Multivariate statistical approach to a hydrogeochemical characterization of the Virttaankangas aquifer, SW Finland

摘要

To reveal hydrochemical processes controlling water chemistry in the. large Quaternary Virttaankangas sedimentary aquifer two multivariate statistical methods, principal component analysis (PCA) and hierarchical cluster analysis (HCA) were applied to classify groundwater samples collected from 50 monitoring wells. The PCA results showed three main factors: (a) "calcite dissolution factor", (b) "anthropogenic factor", and (c) "silicate weathering factor". HCA was applied to PCA factor scores to delineate the spatial variability of hydrogeochemical data. HCA revealed six geochemically distinct clusters. Samples from clusters 1 and 2 show abnormality in water chemistry, whereas samples from clusters 3-6 show a division pattern related to hydrogeological units and flow paths. Inverse geochemical modelling with PHREEQC indicates that calcite dissolution is the most important reaction controlling water chemistry in fine-grained and coarse-grained units, whereas silicate weathering reactions are responsible for hydrochemical characteristics in the areas of littoral sand and perched groundwater.