ECOMatters' Recent Projects
A nutrient budget for the peri-urban Lower Fraser Valley, British Columbia, Canada
The Lower Fraser Valley (LFV) is a climatically unique region of Canada, isolated by mountains and with a substantial population density. Agriculture is dominated by high-value crops and livestock and amenity operations such as horses and fur production. The entire valley is essentially a peri urban setting, and nutrient influxes, especially of phosphorus (P) are an emerging issue. ECOMatters undertook a study to complete a P budget of the LFV to quantify the largest influxes and effluxes. Livestock feed is the largest influx of P: the land is too valuable and too limited to grow forages and feed grains and they are imported from the rest of Canada. Fertilizer and import of food are the next largest influxes of P. Export of specialty food crops (berries and greenhouse crops) represents effluxes that partially offset the influxes. After considering all influxes and effluxes, the net influx was 11,800 tonnes P per year or 4.4 kg P per person per year. The efflux in sewage effluent to the sea is 1150 tonnes P and exported sewage solids is 450 tonnes P. Municipal solid waste accounts is most difficult to quantify and may be about 2100 tonnes P, most of which is sequestered in landfill, which we consider an efflux. Sensitivity analysis showed that variation in human population and the amount of P consumed per person in chicken and dairy products had the most influence on the total movement of P from rural to urban portions of the LFV, and that the overall influx of P to the LFV was dominated by import of animal feeds.
Transfer factors to wildlife: comparison of stomach-content, plant-sample and soil-sample concentrations as the denominator.
A recent study by ECOMatters measured transfer factors for 49 elements in hunter-killed Whitetail deer (Odocoileus virginianus), using concentrations in the stomach content as the substrate/denominator to compute muscle/vegetation concentration ratios (CRm stomach) and daily fractional transfer factors (Ff). Using the stomach content ensured an accurate representation of what the deer ate, except that it was limited in time to the vegetation selected by the animal just before it was killed. Here, ECOMatters investigated two alternatives, one where the feed is represented by samples of 21 different vegetation types that deer may have eaten in the area (CRm plant), and the other is using soil concentration in the region as the denominator (CRm soil). The latter is the formulation used in the ERICA tool, and other sources, for risk assessment to non human biota. Across elements, (log) concentrations in all the media were highly correlated. The stomach contents had consistently higher ash and rare earth element concentrations than the sampled (and washed) vegetation and this was attributed to soil or dust ingestion. This lends credence to the use of soil based CRm soil values, despite (or more accurately because of) the inclusive yet gross simplicity of the approach. However, it was clear that variation of CRm soil values was larger than for CRm stomach or CRm plant , even if soil load on vegetation was included in the latter values. It was also noted that the variation in CRm soil computed from the product of CRm plant and CRplant soil (where CRplant soil is the plant/soil concentration ratio) was somewhat larger than the variation inherent in CRm soil data. Thus it is reasonable to estimate CRm soil from CRm plant and CRplant soil if observed CRm-soil values are not available, but this introduces further uncertainty.
Beef cattle husbandry practices across ecoregions Canada in 2012
Beef production in Canada is diverse in many dimensions: numbers of cattle per operation range over 10,000 fold, husbandry practices range from 0 to 100% grazing, and types of operations vary marked from region to region. ECOMatters undertook the statistical analysis and reporting of a survey done by Ipsos Forward Research. This study summarizes production and management information obtained from a survey conducted in 2012 on1009 beef operations in Canada. Many of the results clearly differentiate the practices on the Prairies (semi arid continental climate) from those in Ontario and Quebec (humid temperate climate). Compared to eastern Canada, the Prairies had: earlier and shorter calving seasons, higher weaning weights, utilized more winter grazing with a variety of strategies (mostly using rolled or baled forages), grew and fed more barley than corn, used more seasonal feeding areas and feedlots (and hence fewer barns), and more commonly spread manure in the fall. Many other factors also differed by region. Rationale regarding the adoption of many of the management strategies was reported by the producers. For example, winter grazing was adopted primarily to reduce costs and labour, but for some it was also linked to a late calving season. Preferred sources of technical information included their own experience, farm print media, producer organisations and demonstrations at field days.
Trace element transfer from feed to manure and soil
Trace elements are commonly added to animal feeds as mineral supplements, as well as being present in the basic organic feed materials. These trace elements include elements added because they are essential for animal growth and productivity, they also include elements inadvertently added along with the essential elements, and they may include elements added because they confer a pharmaceutical benefit (e.g., zinc oxide added to lessen gastric issues in piglets). A large proportion of the elements in feed ultimately are excreted in manure and applied to soil. Some preliminary estimates showed that the concentrations of some trace elements in soils could be doubled or more within 100 years, and toxic soil conditions are (remotely) possible.
This project measured ~60 elements in 124 manure samples from broiler, layer, turkey, swine grower, swine nursery, sow, dairy and beef operations. The corresponding feeds were also analyzed. To evaluate the effect of trace elements in manure on soil concentrations, detailed sampling was done of soil profiles on 10 heavily manured sites and 10 paired (adjacent) un manured sites. Sixty two elements were analyzed using near total extraction, and soil test P was also measured. The concentration profiles were interpreted with the aid of element/yttrium (Y) ratios, which controlled for some of the natural mineralogical variability. The results indicate that it is possible to measure trace element accumulations in soil because of manure application, but these are limited to specific cases.
Hunter/gatherer transfer factors for iodine
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.
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.
Automated Soil Gas Grid Sampling System Interim ReportThe 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, OntarioProbabilistic Performance Assessment of Geological Disposal of CO2 (2002-2004)
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.
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.
Waste Characterization and Nuclear Fuels (ongoing)
ECOMatters personnel have extensive experience in the analysis, characterization and prediction of low-, intermediate- and high-level nuclear waste inventories. Because of the complexity of the nuclear power plant structure, operation and waste generation processes, a comprehensive knowledge of physics, chemistry and materials science is essential to the successful completion of waste inventory assessments. This includes performing characterization of radionuclide release from CANDU fuels, developing release models and conducting performance assessments on the viability of direct disposal. This knowledge was also applied nationally and internationally to contracts on the Mixed Oxide (MOX) Reactor, Pressurized-Water Reactor (PWR), Advanced Gas-cooled Reactor (AGR) and Research Reactor fuels. ECOMatters personnel continue to provide support to nuclear utilities around the world in the area of waste characterization and waste hazard assessment.
Ecological Risk Assessment of Releases from an Abandoned Sulphide Tailings Area in Lynn Lake, Manitoba (2002-2003)
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 (1999 - 2000, 2001-2002)
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.
Development and quality assurance of the BETRAC code (to 2002).
ECOMatters completed development of the BETRAC (Boundary Element Transport of Radionuclides and Contaminants) code. BETRAC is a general-purpose groundwater flow and radionuclide transport code. It solves for steady state groundwater flow and transient radionuclide transport for arbitrary geometry with heterogeneous material properties. It was developed to model radionuclide mass transport from an underground disposal vault. It can be applied to contaminant transport and heat transport problems as well as systems requiring solutions to Laplace's equation such as electrostatics. It uses boundary element methods based on the free space Green's function for the governing differential equation. For time dependent problems, Laplace transform methods are used. The development of the BETRAC code was done in accordance with the quality assurance procedures of CSA draft standard, N286.7.
Parameter Values to Model the Impacts in the Biosphere of Cesium Released into Cold Climate Regimes (2001-2002)
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 (2000-2002)
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.
Quality assurance of the INROC code (2001).
INROC uses boundary integral methods with numerical inversion of Laplace transforms to determine radionuclide release rates from pinhole defects in containers emplaced in underground disposal rooms. The INROC code, developed for the second case study submitted for the 1996 CEAA hearings into the Canadian concept for the disposal of Canada's nuclear fuel waste had not been fully quality assured. ECOMatters was subcontracted to perform the quality assurance of the code in accordance with the CSA draft standard N286.7.
Preparation of a new standard for calculation of routine release limits (2000)
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 (2000).
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 (1999 and ongoing)
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.
Validation of evidence for fast groundwater flow in the tuffaceous rocks at Yucca Mountain, Nevada (1999 and ongoing)
ECOMatters is assisting in a project to validate chlorine-36 analytical evidence for 'fast-tracking' of groundwaters (pore fluids) at Yucca Mountain, through faults and fractures in the unsaturated zone rock. The work involves analysing freshly drilled core samples from the tuff at depth utilising technologists and analytical facilities at AECL's Whiteshell Laboratories. The rocks are being analysed for isotopes of uranium and thorium whose relative concentrations will indicate if recent groundwater/rock interactions have occurred at depth.
Groundwater chemistries of crystalline rock sites in Finland (1998-1999)
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.
Scoping assessment of in situ disposal of the Nuclear Power Demonstration (NPD) reactor (1998-1999)
ECOMatters was the prime contractor in the scoping evaluation of the in situ approach to decommission the NPD reactor which was built in an excavation below bedrock on the shores of the Ottawa River, Rolphton, Ontario. Much of the equipment and all of the fuel has been removed, but the irradiated core and other irradiated materials are still in place. The concept calls for backfilling with a clay/sand mixture and capping the buried facility with clay. This makes the facility a direct analogue of a Low and Intermediate Level Waste (L&ILW) repository. Eleven groundwater leaching scenarios and a human intrusion scenario were evaluated.
The intrusion of oxygen into deep Shield rocks during glacial/interglacial cycles (1998-1999)
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.
Mathematical development and code quality assurance of two boundary-element models of the release and behaviour of contaminants from a complex buried waste form. These models are considered superior to finite element and finite difference models for both stability and accuracy.
Contributions to the comprehensive study report (CSR under the Canadian Environmental Assessment Act) for the decommissioning of the Whiteshell Nuclear Research Laboratories, including impacts screening, cumulative effects and local economic effects. 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.
Darlington Nuclear Generating Station Ecological Effects Review (2000 -2001)
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 (1999)
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 (1998)
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.
Investigation of the ability of artificial neural network programming to ‘mine’ information from data on nuclear waste stream composition. The objective was to gain maximum information for inventory planning.
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).
Using adaptations of the BIOTRAC code, estimates were made of the ability of lakes and soils to assimilate contaminants deposited from the atmosphere. The critical load was defined as the flux (deposition) of contaminants from the atmosphere that will increase soil or water concentrations to a level that approaches but does not exceed concentrations where ecotoxicological effects may be observed. The models dealt with the major environmental processes, and were run in a stochastic mode in order to assess long term impacts and the effect of spatial variability on the results. This work will lead to identification of where there is potential for ecological impact, and may lead to emissions controls. (Report to Environment Canada).Toxic effects of metals in the environment were assessed relative to free-ion concentrations instead of the conventional approach of total metal concentrations. The new approach required simplified geochemical modelling for each ecotoxicology study. Both aquatic and terrestrial ecotox data were re-interpreted. The results were used to address heavy metal emissions under the Canadian Environmental Protection Act, Priority Substance List 2 (CEPA-PSL2). (Report to Environment Canada).
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.
(Return to ECOMatters home page)
this page last updated April 30, 2009
© ECOMatters 1998.