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  • 1
    Publication Date: 2022-01-13
    Description: Dissolved organic matter (DOM) is an important component in marine and freshwater environments and plays a fundamental role in global biogeochemical cycles. In the past, optical and molecular-level analytical techniques evolved and improved our mechanistic understanding about DOM fluxes. For most molecular chemical techniques, sample desalting and enrichment is a prerequisite. Solid-phase extraction has been widely applied for concentrating and desalting DOM. The major aim of this study was to constrain the influence of sorbent loading on the composition of DOM extracts. Here, we show that increased loading resulted in reduced extraction efficiencies of dissolved organic carbon (DOC), fluorescence and absorbance, and polar organic substances. Loading-dependent optical and chemical fractionation induced by the altered adsorption characteristics of the sorbent surface (styrene divinylbenzene polymer) and increased multilayer adsorption (DOM self-assembly) can fundamentally affect biogeochemical interpretations, such as the source of organic matter. Online fluorescence monitoring of the permeate flow allowed to empirically model the extraction process and to assess the degree of variability introduced by changing the sorbent loading in the extraction procedure. Our study emphasizes that it is crucial for sample comparison to keep the relative DOC loading (DOCload [wt %]) on the sorbent always similar to avoid chemical fractionation.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 2
    Publication Date: 2022-09-23
    Description: Understanding the biogeochemical transformation of dissolved organic matter (DOM) across fluvial networks will ultimately help to predict anthropogenic influences. To date, few studies have evaluated the anthropogenic impact on the spatial and temporal changes of DOM composition in large river systems. Here, FT-ICR-MS combined with excitation-emission matrix spectroscopy (EEMs) and biomarkers were applied to resolve chemical differences of DOM collected from the Changjiang basin at different hydrological and environmental conditions. PCA and cluster analysis illustrated that samples collected from lake systems and northern and southern tributaries differed from the two batches of main stream samples, particularly due to higher contribution of nitrogen and sulfur containing compounds. Correlation of land-use information along the tributaries with different PCA loadings indicated that agricultural, forest and wetland areas and wastewater discharge control the composition of DOM within these subregions. Higher heteroatom content (especially CHONx) in the low discharge period (2009) may be contributed by paddy soil leaching into groundwater. The relative peak magnitude of sulfur containing formulas was elevated during flood season (2010), which may be related to pollutions in areas of high population density. In addition, lignin phenol concentrations were higher in the flood season because of elevated soil erosion. Consequently, land use and human activities can strongly alter the quality and composition of DOM in watersheds flowing through densely populated regions, which may also impact or influence the riverine carbon flux in anthropogenically disturbed river systems.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 3
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Kharbush, J. J., Close, H. G., Van Mooy, B. A. S., Arnosti, C., Smittenberg, R. H., Le Moigne, F. A. C., Mollenhauer, G., Scholz-Boettcher, B., Obreht, I., Koch, B. P., Becker, K. W., Iversen, M. H., & Mohr, W. Particulate organic carbon deconstructed: molecular and chemical composition of particulate organic carbon in the ocean. Frontiers in Marine Science, 7, (2020): 518, doi:10.3389/fmars.2020.00518.
    Description: The dynamics of the particulate organic carbon (POC) pool in the ocean are central to the marine carbon cycle. POC is the link between surface primary production, the deep ocean, and sediments. The rate at which POC is degraded in the dark ocean can impact atmospheric CO2 concentration. Therefore, a central focus of marine organic geochemistry studies is to improve our understanding of POC distribution, composition, and cycling. The last few decades have seen improvements in analytical techniques that have greatly expanded what we can measure, both in terms of organic compound structural diversity and isotopic composition, and complementary molecular omics studies. Here we provide a brief overview of the autochthonous, allochthonous, and anthropogenic components comprising POC in the ocean. In addition, we highlight key needs for future research that will enable us to more effectively connect diverse data sources and link the identity and structural diversity of POC to its sources and transformation processes.
    Description: We thank the Hanse Institute for Advanced Studies (HWK) and the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) project number 422798570, as well as the Geochemical Society, for funding which made the workshop possible. CA was additionally supported by OCE-1736772. BV was additionally supported by NSF OCE-1756254.
    Keywords: Marine particles ; Water column ; Phytoplankton ; Marine microbes ; Structural analysis ; Organic matter characterization ; Biomarkers
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 4
    Publication Date: 2022-10-26
    Description: © The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Steen, A. D., Kusch, S., Abdulla, H. A., Cakic, N., Coffinet, S., Dittmar, T., Fulton, J. M., Galy, V., Hinrichs, K., Ingalls, A. E., Koch, B. P., Kujawinski, E., Liu, Z., Osterholz, H., Rush, D., Seidel, M., Sepulveda, J., & Wakeham, S. G. Analytical and computational advances, opportunities, and challenges in marine organic biogeochemistry in an era of "Omics". Frontiers in Marine Science, 7, (2020): 718, doi:10.3389/fmars.2020.00718.
    Description: Advances in sampling tools, analytical methods, and data handling capabilities have been fundamental to the growth of marine organic biogeochemistry over the past four decades. There has always been a strong feedback between analytical advances and scientific advances. However, whereas advances in analytical technology were often the driving force that made possible progress in elucidating the sources and fate of organic matter in the ocean in the first decades of marine organic biogeochemistry, today process-based scientific questions should drive analytical developments. Several paradigm shifts and challenges for the future are related to the intersection between analytical progress and scientific evolution. Untargeted “molecular headhunting” for its own sake is now being subsumed into process-driven targeted investigations that ask new questions and thus require new analytical capabilities. However, there are still major gaps in characterizing the chemical composition and biochemical behavior of macromolecules, as well as in generating reference standards for relevant types of organic matter. Field-based measurements are now routinely complemented by controlled laboratory experiments and in situ rate measurements of key biogeochemical processes. And finally, the multidisciplinary investigations that are becoming more common generate large and diverse datasets, requiring innovative computational tools to integrate often disparate data sets, including better global coverage and mapping. Here, we compile examples of developments in analytical methods that have enabled transformative scientific advances since 2004, and we project some challenges and opportunities in the near future. We believe that addressing these challenges and capitalizing on these opportunities will ensure continued progress in understanding the cycling of organic carbon in the ocean.
    Description: The Hanse-Wissenschaftskolleg Delmenhorst, Germany, sponsored the “Marine Organic Biogeochemistry” workshop in April 2019, of which this working group report was a part. The workshop was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – project number: 422798570. The Geochemical Society provided additional funding for the conference. AS was supported by DOE grant DE-SC0020369.
    Keywords: Chemometrics ; Natural marine organic matter ; FT-ICR-MS ; Analytical challenges ; HR-NMR ; Marine organic biogeochemistry
    Repository Name: Woods Hole Open Access Server
    Type: Article
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