The likelihood nr phosphorus release from lake bottom sediments inio bulk water as a result or changes in the physicochcmical conditions in the lake has been analyzed by the method or sequential extraction proposed by Tessier et al. The procedure developed for estimation of the threat to waler ecosystems posed by heavy metals accumulated in the bottom sediments, can be successfully applied in estimation of the release or other substances, including biogenie ones, as the subsequent states of extraction simulate the abioric conditions and processes that can naturally take place in the near-bottom water layer and in the bottom sediment.

No adequate reaction has been observed of the decreased contaminant loads discharged by Łódź, particularly the loads of phosphorus, on its concentration in the Ner River. That’s why the im-pact of sediment on phosphorus content in the water was evaluated. Not only was the amount of phosphorus taken under consideration but also the equilibrium phosphate concentration (EPCo). The meaning of EPCo is that any phosphate concentration in the water below this value will lead to phos-phorus release from sediments. Performed study shows that in the Puczniew cross-section EPCo is higher then phosphorus concentration in water, thus with mean concentration of PO4 equal to 9.5 mg PO4·dm–3 phosphorus could be released from sediments. This concentration in Lutomiersk cross-section, however, equals 1.2 mg PO4·dm–3.