Acceptable Soil Baseline Levels in Taltal, Chile, and in Tampere, Finland

Soil geochemical baselines of potentially toxic elements were studied in two cities: Tampere in Finland and Taltal in Chile. Soil samples were sieved to the <2 mm grain-size fraction and the concentrations of As, Cd, Co, Cr, Cu, Hg, Ni, Pb, Sb, V and Zn were measured after aqua regia extraction. The upper limit of baseline variation was defined for the topsoils of Tampere and for soil samples from various lithological units in Taltal. Arsenic was the potentially toxic element of most concern in both towns. In both cases, arsenic concentrations were mostly geogenic. Anthropogenic activities related to the long mining history had caused elevated As concentrations in the topsoil samples in parts of Taltal city and soils surrounding abandoned mining wastes. In the case of this study, the geochemical baseline was useful to show the pollution level of As. Vanadium concentrations were also higher than the global average values in soils of Taltal commune. Heatmap plots based on compositional data analysis revealed that the abundance of mica minerals and soil organic matter controlled the distribution of most of the studied elements in Tampere, while the clustering of metals in Taltal was probably related to either abandoned mining sites or active mining operations. Regional baseline values should be used for the assessment of soil contamination with these elements in both cities.