Das Projekt "DYTRAC: Dynamik des Transports und der Transforamtion von Colloiden und Partikeln im Lago Ceresio (Lugano-See)" wird vom Umweltbundesamt gefördert und von Universite de Geneve, Institut F.-A. Forel durchgeführt. Removal rates of many pollutants in lake water are controlled by their partition between dissolved, colloidal and particulate fractions. We are investigating this partition using natural radioactive Be isotopes as surrogates for these pollutants. A new particle separation system for big lake water samples (1000 liters) consisting of a continuous flow centrifuge and an ultra filtration device has been developed. In epilimnion of Lake Lugano we are able to measure Be-7 in all 3 fractions. The largest part is found in the dissolved fraction. This may explain the relatively long residence time of Be in lakes. The work has been accompanied by a series of methods aimed at characterising the physico-chemical conditions in the lake at the time of sampling, the nature of the recovered particles, as well as the performance of the system. Electron microscope observations show decreasing number of particles and their sizes from raw to centrifuged and to ultra filtered water. Pilot measurements to study particle dynamics in the deep water have been carried out including tritium-helium water age measurements. Leading Questions: - What is the role of colloids in removal of metals and radionuclides from lake water? - Can Be-7 be used to determine coagulation rate in lakes? - What is the importance of Fe and Mn cycling at redox interface in permanently stratified lake for phosphorous transport? Other objectives of this project are the following: - Determine the role and importance of Fe and Mn cycling at the oxic-anoxic interface for phosphorous fluxes, - assess the nature of fine particles in lower hypolimnion and their transport mechanism (coagulation, settling, resuspension, focusing)?
Das Projekt "RIACOL: Der Eintrag von Kolloiden und Partikeln in den Lago Ceresio (Lugano) durch Fluesse und die Atmosphaere (RIACOL)" wird vom Umweltbundesamt gefördert und von Eidgenössische Anstalt für Wasserversorgung, Abwasserreinigung und Gewässerschutz, Department of Biogeochemistry durchgeführt. Particulate inputs contribute significantly to the mass balances and to the cycling of various components in lakes. The goal of this project is to characterize particulate inputs of nutrients and trace elements into Lake Lugano, from riverine and atmospheric sources. Because of their significance for the eutrophic state of the lake, phosphorus inputs will be studied in detail, considering especially colloidal particles. The present research aims at developing sampling methods for particulate matter in rivers, especially under high flow conditions, and at characterizing riverine particulate matter in terms of size distribution, chemical and mineralogical composition, adsorption characteristics, and bioavailability of phosphorus in the various fractions. In a microbiological part, the role of bacterial adhesion and aggregation for the transport of particulate matter will be considered. Two river sampling sites (Cassarate and Vedeggio), representing different pollutant sources, and various hydrological conditions will be compared.
Das Projekt "Wie tragen Mikroorganismen zur Bildung und Aufloesung von Kolloiden und Partikeln in Wasseroekosystemen bei? - MICOL" wird vom Umweltbundesamt gefördert und von Universität Zürich, Institut für Pflanzenbiologie durchgeführt. Sedimente eutropher Seen sind Senken und Quellen von Naehrstoffen, die durch biogeochemische Prozesse rezykliert werden koennen. Bei der Katalyse dieser Reaktionen spielen Mikroorganismen eine wichtige Rolle. Anhand von Untersuchungen am eutrophen Luganersee wurden von 1989 bis 1993 die Auswirkungen natuerlicher saisonaler Zyklen auf die mikrobiell vermittelten Stoffaustausche zwischen Sediment und Hypolimnion studiert. Dabei wurde an zwei Stellen im Suedbecken des Sees eine enge Kopplung zwischen dem Phosphor- und dem Eisenkreislauf beobachtet. Als Fortsetzung dieser Arbeit soll nun in einem interdisziplinaeren Projekt die Rolle, welche eisenreduzierende Bakterien bei der Naehrstoffrueckloesung spielen, genauer untersucht werden. Insbesondere soll versucht werden, solche Bakterien aus dem Tiefenwasser des Sees zu isolieren und die Bedingungen (chemische und physikalische Umgebungsparameter, Algen als Naehrstoffquelle), unter welchen Eisen reduziert wird, zu erfassen.
Das Projekt "DYSPART: Dynamik der Resuspension von Sedimentpartikeln und deren Transport in eutrophierten Seen - Teil 1: biogeochemikalischer Zyklus von Kohlenstoff und Stickstoff im Luganer See" wird vom Umweltbundesamt gefördert und von Eidgenössische Technische Hochschule Zürich, Geologisches Institut durchgeführt. The main goal of the project is to understand and calibrate the factors controlling the nitrogen and carbon isotopic composition of lacustrine organic matter by measuring the C and N isotope composition of particulate organic matter and dissolved inorganic Nitrogen and Carbon over two yearly cycles. We anticipate that these results will allow for a improved understanding of the biogeochemical cycles in an eutrophic lake and our capability to reconstruct paleoenvironmental changes from carbon and nitrogen isotope composition of sedimentary organic matter. Lake Lugano offers an unique situation to study these processes because of the large amount and long time-series of limnological data available including: water column chemistry, primary productivity, phyto-and zooplankton populations sediment fluxes and sediment trap samples. The second main goal of this project will be to determine the incidence of lateral sediment transport processes in Lake Lugano. Resuspension and transport of sediment particles will be quantified measuring the fluxes of organic matter with sediment traps and allochtonous inputs from the main tributaries, coupled with the determination of isotopic ratios of carbon and nitrogen in the sedimenting organic matter. These isotopic measurements will verify the possibility of using C-isotopes to determine the origin of the excess C and N accumulation in hypolimnetic sediment traps. In addition, analysis of already available daily records of turbidity collected during 1994-1995 will be used to further constrain these processes.