Atmospheric CO2 Levels Research Articles

Electrochemical ocean alkalinity enhancement using a calcium ion battery

The oceans play a major role in moderating atmospheric CO2 levels. Enhanced CO2 uptake into ocean waters can be achieved by the provision of appropriate cations to the surface ocean, an approach known as ocean alkalinity enhancement (OAE). Here, we present a calcium ion battery approach that enhances alkalinity via electrochemical manipulation of seawater calcium concentrations. We demonstrate the efficacy of this approach using a potassium barium iron cyanide [K2BaFe(CN)6] (PBFC) electrode, a Prussian blue analogue, to move calcium ions from one reservoir of seawater to another. Using material and electrochemical characterization of the Ca2+ ion insertion and expulsion properties of PBFC in synthetic seawater, we determine the repeatability of Ca2+ ion insertion and expulsion from the PBFC electrode. Our analyses prove a 2.75 % increase in seawater alkalinity via the PBFC electrode, which yields 2.64 mg CO2 (0.72 mg C) uptake per liter of seawater. This proof-of-concept method offers a unique, low-cost, energy efficient electrochemical approach for atmospheric carbon dioxide removal that can combine with marine-based renewable energy to enable a new family of effective, scalable climate change solutions.

The ocean carbon pool: a vital component of the global carbon cycle

The global carbon cycle is an integral part of the Earth System. Of the land, atmosphere, and ocean components of the global carbon cycle that exchange carbon on the timescales of decades to centuries, the ocean contains more than 90% of carbon. The ocean carbon pool represents a critical component of the Earth's carbon cycle, playing a pivotal role in regulating atmospheric carbon dioxide (CO2) levels and influencing climate dynamics. The exponential increase of total anthropogenic CO2 emissions in the industrial era implies the ocean's uptake has increased exponentially, reaching 2.5 ± 0.6 Pg C yr-1 for 2009-2018. Without the ocean and land sinks, atmospheric CO2 levels would be close to 600 ppm. The ocean carbon pool comprises dissolved inorganic carbon (DIC), organic carbon, and particulate organic matter, collectively responsible for the sequestration and release of carbon into the atmosphere. Phytoplankton, the microscopic marine plants, play a fundamental role in the oceanic carbon cycle by photosynthesizing and fixing atmospheric CO2 into organic matter. This organic matter can be transferred to the deep ocean through the biological pump, further contributing to the storage of carbon in the form of sinking particles. The bulk of the global ocean margin represents a carbon sink of ~0.1-0.2 Pg C. Oceanic processes, such as ocean circulation and upwelling, help redistribute carbon from surface waters to the deep ocean. The solubility pump, which is driven by changes in temperature and salinity, also affects the solubility of CO2 in seawater. These natural processes work to mitigate the increase in atmospheric CO2 concentrations and help regulate global temperatures.

Silicon-mediated herbivore defence in a pasture grass under reduced and Anthropocene levels of CO2.

The uptake and accumulation of silicon (Si) in grass plants play a crucial role in alleviating both biotic and abiotic stresses. Si supplementation has been reported to increase activity of defence-related antioxidant enzyme, which helps to reduce oxidative stress caused by reactive oxygen species (ROS) following herbivore attack. Atmospheric CO2 levels are known to affect Si accumulation in grasses; reduced CO2 concentrations increase Si accumulation whereas elevated CO2 concentrations often decrease Si accumulation. This can potentially affect antioxidant enzyme activity and subsequently insect herbivory, but this remains untested. We examined the effects of Si supplementation and herbivory by Helicoverpa armigera on antioxidant enzyme (catalase, CAT; superoxide dismutase, SOD; and ascorbate peroxidase, APX) activity in tall fescue grass (Festuca arundinacea) grown under CO2 concentrations of 200, 410, and 640 ppm representing reduced, ambient, and elevated CO2 levels, respectively. We also quantified foliar Si, carbon (C), and nitrogen (N) concentrations and determined how changes in enzymes and elemental chemistry affected H. armigera relative growth rates and plant consumption. Rising CO2 concentrations increased plant mass and foliar C but decreased foliar N and Si. Si supplementation enhanced APX and SOD activity under the ranging CO2 regimes. Si accumulation and antioxidant enzyme activity were at their highest level under reduced CO2 conditions and their lowest level under future levels of CO2. The latter corresponded with increased herbivore growth rates and plant consumption, suggesting that some grasses could become more susceptible to herbivory under projected CO2 conditions.

Comparison of Atmospheric Carbon Dioxide Concentrations Based on GOSAT, OCO-2 Observations and Ground-Based TCCON Data

Carbon dioxide (CO2) is one of the most significant greenhouse gases, and its concentration and distribution in the atmosphere have always been a research hotspot. To study the temporal and spatial characteristics of atmospheric CO2 globally, it is crucial to evaluate the consistency of observation data from different carbon observation satellites. This study utilizes data from the Total Carbon Column Observing Network (TCCON) to verify the column-averaged dry air mole fractions of atmospheric CO2 (XCO2) retrieved by satellites from October 2014 to May 2016, specifically comparing the XCO2 distributions from the Greenhouse Gases Observing Satellite (GOSAT) and Orbiting Carbon Observatory 2 (OCO-2). Our analysis indicates a strong correlation between the TCCON and both the GOSAT (correlation coefficient of 0.85) and OCO-2 (correlation coefficient of 0.91). Cross-validation further reveals that the measurements of the GOSAT and OCO-2 are highly consistent, with an average deviation and standard deviation of 0.92 ± 1.16 ppm and a correlation coefficient of 0.92. These differences remain stable over time, indicating that the calibration in the data set is reliable. Moreover, monthly averaged time-series and seasonal climatology comparisons were also performed separately over the six continents, i.e., Asia, North America, Europe, Africa, South America, and Oceania. The investigation of monthly XCO2 values across continents highlights greater consistency in Asia, North America, and Oceania (standard deviation from 0.15 to 0.27 ppm) as compared to Europe, South America, and Africa (standard deviation from 0.45 to 0.84 ppm). A seasonal analysis exhibited a high level of consistency in spring (correlation coefficient of 0.97), but lower agreement in summer (correlation coefficient of 0.78), potentially due to cloud cover and aerosol interference. Although some differences exist among the datasets, the overall findings demonstrate a strong correlation between the satellite measurements of XCO2. These results emphasize the importance of continued monitoring and calibration efforts to ensure the accurate assessment and understanding of atmospheric CO2 levels.

BioGeoChemical‐Argo Floats Reveal Stark Latitudinal Gradient in the Southern Ocean Deep Carbon Flux Driven by Phytoplankton Community Composition

AbstractThe gravitational sinking of particles in the mesopelagic layer (∼200–1,000 m) transfers to the deep ocean a part of atmospheric carbon fixed by phytoplankton. This process, called the gravitational pump, exerts an important control on atmospheric CO2 levels but remains poorly characterized given the limited spatio‐temporal coverage of ship‐based flux measurements. Here, we examined the gravitational pump with BioGeoChemical‐Argo floats in the Southern Ocean, a critically under‐sampled area. Using time‐series of bio‐optical measurements, we characterized the concentration of particles in the productive zone, their export and transfer efficiency in the underlying mesopelagic zone, and the magnitude of sinking flux at 1,000 m. We separated float observations into six environments delineated by latitudinal fronts, sea‐ice coverage, and natural iron fertilization. Results show a significant increase in the sinking‐particle flux at 1,000 m with increasing latitude, despite comparable particle concentrations in the productive layer. The variability in deep flux was driven by changes in the transfer efficiency of the flux, related to the composition of the phytoplanktonic community and the size of particles, with intense flux associated with the predominance of micro‐phytoplankton and large particles at the surface. We quantified the relationships between the nature of surface particles and the flux at 1,000 m and used these results to upscale our flux survey across the whole Southern Ocean using surface observations by floats and satellites. We then estimated the basin‐wide Spring‐Summer flux of sinking particles at 1,000 m over the Southern Ocean (0.054 ± 0.021 Pg C).

Disentangling artificial and natural benthic weathering in organic rich Baltic Sea sediments

Enhanced mineral dissolution in the benthic environment is currently discussed as a potential technique for ocean alkalinity enhancement (OAE) to reduce atmospheric CO2 levels. This study explores how biogeochemical processes affect the dissolution of alkaline minerals in surface sediments during laboratory incubation experiments. These involved introducing dunite and calcite to organic-rich sediments from the Baltic Sea under controlled conditions in an oxic environment. The sediment cores were incubated with Baltic Sea bottom water. Findings reveal that the addition of calcite increased the benthic alkalinity release from 0.4 μmol cm−2 d−1 (control) to 1.4 μmol cm−2 d−1 (calcite) as well as other weathering products such as calcium. However, these enhanced fluxes returned to lower fluxes after approximately 4 weeks yet still higher than the un-amended controls. Microbial activity appeared to be the primary driver for lowering pore water pH and thus enhanced weathering. In several sediment cores, pH profiles taken at the start of the experiments indicated activity of sulfur oxidizing Beggiatoa spp, which was verified by RNA-profiling of 16S rRNA genes. The pH profiles transitioned to those commonly associated with the activity of cable bacteria as the experiments progressed. The metabolic activity of cable bacteria would explain the significantly lower pH values (~5.6) at sediment depths of 1–3 cm, which would favor substantial calcite dissolution. However, a high abundance of cable bacteria was not reflected in 16S rRNA sequence data. Total alkalinity (TA) fluxes in these cores increased by a factor of ~3, with excess TA/calcium ratios indicating that the enhanced flux originated from calcite dissolution. The dissolution of dunite or the potential formation of secondary minerals could not be identified due to the strong natural flux of silicic acid, likely due to biogenic silica dissolution. Furthermore, no accumulation of potentially harmful metals such as nickel was observed, as highlighted as a potential risk in other studies concerning OAE. Given the complexity of sediment chemistry and changes of the benthic conditions induced by the incubation, it remains challenging to distinguish between natural and enhanced mineral weathering. Further investigation, including the identification of suitable tracers for mineral dissolution, are necessary to assess the feasibility of benthic weathering as a practical approach for OAE and climate change mitigation.

Evaluation of Morpho-Physiological and Yield-Associated Traits of Rice (Oryza sativa L.) Landraces Combined with Marker-Assisted Selection under High-Temperature Stress and Elevated Atmospheric CO2 Levels.

Rice (Oryza sativa L.) is an important cereal crop worldwide due to its long domestication history. North-Eastern India (NEI) is one of the origins of indica rice and contains various native landraces that can withstand climatic changes. The present study compared NEI rice landraces to a check variety for phenological, morpho-physiological, and yield-associated traits under high temperatures (HTs) and elevated CO2 (eCO2) levels using molecular markers. The first experiment tested 75 rice landraces for HT tolerance. Seven better-performing landraces and the check variety (N22) were evaluated for the above traits in bioreactors for two years (2019 and 2020) under control (T1) and two stress treatments [mild stress or T2 (eCO2 550 ppm + 4 °C more than ambient temperature) and severe stress or T3 (eCO2 750 ppm + 6 °C more than ambient temperature)]. The findings showed that moderate stress (T2) improved plant height (PH), leaf number (LN), leaf area (LA), spikelets panicle-1 (S/P), thousand-grain weight (TGW), harvest index (HI), and grain production. HT and eCO2 in T3 significantly decreased all genotypes' metrics, including grain yield (GY). Pollen traits are strongly and positively associated with spikelet fertility at maturity and GY under stress conditions. Shoot biomass positively affected yield-associated traits including S/P, TGW, HI, and GY. This study recorded an average reduction of 8.09% GY across two seasons in response to the conditions simulated in T3. Overall, two landraces-Kohima special and Lisem-were found to be more responsive compared to other the landraces as well as N22 under stress conditions, with a higher yield and biomass increment. SCoT-marker-assisted genotyping amplified 77 alleles, 55 of which were polymorphic, with polymorphism information content (PIC) values from 0.22 to 0.67. The study reveals genetic variation among the rice lines and supports Kohima Special and Lisem's close relationship. These two better-performing rice landraces are useful pre-breeding resources for future rice-breeding programs to increase stress tolerance, especially to HT and high eCO2 levels under changing climatic situations.

Decoding spatiotemporal dynamics in atmospheric CO2 in Chinese cities: Insights from satellite remote sensing and geographically and temporally weighted regression analysis

Understanding the primary factors influencing atmospheric carbon dioxide (CO2) dynamics is essential for addressing global climate change. However, these factors' spatial and temporal impact is seldom considered in the extant literature. This study employs a geographically and temporally weighted regression (GTWR) to examine the magnitude and direction of the effects that human activities, ecological conditions, and meteorological parameters exert on atmospheric CO2 variations. This examination encompasses 356 Chinese cities, utilizing satellite-derived column-averaged dry air mole fraction of carbon dioxide (XCO2) data from 2010 to 2019. Our findings reveal that cities in eastern China predominantly exhibit higher atmospheric CO2 concentrations, with most average values exceeding 399.34 ppm. Conversely, western regions generally maintain levels below 398.98 ppm. Trend analyses show a consistent increase over the decade, with a rate of 2.25–2.54 ppm/yr, coupled with pronounced seasonal variations. Anthropogenic emissions are found to amplify atmospheric CO2 concentrations during springs (overall-averaged GTWR coefficient of 0.72 ppm), autumns (0.51 ppm), and winters (0.87 ppm), especially in western cities. Vegetative activities can effectively reduce atmospheric CO2 during summers nationwide (temporally-averaged GTWR coefficients of −5.67 ~ −0.41 ppm) and autumn in southern cities (−1.32–0.00 ppm). From a meteorological perspective, increased summer relative humidity (overall-averaged coefficient of 2.41 ppm) and precipitation (1.57 ppm) can intensify atmospheric CO2 in most Chinese Cities. At the same time, warmer winter temperatures (−0.63 ppm) can mitigate it. Wind speed generally reduces atmospheric CO2 levels during spring (−1.02 ppm), autumn (−1.55 ppm), and winter (−1.76 ppm). Yet, it can heighten atmospheric CO2 concentrations during summers, particularly in eastern cities (0.07 ppm). The relationships between atmospheric CO2 concentrations and their influencing factors present significant spatial and seasonal variations. These findings offer comprehensive guidance for regions in developing targeted carbon emission control policies and enable a more practical approach to sustainable development.

An Experimental and Computational Study of Zeolitic Imidazole Framework (ZIF-8) Synthesis Modulated with Sodium Chloride and Its Interaction with CO2

The increase of CO2 level in atmosphere becomes one of the driving forces for research on functional materials. Capturing and utilizing of CO2 are more important than ever, both to reduce CO2 emission and to increase the economic value of CO2 derivatives. In this study, synthesis of metal-organic frameworks (MOFs) was conducted by combining Zn2+ metal nodes and 2-methylimidazolate ligand to form zeolitic imidazolate frameworks (ZIF-8) materials. ZIF-8 was synthesised with the addition of sodium chloride to modulate the crystal morphology during the in-situ synthesis, using either water or methanol as the solvent. According to the refinement of the X-ray diffraction pattern, the ZIF-8 materials were successfully prepared and have unit cell parameters that are reasonably close to the available standard. The formation of ZIF-8 is also confirmed by IR spectroscopy, which reveals the stretching vibration mode of Zn−N from the coordination between Zn2+ and 2-methylimidazolate ligand. The crystal morphology exhibits different shape, as observed in SEM and TEM studies, with the dominant shape being a rhombic dodecahedron. The interaction between ZIF-8 and CO2 was investigated via ex-situ IR spectroscopy, combined with several computational techniques such as density functional theory and molecular dynamics, to elucidate the nature of the CO2 binding sites. Copyright © 2023 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Diverse glacial ventilation in deep Pacific: An integrated record from Mariana Trench and Magellan Seamounts over last 1.2 Myr

Antarctic bottom water production is one of the most important components in oceanic circulation, yet its long-term impact on Earth's climate remains poorly known. In this study, three sediment cores collected from the Mariana Trench and the Magellan Seamounts of the western Pacific are examined to investigate regional deep-sea ventilation over the past 1.2 Myr. The main results are as follows. 1) By integrating magnetostratigraphy, beryllium isotopes and element-based tuning, a geochronological framework is precisely established for the deep-sea sediments. 2) An Mn-based proxy for deep-sea ventilation is developed to provide an indication of paleoceanographic evolution in the western Pacific. 3) Diverse variations in regional ventilation associated with glacial-interglacial alternations are observed. Based on these results, a strong consistency in deep-sea ventilation between the North Atlantic and the western Pacific is found, indicating that deep-sea ventilation generally intensified during interglacial periods in the western Pacific. It is also highlighted the occurrence of enhanced deep-sea ventilation during several glacial periods in the study area, particularly at the end of the middle Pleistocene Transition and prior to the Mid-Brunhes Event. These findings suggest a reorganization of oceanic circulation in the deep Pacific around 0.6 Myr, which may have had implications for modulating atmospheric CO2 levels. Overall, the sedimentary records from the Mariana Trench and the Magellan Seamounts present great potentials for investigating the long-term influence of Antarctic bottom water production during the Pleistocene.

Atmospheric CO2 Level Measurement and Discomfort Index Calculation with the use of Low-Cost Drones

Unmanned Aerial Vehicle (UAV) platforms are emerging as an essential tool for various studies in environmental engineering. The quadcopters drones have immense potential for sensor interfacing and stable data acquisition. These UAVs can perform critical activities like volcanic eruption monitoring, stack emission monitoring, urban air quality monitoring, identification of pollution levels in 3D space, etc. Carbon dioxide (CO2) and the Discomfort Index (DI) are essential indicators of air quality and climate comfort. Hence, it is critical to monitor them with extreme accuracy. This study demonstrates a novel application of CO2 profiling using low-cost drones at varied altitudes. The drone-aided vertical CO2 profiling was carried out at 60 m AGL (Above Ground Level) during summer and winter, in Nagpur city of India. This study retrieved some exciting data on the DI. It was found that CO2 concentration in the range of 20-70 m AGL was lower than the surface level. The derived DI was maximum at the height range of 40-50 m. Inversion was observed in the range of 30-40 m. A positive correlation between CO2 and temperature was observed in both seasons. The lightweight commercial drones are capable of tethering sensor modules to get accurate results in less cost and effort. This type of novel tethered sensor technique could be applicable in weather forecasting, landfill surface monitoring, volcanic eruption monitoring, and other probable applications with few drone flight limits.

Reconstructing the ocean's mesopelagic zone carbon budget: sensitivity and estimation of parameters associated with prokaryotic remineralization

Abstract. Through the constant rain of sinking marine particles in the ocean, carbon (C) trapped within is exported into the water column and sequestered when reaching depths below the mesopelagic zone. Atmospheric CO2 levels are thereby strongly related to the magnitude of carbon export fluxes in the mesopelagic zone. Sinking particles represent the main source of carbon and energy for mesopelagic organisms, attenuating the C export flux along the water column. Attempts to quantify the amount of C exported versus C consumed by heterotrophic organisms have increased in recent decades. Yet, most of the conducted estimations have led to estimated C demands several times higher than the measured C export fluxes. The choice of parameters such as growth efficiencies or various conversion factors is known to greatly impact the resulting C budget. In parallel, field or experimental data are sorely lacking to obtain accurate values of these crucial overlooked parameters. In this study, we identify the most influential of these parameters and perform inversion of a mechanistic model. Further, we determine the optimal parameter values as the ones that best explain the observed prokaryotic respiration, prokaryotic production and zooplankton respiration. The consistency of the resulting C budget suggests that such budgets can be adequately balanced when using appropriate parameters.

A synthesis of the Cretaceous wildfire record related to atmospheric oxygen levels?

The Cretaceous was a significant greenhouse period in Earth's history with higher atmospheric CO2 levels and temperatures than today. Although evidence of combustion has been widely described from the Cretaceous deposits, our understanding of the spatiotemporal diversification pattern and process of the Cretaceous wildfires is still limited. In this study, we comprehensively synthesize a total of 271 published Cretaceous wildfire occurrences based on the by-products of burning, including fossil charcoal, pyrogenic inertinite (fossil charcoal in coal), and pyrogenic polycyclic aromatic hydrocarbons (PAHs). Spatially, the dataset shows a distinctive distribution of reported wildfire evidence characterized by high concentration in the middle latitudinal areas of the Northern Hemisphere (30°N–60°N) over the Cretaceous. Temporally, an overall increasing trend of the reported wildfire data from the Early Cretaceous to the Late Cretaceous is coincident with higher atmospheric O2 levels. However, the spatial and temporal patterns may result from many types of factors, such as taphonomy, preservation, and researcher biases, instead of a real picture of the Cretaceous wildfire evolution. To better understand the spatiotemporal diversification of the Cretaceous wildfire, more investigations on the record of wildfire occurrences during this period would be necessary in the future.

Impacts on South America moisture transport under Amazon deforestation and 2 °C global warming

The increase in greenhouse gasses (GHG) anthropogenic emissions and deforestation over the last decades have led to many chemical and physical changes in the climate system, affecting the atmosphere's energy and water balance. A process that could be affected is the Amazonian moisture transport in the South American continent (including La Plata basin), which is crucial to the southeast Brazilian water regime. The focus of our research is on evaluating how local (i.e. Amazon deforestation) and global forcings (increase of atmospheric GHG concentration) may modify this moisture transport under climate change scenarios. We used two coupled land-atmosphere models forced by CMIP6 sea surface temperatures to simulate these processes for two scenarios: i) increase in carbon dioxide (CO2) — RCP8.5 atmospheric levels (00DEF), and ii) total Amazon deforestation simultaneous with atmospheric CO2 levels increased (100DEF). These scenarios were compared with a control simulation, set with a constant CO2 of 388 ppm and present-day Amazon Forest cover. The 30-year Specific Warming Level 2 (SWL2) index evaluated from the simulations is set to be reached 2 years earlier due to Amazon deforestation. A reduction in precipitation was observed in the Amazon basin (−3.1 mm·day−1) as well as in La Plata Basin (−0.5 mm·day−1) due to reductions in the Amazon evapotranspiration (−0.9 mm·day−1) through a stomatal conductance decrease (00DEF) and land cover change (100DEF). In addition, the income moisture transport decreased (22 %) in the northern La Plata basin in both scenarios and model experiments. Our results indicated a worse scenario than previously found in the region. Both Amazon and La Plata hydrological regimes are connected (moisture and energy transport), indicating that a large-scale Amazon deforestation will have additional climate, economic and social implications for South America.

Quantitative evidence for Arctic continental freezing in a high-CO 2 world: Junggar Basin, NW China

Abstract We show that the Late Triassic–Early Jurassic continental Arctic experienced wintertime freezing conditions, despite the exceptionally high atmospheric CO 2 levels, by quantifying common lake ice-rafted debris (L-IRD) identified in the Junggar Basin of Xinjian, NW China. This L-IRD consists of outsized (0.1–12 mm) lithic clasts ‘floating’ in otherwise fine-grained, profundal lake sediment matrix. Laser-diffraction grain-size analysis demonstrates that the grain-size distribution for lacustrine strata of Junggar Basin is very similar to modern sediments from the seasonally ice-covered Sea of Okhotsk, reflecting a similar depositional mechanism. Three-dimensional computed tomography and two-dimensional thin sections demonstrate that the outsized clasts are dispersed, rather than confined to sand lenses or layers. These results are inconsistent with alternative methods of bimodal sediment deposition such as mud flows, algae rafting or root rafting. The discovery of Triassic–Jurassic continental freezing provides new context for understanding global climate during periods with high-CO 2 conditions and climate and biotic changes in the Mesozoic Era.

Significant Daily CO2 Source–Sink Interchange in an Urbanizing Lake in Southwest China

Inland lake water–air interfaces, particularly the partial pressure of CO2 (pCO2), have become key parameters in the study of global carbon cycle changes. However, there are few studies on short-term daily variations in pCO2 in urbanizing lakes. The fluctuations in pCO2 and CO2 fluxes (fCO2) were monitored biweekly on-site for pCO2 assessments during daytime hours (7:00–17:00 CST) from January to September 2020 in an urbanizing lake located in Southwest China. We found a pronounced and uninterrupted decline in the average levels of pCO2 and fCO2 from 7:00 to 17:00 CST. Notably, the mornings (7:00–12:00 CST) exhibited substantially elevated pCO2 and fCO2 values compared to the afternoons. Specifically, compared to 7:00, the mean pCO2 and fCO2 at 17:00 CST decreased by ca. 74% and 112%, respectively. The average daytime pCO2 was 707 ± 642 μatm, significantly higher than the typical atmospheric CO2 levels of 380–420 μatm, while the average pCO2 on 9 January, 1 April, and 27 July was lower than typical atmospheric CO2. Each month, all water environmental parameters showed significant differences. pCO2 and fCO2 reached maximums in September; water temperature and turbidity significantly increased; and pH, dissolved oxygen and transparency markedly decreased. Additionally, the correlation between pCO2 and environmental factors demonstrated that the nutrient levels, dissolved oxygen, pH, and transparency/turbidity had significant roles in CO2 dynamics in this lake. Therefore, this urbanizing lake could serve as a CO2 source and sink during the daytime.

Synthesis, physical properties, and carbon dioxide uptake of new metal-sulfamethoxazole complexes

Considerable research is currently being undertaken to reduce atmospheric CO2 levels, and a promising approach is capturing and storing the gas using adsorbents. In this regard, the synthesis and investigation of the potential use of new materials as CO2 storage media has attracted attention from both industry and academia. Metal-organic frameworks have a range of unique chemical and physical properties with many applications. Reported here is the synthesis of three new sulfamethoxazole-metal complexes and their use as models for investigation of the influence of the metal on their ability to absorb CO2. A new Schiff base was first synthesized, in 89 % yield, from the condensation of sulfamethoxazole and 4-(dimethylamino)benzaldehyde under acidic conditions. The reaction of the Schiff base with metal (nickel, copper, and cobalt) chlorides in ethanol under reflux gave the corresponding sulfamethoxazole-metal complexes in 71–80 % yield. Several experiments were conducted to assess the uptake of CO2 under different conditions. The complexes have low surface areas (1.36–5.82 m2/g) and average pore volume and diameters of 0.008–0.018 cm3/g and 2.17–4.08 nm, respectively. They showed some ability to adsorb CO2 (323 K and 40 bars), and the storage capacity was 11.2–26.1 cm3/gm. The cobalt-containing complex had the highest CO2 storage capability (26.1 cm3/g) due to its relatively high surface area (5.82 m2/g), pore volume (0.018 cm3/g), pore diameter (4.08 nm), and surface roughness (11.6) compared to the nickel and copper complexes.

Continental Thermal Structure and Carbonate Storage of Subducted Sedimentary Origin Control on Different Increases in Atmospheric CO2 in Late Ediacaran and Jurassic

AbstractCarbon release during continental rifting is thought to regulate atmospheric CO2 levels. Supercontinent dispersal‐induced extensional tectonics is similar during the Late Ediacaran and Jurassic, while they exhibit different increases in atmospheric CO2 concentration. The underlying mechanism of distinct CO2 emissions remains to be understood. Here, we conduct petrological‐thermomechanical modeling to show that metamorphic decarbonation and melting of carbonates that are derived from subducted sediments are ubiquitous during continental extension. We find that the hotter lithosphere and deeper storage of these carbonates cause more significant amounts of rift‐related CO2 release through volcanoes and faults. They may cause ∼12%–77% larger decarbonation efficiency, providing an efficient driving mechanism for a ∼31% larger increase in atmospheric CO2 levels during the Late Ediacaran than throughout the Jurassic. The rapid eruption and deposition of recycled carbonatite volcanic ash may contribute to the production of Late Ediacaran marine carbonates with the largest negative δ13C (−12‰).

Carbon dioxide's direct impact on down-regulating the human species

Much is said about carbon dioxide (CO2) affecting climate; rising global temperatures, rising sea levels, and stagnating ocean currents being often cited results. Less is said about what CO2 does directly to human physiology should anthropogenic trends not abate. Past mass extinctions have been correlated to airborne CO2 levels rapidly rising above 1000 ppm (Ward, 2007); a value that may be seen by the end of this century. This study proposes as humankind confronts climate changes brought on by rising atmospheric CO2 concentration, as levels rise over 1000 ppm humans may also be inundated by the direct effects of CO2. While this has already been proposed by others, this study goes on to introduce a straight forward model for helping quantify the impact of airborne CO2 on human physiology which shows the onset of hypercapnic bloodstream pH levels in humans begin to appear when atmospheric CO2 levels approach 3000 ppm. However, upon examination of data from past submarine studies, a physiological response may occur in humans at much lower atmospheric CO2 levels due to a slow buildup of CO2 in the body over time. A casual link between atmospheric CO2 levels and the calcium balance in the human body is established providing rationale for the possibility of a greater occurrence of vascular calcification and concurrent bone demineralization in the greater general population when atmospheric CO2 levels rise. Noted is the likelihood of neurological effects at CO2 levels around 1000 ppm is suggested by several past studies. Note is also made of other organisms such as fish having much lower arterial pressures than humans making them more vulnerable to environmental CO2 changes as found by other studies. This study concludes CO2's direct impact to the human physiology as well as other life is not as benign as many like to suggest, and beyond climate change, appears as a mechanism for undermining human sustainability deserving closer scrutiny, and greater discussion.

Responses of Tree Growth and Intrinsic Water Use Efficiency to Climate Factors and Human Activities in Upper Reaches of Tarim River in Alaer, Xinjiang, China

With global warming and increasing human activities, exploring the impact of the rising atmospheric carbon dioxide concentration and climate change on forest ecosystems is crucial. In this study, we focus on Euphrates poplar (Populus euphratica Oliv.) in the upper reaches of the Tarim River in the Alaer region of Xinjiang. We use dendrochronological methods, tree-ring width, and stable carbon isotope series to explain basal area increment (BAI) and intrinsic water use efficiency (iWUE) changes. We further explore the influence of past climate change and human activities on the radial growth and iWUE of P. euphratica through stable oxygen isotope analysis combined with historical literature records. The results showed that relative humidity had an essential effect on Δ13C and δ18O fractionation in P. euphratica tree rings, whereas the vapor pressure deficit (VPD) was considered the main factor influencing the inter-annual variability of the iWUE and BAI. Since 1850, long-term variations in iWUE have exhibited an upward trajectory correlated with rising atmospheric CO2 levels. Approximately 13% of this iWUE increase can be attributed to changes in carbon-concentration-induced water use efficiency (cciWUE). Although Δ13C and δ18O were generally uncorrelated between 1850 and 2018, around 1918, their relationship changed from being weakly correlated to being significantly negatively correlated, which may record changes related to the upstream Tarim River diversion. During the period from 1850 to 2018, both the BAI and iWUE showed an increasing trend for P. euphratica growth; however, the relationship between them was not stable: during 1850–1958, both variables were mainly influenced by climatic factors, while during 1959–2018, the most important influence was due to human activities, specifically agricultural development and irrigation diversions. An abrupt surge in the BAI was observed from 1959 to 1982, reaching its peak around 1982. Surprisingly, post-1983, the escalating iWUE did not correspond with a continuation of this upward trajectory in the BAI, highlighting a divergence from the previous trend where the enhanced iWUE no longer facilitated the growth of P. euphratica. Despite P. euphratica having adapted to the continuously rising Ca, improving its iWUE and growth capacity, this adaptive ability is unstable and may easily be affected by human activities. Overall, the increase in Ca has increased the iWUE of P. euphratica and promoted its growth at a low frequency, while human activities have promoted its development at a high frequency.