Laserfiche WebLink
<br />upper part of the table. Saturation Indices (SI's) are presented in the lacer part of the <br />table. <br />Sl ~ log <br />ion Aeti vtty Product <br />Solubility Constant <br />The Ian Acti vSty Product (1AP) is, as the name auggnats, the product of thermotlynamie <br />acts vi ilea of the ions directly TnvOived to the preei pS tati on or di asoluti on of the <br />mineral, When equilibrium exists, the ratio IAP to Sol uh111ty Constant (SC} equals 1, and <br />the 51 equals zero. When Sf 1a greater than zero, the water is probably supersaturated <br />with the mineral. A negative 51 indi tales undersa CUrati on. Because of analytical ar coca <br />and uncertainty in the theroodynamSc constants, an SI of Ot 0.5 is tomnonly interpreted as <br />reprasanti ng equilibrium, although this range is approxtmata. A blank in the table <br />indleatea that an 51 could not he calculated, either because an analysis or a eonsti tuent <br />element was not perforoed or the element was cwt present at concentrations above the <br />detection limit. The table inclutles SI's for only a fen roi nerals. The modal PHREEOE <br />actually calculates S1's for a ouch larger suite 'of minerals; those selected to be <br />• included in this table ware those that, for several different samplf ng sites, appeared to <br />be approxi mataly at aquilibri un with the waters analyzed. <br />Hi neral ogSc Controls. To illustrate the concept of aaturati on indices, consider the <br />analysts for the Spoil Spring i1. The water appears to be effectively at equilSbri um with <br />calcite, dolomite, and gypsum (CaC03, CaNg(C03)Z, and CaSO4 ~ 2HZ0). ,These minerals a~ay <br />be di seal vl ng or preefpt tali ng. Typically, calcite dissolves, p7 eci ng calci ws ions Sn <br />solution, which then combines with sulfate to fora gypsum. However, both nay Da <br />diaaol vtng; the analysts by itself does not provide suffi ct ant information to di sii ngui sh <br />whl ch is occurring. Conti nul ng down the list, SI's were not calculable for .otavite <br />(CdC03) and eerrual to (PbC03) because the di ssolvad concentrati ens were leas than Use <br />deteeii on limit. Tha water 1a effectively et equilibriw with f]uorite (Cafe), barite <br />(Ba504), nagnesi to (NgC03 ), and rhodochrosi to (MnC03). Saturation index ealeulaci ons <br />could not be made for gibbsite (A1(OH)3), because a]uminwo was not detected. Note the <br />dowl nanca of sulfate arM carbonate mi nera]s. <br />In general, the waters are at equilibrium with calcite and gypsum, indicating Nat these <br />minerals have an important role in determining the water chemistry in both the Nuela and <br />17-46 Revised 04/t1/88 <br />• REVISED MARCH 2006 Attachment 2.05.6(3)-2-55 <br />