Turnewitsch Robert

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Turnewitsch
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Robert
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  • Article
    Intercalibration studies of short-lived thorium-234 in the water column and marine particles
    (Association for the Sciences of Limnology and Oceanography, 2012-09) Maiti, Kanchan ; Buesseler, Ken O. ; Pike, Steven M. ; Benitez-Nelson, Claudia R. ; Cai, Pinghe ; Chen, Weifang ; Cochran, Kirk ; Dai, Minhan ; Dehairs, Frank ; Gasser, Beat ; Kelly, Roger P. ; Masqué, Pere ; Miller, Lisa A. ; Miquel, Juan Carlos ; Moran, S. Bradley ; Morris, Paul J. ; Peine, Florian ; Planchon, Frederic ; Renfro, Alisha A. ; Rutgers van der Loeff, Michiel M. ; Santschi, Peter H. ; Turnewitsch, Robert ; Waples, James T. ; Xu, Chen
    Intercomparision of 234Th measurements in both water and particulate samples was carried out between 15 laboratories worldwide, as a part of GEOTRACES inter-calibration program. Particulate samples from four different stations namely BATS (both shallow and deep) and shelf station (shallow) in Atlantic and SAFE (both shallow and deep) and Santa Barbara station (shallow) in Pacific were used in the effort. Particulate intercalibration results indicate good agreement between all the participating labs with data from all labs falling within the 95% confidence interval around the mean for most instances. Filter type experiments indicate no significant differences in 234Th activities between filter types and pore sizes (0.2-0.8 μm). The only exception are the quartz filters, which are associated with 10% to 20% higher 234Th activities attributed to sorption of dissolved 234Th. Flow rate experiments showed a trend of decreasing 234Th activities with increasing flow rates (2-9 L min-1) for > 51 μm size particles, indicating particle loss during the pumping process. No change in 234Th activities on small particles was observed with increasing flow-rates. 234Th intercalibration results from deep water samples at SAFe station indicate a variability of < 3% amongst labs while dissolved 234Th data from surface water at Santa Barbara Station show a less robust agreement, possibly due to the loss of 234Th from decay and large in-growth corrections as a result of long gap between sample collection and processing.
  • Preprint
    A review of present techniques and methodological advances in analyzing Th-234 in aquatic systems
    ( 2005-10-10) Rutgers van der Loeff, Michiel M. ; Sarin, Manmohan M. ; Baskaran, Mark ; Benitez-Nelson, Claudia R. ; Buesseler, Ken O. ; Charette, Matthew A. ; Dai, Minhan ; Gustafsson, Orjan ; Masqué, Pere ; Morris, Paul J. ; Orlandini, Kent ; Rodriguez y Baena, Alessia ; Savoye, Nicolas ; Schmidt, Sabine ; Turnewitsch, Robert ; Voge, Ingrid ; Waples, James T.
    The short-lived thorium isotope 234Th (half-life 24.1 days) has been used as a tracer for a variety of transport processes in aquatic systems. Its use as a tracer of oceanic export via sinking particles has stimulated a rapidly increasing number of studies that require analyses of 234Th in both marine and freshwater systems. The original 234Th method is labour intensive. Thus, there has been a quest for simpler techniques that require smaller sample volumes. Here, we review current methodologies in the collection and analysis of 234Th from the water column, discuss their individual strengths and weaknesses, and provide an outlook on possible further improvements and future challenges. Also included in this review are recommendations on calibration procedures and the production of standard reference materials as well as a flow chart designed to help researchers find the most appropriate 234Th analytical technique for a specific aquatic regime and known sampling constraints.