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Mato and Associates, LC <br />• 4.0 SOLUTE AND ISOTOPE CHEMISTRY <br />4.1 Explanation of Chemical Reporting Units and Terms <br />Reporting units are milligrams per liter (mg 1') and milliequivalents per liter (meq I-') for <br />ionic solutes and per mil (%o) for stable isotopes. Stable isotopic reference standards are <br />Standard Mean Oceanic Water (SMOW) for S'H and 5180, Pee Dee Formation Belemnite <br />(PDB) for S"C, and the Canyon Diablo Meteorite (CD) for S"S. The radioactive isotope '"C <br />is reported relative to percent modem (1950) carbon (pmc), and the radioactive isotope'H is <br />reported in tritium units (TU). One TU is equivalent to 3.2 pCi I' (pico-Caries per liter). <br />In addition to the familiar mg I-' concentration unit, laboratory solute data have been <br />converted to meq I-' for analysis and reporting purposes. The meq I-' unit allows direct <br />• comparison of reacting concentrations of cations and anions. Conversion factors between <br />meq 1-' and mg I-' for major ions follow: <br />mea l-' M~-~ <br />Ca" 1 20.0 <br />MgZ' 1 12.2 <br />Na' 1 23.0 <br />K' l 39.1 <br />HCO, 1 61.0 <br />SO;- 1 48.0 <br />Cl 1 35.5 <br />From the conversion factors i[ is apparent that heavy anion molecules such as SO; and HCO; <br />contribute disproportionately to TDS relative to [heir reacting cation counterparts, such as <br />Caz+. <br />Characterization of Groundwater Systems in the Vicinity of the West Elk Mine, Somerset, Colorado <br />29 January 1999 <br />Page 23 <br />