SOIL ACIDIFICATION AND BUFFERING MECHANISMS IN THE BOREAL BIOGEOGRAPHICAL REGION
Authors: Ryunosuke Kikuchi and Tamara T. Gorbacheva
Abstract: Large tracts of land are in almost pristine condition in the Kola Peninsula, the most northern region of the European fringe of the Russian Federation, but mining and its associated activities release large amounts of sulfur dioxide and heavy metal pollutants to the surroundings. In-situ environmental monitoring was conducted in tree-grown areas (Picea obovata) 260 km away from the Monchegorsk smelter complex from 1999 to 2003 in order to observe the effect of pollution on forested podzolic land in the Kola region. Throughfall in these areas sometimes showed a strong acidity (below pH 4). It was observed that acidic deposition accumulates on the snow during the winter and snowmelt water with a high flux of hydrogen ions (about 30 mg/m2) streams into the soil in spring. However, the soil system showed a high acid neutralization capacity under natural conditions. That is, the flux of hydrogen ions in the soil solution varied between 1 and 3 mg/m2 throughout the year. As the amount of exchangeable cations in the podzolic horizon is comparatively low, attention was focused on the soil surface (litter layer of a few cm) to examine the high neutralization capacity. A laboratorial experiment was conducted. It follows from the obtained data that the mixture of young litter with old litter has a higher neutralization capacity than young litter. It is considered that the consumption of hydrogen ions by organic matter contained in the litter takes place as a main reaction, and the neutralization of the soil solution by cation exchange takes place in the litter layer as a side reaction. The event cycle of the soil (frost, freeze and thaw) no doubt has an important role in the soil system, but it is difficult to clearly characterize this role due to the multiple effects of biological, physical and chemical variables. In particular, its relation with the acid buffer effect of the litter is an important subject for future study.