Summary:

Presence in leachate waters very broad range of contaminants (both organic and mineral), causes, that the assessment of leachate composition is limited to indicators chosen by the researcher or imposed by regulations specifying the scope of monitoring. Comparing different objects can be facilitated by the Leachate Pollution Index (the LPI), which is calculated based on parameters, which have been acknowledged to have potentially the biggest impact on environment.
The paper presents a method of determining the value of the LPI, also in the case where the results of some of the required physiochemical analyses are missing. On the basis of the information available in literature as well as the author's own research values obtained for selected national landfills have been compared. Using Maślice municipal landfill site in Wrocław as a case study, changes in the level of the LPI linked with age and changing ways of using the landfill site have been analyzed.
The range of values of the indicator calculated for national landfill sites revealed extensive variation, however not diverging significantly from their Euro-pean counterparts. In all of the cases the leachate waters were characterizing high levels of chemical demand for oxygen (COD(Cr)), concentrations of ammonia ni-trogen and to some extent chlorides. The main effect of the closure and rehabilita-tion of Maślice landfill site was a decrease in COD(Cr) of leachate, which was
a major factor in the drop of the LPI level for that landfill site.