Lichen Radionuclide Baseline Research. By Loda Griffeth

Transcription

1 Lichen Radionuclide Baseline Research By Loda Griffeth

2 Overview Definitions Importance Background: Radiation in Alaska Past Research Current Research

3 Definitions Units Becquerel (Bq) = 1 Disintegrations/min (dpm) Curie (Ci) = 2.2 X dpm = 3.7 X Bq Gray (Gy) = 1 Joules/kg of material Sievert (Sv) = 1 Gy*Quality Factor (Q) Megaton (MT) = 4.6 X Joules

4 Importance Arctic is a sink for radioactive contamination Effect on subsistence lifestyles Major source nuclear weapons testing (1960 s) Other sources nuclear power plants and Chernobyl fallout.

5 Radiation in Alaska Bilibino Nuclear Power Plant Fort Greely Nuclear Power Plant Amchitka Underground Nuclear Tests

6 Bilibino Nuclear Power Plant Source: Chukotka, Russia Above Arctic Circle 4 - Light water graphite- 12MW (LWGR-12) Built 1974 (30 yrs) No containment structure Shutdown

7 Bilibino Nuclear Power Plant Fairbanks: 2012-km and Nome: 1304-km

8 Ft. Greely Nuclear Power Plant Near Delta Junction Operated MW Stationary Medium Power (SM-1A) 1997 leakage detected Clean-up and decommissioning is ongoing

9 Amchitka Island Summary of the three nuclear test conducted on the island. Project Year Est. Yield Depth (m) Purpose Longshot kt 716 Seismic Testing Milrow Mt 1220 Seismic Calibration Cannikin Mt 1790 Device Testing Hydrological study Sampling Long term monitoring

10 1920 5R/mo Dose-Limits

11 Previous Research Research conducted in 1987, a year after the Chernobyl accident: Sampling Locations Barrow (71N, 156W) Colville River (70N, 151W) Anaktuvuk Pass (68N, 151W) Nome (64N, 165W) Fairbanks (64N, 147W)

12 Previous Research Sampling Materials Vegetation Moss Lichen Mushrooms Lake Sediment Soil Subsistence Foods White Fish Caribou Bowhead Whale

13 Previous Research Results from a radiocesium study conducted in 1987 Cs-137 levels were low in all samples Deposition of Cs-137 varied by a factor of 28+ Cs-137 was greater in samples collected in Fairbanks Cs-137 levels were generally lower in soils than lichen

14 Previous Research Transport via Western Canada:

15 Previous Research Results from a radiocesium study conducted in 1987 Cs-137 levels were low in all samples Deposition of Cs-137 varied by a factor of 28+ Cs-137 was greater in samples collected in Fairbanks Cs-137 levels were generally lower in soils than lichen

16 Current Research Objectives Sampling Methodology Gamma Counter Data Results Future Research

17 Objectives Establish composition and spatial distribution radionuclides in Alaska Assess known and potential lichen indicator species Derive correlation between baseline lichen data and radiological data Derive correlation between current baseline lichen data and potential bioconcentration effects in caribou

18 Methodology - Lichen Separate lichen from other natural materials, store in sealed, tared plastic bags. Sample area 1/4-meter (smaller, if lichen abundance is low). Drying time 24-hours at 100 C. Ash for 24-hours at 450 C and store in tared plastic bags. Upper Right: Lichen abundance at Moose Pass. Lower Right: Sampling area at Moose Pass containing Cadina stellaris.

19 Methodology - Soil Metal corer 5x10-cm Split 8-10-cm plugs into 1-5-cm and 6-10-cm plugs Obtained replicate samples from lichen plots & 1-2 additional samples per site. Dried and ashed samples Sifted samples discarded particles >2-mm size Upper Right: Soil sampling using a metal corer at Moose Pass along the Seward Highway. Lower Right: Soil sample collected at Moose Pass along the Seward Highway.

20 Sampling Sites * Indicates one of several types of lichen collected from site.

21 Data Lichen Samples (30) Soil Samples (46) 35% Analyzed Replicate measurements to ensure precision Multiple vials to ensure homogeneity

22 Gamma Counter Canberra Germanium Detector:

23 Gamma Counter Genie 2000 Spectroscopy and Analysis Software:

24 Results Cosmogenic Nuclide Be-7 Fission Product Cs-137 U-235?? Primordial Nuclides K-40 Decay Series Decay Series Bi-214 Pb-214 Pa-234M Ra-226

25 Results Activity in Lichen Samples Avg. Cs-137 Cs-137 Avg. U-235 U Log(Cs-137 µci/ml) Log(U-235 µci/ml) Bethel Eagle Summit SH - Moose Pass SH - Turnagain Pass Wickersham Dome Location

26 Results Log(Cs-137 µci/ml) Activity in Soil Samples Avg. Cs-137 Cs-137 Avg. U-235 U-235 Barrow Bethel Denali Highway Moose Pass Turnagain Pass Location Log(U-235 µci/ml)

27 Results 0.6 PC2 X-loading Weights and Y-loadings Longitude Bethel Location lich(4) soil(6) SH Wickersham Dome Cs-137/vol Eagle Summit Latitude -0.4 DH -0.6 PC Cs-137 vol, X-expl: 36%,26% Y-expl: 59%,3%

28 Results 1.0 PC2 X-loading Weights and Y-loadings 0.5 lich(4) soil(6) Eagle Summit 0 SH DH Location U-235 / vol Bethel Longitude Barrow Latitude -0.5 Wickersham Dome -1.0 PC U-235 vol,x-expl: 21%,18% Y-expl: 63%,5%

29 Results Correlation Graph Log(Cs-137µCi/mL) Latitude

30 Results Correlation Graph Log(Cs-137µCi/mL) Sample Type

31 Results Cs-137 Good Model Activity increases with Latitude Higher activity in lichen than activity in soil samples Low activity in Seward Hwy (SH) and Denali highway (DH) samples U-235 Good to Marginal Model Activity increases with latitude and longitude Bethel samples have high activity Low activity in Seward Hwy and Denali Hwy samples Higher activity in lichen than activity in soil samples

32 Current Deposition: Results

33 Results Cs-137 Good Model Activity increases with Latitude Higher activity in lichen than activity in soil samples Low activity in Seward Hwy (SH) and Denali highway (DH) samples U-235 Good to Marginal Model Activity increases with latitude and longitude Bethel samples have high activity Low activity in Seward Hwy and Denali Hwy samples Higher activity in lichen than activity in soil samples

34 Future Research Establish composition and spatial distribution radionuclides in Alaska Assess known and potential lichen indicator species Derive correlation between baseline lichen data and radiological data Derive correlation between current baseline lichen data and potential bioconcentration effects in caribou

35 Acknowledgements John Kelley (IMS) Larry Duffy Adrienne Orr Stan Read and Doug Dasher (ADEC) Richard Stolzberg Chemistry Department Pacific Northwest National Laboratories Laodong Guo and Celine Gueguen (IARC)