Water vapor adsorption by dry soils: A potential link between the water and carbon cycles

Water vapor adsorption (WVA) by soil is a potential contributor to the water cycle in drylands. However, continuous in-situ estimates of WVA are still scarce and the understanding of its coupling with carbon cycle and ecosystem processes remains at an incipient stage. Here we aimed to (1) identify periods of WVA and improve the understanding of the underlying processes involved in its temporal patterns by using the gradient method; (2) characterize a potential coupling between water vapor and CO₂ fluxes, and (3) explore the effect of soil properties and biocrusts ecological succession on fluxes. We assumed that the nocturnal soil CO₂ uptake increasingly reported in those environments could come from WVA enhancing geochemical reactions involving calcite. We measured continuously during ca. 2 years the relative humidity and CO₂ molar fraction in soil and atmosphere, in association with below- and aboveground variables, over the biocrusts ecological succession. We estimated water vapor and CO₂ fluxes with the gradient method, and cumulative fluxes over the study. Then, we used statistical modelling to explore relationships between variables. Our main findings are (1) WVA fluxes during hot and dry periods, and new insights on their underlying mechanisms; (2) a diel coupling between water vapor and CO₂ fluxes and between cumulative fluxes, well predicted by our models; and (3) cumulative CO₂ influxes increasing with specific surface area in early succession stages, thus mitigating CO₂ emissions. During summer drought, as WVA was the main water source, it probably maintained ecosystem processes such as microbial activity and mineral reactions in this dryland. We suggest that WVA could drive the nocturnal CO₂ uptake in those moments and discuss biogeochemical mechanisms potentially involved. Additional research is needed to monitor soil water vapor and CO₂ uptake and separate their biotic and abiotic components as those sinks could grow with climate change.

The relationship between volcanism and global climate changes in the Tropical Western Pacific over the mid-Pleistocene transition: Evidence from mercury concentration and isotopic composition

Volcanoes are a significant component of the Earth system, influencing the interaction between oceans and the atmosphere over large spatial and temporal scales. Being a volcanically dynamic region, the Tropical Western Pacific (TWP) can significantly impact variations in global climate. However, high-resolution continuous records of volcanic activity in this region are lacking, resulting in significant uncertainties regarding the coupling between the deep earth, climate changes, and atmospheric CO₂ in the TWP. To address this issue, mercury (Hg) levels, isotopic compositions, and Hg/total organic carbon (Hg/TOC) ratios were determined at site U1486 to track volcanic activity throughout the mid-Pleistocene transition (MPT) from 1.3 Myr to 0.6 Myr. Our results of anomalously high Hg concentrations and Hg/TOC ratios provide evidence of time-varying volcanism throughout the MPT. Mercury isotopes in the Hg-enriched sediments were characterized by near-zero Δ¹⁹⁹Hg values, which is consistent with volcanism acting as the primary source of Hg to the sediments. Spectral analysis of the Hg/TOC ratio showed significant periodicity at ~100 kyr and ~ 23 kyr as well as a weaker signal at ~41 kyr consistent with Milankovitch cycles. A cross spectral analysis of Hg/TOC and the LR04 δ¹⁸O stack record suggests that the peak in volcanism lags the temperature minimum by ~6 kyr, and occurs prior to the δ¹⁸O minimum known as the glacial termination by ~14 ± 2 kyr. The records of volcanic activity in this site are also consistent with a prominent rise in atmospheric CO₂ and negative excursion of benthic carbon isotopes throughout the MPT. This study provides direct sedimentary evidence in the TWP of the feedback between volcanic activity, climate change and atmospheric CO₂.

Postprandial nitrogen and acid-base regulation in the seawater acclimated green crab, Carcinus maenas

The effects of feeding (meal of 3% of body mass) on acid-base and nitrogen homeostasis were investigated in the seawater acclimated green shore crab, Carcinus maenas. Feeding did not change gastric fluid pH (~pH 6); however, feeding was associated with a respiratory acidosis. Hemolymph HCO₃^- did not increase during this acidosis, although titratable and net acid efflux changed from an uptake to an excretion. Feeding affected the crabs' nitrogen homeostasis causing a substantial increase in hemolymph ammonia and urea concentrations after six hours. At this point, hemolymph urea accounted for ~1/3 of nitrogenous waste accumulated within the hemolymph, suggesting a potential role in ammonia detoxification. The postprandial increase in hemolymph ammonia coincided with an 18-fold increase in ammonia excretion rates that accounted for the majority of net acid excreted by the crabs. Urea excretion rates did not increase after feeding; however, branchial urease activity increased, implying that the gills may possess a mechanism to form excretable ammonia through the catabolism of urea. Our results demonstrate that despite an acidic gastric compartment, C. maenas does not experience a postprandial alkaline tide and that any feeding related acid-base challenges are primarily derived from metabolic acid production. Our findings also indicate that unlike the bicarbonate buffering acid-base compensatory response induced by hypercapnia and emersion, acid-base challenges upon feeding are compensated through changes in the excretion of acid equivalents, mainly in the form of ammonia.

Does liming grasslands increase biomass productivity without causing detrimental impacts on net greenhouse gas emissions?

Soil acidification has negative impacts on grass biomass production and the potential of grasslands to mitigate greenhouse gas (GHG) emissions. Through a global review of research on liming of grasslands, the objective of this paper was to assess the impacts of liming on soil pH, grass biomass production and total net GHG exchange (nitrous oxide (N₂O), methane (CH₄) and net carbon dioxide (CO₂)). We collected 57 studies carried out at 88 sites and covering different countries and climatic zones. All of the studies examined showed that liming either reduced or had no effects on the emissions of two potent greenhouse gases (N₂O and CH₄). Though liming of grasslands can increase net CO₂ emissions, the impact on total net GHG emission is minimal due to the higher global warming potential, over a 100-year period, of N₂O and CH₄ compared to that of CO₂. Liming grassland delivers many potential advantages, which justify its wider adoption. It significantly ameliorates soil acidity, increases grass productivity, reduces fertiliser requirement and increases species richness. To realise the maximum benefit of liming grassland, we suggest that acidic soils should be moderately limed within the context of specific climates, soils and management.

High-efficient carbon dioxide-to-formic acid conversion on bimetallic PbIn alloy catalysts with tuned composition and morphology

CO₂ electroreduction to value-added chemicals and fuels has gained increasing attention; however, there are only a few catalysts with high performance under mild conditions that can be used in this technique. In this study, single metal Pb, In and bimetallic PbIn catalysts for aqueous CO₂ electroreduction were prepared using a facile 3-step process including PbIn granulation by reducing Pb(NO₃)₂/In(NO₃)₃ aqueous solution with NaBH₄, calcination in air, and in situ electroreduction. The bimetallic PbIn catalysts had better catalytic performance on CO₂ electroreduction than single metal catalysts. The bimetallic Pb₇In₃ catalyst (atomic ratios of Pb and In is 7:3) presented the highest formic acid faradaic efficiency of 91.6% at -1.26 V vs reversible hydrogen electrode in a 0.5 M CO₂-saturated KHCO₃ aqueous solution, which was 13% and 9.7% higher than that of single Pb and In catalysts, respectively. Moreover, the catalyst remained active after 10 h of continuous CO₂ electrolysis with a stale current density of -17 mA cm^-2. The experimental results showed that the excellent catalytic performance of Pb₇In₃ catalyst may stem from its higher electrochemical active surface area, lower charge-transfer resistance and the synergistic effect of Pb and In in the catalyst. The presented bimetallic PbIn catalysts may have a wide of application prospect, and they may be synthesized from heavy metals in industrial wastewaters.

Amygdala-driven apnea and the chemoreceptive origin of anxiety

Although the amygdala plays an important part in the pathogenesis of anxiety and generation of exteroceptive fear, recent discoveries have challenged the directionality of this brain-behavior relationship with respect to interoceptive fear. Here we highlight several paradoxical findings including: (1) amygdala lesion patients who experience excessive fear and panic following inhalation of carbon dioxide (CO₂), (2) clinically anxious patients who have significantly smaller (rather than larger) amygdalae and a pronounced hypersensitivity toward CO₂, and (3) epilepsy patients who exhibit apnea immediately following stimulation of their amygdala yet have no awareness that their breathing has stopped. The above findings elucidate an entirely novel role for the amygdala in the induction of apnea and inhibition of CO₂-induced fear. Such a role is plausible given the strong inhibitory connections linking the central nucleus of the amygdala with respiratory and chemoreceptive centers in the brainstem. Based on this anatomical arrangement, we propose a model of Apnea-induced Anxiety (AiA) which predicts that recurring episodes of apnea are being unconsciously elicited by amygdala activation, resulting in transient spikes in CO₂ that provoke fear and anxiety, and lead to characteristic patterns of escape and avoidance behavior in patients spanning the spectrum of anxiety. If this new conception of AiA proves to be true, and activation of the amygdala can repeatedly trigger states of apnea outside of one's awareness, then it remains possible that the chronicity of anxiety disorders is being interoceptively driven by a chemoreceptive system struggling to maintain homeostasis in the midst of these breathless states.

Subfornical organ interleukin 1 receptor: A novel regulator of spontaneous and conditioned fear associated behaviors in mice

Impaired threat responding and fear regulation is a hallmark of psychiatric conditions such as post-traumatic stress disorder (PTSD) and Panic Disorder (PD). Most studies have focused on external psychogenic threats to study fear, however, accumulating evidence suggests a primary role of homeostatic perturbations and interoception in regulating emotional behaviors. Heightened reactivity to interoceptive threat carbon dioxide (CO₂) inhalation associates with increased risk for developing PD and PTSD, however, contributory mechanisms and molecular targets are not well understood. Previous studies from our group suggested a potential role of interleukin 1 receptor (IL-1R1) signaling within BBB-devoid sensory circumventricular organ, the subfornical organ (SFO) in CO₂-evoked fear. However, the necessity of SFO-IL-1R1 in regulating CO₂-associated spontaneous fear as well as, long-term fear potentiation relevant to PD/PTSD has not been investigated. The current study tested male mice with SFO-targeted microinfusion of the IL-1R1 antagonist (IL-1RA) or vehicle in a recently developed CO₂-startle-fear conditioning-extinction paradigm. Consistent with our hypothesis, SFO IL-1RA treatment elicited significant attenuation of freezing and increased rearing during CO₂ inhalation suggesting SFO-IL1R1 regulation of spontaneous fear to CO₂. Intriguingly, SFO IL-1RA treatment normalized CO₂-associated potentiation of conditioned fear and impaired extinction a week later suggesting modulation of long-term fear by SFO-IL-1R1 signaling. Post behavior FosB mapping revealed recruitment of prefrontal cortex-amygdala-periaqueductal gray (PAG) areas in SFO-IL-1RA mediated effects. Additionally, we localized cellular IL-1R1 expression within the SFO to blood vessel endothelial cells and observed CO₂-induced alterations in IL-1β/IL-1R1 expression in peripheral mononuclear cells and SFO. Lastly, CO₂-evoked microglial activation was attenuated in SFO-IL-1RA treated mice. These observations suggest a peripheral monocyte-endothelial-microglia interplay in SFO-IL-1R1 modulation of CO₂-associated spontaneous fear and delayed fear memory. Collectively, our data highlight a novel, "bottom-up" neuroimmune mechanism that integrates interoceptive and exteroceptive threat processing of relevance to fear-related pathologies.

Combined effect of CO2 concentration and low-cost urea repletion/starvation in Chlorella vulgaris for ameliorating growth metrics, total and non-polar lipid accumulation and fatty acid composition

Different CO₂ concentration such as 0.03, 5, 10 and 15% and low-cost urea repletion/starvation in Chlorella vulgaris on growth, total and non-polar lipid content and fatty acid composition was studied. Chlorella vulgaris grown at 0.03% CO₂ apparently revealed inferior biomass yield 0.55 g/L on 14th day compared to CO₂ supplemented cells. In the case of CO₂ supply, 15% CO₂ has unveiled higher biomass yield at about 1.83 g/L on day 12 whereas biomass yield for 5 and 10% CO₂ supplemented cells was 1.61 and 1.73 g/L, respectively on 12th day of cultivation. The biomass productivity (g) per liter per day was 32 mg in control condition whereas it was 125, 134 and 144 mg/L/d in 5, 10 and 15% CO₂ supplied cells, respectively. Lipid content of the strain grown at control, 5, 10 and 15% CO₂ was 21.2, 22.1, 23.4 and 24.6%, respectively and however, without CO₂ addition in low-cost urea repleted and urea depleted medium grown cells revealed 21.2 and 24.2%, respectively. Interestingly, strain grown at 15% CO₂ supply in urea deplete medium yielded 28.7% lipid and contribution of non-polar lipids in total lipids is 69.7%. Further, the fatty acid composition of the strain grown in 15% CO₂ supply in urea depleted medium showed C16:0, C16:1, C18:1 and C18:3 in the level of 30.12, 9.98, 23.43, and 11.97%, respectively compared to control and urea amended condition.

Effect of CO2 on biogeochemical reactions and microbial community composition in bioreactors with deep groundwater and basalt

Changes in subsurface microbiology following CO₂ injection have the potential to impact carbon trapping in CO₂ storage reservoirs. However, much remains to be learned about responses of natural microbial consortia to elevated CO₂ in basaltic systems. This study asks: how will microbes from deep (700 m) groundwater change along a gradient in CO₂ (0-20 psi) in batch reactor systems containing basalt chips and groundwater amended with lactate? Reactors incubated for 87 days at 23 °C. Results for reactors with low CO₂ (0 and 3 psi) differed considerably from those with high CO₂ (10 and 20 psi). In reactors with low CO₂, pH was >6.5 and lactate started to be used within 24 days. By 40 days, lactate was completely consumed and acetate increased to ~4 mM. As lactate was consumed, sulfate decreased from 0.16 to 0 mM after 40 days. In contrast, in reactors with high CO₂, pH was <6.5, lactate and sulfate concentrations varied little and acetate was not produced. Biogeochemical modeling and community analyses indicate that differences between reactors with low and high CO₂ reflect tolerances of reactor microbes to CO₂ exposure. Communities in the low CO₂ reactors carried out syntrophic lactate oxidation coupled with methanogenesis and sulfate reduction. Bacteroidota and Firmicutes became dominant phyla after 24 days and groups capable of sulfate reduction and methanogenesis were detected. In reactors with high CO₂, however, biogeochemical activity was insignificant, no groups capable of sulfate reducion or methanogenesis were observed, and the community became less diverse during the incubation. These findings show that the response of microbial consortia can vary sharply along a CO₂ gradient, creating significant differences in community composition and biogeochemistry, and that the timescale of basalt weathering is likely not rapid enough to prevent significant stress following a rapid increase in CO₂ abundance.

Elevated CO2 levels alleviated toxicity of ZnO nanoparticles to rice and soil bacteria

Rising CO₂ levels will change the behavior and toxicity of soil contaminants. However, it remains unclear whether elevated CO₂ levels will change the nanoparticle dissolution or their biological effects in soil. In this study, we used a free-air CO₂ enrichment system to examine the effects of elevated CO₂ on phytotoxicity and bacterial toxicity of zinc oxide nanoparticles (nZnO) in a paddy soil system. The elevated CO₂ changed the nZnO diffraction in soil, slightly increasing its dissolution but remarkably improving its bioavailability. Elevated CO₂ did not change Zn accumulation in rice, but still alleviated the adverse effects of nZnO on rice growth, although grain protein, K and P decreased. Moreover, nZnO alone significantly decreased the number of observed soil bacterial species and altered the community organization, while elevated CO₂ moderated such changes. Overall, these results increase our understanding of plant response and microbial variation in nanoparticle-contaminated soil under elevated-CO₂ conditions. It is necessary to pay attention to soil pollution while facing climate change.

Study on the polystyrene plastic degradation in supercritical water/CO2 mixed environment and carbon fixation of polystyrene plastic in CO2 environment

Through the degradation of organic waste, the carbon can be extracted and converted into syngas with calorific value, and the CO₂ generated can also be used after fixed. In this work, the gasification of polystyrene (PS) in supercritical water with CO₂ was studied in the temperature range of 400 °C-700 °C and time range of 0-30 min. In addition, PS containing only carbon and hydrogen can react with CO₂ to generate CO in CO₂ atmosphere. Therefore, the degradation of PS plastics in CO₂ atmosphere was also studied. The results showed that PS plastic was hardly gasified at 400 °C, and as the temperature rose, the liquid composition changed. In supercritical water, under certain feedstock conditions, reacting for 20 min, the carbon conversion efficiency of PS plastic reached 47.6% at 700 °C. Under all CO₂ atmosphere conditions in this experiment, the highest proportion of CO₂ consumed by PS degradation was 12.5%. Moreover, the higher the temperature, the smaller the average diameter of carbon microspheres in the solid product. The morphology of carbon microsphere was also related to the reaction time, and the main change came from the gasification of carbon microspheres and the precipitation and adhesion of carbon element in liquid product.

Sudden unexpected death in epilepsy: Respiratory mechanisms

Epilepsy is one of the most common chronic neurologic diseases, with a prevalence of 1% in the US population. Many people with epilepsy live normal lives, but are at risk of sudden unexpected death in epilepsy (SUDEP). This mysterious comorbidity of epilepsy causes premature death in 17%-50% of those with epilepsy. Most SUDEP occurs after a generalized seizure, and patients are typically found in bed in the prone position. Until recently, it was thought that SUDEP was due to cardiovascular failure, but patients who died while being monitored in hospital epilepsy units revealed that most SUDEP is due to postictal central apnea. Some cases may occur when seizures invade the amygdala and activate projections to the brainstem. Evidence suggests that the pathophysiology is linked to defects in the serotonin system and central CO₂ chemoreception, and that there is considerable overlap with mechanisms thought to be involved in sudden infant death syndrome (SIDS). Future work is needed to identify biomarkers for patients at highest risk, improve ascertainment, develop methods to alert caregivers when SUDEP is imminent, and find effective approaches to prevent these fatal events.

Multifaceted strategies for economic production of microalgae Haematococcus pluvialis-derived astaxanthin via direct conversion of CO2

Owing to its strong antioxidant properties, astaxanthin has a high market price in the nutraceutical and pharmaceutical fields, and its demand is increasing. Furthermore, with an increase in the demand for green technology, astaxanthin production through direct CO₂ conversion using the autotrophic green microalga Haematococcus pluvialis as a bio-platform has received much attention. Large-scale outdoor cultivation of H. pluvialis using waste CO₂ sources and sunlight can secure sustainability and improve economic efficiency. However, low strain performance, reduced light utilization because of increased cell density, and inefficient transfer of gaseous CO₂ into liquid culture broth hinder its large-scale commercialization of astaxanthin. Herein, we presented a multifaceted strategy, including the development of high-efficiency strains, a culture system for astaxanthin accumulation, and astaxanthin extraction from biomass, for economically producing astaxanthin from H. pluvialis through direct CO₂ conversion. Future perspectives were presented by comparing and analyzing various previous studies conducted using the latest technology.

Performance intensification of CO2 absorption and microalgae conversion (CAMC) hybrid system via low temperature plasma (LTP) treatment

CO₂ absorption and microalgae conversion (CAMC) hybrid system is a promising alternative for simultaneous carbon capture and utilization. It can not only overcome the challenge of high energy consumption solvent thermal regeneration in chemical CO₂ absorption, but also enhance the carbon conversion efficiency in biological conversion process. However, the discordance between CO₂ absorption and bio-conversion rate has become the key to limiting the development of CAMC system. Therefore, in this study, low temperature plasma (LTP) mutation breeding technology was used to training Chlorella strains by combining undirected mutagenesis and directional screening. Then, the mutagenic microalgae were cultivated and evaluated in CAMC system. It was found that compared with original Chlorella L166, the OD₆₈₀ of mutant strain L166-M₃ in CAMC system increased 7.8%, and the maximum specific growth rate improved 27.5%. The carbon sequestration rate of wild Chlorella L166 increased from 82.9% to 93.7% after mutation treatment, the activity of RubisCO, and the content of NADPH produced by photoreaction increased 37.2% and 17.2%. In addition, lipid production of L166-M₃ increased to 6.89 mg/L, which was 15.4% higher than original Chlorella L166. It could be observed that LTP mutation breeding could be used as a potential method for training algae species and improve the overall performance of CAMC system.

Sc-functionalized porphyrin-like porous fullerene for CO2 storage and separation: A first-principles evaluation

In recent years, there has been a lot of interest in capturing and storing carbon dioxide (CO₂) on porous materials as an efficient method for decreasing the adverse effects of this greenhouse gas on the environment and climate change. The current work introduces a Sc-decorated porphyrin-like porous fullerene (Sc₆@C₂₄N₂₄) as an efficient material for CO₂ capture, storage, and separation using density functional theory calculations. While CO₂ is physisorbed over pristine C₂₄N₂₄, the addition of Sc atoms on the N₄ sites of C₂₄N₂₄ greatly enhances CO₂ adsorption energy. Each Sc atom in Sc₆@C₂₄N₂₄ may adsorb up to three CO₂ molecules, resulting in a gravimetric density of 48%. Moreover, temperature may be used to modulate CO₂ adsorption/desorption over the substrate. The Sc-decorated C₂₄N₂₄ fullerene exhibits a lower affinity for adsorbing N₂, CH₄, and H₂ molecules than CO₂. As a consequence, this material might be considered for purifying CO₂ molecules from CO₂/N₂, CO₂/CH₄, and CO₂/H₂ mixtures. This study also sheds light on the nature of the Sc-CO₂ interaction as well as the underlying mechanism of selective CO₂ adsorption on Sc decorated C₂₄N₂₄.

Nest guarding behaviour of a temperate wrasse differs between sites off Mediterranean CO2 seeps

Organisms may respond to changing environmental conditions by adjusting their behaviour (i.e., behavioural plasticity). Ocean acidification (OA), resulting from anthropogenic emissions of carbon dioxide (CO₂), is predicted to impair sensory function and behaviour of fish. However, reproductive behaviours, and parental care in particular, and their role in mediating responses to OA are presently overlooked. Here, we assessed whether the nesting male ocellated wrasse Symphodus ocellatus from sites with different CO₂ concentrations showed different behaviours during their breeding season. We also investigated potential re-allocation of the time-budget towards different behavioural activities between sites. We measured the time period that the nesting male spent carrying out parental care, mating and exploring activities, as well as changes in the time allocation between sites at ambient (~400 μatm) and high CO₂ concentrations (~1000 μatm). Whilst the behavioural connectance (i.e., the number of linkages among different behaviours relative to the total amount of linkages) was unaffected, we observed a significant reduction in the time spent on parental care behaviour, and a significant decrease in the guarding activity of fish at the high CO₂ sites, with a proportional re-allocation of the time budget in favour of courting and wandering around, which however did not change between sites. This study shows behavioural differences in wild fish living off volcanic CO₂ seeps that could be linked to different OA levels, suggesting that behavioural plasticity may potentially act as a mechanism for buffering the effects of ongoing environmental change. A reallocation of the time budget between key behaviours may play a fundamental role in determining which marine organisms are thriving under projected OA.

CO2 capture by adsorption on biomass-derived activated char: A review

Carbon capture and storage has been recognized as the most promising method for CO₂ control. Among the many sorbents, char derived from pyrolysis and hydrothermal carbonization (HTC) of biomass have demonstrated excellent CO₂ adsorption capability. This paper reviews the different parameters to produce a higher yield of biochar and hydrochar suitable for carbon sequestration. The mechanism of physisorption and chemisorption is briefly presented. The different kinetic models, diffusion models to describe adsorption mechanism, and adsorption isotherms for CO₂ uptake from biomass-derived hydrochar are reviewed. The different factors that affect the CO₂ uptake are the type of activation, surface area and porosity, the ratio of activation agent to char, activation temperature, adsorption pressure and temperature, additives, and other physicochemical properties. The optimal conditions for CO₂ uptake with chemical activation of KOH is a KOH/char ratio of 2-3, activation temperature of 700 °C, and an adsorption temperature below 50 °C.

Constructing highly porous carbon materials from porous organic polymers for superior CO2 adsorption and separation

The increase in atmospheric carbon dioxide (CO₂) concentration has led to numerous problems related to our living environment, seeking an efficient carbon capture and storage (CCS) strategy associated with low energy consumption and expenditures is highly desirable. Here, we demonstrate a facile approach to synthesize a series of highly porous carbon materials derived from porous organic polymers synthesized from three low-cost isomers of triphenyl using chemical activation with KOH at different temperatures. Compared with the precursor porous organic polymers, the porosity of the prepared porous carbon materials is significantly enhanced with surface areas as high as 3367 m² g^-1 and pore volumes up to 1.224 cm³ g^-1. Notably, such porous carbon materials deliver an exceptionally high CO₂ adsorption capacity of 7.78 mmol g^-1 at 273 K and 1 bar, a value that is superior to most of the previously reported adsorbents. In addition, these porous organic polymers and derived porous carbon materials exhibit high CO₂/N₂ selectivity at ambient conditions. Therefore, the facile construction of highly porous carbon materials from porous organic polymers may offer an efficient strategy for CO₂ adsorption and separation and further mitigates greenhouse effect.

Unveiling the changes in urban atmospheric CO2 in the time of COVID-19 pandemic: A case study of Florence (Italy)

The outbreak of COVID-19 pandemic was accompanied by global mobility restrictions and slowdown in manufacturing activities. Accordingly, cities experienced a significant decrease of CO₂ emissions. In this study, continuous measurements of CO₂ fluxes, atmospheric CO₂ concentrations and δ¹³C-CO₂ values were performed in the historical center of Florence (Italy) before, during and after the almost two-month long national lockdown. The temporal trends of the analyzed parameters, combined with the variations in emitting source categories (from inventory data), evidenced a fast response of flux measurements to variations in the strength of the emitting sources. Similarly, the δ¹³C-CO₂ values recorded the change in the prevailing sources contributing to urban atmospheric CO₂, confirming the effectiveness of carbon isotopic data as geochemical tracers for identifying and quantifying the relative contributions of emitting sources. Although the direct impact of restriction measurements on CO₂ concentrations was less clear due to seasonal trends and background fluctuations, an in-depth analysis of the daily local CO₂ enhancement with respect to the background values revealed a progressive decrease throughout the lockdown phase at the end of the heating season (>10 ppm), followed by a net increase (ca. 5 ppm) with the resumption of traffic. Finally, the investigation of the shape of the frequency distribution of the analyzed variables revealed interesting aspects concerning the dynamics of the systems.

Recent progress and challenges in microbial polyhydroxybutyrate (PHB) production from CO2 as a sustainable feedstock: A state-of-the-art review

The recalcitrance of petroleum-based plastics causes severe environmental problems and has accelerated research into production of biodegradable polymers from inexpensive and sustainable feedstocks. Various microorganisms are capable of producing Polyhydroxybutyrate (PHB), a representative biodegradable polymer, under nutrient-limited conditions, among which CO₂-utilizing microorganisms are of primary interest. Herein, we discuss recent progress on bacterial strains including proteobacteria, purple non-sulfur bacteria, and cyanobacteria in terms of CO₂-containing carbon sources, PHB-production capability, and genetic modification. In addition, this review introduces recent technical approaches used to improve PHB production from CO₂ such as two-stage bioprocesses and bioelectrochemical systems. Challenges and future perspectives for the development of economically feasible PHB production are also discussed. Finally, this review might provide insights into the construction of a closed-carbon-loop to cope with climate change.

CO2 concentration monitoring inside educational buildings as a strategic tool to reduce the risk of Sars-CoV-2 airborne transmission

In order to avoid SARS-CoV-2 transmission inside educational buildings and promote the safe reopening of schools, the Italian Government, in line with the other European countries and in accordance with the WHO recommendations, adopted a contingency plan including actions able to guarantee adequate air ventilation in classrooms. Therefore, in this pilot study, a surveillance activity based on the real-time monitoring of CO₂ levels as a proxy of SARS-CoV-2 transmission risk, was conducted inside 9 schools (11 classrooms) located in Apulia Region (South of Italy) during the reopening of schools after the lockdown due to COVID-19 pandemic. More specifically, monitoring activities and data treatment were conducted to evaluate the initial scenario inside the classrooms (first stage of evaluation) and the potential improvements obtained by applying a detailed operating protocol of air ventilation based on specific actions and the simultaneous real time visualization of CO₂ levels by non-dispersive infrared (NDIR) sensors (second stage of evaluation). Although, during the first evaluation stage, air ventilation through the opening of windows and doors was guaranteed, 6 (54%) classrooms showed mean values of CO₂ higher than 1000 ppm and all classrooms exceeded the recommended CO₂ concentration limit value of 700 ppm. The development and implementation of tailored ventilation protocol including the real time visualization of CO₂ levels allowed to depict better scenariosAn overall improvement of CO₂ levels was indeed registered for all classrooms where teachers were compliant and helpful in the management of the air ventilation strategy. Therefore, this study reports the first evidence-based measures demonstrating that, with the exception of few environments affected by structural limits, the real-time visualization and monitoring of CO2 concentrations allowes effective air exchanges to be implemented and contributes to prevent SARS-CoV-2 transmission. Moreover, on the basis of the monitoring outcomes and in order to ensure adequate air ventilation in educational buildings, a 4 level-risk classification including specific corrective actions for each level was provided.

Enhanced light-driven CO2 reduction on metal-free rich terminal oxygen-defects carbon nitride nanosheets

Exploiting highly-efficient and metal-free photocatalyst for CO₂ conversion into useful chemicals is a promising pathway to solve the energy and environmental crises. In this work, through a facile exfoliation process, an ultra-thin and short-range order g-C₃N₄ nanosheet with rich terminal oxygen defects is successfully constructed, which presents total electron yield of 36.30 μmol g^-1h^-1, 3.05 times higher than that of bulk one. The results affirms that both the van der Waals forces between the C₃N₄ layers and the CN bonds on the periodic heptazine units could be disrupted during the sonication process, thus achieving the ultra-thin and ultra-small g-C₃N₄ nanosheet, which enables the improvement of optical absorption and carrier separation abilities. The π-conjugated triazine rings structure is still remained but the terminal active C radicals tend to transform into oxygen defects which become the sites to bind and activate CO₂. The in-situ DRIFTS provides the direct evidence that the size regulation and oxygen-defects design strategy can effectively promote the CO₂ adsorption and activation process upon the photocatalyst, thus turning out to boost the reactivity toward CO₂.

Synergistic effects of CO2 on complete thermal degradation of plastic waste mixture through a catalytic pyrolysis platform: A case study of disposable diaper

Consumption of diverse plastics has posed an environmental threat because their disposal practices, landfilling and incineration, release toxic chemicals and microplastics into all environmental media. Indeed, heterogeneous matrix of plastic wastes makes them hard to be disposed. As such, this study aimed to introduce an environmentally benign/reliable disposal platform for complete decomposition of plastic wastes. Pyrolysis process was adapted to convert plastics into syngas, and a disposable diaper (DD) was used as model plastic waste, because it is composed of a variety of polymeric materials. Pyrolysis of DD resulted in the formation of gaseous products and pyrogenic oils, composed of (oxygenated) hydrocarbons. Nonetheless, reactivity of CO₂ as an oxidant in pyrolysis of DD was negligible. To impart the strong/desired reactivity of CO₂, Ni-based catalyst was adopted. Ni catalyst enhanced H₂ and CO formations 4 and 15 times more than pyrolysis without catalyst at 700 °C under CO₂. The value-added syngas production was originated from the reduction of polymeric waste, and its derivatives including aromatic compounds. Thus, CO₂ offered a strategic means to produce value-added chemicals and reduce aromaticity of pyrogenic products. The observations could offer an innovative way to control the fate of toxic chemicals derived from plastic pyrolysis.

Effect of eggshell- and homo-type Ni/Al2O3 catalysts on the pyrolysis of food waste under CO2 atmosphere

This study highlights the potential of pyrolysis of food waste (FW) with Ni-based catalysts under CO₂ atmosphere as an environmentally benign disposal technique. FW was pyrolyzed with homo-type Ni/Al₂O₃ (Ni-HO) or eggshell-type Ni/Al₂O₃ (Ni-EG) catalysts under flowing CO₂ (50 mL/min) at temperatures from 500 to 700 °C for 1 h. A higher gas yield (42.05 wt%) and a lower condensable yield (36.28 wt%) were achieved for catalytic pyrolysis with Ni-EG than with Ni-HO (34.94 wt% and 40.06 wt%, respectively). In particular, the maximum volumetric content of H₂ (21.48%) and CO (28.43%) and the lowest content of C₂-C₄ (19.22%) were obtained using the Ni-EG. The formation of cyclic species (e.g., benzene derivatives) in bio-oil was also effectively suppressed (24.87%) when the Ni-EG catalyst and CO₂ medium were concurrently utilized for the FW pyrolysis. Accordingly, the simultaneous use of the Ni-EG catalyst and CO₂ contributed to altering the carbon distribution of the pyrolytic products from condensable species to value-added gaseous products by facilitating ring-opening reactions and free radical mechanisms. This study should suggest that CO₂-assisted catalytic pyrolysis over the Ni-EG catalyst would be an eco-friendly and sustainable strategy for disposal of FW which also provides a clean and high-quality source of energy.

Development of an extended model for the permeation of environmentally hazardous CO2 gas across asymmetric hollow fiber composite membranes

This study presents an extended thermodynamic and phenomenological combined model to mitigate the environmental hazardous acid gas over composite membranes. The model has been applied to an acid gas such as carbon dioxide (CO₂) for its permeation through polyetherimide incorporated montmorillonite (Mt) nanoparticles hollow fiber asymmetric composite membranes. The well-established non-equilibrium lattice fluid (NELF) model for penetrating low molecular weight penetrant in a glassy polyetherimide (PEI) was extended to incorporate the other important polymer/filler system features such as tortuosity in acid gas diffusion pathways resulted from layered filler aspect ratio and concentration. The model mentioned above predicts the behavior of acid gas in PEI-Mt composite membranes based on thermodynamic characteristics of CO₂ and PEI and tortuosity due to Mt. The calculated results are compared to experimentally determined values of CO₂ permeability through PEI-Mt composite asymmetric hollow fiber membranes at varying transmembrane pressures and Mt concentrations. A reasonable agreement was found between the model predicted behavior and experimentally determined data in terms of CO₂ solubility, Mt concentration and aspect ratio were calculated based on average absolute relative error (%AARE). The proposed modified model efficiently predicts the CO₂ permeance across MMMs up to 3 wt% Mt loadings and 6 bar pressure with ± 10%AARE.

Pharmacological MRI with Simultaneous Measurement of Cerebral Perfusion and Blood-Cerebrospinal Fluid Barrier Function using Interleaved Echo-Time Arterial Spin Labelling

Pharmacological MRI (phMRI) studies seek to capture changes in brain haemodynamics in response to a drug. This provides a methodological platform for the evaluation of novel therapeutics, and when applied to disease states, may provide diagnostic or mechanistic information pertaining to common brain disorders such as dementia. Changes to brain perfusion and blood-cerebrospinal fluid barrier (BCSFB) function can be probed, non-invasively, by arterial spin labelling (ASL) and blood-cerebrospinal fluid barrier arterial spin labelling (BCSFB-ASL) MRI respectively. Here, we introduce a method for simultaneous recording of pharmacological perturbation of brain perfusion and BCSFB function using interleaved echo-time ASL, applied to the anesthetized mouse brain. Using this approach, we capture an exclusive decrease in BCSFB-mediated delivery of arterial blood water to ventricular CSF, following anti-diuretic hormone, vasopressin, administration. The commonly used vasodilatory agent, CO2, induced similar increases (~21%) in both cortical perfusion and the BCSFB-ASL signal. Furthermore, we present evidence that caffeine administration triggers a marked decrease in BCSFB-mediated labelled water delivery (41%), with no significant changes in cortical perfusion. Finally, we demonstrate a marked decrease in the functional response of the BCSFB to, vasopressin, in the aged vs adult brain. Together these data, the first of such kind, highlight the value of this translational approach to capture simultaneous and differential pharmacological modulation of vessel tone at the blood brain barrier and BCSFB and how this relationship may be modified in the ageing brain.

Lichen, moss and peat control of C, nutrient and trace metal regime in lakes of permafrost peatlands

Permafrost thaw in continental lowlands produces large number of thermokarst (thaw) lakes, which act as a major regulator of carbon (C) storage in sediments and C emission in the atmosphere. Here we studied thaw lakes of the NE European permafrost peatlands - shallow water bodies located within frozen peat bogs and receiving the majority of their water input from lateral (surface) runoff. We also conducted mesocosm experiments via interacting lake waters with frozen peat and dominant ground vegetation - lichen and moss. There was a systematic decrease in concentrations of dissolved C, CO₂, nutrients and metals with an increase in lake size, corresponding to temporal evolution of the water body and thermokarst development. We hypothesized that ground vegetation and frozen peat provide the majority of C, nutrients and inorganic solutes in the water column of these lakes, and that microbial processing of terrestrial organic matter controls the pattern of CO₂ and nutrient concentrations in thermokarst lakes. Substrate mass-normalized C, nutrient (N, P, K), major and trace metal release was maximal in moss mesocosms. After first 16 h of reaction, the pCO₂ increased ten-fold in mesocosms with moss and lichen; this increase was much less pronounced in experiments with permafrost peat. Overall, moss and lichen were the dominant factors controlling the enrichment of the lake water in organic C, nutrients, and trace metals and rising the CO₂ concentration. The global significance of obtained results is that the changes in ground vegetation, rather than mere frozen peat thawing, may exert the primary control on C, major and trace element balance in aquatic ecosystems of tundra peatlands under climate warming scenario.

Polyethylene terephthalate (PET) recycling via steam gasification - The effect of operating conditions on gas and tar composition

Polyethylene terephthalate (PET) is widely used in textile fiber, film, and bottles. Although PET bottle recycling has made great progress, other PET waste is still not recycled. Gasification could be an option for recycling or recovering energy and chemicals from PET waste. However, single stream PET steam gasification in fluidized bed is seldom investigated. In this paper, individual PET gasification experiments were then conducted in a lab-scale bubbling fluidized bed to investigate how gasifying agents, temperature, residence time and steam/fuel ratio affect the product composition. The results showed that, in steam gasification, steam was the main source of H₂, but increasing the steam to fuel ratio cannot increase the H₂ yield remarkably. Temperature was an essential parameter. Increasing temperature from 750 to 800 °C improved the yields of H₂ (+87.7%), the dominant gas product CO₂ (+40.3%), and biphenyl (+123%) notably. In contrast to other common thermoplastics, high concentrations of CO₂ and biphenyl are the prominent characteristics of PET steam gasification. In addition, plastic steam gasification optimizations for syngas applications were discussed.

How to reduce the greenhouse gas emissions and air pollution caused by light and heavy duty vehicles with battery-electric, fuel cell-electric and catenary trucks

The reduction of greenhouse gas emissions is one of the greatest global challenges through 2050. Besides greenhouse gas emissions, air pollution, such as nitrogen oxide and particulate matter emissions, has gained increasing attention in agglomerated areas with transport vehicles being one of the main sources thereof. Alternative fuels that fulfill the greenhouse gas reduction goals also offer the possibility of solving the challenge of rising urban pollution. This work focuses on the electric drive option for heavy and light duty vehicle freight transport. In this study, fuel cell-electric vehicles, battery-electric vehicles and overhead catenary line trucks were investigated, taking a closer look at their potential to reduce greenhouse gas emissions and air pollution and also considering the investment and operating costs of the required infrastructure. This work was conducted using a bottom-up transport model for the federal state of North Rhine-Westphalia in Germany. Two scenarios for reducing these emissions were analyzed at a spatial level. In the first of these, selected federal highways with the highest traffic volume were equipped with overhead catenary lines for the operation of diesel-hybrid overhead trucks on them. For the second spatial scenario, the representative urban area of the city of Cologne was investigated in terms of air pollution, shifting articulated trucks to diesel-hybrid overhead trucks and rigid trucks, trailer trucks and light duty vehicles to battery-electric or fuel cell-electric drives. For the economic analysis, the building up of a hydrogen infrastructure in the cases of articulated trucks and all heavy duty vehicles were also taken into account. The results showed that diesel-hybrid overhead trucks are only a cost-efficient solution for highways with high traffic volume, whereas battery overhead trucks have a high uncertainty in terms of costs and technical feasibility. In general, the broad range of costs for battery overhead trucks makes them competitive with fuel cell-electric trucks. Articulated trucks have the highest potential to be operated as overhead trucks. However, the results indicated that air pollution is only partially reduced by switching conventional articulated trucks to electric drive models. The overall results show that a comprehensive approach such as fuel cell-electric drives for all trucks would most likely be more beneficial.

A practical modification to a resting state fMRI protocol for improved characterization of cerebrovascular function

Cerebrovascular reactivity (CVR), defined here as the Blood Oxygenation Level Dependent (BOLD) response to a CO₂ pressure change, is a useful metric of cerebrovascular function. Both the amplitude and the timing (hemodynamic lag) of the CVR response can bring insight into the nature of a cerebrovascular pathology and aid in understanding noise confounds when using functional Magnetic Resonance Imaging (fMRI) to study neural activity. This research assessed a practical modification to a typical resting-state fMRI protocol, to improve the characterization of cerebrovascular function. In 9 healthy subjects, we modelled CVR and lag in three resting-state data segments, and in data segments which added a 2–3 minute breathing task to the start of a resting-state segment. Two different breathing tasks were used to induce fluctuations in arterial CO₂ pressure: a breath-hold task to induce hypercapnia (CO₂ increase) and a cued deep breathing task to induce hypocapnia (CO₂ decrease). Our analysis produced voxel-wise estimates of the amplitude (CVR) and timing (lag) of the BOLD-fMRI response to CO₂ by systematically shifting the CO₂ regressor in time to optimize the model fit. This optimization inherently increases gray matter CVR values and fit statistics. The inclusion of a simple breathing task, compared to a resting-state scan only, increases the number of voxels in the brain that have a significant relationship between CO₂ and BOLD-fMRI signals, and improves our confidence in the plausibility of voxel-wise CVR and hemodynamic lag estimates. We demonstrate the clinical utility and feasibility of this protocol in an incidental finding of Moyamoya disease, and explore the possibilities and challenges of using this protocol in younger populations. This hybrid protocol has direct applications for CVR mapping in both research and clinical settings and wider applications for fMRI denoising and interpretation.

Effects of CO2 and temperature on phytolith dissolution

Phytoliths, silica structures derived from plant residues in silicon (Si)-accumulating plant species, have recently been recognized as a sink and source of nutrients and a hosting phase for carbon sequestration in soil. While the solubility of phytoliths in relation to their respective nature and solution chemistry has been intensively studied, the combined effects of CO₂ and temperature, two highly variable parameters in soil, have not been fully understood. We hypothesized that changes in CO₂ and temperature may affect the dissolution rate, thereby resizing the soil phytolith pool. Rice straw phytoliths were obtained from either open burning or controlled heating of straw from 300 to 900 °C and used to determine their batch incubation kinetics in a closed chamber at CO₂ concentrations of 0 to 15% vol. and a temperature range of 20 to 50 °C for six days. The results revealed a contrasting effect in which temperature and CO₂ were correspondingly found to accelerate or decelerate the dissolution rate of phytoliths. Under the most dissimilar conditions, i.e., 0% vol. CO₂ and 50 °C and 15% vol. CO₂ and 20 °C, the discrepancy in solubility was approximately six-fold, indicating a high vulnerability of phytoliths to CO₂ and temperature changes. This finding also suggests that the soil phytolith pool can be diminished in the case of either increasing soil temperature or decreasing CO₂ flux. Calculations based on these data revealed that the dissolution rate of phytoliths could be increased by an average of 4.5 to 7.3% for each 1 °C increase in temperature. This finding suggests a possible impact of current global warming on the global biogenic silica pool, and more insight into the relationship between this pool and climate change is, therefore, necessary to maintain the function of the phytolith phase in soil.

Visible-light-driven photocatalysis of carbon dioxide and organic pollutants by MFeO2 (M = Li, Na, or K)

In recent years, lithium-containing ceramic materials have attracted considerable research attention as high-temperature adsorbents of carbon dioxide. The recycling of electrode materials from spent lithium-ion batteries for use as photocatalysts in recovering CO₂ and degrading organic pollutants is worthy of exploration. Solid, magnetic ferrite-containing photocatalysts are easily separated from reaction solutions by using magnetic devices. Solid catalysts (e.g., LiFeO₂, LiFe₅O₈, NaFeO₂, and K₂Fe₂O₄) were prepared through the calcination of Fe₂O₃ and M₂CO₃. CO₂ was photoreduced and crystal violet (CV) and 2-hydroxybenzoic acid (2-HBA) were photodegraded under visible light irradiation. The optimized K₂Fe₂O₄ photocatalyst increased the rate of photocatalytic conversion from CO₂ to methane at 20.9 µmol g^-1 h^-1. The catalytic efficiency indicated that the optimized reaction rate constants of CV with LiFeO₂, NaFeO₂, and K₂Fe₂O₄ were 2.98 × 10^-1, 5.32 × 10^-1, and 4.36 × 10^-1 h^-1, respectively. The quenching effect achieved through the use of various scavengers and the electron paramagnetic resonance in CV degradation revealed the substantial contribution of the reactive superoxide anion radical O₂^- and the minor roles of h⁺ and the OH radical. Its usefulness in the synthesis of solid-base catalyst MFeO₂ is promising for environmental control and relevant applications, particularly in solar energy manufacturing.

Efficient carboxylation of styrene and carbon dioxide by single-atomic copper electrocatalyst

Electrocarboxylation of olefins with carbon dioxide (CO₂) is a potential approach to produce carboxylates as synthetic intermediates of polymer and pharmaceuticals. Nonetheless, due to the intrinsic inertness of CO₂ at ambient conditions, the electrocarboxylation efficiency has been quite limited, typically with high applied potentials and low current densities. In this work, we demonstrate that nitrogen-coordinated single-atomic copper sites on carbon framework (Cu/NC) served as an excellent electrocatalyst for electrocarboxylation of styrene with CO₂. The Cu/NC catalyst allowed to efficiently activate CO₂, followed by nucleophilic attack to carboxylate styrene to produce phenylsuccinic acid, thus leading the reaction toward the CO₂ activation pathway. The enhanced CO₂ activation capability enabled increased selectivity and activity for electrocarboxylation of styrene. The Faradaic efficiency of electrocarboxylation was 92%, suggesting most of the activated CO₂ proceeded to react with styrene rather than direct reduction to CO or CH₄. The electrocarboxylation exhibited almost 100% product selectivity toward phenylsuccinic acid, with a high partial current density of 58 mA·cm^-2 at -2.2 V (vs. Ag/AgI), corresponding to an outstanding production rate of 216 mg·cm^-2·h^-1, substantially exceeding previously reported works. Our work suggests an exciting perspective in electrocarboxylation of olefins by rational design of CO₂ activation electrocatalysts.

A review on the emerging applications of cellulose, cellulose derivatives and nanocellulose in carbon capture

Carbon capture can be implemented at a large scale only if the CO₂ selective materials are abundantly available at low cost. Since the sustainable requirement also elevated, the low-cost and biodegradable cellulosic materials are developed into CO₂ selective adsorbent and membranes recently. The applications of cellulose, cellulosic derivatives and nanocellulose as CO₂ selective adsorbents and membranes are reviewed here. The fabrication and modification strategies are discussed besides comparing their CO₂ separation performance. Cellulose nanofibrils (CNFs) and cellulose nanocrystals (CNCs) isolated from cellulose possess a big surface area for mechanical enhancement and a great number of hydroxyl groups for modification. Nanocellulose aerogels with the large surface area were chemically modified to improve their selectivity towards CO₂. Even with the reduction of surface area, amino-functionalized nanocellulose aerogels exhibited the satisfactory chemisorption of CO₂ with a capacity of more than 2 mmol/g was recorded. Inorganic fillers such as silica, zeolite and MOFs were further incorporated into nanocellulose aerogels to enhance the physisorption of CO₂ by increasing the surface area. Although CO₂ adsorbents developed from cellulose and cellulose derivatives were less reported, their applications as the building blocks of CO₂ separation membranes had been long studied. Cellulose acetate membranes were commercialized for CO₂ separation, but their separation performance could be further improved with silane or inorganic filler. CNCs and CNFs enhanced the CO₂ selectivity and permeance through polyvinyl alcohol coating on membranes, but only CNF membranes incorporated with MOFs were explored so far. Although some of these membranes surpassed the upper-bound of Robeson plot, their stability should be further investigated.

Impact of substrate moisture content on growth and metabolic performance of black soldier fly larvae

Substrate moisture content is an important but not well-understood variable in production and waste reduction processes that involves black soldier fly (BSF) larvae. The purpose of this paper is to characterise growth and metabolic performance of BSF larvae on substrate moisture contents from 45 to 85%. Larvae developed into prepupae only at 45-75% substrate moisture content. Within this interval, the maximal specific growth rate was highest (0.73 day^-1), the growth period shortest (13 days), and the maximal dry weight lowest (88 mg) at 45% moisture content. Differences in cost of growth and maintenance were not observed at the different substrate moisture contents, and differences in larval performance were likely associated to differences in co-occurring microbial activities. As much as 22% of the substrate carbon was emitted as CO₂ at 45% moisture content by microorganisms, measured as the difference between total respiration and larval respiration, whereas microbial CO₂ production amounted to only 3% of the substrate carbon at 75% moisture content. As consequence of the high specific growth rate and short growth phase, the overall net growth efficiency was higher at 45% moisture content (0.62) than at 75% moisture content (0.52). Overall, the metabolic performance of the BSF larvae was insensitive to differences in substrate moisture content. Their performance was, however indirectly affected by the substrate moisture content due to differences in co-occurring microbial processes in the substrate.

Comparison of two methods for converting central venous values of acid-base status to arterial values in critically ill patients

BACKGROUND

Assessment of the critically ill patient requires arterial acid-base status. Venous blood could provide a surrogate, with methods transforming venous values to arterial, improving their utility. This manuscript compares two of these methods, a statistical and a physiological method. Where these methods are inadequate to describe critically ill patients, physiological mechanisms are explored to explain discrepancies.

METHODS

1109 paired arterial and central-venous blood samples, from patients diagnosed with acute circulatory failure, were available for retrospective analysis. Of these, 386 samples were used previously to validate the statistical model. The statistical method of Boulain et al. 2016 and the physiological method of Rees et al. 2006 were applied to the 386 sample pairs, and compared using Bland-Altman analysis. A subset of the 1109 samples, where the physiological method could not accurately calculate arterial values, were analysed further to assess the necessary addition of CO₂ or strong acid at the tissues to account for arterio-venous differences.

RESULTS

Bias (LoA) for comparison of calculated and measured arterial values (n = 386) were similar for the statistical method (pH: -0.003 (-0.051 to 0.045), PCO₂: -0.02 (-1.33 to 1.29 kPa)) and physiological method (pH: 0.009 (-0.033 to 0.052), PCO₂: -0.08 (-1.20 to 1.03 kPa)). In the 381 cases (of the 1109 sample pairs) defined as not accurately described, addition of a median CO₂ concentration of 0.72 mmol/l in excess of aerobic metabolism, explained this for 333 cases, with the remainder requiring simultaneous strong acid transport.

CONCLUSION

Both methods appear equal in their ability to transform central-venous values to arterial, albeit warranting caution when using either in a critically ill population. The physiological approach was able to describe arterio-venous differences not explained by aerobic metabolism alone.

How do elevated atmosphere CO2 and temperature alter the physiochemical properties of starch granules and rice taste?

Elevated atmospheric CO₂ (EC) and temperature (ET) strongly affect agricultural production, but the mechanism through which EC and/or ET influence starch granules and their relationship to cooked rice taste remain largely unknown. Therefore, a field experiment using a popular japonica cultivar grown in a temperature/free-air CO₂ enrichment environment was conducted to investigate the responses of volume and fine structure of starch granules and their formation physiology to EC (+200 ppm) and/or ET (+1 °C) in 2015-2016. EC markedly enhanced the activity of soluble-starch synthase and granule-bound starch synthase by 28.0% and 27.9% respectively, thereby increasing the long chains and the volume of starch granules. However, EC decreased the activity of starch-branch enzyme by 7.5% possibly via the pathway of ethylene signalling (EC prominently decreased the ethylene evolution rate of rice grains by 28.8%), resulting in a remarkable decrease in α-1'6 glucosidic bonds and significant increase in the iodine-binding capacity and double helix in starch molecules. These EC-induced changes in morphology and fine structure of starch granules synergistically altered the thermal properties of rice flour and eventually improved the cohesiveness and taste of cooked rice, as suggested by the significant relationships between them. ET partially offset the beneficial EC effects in most cases. However, few remarkable CO₂ × temperature or CO₂ × year effects were detected, indicating that the effects of EC on starch granules and rice taste less varied with meteorological conditions. These findings have important implications on rice palatability and for the development of adaptive strategies in the starch industry in future environment.

Modelling CO2 and CH4 emissions from drained peatlands with grass cultivation by the BASGRA-BGC model

Cultivated peatlands under drainage practices contribute significant carbon losses from agricultural sector in the Nordic countries. In this research, we developed the BASGRA-BGC model coupled with hydrological, soil carbon decomposition and methane modules to simulate the dynamic of water table level (WTL), carbon dioxide (CO₂) and methane (CH₄) emissions for cultivated peatlands. The field measurements from four experimental sites in Finland, Denmark and Norway were used to validate the predictive skills of this novel model under different WTL management practices, climatic conditions and soil properties. Compared with daily observations, the model performed well in terms of RMSE (Root Mean Square Error; 0.06-0.11 m, 1.22-2.43 gC/m²/day, and 0.002-0.330 kgC/ha/day for WTL, CO₂ and CH₄, respectively), NRMSE (Normalized Root Mean Square Error; 10.3-18.3%, 13.0-18.6%, 15.3-21.9%) and Pearson's r (Pearson correlation coefficient; 0.60-0.91, 0.76-0.88, 0.33-0.80). The daily/seasonal variabilities were therefore captured and the aggregated results corresponded well with annual estimations. We further provided an example on the model's potential use in improving the WTL management to mitigate CO₂ and CH₄ emissions while maintaining grass production. At all study sites, the simulated WTLs and carbon decomposition rates showed a significant negative correlation. Therefore, controlling WTL could effectively reduce carbon losses. However, given the highly diverse carbon decomposition rates within individual WTLs, adding indicators (e.g. soil moisture and peat quality) would improve our capacity to assess the effectiveness of specific mitigation practices such as WTL control and rewetting.

Exploring the relationships among innovation, financial sector development and environmental pollution in selected industrialized countries

The Paris Climate Conference commits countries to contribute to reducing global warming through a Nationally Determined Contributions (NDCs) which implore on countries to reduce emissions for improved environmental quality. Recognizing the importance of innovation and financial sector development to environmental quality, several countries have embarked on identifying ways to improve environmental quality. However, studies on the tripartite linkages among innovation, financial development and pollution relationships have produced mixed findings. Furthermore, a plethora of the existing studies have relied on only carbon dioxide (CO₂) emissions thus neglecting other anthropogenic activities which impact on the environment. More tellingly, how countries' levels of innovation moderate financial development-pollution link is yet to be studied. By relying on data from 27 selected industrialized countries spanning 1991-2014 in examining the tripartite relationships, we find that, while innovation lowers environmental pollution, beyond a certain threshold level, higher innovation exacerbates environmental degradation. Furthermore, while improved financial development increases pollution, higher innovation dampens the environmental quality-reducing effect of finance. Results from our panel causality tests also reveal a feedback causal linkage between innovation and ecological footprint, and a one-way causality from CO₂ emissions to innovations. However, irrespective of the indicator of environmental pollution, financial development and pollution evolve independently, albeit differences at the country levels.

Effectively removing tetracycline from water by nanoarchitectured carbons derived from CO2: Structure and surface chemistry influence

Understanding of the correlation between physico-chemical property of adsorbent and the adsorption performance of contaminant is very significant for developing high-efficient materials to remove antibiotic contamination from water. In this work, a novel kind of carbon adsorbent (EC) derived from CO₂ and activated ECs with modified structure via a facile chemical method using H₂ and KOH were prepared. The synthetic carbon materials (EC, EC-H₂, and EC-KOH) were then applied to remove tetracycline (TC). The kinetics of adsorption for these three carbon materials all well fitted the pseudo-second-order kinetic model. The experimental data of adsorption isotherm had good compatibility with Langmuir and Freundlich models (R² > 0.90), but the Temkin model was the most applicable for all adsorbents (R² > 0.98). A super-high adsorption capacity of EC-KOH obtained from Langmuir fitting was 933.56 mg g^-1, which was much higher than that of EC-H₂ (538.91 mg g^-1) and EC (423.30 mg g^-1), possibly due to its larger specific surface area (S_BET), pore volume, and specific surface chemical structure. Moreover, it was found that surface functional groups and large aperture of adsorbents had a positive effect on adsorption rate. More adsorption sites and surface functional groups of adsorbents were beneficial to enhance the adsorption affinity. These results are of great benefit to the directional control of carbon structure to increase the adsorption performance in rate, capacity, and affinity of antibiotics.

Recent advances in visible-light-driven carbon dioxide reduction by metal-organic frameworks

Metal-organic frameworks (MOFs) have emerged as promising materials and have attracted researchers due to their unique chemical and physical properties-design flexibility, tuneable pore channels, a high surface-to-volume ratio that allow their distinct application in diverse research fields-gas storage, gas separation, catalysis, adsorption, drug delivery, ion exchange, sensing, etc. The rapidly growing CO₂ in the atmosphere is a global concern due to the excessive use of fossil fuels in the current era. CO₂ is the prime cause of global warming and should be ameliorated either through adsorption or conversion into value-added products to protect the environment and mankind. Nowadays, MOFs are exploited as a photocatalyst for applications of CO₂ reduction. Since the use of semiconductors limits the use of visible light for photocatalytic reduction of CO₂, MOFs are promising options. The current review describes recent development in the application of MOFs as host, composites, and their derivatives in photocatalytic reduction of CO₂ to CO and different organic chemicals (HCOOH, CH₃OH, CH₄). Efficient charge separation and visible light absorption by incorporation of active sites for efficient photocatalysis have been discussed. The selection of material for high CO₂ uptake and potential strategies for the rational design and development of high-performance catalysts are outlined. Major challenges and future perspectives have also been discussed at the last of the review.

Photosynthesis and calcification of the coccolithophore Emiliania huxleyi are more sensitive to changed levels of light and CO2 under nutrient limitation

Photophysiological responses of phytoplankton to changing multiple environmental drivers are essential in understanding and predicting ecological consequences of ocean climate changes. In this study, we investigated the combined effects of two CO₂ levels (410 and 925 μatm) and five light intensities (80 to 480 μmol photons m^-2 s^-1) on cellular pigments contents, photosynthesis and calcification of the coccolithophore Emiliania huxleyi grown under nutrient replete and limited conditions, respectively. Our results showed that high light intensity, high CO₂ level and nitrate limitation acted synergistically to reduce cellular chlorophyll a and carotenoid contents. Nitrate limitation predominantly enhanced calcification rate; phosphate limitation predominantly reduced photosynthetic carbon fixation rate, with larger extent of the reduction under higher levels of CO₂ and light. Reduced availability of both nitrate and phosphate under the elevated CO₂ concentration decreased saturating light levels for the cells to achieve the maximal relative electron transport rate (rETR_max). Light-saturating levels for rETR_max were lower than that for photosynthetic and calcification rates under the nutrient limitation. Regardless of the culture conditions, rETR under growth light levels correlated linearly and positively with measured photosynthetic and calcification rates. Our findings imply that E. huxleyi cells acclimated to macro-nutrient limitation and elevated CO₂ concentration decreased their light requirement to achieve the maximal electron transport, photosynthetic and calcification rates, indicating a photophysiological strategy to cope with CO₂ rise/pH drop in shoaled upper mixing layer above the thermocline where the microalgal cells are exposed to increased levels of light and decreased levels of nutrients.

Social facilitation of long-lasting memory is mediated by CO2 in Drosophila

How social interactions influence cognition is a fundamental question, yet rarely addressed at the neurobiological level. It is well established that the presence of conspecifics affects learning and memory performance, but the neural basis of this process has only recently begun to be investigated. In the fruit fly Drosophila melanogaster, the presence of other flies improves retrieval of a long-lasting olfactory memory. Here, we demonstrate that this is a composite memory composed of two distinct elements. One is an individual memory that depends on outputs from the α'β' Kenyon cells (KCs) of the mushroom bodies (MBs), the memory center in the insect brain. The other is a group memory requiring output from the αβ KCs, a distinct sub-part of the MBs. We show that social facilitation of memory increases with group size and is triggered by CO₂ released by group members. Among the different known neurons carrying CO₂ information in the brain, we establish that the bilateral ventral projection neuron (biVPN), which projects onto the MBs, is necessary for social facilitation. Moreover, we demonstrate that CO₂-evoked memory engages a serotoninergic pathway involving the dorsal-paired medial (DPM) neurons, revealing a new role for this pair of serotonergic neurons. Overall, we identified both the sensorial cue and the neural circuit (biVPN>αβ>DPM>αβ) governing social facilitation of memory in flies. This study provides demonstration that being in a group recruits the expression of a cryptic memory and that variations in CO₂ concentration can affect cognitive processes in insects.

Bacterial phenotype dependency from CO2 measured by Raman spectroscopy

In recent years, Raman spectroscopy has become an established method to study medical, biological or environmental samples. Since Raman spectroscopy is a phenotypic method, many parameters can influence the spectra. One of these parameters is the concentration of CO₂, as this never remains stable in nature, but always adjusts itself in a dynamic equilibrium. So, it is obvious that the concentration of CO₂ cannot be controlled but it might have a big impact on the bacteria and bacterial composition in medical samples. When using a phenotypic method like Raman spectroscopy it is also important to know the influence of CO₂ to the dataset. To investigate the influence of CO₂ towards Raman spectra we cultivated E. coli at different concentration of CO₂ since this bacterium is able to switch metabolism from aerobic to microaerophilic conditions. After applying statistic methods small changes in the spectra became visible and it was even possible to observe the change of metabolism in this species according to the concentration of CO₂.

Temporal characteristics of carbon dioxide and ozone over a rural-cropland area in the Yangtze River Delta of eastern China

In this study, rural atmospheric carbon dioxide (CO₂) and ozone (O₃) were measured from January 2015 to December 2018 to investigate characteristics of greenhouse gases in eastern China. Results showed that the annual average CO₂ (O₃) concentration in 2018 decreased by 2% (increased by 19%) when compared with that in 2015. CO₂ concentrations exhibited monthly variability, peaking in February (443.7 ppm) and reaching their lowest levels in July (363.0 ppm); whereas, monthly O₃ showed a bimodal pattern with peaks in June (51.3 ppb) and September (34.5 ppb). Regarding the diurnal variation, the maximum CO₂ (O₃) concentration occurred at nighttime (in the daytime) and a minimum CO₂ (O₃) in the daytime (at nighttime). As demonstrated by correlation analysis, CO₂ and O₃ variations were partly modulated by NOx and PM_2.5. Furthermore, CO₂ showed significant positive correlations with relative humidity in winter, while O₃ showed strong positive correlations with temperature in spring. CO₂ was accumulated from local sources under calm conditions (< 2 m s^-1) and derived from remote sources at high wind speeds (> 4 m s^-1), while O₃ concentrations were peaking at medium wind speeds of 2-4 m s^-1. CO₂ was found to derive from long-distance (short-distance transport) transport in spring (the other three seasons), whereas O₃ is mainly from long-distance (short-distance) transport in winter (the other three seasons). This work sheds light on the temporal characteristics of CO₂ and O₃, which has important implications for implementing practices to mitigate source emissions over cropland areas.

Detection of Alternaria alternata in tomato juice and fresh fruit by the production of its biomass, respiration, and volatile compounds

Tomato is widely consumed and marketed as juice, puree, or fresh product. Nevertheless, 30% of its harvest volume is lost because of the fungus Alternaria alternata. This research aimed to provide early detection methods for this fungal decay on tomato juice and fresh fruit. Biomass content, CO₂, O₂ and volatile compounds (VOCs) during A. alternata growth in tomato juice and fruit at two ripening stages (breaker and red colour) were evaluated. Additionally, CO₂ and VOCs data set were analysed with a hierarchical cluster technique (HCA) to explore the differences between inoculated and non-inoculated samples. Biomass was determined by gravimetry, CO₂ and O₂ by gas chromatography (GC), and VOCs by GC-mass spectrometry. Biomass content was not drastically modified by tomato's ripening stage (3-6 mg of dry weight). CO₂ in tomato juice was considerably higher in the inoculated samples with A. alternata (27-63%) than in the non-inoculated ones (2.8-6.6%), regardless of the ripeness stage; while in tomato fruit CO₂ was higher at breaker stage and inoculated with A. alternata (33-41%) than the remaining treatments (9-23%). It was also observed that, except for limonene, trans-sabinene hydrate, and rhodovibrin, VOCs' release during the interaction between tomato juice and A. alternata was different from the fresh tomato and A. alternata interaction. Only the HCA based on CO₂ data showed clear differences between the inoculated and non-inoculated tomato juice and fruit at both ripening stages.

Stable isotope evidence from archived fish scales indicates carbon cycle changes over the four-decade history of the Římov Reservoir (Czechia)

Using archived fish scale samples together with long-term monitoring data, this study investigates the potential of fish scales to record historical changes in the aquatic environment. We analysed stable carbon (δ¹³C) and nitrogen (δ¹⁵N) isotopes in the scales of two planktivorous cyprinid species collected from the meso-eutrophic Římov Reservoir, Czechia, over its entire four-decade history (1979-2016). The δ¹³C of the fish scales varied greatly throughout the reservoir history. The lowest δ¹³C values were observed immediately after the reservoir was filled in 1979, indicating that fish production at that time was likely partially supported by ¹³C-depleted CO₂ released from the inundated soil. During the 1980s, due to the high levels of phytoplankton production stimulated by high phosphorus inputs from the catchment, the δ¹³C values substantially increased. However, since 1990, the δ¹³C values have generally decreased, reflecting a gradual reduction in reservoir primary production caused by the decreasing input of phosphorus and increasing input of dissolved organic carbon from the catchment. The δ¹³C of fish scales was also used to reconstruct the CO₂ concentration of the surface water. The reconstructed CO₂ varied significantly during the four-decade history, but it was always below the air-equilibrium concentration, suggesting that the surface water of the reservoir has consistently absorbed atmospheric carbon. The fish-scale δ¹⁵N values remained relatively stable, while slightly increasing within three years after impoundment, likely because the nitrogen supply was high throughout the studied period. Our study contributes to the growing body of literature demonstrating that stable isotope analysis of archived biological samples is a promising approach for understanding historical trends in the biogeochemistry of aquatic environments. In particular, our results highlight the potential of δ¹³C in archived fish scales in reconstructing carbon cycle changes and evaluating human impacts on aquatic ecosystems.

Bioprocessing of Chaetoceros calcitrans for the recovery of fucoxanthin using CO2-based alkyl carbamate ionic liquids

Ionic liquids (ILs) have emerged as an alternative solvent used in the bioprocessing of microalgae for recovery of valuable biomolecules. The aim of this work is to extract fucoxanthin from Chaetoceros calcitrants (C. calcitrans) by using the readily distillable CO₂-based alkyl carbamate ILs. The degree of cell permeabilization was analysed by the quantification of extracted fucoxanthin and the analyses of cell surface morphology. Among the tested CO₂-based alkyl carbamate ILs, diallylammonium diallylcarbamate (DACARB) extraction system gave the maximal yield of fucoxanthin at 17.51 mg/g under the optimal extraction conditions [90% (v/v), 3 min and 25 °C]. Moreover, the extracted fucoxanthin fraction exhibited the satisfactory antioxidant activities. The recyclability of DACARB was demonstrated in the multiple batches of fucoxanthin extraction. Hence, CO₂-based alkyl carbamate ILs can prospectively substitute conventional organic solvents in the downstream processing of bioactive compounds from microalgae.

Improved robustness of microbial electrosynthesis by adaptation of a strict anaerobic microbial catalyst to molecular oxygen

Microbial electrosynthesis (MES) and other bioprocesses such as syngas fermentation developed for energy storage and the conversion of carbon dioxide into valuable chemicals often employs acetogens as microbial catalysts. Acetogens are sensitive to molecular oxygen, which means that bioproduction reactors must be maintained under strict anaerobic conditions. This requirement increases cost and does not eliminate the possibility of O₂ leakage. For MES, the risk is even greater since the system generates O₂ when water splitting is the anodic reaction. Here, we show that O₂ from the anode of a MES reactor diffuses into the cathode chamber where strict anaerobes reduce CO₂. To overcome this drawback, a stepwise adaptive laboratory evolution (ALE) strategy is used to develop the O₂ tolerance of the acetogen Sporomusa ovata. Two heavily-mutated S. ovata strains growing well autotrophically in the presence of 0.5 to 5% O₂ were obtained. The adapted strains were more performant in the MES system than the wild type converting electrical energy and CO₂ into acetate 1.5 fold faster. This study shows that the O₂ tolerance of acetogens can be increased, which leads to improvement of the performance and robustness of energy-storage bioprocesses such as MES where O₂ is an inhibitor.

Study of the emissions and spatial distributions of various power-generation technologies in China

The power sector is the main contributor to climate change and atmospheric pollution, and reducing the emissions from the power sector is essential for achieving sustainable development. However, few studies have accounted for the emissions from various power-generation technologies. In this paper, a high-resolution inventory of power plants with more than 6 MW accounting for 93% of the national power generation in China is established for the first time. Based on this inventory, the CO2, NOx and SO2 emissions of China's hard coal power, natural gas power, hydropower, wind power, photovoltaic power, biomass power and nuclear power are calculated by using the life cycle assessment method, and their spatial distributions in 2014 are further analyzed. The results show that China's power plants emitted 3.44 E+09 t CO2, 8.56 E+06 t NOx, and 1.19 E+07 t SO2, and the uncertainties were (-18.66%, +19.14%), (-67.10%, +66.41%) and (-88.69%, +87.61%) in 2014, respectively. Renewable-energy power plants accounted for approximately 15% of the national power generation but only contributed less than 1% of the total emissions. Meanwhile, in China's eastern cities, renewable-energy power accounts for the lowest proportion of the total installed capacity. In addition, both the emission amount and intensity were significantly higher in eastern cities than central and western cities. This study will help improve research on the emissions of all power-generation technologies in China and help achieve a comprehensive and systematic emissions reduction strategy.