Browsing by Author "Bigler, Paula"

Viiankiaapa mire, located in the municipality of Sodankylä, has drawn public attention after mining company, AA Sakatti Mining Oy published their discovery in 2011. The discovered Ni-Cu-PGE ore deposit, Sakatti, is located mainly under the Natura 2000 protected Viiankiaapa. Viiankiaapa is Natura 2000 protected due to the several natural habitat types and plant species one of these, H. vernicosus is known to thrive at the areas of groundwater influence. The Sakatti deposit is in exploration phase but it is possible that mining will start in future. Knowing the hydrogeology of the area is crucial for preventing possible negative changes if the mining starts. In this study the objectives were to study 1) the influence of groundwater at the western margin of Viiankiaapa, 2) the influence of Sakatti ore deposit to the hydrogeochemistry of the area, 3) the influence of hydrology and hydrogeochemistry to the endangered H. vernicosus species. The sampling was done in September and October 2016, March and April 2017 and continued in summer 2017. Samples were collected from surface water of the mire, groundwater, spring water as well as from different depth of peat pore water using mini-piezometer. EC, pH, temperature, stable isotopes, DSi, main ions, trace elements and dissolved organic carbon (DOC) were analyzed. The groundwater influence was visible at the area of Lake Viiankijärvi and Särkikoskenmaa fluvial sediment deposit. Depth profiles of stable isotopes and main ions indicated groundwater flow in deep peat layer and mixing with surface water as the groundwater flow upwards through the peat layer. At the Sakatti ore deposit area the isotopic composition of surface water samples represented mainly season’s precipitation with few exceptions. Possible groundwater discharge was visible at the area between Sakatti main deposit and River Kitinen as well as near Pahanlaaksonmaa. The isotopic chemistry of spring water samples at the bend of River Kitinen had values of mixed groundwater and surface water. It is likely that the mire water infiltrates through the peat layer and fluvial sediments and discharges to the springs and River Kitinen. The bedrock of the area is known to be weathered, which could explain surface water like isotope values in springs and in some of the bedrock groundwater observation wells. Positive correlation was found between H. vernicosus ecosystems and the depth of peat. A ribbon-shaped zone of habitats and 2 – 4 m thick peat layer crosses the mire. The correlation with groundwater discharge was not clear. Ca and Mg concentrations were smaller but pH and alkalinity were higher at the areas of H. vernicosus ecosystems. However the Ca and Mg concentrations resembled areal spring water chemistry, which could indicate groundwater influence. Areas without the ecosystems are located mainly near the Sakatti ore deposit. The influence of the deposit in hydrogeochemistry was locally visible as elevated electric conductivity, main ion and trace element concentrations of the surface water and peat pore water. This most likely explains why the areas without the ecosystems had higher element concentrations.