Assessment of heavy metals contamination in surface layers of Roztocze National Park forest soils (SE Poland) by indices of pollution

•Absolute content of heavy metals and pollution indices on the area of Roztocze National Park (RNP) were presented.•Forest soils of the area of the RNP were characterized by heavy metal enrichment, especially in organic horizon.•BGI values showed a high ability of the organic horizon for heavy metal accumulation in studied soils.•Indices of pollution showed heavy metals enrichment resulted from human activity as well as intrinsic soil conditions.

In most cases, in soils exposed to heavy metals accumulation, the highest content of heavy metals was noted in the surface layers of the soil profile. Accumulation of heavy metals may occur both as a result of natural processes as well as anthropogenic activities. The quality of the soil exposed to heavy metal contamination can be evaluated by indices of pollution. On the basis of determined heavy metals (Pb, Zn, Cu, Mn, Ni and Cr) in the soils of Roztocze National Park the following indices of pollution were calculated: Enrichment Factor (EF), Geoaccumulation Index (Igeo), Nemerow Pollution Index (PINemerow) and Potential Ecological Risk (RI). Additionally, we introduced and calculated the Biogeochemical Index (BGI), which supports determination of the ability of the organic horizon to accumulate heavy metals. A tens of times higher content of Pb, Zn, Cu and Mn was found in the surface layers compared to their content in the parent material. This distribution of heavy metals in the studied soils was related to the influence of anthropogenic pollution (both local and distant sources of emission), as well as soil properties such as pH, organic carbon and total nitrogen content.

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