Anderson Robert F. author Columbia University. Lamont-Doherty Earth Observatory Columbia University. Earth and Environmental Sciences Fleisher Martin Q. author Columbia University. Lamont-Doherty Earth Observatory Robinson Laura F. author Edwards R. Lawrence author Hoff John A. author Moran S. Bradley author Loeff Michiel Rutgers van der author Thomas Alexander L. author Francois Roger author Roy-Barman Matthieu author Columbia University. Lamont-Doherty Earth Observatory originator text Articles 2012 English Nineteen labs representing nine nations participated in the GEOTRACES intercalibration initiative that determined concentrations of 232Th, 230Th, 231Pa, or 10Be 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 232Th. 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 232Th, 230Th, or 231Pa were observed among samples of seawater filtered through Nuclepore, Supor, or QMA (quartz) filters with pore diameters ranging between 0.4 and 1.0 μm. 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 232Th and 230Th 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. Chemical oceanography 10 179 213 2012 http://dx.doi.org/10.4319/lom.2012.10.179 http://hdl.handle.net/10022/AC:P:14508 NNC NNC 2012-08-27 13:37:23 -0400 2012-08-27 15:45:22 -0400 8528 eng