Details:

Journal Title:
Geochimica et Cosmochimica Acta
Personal Author:
Lu, Kaijun ; Li, Xiaolin ; Chen, Hongmei ; Liu, Zhanfei
Lu, Kaijun ; Li, Xiaolin ; Chen, Hongmei ; Liu, Zhanfei Less -
NOAA Program & Office:
OAR (Oceanic and Atmospheric Research)
Description:
Elucidating the chemical structure of dissolved organic matter (DOM) is key to understanding this large yet enigmatic carbon pool. Over the last two decades much progress has been made in assigning exceptionally accurate molecular formulas of DOM owing to the application of ultrahigh resolution mass spectrometry, but little is known about the number of isomers in each molecular formula, a question essentially related to the total number of organic molecules in DOM. Such information is critical for a further understanding of the formation and long-term stability of refractory DOM in the ocean. In this work, we used ion mobility quadrupole time of flight liquid chromatography tandem mass spectrometry (IM Q-TOF LC/MS/MS) to analyze DOM samples collected in different aquatic environments including south Texas rivers, Gulf of Mexico, and South China Sea. Our data showed that generally less than 23% of all detected DOM formulas, which shared a small fraction of common molecules (ca. 12%) detected by direct-infusion Fourier transform ion cyclotron resonance MS, contained structurally distinct isomers (represented by “isomer clusters”). In addition, isomer diversity, in terms of how different the structures are, decreased with degradation in both natural and incubation samples. Specifically, the number of structurally distinct isomers was lower at river mouth and open ocean than coastal waters, where organic matter tends to be fresher due to high primary production; and with depth in water column, isomer diversity of DOM also decreased. Results from a set of incubation experiments also showed that the percentages of riverine DOM molecules that have multiple isomer clusters decreased with time, suggesting that biodegradation decreases the diversity of molecules from an isomer perspective. Overall, these results suggested that isomers, at least in a certain fraction of DOM, are highly constrained, and that degradation decreases its isomeric diversity.
Keywords:
[+]
Geochemistry and Petrology
Source:
Geochimica et Cosmochimica Acta, 308, 353-372
DOI:
https://doi.org/10.1016/j.gca.2021.05.007
ISSN:
0016-7037
Format:
PDF
Publisher:
Elsevier BV
Document Type:
Journal Article
Funding:
Grant no. NA14OAR4170102
Rights Information:
Accepted Manuscript
Compliance:
Library
Main Document Checksum:
[+]
urn:sha256:0c752116d86735252d7e09cd381a505eb71378a5b1298b6c570f155cf10c6122
Download URL:
https://repository.library.noaa.gov/view/noaa/57408/noaa_57408_DS1.pdf
File Type:

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