A Simple Compartment Model for the Dynamical Behavior of Medically Derived 131I in a Municipal Wastewater Treatment Plant.

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 environmental behavior is predicted by models. The present work can contribute to these efforts by improving predictions of radioiodine transport in the public sewer system.

Pacific Proving Grounds radioisotope imprint in the Philippine Sea sediments.

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.

The physicochemical distribution of 131I in a municipal wastewater treatment plant.

As a consequence of therapeutic and diagnostic treatment of patients with thyroid diseases, 131I is introduced into the sewage system on a regular basis. This presents an opportunity to use the 131I as a tracer to study its partitioning and transport within a wastewater treatment plant (WWTP). In the case of nuclear accidents where 131I 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 131I 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 131I bound to organic matter in the return sludge and by a transfer of 131I from the inorganic to the organic fractions, most likely mediated by microbial action. In the outflow, inorganic and low-molecular 131I is dominant, but the overall activity concentration is reduced to about 50-75%.

Continuous transport of Pacific-derived anthropogenic radionuclides towards the Indian Ocean.

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.

Detection of long-lived europium-152 in samarium-153-lexidronam.

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 13.5years 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±1.1kBq europium-152 per GBq (153)Sm was detected. 62days after isotope application, 15.8±4.0kBq 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 2.1mSv/GBq (153)Sm-lexidronam and the total effective dose from all impurities was 6.1mSv/GBq (153)Sm-lexidronam. The total absorbed dose to third persons caused by the europium impurities was estimated as 0.6mGy/GBq (153)Sm-lexidronam.

Estimating the distribution of radionuclides in agricultural soils - dependence on soil parameters.

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).

Time series data from routine in situ gamma spectroscopy measurements.

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.

The use of dinoflagellate cysts to separate human-induced from natural variability in the trophic state of the Po River discharge plume over the last two centuries.

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.

Fukushima fallout in Northwest German environmental media.

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.

Increase in African dust flux at the onset of commercial agriculture in the Sahel region.

The Sahara Desert is the largest source of mineral dust in the world. Emissions of African dust increased sharply in the early 1970s (ref. 2), a change that has been attributed mainly to drought in the Sahara/Sahel region caused by changes in the global distribution of sea surface temperature. The human contribution to land degradation and dust mobilization in this region remains poorly understood, owing to the paucity of data that would allow the identification of long-term trends in desertification. Direct measurements of airborne African dust concentrations only became available in the mid-1960s from a station on Barbados and subsequently from satellite imagery since the late 1970s: they do not cover the onset of commercial agriculture in the Sahel region approximately 170 years ago. Here we construct a 3,200-year record of dust deposition off northwest Africa by investigating the chemistry and grain-size distribution of terrigenous sediments deposited at a marine site located directly under the West African dust plume. With the help of our dust record and a proxy record for West African precipitation we find that, on the century scale, dust deposition is related to precipitation in tropical West Africa until the seventeenth century. At the beginning of the nineteenth century, a sharp increase in dust deposition parallels the advent of commercial agriculture in the Sahel region. Our findings suggest that human-induced dust emissions from the Sahel region have contributed to the atmospheric dust load for about 200 years.

Krypton gas cylinders as a source of radiation.

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).

Medical radioisotopes in the environment - following the pathway from patient to river sediment.

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.

Comparison of activation products and induced dose rates in different high-energy medical linear accelerators.

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.

Activation processes in a medical linear accelerator and spatial distribution of activation products.

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.