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Understanding process water characteristics and variations is important for ensuring the quality of mineral processing of iron ore. Large amounts of water are used, and the quality of the water can be crucial for processes such as flotation, agglomeration and balling. In this study, changes and variations in process water geochemistry at the Kiirunavaara iron mine have been studied in a time series from 1989 to 2008. Long-term trends at single sampling stations in the process chain as well as changes along the process chain have been studied by statistical methods. This study also quantifies the amounts of major elements such as Ca, Mg, Na, S and Cl carried by process water and by magnetite grain surfaces to the end product, iron ore pellets made from magnetite ore.Ca, S, Na and Cl are the major elements in the process water, accounting for over 80% of the dissolved concentration. Ca has the highest concentrations with an average of 183 mg/l and a maximum of 303 mg/l in the clarifying pond. Corresponding values for S are 162 and 292 mg/l for Cl 132 and 250 mg/l and for Na 88 and 172 mg/l. At all investigated sampling stations (ingoing water and water in the sorting plant, concentration plant, pelletizing plant and clarifying pond) dissolved elemental concentrations increase over the time period. This increase is mainly caused by the increase in production. It is probable that the high concentrations of Ca and S are results of sulfide oxidation and calcite buffering in the drainage area, while the main source of Na, Cl, K and Mg is fluid inclusions liberated during milling of the ore. A prediction of future concentrations of Ca in the process water shows that in future production planning, it will be important to calculate on the basis of higher concentrations in the process water in the whole process chain than are present today. In addition, the amount of colloids (0.22µm – 1kD) in the process water was examined by ultrafiltration. The amounts of various elements sorbed to the magnetite surfaces were estimated by leaching with Milli-Q water, MgCl2, NH4-acetate and Na-acetate. The colloidal fraction was very small, a few percent. For Ca and Mg, sorption to magnetite surfaces was a much more important transport mechanism to the pelletizing process than evaporated process water, but for Na, and S process water was an important carrier.

Forest wildfires are important for the structure and functioning of boreal ecosystems including biogeochemical processes. During the last decades, natural forest fires have been successfully suppressed in Fennoscandia. Therefore, our knowledge on the biogeochemical effects of forest fires is limited. In August 2006, a 1500 ha forest fire occurred near Bodträskfors, northern Sweden. The intensity of the fire varied among vegetation types. Especially in areas dominated by pine forest of the lichen type, vegetation and the humus layer were burnt to a large extent whereas the impact in moist-wet forest patches was less pronounced. Burning and subsequent leaching of plant remainders was expected to affect local surface waters. The main objectives with this thesis were to: 1) investigate the behavior of water quality parameters (pH, conductivity) and dissolved major elements including TOC (Total Organic Carbon) due to leaching of burnt plant remainders and, 2) measure the dissolved concentration and isotopic composition of boron as a potential tracer of forest fires. The project was performed in 2007 – 2009 in a creek draining the burnt area. A creek in a neighboring catchment not affected by the fire was sampled as a reference. Both catchments are characterized by the same type of bedrock and soil cover.The results indicate that leaching of the burnt plant remainders was mainly contributing P, K, Ca and Mg to creek water run-off. This is consistent with the naturally high concentrations of these elements in plant tissue. Na was not leached to any greater extent. Compared to the reference creek, burnt creek concentrations of N were slightly higher and slightly lower for TOC. The pH was ~ 0.5 units lower in the burnt creek during all years of measurement. Conductivity was higher in the burnt creek in 2007 but had decreased to the levels of the reference creek in 2009. Conductivity appeared to be controlled by Ca and Mg concentration as the temporal variations of these parameters/elements were closely correlated. During leaching from burnt plant remainders, P and K concentrations showed similar variation with time. The co-variation of Ca and Mg concentrations marks another behavior but TOC and N each exhibit unique changes of concentration with time. P and K are important nutrients associated to the burnt biomass. This caused extensive leaching of these elements for more than three years after the fire. Ca and Mg are contributed from groundwater to a great extent which was the likely reason for the more short-term post-fire leaching of these elements. As N is also considered an important nutrient it was unexpected that leaching was not as extensive as for P or K. However, the release of N after disturbances in boreal forest catchments has previously been observed to be erratic and depends greatly on the properties of the soil. The hypothesized inhibited release of TOC to the burnt creek was not obvious and the pH difference between both catchments was not considered an effect of the fire. However, since sampling was not conducted for longer than three years after the fire it could not be ruled out that TOC and pH were influenced on a longer term than that.The dissolved B concentrations were substantially higher in the burnt creek in 2007 compared to the reference creek and the isotopic composition (δ11B) was lighter. δ11B was not measured in 2009 but the burnt creek B concentrations were only slightly lower relative to 2007. The measured concentration and isotopic composition of dissolved B in the burnt creek were in line with anomalies of B measured in lake sediments. These anomalies were concluded to be the result of leaching of burnt wood remainders. The lighter B isotopic composition detected in both the present and the previous studies is in line with other findings concluding that forest plants utilize mainly the lighter B isotope (10B) during nutrient uptake from the soil solution. This B is normally released during the winter season inducing a seasonal oscillation of δ11B in the soil solution. The seasonal variation of δ11B was observed in the results from the reference creek. The more extensive leaching of lighter B from the burnt plant remainders most likely caused the overall lighter B isotopic composition and higher B concentrations in the burnt creek relative to the reference creek.

Reclamation of mine sites is a very recent concept on the scale of mining history. It involves the prevention or mitigation of the environmental impacts from mining, and the establishment of sustainable post-mining uses of the land. Many methods have been tested to reduce the contamination from mining waste, but their actual performance depends highly on the nature of the site. In this thesis, the effectiveness of reclamation is investigated at Kimheden open-pit copper mine in Västerbotten, northern Sweden.Sulphide-containing waste rock left from the extraction of the ore was originally dumped on the surface close to the two open pits at Kimheden. The contact of sulphides with water and oxygen induced the generation of copper- and zinc-rich acid mine drainage. Therefore, reclamation of the mine involved backfilling of the mine waste into the open pits and covering with a till composite dry cover including a sealing layer, in order to reduce the oxygen ingress to the waste.Geochemical and geophysical studies conducted in 2009-2010, complemented by monitoring data from the mining company, were interpreted to assess the success of the reclamation. Long-term annual monitoring of the contaminated drainage by the mining company showed that concentrations of copper and zinc added together have decreased by more than 87% since the completion of reclamation in 1996. However, the decrease occurred rapidly, and metal concentrations in the last ten years have remained stable at values that are still not satisfactory for discharge into the environment. Furthermore, pH in the drainage increased only slightly after reclamation. In 2009, seepage water from one of the pits exhibited a pH of 3.0, and copper, zinc and aluminium concentrations of 3 mg/L, 0.3 mg/L and 20 mg/L, respectively. The partial success of the reclamation in mitigating the acid mine drainage may be explained by persistent oxidation of the backfilled mine waste in spite of the application of the dry cover. This would imply that oxygen gas or oxygenated water is still accessing the waste rock, either through the dry cover, or through fractures in the pit walls. These hypotheses were investigated in the field with two different geophysical methods, ground penetrating radar and direct current resistivity.With ground penetrating radar, good-quality image of the sealing layer could be obtained at one of the two backfilled pits, and no evident sign of disturbance in the layer could be found. Resistivity surveys succeeded to image the drainage from the backfill, and suggested that it was seeping out through the dry cover, with a risk of erosion of the sealing layer. Water discharge measurements and resistivity data indicated that the current channelling of the mine drainage to a treatment pond is inadequate, since a large proportion of the contaminated water disappears as groundwater. The interpretation of the resistivity profiles supported by archive data suggested that fractures in the bedrock close to the pits could explain the ingress of oxygen gas or oxygenated water through the pit walls, and would be the primary reason for on-going sulphide oxidation.The results of these studies may help to improve the reclamation of the mine, and in a broader perspective, provide information for reclamation at other sites.