Department of Physics, Chemistry and Biology (IFM)

Eutrophication is a major issue faced in the water management services. In freshwater systems phosphorus (P) is the limiting element in the cause of eutrophication. Two main sources of P in freshwater systems have been identified; the external and internal sources. The external are mainly run-offs from farmlands, forestry and or sewage treatment plants. The internal, on the other hand, is mainly due to the release from sediments during certain environmental conditions, like depletion of Dissolved Oxygen (DO) and high pH.

Evaluating and estimating of P in sediments could be done by phosphorus fractionation, which gives an idea of how much P is readily available for biota and could be released in certain environmental conditions. 

In this study, a eutrophic lake, Lake Hällerstadsjön in the county of Östergötland, Sweden was studied with respect to sediment bound P. The Bioavailable P (BAP) as well as the sediment P flux from the sediment to the water column were studied by fractionation technique and incubation of sediments in both oxic and anoxic conditions, respectively. Spatial variation in the distribution of P forms in sediments was also studied, from the main inlet to the outlet. Sediment was collected at two depths, 0-5cm and 5-10 cm.

BAP was estimated to be 0.15 g P/Kg DM and 0.0812 g P/Kg DM for both 0-5 cm and 5-10 depth regions. Sediment P flux for oxic and anoxic were -6.43 µgd^-1m^-2 and 120.17 µgd^-1m^-2 respectively. Pattern of P distribution varied in both sediment depth and latitudinal transects- Data from P fractionation showed a trend of Residual-P > Al-P > Ca-P > Fe-P > Loosely-P.