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and Assotlafes, Lt <br />• dissolution will increase [he overall solute concentration (i.e. TDS) and will yield equal Na` <br />and CI" contents when the solute compositions are reported in meq I"'. Ion exchange will not <br />directly elevate the overall solute content, but will result in increased Na` concentrations at <br />the expense of reduced Ca" and/or Mg" concentrations. Halite dissolution may be <br />represented as <br />NaCI = Na` + CI", <br />(6) <br />and ion exchange may be represented by reactions involving the sodium zeolite analcime, <br />2NaA1Si,06•H,O + Ca" = Ca(AlSi,06),•H,O + 2Na', (7) <br />2NaA1SiZ06 H,O + Mg" = Mg(AlSiZ06),•H,O + 2Na`, (8) <br />or clay mineral exchange which maybe represented as <br />Ca2+ + Na-clay = 2Na` + Ca-clay (9) <br />• Mg" + Na-clay = 2Na`+ Mg-clay (l0) <br />4.2.2 Groundwater Solute Compositions <br />The mean solute compositions of flowing surface waters and groundwaters for the l23 sites <br />that have been monitored over the years and from eight in-mine locations, which are <br />associated with fault-related groundwater inflows, are listed in Table 2. Locations of these <br />sites are shown on Plate 1. Not all of the locations shown on the Plate are listed in Table 2, <br />because incomplete solute data are available for some of the sites. The data in the table are <br />organized into three broad categories: surface waters, springs and wells, and in-mine <br />groundwater. Within each category the locations are further subdivided according to the <br />combination of type of location (i.e. stream, well, spring) and the lithology of the stream bed, <br />the spring discharge location, the open interval of the well, or the source of the in-mine <br />• <br />Charactenzation of Groundwater Systems in the V icinity of the Wes Elk Mine, Somerset, Colorado <br />29 January 1999 <br />Page 26 <br />