Transfers between forms of sedimentary phosphorus induced by nitrate treatment

Summary

Sediments from accumulation bottom areas in Lake Finjasjön, Lake Vallentunasjön and Lake Balaton were treated with nitrate in order to evaluate the significance of mineralization for the transfers between forms of sedimentary P. Fractional composition of sedimentary P was determined before and after incubation with nitrate at 10 and 20 °C. NaOH-extracted organic P decreased with 47%, 33% and 43% corresponding to 16.2%, 12.8 % and 5.6 % of the total P content in the sediments of Lake Finjasjön, Lake Vallentunasjön and Lake Balaton, respectively, after incubation at 20 °C for 16 days. The liberated P was to a large part incorporated in bacterial biomass (41% to 66%). Concerning the Lake Finjasjön sediment about 50% of the decrease in NaOH-extracted organic P was transferred to iron- and aluminium-bound P. In Lake Vallentunasjön sediment both loosely bound P and calcium-bound P increased with about 2% of total P at 20°C. Loosely sorbed P increased with 2% of total P also in the sediment of Lake Balaton.