『Abstract
　The amount of potentially mobile phosphorus (P) in Lake Erken sediments was determined by P release experiments, and forms of mobile P were identified by P fractionation. Amounts and forms of this P were compared to P released by sediment diagenesis. Calculated on the top 30 cm of a sediment core, the amount of potentially mobile P was 5 g/cm², consisting mainly of organic-P (NaOH-nrP) but also of P associated to iron (BD-P). P release experiments were performed by maintaining steep diffusion gradients in flow-through chambers under oxic or anoxic conditions. Using this method it took no longer than three weeks to release an amount of P from the main P mobile pools (NaOH-nrP, BD-P) corresponding to P naturally lost during sediment diagenesis, a process which normally takes years. Release rates as well as mobile amounts of P in the NaOH-nrP pool varied significantly depending on the redox status. In conclusion, the release method applied made it possible to determine potentially mobile P under specified conditions and to detect ecologically important P fractions in the surface sediments.

Key words: phosphorus; sediment; diagenesis; release experiment; P fractionation』

Introduction
Materials and methods
　Release experiment design
　Chemical analyses
Results
　Phosphorus in the sediment profile
　Release experiments
Discussion
Conclusion
Acknowledgements
References

図1．Psenner et al.（1988）に基本的に倣った、本研究で用いたリン分別法．（元は図）

堆積物試料	1M NH4Cｌ、pH 7で2.2時間		NH4Cｌ−P『ゆるく吸着したP』（Loosely sorbed-P）
残渣	0.11M Na2S2O4/NaHCO3、1時間		BD-P『Fe-P』
残渣	0.1M NaOH、16時間		NaOH−ｒP『Al-P』
		温浸（digestion）	NaOH−Tot P
残渣	0.5M HCｌ、16時間		HCｌ−P『Ca-P』
			残渣P（residual-P）（計算による）『Res-P』