Temporal and spatial trends of heavy metal leakage from acid sulfate soils : Leakage of Ni, Zn, Cu and Fe to freshwater and marine sediments, North-eastern Sweden

Abstract: Acid Sulfate soils (AS) are recognized for being a source of acidity in freshwaters in America, Europe, Australia, and Asia. Apart from the problematic acid leachate, AS soil serves as a possible source of toxic heavy metals in freshwaters, a problem which has received far less attention than problems related to acid leachate. This study assessed to what extent heavy metals enriched in sediments from the area around lake Persöfjärden (North-eastern Sweden) could be attributed to export from AS soils. I found that: i) Nickel (Ni), Zink (Zn), Copper (Cu) and Iron (Fe) in the sediments had a partial likely origin from AS soils; ii) vertical variations in Ni, Zn, Cu and Fe concentrations suggested events of increased metal transport in the past; and iii) there is a tendency that Zn and Ni assumed from AS soils have caused elevated metal concentration in marine sediment deposited in Persöfjärden. Inferred sediment rates suggest that elevated metal concentrations occurred in sediment deposited during the 18-19th and 20th century. I argue that these periods correspond to periods of increased drainage of the AS soils during past agricultural activities in the catchment.