| Summary: | Global environmental concerns arise when marine deposits with fine-grained iron sulfide-rich sediments (FeS and FeS2), now situated above sea level, oxidize from anthropogenic lowering of the groundwater table. The oxidation of iron sulfides decreases the soil pH and the acidic environment of these Acid Sulfate Soils (AS) soils increase weathering and mobilization of metals into adjacent watercourses, lakes and estuaries. Low pH and enhanced concentrations of metals are known to influence water quality negatively, causing fish kills and reduced aquatic diversity. Sulfide rich sediments were deposited in the Baltic Sea after the last glaciation and are now abundantly found along the coasts of for example the Bothnian Bay as a result of isostatic rebound. Recent studies from Finland have stated associations between leached (AS) soils and increased concentrations of metals in estuary sediments, thus the effects are likely to be similar in Sweden. With financial support from the Interreg Nord project “Ecological restoration in coastal river basins in the Bothnian Bay” in cooperation with the Geological Survey of Sweden (SGU), sediments from three lakes and two estuarine sites in the Rosån catchment in Norrbotten county, northern Sweden, were sampled and analyzed with fpXRF, ICP-MS and LOI methods. Elemental concentrations and organic contents were compared to establish accumulation trends over time and relationships between metal concentrations in recently deposited sediments and potential influence from previously sampled (AS) soils. Correlations in time, to anthropogenic activity, such as ditching were also considered. A primary allover trend with increasing concentrations of Aluminum (Al), Arsenic (As), Cadmium (Cd), Cobalt (Co), Cupper (Cu), Iron (Fe), Manganese (Mn), Nickel (Ni), Lead (Pb), Rare Earth Elements (REE) and Zinc (Zn), was noticed in a majority of the lake and estuary sediment samples. With some site variation, also two discrete peaks at different depth, were found in the upper 20 to 30 cm of the ...
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