The geochemistry, availability and abundance of different forms of phosphorus in soil, water and sediments are reviewed. The present knowledge of phosphorus pathways in ecosystems and their regulation is discussed.In a drainage basin, anthropogenic phosphorus is brought into the system mainly as fertilizers and detergents. Sewer systems and outwash processes transfer the phosphorus from the terrestrial environment to the aquatic part of the ecosystem where an accumulation occurs in the sediments of the watercourse.A great part of the phosphates in soil is sorbed to soil particles or incorporated into soil organic matter. The release and export of phosphorus from uncultivated soil is a function of the geology and soil composition, but also of the air temperature, precipitation and the hydrological condition, pH etc.The solubility of phosphates is controlled by either sorption-desorption or precipitation-dissolution reactions depending on the environment in the soil or sediments. In soil and sediments with large amounts of iron and aluminium hydrous oxides, sorption-desorption reactions are largely responsible for determining the level of orthophosphate in the solution at equilibrium.Algal availability of phosphorus associated with soil-derived materials present in aquatic systems deserves more research. In addition, processes responsible for transport of phosphorus from cropland to aquatic systems and chemical and microbial transformations of phosphorus in lakes and streams deserve more attention.
During the last twenty years, studies on freshwater algae in Norway have documen recent alterations in the trophic nature of several inland waters. Blooms and changes in type of algae were observed. Mass development of algae, e.g., cyano-phytes, upset normal lake metabolism. Objectionable effects on taste and odour in water supplies were reported. The bloom of Oscillatoria bornetii f. tenuis in the Lake Mjøsa - River Glåma system caused several problems in the waterworks Limnological, biological and chemical data from case studies in Norway were summarized, and some practical implications discussed.
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