Aim of the study:
Landfilling is an activity, which may threaten the destruction or contamination of the soil and water environment. Pollution can be generated both by leachate and by landfill gas. Legal conditions impose on landfill managers to monitor groundwater in the area of the landfills. The impacted soils and groundwater show high chlorides, sulphates, heavy metal concentrations especially as compared to natural hydrochemical background values. Monitoring results can be analyzed using pollution indicators. The objective of this study was to determine the quality of groundwater in a landfill in Wojkowice (southern Poland) using the Backman index.

Material and methods:
The novelty of the paper results from the use of a different range of parameters than initially included in the formula. The results of water quality monitoring for three piezometers from 2013-2020 were taken into account. The contamination index was calculated separately for each of the analysed water samples, taking into account the electrolytic conductivity and the concentration of total organic carbon (TOC), Cd, Pb, Zn, Cu, Cr and the sum of N-NO3, N-NO2 and N-NH4.

Results and conclusions:
The Backman index values range in the groundwater samples were -5.3 to 603. The value of the Backman index increases with the increase in the concentration of individual parameters in groundwater. In the case of heavily transformed areas, the water pollution index has high values, exceeding 3. The results of this index indicated that the quality of the groundwater around the landfill is bad. In the future, it is planned to expand the range of parameters for calculating the index.