Sedimentation Processes and Nutrients Turnover in Acidic Water Bodies during Experimental Treatment for Lake Remediation

Bachelor Thesis from the year 2006 in the subject Environmental Sciences, grade: 1,7, Brandenburg Technical University Cottbus, language: English, abstract: The objective of the study is charactering of the primary flux in an enclosure experiment of chemical and/or biological neutralisation in one of the numerous acidified lakes in the Lusatian mining district, (Germany) and tracing the consequences for the water chemistry, reps. water quality. Sedimentation as one of the most important physical process in the water controls the energy flow through aquatic ecosystems thus normally transporting nutrients to the lake bottom. The rate of seston deposition has great importance for understanding the circulation of organic and mineral matter within a lake and can be regarded as a measure of the nutrient recycling there. Acidity removal amendments (soda ash, organic mater and phosphate) added to the enclosures in different combinations resulted in components specific seston fluxes and in changes in the biological and chemical parameters of the water column. It was found that the addition of neutraliser and organic amendments (ENePo) resulted in a flux of authochthonous particulate matter of 6 - 4g/(m²d) and enhanced at most and in a long term (in the course of the experiment) the nutrients (P, C, N) cycling and the water quality (as increasing from the bottom pH gradient was observed). The addition of organic matter to the acidic water column (EPo) resulted in similarly enhanced gross sedimentation but with a small time lag compared to the same treatment of the neutralized water as the assimilation of the nutrients was hindered by the low pH (retaining P in the sediment) and the initially low primary production. The addition of phosphates (ENePo, EP) did not result in a long term and self-sustained enhancement of the primary flux as after P being assimilated and transported to the sediment it remained immobilized there, thus the P elemental flux as well as the flux of particular matter dropped down to the usual for the lake values.