Radioecological sensitivity Brenda Howard Outline Background - PDF document

Radioecological sensitivity Brenda Howard

Outline • Background • Exposure pathways • Quantification of radioecological sensitivity – Four quantities • Examples • Application

Background • Prior use of critical group approach – critical pathways • Post-Chernobyl focus on certain key exposure routes and their spatial attribution • application of GIS allows spatial analysis

Why? Considerable variability in radiation doses Generalizations can mask high individual exposure Factors leading to high exposure need identification, quantification and locating Enabling improved preparedness and response

Criteria • pathways – high transfer capacity – need to identify “sensitive” parts of pathways – habits effects (occupancy, self- sufficiency, diet) • regions – proximity to nuclear sites – presence of “sensitive” features • social – Economic and social costs

Vulnerable (or sensitive) ecosystems • vulnerability to radioactive contamination can be considered in terms of the extent of radiation dose to man or biota • regions, pathways or communities can all be considered to be vulnerable to radioactive contamination if they give rise to, or receive relatively high radiation doses

Comparison of indigenous peoples in the Arctic Berries Mushrooms Fish Reindeer and wild Meat Meat (other) Fruit and vegetables Potatoes Cereals and Flour Milk and Cheese AMAP -Norway AMAP - Russia

Comparison of 137 Cs Dose in Lovozero 0% 0% 8% 1% 3% 18% 5% 0% 9% Reindeer herders Locals 8% 64% 84% Milk Reindeer meat Mushrooms Berries Potatoes Freshwater fish

Sources of 137 Cs for rural people in Chernobyl affected areas 1400.0 Total dietary radiocaesium (Bq d-1) R 2 = 0.994 1200.0 1000.0 800.0 600.0 400.0 200.0 0.0 0 500 1000 1500 Dietary radiocaesium from fungi and milk combined (Bq d-1)

Vulnerability - quantification l FLUX l SPECIFIC • specific activity • total Bq output in (Bq/kg) in a product a product (Bq) – predicted using – needs estimates of deposition, production or transfer rates of harvesting coefficients and effective ecological half-lives

Vulnerability -Spatial analysis • compiling variation in food production and harvesting rates • mapping the distribution of food products, especially wild foods • quantification of transfer, relevant to soil type and species • incorporating changes with time in contamination of important foodstuffs

Vulnerable areas or groups • proximity to potential sources • high precipitation rate • high milk production rate dominance of “small” animals • presence of semi-natural ecosystems – organic soils, forests • special groups, with high consumption rates of contaminated products – mushroom foragers, game consumers

Vulnerability Generalizations can mask high individual exposure Consideration of vulnerability at a small spatial scale can improve estimates of: l collective dose l individual dose l provide guidance on uncertainities

Vulnerability - emergency response • prior studies of vulnerability and its spatial and temporal variation can identify areas, and types of foods which would be contaminated above intervention limits • Identification of vulnerable areas, combined with contamination maps can guide monitoring and implementation of countermeasures

Radioecological sensitivity • Radionuclide specific • Spatially variable • Time dependent

Time dependency • speciation effects Fish, UK Bq/kg • ecological half-lives Fish, Norway Bq/kg Vegetation Bq/kg 10000 137 Cs activity concentration Water mBq/l 1000 • acute vs mid-long term 100 – surface effects – seasonality 10 1 1986 1990 1994 1998 Date

Quantification Contamination Environmental transfer Biota exposure Aggregated transfer coefficient Production / (m 2 kg -1 ) Intervention harvesting limit (Bq kg -1 ) Diet and social habits Food Flux distribution Dose (Bq y -1 ) Action loads coefficients (Bq m -2 ) Individual exposure of humans (mSv Bq -1 m 2 )

Radionuclide transfer • Environmentally mobile radionuclides – Cs, Sr, I • Radionuclide with high accumulation factors – Tc and lobsters – Ru/Tc and seaweed

Radiocaesium contamination of Arctic foodstuffs Molluscs Shrimp Potatoes Seal Marine fish Whale Hare * Cow milk Normal cheese Berries Vegetables Ptarmigan Moose Other meat Brown Cheese Lamb Mushrooms Fresh water fish Reindeer / Caribou 0.1 1 10 100 1000

Site studies – Faroe Islands Cs-137 transfer to lamb meat, 1990-2000 25 Tag value 137 cs 10 -3 m 2 /kg ww 20 15 10 5 0 Bøur Velbastað Hvalvík Skáli Norðoyri Sandur Hvalba Sumba

Reindeer- Finland W inter Summer Kemin Sompio 1200 Paistunturi 1000 Ivalo 137 Cs Bq7kg (w.w) 137 Cs Bq/kg fw 800 600 400 200 0 86 87 88 89 90 91 92 93 94 95 96 97 98 99 00

Fluxes • Activity concentrations and production rates • Fluxes – The total amount of radioactivity transferred to Man or leading to exposure of biota ∗ ∗ ⇒ -2 2 -1 -1 -1 Flux : Bq m m kg kg y Bq y • Dependent on – transfer rates – production • Intensive, extensive • quantities

Critical load concept The highest pollution load for which there are no negative effects on the environment Considers deposition, transport and retention Comparison with standard values characterising impact (or upper acceptable limits) - uses “significant harmful effects” concept - emphasis on 100 ecosystem functioning Effect % Critical /population interactions load/level 0 Deposition (load) or concentration (level)

Intervention limits in the EC Maximum Permissible activity levels in foodstuffs (Bq kg -1 ) Radionuclides Baby Food Dairy Other Products Liquid food Products 400 1000 1250 1000 Caesium 150 500 2000 500 Iodine 75 125 750 125 Strontium Plutonium 1 20 80 20

Action or Critical loads • The amount of radionuclide deposition necessary to produce radionuclide concentrations in food products exceeding intervention limits for areas used in the production or harvesting of foodstuffs • Action load– short term (surface) • Critical load – mid-long term

Critical Load - radioecological perspective The deposition level of a specific radionuclide which results in an activity concentration in a foodstuff equal to the intervention level dependent on: • soil type • pathway considered • agricultural practice

Action loads – Agroland predictions I-131 14 days Cs-137 14 days Cs-137 180 days 1.00E +06 1.00E +05 1.00E +04 1.00E +03 0.1 0.2 0.4 0.6 0.8 1 Biomass (kg m -2 )

Variation in radiocaesium Tag with soil category Clay Sand 15 15 Frequency Frequency 10 10 5 5 0 0 -10 -5 0 -10 -5 0 log Tag (m²/kg) log Tag (m²/kg) Loam Organic 15 15 Frequency Frequency 10 10 5 5 0 0 -10 -5 0 -10 -5 0 log Tag (m²/kg) log Tag (m²/kg)

Critical load for mid-term 137 Cs transfer to milk

Additional critical loads for 137 Cs in arctic systems -2 ) 160 Cs-137 Critical additional load (kBq m 120 80 40 0 0 25 50 75 100 137 Cs deposition (kBq m -2 ) Global fallout

Additional critical loads -2 ) 160 Cs-137 Critical additional load (kBq m Moose 120 80 Cow milk 40 Reindeer 0 0 25 50 75 100 137 Cs deposition (kBq m -2 ) Global fallout

Action or Critical loads • Potential method of addressing issues of vulnerability to radionuclide contamination • Can be defined as the amount of radionuclide deposition necessary to produce radionuclide concentrations in food products exceeding intervention limits for areas used in the production or harvesting of foodstuffs

Application • Policy and planning – Prior identification of “sensitive” pathways, areas, communities and individuals – Environmental impact assessment for location of nuclear facilities • Targeted routine sampling • Improved, better focused emergency response • Identify data requirements

WG 8 ? • Critical and/or action loads? • Doses to biota (co-op with Theme 2)