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Centre for Ecology & Hydrology – Lancaster 27 th – 29 th June 2012.

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Presentation on theme: "Centre for Ecology & Hydrology – Lancaster 27 th – 29 th June 2012."— Presentation transcript:

1 Centre for Ecology & Hydrology – Lancaster 27 th – 29 th June 2012

2  Estimation of the radiation doses (wholebody absorbed dose rates) that living organisms receive in the environment  External and internal  Quantification of the likely effect of the dose received

3  Overview of environmental transfer processes  Introduction to available assessment tools  How to cope with vast range of species?  How transfer is simplified in assessment tools  Potential deficiencies of approach used

4 Discharge Direct uptake from water column Ingestion of food, water sediment Source characteristics

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6  Soil properties determine biological uptake (and redistribution - leaching etc.) Cs-137 in semi- natural grasslands 1 yr after deposition assuming 1Bq m -2 High transfer = Low K + Low clay mineral/high organic matter circa x10

7  Water chemistry can influence transfer or radionuclides through foodchains pH M n+ DOC NaCl... and water sediment interaction:

8 Bq/kg in sediment assuming 1 Bq/L in water

9 Gut absorption coefficients

10  Many reasons why equilibrium between various components of ecosystem may not be reached, e.g.:  Fluctuating releases (e.g. marine environment)

11 Ln activity concentration

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14  Many reasons why equilibrium between various components of ecosystem may not be reached, e.g.:  Fluctuating releases  Chronic aerial releases DRY DEPOSITION What dominates: root uptake or surface deposition?

15  Many reasons why equilibrium between various components of ecosystem may not be reached, e.g.:  Fluctuating releases  Chronic aerial releases  Biological half-life v’s lifespan

16  Sr in 200 g animal ≈ 1.2 years  Pu in 10 kg animal ≈ 4 years  Cs in 10 kg animal ≈ 30 days  Am in 450 kg animal ≈ 80 years

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18  Software implementing the ERICA Integrated Approach – European Commission funded  Freshwater, terrestrial and marine ecosystems  38 (reference) organisms considered  Default parameters for 63 radionuclides of 31 elements  Can add radionuclides and organisms  Probabilistic ability  Linked to on-line radiation effects [FREDERICA] database

19  Code which implements the USDOE’s Graded approach (replaces BCG-calculator)  Part of the RESRAD suite of models  Freshwater and terrestrial ecosystems  Database contains 46 radionuclides  Four organisms – terrestrial animal, terrestrial plant, riparian animal and aquatic animal  Can create organisms & simple foodchains

20  Freely available (documented) spreadsheet model for coastal, freshwater & terrestrial ecosystems  Limited radionuclide list and transfer parameter database ( ) Only approach considering noble gases – significant component of aerial releases from nuclear power plants

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22 ‘A series of imaginary entities that provides a basis for the estimation of the radiation dose rate to a range of organisms that are typical, or representative, of a contaminated environment. These estimates, in turn, would provide a basis for assessing the likelihood and degree of radiation effects. It is important to recognise that they are not a direct representation of any identifiable animal or plant species’

23 Selection criteria, reference organisms should encompass: Organisms likely to have comparatively high exposures Radiosensitive organisms Protected (European) species Range of trophic levels (ICRPs proposed Reference Animals and Plants)

24 Lichen & bryophytesReptile Grasses & herbsMammal ShrubBird TreeBird egg Detritivorous invertebrate Flying insect Soil invertebrate (worm) Amphibian Transfer (& effects) data collated at these broad levels ‘Representative’ geometry selected for dosimetry

25 For human protection, the reference individuals and Reference Person are idealised models developed for the specific purposes of relating exposure to dose, and dose to effect.  They do not represent any specific type of human being (the reference individuals are phantoms, and the Reference Person is a hermaphrodite), but nevertheless have to be discretely defined to serve their basic purpose. To be consistent with the original concept of Reference Man, a Reference Animal or Plant can be described as follows:  “A Reference Animal or Plant is a hypothetical entity, with the assumed basic biological characteristics of a particular type of animal or plant, as described to the generality of the taxonomic level of family, with defined anatomical, physiological, and life-history properties, that can be used for the purposes of relating exposure to dose, and dose to effects, for that type of living organism.”

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29 Most approaches use concentration ratios (CR) (referred to as Bivs in RESRAD- BIOTA & CFs in R&D128): H-3, C-14, S-35, P- isotopes

30 distribution coefficients (K d ): Water Sediment

31  To derive concentration limits (EMCLs, BCGs) for Tier 1  Provide user with ‘best estimate’ CR & k d values for Tier 2/3 if no/insufficient:  measured activity concentrations in biota (water/ sediment)  site specific CR or k d values  Therefore need:  Complete set of CR & k d values for all organism- radionuclide combinations considered in tool (Tier 1)  Probability distribution function (maximum CR RESRAD-BIOTA) (Tier 1 & 3)

32  The ERICA tool considers 31 elements for 13 terrestrial, 12 freshwater and 12 marine reference organisms  1147 CR values required  Data available for 453

33  Set out a ‘guidance approach’ e.g.:  Use data for similar organism [e.g. apply mammal CR to birds]  Use data for analogous element [e.g. Am CR for Pu]  Modelling approaches  Assume highest available CR for any given radionuclide

34  ERICA guidance approach based on that originally developed for application with R&D128

35  Also uses CRs (or Bivs), but:

36 Soil contamination Fugitive dust Vegetation Soil invertebrate Herbivorous mammals Herbivorous birds Carnivorous mammals Water contamination Root uptake  Can use kinetic-allometric approach with simple foodchains for terrestrial/riparian vertebrates Y = aM b

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38  Input water and sediment concentrations  Biota concentration estimated as water conc. x CR  Sediment used in external dose calculation .... But if do not have water concentrations – what then?  Water concentrations estimated as biota conc./CR and/or sediment conc./Kd  Missing biota and/or sediment concs then estimated using predicted water concs and CRs & Kd respectively

39  Freshwater ecosystem  Select Pu-240 & all organisms  No water data but have sediment (n=15), fish (n=150) & amphibian (n=3) activity concentrations  Sediment 8000 Bq/kg DM (70% DM content)  Fish 1E-1 Bq/kg FW  Amphibian 1E-3 Bq/kg (FW)

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41  Model comparison programme (EMRAS) demonstrated need for guidance on transfer to wildlife  Initiated activities to develop a ‘Technical report series’ handbook on wildlife transfer parameters  At same time ICRP initiated a task group to provide report with transfer parameters for RAPs  Data collation facilitated through common database  Pragmatically both opted for CR approach

42 Elements - for all radionuclides in ICRP-38 Expanded list of organisms (wildlife groups)

43 ERICA New & review data EA R&D128 EPIC FASSET IAEA 422 Wildlife TRS ICRP-114 Canadian U-mine industry COG monitoring data Russian language literature SKB reports Japanese estuaries Australian data Reptile review Data from new studies Post ERICA literature review and more

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45 MarineCaHgMgNaZn FreshwaterAlAsBBaCaCrCuDyErFe GdHoHgLaMgMoNaNdPmPr RbSaScSnTiTmVYYbZn TerrestrialAcAsBBaBeBrCrCuFeHf HgLaLuMoNaNdRbScSmSn TaTbTiVWYbZn EstuarineAlAsBaBrCaCrCuDyErFe GdHoLaLiLuMgMoNaNdPr RbSiSlSmTbTiTmVYZn

46 Terrestrial wildlife groups

47  Report published November 2011 (although confusingly dated 2009!)  ICRP-114 Environmental Protection: Transfer Parameters for Reference Animals and Plants

48  Considers 12 RAPs (adult life stages) and 39 elements  RAPs defined at taxonomic level of Family

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50 RAPFamily BeeApidea Brown SeaweedFucaceae CrabCancridae DeerCervidae DuckAnatidae EarthwormLumbricidae FlatfishPleuronectidae FrogRanidae Pine TreePinaceae RatMuridae TroutSalmonidae Wild GrassPoaceae

51  Considers 12 RAPs (adult life stages) and 39 elements  RAPs defined at taxonomic level of Family  Few(er) data available for many RAPs for species falling into these Families than broader wildlife groups (e.g. data only available for 4 elements specifically for Cervidae (deer); no data for Apidea (bee))  Advice how to use the ICRP information presented in ICRP 114 and 108 within assessments is in-preparation

52  Submitted early 2011 (publication ‘pending’)  Values presented for generic Freshwater, Marine, Terrestrial and Brackish water ecosystems  Summarises CR data for >800 wildlife- element combinations  Values from the initial submitted text available from:

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54  IAEA summarises data only  Suggests how users may extrapolate available knowledge to derive values if required  Simplified version of the ERICA approach  ICRP uses approaches based on those presented in ERICA to derive values when data are not available for the 39 elements & 12 RAPs consider (most values are derived)

55  Is being added to:  If you have appropriate data - please enter  If those you regulate have appropriate data – please encourage them to enter

56  Hopefully have appreciation of how wholebody radionuclide concentrations are estimated in available tools  There are some short comings in approaches - not least data availability - but to cover wide range of organism-radionuclide combinations currently ‘best we can do’  Can be considerable variability between models  Lack of equilibrium  Probably – but if sufficient data should reflect ‘reality’(?) (e.g. Pu will never reach equilibrium)

57  Some radionuclides are heterogeneously distributed throughout the body  Sr (bone), Am (bone & liver), I (thyroid), Ru (kidney)  Uncertainty this adds to dose & interpretation should be assessed (... available effects data are for wholebody dose rates?)  If required some dynamic models are available & scope to adapt human assessment models  If predictions are required spatially - relatively easy to use parameters from models such as ERICA in a GIS


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