GEOTRACES intercalibration of Th-230, Th-232, Pa-231, and prospects for Be-10

Robert F. Anderson*, Martin Q. Fleisher, Laura F. Robinson, R. Lawrence Edwards, John A. Hoff, S. Bradley Moran, Michiel Rutgers van der Loeff, Alexander L. Thomas, Matthieu Roy-Barman, Roger Francois

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

47 Citations (Scopus)

Abstract

Nineteen labs representing nine nations participated in the GEOTRACES intercalibration initiative that determined concentrations of Th-232, Th-230, Pa-231, or Be-10 in seawater, suspended particles or sediments. Results generally demonstrated good agreement among labs that analyzed marine sediments. Two sets of seawater samples, aliquots of particulate material filtered in situ, and/or aliquots of biogenic sediments were distributed to participating labs. Internal consistency among participating labs improved substantially between the first and second set of seawater samples. Contamination was a serious problem for Th-232. Standard Niskin bottles introduced no detectable contamination, whereas sample containers, reagents, and labware were implicated as sources of contamination. No detectable differences in concentrations of dissolved Th-232, Th-230, or Pa-231 were observed among samples of seawater filtered through Nuclepore, Supor, or QMA ( quartz) filters with pore diameters ranging between 0.4 and 1.0 mu m. Isotope yield monitors equilibrate with dissolved Th in seawater on a time scale of much less than 1 day. Samples of filtered seawater acidified to a pH between 1.7 and 1.8 experienced no detectable loss of dissolved Th or Pa during storage for up to 3 years. The Bermuda Atlantic Time Series station will serve as a GEOTRACES baseline station for future intercalibration of Th-232 and Th-230 concentrations in seawater. Efforts to improve blanks and standard calibration are ongoing, as is the development of methods to determine concentrations of particulate nuclides, tests of different filtration methods, and an increasing awareness of the need to define protocols for reporting uncertainties.

Original languageEnglish
Pages (from-to)179-213
Number of pages35
JournalLimnology and Oceanography Methods
Volume10
DOIs
Publication statusPublished - Apr 2012

Keywords

  • THORIUM ISOTOPES
  • PARTICLE-FLUX
  • MASS-SPECTROMETRY
  • ATLANTIC-OCEAN
  • WATER COLUMN
  • SEAWATER
  • SECTOR
  • SEA
  • PA-231/TH-230
  • CONSTRAINTS

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