City of Vaasa

Sampling year: 2017

Sample media: topsoil (0–10 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 Vaasa. Altogether, 220 topsoil samples were collected from the city centre in 2017. 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 arsenic exceed the threshold value 5 mg As/kg (Decree VNa 214/2007) in 33% of the samples. An arsenic concentration exceeding the threshold value does not mean that the soil is contaminated but it is usually a trigger value to start assessment of soil contamination. Vaasa belongs to the South-Finland arsenic province and the elevated arsenic concentrations are mostly geogenic. Metal concentrations are usually low in urban soil in Vaasa. The concentrations of arsenic, mercury, cadmium, chromium, copper, lead, vanadium and zinc in single urban soil samples exceeded the threshold values given in the Decree (VNa 214/2007). Concentrations in some samples exceeded even the guideline values.

The upper limit of baseline variation 11 mg As/kg can be used as trigger value for urban topsoil in Vaasa. Because of the small number of samples, trigger value could not be calculated for various urban soil types separately. The threshold values given in the Decree (VNa 214/2007) can be applied for all other metals in Vaasa, while the upper limit of baseline variation was lower than the threshold value for all elements. Upper limit of baseline variation was calculated for several elements that are not included in the Decree.

Report

Tarvainen, T. & Eklund, M. 2017. Vaasan taajama-alueiden maaperän taustapitoisuudet. Geologian tutkimuskeskus. Arkistoraportti 66/2017. 41 s. https://tupa.gtk.fi/raportti/arkisto/66_2017.pdf

Upper recommended limits of baseline variation (SSTP) of selected elements in soils of City of Vaasa and the threshold values (Decree 214/2007).