『Abstract
　The phosphorus release from surface sediments of eight lakes, mainly shalllow lakes in agricultural areas, was studied in laboratory batch experiments with additions of acetate and/or nitrate. The lake sediments could be separated into three categories. Some sediments did not release phosphorus under any conditions. The second category showed a high phosphorus release rate when acetate was added. in order to simulate bacterial activity and oxygen consumption. The addition of nitrate, only, stabilized the redox conditions and prevented phosphorus release. This pattern followed the classical theories of Einsele and Mortimer. The third sediment category released phosphorus up to some level which remained constant throughout the experiment, and was independent of acetate and/or nitrate additions.
　Several extraction procedures and adsorption-desorption experiments were performed in order to characterize the sediment phosphorus and thus explain the different behaviours of the three sediment categories.』

Introduction
Lake descriptions
Materials and methods
　Batch experiments
　Adsorption-desorption experiment
　　Fractionation of sediment phosphorus
　　Neutral hydrolysis in distilled water at 100℃ for 1 h
　　Hydrolysis with 1 mol^-1 HCl for 7 min at 100℃
　　Extractions according to Williams et al. (1976)
　　Extraction with nitrilotriacetic acid (NTA)
Results
　Sediment chemistry
　Batch experiments
　Adsorption-desorption experiment
　Fractionations of sediment phosphorus
Discussion
Summary
Acknowledgements
References