ECOMatters' Recent Projects
Hunter/gatherer transfer factors for iodine (ongoing)This figure shows the fish muscle iodine concentrations measured in 2007, ranging 39-fold across the 6 lakes. Interestingly, the strongest correlate was with stable cesium concentrations (r = 0.52, P < 0.007), which ranged 54-fold across the 6 lakes. Even though cesium is another element of concern for NFW disposal, the reason for the correlation in undisturbed settings is as yet unexplained. The range in iodine muscle concentrations was larger than expected, given that iodine is subject to strong homeostatic control at least in thyroid tissue. Only part of this variation seems to be explained by water concentrations.
Quantitative assessment of the disposal of nuclear fuel waste (NFW) requires data that are not commonly available. This is because the elements and settings of concern are not investigated for other environmental safety assessments. In particular, iodine is a key element for NFW because of the long-lived 129I present in the spent fuel. In terms of settings, hunter/gatherer pathways in boreal environments are important to the assessment of NFW but are not well parameterized.
As a result, ECOMatters undertook a study of iodine transfer factors for fish and game (deer, moose, elk and geese). We included a limited survey of iodine concentrations in Canadian Shield lakes, sediment and soil solid/liquid partition coefficients, and plant/soil concentration ratios for wild berries. This study was possible because of a new analytical technique that lowered detection limits in biological specimens by about 200-fold.
Automated Soil Gas Grid Sampling SystemThe purpose of the project was to design, test and use an automated soil-gas CO2 sampling and analytical system, for detection of leakage to the surface of sequestered CO2 past well-bore seals and along geological fractures.
The sampling and analytical system was designed and set up in ECOMatters' Whiteshell laboratory by fixing five solenoids and a data logger to a work board and mounting it in a weather-proof box. The analyzer was calibrated using standard laboratory air (CO2 = ~365 ppm) and zero CO2 air (laboratory air stripped of CO2 using Ascerite (soda-lime)).
A field trial experiment was then devised on a grid with 5 m spacing of sampling probes. The probes had been previously manufactured for soil gas sampling of radon and helium and were found to perform well in this application for CO2. Soil gases were sampled at a depth of 50 cm in the overburden and routed through a multi-port manifold to the CO2 analyser
The system was tested over the period October-November. The tests were successful and CO2 concentrations as high as ~12,000 ppm were measured in the upper 50 cm of soils at the station.
Assessment of Geological Barriers for CO2 Storage in Coal Deposits
Coalbeds in the Alberta Basin are being investigated both as potential sites for enhanced coalbed methane recovery (ECBM) and for the long-term storage of CO2 and flue gas. While numeric reservoir models are used to assess movement of fluids within the coalbeds, more computationally efficient models are required to make a long term, holistic assessment of the impact of potential CO2 leakage into the surrounding geosphere from the proposed coalbed storage formations. CQUESTRA-2, a semi-analytical model, has been developed to fulfill this latter role.
Probabilistic Risk Assessment of the IEA Weyburn CO2 Monitoring and Storage ProjectDeveloping a Canadian Environmental Indicator and Inventory for Ammonia Emissions from Agricultural Sources (ongoing)
This report describes the work carried out by ECOMatters Inc. as part of the IEA Weyburn CO2 Monitoring and Storage Project (the "IEA Weyburn Project). Our project goal was to understand and evaluate the geological storage of CO2 from a risk assessment perspective within the context of a large EOR project being carried out in the Weyburn field, located in the Williston Basin straddling Saskatchewan, Canada and North Dakota, USA.
To assess long-term risk in complex problems, a methodology called Probabilistic Risk Assessment (PRA) is the industry standard. Process-driven problems over long timeframes such as geological storage of CO2 are best solved using PRA. In the case of the IEA Weyburn Project, we employed a unique PRA model called CQUESTRA-1 (CQ-1).
The National Agri-Environmental Health Analysis and Reporting Program - NAHARP - and the National Agri-Environmental Standards Initiative (NAESI) have been tasked to create a quantitative indicator and inventory of agricultural ammonia (NH3) emissions. ECOMatters is working with these agencies to develop an indicator and inventory of ammonia emissions from agriculture, using input data suitable for Canada. Ammonia emissions from agriculture, and primarily from livestock operations, have become an issue in many regions of the world. In Europe, there was an international protocol, the Gothenburg protocol (http://www.unece.org/env/lrtap/multi_h1.htm), whereby all signatory nations would attempt to quantify and mitigate emissions, and this included NH3. Canada has signed the Gothenburg protocol but has not yet ratified it. In Europe, it is usually the direct toxicity of NH3 to plants or eutrophication of nutrient poor ecosystems that is the concern. In North America, although direct toxicity to vegetation and other environmental consequences may occur, the current concern has been more related to the production of aerosols by the reaction of NH3 with SOx and NOx in the atmosphere. The resulting smog is unsightly and a health concern because it is comprised of particles smaller than 2.5 µm diameter (PM2.5) that are harmful when inhaled by humans. Concern about health impact from PM2.5 and the role of ammonia as a precursor led Environment Canada to declare ammonia as a toxic substance under CEPA in June of 2003. This health concern is the specific driver or "need" for this project.Soil Studies - Update, Enhance and Assist to Implement an Agro-environmental Trace Element Risk Indicator for Canada (ongoing)
As a result of these concerns, several nations have developed inventories of NH3 emissions, particularly from agricultural sources. Obviously, the present NH3 indicator can be built upon a large amount of experience, and there is no question of the feasibility of the Project's objective - to create an NH3 indicator. The challenge of this project is to make the present NH3 indicator suited to Canadian farming practices, environmental conditions and geographical and spatial complexities. The most probable users and benefactors of this information are people interested in agro environmental policy, including elected decision-makers and environmental specialists. The information will also be targeted to the industry itself and to the public as a whole.
Canadians are concerned about the impact of agriculture on land, water and air quality. Many sectors of the agricultural industry have been implementing conservation programs resulting in improvements to the quality of soil, water and air. It is important that the results of these efforts be clearly understood and measurable. Agro-environmental indicators (AEI) help to summarize these complex issues and provide a mechanism to evaluate the effectiveness of agricultural and environmental policies and programs. An effective Trace Element Indicator (TEI) will not only assist in determining long-term changes in trace element impacts, it will elucidate the timeframes and seriousness of the increasing rates for each trace element and help identify potential farm management practices that could reduce risk of soil deterioration. The TEI would enable the agriculture industry to priorize trace element contaminants and resource Best Management Practices (BMPs) applicable to each additive, soil type and crop to ensure the industry responds to public concern and product demand. The recent Agriculture Policy Framework (APF) has resulted in a renewed mandate within Agriculture and Agri-Food Canada for using AEI to track performance of environmental goals for Canadian agriculture in the areas of soil, water and air quality, and biodiversity. The Trace Element Indicator (TEI) fits into this Framework.
The objective and scope of this project is to update and enhance models to estimate trace element loading to Canadian agricultural soils. This includes supply of data and support for the completion of a GIS-based, trace element risk indicator for all agricultural soils in Canada as part of the National Agri-Environmental Health Analysis and Reporting Program (NAHARP).
Update of Biosphere Parameter Values for 129I, 36Cl, 237Np, 238U, 226Ra and 222Rn . (ongoing)
Biosphere model parameters are continuously being measured, and periodically it is important to summarize the findings. ECOMatters completed reviews on the most important, nuclide specific parameter values for these radionuclides. In some cases, many more data were available since the previous summarizations.
Literature Review on Ecotoxicity of Elements on Soil and Freshwater Organisms
The objective of this project is to derive PNEC values for B, Sb, Ni, Se, Hg (inorganic and organic form), Pb, Cd, Cr (III and VI) and the radionuclides 36Cl, 129I, 99Tc, 79Se, 135Cs and 94Nb. The endpoints of interest involve soil biota other than plants (micro-organisms, earthworms, other invertebrates, snail…) as well as freshwater organisms (bacteria, algae, invertebrates, benthic flora and fauna, fish, plants, moss….). The ideal PNEC will be based on literature describing sub lethal, low effect level (EC25) responses to chronic exposure, but in the absence of ideal information, PNEC can be proposed from other data along with appropriate adjustment factors.
Background Concentrations of Primordial Radionuclides in Natural Settings (ongoing)
ECOMatters has established an integrated sampling protocol designed to sample multiple components of a specific ecological setting, and measure several members of the U and Th decay series. Key questions relate to the degree of secularly equilibrium, and whether concentrations and transfer factors vary in some systematic way among the ecological settings.
Effectiveness of Vegetated Buffer Strips to Mitigate Runoff of Phosphorus from Agricultural Land
Following up on the Nutrient Loading Model developed earlier, ECOMatters identified that there are large uncertainties related to the effectiveness of designed and inadvertent buffer strips to retain phosphorus (P). These buffer strips may retain particulate P, but may be an equal or larger source of soluble P. This is a field investigation using measurements collected on actual farm fields.
Background Paper on the Current Status of Biosphere Research Related to High-Level Radioactive Waste Management
NWMO commissioned this background paper as part of a series, which presents factual information about the state of our knowledge on important topics related to radioactive waste. The purpose of the background papers is to provide input to defining possible approaches for the long-term management of used nuclear fuel. As well, the background papers are intended to contribute to an informed dialogue with the public and other stakeholders. All of the papers will be posted on the NWMO web site.
Literature survey regarding the radiotoxicity and the chemical toxicity of uranium on organisms other than humans
Uranium (U) is the dominant radionuclide in fuel waste on the basis of mass, and it is essential to have a thorough understanding of the potential ecological impacts of U if some small amount becomes dispersed at the surface. A literature review was completed to develop predicted no effect concentrations (PNEC) for U. New interpretations of some data were possible, and PNEC values were derived for a number of ecological endpoints.
Toxicity and Long-Term Fate of Uranium (U) in the Soils of Port Hope, Ontario
ECOMatters staff published the soil ecotoxicology data being used now to assess the impacts of continued emissions of U in the Port Hope area. The same staff were asked to validate the results with field observations. Migration in soil, uptake by plants and chemical-toxic effects on soil organisms are the key aspects studied.
Probabilistic Performance Assessment of Geological Disposal of CO2
Supercritical CO2 is used as part of enhanced oil recovery processes in older oil fields. It mobilises trapped or heavy oil. Large amounts of CO2 are used, and this may represent an effective sequestration of CO2, in keeping with climate change initiatives. ECOMatters and partners developed an analytical model of the behaviour of supercritical CO2 in deep geological formations, including wells as a conduit to the biosphere, a computational tool ideal for probabilistic risk assessment.
Ecological Risk Assessment of Releases from an Abandoned Sulphide Tailings Area in Lynn Lake, Manitoba
Acid mine drainage with very low pH and very high concentrations of toxic metals are leaching into the river adjacent to this tailings area. The study quantified the impact, and will lead to decisions about remediation of the area.
Model to Setting Phosphorus Application Limits
ECOMatters developed a state-of-the-art loading model to address a concern in manure management, the phosphorus in the manure, which may runoff or erode in the spring and cause impacts in streams and rivers. The second phase of the project involved model improvements and successful validation on agricultural land along four rivers in Manitoba.
Parameter Values to Model the Impacts in the Biosphere of Cesium Released into Cold Climate Regimes
In the context of nuclear waste disposal, it is important to understand the behaviour of radionuclides in future environments, including environments associated with the onset of the next glaciation. Considerable data are available on the behavior of cesium (Cs) in arctic and boreal environments, as the result of weapons and nuclear accidents. ECOMatters used its previous experience with modeling glaciation (for the Canadian nuclear fuel waste disposal program) and its modeling experience to derive parameter values from the literature.
Study of radiation doses to transport workers
Non-radiation workers in the transport industry are obliged to handle shipments of radioactive materials and devices. These workers include drivers and parcel handlers. With the advent of more stringent dose limits for the public, ECOMatters staff were contracted to survey the practices of transport companies and workers to determine where doses might be greatest. This included on site observation of workers at selected locations and a questionnaire survey of other companies. Work continued in Phase II, a dosimetry project involving a wide spectrum of transport companies, to confirm the first phase observations.
Preparation of a new standard for calculation of routine release limits
The previous standard, CSA N288.1, is outdated. ECOMatters and two other firms were contracted to write a new standard. The new standard includes greater use of specific activity models, a model for migration in soil, model development and many more food pathways. ECOMatters staff has strong publication backgrounds in soil models and alternative and unusual exposure pathways, and so were responsible for the terrestrial pathways and special model.
Transfer of 36Cl in the Biosphere: Bibliography, Benchmarking and Model Development .
Chlorine-36 is one of the most critical radionuclides to consider in intermediate- and high-level nuclear waste management. Special attributes are long half-life, high mobility, biologically essential element, and massive isotopic dilution in the geosphere and biosphere. A model was developed to predict the radiological consequences of 36Cl to human dose receptors. The approach included three parts, a literature review, a benchmarking review of other models and programs, and the development of a model suitable for ANDRA applications within Aquabios. Model development included a conceptual model, a mathematical expression of the conceptual model, a spreadsheet version of the model, and the assemblage of the required and appropriate parameter values.
Environmental assessment of the Phase I Decommissioning of Whiteshell Laboratories
ECOMatter's role was to provide quantitative risk assessment and socio-economic impact assessment of the decommissioning of the Whiteshell Laboratories, a former nuclear research facility in Manitoba. This is a Comprehensive Study under the Canadian Environmental Assessment Act. For the quantitative risk assessment, ECOMatters quantified sources, exposure pathways and exposure probabilities, and presented the results in a manner presentable to the regulator and to the general public. Both radioactive and non-radioactive contaminants were included, as well as cumulative effects of various facilities and operations. ECOMatters made major contributions to the technical evaluation of in-situ abandonment of contaminated sediments (Sheppard and Helbrecht 2000) and continued storage of waste in below-ground trenches. ECOMatters Inc. consortium partners were Wardrop Engineering Inc., SENES Consultants Limited and the Centre for Indigenous Environmental Resources who performed other aspects of the assessment.
Groundwater chemistries of crystalline rock sites in Finland
ECOMatters assisted POSIVA by reviewing information on the groundwater chemistry of several potential nuclear waste disposal sites in crystalline bedrock. In addition to the hydrogeochemistry, the reviews included past groundwater flow conditions, the ages of groundwaters, and the chemical reactions that have occurred between the enclosing rock minerals and the groundwater.
The intrusion of oxygen into deep Shield rocks during glacial/interglacial cycles
ECOMatters reviewed documents and models that describe potential climatic changes over a glacial/interglacial cycle and the possibility of oxygen intrusion into a hypothetical nuclear waste disposal vault during deglaciation, a time when large amounts of meltwater could be injected into deep fractures in the bedrock.
Darlington Nuclear Generating Station Ecological Effects Review
ECOMatters assisted in an ecological effects review of the Darlington Nuclear Generating Station. The review, required by the CNSC, encompassed pre-construction to present. All stresses on the environment including thermal and radionuclide effects were considered. ECOMatters was primarily responsible for the conceptual biophysical model of the site, exposure assessment and effects characterization.
Development of the terrestrial components for models used to define the Derived Release Limits for 20 power reactors and associated facilities in Ontario. This was a revision of the Canadian Standards Association model, and new pathways related to game, honey and offal were included, as well as many more radionuclides.
Effect of atmospheric ammonia on terrestrial plants and ecosystems
ECOMatters quantified the potential toxic and deleterious effects of atmospheric ammonia gas, which is toxic to plants. In addition, because it is a nitrogen source, atmospheric ammonia can be disruptive to natural ecosystems. The results were documented in a manner consistent with CEPA needs. This project is also related to CEPA PSL2 assessments.
Effect of radionuclides on plants, for CEPA PSL2 assessments
As recognized experts on transfer of radionuclides through the biosphere and on effects of radiation on natural systems, ECOMatters prepared parts of the CEPA PSL2 assessment of the effects of emissions from power reactors. The submission by ECOMatters will become part of the CEPA assessment, and will result in an Environment Canada regulatory decision about environmental effects of reactor emissions.
Farm practices survey and modelling to estimate monthly NH3 emissions from swine production in 12 Ecoregions of Canada (2010)
The swine industry in Canada has undergone rapid growth in some areas, but has also been restricted by a variety of environmental issues. Ammonia (NH3) emissions are seldom mentioned among these issues, but emissions do occur and atmospheric NH3 causes a number of impacts including contributing to odour, deposition into sensitive ecosystems and formation of secondary particulate matter, which is a health concern in some regions of North America. This paper describes a new model to estimate NH3 emissions from the swine sector, relying heavily on a recent survey of swine producers to determine the present N and manure management practices. The key hypothesis was that NH3 emission rates vary across Ecoregions and over time in a way that affects the degree of impact. The survey showed many differences across Ecoregions, most importantly related to feed crude protein and landspreading practices. The model estimated that grower pigs (>20 kg to market size) excreted on average about 8.5 kg total ammoniacal N (TAN) per (occupied) pig place per year, and based on the national average farm practices, 25% of this TAN was emitted from barns, 5.3% was emitted from manure storage, and 17% was emitted during landspreading for a total of 4.8 kg NH3 pig-place-1 yr-1. The total loss for grower pigs ranged from 40 to 53% of excreted TAN across the 12 Ecoregions. Nursing sows emitted over twice as much per pig. Regions varied in reliance on homegrown feeds, which affected crude protein feeding and TAN excretion rates. Western regions had relatively low emissions from land application of slurry because of more extensive use of injectors. Emissions from grower pigs in winter were about 0.2 kg NH3 pig-place-1 month-1, mostly from barns, to as high as 0.7 kg NH3 pig-place-1 month-1 in May, mostly from landspreading. Total emission for all of Canada in 2006 was 73 × 106 kg NH3 or about 13% of agricultural emissions in Canada. The results indicate that emission reductions can be achieved with greater use of low-emission application methods and reduced crude protein in feed. The emissions model can be used in future to assess the impacts from changes in feeding regimes and barn designs, and changes in practices such as animal density and increased access to outdoor spaces.
Monthly ammonia emissions from fertilizers in 12 Canadian Ecoregions (2010)
Emissions of ammonia (NH3) from agriculture have been associated with transboundary atmospheric pollutant transport and potential human health problems. Specifically, NH3 gas reacts in the atmosphere to form fine particles (PM2.5) that are subject to long range transport and are considered to be associated with elevated risk of all-cause, lung-cancer and cardiopulmonary mortality. Agriculture is a major source of atmospheric NH3, and, of this, NH3 from fertilizers is perhaps the most easily managed. Recent shifts in nitrogen (N) fertilizer materials and improved placement of urea and related fertilizers have resulted in marked changes in emissions. This paper describes a model developed to predict month-by-month emissions of fertilizer NH3, supported by surveys of farmers and fertilizer industry personnel that update information on fertilizer use. Compared with previous estimates by Environment Canada, the fraction of fertilizer N emitted as NH3 is estimated to be 50% lower in the vast prairie regions (a very large reduction in total NH3), and about 30% lower in eastern Canada. The estimate for 2006 is 1.0 × 108 kg NH3 emitted directly from fertilizer application, 73% of this in the prairie region, and much of this in May. Overall, this indicates 6% of the applied fertilizer N is lost as NH3 gas. Clearly, emission estimates are strongly dependent on up-to-date information about farm practices.
Trace elements in Ontario soils - mobility, concentration profiles, and evidence of non-point-source pollution. (2009)
Agricultural soils are the recipients of trace elements from general atmospheric pollution and from agricultural inputs such as fertilizer, feeds and urban biosolids. These input fluxes are usually small, and there are processes such as leaching and crop off-take to counterbalance the trace element inputs. Thus, it is difficult to evaluate the changes of trace element concentrations in agricultural soils. This paper examined a survey of 59 soil profiles in Southern Ontario, combining analysis of ~50 elements in three soil depths and corresponding measurements of the soil solid/liquid partition coefficient, Kd. The profile data were adjusted for yttrium concentrations to account for vertical particle migration. Increased concentration in the surface profile relative to the subsurface was considered an indication of enrichment, indicating the possible effects of human activity. For most elements, the surface (0–15 cm) and subsoils (30–60 cm) had similar concentrations. The notable exceptions were Cd, Pb, Sb, Se, Nb, U, and Zn, where surface soils had 1.4- to 2.2.fold higher concentrations than subsoils. Most of these increases can be attributed to human activity. Additional interpretation using the Kd data was useful to identify Ba and Mo as potentially among the contaminant elements. Surface soil concentrations of these elements were not markedly elevated compared with the subsoil, but their Kd values indicated that they were sufficiently mobile that depletion would be expected. Thus, perhaps continued input has supported the concentrations of Ba and Mo in the surface soils. Both are noted contaminants in dust from urban sources. Thus, the results show that several elements that are often of concern because of environmental toxicity or health impacts are at elevated concentrations in agricultural soils, and because these are rural locations the implication is that this has resulted from non.point.source pollution.
Risk Indicator for Agricultural Inputs of Trace Elements to Canadian Soils (2009)
Trace elements (TEs) are universally present in environmental media, including soil, but agriculture uses some materials that have increased TE concentrations. Some TEs (e.g., Cu, Se, and Zn) are added to animal feeds to ensure animal health. Similarly, TEs are present in micronutrient fertilizers. In the case of phosphate fertilizers, some TEs (e.g., Cd) may be inadvertently elevated because of the source rock used in the manufacturing. The key question for agriculture is "After decades of use, could these TE additions result in the deterioration of soil quality?" An early warning would allow the development of best management practices to slow or reverse this trend. This paper discusses a model that estimates future TE concentrations for the 2780 land area polygons composing essentially all of the agricultural land in Canada. The development of the model is discussed, as are various metrics to express the risk related to TE accumulation. The elements As, Cd, Cu, Pb, Se, and Zn are considered, with inputs from the atmosphere, fertilizers, manures, and municipal biosolids. In many cases, steady-state concentrations could be toxic, but steady state is far in the future. In 100 yr, the soil concentrations (Century soil concentrations) are estimated to be up to threefold higher than present background, an impact even if not a problematic impact. The geographic distribution reflects agricultural intensity. Contributions from micronutrient fertilizers are perhaps the most uncertain due to the limited data available on their use.
Monthly NH3 emissions from poultry in 12 Ecoregions of Canada (2009)
Management of ammonia (NH3) is a multi faceted issue for farmers. It is simultaneously a toxicant that can affect farm worker and animal health, a volatile plant nutrient that is expensive to replace if lost, and a potential contributor to environmental degradation. The environmental implications have important spatial and temporal dimensions, beyond the farm. This paper describes a model developed to estimate NH3 emissions from poultry (broiler, layer and turkey) production in 2780 mapping units across Canada on a monthly time scale. It includes estimates of daily emission peaks within critical months. The results will contribute to estimates of haze and atmospheric aerosol production, as well as contributions to other potential impacts such as eutrophication of sensitive ecosystems. The model is based on a detailed survey of farm practices. Emissions vary strongly throughout the year, and in many regions there are peak emissions in early spring and late fall, associated with landspreading of manure. There are also markedly different nitrogen excretion rates among regions, and these and bird populations are the key factors controlling emissions. On average, 22% of excreted uric acid or ammoniacal N is emitted from barns, 2% from storage and 26% from landspreading, resulting in a total loss of 50%. Key words: Ammonia, PM2.5, acid rain, nitrogen
Ecoregion and farm size differences in feed and manure nitrogen management: 1. Survey methods and results for poultry (2009)
Environmental issues related to agriculture, and especially to animal production, are prominent in the regulatory agenda and are an area where the general public expects improvements. Many of the issues can be mitigated with changes in farm management practices. There is considerable potential for improvement, but before actions are recommended or mandated, it is important to document what are the current management practices and how they vary across the country and with farm size. This is the first of a series of papers that describes a large-scale livestock farm practices survey (LFPS) conducted across livestock farms in Canada, emphasizing manure nitrogen (N) management as it affects ammonia (NH3) emissions to the atmosphere. However, the survey results have much broader applicability. In this paper, the development of the survey and sampling strategy is described along with the results for the three main poultry sectors in Canada: broiler, layer and turkey. Husbandry in each poultry sector is generally uniform, but there were statistically significant regional differences in feeding practices and feed conversion efficiencies, and these imply differences in N excretion rates. Farm size was seldom significant as a covariate, suggesting that both small and large poultry farms have adopted similar husbandry and feeding practices.
Critical Loads Changing with Time (2008)
The critical load is the maximal rate of contaminant addition that, over time, will result in environmental concentrations that do not exceed the highest acceptable concentration (i.e., the critical limit). Computationally, critical loads depend solely on critical limits and the expected rates at which contaminants are lost from the environmental media of concern. Losses include processes such as flushing (water bodies) or leaching (soils), sequestration in sediment, volatilization, and crop removal. A significant challenge is that loss rates will vary with time, especially in response to processes such as climate change. How should regulators deal with these changes with time? This Perspective compares the implications of three options where conditions are: (1) fixed to represent the present, (2) variable with no trend over time, and (3) variable with systematic trends (monotonic and cyclical) over time, and a fourth option using stochastic (probabilistic) evaluation of all plausible future conditions. Soil concentrations over 250 years were computed for each option. As expected, conditions that vary systematically with time can drastically change estimates of environmental concentration, and hence critical loads. However, if it is assumed that regulators periodically revisit critical load estimates taking into account changing conditions, long-term objectives can be achieved. One approach to changing conditions is to stochastically create a family of possible time series of conditions and outcomes. In the example developed here, the range of outcomes from the stochastic treatment encompassed those of the various time-series calculations. The regulatory implications of these findings are discussed.
Primordial radionuclides in Canadian background sites: secular equilibrium and isotopic differences
A literature review and field sampling were done to obtain information on primordial (natural-series) radionuclide concentrations in terrestrial environments in diverse locations across Canada. Of special interest was the degree of secular equilibrium among members of decay series. The analytes measured in soils and plants were natU by neutron activation-delayed neutron counting, 228Th, 230Th, 232Th, 226Ra and 210Po by alpha spectroscopy, 210Pb by gas flow proportional counting, 228Ra by beta counting and 137Cs by gamma spectroscopy. In addition, ICP-MS was used to obtain concentrations of about 50 analytes including elemental U, Pb, and Th. Samples were from seven representative background sites with a total of 162 plant samples from 38 different species. These data were supplemented by a review that gathered a large portion of the similar data from published sources. The sites chosen were semi-natural, far from any nuclear industry, although several were specifically located in areas with slightly elevated natural U concentrations. As might be expected, there were many cases of non-detectable concentrations. However, certain trends were evident. The activity ratio 210Po/210Pb was unity in soils and non-annual plant tissues such as lichens. It was about 0.6 in annual plant tissues. These results are consistent with the time required for ingrowth of 210Po to reach secular equilibrium. There was evidence from several sources that 210Pb in plants came predominantly from deposition of 210Pb from air after the decay of airborne 222Rn. This was expected. Somewhat unexpected was the observation that 228Th seemed to be much more plant available than 232Th, even though both are in the same decay series and should be chemically similar. The difference was attributed to the combined effects of ingrowth from 228Ra in the plant and effects of alpha recoil in mobilizing 228Th in the soil. In general, the results of this study will benefit risk assessment, both in providing background concentrations, but also some indication of where isotope activity ratios can and cannot be used to estimate concentrations.
Estimation of ammonia emission episodes for a national inventory using a farmer survey and probable number of field working days (2007)
Emissions of ammonia (NH3) and odor from livestock operations, and particularly from the landspreading of manure, are an issue from many aspects. Regional and national issues include production of inhalable aerosols (PM2.5), where NH3 from agriculture is a critical precursor. This process is episodic. As a result, it is important to characterize the episodic nature of NH3 emissions. This paper addresses the fact that weather and soil conditions can focus manure landspreading into a relatively few days each year. The Versatile Soil Moisture Budget (VSMB) was used with 30 yr of weather data on 2576 soil landscape units in Canada to estimate the number of days in each month when manure spreading would be possible. In addition, a national survey of about 3100 livestock farmers was used to quantify common practice. The stochastic information from the VSMB and the survey were applied to an NH3 emissions model. The base case, invoked by most national NH3 emission inventory calculations, is that emissions are uniformly distributed throughout each month. The result of our study was that daily NH3 emission fluxes could be up to 20-fold higher in the spring and fall months when manure landspreading is common but when weather and soil conditions limit the number of days available for field work. This has direct implications for estimating the role of agricultural NH3 on the episodic production of PM2.5, and this approach also has application to odor management.
Sensitivity analysis of alternative model structures for an indicator of ammonia emissions from agriculture (2007)
Ammonia (NH3) emission from agriculture is an environmental and health concern in many nations, and has trans-border impacts. Direct toxicity, terrestrial eutrophication and production of inhalable aerosols (< 2.5 µm diameter) are the specific concerns. Canada, among other northern hemisphere nations, has computed a national inventory of NH3 emissions, and a new emission inventory estimate is being prepared jointly under the National Agri-Environmental Health Analysis and Reporting Program (NAHARP) and National Agri-Environmental Standards Initiative (NAESI). However, there has been a rapid evolution in the models used, and a concomitant change in the NH3-specific data required. This paper compares several model structures and options using Monte Carlo simulation and sensitivity analysis methods. The results indicate the more recent models, that compute a mass balance of NH3 from excretion to landspreading, have tended to focus uncertainty onto the dietary efficiency of animal N nutrition. After excretion, the total ammoniacal nitrogen (TAN) in the manure contributes to NH3 emissions at each stage as the manure passes from the animal housing to storage and to landspreading. There are many variants of these processes because every farm is different, resulting in diminished sensitivity to any one NH3-loss mechanism after excretion. This finding suggests that although NH3-emission factors, the empirical data at the core of the models, are not well characterised (especially for Canadian conditions), it is at least as important to expend research effort on factors that influence TAN excretion. Results of this paper will also guide development of the NAHARP/NAESI model.
Revision and meta-analysis of selected biosphere parameter values for chlorine, iodine, neptunium, radium, radon and uranium (2006)
There is a continual supply of new experimental data that are relevant to the assessment of the potential impacts of nuclear fuel waste disposal. In the biosphere, the traditional assessment models are data intensive, and values are needed for several thousand parameters. This is augmented further when measures of central tendency, statistical dispersion, correlations and truncations are required for each parameter to allow probabilistic risk assessment. Recent reviews proposed values for 10–15 key element-specific parameters relevant to 36Cl, 129I, 222Rn, 226Ra, 237Np and 238U, and some highlights from this data update are summarized here. Several parameters for Np are revised downward by more than 10-fold, as is the fish/water concentration ratio for U. Soil solid/liquid partition coefficients, Kd, are revised downward by 10–770-fold for Ra. Specific parameters are discussed in detail, including degassing of I from soil; sorption of Cl in soil; categorization of plant/soil concentration ratios for U, Ra and Np; Rn transfer from soil to indoor air; Rn degassing from surface water; and the Ca dependence of Ra transfers.
Ecotoxicological Probable-No-Effect Concentrations for Elements Related to Nuclear Waste. (2005)
The safety of storage and disposal of nuclear waste is assessed not only on the potential radiological consequences, but also on the potential for chemical ecotoxicity. The waste contains many elements, but the potential for chemical toxicity was considered here for antimony (Sb), beryllium (Be), boron (B), cadmium (Cd), chromium (Cr(III) and Cr(VI)), iodine (I), lead (Pb), mercury (Hg, organic and inorganic forms), nickel (Ni), selenium (Se) and technetium (Tc). The endpoints of interest were soil biota other than plants, specifi cally micro-organisms, mycorrhizal associations and invertebrates, as well as freshwater plants, invertebrates, fi sh and amphibians. The ideal probable-no-effect concentration (PNEC) was based on several reports of EC25 (the concentration causing 25% reduction from control) for endpoints relevant to population survival and from chronic, realistic exposure studies. Where possible, the PNEC was the 5th percentile of the population of relevant effect concentrations. A tiered search strategy was used to focus on recent and especially sensitive studies, from this over 650 papers were reviewed and considered, and 55 PNEC values proposed. There remains a scarcity to data for certain element and endpoints, whereas others are well represented in the literature. Key words: PNEC; antimony; beryllium; boron; cadmium; chromium; iodine; lead; mercury; nickel; selenium; technetium.
Runoff phosphorus retention in vegetated field margins on flat landscapes (2006)
Vegetated buffer strips (VBS) are often recommended as a management practice that farmers can use to help mitigate the environmental effects of runoff from agricultural fields. Previous research has shown that VBS can be effective at trapping phosphorus (P) and other farm-sourced environmental contaminants. This project measured the effectiveness of established vegetated strips at decreasing P in runoff from agricultural fields in Manitoba. Paired samples of runoff, taken at the field edge and in the vegetated strip, indicated that in 11 of the 22 cases sampled (50%), P concentrations in the runoff decreased (on average 30%) as the flow passed through the vegetated strip. In 7 of the 22 case (32%) there was no difference; however, in four of the 22 cases (18%), runoff P concentrations increased, indicating the vegetated strip had become a source of runoff P. Soil samples from the VBS showed high available P concentrations at positions within the vegetated strip along the runoff flow path, and in 7 of 10 cases these concentrations were higher (33% on average) than in the field soil. Although the observations and numerical results suggest that VBS can be effective at removing P in runoff, perhaps the major limitation in this flat-land region is that runoff tends to flow through rather small portions of the VBS, and these may not have sufficient capacity to retain the runoff P in the longer term.
Parameterization of a dynamic specific activity model of 14C transfer from surface water-to-humans (2006)
Carbon-14 is a particularly interesting radionuclide from the perspective of dose estimation because it mixes readily with stable CO2, and hence enters the food-chain as fundamental biomolecules. A model was developed for the situation of 14C releases to surface waters, where there are distinct changes in the water 14C activity concentrations throughout the year. The model computes the specific activity in water, phytoplankton, fish, crops, meat, milk and air, following a typical irrigation-based food-chain scenario. This paper describes the derivation of the required 14C-specific parameter values. Many of the key parameters are not commonly measured, at least not in the context of dose assessment. Thus, inference from other sources of data was required, and this is the scientific contribution described in this paper. The best estimates and appropriate measures of statistical dispersion are provided. This required consideration of both the temporal and spatial averaging domains to ensure they were correct for parameters as defined in the model. The model coupled with these parameter values represents several new developments for modelling 14C. transfers.
Conceptual approaches for the development of dynamic specific activity models of 14C transfer from surface water to humans (2006)
Carbon-14 is a particularly interesting radionuclide from the perspective of dose estimation. Many nuclear facilities, including power reactors, release 14C into the environment, and much of this is as 14CO2. This mixes readily with stable CO2, and hence enters the food chain as fundamental biomolecules. This isotopic mixing is often used as the basis for dose assessment models. The present model was developed for the situation of 14C releases to surface waters, where there are distinct changes in the water 14C activity concentrations throughout the year. Complete isotopic mixing (equilibrium) cannot be assumed. The model computes the specific activity (activity of 14C per mass of total C) in water, phytoplankton, fish, crops, meat, milk and air, following a typical irrigation-based food-chain scenario. For most of the biotic compartments, the specific activity is a function of the specific activity in the previous time step, the specific activity of the substrate media, and the C turnover rate in the tissue. The turnover rate is taken to include biochemical turnover, growth dilution and mortality, recognizing that it is turnover of C in the population, not a tissue or an individual, that is relevant. Attention is paid to the incorporation of 14C into the surface water biota and the loss of any remaining 14CO2 from the surface water–air interface under its own activity concentration gradient. For certain pathways, variants in the conceptual model are presented, in order to fully discuss the possibilities. As an example, a new model of the soil-to-plant specific activity relationship is proposed, where the degassing of both 14C and stable C from the soil is considered. Selection of parameter values to represent the turnover rates as modeled is important, and is dealt with in a companion paper.
Transfer Parameters—Are On-Site Data Really Better? (2005)
Transfer parameters for contaminants in the environment are notoriously variable. It is not unusual to measure a geometric standard deviation (GSD) of tenfold, so that the 5th and 95th percentiles are 10,000-fold apart. Despite many years of research, there remain large uncertainties, and often risk assessors will use on-site data for the transfer parameters. This Perspective assesses, using radionuclides as an example, whether a few site-specific measurements are more reliable than the more generic data compiled by researchers around the world. Using the example of plant/soil concentration ratios for several radionuclides, if one knew nothing about the soils and plants to be assessed, the GSD would be about 5.7-fold. If one had extensive knowledge about the soils and plants, the GSD would only diminish to about 3.2-fold. If a GSD of 3.2 is the level of residual natural variation to expect for plant/soil concentration ratios (the error term in a formal analysis of variance), then any on-site data that are within an order of magnitude of generic data could not be considered significantly different from the generic data. An appropriate conclusion in this case would be that unless on-site data are significantly different from the generic data, then the on-site data should not be used exclusively and the generic data should be considered suitable. The inherent variability of transfer parameters is so large that generic data may often be the best choice.
Assessment of long-term fate of metals in soils: Inferences from analogues (2005)
The assessment of the health and environmental impacts of metal contamination in soils is complicated, and in different ways than is the assessment of many other contaminants. One of the foremost problems is that the metals are often relatively immobile, so that it is necessary to verify predictions of mobility and impact far into the future. One approach is to seek analogue information: information from studies that may not have set out to measure attributes related to metal behaviour, but that none the less provide useful insights. One example would be the information on the mobility of natural clays and pedogenic metals such as iron and aluminum in soils. It is well accepted that clay particles will move downward in soils; what is less commonly inferred is that any contaminants associated with the clays will also move downward. For mobility of some metals, this may be a dominant process. Similarly, bioturbation has proven to markedly outpace leaching for many metals. This paper considers analogues related to cesium from bomb-fallout and Chernobyl, other natural radionuclide inputs to the soil, soil pedogenesis, pollen and non-metal industrialage inputs, ancient metal works, and soil fertility management. Related to biological transfers and toxicity, it considers analogy among elements an d among biota, and analogy to ecotoxicology of metals to freshwater biota. Where possible, limiting values for parameters of assessment models have been derived.
Derivation of ecotoxicity thresholds for uranium (2005)
Assessment of the risk of impact from most radionuclides is based on the total radiological dose rate to the organism of concern. However, for uranium (U) there can be greater risk from chemical toxicity than radiological toxicity (depending on the isotopic composition). Chemical ecotoxicity of U is dependent on several environmental parameters. The most important are carbonate content, because of the formation of soluble carbonate complexes, and divalent cation content (Ca++ and Mg++), because of their competitive interaction with the uranyl ion (UO2++). This study summarizes the literature available to set PNECs (predicted no-effect concentrations) for chemical toxicity of U to non-human biota. The corresponding radiological doses were estimated, and as expected chemical toxicity proved to be the greater concern. There were limited data from some types of biota; however, PNECs for the types of biota of interest were as follows: • terrestrial plants—250 mg U kg-1 dry soil; • other soil biota—100 mg U kg-1 dry soil; • freshwater plants—0.005 mg U L-1 water; • freshwater invertebrates—0.005 mg U L-1 water; • freshwater benthos—100 mg U kg-1 dry sediment; • freshwater fish at water hardnesses of: – <10 mg CaCO3 L-1 (very soft water)—0.4 mg U L-1 water; – 10–100 mg CaCO3 L-1 (soft water)—2.8 mg U L-1 water; and – >100 mg CaCO3 L-1 (hard water)—23 mg U L-1 water; or – as a function of hardness—0.26 (hardness as mg CaCO3 L-1) • mammals—0.1 mg U kg-1 body weight d-1.
Literature survey regarding the radiotoxicity and the chemical toxicity of uranium on organisms other than humans (2003)
Assessment of the risk of impact from most radionuclides is based on the total radiological dose rate to the organism of concern. However, for uranium (U) there can be greater risk from chemical toxicity than radiological toxicity (depending on the isotopic composition). Chemical ecotoxicity of U is dependent on several environmental parameters. The most important are carbonate content, because of the formation of soluble carbonate complexes, and divalent cation content (Ca++ and Mg++), because of their competitive interaction with the uranyl ion (UO2++).
This study summarizes the literature available to set PNECs (predicted no-effect concentrations) for chemical toxicity of U to non-human biota. The corresponding radiological doses were estimated, and as expected chemical toxicity proved to be the greater concern. There were limited data from some types of biota; however, PNECs for the types of biota of interest were as follows:
- terrestrial plants - 250 mg U kg-1 dry soil;
- other soil biota - 100 mg U kg-1 dry soil;
- freshwater plants - 0.005 mg U L-1 water;
- freshwater invertebrates - 0.005 mg U L-1 water;
- freshwater benthos - 100 mg U kg-1 dry sediment;
- freshwater fish at water hardnesses of :
- <10 mg CaCO3 L 1 (very soft water) - 0.4 mg U L-1 water;
- 10 100 mg CaCO3 L 1 (soft water) - 2.8 mg U L-1 water; and
- >100 mg CaCO3 L 1 (hard water ) - 23 mg U L-1 water; or
- as a function of hardness - 0.26 · (hardness as mg CaCO3 L 1)
- mammals - 0.1 mg U kg-1 body weight d-1.
Toxicity and Long-Term Fate of Uranium (U) in the Soils of Port Hope, Ontario (2002-2004)
ECOMatters Inc. and subcontractors conducted a study in the Port Hope area funded by the CNSC specifically to obtain site-specific data relevant to environmental and human health assessments. Three aspects were identified by the CNSC as particularly important: data to verify models of long-term fate of uranium (U) in Port Hope soils, bioavailability of soil U especially for the soil-to-plant pathway, and effects of soil U on soil organisms. There was also a need to support a long-term monitoring plan. There were three approaches followed. The first was to sample in detail soil profiles where U concentrations were relatively high but where contamination was thought to be solely atmospheric. These profiles were useful to investigate the general mobility of U in soil. The second approach was to gather site specific plant/soil concentration ratios, and this involved sampling vegetation and surface soil from a range of sites. A broader range of soil U concentrations could be included for these sites. The third approach was to evaluate potential ecotoxicity, and after consideration that few if any soils in Port Hope would have U concentrations high enough to show toxicity, a series of aged spiked soils including a soil from Port Hope were used. The bioassays were chosen from those developed and promulgated by Environment Canada.
After careful planning and consultation with local experts and landowners, sampling sites were identified and samples were collected in September 2002. Soil samples were solubilised and measurements of about 50 elements, including U, Th, Pb, As and Sb, known contaminants in Port Hope, were made by ICP-MS. Plant samples were ashed to improve detection limits and were similarly analysed by ICP-MS. Soil properties such as texture, pH, carbonate content and organic matter content were determined. Soil solid/liquid partition coefficients, Kd, were determined using centrifugally expressed soil pore water. Plant/soil concentration ratios, CR, were computed for about 70 different plant samples. The plants were chosen to represent both native and cultured plants, with emphasis on those that might be consumed by humans.
In general, the concentrations of U were positively correlated to those of Ag, As, B, Ba, Bi, Cd, Co, Cu, Mo, Ni, Pb, Sb, Sn, Tl and Zn with depth in the soil profiles, whereas there was a weak negative correlation with Th concentrations. This suggests the Th was native as opposed to a contaminant, and that the processes that influenced U distribution also influenced many other metals and potential inorganic contaminants. It is not clear if all these elements are from the same source, but they were considered co contaminants in the soil profiles. Several profiles showed monotonic decreases in U concentration with depth, and these were interpreted as being the result of migration of U deposited from the atmosphere. However, because the distribution of U in the soil profiles was similar to those of less- and more mobile co contaminants, it is suggested that at least some of the migration may have resulted from physical processes such as particle migration. Profiles of soil solid/liquid partition coefficients (Kd) were obtained, and, in general, there were progressive changes in Kd with depth. However, sometimes Kd increased with depth and sometimes it decreased with depth. The relationship of Kd to soil pH conformed well to expectation from the literature.
Plant/soil dry weight concentration ratios (CR) for U were computed, and the geometric means (n, geometric standard deviations) were overall: 0.0068 (63, 4.9), fruit: 0.00076 (15, 3.5), vegetables 0.0041 (2, 2.0) and edible roots: 0.0093 (4, 4.9), trees, shrubs, non edible annuals and forages: 0.014 (43, 2.4). These conform well to expectation. It is probable that some portion of this U was as surface deposition on the plants that resisted washing with detergent, but the majority was probably present by root uptake. The key soil properties to influence plant uptake of U are pH and U concentration. Soil pH is quite uniform in Port Hope and an effect of soil pH could not been shown. Soil U concentration may be a useful parameter to account for a small portion of the variation in CR.
The soils used for the bioassays were those used previously by Sheppard et al. (1992). They had been stored moist, outdoors in covered, in ground containers for over 10 a. This makes them ideal soils for study because the U was well aged, and was not confounded by the presence of co contaminants. There were three soils, a fine sand forest soil (limed in 1992 to allow plant growth and earthworm survival), an organic rich garden soil, and a loam from Port Hope. Analysis of the soils showed that U concentrations had not changed, and ranged from background to ~1000 mg U kg 1 dry soil. The bioassays used were northern wheatgrass (Elymus lanceolatus) early seedling growth; earthworm (Eisenia andrei) acute (14 d) survival and a chronic (56 d) reproduction bioassay; and two soil arthropod (Onychiurus folsomi and Folsomia candida) reproduction tests. Preliminary screening showed no effect at ~1000 mg U kg 1, so a small aliquot of each soil was spiked to achieve ~3000 mg U kg 1. An additional series of bioassays with the soil arthropods was done to compare aged versus recently spiked soils. Only O. folsomi proved to be especially sensitive to U, in both the screening and definitive bioassays. The plant and earthworm bioassays were not affected by U concentrations of ~1000 mg U kg 1, and F. candida was not affected by U concentrations below about 350 mg kg 1. Survival and reproduction of O. folsomi were diminished to 20% less than controls (EC20, an interpolated value in this case between the no observed effect concentration and the lowest observed effect concentration) at U concentrations of 92 to 190 mg kg 1 in the Limed sand soil, 710 mg kg 1 in the Port Hope soil and 480 mg kg 1 in the garden soil. The Limed sand was an exceptional soil, very low in organic matter content and clay materials. In general, these data support the Expected No Effect Value (ENEV) of 250 mg kg 1 derived from the literature for most soils and endpoints.
Ecological Risk Assessment of Releases from an Abandoned Sulphide Tailings Area in Lynn Lake, Manitoba (2002-2003)
The objective of the Environmental Risk Assessment was to evaluate the degree of impact of the ETMA on the natural environment. The degree of impact considered was the spatial extent of the impacted environment, the severity of the impact near the emission locations, and the effect of the impacted areas on biota that may transit the area. The results indicated that localized impact is certain, where localized describes the Lynn River from the mouth of the Town ditch to the confluence of the Keewatin River, and portions of the terrestrial environment related to surface runoff features from the ETMA to the southwest and southeast to the Lynn River.
Significant impacts further afield, particularly into Cockeram Lake, were not manifested, but there were indications that sediments in Cockeram Lake have some contamination. Data to assess if this potential contamination is increasing were not available. By logic, there were contaminants entering Cockeram Lake, and sediment concentrations should increase until a steady state is reached between the influx rate of contaminants from the Lynn River and the rates of flushing and sediment burial in Cockeram Lake. Elevated concentrations in sediment and water in Cockeram Lake would lead to elevated concentrations in biota, but it would seem that biological effects would be unlikely unless concentrations increased markedly from where they have been over the past decade.
Although local impacts were present, none of the VECs were specifically dependent on the impacted area, so that on a regional basis, there were no significant impacts to the VECs. Thus, populations of fish, terrestrial plants and small mammals in the region will not be significantly impacted by the local impacts.
Parameter Values to Model the Impacts in the Biosphere of Cesium Released into Cold Climate Regimes (2001-2002)
The ultimate disposal of high-level radioactive waste deep in geologic media requires very careful consideration of possible consequences far in the future. Several of the important radionuclides in the waste have half-lives of over 100,000 years. On this time frame, very significant changes in global climate are expected, primarily related to the long-term cycle of glaciation. It is expected, based on the periodicity of the cycle in the past, that there will be marked global cooling in the next 10,000 years. The assessment of geological nuclear waste disposal requires the capability to evaluate the direct and indirect impacts of this lower temperature.
Three climatic regimes are considered important: boreal, cold steppe and tundra. Within these, four settings are considered: natural/semi-natural, agricultural, urban and industrial. Many parameters can remain unchanged from values used in temperate settings. For example, feed-to-meat transfers in domestic livestock are not expected to change appreciably in cooler climates. In contrast, the cooler climatic regimes introduce new species and pathways, such as the lichen-reindeer pathway. This report proposes values for the additional transfer parameters needed to model impacts in these regimes and settings. Emphasis was placed on selecting data for 137Cs, in part because this radionuclide has been extensively studied in cold regions. In all cases, data were selected from studies that were directly relevant to lower temperatures or cooler climates.
The parameter values compiled include solid/liquid partition coefficients for soils and sediments; plant/soil concentration ratios, plant environmental half-times and aggregate transfer factors for cereals, trees, shrubs, pasture, lichens and mosses; and animal daily fractional transfer factors and aggregate transfer factors for meat and offal of moose, deer, reindeer, and rabbits. The approach was to compile and critically evaluate the available literature, list the appropriate data, and propose an assessment value. This was typically a geometric mean value. In several cases, it was possible to find or develop functional relationships between parameter values and climate-related variables. These were used to support the selected values.
In general, the behavior of Cs in cold regions is well known. There seems to be enhanced transfer and bioavailability in cooler climatic regimes, probably related more to indirect effects of temperature on features such as moisture supply, soil organic matter content, soil depth and general nutrient availability.
Study of radiation doses to transport workers (2000-2002)
The Canadian Nuclear Safety Commission (CNSC) is required by legislation to develop guidelines and criteria for companies to establish a written radiation protection program for carriers, consignors and consignees of radioactive materials (RAM). This requirement comes into force on June 1, 2004. The goal of the current study, Phase 2 of a multi-phase project, is to provide information that the CNSC can use to develop these guidelines and criteria.
The major tasks of the study were to
Seventeen companies participated in the project, at 25 sites in four provinces. Over 250 workers were monitored. Participating companies included
- measure doses of ionizing radiation received by a selected population of transport workers over a defined period of time
- collect shipping documents related to the period of time in which the doses are measured
- collect dose rate records from transport companies having such records
- collect radiation protection policies, etc. from a representative sample of companies
- develop a correlation between the doses received and the radioactive packages transported.
The most important factor determining worker doses is the type of transport. The highest doses are associated with road transport (couriers and truckers). Some of these high doses are for drivers, others are for handlers. All doses associated with transport by air, sea, and rail were zero or near-zero. Doses associated with internal transport in hospitals and a university were all zero. There was no clear demonstration of the effectiveness of having an RPP on the level of doses. Although some companies/sites without an RPP had high doses (couriers 1 and 4, trucker 2), and some that had an RPP had low doses (air cargo workers, port, trucker 1 and 7), there were numerous exceptions. However, there are no very high doses among companies with an RPP. This suggests that an RPP may have some effectiveness, although its presence does not ensure low doses.
- a courier company
- 8 trucking companies
- a provincial Department of Highways whose workers transported and used moisture gauges containing RAM
- a manufacturer
- shipping/receiving workers at hospitals and a university, involved in internal transport
- air cargo terminals
- a railway and
- a port.
An important factor in determining worker doses appears to be the size and weight of the package. Small, light packages such as those handled by couriers, are usually contact-handled and carried close to the body. Intermediate-sized packages, such as those handled by air cargo handlers, are usually moved by hand-cart, conveyor belt or truck. Large packages such as those handled in a port or railway yard or by some truckers, are usually handled only by remotely controlled equipment. Thus, doses are inversely related to package size and weight.
Examination of the relationship between dose and TI indicates that
Once a dose monitoring program is established, it might be possible to decrease the frequency of monitoring by supplementing it with frequent or continuous monitoring of TI.
- It would not be appropriate to use it as a criterion for requiring a RPP.
- It might be possible to use it to provide a rough, a priori estimate of dose within a category of companies, while keeping in mind that the estimate may be unreliable. The correlation should be based on the log of TI.
Specific Activity Model for 36Cl in the EnvironmentChlorine-36 is one of the most critical radionuclides to consider in intermediate- and high-level nuclear waste management. Special attributes are long half-life, high mobility, biologically essential element, and massive isotopic dilution in the geosphere and biosphere. A model of 36Cl was developed to predict the radiological consequences to human dose receptors. The approach had three parts, a literature and benchmarking review of other 36Cl models and programs, the development of a 36Cl model suitable for our client's applications within Aquabios, and the measurement of stable Cl concentrations and parameter values in the relevant landscape. A major issue was to resolve the degree to which specific activity relationships were useful. Soil-to-plant and aquatic food pathways were modeled using specific activity relationships. For subsequent transfers, the model used more traditional transfer factors. The use of the partial specific activity model simplified the problem and made the model and parameters more general. This is especially relevant for transfers of 36Cl because the concentrations of stable Cl in the environment can vary substantially as a result of oceanic effects and local mineralizations. The preliminary field study confirmed some of the key parameters to add confidence to the chosen parameter values and their ranges.
Solid-Liquid Partition Coefficients, Kds: What’s The Value And When Does It Matter?Environmental risk assessments hinge on our ability to predict the fate and mobility of radionuclides and metals in terrestrial soils and aquatic sediments. Solid-solution partitioning (the Kd approach), despite its shortcomings, has been used extensively. Much attention has been devoted to grooming the existing key compendia for values applicable for each nuclear risk assessment carried out worldwide. This appears to be an important task. For example, soil Kd values for a single nuclide can vary over several orders of magnitude, yet the soil Kd value is the most important parameter in the soil leaching model. Similarly, plant uptake depends primarily on the nuclide present in solution phase. Despite this apparent sensitivity, our experience has shown that risk assessors dwell too much on the precision of the Kd value for all nuclides. This paper discusses the effect of the Kd value on the resulting soil concentration during leaching and identifies those radionuclides and assessment conditions where a precise value is required. Only those radionuclides that typically have a soil Kd value of 10 L/kg or less (Tc, Cl, I, As) need be accurately described for timeframes of up to 10,000 years for desired soil model prediction outcomes (soil concentrations within two-fold).(ECORAD 2001 Conference, Aix-en-Provence, France).
Toxicants in the Environment: Bringing radioecology and ecotoxicology togetherRadioecology and ecotoxicology are both well-established disciplines, and both deal with the fate and effects of contaminants in the environment. Until the last few years, there was not a strong need for interaction between these disciplines. However, as the nuclear industries and regulators place greater emphasis on investigating the protection of non human biota, the opportunity for synergy between the disciplines has increased. Radioecology is very strong in understanding the fate of radionuclides, in dealing with the additivity of doses, and in understanding physiological effects of radiation. Ecotoxicology has particular strengths in identifying the level of biological organization to protect and in extrapolation among species, toxicity endpoints and contaminants. The synergy of these disciplines will result in a very powerful assessment capability. This paper explores the opportunities for synergy, illustrated with a few specific examples drawn from recent radionuclide ecological risk assessments.(ECORAD 2001 Conference, Aix-en-Provence, France).
ECOMatters quantified the potential toxic and deleterious effects of atmospheric ammonia gas, which is toxic to plants. In addition, because it is a nitrogen source, atmospheric ammonia can be disruptive to natural ecosystems. The results were documented in a manner consistent with CEPA needs. This project is also related to CEPA PSL2 assessments. (Report to Environment Canada). Article in Canadian Journal of Soil Science.
Manitoba Farms and the Environment
Information brochure prepared and distributed to over 20,000 farmers to improve their understanding of environmental laws that effect their operations.
Advances in Earthworm Ecotoxicology
Recent book on advances in ecotoxicology edited by ECOMatters staff.
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