Pollution indices as comprehensive tools for evaluation of the accumulation and provenance of potentially toxic elements in soils in Ojców National Park

The Ojców National Park (ONP) is located nearby several currently operating, large industrial centres, which can be sources of potentially toxic elements (PTE). Over the last two decades, the ONP has been the subject of several studies. However, there have not been any comprehensive studies concerning the assessment of PTE-rich pollution within the soils of ONP; namely, what constitutes the basis for: i) determining the content, abundance, and distribution of PTE in soils within the park; ii) quantitatively estimating the degree of pollution of these soils using different indices; and iii) assessing the impact of the geochemical background as applied in indices of pollution. The PTE content of the soil samples analysed in this study showed that the ONP's surface A horizons were characterized by PTE values ranging from two to ten times higher than the measured levels in the C horizon. In order to comprehensively assess the degree of pollution, a wide range of pollution indices – Geoaccumulation Index (Igeo); Single Pollution Index (PI); Contamination Factor (Cf); Degree of Contamination (Cdeg); Potential Ecological Risk (RI); The Probability of Toxicity (MERMQ) and ‘Improved’ Nemerow Index (INI) were calculated using various types of geochemical backgrounds. High levels of PTE in soil were caused mostly by the influence of anthropogenic inputs from neighbouring (Kraków) and distant industrial centres (Olkusz-Jaworzno, Bukowno and Upper Silesia Industrial Region). Deposition of PTE-rich pollutants from local emitters is also determined to a large extent by the prevailing transboundary SW winds. The different distribution of PTE within the profile was dependent on the type of soil and its properties (texture, content of total organic carbon), as well as perhaps a reflection of a geochemical-anthropogenic anomaly occurring in the ONP region. Based on RI and MERMQ values, the area of the ONP should be subject to evaluation and further assessment of PTE pollution levels in order to minimize further exposure and contamination of the ONP. Furthermore, choice of the proper geochemical background plays an important role in the soil contamination assessment. Authors suggest applying of both the local and reference geochemical background in order to comprehensively assess the degree of soil contamination.