Journal of Environmental Radioactivity special issue: international topical conference on Po and radioactive Pb isotopes

An international conference on polonium (Po) and radioactive isotopes was held in Seville Spain, 26-28 October 2009 at the Centro Nacional de Aceleradores. It was attended by 138 participants from 38 different countries. The sessions covered all aspects on Po and lead (Pb) such as radiochemistry, terrestrial and marine radioecology, kinetics, sedimentation rates, atmospheric tracers, NORM industries and dose assessment     

Mapping radioactivity in groundwater to identify elevated exposure in remote and rural communities

A survey of radioactivity in groundwater (110 sites) was conducted as a precursor to providing a baseline of radiation exposure in rural and remote communities in Queensland, Australia, that may be impacted upon by exposure pathways associated with the supply, treatment, use and wastewater treatment of the resource. Radionuclides in groundwater, including ²³⁸U, ²²⁶Ra, ²²²Rn, ²²⁸Ra, ²²⁴Ra and ⁴⁰K were measured and found to contain activity concentration levels of up to 0.71 BqL⁻¹, 0.96 BqL⁻¹, 108 BqL⁻¹, 2.8 BqL⁻¹, 0.11 BqL⁻¹ and 0.19 BqL⁻¹ respectively. Activity concentration results were classified by aquifer lithology, showing correlation between increased radium isotope concentration and basic volcanic host rock. The groundwater survey and mapping results were further assessed using an investigation assessment tool to identify seven remote or rural communities that may require additional radiation dose assessment beyond that attributed to ingestion of potable water.     

Mapping of the geogenic radon potential in France to improve radon risk management: methodology and first application to region Bourgogne

In order to improve regulatory tools for radon risk management in France, a harmonised methodology to derive a single map of the geogenic radon potential has been developed. This approach consists of determining the capacity of the geological units to produce radon and to facilitate its transfer to the atmosphere, based on the interpretation of existing geological data. This approach is firstly based on a classification of the geological units according to their uranium (U) content, to create a radon source potential map. This initial map is then improved by taking into account the main additional parameters, such as fault lines, which control the preferential pathways of radon through the ground and which can increase the radon levels in soils. The implementation of this methodology to the whole French territory is currently in progress. We present here the results obtained in one region (Bourgogne, Massif Central) which displays significant variations of the geogenic radon potential. The map obtained leads to a more precise zoning than the scale of the existing map of radon priority areas currently based solely on administrative boundaries.     

The role of analogues in radioecology

If no data are available for a specific radionuclide its analogue could be used in radioecological models. They might be used not only in the frame of screening modelling. Relevant processes and features have to be known, such as time scales of these processes, physical, chemical and biological properties of the environment and relevant media. An analogue could only be proven to be valid by comparing its behaviour in the conditions of interest, while confidence in the validity of an analogue will increase as the quality of the justification increases, there will always be some residual uncertainty. Several main types of analogy can be used when measured or recommended values are not available: the same parameter obtained for another isotope of the same element; the same parameter obtained for another element; a different parameter obtained for the same element. There are several cases, when analogues might be applied as indicators of the determining processes in the radioecological studies.     

Radiological risk assessment and biosphere modelling for radioactive waste disposal in Switzerland

Long-term safety assessments for geological disposal of radioactive waste in Switzerland involve the demonstration that the annual radiation dose to humans due to the potential release of radionuclides from the waste repository into the biosphere will not exceed the regulatory limit of 0.1 mSv. Here, we describe the simple but robust approach used by Nagra (Swiss National Cooperative for the Disposal of Radioactive Waste) to quantify the dose to humans as a result to time-dependent release of radionuclides from the geosphere into the biosphere. The model calculates the concentrations of radionuclides in different terrestrial and aquatic compartments of the surface environment. The fluxes of water and solids within the environment are the drivers for the exchange of radionuclides between these compartments. The calculated radionuclide concentrations in the biosphere are then used to estimate the radiation doses to humans due to various exposure paths (e.g. ingestion of radionuclides via drinking water and food, inhalation of radionuclides, external irradiation from radionuclides in soils). In this paper we also discuss recent new achievements and planned future work.     

Modelling the long-term consequences of a hypothetical dispersal of radioactivity in an urban area including remediation alternatives

The Urban Remediation Working Group of the International Atomic Energy Agency's EMRAS (Environmental Modelling for Radiation Safety) program was organized to address issues of remediation assessment modelling for urban areas contaminated with dispersed radionuclides. The present paper describes the second of two modelling exercises. This exercise was based on a hypothetical dispersal of radioactivity in an urban area from a radiological dispersal device, with reference surface contamination at selected sites used as the primary input information. Modelling endpoints for the exercise included radionuclide concentrations and external dose rates at specified locations, contributions to the dose rates from individual surfaces, and annual and cumulative external doses to specified reference individuals. Model predictions were performed for a “no action” situation (with no remedial measures) and for selected countermeasures. The exercise provided an opportunity for comparison of three modelling approaches, as well as a comparison of the predicted effectiveness of various countermeasures in terms of their short-term and long-term effects on predicted doses to humans.     

Waste disposal and the recommendations of the International Commission on Radiological Protection – Challenges for radioecology and environmental radiation protection

The 2007 Recommendations of the International Commission on Radiological Protection (ICRP) represent a change from a process-based to an exposure-based approach, where exposure situations are categorised as planned, emergency, and existing exposure situations. Although the new Recommendations contain further changes based on, inter alia, scientific developments since the publication of the 1990 Recommendations, they overall represent more continuity than change – a notable exception being the direct consideration of environmental protection. The implications of the new Recommendations for radioactive waste management are fairly marginal, as earlier recommendations in this area are still considered valid. This communication provides a brief overview of the current ICRP system for radiological protection as applied to radioactive waste management, as well as an outlook including the possibility of using the developing ICRP system for management of environmental effects as an ‘alternative way of reasoning’ when building the safety case for a specific waste disposal concept.     

Status report on standard-setting work in the area of environmental radioactivity measurement

Environmental assessment studies are regularly commissioned to study the impact of radioactive substances on the environment and the public, in response to concern about the presence of such substances. The credibility of such studies relies on the quality and reliability of radionuclide analysis as well as the sample representativity of the radiological situation. The recent expansion from national stakeholders to those involving other states requires that activity measured in effluents or environmental samples in a country are reliable and reproducible so as to be accepted by all states potentially concerned by regional contamination. The standard-setting approach, based on consensus, seemed to lend itself to a settlement of technical aspects of potential dispute. This document describes standardization organizations, French and international, the standards published, as well as standardization work under way on the measurement of radionuclides found in environmental matrices.     

Survey of natural and anthropogenic radioactivity in environmental samples from Yugoslavia

The radioactivity of 238U, 226Ra, 232Th, 40K and 137Cs in sediments, soil, turf and honey from Serbia and Kosovo (Yugoslavia) was measured using gamma and alpha spectrometry in order to estimate the radiation hazard from natural and man-made sources, as well as to compile a database for radioactivity levels in those regions. One sample, collected in the vicinity of a "depleted uranium" (DU) shell of the recent Balkan war, revealed a high 238U activity and a non-natural 235U/238U activity ratio, confirming therefore its anthropogenic origin. However, some other soil samples coming from characteristic DU craters did not show any characteristic level of radioactivity. The other sediment and turf samples taken all around the country show low radioactivity levels for all the isotopes here considered. With the aim of obtaining some indication about radioactivity migration in the food chain, several honey samples have been examined too. All samples show very low radioactivity content, often indistinguishable from natural background.     

Natural radioactivity in farm soil and phosphate fertilizer and its environmental implications in Qena governorate, Upper Egypt

Samples of phosphate fertilizers and farm soils, taken to a depth of up to 30 cm in cultivated land, were collected over the Qena governorate, Upper Egypt. Activity concentration of background radionuclides such as (226)Ra, (232)Th and (40)K of these samples were determined by gamma-ray spectrometry. The results show that these radionuclides were present in concentrations of 366+/-10.5, 66.7+/-7.3 and 4+/-2.6 Bq/kg for phosphate fertilizers. For farm soil and Nile island's soil the corresponding values were 13.7+/-7, 12.3+/-4.6, 1233+/-646 and 11.9+/-6.7, 10.5+/-6.1, 1636+/-417 Bq/kg, respectively. The radium equivalent activity (Ra(eq)), the representative level index, I(gamma r), and absorbed dose in air for all samples were calculated. The data were discussed and compared with those given in the literature.     

Evaluation and assessment of 25 years of environmental radioactivity monitoring data at Tarapur (India) nuclear site

The evaluation and assessment of monitoring data generated over a period of 1983-2007 (25 years) of a nuclear facility is presented. Time trends of particulate radioactivity, correlation between ¹³⁷Cs in discharge canal seawater and station discharged activity and correlation of ¹³⁷Cs, ⁶⁰Co, and ¹³¹I in marine species such as sponge and Nerita (gastropod) and corresponding discharged activity are discussed. The concentration of ¹³⁷Cs and ¹³¹I in seawater versus biota are discussed. A good correlation between ¹³⁷Cs in seawater and ¹³⁷Cs in liquid waste discharged was observed (R² = 0.8, p < 0.001). Similarly, correlation was good for Nerita and discharged concentration of ¹³⁷Cs, ¹³¹I and ⁶⁰Co (R² = 0.55-0.73 and p < 0.001). The measurements over the years indicated that there is no accumulation of radionuclides in either the terrestrial or aquatic environments. The mean ¹³⁷Cs decreased from the pre-operational levels: 7.0-3.6 Bq kg⁻¹ in soil, 0.91-0.016 Bq L⁻¹ in milk and 0.28-0.036 Bq kg⁻¹ in vegetation. Similarly, the mean ⁹⁰Sr in these matrixes decreased from 3.9 to 0.26 Bq kg⁻¹; 0.37-0.011 Bq L⁻¹ and 0.34-0.022 Bq kg⁻¹ respectively. Cesium-137 of about 700 μBq m⁻³ was measured in the air filter disks during 1986 and there was a decrease of three orders of magnitude in concentration over the 25 years. The evaluation of environmental data indicated that the radionuclide concentrations and potential impacts, in terms of effective dose to the members of public, have significantly reduced since 1969.     

A heuristic for setting effective standards to ensure global environmental sustainability

Most environmental professionals and decision-makers, and certainly the public at large, hold the view that the integrity of earth’s natural environment will be conserved for posterity and sustainable development achieved if all the nations rigorously enforced their environmental and emission standards. It is argued in this paper that this view, sincerely held by many as an “axiomatic truth,” is mistaken and misplaced. This is because as a biogeochemical entity the Earth has limited self-regenerative capacity (SRC) to cope with anthropogenic pollution, and all kinds of environmental problems ensue when that limit is exceeded. Indeed, mounting environmental problems now occurring on all fronts amply testify to the fact that the limit has already been exceeded. They also provide necessary and sufficient proof that environmental and emission standards have been woefully inadequate for protecting earth’s natural environment and life-support systems. It is argued that true global environmental sustainability will be achieved, paving the way to true global sustainable development, if and only if global environmental and emission standards are set so that global anthropogenic pollution does not exceed the limit of earth’s natural SRC to cope with such pollution. These and related issues are discussed in this paper. A simple mathematical model using basic mathematics is also presented to explain how the phenomenon of “positive feedback” works in some of the environmental problems to exacerbate environmental degradation and progressively to erode nature’s SRC.

The radioactivity measurements in soils and fertilizers using gamma spectrometry technique

Because of their mineral content, soils are naturally radioactive and one of the sources of radioactivity other than those of natural origin is mainly due to the extensive use of fertilizers. The main aim of this paper is to evaluate the fluxes of natural radionuclides in local production of phosphate fertilizers to determine the content of radioactivity in several commercial fertilizers produced in Algeria and to estimate their radiological impact in a cultivated soil even for the long-term exposure due to their application.For these purposes, virgin and fertilized soils were collected from outlying Setif region in Algeria and from phosphate fertilizers used in this area.Gamma spectrometry was exploited to determine activity concentration due to naturally occurring ²²⁶Ra, ²³²Th and ⁴⁰K in five types of samples (two different sorts of fertilizers, virgin and fertilized soils and well water used for irrigation) taken from Setif’s areas.The results show that these radionuclides were present in an average concentration of 134.7 ± 24.1, 131.8 ± 16.7, 11644 ± 550 Bq/kg for the first fertilizer NPK and 190.3 ± 30, 117.2 ± 10.3, 5312 ± 249 Bq/kg for the second fertilizer (NPKs). For the virgin and the fertilized soils, the corresponding values were respectively 47.01 ± 7.3, 33 ± 7, 329.4 ± 19.7 Bq/kg and 53.2 ± 10.6, 50.0 ± 7, 311.4 ± 18.7 Bq/kg. For well water, the values were 1.93 and 0.12 Bq/kg; however the third value was below the Minimum Detectable Activity (MDA).The radium equivalent activity (Raeq) and the representative level index I_γr for all samples were also calculated. The data were discussed and compared with those given in the literature.     

The Oslo consensus conference on protection of the environment

A number of international organisations are focussing on a revision of radiation protection policy from the existing system which addresses only effects on man, to one which also addresses effects on the wider environment. These developments are expected to effect a wide range of stakeholders, including industry, regulators, scientists, users and the public. With this in mind a "Consensus Conference on Protection of the Environment" was arranged as part of an International Seminar on "Radiation Protection in the 21st Century: Ethical, Philosophical and Environmental Issues" held at the Norwegian Academy of Science and Letters. The conference attracted 46 international experts representing various disciplines and affiliations including Environmental Science, Health Physics, Radioecology, Ethics and Philosophy and a wide spectrum of perspectives bearing on the question of radiation protection of the environment. The conference was novel in that the participants were professionals rather than laypersons, and the purpose of the consensus procedure was to identify areas of agreement as an input to the ongoing regulatory developments. The success and innovation of the model is reflected in the significant areas of agreement identified in the final consensus statement, and the subsequent interest at an international level. Participants also noted the need for furthering the debate through ongoing work. Notable issues were the harmonisation of standards for radiation with other environmental stressors, guidance for balancing different interests and values within practical management, and the need for assessment criteria.     

Modeling of Cs migration in soils using an 80-year soil archive: role of fertilizers and agricultural amendments

An 80-year soil archive, the 42-plot experimental design at the INRA in Versailles (France), is used here to study long-term contamination by ¹³⁷Cs atmospheric deposition and the fate of this radioisotope when associated with various agricultural practices: fallow land, KCl, NH₄(NO₃), superphosphate fertilizers, horse manure and lime amendments. The pertinence of a simple box model, where radiocaesium is supposed to move downward by convectional mechanisms, is checked using samples from control plots which had been neither amended, nor cultivated since 1928. This simple model presents the advantage of depending on only two parameters: α, a proportional factor allowing the historical atmospheric ¹³⁷Cs fluxes to be reconstructed locally, and k, an annual loss coefficient from the plow horizon. Another pseudo-unknown is however necessary to run the model: the shape of historical ¹³⁷Cs deposition, but this function can be easily computed by merging several curves previously established by other surveys. A loss of ∼1.5% per year from the plow horizon, combined with appropriate fluxes, provides good concordance between simulated and measured values. In the 0–25 cm horizon, the residence half time is found to be ∼18 yr (including both migration and radioactive decay). Migration rate constants are also calculated for some plots receiving continuous long-term agricultural treatments. Comparison with the control plots reveals significant influence of amendments on ¹³⁷Cs mobility in these soils developed from a unique genoform.     

IAEA programme on the quality of marine radioactivity data

Society's growing interest in environmental issues requires the production of reliable information for policy-makers, stakeholders and society in general. This information must be based on accurate data produced by qualified laboratories and data need to be comparable between numerous laboratories for joint assessments, e.g. in International Conventions. The Marine Environment Laboratories of the International Atomic Energy Agency has been providing Quality Assurance services to laboratories involved in marine radioactivity studies for the past 30 years. This has included training, organization of laboratory intercomparison exercises, production of Reference Materials (RMs) and more recently, production of Certified Reference Materials (CRMs) that comply with relevant ISO standards. Here, the overall process of Certification of Reference Materials is reviewed, past work summarized and future needs of marine radioactivity laboratories briefly discussed.     

Ecological half-life of Cs in mosses and lichens in the Ordu province,Turkey by Cevik and Celik

Twenty-one years after the Chernobyl accident, lichen and moss samples were collected from the Ordu province, which was already chosen for a related study some years ago. It was observed that ¹³⁷Cs activity concentration ranged from 31 to 469 Bq kg⁻¹ in the moss and from 132 to 1508 Bq kg⁻¹ in the lichen samples. The decrease of the activity concentrations in the present measurements (2007) relative to those in 1997 (over a period of 10 y) indicated ecological half-lives between 1.8 and 10.4 y for the moss and between 2.1 and 13.7 y for the lichen samples. It was observed that ¹³⁷Cs was still eminent in the area studied. Moreover, ⁴⁰K activity concentrations and K element concentrations were measured and their relationships were discussed.