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A6 <br /> i <br /> in the form of ferrous sulfate complex , and other contaminants <br /> including numerous heavy and toxic metals . Radiochemical <br /> contaminants are strongly sorbed on aquifer clays and rarely move <br /> more than a few meters. <br /> The acid or core zone described above is characterized by an area <br /> in which all calcite minerals present in the soil column or rock <br /> have been dissolved and reacted and the ground water is similar <br /> in quality to that of the source. For the case of seepage into <br /> calcite-rich soil or rock , such reaction , and the resultant acid <br /> or core zone would be only a few meters in extent. By contrast, <br /> the second conceptual zone , termed the "neutralizing " zone, is <br /> the site of active calcite dissolution and the formation of <br /> chemical precipitates including metal hydroxides and gypsum. This <br /> Izone is further characterized by continuing high values of <br /> dissolved metals, in accordance with the order of metal hydroxide <br /> removal . The types of metals involved can be directly related to <br /> the resultant pH of the solution. The front and rear boundaries <br /> of this zone are not sharp lines , but rather tend to be zones <br /> which advance downgradient in response to chemical reactions. <br /> Radiochemical contaminants are generally absent , having been <br /> sorbed and coprecipitated in the acid zone. <br /> t <br /> Downgradient of the neutralizing zone is an area which can be <br /> i <br /> termed the "neutralized " zone , which is characterized by high <br /> iconcentrations of total dissolved solids , representing a <br /> saturated calcium sulfate solution . The area is further <br /> i <br />