City of Kotka

Sampling year: 2023

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 Kotka. Altogether, 220 topsoil samples were collected from the city centre. 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 upper limit of baseline variation values of arsenic exceed the threshold values (Decree VNa 214/2007) in Kotka. The threshold values given in the Decree (VNa 214/2007) can be applied for all other metals in Kotka. Upper limit of baseline variation was calculated for several elements that are not included in the Decree.

 Report:

Tarvainen, T. 2024. Kotkan taajama-alueiden maaperän taustapitoisuudet. Geologian tutkimuskeskus. GTK Työraportti 10/2024. 38 s. https://tupa.gtk.fi/raportti/arkisto/10_2024.pdf

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

Soil parent material	As SSTP mg/kg
Sand (N=49)	6
Till (N=24)	10
Silt and clay (N=21)	7
Fill-derived soil, varying grain size (N=28)	4 (use value 5)
Fine-grained fill-derived soil (N=28)	6
Fill-derived soil rich in organic matter (N=70)	6
All soil parent materials, average (N=220)	6
Threshold value (VNa 214/2007)	5