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Title: Setting a limit on anthropogenic sources of atmospheric 81Kr through Atom Trap Trace Analysis

Abstract

In this study, we place a 2.5% limit on the anthropogenic contribution to the modern abundance of 81Kr/Kr in the atmosphere at the 90% confidence level. Due to its simple production and transport in the terrestrial environment, 81Kr (half-life = 230,000 years) is an ideal tracer for old water and ice with mean residence times in the range of 105–106 years. In recent years, 81Kr-dating has been made available to the earth science community thanks to the development of Atom Trap Trace Analysis (ATTA), a laser-based atom counting technique. Further upgrades and improvements to the ATTA technique now allow us to demonstrate 81Kr/Kr measurements with relative uncertainties of 1% and place this new limit on anthropogenic 81Kr. As a result of this limit, we have removed a potential systematic constraint for 81Kr-dating.

Authors:
 [1];  [2];  [3];  [2];  [2];  [2];  [4]
  1. Argonne National Lab. (ANL), Argonne, IL (United States). Physics Division; Univ. of Chicago, IL (United States). Department of Physics and Enrico Fermi Institute
  2. Argonne National Lab. (ANL), Argonne, IL (United States). Physics Division
  3. University of Science and Technology of China, Hefei (China). School of Nuclear Science and Engineerin
  4. University of Bern (Switzerland). Climate and Environmental Physics Division, Physics Institute
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1356576
Alternate Identifier(s):
OSTI ID: 1413359
Grant/Contract Number:
AC02-06CH11357; DEAC02-06CH11357
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Chemical Geology
Additional Journal Information:
Journal Volume: 453; Journal Issue: C; Journal ID: ISSN 0009-2541
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 81 Kr; Groundwater dating; Anthropogenic effects; Radioisotope tracers; Noble gas tracers; Atom Trap Trace Analysis

Citation Formats

Zappala, J. C., Bailey, K., Jiang, W., Micklich, B., Mueller, P., O’Connor, T. P., and Purtschert, R.. Setting a limit on anthropogenic sources of atmospheric 81Kr through Atom Trap Trace Analysis. United States: N. p., 2017. Web. doi:10.1016/j.chemgeo.2017.02.007.
Zappala, J. C., Bailey, K., Jiang, W., Micklich, B., Mueller, P., O’Connor, T. P., & Purtschert, R.. Setting a limit on anthropogenic sources of atmospheric 81Kr through Atom Trap Trace Analysis. United States. doi:10.1016/j.chemgeo.2017.02.007.
Zappala, J. C., Bailey, K., Jiang, W., Micklich, B., Mueller, P., O’Connor, T. P., and Purtschert, R.. Thu . "Setting a limit on anthropogenic sources of atmospheric 81Kr through Atom Trap Trace Analysis". United States. doi:10.1016/j.chemgeo.2017.02.007. https://www.osti.gov/servlets/purl/1356576.
@article{osti_1356576,
title = {Setting a limit on anthropogenic sources of atmospheric 81Kr through Atom Trap Trace Analysis},
author = {Zappala, J. C. and Bailey, K. and Jiang, W. and Micklich, B. and Mueller, P. and O’Connor, T. P. and Purtschert, R.},
abstractNote = {In this study, we place a 2.5% limit on the anthropogenic contribution to the modern abundance of 81Kr/Kr in the atmosphere at the 90% confidence level. Due to its simple production and transport in the terrestrial environment, 81Kr (half-life = 230,000 years) is an ideal tracer for old water and ice with mean residence times in the range of 105–106 years. In recent years, 81Kr-dating has been made available to the earth science community thanks to the development of Atom Trap Trace Analysis (ATTA), a laser-based atom counting technique. Further upgrades and improvements to the ATTA technique now allow us to demonstrate 81Kr/Kr measurements with relative uncertainties of 1% and place this new limit on anthropogenic 81Kr. As a result of this limit, we have removed a potential systematic constraint for 81Kr-dating.},
doi = {10.1016/j.chemgeo.2017.02.007},
journal = {Chemical Geology},
number = C,
volume = 453,
place = {United States},
year = {Thu Feb 09 00:00:00 EST 2017},
month = {Thu Feb 09 00:00:00 EST 2017}
}

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  • In this paper, we report a methodology for measuring 85Kr/Kr isotopic abundances using Atom Trap Trace Analysis (ATTA) that increases sample measurement throughput by over an order of magnitude to six samples per 24 h. The noble gas isotope 85Kr (half-life = 10.7 years) is a useful tracer for young groundwater in the age range of 5–50 years. ATTA, an efficient and selective laser-based atom counting method, has recently been applied to 85Kr/Kr isotopic abundance measurements, requiring 5–10 μL of krypton gas at STP extracted from 50 to 100 L of water. Previously, a single such measurement required 48 h.more » In conclusion, our new method demonstrates that we can measure 85Kr/Kr ratios with 3–5% relative uncertainty every 4 h, on average, with the same sample requirements.« less
  • {sup 81}Kr (t{sub 1sol2}=2.3x10{sup 5} yr, {sup 81}Kr/Kr{approx}6x10{sup -13}) is a long-lived cosmogenic isotope, which is ideal for dating old groundwater and ice in the age range of 50,000 years to 1 million years. Here, we describe the apparatus and performance of an atom-counting system for practical {sup 81}Kr dating. This system is based upon the atom trap trace analysis method that was first demonstrated in 1999. Since then, significant improvements have been made to increase the system efficiency and to reduce the required krypton sample size. For a modern krypton gas sample of 100 {mu}l STP, which contains 1.2x10{supmore » 6} {sup 81}Kr atoms, the system can accumulate approximately 240 {sup 81}Kr counts in 20 h, thereby reaching a counting efficiency of 2x10{sup -4}. Detailed studies have been conducted to characterize the performance of this system. This system has been calibrated with a low-level counting method and has been used for {sup 81}Kr dating of ancient groundwater from the Nubian Aquifer (Egypt). It can also be used to measure the isotopic abundance of a fission-produced isotope {sup 85}Kr (t{sub 1sol2}=10.76 year,{sup 85}Kr/Kr{approx}2x10{sup -11})« less
  • Atom trap trace analysis, a laser-based atom counting method, has been applied to analyze atmospheric {sup 39}Ar (half-life=269 yr), a cosmogenic isotope with an isotopic abundance of 8x10{sup -16}. In addition to the superior selectivity demonstrated in this work, the counting rate and efficiency of atom trap trace analysis have been improved by 2 orders of magnitude over prior results. The significant applications of this new analytical capability lie in radioisotope dating of ice and water samples and in the development of dark matter detectors.
  • A technique is described and results are presented for measurement of the total cross section for the reactions /sup A/>81Kr(p,pXn)/sup 81/Kr and the cross section for /sup 86/Kr(p,pn)/sup 85/Kr for 600-MeV protons, and also the cross sections for /sup 80/Kr(n,..gamma..)/sup 81/Kr for reactor neutrons. The values obtained are sigma(p,pXn) = 35 +- 3 mb, sigma(p,pn) = 36.7 +- 0.8 mb, and sigma(n,..gamma..) = 12.5 +- 0.4 +- 2.6 b.