Background concentrations and spatial distribution of heavy metals in Albania's soils

This research aimed to determine the background and precautionary values of Cd, Cr, Cu, Ni, Pb, Zn, Co, As, and Hg and provide the spatial distribution of these metals in Albania's soils using statistical and geostatistical methods. Since the distribution of the data was commonly not Gaussian, they were transformed into their natural logarithm for deriving background concentrations and precautionary values. Background concentrations were defined as antilog of the median. Precautionary concentration values for soil protection were defined as antilog of 90th percentile of the ln-transformed data. Background concentrations in forest soils were larger compared to those in soils under other land use types. The largest background concentrations for Cd, Cr, Ni, Cu, Co, and Zn were found in forest soils formed on magmatic rocks, while largest concentrations of Pb and Hg were found in soils formed on flysch and molasse. The background values and precautionary concentration values (in brackets) (mg kg^-1) for agricultural soils across flysch/molasses and quaternary deposits were as follows: Cd 0.24 (0.82), Cr 131.63 (527.42), Cu 41.26 (72.75), Ni 287.15 (632.70), Pb 19.11 (284.86), Zn 81.80 (113.90). The largest background values for Cd and Zn were found in Phaeozems, for Cr, Pb, and Co in Luvisols and Cambisols, and for Cu, Hg, and Ni in Fluvisols. The proposed background concentrations and precautionary values complete the picture of metal contents in European soils, can be used as reference concentrations for the Albanian environmental legislation, and allow the identification of potential contamination hot spots.