Resistance of Organic Horizon to Acidification from Snowmelt in Podzolic Soil of the Kola Peninsula (6 pp)

Abstract

Background

The Kola Peninsula (the most northern region of the European fringe of Russia) is covered with podzolic soil and is considered the most sensitive area to acidification in Europe because of the low input rate of base cations by weathering. About 300 thousand tons of SO2 are annually emitted from stationary sources in this region. Acidic precipitation accumulates in the snow during winter, and acidic water suddenly flushes into the soil during spring snowmelt (so-called acid shock). It is therefore important to assess how the acid-sensitive podzol responds to an intensive increase in acid load. The main purpose of this paper is to show the observed data rather than to provide an analytical interpretation of the observed phenomenon.

Methods

Field sampling of the water as it passes through the canopy and forest floor were conducted in areas 7 and 260km away from the Monchegorsk smelter complex (a main emitter of SO2) during 1996-2003 in order to study in situ soil acidification in this region. The following parameters were measured: H+ flux, major base cations and total organic matter.

Results and Discussion

The H+ flux in the throughfall showed high values particularly in the snowmelt season (e.g. 31.61mg m-2 in June 2003). In spite of this acid shock, a considerable buffer effect was observed in the O-horizon. H+ fluxes in the soil water remained low (e.g. 2.80mg m-2 in June 2003) in this horizon. The main explanation for this phenomenon could be that the high value of H+ flux in throughfall was buffered by both base cation exchange and protonation of organic anions in the O-horizon.

Conclusion

Considering only the low input of base cations released from mineral weathering, podzolic soil may be classified as sensitive to acidification. On the other hand, considering also the neutralizing effect of organic matter in the first few centimeters of the litter layer, it is concluded that podzolic soil has a high capacity to act as an acid buffer during the snowmelt season under natural conditions.