Plutonium in Lichen Communities of the Thule, Greenland Region During the Summer of 1968 (Health Physics, Vol. 22)

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uk Physics Pergamon Press 1972. Vol. 22 (Jan.', pp. 39-42. Printed in Northern Ireland PLUTONIUM IN LICHEN COMMUNITIES OF THE THULE, GREENLAND REGION DURING THE SUMMER OF 1968* Ecosystems Department, Battelle Memorial Institute, Pacific Northwest Laboratory, {Received 22 December 1970; in reused form 22 March 1971) Abstract—Modest amounts of 239Pu, 240Pu attributable to the January 1968 aircraft accident near Thule, Greenland were found in lichens collected near that site during July-August 1968. It was mostly associated with particles of estimated 0.5-1.0 /r diameter that contained slightly greater than background levels of plutonium radioactivity. O 21 January 1968 a United States Air Force bomber carrying nuclear weapons crashed the sea ice of Bylot sound near Thule, Greenland. The incident in no way involved rwlear fission; however, conventional explo sives contained in the weapons and aircraft tutl produced a substantial explosion and fire that scattered about 3150 g of plutonium over a operation (Project Crested Ice) was promptly and effectively conducted by Danish and U.S. personnel, and most of the contamination was removed. Environmental consequences of the small amount of radioactivity released to the er.\ irons was investigated by a Danish-American expedition during the summer of 1968.(21 Emphasis was placed upon marine aspects because (i) most of the contamination was associated with the sea ice of By lot Sound, and u marine ecosystems are of the greatest importance to the Eskimo populations of that region. Terrestrial food webs in the Thule region are restricted because of the limited land area available and rigorous environment.,3) A cloud of smoke and debris, which contained an estimated 1-5 Ci of plutonium, drifted "est-southwesterly from the crash site and deposited in uncertain amounts on the sea ice and landscape.(1) Terrestrial aspects of this investigation included collection and analyses * I\ork performed under United States Atomic + Present address: Department of Radiology and Radiation Biology, Colorado State University, Ft. of lichen samples for various radionuclides, the ability of the lichens to retain appreciable amounts of airborne materials. Samples of foliose and fruticose lichens were collected from 27 sampling sites in the Thule region (Fig. 1) during the period 26 July-26 August 1968. Samples were air dried at Thule and returned to the home laboratory, where they were moisturized and meticulously handseparated into the various lichen species, vascular plants, plant debris and soil that normally comprise a lichen community. This was necessary to make interspecific comparisons at various sampling locations and to remove extraneous material that would modify true weights and radionuclide determinations. These components were dried to constant weight at 70rC for 48 hr to determine percentage of the total community, were then separately ground in a Wiley mill, and aliquots processed according to standard procedures(4) to obtain standard dry and ash weights. Selected samples repre sentative of the Thule lichen communities were radiochemical procedures ;(5) the number of samples was necessarily restricted by the time and expense involved. The term community included all lichen species (populations) within a sample, which was then designated by the dominant lichen species at that location. The dominant species contributed an average of 90 % of the lichen biomass in the 80 samples obtained and the remainder consisted of varying amounts of several species. Cetraria nivalis was the most common fruticose BEST AVAILABLE COPY

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40 PLUTONIUM IN LICHEN COMMUNIURS OF THE THREE ISLAND YLOT SOUND GREENLAND ICE CAP Fig. 1. Map of Thule, Greenland environs showing lichen sampling locations. lichen community of the Thule region and serv ed as a standard for comparison with other major lichen communities that were represented in the region, including Stereocaulon paschale, Alectoria ochroleuca, Cetraria cuculata, Cetraria delisei, Cornicularia divergent, Cornicularia nigricans, Neuropogon sulphureus, Thamnolia vermicularis, Umbrtlicaria The fruticose lichen communities of the Thule region were discontinuously distributed over the landscape. Most lichens were found in rills, stone stripes and nets or other irregular surface features that provided moisture, sites for organic matter accumulation and shelter from the substantial winds. Moisture appeared to be one of the more apparent limiting factors for both plant growth and fallout deposition. Annual precipitation at Thule during the to 32 cm at Fairbanks, Alaska.161 When weighted for the differing precipitation regimes at Thule and Fairbanks, fallout deposition at the two sites was nearly equal during the maximum fallout period 1962-1965 and was more efficient (greater deposition per a precipitation) at Thule during low Plutonium analyses of Thule lichens and ciated plant debris showed a general backgr vatf dry weight, with a mean of about 0 + Cr -'■«* samples (Table 1). Similar amounts found in 2 lichen samples collected n -*-*• them Alaska 1 month prior to the 1 survey. Four lichen samples contained 1 - and two lichens and one plant debns were significantly above background U1 6. red in samples collected at locations 7, * and 19, which were adjacent to the irnpac- ** or on the downwind trajectory of the The mean acdvity ratio ^Pu^’P'-V**^* in the ten lichen samples and three plant de-x* samples considered to contain no acc:<x* than the ratios of about 0.02,7'j) and

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Table 1. Plutonium concentrations and activity ratios in lichen components from Thule, Greenland and Alaskan locations Greenland lichen communities Location C. nu alts lichens 12 0.59 - 0.04 0.024 - 0.004 C. nu ahs lichens 5 0.36 - 0.03 0.031 ± 0.004 Alaskan lichen communities * Separated from lichen samples. reported to represent background in air and precipitation samples prior to the entry of SNAP-9A generator debris in April 1964. However, the longevity and radionuclide reten tion capacity of lichens provide an integrated history of fallout deposition that has contained variable amounts and ratios of plutonium following each series of nuclear weapons tests Most of the mPu, 240Pu radioactivity in the pound” was associated with particles of in determinate size but tending toward a diameter of 0.5-1.0 pi. This estimate was based upon variation of about 30 % among several replica tions of the samples (whereas the analytical method usually yielded results with a variation of only 10%), repeated analyses, and radio autographic techniques. This is considerably and indicates that they originated from the Thule accident. This was corroborated by photomicrographs of contaminated snow and ice samples obtained in the downwind vector of the accident cloud1111 and was consistent BEST AVAILABLE COPY

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42 PLUTONIUM IN LICHEN COMMUNITIES OF THE THULE with projected particle sizes observed in labor atory studies of ignited and oxidized metallic There is no immediate explanation for the greater 23sPu concentrations in the Alaskan lichens compared with Thule background samples. It may be due to local fallout deposi tion phenomena associated with atmospheric Tuominen*131 suggested that variable cation composition of lichens from different regions might indicate a close relation between thalli and their substrate. We have not made such observations and can, therefore, only speculate upon the differences. It is concluded that plutonium concentrations slightly greater than background and attribut able to the Thule, Greenland Broken Arrow incident occurred in about one-third of the lichen samples collected at locations adjacent to and downwind from the impact site. of the Radiochemical Analysis Section for plutonium 2. A. Aarkrog, op. cit. 70 (1970). 3. Ch. Vibe, op. cit. 70 (1970). 4. Association of Official Agricultural Chemisu, Official Methods of Analysis pp. 327, 346. Associa tion of Official Agricultural Chemists, WashL-j. E. Van der Stricht, in: Radiation Protect-on Pergamon Press, New York (1968). 9. H. L. Volchok, Health and Safety Lab. Rept 11. H. L. Gjorup, USAF Nucl. Safety 65 (2), 57 (1970'. 12. J. Michima, Battelle Memorial Institute, Pac:f.c Northwest Lab. Report BNWL-357 (1966). 13. Y. Tuomexen, Ann. Bot. Fenn. 5, 102 (1968).