Geochemical baselines
Sample media: topsoil (0–5 cm) and subsoil (50–100 cm): concentrated nitric acid extractable concentrations from the <0.06 mm grain-size fraction
Land use: topsoil samples represent urban soils rich in organic matter; subsoil samples represent natural soil (background values)
The University of Turku studied geochemical baselines in the Turku region in co-operation with the cities of Turku, Naantali, Raisio, Lieto and Kaarina.
Background values are available from 50 sampling sites for subsoil or sediment. The sampling sites represent the natural soil parent materials of the mapping area. Background samples were taken from a depth of 50–100 cm from soil parent material. Each analytical sample was composed of 3–4 subsamples. The subsamples were taken from an area of ca. 100 square metres. Background samples represent the following soil parent materials or sediment types:
A. Till samples (n = 13). Glacial till samples were taken from a sandy end moraine formation in the southern part of the mapping area. Some samples represent the washed upper part of the till layer, while other samples were taken from basal till.
B. Sand samples (n = 10). Glaciofluvial or littoral sand samples mainly represent terraces related to the Baltic Sea stages, while some samples represent primary glaciofluvial deposits
C. Clay samples (n = 19). Clay samples were mainly taken from areas that have been deposited in the brackish Litorina Sea.
D. Peat samples (n = 4). Peat samples were taken from Sphagnum bogs
E. Marine mud samples (n = 4). Marine mud samples were taken from surface sediments close to the estuary of the River Aurajoki, Pitkäsalmi and Airisto representing recent sediment deposition
Topsoil samples were taken from 100 locations. The samples were taken from the uppermost 0–5 cm layer with a spade. Each analytical sample was composed of four subsamples.
Samples from Turku were sieved to the <0.06 mm grain-size fraction before analysis. The concentrations can be different from soil samples that are sieved to <2 mm size fraction before analysis. Thus, the samples from the Turku district have not been stored in the TAPIR database. The trace elements concentrations are probably higher in the <0.06 mm fraction compared to the <2 mm fraction.
Publication:
Salonen, Veli-Pekka; Korkka-Niemi, Kirsti 2007. Influence of parent sediments on the concentration of heavy metals in urban and suburban soils in Turku, Finland. Applied Geochemistry 22 (5), 906-918
