ANSTO :: Browsing by Author "Twining, JR"

Browsing by Author "Twining, JR"

Now showing 1 - 20 of 49

Accumulation of plutonium in mammalian wildlife tissues following dispersal by accidental-release tests
(Elsevier, 2016-01-01) Johansen, MP; Child, DP; Caffrey, EA; Harrison, JJ; Hotchkis, MAC; Payne, TE; Ikeda-Ohno, A; Thiruvoth, S; Beresford, NA; Twining, JR; Davis, E
We examined the distribution of plutonium (Pu) in the tissues of mammalian wildlife inhabiting the relatively undisturbed, semi-arid former Taranaki weapons test site, Maralinga, Australia. The accumulation of absorbed Pu was highest in the skeleton (83% ± 6%), followed by muscle (10% ± 9%), liver (6% ± 6%), kidneys (0.6% ± 0.4%), and blood (0.2%). Pu activity concentrations in lung tissues were elevated relative to the body average. Foetal transfer was higher in the wildlife data than in previous laboratory studies. The amount of Pu in the gastrointestinal tract was highly elevated relative to that absorbed within the body, potentially increasing transfer of Pu to wildlife and human consumers that may ingest gastrointestinal tract organs. The Pu distribution in the Maralinga mammalian wildlife generally aligns with previous studies related to environmental exposure (e.g. Pu in humans from worldwide fallout), but contrasts with the partitioning models that have traditionally been used for human worker-protection purposes (approximately equal deposition in bone and liver) which appear to under-predict the skeletal accumulation in environmental exposure conditions. © 2015, Elsevier Ltd.
Accumulation of plutonium in mammalian wildlife tissues: comparison of recent data with the ICRP distribution models
(International Conference on Radioecology and Environmental Radioactivity, 2014-07-01) Johansen, MP; Child, DP; Davis, E; Hotchkis, MAC; Payne, TE; Ikeda-Ohno, A; Twining, JR
We examined the distribution of plutonium (Pu) in the tissues of mammalian wildlife to address the paucity of such data under environmental exposure conditions. Pu activity concentrations were measured in Macropus rufus (red kangaroo), Oryctolagus cuniculus (European rabbit), and Pseudomys hermannsburgensis (sandy inland mouse)inhabiting the relatively undisturbed, semi-arid conditions at the former Taranaki weapons test site at Maralinga, Australia. Of the absorbed Pu (distributed via circulatory and lymph systems) accumulation was foremost in bone (83% ±10% SD), followed by muscle (9% ±10%), liver (7% ±7%), kidneys (0.5% ±0.3%), and heart (0.4% ±0.4%). The bone values are higher than those reported in ICRP 19 and 48 (45-50% bone), while the liver values are lower than ICRP values (30-45% liver). The ICRP values were based on data dominated by relatively soluble forms of Pu, including prepared solutions and single-atom ions produced by decay following the volatilisation of uranium during nuclear detonation (fallout Pu, ICRP 1986). In contrast, the Maralinga data relates to low-soluble forms of Pu used in tests designed to simulate accidental release and dispersal. We measured Pu in lung, GI-tract and the skin and fur as distinct from the absorbed Pu in bone, liver, muscle, and kidneys. Compared with the mean absorbed activity concentrations, the results for lung tissues were higher by up to one order of magnitude, and those in the GI tract contents and the washed skin/fur were higher by more than two orders of magnitude. These elevated levels are consistent with the presence of low-soluble Pu, including particulate forms, which pass through, or adhere upon, certain organs, but are not readily absorbed into the bloodstream. This more transitory Pu can provide dose to the lung and GI tract organs, as well as provide potential transfer of contamination when consumed in predator-prey food chains, or during human foodstuff consumption. For example, activity concentrations in O. cuniculus edible samples prepared according to traditional aboriginal methods were more than two orders of magnitude higher than in muscle alone. The increase was due to inclusion of GI tract components and contents in the traditional method. Our results provide new insights into the sequestration of Pu in mammalian tissues under environmental exposure conditions. These results contrast with those related to the specific forms of Pu and exposure conditions upon which the ICRP models were based. However, they provide data relevant to the assessment of key environmental legacy waste sites, and of potential release scenarios for the low-soluble oxide forms in the growing worldwide inventory of Pu associated with power production.
Analytical method development for tritium in tree transpirate from the Little Forest Burial Ground
(Australian Nuclear Science and Technology Organisation, 2009-08) Twining, JR; Harrison, JJ; Vine, M; Creighton, NM; Neklapilova, B; Hoffmann, EL
The Little Forest Burial Ground (LFBG) is a near-surface low-level nuclear waste repository located within the buffer zone surrounding the Lucas Heights Research Laboratories of ANSTO (Figure 1). Tritium (3H, ‘T’), as tritiated water (HTO), was one of the radioactive substances placed into the trenches located within the LFBG (Isaacs and Mears, 1977). This material will behave conservatively in regard to any seepage from the site of deposition. As such, it should be a good indicator of groundwater movement at the site. Water is a vital requirement of plants. Hence, it was proposed that samples from herbs and trees may be useful to assess the biologically available HTO and also provide an indication of a potential exposure for environmental dose assessment, not only for 3H but also for the other radionuclides potentially migrating with the water from the trenches. As part of the initial draft plan for a vegetation survey in the LFBG (Twining and Creighton, 2007) the following two null hypotheses were established: H0a that there is no significantly higher concentration of specific contaminants in foliage of trees growing over, or adjacent to, the pits than there is in the foliage of the same species growing away from the pits; H0b that there is no correlation between contaminant levels in the seepage plume and surface vegetation. These hypotheses are to be tested using the acquired data. However, as part of the process of applying HTO in transpirate as a monitoring tool, some method development has been required. This report covers all aspects of that development and provides a recommended approach to acquiring such data and recording the information.
Assessing doses to terrestrial wildlife at a radioactive waste disposal site: Inter-comparison of modelling approaches
(Elsevier Science BV, 2012-06-15) Johansen, MP; Barnett, CL; Beresford, NA; Brown, JE; Černe, M; Howard, BJ; Kamboj, S; Keum, DK; Smodiš, B; Twining, JR; Vandenhove, H; Vives i Batlle, J; Wood, MD; Yu, C
Radiological doses to terrestrial wildlife were examined in this model inter-comparison study that emphasised factors causing variability in dose estimation. The study participants used varying modelling approaches and information sources to estimate dose rates and tissue concentrations for a range of biota types exposed to soil contamination at a shallow radionuclide waste burial site in Australia. Results indicated that the dominant factor causing variation in dose rate estimates (up to three orders of magnitude on mean total dose rates) was the soil-to-organism transfer of radionuclides that included variation in transfer parameter values as well as transfer calculation methods. Additional variation was associated with other modelling factors including: how participants conceptualised and modelled the exposure configurations (two orders of magnitude); which progeny to include with the parent radionuclide (typically less than one order of magnitude); and dose calculation parameters, including radiation weighting factors and dose conversion coefficients (typically less than one order of magnitude). Probabilistic approaches to model parameterisation were used to encompass and describe variable model parameters and outcomes. The study confirms the need for continued evaluation of the underlying mechanisms governing soil-to-organism transfer of radionuclides to improve estimation of dose rates to terrestrial wildlife. The exposure pathways and configurations available in most current codes are limited when considering instances where organisms access subsurface contamination through rooting, burrowing, or using different localised waste areas as part of their habitual routines. Crown Copyright © 2012 Published by Elsevier B.V
Assessment of radionuclide distributions at an Australian legacy radioactive waste site
(South Pacific Radioactivity Association, 2010-09-01) Payne, TE; Cendón, DI; Collins, RN; Dore, M; Hankin, SI; Harrison, JJ; Hughes, CE; Johansen, MP; Thiruvoth, S; Twining, JR; Wilsher, KL
During the 1960s, low level radioactive waste was buried in shallow trenches at a disposal site in south-eastern Australia, known as the Little Forest Burial Ground. This paper discusses preliminary findings of research into the distribution of radionuclides at the site, including soils, groundwater and biota. In particular, we are studying the mobility of radionuclides; and their uptake by plants, insects and small animals. Groundwater monitoring indicates that there has been limited movement of radioactivity, other than a tritium plume that extends at least 100 m. The tritium results are being used to define the groundwater flowpaths, and the effects of seasonal and climatic factors. The pattern of tritium distribution suggests that the source of tritium is predominantly within the waste materials. However, tritium derived from a nearby municipal landfill contributes to tritium concentrations in some groundwaters, with smaller amounts from cosmogenic tritium and atmospheric deposition originating from the nearby HIFAR reactor (shut down in 2007). The tritium data provide a record of water movement against which the relative mobility of other radionuclides can be assessed. There are measurable amounts of 60Co, 90Sr, 137Cs and traces of actinides in some soils, groundwater and vegetation samples taken in close proximity to the disposal area. Isotopic ratios such as δ13C, δ180, δ2H, δ34S and 87Sr/86Sr are being measured in groundwater, in addition to the radioactive isotopes originating from the disposed wastes. Synchrotron EXAFS and XANES studies are being applied to study elemental chemical environments and oxidation states in the soils at the site. We have recently undertaken a major geophysical investigation and drilling program; and installation of an improved array of water sampling boreholes is planned. Therefore, many more samples of groundwater and soils are becoming available for analysis.
Assessment of radionuclide movement at an Australian legacy radioactive waste site
(EMSL, 2009-09-20) Payne, TE; Cendón, DI; Collins, RN; Hankin, SI; Harrison, JJ; Hughes, CE; Johansen, MP; Twining, JR; Waite, TD
Not available
Australian inputs into the IAEA EMRAS program: terrestrial animal concentration factors and the LFBG environmental dose assessment scenario
(South Pacific Radioactivity Association, 2010-08-31) Twining, JR; Johansen, MP
There has been a recent international emphasis placed on assessing radiological dose and its impacts on ecosystems in addition to those directly affecting humans. This is reflected in the development of the IAEA Environmental Modelling for Radiation Safety (EMRAS) Program. As part of Australia's contribution to EMRAS, we have been looking at ecosystems previously affected by nuclear activities within the country and acquiring data pertinent to Australian animals and plants, many of which are unique. Within Australia, one area of concern has been identified as the yet-to-be-developed national nuclear waste repository and we are acquiring data to help in modelling any potential effects. The Little Forest Burial Ground (LFBG) is a near surface nuclear waste site dating from the 19605. As well as providing data on the behaviour of radioactivity within an Australian ecosystem, it is also a case study site for EMRAS dose assessment modelling where a range of methods for estimating bio-uptake in plants and animals are being applied by IAEA participants. Further, there are a number of uranium mines or deposits and a weapons test site, Maralinga, that give us additional radioecological information as input to those models. A summary of the Australian terrestrial fauna concentration factors will be presented.
Best practices for predictions of radionuclide activity concentrations and total absorbed dose rates to freshwater organisms exposed to uranium mining/milling
(Elsevier, 2022-02) Goulet, R; Newsome, L; Vandenhove, H; Keum, DK; Horyna, J; Kamboj, S; Brown, JE; Johansen, MP; Twining, JR; Wood, MD; Černe, M; Beaugelin-Seiller, K; Beresford, NA
Predictions of radionuclide dose rates to freshwater organisms can be used to evaluate the radiological environmental impacts of releases from uranium mining and milling projects. These predictions help inform decisions on the implementation of mitigation measures. The objective of this study was to identify how dose rate modelling could be improved to reduce uncertainty in predictions to non-human biota. For this purpose, we modelled the activity concentrations of 210Pb, 210Po, 226Ra, 230Th, and 238U downstream of uranium mines and mills in northern Saskatchewan, Canada, together with associated weighted absorbed dose rates for a freshwater food chain using measured activity concentrations in water and sediments. Differences in predictions of radionuclide activity concentrations occurred mainly from the different default partition coefficient and concentration ratio values from one model to another and including all or only some 238U decay daughters in the dose rate assessments. Consequently, we recommend a standardized best-practice approach to calculate weighted absorbed dose rates to freshwater biota whether a facility is at the planning, operating or decommissioned stage. At the initial planning stage, the best-practice approach recommend using conservative site-specific baseline activity concentrations in water, sediments and organisms and predict conservative incremental activity concentrations in these media by selecting concentration ratios based on species similarity and similar water quality conditions to reduce the uncertainty in dose rate calculations. At the operating and decommissioned stages, the best-practice approach recommends relying on measured activity concentrations in water, sediment, fish tissue and whole-body of small organisms to further reduce uncertainty in dose rate estimates. This approach would allow for more realistic but still conservative dose assessments when evaluating impacts from uranium mining projects and making decision on adequate controls of releases. © 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.
Bioaccumulation and retention kinetics of cadmium in the freshwater decapod Macrobrachium australiense
(Elsevier, 2014-03) Cresswell, T; Simpson, SL; Smith, REW; Nugegoda, D; Mazumder, D; Twining, JR
The potential sources and mechanisms of cadmium bioaccumulation by the native freshwater decapods Macrobrachium species in the waters of the highly turbid Strickland River in Papua New Guinea were examined using 109Cd-labelled water and food sources and the Australian species Macrobrachium australiense as a surrogate. Synthetic river water was spiked with environmentally relevant concentrations of cadmium and animals were exposed for 7 days with daily renewal of test solutions. Dietary assimilation of cadmium was assessed through pulse-chase experiments where prawns were fed separately 109Cd-labelled fine sediment, filamentous algae and carrion (represented by cephalothorax tissue of water-exposed prawns). M. australiense readily accumulated cadmium from the dissolved phase and the uptake rate increased linearly with increasing exposure concentration. A cadmium uptake rate constant of 0.10 ± 0.05 L/g/d was determined in synthetic river water. During depuration following exposure to dissolved cadmium, efflux rates were low (0.9 ± 5%/d) and were not dependent on exposure concentration. Assimilation efficiencies of dietary sources were comparable for sediment and algae (48–51%), but lower for carrion (28 ± 5%) and efflux rates were low (0.2–2.6%/d) demonstrating that cadmium was well retained by M. australiense. A biokinetic model of cadmium accumulation by M. australiense predicted that for exposures to environmentally relevant cadmium concentrations in the Strickland River, uptake from ingestion of fine sediment and carrion would be the predominant sources of cadmium to the organism. The model predicted the total dietary route would represent 70–80% of bioaccumulated cadmium © 2014, Elsevier B.V.
Bioaccumulation from food and water of cadmium, selenium and zinc in an estuarine fish, Ambassis jacksoniensis
(Elsevier, 2010-10) Creighton, NM; Twining, JR
The glassfish, Ambassis jacksoniensis, is a key, mid-level species in an estuarine food web on the east coast of Australia. Estuaries are subject to contamination from urban and industrial activities. The biokinetics of Cd, Se and Zn accumulation by glassfish from water and food were assessed using radioisotopes. Metal uptake from water was not regulated over the range of water metal concentrations examined. Metal uptake from food was assessed using brine shrimp (Artemia sp.) fed radio-labelled algae. The assimilation efficiency from food was 9.5 ± 2.5%, 23 ± 2.2% and 4.6 ± 0.6% for Cd, Se and Zn, respectively. The potential for biomagnification was low for all metals. Food is the main metal uptake pathway for glassfish, with 97%, 99% and 98% of the uptake of Cd, Se and Zn, respectively, estimated to be from food. © 2010, Elsevier Ltd.
Biokinetics and discrimination factors for delta C-13 and delta N-15 in the omnivorous freshwater crustacean, Cherax destructor
(CSIRO Publishing, 2012-10-29) Carolan, JV; Mazumder, D; Dimovski, C; Diocares, R; Twining, JR
Knowledge and understanding of biokinetics and discrimination factors for carbon-13 (delta C-13) and nitrogen-15 (delta N-15) are important when using stable isotopes for food-web studies. Therefore, we performed a controlled laboratory diet-switch experiment to examine diet-tissue and diet-faeces discrimination factors as well as the biokinetics of stable-isotope assimilation in the omnivorous freshwater crustacean, Cherax destructor. The biokinetics of delta C-13 could not be established; however, the delta N-15 value of C. destructor tissue reached equilibrium after 80 +/- 35 days, with an estimated biological half-time for N-15 of 19 +/- 5 days. Metabolic activity contributed to the turnover of N-15 by nearly an order of magnitude more than growth. The diet-tissue discrimination factors at the end of the exposure were estimated as -1.1 +/- 0.5% for delta C-13 and +1.5 +/- 1.0% for delta N-15, indicating that a delta N-15 diet-tissue discrimination factor different from the typically assumed +3.4% may be required for freshwater macroinvertebrates such as C. destructor. The diet-faeces discrimination factor for delta N-15 after 120 days was estimated as +0.9 +/- 0.5%. The present study provides an increased understanding of the biokinetics and discrimination factors for a keystone freshwater macroinvertebrate that will be valuable for future food-web studies in freshwater ecosystems. © 2012, CSIRO Publishing.
Biota dose modelling: Little Forest Burial Ground scenario
(Australian Nuclear Science and Technology Organisation, 2012-10-16) Johansen, MP; Barnett, CL; Beresford, NA; Brown, JE; Černe, M; Howard, BJ; Kamboj, S; Keum, DK; Payne, TE; Smodiš, B; Twining, JR; Vandehnove, H; Vives i Batlle, J; Wood, MD; Yankovich, TL; Yu, C
Radiation doses to terrestrial wildlife were examined in a model inter-comparison study on a diverse range of terrestrial plants and animals at the Little Forest Burial Ground, NSW, Australia. This inter-comparison was one in a series conducted under the IAEA Environmental Modelling for Radiation Safety Programme (EMRAS), which indicated general agreement among available biota dose models in the use of dose conversion parameters for standard organisms and geometries. However, notable variation in dose estimates emerged when the models were applied to a terrestrial deposition scenario (Chernobyl exclusion zone, Ukraine); a freshwater aquatic scenario (Perch Lake, Canada; a low-level burial ground scenario (Little Forest Burial Ground, Australia;), as well as additional aquatic (Beaverlodge, Canada) and wetlands (various locations) scenarios currently underway. Given the range in outcomes from the various modelling approaches of the previous EMRAS studies, the Little Forest Burial Ground scenario focused on quantifying the factors causing variation. The dominant variable factor (up to orders of magnitude on mean total dose rates) was the soil-to-organism transfer of radionuclides. Additional variation was associated with: exposure configurations (two orders of magnitude when considering trees growing on the waste trenches); inclusion/exclusion of progeny in Th and U isotopes (typically less than one order of magnitude); and radiation weighting factors and dose conversion coefficients (typically less than one order of magnitude). At Little Forest, results suggest radionuclide uptake is occurring in wildlife, but at low levels as most organisms only access the relatively clean surface soils above the buried wastes. Doses to acacia tree were elevated, however, due to its deeper roots having direct access to the buried wastes, with predictions of 95th percentile doses above the screening levels indicating further study is warranted. Our study confirms and adds to the outcomes of previous EMRAS studies in quantifying the sources of variation in biota dose modelling, and highlights soil to-organism transfer as a key source of uncertainty. It prompts continued evaluation of the underlying mechanisms governing soil-to-organism transfer of radionuclides to improve estimation of dose rates to terrestrial wildlife.
Biotic, temporal and spatial variability of tritium concentrations in transpirate samples collected in the vicinity of a near-surface low-level nuclear waste disposal site and nearby research reactor
(Elsevier Science Ltd, 2011-06-01) Twining, JR; Hughes, CE; Harrison, JJ; Hankin, SI; Crawford, J; Johansen, MP; Dyer, LL
The results of a 21 month sampling program measuring tritium in tree transpirate with respect to local sources are reported. The aim was to assess the potential of tree transpirate to indicate the presence of sub-surface seepage plumes. Transpirate gathered from trees near low-level nuclear waste disposal trenches contained activity concentrations of (3)H that were significantly higher (up to similar to 700 Bq L(-1)) than local background levels (0-10 Bq L(-1)). The effects of the waste source declined rapidly with distance to be at background levels within 10s of metres. A research reactor 1.6 km south of the site contributed significant (p < 0.01) local fallout (3)H but its influence did not reach as far as the disposal trenches. The elevated (3)H levels in transpirate were, however, substantially lower than groundwater concentrations measured across the site (ranging from 0 to 91% with a median of 2%). Temporal patterns of tree transpirate (3)H, together with local meteorological observations, indicate that soil water within the active root zones comprised a mixture of seepage and rainfall infiltration. The degree of mixing was variable given that the soil water activity concentrations were heterogeneous at a scale equivalent to the effective rooting volume of the trees. In addition, water taken up by roots was not well mixed within the trees. Based on correlation modelling, net rainfall less evaporation (a surrogate for infiltration) over a period of from 2 to 3 weeks prior to sampling seems to be the optimum predictor of transpirate (3)H variability for any sampled tree at this site. The results demonstrate successful use of (3)H in transpirate from trees to indicate the presence and general extent of sub-surface contamination at a low-level nuclear waste site. Crown Copyright © 2011, Elsevier Ltd.
A combined multidisciplinary kinetic modeling approach for determination of coastal ecosystem contaminant fluxes
(Goldschmidt, 2006-08-26) Szymczak, R; Twining, JR; Hollins, SE; Mazumder, D; Creighton, NM
The historical operation of manufacturing, chemical and other industries in the Sydney Harbour catchment over many decades has left a legacy of high chemical contamination in the surrounding catchment. These contaminants are now seriously impacting on incident commercial fisheries and public utilisation of estuarine resources. Elucidation of environmental processes is the key to effective ecosystem management, however few tools are available to predict their inter-relationships, rates and directions. This work seeks to combine GIS, contaminant transport, ecological, and bioaccumulation models to improve the accuracy and specificity of a probabilistic ecological risk assessment strategy. This study has four components: (1) determination of chemical linkages between high trophic order species and different habitats resources using stable isotopic analyses of carbon and nitrogen. These studies identify trophic cascades forming the basis for selection of biota for contaminant transfer experiments; (2) short-term (weeks – months) chronology and geochemistry of sediment cores and traps in Homebush Bay to determine rates of sedimentation and resuspension (using environmental/cosmogenic 7-Be). Models derived from these studies provide the contaminants levels against which risk is assessed; (3) biokinetic studies using proxy radiotracer isotopes (eg. 75-Se & 109-Cd for analogous stable metals) of the uptake and trophic transfer of contaminants by specific estaurine biota. Here we identify the rates and extent to which contaminants accumulated and transferred to predators/seafoods; and (4) application of a probabilistic ecological risk assessment model (AQUARISK) set to criteria determined by stakeholder consensus. Here we report initial results of the distribution of natural isotopes and redistribution of artificial isotopes injected into ecological compartments to determine the key trophic linkages, contaminant pathways and their rates in temperate estuarine systems of Sydney Harbour & Botany Bay (Australia).
Comparative accumulation of Cd-109 and Se-75 from water and food by an estuarine fish (Tetractenos glaber)
(Elsevier, 2008-01) Alquezar, R; Markich, SJ; Twining, JR
Few data are available on the comparative accumulation of metal(loid)s from water and food in estuarine/marine fish. Smooth toadfish (Tetractenos glaber), commonly found in estuaries in south-eastern Australia, were separately exposed to radio-labelled seawater (14 kBq L-1 of Cd-109 and 24 kBq L-1 of Se-75) and food (ghost shrimps; Trypaea australiensis: 875 Bq g(-1) Cd-109 and 1130 Bq g(-1) Se-75) for 25 days (uptake phase), followed by exposure to radionuclide-free water or food for 30 days (loss phase). Toadfish accumulated Cd-109 predominantly from water (85%) and Se-75 predominantly from food (62%), although the latter was lower than expected. For both the water and food exposures, Cd-109 was predominantly located in the gut lining (60-75%) at the end of the uptake phase, suggesting that the gut may be the primary pathway of Cd-109 uptake. This may be attributed to toadfish drinking large volumes of water to maintain osmoregulation. By the end of the loss phase, Cd-109 had predominantly shifted to the excretory organs - the liver (81%) in toadfish exposed to radio-labelled food, and in the liver, gills and kidney (82%) of toadfish exposed to radio-labelled water. In contrast, Se-75 was predominantly located in the excretory organs (gills, kidneys and liver; 66-76%) at the end of the uptake phase, irrespective of the exposure pathway, with minimal change in percentage distribution (76-83%) after the loss phase. This study emphasises the importance of differentiating accumulation pathways to better understand metal(loid) transfer dynamics and subsequent toxicity, in aquatic biota. © 2007, Elsevier Ltd.
Comparison of concentrations of natural and artificial radionuclides in plankton from French Polynesian and Australian coastal waters
(The Institution of Engineers Australia, 1994-05-01) Poletiko, C; Twining, JR; Jeffree, RA
Zooplankton samples from French Polynesian and Australian coastal waters were analysed for natural and artificial radionuclides. Quality control was assured by correlating replicate analyses between three laboratories and by participation in an international intercomparison exercise. Pu239/240 was detected sporadically among samples from both regions, with the highest levels being more consistently found in Tuamotu-Gambier samples. The artificial radionuclides Cs-137, Cs-134, Sr-90 and Co-60 were not detected. Of the natural nuclides, Ac-228 was detected in shallow continental waters off Northern Australia and an inverse relationship (P<0.02) was established between plankton density and their Po-210 concentration.
Dose modelling comparison for terrestrial biota: IAEA EMRAS II Biota Working Group's Little Forest Burial Ground scenario
(International Union of Radioecology, 2011-06-19) Johansen, MP; Barnett, CL; Beresford, NA; Brown, JE; Černe, M; Howard, BJ; Kamboj, S; Keum, DK; Smodiš, B; Twining, JR; Vandenhove, H; Vives i Batlle, J; Wood, MD; Yu, C
Radiological doses to terrestrial biota have been examined in a model inter-comparison study that emphasised the identification of factors causing variability in dose estimation. Radiological dose rates were modelled for ten species representing a diverse range of terrestrial plant and animals with varying behavioural and physical attributes. Dose to these organisms may occur from a range of gamma (Co-60, Cs-137), beta (Sr-90) and alpha (Th-232, U-234 and U-238, Pu-238, Pu-239/240 and Am-241) emitting radionuclides. Whilst the study was based on a specific site - the Little Forest Burial Ground, New South Wales, and Australia - it was intended to be representative of conditions at sites throughout the world where low levels of radionuclides exist in soil due to waste disposal or similar activities.
Environmental studies in Australia: current radioecological priorities.
(International Radiation Protection Association, 2010-05-24) Twining, JR; Johansen, MP
There has been a recent international emphasis placed on assessing radiological dose and its impacts on ecosystems in addition to those directly affecting humans. This is reflected in the development of the IAEA EMRAS Program. As part of Australia’s contribution to EMRAS, we have been looking at ecosystems previously affected by nuclear activities within the country and acquiring data pertinent to Australian animals and plants, many of which are unique. Within Australia, one area of concern has been identified as the yet-to-be developed national nuclear waste repository and we are acquiring data to help in modelling any potential effects. The Little Forest Burial Ground is a near surface nuclear waste site dating from the 1960s. As well as providing data on the behaviour of radioactivity within an Australian ecosystem, it is also a case study site for EMRAS dose assessment modelling. Further, there are a number of uranium mines or deposits and a weapons test site, Maralinga, that give us additional radioecological information as input to those models. A summary of the Australian terrestrial fauna concentration factors will also be presented.
Factors controlling mobility of radionuclides in tropical soils and groundwaters
(Australian Nuclear Science and Technology Organisation, 2012-10-18) Payne, TE; Edis, R; Twining, JR
Due to the possible expansion of nuclear power into equatorial regions, there is an imperative to better understand the mobility of radionuclides in the tropics. The migration of radionuclides in tropical soils and groundwaters is subject to the same basic scientific principles as many other environments. However, the behaviour of radionuclides is also modified by many unique features of tropical systems, including: climate and rainfall characteristics, soil mineralogy and properties, content and cycling of organic matter, specific land-use practices and the presence of unique, potentially impacted environments (for example, coral atolls in the case of weapons tests). Many tropical environments involve combinations of climatic and geochemical conditions not experienced elsewhere, and are also subject to environmental modifications including urbanisation and climate change. These characteristics will influence the impact of potential radionuclide releases in the tropics. An increased focus of scientific research is required to enhance knowledge on this topic.
Field and laboratory applications of radionuclides in environmental research
(Committee on Radiochemistry of the Hungarian Academy of Sciences (HAS), 2008-08-27) Payne, TE; Hughes, CE; Creighton, NM; Twining, JR
Radionuclides have numerous applications in environmental research. They can be utilised in plant uptake and bioaccumulation studies in both field and laboratory experiments, thereby providing valuable information on elemental and radionuclide pathways and dynamics in ecological systems. In the estuarine environment, radiotracer studies enable experimental evaluation of the numerical models underpinning engineering studies, as well as enabling research into the dynamics of coastal ecosystems. The advantages of radionuclides in laboratory experiments include the wide range of elemental concentrations that can be studied, the capability to study several isotopes simultaneously, and the ability to study the mechanisms, reversibility and kinetics of environmental reactions under controlled conditions. The results of the studies are applicable to the behaviour of both radioactive and non-radioactive environmental contaminants. These attributes are demonstrated using specific examples drawn from case studies in Australia and South East Asia.

Browsing by Author "Twining, JR"

Results Per Page

Sort Options