Environmental factors affecting the acid neutralization capacity of Finnish glacial till deposits†

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Abstract
A batch titration method for acid neutralization buffer capacity (ANC) was used to monitor the stage of leaching and resistance to acid precipitation of surficial deposits. Four till profiles, including podzol horizons, were sampled at different geographical, climatological and environmental sites in Finland. The fresh samples (‐1 of H2SO4) in capped polyethylene tubes. After centrifugation and measurement of the pH in the tubes, the contents of leached elements were analysed using colorimetric methods for Fe(II), Al and Si, and flame‐AAS methods for other elements (K, Ca, Fe, Mn and Zn). A sequential extraction procedure at different time intervals was used for Fe oxides. The results indicate that the ANC is strongly affected by the environmental geochemistry of iron. The leaching of Fe from bedrock and sediments accompanied by seasonal and biogeochemical cycles, and rprecipitation of Fe is widespread in Finnish soils. As a consequence, the loosely bound Fe forms seem to constitute the main ANC factor in sediments. Occasionally Al as well as alkali and alkaline earth metals may contribute to the formation of ANC; in the uppermost soil layers, humic substances play the major role.