APPLICATION OF LAKE MARL AT LAKE ARENDSEE, NE GERMANY - FIRST RESULTSOF A GEOCHEMICAL MONITORING DURING THE RESTORATION EXPERIMENT

The application of lake marl for the in-situ restoration of eutrophic hard-water lakes with very low fresh water input has recently been car ried out during a pilot study at Lake Arendsee, NE Germany. Calcite-ri ch lake marl taken from a natural deposit in the littoral zone was spr ead over the lake surface in order to co-precipitate phosphorus and cy anobacteria as well as to cover the sediment surface. The aim of this measure was to reduce the release of phosphorus from the nutrient-rich sediments into the water column under the anoxic conditions which pre vail during periods of stratification. Monitoring the dispersion, tran sport and sedimentation of the lake marl in the water column was carri ed out using the in-situ multi-sensor system MINIBAT as well as by lim nological studies and sediment core observations. During summer stagna tion of the lake waters, suspended fine-grained calcite up to 15 mu m was found at the thermocline whereas the coarser particles sedimented immediately. Following the application of the lake mart, bottom sedime nts were covered by a 20-120-mm calcareous layer. (C) 1998 Elsevier Sc ience B.V. All rights reserved.