Multi-Indicator Assessment of Heavy Metals Contamination and Ecological Risk Around the Landfills of the Boruta Zgierz Dye Industry Plant in Central Poland

This study assesses the extent of heavy metals (HMs) contamination and the associated ecological risks in soils surrounding waste landfills at the former Boruta Dye Industry Plant in Zgierz, Poland. Soil samples were collected during two sampling campaigns (summer 2023 and winter 2024) from 13 locations. Concentrations of Cu, Ni, Zn, Pb, and Cd were measured, and contamination levels were evaluated using several indices: geoaccumulation index (I geo ), pollution index (PI), pollution load index (PLI), Nemerow integrated pollution index (NIPI), ecological risk factor for a single metal (E r i ), index of potential ecological risk (ERI). The highest I geo value (10.95) was recorded for Cu in the area of the old landfill, which had been in operation for 90 years. The average PI values were Cu—120.97, Pb—52.46, Cd—46.70, Zn—22.19, and Ni—5.38, indicating considerable (3 ≤ PI < 6) to high (PI ≥ 6) contamination levels. The NIPI values, in descending order, were Cu (2102.2) > Pb (270.7) > Zn (88.3) > Cd (62.8) > Ni (21.5), all reflecting high (NIPI >3) contamination levels. The highest PLI was 5.10, with all remaining values exceeding the contamination threshold (PLI >1). The E r i value for Cu reached 14,852.75, indicating an extremely high (E r i ≥ 320) ecological risk. The average ERI value across the study area was 1347.2, suggesting a severe (ERI ≥ 600) ecological threat. These findings confirm that the industrial landfills associated with the dye plant constitute a critical pollution hotspot. The results underscore the urgent need for ongoing environmental monitoring, risk mitigation, and site remediation to prevent further environmental degradation and potential contamination of nearby water bodies.