| Summary: | The groundwater composition in Impoundment 1 at the Kristineberg mine in northern Sweden was studied. Two types of soil covers have been applied on the impoundment, and data from four groundwater pipes was interpreted (pipe P as reference pipe for pipes L, O, and K). Significant variations in groundwater quality were observed even when the same remediation method was used. Iron, Mn, Al, S and Zn showed concentration maxima suggesting that a wash-out of weathering products occurred as a result of the raised groundwater level in the impoundment. Copper appeared to be secondarily retained in the tailings, possibly due to an increase in pH resulting in sorption and/or co-precipitation of Cu. The general decrease in elemental concentrations with time suggests a decrease of sulphide oxidation and inflow of less contaminated groundwater into the impoundment. The groundwater sampled in till underlying Impoundment 1 is most likely affected by groundwater seepage from the overlying tailings. This is indicated by an increase in the concentration of dissolved organic carbon with time, which is interpreted to be a result of groundwater seepage through a layer of peat underlying the tailings. Validerat; 20101217 (root)
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