Representativeness of the groundwater monitoring results in the context of its methodology: case study of a municipal landfill complex in Poland

A representative monitoring of groundwater quality is the basis for a reliable assessment of the impact of pollutant sources on groundwater. This is especially the case in the area around old closed landfills. A study of different methods of groundwater sampling was conducted at a municipal landfill site in Tychy-Urbanowice (southern Poland). The study compared the results of the electrolytic conductivity values obtained during vertical profiling both before and after purging with a passive bailer. The results obtained from the well volume approach after purging up to nine volumes of stagnant water in the piezometer were also taken into account, as were the results of the purging of water volume equal to the double volume of the filtered part of the piezometer. Particular attention was paid to the nested piezometers. The presented values confirm very large differences in the research results of both the sampling technology and the depth of sampling, the piezometer construction and its lithological profile and in the duration and intensity of the tests carried out. In order to determine the real-time variabilit