Spatial Distribution and Mobility of Potentially Toxic Elements in the Soils of Romania

Illustrating the spatial distribution of potentially toxic elements (PTE) concentration in soil is not enough for understanding the environmental and human health-related issues. Mobility and speciation of PTE in soils are essential prerequisites for performing a complete risk assessment. This study aims to perform a correlation of the As, Cd, Cu and Pb total concentration in the soils of Romania from the European Soil Data Center (ESDAC) dataset with the soil pH from LUCAS Soil (the largest expandable soil dataset) in order to identify the PTE mobility and their associated risks. The spatial distribution maps of PTE emphasize the impact of the intensive mining activities performed in the Zlatna, Copsa Mica and Baia Mare areas. The multivariate statistical analysis shows a positive correlation between Cd and Pb and between Cu and As, as a specificity of the local ore deposits. In many regions where smelting and mining activities occur, are produced sulfates and sulfuric acid (due to sulfide deposits oxidation) that often lead to wet and dry deposition of sulfate species and of other pollutants. In the respective areas, the soil pH is low; therefore, the marginal histograms of the PTE in relation to soil pH reveal a high probability to mobilize the PTE that were once stable (as adsorbed or precipitated complexes, but not only). Even in the areas where PTE concentration is below the threshold values for soil, as stated in the national legislation, the correlation of their concentration with soil pH highlights the existence of associated risks.