| Summary: | Abstract. Long Term use of mining peatlands in the north of Finland is raising a threat to the environment due to contaminant loading and its remobilization under specific conditions. In this study, we replicated two scenarios in two different sets of peat columns for understanding the contaminant mobilization (focusing on antimony and arsenic) that takes place in the treatment peatlands of a gold mine located in northern Finland. One of the sets was subjected to contaminant loading and leaching to observe the contaminant mobilization characteristics when inflow water composition changes. The other set was subjected to loading, draining, and leaching phases to represent a scenario of contaminant mobilization during the event of groundwater level depletion followed by high inflows to the peatland e.g., mine water after mine closure. In both cases, contaminant leaching was evident, and sulfate concentration was significantly high in the outflow compared to the inflow during the leaching phases. Arsenic and antimony leaching was not so high in numerical values throughout the cycles; however, antimony was found to leach more than arsenic. The results were similar in both sets of columns and it raises a major concern as in the long-term, contaminant leaching could disturb the environment in the area surrounding mines. As the contaminant leaching is also visible after the draining phase, controlled groundwater alternation can be a promising method to restore the treatment peatland to their pre-mining pristine situation. However, further research is required regarding setting up an intermediate step downstream of treatment peatlands to safeguard against the risk of leached contaminants reaching water bodies.
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