Guillaume Paris

@article{Dasari_etal2022,

title = {Sulfur-isotope anomalies recorded in Antarctic ice cores as a potential proxy for tracing past ozone layer depletion events},

author = {S. Dasari and G. Paris and J. Charreau and J. Savarino},

doi = {10.1093/pnasnexus/pgac170},

year  = {2022},

date = {2022-01-01},

journal = {PNAS Nexus},

volume = {1},

pages = {1--9},

abstract = {Changes in the cosmic-ray background of the Earth can impact the ozone layer. High-energy cosmic events [e.g. supernova (SN)] or rapid changes in the Earth’s magnetic field [e.g. geomagnetic Excursion (GE)] can lead to a cascade of cosmic rays. Ensuing chemical reactions can then cause thinning/destruction of the ozone layer---leading to enhanced penetration of harmful ultraviolet (UV) radiation toward the Earth’s surface. However, observational evidence for such UV ‘‘windows’’ is still lacking. Here,we conduct a pilot study and investigate this notion during two well-known events: the multiple SN event (≈10 kBP) and the Laschamp GE event (≈41 kBP).We hypothesize that ice-core-$Delta$33S records---originally used as volcanic fingerprints---can reveal UV-induced background-troposphericphotochemical imprints during such events. Indeed, we find nonvolcanic S-isotopic anomalies ($Delta$33S ≠ 0texttenthousand) in background Antarctic ice-core sulfate during GE/SN periods, thereby confirming our hypothesis. This suggests that ice-core-$Delta$33S records can serve as a proxy for past ozone-layer-depletion events},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Laurent_etal2021,

title = {Epigenic vs. hypogenic speleogenesis governed by H2S/CO2 hydrothermal input and Quaternary icefield dynamics (NE French Pyrenees)},

author = {D. Laurent and C. Durlet and G. Barr\'{e} and P. Sorriaux and P. Audra and P. Cartigny and C. Carpentier and G. Paris and P. Collon and T. Rigaudier and J. Pironon and E. C. Gaucher},

doi = {10.1016/j.geomorph.2021.107769},

year  = {2021},

date = {2021-01-01},

journal = {Geomorphology},

volume = {387},

pages = {107769},

abstract = {Hypogenic caves, linked to carbonate rock dissolution due to CO2- and H2S-rich ascending deep waters, represent more than 10% of karstic networks worldwide; a proportion that increases as these systems are better constrained. However, interaction between hypogenic and epigenic processes is still poorly understood, especially since the subsequent invasion of surface water often obliterates the morphological and mineral markers of hypogenic activities. The Ari`ege Valley (French Pyrenean foothills) hosts significant karstic networks epigenically reworked by several episodes of glacier meltwater penetration during the successive coverage of Quaternary icefields. Among these karstic systems, the Vapeur and Ermite caves were probably initiated by a hypogenic component during the Miocene. In particular, multiple-S, Sr, H, C, and O isotopes of thermo-mineral waters and calcite-sulfate speleothems confirm that hydrothermal fluids reached the caves, and subsequently interacted with Quaternary glacial epigenic phases. Deep fluids conveyed CO2 and H2S, both produced from the thermochemical reduction of Triassic evaporites at depth. H2S oxidation and CO2 hydration in the cave atmosphere, above the water table, created sulfuric and carbonic acids responsible for an intense karstification. Interpretation of isotopic data, together with a geomorphological, mineralogical and textural study of cave minerals, allow us to propose a speleogenetic model in which the respective impact of epigenic and hypogenic processes was driven by base-level changes during successive Quaternary glacial/interglacial epochs: (i) during glacial periods, invasion of glacier meltwater within the karst led to the dilution of the hydrothermal water, and was responsible for an textquotelefttextquoteleftepigenic mechanical-dominanttextquoterighttextquoteright speleogenesis through water-related abrasion; (ii) interglacial epochs were marked by base-level drops and the establishment of a vadose domain in caves, favoring the widening of karstic conduits through carbonic and sulfuric acid condensation-corrosion during thermal water degassing. This textquotelefttextquotelefthypogenic chemical-dominanttextquoterighttextquoteright speleogenesis was active until a new advance of glaciers, and this cycle occurred several times.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Barkan_etal2020,

title = {Sulfur isotope fractionation between aqueous andcarbonate-associated sulfate in abiotic calcite and aragonite},

author = {Y. Barkan and G. Paris and S. M. Webb and J. F. Adkins and I. Halevy},

doi = {10.1016/j.gca.2020.03.022},

year  = {2020},

date = {2020-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {280},

pages = {317--339},

abstract = {Sulfate (SO42-) incorporated into calcium carbonate minerals enables measurements of sulfur (S) isotope ratios in carbon-ate rocks. This Carbonate Associated Sulfate (CAS) in marine carbonate minerals is thought to faithfully represent the S iso-tope composition of the seawater sulfate incorporated into the mineral, with little or no S isotope fractionation in the process.However, comparison between different calcifying species reveals both positive and negative S isotope fractionation betweenCAS and seawater sulfate, and a large range of S isotope ratios can be found within a single rock sample, depending on thecomponent measured. To better understand the isotopic effects associated with sulfate incorporation into carbonate minerals,we precipitated inorganic calcite and aragonite over a range covering more than two orders of magnitude of sulfate concen-tration and precipitation rate. Coupled measurements of CAS concentration, S isotope composition and X-ray absorptionnear-edge spectra (XANES) permit characterization and explanation of the observed dependence of S isotope fractionationbetween CAS and aqueous sulfate (CAS-SO42-isotope fractionation) on sulfate concentration and precipitation rate. In arag-onite, the CAS-SO42
isotope fractionation is 1.0 textpm 0.3texttenthousandand independent of the sulfate (and CAS) concentration. In contrast,the CAS-SO42-isotope fractionation in calcite covaries strongly with the sulfate concentration and weakly with the precipi-tation rate, between values of 1.3 textpm 0.1 and 3.1 textpm 0.6texttenthousand. We suggest that the correlation between aqueous sulfate concentra-tion and CAS-SO42-isotope fractionation in calcite reflects a dependence of the equilibrium S isotope fractionation on theconcentration of CAS, through the effect of the sulfate impurity on the carbonate mineraltextquoterights energetic state.\'{O}2020 Elsevier Ltd. All rights reserved.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Bekaert_etal2020,

title = {Xenon isotopes in Archean and Proterozoic insoluble organic matter: A robust indicator of syngenecity?},

author = {D. V. Bekaert and M. W. Broadley and F. Delarue and Z. Druzhinina and G. Paris and F. Robert and K. Sugitani and B. Marty},

doi = {10.1016/j.precamres.2019.105505},

year  = {2020},

date = {2020-01-01},

journal = {Precambrian Research},

volume = {336},

pages = {105505},

abstract = {Insoluble organic materials (kerogens) isolated from ancient sedimentary rocks provide unique insights into the evolution of early life. However, establishing whether these kerogens are indeed syngenetic with the deposition of associated sedimentary host rocks, or contain contribution from episodes of secondary deposition, is not straightforward. Novel geochemical criterions are therefore required to test the syngenetic origin of Archean organic materials. On the one hand, the occurrence of mass-independent fractionation of sulphur isotopes (MIF-S) provides a tool to test the Archean origin of ancient sedimentary rocks. Determining the isotope composition of sulphur within kerogens whilst limiting the contribution from associated minerals (e.g., nano-pyrites) is however challenging. On the other hand, the Xe isotope composition of the Archean atmosphere has been shown to present enrichments in the light isotopes relative to its modern composition, together with a mono-isotopic deficit in 129Xe. Given that the isotopic composition of atmospheric Xe evolved through time by mass dependent fractionation (MDF) until textasciitilde2.5 to 2.0 Ga, the degree of MDF of Xe isotopes trapped in kerogens could provide a time stamp for the last chemical equilibration between organic matter and the atmosphere. However, the extent to which geological processes could affect the signature of Xe trapped in ancient kerogen remains unclear. In this contribution, we present new Ar, Kr and Xe isotopic data for four kerogens isolated from 3.4 to 1.8 Gy-old cherts and confirm that Xe isotopes from the Archean atmosphere can be retained within kerogens. However, new Xe-derived model ages are lower than expected from the ages of host rocks, indicating that initially trapped Xe components were at least partially lost and/or mixed together with some Xe carried out by younger generations of organic materials, therefore complicating the Xe-based dating method. Whilst non-null $Delta$33S values and 129Xe deficits relative to modern atmosphere constitute reliable imprints from the Archean atmosphere, using Xe isotopes to provide information on the syngenetic origin of ancient organic matter appears to be a promising -- but not unequivocal -- tool that calls for further analytical development.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Paris_etal2020,

title = {Deposition of sulfate aerosols with positive D33S in the Neoarchean},

author = {G. Paris and W. W. Fischer and J. E. Johnson and S. M. Webb and T. M. Present and A. L. Sessions and J. F. Adkins},

doi = {10.1016/j.gca.2020.06.028},

year  = {2020},

date = {2020-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {285},

pages = {1--20},

abstract = {Anomalous sulfur isotope compositions present in Archean rocks have been intensely scrutinized over the last 20 years because they record key aspects of Earthtextquoterights atmospheric composition prior to the appearance of free molecular oxygen ca. 2.3 billion years ago. These isotopic compositions can be described as mass anomalous fractionations (MAF) and are produced in the atmosphere as UV light interacts with SO2 molecules. Most interpretations suggest that atmospheric processes generate a reduced S-phase with a positive (33S-enriched) MAF signature, as measured in pyrites, and an oxidized S-phase with a negative anomaly, as measured in bedded barite deposits. However, recent data for carbonate-associated sulfate (CAS) --- a direct proxy for the isotopic composition of sulfur from seawater sulfate --- in Neoarchean rocks showed no such negative values, but rather the opposite. To understand if the positive MAF anomalies we measured in Neoarchean CAS reflect secondary processes (diagenetic, metamorphic, handling) instead of original signals of Archean seawater sulfate, we collected additional sample suites with various degrees of preservation and metamorphic alteration across the Campbellrand-Malmani platform in South Africa. Results illustrate that within this comprehensive suite, less-altered samples all contain positive MAF values while secondary processes tend to either remove CAS from the sample and/or decrease the 33S-enrichment. This positive MAF signal in sulfate is therefore reasonably interpreted as a primary depositional origin, and implies that the assumption that sulfate always carries a negative MAF anomaly throughout the Archean rock record needs to be reconsidered. Our CAS observations suggest that future experiments and calculations should also consider atmospheric and/or sulfur cycling processes that can produce oxidized sulfur with a positive MAF signature.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Present_etal2019,

title = {Diagenetic controls on the isotopic composition of carbonateassociated sulphate in the Permian Capitan Reef Complex, West Texas},

author = {T. M. Present and M. Gutierrez and G. Paris and C. Kerans and J. P. Grotzinger and J. F. Adkins},

doi = {10.1111/sed.12615},

year  = {2019},

date = {2019-01-01},

journal = {Sedimentology},

abstract = {Late Palaeozoic-age strata from the Capitan Reef in west Texas showfacies dependent heterogeneity in the sulphur isotopic composition of carbonate associated sulphate, which is trace sulphate incorporated into carbonate minerals that is often used to reconstruct the sulphur isotopic composition of ancient seawater. However, diagenetic pore fluid processes may influence the sulphur isotopic composition of carbonate-associated sulphate. These processes variously modify the sulphur isotopic composition of incorporated sulphate from syndepositional seawater in shelf crest, outer shelf, shelf margin and slope depositional settings. This study used a new multicollector inductively- coupled plasma mass spectrometry technique to determine the sulphur isotopic composition of samples of individual depositional and diagenetic textures. Carbonate rocks representing peritidal facies in the Yates and Tansill formations preserve the sulphur isotopic composition of Guadalupian seawater sulphate despite alteration of the carbon and oxygen isotopic compositions by meteoric and dolomitizing diagenetic processes. However, sulphur isotopic data indicate that limestones deposited in reef and slope facies in the Capitan and Bell Canyon formations largely incorporate sulphate from anoxic marinephreatic pore fluids isotopically modified from seawater by microbial sulphate reduction, despite generally preserving the carbon and oxygen isotopic compositions of Permian seawater. Some early and all late meteoric calcite cements have carbonate-associated sulphate with a sulphur isotopic composition distinct from that of Permian seawater. Detailed petrographic and sedimentary context for carbonate-associated sulphate analyses will allow for improved reconstructions of ancient seawater composition and diagenetic conditions in ancient carbonate platforms. The results of this study indicate that carbonate rocks that diagenetically stabilize in high-energy environments without pore fluid sulphate gradients can provide a robust archive of ancient seawatertextquoterights sulphur isotopic composition.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Burke_etal2018,

title = {Sulfur isotopes in rivers: Insights into global weathering budgets, pyrite oxidation, and the modern sulfur cycle},

author = {Burke and A. and T. M. Present and G. Paris and E. C. M. Rae and B. H. Sandilands and J. Gaillardet and B. Peucker-Ehrenbrink and W. W. Fischer and J. W. McClelland and R. G. M. Spencer and B. M. Voss and J. F. Adkins},

doi = {https://doi.10.1016/j.epsl.2018.05.022},

year  = {2018},

date = {2018-01-01},

journal = {Earth and Planetary Science Letters},

volume = {496},

pages = {168--177},

abstract = {The biogeochemical sulfur cycle is intimately linked to the cycles of carbon, iron, and oxygen, and plays an important role in global climate via weathering reactions and aerosols. However, many aspects of the modern budget of the global sulfur cycle are not fully understood. We present new $delta$34S measurements on sulfate from more than 160 river samples from different geographical and climatic regions---more than 46% of the worldtextquoterights freshwater flux to the ocean is accounted for in this estimate of the global riverine sulfur isotope budget. These measurements include major rivers and their tributaries, as well as time series, and are combined with previously published data to estimate the modern flux-weighted global riverine $delta$34S as 4.4 textpm4.5textdegree/textdegreetextdegree(V-CDT), and 4.8 textpm4.9textdegree/textdegreetextdegreewhen the most polluted rivers are excluded. The sulfur isotope data, when combined with major anion and cation concentrations, allow us to tease apart the relative contributions of different processes to the modern riverine sulfur budget, resulting in new estimates of the flux of riverine sulfate due to the oxidative weathering of pyrites (1.3 textpm0.2TmolS/y) and the weathering of sedimentary sulfate minerals (1.5 textpm0.2 Tmol S/y). These data indicate that previous estimates of the global oxidative weathering of pyrite have been too low by a factor of two. As pyrite oxidation coupled to carbonate weathering can act as a source of CO2to the atmosphere, this global pyrite weathering budget implies that the global CO2weathering sink is overestimated. Furthermore, the large range of sulfur isotope ratios in modern rivers indicates that secular changes in the lithologies exposed to weathering through time could play a major role in driving past variations in the $delta$34S value of seawater.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Dellinger_etal2018,

title = {The Li isotope composition of marine biogenic carbonates: Patterns and mechanisms},

author = {M. Dellinger and A. J. West and G. Paris and J. F. Adkins and P. A. E. Pogge von Strandmann and C. V. Ullmann and R. A. Eagle and P. Freitas and M. L. Bagard and J. B. Ries and F. A. Corsetti and A. Perez-Huerta and A. R. Kampf},

doi = {10.1016/j.gca.2018.03.014},

year  = {2018},

date = {2018-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {236},

pages = {315--335},

abstract = {Little is known about the fractionation of Li isotopes during formation of biogenic carbonates, which form the most promising geological archives of past seawater composition. Here we investigated the Li isotope composition (d7Li) and Li/Ca ratios of organisms that are abundant in the Phanerozoic record: mollusks (mostly bivalves), echinoderms, and brachiopods. The measured samples include (i) modern calcite and aragonite shells from various species and natural environ-ments (13 mollusk samples, 5 brachiopods and 3 echinoderms), and (ii) shells from mollusks grown under controlled conditions at various temperatures. When possible, the mollusk shell ultrastructure was micro-sampled in order to assessintra-shell heterogeneity. In this paper, we systematically characterize the influence of mineralogy, temperature, and biological processes on the d7Li and Li/Ca of these shells and compare with published data for other taxa (foraminifera and corals).Aragonitic mollusks have the lowest d7Li, ranging from +16 to +22texttenthousand, echinoderms have constant d7Li of about +24texttenthousand, brachiopods have d7Li of +25 to +28 texttenthousand, and finally calcitic mollusks have the largest range and highest d7Li values, ranging from +25texttenthousand to +40texttenthousand. Measured brachiopods have similar d7Li compared to inorganic calcite precipitated from seawater (d7Li of +27 to +29texttenthousand), indicating minimum influence of vital effects, as also observed for other isotope systems and making them a potentially viable proxy of past seawater composition. Calcitic mollusks, on the contrary, are not a good archive for seawater paleo--d7Li because many samples have significantly higher d7Li values than inorganic calcite and display large interspecies variability, which suggests large vital effects. In addition, we observe very large intra-shell variability, in particular for mixed calcite-aragonite shells (over 20texttenthousand variability), but also in mono-mineralic shells (up to 12texttenthousand variability). Aragonitic bivalves have less variable d7Li (7texttenthousand variability) compared to calcitic mollusks, but with significantly lower d7Li comparedto inorganic aragonite, indicating the existence of vital effects. Bivalves grown at various temperatures show that temperature has only a minor influence on fractionation of Li isotopes during shell precipitation. Interestingly, we observe a strong correlation (R2= 0.83) between the Li/Mg ratio in bivalve Mytilus edulisand temperature, with potential implications for paleo-temperature reconstructions.Finally, we observe a negative correlation between the d7Li and both the Li/Ca and Mg/Ca ratio of calcite mollusks, which we relate to biomineralization processes. To explain this correlation, we propose preferential removal of 6Li from the calci-fication site of calcite mollusks by physiological processes corresponding to the regulation of the amount of Mg in the calcifying medium. We calculate that up to 80% of the initial Li within the calcification site is removed by this process, leading to high d7Li and low Li/Ca in some calcite mollusk specimens. Collectively, these results suggest that Mg (and thus [Li]) is strongly biologically controlled within the calcifying medium of calcite mollusks.Overall, the results of this study show that brachiopods are likely to be suitable targets for future work on the determination of paleo-seawater Li isotope composition---an emerging proxy for past weathering and hydrothermal processes.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Guinoiseau_etal2018,

title = {Are boron isotopes a reliable tracer of anthropogenic inputs to rivers over time?},

author = {D. Guinoiseau and P. Louvat and G. Paris and J. B. Chen and B. Chetelat and V. Rocher and S. Gu\'{e}rin and J. Gaillardet},

doi = {10.1016/j.scitotenv.2018.01.159},

year  = {2018},

date = {2018-01-01},

journal = {Science of the Total Environment},

volume = {626},

pages = {1057--1068},

abstract = {This study aims at determining how the boron signal of the Seine River evolved in terms of concentration and isotopic signatures over eighteen years (1994--95 and 2006--12) and if boron isotopes can reliably trace anthropogenic inputs over time. In the anthropised Seine River watershed, boron is widely released by human activities, and even if boron concentrations ([B]) are below the potability limit, our study confirms the potential of boron isotopes ($delta$11B) to trace urban anthropogenic contaminations. Between 1994 and 2012, [B] have decreased across the anthropised part of the Seine River basin (and by a factor of two in Paris) while $delta$11B has increased. This means either that urban inputs have been reduced or that the boron signature of urban inputs has changed over time. Both hypotheses are in agreement with the decrease of perborate consumption in Europe over 15 years and are not mutually exclusive.Results of a thorough analysis of urban effluents from the sewage network of Paris conurbation that are in fine released to the Seine River suggest a shift of the urban $delta$11B from −10texttenthousand in 1994 to 1.5 textpm 2.0texttenthousand in 2012, in agreement with our second hypothesis. We attribute this change to the removal of perborates from detergents rather than to the modernisation of wastewater treatment network, because it does not significantly impact the wastewater boron signatures. Eighteen years after the first assessment and despite the decreased use of perborates, geochemical and isotopic mass budgets confirm, that boron in the Seine River basin is mainly released from urban activities (60--100%), especially in Paris and the downstream part of the basin. Contrastingly, in headwaters and/or tributaries with low urbanisation, the relative boron input to river from agricultural practices and rains increased, up to 10% and by 10 to 30%, respectively.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Rennie_etal2018,

title = {Cenozoic record of $delta$ 34 S in foraminiferal calcite implies an early Eocene shift to deep-ocean sulfide burial},

author = {V. C. F. Rennie and G. Paris and A. L. Sessions and S. Abramovich and A. V. Turchyn and J. F. Adkins},

doi = {10.1038/s41561-018-0200-y},

year  = {2018},

date = {2018-01-01},

journal = {Nature Geoscience},

volume = {11},

number = {10},

pages = {761--765},

abstract = {Understanding the changes in, and drivers of, isotopic variability of sulfur in seawater sulfate ($delta$34SSO4-sw) over geological time remains a long-standing goal, particularly because of the coupling between the biogeochemical sulfur and carbon cycles. The early Cenozoic has remained enigmatic in this regard, as the existing seawater sulfate isotopic records appear to be decoupled from the well-defined carbon isotope composition of the ocean. Here, we present a new Cenozoic record of sulfur isotopes, using carbonate-associated sulfate hosted in the calcite lattice of single-species foraminifera. The vastly improved stratigraphy afforded by this record demonstrates that carbon and sulfur cycles, as recorded by their isotopes, are not fully decoupled in the early Cenozoic. With a model driven by partial coupling of the carbon and sulfur cycles, we demonstrate that a change in sulfur isotopic fractionation of the pyrite burial flux best explains the large increase in $delta$34SSO4-sw textasciitilde53 million years ago (Ma) and the subsequent long steady state. We suggest that the locus of pyrite burial changed from shallow epicontinental seas and shelf environments to more open-ocean sediments around 53 Ma. Loss of extensive shelf environments corresponds to Cretaceous--Palaeogene sea-level changes and tectonic reorganization, occurring as the Himalayan arc first collided with Asia.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Torres_etal2018,

title = {Riverine evidence for isotopic mass balance in the Earthtextquoterights early sulfur cycle},

author = {M. A. Torres and G. Paris and J. F. Adkins and W. W. Fischer},

doi = {10.1038/s41561-018-0184-7},

year  = {2018},

date = {2018-01-01},

journal = {Nature Geoscience},

volume = {11},

number = {9},

abstract = {During a time of negligible atmospheric pO2, Earthtextquoterights early sulfur cycle generated a spectacular geological signal seen as the anomalous fractionation of multiple sulfur isotopic ratios. The disappearance of this signal from the geologic record has been hypothesized to constrain the timing of atmospheric oxygenation, although interpretive challenges exist. Asymmetry in existing S isotopic data, for example, suggests that the Archaean crust was not mass balanced, with the implication that the loss of S isotope anomalies from the geologic record might lag the rise of atmospheric O2. Here, we present new S isotopic analyses of modern surface and groundwaters that drain Archaean terrains in order to independently evaluate Archaean S cycle mass balance. Natural waters contain sulfur derived from the underlying bedrock and thus can be used to ascertain its S isotopic composition at scales larger than typical geological samples allow. Analyses of 52 water samples from Canada and South Africa suggest that the Archaean crust was mass balanced with an average multiple S isotopic composition equivalent to the bulk Earth. Overall, our work supports the hypothesis that the disappearance of multiple S isotope anomalies from the sedimentary record provides a robust proxy for the timing of the first rise in atmospheric O2.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Blttler_etal2017,

title = {Constraints on ocean carbonate chemistry and pCO2in the Archaean and Palaeoproterozoic},

author = {C. L. Bl\"{a}ttler and L. R. Kump and W. W. Fischer and G. Paris and J. J. Kasbohm and J. A. Higgins},

year  = {2017},

date = {2017-01-01},

journal = {Nature Geoscience},

volume = {10},

pages = {41--45},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{Sim_etal2017,

title = {Quantification and isotopic analysis of intracellular sulfur metabolites in the dissimilatory sulfate reduction pathway},

author = {M. S. Sim and G. Paris and J. F. Adkins and V. J. Orphan and A. L. Sessions},

doi = {10.1016/j.gca.2017.02.024},

year  = {2017},

date = {2017-01-01},

journal = {Geochimica et Cosmochimica Acta},

volume = {206},

pages = {57--72},

abstract = {Microbial sulfate reduction exhibits a normal isotope effect, leaving unreacted sulfate enriched in 34S and producing sulfide that is depleted in 34S. However, the magnitude of sulfur isotope fractionation is quite variable. The resulting changes in sulfur isotope abundance have been used to trace microbial sulfate reduction in modern and ancient ecosystems, but the intracellular mechanism(s) underlying the wide range of fractionations remains unclear. Here we report the concentrations and isotopic ratios of sulfur metabolites in the dissimilatory sulfate reduction pathway of Desulfovibrio alaskensis. Intracellular sulfate and APS levels change depending on the growth phase, peaking at the end of exponential phase, while sulfite accumulates in the cell during stationary phase. During exponential growth, intracellular sulfate and APS are strongly enriched in 34S. The fractionation between internal and external sulfate is up to 49texttenthousand, while at the same time that between external sulfate and sulfide is just a few permil. We interpret this pattern to indicate that enzymatic fractionations remain large but the netfractionation between sulfate and sulfide is muted by the closed-system limitation of intracellular sulfate. This textquoteleftreservoir effecttextquoterightdiminishes upon cessation of exponential phase growth, allowing the expression of larger net sulfur isotope fractionations. Thus, the relative rates of sulfate exchange across the membrane versus intracellular sulfate reduction should govern the overall (net) fractionation that is expressed. A strong reservoir effect due to vigorous sulfate reduction might be responsible for the well-established inverse correlation between sulfur isotope fractionation and the cell-specific rate of sulfate reduction, while at the same time intraspecies differences in sulfate uptake and/or exchange rates could account for the significant scatter in this relationship. Our approach, together with ongoing investigations of the kinetic isotope fractionation by key enzymes in the sulfate reduction pathway, should provide an empirical basis for a quantitative model relating the magnitude of microbial isotope fractionation to their environmental and physiological controls.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}