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• pH. The soil reaction (or pH) of the gro+.vth mediwn significantly <br />affects the availability of essential nutrients in addition to the <br />solubility of potentially toxic ions. The pH ranges from extremely acid <br />(2.8) to moderately alkaline (8.2). The extremely acidic pH values <br />occur in the overburden and interburden when shallow coal is <br />encountered. Core hole site 2C, located near Mine Areas 2 and 3 had the <br />lowest pH values. Based upon the data presented in Tables 6-6 and 6-7 <br />and Figure 6-4 (also see Figure 6-3), pH values were determined on Phase <br />II samples and will continue to be determined on all. subsequent samples <br />collected at Nucla Mine. <br />Total Sulfur - Acid Base Potential. The sulfur content of overburden <br />and interburden is determined to predict the acid - producing potential <br />of this material. In conjunction with potential acidity, the <br />neutralization potential from alkaline carbonates, exchangeable bases <br />and weaLherable silicates is measured. After the potential acidity and <br />the neutralization potential are determined, an acid base balance is <br />• determined by subtracting the potential acidity from the neutralization <br />potential. <br />The sulfur content and acid-forming potential is greatest far the <br />interburden and also the 5 to 15 feet of overburden immediately above <br />the upper Dakota coal seam. Core hole site 2C located near .Mine Areas 2 <br />and 3, had the lowest acid base potential values (Figures 6-3 and 6-4). <br />These strata correlate well with the extremely acidic zones identified <br />previously in the pH section. Potential acidity and neutralization <br />potential were determined on all samples collected from (line Areas 2 and <br />3. Sulfur fractionation (i.e., pyritic, sulfate and organic) analyses <br />were performed when potential acidity exceeded the neutralization <br />potential and/or when the total sulfur content was greater than 0.5 <br />percent. <br />Ca, Mg, Na and SAR. The water soluble Ca, Mg and Na analyses reveal the <br />type and concentration of salt that exists in solution. The ion <br />• concentration is directly proportional to the soil conductivity. The <br />ratio of soluble Na to Ca plus Mg, referred to as SAR, is commonly used <br />to predict both chemical and physical properties of a growth mediwn. <br />6-25 Revised 3/6/81 <br />