Confronting the vicinity of the surface water and sea shore in a shallow glaciogenic aquifer in southern Finland

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http://hdl.handle.net/10138/161976

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Luoma , S , Okkonen , J , Korkka-Niemi , K , Hendriksson , N & Backman , B 2015 , ' Confronting the vicinity of the surface water and sea shore in a shallow glaciogenic aquifer in southern Finland ' , Hydrology and Earth System Sciences , vol. 19 , no. 3 , pp. 1353-1370 . https://doi.org/10.5194/hess-19-1353-2015

Title: Confronting the vicinity of the surface water and sea shore in a shallow glaciogenic aquifer in southern Finland
Author: Luoma, S.; Okkonen, J.; Korkka-Niemi, K.; Hendriksson, N.; Backman, B.
Contributor: University of Helsinki, Department of Geosciences and Geography
Date: 2015
Language: eng
Number of pages: 18
Belongs to series: Hydrology and Earth System Sciences
ISSN: 1027-5606
URI: http://hdl.handle.net/10138/161976
Abstract: 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 delta H-2 and delta O-18, 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 delta O-18 and delta H-2 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.
Subject: GROUNDWATER RECHARGE
CLIMATE-CHANGE
COASTAL AQUIFERS
GEOCHEMICAL DATA
ISOTOPE RATIOS
LEVEL RISE
INTRUSION
IMPACTS
BASIN
LAKE
1172 Environmental sciences
114 Physical sciences
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