Assessment of heavy metal contamination of agricultural soils in Poland using contamination indicators

Heavy metals are considered a major pollutant due to their resistance to biodegradation, toxic effects on organisms, the fact that they can persist for long periods of time in soils and translocation. So far, no comprehensive, retrospective analyses have been carried out in Poland to assess spatial and temporal changes in contamination of agricultural soils with heavy metals (Cr, Cd, Cu, Ni, Pb, Zn, Co, V) using toxicity indices. The main objectives of the present study were to comprehensively assess the status of contamination of agricultural soils in Poland with selected heavy metals based on several indicators: Geoaccumulation Index (Igeo), Contamination Factor (CF), Potential Ecological Risk Index (ER), Enrichment Factor (EF), Pollution Index (PI) and Nemerow Pollution Index (NPI). Multivariate statistical analysis was also carried out, including principal component analysis (PCA) and descriptive statistics presented in box plots. Analyses were conducted over a period of 25 years at 216 study points within the framework of the chemistry monitoring of Poland's arable soils. This study will provide considerable assistance in the different soil types of Poland on the basis of toxicity indices. The presented research results show the spatial and structural diversification of soil contamination with metals and can be used in practice to formulate recommendations for rational soil use and planning investment activities in the field of environmental protection. In addition, these studies may be useful in the development of planning documents, especially in the development of postindustrial areas. At the analysed points, the potential toxicity of soils in relation to heavy metals was influenced by industrial activities in southern Poland (Upper Silesia) and south-western Poland (Lower Silesia); however, these exceedances affected few points (usually 2–3 of the 216 assessed). This situation persisted at these sites throughout the study period. The dominant type of contaminated soils was cambisols and phaeozems.