Acid Sulfate Soils in Finland

Acid Sulfate Soils in Finland Measures to prevent and reduce damages

During the Holocene Epoch large areas of sulfide-bearing sediments were deposited under reducing conditions on the bottom of the Baltic Sea between Finland and Sweden. Because of the rapid postglacial land uplift (today up to 8 mm/a) in the area, a large portion of these sediments have been raised up to 100 m above current sea level. Due to reclamation, the upper 1-2 meters have generally been oxidized into acid sulfate soils (AS soils, minimum pH 3-4), giving Finland the largest known occurrence of AS soils in Europe, roughly 1000 km 2 using Soil Taxonomy criteria (Yli-Halla et al . 1999). It is well documented that these soils leach huge amounts of metals into watercourses (Österholm and Åström 2004), and for several heavy metals the amounts exceed the total metal discharge in effluents from the entire Finnish industry (Sundström et al . 2002) causing severe damage on the ecology.

Systematic mapping of AS soils in Finland has started in 2009 with the Geological Survey of Finland (GTK) as responsible partner and in cooperation with the Åbo Akademi University and the University of Helsinki. It was initiated after massive fish kills in 2006 and in order to meet the Water Frame Directive of the European Union, aiming at good chemical and ecological status of surface waters till 2015. A national strategy aiming at the elimination or reduction of damages caused by AS soils was published in 2011.

Acid Sulfate Soils and Mapping of them on GTK’s pages:

Projects: (in Swedish and Finnish) (in Finnish)

Doctoral program:

ASS landscape near Seinäjoki, 70 kilometers inland from Vaasa. Photo: Peter Edén 2011

Dark grey sulfidic sediment (potential acid sulfate soil) on light grey – brown sulfuric (oxidised) sediment (actual acid sulfate soil). Photo: Peter Edén 2008. 

Extent of the former Litorina Sea (8000 BP).  Nearly all indicated AS soils in Finland occur below the highest shoreline of the former Litorina Sea.