been oxidized and the NAG pH has been measured, <br /> a titration is performed to quantify the amount of acidity present in the leachate filtered from <br /> the sample mixture. The leachate is titrated with sodium hydroxide. The titrated acidity is <br /> referred to as the NAG, and values are reported in units of kilograms of sulfuric acid per ton (kg <br /> H2SO4/t). <br /> 3.2.2 Results <br /> The NAG test results are listed in Table 3-2, and NAG pH versus NAG is plotted in Figure 3-3. The <br /> original laboratory reports are provided in Appendix B. As shown in Figure 3-3, the NAG pH <br /> ranged from 2.0 to 8.1, with an average of 4.2, and NAG ranged from < 1 to 81 kg H2SO4/t, with <br /> an average of 25.5 kg H2SO4/t. <br /> 18 <br />