Attenuation of metals from mining areas by natural processes

Lead Author Lars, Lövgren
Institution Contact Department of Chemistry Umeå University SE-901 87 Umeå Sweden
Theme Theme 1: Vulnerability of Arctic Environments
Session Name 1.6 Strategies for ecosystem services and sustainable environmental management of soils and contaminated areas in the Arctic
Datetime Wed, Sep 14, 2016 02:15 PM - 02:30 PM
Presentation Type Oral
Abstract text The major cause of severe environmental impact of mining is oxidation of sulphide minerals in soils and residues from milling and processing of the ore (tailings) and waste rock. Oxidation results in extensive generation of, commonly acidic, metal laden leachates. To minimize these effects, it is necessary to undertake remediation measures, commonly aiming at reduced entrance of oxygen into the sulphidic materials and at neutralizing the acidity. This is a particular challenge in the Arctic due to the scarcity of fine-grained geologic materials and lack of alkaline industrial residues (e.g. ashes from combustion of wood products or residues from the pulp industry) which are suitable materials in this context. Instead, geochemical processes providing opportunities of natural attenuation of heavy metals can be of significance. This is about metal ions which can be re-associated to solid matter by precipitation of secondary solid minerals and adsorption to mineral surfaces. Within unoxidised tailings heavy metals may be immobilised from anoxic porewater by forming secondary metal sulphides or carbonates. Under aerobic conditions secondary iron minerals can remove metals from water by co-precipitation and adsorption processes. These natural attenuation processes can be important parts of barrier systems protecting recipients of discharged water. In this paper is presented and discussed results from field and laboratory studies aiming at determining the potential of natural attenuation processes. Unoxidized sulphidic tailings as well as secondary iron precipitates have been sampled at Swedish mines and investigated by various laboratory experiments.
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