The composition and diagenesis of interstitial solutions—I. Fluxes across the seawater-sediment interface in the Atlantic Ocean |
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| Authors: | FL Sayles |
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| Institution: | Department of Chemistry, Woods Hole Oceanographic Institution, Woods Hole, MA 02543, U.S.A. |
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| Abstract: | Studies of the composition of interstitial solutions of marine sediments have been carried out utilizing in situ sampling techniques. Samples were obtained from the Caribbean, North Atlantic and South Atlantic. In virtually all cases, diagenesis has led to the uptake of Mg2+ and K+ and the release of Ca2+, HCO?3 and Na+ by the solid phases. SO2?4 is slightly enriched at nearly all stations, reduction being observed only at continental margin stations. Cl? is conservative within experimental precision.The reactions controlling the fluxes of most components across the water-sediment interface occur almost entirely in the upper 100 cm of sediment. Contributions of Mg 2+, Ca 2+, K+ and HCO?3 from below 100 cm amount to less than 15% of the calculated fluxes across the interface. Reactions in the upper 30 cm account for 70–90% of the fluxes of these components across the interface. Only Na+ has a deep source, gradients often being linear in the upper 2m of sediment.Calculated fluxes across the sediment-water interface are of the same order of magnitude as river inputs for the components studied. In the case of Mg2+ and K +, 60–100% of the river input can be balanced by diagenetic uptake in the sediment. For Ca2+ and HCO?3 additions to seawater augment the river supply by 25–50%. When the uptake of Mg2+ and K+ by the sediment is calculated by integrating the fluxes across the interface, calculated concentrations of both of these elements are inconsistent with published average concentrations for the types of sediment studied. |
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