Geochemical background of potentially toxic trace elements in soils of the historic copper mining area: a case study from Miedzianka Mt., Holy Cross Mountains, south-central Poland

The aim of this study was to evaluate the geochemical background and spatial distribution patterns of selected trace elements (As, Cd, Cr, Cu, Mn, Ni, Pb, U and Zn) in 62 surface soil samples collected in the historic Cu mining area (Miedzianka Mt., Holy Cross Mountains, south-central Poland). In the study area the mining activity dates back to the fourteenth century. After the shutdown of mining operations in 1953, the soil was not remediated and neither its mineralogy nor chemistry was examined. The examined soils showed a high variability in the element concentrations. The threshold values defined as the upper limits of geochemical background range (mg kg−1 in parentheses) were Cr (63), Mn (2156), Ni (39), Cu (52), Zn (175), As (36), Cd (2), Pb (73) and U (1.9). A high percentage of the samples exhibited trace element concentrations above the upper limit of the geochemical background range. The threshold values were evaluated in this study with application of the iterative 2σ-technique. All of these values exceeded the standards recommended for soils in protected areas of Poland. The sampling points with anomalous concentrations of potentially toxic trace elements were located mostly in southern and western parts of the study area close to the sites of former mining activities. Very high concentrations of As, Cr and Ni at several sites may adversely influence the environment. High positive correlations between all the determined elements may be indicative of a common geogenic source of these elements and their geochemical affinity.