Nitrogen effluents from mine sites in northern Sweden - environmentaleffects and removal of nitrogen in recipients

摘要

Mine water may contain elevated concentrations of nitrogen caused byundetonated ammonium nitrate-based explosives and the cyanide used in goldextraction. The aims of this paper are to give an overview of a Swedishresearch program addressing environmental issues regarding nitrogen inwaters receiving mining effluents and to present preliminary data from the twofield sites in the project. The program runs during the period 2008-2011 andwill be performed in cooperation with the mining companies LKAB, BolidenMineral and Adolf H Lundin Charitable Foundation. It consists of fourintegrated research tasks, concerning release, transformation and removal ofnitrogen from mine water through denitrification and ammonia volatilizationin cold climate. Fieldwork will be carried out in two waters receiving miningeffluents with high concentrations of nitrate-nitrogen (≤25 mg/L) andammonium-nitrogen (<≤15 mg/L) from the Kiruna and Boliden mine sitesrespectively. Part of the fieldwork includes year-round water sampling and thestudy of yearly variations of the distribution of phosphorus, nitrate andammonium in the water column of clarification ponds and lakes. Laboratorystudies include the investigation of the relative importance of nitrogen andphosphorus as limiting nutrient in recipient waters. Laboratory columnexperiments will be used in the design of a pilot-scale barrier system fornitrate removal in effluents from the Malmberget iron mine. Both nitrate-nitrogen and ammonium-nitrogen showed distinct seasonalvariations that could be explained by dilution effects, biological uptake anddenitrification/ammonia volatilization.