Evolution of inorganic pollutants from landfills in shallow aquifers of different hydrogeological systems in Lithuania.

This study examines the patterns of evolution in inorganic macrocomponent speciation and the saturation state of the landfill leachate-polluted groundwater of three closed unlined landfills that are located in different hydrogeological systems (open, semi-open and closed) but are similar in both their volumes of landfill waste and the hazard levels of their landfill pollutants. Multivariate statistical analysis and geochemical modelling were conducted. The results showed that as the intensity of landfill pollution dispersion in groundwater along the flow path decreased, hydrochemical and hydrodynamic processes occurred with different intensities in open, semi-open and closed hydrogeological systems. In the open hydrogeological system, the processes of sulphate reduction, iron oxidation and chloride dilution and dispersion were up to 10-30% more intensive than those in the semi-open and closed hydrogeological systems. In the semi-open and closed hydrogeological systems, the processes of calcium, magnesium and iron carbonate equilibrium shifting towards carbonate precipitation were up to 15-40% more intensive than those in the open hydrogeological system. The results obtained in this research may be used to predict the dispersion of pollution in the groundwater of landfills located in similar hydrogeological systems and to facilitate the selection of prevention measures to limit pollution dispersion in groundwater.