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detectable concentrations of Al.Fe,and Mn,although Fe and Mn are at or near the MDL of 0.02 2.0 <br /> and 0.01 mg/L respectively. The pH of the leachate appears to be independent of lixiviant pH, Al, dissolved + 3-dam(tailings-rich) <br /> since both the delta and 6-riser leachates have pH values of approximately 8.5(Figure 2). When + Delta(sludge-rich) <br /> the concentration of metals and other parameters in the leachate are divided by their initial &nser(sludge-rich) <br /> concentration in the lixiviant (C/C.; Figures 3, 4, 5) the two sludge samples show strong 1.5 + 6-dam(callings-dch) <br /> attenuation of Fe and Mn,but Ce and conductivity remain essentially constant. Aluminum <br /> concentrations do not show any consistent pattern in these two samples,as C/C,is greater then <br /> unity in the delta sample and less then unity in the 6-riser sample(Figure 3). u <br /> The tailings-rich sample leachates(3-dam and 5-dam)have low but detectable concentrations U 1.0 <br /> of Al,Fe and Mn. The 5-dam leachate has greatly elevated Mn compared to the other sludge and U <br /> tailings-rich samples,and a pH that is only one standard unit elevated over that of the lixiviant r"",,A....— <br /> (Figures 2,4). The pH of the 3-dam leachate is significantly higher than that of the lixiviant. <br /> Dissolved Ca concentrations are comparable to those of the sludge-rich samples. When the 0.5 <br /> concentration of metals and other physical parameters in the leachate from the 3- and 5-dam <br /> samples are divided by the initial concentration of the same analytes in the lixiviant,the two <br /> samples show strong attenuation of At and Fe. The behavior of Mn diffen between the two <br /> samples with the 3-dam sample showing strong attenuation of Mn. Mn concentrations in the 5- • <br /> dam leachate indicate progressively less attenuation of Mn u fluid-sludge ratios increase(Figure 00 <br /> 4) <br /> 0 5 10 15 20 25 <br /> 3.2 Results of leaching with pH 9 Uxivia t Fluid-sludge ratio <br /> Leaching of the two sludge-rich samples with pH 9 lixiviant resulted in leachate with At,Ca, <br /> acidity and alkalinity values comparable to those of the pH 7 leachate. Concentrations of Fe and 0.04120 <br /> Mn are at or new the MDL. Conductivity values at pH 9 art slightly lower than those at pH 7. <br /> The pH of the sludge leachate for the two samples varies between 7.9 and&7 and generally Fe, dissolved +'(ti87ngs-rich) <br /> appears to increase slightly with increasing fluid-sludge ratios (Figure 2). Plots of GC. t Delta(studge-rich) <br /> demonstrate effective attenuation of Fe and Mn(Figures 6,7). Aluminum shows a pattem similar 0.0015 �-&rise.isludge-rich) <br /> to that at pH 1,with the delta sample initially contributing Alto the leachate at low fluid-sludge + 5-dam(tailings-nch) <br /> ratios,progressively demonstrating At attenuation at elevated fluid-sludge ratios. The 6-riser <br /> sample effectively attenuates lixiviant At.although C/C.rises somewhat at intermediate fluid• <br /> sludge ratios(Figure 6)in a pattern similar to that at pH 7. Alkalinity is imparted to the leachate U 0.0010 <br /> by both sludge-rich samples. Calcium remains near unity for the delta sample,but is contributed V <br /> to the leachate by the 6-riser sample. I <br /> Leachate from the tailings-rich samples at pH 9 are characterized by low but measurable <br /> concentrations of At and Mn. Manganese concentrations for the 5-dam sample at pH 9 are more <br /> OF <br /> than two orders of magnitude lower than those at pH 7. Iron concentrations for both samples am <br /> 0.0005 <br /> below the MDL,Ca concentrations ere somewhat elevated in the 3-dam sample compared to pH • <br /> 7,and somewhat lower in the 5-dam sample. Alkalinity values for the two samples are comparable <br /> to the pH 7 values,and both samples show an overall reduction in alkalinity with increasing fluid- <br /> sludge ratios. The pH of the 5-dam leachate is below that of the lixiviant PH at all fluid-rock ratios 0.0000 <br /> (Figure 2), The pH of 3-dam leachate is elevated above that of the lixiviant and the leachate of the o 5 10 15 20 25 <br /> two sludge-rich samples. Plots of GC.show that Al,Fe and Ma are effectively attenuated by the <br /> two samples(Figures 6,7). Manganese is variably attenuated by the 5-dam sample,although there Fluid-sludge ratio <br /> is an indication of less effective attenuation as fluid-sludge ratios increase,similar to the pattern Figure 3. Plots of the concentration of Aland Fe versus fluid-sludge ratio in leachate derived fmm <br /> observed at pH 7 for this sample. Attenuation of Ca is accomplished by the 3-dam sample, the SBE for the four Ma flower samples, 8 <br /> although somewhat less effectively than at pH 7. Conductivity values remain at or near unity;the Y p s,using lixiviant with initial pH of 7. <br /> 5-dam sample CICe values remain constant with differing fluid-sludge ratios,conductivity C/C. <br /> values for the 3-dam ample decrease to unity with increasing fluid-sludge ratios(Figure 5). <br /> 660 I 661 <br />