Report on Survey of Phosphorus in sediments at Sæbyvannet

The concentrations of total phosphorus and phosphorus pools in the sediments of Sæbyvannet have been determined. The levels of total phosphorous are found to be between 1.1 and 1.3 mg g-1. This is within the upper range of what was reported for Lake Vansjø. The major phosphorus fraction is non-apatite inorganic phosphorus, accounting for between 43 and 53% of the total phosphorus. Labile phosphorus (i.e. the sum of non-apatite inorganic phosphorus and organic phosphorus) ranges from 69 - 81% of the total phosphorus. This is the pool of phosphorous that is in the literature conceived to be potentially released to overlying water, acting as internal phosphorus loading. No clear spatial gradients are found in the phosphorous levels in the sediments. The sediment minerals consist mainly of quartz, albite and muscovite. Total clay constitutes 30 – 42 w/w% of the total sediment mass. The organic content of the sediments varied between 8 – 11 w/w%. A principal component analysis suggests that the spatial variation in all P pools in the sediments, with the exception of apatite bound P, are linked to the content of organic matter and clay in the sediments. The apatite bound P is on the contrary associated with the amount of quarts and albite, common minerals found in sand.