Smith Richard W.

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Smith
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Richard W.
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  • Article
    An interlaboratory study of TEX86 and BIT analysis using high-performance liquid chromatography–mass spectrometry
    (American Geophysical Union, 2009-03-20) Schouten, Stefan ; Hopmans, Ellen C. ; van der Meer, Jaap ; Mets, Anchelique ; Bard, Edouard ; Bianchi, Thomas S. ; Diefendorf, Aaron ; Escala, Marina ; Freeman, Katharine H. ; Furukawa, Yoshihiro ; Huguet, Carme ; Ingalls, Anitra ; Menot, Guillemette ; Nederbragt, Alexandra J. ; Oba, Masahiro ; Pearson, Ann ; Pearson, Emma J. ; Rosell-Mele, Antoni ; Schaeffer, Philippe ; Shah, Sunita R. ; Shanahan, Timothy M. ; Smith, Richard W. ; Smittenberg, Rienk ; Talbot, Helen M. ; Uchida, Masao ; Van Mooy, Benjamin A. S. ; Yamamoto, Masanobu ; Zhang, Zhaohui ; Sinninghe Damste, Jaap S.
    Recently, two new proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) were proposed, i.e., the TEX86 proxy for sea surface temperature reconstructions and the BIT index for reconstructing soil organic matter input to the ocean. In this study, fifteen laboratories participated in a round robin study of two sediment extracts with a range of TEX86 and BIT values to test the analytical reproducibility and repeatability in analyzing these proxies. For TEX86 the repeatability, indicating intra-laboratory variation, was 0.028 and 0.017 for the two sediment extracts or ±1–2°C when translated to temperature. The reproducibility, indicating among-laboratory variation, of TEX86 measurements was substantially higher, i.e., 0.050 and 0.067 or ±3–4°C when translated to temperature. The latter values are higher than those obtained in round robin studies of Mg/Ca and U37 k′ paleothermometers, suggesting the need to primarily improve compatibility between labs. The repeatability of BIT measurements for the sediment with substantial amounts of soil organic matter input was relatively small, 0.029, but reproducibility was large, 0.410. This large variance could not be attributed to specific equipment used or a particular data treatment. We suggest that this may be caused by the large difference in the molecular weight in the GDGTs used in the BIT index, i.e., crenarchaeol versus the branched GDGTs. Potentially, this difference gives rise to variable responses in the different mass spectrometers used. Calibration using authentic standards is needed to establish compatibility between labs performing BIT measurements.
  • Article
    An interlaboratory study of TEX86 and BIT analysis of sediments, extracts, and standard mixtures
    (John Wiley & Sons, 2013-12-20) Schouten, Stefan ; Hopmans, Ellen C. ; Rosell-Mele, Antoni ; Pearson, Ann ; Adam, Pierre ; Bauersachs, Thorsten ; Bard, Edouard ; Bernasconi, Stefano M. ; Bianchi, Thomas S. ; Brocks, Jochen J. ; Carlson, Laura Truxal ; Castaneda, Isla S. ; Derenne, Sylvie ; Selver, Ayca Dogrul ; Dutta, Koushik ; Eglinton, Timothy I. ; Fosse, Celine ; Galy, Valier ; Grice, Kliti ; Hinrichs, Kai-Uwe ; Huang, Yongsong ; Huguet, Arnaud ; Huguet, Carme ; Hurley, Sarah ; Ingalls, Anitra ; Jia, Guodong ; Keely, Brendan ; Knappy, Chris ; Kondo, Miyuki ; Krishnan, Srinath ; Lincoln, Sara ; Lipp, Julius S. ; Mangelsdorf, Kai ; Martínez-Garcia, Alfredo ; Menot, Guillemette ; Mets, Anchelique ; Mollenhauer, Gesine ; Ohkouchi, Naohiko ; Ossebaar, Jort ; Pagani, Mark ; Pancost, Richard D. ; Pearson, Emma J. ; Peterse, Francien ; Reichart, Gert-Jan ; Schaeffer, Philippe ; Schmitt, Gaby ; Schwark, Lorenz ; Shah, Sunita R. ; Smith, Richard W. ; Smittenberg, Rienk H. ; Summons, Roger E. ; Takano, Yoshinori ; Talbot, Helen M. ; Taylor, Kyle W. R. ; Tarozo, Rafael ; Uchida, Masao ; van Dongen, Bart E. ; Van Mooy, Benjamin A. S. ; Wang, Jinxiang ; Warren, Courtney ; Weijers, Johan W. H. ; Werne, Josef P. ; Woltering, Martijn ; Xie, Shucheng ; Yamamoto, Masanobu ; Yang, Huan ; Zhang, Chuanlun L. ; Zhang, Yige ; Zhao, Meixun ; Sinninghe Damste, Jaap S.
    Two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers (GDGTs) are the TEX86 (TetraEther indeX of 86 carbon atoms) paleothermometer for sea surface temperature reconstructions and the BIT (Branched Isoprenoid Tetraether) index for reconstructing soil organic matter input to the ocean. An initial round-robin study of two sediment extracts, in which 15 laboratories participated, showed relatively consistent TEX86 values (reproducibility ±3–4°C when translated to temperature) but a large spread in BIT measurements (reproducibility ±0.41 on a scale of 0–1). Here we report results of a second round-robin study with 35 laboratories in which three sediments, one sediment extract, and two mixtures of pure, isolated GDGTs were analyzed. The results for TEX86 and BIT index showed improvement compared to the previous round-robin study. The reproducibility, indicating interlaboratory variation, of TEX86 values ranged from 1.3 to 3.0°C when translated to temperature. These results are similar to those of other temperature proxies used in paleoceanography. Comparison of the results obtained from one of the three sediments showed that TEX86 and BIT indices are not significantly affected by interlaboratory differences in sediment extraction techniques. BIT values of the sediments and extracts were at the extremes of the index with values close to 0 or 1, and showed good reproducibility (ranging from 0.013 to 0.042). However, the measured BIT values for the two GDGT mixtures, with known molar ratios of crenarchaeol and branched GDGTs, had intermediate BIT values and showed poor reproducibility and a large overestimation of the “true” (i.e., molar-based) BIT index. The latter is likely due to, among other factors, the higher mass spectrometric response of branched GDGTs compared to crenarchaeol, which also varies among mass spectrometers. Correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of BIT index measurements among laboratories, as well as a substantially improved estimation of molar-based BIT values. This suggests that standard mixtures should be used in order to obtain consistent, and molar-based, BIT values.
  • Article
    Contribution of hurricane-induced sediment resuspension to coastal oxygen dynamics
    (Nature Publishing Group, 2018-10-24) Bianucci, Laura ; Balaguru, Karthik ; Smith, Richard W. ; Leung, L. Ruby ; Moriarty, Julia M.
    Hurricanes passing over the ocean can mix the water column down to great depths and resuspend massive volumes of sediments on the continental shelves. Consequently, organic carbon and reduced inorganic compounds associated with these sediments can be resuspended from anaerobic portions of the seabed and re-exposed to dissolved oxygen (DO) in the water column. This process can drive DO consumption as sediments become oxidized. Previous studies have investigated the effect of hurricanes on DO in different coastal regions of the world, highlighting the alleviation of hypoxic conditions by extreme winds, which drive vertical mixing and re-aeration of the water column. However, the effect of hurricane-induced resuspended sediments on DO has been neglected. Here, using a diverse suite of datasets for the northern Gulf of Mexico, we find that in the few days after a hurricane passage, decomposition of resuspended shelf sediments consumes up to a fifth of the DO added to the bottom of the water column during vertical mixing. Despite uncertainty in this value, we highlight the potential significance of this mechanism for DO dynamics. Overall, sediment resuspension likely occurs over all continental shelves affected by tropical cyclones, potentially impacting global cycles of marine DO and carbon.