title: A multi-scale comparison of dissolved Al, Fe and S in a boreal acid sulphate soil.
abstract: Acid sulphate (AS) soils are most prevalent in the tropics, but the acidic discharge from cultivated AS soils also threatens water bodies under boreal conditions. Feasible options to reduce the acid load are needed. In this study, the groundwater of an AS field was monitored for 3.5 years, and the efficiency of waterlogging in mitigating the environmental risks caused by acidic discharge was investigated in a 2.5-year experiment with 10 monolithic lysimeters taken from the same field. In order to unravel the transferability of the results from lysimeters to the field scale, the Al, Fe and S concentrations in discharge water from the lysimeters were compared with those in the groundwater of the AS field (pedon and field scale), and in pore water (pedon and horizon scale). In the waterlogged bare lysimeters (HWB), the Al, Fe and S concentrations in discharge waters were broadly similar to those measured in the groundwater and followed the changes in the pore water. In the waterlogged cropped (reed canary grass, Phalaris arundinacea) lysimeters (HWC), in contrast, the discharge waters were markedly higher in Fe and lower in Al than the groundwater in the field. This outcome was attributable to the reduction of Fe(3+) to the more soluble Fe(2+) and the reduction-induced increase in pH, which enhanced the formation of Al(3+) hydroxy species. Lowering of the water table (LWC) caused soil ripening, which resulted in increased saturated hydraulic conductivity and porosity and enhanced the oxidation of sulphidic materials and acid formation. The responses of Al, Fe and S in drainage waters from HWC and LWC lysimeters resembled previous findings in AS soils. Based on this and the similarity between dissolved element concentrations in the discharge water of HWB lysimeters and groundwater in the field, we conclude that our monolithic lysimeters yielded realistic results concerning the efficiency of various methods in mitigating environmental risks related to cultivated AS soils.
authors.affiliation: Department of Food and Environmental Sciences, P.O. Box 27, Latokartanonkaari 11, Environmental Soil Science, FI-00014 University of Helsinki, Helsinki, Finland; Finnish Drainage Foundation, Simonkatu 12 B 25, 00100 Helsinki, Finland. Electronic address: seija.virtanen@tukisaatio.fi.
authors.forename: Seija
authors.initials: S
authors.lastname: Virtanen
authors.affiliation: Department of Food and Environmental Sciences, P.O. Box 27, Latokartanonkaari 11, Environmental Soil Science, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Asko
authors.initials: A
authors.lastname: Simojoki
authors.affiliation: Department of Forest Sciences, FI-00014 University of Helsinki, Finland, Helsinki, Finland.
authors.forename: Hannu
authors.initials: H
authors.lastname: Rita
authors.affiliation: Åbo Akademi University, Geology and Mineralogy, Domkyrkotorget 1, 20500 Åbo, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Toivonen
authors.affiliation: Department of Food and Environmental Sciences, P.O. Box 27, Latokartanonkaari 11, Environmental Soil Science, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Helinä
authors.initials: H
authors.lastname: Hartikainen
authors.affiliation: Department of Food and Environmental Sciences, P.O. Box 27, Latokartanonkaari 11, Environmental Soil Science, FI-00014 University of Helsinki, Helsinki, Finland.
authors.forename: Markku
authors.initials: M
authors.lastname: Yli-Halla
mesh_terms: D000535:Aluminum / Q000032:analysis*; D004784:Environmental Monitoring; D060587:Groundwater / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007501:Iron / Q000032:analysis*; D012987:Soil / Q000737:chemistry*; D013431:Sulfates / Q000032:analysis*; D013455:Sulfur / Q000032:analysis*
chemical_list: D012987:Soil; D013431:Sulfates; D013455:Sulfur; D000535:Aluminum; D007501:Iron
keywords: Aaluminium; Acid sulphate soil; Iron; Scales; Similarity; Sulphur