The groundwater in a shallow, unconfined, low-lying coastal aquifer in Santala, southern Finland, was chemically characterised by integrating multivariate statistical approaches, principal component ...analysis (PCA) and hierarchical cluster analysis (HCA), based on the stable isotopes δ2H and δ18O, hydrogeochemistry and field monitoring data. PCA and HCA yielded similar results and classified groundwater samples into six distinct groups that revealed the factors controlling temporal and spatial variations in the groundwater geochemistry, such as the geology, anthropogenic sources from human activities, climate and surface water. High temporal variation in groundwater chemistry directly corresponded to precipitation. With an increase in precipitation, KMnO4 consumption, EC, alkalinity and Ca concentrations also increased in most wells, while Fe, Al, Mn and SO4 were occasionally increased during spring after the snowmelt under specific geological conditions. The continued increase in NO3 and metal concentrations in groundwater indicates the potential contamination risk to the aquifer. Stable isotopes of δ18O and δ2H indicate groundwater recharge directly from meteoric water, with an insignificant contribution from lake water, and no seawater intrusion into the aquifer. Groundwater geochemistry suggests that local seawater intrusion is temporarily able to take place in the sulfate reduction zone along the freshwater and seawater mixed zone in the low-lying coastal area, but the contribution of seawater was found to be very low. The influence of lake water could be observed from higher levels of KMnO4 consumption in wells near the lake. The integration of PCA and HCA with conventional classification of groundwater types, as well as with the hydrogeochemical data, provided useful tools to identify the vulnerable groundwater areas representing the impacts of both natural and human activities on water quality and the understanding of complex groundwater flow system for the aquifer vulnerability assessment and groundwater management in the future.
A low-altitude aerial infrared (AIR) survey was conducted to identify hydraulic connections between aquifers and rivers and to map spatial surface temperature patterns along boreal rivers. In ...addition, the stable isotopic compositions (δ18O, δD), dissolved silica (DSi) concentrations and electrical conductivity of water in combination with AIR data were used as tracers to verify the observed groundwater discharge into the river system in a boreal catchment. Based on low temperature anomalies in the AIR survey, around 370 groundwater discharge sites were located along the main river channel and its tributaries (203 km altogether). On the basis of the AIR survey, the longitudinal temperature patterns of the studied rivers differed noticeably. The stable isotopes and DSi composition revealed major differences between the studied rivers. The groundwater discharge locations identified in the proximity of 12 municipal water intake plants during the low-flow seasons should be considered as potential risk areas for water intake plants during flood periods (groundwater quality deterioration due to bank infiltration), and should be taken under consideration in river basin management under changing climatic situations.
This paper presents the first attempt in Finland to collect detailed observations on surface water and groundwater interactions. We focused on a 10-km northeastern shoreline of Pyhäjärvi, where the ...potential groundwater discharge areas are associated with the esker aquifers. The methods used during 2008 and 2009 involved winter mapping, lake water and lake bed sediment temperature measurements, pH and electrical conductivity measurements, seepage meters, mini-piezometers, and chemical (PCE/TCE) and isotopic tracers. The main aims of this study were to compare the applicability of the methods used and evaluate the results obtained. The results from the various methods correlated and confirmed the groundwater discharge (4.69 x 10–5 cm s–1 to 4.80 x 10–3 cm s–1) into lake water at the shoreline. Further research is needed to obtain a quantitative estimation of groundwater seepage in Pyhäjärvi.
Areas of groundwater–surface water interaction in riverbanks and open mires are important habitats for groundwater-dependent species. In order to preserve these ecosystems, the planning and ...development of mining operations on such locations require a fundamental understanding of the groundwater discharge–recharge and flow patterns. In this study, 3D flow modelling and a TIR survey were used to define the groundwater discharge. Simultaneously, the flow modelling and groundwater table fluctuation were used for defining groundwater recharge at a mining development site in northern Finland. The results indicated flow towards the River Kitinen and the discharge of groundwater in the banks of the river. The discharge also occurred within the mire area, which may provide suitable habitats for groundwater-dependent plant species. The modelling results and stable isotope variations indicated complex flow patterns and a potential groundwater connection from the Viiankiaapa mire through possible bedrock fractures to the river. Recharge mainly occurred in the sorted sediment accumulations of the riverbanks and partly also in the mire area.
Complicated Quaternary sediment strata have been preserved within the ice-divide zone of northern Finland because of weak glacial erosion. Geographic Information System (GIS) databases, 3D modelling ...and ground penetrating radar surveys were used to construct the 3D structure of unconsolidated sediments and bedrock topography for Kersilö, Sodankylä, to provide information for freshwater management and environmental studies in the mineral exploration area. The model was created using a combination of explicit and implicit modelling covering an area of 10.5 km2. The surficial deposits in the study area are a few metres thicker than their average thickness in northern Finland. They include three till units and four sandy or gravelly units. Fluvial action has repeatedly deposited sorted sediments in the channel valley of the Kitinen river. Basins in the bedrock have preserved thick sediment packages (> 15 m), indicating that the bedrock topography controls the sedimentary features. Aquifers in the area are small and disconnected, and perched aquifers exist due to the low hydraulic conductivity of interlayered tills.
The effects of forest cuttings on the level of the groundwater table and the quality of groundwater in large aquifers in Finland were studied by interpreting the long-term data from three groundwater ...monitoring stations together with information about the forest management history. Groundwater nitrate concentrations increased after clear-cuttings and thinnings for several years after the operations. However, the nitrate concentrations remained low (< 2 mg l–1) even after the treatments. None of the changes in the groundwater level or in the other studied variables (electrical conductivity, alkalinity, pH, ammonium, chloride, sulphate, sodium, potassium, calcium and magnesium) could be attributed to the forestry operations.
One hundred wells, previously sampled 30 years ago, were selected in 5 areas of Finland with varying amounts of sulphur compounds in their rainfall. Samples were taken from the wells whose physical ...condition was also noted. Alkalinity and pH were compared statistically with previous results using the t-test. Both values had fallen in 4 of the areas, the exception being the one with low sulphur deposition. About half the wells suffered surface water intrusion, but when these were eliminated acidification was still evident. The number of wells yielding corrosive water, defined as pH, alkalinity and hardness (both mM per litre) of 6.7, 0.6 and 0.54 respectively, had risen in the 4 areas. This was most marked where sulphur deposition was highest. The totals had risen over the 30 years from 18 to 37. As the investigation covered only a small area, no general conclusion could be drawn for the whole country.
The purpose of this study was to examine the influence of parent sediment material on soil geochemistry and to locate possible pollution sources in the area of Turku town in southwestern Finland. The ...study area is glaciated terrain and subsurface samples were chosen to represent five different parent sediment materials: glacial till, glaciofluvial or littoral sand, clay, peat and marine mud. Elemental concentrations of surface (100 samples) and background soil (50 samples) were analysed by ICP-AES (Al, Ba, Ca, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, S, Sr, Ti, V) and by graphite furnace AAS (As, Cd, Mo, Se). Loss-on -ignition was determined as an indicator of organic matter. Analytical results were examined using multivariate statistical methods. The results indicate that the studied soils are not heavily contaminated; there were only few sample sites with elevated heavy metal concentrations. High Pb concentrations were observed along main traffic routes, and also in places where there has been small-scale use of antifouling paints. However, concentrations of heavy metals in topsoil were in general significantly lower than those measured in large cities elsewhere. The parent material strongly affects the geochemical character of the soils. Clays naturally have a significantly higher concentration of heavy metals than sands or till material. This is also reflected in concentrations in organic topsoil. When assessing target levels for polluted soil, the primary sediment appears to be a more important factor than the amount of organic matter.
This research is based on information about approximately a hundred dug wells in five different areas in Finland. The fallout of sulphur compounds has determined the choice of the areas and the goal ...is to find out the degree of acidification of ground waters. The current situation has been compared to that 30 years ago as there was an investigation concerning the same wells at that time. The pH-value and degree of alkalinity of well water have systematically diminished in all the areas - most of all in areas of major sulphur compounds fallout. The observations and areas being few in number, no decisive conclusions should be drawn concerning the whole country.
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