ACKNOWLEDGMENT N~~~~ of Wright We wish to thank
stateu n i versitv for the sediment samule from Grand Lake St. Mary's. Appreciation is also due Tom Bellar, of this laboratory, who extracted the sediment sample, and Ron
Webb. of the Southeast Environmental Research Laboratory, who provided the samples of characterized P C B isomers. Received for review July 11, 1973. Accepted September 18, 1973.
Determination of the Noble Metals in Geological Materials by Neutron Activation Analysis R. A.
Nadkarni and G.
H. Morrison
Department of Chemistry, Cornell University, Ithaca, N. Y . 74850
Gold, ruthenium, palladium, osmium, iridium, and platinum have been determined in geological materials using thermal neutron irradiation, selective adsorption of the noble metal group on Srafion NMRR ion exchange resin, and high resolution gamma spectrometry. The method was used to analyze three USGS standard rocks, a meteorite, and a lunar soil sample.
The noble metals, which are strongly siderophilic and to a lesser extent chalcophilic, are important trace chemical indicators of geological processes of differentiation. A knowledge of the abundance of these elements in some meteorites is useful in estimating values for solar system atomic abundances. They provide information on the mechanisms of meteoritic and lunar evolution and permit the computation of accretion rates of cosmic material on earth and on the moon. Because of the very low abundances of noble metals in most terrestrial materials, very few data exist on their concentrations in common igneous and sedimentary rocks, even though considerable effort has been expended to develop adequate methods for their determination. These analytical methods and techniques have recently been exhaustively reviewed ( I , 2), and a t the low parts-per-billion level the most widely used method is neutron activation analysis. Instrumental neutron activation analysis has been used directly only for the determination of one or two elements-Le., Au and Ir in favorable cases where their concentrations are high such as in meteorites, gold ores, matte, and lead assay beads (3-5). To determine all of the noble metals in a diverse variety of geological materials, radiochemical separation procedures have had to be used with neutron activation analysis. These published methods have involved fire assay, cupellation, volatilization, ion exchange, solvent extraction, and final precipitation of (1) F. E. Beamish and J . C. Van Loon, "Recent Advances in Analytical Chemistry of the Noble Metals," Pergamon Press, Oxford, 1972. (2) F . E. Beamish and J. C. Van Loon, Minerals Sci. Eng., 4, 3 (1972) (3) P. W. delange, W. J. de Wet, J. Turkstra, and J. H Venter, Anai. Chem.. 40, 451 (1968). ( 4 ) J Turkstra, P. J. Pretorius, and W . J. de Wet, Anal. Chem , 42, 835 (1970). (5) T A. Linn. Jr., and C. B. Moore, Earth Planet. Sci. Lett., 3, 453 (1967).
232
individual noble metals for counting (6-19), with the disadvantages of length of time and potential losses during the radiochemical procedures. A relatively rapid and comprehensive neutron activation meth,od for the determinization of Au, Ru, Pd, Os, Ir, and P t in a variety of geological materials is described here, based on an ion exchange separation of these elements as a group followed by high resolution gamma spectrometry. The key aspect of the method is the use of a resin discovered in 1967 that is specific for the noble metals (20). This resin contains a guanidine group coupled to a styrene-divinylbenzene copolymer matrix. Its selectivity for noble metals is attributed to the fact that it will bind only ions with the d8 electronic configuration forming square planar complexes. The resin has reducing properties because of the double bonds enabling it to collect species such as P t 4 + and Ir4+ which are reduced to Pt2+ and Ir+ and then bound as square planar complexes. Since publication of the original paper (20), the resin or resin-loaded paper has been used for the determination of Au (21-23) and Ir in rocks (24) by neutron activation or X-ray fluorescence spectrometry. It was also discovered that in addition to the noble metals, methylmercury and (6) J. H. Crocket and G. 8 . Skippen, Geochim. Cosmochrm. Acta. 30, 129 (1966). (7) J. H. Crocket, R. R . Keays, and S. Hsieh, ;bid., 31, 1615 (1967). (8) J. H. Crocket, R. R. Keays. and S. Hsieh. J. Radioanal. Chem., 1, 487 (1968). (9) R. C. Harriss, J. H . Crocket. and M . Stainton, Geochfm. Cosmochim. Acta, 32, 1049 (1968). (10) R . Gijbels and J. Hoste, A n a l . Chim. Acta. 41, 419 (1968). (11) F. 0. Simonand H. T. Millard, Jr..Anal. Chem.. 40, 1150 (1968). (12) W. D. Ehmann, P. A. Baedecker. and D.M. McKown, Geochim. Cosmochm. Acta. 34, 493 (1970). (13) R . R . Ruch, Anal. Chim. Acta. 49, 381 (1970). (14) H. T. Millard and A. J. Bartel in "Activation Analysis in Geochemistry and Cosmochemistry," A. 0. Brunfelt and E. Steinnes, Ed.; Universitetsforlaget, Oslo, 1970, p 353. (15) J. H. Crocket. ibfd., p 3 3 9 . (16) R. R. Keays and J. M. Crocket, €con. Geol., 65, 438 (1970). (17) D. E. Gillum and W. D. Ehmann. Radiochim. Acta. 16, 123 (1971). (18) W. D.Ehmann and D. E Gtllum, Chem. G e o l , 9, 1 (1972). (19) J. J Rowe and F. 0. Simon, U . S Geol. Surv. Circ.. 599 (1968) (20) G. Koster and G. Schmuckler, A n a l . Chim. Acta. 38, 179 (1967). (21) T. E. Green and S. L. Law, U S . Bur. Mines Rep. i n v e s l , 7358 (1970). (22) T. E. Green, S. L Law, and W. J. Campbell, Anal. Chem.. 42, 1749 (1970). (23) C. W. Blount, D. E. Leyden, T L. Thomas, and S. M. Guill, A n a l . Chem.. 45, 1045 (1973). (24) H. A. Das, R. Janssen, and J . Zonderhuis, Radiochem. Radioanal. Lett.. 8, 257 (1971).
A N A L Y T I C A L C H E M I S T R Y , VOL. 46, NO. 2, F E B R U A R Y 1974
inorganic Hg are quantitatively collected by the resin under similar conditions (2.5, 26). EXPEKI3IE:N'I'AL Reagents. S a r n p h . Terrestrial rock samples analyzed included the USGS standards diabase W-1, periodite PCC-1, and dunite DTS-1. A type C3 carbonaceous chondrite meteorite Allende was also analyzed as waa luilar >oil 72701 returned b\ A p d l u 17. The samples were dried for 24 hours at 80 "C before taking aliquots for analysis. Stundardb N ~ i b kmetal irradiativn standard> a, well ab the carrier solution were prepared from "Specpure" Au metal, ammonium chloroiridate ((SH4I2IrClt;). ammonium chlorosmate ( ( N H + J ~ O S C I ammonium ~J, chloroplatinate ~ ( N t i 4 ) Z P c C l ~a m j,monium chloropalladire ((", IsI'dCIej. and aninimium chluroi . Appropriately diluted solutions ruthenite ((NH4)2(Ru(H20)C15) of these were weighed out on approximately 20 mg of "Spex" high purity Si02 contained in quartz vials. T h e solhtions were carefully evaporated and the vials sealed. The carrier solution contained 0.1 to 0.5 mglrnl of each o f t h e noble metals. Ion I:xchungcJ l ( i , , b i n . Sraf'ior, N M H H resin was obtained from Ayalon \Yater Conditioning Co.. L:d.. Haila. Israel. It was previously marketed under the name SICiL by lonac Chemical Co.. Birmingham. N . J . The resin was soaked in 0.05.Y HC1 for several hours before use. T h e resin was packed in a glass column 10 cm in length and 1.5-cm inner diameter. Procedure. Irradiations. Geological samples weighing 0,:3-0,5 gram each were sealed in high purity quartz ampoules. In the case of the lunar soil. 1.0 gram was used. The irradiation stanI iridii .Jus1 nohit metals i j a h alsu dard cuntriiiiing 1 I ~ J 5 p g ~ Jr!w sealed in a quartz ampoule. Stimplea and standard were irradiated in the central thimble facility of the Cornel1 TRIGA Mark I1 reactor for eight hours at a Thermal neutron flux 01' 3.5 X 1012 n.cm*.sec-'. The samples were allowed to decay overnight before processing. Kudiuchernicui Proctdurr.. The quartz vials were opened and the samples and standard were translerred t o individual nickel crucibles. T h e interior of the ampoules were repeatedly washed with 8N HCl and the washings transferred to the crucibles. One milliliter of carrier solution was added to each crucible, and the solutions were carefully evaporated t o dryness. Five grams of N a z 0 2 and 2 grams of NaOH were added to each crucible which was then heated to red heat. They were further heated tor 10 minutes while continually swirling the contents. This fusion step ensured isotopic exchange between the added carrier and the corresponding radionuclide. T h e crucibles were allowed to cool and the melts in each were dissolved in 75 ml of water in a beaker. T h e solutions were acidified with 8N HCI. being careful to avoid any loss by effervescence. When acidic, the solutions should be clear green in color if all of the sample has completely dissolved. T h e solutions were heated and oxidized by adding 2 mi o! concentrated " 0 3 . The excess peroxide was destroyed by boiling. The p H of the solutions were then adjusted to 1.5-2 using dilute ammonia. Each solution was passed through a n ion exchange column a t the rate 01 1 m l per minute. T h e resin will turn from pale yellow to rose-orange color as the noble metals are adsorbed. The effluent was passed over a second resin column. T h e columns were then washed ten times with 10 ml each of 0.05.~'HCI. T h e resin in the two columns was transferred to a 125-m1 Erlenmeyer flask and the volume adjusted to 30 mi with O.OtLY HCI to provide a standard geometry for counting of samples and srandard. The radiochemical procedure takes about three hours for completion. C o u n t i n g und Data Processing. T h e samples and standard were counted using a 30 cm3 coaxial Ge(Li) detector and 4096 channel analyzer. T h e system resolution was better than 2.8 KeV (FU'HM) and the peak-to-Compton ratio was better than 15:1, '-Me\ peak of "Oca. The samples were counted at various decay periods to check isotopic half-lives. Counting times were usually on the order of one huur for the standard and 2 t u 3 hours for t h e sanipleh. The dara t'rom t h e analyzer were transferred on a magnetic tape which was then processed on a PDP-11 computer. T h e final computer output provided digital tables of d a t a and calculated the peak areas corrected for background. T h e peaks of interest were then corrected for decay wher necessary.
RESULTS AND DISCUSSION The Srafion h W K R resin adsorbed the noble metals and Hg at pH 0.5 to 2.5. 'I'he capacity of the resin for these elements in gramsl'liter is given as 150 for Au, 65 for Pt, 58 for Pd, 25 for Ir. 25 for Kh, and 75 for Hg (27). Since the only radioisotope of Rh produced by thermal wirh a h ! : - l i l c of 1.1minutes. neutron activation is L(J411h this element could not be determined using the radiochemicsl procedure rmployeti in t h k study and will not be considered in the furiher. discussion. Using radioactive tracers of the noble metals and Hg in the presence of carriers of these element>, their adsorption behaviur on the resin nzas inVeStigsK?d. In all cases the adsorption was 97-1007~ complete. Only 9 7 K ~and lS4Ir required two passes through the column to attain this level of' adsorption. Another experiment was performed where two irradiated standards were passed through columns. The first was run directly. ivhile Lht- second was mixed with a solution prepared by diS;olvii1g 500 nig of unirradiated LV-1 rock powder prior t o eluting on the column. In both cases the adsorption on the resin was complete, indicating that separation is quantitative either in the presence or absence o f a rock matrix. Counting of the effluent from the standard to determine loss of the noble metals from the column revealed that the acrivity !\as i!?c o r ley> !or nit,>: t . i t > ~ i e n bur t + occasiorially as high as 5% lor Ku arid Ir. IL was nut possible to check the effluent from geological samples because of the presand other isotopes formed ence of high activity from '"a from the major elements present in the samples. The adsorbed noble metals can be recovered from the resin by eluting immediately after adsorption with a 5% aqueous solution of thiourea which is 0.05,V in HCI. Alternatively, the resin can he slowly heated a t 900-1000 "C leaving the metals in a very pure metallic form. However, in view of the quantitative adsorption of the metals on the resin, no removal step was included in the proposed procedure, and no chemical yield determinations were necessary. Although the resin is highly selective for Hg, Au, and the platinum metals, some of the common and base metal ions can be physically retained on the column. However, washing with 0.05N HC1 appears to remove thi? contamination as evidenced by its absence in the gamma spectra of the resin phase. Even 21Na which is produced in large amounts on irradiating most geological samples was detected in only low trace amounts on the resin. Only in the analysis ot PCC-1 and D E - 1 samples was appreciable contamination of the resin spectra by 5ICr observed. Both of these rocks contain very high amount of chromium, 2730 and 3000 ppm, respectively (28). Similar adsorption of 51Cr on this resin has been observed by Das c.t ol. ( 2 4 ) . However, this in no way affected .the determination of the noble metals. since the Ge(Li) detector could resolve all photopeaks of interest, without interference. Das et al. (24) using a n NaI(T1) detector were unable to resolve the interference of the 51Cr 320-KeV peak with the 396.. 309-. and 317-KeV peaks of'"2Ir. Although tracer experiments indicated that Hg is quantitatively retained on the resin, analyses of geological samples using the proposed method ga\'t consistently high results for this element. This can probably be attributed to loss or incomplete isotopic exchange in the preparation and processing of the standard. Therefore, the determination of Hg in these samples was temporarily abandoned. (27) Ayalon Water Conditioning Co.. Ltd., Haifa. Israel. Srafion NMRR
(25) S L Law, Science 174, 285 (1971) (26) P J Ke and R J Thibert M!Krucnirn Acta 1973, 417
Product Information Bulletin ( 2 8 ) F J Flanagan. Geochirr:. Cosnioch!m Actd. 3 7 , 1189 (1973) A N A L Y T I C A L C H E M I S T R Y , VOL. 46, NO. 2, F E B R U A R Y 1974
233
Table I. Nuclear Data (29) Element
Isotope produced
Ruthenium
97R~ lo3Ru
Palladium
lo4Rh lo9Pd
Osmium
1910s
Iridium
1921r
Platinum
197Pf
Rhodium
19305 lg4Ir
'99Pt
lg9Au
Gold Mercury
19*Au 1 9 7 r n ~ ~
lg7Hg
203Hg
% Abundance of target isotope
5.46 31.5 100 26.7 26.4 41.0 38.5 61.5 25.2 7.19 ( @ - d e c a yof l g 9 P f ) 100
0.2 1.4 11 12 3.9 1.6 750 110 0.9 4 98.8 25 880 4
0.15 0.15 29.8
Table I presents the nuclear data for the elements of interest (29). In those cases where two or more isotopes of an element are produced, the shorter half-lived isotope was used where possible. Although additional gamma rays are associated with the isotopes listed, only the preferred interference-free ones have been included. Others were used for confirmation of the isotopes. A detailed discussion of the nuclear considerations and interfering reactions has been given by Gijbels (30). The (n,p) and ( n p ) secondary nuclear reactions are of considerable importance in determining noble metals in other noble metals; however, in the analysis of rock samples where the concentrations of all of the noble metals are comparably low, these reactions do not pose any serious interference. In those geological samples containing uranium a t levels well in excess of the noble metals, reactions such as 235U(n,f)103R~and 235U(n,f)lO9Pd with a high fission yield can interfere with the determination of Ru and Pd uia 103Ru and 109Pd, respectively. Gijbels (30) has shown using detailed calculations that for lo9Pd the interference is only 0.025%, whereas for 103Ru it is 13%. Based on the presence of 1 ppm natural uranium, an apparent P d content of 0.0025 ppb will be found using l09Pd and a Ru content of 0.13 ppb using 103Ru. Thus, the fission product contribution can be neglected in the determination of Pd. If 97Ru, which is not produced by fission, is used instead of 103Ru, t h e n , R u can be determined with no interference as was the case in this study. For more detailed discussion of this problem see Gijbels (30), Crocket et al. (8),and Crocket (15).
Self-absorption and self-shielding problems were minimized by using standards containing less than 5 pg of each noble metal, which is about the amount present in the samples. Platinum can be determined by counting the 19-hour nuclide 197Pt or by measuring I99Au, the @ - decay product of the reaction, 19sPt(n,y)199Pt.Since Au is present in geological samples, 199Au will also be produced from the reactions 197Au(n,y)19sAu followed by 19*Au(n,y)199Au. However, the production of l99Au uia the second path is serious only after long irradiations at high neutron fluxes. For the determination of traces of Pt in a Au matrix, these reactions present, a serious problem, but in ordinary geological materials where the concentrations of both Au and Pt are about the same, this interference is not serious. Both 197Ptand lg9Au were measured in this study, and (29) C. M. Lederer, J. M . Hollander, and I . Perlman. "Tables of Isotopes," 6th ed.. John Wiley 8 Sons, New York, N.Y., 1967. (30) R. Gijbeis, Taianta. 18, 587 (1971).
234
Cross-section,
(r
Half-life of produced nuclide 69.1 h 39.5 d 4 . 3 rn 13.5 h 15 d 31.5 h 74 d 17.4 h 19h 30 m 3.15 d 64.8 h 24 h 65 h 47 d
Principal y-ray used, MeV 0.215 0.497 0.051 0.088 0.129 0.139 0 . 3 1 7 , 0.468 0.328 0.077 t
.
.
0.158 0.412 0.134 0.077 0.279
where necessary, appropriate correction was made for the production of I99Au from l97Au. Results of the analysis of three terrestrial rocks, a meteorite, and a lunar sample using the proposed method are given in Table 11. The results are based on triplicate analyses for all samples except the lunar soil, where a limited supply of the sample allowed only a single determination. The relative standard deviation for a single determination is included. Literature values based on the work of other investigators using a wide variety of methods are included in the table for comparison. The agreement of our results with these literature values for the diabase W - 1 and the Allende meteorite is excellent considering the range of values obtained by others on these samples. With regard to PCC-1, our values lie in the range of reported values except for Au and Pd, and in the case of DTS-1 only our value for Au lies outside the range. In view of the large range of values reported, there is obviously some question as to the "true" values for these samples. There may not be a "true" value for these elements because of sampling problems for noble metals in terrestrial rocks. There are no values available for comparison of the Apollo 17 lunar soil 72701; however, the values obtained are in the same concentration range obtained by others on other lunar samples. The Pt value reported here is the (31) J. C. Laul, D. R. Case, M . Wechter, F. Schmidt-Bleek, and M. E. Lipschutz, J . Radioanal. Chem.. 4, 241 (1970). (32) J. Haffty and L. 8.Riley, Taianta. 15, 111 (1968). (33) L. P. Greenland, J. J. Rowe, and J. I . Dinnin, U.S. Geoi. Surv. Prof. Pap.. 7508, 8-175 (1971). (34) P. A. Baedecker, C. L. Chou, and J. T. Wasson, "Proceedings 3rd Lunar Science Conference." Vol. 2. M. I.T. Press, Cambridge, Mass., 1972. p 1343. (35) R. Gijbels, M. T. Millard, G. A. Desborough, and A. J. Bartel, in "Activation Analysis in Geochemistry and Cosmochemistry," A . 0. Brunfelt and E. Steinnes. Ed., Universitetsforlaget, Oslo, 1971, p 359. (36) P. A. Baedecker, R . Schaudy, J. L. Eizie, J, Kimberlain, and J. T. Wasson, "Proceedings 2nd Lunar Science Conference," Vol. 2, M.I.T. Press, Cambridge, Mass., 1971, p 1037. (37) R . Gijbels and A. Govaerts, International Conferences on Activation Analysis, Paris, 1972, paper M-30. (38) L. Grossman, Geochim. Cosmochim. Acta, 37, 1119 (1973). (39) H. Malissa, F. Hermann. F. Kluger, and W. Kiesi, Mikrochim. Acta, 1972,434. (40) J. W. Morgan. T. V. Rebagay. D. L. Showalter, R. A. Nadkarni, D . E. Gillum, D. M . McKown, and W. D . Ehmann. Nature, 224, 789 (1969). (41) M . Vobecky. J. Frana. 2. Randa, J. Benada, and J. Kuncir, Radiochem. Radioanal. Lett. 6 , 237 (1971) (42) R. G. Warren, M . S. Thesis, Oregon State University, Corvaliis, Ore., 1971 (43) H. Hintenberger. K. P. Jochum, and M. Seufert. 36th Ann. Meet. Meteoritical SOC.,Davos, Switzerland, 1973, p 68.
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first value for this element to be reported for any lunar sample. The overall precision of our results is on the order of 10-40%, which is reasonable considering the fact that the method involves the determination of nanogram and subnanogram amounts of these elements. In addition to analytical errors, there is a strong possibility of sample inhomogeneiety for these elements. In favorable cases, such as the analysis of Allende where the concentrations of the noble metals are considerably higher, the precision expressed as relative standard deviation for a single determination varied from 0.7% for platinum to 14% for ruthenium. Thus, the proposed method for the determination of
noble metals in geological samples is capable of providing good analytical data for the platinum metals and gold. Although Ru and Os could not be determined in every terrestrial rock in this study because of their low concentrations, use of a higher neutron flux, longer irradiation time, and/or larger samples should make their determination possible using this method. The method is simple and rapid and provides data on all six elements in the same aliquot of sample. Received for review July 9, 1973. Accepted August 23, 1973. This work was supported in part by the National Aeronautics and Space Administration under Grant NGR-33-010-166.
Instrumental Neutron Activation Analysis for Mercury in Dogs Administered Methylmercury Chloride: Use of a Low Energy Photon Detector Melvin
H. Friedman, Eugene Miller,
and James T. Tanner
Bureau of Foods, Food and Drug Administration, Washington, D. C. 20204
Mercury has been determined by nondestructive neutron activation analysis in samples of brain tissue from beagles which had been fed methylmercury chloride. The mercury concentration was not uniformly distributed throughout the central nervous system and the fastest rise in concentration occurred in components of the visual system. The analytical procedure was capable of measuring mercury instrumentally and routinely in small samples of biological materials at approximately the 0.2-ppm level within a few days after irradiation with short counting times. Comparative measurements showed that mercury determination based on lg7Hg could be done with greater sensitivity by using a Ge(Li) low energy photon detector rather than a conventional high resolution, high efficiency coaxial Ge(Li) detector.
The Food and Drug Administration, as part of its continuing toxicological program, initiated a histopathological study of possible damage to the central nervous system of animals exposed to lethal and sublethal doses of methylmercury. T w o comprehensive reports have appeared ( I , 2) which pointed out the need for accurate studies of the toxicological effects of methylmercury compounds on the brain. Tissues from the central nervous system were chosen for these studies since these tissues were shown to be the ones most critically affected in methylmercury poisoning (2). Tissues from discrete parts of the central nervous system were used, rather than brain homogenates, since it was suspected that mercury might not be distributed uniformly in the brain. ( 1 ) "Mercury in the Environment-A Toxicoiogical and Epidemiological Appraisal," L. Friberg and J. Vostal, Ed., Environmental Protection Agency Report (Nov. 1971), Contract No. CPA 70-30. ( 2 ) G . Lofroth. "Methylmercury," Ecological Research Committee, Bulletin No. 4 . Swedish Naturai Science Research Council, 1970.
236
The main emphasis in this report will be on the analytical technique used t o determine mercury in small brain tissue samples. In addition, a summary of the major biological implications will be given. The technique employs neutron activation analysis as the analytical method. Typically, neutron activation analysis measurements have been based on 197Hg or z03Hg. The 197Hg nuclide initially has a much greater activity than the 203Hg nuclide (3) and so offers the possibility of a more sensitive measurement. However, the electromagnetic radiation (X-ray or gamma-ray) associated with the decay of 197Hg is low in energy ( < l o 0 keV), and conventional measurements of low levels of mercury have been hampered by a large Compton continuum in this region and by a resolution inadequate to resolve possibly interfering X-rays from elements with adjacent atomic numbers. A Ge(Li) low energy photon detector (LEPD) was used in this work because of the smaller continuous background in the low energy region and better resolution, and so was expected to reduce these problems ( 4 ) . Instrumental neutron activation analyses for mercury have been reported with a sensitivity of approximately 0.02 ppm. In these analyses, a large volume Ge(Li) detector was used. These measurements ( 5 ) involved 3-hour irradiations, 2-gram samples, and counting times of approximately 2 hours per sample. In this work, a comparison was made between a conventional large volume Ge(Li) detector and the Ge(Li) LEPD for the determination of mercury based on 197Hg.
(3) F. Baumgartner, "Table of Neutron Activation Constants," Verlag Karlthiemig KG, Munchen, 1967, p 30. (4) J. Weaver, Amer. L a b . , Mar,ch, 1973, p 36. (5) V. P. Guinn and R. Kishore, "Proceedings of the Amerlcan Nuclear Society Topical Meeting on Nuclear Methods in Environmental Research, University of Missouri, Columbia, Mo., Aug. 23-24, 1971, p
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