Quaternary groundwater vulnerability assessment in Latvia using multivariate statistical analysis
2016
Retike, I., University of Latvia, Riga (Latvia);Latvian Environment, Geology and Meteorology Centre, Riga (Latvia) | Delina, A., University of Latvia, Riga (Latvia) | Bikse, J., University of Latvia, Riga (Latvia) | Kalvans, A., University of Latvia, Riga (Latvia) | Popovs, K., University of Latvia, Riga (Latvia) | Pipira, D., University of Latvia, Riga (Latvia);Latvian Environment, Geology and Meteorology Centre, Riga (Latvia)
Groundwater is the main drinking water source in Latvia, and Quaternary groundwater is widely used in households due to shallow occurrence. The identification of vulnerable areas is important for better water management and protection of deeper, more intensively used aquifers. The existing groundwater vulnerability map of Latvia does not take into account land use which can be an important factor affecting natural groundwater quality. Multivariate statistical methods - principal component analysis (PCA) and hierarchical cluster analysis (HCA) - were applied to identify groundwater groups with distinct water quality in Quaternary sediments in Latvia. On the basis of major ion concentrations and nitrogen compounds four distinct groundwater groups were identified. First group represents natural and most common calcium- magnesium bicarbonate water type in Latvia with low nitrate and ammonium concentrations. Samples from second and third group both reflect anthropogenic influence: diffuse agricultural contamination mostly with nitrates and/or contamination derived from artificial surfaces. Fourth group belongs to calcium bicarbonate water type and is characterised as a very young groundwater formed in sandy deposits. The results show that the highest concentrations of nitrogen compounds can be found in areas with agricultural land use or in artificial surfaces which are often classified as medium low or low vulnerability areas (mostly samples from group two and three). Meanwhile the lowest values of nitrogen compounds are present in areas where dominant land covers are forests and semi-natural areas or wetlands, and groundwater vulnerability classes are medium to high (samples from the first and fourth group).
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