Phosphorus immobilization in Lake Głęboczek following treatment with polyaluminum chloride

In 2001-2003, a survey was conducted of the effectiveness of restoration in the heavily eutrophic polymictic Lake Głęboczek, located in Tuchola. The application of the phosphorus inactivation method with polyaluminum chloride PAX 18 resulted in the complete removal of phosphates, and in a considerable (up to 50-60%) reduction of total phosphorus in the lake water. The sorptive capacity of the bottom sediments was enhanced after the restoration, particularly in the top layer (0-5 cm). An increase of the aluminum content and of mineral forms of phosphorus was observed, mainly the aluminum-bound fraction (at its greatest, by over 330%). The amount of mobile phosphorus in the sediments decreased by 40%. The evidence of the durable immobilization of phosphorus in the aquatic ecosystem was the limited phosphorus release from the bottom sediments. This was confirmed by a significant decrease of total phosphorus in the interstitial waters (from 4-6 mg dm^-3 to 2-3 mg dm^-3), and by a practically complete removal of phosphates from the near-bottom waters.