Soil attenuation of the seepage potential of metallic elements (Cu, Zn, As(V), Cd, and Pb) at abandoned mine sites: A batch equilibrium sorption and seepage column study

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Soil attenuation of off-site leaching potential of metallic elements at the two abandoned mine sites was investigated using batch sorption and layered column studies. In batch study, the leachate concentration-specific sorption (<I>K</I> <SUB>d</SUB> <SUP>*</SUP>) by downgradient clean soils was in the order of Pb>Cu>Cd>Zn>As for DY site and Pb>As>Cu>Cd>Zn for BS site. In the layered (mine+clean) soil column, element elution was significantly reduced (e.g., no initial flush, retarded peak arrival, and lower peak concentration) while sulfate elution can be an indicator of the dissolution of sulfur-bearing minerals in mine soils. The greatest reduction was observed for Pb and Cu while the lowest was for Cd (2–19%) and Zn (6–51%), consistent with the batch data. Both the reduced elution at slow seepage and concentration drop after flow interruption support the time-limited propensity. In column segments, the sorptive elements (Cu, Pb, and As) were dominantly found in the inlet while less sorptive ones (Zn and Cd) in the outlet. Both batch and column data suggest that the element leaching with mine leachate movement can be greatly attenuated by the interactions with the surrounding downgradient soil during the seepage process.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Discharge of metals with leachate was greatly reduced by seepage through downgradient soils. </LI> <LI> Leachate acidity was also ameliorated during downward seepage. </LI> <LI> Negligible elution of Pb and Cu was due to their high selectivity on soil matrix. </LI> <LI> Both element release and its retention by clean soils were seepage rate-limited. </LI> <LI> Leachate sulfate levels can be an awareness of off-site mobilization of metallic elements. </LI> </UL> </P>