Oyster Bay, Australia
Oyster Bay, Australia

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Airey P.,Australian Nuclear Science and Technology Organisation | Hinton T.,Institute for Radiological Protection and Nuclear Safety | Twining J.,Austral Radioecology
Radioactivity in the Environment | Year: 2012

Tropical radioecology is the study of the behaviour of radionuclides in tropical ecosystems and of their potential human and environmental consequences. The scientific bases include introductions to radioactivity and radiation science, the radiological protection of humans and the environment, and the sources of environmental radionuclides, both naturally occurring and anthropogenic. These sources include primordial radionuclides (U- and Th-series), cosmogenic radionuclides, and the fallout products from atmospheric nuclear testing programs. Information on the detection of radioactivity, measurement precision, and shielding is relevant to practitioners. Efforts are now made to minimise the dispersion of radionuclides through all environments because of their potential detrimental effects. However, it is recognised that careful studies of the dispersion of radionuclides have yielded invaluable information on ecosystem dynamics that would not otherwise be available. Examples relevant to tropical systems are presented. © 2012 Elsevier Ltd.


Jeffree R.A.,University of Technology, Sydney | Markich S.J.,Aquatic Solutions International | Twining J.R.,Austral Radioecology
PLoS ONE | Year: 2014

Bony bream (Nematalosa erebi) and black catfish (Neosilurus ater) were sampled from the fresh surface waters of the Finniss River in tropical northern Australia, along a metal pollution gradient draining the Rum Jungle copper/uranium mine, a contaminant source for over five decades. Paradoxically, populations of both fish species exposed to the highest concentrations of mine-related metals (cobalt, copper, lead, manganese, nickel, uranium and zinc) in surface water and sediment had the lowest tissue (bone, liver and muscle) concentrations of these metals. The degree of reduction in tissue concentrations of exposed populations was also specific to each metal and inversely related to its degree of environmental increase above background. Several explanations for diminished metal bioaccumulation in fishes from the contaminated region were evaluated. Geochemical speciation modeling of metal bioavailability in surface water showed no differences between the contaminated region and the control sites. Also, the macro-nutrient (calcium, magnesium and sodium) water concentrations, that may competitively inhibit metal uptake, were not elevated with trace metal contamination. Reduced exposure to contaminants due to avoidance behavior was unlikely due to the absence of refugial water bodies with the requisite metal concentrations lower than the control sites and very reduced connectivity at time of sampling. The most plausible interpretation of these results is that populations of both fish species have modified kinetics within their metal bioaccumulation physiology, via adaptation or tolerance responses, to reduce their body burdens of metals. This hypothesis is consistent with (i) reduced tissue concentrations of calcium, magnesium and sodium (macro-nutrients), in exposed populations of both species, (ii) experimental findings for other fish species from the Finniss River and other contaminated regions, and (iii) the number of generations exposed to likely selection pressure over 50 years. © 2014 Jeffree et al.


Tagami K.,Japan National Institute of Radiological Sciences | Twining J.R.,Austral Radioecology | Wasserman M.A.V.,Brazilian Nuclear Engineering Institute (IEN)
Radioactivity in the Environment | Year: 2012

In this Chapter we consider radionuclide uptake and translocation in tropical crops and ecosystems. There are many commonalities across all ecosystems because of the consistent, underlying mechanisms controlling the fate and behaviour of radioactivity in any environment. The basic radioecological concepts and models are described to cover these processes.However, the tropics and sub-tropics include much dissimilarity by way of soil types, agricultural methods, climate, plants and animals which give rise to different outcomes from those processes. Billions of people across the tropics and sub-tropics are supported by agricultural systems very different from those traditionally applied in more developed regions of the planet. Higher populations will do so in the foreseeable future. Given the push for nuclear developments in the region, the tropics will need greater attention now. Much of the science is under review but the available data, pertinent to tropical systems, has been summarised or the database identified for the reader.The conditions of tropical soil types and the factors influencing radionuclide biogeochemistry (which affects bioavailability and bioaccessibility) are discussed. Specific sections covering rice, tropical fruits and the limited data for tropical animals are included. © 2012 Elsevier Ltd.


Markich S.J.,Aquatic Solutions International | Twining J.R.,Austral Radioecology
Radioactivity in the Environment | Year: 2012

Radionuclides in (sub-) tropical freshwater systems generally behave in a predictable manner, based on what is known from lakes and streams in the better studied temperate climes. Within the water column, the fate and behaviour of radionuclides and their stable element analogs are typically governed by key physicochemical variables such as pH, redox potential, the concentrations of dissolved ions and the presence and type of organic matter. The chemical form (or speciation) of a radionuclide or stable element is generally of greater biological importance (i.e. bioavailability) than the total concentration. This concept is currently being integrated into mechanistic frameworks (e.g. biotic ligand and bioaccumulation models) by national regulators for protecting freshwater ecosystems. Given that the volume of fresh surface waters (i.e. rivers and lakes) is relatively small (0.01%) in comparison to seas and oceans, then the biota living within them can also substantially influence the chemistry of a radionuclide, by effectively acting as " large particles" available for surface complexation. For example, wetlands serve as effective biofilters to remove radionuclides from the water column. Once radionuclides have been accumulated by organisms, their behaviours generally reflect their similarities to essential (macro and micro nutrients) and non-essential elements. Metabolic mechanisms tending toward homeostasis typically make internal organism chemistry less dynamic than that in the external water column. Again, this is to be expected and radionuclide biokinetics generally follow the patterns observed for freshwater organisms in temperate climates. This constancy has enabled models to be developed to describe the rate and extent of radionuclide bioaccumulation. These models can be adapted to include various uptake pathways (from water, food or sediment) via gills, skin or gut and modes of excretion or dilution (e.g. diffusion, egestion, moulting and growth) and different parameters can be estimated for each radionuclide and organism. Key biotic factors known to influence radionuclide bioaccumulation are size, age and gender. There are also differences within and between species that reflect the natural variability within any system. Despite the similarities that exist between tropical and temperate freshwater systems, it should be noted that there is still a paucity of data for (sub-) tropical freshwater organisms and systems, and hence there is the chance for exceptions to the consistency to exist. Data are presented that show that the uptake of Sr and Cs by tropical freshwater fishes is much lower than would be expected based on the studies of freshwater temperate fishes. These observations point to the need to undertake additional site- and species- specific investigations on the radioecology of key radionuclides, whenever future nuclear developments in tropical systems are initiated. © 2012 Elsevier Ltd.


Prohl G.,International Atomic Energy Agency | Twining J.R.,Austral Radioecology | Crawford J.,Australian Nuclear Science and Technology Organisation
Radioactivity in the Environment | Year: 2012

Radiological consequences for humans, flora and fauna due to discharges of radionuclides into the environment are key issues in impact assessments prepared for nuclear installations. So far, radioecological studies have mainly focussed on temperate zones. Due to the foreseeable development of nuclear facilities in tropical and subtropical countries, the question arises whether radiological dose assessment in those regions needs special consideration. This chapter describes the radioecological processes affecting transport and migration from one environmental compartment to another. Since these mechanisms are generally universal, it could be concluded that no special tropical radioecological processes exist. However, it is also demonstrated that the degree of such environmental transfers is dependent on site-specific climatic and environmental conditions, the land use and habits of the people, as well as on endemic biota. From that, radiological outcomes may vary in tropical compared with temperate systems. To address specific features of the environmental transport of radionuclides in tropical areas appropriately, key processes and features needed for reliable radioecological assessments are identified. © 2012 Elsevier Ltd.


Cresswell T.,CSIRO | Cresswell T.,RMIT University | Cresswell T.,Australian Nuclear Science and Technology Organisation | Simpson S.L.,RMIT University | And 4 more authors.
Aquatic Toxicology | Year: 2014

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.


Johansen M.P.,Australian Nuclear Science and Technology Organisation | Child D.P.,Australian Nuclear Science and Technology Organisation | Davis E.,Australian Nuclear Science and Technology Organisation | Doering C.,AUSn Radiation Protection and Nuclear Safety Agency | And 6 more authors.
Journal of Environmental Radioactivity | Year: 2014

The mobility of plutonium (Pu) in soils, and its uptake into a range of wildlife, were examined using recent and ~25 year old data from the Taranaki area of the former Maralinga weapons test site, Australia. Since its initial deposition in the early 1960s, the dispersed Pu has been incorporated into the soil profile and food chain through natural processes, allowing for the study of Pu sequestration and dynamics in relatively undisturbed semi-arid conditions.The data indicate downward mobility of Pu in soil at rates of ~0.2-0.3cm per year for the most mobile fraction. As a result, while all of the Pu was initially deposited on the ground surface, approximately 93% and 62% remained in the top 0-2cm depth after 25- and 50-years respectively. No large-scale lateral spreading of the Taranaki plume was observed. Pu activity concentrations in 0-1cm soils with biotic crusts were not elevated when compared with nearby bare soils, although a small number of individual data suggest retention of Pu-containing particles may be occurring in some biotic crusts.Soil-to-animal transfer, as measured by concentration ratios (CRwo-soil), was 4.1E-04 (Geometric Mean (GM)) in mammals, which aligns well with those from similar species and conditions (such as the Nevada Test Site, US), but are lower than the GM of the international mammal data reported in the Wildlife Transfer Database (WTD). These lower values are likely due to the presence of a low-soluble, particulate form of the Pu in Maralinga soils. Arthropod concentration ratios (3.1E-03 GM), were similar to those from Rocky Flats, US, while values for reptiles (2.0E-02 GM) were higher than the WTD GM value which was dominated by data from Chernobyl. Comparison of uptake data spanning approximately 30 years indicates no decrease over time for mammals, and a potential increase for reptiles. The results confirm the persistence of bioavailable Pu after more than 50 years since deposition, and also the presence of larger-sized particles which currently affect CRwo-soil calculations, and which may serve as an ongoing source of bioavailable Pu as they are subjected to weathering into the future. © 2013 .


PubMed | Australian Nuclear Science and Technology Organisation, RMIT University, Austral Radioecology and Hydrobiology
Type: | Journal: Aquatic toxicology (Amsterdam, Netherlands) | Year: 2014

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 (109)Cd-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 (109)Cd-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.


PubMed | Australian Nuclear Science and Technology Organisation, Austral Radioecology, University of Salford and Australian Radiation Protection and Nuclear Safety Agency
Type: | Journal: Journal of environmental radioactivity | Year: 2014

The mobility of plutonium (Pu) in soils, and its uptake into a range of wildlife, were examined using recent and 25 year old data from the Taranaki area of the former Maralinga weapons test site, Australia. Since its initial deposition in the early 1960s, the dispersed Pu has been incorporated into the soil profile and food chain through natural processes, allowing for the study of Pu sequestration and dynamics in relatively undisturbed semi-arid conditions. The data indicate downward mobility of Pu in soil at rates of 0.2-0.3cm per year for the most mobile fraction. As a result, while all of the Pu was initially deposited on the ground surface, approximately 93% and 62% remained in the top 0-2cm depth after 25- and 50-years respectively. No large-scale lateral spreading of the Taranaki plume was observed. Pu activity concentrations in 0-1cm soils with biotic crusts were not elevated when compared with nearby bare soils, although a small number of individual data suggest retention of Pu-containing particles may be occurring in some biotic crusts. Soil-to-animal transfer, as measured by concentration ratios (CRwo-soil), was 4.1E-04 (Geometric Mean (GM)) in mammals, which aligns well with those from similar species and conditions (such as the Nevada Test Site, US), but are lower than the GM of the international mammal data reported in the Wildlife Transfer Database (WTD). These lower values are likely due to the presence of a low-soluble, particulate form of the Pu in Maralinga soils. Arthropod concentration ratios (3.1E-03 GM), were similar to those from Rocky Flats, US, while values for reptiles (2.0E-02 GM) were higher than the WTD GM value which was dominated by data from Chernobyl. Comparison of uptake data spanning approximately 30 years indicates no decrease over time for mammals, and a potential increase for reptiles. The results confirm the persistence of bioavailable Pu after more than 50 years since deposition, and also the presence of larger-sized particles which currently affect CRwo-soil calculations, and which may serve as an ongoing source of bioavailable Pu as they are subjected to weathering into the future.


PubMed | Australian Nuclear Science and Technology Organisation, Center for Ecology & Hydrology, Austral Radioecology and Oregon State University
Type: | Journal: Journal of environmental radioactivity | Year: 2015

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.

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