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International audience; On August 8, 2019, an explosion of a military missile occurred at the Nenoksa (also transcribed as Nyonoksa) Missile Test Center (Russian Federation). Russian authorities confirmed arelease of radioactive material in the course of this incident,which fueled rumors that it could have involved a nuclear-propelled missile of the Burevestnik/Skyfall type. In this study,our radioanalytical efforts are summarized searching for the“smoking gun” of the incident. These included the gamma-measurements of air filters from two vessels that were in someproximity to the event as well as one Greek high-volume airfilter. In addition, we tested the hypothesis that radioactive 42Ar may have been used to operate a radiothermal generator. If the incident had released 42Ar, it may have become detectable by measuring characteristic gamma radiation emitted from a tank containing liquefied atmospheric argon. No traces what so ever were found that could provide clues about the release. It is possible that the presumably small amounts of radionuclides released from either a small nuclear reactor or a powerful radionuclide source dispersed quickly over Russian territory to non-detectable levels before reaching any of our assayed samples.

Viele Politikfelder und Wirtschaftssektoren sind durch die Folgen des Klimawandels betroffen. Extremereignisse wie Hitzewellen, Dürren, Starkregen und Stürme oder auch allmähliche Verschiebungen in langjährigen Mittelwerten (Meeresspiegelniveau, Wasserdargebot, Globalstrahlung, Wind, Temperatur-, Niederschlags- und Abflussregime) setzen Wirkungsketten in Gang, an deren Ende ökologische und ökonomische Funktionen beeinträchtigt und Aspekte der Daseinsvorsorge sowie der Sicherheit berührt sind. Eine vorausschauende Planung und ein auf Resilienz ausgerichtetes Handeln müssen den Aspekt Klimawandel berücksichtigen. Dafür sind eine einheitliche Datengrundlage und abgestimmte Methoden notwendig. Diese Grundlagen zur Bewertung der regionalen und sektoralen Wirkungen des Klimawandels und zur Erarbeitung und Bewertung von Anpassungsoptionen werden durch den DAS-Basisdienst "Klima und Wasser" bereitgestellt, der 2019 durch das Bundesministerium für Verkehr und digitale Infrastruktur ins Leben gerufen wurde. Der DAS-Basisdienst "Klima und Wasser" soll u.a. die Bereiche Verkehr, Wasser- und Energiewirtschaft, Bauwesen, Küsten-, Meeres- und Bevölkerungsschutz, Industrie und Gewerbe mit einheitlichen Informationen zu extremen Witterungsereignissen sowie zu Änderungen mittlerer Bedingungen versorgen. Die zentralen Aspekte des in Abstimmung befindlichen Konzepts des DAS-Basisdienstes "Klima und Wasser" werden vorgestellt.

A method is presented to obtain efficiency calibration for samples of unknown composition in gamma spectrometry. It is based on photon transmission measurements using 155Eu, a multi-energetic gamma emitter. An iterative algorithm produces a virtual chemical composition reproducing the measured sample self-absorption in the range 43–146 keV. The composition is then used to numerically create a sample-specific efficiency calibration. The procedure was tested with IAEA certified sediment materials containing 210Pb, 241Am, 155Eu, and 226Ra. The deviation from certified values ranged between 3 and 22%, within the range of experimental uncertainty (between 5 and 35%, due to low isotope concentrations).

A compartmental model for the reactive flow of the radioisotope 131I, frequently introduced into the sewer system at varying concentrations through radiotherapy of thyroid diseases, has been developed for an existing municipal wastewater treatment plant (WWTP). It includes the transition of activity from dissolved to suspended particulate and colloid matter, and the separation of phases in sedimentation basins. It has been parametrized by experimental data obtained at key locations in the plant, and validated by measured time series of activity concentration of inflow and outflow. It can be used to predict concentrations at various locations in the WWTP, including outflow and primary sludge. It can also be reparameterized to be applied to other WWTPs based on activated sludge systems. In principle, a modification for the simulation of other nuclides is possible as well. As radioisotopes of iodine form an important part of accidental releases from nuclear power plants, they are monitored, and their environ...

International audience; Traces of particulate radioactive iodine (131I) were detected in the European atmosphere in January/February 2017. Concentrations of this nuclear fission product were very low, ranging 0.1 to 10 μBq m-3 except at one location in western Russia where they reached up to several mBq m-3. Detections have been reported continuously over an 8-week period by about 30 monitoring stations. We examine possible emission source apportionments and rank them considering their expected contribution in terms of orders of magnitude from typical routine releases: radiopharmaceutical production units > sewage sludge incinerators > nuclear power plants > spontaneous fission of uranium in soil. Inverse modeling simulations indicate that the widespread detections of 131I resulted from the combination of multiple source releases. Among them, those from radiopharmaceutical production units remain the most likely. One of them is located in Western Russia and its estimated source term complies with authorized limits. Other existing sources related to 131I use (medical purposes or sewage sludge incineration) can explain detections on a rather local scale. As an enhancing factor, the prevailing wintertime meteorological situations marked by strong temperature inversions led to poor dispersion conditions that resulted in higher concentrations exceeding usual detection limits in use within the informal Ring of Five (Ro5) monitoring network. © 2018 American Chemical Society.

Identifying sources and fluxes of suspended matter within the catchment is vitally important for the water quality of rivers and for establishing sediment management plans. Constituents of suspended particles are of abiotic and biotic origin. In the Elbe, the biotic fraction of suspended particles is mainly composed of phytoplankton biomass. In this study, total seston and phytoplankton are analyzed for their seasonality, their interdependence and temporal trends over three or five decades, respectively. The biotic load was separated from the total suspended matter load, and time series of total suspended substances (seston) (1964 to 2015) and chlorophyll a values (1985 to 2015) were analyzed. Our analyses focused on the seasonal dynamics, long-term trends, and the correlation to hydrological events. The mean share of phytoplankton in total seston accounted for 24% in summer months (April–September), with a negative correlation between discharge and total seston, and 11% in winter months (October–March), with a weak positive correlation between discharge and total seston. The long-term trend of seston load was decreasing, while phytoplankton load did not show a significant trend. Autochthonous biogenic portions should not be neglected in the budget of total suspended matter loads in the Elbe catchment. Our results indicate that land-use and industrial changes subsequent to the German reunification mainly caused the observed trend. Phytoplankton growth superimposes the seasonal dynamics of seston in summer, whereas in the long term, decreasing mineral fraction dominates the significantly decreasing trend.

As a consequence of therapeutic and diagnostic treatment of patients with thyroid diseases, 131 I is introduced into the sewage system on a regular basis. This presents an opportunity to use the 131 I as a tracer to study its partitioning and transport within a wastewater treatment plant (WWTP). In the case of nuclear accidents where 131 I is one of the most prominent nuclides, an understanding of iodine partitioning and transport will be valuable for developing models that may prognosticate the activity concentrations in sludge and outflow, especially after an accidental input. In this study, samples from various locations inside a municipal WWTP were taken and for each sample, three different fractions were separated by a chemical extraction process. These fractions were analysed for their 131 I activity concentrations by gamma-ray spectroscopy. While about 30% of the radioiodine activity in the inflow is associated with organic molecules, this amounts to about 90% after biological treatment. This is caused by the accumulation of 131 I bound to organic matter in the return sludge and by a transfer of 131 I from the inorganic to the organic fractions, most likely mediated by microbial action. In the outflow, inorganic and low-molecular 131 I is dominant, but the overall activity concentration is reduced to about 50–75%.

Significance A massive atmospheric release of radioactive 106Ru occurred in Eurasia in 2017, which must have been caused by a sizeable, yet undeclared nuclear accident. This work presents the most compelling monitoring dataset of this release, comprising 1,100 atmospheric and 200 deposition data points from the Eurasian region. The data suggest a release from a nuclear reprocessing facility located in the Southern Urals, possibly from the Mayak nuclear complex. A release from a crashed satellite as well as a release on Romanian territory (despite high activity concentrations) can be excluded. The model age of the radioruthenium supports the hypothesis that fuel was reprocessed ≤2 years after discharge, possibly for the production of a high-specific activity 144Ce source for a neutrino experiment in Italy., In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m−3 to more than 150 mBq·m−3. The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.

Mangrove ecosystems are an important natural carbon sink that accumulate and store large amounts of organic carbon (Corg), in particular in the sediment. However, the magnitude of carbon stocks and the rate of carbon accumulation (CAR) vary geographically due to a large variation of local factors. In order to better understand the blue carbon sink of mangrove ecosystems, we measured organic carbon stocks, sources and accumulation rates in three Indonesian mangrove ecosystems with different environmental settings and conditions; (i) a degraded estuarine mangrove forest in the Segara Anakan Lagoon (SAL), Central Java, (ii) an undegraded estuarine mangrove forest in Berau region, East Kalimantan, and (iii) a pristine marine mangrove forest on Kongsi Island, Thousand Islands, Jakarta. In general, Corg stocks were higher in estuarine than in marine mangroves, although a large variation was observed among the estuarine mangroves. The mean total Corg stock in Berau (615 ± 181 Mg C ha−1) is twice as high as that in SAL (298 ± 181 Mg C ha−1). However, the Segara Anakan Lagoon displayed large within-system variation with a much higher Corg stock in the eastern (483 ± 124 Mg C ha−1) than in the central lagoon (167 ± 36 Mg C ha−1). The predominant accumulation of autochthonous mangrove organic matter likely contributed to the higher Corg stocks in Berau and the eastern SAL. Interestingly, the CAR distribution pattern in SAL is opposite to that of its Corg stocks. The central SAL that receives high sediment inputs from the hinterland has a much higher CAR than the eastern SAL (658 ± 311 g C m−2 yr−1 and 194 ± 46 g C m−2 yr−1, respectively), while Berau has one of the highest CAR (1722 ± 183 g C m−2 yr−1) ever measured. It appears that these large differences are driven by the environmental setting and conditions, mainly sediment dynamics and hydrodynamics, landform, and vegetation conditions. It is inferred that quantifying carbon accumulation in sediments is a useful tool in estimating the present-day carbon storage of mangrove ecosystems. This is a precondition for taking measures under REDD+ (Reducing Emissions from Deforestation and Forest Degradation and the role of conservation, sustainable management of forests and enhancement of forest carbon stocks in developing countries) schemes.

The weir pool Serrig is the deepest one along the impounded river Saar. Damming caused massive changes in the river's hydrodynamics. We analyzed the spatio-temporal variability of thermal density s ...

The present study analyzes climate change effects on the water temperature of the Rhine, one of the largest rivers in Central Europe. Simulation calculations were performed based on a range of climate and river flow projections for the near (2021–2050) and for the far future (2071–2100) compared to a reference period (1961–1990). Changes in mean annual water temperature in the near future range between +0.6 and +1.4 °C and between +1.9 and +2.2 °C in the far future (average of nine stations). Monthly mean values of the far future change in a more differentiated way by +0.4 to +1.3 °C in spring and +2.7 to +3.4 °C in late summer. The length of periods of high water temperature, expressed as successive days with water temperatures over 27 °C, increases by a factor of four until 2100. These prolonged durations of periods with unusually high water temperatures may provoke changes in the food web and in the rates of biological processes in the Rhine.

A compartmental model for the reactive flow of the radioisotope

Radionuclide concentrations were studied in sediment cores taken at the continental slope of the Philippine Sea off Mindanao Island in the equatorial Western Pacific. High resolution deposition records of anthropogenic radionuclides were collected at this site. Excess 210Pb together with excess 228Th and anthropogenic radionuclides provided information about accumulation rates. Concentrations of Am and Pu isotopes were detected by gamma spectrometry, alpha spectrometry and ICP-MS. The Pu ratios indicate a high portion (minimum of 60%) of Pu from the Pacific Proving Grounds (PPG). This implies that the transport of PPG derived plutonium with the Mindanao Current southward is similarly effective as the previously known transport towards the north with the Kuroshio Current. The record is compared to other studies from northwest Pacific marginal seas and Lombok basin in the Indonesian Archipelago. The sediment core top was found to contain a 6 cm thick layer dominated by terrestrial organic matter, which was interpreted as a result of the 2012 Typhoon Pablo-related fast deposition.

Unusually high concentrations of americium and plutonium have been observed in a sediment core collected from the eastern Lombok Basin between Sumba and Sumbawa Islands in the Indonesian Archipelago. Gamma spectrometry and accelerator mass spectrometry data together with radiometric dating of the core provide a high-resolution record of ongoing deposition of anthropogenic radionuclides. A plutonium signature characteristic of the Pacific Proving Grounds (PPG) dominates in the first two decades after the start of the high yield atmospheric tests in 1950's. Approximately 40-70% of plutonium at this site in the post 1970 period originates from the PPG. This sediment record of transuranic isotopes deposition over the last 55 years provides evidence for the continuous long-distance transport of particle-reactive radionuclides from the Pacific Ocean towards the Indian Ocean.

Samarium-153-lexidronam is a radiopharmaceutical used for pain palliation therapy in patients suffering from multilocular bone metastases. The postinjection residual of four pharmaceutical vials of 153 Sm-lexidronam and one patient were investigated for contamination with other isotopes using high-resolution gamma spectroscopy. In the spectra besides the already known contaminants europium-154, 155 Eu and 156 Eu, europium-152 was discovered in vitro and also in vivo. 152 Eu disintegrates with a half-life of 13.5 years emitting a multitude of high energy photons. Due to these properties, it does not only affect radioactive waste management regarding e.g. the disposal of the postinjection residual, but also poses an additional dose burden to the patient and to third persons. In the postinjection residual a mean activity concentration of 10.4±1.1 kBq europium-152 per GBq 153 Sm was detected. 62 days after isotope application, 15.8±4.0 kBq of 152 Eu were found within the patient. The lifetime effective dose to the patient from the europium impurities was determined using a multicompartment model. For 152 Eu the effective dose was 2.1 mSv/GBq 153 Sm-lexidronam and the total effective dose from all impurities was 6.1 mSv/GBq 153 Sm-lexidronam. The total absorbed dose to third persons caused by the europium impurities was estimated as 0.6 mGy/GBq 153 Sm-lexidronam.

Natural radionuclides and man-made 137Cs were analyzed in five short sediment cores taken in northern part of the Gulf of Eilat (Gulf of Aqaba) in order to provide information on sedimentation and mixing rates and sediment sources. The maximum estimates of sedimentation rates based on excess 210Pb were found to vary between 0.105 ± 0.020 and 0.35 ± 0.23 cm · year− 1. Even the lowest estimates are significantly higher than those expected from dust deposition, suggesting other sources and processes being responsible for most of the allochthonous material accumulation, including periodical floods following heavy rain events, internal erosion or triggers, like earthquakes. In 137Cs depth profiles no 1963 related nuclear weapon test maxima were found; instead, the activities decrease monotonically, suggesting that a major process leading to radionuclides' depth distribution might be mixing. The mixing rates calculated from 137Cs, excess 210Pb and excess 228Th reach values up to 2.18 ± 0.69 cm2 · year− 1.

The Australian–Indonesian monsoon has a governing influence on the agricultural practices and livelihood in the highly populated islands of Indonesia. However, little is known about the factors that have influenced past monsoon activity in southern Indonesia. Here, we present a ∼6000 years high-resolution record of Australian-Indonesian summer monsoon (AISM) rainfall variations based on bulk sediment element analysis in a sediment archive retrieved offshore northwest Sumba Island (Indonesia). The record suggests lower riverine detrital supply and hence weaker AISM rainfall between 6000 yr BP and ∼3000 yr BP compared to the Late Holocene. We find a distinct shift in terrigenous sediment supply at around 2800 yr BP indicating a reorganization of the AISM from a drier Mid Holocene to a wetter Late Holocene in southern Indonesia. The abrupt increase in rainfall at around 2800 yr BP coincides with a grand solar minimum. An increase in southern Indonesian rainfall in response to a solar minimum is consistent with climate model simulations that provide a possible explanation of the underlying mechanism responsible for the monsoonal shift. We conclude that variations in solar activity play a significant role in monsoonal rainfall variability at multi-decadal and longer timescales. The combined effect of orbital and solar forcing explains important details in the temporal evolution of AISM rainfall during the last 6000 years. By contrast, we find neither evidence for volcanic forcing of AISM variability nor for a control by long-term variations in the El Nino-Southern Oscillation (ENSO).

Direct radiometric determination of (14)N (γ, n) (13)N air activation was achieved at a 15-MV medical linear accelerator operating in a high-energy photon mode. (13)N was identified by irradiating a gas-tight Marinelli beaker filled with nitrogen gas and later observing the 10-min half-life of the 511-keV positron-electron annihilation line using high-resolution gamma spectroscopy. Quantitative evaluation of the spectral signal yielded a (13)N production rate of 836.8 ± 32 Bq Gy(-1) in air per 40 × 40 cm(2) field cross section at 100 cm source-surface distance.

Radioisotope concentrations (Cs-137 and I-131) in sewage sludge, obtained on a daily basis in the Fukushima city wastewater treatment plant from end of April 2011 until end of December 2013, have been analysed for their evolution with time, and the time series have been compared to similar data from central Europe after the Chernobyl accident. Additionally, daily rainfall data have been considered for Fukushima. The long-term trends for Cs-137 are very similar between Japan and Europe, indicating a decrease of concentration with an initial half-life of about 1 year with a tendency towards a slower decrease at later times. Short-term Cs-137 data indicate a dominating influence of rainfall – each significant rainfall event leads to a sharp increase of sludge Cs-137 concentration. Absolute values (maximum: ca. 6000 Bq kg -1 ) are relatively low compared to Europe after 1986 – this is attributed to the different types of sewer systems: separated in Fukushima, collecting only small amounts of rainfall with the wastewater, mixed in many cities in Europe, collecting rainwater and wastewater in the same sewer. I-131 was detectable during short intervals and at relatively constant maximum concentration (ca. 1000 Bq kg -1 ) during the whole observation period. The origin is suspected to be routine medical application of the isotope, which has been shown to contribute significantly to sewage sludge concentration wherever it is in use.

In this study it is shown how radionuclide distributions in agricultural soils and their dependence on soil parameters can be quantitatively estimated. The most important sorption and speciation processes have been implemented into a numerical model using the geochemical code PHREEQC that is able to include specific soil and soil solution compositions. Using this model, distribution coefficients (Kd values) for the elements Cs, Ni, U and Se have been calculated for two different soil types. Furthermore, the dependencies of these Kd values on various soil parameters (e.g. pH value or organic matter content) have been evaluated. It is shown that for each element, an individual set of soil parameters is relevant for its solid-liquid distribution. The model may be used for the calculation of input parameters used by reference biosphere models (e.g. used for the risk assessment of nuclear waste repositories).

In this paper, it is shown how free induction decay signals recorded in the Earth’s magnetic field from water protons confined in porous media can be used to derive transversal relaxation times (T 2) and their distributions. After T 2 determination of six sintered glass samples with various pore sizes, the common theoretical model can be fitted to the data set. The T 2 distribution of water protons in a bimodal porous system is analyzed and compared to mercury porosimetry results. The implications for the calculation of pore sizes and pore size distributions of porous media by this method are discussed.

In literature quite a lot of data is available on uptake of radioactive caesium in mushrooms. There is less available on the evolution of concentration in fruitbodies after several years and on “outbound” transfer of radiocaesium from fruitbodies to their direct environment, i.e. dilution according to cooking techniques. The recent event at Fukushima has put the question of radionuclides in food, and the following exposure of consumers, high on the agenda. The purpose of this paper is twofold: (1) in order to investigate the variation in time of caesium uptake by fungi, analyses of the same species having grown on the same spot at different intervals during the last 25 years have been performed and (2) in terms of radiation protection the most important thing is the activity taken in by the consumer and not the contamination of raw products. Preparation can have a great impact on activity concentration. Various species of mushrooms frequently eaten have been sampled in Europe and contaminated areas in Japan. Different preparation techniques that can break the walls of the hyphae (drying, deepfreezing etc.) have been applied as well as different treatments: boiling or macerating in water with salt, in acid and basic media. The pH of different media was adjusted and measured. The samples and the medium were analysed separately in gamma spectrometry.

As a consequence of therapeutic and diagnostic treatment of patients with thyroid diseases

Traces of short- and long-lived fallout isotopes ((131)I, (134)Cs and (137)Cs) were found in environmental samples collected in Northwest Germany (rain water, river sediment, soil, grass and cow milk) from March to May 2011, following the radioactivity releases after the nuclear accident in Fukushima, Japan. The measured concentrations are consistent with reported concentrations in air, amount of rainfall and expected values applying simple radioecological models. The [(134)Cs]/[(137)Cs] ratio reported for air (about 1) allows for discrimination between "recent" and "old"(137)Cs. Expected (136)Cs values fell below the detection limits of the instrumentation, despite large sample masses and long counting times.

Traces of short- and long-lived fallout isotopes ( 131 I, 134 Cs and 137 Cs) were found in environmental samples obtained in northwest Germany (river sediment, rainwater, grass and milk) from March to May 2011, following the radioactivity releases after the nuclear accident in Fukushima, Japan. The found concentration values are consistent with reported concentrations in air, amount of rainfall and expected values applying simple radioecological models. The [ 134 Cs]/[ 137 Cs] ratio reported for air (about 1:1) allows for discrimination between “recent” and “old” 137 Cs. Expected 136 Cs values fell below the detection limits of the instrumentation, despite large sample masses and long counting times.

A widely applied method of supported lead estimation in sediments using gamma spectrometric 226 Ra determination via 222 Rn short lived daughter products relies on radioactive equilibrium between 226 Ra and 222 Rn being established after sealing the samples. Advantages and disadvantages of methods of 226 Ra estimation in sediments, using either 226 Ra daughter products or direct estimation by the 186.2 keV gamma-emissions are discussed. An equilibrium experiment was performed using test samples and in one case radioactive equilibrium was not reached. On theoretical sediment profiles it is shown how systematic errors in supported 210 Pb estimation can lead to wrong interpretations of 210 Pb xs profiles and therefore affect 210 Pb derived chronologies.

In this study it is shown how the behaviour of radionuclides in agricultural soils can be quantitatively estimated. The sorption of those nuclides onto soil particle surfaces is a key process which every predictive model has to take into account. This has been accomplished by implementing a component additivity (CA-) model into the well known geochemical code PHREEQC that includes the most important sorbents clay, amorphous iron oxide and organic matter. For uranium and cesium it is shown that model calculations are in excellent agreement with experimental data.

The effects of changing climatic and socioeconomic conditions on the water quality of the Elbe River were investigated using the deterministic model QSim. Since the impact of global change on river water quality marks the endpoint of various processes in the catchment and in the atmosphere, this study was performed within a network of interacting models that determined input parameters for water quality simulations. The development of phytoplankton and nutrient concentrations under conditions of global change was modeled along a 700 km stretch of the river. The simulations revealed a strong, scale-dependent effect of climate change on phytoplankton biomass, leading to a longitudinal shift of the dominating processes (primary productivity vs. respiration) along the river continuum. Under reduced flow, combined with increasing temperature and global radiation, phytoplankton biomass increased and phytoplankton maxima shifted in upstream direction, followed by higher system respiration rates in the adjacent downstream sections. In contrast, higher flow shifted the phytoplankton maximum toward the downstream sections. Even a drastic reduction of phosphorus inputs from anthropogenic sources had only limited influence on algal biomass, due to the ability of algal cells to store phosphorus. A strong reduction in P-inputs especially in the headwaters would be necessary to counterbalance the possible climate-induced effects on algal biomass.

A standard 40 foot shipping container with a cargo of pressurized krypton gas in 159 steel cylinders, which had triggered a radiation alarm, was investigated to address radiation safety and illicit nuclear trafficking concerns. The investigation included contamination and dose rate measurements as well as in situ high resolution gamma spectroscopy. The dose rate measurements gave a maximum value of 0.07 microSv h(-1) above background (0.08 to 0.11 microSv h(-1)) on the cylinder surface and no detectable increase above background at distances of 1 m and higher. Contamination monitor readings showed a similar relative increase (plus 8 cpm) above background (about 12 cpm) to the dose rate readings. Quantitative gamma spectroscopy revealed a contamination of the gas with 85Kr at a level of 3.5 x 10(5) Bq kg(-1). This value was found to be consistent with analytical and numerical estimates based on current data for atmospheric 85Kr, which is captured from ambient air together with stable krypton during the production process. This incident demonstrates an apparent lack of radiation-related knowledge by those who handle krypton gas, as well as by border control personnel and emergency responders. We therefore propose to improve labeling and documentation standards for such shipments. This effort may be facilitated by introducing the new category of "technically enhanced artificial radioactive material," or "TEARM" (similar to the existing "naturally occurring radioactive material" or "NORM" and "technically enhanced naturally occurring radioactive material" or "TENORM" categories).

Sequences of in situ gamma spectra, accompanied by continuous dose rate measurements, have been obtained at the isocenters of four different brands of high-energy medical linear accelerators shortly after beam-off in order to study the effects of radioactivation. Spectral analysis revealed up to 20 different radionuclides per machine, with a total of 21 found isotopes having half-lives between 2.3 min and 5.3 y. Important isotopes as judged from activity, dose rate, and half-life were Al, Mn, Mn, Ni, Co, Cu, Cu, Sb, W, and Au. Dose rates at isocenter calculated from the results of spectrum analysis ranged between 0.78 and 3.16 microSv h after beam-off, decaying to values between 0.18 and 0.54 microSv h within 30 min. Measured dose rates were systematically higher by up to a factor of 2, which is attributed mainly to the effect of beta radiation. No systematic dependence on machine properties or manufacturer could be identified. Assuming realistic working scenarios, absorbed dose values for the radiotherapy technologist staff range between 0.62 and 2.53 mSv y.

Time series of in situ gamma spectroscopy data from 6 sites, obtained over a period of 13 years as part of a routine surveillance program, have been investigated for variability, reproducibility and occurrence of trends. Natural isotopes ((40)K, (208)Tl, (212)Pb and (214)Pb) show variability up to a factor of 2, with time patterns varying from site to site. At five (level) sites (137)Cs values decreased at a rate higher than given by the physical half-life, consistent with literature data on migration of Cs. At one (downhill) site, an increase of (137)Cs with time was observed. The finding can be explained by erosion processes from uphill territories. The observed variations were larger than the experimental uncertainty, and the equipment long-term stability appeared to be satisfactory. It can be concluded that the obtained routine in situ data provide a valuable data pool with potential usefulness for scientific work.

In the majority of large river systems, flow is regulated and/or otherwise affected by operational and management activities, such as ship locking. The effect of lock operation on sediment-water oxygen fluxes was studied within a 12.9 km long impoundment at the Saar River (Germany) using eddy-correlation flux measurements. The continuous observations cover a time period of nearly 5 days and 39 individual locking events. Ship locking is associated with the generation of surges propagating back and forth through the impoundment which causes strong variations of near-bed current velocity and turbulence. These wave-induced flow variations cause variations in sediment-water oxygen fluxes. While the mean flux during time periods without lock operation was 0.5 6 0.1 g m�2 d�1, it increased by about a factor of 2 to 1.0 6 0.5 g m�2 d�1 within time periods with ship locking. Following the daily schedule of lock operations, fluxes are predominantly enhanced during daytime and follow a pronounced diurnal rhythm. The driving force for the increased flux is the enhancement of diffusive transport across the sediment-water interface by bottom-boundary layer turbulence and perhaps resuspension. Additional means by which the oxygen budget of the impoundment is affected by lock-induced flow variations are discussed.

To obtain insight into the natural and/or human-induced changes in the trophic state of the distal portion of the Po River discharge plume over the last two centuries, high temporal resolution dinoflagellate cyst records were established at three sites. Cyst production rates appear to reflect the natural variability in the river's discharge, whereas cyst associations reflect the trophic state of the upper waters, which in turn can be related to agricultural development. The increased abundances of Lingulodinium machaerophorum and Stelladinium stellatum found as early as 1890 and 1920 correspond to the beginning of the industrial revolution in Italy and the first chemical production and dispersion of ammonia throughout Europe. After 1955, the increased abundances of these species and of Polykrikos schwartzii, Brigantedinium spp. and Pentapharsodinium dalei correspond to agriculturally induced alterations of the hypertrophic conditions. A slight improvement in water quality can be observed from 1987 onward.

Motivated by the detection of 131 I in river sediment in routine long-term surveillance samples, a systematic short-term study of the wastewater treatment chain was planned and conducted. Inflow, effluent and primary sludge were collected on a daily basis during two weeks at a regional wastewater treatment plant. Samples were investigated by gamma spectroscopy. Four medically used isotopes could be identified ( 131 I and 99m Tc regularly, 153 Sm and 123 I sporadically). The concentration levels coincide well with literature data for 131 I, and with our own long-term data for 131 I and 99m Tc for the same plant. Cosmogenic 7 Be activity in primary sludge correlated well with rainfall intensity. Surface sediment was sampled at low tide at both shores of the river, up- and downstream of the plant. 131 I was identified in all samples, with a sharp maximum (about 100 Bq kg −1 d.m.) at the discharge point of the plant and lower levels elsewhere, decreasing monotonically in downstream direction. 7 Be and 137 Cs showed the same behaviour, but no peak at the discharge point. Predictions from simple equilibrium models for the transport and sedimentation of 131 I show good agreement with the experimental data and suggest that the wastewater treatment plant is the main source for this isotope.

Near-shore waters along the northwest African margin are characterized by coastal upwelling and represent one of the world's major upwelling regions. Sea surface temperature (SST) records from Moroccan sediment cores, extending back 2500 years, reveal anomalous and unprecedented cooling during the 20th century, which is consistent with increased upwelling. Upwelling-driven SSTs also vary out of phase with millennial-scale changes in Northern Hemisphere temperature anomalies (NHTAs) and show relatively warm conditions during the Little Ice Age and relatively cool conditions during the Medieval Warm Period. Together, these results suggest that coastal upwelling varies with NHTAs and that upwelling off northwest Africa may continue to intensify as global warming and atmospheric CO 2 levels increase.

Activation products have been identified by in situ gamma spectroscopy at the isocentre of a medical linear accelerator shortly after termination of a high energy photon beam irradiation with 15 x 15 cm field size. Spectra have been recorded either with an open or with a closed collimator. Whilst some activation products disappear from the spectrum with closed collimator or exhibit reduced count rates, others remain with identical intensity. The former isotopes are neutron-deficient and mostly decay by positron emission or electron capture; the latter have neutron excess and decay by beta(-) emission. This new finding is consistent with the assumption that photons in the primary beam produce activation products by (gamma, n) reactions in the treatment head and subsequently the neutrons created in these processes undergo (n, gamma) reactions creating activation products in a much larger area. These findings are expected to be generally applicable to all medical high energy linear accelerators.

The Scaling-Index-Method (SIM) has been extended by applying weighting functions which take into account the information available on the noise characteristics. The transformation of an image by applying the weighted Scaling-Index-Method yields a measure which depends on the local correlation of the image pixels and the noise structure in the image. In nuclear medicine imaging, the methods based on the SIM enables to extract sources superimposed by strong noise or to discriminate real sources from tomographic artifacts.

Human brain white matter exhibits an uncommonly strong dispersion of 1/T1 at high fields. An additional relaxation pathway via the myelin lipids, which are not directly visible to medical NMR due to their fast T2 decay, is proposed. Relaxation dispersion data are successfully analyzed on the basis of this model. © 1989 Academic Press, Inc.

Relaxometry between 10 kHz and 200 MHz (0.2 mT and 4.7 T) with a field-cycling device and a high-field-strength magnetic resonance (MR) unit permitted the determination of longitudinal relaxation rates of tissues and chemical compounds at numerous field strengths. The resulting nuclear magnetic relaxation dispersion profiles allowed the prediction of tissue contrast and efficacy of contrast agents at any field strength. Pure T1 contrast of normal brain tissue and pathologic lesions (multiple sclerosis, astrocytoma) increased from low field strengths to a maximum between 10 and 20 MHz and decreased afterward. Quadripolar dips reflecting the interaction between water and nitrogen atoms of the protein backbone appeared at 2.15 and 2.8 MHz, reducing T1 and opening the possibility of shorter imaging times and better tissue discrimination at these field strengths. Furthermore, it was shown that zero T1 contrast between normal and pathologic tissue samples may exist at certain field strengths. Gadolinium diethylenetriaminepentaacetic acid and gadolinium tetraazacyclododecanetetraacetic acid provided different contrast enhancement depending on the field strength.

Knowledge about the dependence of NMR parameters of excised tissues on time and storage conditions is important for correct interpretation of in vivo clinical results based upon in vitro measurements which in many cases are easier to perform. Literature data on this topic are scarce and sometimes contradictory. In this study, we investigated the change of the proton longitudinal relaxation rate (1/T1) of freshly excised rat tissues with storage conditions over a wide range of proton Larmor frequencies (0.01-50 MHz). Special interest was paid to long-term storage in the deep frozen state. After deep freezing of tissue samples on dry ice, no significant changes in 1/T1 over the whole frequency range could be observed for brain tissue, whereas for muscle and liver tissue characteristic alterations were detected. We conclude that for normal brain tissue this storage procedure is suitable for the prediction of in vivo 1/T1 results from in vitro studies. © 1989 Academic Press, Inc.

Observation of the relaxivity of MRI contrast media over a wide range of magnetic fields is not only necessary for predicting their efficiency at any field but also compulsory for understanding and improving their mechanisms of action. The best experimental approach to this problem is the field cycling method, which allows the exploration of nuclear relaxation over a broad interval of magnetic field intensity but requires a specially dedicated instrument called a relaxometer. Particularly relevant are the relaxivity profiles of the two chelates Gd-DOTA and Gd-DTPA. Both show an important decrease from low to high fields within the current imaging range (0.02 T to 1.5 T). Although high field relaxivities of these chelates are similar, Gd-DTPA becomes less efficient in facilitating water protons relaxation at fields lower than 0.15 T. This behavior has to be related to different electronic relaxation times due to a different chelate symmetry.