1. Introduction
In shallow lakes, sediments play an important role in determining water quality due to the fact that a unit volume of water with a larger amount of sediment has a larger sediment surface. Internal release from sediments can maintain high nutrient levels in water even after dramatic reductions in external loading (van der Molen and Boers, 1994 and Søndergaard et al., 2003). Phosphorus (P) in sediments, especially soluble reactive phosphorus (SRP), is significant to the internal release of nutrients in shallow lakes (Holdren and Armstrong, 1986). The SRP release in shallow lakes must be considered because it will considerably affect pelagic algae production (Søndergaard et al., 2003 and Smolders et al., 2006).