Focus
Glacial Analysis Probes Man's Technological on the Global
Impact
Environment
PLUTONIUM IN GLACIERS Investigators from a variety of disciplines are paying quite a lot of attention to snow and ice these days. For locked inside some of the world's most forbidding glaciers is information of great potential value to modern man in his a t t e m p t to understand his environment and the effects of technology on the environment. When DDT, transuranic radioactive nuclides, products from the combustion of fossil fuels, inorganic compounds, metals, organochlorine compounds, and hundreds of other substances are released to the atmosphere, they linger for a time before their return to the earth and the seas. And these processes have been going on for millions of years. "Where does one go to find a record of such fallo u t ? " asks Edward D. Goldberg of the University of California at San Diego. "One of the promising places is in glaciers. T h e reason t h a t glaciers are terribly attractive is t h a t they exist at every latitude on the surface of the earth, even the equator." Kilimanjaro, for example, has a permanent glacier.
Michael M. Herron of the State University of New York a t Buffalo. "Once it lands on the ice sheet or ice shelf it remains frozen, so you have a generally continuous record of the composition of the atmosphere over time spans as long as 120 000 years, and up to perhaps several million years in portions of E a s t Antarctica." The goal of this research effort is the elucidation of the impact of man on the global atmosphere. We need a better picture of how atmospheric pollutants are dispersed and how long various species persist in the environment. In addition, we need to establish points of reference wi^h which to evaluate our concerns about pollutant levels. "A few years ago fish were found to contain 'dangerous' levels of mercury," explains Herron. " B u t nobody knew how high the levels had been a hundred years previous to t h a t We can now go back 100, 1000, or more years and find out what the atmosphere of Greenland was like, which can't be done by any other means."
" T h e precipitation in these regions is dominantly affected by what's in t h e atmosphere a t the time," explains
A number of recent investigations in Greenland and Antarctica have focused on the deposition of radionuclides in glaciers, and on the element plutonium (Pu) in particular. Manmade P u is now a global pollutant, though it was but a short time ago t h a t the natural level of Pu in the environment was effectively zero, except for the low-level presence of 2 3 9 Pu in pitchblende.
The ice front of the Ross Ice Shelf (see above photo by M. Herron), which meets the Ross Sea in a 50-meter-high cliff. Some of the most spectacular Antarctic icebergs, which may be several square miles in area, are formed when portions of the ice shelf break away
On a weight basis, P u is one of the most biologically hazardous substances known. T h e more a b u n d a n t isotopes are alpha-emitters with halflives of u p to 379 kiloyears. P u enters the body primarily by inhalation and ingestion. Once it enters it deposits in t h e skeleton and t h e liver, where its highly energetic alpha particles may destroy surrounding tissue (1). Most of the P u in the environment today was produced in atomic bomb tests. Radioactive fallout patterns from nuclear weapons testing depend on the size of the detonation and its location. For instance, fission products in the troposphere usually reach the earth in an irregular band centered roughly at the latitude of the explosion, since prevailing winds are usually easterly or westerly. High-yield explosions propel fission products and other radioactive nuclides into the stratosphere, where material may persist for months or even years before it returns to earth. T h e recent deposition studies in Greenland and Antarctica have added an historical perspective to our understanding of these dispersion processes.
South Greenland One such study is found in a 1977 Nature paper (2) by Minoru Koide and Edward D. Goldberg of Scripps Institution of Oceanography, and Michael M. Herron and Chester C. Langway, Jr. of the State University of New York at Buffalo. T h e group ana-
ANALYTICAL CHEMISTRY, VOL. 51, NO. 14, DECEMBER 1979 • 1419 A
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1979
lyzed samples from the South Green land ice sheet, where t h e snow and as sociated dissolved and particulate substances are essentially immobile following deposition. T h e y dated the ice layers by 2 1 0 P b geochronology, a technique developed by Goldberg in Switzerland in 1960. Radon gas ( 2 2 2 Rn) in the atmosphere from the decay of 2 3 8 U in the earth's crust gives a relatively constant rain of radioac tivity. To date the ice layers, the activ ity of 2 1 0 P b , a persistent daughter of 222 Rn with a half-life of 22 years, is determined at the surface. A layer of ice with half t h a t much radioactivity is then 22 years old, and so on. Drilling for the South Greenland study took place at South Dome (64 °N, 45 °W) in 1975. Plutonium iso topes were first separated from the melted snow samples by ion exchange chromatography, then determined by alpha spectrometry with a pulse height analyzer and a surface barrier detector. T h e detector contains a Si diode capable of distinguishing be tween alpha particles of different en ergy. T h e alpha spectrometer cannot distinguish between 2 3 9 Pu (5.16 MeV) and 2 4 0 Pu (5.17 MeV) because of the similarity of their alpha particle emis sion energies, b u t it can give a com bined reading for these isotopes, and readily distinguishes them from 2 3 8 Pu (5.5 MeV). T h e South Greenland group ob served two distinct 239+240pu m a x i m a of nearly equal size for the periods 1955-60 and 1963-65. Fallout from above-ground tests of nuclear weapons detonated in t h e late 50's and early 60's produced the maxima. Testing ceased during a moratorium between the two series, producing a valley be tween the two peaks. An additional 239+240pu p e a k w a s detected in the strata deposited in 1946-48, a ghostly reminder of the detonations at Almagordo, N.M., Hi roshima, and Nagasaki. Much less 2 3 8 Pu is produced in an atomic blast t h a n 2 3 9 Pu, but the group's data indicated a significant in flux of 2 3 8 Pu in 1966, compared to a background deposition rate t h a t is ef fectively zero. T h e sudden appearance of 2 3 8 Pu in this s t r a t u m is attributed t o t h e b u r n u p of SNAP-9A. On 21 April 1964, a navigational satellite in cluding a Systems for Nuclear Auxilia ry Power generator, SNAP-9A, con taining about one kilogram of 2 3 8 Pu, was launched from Vandenburg Air Force Base in California. T h e rocket failed to boost the satellite into orbit, and the payload came down in the In dian Ocean. Subsequent stratospheric checks indicated t h a t the generator completely burned u p during reentry and turned into small particles at an altitude of about 50 km. T h e Atomic
Energy Commission had, in the words of J o h n W. Finney in the New York Times, "lost $1 million worth of lethal plutonium somewhere in space near Africa" (3).
Dome C Further investigations relating t o Pu deposition were later conducted in Antarctica by G. A. Cutter and K. W. Bruland of the University of California, Santa Cruz, Center for Coastal Marine Studies, and R. W. Risebrough of the University of California, Berkeley, Bodega Marine Laboratory (4). Samples for the work were obtained by Risebrough in J a n u a r y of 1977 at a forbidding spot known as Dome C, where the mean annual temperature is —53.5 °C. Summer temperatures remain well below freezing, preventing vertical percolation through successive layers and reducing potential losses from volatilization, and making Dome C an ideal place for deposition studies. B u t while the site may be favorable, the problems of sampling in Antarctica can be monumental, a fact underscored by a series of airplane accidents in 1974 and 1975 at Dome C, which is only accessible by air. Although no one was hurt, at one time three Hercules LC-130 transports were stranded at the camp. Eventually the disabled planes were repaired and evacuated from the site, but other formidable problems plague Antarctic research teams, including the threat of sample contamination. Risebrough writes: " T h e chances of sample contamination are very high, either from past human activities in the vicinity of the sampling site or from sampling and extraction operations. T h e area about the South Pole is probably much too contaminated to permit such studies: It is much more likely t h a t pollutants originated from the nearby station rather than distant sources many thousands of kilometers away. T h e problem is universal: Wherever we go, we bring and disseminate our pollutants" (5). T h e Dome C analyses, also run by alpha spectrometry, indicated heavy 239+24opu deposition in the late 50's and early 60's, as the South Greenland work had, except t h a t the late 50's peak far and above dominated the early 60's peak, whereas the peaks were of equal magnitude in the South Greenland study. T h e tests in the early 60's were conducted by the USSR at Novaya Zemlya in the Arctic. Fallout from this series was thus much more prominent in Northern latitudes. Significant quantities of 239+240pu first began to appear in the Antarctic snow in 1955. Cutter remarks t h a t the late 50's peak's size and timing suggest t h a t initial fallout was substantially
contributed by the U.S. Castle test Bravo, detonated on 28 February 1954, a t Bikini, a particularly dirty bomb which generated controversy and protest at the time. Ten days after the blast the Atomic Energy Commission admitted t h a t 28 Americans and 236 natives of the Marshall Islands, 330 miles from Bikini, had been exposed to radiation. Cutter et al. also detected the 2 3 8 Pu fallout from SNAP-9A, which appeared as a rapid activity increase in the 1965-66 stratum. Ross Ice Shelf A second Antarctic study was recently conducted by Minoru Koide, Robert Michel, and Edward Goldberg of the University of California at San Diego, and Michael M. Herron and Chester C. Langway, Jr. of the State University of New York a t Buffalo, with ice samples from Antarctica's Ross Ice Shelf (6). Their deposition profiles also indicated heavy accumulations of 239+240pu ; n t n e late 50's and early 60's, light accumulations in between due to the testing moratorium, and moderate fallout due to the French and Chinese tests in the late 60's and early 70's. Fallout from the SNAP-9A b u r n u p was evident in their 238p u profile. T h e researchers also analyzed for a number of fission products such as 9 0 Sr and 1 3 7 Cs. Glaciological research is today proceeding on many fronts. There are ongoing and recently completed studies on lead aerosols, dusts, sea salts, trace metals, sulfate, combustion products, aliphatic and aromatic hydrocarbons, and pesticides in snow. Edward Goldberg is presently interested in soot deposition. "We can identify the source of carbon by its surface characteristics and size, the morphology and dimensions of the carbon particles," he explains. "We can distinguish between coal particles, wood particles, and oil particles. Now we want to look at the history of burning by studying carbon particle deposition in glaciers." Much additional work remains to be done on the transuranics and fission products as well. Deposition studies in mid-latitudinal glaciers could lead to a better understanding of interhemispheric transport. Ice sheets in the Arctic could be examined for fallout from t h e Russian tests at Novaya Zemlya. This work and many other projects planned or already conducted are helping to give us a better understanding of the historical context of pollution. As Michael Herron puts it, "In the coming years we will stage a full-scale research assult on as many elements and organic compounds as possible, in old snow and in new snow. This will enable us to monitor changes in concentration
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indicating the influence of man's ac tivities on the environment."
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(1) "Cleaning Our Environment: A Chemi cal Perspective," Second Edition, Ameri can Chemical Society, Washington, D.C., 1978. (2) Minoru Koide, Edward D. Goldberg, Michael M. Herron, Chester C. Langway, Jr., Nature. 269,137-39 (1977).
5th Australian Symposium on Analytical Chemistry T h e 5th Australian Symposium on Analytical Chemistry (5 AC) was held in P e r t h from Aug. 20-29, 1979. T h e setting of this conference was especial ly appropriate, since this year marks the sesquicentennial of the establish ment of Western Australia. From the start, this meeting was clearly the product of extraordinarily good plan ning. T h e 350 participants from Aus tralia and overseas gathered for a se ries of seven plenary lectures, 17 invit ed review papers, and 85 shorter pre sentations. T h e latter category includ ed workshop and poster sessions as well as conventional lectures. T h e theme of the conference, "Setting the Standard," addressed the concern for accuracy, simplification, and innova tion in analytical chemistry. Although submitted papers covered a range of topics, most plenary and invited re view lectures appropriately revolved about this theme.
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(3) John W. Finney, New York Times, 24 May 1964,1. (4) G. A. Cutter, K. W. Bruland, R. W. Risebrough, Nature. 279, 628-29 (1979). (5) Robert W. Risebrough, Antarct. J. U.S. 12,131-32 (1977). (6) Minoru Koide, Robert Michel, Edward D. Goldberg, Michael M. Herron, Ches ter C. Langway, Jr., Earth Planet. Sci. Lett. 44, 205 (1979).
Plenary lectures were presented by a number of overseas individuals and covered a range of scientific topics. These papers included a discussion of standardization and data substantia tion in water quality assessment by M. W. Skougstad of the U.S. Geological Survey; an examination of plasma sources for analytical atomic emission spectroscopy by G. F. Kirkbright of Imperial College, London; a tutorially oriented exposition of laboratory com puter systems by R. E. Dessy of Vir ginia Polytechnic Institute and State University; recent advances in liquid chromatography by D. H. Freeman of the University of Maryland; an evalu ation of improved instrumentation for multielement atomic spectroscopy by G. M. Hieftje of Indiana University; and new developments in forensic chemistry by R. L. Williams of the Metropolitan Police Forensic Science Laboratory in London. In addition to the plenary lectures, interesting lectures were presented by P. L. Boar of the State Electricity Commission of Victoria, who evalu ated present standards for safety in the analytical laboratory; Alan Bond
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of Deakin University, Australia, who provided present and futuristic glimpses of electroanalytical chemis try's role in the surgical theatre; Doris Gardner of CSIRO-Cronulla, Austra lia, who discussed trace metal analysis by anodic stripping voltammetry and atomic emission spectroscopy within a modern clean-room facility; and B u r t Halpern of the University of Wollongong, Australia, on a $20 000 com puterized mass spectrometer to be marketed in Australia in the near fu ture. T h e conference was well organized; the lecture theatres were of high acoustic quality and were equipped with excellent audio-visual facilities. Plenary lectures were videotaped for later use. Individuals wishing to exam ine them should contact Dr. H. C. Hughes, the conference chairman, for further details. Dr. Hughes can be reached at the Government Chemical Laboratories, 30 Plain Street, Perth, W.A. 6000. Following the conference, each of the plenary lecturers had the opportu nity to visit other parts of Australia. In the case of these two writers, fasci nating visits were made to several gov ernment-operated CSIRO laborato ries, the University of Melbourne, the new Deakin University at Geelong, the beautiful national capitol at Canberra, the marine research laboratory at Cronulla, the School of Chemistry a t the University of New South Wales, and the Department of Chemistry at the University of Tasmania. It is worthy of note t h a t the next Australian Symposium on Analytical Chemistry (6 AC) will be held in Can berra in 1981. Based on our experi ences, overseas visitors who are able to attend t h a t conference are encouraged to do so. Further details can be ob tained from Joyce Fildes, Department of Chemistry, Australian National University, Canberra, Australian Cap itol Territory, Australia. David H. Freeman Gary M. Hieftje
