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  • Simultaneous onboard analysis of seawater dissolved inorganic carbon (DIC) concentration and stable isotope ratio ( δ 13 C‐DIC)
Title: Simultaneous onboard analysis of seawater dissolved inorganic carbon (DIC) concentration and stable isotope ratio ( δ 13 C‐DIC)
Abstract 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 forδ13C‐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 andδ13C‐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 andδ13C‐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 ofδ13C‐DIC onboard of any oceanographic expedition. We evaluated the method's uncertainty, which was 1.2 μmol kg−1for the DIC concentration and 0.03‰ for theδ13C‐DIC value (1σ). An interlaboratory comparison of onboard DIC concentration analysis revealed an average offset of 2.0 ± 3.8 μmol kg−1between CRDS and the coulometry‐based results. The cross‐validation ofδ13C‐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.  more » « less
Award ID(s):
2123768
PAR ID:
10541480
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
Wiley
Date Published:
Journal Name:
Limnology and Oceanography: Methods
ISSN:
1541-5856
Subject(s) / Keyword(s):
dissolved inorganic carbon stable carbon isotope cavity ring-down spectroscopy onboard measurement discrete sample US Atlantic Ocean margin
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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