Polymerisation von β-Pinen und Δ bei UV-Bestrahlung

The Science of Nature -     

Identification of metal toxicity in sewage sludge leachate

Sewage sludge is a source of organic matter and nutrients with the potential for being used as a fertilizer. However, metals in sewage sludge might accumulate in soil after repeated sludge applications, and metal concentrations might reach concentrations that are toxic to microorganisms, soil organisms and/or plants. This toxicity might change with time due to kinetic factors or abiotic factors such as freezing, drying or rainfall. The objective of this study was to determine toxicity of sewage sludge leachate from a lysimeter with 50 cm of sludge applied. Attempts were also made to identify the cause of toxicity of the sludge leachate by toxicity identification and evaluation (TIE) techniques. Sludge leachate was collected monthly during 1 experimental year (August 2001 to August 2002). Metal concentrations were analysed, and the toxicity was determined with Daphnia magna (48-h immobility). The effect of EDTA or sodium thiosulphate addition, filtration through a CM-resin or a Millex-resin on toxicity was also tested. The results showed that toxicity of the sludge leachate apparently varied during the year, and that filtration through the CM-resin reduced most of the toxicity followed by the addition of EDTA. None of the other treatments reduced the toxicity of the sludge leachate. This indicated that one or more metals were responsible for the observed toxicity. Further calculations of toxic units (TU) suggested that Zn contributed most to the toxicity. Results also indicated that Ca concentrations in the sludge leachate reduced the toxicity of Zn.     

Social sustainability and collaborative learning

The social dimension is central to sustainable development of agri-food systems. If farmers are not satisfied with their situation or motivated to continue farming, many of today's environmental goals will be impossible to achieve. Between 1997 and 2003, several case studies were carried out on social sustainability, the importance of recognition in the farming system, and the potential role of increased collaboration between actors. The main hypothesis was that improved recognition is a basis for sustainable social conditions. Our findings show that many farmers today perceive an impoverished social situation. They believe they lack control over decisions, which hinders their ability to continue farming. Public images and political decisions show a lack of respect for farmers' skills and knowledge. However, increased collaboration among actors is believed to be one important way forward, creating stronger relationships and networks, as well as a stronger identity for farmers. Our findings emphasize the need for authorities and other organizations to support farmers and to facilitate collaborative learning and decision-making processes for socioecological sustainability.