## 3 Results and Discussion
Figure 4: HR index values in years 2003, 2010, and 2021. The second selected index is the Nemerow Pollution Index. This indicator was calculated for 1995, 2003, 2010, and 2021 (Figure 5). The structure of the indicator, despite its simplicity, allows the degree of groundwater pollution in this area to be determined. The NPI values obtained for 1995 indicate that the downstream water of the piezometers was the most polluted. The calculated value for the P10 piezometer was more than five times that of the P2 piezometer. Figure 5: Nemerow Pollution Index values in 1995, 2003, 2010, and 2021. The following years in which the index was calculated made it possible to indicate the differences between the upstream piezometer (P16) and other localized piezometers. The year 2003 confirmed the further negative impact of the closed landfill. During this year, the value of the index for P10 was over 50 times higher than for the P2 piezometer. Figure 6: EF values in 1995, 2003, 2010, and 2021. In 2010 and 2021, it was possible to determine the pollution both in the upper and lower parts of the aquifer due to measurements from the nest piezometers. The P18 piezometer also operated in the same years. The results for both years are very different. The values of the index suggest that the quality of water flowing into the landfill has deteriorated (the NPI value in this period doubled in P16). At the same time, the results for all the piezometers, except for the P18 piezometer and for the nest piezometers monitoring the lower part of the aquifer, deteriorated. In 2010 and 2021, it was possible to determine the pollution both in the upper and lower parts of the aquifer due to measurements from the nest piezometers. The P18 piezometer also operated in the same years. The results for both years are very different. The values of the index suggest that the quality of water flowing into the landfill has deteriorated (the NPI value in this period doubled in P  
piezometer also operated in the same years. The results for both years are very different. The values of the index suggest that the quality of water flowing into the landfill has deteriorated (the NPI value in this period doubled in P16). At the same time, the results for all the piezometers, except for the P1 and P18 piezometers and for the nest piezometers monitoring the lower part of the aquifer, deteriorated. A big change took place within the P19A piezometer. The value decreased by about six times between 2010 and 2021. At the same time, for the P17A piezometer, the index value was about two times lower. Compared to other publications where the NPI was used [60; 61; 62], the obtained values are higher. This applies primarily to the water in piezometers P10, P17A, P18, and P19A. In the cited works, the index values for a single component rarely exceeded 1 when the main ions were not analyzed. In one work [61], values as high as those found in the landfill in Tychy were obtained for the ammonium ion. The Nemerow index was used in the work [63], which concerns a landfill located in north-eastern Poland (Podlasie Province). However, the authors of the paper used these other parameters to assess the value of the indicator: pH, electrolytic conductivity, total suspension, chemical oxygen demand, biochemical oxygen demand, total organic carbon, dissolved organic carbon, total nitrogen, total dissolved nitrogen, total phosphorus, and orthophosphates. In this article, high index values were obtained for chemical oxygen demand (about 20) and total organic carbon (5.81). The enrichment factor (EF) values varied considerably in the individual measurement years. In 1995 and 2003, the values obtained in most of the piezometers are comparable. Very high values were obtained in the P2 piezometer--about 18,000 in 1995 and almost 300 in 2003 (Figure 6). Within these two measurement years, the value of the indicators for water in the P9 piezometer decreased by six times, by more than four times for the P10 piezometer, and by more than 60 times for the P2 piezometer.