Gerald Kirchner

University of Hamburg, Hamburg, Hamburg, Germany

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Publications (30)76.43 Total impact

  • Abhinand Jha, Uwe Schkade, Gerald Kirchner
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    ABSTRACT: The 7Be method is a promising tool for estimating soil erosion rates at time scales of days to months. However, so far its applicability is limited to steady state concentrations of the tracer. In this paper a diffusion-sorption model is presented, which takes into account atmospheric input rates, transport down the soil column and radioactive decay of 7Be. It allows simulation of the non-steady-state 7Be inventories and depth distributions in soil and their modification by discrete erosion events as well as by tillage. This model is used to quantify erosion rates for 12 individual heavy rainfall events over a period of two years at an agricultural study site in Germany. Comparisons of soil collected at the bottom of our study site with predictions made using our proposed radioberyllium technique generally show good to excellent agreement even for multiple erosion events.
    Geoderma 04/2015; 243. DOI:10.1016/j.geoderma.2014.12.020 · 2.51 Impact Factor
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    ABSTRACT: Measurements of radionuclides (RNs) in air made worldwide following the Fukushima accident are quantitatively compared with air and soil measurements made in Japan. Isotopic ratios RN:(137)Cs of (131)I, (132)Te, (134,136)Cs, are correlated with distance from release. It is shown, for the first time, that both within Japan and globally, ratios RN:(137)Cs in air were relatively constant for primarily particle associated radionuclides ((134,136)Cs; (132)Te) but that (131)I shows much lower local (<80 km) isotope ratios in soils relative to (137)Cs. Derived isotope ratios are used to reconstruct external dose rate during the early phase post-accident. Model "blind" tests show more than 95% of predictions within a factor of two of measurements from 15 sites to the north, northwest and west of the power station. It is demonstrated that generic isotope ratios provide a sound basis for reconstruction of early-phase external dose rates in these most contaminated areas.
    Scientific Reports 09/2013; 3:2520. DOI:10.1038/srep02520 · 5.08 Impact Factor
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    ABSTRACT: Fine-grained sediments constitute a major stressing factor for the aquatic ecosystem in the 15 000 km2 Kharaa River catchment in Northern Mongolia. The objectives of this study were to identify the suspended sediment (SS) sources and quantify the sediment budget of the basin. Sediment sources were identified with the help of sediment tracing methods utilizing Be-7, Cs-137 and Pb-210 radionuclides. High-resolution discharge data were used in combination with daily suspended solid measurements to calculate the SS budget. These calculations were compared with the monthly archive data on SS and discharge to investigate temporal load variations. In addition, the sediment budget model SedNet was used to estimate the SS budget and test its applicability in a cold semi-arid region. Results of the sediment tracing showed that riverbank erosion generates 74.5% of the suspended sediment load, whereas surface erosion contributes 21.7% and gully erosion only 3.8%. In the most intensely used agricultural tributary catchment Zagdelin Gol, upland erosion contributed only 12.7% to the total SS losses. The calculated mean annual sediment load for the years 1990–2002 was 20.3 kt⋅a−1. The SedNet model computed SS export from the catchment in the same order of magnitude as measured data (16.2 kt⋅a−1). The results help to identify effective management measures to reduce sediment loads and mitigate its impact on the aquatic environment. Copyright © 2012 John Wiley & Sons, Ltd.
    Hydrological Processes 03/2013; 27(6). DOI:10.1002/hyp.9684 · 2.70 Impact Factor
  • F Gering, B Gerich, E Wirth, G Kirchner
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    ABSTRACT: The Fukushima accident led to high radionuclide releases into the atmosphere for more than 3 weeks. This situation has not been assumed when the concepts of nuclear emergency preparedness were developed internationally. The results of simulations studying potential implications of Fukushima-like source terms on nuclear emergency preparedness are presented. Two hypothetical source terms are considered. Radiological consequences are assessed with the decision support system RODOS. Atmospheric dispersion calculations are based on meteorological monitoring data from June and December 2010, respectively, to study potential seasonal effects. Simulations are performed for two nuclear power plant sites in Northern and Southern Germany, respectively. These sites are chosen due to their differing meteorology and topography. Predicted radiation doses of members of the population are compared with dose reference levels actually recommended for initiating protective measures in Germany. Potential implications of general interest for nuclear emergency planning are discussed.
    Radiation Protection Dosimetry 01/2013; 155(2). DOI:10.1093/rpd/ncs323 · 0.86 Impact Factor
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    IAEA TECDOC 1678 06/2012; IAEA., ISBN: ISBN 978-92-0-129810-2 , ISSN 1011-4289
  • G Kirchner, P Bossew, M De Cort
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    ABSTRACT: It is shown which information can be extracted from the monitoring of radionuclides emitted from the Fukushima Dai-ichi nuclear power plant and transported to Europe. In this part the focus will be on the analysis of the concentration ratios. While (131)I, (134)Cs and (137)Cs were reported by most stations, other detected radionuclides, reported by some, are (95)Nb, (129m)Te, (132)Te, (132)I, (136)Cs and (140)La. From their activity ratios a mean burn-up of 26.7 GWd/t of the fuel from which they originated is estimated. Based on these data, inventories of radionuclides present at the time of the accident are calculated. The caesium activity ratios indicate emissions from the core of unit 4 which had been unloaded into the fuel storage pool prior to the accident.
    Journal of Environmental Radioactivity 01/2012; 114:35-40. DOI:10.1016/j.jenvrad.2011.12.016 · 3.57 Impact Factor
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    ABSTRACT: Radionuclides emitted from the Fukushima I nuclear power plant have been detected in air all over Europe. Concentrations remained far below levels which could have caused radiological concern: probably the committed thyroid dose due to inhalation remained below about 1 μSv (for 10 y children), within the investigated region. They provided, however, a spatio-temporal signal which could be used to develop and test tools to provide additional information on the large-scale situation (Europe-wide, in this case) during a nuclear emergency. In this part we discuss the spatial distribution of the contaminated air masses over Europe. Using (131)I as an example, we present a method to construct maps of the time-cumulated (131)I concentration in air and of the peak concentrations. Procedures to deal with the statistical limitations of a data set stemming from different monitoring schemes are discussed. As over all results, the mean (over the investigated region) cumulated concentration of particular (131)I is estimated about 9 mBq d/m(3), with observed maximum of about 23 mBq d/m(3). The probability that much higher concentrations occurred at unsampled locations, than have been observed anywhere, is assessed low, e.g. about 2.5% for the cumulated (131)I(part.) concentration to exceed 30 mBq d/m(3). Our method can be used in nuclear emergencies for providing spatial analyses if radionuclide concentrations of health concern are detected by atmospheric monitoring stations. We suggest considering such methods of data harmonization if synoptic assessment based on heterogeneous datasets is attempted.
    Journal of Environmental Radioactivity 01/2012; 114:22-34. DOI:10.1016/j.jenvrad.2011.11.019 · 3.57 Impact Factor
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    V Hormann, G Kirchner, H W Fischer
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    ABSTRACT: In another batch equilibrium experiment, Nisbet [9] treated 134 Cs contaminated soils with a solution of 11.5 m potassium sulphate. The 134 Cs concentration in the soil increased due to replacement by potassium on the surfaces. The partial PHREEQC model for illite is able to excellently predict this behaviour. Introduction References A current approach to estimate radiological doses and risks to humans living far in the future in the vicinity of nuclear waste disposals is the concept of so-called "Reference Biospheres". Within this framework, the irrigation of agricultural soils by contaminated well water and the subsequent transfer of radionuclides within the biosphere is an important pathway to be considered. The transfer of radionuclides into the food chain is strongly influenced by their speciation, distribution and transport within the soil. These processes depend on soil parameters such as pH value, mineralogical composition and organic matter. These parameters, in turn, may vary considerably with soil type and agricultural conditions. In this study it is shown that the distribution of radionuclides in soils after irrigation can be satisfactorily estimated by a CA (component additivity) model implemented into a geochemical code. The concept of Reference Soils (e.g. the German Refesol system [1]) offers an attractive possibility of choosing representative soils that may be used to characterize a Reference Biosphere. By definition, Reference Soils are thoroughly specified and particularly their basic physicochemical properties are known. Our model is intended to be applied to these soils. Description of the model Vandenhove et al. [8] studied the influence of soil parameters on soil solution concentration of uranium, which is sorbed by clay, HFO and organic matter as well. They performed batch equilibrium experiments with 18 different soils that covered a comparatively wide range of soil parameters such as pH, cation exchange capacity, clay content, HFO content and percentage of organic matter. Four weeks after contamination of these soils with 238 U, soil parameters were measured and the soil solutions were analysed. DOM was not measured; therefore, an average content of 36 mg/l was used for the PHREEQC simulations. The maximum deviation of the calculated U concentration compared to the measurement is by a factor of 2.5. Caesium Conclusions The calculations presented above show that our model is capable of reasonably estimating the content of uranium and cesium in soil solution after contamination with these elements. This opens the possibility to predict the influence of soil parameters on the distribution of radionuclides in soils.
    Radioprotection 01/2011; 46(6):S487-S490. DOI:10.1051/radiopro/20116705s · 0.60 Impact Factor
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    ABSTRACT: Facies analysis, magnetic susceptibility, and analysis of grain size, TOC content and isotopes (137Cs, 210Pb, 226Ra, 228Ra, and 238U concentrations) were used to determine the history of the modern deposits of the Brno reservoir. The sedimentary succession can be subdivided into two main units. The lower unit is formed predominantly by medium- to coarse-grained silty sands and is interpreted as a fluvial succession deposited before the Svratka River was dammed. The upper unit consists of brownish planar laminated silts and rarely of clayey or sandy silts and is interpreted as a product of the reservoir deposition. The concentrations of 238U reflect the history of uranium mining in the upper part of the Svratka River catchment. As a consequence, 210Pb radionuclide concentrations cannot be used for establishing a sediment chronology. Concentrations of 137Cs show two marked peaks, the upper of which is attributed to the Chernobyl reactor accident in 1986, and the lower one is attributed to the maximum rate of atomic weapons testing in 1963. From these peaks, mean depositional rates of 3.2cmyear−1 for the time period of 1986–2007 and of 3.4cmyear−1 between 1963 and 1986 are calculated. Based on the known age of the reservoir, which was constructed in 1939, we can also calculate mean depositional rate for the time period of 1939–1963, which is 3.1cmyear−1. KeywordsReservoir deposits-Radiometric dating-Depositional rate-Hydrological changes-Human impact
    Journal of Paleolimnology 01/2011; 45(1):41-55. DOI:10.1007/s10933-010-9478-5 · 2.14 Impact Factor
  • Gerald Kirchner
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    ABSTRACT: For aquatic sediments, the use of (210)Pb originating from the decay of atmospheric (222)Rn is a well-established methodology to estimate sediment ages and sedimentation rates. Traditionally, the measurement of (210)Pb in soils and sediments involved laborious and time-consuming radiochemical separation procedures. Due to the recent development of advanced planar ('n-type') semi-conductors with high efficiencies in the low-energy range which enable the gamma-spectrometric analysis of the 46.5 keV decay line of (210)Pb, sediment dating using this radionuclide has gained renewed interest. In this contribution, potentials and limitations of the (210)Pb methodology and of the models used for estimating sediment ages and sedimentation rates are discussed and illustrated by examples of freshwater and marine sediments. Comparison with the use of (137)Cs shows that the information which may be gained by these two tracers is complementary. As a consequence, both radionuclides should be used in combination for dating of recent sediments. It is shown that for various sedimentation regimes additional information from other sources (e.g. sediment lithology) may be needed to establish a reliable chronology. A strategy for sediment dating using (210)Pb is recommended.
    Journal of Environmental Radioactivity 12/2010; 102(5):490-4. DOI:10.1016/j.jenvrad.2010.11.010 · 3.57 Impact Factor
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    ABSTRACT: Samples of pasture vegetation, mainly Trifolium pratensis, were collected at the Botanic Garden of the University of Bologna during the period 1998-2000 and measured by gamma-spectrometry for determining thoron progeny. Concentrations of (212)Pb were between 1.5 and 20 Bq m(-2), with individual peaks up to 70 Bq m(-2). Soil samples were collected at the same location and physically characterised. Their chemical composition (particularly Th and U) was determined by X-ray fluorescence spectroscopy. Lead-212 on plants mainly originates from dry and wet deposition of this isotope generated in the lower atmosphere by the decay of its short-lived precursor (220)Rn, which is produced in the upper soil layers as a member of the natural thorium decay chain and exhales into the atmosphere. Concentrations of (220)Rn in the atmosphere depend on (1) the amount of Th present in soil, (2) the radon fraction which escapes from the soil minerals into the soil pore space, (3) its transport into the atmosphere, and (4) its redistribution within the atmosphere. The mobility of radon in soil pore space can vary by orders of magnitude depending on the soil water content, thus being the main factor for varying concentrations of (220)Rn and (212)Pb in the atmosphere. We present a simple model to predict concentrations of thoron in air and its progeny deposited from the atmosphere, which takes into account varying soil moisture contents calculated by the OPUS code. Results of this model show close agreement with our observations.
    Journal of Environmental Radioactivity 11/2010; 101(11):992-1001. DOI:10.1016/j.jenvrad.2010.07.007 · 3.57 Impact Factor
  • G Kirchner, M Steiner, M Zähringer
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    ABSTRACT: Measurements of low-level radioactivity often give results of the order of the detection limit. For many applications, interest is not only in estimating activity concentrations of a single radioactive isotope, but focuses on multi-isotope analyses, which often enable inference on the source of the activity detected (e.g. from activity ratios). Obviously, such conclusions become questionable if the measurement merely gives a detection limit for a specific isotope. This is particularly relevant if the presence of an isotope, which shows a low signal only (e.g. due to a short half-life or a small transition probability), is crucial for gaining the information of interest. This paper discusses a new approach which has the potential to solve these problems. Using Bayesian statistics, a method is presented which allows statistical inference on nuclide ratios taking into account both prior knowledge and all information collected from the measurements. It is shown that our method allows quantitative conclusion to be drawn if counts of single isotopes are low or become even negative after background subtraction. Differences to the traditional statistical approach of specifying decision thresholds or detection limits are highlighted. Application of this new approach is illustrated by a number of examples of environmental low-level radioactivity measurements. The capabilities of our approach for spectrum interpretation and source identification are demonstrated with real spectra from air filters, sewage sludge and soil samples.
    Journal of Environmental Radioactivity 05/2009; 100(6):484-8. DOI:10.1016/j.jenvrad.2009.03.009 · 3.57 Impact Factor
  • Gerald Kirchner
    Journal of Environmental Radioactivity 03/2009; 100(5):435-7. DOI:10.1016/j.jenvrad.2009.01.007 · 3.57 Impact Factor
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    ABSTRACT: Literature data on numerical values obtained for the parameters of the two most popular models for simulating the migration of radionuclides in undisturbed soils have been compiled and evaluated statistically. Due to restrictions on the applicability of compartmental models, the convection-dispersion equation and its parameter values should be preferred. For radiocaesium, recommended values are derived for its effective convection velocity and dispersion coefficient. Data deficiencies still exist for radionuclides other than caesium and for soils of non-temperate environments.
    Journal of Environmental Radioactivity 12/2008; 100(9):716-20. DOI:10.1016/j.jenvrad.2008.10.010 · 3.57 Impact Factor
  • Matthias Zähringer, Gerald Kirchner
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    ABSTRACT: Ratios of radionuclide activity concentrations are often used to identify sources of small traces of radioactivity in environmental samples. A new approach is presented to consider statistical uncertainties and their impact on decisions based on nuclide ratios particularly for cases where nuclide ratios are calculated from measurements close to or below detection limit. It is pointed out that decision threshold and detection limit are adequate for decisions on the presence of a single nuclide but not necessarily on decisions on nuclide ratios. A statistical analysis based on a Bayesian approach is presented which allows inference on probabilities of nuclide ratio values taking into account jointly the information available for all radionuclides of interest. Examples are discussed to demonstrate the improvements of this approach in spectrum analysis and in source identification. As an important case the detection of Xenon isotopes (135Xe, 133mXe, 133Xe and 131mXe) that are relevant for detecting underground nuclear explosions in the context of the verification of the Comprehensive Nuclear Test-Ban Treaty (CTBT) is discussed. Nuclide ratios are crucial in order to distinguish civil releases from CTBT-relevant sources. A new method is presented for graphical evaluation of the xenon isotope measurements and for assigning potential sources using the statistical approach proposed in this paper.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 09/2008; 594(3):400-406. DOI:10.1016/j.nima.2008.06.044 · 1.32 Impact Factor
  • G Kirchner, M Steiner
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    ABSTRACT: Radioecological assessment models are necessary tools for estimating the radiation exposure of humans and non-human biota. This paper focuses on factors affecting their predictive accuracy, discusses the origin and nature of the different contributions to uncertainty and variability and presents approaches to separate and quantify them. The key role of the conceptual model, notably in relation to its structure and complexity, as well as the influence of the number and type of input parameters, are highlighted. Guidelines are provided to improve the degree of reliability of radioecological models.
    Applied Radiation and Isotopes 06/2008; 66(11):1750-3. DOI:10.1016/j.apradiso.2007.09.021 · 1.06 Impact Factor
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    ABSTRACT: This paper describes the long-term behaviour of (90)Sr and (137)Cs in foods, feeds and a variety of environmental media. The long-term behaviour is quantified by means of the ecological half-life which integrates all processes that cause a decrease of activity in a given medium such as leaching, fixation and erosion. A large number of long-term time series of concentrations of radiocaesium and radiostrontium in these media have been identified and re-evaluated using a standardised statistical procedure to establish reference data sets of ecological half-lives. By example of undisturbed soils and marine water bodies it is shown that the ecological half-life concept is questionable if the distribution of the radionuclide of interest within the medium studied is non-uniform and if mixing and transport processes within this medium, therefore, are of considerable importance during the time period of observation.
    Journal of Environmental Radioactivity 02/2006; 91(1-2):41-72. DOI:10.1016/j.jenvrad.2006.08.004 · 3.57 Impact Factor
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    ABSTRACT: Lichens were collected in France in the surroundings of a military nuclear facility in Burgundy, near the la Hague reprocessing plant and in an area away from any direct source of contamination. Organically bound tritium (OBT) has been analysed on 18 samples and radiocarbon on 11. It appeared that on the most contaminated spots, the OBT activity in lichens was higher than the background by a factor of 1000 and was still a factor 10-100 at a distance of 20 km from the source. Radiocarbon from la Hague could be traced by lichens. The slow metabolism of lichens makes them suitable for the follow-up of (3)H and (14)C, which have been incorporated by photosynthesis.
    Science of The Total Environment 06/2004; 323(1-3):253-62. DOI:10.1016/j.scitotenv.2003.09.030 · 3.16 Impact Factor
  • Volker Hormann, Gerald Kirchner
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    ABSTRACT: For agriculturally used areas, which are contaminated by the debris from a nuclear accident, the use of chemical amendmends (e.g. potassium chloride and lime) is among the most common soil-based countermeasures. These countermeasures are intended to reduce the plant uptake of radionuclides (mainly 137Cs and 90Sr) by competitive inhibition by chemically similar ions. So far, the impacts of countermeasures on soil solution composition - and thus, their effectiveness - have almost exclusively been established experimentally, since they depend on mineral composition and chemical characteristics of the soil affected. In this study, which focuses on caesium contamination, the well-established code PHREEQC was used as a geochemical model to calculate the changes in the ionic compositions of soil solutions, which result from the application of potassium or ammonium in batch equilibrium experiments. The simple ion exchange model used by PHREEQC was improved by taking into account selective sorption of Cs+, NH4+ and K+ by clay minerals. Calculations were performed with three different initial soil solution compositions, corresponding to particular soil types (loam, sand, peat). For loamy and sandy soils, our calculational results agree well with experimental data reported by Nisbet (Effectiveness of soil-based countermeasures six months and one year after contamination of five diverse soil types with caesium-134 and strontium-90. Contract Report NRPB-M546, National Radiation Protection Board, Chilton, 1995.). For peat, discrepancies were found indicating that for organic soils a reliable set of exchange constants of the relevant cations still has to be determined experimentally. For cesium, however, these discrepancies almost disappeared if selective sites were assumed to be inaccessible. Additionally, results of sensitivity analyses are presented by which the influence of the main soil parameters on Cs+ concentrations in solution after soil treatment has been systematically studied. It is shown that calculating the impacts of soil-based chemical countermeasures on soil solution chemistry using geochemical codes such as PHREEQC offers an attractive alternative to establishing these impacts by often time-consuming and site-specific experiments.
    Science of The Total Environment 05/2002; 289(1-3):83-95. DOI:10.1016/S0048-9697(01)01026-9 · 3.16 Impact Factor
  • Sabine Ehlke, Gerald Kirchner
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    ABSTRACT: Soil-to-plant transfer factors are commonly used to estimate the food chain transfer of radionuclides. Their definition assumes that the concentration of a radionuclide in a plant relates linearly solely to its average concentration in the rooting zone of the soil. However, the large range of transfer factors reported in the literature shows that the concentration of a radionuclide in a soil is not the only factor influencing its uptake by a plant. With emphasis on radiocesium and -strontium, this paper reviews the effects of competition with major ions present in the soil-plant system, the effects of rhizosphere processes and soil micro-organisms on bioavailability, the factors influencing transport to and uptake by roots and the processes affecting long-term uptake rates. Attention is given to summarizing the results of recent novel electrophysiological and genetic techniques which provide a physiologically based understanding of the processes involved in the uptake and translocation of radiocesium and -strontium by plants.
    Journal of Environmental Radioactivity 02/2002; 58(2-3):97-112. DOI:10.1016/S0265-931X(01)00060-1 · 3.57 Impact Factor