Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2018
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Ngo Tien Dung Sekhar Udaya Nagothu Alma Linda Morales-Abubakar Jan Willem Ketelaar Mehreteab TesfaiAbstract
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Isaiah Nyagumbo Mehreteab Tesfai Sekhar Udaya Nagothu Peter Setimela James K. Karanja Munyaradzi Mutenje Connie MademboAbstract
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Annette Dathe Attila Nemes Matthew Patterson Anna Angyal Julia Szocs Szilvia Kendra Esther Bloem Daniel GimenezAbstract
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Degradation of organic chemicals in natural soils depends on oxidation-reduction conditions. To protect our groundwater resources we need to understand the degradation processes under anaerobic conditions. Available iron and manganese oxides are used as electron acceptors for anaerobic degradation and are reduced to the dissolved form of metallic cations in pore water. To monitor this process is a challenge, because anaerobic conditions are difficult to sample directly without introducing oxygen. A few studies have shown an impact of iron reduction on spectral induced polarisation (SIP) signature, often associated with bacterial growth. Our objective is to study the impact of iron and manganese oxide dissolution, caused by degradation of an organic compound, with spectral induced polarisation signatures. Twenty-six vertical columns (30 cm high, inner diameter 4.6 cm) were filled with a sand rich in oxides (manganese and iron) with a static water table in the middle. In half of the columns, a 2 cm high contaminated layer was installed just above the water table. As the contaminant degrades, the initial oxygen is consumed and anaerobic conditions form Every three days over a period of one month, spectral induced polarisation (twenty frequencies between 5mHz and 10 kHz) data were collected on six columns: three contaminated replicates and three control replicates. Chemical analysis was done on twenty columns assigned for destructive water sampling, ten contaminated columns and ten control. The results show an increase of the real conductivity associated with the degradation processes, independent of frequency. Compared with the pore water electrical conductivity in the saturated zone, the real conductivity measurement revealed the formation of surface conductivity before iron was released in the pore water. In parallel, we also observed an evolution of the imaginary conductivity in both saturated and unsaturated zones at frequencies below 1 Hz. Overall, the anaerobic reduction of iron and manganese oxide during the organic degradation increased both the conductive and polarisation component of the complex conductivity.
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Jon Aars Tiago A. Marques Karen Lone Magnus Andersen Øystein Wiig Ida Marie Bardalen Fløystad Snorre Hagen Stephen T. BucklandAbstract
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Academic – Contributors to faecal water contamination in urban environments
Lisa Paruch, Adam Paruch
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Faecal contamination of water has both anthropogenic and zoogenic origins that can shade various point and nonpoint/diffuse sources of pollution. Due to the dual origin and number of sources of faecal contamination, there are immense challenges in the implementation of effective measures to protect water bodies from pollution that poses threats to human and environmental health. The main health threats refer to infections, illnesses and deaths caused by enteric pathogenicmicrobes, in particular those responsible for waterborne zoonoses. To detect and identify the origins and sources of faecal pollution simultaneously, various methods and indicators have been compiled into a comprehensivemeasuring toolbox. Molecular diagnostics using genetic markers derived from Bacteroidales 16S rRNA gene sequences are quite prevalent in the current methodological implementation for the identification of faecal contamination sources in water. For instance, a culture- and library-independent microbial source tracking toolbox combining micro- and molecular biology tests run as a three-step procedure has been implemented in Norway. Outcomes from the Norwegian studies have identified two general trends in dominance of contributors to faecal water contamination in urban environments. Firstly, there is a tendency of higher contributions from anthropogenic sources during the cold season. Secondly, the identification of the dominance of zoogenic sources in faecalwater contamination during warm periods of the year.