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Published June 2014 | Supplemental Material + Published
Journal Article Open

Rhizon sampler alteration of deep ocean sediment interstitial water samples, as indicated by chloride concentration and oxygen and hydrogen isotopes

Abstract

Despite their potential to inform past ocean salinity, δ^(18)O, and temperature, high-resolution depth profiles of interstitial water chloride concentration and hydrogen and oxygen isotopes exist in very few locations. One of the primary limitations to the recovery of these depth profiles is that traditional interstitial water sampling requires 5–10 cm whole rounds of the sediment core, which has the potential to interfere with stratigraphic continuity. The Rhizon sampler, a nondestructive tool developed for terrestrial sediment interstitial water extraction, has been proposed for efficient and nondestructive sampling of ocean sediment pore waters. However, there exists little documentation on the reliability and performance of Rhizon samplers in deep ocean sediments, particularly in regard to their effect on chloride concentration and oxygen and hydrogen isotopic measurements. We perform an intercomparison of chloride concentration and oxygen and hydrogen isotopic composition in samples taken using traditional squeezing versus those taken with Rhizon samplers. We find that samples taken with Rhizons have positive biases in both chloride concentration and stable isotopic ratios relative to those taken by squeezing water from sediments in a hydraulic press. The measured offsets between Rhizon and squeeze samples are consistent with a combination of absorption by and diffusive fractionation through the hydrophilic membrane of the Rhizon sampler. These results suggest caution is needed when using Rhizons for sampling interstitial waters in any research of processes that leave a small signal-to-noise ratio in dissolved concentrations or isotope ratios.

Additional Information

© 2014 American Geophysical Union. Received 24 FEB 2014; Accepted 26 APR 2014; Accepted article online 2 MAY 2014; Published online 16 JUN 2014. This research was made possible by the Integrated Ocean Drilling Program. We thank all of the IODP Expedition 339 Scientists and Technical Staff for their generous support of our sampling efforts, and particularly Christopher Bennight, Erik Moortgat, Alexandrina Tzanova, and Jin Kyoung Kim for their assistance in the shipboard chemistry laboratory. Richard Murray provided very helpful comments on a draft of this manuscript and Heather Schrum kindly shared the original data used for Figure 1. M.D.M. was supported by the Consortium for Ocean Leadership, both for participation in IODP Expedition 339 and through Post- Expedition Award T339A89. M.D.M. and J.F.A. were supported by the National Science Foundation's P2C2 program through grant 1204211. D.A.H. was supported by the Natural Environment Research Council grant NE/J017922/1. Data for Figures 2–8 are available as supporting information in Table S1.

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Supplemental Material - ggge20468-sup-0001-suppinfo01.doc

Supplemental Material - ggge20468-sup-0002-suppinfotabS1.xls

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August 22, 2023
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