ANSTO :: Browsing by Author "Johansen, MP"

Browsing by Author "Johansen, MP"

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Analysis of hot particle characteristics affecting environmental fate and interaction with living organisms
(SPERA, 2016-09-09) Johansen, MP; Child, DP; Collins, RN; Hotchkis, MAC; Howell, NR; Payne, TE; Ikeda-Ohno, A; Mokhber-Shahin, L
The 2nd International Conference on the Sources, Effects and Risks of Ionizing Radiation (SERIR-2) and the 14th Biennial Conference of the South Pacific Environmental Radioactivity Association (SPERA-2016) and will be held in Bali, Indonesia 5-9 September 2016. The South Pacific Environmental Radioactivity Association (SPERA), in conjunction with the Indonesian National Nuclear Energy Agency (BATAN) and the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA) made the decision to jointly hold these conferences in one week at the same venue to avoid topical overlap and to strengthen regional participation at both events. SERIR2 will be a 1-day conference (5 September) and deals with the efforts to enhance data collection and disseminate scientific findings related to the issues of sources, effects and risks of the ionizing radiation, as well as to seek ways of communicating with stakeholders (scientific communities, regulatory authorities and general public) on those issues. The 14th Biennial Conference of the South Pacific Environmental Radioactivity Association (SPERA), to be held 6-9 September, provides a platform for discussion and debate among scientists on the occurrence, behaviour, impact and measurement of radioactive species present in the environment through natural processes, or resulting from human activities. This international conference facilitates knowledge sharing on environmental radioactivity and related topics of local and global significance. The joint conference will be held 5-9 September 2016, with a welcome reception on 4 September, at the Sanur Paradise Plaza Hotel in Bali. The joint conference will include a one-day workshop on the 6 September on topic(s) to be decided.
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 radioactive ‘Hot Particles’ and marine sediment plutonium and americium levels from the Montebello Islands, Western Australia
(South Pacific Environmental Radioactivity Association, 2018-11-06) Hoffman, M; Johansen, MP; Cook, M; Howell, NR; Kleinschmidt, R; Clegg, JK
The Montebello islands are an archipelago off the Western Australian coast that to this day display an artificial radioactive legacy. The legacy is the result of nuclear testing from 1952-1956. that produced long-lived radionuclides such as americium (Am-241) and plutonium (Pu-239/240). This study investigated the extent and characteristics of radioactive contamination in marine sediments near the former Operation Hurricane and Operation Mosaic G2 detonation sites in hopes of contributing to future management strategies and updated assessment of health risks to native flora, fauna and human populations. The project was conducted with samples collected in 2015 by the Australian Nuclear Science and Technology Organisation (ANSTO) as two series; Series 1 chosen to monitor the activity from the Operation Mosaic G2 detonation and Series 2 aiming to determine residual activity from the Operation Hurricane HMS Plymouth detonation. Samples were initially sieved to separate the bulk samples into four size-based fractions for analysis of activity fractionation among sediment grain sizes. Radiation counting processes included alpha spectrometry and gamma spectrometry, back-scatter electron mode scanning electron microscopy (BEI-SEM) and photo-stimulated luminescent (PSL) autoradiography to evaluate the overall radiative status of the sediment locations and to investigate the presence of ‘hot’ particles or heterogenous dispersion of radioactivity. Both spectrometry processes revealed that Series 1 Am-241 and Pu-239/240 activity was dispersed preferentially in the two larger fractions (>500 um and 500-200 um). Activity determined as Am241 and Pu-289/240 vi/as observed across Series 2 as well but as values an order of magnitude lower. Environmental plutonium from Series 1 was present in hot particle form, specifically within particles from the more active >500 um [largest] fraction which revealed gamma emissions of the plutonium progeny Am241. imaging and subsequent analysis by BE!-SEM and energy dispersive X-ray spectroscopy (EDS) of the particles revealed that the majority of the particle material was calcium carbonate, indicative of the dominant geology at the detonation site. Study results provide insights into the radioactive characteristics of hot-particles and bulk sediments at the Montebello site. it is believed and hoped that this investigation will aid decisions on the future management of the Montebello wildlife resources and marine park management, and provide insights into potential risks and protective measures for site visitors and researchers.
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.
Beryllium in contaminated soils: implication of beryllium bioaccessibility by different exposure pathways
(Elsevier, 2022-01-05) Islam, MR; Sanderson, P; Naidu, R; Payne, TE; Johansen, MP; Bari, ASMF; Rahman, MM
Inhalation exposure and beryllium (Be) toxicity are well-known, but research on bioaccessibility from soils via different exposure pathways is limited. This study examined soils from a legacy radioactive waste disposal site using in vitro ingestion (Solubility Bioaccessibility Research Consortium [SBRC], physiologically based extraction test [PBET], in vitro gastrointestinal [IVG]), inhalation (simulated epithelial lung fluid [SELF]) and dynamic two-stage bioaccessibility (TBAc) methods, as well as 0.43 M HNO3 extraction. The results showed, 70 ± 4.8%, 56 ± 16.8% and 58 ± 5.7% of total Be were extracted (gastric phase [GP] + intestinal phase [IP]) in the SBRC, PBET, and IVG methods, respectively. Similar bioaccessibility of Be (~18%) in PBET-IP and SELF was due to chelating agents in the extractant. Moreover, TBAc–IP showed higher extraction (20.8 ± 2.0%) in comparison with the single-phase (SBRC–IP) result (4.8 ± 0.23%), suggesting increased Be bioaccessibility and toxicity in the gastrointestinal tract when the contamination derives from the inhalation route. The results suggested Be bioaccessibility depends on solution pH; time of extraction; soil reactive fractions (organic–inorganic); particle size, and the presence of chelating agents in the fluid. This study has significance for understanding Be bioaccessibility via different exposure routes and the application of risk-based management of Be-contaminated sites. © 2021 Elsevier B.V.
Beryllium sorption to sandy soil at a legacy waste site
(CRC CARE Pty Ltd,, 2019-09-08) Islam, MR; Sanderson, P; Naidu, R; Johansen, MP; Payne, TE
Beryllium (Be) is utilized in various science and technology applications including aerospace, defence, electronics and nuclear energy (USGS, 2018). Beryllium and its compounds are highly toxic and considered carcinogenic to humans (IARC, 2001). In soil, Be is highly reactive, amphoteric, hydrates readily and reacts with different organic and inorganic elements due to its high charge to size ratio (Alderighi et al., 2000, Boschi and Willenbring, 2016, Rudolph et al., 2009, Edmunds, 2011). The sorption mechanism strongly depends on soil physicochemical properties like pH, cation exchange capacity (CEC), soil texture, soil organic matter (SOM) content, and the presence of sulphur, nitrogen, phosphorous, aluminium etc. (Sutton et al., 2012, Boschi and Willenbring, 2016). Of these, pH is a strong controller of Be sorption, with chemisorption increasing substantially from pH 4 to 6 with precipitation being the predominant mechanism between pH 6-12 (Boschi and Willenbring, 2016). This study examined the sorption of Be in surface soils of a legacy waste site that contains Be and low-level radioactive wastes disposed in shallow trenches to determine how Be may be retained in the surface soil if it is mobilised from the wastes. The sorption of Be with respect to physiochemical properties and the applicability of the Langmuir, Freundlich and Temkin sorption models was examined
Bioaccumulation kinetics and internal distribution of the fission products radiocaesium and radiostrontium in an estuarine crab
(Elsevier, 2021-04-15) Cresswell, T; Prentice, E; Howell, NR; Callaghan, PD; Metian, M; Johansen, MP
Crab has been designated by the ICRP as one of twelve reference/model organisms for understanding the impacts of radionuclide releases on the biosphere. However, radionuclide-crab interaction data are sparse compared with other reference organisms (e.g. deer, earthworm). This study used an estuarine crab (Paragrapsus laevis) to investigate the contribution of water, diet and sediment sources to radionuclide (134Cs and 85Sr) bioaccumulation kinetics using live-animal radiotracing. The distribution of each radionuclide within the crab tissues was determined using dissection, whole-body autoradiography and synchrotron X-ray Fluorescence Microscopy (XFM). When moulting occurred during exposure, it caused significant increases in 85Sr bioaccumulation and efflux of 134Cs under constant aqueous exposure. Dietary assimilation efficiencies were determined as 55 ± 1% for 134Cs and 49 ± 3% for 85Sr. 85Sr concentrated in gonads more than other organs, resulting in proportionally greater radiation dose to the reproductive organs and requires further investigation. 134Cs was found in most soft tissues and was closely associated with S and K. Biodynamic modelling suggested that diet accounted for 90–97% of whole-body 137Cs, while water accounted for 59–81% of 90Sr. Our new data on crab, as a representative invertebrate, improves understanding of the impacts of planned or accidental releases of fission radionuclides on marine ecology. Crown Copyright © 2020 Published by Elsevier B.V.
Biota dose assessment for environmental radiotracer releases in aquatic environments
(Australian Nuclear Science and Technology Organisation, 2012-10-17) Hughes, CE; Johansen, MP; Wilson, RC; Copplestone, D; Vives i Batlle, J
The intentional release of short lived radioisotopes to trace transport and partitioning processes in the environment has been in decline in recent decades due to negative regulatory and public perceptions of the associated risks. Radiotracing is subject to significant regulatory requirements; in some jurisdictions one of these requirements is to demonstrate that radiation exposure to ecosystems is limited to ensure protection of populations of species. Radiation exposures from radiotracer studies are localised, transient and infrequent by nature, making it difficult to apply guidelines and biota dose assessment tools that are designed for chronic and widespread exposure scenarios. We will discuss the limitations of available guidelines and dose assessment methodologies when applied to radiotracer studies. A range of case studies for biota dose assessment will be presented using a variety of available tools including the ERICA Assessment Tool, the methodology of Copplestone et al. (2001) and a dynamic dose assessment model (Vives I Batlle et al., 2008). These case studies demonstrate that steady state, spatial homogeneity and bioavailability assumptions inherent in available dose assessment tools may lead to an over-estimate of dose to biota from radiotracer studies, and that many radiotracer studies can be conducted with minimal dose to biota.
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.
Challenges in the radiochemical separation of marine samples from the Montebello Islands
(South Pacific Environmental Radioactivity Association, 2018-11-06) Thiruvoth, S; Child, DP; Harrison, JJ; Johansen, MP; Silitonga, A; Vardanega, CR; Wilsher, KL; Wong, HKY
The Montebello Islands, located off the North Western coast of Western Australia, was used as a nuclear weapons test site by the British government in the 1950s. Three nuclear tests were conducted around the islands. The first in 1952 (W818) detonated in the hull of the HMS Plym anchored in 12 m of water between Alpha and Trimouille Islands, and the second and third tests (MOSAIC G1 and G2) were detonated on 30 m Aluminium towers in May and June 1956, G1 on the Northern Western tip of Trimouille island and G2, the largest test conducted in Australian territory, on Alpha island. The fallout from these tests deposited long-lived anthropogenic radionuclides on nearby islands and ocean surface, host to an array of animals and plants. Marine sand, marine sediment, algae, fish, turtles and turtle eggs, among others, were sampled from the surrounding zones for dose assessment studies, thirty-nine of which were processed for actinide and strontium analysis. Due to the expected presence of discrete radioactive particles in some matrices a three step digestion method was applied to obtain complete dissolution of sample material. To overcome sample heterogeneity, the digest solution was sub-sampled for actinide and Sr-90 analysis by alpha spectrometry and liquid scintillation analysis, for plutonium isotopic analysis by AMS, and for elemental analysis by ICPAES/MS. The radiochemical separation method developed at ANSTO for Am, Pu, Th, U, and Sr for terrestrial soils and sediments (Harrison et al, 2011) was adapted to samples from the marine environment. However, some sample matrices proved to be challenging in achieving acceptable chemical recoveries of strontium due to the high concentrations of native calcium. This current study will discuss the methods used, and challenges overcome, in radiochemical separation for alpha spectrometry and liquid scintillation analysis for a wide range of sample types.
Characterisation of anthropogenic radioactive particles from former weapon test sites in Australia
(South Pacific Environmental Radioactivity Association, 2018-11-06) Young, EL; Johansen, MP; Child, DP; Hotchkis, MAC; Howell, NR; Pastuovic, Z; Howard, DL; Palmer, T; Davis, J
Former nuclear test sites on Australian territories such as those at Maralinga and the Montebello islands have been remediated to varying extents but wide-spread radioactivity still remains. Fission and neutron-activation products at the test sites have been decaying over time but long-lived radioisotopes such as uranium and plutonium persist within the environment, predominantly in the form of discrete particles. These particles vary widely in composition depending upon the detonation characteristics and local geology, and are widely dispersed around each site. Radioactive particles are the dominant form of radionuclides at the former test sites and the future distribution of radioactive contaminants in the environment at these sites is largely dependent upon their fate and behaviour. The weathering of particles in the environment and the potential release of the radioactivity they contain is influenced by a range of factors including particle morphology, elemental composition and chemical form, and the prevailing environmental conditions. Radioactive particles have been isolated from soils and sediments from Australian test sites and characterised using photostimulated luminescence (PSL)-autoradiography, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), Synchrotron X-ray fluorescence microscopy (XFM) and particle-induced X-ray emission (PIXE). The characteristics of the particles and potential implications for their long term fate will be discussed in the context of the techniques applied and the environments in which the particles were found.
Climate change and groundwater
(Springer, 2011-09-23) Hughes, CE; Cendón, DI; Johansen, MP; Meredith, KT
Desorption and migration behavior of beryllium from contaminated soils: insights for risk-based management
(American Chemical Society, 2021-11-02) Islam, R; Sanderson, P; Payne, TE; Johansen, MP; Naidu, R
Factors influencing the desorption, distribution, and vertical migration behavior of Be in contaminated soils are not fully understood. This study examined the desorption and migration of Be in a soil profile from a legacy radioactive waste disposal site using different batch leaching [monofilled waste extraction procedure (MWEP); synthetic precipitation leaching procedure (SPLP); simulated acid rain solution (SARS); and toxicity characteristic leaching procedure] and sequential leaching [community bureau of reference (BCR)] methods for insights relevant to the application of risk-based management. The results showed that Be desorption was higher in the presence of organic than the inorganic leachate composition (MWEP < SPLP < SARS < TCLP < BCR first-step). The desorption followed three diffusion control mechanisms, which resulted in three desorption rate constant estimates of 157, 87.1, and 40.4 Be/kg.h0.5, and the estimated desorption maximum was 556 μg/kg. The desorption process was, spontaneous (δG > 0), enthalpically and entropically influenced. Increasing the incubation period and heat treatment resulted in a decrease of Be desorption and migration. The soil clay content and pH were the primary factors influencing Be desorption, and the results suggested that Be was desorbed from metal oxyhydroxides and surfaces of silicates (e.g., reactive surfaces of clay minerals), organic matters, and soil pores. Because of high Kd values, the mobility of Be was limited, and no exceedances of ecological or human health risk index or guidelines were determined for the current contamination levels at the site. However, Be released from the waste trenches has the ongoing potential to increase Be concentration in the soil. © 2021 The Authors. Published by American Chemical Society. This publication is licensed under CC-BY-NC-ND 4.0.
Developing international radiological risk assessment tools for Australian arid environments
(South Pacific Environmental Radioactivity Association, 2018-11-06) Popelka-Filcoff, RS; Pring, A; Pandelus, SB; Johns, SM; Tucker, W; Rossouw, D; Lenehan, CE; Hondros, J; Hirth, GA; Carpenter, JG; Johansen, MP; Payne, TE; Roberts, M; Levingstone, K; Tuft, K; Duff, T
Recent international and Australian regulatory guidance llCRP 108 and ARRANSA Env. Prot. Guide, 2015) has increased the need for effective tools to assess radiological impacts in the environment. The existing internationally accepted methods and models are generally based on data collected in the northern hemisphere and there is a recognised lack of southern hemisphere data, particularly from Australia. When applying the models and methods in Australia, acknowledgement of this lack of data is required which tends to undermine public and regulatory confidence in the assessment. Development of an Australian-specific data set is essential to a better understanding and more credible environmental impact assessment process. In addition, decision-making by operators and regulatory authorities will be based on more relevant local information This presentation describes a collaborative project between university, government and industry researchers and a national industry funding body, aimed at developing a more complete understanding of radiological uptake of native flora and fauna in arid Australian environments. The presentation will cover the framework and sampling and analysis approaches from arid environments, and how these fit into international practice. lnitial data and concentration ratios from analysis of Dodonaea viscosa and Acacia ligulata, rabbits and feral cats and corresponding soil will be presented. Analytical methods include high-resolution gamma spectroscopy with low limits of detection, alpha spectroscopy, elemental analysis by inductively coupled plasma mass spectrometry, scanning electron microscopy. ant"; 3."; 5 Novel approaches to data collection and analysis protocols are used, which form the basis of the databases use: :. i"e internationally accepted models and comparison to extant studies. The project lays the infrastructure towards an effective Australian intenface with existing tools (e.g. ERICA) and assessment for extended long-term studies for industry and regulators. The results of this project build a foundation for environmental radionuclide assessment for Australia's specific climate and species, and build a framework for a comprehensive Australian context and understanding of radionuciides and their concentration ratios as well as towards screening levels which may vary depending on location and species. This project has an industry-wide impact in the generation of robust data sets towards modelling in arid environments.
Diet-tissue discrimination of δ13C and δ15N in freshwater crustacean
(University of Western Australia, 2013-07-10) Mazumder, D; Johansen, MP; Davis, E
Knowledge and understanding of discrimination factors (d13C and d15N) for carbon-13(d13C) and nitrogen-15 (d15N) are important when using stable isotopes for trophodynamic studies. We performed a controlled laboratory diet-switch experiment to examine diet–tissue discrimination factors for muscle, carapace and stomach tissues of freshwater crustacean, Cherax destructor. A range of diets of differing d13C and d15N isotopic values were fed to C. destructor until equilibrium. For the various tissue types, d15N discrimination was highest in muscle, followed by carapace then stomach, whilst d13C was highest in carapace followed by stomach, then muscle. The resulting diet–muscle discrimination factors were similar to, but varied from the 1‰ for d13C and 3.4‰ for and d15N values that are often used for diet-muscle discrimination. The results highlight variation among differing diet types, and consumer tissue types as applied to stable carbon and nitrogen isotopes in the food-web studies.
Dietary ingestion of fine sediments and microalgae represent the dominant route of exposure and metal accumulation for Sydney rock oyster (Saccostrea glomerata): a biokinetic model for zinc
(Elsevier, 2015-08-01) Lee, JH; Birch, GF; Cresswell, T; Johansen, MP; Adams, MS; Simpson, SL
Past studies disagree on the extent to which dissolved or dietary uptake contribute to metal bioaccumulation in the filter-feeding Sydney rock oyster (Saccostrea glomerata) in urbanized estuaries. Although most data support the assumption that fine sediments are a major route of metal uptake in these bivalves, some studies based in the Sydney estuary, Australia, have indicated a poor correlation. In the present study, seawater, sediment and microalgae were radiolabelled with 65Zn tracer and exposed to S. glomerata to assess the influence of dissolved and dietary sources to Zn bioaccumulation. Oysters in the dissolved-phase uptake experiment (5, 25 and 50 μg L−1 65Zn for 4 d followed by 21 days of depuration) readily accumulated 65Zn for all three concentrations with an uptake rate constant of 0.160 ± 0.006 L dry weight g−1 d−1. Oysters in the dietary assimilation experiment (1 h pulse-feed of either 65Zn-radiolabelled suspended fine-fraction (<63 μm) sediment or the microalgae Tetraselmis sp.) accumulated 65Zn, with assimilation efficiencies of 59 and 67% for fine sediment and microalgae, respectively. The efflux rates were low for the three experiments (0.1–0.5% d−1). A bioaccumulation kinetic model predicts that uptake of Zn will occur predominantly through the dietary ingestion of contaminated fine sediment particles and microalgae within the water column, with considerably greater metal bioaccumulation predicted if oysters ingested microalgae preferentially to sediments. However, the model predicts that for dissolved Zn concentrations greater than 40 μg L−1, as observed during precipitation events, the uptake of the dissolved phase may contribute ≥50% to accumulation. Overall, the results of the present study suggest that all three sources may be important exposure routes to S. glomerata under different environmental conditions, but contributions from dietary exposure will often dominate. © 2015 Elsevier
Ensuring robust radiological risk assessment for wildlife: insights from the International Atomic Energy Agency EMRAS and MODARIA programmes
(Published on behalf of the Society for Radiological Protection by IOP Publishing Limited, 2022-05-03) Beresford, NA; Beaugelin-Seiller, K; Barnett, CL; Brown, JE; Caffrey, EA; Johansen, MP; Melintescu, A; Ruedig, E; Vandenhove, H; Vives i Batlle, J; Wood, MD; Yankovich, TL; Copplestone, D
In response to changing international recommendations and national requirements, a number of assessment approaches, and associated tools and models, have been developed over the last circa 20 years to assess radiological risk to wildlife. In this paper, we summarise international intercomparison exercises and scenario applications of available radiological assessment models for wildlife to aid future model users and those such as regulators who interpret assessments. Through our studies, we have assessed the fitness for purpose of various models and tools, identified the major sources of uncertainty and made recommendations on how the models and tools can best be applied to suit the purposes of an assessment. We conclude that the commonly used tiered or graded assessment tools are generally fit for purpose for conducting screening-level assessments of radiological impacts to wildlife. Radiological protection of the environment (or wildlife) is still a relatively new development within the overall system of radiation protection and environmental assessment approaches are continuing to develop. Given that some new/developing approaches differ considerably from the more established models/tools and there is an increasing international interest in developing approaches that support the effective regulation of multiple stressors (including radiation), we recommend the continuation of coordinated international programmes for model development, intercomparison and scenario testing. © 2022 Society for Radiological Protection.
Environmental chemistry response of beryllium to diverse soil-solution conditions at a waste disposal site
(Royal Society of Chemistry, 2022-11-29) Islam, MR; Sanderson, P; Johansen, MP; Payne, TE; Naidu, R
This study evaluated how the variation in different sorption conditions of beryllium (Be) in soil–water systems (electrolytes; ionic strengths; competing, counter, and co-existing ions; concentrations of Be and soil; and temperature) affected Be's environmental behaviour. For this reason, potentially contaminated soil was collected from a legacy waste site near Sydney, Australia. The sorption–desorption plateau for Be was found at >12.5 g L−1 (soil/solution), considering higher sorption and limited desorption. Variable surface charges developed by different added ions (competing ions, counter ions, and co-existence of all ions) were not always correlated with Be sorption. However, effects of added ions in Be sorption (increased by counter ions and decreased by competing ions) primarily occurred at low pH, with no noticeable changes at pH > 6 due to the hydration and precipitation behaviour of Be at higher pH. Both laboratory data and modelling indicated the substantial effect of counter ions on increased sorption of Be. Relatively higher amounts of sorption under the co-existence of all added ions were suggested from synergistic actions. Sorption was favourable (KL > 0, and 0 < RL < 1) across all concentrations and temperatures at pH 5.5, and high retention (84–97%) occurred after four desorption cycles indicated specific sorption. The sorption process was exothermic (ΔH > −43 kJ mole−1), while desorption was endothermic (ΔH > +78.4 kJ mole−1). All sorption–desorption reactions were spontaneous (ΔG = −Ve), and executed without any structural deformation (ΔS = nearly zero) of soil particles. However, the effect of temperature on desorption was influenced by the concentrations of Be. Higher retention and different sorption–desorption parameters (Kd-desorption > Kd-sorption; Kf-desorption > Kf-sorption; ndesorption/nsorption < 1) indicate limited mobility of Be and the presence of desorption hysteresis in the studied soil under the experimental conditions. © Royal Society of Chemistry

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