『Abstract
　Suspended sediments collected during rain events were analysed to assess the maximum potential bioavailability of particulate phosphorus (PP). Physical (separation by particle size) and chemical (sequential extraction) fractionation techniques were applied. Time differentiated sampling during rain events revealed that changes in the concentrations of soluble and particle bound phosphorus, and in the proportion of different PP phases, are due to the changing contribution of various sources of runoff and to flow related variations in particle size. Size fractionation and the extraction of PP phases, can help to distinguish resuspended sediments from sediments coming directly from outside the channel. In light of a formerly study, investigating PP sedimentation and transformations within the sediments of Lake Sempach, our results lead to the conclusion that, at least 25％ (particulate inorganic and reductive soluble P) and at most 70％ of the allochthonous PP supply transported during a single rain event, may become bioavailable after early diagenesis in the lake sediments. The uncertainty is due to the unknown time span necessary for the diagenesis, at the lake sediment surface, of particulate organic phosphorus of allochthonous origin.

Keywords: sequential phosphorus extraction; suspended sediment; size fractions; storm runoff』

Introduction
　The Kleine Aa catchment
Methods
　General sample treatment
　Sequential P extraction
Results
　Effect of the litter
　Effect of phosphate adsorption
　Streamwater and suspended sediment analysis
　Sequential extraction of PP during storms
　Particle size of suspended sediment
　Fluxes
Discussion
　Influence of particle size on P transport
　The source of BD-P
　The “iron curtain”
　Fluxes of PP during storm events
　Bioavailability
Conclusions and recommendations
Acknowledgments
References