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Environmental and Radiochemistry

 

Responsible: Regina Krachler, Gabriele Wallner, Franz Jirsa, together with Bernhard Keppler.

The working group, consisting of about 10 diploma and PhD students, is jointly supervised by the scientists mentioned above.

 

R E S E A R C H    T O P I C S

 

Radiochemistry

The main interest of our group is the development of new methods for the measurement of natural and anthropogenic radionuclides in environmental samples. Modern ion exchange methods are used for pre-concentration and separation of the nuclides of interest before appropriate radiometric measurement. The investigated samples are e.g. water, aerosol and soil samples, or animal bones and thyroids.
 
Anthropogenic nuclides widely investigated in our environment during the last years were the fission products Cs-137 and Sr-90 as well as the activation products Pu-238 and Pu-(239+240). Natural radionuclides like Rn-222, Ra-226, Ra-228, Pb-210, Po-210 and the uranium isotopes are measured in Austrian tap-waters as well as in mineral waters to get an overview about the exposure to the public due to drinking water uptake. On aerosols the long-lived radon progeny Pb-210 and its daughter products were measured in order to calculate aerosol residence times. Pb-210 was also successfully used for dating of lake sediments.
 
Beyond the measurement of these “classical” radionuclides the determination of nuclides with very low natural abundance is of growing interest. We measure the distribution of the long-lived uranium fission product I-129 in the environment and plan to use the I-129/U ratio for dating of samples which represent a closed system. Another important topic is the determination of the long-lived uranium isotope U-236 and its applications in geoscience, nuclear safeguards and environmental protection. These investigations are done in cooperation with VERA, the Vienna Environmental Research Accelerator, Faculty of Physics, University of Vienna.
 
Environmental Chemistry
 
Global warming is gaining recognition as one of the most pressing issues of our time, impacting literally every part of the earth's system. It is, in turn, linked to the global carbon and iron cycles. Iron as a micronutrient limits phytoplankton production in major ocean regions i.e. iron bioavailability regulates atmospheric partial pressure of carbon dioxide via the flux of carbon from the atmosphere to the deep sea. Unfortunately, the ocean's least productive waters are currently expanding. In our research, the emphasis is put on a fundamental chemical link between terrestrial and oceanic carbon sinks: Naturally occurring organic chelating ligands, commonly found in leachates from peat soils, have been proposed to serve as colloidal iron carriers in aquatic systems. To date, very little is known about the structure and functioning of these substances. We performed mixing experiments of river water with seawater, using a 59Fe radiotracer method, and observed the Fe sedimentation as a function of particle size and increasing salinity. Our results point to an unexpectedly high stability of peat-bog derived small organic Fe colloids even under conditions of strong salinity. Samples from Sphagnum peat–bog sites in Austria, Scotland and Japan show similar behaviour. Complexation reactions of several benzoic acid derivatives like sphagnum acid, vanillic acid, gallic acid, protocatechuic acid, 3,4,5-trimethoxybenzoic acid, and caffeic acid with different iron(III) and iron(II) salts in various molar ratios and different solvents are currently under investigation. The resulting substances act as model Fe-humic acid complexes and are characterised by elemental analysis, IR- and mass spectroscopy, by means of X-ray diffraction, Mössbauer spectroscopy, magnetic susceptibility measurements, cascade cross-flow ultrafiltration, and thermogravimetry

Sphagnum acid

 

 

Another field is the extraction of heavy metals from communal waste water. According to the European water frame directive, heavy metals are priority water pollutants. In order to achieve a good chemical status of surface waters as described in the water frame directive, efforts for the reduction of heavy metal concentrations in sewage plant effluents have to be enhanced. Among others, cadmium, nickel, lead and their compounds are included in the list of “priority” substances and show concentrations transcending the claimed quality standards in many European surface water bodies. Methods for the reduction of these metals are numerous e.g. precipitation, filtration, biological methods and many more. In spite of a widespread use of the mentioned techniques, they are not sufficient to achieve required quality standards. We developed a new approach for an efficient and selective elimination of heavy metals from natural waters and wastewater. A new class of extracting agents – based on the concept of functionalized hydrophobic ionic liquids - are currently synthesized and evaluated for their extracting potential.

Another focus of our research lies on biogeochemistry and microbiology of saline-alkaline shallow lakes. Among other activities, we investigated the role of pH in aquatic biodegradation processes. Our results suggest that the pH stimulated remineralisation of organic matter plays a major role in maintaining the long-term integrity of saline lake/wetland systems.

Decomposition of reed litter granules in unfiltered air saturated
Lake Neusiedler See water at 15°C in the dark, dry mass loss (%)
during 35 days as a function of pH.

Further information