Murray James W.

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Murray
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James W.
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  • Preprint
    Thorium speciation in seawater
    ( 2005-07) Santschi, Peter H. ; Murray, James W. ; Baskaran, Mark ; Benitez-Nelson, Claudia R. ; Guo, L. D. ; Hung, C.-C. ; Lamborg, Carl H. ; Moran, S. Bradley ; Passow, Uta ; Roy-Barman, Matthieu
    Since the 1960’s, thorium isotopes occupy a special place in the oceanographer’s toolbox as tracers for determining rates and mechanisms of oceanic scavenging, particle dynamics, and carbon fluxes. Due to their unique and constant production rates from soluble parent nuclides of uranium and radium, their disequilibrium can be used to calculate rates and time scales of sinking particles. In addition, by ratio-ing particulate 234Th (as well, in principle, other Thnuclides) to carbon (and other elements), and linking this ratio to the parent-daughter disequilibrium in the water column, it is possible to calculate fluxes of carbon and other elements. Most of these applications are possible with little knowledge of the dissolved chemical properties of thorium, other than its oxidation state (IV) and tendency to strongly sorb to surfaces, i.e., its “particle- or surface-activity”. However, the use of any tracer is hindered by a lack of knowledge of its chemical properties. Recent observations in the variability of carbon to 234Th ratios in different particle types, as well as of associations of Th(IV) with various marine organic biomolecules has led to the need for a review of current knowledge and what future endeavors should be taken to understand the marine chemistry of thorium.
  • Dataset
    Hydrographic, nutrient, and carbonate system data from R/V Janan cruises in the Arabian Gulf in December 2018 and May 2019
    (Biological and Chemical Oceanography Data Management Office (BCO-DMO). Contact: bco-dmo-data@whoi.edu, 2022-01-27) Murray, James W. ; Yigiterhan, Oguz
    The data show that the average value of pCO2 in surface seawater in the Exclusive Economic Zone of Qatar is supersaturated with respect to the atmosphere. The excess pCO2 reflects a balance between a source due to the impact of increasing T and S on the carbonate system equilibrium constants and a sink due to CO2 loss due to gas exchange from surface seawater after it enters the Gulf through the Strait of Hormuz. Nevertheless, CaCO3 formation was still more important, relative to net biological production, than in the open ocean. The tracer Alk* has values determined by CaCO3 formation and had values suggesting substantial CaCO3 formation. For a complete list of measurements, refer to the full dataset description in the supplemental file 'Dataset_description.pdf'. The most current version of this dataset is available at: https://www.bco-dmo.org/dataset/833517
  • Article
    An inland sea high nitrate-low chlorophyll (HNLC) region with naturally high pCO2
    (John Wiley & Sons, 2015-02-19) Murray, James W. ; Roberts, Emily ; Howard, Evan M. ; O'Donnell, Michael ; Bantam, Cory ; Carrington, Emily ; Foy, Mike ; Paul, Barbara ; Fay, Amanda
    We present a time series of data for temperature, salinity, nitrate, and carbonate chemistry from September 2011 to July 2013 at the University of Washington's Friday Harbor Laboratories. Samples were collected at the Friday Harbor dock and pump house. Seawater conditions at Friday Harbor were high nitrate-low chlorophyll, with average nitrate and pCO2 concentrations of ∼ 25 ± 5 μmol L−1 and ∼ 700 ± 103 μatm (pH 7.80 ± 0.06). Transient decreases in surface water nitrate and pCO2 corresponded with the timing of a spring bloom (April through June). The high nitrate and pCO2 originate from the high values for these parameters in the source waters to the Salish Sea from the California Undercurrent (CU). These properties are due to natural aerobic respiration in the region where the CU originates, which is the oxygen minimum zone in the eastern tropical North Pacific. Alkalinity varies little so the increase in pCO2 is due to inputs of dissolved inorganic carbon (DIC). This increase in DIC can come from both natural aerobic respiration within the ocean and input of anthropogenic CO2 from the atmosphere when the water was last at the sea surface. We calculated that the anthropogenic “ocean acidification” contribution to DIC in the source waters of the CU was 36 μmol L−1. This contribution ranged from 13% to 22% of the total increase in DIC, depending on which stoichiometry was used for C/O2 ratio (Redfield vs. Hedges). The remaining increase in DIC was due to natural aerobic respiration.
  • Thesis
    The interaction of metal ions at the hydrous manganese dioxide-solution interface
    (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1973-06) Murray, James W.
    An experimental study of the interaction of metal ions with the surface of hydrous manganese dioxide has been completed. The results of these experiments have greatly improved our qualitative understanding of the adsorption mechanism and have also provided a means of testing quantitatively the proposal that the concentration of cobalt in manganese rich marine samples is due to adsorption of cobalt from sea water by hydrous manganese dioxide. This study has shown that there are two reasons why manganese dioxide is an efficient scavenger of metal ions from sea water. These are coulombic attraction and specific adsorption. The coulombic attraction is in response to the surface charge that originates because of acid-base reactions at the surface. The surface charge is pH dependent, and the pH of zero point of charge for the hydrous manganese dioxide used in this study was 2.25. The surface charge increases rapidly for pH values greater than the pH of zero point of charge and reaches values of -100 μcoul/cm2 by pH 8.0. However, the high surface charge cannot explain all the adsorption. This is because some metal ions exhibìt a strong specific adsorption on the surface. This specific adsorption is a direct reaction of the metal ions with the surface, releasing one proton from the surface for each metal ion adsorbed. The energy of this specific interaction is frequently greater than the energy of electrostatic attraction. Adsorption on hydrous manganese dioxide and the magnitude of the specific adsorption both increased in the order: Na = K < Mn < Ca < Sr < Ba < Ni < Zn < Mn ≤ Co This suggests that the specific adsorption potential controls the adsorption selectivity of δMn02. An adsorption isotherm was constructed for cobalt, and these data were used to test the hypothesis that the enrichment of cobalt in the suspended matter of the Black Sea and in ferromanganoan sediments from the East Pacific Rise is due to adsorption of cobalt from sea water by manganese dioxide. The calculations indicate that adsorption is a feasible explanation for these examples.