Biosphere modelling for the assessment of radioactive waste repositories; the development of a common basis by the BIOMOVS II reference biospheres working group

Performance criteria for radioactive waste repositories are often expressed in terms of dose or risk. The characteristics of biosphere modelling for performance assessment are that: (a) potential release occurs in the distant future, (b) reliable predictions of human behaviour at the time of release are impracticable, and (c) the biosphere is not considered to be a barrier as the geosphere and the engineered barriers. For these and other reasons, differences have arisen in the approaches to biosphere modelling for repository dose and risk assessment. The BIOMOVS II Reference Biospheres Working Group has developed (a) a recommended methodology for biosphere model development, (b) a structured list of features, events and processes (FEPs) which the model should describe, and (c) an illustrative example of the recommended methodology. The Working Group has successfully tested the Interaction Matrix (or Rock Engineering Systems, RES) approach for developing conceptual models. The BIOMOVS II Working Groups on Reference Biospheres and Complementary Studies have laid the basis for considerable harmonisation in approaches to biosphere modelling of long term radionuclide releases.     

A review of regulatory decisions for environmental protection: part II - the case-study of contaminated land management in Portugal

This paper provides a case-study analysis of the challenges in the implementation of national soil policies, which was developed by the authors in Part I of the review of regulatory decisions for environmental protection [Rodrigues SM, Pereira ME, Ferreira da Silva E, Hursthouse A, Duarte AC. A review of regulatory decisions for environmental management: Part I-challenges in the implementation of national soil policies. Environ Int 2009. doi:10.1016/j.envint.2008.08.007]. The Portuguese case was selected as a case-study since specific regulatory decisions for contaminated land management are still in the early stages of development. Given the gap between the situation at the EU level and the state of Portuguese soil policy development, it is of merit to consider national contaminated land policy regimes already in place within the EU and to see if these provide a suitable basis to define the main challenges and research needs for the implementation of a Portuguese contaminated land management strategy. A framework combining the D-P-S-I-R (drivers-pressures-sources-impacts-responses) structure of policy evaluation with the Source-Pathway-Receptor approach to health risk assessment is proposed to derive an effective regulatory framework for managing contaminated land in Portugal, using available information and only to develop new data and research where knowledge gaps exist. Funding site clean-up and assigning liability were identified as relevant factors currently hampering site remediation. Most relevant research needs for the development of contaminated land management practices in Portugal are those associated to the definition of a risk assessment framework and setting guidelines for the evaluation of risks posed to both humans and ecosystems. Other relevant and innovative features are the integration of soil function analysis into site investigations and the definition of a framework that combines risk assessment with soil function analysis. The analysis of the Portuguese case also provides insight into the discussions needed for the effective development of regulatory decisions for contaminated land management in countries with no history of implementing specific soil policies.     

Evaluation and ranking of restoration strategies for radioactively contaminated sites.

An international project, whose aim was the development of a transparent and robust method for evaluating and ranking restoration strategies for radioactively contaminated sites (RESTRAT), was carried out under the Fourth Framework of the Nuclear Fission Safety Programme of the EU. The evaluation and ranking procedure used was based on the principles of justification and optimisation for radiation protection. A multi-attribute utility analysis was applied to allow for the inclusion of radiological health effects, economic costs and social factors. Values of these attributes were converted into utility values by applying linear utility functions and weighting factors, derived from scaling constants and expert judgement. The uncertainties and variabilities associated with these utility functions and weighting factors were dealt with by a probabilistic approach which utilised a Latin Hypercube Sampling technique. Potentially relevant restoration techniques were identified and their characteristics determined through a literature review. The methodology developed by this project has been illustrated by application to representative examples of different categories of contaminated sites; a waste disposal site, a uranium tailing site and a contaminated freshwater river.     

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.     

Addressing uncertainties in the ERICA Integrated Approach

Like any complex environmental problem, ecological risk assessment of the impacts of ionising radiation is confounded by uncertainty. At all stages, from problem formulation through to risk characterisation, the assessment is dependent on models, scenarios, assumptions and extrapolations. These include technical uncertainties related to the data used, conceptual uncertainties associated with models and scenarios, as well as social uncertainties such as economic impacts, the interpretation of legislation, and the acceptability of the assessment results to stakeholders. The ERICA Integrated Approach has been developed to allow an assessment of the risks of ionising radiation, and includes a number of methods that are intended to make the uncertainties and assumptions inherent in the assessment more transparent to users and stakeholders. Throughout its development, ERICA has recommended that assessors deal openly with the deeper dimensions of uncertainty and acknowledge that uncertainty is intrinsic to complex systems. Since the tool is based on a tiered approach, the approaches to dealing with uncertainty vary between the tiers, ranging from a simple, but highly conservative screening to a full probabilistic risk assessment including sensitivity analysis. This paper gives on overview of types of uncertainty that are manifest in ecological risk assessment and the ERICA Integrated Approach to dealing with some of these uncertainties.     

A review of regulatory decisions for environmental protection: part I - challenges in the implementation of national soil policies

Since many soil studies have already revealed the possible risks to human health and the environment arising from contaminated soils it is therefore crucial to preserve soil quality under current and future conditions. In the last three decades a number of countries already introduced national policies and practices for the management of contaminated sites, and in 2002, an EU Thematic Strategy for Soil Protection was proposed by the European Commission. In this paper we review and analyse several national contaminated land policy regimes already in place in order to assess common elements and to identify specific needs in the development of national soil policies. We propose a framework that combines the D-P-S-I-R structure of policy evaluation with the Source-Pathway-Receptor approach to health risk assessment to support the development of effective country specific regulatory decisions for managing contaminated land in countries where these are yet to be implemented. The framework proposed allows decision makers to effectively use available information and to identify existing data gaps. As a result it is apparent that while there are technical aspects of site characterisation, risk assessment and remediation processes that could be commonly implemented at an EU level there are certain trans-scientific aspects that require political choices and need to be customized by EU Member States.     

Release,distribution, and impacts of polychlorinated biphenyls (PCB) induced by dredged material disposal activities at a deep-water estuarine site

The aquatic disposal field investigation initiated in Elliott Bay, Puget Sound, WA, in February 1976, was designed to evaluate the ecological effects of open-water disposal of dredged material. The experimental disposal site was located at a depth of 60 m in marine estuary with generally weak circulation. Approximately 114,000 m³ of dredged material contaminated with polychlorinated biphenyls (PCBs) were dumped at the site from split-hull barges. The material presented in this paper is limited to a discussion of PCB impacts. It imcludes (a) a summary of results from the studies conducted between 1976 and 1977 to assess short-term impacts during and after the disposal of PCB contaminated sediments at the Elliott Bay disposal site; (b) a presentation of preliminary results from the continuation studies initiated in February 1979 to determine long-term impacts of the disposal operations. The preliminary data indicate that both dredged-material deposit and the associated PCBs appear to be stable. No major long-term impact on benthic organisms is apparent from this analysis.     

Beyond contaminated land assessment: On costs and benefits of bioaccessibility prediction

Advances towards sustainable land management necessitate application of a broader portfolio of decision-support tools that improve evaluation of contaminated land. Over the last decade regulators have directed concerted effort towards rationalization of risk-based contaminated land policies recognizing bioavailability and bioaccessibility as concepts to be incorporated into risk assessments. The desire for a precise and rapid method to inform consideration of bioavailability and bioaccessibility to support risk assessment of contaminated land has never been greater. This study presents a comprehensive appraisal of both emerging non-exhaustive extraction techniques (subcritical water extraction and Brij 700 extraction) developed to reflect polycyclic aromatic hydrocarbon (PAH) bioaccessibility to microorganisms as well as formerly demonstrated methodologies (the use of cyclodextrins and butanol extraction). Application of unified evaluation criteria across different techniques enabled comparison not only from the bioaccessibility prediction perspective but also analysis of economical (cost of extraction) and practical (such as extraction time) measures. Whilst the use of cyclodextrins was the best predictor of the bioaccessible fraction for the majority of compounds, other methods appeared more cost- and time-effective. Juxtaposition of the techniques presented in this study assists establishing cost-benefit trade-offs of different non-exhaustive extraction techniques and contributes to tailoring information on contaminant bioaccessibility to support risk evaluation on contaminated sites.     

Regional risk assessment for contaminated sites Part 3: Spatial decision support system

Large scale (e.g. regional or national) assessments of contaminated sites may be very costly in terms of investigation and methodological (i.e. risk assessment procedures) requirements and may produce a quantity of information that usually discourages examination by decision-makers. Moreover, most of the existing tools effectively support local environmental risk assessment and management, but lack the capabilities of larger scale analysis, not mentioning the absence of the relevant component of socio-economic prioritization. To respond to the concerns and the management needs of experts and decision makers, the Spatial decision support sYstem for Regional rIsk Assessment of Degraded land (SYRIADE DSS) was developed and is presented according to its three modules: Regional Risk Assessment, Socio-economic Assessment and Integrated Assessment, respectively. The system allows to rank potentially contaminated sites for priority of investigation, when no information on characterization and risk by site specific methodologies is available. This GIS-based system embeds an innovative spatial and relative risk assessment procedure, and proposes the integrated analysis of different data (environmental and socio-economic) for the concerned sites, eliciting when necessary experts' knowledge and stakeholders' values (through Multi Criteria Decision Analysis, MCDA, methodologies). The application to a Polish case-study shows the performance and the flexibility of the system in investigating and mapping (potentially) contaminated sites at the regional scale.     

Soil migration and plant uptake of technetium from a fluctuating water table

Soil columns (50x15 cm) were used to determine the potential for 95mTc (as a surrogate for 99Tc which is an important component of some radioactive waste) to migrate from a contaminated, fluctuating water table, through sandy loam soil and into perennial ryegrass. Upward migration was significantly retarded with, generally, only the bottom few centimetres of soil becoming contaminated over the 6 months of the experiment. This is thought to have been due to the presence of anoxic conditions within the water table leading to the reduction of pertechnetate to Tc(IV) species which are relatively insoluble. However, some evidence of very slow upward migration over time was found. Only a small and inconsistent transfer of activity into the perennial ryegrass was observed. Whilst these observations would suggest that 99Tc is less important than radionuclides such as 129I and 36Cl in terms of the risk associated with radioactive waste disposal, the potential for a slow upward migration, and/or a pulse-release following the re-oxidation of reduced soil in which 99Tc has accumulated should not be overlooked.     

城市土地置换过程中土壤多环芳烃污染的健康风险评价

利用健康风险评价方法判定污染土壤是否需要修复或再次开发已成为一个新的研究领域。以某区域土地置换开发为案例，结合区域未来土地利用类型，采用健康风险评价模型对土壤多环芳烃（PAHs）污染可能给未来入住人群带来的健康风险进行初步评价。结果显示，在正常情况与极端情况两种暴露场合下，考虑直接接触不慎摄入、呼吸土壤尘和皮肤直接接触土壤3种途径，计算出的土壤PAHs污染的致癌风险相对较高，部分点位已经超过了人体健康可接受的致癌风险程度。且以敏感人群儿童为例，利用摄入量和风险评价反推得出，当土壤中PAHs含量低于634 μg/kg时，在极端情况下，儿童致癌风险可降低到可接受的致癌风险水平。随着环境管理工作的深入发展，在城市土地置换过程中应逐步加强环境健康风险评价方面的研究。     

Model testing using data on 131I released from Hanford

The Hanford test scenario described an accidental release of 131I to the environment from the Hanford Purex Chemical Separations Plant in September 1963. Based on monitoring data collected after the release, this scenario was used by the Dose Reconstruction Working Group of BIOMASS to test models typically used in dose reconstructions. The primary exposure pathway in terms of contribution to human doses was ingestion of contaminated milk and vegetables. Predicted mean doses to the thyroid of reference individuals from ingestion of 131I ranged from 0.0001 to 0.8 mSv. For one location, predicted doses to the thyroids of two children with high milk consumption ranged from 0.006 to 2 mSv. The predicted deposition at any given location varied among participants by a factor of 5-80. The exercise provided an opportunity for comparison of assessment methods and conceptual approaches, testing model predictions against measurements, and identifying the most important contributors to uncertainty in the assessment result. Key factors affecting predictions included the approach to handling incomplete data, interpretation of input information, selection of parameter values, adjustment of models for site-specific conditions, and treatment of uncertainties.     

Speciation of radionuclides - analytical challenges within environmental impact and risk assessments

The mobility, biological uptake and accumulation of radionuclides are essentially dependent on the physico-chemical form of the nuclides. As a major fraction of refractory radionuclides released during historical nuclear events is associated with particles, a key analytical challenge within environmental impact and risk assessments is to characterise radioactive particles with respect to properties influencing particle weathering, remobilisation and the subsequent ecosystem transfer of associated radionuclides. Preanalysis techniques are needed to fractionate, identify and localize individual particles in contaminated samples. To obtain information on particle characteristics such as particle size distributions, structures, elemental and radionuclide particle composition as well as oxidation state of matrix elements, solid-state speciation techniques are needed. Electron microscopy as well as X-ray microscopic techniques utilising synchrotron X-ray radiation have proved most useful in providing such information. The present paper summarises the present status on advanced techniques and presents historical sources that have contributed to radioactive particle contamination.     

Aspects of the uptake of radionuclides by sheep grazing on an estuarine saltmarsh. 1. The influence of grazing behaviour and environmental variability on daily intake

Sea water contaminated with diluted radioactive effluent originating from the Sellafield reprocessing plant inundates saltmarshes in the Esk estuary in west Cumbria (UK). Much of the radioactivity on the saltmarsh vegetation was found to be associated with a surface deposit of silt, brought onto the area during tidal inundation. Large temporal variations in the radionuclide concentrations of the vegetation were found, these being due probably to seasonal fluctuation in the extent of silt deposition.The grazing habits of sheep were studied on one of these saltmarshes and the consequent ingestion of radionuclides by the sheep was estimated. The sheep ingested different quantities of radionuclides according to time of year as a result of a combination of two factors; the considerable temporal variation in the concentration of radionuclides on the saltmarsh vegetation and the seasonal grazing behaviour of the sheep.     

Environmental biodosimetry: a biologically relevant tool for ecological risk assessment and biomonitoring

Biodosimetry, the estimation of received doses by determining the frequency of radiation-induced chromosome aberrations, is widely applied in humans acutely exposed as a result of accidents or for clinical purposes, but biodosimetric techniques have not been utilized in organisms chronically exposed to radionuclides in contaminated environments. The application of biodosimetry to environmental exposure scenarios could greatly improve the accuracy, and reduce the uncertainties, of ecological risk assessments and biomonitoring studies, because no assumptions are required regarding external exposure rates and the movement of organisms into and out of contaminated areas. Furthermore, unlike residue analyses of environmental media, environmental biodosimetry provides a genetically relevant biomarker of cumulative lifetime exposure. Symmetrical chromosome translocations can impact reproductive success, and could therefore prove to be ecologically relevant as well. We describe our experience in studying aberrations in the yellow-bellied slider turtle as an example of environmental biodosimetry.     

Air pollution assessment of toxic emissions from hazardous waste lagoons and landfills

The air quality impacts of hazardous waste disposal sites can be assessed on the basis of their contribution to each of the toxic contaminants. The purpose of this paper is to discuss the available methods of air quality assessment and their drawbacks. The need of air quality assessment is to assure that ambient concentrations of specific contaminants resulting from emissions will not exceed the acceptable levels for protection of public health and the ecosystem. Ambient concentrations of toxic contaminants are generally obtained by field measurements or air monitoring. However, field measurements and air monitoring of low-level toxic contaminants are costly and time consuming. As a result, most hazardous waste land disposal sites have not been adequately assessed. This paper describes current regulatory requirements in the United States for air quality assessment of hazardous waste land disposal sites. Emphasis is directed toward air quality assessment methodology. The paper also discusses emission predicting models based on the waste quantity and composition, scientific analysis of the waste conversion process together with meteorological conditions. The emission models are especially useful where emission cannot be reliably monitored or where a new disposal site is proposed.     

Regional risk assessment for contaminated sites Part 2: Ranking of potentially contaminated sites

Environmental risks are traditionally assessed and presented in non spatial ways although the heterogeneity of the contaminants spatial distributions, the spatial positions and relations between receptors and stressors, as well as the spatial distribution of the variables involved in the risk assessment, strongly influence exposure estimations and hence risks. Taking into account spatial variability is increasingly being recognized as a further and essential step in sound exposure and risk assessment. To address this issue an innovative methodology which integrates spatial analysis and a relative risk approach was developed. The purpose of this methodology is to prioritize sites at regional scale where a preliminary site investigation may be required. The methodology aimed at supporting the inventory of contaminated sites was implemented within the spatial decision support sYstem for Regional rIsk Assessment of DEgraded land, SYRIADE, and was applied to the case-study of the Upper Silesia region (Poland).The developed methodology and tool are both flexible and easy to adapt to different regional contexts, allowing the user to introduce the regional relevant parameters identified on the basis of user expertise and regional data availability. Moreover, the used GIS functionalities, integrated with mathematical approaches, allow to take into consideration, all at once, the multiplicity of sources and impacted receptors within the region of concern, to assess the risks posed by all contaminated sites in the region and, finally, to provide a risk-based ranking of the potentially contaminated sites.     

Regional risk assessment for contaminated sites part 2: ranking of potentially contaminated sites

Environmental risks are traditionally assessed and presented in non spatial ways although the heterogeneity of the contaminants spatial distributions, the spatial positions and relations between receptors and stressors, as well as the spatial distribution of the variables involved in the risk assessment, strongly influence exposure estimations and hence risks. Taking into account spatial variability is increasingly being recognized as a further and essential step in sound exposure and risk assessment. To address this issue an innovative methodology which integrates spatial analysis and a relative risk approach was developed. The purpose of this methodology is to prioritize sites at regional scale where a preliminary site investigation may be required. The methodology aimed at supporting the inventory of contaminated sites was implemented within the spatial decision support sYstem for Regional rIsk Assessment of DEgraded land, SYRIADE, and was applied to the case-study of the Upper Silesia region (Poland). The developed methodology and tool are both flexible and easy to adapt to different regional contexts, allowing the user to introduce the regional relevant parameters identified on the basis of user expertise and regional data availability. Moreover, the used GIS functionalities, integrated with mathematical approaches, allow to take into consideration, all at once, the multiplicity of sources and impacted receptors within the region of concern, to assess the risks posed by all contaminated sites in the region and, finally, to provide a risk-based ranking of the potentially contaminated sites.     

Framing climate uncertainty: socio-economic and climate scenarios in vulnerability and adaptation assessments

Scenarios have become a powerful tool in integrated assessment and policy analysis for climate change. Socio-economic and climate scenarios are often combined to assess climate change impacts and vulnerabilities across different sectors and to inform risk management strategies. Such combinations of scenarios can also play an important role in enabling the interaction between experts and other stakeholders, framing issues and providing a means for making explicit and dealing with uncertainties. Drawing on experience with the application of scenarios to climate change assessments in recent Dutch research, the paper argues that scenario approaches need to be matched to the frames of stakeholders who are situated in specific decision contexts. Differentiated approaches (top-down, bottom-up and interactive) are needed to address the different frames and decision-making contexts of stakeholders. A framework is proposed to map scenarios and decision contexts onto two dimensions: the spatial scale of the context and the starting point of approach used in scenario development (top-down, bottom-up or incident-driven). Future climate and socio-economic scenario development will be shaped by the need to become better aligned with multiple interacting uncertainties salient to stakeholders.