<p><strong>Abstract.</strong> Regions in the Amazon Basin have been associated with specific biogeochemical processes, but a detailed chemical classification of the abundant and ubiquitous dissolved organic matter (DOM), beyond specific indicator compounds and bulk measurements, has not yet been established. We sampled water from different locations in the Negro, Madeira/Jamari and Tapaj&#243;s River areas to characterize the molecular DOM composition and distribution. Ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) combined with excitation emission matrix (EEM) fluorescence spectroscopy and Parallel Factor Analysis (PARAFAC) revealed a large proportion of ubiquitous DOM but also unique area-specific molecular signatures. Unique to the DOM of the Rio Negro area was the large abundance of high molecular weight, diverse hydrogen-deficient and highly oxidized molecular ions deviating from known lignin or tannin compositions, indicating substantial oxidative processing of these ultimately plant-derived polyphenols indicative of these black waters. In contrast, unique signatures in the Madeira/Jamari area were defined by presumably labile sulfur and nitrogen-containing molecules in this white water river system. Waters from the Tapaj&#243;s confluence area did not show any substantial unique molecular signatures relative to those present in the Rio Madeira and Rio Negro, which implied a lower organic molecular complexity in this clear water tributary. Beside ubiquitous DOM at average H/C and O/C elemental ratios, a distinct and significant unique DOM pool prevailed in the black, white and clear water areas that were also highly correlated with EEM-PARAFAC components and define the frameworks for primary production and other aspects of aquatic life.</p>
<p><strong>Introduction</strong></p> <p>Carbonaceous chondrites (CCs) are fragments of primitive asteroids that are known to contain up to 6 wt.% of organic matter (OM). The insoluble organic matter (IOM) represents 75 to 95 wt.% of the total recovered organic matter. It is therefore the major organic carbon component of CCs. Its Analyses revealed that the IOM is constituted of aromatic units with aliphatic structures bridging aromatic units. Heteroatoms also compose the IOM with mostly oxygen next to nitrogen and sulfur. As a result, the IOM is schematically represented as a cross-linked structure of aromatic and aliphatic units with some heteroatoms, constituting macromolecules. Here, we used a new analytical method to analyse an IOM fraction of Paris meteorite: Laser desorption ionization (LDI) coupled to an ultra-high-resolution mass spectrometer (FT-ICR-MS) on a Paris IOM, which demonstrate that an important molecular diversity with low masses also forms IOM of meteorites.</p> <p><strong>Results</strong></p> <p>The coupling of LDI with a high-resolution mass spectrometer allows obtaining information on the molecular diversity present in this IOM. We indeed reveal new and original information on the molecular composition, diversity and aromaticity of the Paris IOM that can be related to synthesis environments during the early ages of the solar system.</p> <ul> <li>An unprecedented molecular diversity is observed with a wide range of molecular family.</li> <li>Molecules observed present low masses with a high aromaticity and the presence of low amounts of heteroatom such as N, O and S.</li> <li>The molecular cores are based on aromatic rings with various aliphatic branching depending on the molecular family.</li> <li>Pure PAH are also observed, and fullerenes are observed at higher laser energy, suggesting a formation from high PAH structures that could correspond to a part of the IOM macromolecular structure.</li> </ul> <p><strong>Acknowledgements</strong></p> <p>We are grateful to the meteorite collection of the Mus&#233;um National d&#8217;Histoire Naturelle in Paris for providing the sample of the Paris meteorite.</p> <p>N.C. and L.R. thank the European Research Council for funding via the ERC projects PrimChem (grant agreement No. 636829) and HYDROMA (grant agreement No. 819587). This work was supported by the European Regional Development Fund (ERDF) No. HN0001343, the European Union&#8217;s Horizon 2020 Research Infrastructures program (Grant Agreement 731077), the R&#233;gion Normandie, and the Laboratoire d&#8217;Excellence (LabEx) SynOrg (ANR-11-LABX-0029). Access to a CNRS FTICR research infrastructure (FR3624) is gratefully acknowledged. G.D., A.R., and L.R. thank the Agence nationale de la recherche (RAHIIA_SSOM, ANR-16-CE29-0015), the Centre National d&#8217;Etudes Spatiales from its exobiology program, and the Centre National de la Recherche Fran&#231;aise (CNRS, &#8220;Physique et Chimie du Milieu Interstellaire&#8221; (PCMI) and &#8220;Programme National de Plan&#233;tologie&#8221; (PNP) programs) for their financial support..</p> <p><strong>References</strong></p> <p>[1] Unprecedented molecular diversity revealed in meteoritic insoluble organic matter : The Paris meteorite&#8217;s case. G. Danger*, A. Ruf, J. Maillard, J. Hertzog, V. Vinogradoff, P. Schmitt-Kopplin, C. Afonso, N. Carrasco, I. Schmitz-Afonso, L. Le Sergeant d&#8217;Hendecourt, Laurent Remusat. Planetary Science Journal, 2020, 1, 55.</p>
<p><strong>Introduction</strong></p> <p>Carbonaceous chondrites are sources of information witness on the origin of the solar system. Their organic content is conventionally classified as soluble (SOM) and insoluble organic matter (IOM), where the latter represents the majority of their organic content. Relationships between SOM and IOM are still unknown, and their possible link is still debated. Using laboratory experiments, processes possibly at the origin of SOM and IOM are investigated, by assuming that dense molecular ices is one of the sources of organic matter of the solar system. Each organic fraction is analyzed by different analytical technics providing a complete information on their composition and evolution.</p> <p><strong>Results</strong></p> <p>Laboratory experiments are used to simulate the organic matter that could be formed at the surface of grains of dense molecular clouds during the formation and evolution of the solar nebula evolution. Organics formed in laboratory are then considered as analogues to the ones present in protoplanetary grains that could be then incorporated in the forthcoming asteroids and comets. In these interplanetary bodies, they could endure secondary alteration such as aqueous alteration or metamorphism. These simulations from dense molecular clouds to asteroids provide the formation of soluble and insoluble organic matter, which compositions differ depending on local environments.</p> <p>Results on laboratory are then compared to organic content of natural objects that are SOM and IOM of meteorites. This approach provide information on the scenario in which icy grains of dense molecular clouds could have been at the origin of the organic content of interplanetary bodies of the solar systems.</p> <ul> <li>Dense molecular ices are a source of a high molecular diversity.</li> <li>Organics generated from icy grains differ from the ones observed in the SOM of meteorites.</li> <li>Aqueous alteration of organics generated form icy grains simulating secondary alteration inside asteroids present an important evolution that gives molecular similarities with meteorite SOM.</li> <li>The soluble organics formed from icy grains can be a source of insoluble organic matter at the surface of grains.</li> <li>The insoluble organics formed from the soluble organic processing present similarities with the IOM of meteorites.</li> </ul> <p><strong>Acknowledgements</strong></p> <p>We are grateful to the meteorite collection of the Mus&#233;um National d&#8217;Histoire Naturelle in Paris for providing the sample of the Paris meteorite.</p> <p>N.C. and L.R. thank the European Research Council for funding via the ERC projects PrimChem (grant agreement No. 636829) and HYDROMA (grant agreement No. 819587). This work was supported by the European Regional Development Fund (ERDF) No. HN0001343, the European Union&#8217;s Horizon 2020 Research Infrastructures program (Grant Agreement 731077), the R&#233;gion Normandie, and the Laboratoire d&#8217;Excellence (LabEx) SynOrg (ANR-11-LABX-0029). Access to a CNRS FTICR research infrastructure (FR3624) is gratefully acknowledged. G.D., A.R., and L.R. thank the Agence nationale de la recherche (RAHIIA_SSOM, ANR-16-CE29-0015), the Centre National d&#8217;Etudes Spatiales from its exobiology program, and the Centre National de la Recherche Fran&#231;aise (CNRS, &#8220;Physique et Chimie du Milieu Interstellaire&#8221; (PCMI) and &#8220;Programme National de Plan&#233;tologie&#8221; (PNP) programs) for their financial support..</p> <p><strong>References</strong></p> <ul> <li>Unprecedented molecular diversity revealed in meteoritic insoluble organic matter : The Paris meteorite&#8217;s case. G. Danger*, A. Ruf, J. Maillard, J. Hertzog, V. Vinogradoff, P. Schmitt-Kopplin, C. Afonso, N. Carrasco, I. Schmitz-Afonso, L. Le Sergeant d&#8217;Hendecourt, Laurent Remusat. Planetary Science Journal, 2020, 1, 55.</li> <li>Characterization of interstellar/cometary organic residue analogs using very high resolution mass spectrometry, G. Danger*, F-R. Orthous-Daunay, P. de Marcellus, P. Modica, V. Vuitton, F. Duvernay, L. Le Sergeant d&#8217;Hendecourt, R. Thissen, and T. Chiavassa, Geochimica & Cosmochimica Acta, 2013, 118, 184-201</li> <li>Photo and thermochemical evolution of astrophysical ice analogs as a source of soluble and insoluble organic materials in Solar System minor bodies. P. de Marcellus, A. Fresneau, R. Brunetto, G. Danger*, F. Duvernay, C. Meinert, U. J. Meierhenrich, F. Borondics, T. Chiavassa, L. Le Sergeant d&#8217;Hendecourt. Monthly Notices of the Royal Astronomical Society, 2017, 464, 114-120.</li> <li>Cometary materials originating from interstellar ices : clues from laboratory experiments. A. Fresneau, N. Abou Mrad, L. LS d&#8217;Hendecourt, F. Duvernay, L. Flandinet, F-R Orthous-Daunay, V. Vuitton, R. Thissen, T. Chiavassa, G. Danger*. The Astrophysical Journal, 2017, 837, 168.</li> <li>Laboratory experiments to unveil the molecular reactivity occurring during the processing of ices in the protosolar nebula. T. Gautier*, G. Danger*, O. Mousis, F. Duvernay, V. Vuitton, L. Flandinet, R. Thissen, F.-R. Orthous-Daunay, A. Ruf, T. Chiavassa, L. S. d&#8217;Hendecourt. Earth and Planetary Science Letters, 2020, 531, 116011</li> <li>Exploring the link between molecular cloud ices and chondritic organic matter in laboratory. G. Danger*, V. Vinogradoff*, M. Matzka, J-C. Viennet, L. Remusat, S. Bernard, A. Ruf, L. Le Sergeant d&#8217;Hendecourt and P. Schmitt-Kopplin. Nature Communication, 2021, 12, 3538</li> <li>The transition from soluble to insoluble organic matter in interstellar ice analogs and meteorites, G. Danger , A. Ruf, T. Javelle, J. Maillard 5, V. Vinogradoff, Carlos Afonso, Isabelle Schmitz-Afonso, L. Remusat, Z. Gabelica, P. Schmitt-Kopplin, 2022, submitted.</li> </ul>
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