Environmental impacts and acid loads from deep sulfidic layers of two well-drained acid sulfate soils in western Finland

摘要

Discharge from acid sulfate soils (a.s. soils) poses a threat to the living organisms of about 30 rivers in western Finland. Most agricultural a.s. soils in the country are well drained with subsurface piping at a depth of I m, resulting in oxidation of the sulfidic materials. Consequently, acidic solutes, hazardous to fish and other aquatic organisms, are effectively leached to watercourses. Many of the soils are not recognised as a.s. soils by international classification systems, such as the FAO-UNESCO system, Soil Taxonomy and the World Reference Base for Soil Resources (WRB), because the acidic horizon and sulfidic materials are too deep to be diagnostic. The purpose of this study was to (1) investigate the influence of sulfidic materials on the quality of drainage water where these materials are below the depth of the drainage pipes, (2) test the effectiveness of controlled drainage as a means to decrease the production of acidic solutes and (3) assess the criteria for a.s. soils in international classification systems against the actual characteristics of well-drained a.s. soils of Finland.