Absence of hexavalent chromium in marine carbonates: implications for chromium isotopes as paleoenvironment proxy

Abstract The oxygenation of Earth's atmosphere is widely regarded to have played an important role in early-life evolution. Chromium (Cr) isotopes recorded in sedimentary rocks have been used to constrain the atmospheric oxygen level (AOL) over geological times based on the fact that a positive Cr isotopic signature is linked to the presence of Cr(VI) as a result of oxidative continental weathering. However, there is no direct evidence of the presence of Cr(VI) in sedimentary rocks yet. Carbonates are most widely distributed over geological times and were thought to have incorporated Cr(VI) directly from seawater. Here, we present results of Cr valence states in carbonates which show Cr(III) is the dominant species in all samples spanning a wide range of geological times. These findings indicate that Cr(VI) in seawater was reduced either before or after carbonate precipitation, which might have caused Cr isotopic fractionation between seawater and carbonates, or marine carbonates preferentially uptake Cr(III) from seawater. As Cr(III) can come from non-redox Cr cycling, which also can cause isotopic fractionation, we suggest that positively fractionated Cr isotopic values do not necessarily correspond to the rise in AOL.

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Oxygen isotopic signature of CO<sub>2</sub> from combustion processes

Atmospheric Chemistry and Physics Discussions ◽

10.5194/acpd-8-18993-2008 ◽

2008 ◽

Vol 8 (6) ◽

pp. 18993-19034 ◽

Cited By ~ 1

Author(s):

M. Schumacher ◽

R. E. M. Neubert ◽

H. A. J. Meijer ◽

H. G. Jansen ◽

W. A. Brand ◽

...

Keyword(s):

Carbon Cycle ◽

Raw Materials ◽

Atmospheric Oxygen ◽

Isotopic Fractionation ◽

Isotopic Signature ◽

Specific Rate ◽

Atmospheric Conditions ◽

Precise Knowledge ◽

Wide Range ◽

Combustion Processes

Abstract. For a comprehensive understanding of the global carbon cycle precise knowledge of all processes is necessary. Stable isotope (13C and 18O) abundances provide information for the qualification and the quantification of the diverse source and sink processes. This study focuses on the δ18O signature of CO2 from combustion processes, which are widely present both naturally (wild fires), and human induced (fossil fuel combustion, biomass burning) in the carbon cycle. All these combustion processes use atmospheric oxygen, of which the isotopic signature is assumed to be constant with time throughout the whole atmosphere. The combustion is generally presumed to take place at high temperatures, thus minimizing isotopic fractionation. Therefore it is generally supposed that the 18O signature of the produced CO2 is equal to that of the atmospheric oxygen. This study, however, reveals that the situation is much more complicated and that important fractionation effects do occur. From laboratory studies fractionation effects in the order of about 26‰ became obvious, a clear differentiation of about 7‰ was also found in car exhausts which were sampled directly under ambient atmospheric conditions. We investigated a wide range of materials (both different raw materials and similar materials with different inherent 18O signature), sample geometries (e.g. texture and surface-volume ratios) and combustion circumstances. We found that the main factor influencing the specific isotopic signatures of the combustion-derived CO2 and of the concomitantly released oxygen-containing side products, is the case-specific rate of combustion. This points firmly into the direction of (diffusive) transport of oxygen to the reaction zone as the cause of the isotope fractionation. The original 18O signature of the material appeared to have little or no influence.

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Oxygen isotopic signature of CO<sub>2</sub> from combustion processes

Atmospheric Chemistry and Physics ◽

10.5194/acp-11-1473-2011 ◽

2011 ◽

Vol 11 (4) ◽

pp. 1473-1490 ◽

Cited By ~ 19

Author(s):

M. Schumacher ◽

R. A. Werner ◽

H. A. J. Meijer ◽

H. G. Jansen ◽

W. A. Brand ◽

...

Keyword(s):

Carbon Cycle ◽

Raw Materials ◽

Atmospheric Oxygen ◽

Isotopic Fractionation ◽

Isotopic Signature ◽

Specific Rate ◽

Atmospheric Conditions ◽

Precise Knowledge ◽

Wide Range ◽

Combustion Processes

Abstract. For a comprehensive understanding of the global carbon cycle precise knowledge of all processes is necessary. Stable isotope (13C and 18O) abundances provide information for the qualification and the quantification of the diverse source and sink processes. This study focuses on the δ18O signature of CO2 from combustion processes, which are widely present both naturally (wild fires), and human induced (fossil fuel combustion, biomass burning) in the carbon cycle. All these combustion processes use atmospheric oxygen, of which the isotopic signature is assumed to be constant with time throughout the whole atmosphere. The combustion is generally presumed to take place at high temperatures, thus minimizing isotopic fractionation. Therefore it is generally supposed that the 18O signature of the produced CO2 is equal to that of the atmospheric oxygen. This study, however, reveals that the situation is much more complicated and that important fractionation effects do occur. From laboratory studies fractionation effects on the order of up to 26%permil; became obvious in the derived CO2 from combustion of different kinds of material, a clear differentiation of about 7‰ was also found in car exhausts which were sampled directly under ambient atmospheric conditions. We investigated a wide range of materials (both different raw materials and similar materials with different inherent 18O signature), sample geometries (e.g. texture and surface-volume ratios) and combustion circumstances. We found that the main factor influencing the specific isotopic signatures of the combustion-derived CO2 and of the concomitantly released oxygen-containing side products, is the case-specific rate of combustion. This points firmly into the direction of (diffusive) transport of oxygen to the reaction zone as the cause of the isotope fractionation. The original total 18O signature of the material appeared to have little influence, however, a contribution of specific bio-chemical compounds to individual combustion products released from the involved material became obvious.

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Prey tell: what quillback rockfish early life history traits reveal about their survival in encounters with juvenile coho salmon

Marine Ecology Progress Series ◽

10.3354/meps13300 ◽

2020 ◽

Vol 650 ◽

pp. 7-18 ◽

Cited By ~ 1

Author(s):

HW Fennie ◽

S Sponaugle ◽

EA Daly ◽

RD Brodeur

Keyword(s):

Life History ◽

Early Life ◽

Life History Traits ◽

Direct Evidence ◽

Coho Salmon ◽

Larval Fish ◽

Early Life History ◽

In The Wild ◽

Otolith Microstructure Analysis ◽

Pelagic Juvenile

Predation is a major source of mortality in the early life stages of fishes and a driving force in shaping fish populations. Theoretical, modeling, and laboratory studies have generated hypotheses that larval fish size, age, growth rate, and development rate affect their susceptibility to predation. Empirical data on predator selection in the wild are challenging to obtain, and most selective mortality studies must repeatedly sample populations of survivors to indirectly examine survivorship. While valuable on a population scale, these approaches can obscure selection by particular predators. In May 2018, along the coast of Washington, USA, we simultaneously collected juvenile quillback rockfish Sebastes maliger from both the environment and the stomachs of juvenile coho salmon Oncorhynchus kisutch. We used otolith microstructure analysis to examine whether juvenile coho salmon were age-, size-, and/or growth-selective predators of juvenile quillback rockfish. Our results indicate that juvenile rockfish consumed by salmon were significantly smaller, slower growing at capture, and younger than surviving (unconsumed) juvenile rockfish, providing direct evidence that juvenile coho salmon are selective predators on juvenile quillback rockfish. These differences in early life history traits between consumed and surviving rockfish are related to timing of parturition and the environmental conditions larval rockfish experienced, suggesting that maternal effects may substantially influence survival at this stage. Our results demonstrate that variability in timing of parturition and sea surface temperature leads to tradeoffs in early life history traits between growth in the larval stage and survival when encountering predators in the pelagic juvenile stage.

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Protector and Casualty

The Oxford Handbook of Positive Emotion and Psychopathology ◽

10.1093/oxfordhb/9780190653200.013.31 ◽

2019 ◽

pp. 495-522

Author(s):

Meg Dennison ◽

Katie McLaughlin

Keyword(s):

Early Life ◽

Positive Emotion ◽

Positive Emotions ◽

Protective Factor ◽

Mental Health Problems ◽

Positive Emotionality ◽

Early Life Adversity ◽

Adverse Experiences ◽

Wide Range ◽

Positive Valence

Early-life adversity is associated with elevated risk for a wide range of mental disorders across the lifespan, including those that involve disruptions in positive emotionality. Although extensive research has evaluated heightened negative emotionality and threat processing as developmental mechanisms linking early-life adversity with mental health problems, emerging evidence suggests that positive emotions play an integral, but complex, role in the association of early-life adversity with psychopathology. This chapter identifies two pathways through which positive emotion influences risk for psychopathology following early-life adversity. First, experiences of early-life adversity may alter the development of the “positive valence system”, which in turn increases risk for psychopathology. Second, the association between adversity and psychopathology may vary as a function of individual differences in positive emotionality. We consider how the development of positive emotionality—measured at psychological, behavioral and neurobiological levels—may be altered by early-life adversity, creating a diathesis for psychopathology. We additionally review evidence for the role of positive emotion, measured at multiple levels, as a protective factor that buffers against the adverse impacts of adversity. In integrating these two roles, it is proposed that characteristics of environmental adversity, including developmental timing, duration, and type of adversity, may differentially impact the development of positive emotionality, leading to a better understanding of risks associated with specific adverse experiences. Methodological issues regarding the measurement of adverse environments as well as implications for early intervention and treatment are discussed.

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Isotopic Fractionation Accompanying CO2 Hydroxylation and Carbonate Precipitation from High pH Waters at The Cedars, California, USA

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2021.01.003 ◽

2021 ◽

Author(s):

John N. Christensen ◽

James M. Watkins ◽

Laurent S. Devriendt ◽

Donald J. DePaolo ◽

Mark E. Conrad ◽

...

Keyword(s):

Isotopic Fractionation ◽

Carbonate Precipitation ◽

High Ph

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More than redox, biological organic ligands control iron isotope fractionation in the riparian wetland

Scientific Reports ◽

10.1038/s41598-021-81494-z ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Elaheh Lotfi-Kalahroodi ◽

Anne-Catherine Pierson-Wickmann ◽

Olivier Rouxel ◽

Rémi Marsac ◽

Martine Bouhnik-Le Coz ◽

...

Keyword(s):

Redox Reactions ◽

Isotope Fractionation ◽

Isotopic Fractionation ◽

Isotopic Signature ◽

Organic Ligands ◽

Riparian Wetland ◽

Fe Isotopes ◽

Preferential Binding ◽

Isotope Systematics

AbstractAlthough redox reactions are recognized to fractionate iron (Fe) isotopes, the dominant mechanisms controlling the Fe isotope fractionation and notably the role of organic matter (OM) are still debated. Here, we demonstrate how binding to organic ligands governs Fe isotope fractionation beyond that arising from redox reactions. The reductive biodissolution of soil Fe(III) enriched the solution in light Fe isotopes, whereas, with the extended reduction, the preferential binding of heavy Fe isotopes to large biological organic ligands enriched the solution in heavy Fe isotopes. Under oxic conditions, the aggregation/sedimentation of Fe(III) nano-oxides with OM resulted in an initial enrichment of the solution in light Fe isotopes. However, heavy Fe isotopes progressively dominate the solution composition in response to their binding with large biologically-derived organic ligands. Confronted with field data, these results demonstrate that Fe isotope systematics in wetlands are controlled by the OM flux, masking Fe isotope fractionation arising from redox reactions. This work sheds light on an overseen aspect of Fe isotopic fractionation and calls for a reevaluation of the parameters controlling the Fe isotopes fractionation to clarify the interpretation of the Fe isotopic signature.

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Distribution, feeding behaviour, and condition of Cape horse mackerel early life stages, Trachurus capensis, under different environmental conditions in the northern Benguela upwelling ecosystem

ICES Journal of Marine Science ◽

10.1093/icesjms/fsu087 ◽

2014 ◽

Vol 72 (2) ◽

pp. 543-557 ◽

Cited By ~ 3

Author(s):

S. J. Geist ◽

A. Kunzmann ◽

H. M. Verheye ◽

A. Eggert ◽

A. Schukat ◽

...

Keyword(s):

Dissolved Oxygen ◽

Feeding Ecology ◽

Environmental Conditions ◽

Early Life ◽

Early Life History ◽

Horse Mackerel ◽

Larval Phase ◽

Recruitment Success ◽

Wide Range ◽

Variable Recruitment

Abstract Early life history (ELH) traits are key to understand variable recruitment success and hence the stock size of marine fish. One of the currently most puzzling ecosystems in this regard is the northern part of the Benguela Current upwelling system off Namibia. Here, populations of the formerly dominant pelagic species, sardine and anchovy, failed to recover during the last three decades after a dramatic decline. In contrast, Cape horse mackerel, Trachurus capensis, maintained a constant population size. Warming of the system and shoaling of hypoxic zones together with feedback loops within an altered foodweb are discussed to be responsible for this regime shift. In this study, we address the role of larval traits for the successful performance of the T. capensis population under the present environmental conditions with the focus on feeding ecology. We investigated seasonal variations of the geographical distribution, growth rate, feeding ecology, and nutritional condition of their ELH stages and examined relationships with water temperature, dissolved oxygen concentration, and micro-zooplankton composition. T. capensis' ELH stages showed a wide spatial and seasonal distribution, a preference for higher water temperatures (18–21°C) and presence over a wide range of dissolved oxygen concentrations (0.13–6.35 ml O2 l−1). Feeding success was high and mainly different groups of Copepoda were targeted, which were strongly size selected. The high dietary importance of micro-copepods during large parts of the larval phase indicates successful exploitation of this food source, which has increased in abundance during the last decade. It also explains observed best nutritional conditions at temperatures between 18 and 21°C, since these small copepods are commonly associated with warmer temperatures. Altogether, these traits enhance the species' probability to encounter suitable environments for the survival of their ELH stages, which is likely to lead to their high recruitment success in the northern Benguela ecosystem.

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The Relationship between Fluid Flow, Structures, and Depositional Architecture in Sedimentary Rocks: An Example-Based Overview

Geofluids ◽

10.1155/2020/3506743 ◽

2020 ◽

Vol 2020 ◽

pp. 1-19 ◽

Cited By ~ 1

Author(s):

Vilde Dimmen ◽

Atle Rotevatn ◽

Casey W. Nixon

Keyword(s):

Fluid Flow ◽

Sedimentary Rocks ◽

Structure Type ◽

Mineral Dissolution ◽

Rock Properties ◽

Hydrocarbon Migration ◽

Geological Processes ◽

Wide Range ◽

Depositional Architecture ◽

The Relationship

Fluid flow in the subsurface is fundamental in a variety of geological processes including volcanism, metamorphism, and mineral dissolution and precipitation. It is also of economic and societal significance given its relevance, for example, within groundwater and contaminant transport, hydrocarbon migration, and precipitation of ore-forming minerals. In this example-based overview, we use the distribution of iron oxide precipitates as a proxy for palaeofluid flow to investigate the relationship between fluid flow, geological structures, and depositional architecture in sedimentary rocks. We analyse and discuss a number of outcrop examples from sandstones and carbonate rocks in New Zealand, Malta, and Utah (USA), showing controls on fluid flow ranging from simple geological heterogeneities to more complex networks of structures. Based on our observations and review of a wide range of the published literature, we conclude that flow within structures and networks is primarily controlled by structure type (e.g., joint and deformation band), geometry (e.g., length and orientation), connectivity (i.e., number of connections in a network), kinematics (e.g., dilation and compaction), and interactions (e.g., relays and intersections) within the network. Additionally, host rock properties and depositional architecture represent important controls on flow and may interfere to create hybrid networks, which are networks of combined structural and stratal conduits for flow.

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Technical Note: Evaluation of a low-cost evaporation protection method for portable water samplers

10.5194/hess-2020-341 ◽

2020 ◽

Author(s):

Jana von Freyberg ◽

Julia L. A. Knapp ◽

Andrea Rücker ◽

Bjørn Studer ◽

James W. Kirchner

Keyword(s):

Water Samples ◽

Low Cost ◽

Isotopic Fractionation ◽

Field Tests ◽

Isotopic Signature ◽

Technical Note ◽

Stable Water Isotopes ◽

Sample Collection ◽

Protection Method ◽

Cost Efficient

Abstract. Automated field sampling of streamwater or precipitation for subsequent analysis of stable water isotopes (2H and 18O) is often conducted with off-the-shelf automated samplers. However, water samples stored in the field for days and weeks in open bottles inside autosamplers undergo isotopic fractionation and vapor mixing, thus altering their isotopic signature. We therefore designed an evaporation protection method which modifies autosampler bottles using a syringe housing and silicone tube, and tested whether this method reduces evaporative fractionation and vapor mixing in water samples stored for up to 24 days in ISCO autosamplers (Teledyne ISCO., Lincoln, US). Laboratory and field tests under different temperature and humidity conditions showed that water samples in bottles with evaporation protection were far less altered by evaporative fractionation and vapor mixing than samples in conventional open bottles. Our design is a cost-efficient approach to upgrade the 1-litre sample bottles of ISCO 6712 Full-size Portable Samplers, allowing secure water sample collection in warm and dry environments. Our design can be readily adapted (e.g., by using a different syringe size) to fit the bottles used by many other field autosamplers.

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Abstract 17: Early Life Stress Sensitizes The Angiotensin II-elicited Hypertensive Response

Hypertension ◽

10.1161/hyp.76.suppl_1.17 ◽

2020 ◽

Vol 76 (Suppl_1) ◽

Author(s):

Baojian Xue ◽

Terry Beltz ◽

Fang Guo ◽

David M Pollock ◽

Jennifer S Pollock ◽

...

Keyword(s):

Mrna Expression ◽

Proinflammatory Cytokines ◽

Life Stress ◽

Early Life ◽

Early Life Stress ◽

Male Rats ◽

Sprague Dawley ◽

Cns Inflammation ◽

Wide Range ◽

The Brain

Separation of neonatal rodent pups from their mothers has been used as a model to study the effects of early life stress (ELS) on behavioral and physiological responses in adults. Using an Induction-Delay-Expression experimental paradigm, our previous studies demonstrate that a wide range of stressors administered during an induction period produces hypertensive response sensitization (HTRS) in response to a subsequent pro-hypertensive stimulus. HTRS is accompanied by activation of the brain renin-angiotensin system (RAS) and CNS inflammation. The present study investigated whether ELS induces HTRS and changes in brain-related underlying mechanisms. Rat neonates from Sprague-Dawley breeders were subjected to ELS by separating them each morning from their mothers for 3 h on postnatal days 2 to 14. Pups from non-handled litters formed control groups. At 10 weeks of age, male rats were used to evaluate blood pressure and autonomic function using telemetric probes and pharmacological methods. In addition, in separate control and ELS groups, the lamina terminalis (LT) structures and the hypothalamic paraventricular nucleus (PVN) were analyzed for mRNA expression of RAS components and proinflammatory cytokines. Adult ELS rats as compared to non-separated controls exhibited 1) HTRS during expression testing using 2 week ANG II infusions (120 ng/kg/min s.c.; ELS animals, Δ45.5±4.5 mmHg vs. controls, Δ22.4±3.1 mmHg); 2) a greater reduction in mean arterial pressure following ganglionic blockade (hexamethonium, 30 mg/kg, ip), 3) increased sympathetic drive to the heart (atenolol, 8 mg/kg, ip), 4) decreased vagal tone (atropine, 8 mg/kg, ip), and 5) increased mRNA expression of several components of the brain RAS and proinflammatory cytokines in the LT and PVN. These results suggest that maternal ELS may predispose individuals to hypertension that is mediated by upregulation of the brain RAS and proinflammatory cytokines and increased sympathetic drive to the cardiovascular system.

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