Imaging of I, Re and Tc plant uptake on the single-cell scale using SIMS and rL-SNMS.

In radioecological studies, there is a significant need for understanding the plant uptake of radionuclides on a cellular level. The present work applies mass spectrometry to image the radionuclide distribution within the cellular structures of plants at varying concentrations. In a first step, plants of Daucus carota and Pisum sativum labelled with iodine and rhenium were examined, at concentrations in the range of 10 mM. Cross sections of several plant parts were imaged by secondary ion mass spectrometry (SIMS) after cryogenation in order to preserve cell structure. In a second step, the distribution of 99Tc in the two plant species was determined. For radiological reasons, a concentration three orders of magnitude lower was used, rendering measurements with SIMS impossible. Therefore, resonant laser secondary neutral mass spectrometry (rL-SNMS) was used for the first time to image 99Tc with suppression of molecular isobaric interferences. The measurement of only about 1010 atoms of 99Tc atoms is demonstrated and the distribution of 99Tc within a single epidermal cell is imaged.

Sorption of iodine in soils: insight from selective sequential extractions and X-ray absorption spectroscopy.

The environmental fate of iodine is of general geochemical interest as well as of substantial concern in the context of nuclear waste repositories and reprocessing plants. Soils, and in particular soil organic matter (SOM), are known to play a major role in retaining and storing iodine. Therefore, we investigated iodide and iodate sorption by four different reference soils for contact times up to 30 days. Selective sequential extractions and X-ray absorption spectroscopy (XAS) were used to characterize binding behavior to different soil components, and the oxidation state and local structure of iodine. For iodide, sorption was fast with 73 to 96% being sorbed within the first 24 h, whereas iodate sorption increased from 11-41% to 62-85% after 30 days. The organic fraction contained most of the adsorbed iodide and iodate. XAS revealed a rapid change of iodide into organically bound iodine when exposed to soil, while iodate did not change its speciation. Migration behavior of both iodine species has to be considered as iodide appears to be the less mobile species due to fast binding to SOM, but with the potential risk of mobilization when oxidized to iodate.

MEASUREMENTS IN AFGHANISTAN USING AN ACTIVE RADON EXPOSURE METER AND ASSESSMENT OF RELATED ANNUAL EFFECTIVE DOSE.

Radon gas concentrations in eight basements, four living rooms and four caves from different locations in Kabul and Panjsher, Afghanistan, were measured by using eight active radon exposure meters recently developed by the Helmholtz Center in Munich, Germany. The two-phase measurements lasted from a week to a year. In the first phase of measurements which lasted one week, the mean activity concentrations ranged from 6 to 120 Bq/m3 and 25 to 139 Bq/m3 for the basements and caves, respectively. In the second phase of measurements which lasted one year, the mean activity concentrations ranged from 33 to 2064 Bq/m3 and the corresponding effective annual doses calculated for the inhabitants were in the range between 0.6 and 33.4 mSv. As some of the values are rather high and exceed the recommended recommendations by IAEA and ICRP, based on the local conditions a number of simple recommendations has been proposed for the possible reduction of effective annual dose caused by radon in the measurement locations.

Radioecological investigation of 3H, 14C, and 129I in natural waters from Fuhrberger Feld catchment, Northern Germany.

Ongoing radionuclide releases from nuclear facilities, e.g. from reprocessing plants, but also from nuclear reactors require monitoring of the environment. Particularly drinking water reservoirs are prone to possible radionuclide accumulation fostering the need for routine surveillance. In this work, we investigated tritium (3H), radiocarbon (14C), and iodine-129 (129I) activity levels in natural aquatic samples at the water protection area of Fuhrberger Feld near Hannover city, Northern Germany. For that aim, a low-level liquid scintillation counting (LSC) technique was used to measure 3H in the water samples based on a distillation process after alkaline permanganate treatment. Isotopic ratios for both 14C and 129I were measured by accelerator mass spectrometry (AMS) after chemical separation and purification of the samples. Mean 3H levels in precipitation (8.8 ± 3.4 TU) were found to be comparable to its levels in precipitation data in Germany. Rivers and small streams revealed similar mean 3H value (11.0 ± 3.3 TU) as in lake water (10.6 ± 3.4 TU). Variations in 3H concentrations in groundwater samples were observed and discussed. 14C levels in all groundwater samples were below the atmospheric natural level of 100 pMC indicating no anthropogenic input of radiocarbon. The 129I/127I isotopic ratios in all investigated water samples were in the order of 10-8 to 10-7, which is significantly higher than the pre-nuclear natural equilibrium isotopic ratio (∼1.5 × 10-12). In strong contrast to all other regional groundwaters, the Fuhrberger Feld groundwater has much higher values of 129I concentration and 129I/127I isotopic ratio close to the ones of surface water. The overall annual effective dose via ingestion for all nuclides in the investigated groundwater remains substantially below the reference dose level of 0.1 mSv a-1.

Fukushima-derived radionuclides in sediments of the Japanese Pacific Ocean coast and various Japanese water samples (seawater, tap water, and coolant water of Fukushima Daiichi reactor unit 5).

We investigated Ocean sediments and seawater from inside the Fukushima exclusion zone and found radiocesium (134Cs and 137Cs) up to 800 Bq kg-1 as well as 90Sr up to 5.6 Bq kg-1. This is one of the first reports on radiostrontium in sea sediments from the Fukushima exclusion zone. Seawater exhibited contamination levels up to 5.3 Bq kg-1 radiocesium. Tap water from Tokyo from weeks after the accident exhibited detectable but harmless activities of radiocesium (well below the regulatory limit). Analysis of the Unit 5 reactor coolant (finding only 3H and even low 129I) leads to the conclusion that the purification techniques for reactor coolant employed at Fukushima Daiichi are very effective.