Celje and Idrija stand out for the presence of pollutants in the soil

In June 2026, the Agency for Environment of the Republic of Slovenia (Arso) released findings from its annual soil quality monitoring program conducted in 2025. The results indicated that while most sampled locations showed minimal contamination despite industrial use, certain areas—particularly in the cities of Celje and Idrija—exhibited significant levels of heavy metal pollution. These findings were part of a broader effort to assess the impact of human activity on soil quality across 15 sites, including 13 industrial zones and two abandoned industrial areas. The study aimed to provide reliable data on the extent of soil contamination, changes in soil quality over time, and potential consequences of land usage patterns.

The monitoring process involved collecting soil samples from various regions across Slovenia, including Celje, Idrija, Šempeter in Savinjska Dolina, Ljubljana’s Litostroj area, Kranj, Podnart, Trebnje, Ilirska Bistrica, Zreče, Maribor, Murska Sobota, Krško-Vrbina, and Zgornji Brnik. At these locations, researchers tested for both organic and inorganic pollutants. Among the contaminants identified, inorganic substances such as arsenic, cadmium, chromium, copper, lead, zinc, and silver were found to be the most prevalent. Organic pollutants, however, posed less of a concern compared to their inorganic counterparts.

In particular, the highest levels of contamination exceeding legal thresholds were recorded in the upper layers of soil in Celje and Idrija. These areas exceeded critical immission values for several heavy metals, including arsenic, cadmium, chromium, copper, lead, zinc, and mercury. In contrast, the lowest levels of exceedance were observed in soils currently used for industrial purposes, suggesting that historical industrial activities might have had a more lasting impact than current operations.

The Arso agency noted that the elevated concentrations of pollutants in the soil were primarily attributed to past human activities, especially industrial practices and improper environmental management. Some locations exhibited signs of mixed soil composition containing artificial additives, which further complicated the assessment of contamination levels. For example, in Ilirska Bistrica, nickel levels surpassed the warning threshold, and this was linked to the underlying geological structure, where concentrations increased with depth. Similarly, in Šempeter in Savinjska Dolina, Ljubljana–Litostroj, Kranj, Podnart, and Trebnje, the measured levels of cadmium, zinc, and fluoride exceeded the regulatory limits.

To address modern contaminants, the monitoring included analyses of additional parameters associated with contemporary pollutants such as per- and polyfluoroalkyl substances (PFAS), cyanide, hexavalent chromium, and tetrachloroethylene (PCE). Despite expectations of higher concentrations due to industrial use, the measured levels of these modern pollutants remained low and well below international standards. In some cases, the detected concentrations were even below the detection limit, indicating minimal presence of these substances in the soil.

The findings highlight the complex relationship between industrial history and current soil conditions. While many areas showed relatively clean soil profiles, the presence of heavy metals in specific locations underscores the need for continued monitoring and environmental stewardship. The Arso agency emphasized that ongoing efforts would focus on understanding the long-term effects of past industrial practices and ensuring that future land use does not exacerbate existing contamination issues. This comprehensive approach aims to safeguard soil health and support sustainable development across Slovenia.