Increased environmental gamma-ray dose rate during precipitation: a strong correlation with contributing air mass

It has long been observed that the environmental gamma-ray dose rate increases noticeably during precipitation intervals. This increase, due to the presence of radon progeny in the rain droplets (or snow flakes), can affect the reliability of the monitoring of artificial radioactivity and long term estimates of exposure to ambient natural radionuclides in surveillance network. Predicting the amplitude of the dose increase has been shown to be surprisingly challenging. In this work, standard air mass back trajectory analysis is used to show that the amplitude of the increase can be quantitatively linked to the history of the air mass where the precipitation is occurring. Furthermore, we show how back trajectory analysis, environmental gamma and rain data can be used to obtain estimations of relative radon emanation rates for locations far from the actual point of detection.     

Computerised Decision Support Systems for the management of freshwater radioecological emergencies: assessment of the state-of-the-art with respect to the experiences and needs of end-users

Assessment of the environmental and radiological consequences of a nuclear accident requires the management of a great deal of data and information as well as the use of predictive models. Computerised Decision Support Systems (CDSS) are essential tools for this kind of complex assessment and for assisting experts with a rational decision process. The present work focuses on the assessment of the main features of selected state-of-the-art CDSS for off-site management of freshwater ecosystems contaminated by radionuclides. This study involved both developers and end-users of the assessed CDSS and was based on practical customisation exercises, installation and application of the decision systems. Potential end-users can benefit from the availability of several ready-to-use CDSS that allow one to run different kinds of models aimed at predicting the behaviour of radionuclides in aquatic ecosystems, evaluating doses to humans, assessing the effectiveness of different kinds of environmental management interventions and ranking these interventions, accounting for their social, economic and environmental impacts. As a result of the present assessment, the importance of CDSS “integration” became apparent: in many circumstances, different CDSS can be used as complementary tools for the decision-making process. The results of this assessment can also be useful for the future development and improvement of the CDSS.     

Radionuclides in terrestrial ecosystems of the zone of Kyshtym accident in the Urals

It was shown that along the Eastern Ural Radioactive Trace central axis, about 100 km in length, decrease of the ⁹⁰Sr and ¹³⁷Cs deposition densities in soil samples may be described as an exponential function. At the western and eastern periphery of the trace, ⁹⁰Sr contents in soils approached to the background level due to global fallout. ⁹⁰Sr and ¹³⁷Cs concentrations in seeds of some herbaceous plants have been determined. The radionuclide concentrations and the resulting dose loads upon plant seeds showed an excess over the background level of about two or three orders of magnitude.     

Vertical Distribution and Inventories of 239,240Pu in Deep Sea Sediments of the Mediterranean Sea (Algerian Basin, Ionian Sea)

Deep-sea sediments collected in two areas of the Mediterranean Sea having different sedimentological characteristics have been analyzed to determine present concentrations and inventories of ^239,240Pu and to study the main mechanisms controlling them. Plutonium distribution in the deepest part of a submarine canyon (Taranto Valley, Ionian Sea) is compared to that obtained in an abyssal plain (north Algerian Plain). in the latter case, sedimentation is mainly due to the sinking of biogenic particles, while in the former lateral transport of terrigenous material along the slope of the canyon can significantly contribute to sediment accumulation on the bottom.

^239,240Pu surface concentration in the canyon ranged from 0.2 to 1 Bq kg^-1 (dry weight) and this was lower in the abyssal plain. in this area, plutonium was detectable only in the first 4 cm, while in the canyon it was present down to 11-15 cm. ^239,240Pu inventories are 3 Bq m^-2 in the plain and 45-60 Bq m^-2 in the canyon, indicating considerable input of terrigenous material towards the final part of the Taranto Valley.     

Radionuclides and heavy metals in Borovac,Southern Serbia

BACKGROUND, AIM, AND SCOPE: The paper presents the complex approach to the assessment of the state of the environment in Southern Serbia, surroundings of Bujanovac, the region which is of great concern as being exposed to contamination by depleted uranium (DU) ammunition during the North Atlantic Treaty Organization (NATO) attacks in 1999. It includes studies on concentrations of radionuclides and heavy metals in different environmental samples 5 years after the military actions. MATERIALS AND METHODS: In October 2004, samples of soil, grass, lichen, moss, honey, and water were collected at two sites, in the immediate vicinity of the targeted area and 5 km away from it. Radionuclide ((7)Be, (40)K, (137)Cs, (210)Pb, (226)Ra, (232)Th, (235)U, (238)U) activities in solid samples were determined by standard gamma spectrometry and total alpha and beta activity in water was determined by proportional alpha-beta counting. Concentrations of 35 elements were determined in the samples of soil, moss, grass, and lichen by instrumental neutron activation analysis (INAA). RESULTS: The results are discussed in the context of a possible contamination by DU that reached the environment during the attacks as well as in the context of an environmental pollution by radionuclides and heavy metals in Southern Serbia. The results are compared to the state of environment in the region and other parts of the country both prior to and following the attacks. DISCUSSION: This is the first comprehensive study of the contents of radionuclides and heavy metals in Southern Serbia and consequently highly important for the assessment of the state of environment in this part of the country concerning possible effects of DU ammunition on the environment, as well as anthropogenic source of pollution by radionuclides and heavy metals and other elements. Also, the highly sensitive method of INAA was used for the first time to analyze the environmental samples from this area. CONCLUSIONS: The results of the study of radionuclides in the samples of soils, leaves, grass, moss, lichen, honey, and water in Southern Serbia (Bujanovac) gave no evidence of the DU contamination of the environment 5 years after the military actions in 1999. Activities of radionuclides in soils were within the range of the values obtained in the other parts of the country and within the global average. The ratio of uranium isotopes confirmed the natural origin of uranium. In general, concentrations of heavy metals in the samples of soils, plant leaves, mosses, and lichen are found to be less or in the lower range of values found in other parts of the country, in spite of the differences in plant and moss species or soil characteristics. Possible sources of heavy metal contamination were identified as a power coal plant in the vicinity of the sampling sites and wood and waste burning processes. RECOMMENDATIONS AND PERSPECTIVES: The collected data should provide a base for the health risk assessments on animals and humans in the near future. It should be emphasized that the sampling was carried out 5 years after the military action and that the number of samples was limited; therefore, the conclusions should be accepted only as observed tendencies and a detailed study should be recommended in the future.     

A new general mechanistic river model for radionuclides from single pulse fallouts which can be run by readily accessible driving variables

This paper presents a new general, process-based river model for substances such as radionuclides from single pulse fallouts. The new model has been critically tested using data from 13 European rivers contaminated by radiocesium from the Chernobyl accident. This modelling approach gives radionuclide concentrations in water (total, dissolved and particulate phases; and also concentrations in sediments and fish, but the latter aspects are not discussed in this paper) at defined river sites. The model is based on processes in the upstream river stretch and in the upstream catchment area. The catchment area is differentiated into inflow ( approximately dry land) areas and outflow ( approximately wetland) areas. The model also accounts for time-dependent fixation of substances in the catchment. The catchment area sub-model is based on a previous catchment model, which has been tested with very good results for radiocesium, radiostrontium and Ca-concentrations (from liming operations). The new river model is simple to apply in practice since all driving variables may be readily accessed from maps and standard monitoring programs. The driving variables are: latitude, altitude, continentality, catchment area, mean annual precipitation, soil type (percentages or organic and sandy soils), fallout and month of fallout. Modelled values have been compared to independent empirical data from 10 rivers sites (91 data on radiocesium in water) covering a wide domain (catchment areas from 4000 to 180 000 km(2), precipitation from 500 to 960 mm/yr and fallout from 1700 to 660 000 Bq/m(2)). The new model predicts very well--when modelled values are compared to empirical data, the slope is perfect (1.0) and the r(2)-value is 0.90. This is good giving the fact that there are also uncertainties in the empirical data, which set a limit to the achieved predictive power, as expressed by the r(2)-value.     

Science, Policy, and Stakeholders: Developing a Consensus Science Plan for Amchitka Island, Aleutians, Alaska

With the ending of the Cold War, the US Department of Energy is responsible for the remediation of radioactive waste and disposal of land no longer needed for nuclear material production or related national security missions. The task of characterizing the hazards and risks from radionuclides is necessary for assuring the protection of health of humans and the environment. This is a particularly daunting task for those sites that had underground testing of nuclear weapons, where the radioactive contamination is currently inaccessible. Herein we report on the development of a Science Plan to characterize the physical and biological marine environment around Amchitka Island in the Aleutian chain of Alaska, where three underground nuclear tests were conducted (1965–1971). Information on the ecology, geology, and current radionuclide levels in biota, water, and sediment is necessary for evaluating possible current contamination and to serve as a baseline for developing a plan to ensure human and ecosystem health in perpetuity. Other information required includes identifying the location of the salt water/fresh water interface where migration to the ocean might occur in the future and determining groundwater recharge balances, as well as assessing other physical/geological features of Amchitka near the test sites. The Science Plan is needed to address the confusing and conflicting information available to the public about radionuclide risks from underground nuclear blasts in the late 1960s and early 1970s, as well as the potential for volcanic or seismic activity to disrupt shot cavities or accelerate migration of radionuclides into the sea. Developing a Science Plan involved agreement among regulators and other stakeholders, assignment of the task to the Consortium for Risk Evaluation with Stakeholder Participation, and development of a consensus Science Plan that dealt with contentious scientific issues. Involvement of the regulators (State of Alaska), resource trustees (U S Fish and Wildlife Service), representatives of the Aleut and Pribilof Island communities, and other stakeholders was essential for plan development and approval, although this created tensions because of the different objectives of each group. The complicated process of developing a Science Plan involved iterations and interactions with multiple agencies and organizations, scientists in several disciplines, regulators, and the participation of Aleut people in their home communities, as well as the general public. The importance of including all parties in all phases of the development of the Science Plan was critical to its acceptance by a broad range of regulators, agencies, resource trustees, Aleutian/Pribilof communities, and other stakeholders.     

Modelling radioactivity in the Irish Sea: From discharge to dose

In order to support authorised discharges of low level radioactive liquid effluent into coastal regions, mathematical models are required to robustly predict radiological impacts on critical groups of current and proposed changes to liquid discharges. The grid model presented here simulates the long term dispersion and transport of radioactivity discharged from the Sellafield site in Cumbria, UK, and the subsequent exposure of critical groups in Cumbria and across the Irish Sea in Northern Ireland. The fine grid of the model allows a good resolution of the seabed sediment distribution. This benefits the predictions for the last decades of low discharge level, when bed sediment can become a source of contamination by bringing back the legacy of past high discharges. This is highlighted by the dose comparison, where the predicted dose to Cumbria critical group follows well the dose estimated from environmental data during the low discharge level period.     

The effect of air mass origin on the ambient concentrations of Be and Pb in Islamabad, Pakistan

Concentration of radionuclides ²¹⁰Pb and ⁷Be, having half lives of 22.3 years and 53.29 days, respectively, in the surface air samples of Islamabad (33.38° N, 73.10° E and Altitude ∼536 m asl.) are measured. The non-destructive technique of gamma-spectrometry, with a high purity germanium HPGe detector, was employed for the analysis of all samples. The annual average concentrations of ²¹⁰Pb and ⁷Be in the surface air samples were determined as 0.284 ± 0.15 and 3.171 ± 1.14 mBq m⁻³, respectively. Our results have shown a seasonal variation of the concentration of ⁷Be in air samples with high values for the spring season. High concentrations for ²¹⁰Pb are obtained when air masses originate from plain areas of Pothohar region, located in the South-West, West and North West of Islamabad. Our values of concentrations show a nice agreement with the relevant reported results.