Vertical profiles of arsenic and arsenic species transformations in deep-sea sediment, Nankai Trough, offshore Japan

Harue Masuda, Haruka Yoshinishi, Shigeshi Fuchida, Tomohiro Toki, Emilie Even

Research output: Contribution to journalArticle

Abstract

Concentrations of arsenic (As) and its chemical forms were determined on deep-sea sediments drilled at three sites of Nankai Trough, off the Kii Peninsula, Japan. Those sediments were analyzed to document the behavior of As in relation to methane hydrate formation and the deep biosphere. The analytical results showed the total As concentration of interstitial water (IW) and squeezed cake (SC) ranged from 0.9 to 380 ppb and from 3 to 14 ppm (average, 6.4 ppm), respectively. The sediments from Site C0002, of which sediment column was the longest down to 2200 m below the seafloor (mbsf) among the studied three drilling sites, were analyzed for the host phase transformation of As. The total concentration of As of IW and SC from 200 to 500 mbsf, where methane hydrate zone was included, was higher than those from the uppermost 200 m. Concentration of As was ultimately controlled by pH. Also, organoarsenicals, such as methylarsonic acid (MMA) and arsenobetaine (AsB), were detected in the sediment column, implying that these organoarsenicals appeared in relation to the in situ microbial activities. These observations suggest that As becomes mobilized directly or indirectly as a result of microbial activity in deep-sea sediments. [Figure not available: see fulltext.]

Original languageEnglish
Article number28
JournalProgress in Earth and Planetary Science
Volume6
Issue number1
DOIs
Publication statusPublished - 2019 Dec 1
Externally publishedYes

Keywords

  • Convergent margin
  • Deep biosphere
  • Nankai Trough
  • Organoarsenical

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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