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Section 2 <br />Investigation Approach <br />analysis is also)performed:,Sulfur measured in the various digestions is interpreted to represent •.. :. <br />different types of sulfur-containing minerals. The ABA method assumes that pyrite is the only <br />sulfide mineral present and that the pyrite is oxidized by oxygen producing four moles of <br />hydrogen (H+) per mole of pyrite as shown below. <br />FeS2 + 3.7502 + 3.5H20 -? Fe(OH)3(,) + 2S0?42- + 4H+ <br />Neutralization potential is estimated by adding a known quantity of hydrochloric acid (HCL) to <br />the sample followed by titration of the solution back to a pH of 8.3. The quantity of remaining <br />acid is estimated based on the amount of sodium hydroxide necessary to raise the pH back to a <br />value of 8.3. The quantity of acid consumed by the sample is the neutralization potential, which <br />is estimated by difference and expressed in units of tons per kiloton calcium carbonate <br />equivalent (t/kt CaCO3 eq). <br />In interpretation of ABA analyses, acidity produced by one mole of pyrite is assumed to be <br />neutralized by 2 moles of calcite, which results in a stoichiometric: conversion factor of 31.25 <br />t/kt CaC03 eq. per percent pyritic sulfur. This allows both the acrid potential and neutralization <br />potential of a rock to be expressed in equal units of t/kt CaCO3 eq. However, the acid <br />generation and neutralization reactions used in the ABA interpretation are not unique. <br />Therefore, interpretation of ABA analyses is commonly based on empirically derived <br />thresholds. These thresholds are based on the difference between the acid potential and <br />neutralization potential, referred to as net neutralization potential (NNP), and/or the ratio <br />between the neutralization potential and the acid potential (NP:AP). Commonly applied <br />thresholds for interpretation of ABA data include the following: <br />¦ NNP values relative to the potential to generate acid in the future: <br />¦ <0 t/kt CaC03 eq. indicates a high potential. <br />¦ 0 to 20 t/kt CaCO3 eq. indicates an uncertain potential. <br />¦ >20 t/kt CaC03 eq. indicates an unlikely potential. <br />¦ NRAP relative to the potential to generate acid in the future: <br />¦ <1 indicates a high potential. <br />¦ 1 to 2 indicates a moderate potential. <br />¦ 2 to 4 indicates a low potential. <br />¦ >4 indicates an unlikely potential. <br />These thresholds are used along with evaluation of mineralogical data in order to classify the <br />potential for the source material to generate acid in the future. <br />2.2.2 Total Metals Analyses <br />Total metals analyses measure the total concentration of particular metals or metalloids in a <br />rock. Total metals data do not provide specific information regarding the potential mobility of <br />cm 2-5 <br />TAS4986-Denison Mines\Task Order 3 - DMO Sampling and Analysis PIanlTask 3.12 - Soil, Ore, Rock Data Assessment ReporfiSunday Rock Feportlfinal reportAReporWhal Sunday Mines Group Soil Ore Rock <br />Data Assessment Report_061509.doc