Radiation Protection of the Environment (Environment Agency Course, July 2015)

 be aware of ‘Reference Organisms’  understand how activity concentrations in organisms are predicted (if not known)  appreciate how transfer parameters are selected when data are lacking By the end of this presentation and practical you should….

‘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’

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

Lichen & bryophytes Grasses & herbs Shrub Tree Mollusc - gastropod Flying insect Arthropod – detritivorous Annelid Mammal - large Bird Mammal – small-burrowing Reptile Amphibian Transfer (& effects) data collated at these broad levels ‘Representative’ geometry selected for dosimetry

Mammal –large Mammal – small-burrowing Flying insect Annelid Bird Amphibian Pelagic fish Benthic fish Crustacean Tree Grasses & herbs Macroalgae

Most approaches use concentration ratios (CR)

x CR = Bq/kg

Time   Activity            Statistical exponential process Half-life = Time taken for activity to reduce by 50% CR is by element NOT isotope ‘half-life’ ignored

Water Sediment

Freshwater RadionuclideFishVascular plantMolluscReptileAlgaePhytoplanktonCrustaceanInsect larvaeInsectZooplanktonMammalAmphibian Cs Sr Am Cm Pu Ra Ce Co Mn U Pb Cd Po Sb Se I Ni Th Zr Eu Ru Cl P Np S Tc Te Ag Nb n≤10 n>10<20 n>20<100 n≥100

 To derive concentration limits (EMCLs) 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 & kd values for all organism-radionuclide combinations considered in tool (Tier 1)  Probability distribution function

 The ERICA tool considers 39 elements for 13 terrestrial, 13 freshwater and 13 marine reference organisms  1521 CR values required  Sufficient data available for 622 of these  The rest??

 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

 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)