| Summary: | The industry of mining and metal production has always been in conflict with environmental issues. A problem of major concern is the contamination of freshwater around sulphide-bearing mine waste deposits. In northern Sweden many mine wastes originate from sulphide ores and thus generate acid drainage (AMD). The object of this study, Rävlidmyran pit lake, is an abandoned sulphide mine owned and operated by Boliden Mineral AB between 1951 and 1991. The aim of this study is to getter a better understanding of the aquatic system at Rävlidmyran. This is done by calculating a metal balance for the pit lake, determining the trace metal transport into the recipient Lake Hornträsket and reviewing how the water quality changes in the surface streams draining the area. Rävlidmyran pit lake is a meromictic flow-through water body with no surface inlets or outlets. Downstream of the pit lake, a waste rock dump acts as an embankment. The pit lake partially drains via seepage through the embankment and the outflowing water shows the characteristics of acid mine drainage (i.e. low pH and high levels of trace metals). Field data (pH, conductivity and temperature) were sampled at Rävlidmyran on a weekly basis from four groundwater pipes, five surface stream stations and from the surface water of the pit lake. Water samples were analyzed for total concentrations of Al, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, Hg, Mg, Mn, Na, Ni, Pb and Zn once a month. Additional sampling was performed for this thesis in September and October 2010, when field data was measured at six locations downstream of the pit lake and a profile was measured in the water column of the pit lake (at the deepest point). The metal balance is calculated assuming steady state regarding the pit lake water balance. Inflowing fluxes of water used in the mass balance are: deep groundwater, shallow groundwater and precipitation. Outflowing fluxes are: groundwater and seepage through the embankment. Metal concentrations for the inflowing and outflowing water fluxes are mainly ...
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