CO2 Fluctuations Research Articles

Carbon Dioxide in a Supported Ionic Liquid Membrane: Structural and Rotational Dynamics Measured with 2D IR and Pump-Probe Experiments.

Supported ionic liquid membranes (SILMs) are porous membranes impregnated with ionic liquids (ILs) and used as advanced carbon capture materials. Here, two-dimensional infrared (2D IR) and IR polarization selective pump-probe (PSPP) spectroscopies were used to investigate CO2 reorientation and spectral diffusion dynamics in SILMs. The SILM contained 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonly)imide in the poly(ether sulfone) membrane with average pore size of ∼350 nm. Two ensembles of CO2 were observed in the SILM, one in the IL phase in the membrane pores and the other in the supporting membrane polymer. CO2 in the polymer displayed a red-shifted IR absorption spectrum and a shorter vibrational lifetime of the asymmetric stretch mode compared to the IL phase. Despite the relatively large pore sizes, the complete orientational randomization of CO2 and structural fluctuations of the IL (spectral diffusion) in the pores are slower than in the bulk IL by ∼2-fold. The implication is that the IL structural change induced by the polymer interface can propagate out from the interface more than a hundred nanometers, influencing the dynamics. The dynamics in the polymer are even slower. This study demonstrates that there are significant differences in the dynamics of ILs in SILMs on a molecular level compared to the bulk IL, and the study of dynamics in SILMs can provide important information for the design of SILMs for CO2 capture.

Sensitivity Analysis of the Dynamic CO2 Storage Capacity Estimate for the Bunter Sandstone of the UK Southern North Sea

Carbon capture and storage (CCS) in subsurface reservoirs has been identified as a potentially cost-effective way to reduce CO2 emissions to the atmosphere. Global emissions reductions on the gigatonne scale using CCS will require regional or basin-scale deployment of CO2 storage in saline aquifers. Thus the evaluation of both the dynamic and ultimate CO2 storage capacity of formations is important for policy makers to determine the viability of CCS as a pillar of the greenhouse gas mitigation strategy in a particular region. We use a reservoir simulation model representing the large-scale Bunter Sandstone in the UK Southern North Sea to evaluate the dynamics and sensitivities of regional CO2 plume transport and storage. At the basin-scale, we predict hydrogeological changes in the storage reservoir in response to multiple regional carbon sequestration development scenarios. We test the sensitivity of injection capacity to a range of target CO2 injection rates and fluctuations in CO2 supply. Model sensitivities varying the target injection rates indicate that in the absence of pressure management up to 3.7 Gt of CO2 can be stored in the Bunter region over 50 years given the pressure constraints set to avoid fracturing the formation. Long-term (approx. 1000 years), our results show that up to 16 Gt of CO2 can be stored in the Bunter region without pressure management. With pressure management, the estimate rises to 32 Gt. However, consideration must be given to the additional operational and economic requirements of pressure management using brine production.

Productivity-climate coupling recorded in Pleistocene sediments off Prydz Bay (East Antarctica)

Export-production in the Southern Ocean is thought to be tightly correlated with atmospheric CO2 fluctuations over geological times. Relevant studies are, however, mainly confined to the Atlantic and Pacific sectors of the Southern Ocean and often only cover the last glacial-interglacial cycle. Here, we present a sediment record retrieved off Prydz Bay (East Antarctica) spanning the last ~520kyrs. We show that the distribution pattern of local export production is closely coupled with global climate change on orbital time scales. We propose that the dominant factors controlling local export production include the amount of nutrients supply from the ocean interior and the extent of sea ice cover, thus representing the combined history of deep water exposure/ventilation and the sea ice coverage in the studied area. Sharp increases in the local export production coincide with abrupt increase in atmospheric CO2 concentrations during deglacial periods, indicating drastic outgassing of the upwelled deep water in the Southern Ocean. Gradually decrease in the export production following interglacial peaks concurs with decrease in deep water exposure/ventilation and increase in sea ice cover, explaining the early decline in atmospheric CO2 over a glacial-interglacial cycle.

A biomarker record of temperature and phytoplankton community structure in the Okinawa Trough since the last glacial maximum

AbstractA variety of biomarkers were examined from Ocean Drilling Program Core 1202B to reconstruct temperature and phytoplankton community structures in the southern Okinawa Trough since 20 ka. Two molecular temperature proxies ( $${\rm U}_{{37}}^{{{\rm K}\prime}} $$ and TEX86) show 5°C to ~6°C warming during the glacial-interglacial transition. Prior to the Holocene, the $${\rm U}_{{37}}^{{{\rm K}\prime}} $$ -derived temperature was generally 1°C to 4°C higher than TEX86-derived temperature. This difference, however, was reduced to <1°C in the Holocene. Correspondingly, the phytoplankton biomarkers (e.g., C37:2 alkenone, brassicasterol, C30 1,15 diol, and dinosterol) indicate a shift of planktonic community structures, with coccolithophorids becoming more abundant in the Holocene at the expense of diatoms/dinoflagellates. This shift is related to the variability of nutrients, temperature, and salinity in the Okinawa Trough, likely controlled by the sea level and the intensity of the Kuroshio Current. The phytoplankton community change may have had profound implications for atmospheric CO2 fluctuations during glacial-interglacial cycles since diatoms and dinoflagellates have a higher efficiency of the biological pump than coccolithophorids.

Carbon Dioxide Fluctuations Are Associated with Changes in Cerebral Oxygenation and Electrical Activity in Infants Born Preterm

To evaluate the effects of acute arterial carbon dioxide partial pressure changes on cerebral oxygenation and electrical activity in infants born preterm. This retrospective observational study included ventilated infants born preterm with acute fluctuations of continuous end-tidal CO2 (etCO2) as a surrogate marker for arterial carbon dioxide partial pressure, during the first 72 hours of life. Regional cerebral oxygen saturation and fractional tissue oxygen extraction were monitored with near-infrared spectroscopy. Brain activity was monitored with 2-channel electroencephalography. Spontaneous activity transients (SATs) rate (SATs/minute) and interval between SATs (in seconds) were calculated. Ten-minute periods were selected for analysis: before, during, and after etCO2 fluctuations of ≥5 mm Hg. Thirty-eight patients (mean ± SD gestational age of 29 ± 1.8 weeks) were included, with 60 episodes of etCO2 increase and 70 episodes of etCO2 decrease. During etCO2 increases, brain oxygenation increased (regional cerebral oxygen saturation increased, fractional tissue oxygen extraction decreased; P < .01) and electrical activity decreased (SATs/minute decreased, interval between SATs increased; P < .01). All measures recovered when etCO2 returned to baseline. During etCO2 decreases, brain oxygenation decreased (regional cerebral oxygen saturation decreased, fractional tissue oxygen extraction decreased; P < .01) and brain activity increased (SATs/minute increased, P < .05), also with recovery after return of etCO2 to baseline. An acute increase in etCO2 is associated with increased cerebral oxygenation and decreased brain activity, whereas an acute decrease is associated with decreased cerebral oxygenation and slightly increased brain activity. Combining continuous CO2 monitoring with near-infrared spectroscopy may enable the detection of otherwise undetected fluctuations in arterial carbon dioxide partial pressure that may be harmful to the neonatal brain.

Absence of OsβCA1 causes a CO2 deficit and affects leaf photosynthesis and the stomatal response to CO2 in rice.

Plants always adjust the opening of stomatal pores to adapt to the environment, for example CO2 concentration ([CO2 ]), humidity and temperature. Low [CO2 ] will trigger the opening of stomatal pores to absorb extra CO2 . However, little is known about how CO2 supply affects the carbon fixation and opening of stomatal pores in rice. Here, a chloroplast-located gene coding for β-carbonic anhydrase (βCA) was found to be involved in carbon assimilation and the CO2 -mediated stomatal pore response in rice. OsβCA1 was constitutively expressed in all tissues and its transcripts were induced by high [CO2 ] in leaves. Both T-DNA mutant and RNA interference lines showed phenotypes of lower biomass and CA activities. Knockout of OsβCA1 obviously decreased photosynthetic capacity, as demonstrated by the increased CO2 compensation point and decreased light saturation point in the mutant, while knockout increased the opening ratio of stomatal pores and the rate of water loss. Moreover, the mutant showed a delayed response to low [CO2 ], and stomatal pores could not be closed to the same degree as those of wild type even though the stomatal pores could rapidly respond to high [CO2 ]. Genome-wide gene expression analysis via RNA sequencing demonstrated that the transcript abundance of genes related to Rubisco, photosystem compounds and the opening of stomatal pores was globally upregulated in the mutant. Taken together, the inadequate CO2 supply caused by the absence of OsβCA1 reduces photosynthetic efficiency, triggers the opening of stomatal pores and finally decreases their sensitivity to CO2 fluctuation.

Effect of ocean acidification on the structure and fatty acid composition of a natural plankton community in the Baltic Sea

Abstract. Increasing atmospheric carbon dioxide (CO2) is changing seawater chemistry towards reduced pH, which affects various properties of marine organisms. Coastal and brackish water communities are expected to be less affected by ocean acidification (OA) as these communities are typically adapted to high fluctuations in CO2 and pH. Here we investigate the response of a coastal brackish water plankton community to increasing CO2 levels as projected for the coming decades and the end of this century in terms of community and biochemical fatty acid (FA) composition. A Baltic Sea plankton community was enclosed in a set of offshore mesocosms and subjected to a CO2 gradient ranging from natural concentrations ( ∼ 347 µatm fCO2) up to values projected for the year 2100 ( ∼ 1333 µatm fCO2). We show that the phytoplankton community composition was resilient to CO2 and did not diverge between the treatments. Seston FA composition was influenced by community composition, which in turn was driven by silicate and phosphate limitation in the mesocosms and showed no difference between the CO2 treatments. These results suggest that CO2 effects are dampened in coastal communities that already experience high natural fluctuations in pCO2. Although this coastal plankton community was tolerant of high pCO2 levels, hypoxia and CO2 uptake by the sea can aggravate acidification and may lead to pH changes outside the currently experienced range for coastal organisms.

Cerebrovascular reactivity mapping without gas challenges

Cerebrovascular reactivity (CVR), the ability of cerebral vessels to dilate or constrict, has been shown to provide valuable information in the diagnosis and treatment evaluation of patients with various cerebrovascular conditions. CVR mapping is typically performed using hypercapnic gas inhalation as a vasoactive challenge while collecting BOLD images, but the inherent need of gas inhalation and the associated apparatus setup present a practical obstacle in applying it in routine clinical use. Therefore, we aimed to develop a new method to map CVR using resting-state BOLD data without the need of gas inhalation. This approach exploits the natural variation in respiration and measures its influence on BOLD MRI signal. In this work, we first identified a surrogate of the arterial CO2 fluctuation during spontaneous breathing from the global BOLD signal. Second, we tested the feasibility and reproducibility of the proposed approach to use the above-mentioned surrogate as a regressor to estimate voxel-wise CVR. Third, we validated the “resting-state CVR map” with a conventional CVR map obtained with hypercapnic gas inhalation in healthy volunteers. Finally, we tested the utility of this new approach in detecting abnormal CVR in a group of patients with Moyamoya disease, and again validated the results using the conventional gas inhalation method. Our results showed that global BOLD signal fluctuation in the frequency range of 0.02–0.04Hz contains the most prominent contribution from natural variation in arterial CO2. The CVR map calculated using this signal as a regressor is reproducible across runs (ICC=0.91±0.06), and manifests a strong spatial correlation with results measured with a conventional hypercapnia-based method in healthy subjects (r=0.88, p<0.001). We also found that resting-state CVR was able to identify vasodilatory deficit in patients with steno-occlusive disease, the spatial pattern of which matches that obtained using the conventional gas method (r=0.71±0.18). These results suggest that CVR obtained with resting-state BOLD may be a useful alternative in detecting vascular deficits in clinical applications when gas challenge is not feasible.

Variations in satellite-derived carbon dioxide over different regions of China from 2003 to 2011

Variations of CO2 mole fraction (XCO2) on a global or country-wide scale have been widely examined, while the regional differences within China remain unclear because of the huge differences in the stage of economic development and climatic diversities. In this study, the variations of monthly and yearly XCO2 from 2003 to 2011 are analyzed for the entire China and its six geographical regions. Atmospheric Infrared Sounder (AIRS) data, which are mainly sensitive in the mid-troposphere, were used. During 2003–2011, the mean annual XCO2 increased from 375.7 ± 3.3 to 392.5 ± 3.5 ppm, at a rate of +2.10 ppm/year, which is similar to the previous rate during 2003–2008 (+2.09 ppm/year). However, there are two new findings for different regions of China. First, the XCO2 growth rate and its seasonal amplitude were higher in Northern China than in Southern China. The growth rates of XCO2 over North-East, North, and North-West during 2003–2011 are 2.18, 2.17, and 2.13 ppm/year, respectively, while they are 2.03, 2.05, and 2.09 ppm/year over South-East, Central, and South-West, respectively. The seasonal CO2 fluctuations over the North-East and North are larger than other regions. Second, the highest monthly mean XCO2 of mid-troposphere occurs during April to May for different regions of China in 2003–2011, while the lowest XCO2 is September for southern China and January for northern China. These results offer valuable insights into the regional differences of XCO2 within China.

Diurnal fluctuations in CO2 and dissolved oxygen concentrations do not provide a refuge from hypoxia and acidification for early-life-stage bivalves

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 558:1-14 (2016) - DOI: https://doi.org/10.3354/meps11852 FEATURE ARTICLEDiurnal fluctuations in CO2 and dissolved oxygen concentrations do not provide a refuge from hypoxia and acidification for early-life-stage bivalves Hannah R. Clark, Christopher J. Gobler* Stony Brook University, School of Marine and Atmospheric Sciences, 239 Montauk HWY, Southampton, NY 11968, USA *Corresponding author: christopher.gobler@stonybrook.edu ABSTRACT: This study assessed the effects of constant and diurnally fluctuating acidification and hypoxia on the survival, growth, and development of larval stages of 3 bivalves indigenous to the east coast of North America: bay scallops Argopecten irradians, hard clams Mercenaria mercenaria, and eastern oysters Crassostrea virginica. Bivalves were exposed to ideal (pH = ~7.9, dissolved oxygen [DO] = ~7 mg l-1), acidified (pH = ~7.2, DO = ~7 mg l-1), hypoxic (pH = ~7.9, DO = ~2 mg l-1), and acidified and hypoxic (pH = ~7.2, DO = ~2 mg l-1) conditions, as well as treatments that fluctuated between ideal conditions by day and acidified, hypoxic, or acidified and hypoxic conditions by night. Continuously acidified conditions reduced survival of larvae of all 3 species, slowed growth of larval bay scallops and eastern oysters, and delayed the development of bay scallop larvae. Continuously hypoxic conditions reduced the survival, growth, and development of larval bay scallops and slowed the development of larval hard clams. Simultaneous exposure to continuously low pH and DO yielded more negative effects than each factor independently. Diurnal exposure to low pH and/or low DO rarely altered, and never fully mitigated, the negative effects of hypoxia and/or acidification despite significantly higher mean pH and DO levels. This suggests that pH and DO fluctuations were too intense, and/or the durations of normoxic and normcapnic conditions were not long enough for bivalve larvae to overcome the physiological stress of hypoxia and acidification. Therefore, the diurnal fluctuations of pH and DO in this study did not provide a temporal refuge from hypoxia and acidification for North Atlantic bivalve larvae, suggesting that such fluctuations in an ecosystem setting can be a significant threat to these larvae. KEY WORDS: Ocean acidification · Hypoxia · Estuary · Bivalve · Larvae · Ecosystem metabolism · Diurnal patterns Full text in pdf format Information about this Feature Article NextCite this article as: Clark HR, Gobler CJ (2016) Diurnal fluctuations in CO2 and dissolved oxygen concentrations do not provide a refuge from hypoxia and acidification for early-life-stage bivalves. Mar Ecol Prog Ser 558:1-14. https://doi.org/10.3354/meps11852Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 558. Online publication date: October 25, 2016 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2016 Inter-Research.

Arterial CO2 Fluctuations Modulate Neuronal Rhythmicity: Implications for MEG and fMRI Studies of Resting-State Networks.

A fast emerging technique for studying human resting state networks (RSNs) is based on spontaneous temporal fluctuations in neuronal oscillatory power, as measured by magnetoencephalography. However, it has been demonstrated recently that this power is sensitive to modulations in arterial CO2 concentration. Arterial CO2 can be modulated by natural fluctuations in breathing pattern, as might typically occur during the acquisition of an RSN experiment. Here, we demonstrate for the first time the fine-scale dependence of neuronal oscillatory power on arterial CO2 concentration, showing that reductions in alpha, beta, and gamma power are observed with even very mild levels of hypercapnia (increased arterial CO2). We use a graded hypercapnia paradigm and participant feedback to rule out a sensory cause, suggesting a predominantly physiological origin. Furthermore, we demonstrate that natural fluctuations in arterial CO2, without administration of inspired CO2, are of a sufficient level to influence neuronal oscillatory power significantly in the delta-, alpha-, beta-, and gamma-frequency bands. A more thorough understanding of the relationship between physiological factors and cortical rhythmicity is required. In light of these findings, existing results, paradigms, and analysis techniques for the study of resting-state brain data should be revisited.SIGNIFICANCE STATEMENT In this study, we show for the first time that neuronal oscillatory power is intimately linked to arterial CO2 concentration down to the fine-scale modulations that occur during spontaneous breathing. We extend these results to demonstrate a correlation between neuronal oscillatory power and spontaneous arterial CO2 fluctuations in awake humans at rest. This work identifies a need for studies investigating resting-state networks in the human brain to measure and account for the impact of spontaneous changes in arterial CO2 on the neuronal signals of interest. Changes in breathing pattern that are time locked to task performance could also lead to confounding effects on neuronal oscillatory power when considering the electrophysiological response to functional stimulation.

Estimation of voxel-wise dynamic cerebrovascular reactivity curves from resting-state fMRI data.

In this work, we investigate the linear dynamic interactions between fluctuations in arterial CO2 that occur during normal breathing, and the BOLD fMRI signal. We cast this problem within a systems-theoretic framework, where we employ functional expansions for the estimation of the impulse responses in large regions of interest, as well as in individual voxels. We also implement classification schemes in order to identify different brain regions with similar cerebrovascular reactivity characteristics. Our results reveal that it is feasible to obtain reliable estimates of cerebrovascular reactivity curves from resting-state data and that these curves exhibit considerable variability across different brain regions that may be related to the underlying anatomy.

Temporal variation of near-surface CO2 concentrations over different land uses in Suzhou City

The differences in near-surface CO2 concentration variations over five urban land uses within Suzhou City are investigated from January to December 2014. The selected monitoring sites include a traffic road, a residential district with ~20-story apartments, an institutional office site, an amusement park, and a cultural site at the Yuanquan Temple. The diurnal variations of CO2 show considerable fluctuation and different variable patterns at the monitoring sites controlled by the CO2 emissions and weather condition variability. On rainy days, the variation of diurnal CO2 is clearly smaller than that on sunny and cloudy days, with a reduction from 75 % at the amusement site to 41 % at the office-building site. Monthly variations indicate that the traffic and cultural sites experience the highest level of CO2 in warm months, but the other sites are exactly opposite. In each month, the mean level of CO2 at the cultural site is the lowest, but the traffic and amusement sites have the highest levels in warm months and cold months, respectively. Seasonal variations reveal that the traffic, residential, and office-building sites experience a smaller seasonal mean CO2 fluctuation, and in the spring, autumn, and winter, the amusement site has the highest mean levels compared to the other sites. The urban CO2 concentration is related to land use, local CO2 emissions, temperature, and wind; therefore, it is necessary to establish as many monitoring stations as possible to reveal the urban features of CO2 concentration variation.

Quantitative mapping of cerebrovascular reactivity using resting-state BOLD fMRI: Validation in healthy adults

In conventional neuroimaging, cerebrovascular reactivity (CVR) is quantified primarily using the blood-oxygenation level-dependent (BOLD) functional MRI (fMRI) signal, specifically, as the BOLD response to intravascular carbon dioxide (CO2) modulations, in units of [%ΔBOLD/mmHg]. While this method has achieved wide appeal and clinical translation, the tolerability of CO2-related tasks amongst patients and the elderly remains a challenge in more routine and large-scale applications. In this work, we propose an improved method to quantify CVR by exploiting intrinsic fluctuations in CO2 and corresponding changes in the resting-state BOLD signal (rs-qCVR). Our rs-qCVR approach requires simultaneous monitoring of PETCO2, cardiac pulsation and respiratory volume. In 16 healthy adults, we compare our quantitative CVR estimation technique to the prospective CO2-targeting based CVR quantification approach (qCVR, the “standard”). We also compare our rs-CVR to non-quantitative alternatives including the resting-state fluctuation amplitude (RSFA), amplitude of low-frequency fluctuation (ALFF) and global-signal regression. When all subjects were pooled, only RSFA and ALFF were significantly associated with qCVR. However, for characterizing regional CVR variations within each subject, only the PETCO2-based rs-qCVR measure is strongly associated with standard qCVR in 100% of the subjects (p≤0.1). In contrast, for the more qualitative CVR measures, significant within-subject association with qCVR was only achieved in 50–70% of the subjects. Our work establishes the feasibility of extracting quantitative CVR maps using rs-fMRI, opening the possibility of mapping functional connectivity and qCVR simultaneously.

Carbon dioxide in an ionic liquid: Structural and rotational dynamics.

Ionic liquids (ILs), which have widely tunable structural motifs and intermolecular interactions with solutes, have been proposed as possible carbon capture media. To inform the choice of an optimal ionic liquid system, it can be useful to understand the details of dynamics and interactions on fundamental time scales (femtoseconds to picoseconds) of dissolved gases, particularly carbon dioxide (CO2), within the complex solvation structures present in these uniquely organized materials. The rotational and local structural fluctuation dynamics of CO2 in the room temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EmimNTf2) were investigated by using ultrafast infrared spectroscopy to interrogate the CO2 asymmetric stretch. Polarization-selective pump probe measurements yielded the orientational correlation function of the CO2 vibrational transition dipole. It was found that reorientation of the carbon dioxide occurs on 3 time scales: 0.91 ± 0.03, 8.3 ± 0.1, 54 ± 1 ps. The initial two are attributed to restricted wobbling motions originating from a gating of CO2 motions by the IL cations and anions. The final (slowest) decay corresponds to complete orientational randomization. Two-dimensional infrared vibrational echo (2D IR) spectroscopy provided information on structural rearrangements, which cause spectral diffusion, through the time dependence of the 2D line shape. Analysis of the time-dependent 2D IR spectra yields the frequency-frequency correlation function (FFCF). Polarization-selective 2D IR experiments conducted on the CO2 asymmetric stretch in the parallel- and perpendicular-pumped geometries yield significantly different FFCFs due to a phenomenon known as reorientation-induced spectral diffusion (RISD), revealing strong vector interactions with the liquid structures that evolve slowly on the (independently measured) rotation time scales. To separate the RISD contribution to the FFCF from the structural spectral diffusion contribution, the previously developed first order Stark effect RISD model is reformulated to describe the second order (quadratic) Stark effect--the first order Stark effect vanishes because CO2 does not have a permanent dipole moment. Through this analysis, we characterize the structural fluctuations of CO2 in the ionic liquid solvation environment, which separate into magnitude-only and combined magnitude and directional correlations of the liquid's time dependent electric field. This new methodology will enable highly incisive comparisons between CO2 dynamics in a variety of ionic liquid systems.

Early hydrothermal carbon uptake by the upper oceanic crust: Insight from in situ U-Pb dating

It is widely thought that continental chemical weathering provides the key feedback that prevents large fluctuations in atmospheric CO2, and hence surface temperature, on geological time scales. However, low-temperature alteration of the upper oceanic crust in off-axis hydrothermal systems provides an alternative feedback mechanism. Testing the latter hypothesis requires understanding the timing of carbonate mineral formation within the oceanic crust. Here we report the first radiometric age determinations for calcite formed in the upper oceanic crust in eight locations globally via in-situ U-Pb laser ablation–inductively coupled plasma–mass spectrometry analysis. Carbonate formation occurs soon after crustal accretion, indicating that changes in global environmental conditions will be recorded in changing alteration characteristics of the upper oceanic crust. This adds support to the interpretation that large differences between the hydrothermal carbonate content of late Mesozoic and late Cenozoic oceanic crust record changes in global environmental conditions. In turn, this supports a model in which alteration of the upper oceanic crust in off-axis hydrothermal systems plays an important role in controlling ocean chemistry and the long-term carbon cycle.

Oceans, Ice &amp;amp; Snow and CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Rise, Swing and Seasonal Fluctuation

Carbon dioxide rise, swing and spread (seasonal fluctuations) are addressed in this study. Actual CO2 concentrations were used rather than dry values. The dry values are artificially higher because water vapor must be removed in order for the NDIR instrument to work and is not factored back into the reported numbers. Articles addressing these observations express opinions that are divergent and often conflicting. This investigation resolves many of those inconsistencies. The data were obtained from many measuring stations at various latitudes since 1972 and then graphical compared to changes in sea temperatures, fossil fuel emissions, humidity, and seasonal ice and snow changes. In analyzing the data, various parameters were addressed including: variability, R squared curve values, correlations between curves, residence times, absorption percentages, and Troposphere effects. Mass balance calculations were also made to corroborate viability. The CO2 “rise” over a 33-year period from a slight ocean temperature increase (0.7°F) contributed 2.3 percent of the total rise while fossil fuel emissions contributed 1.5 percent. The overwhelming majority (60 ppmv, 96%+) was caused by other factors including ocean and land biology as well potential errors in fundamental hypotheses. With respect to “spread” (seasonal CO2 fluctuations) at the Polar Circles, graphical analysis with high correlations supported by mass balance calculations confirm that ice and snow are the primary cause and explain why the concentrations are the highest at these cold locations. The global variations in “swing” remain uncertain.

High-temperature in situ crystallographic observation of reversible gas sorption in impermeable organic cages

Crystallographic observation of adsorbed gas molecules is a highly difficult task due to their rapid motion. Here, we report the in situ single-crystal and synchrotron powder X-ray observations of reversible CO2 sorption processes in an apparently nonporous organic crystal under varying pressures at high temperatures. The host material is formed by hydrogen bond network between 1,3,5-tris-(4-carboxyphenyl)benzene (H3BTB) and N,N-dimethylformamide (DMF) and by π-π stacking between the H3BTB moieties. The material can be viewed as a well-ordered array of cages, which are tight packed with each other so that the cages are inaccessible from outside. Thus, the host is practically nonporous. Despite the absence of permanent pathways connecting the empty cages, they are permeable to CO2 at high temperatures due to thermally activated molecular gating, and the weakly confined CO2 molecules in the cages allow direct detection by in situ single-crystal X-ray diffraction at 323 K. Variable-temperature in situ synchrotron powder X-ray diffraction studies also show that the CO2 sorption is reversible and driven by temperature increase. Solid-state magic angle spinning NMR defines the interactions of CO2 with the organic framework and dynamic motion of CO2 in cages. The reversible sorption is attributed to the dynamic motion of the DMF molecules combined with the axial motions/angular fluctuations of CO2 (a series of transient opening/closing of compartments enabling CO2 molecule passage), as revealed from NMR and simulations. This temperature-driven transient molecular gating can store gaseous molecules in ordered arrays toward unique collective properties and release them for ready use.

Arterial CO2 effects modulate dynamic functional connectivity in resting-state fMRI.

It is well known that the blood-oxygen level dependent (BOLD) signal measured by functional magnetic resonance imaging (fMRI) is influenced - in addition to neuronal activity - by fluctuations in physiological signals, including arterial CO2. For instance, even spontaneous CO2 fluctuations have been shown to influence the BOLD fMRI signal regionally. Related to this, studies of functional connectivity between different brain regions, performed when the subject is at rest, may be confounded by the effects of physiological noise. Moreover, resting functional connectivity has been shown to vary with respect to time (dynamic functional connectivity), with the sources of this variation not fully understood at present. In this context, in the present paper we examine the relation between dynamic functional connectivity patterns and the properties of the end-tidal CO2 signal (PETCO2) using resting-state fMRI measurements from 12 healthy subjects. The results demonstrate that there exists a modulatory effect of the correlation strength between PETCO2 and the BOLD signal on dynamic resting functional connectivity. The extent to which this effect was observed was found to be strongly dependent on the data analysis methodology.

Foraging behaviour of the epaulette shark Hemiscyllium ocellatum is not affected by elevated CO2

Abstract Increased oceanic uptake of atmospheric carbon dioxide (CO2) is a threat to marine organisms and ecosystems. Among the most dramatic consequences predicted to date are behavioural impairments in marine fish which appear to be caused by the interference of elevated CO2 with a key neurotransmitter receptor in the brain. In this study, we tested the effects of elevated CO2 on the foraging and shelter-seeking behaviours of the reef-dwelling epaulette shark, Hemiscyllium ocellatum. Juvenile sharks were exposed for 30 d to control CO2 (400 µatm) and two elevated CO2 treatments (615 and 910 µatm), consistent with medium- and high-end projections for ocean pCO2 by 2100. Contrary to the effects observed in teleosts and in some other sharks, behaviour of the epaulette shark was unaffected by elevated CO2. A potential explanation is the remarkable adaptation of H. ocellatum to low environmental oxygen conditions (hypoxia) and diel fluctuations in CO2 encountered in their shallow reef habitat. This ability translates into behavioural tolerance of near-future ocean acidification, suggesting that behavioural tolerance and subsequent adaptation to projected future CO2 levels might be possible in some other fish, if adaptation can keep pace with the rate of rising CO2 levels.