Estimation of leakage of chemical elements from boreal acid sulphate soils

The amount of element leakage from young Finnish (boreal) acid sulphate soils was investigated using hydrochemical and geochemical approaches. These approaches gave similar results for S, Na, Mg, Al, Mn, Zn, Sr, Ni and Co, while Ca, La, Cd, U and Fe displayed higher leakage figures when using the hydrochemical approach and K, Cu, Ba, Ga, Sc, Ti, Pb, Th and Tl higher ones when using the geochemical approach. Total reducible sulphur (TRS) was the dominant sulphur species in the parent sediment and in the transition zone, while in the upper oxidised zone it had to a substantial extent been oxidised into sulphuric acid and subsequently leached, giving rise to typical AS soils and waters. However, also in this zone there was a reservoir of TRS left, which shows that the soils still have a great oxidation and acidification potential. The combination of the two approaches gave a clear picture of the qualitative and quantitative leaching of chemical elements from the soils with more reliable results than if only one approach would have been used. The method applied here can therefore be recommended for future studies and environmental monitoring in areas affected by acid sulphate soils.