Water quality in the Björkdal gold mine recipient, northern Sweden

The Björkdal mine is the largest operating gold mine in the Skellefte district, Northern Sweden. One important objective of this study was to give a general description of dissolved and particulate metals (As, Cd, Co, Cr, Cu, Hg, Mo, Ni, Pb, V, Zn, Al) and sulfate in the Lillträskbäcken-Kågeälven system. Samples were collected from streams and tailings and compared to concentrations according to the Swedish EPA classification systems. Chemical analyses and leaching tests indicate that the tailings metal content is generally low, except for Cr, and tailings can be approved as suitable for construction purposes. This study shows general seasonal trends in element concentrations, pH and conductivity downstream of the mine. Metal concentrations increase during spring melt and periods of rainfall, and decrease during summer. In general, element concentrations decrease downstream of the mine property. To define background metal concentrations upstream of the Björkdal mine a new sampling station (St D) was created. Most of the metals in the discharge waters from the mining area are close to or do not exceed background levels, except for Mo, V and As, that fairly often exceed background levels at different sampling locations. Metal partitioning between suspended and dissolved phases was estimated. The result shows that close to the mine most elements dominate in the suspended phase, while the dissolved phase of As, Ni, V and Mo dominates at some stations. Element concentrations in the Björkdal area were compared with those in drainage waters from acid sulfate soils. The result shows that natural occurrences of acid sulfate soils can result in metal concentrations equal to or higher than those in the Björkdal area.Validerat; 20101217 (root