Geochemical baselines
Sampling year: 2012
Sample media: topsoil (0–25 cm): aqua regia extractable concentrations from the <2 mm grain-size fraction
Land use: various land use classes in the city centre
The Geological Survey of Finland (GTK) has investigated geochemical baseline concentrations in the city of Oulu. Altogether, 260 topsoil samples were collected from the city centre in 2016. The sample sites represented various land uses in urban areas. Samples were collected from 10-cm-deep pits. Concentrations for 40 elements were analysed after aqua regia extraction. In addition to that, carbon content and pH value were determined from all samples
The concentrations of metals and arsenic in urban topsoil were usually low. The concentrations of arsenic, mercury, cobalt, chromium, lead and vanadium in single urban soil samples exceeded the threshold values given in the Decree (VNa 214/2007). Concentrations in some samples exceeded even the lower guideline values.
The threshold values given in the Decree (VNa 214/2007) can be applied for all metals in the Savukoski-Pelkosenniemi region, while the upper limit of baseline variation was lower than the threshold value for all elements.
