Bomb pulse

Last updated
Atmospheric C, New Zealand and Austria. The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear tests almost doubled the concentration of C in the Northern Hemisphere. Radiocarbon bomb spike.svg
Atmospheric C, New Zealand and Austria. The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere. Atmospheric nuclear tests almost doubled the concentration of C in the Northern Hemisphere.

The bomb pulse is the sudden increase of carbon-14 (14C) in Earth's atmosphere due to the hundreds of above-ground nuclear tests that started in 1945 and intensified after 1950 until 1963, when the Limited Test Ban Treaty was signed by the United States, the Soviet Union and the United Kingdom. [2] These blasts were followed by a doubling of the relative concentration of 14C in the atmosphere. [3]

Contents

Measurements of 14C levels by mass spectrometers are most accurately made by comparison to another carbon isotope, often the common isotope 12C. The figure shows how the relative concentration of 14C in the atmosphere, of order only 1 part per 1012, changed following the first bomb test in 1945. The increase in atmospheric 12C since 1955 has reduced the relative concentration of 14C to pre-1955 values, even though the absolute 14C concentration remains elevated.

14C naturally develops in trace amounts in the atmosphere and can be detected in all living things. Carbon of all types is continually used to form the molecules of the cells of organisms. Doubling of the concentration of 14C in the atmosphere is reflected in the tissues and cells of all organisms that lived around the period of nuclear testing. This property has many applications in biology and forensics.

Background

14C is constantly formed from nitrogen-14 (14N) in the upper atmosphere by cosmic rays which generate neutrons. These neutrons hit 14N to produce 14C which then combines with oxygen to form 14CO2. This radioactive CO2 spreads through the lower atmosphere and the oceans where it is absorbed by plants, and animals that eat the plants. 14C thus becomes part of the biosphere, so all living things contain some 14C. Nuclear tests caused a rapid increase in atmospheric 14C (see figure), since a nuclear explosion also creates neutrons which collide with 14N and produce 14C. Since the nuclear test ban in 1963, atmospheric 14C relative concentration is decreasing at 4% per year. This continuous decrease permits scientists to determine among other things the age of deceased people and allows them to study cell activity in tissues. By measuring the amount of 14C in a population of cells and comparing that to the amount of 14C in the atmosphere during or after the bomb pulse, scientists can estimate when the cells were created and how often they've turned over since then. [3]

Difference with classical radiocarbon dating

Carbon dating has been used since 1946 to determine the age of organic material as old as 50,000 years. When an organism dies, the exchange of 14C with the environment ends and the incorporated 14C decays. Given radioactive decay (14C's half-life is about 5,730 years), the relative amount of 14C left in the dead organism can be used to calculate how long ago it died. Bomb pulse dating should be considered a special form of carbon dating. In bomb pulse dating the slow absorption of atmospheric 14C by the biosphere can be considered a chronometer. [4] Starting from the pulse around the year 1963 (see figure), atmospheric radiocarbon relative abundance decreased by about 4% a year. So in bomb pulse dating it is the relative amount of 14C in the atmosphere that is decreasing and not the amount of 14C in dead organisms, as is the case in classical carbon dating. This decrease in atmospheric 14C can be measured in cells and tissues and has permitted scientists to determine the age of individual cells and of deceased people. [5] [6] [7] These applications are very similar to the experiments conducted with pulse-chase analysis in which cellular processes are examined over time by exposing the cells to a labeled compound (pulse) and then to the same compound in an unlabeled form (chase). Radioactivity is a commonly used label in these experiments. An important difference between pulse-chase analysis and bomb-pulse dating is the absence of the chase in the latter.

Around the year 2030 the bomb pulse will die out. Every organism born after this will not bear detectable bomb pulse traces and their cells cannot be dated in this way. Radioactive pulses cannot be ethically administered to people just to study the turnover of their cells, so the bomb pulse results are a useful side effect of nuclear testing. [4]

Applications

The fact that cells and tissues reflect the doubling of 14C in the atmosphere during and after nuclear testing, has been of great use for several biological studies, for forensics and even for the determination of the year in which certain wine was produced. [8]

Biology

Biological studies carried out by Kirsty Spalding demonstrated that neuronal cells are essentially static and do not regenerate during life. [9] She also showed that the number of fat cells is set during childhood and adolescence. Considering the amount of 14C present in DNA she could establish that 10% of fat cells are renewed annually. [10] The radiocarbon bomb pulse has been used to validate otolith annuli (ages scored from otolith sections) across several fish species including the freshwater drum, [11] lake sturgeon, [12] pallid sturgeon, [13] bigmouth buffalo, [14] arctic salmonids, [15] Pristipomoides filamentosus [16] , several reef fishes, [17] among numerous other validated freshwater and marine species. The precision for bomb radiocarbon age validation is typically within ±2 years because the rise period (1956-1960) is so steep. [11] [14] [15] The bomb pulse has also been used to estimate (not validate) the age of Greenland sharks by measuring the incorporation of 14C in the eye lens during development. After having determined the age and measured the length of sharks born around the bomb pulse, it was possible to create a mathematical model in which length and age of the sharks were correlated in order to deduce the age of the larger sharks. The study showed that the Greenland shark, with an age of 392 ± 120 years, is the oldest known vertebrate. [18]

Forensics

At the moment of death, carbon uptake ends. Considering that tissue that contained the bomb pulse 14C was rapidly diminishing with a rate of 4% per year, it has been possible to establish the time of death of two women in a court case by examining tissues with a rapid turnover. [5] Another important application has been the identification of victims of the Southeast Asian tsunami 2004 by examining their teeth. [6]

Carbon Transport Modeling

The perturbation in atmospheric 14C from the bomb testing was an opportunity to validate atmospheric transport models, and to study the movement of carbon between the atmosphere and oceanic or terrestrial sinks. [19]

Other

Atmospheric bomb 14C has been used to validate tree ring ages and to date recent trees that have no annual growth rings. [20] It can also be used to obtain the growth rate of tropical trees and palms that have no visible annual rings. [21]

See also

References

  1. ↑ "Radiocarbon". web.science.uu.nl. Retrieved 2016-08-15.
  2. ↑ "Radioactive Fallout From Nuclear Weapons Testing". USEPA. Retrieved 2016-08-16.
  3. 1 2 Grimm, David (2008-09-12). "The Mushroom Cloud's Silver Lining". Science. 321 (5895): 1434–1437. doi:10.1126/science.321.5895.1434. ISSN   0036-8075. PMID   18787143. S2CID   35790984.
  4. 1 2 "Elements – Radiolab" . Retrieved 2015-10-24.
  5. 1 2 Wild, Eva; Golser, Robin; Hille, Peter; Kutschera, Walter; Priller, Alfred; Puchegger, Stephan; Rom, Werner; Steier, Peter; Vycudilik, Walter (1997). "First 14C results from archaeological and forensic studies at the Vienna environmental research accelerator". Radiocarbon. 40 (1): 273. Bibcode:1997Radcb..40..273W. doi:10.1017/S0033822200018142. ISSN   0033-8222.
  6. 1 2 Spalding, Kirsty L.; Buchholz, Bruce A.; Bergman, Lars-Eric; Druid, Henrik; Frisén, Jonas (2005-09-15). "Forensics: Age written in teeth by nuclear tests". Nature. 437 (7057): 333–334. Bibcode:2005Natur.437..333S. doi:10.1038/437333a. ISSN   0028-0836. PMID   16163340. S2CID   4407447.
  7. ↑ "14C "Bomb Pulse" Pulse Forensics". Lawrence Livermore National Laboratory. Retrieved 2015-10-24.
  8. ↑ Zoppi, U; Skopec, Z; Skopec, J; Jones, G; Fink, D; Hua, Q; Jacobsen, G; Tuniz, C; Williams, A (2004-08-01). "Forensic applications of 14C bomb-pulse dating". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. Proceedings of the Ninth International Conference on Accelerator Mass Spectrometry. 223–224: 770–775. Bibcode:2004NIMPB.223..770Z. doi:10.1016/j.nimb.2004.04.143. S2CID   95325450.
  9. ↑ Spalding, Kirsty L.; Bhardwaj, Ratan D.; Buchholz, Bruce A.; Druid, Henrik; Frisén, Jonas (2005-07-15). "Retrospective birth dating of cells in humans". Cell. 122 (1): 133–143. doi: 10.1016/j.cell.2005.04.028 . ISSN   0092-8674. PMID   16009139. S2CID   16604223.
  10. ↑ Spalding, Kirsty L.; Arner, Erik; Westermark, Pål O.; Bernard, Samuel; Buchholz, Bruce A.; Bergmann, Olaf; Blomqvist, Lennart; Hoffstedt, Johan; Näslund, Erik (2008-06-05). "Dynamics of fat cell turnover in humans". Nature. 453 (7196): 783–787. Bibcode:2008Natur.453..783S. doi:10.1038/nature06902. ISSN   0028-0836. PMID   18454136. S2CID   4431237.
  11. 1 2 Davis-Foust, Shannon L.; Bruch, Ronald M.; Campana, Steven E.; Olynyk, Robert P.; Janssen, John (2009-03-01). "Age Validation of Freshwater Drum using Bomb Radiocarbon". Transactions of the American Fisheries Society. 138 (2): 385–396. Bibcode:2009TrAFS.138..385D. doi:10.1577/T08-097.1. ISSN   0002-8487.
  12. ↑ Janssen, John; Hansen, Michael J.; Davis-Foust, Shannon L.; Campana, Steven E.; Bruch, Ronald M. (2009-03-01). "Lake Sturgeon Age Validation using Bomb Radiocarbon and Known-Age Fish". Transactions of the American Fisheries Society. 138 (2): 361–372. Bibcode:2009TrAFS.138..361B. doi:10.1577/t08-098.1.
  13. ↑ Braaten, P. J.; Campana, S. E.; Fuller, D. B.; Lott, R. D.; Bruch, R. M.; Jordan, G. R. (2015). "Age estimations of wild pallid sturgeon (Scaphirhynchus albus, Forbes & Richardson 1905) based on pectoral fin spines, otoliths and bomb radiocarbon: inferences on recruitment in the dam-fragmented Missouri River". Journal of Applied Ichthyology. 31 (5): 821–829. Bibcode:2015JApIc..31..821B. doi: 10.1111/jai.12873 . ISSN   1439-0426.
  14. 1 2 Lackmann, Alec R.; Andrews, Allen H.; Butler, Malcolm G.; Bielak-Lackmann, Ewelina S.; Clark, Mark E. (2019-05-23). "Bigmouth Buffalo Ictiobus cyprinellus sets freshwater teleost record as improved age analysis reveals centenarian longevity". Communications Biology. 2 (1): 197. doi:10.1038/s42003-019-0452-0. ISSN   2399-3642. PMC   6533251 . PMID   31149641.
  15. 1 2 Campana, Steven E; Casselman, John M; Jones, Cynthia M (2008-04-01). "Bomb radiocarbon chronologies in the Arctic, with implications for the age validation of lake trout (Salvelinus namaycush) and other Arctic species". Canadian Journal of Fisheries and Aquatic Sciences. 65 (4): 733–743. Bibcode:2008CJFAS..65..733C. doi:10.1139/f08-012. ISSN   0706-652X.
  16. ↑ Andrews, Allen H.; DeMartini, Edward E.; Brodziak, Jon; Nichols, Ryan S.; Humphreys, Robert L. (2012-11-01). "A long-lived life history for a tropical, deepwater snapper (Pristipomoides filamentosus): bomb radiocarbon and lead–radium dating as extensions of daily increment analyses in otoliths". Canadian Journal of Fisheries and Aquatic Sciences. 69 (11): 1850–1869. Bibcode:2012CJFAS..69.1850A. doi:10.1139/f2012-109. ISSN   0706-652X.
  17. ↑ Johnston, Justine M.; Newman, Stephen J.; Kalish, John M.; Andrews, Allen H. (2011-11-23). "Bomb radiocarbon dating of three important reef-fish species using Indo-Pacific Δ14C chronologies". Marine and Freshwater Research. 62 (11): 1259–1269. doi:10.1071/MF11080. hdl: 1885/64620 . ISSN   1448-6059. S2CID   84397450.
  18. ↑ Nielsen, Julius; Hedeholm, Rasmus B.; Heinemeier, Jan; Bushnell, Peter G.; Christiansen, Jørgen S.; Olsen, Jesper; Ramsey, Christopher Bronk; Brill, Richard W.; Simon, Malene (2016-08-12). "Eye lens radiocarbon reveals centuries of longevity in the Greenland shark (Somniosus microcephalus)". Science. 353 (6300): 702–704. Bibcode:2016Sci...353..702N. doi:10.1126/science.aaf1703. hdl: 2022/26597 . ISSN   0036-8075. PMID   27516602. S2CID   206647043.
  19. ↑ Caldeira, Ken (1998). "Predicted net efflux of radiocarbon from the ocean and increase in atmospheric radiocarbon content". Geophysical Research Letters. 25 (20): 3811-3814. Bibcode:1998GeoRL..25.3811C. doi: 10.1029/1998GL900010 . S2CID   129623525.
  20. ↑ Rakowski, Andrzej Z.; Barbetti, Mike; Hua, Quan (2013-03-25). "Atmospheric Radiocarbon for the Period 1950–2010". Radiocarbon. 55 (4): 2059–2072. Bibcode:2013Radcb..55.2059H. doi: 10.2458/azu_js_rc.v55i2.16177 .
  21. ↑ del Valle, J.I.; Guarin, J.R.; Sierra, C.A. (2014). "Unambiguous and Low-Cost Determination of Growth Rates and Ages of Tropical Trees and Palms". Radiocarbon. 56 (1): 39–52. Bibcode:2014Radcb..56...39D. doi:10.2458/56.16486.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.