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• <br />L~ <br />i• <br />Dominant Water Soluble Cations (Ca, Mg, and Na), SAR, and ESP. The water soluble Ca, Mg, <br />and Na analyses reveal the type and concentration of salt that exists in solution. The ion <br />concentration is directly proportional to the soil conductivity (USDA, 1969). The ratio of soluble Na <br />to Ca plus Mg, referred to as SAR, is commonly used to predict both chemical and physical <br />properties of growth mediums. The ratio is an indicator of dispersion, flocculation, porosity, <br />infiltration, permeability, erodibility, surface crusting, and seedling emergence. SAR reveals the <br />relative dominance of sodium in the soil water solution whereas ESP reflects the exchangeable <br />(reserve) sodium on the soil particle surface. These tests are complimentary and often <br />interchangeable (USDA, 1969). ESP is often determined only when the SAR is greater than 11. <br />Dominant Water Soluble Anions (Carbonate, Bicarbonate, and Sulfate). Sulfate is used in the <br />formation of many proteins and is therefore essential for both plants and animals. Sulfur is needed <br />by plants in about the same quantities as phosphorous. Spoils within the Northern Great Plains <br />Coal province are typically high in sulfate. (Barth et al., 1977). The sedimentary rocks in <br />association with coal seams will often yield substantial amounts of sulfate ions through the <br />oxidation of pyrite and/or marcasite. Sulfuric acid produced in the oxidation of pyrite and marcasite <br />is commonly dissociated and buffeted by the bicarbonate and carbonate ions dissolved from the <br />associated carbonate rocks, thus liberating sulfate ions into solution. The major portion of sulfate <br />found in spoils may be derived from the dissolution of gypsum. <br />The bicarbonate and carbonate ion content or alkalinity is generally a measure of buffering <br />capacity. Common sources of these anions are the solution of carbonate rocks, digenesis of CQ <br />from organic compounds, and CO2 from the atmosphere and soil. The presence of bicarbonate <br />verses carbonate is usually determined by the pH. Above a pH of 8.2, bicarbonate ions dissociate <br />to carbonate ions. Below a pH of 4.5, most of the bicarbonate ions are converted to carbonic acid <br />(H2C0,). In between these two values, carbonate ions will normally add H+ ions to become <br />bicarbonate ions (Dollhopf et al., 1981). <br />Carbonates and bicarbonates also increase the sodium buildup hazard in soils by precipitating <br />calcium and magnesium as carbonates which have an extremely low solubility. Elevated levels of <br />bicarbonate in soils (i.e., 10 meg/I) can also adversely affect sensitive crops (Traynor, 1980). <br />REVISED Auguat 2006 2.04.6-20 <br />