Eutrophicated lakes: a slow recovery

Eawag News 68, February 2010

complete issue [pdf, 4MB]

Editorial: Late effects of eutrophication
Bernhard Wehrli

In focus: Eutrophicated lakes

Danube Delta: a leading source of greenhouse gases
Edith Durisch-Kaiser
Wetlands such as the Danube Delta act as huge natural water purification systems: anthropogenic nutrients are removed from the water column and incorporated into -biomass. The decomposition of biomass in the Danube Delta gives rise to particularly large amounts of the greenhouse gases methane and carbon dioxide, which are released into the atmosphere. [...]


Daphnia populations affected by eutrophication
Nora Brede
From 1950 onwards, habitats and species composition in Europe’s lakes have been altered by excessive inputs of nutrients. The new environmental conditions favoured one -particular water flea species, and genes were transferred across species via -hybridization. Although eutrophication has now been successfully controlled, the original populations have not been re-established. [...]

CO₂ fixation in Lake Brienz and Lake Lugano
Achim Bechtel
Carbon dioxide (CO2) is removed from the natural global cycle and sequestered in lake sediments in the form of organic carbon. But how is CO2 fixation affected by nutrient concentrations and oxygen availability in lake water? To answer this question, Eawag explored the depths of two lakes, carrying out analyses at the molecular level. [...]

Why Lake Lugano's water remained unmixed for decades
Interview with Rolf Kipfer
In 2009, Eawag published a study on the mixing behaviour of Lake Lugano. In this interview, Rolf Kipfer, Head of the Water Resources and Drinking Water department and Titular Professor at the ETH Zurich, explains how eutrophication and climate change may affect water circula-tion in lakes. [...]

Sounding board

Decentralized systems - future model for wastewater treatment?
Martina Bauchrowitz
In Switzerland, decentralized systems currently play an insignificant role, being used only in remote areas beyond the reach of public sewers. But under what conditions could they be a viable option in this country and other parts of the developed world? And how do researchers and practitioners view the prospects for these systems in developing countries? [...]

Current research

Removing micropollutants and phosphate with ferrate
Saskia Zimmermann
Alongside ozone, ferrate has emerged as a new option for enhanced wastewater treatment at municipal treatment plants. Both substances oxidize anthropogenic organic micropollutants. Ferrate offers the additional advantage of removing phosphate – by precipitation – at the same time. But what doses of ferrate are required? And is the use of ferrate cost-effective? We report here on initial experience from the Eawag laboratory. [...]

Assessment of chemicals: fish cells as an alternative to whole fish
Katrin Tanneberger
Every year, hundreds of thousands of fish die in toxicology tests worldwide. Among the possible alternatives being explored by Eawag, fish cells are particularly promising. However, the toxic effects of chemicals are generally less marked in fish cells than in whole fish. Here, we explain the reasons for this – and discuss how fish cell-based assays can be optimized. [...]

From source to sink: flame retardants
Ruth Scheidegger
Since the mid-1970s, global production of flame retardants has risen from zero to several hundred thousand tonnes per year. Although these substances reduce the flammability of many different products containing plastics or synthetic materials (e. g. computers, cars and textiles), they also raise environmental concerns. We have studied the spread of flame retardants all the way from production to disposal. [...]

Forum

Secrets of the lake floor
Andri Bryner
After a successful pilot project on Lake Lucerne, Eawag has now started surveying the floor of the Swiss part of Lake Maggiore. Using a sophisticated sonar system, images can now be produced with an unprecedented level of detail. But the computer-generated colour images also pave the way for new research projects. [...]

In Kürze