Simultaneous onboard analysis of seawater dissolved inorganic carbon (DIC) concentration and stable isotope ratio (δ13C‐DIC)

Details

• Journal Title:
  Limnology and Oceanography: Methods
• Personal Author:
  Sun, Zhentao ; Li, Xinyu ; Ouyang, Zhangxian ; Featherstone, Charles ; Atekwana, Eliot A. ; Hussain, Najid ; Cai, Wei‐Jun
• NOAA Program & Office:
  NOS (National Ocean Service) ; OAR (Oceanic and Atmospheric Research) ; AOML (Atlantic Oceanographic and Meteorological Laboratory) ; CICOES (Cooperative Institute for Climate, Ocean and Ecosystem Studies)
• Description:
  Dissolved inorganic carbon (DIC) and its stable carbon isotope (δ13C‐DIC) are valuable parameters for studying the aquatic carbon cycle and quantifying ocean anthropogenic carbon accumulation rates. However, the potential of this coupled pair is underexploited as only 15% or less of cruise samples have been analyzed for δ13C‐DIC because the traditional isotope analysis is labor‐intensive and restricted to onshore laboratories. Here, we improved the analytical precision and reported the protocol of an automated, efficient, and high‐precision method for ship‐based DIC and δ13C‐DIC analysis based on cavity ring‐down spectroscopy (CRDS). We also introduced a set of stable in‐house standards to ensure accurate and consistent DIC and δ13C‐DIC measurements, especially on prolonged cruises. With this method, we analyzed over 1600 discrete seawater samples over a 40‐d cruise along the North American eastern ocean margin in summer 2022, representing the first effort to collect a large dataset of δ13C‐DIC onboard of any oceanographic expedition. We evaluated the method's uncertainty, which was 1.2 μmol kg−1 for the DIC concentration and 0.03‰ for the δ13C‐DIC value (1σ). An interlaboratory comparison of onboard DIC concentration analysis revealed an average offset of 2.0 ± 3.8 μmol kg−1 between CRDS and the coulometry‐based results. The cross‐validation of δ13C‐DIC in the deep‐ocean data exhibited a mean difference of only −0.03‰ ± 0.07‰, emphasizing the consistency with historical data. Potential applications in aquatic biogeochemistry are discussed.
• Source:
  Limnology and Oceanography: Methods, 22(11), 862-875
• DOI:
  https://doi.org/10.1002/lom3.10642
• ISSN:
  1541-5856 ; 1541-5856
• Format:
  pdf
• Publisher:
  Wiley
• Document Type:
  Journal Article-Accepted Manuscript
• Funding:
  Grant no. NA21NOS0120096 ; Grant no. NA20OAR4320271
• Rights Information:
  Accepted Manuscript
• Rights Statement:
  The NOAA IR provides access to this content under the authority of the government's retained license to distribute publications and data resulting from federal funding. While users may legally access this content, the copyright owners retain rights that govern the reproduction, redistribution, and re-use of this work. The user is solely responsible for complying with applicable copyright law.
• Compliance:
  Library
• Main Document Checksum:
  urn:sha-512:50f7dd796fd6334828e079dc4c6fad012d5f3986cf91cd4edb64b9e0b20c6fc42e7e819b8e345715f46373d7d2f7bee26f70544d2d569316bc1725a9c023bea3
• Download URL:
  https://repository.library.noaa.gov/view/noaa/67883/noaa_67883_DS1.pdf
• File Type:
  [PDF - 4.26 MB ]