PHOSPHORUS RETENTION IN SEDIMENTS

Phosphate is usually the most important growth limiting nutrient in aq uatic environments. The availability of P is the result of external lo ad and retention in the sediments. This latter is the result of a numb er of transport, microbial and chemical processes. The role of P in th e productivity in systems and in the eutrophication process has initia ted a large number of studies to the behaviour of P in sediments. Case studies in Veluwemeer, IJsselmeer, Wadden Sea and German Eight show t hat sorption on and binding in ferric (oxi)hydroxides, occlusion in ca lcium carbonates and authigenic mineral formation are the most importa nt retention processes. However, all this research did not result in t otally new approaches in lake restoration, nor did knowledge of intern al P loading result in large scale applications of well-known sediment restoration techniques. It did result in more realistic expectations of lake restoration programmes. At the same time, renewed interest in the overall role of phosphate in the functioning and productivity of s ystems is emerging. The most important new items are: the role of the productivity is examined at large scale levels; the coupling of produc tivity with several large scale material cycles and global environment al problems and the study of the behaviour and fate of phosphate withi n the context of the functioning of entire watersheds. (C) 1998 IAWQ. Published by Elsevier Science Ltd.