Laserfiche WebLink
be positive (and thus will have the potential to attract the negative bromide ion) only <br /> if the pH is very low. <br /> Drever (1988, p.89) lists the pH at which several common geological materials switch <br /> the charge on their surface from negative to positive. Quartz only has the potential <br /> to attract anions if the pH is below 2.0. Kaolinite (a clay) only has the potential to <br /> attract anions if the pH is below approximately 3.5. Montmorillonite (a clay) only has <br /> the potential to attract anions if the pH is below 2.5. Smectite (a clay) will not attract <br /> anions at any pH. However, in goethite (iron hydroxide), which exists near spring <br /> discharge zones, the negative to positive transition occurs at a near neutral pH. <br /> Bromide will not naturally be selected for adsorption even in those unusual <br /> circumstances when anions have the potential to be adsorbed. Divalent anions are <br /> strongly favored for adsorption over monovalent anions (Drever, 1988, p. 218) and <br /> among the monovalent anions, chloride and fluoride would be adsorbed preferentially <br /> over bromide. Sulfate is a divalent anion which is common (typically in excess of 900 <br /> ppm) in waters in the Sunnyside Mine. Hence, sulfate is not only preferentially <br /> adsorbed, but it exists in concentrations three orders of magnitude greater than the <br /> proposed bromide concentrations. Thus, other anions which are more strongly <br /> adsorbed than bromide will have already filled available adsorption sites and bromide <br /> will not displace these other anions. <br /> V <br /> I:\ADMIN\WP\DIANE\BROMIDE.RPT 7 <br /> NNl HYDRO-SEARCH, inG A Tetra Tech Company <br />