Affiliation:
1. GEOMAR Helmholtz Centre for Ocean Research Kiel Kiel Germany
2. Department of Earth and Environmental Sciences Ben‐Gurion University Beer Sheva Israel
3. The Interuniversity Institute for Marine Sciences Eilat Israel
4. University of Southern California Los Angeles CA USA
5. Department of Marine Chemistry and Geochemistry Woods Hole Oceanographic Institution Woods Hole MA USA
6. Department of Earth Sciences Carleton University Ottawa ON Canada
7. Department of Earth, Environmental, and Planetary Sciences Rice University Houston TX USA
8. Department of Geology and Planetary Sciences California Institute of Technology Pasadena CA USA
9. Department of Earth Sciences University of Cambridge Cambridge UK
Abstract
AbstractGeochemical analyses of trace elements in the ocean water column have suggested that pelagic clay‐rich sediments are a major source of various elements to bottom‐waters. However, corresponding high‐quality measurements of trace element concentrations in porewaters of pelagic clay‐rich sediments are scarce, making it difficult to evaluate the contributions from benthic processes to global oceanic cycles of trace elements. To bridge this gap, we analyzed porewater and bulk sediment concentrations of vanadium, chromium, cobalt, nickel, copper, arsenic, molybdenum, barium and uranium, as well as concentrations of the major oxidants nitrate, manganese, iron, and sulfate in the top 30 cm of cores collected along a transect from Hawaii to Alaska. The data show large increases in porewater concentrations of vanadium, manganese, cobalt, nickel, copper, and arsenic within the top cm of the sediment, consistent with the release of these elements from remineralized organic matter. The sediments are a sink for sulfate, uranium, and molybdenum, even though conditions within the sampled top 30 cm remain aerobic. Porewater chromium concentrations generally increase with depth due to release from sediment particles. Extrapolated to the global aerial extent of pelagic clay sediment, the benthic fluxes in mol yr−1 are Ba 3.9 ± 3.6 × 109, Mn 3.4 ± 3.5 × 108, Co 2.6 ± 1.3 × 107, Ni 9.6 ± 8.6 × 108, Cu 4.6 ± 2.4 × 109, Cr 1.7 ± 1.1 × 108, As 6.1 ± 7.0 × 108, V 6.0 ± 2.5 × 109. With the exception of vanadium, calculated fluxes across the sediment–water interface are consistent with the variability in bottom‐water concentrations and ocean residence time of the studied elements.
Funder
National Science Foundation
Publisher
American Geophysical Union (AGU)
Subject
Atmospheric Science,General Environmental Science,Environmental Chemistry,Global and Planetary Change