CO2 Treatment Research Articles

CO2 capture and inorganic carbon assimilation of gaseous fermentation effluents using Parachlorella kessleri microalgae

Microalgal cultivation represents a promising technique for the photosynthetic fixation of CO2 present in gas streams while offering the possibility to produce valuable microalgae-based bioproducts and biofuels. CO2 can be captured using an alkaline solution and subsequently used as an inorganic carbon (IC) source for microalgal cultivation. First, the IC removal and growth properties of P. kessleri were investigated using three synthetic NaHCO3 solutions (1, 5 and 10 g/L) with or without pH control. Results indicated that regularly adjusting the pH to 8.5 had a positive effect on the IC removal as well as on the overall microalgal proliferation. However, even if significant IC removal was achieved (> 86.4 %), only a small fraction of the carbon was directly used by P. kessleri. This phenomenon could be due to the partial loss of CO2 during carbonic anhydrase activity under the effect of constant agitation. These findings were used to design a two-step process to first capture CO2 produced during anaerobic fermentation and then convert it into fresh microalgal biomass. Fermentation of sugar-beet molasses generated around 32 g/L of ethanol while most of the CO2 was absorbed in a NaOH-BBM solution using 3.5 L photobioreactors. After P. kessleri inoculation and under low agitation, microalgae accumulated up to 44.9 % of carbohydrates in 34 days achieving 97 % of IC removal and 95 % of biofixation efficency. This study shows the potential of an integrated microalgae-based CO2 treatment process with the concomitant production of microalgal metabolites including but not limited to carbohydrates.

Effects of CO2 on transplantation of grape plantlets cultured in vitro by promoting photosynthesis

Plantlet in vitro is an indispensable step in micropropagation and breeding of grape (Vitis vinifera L.). However, the plantlets rely on the artificially controlled micro-environment, which is difficult to adapt to the field acclimation and transplantation, resulting in low survival rate and qualified plantlets rate. Studying the photosynthetic and growth characteristics of plantlets cultured with CO2 and sucrose as carbon sources presents important references for the acclimation and transplantation. In this context, "Pinot Noir" plantlets in vitro were cultured with S1: medium with 2% sucrose, normal carbon dioxide (CO2) concentration (380 μmol•mol−1), CS: medium with 2% sucrose, high CO2 concentration (1000 μmol•mol−1), C0: medium without sucrose, high CO2 concentration (1000 μmol•mol−1) and S0: medium without sucrose, normal CO2 concentration (380 μmol•mol−1). The results indicated that the growth status and survival rate (an average increase of 19.4%) of plantlets were significantly improved by high concentration CO2 treatments. The photosynthetic parameters of high-concentration CO2 treatments had a positive effect on photosynthetic products, which were consistent with the up-regulated trend of the relative expression of related synthesis and transport genes. Interestingly, the sugar content of photosynthetic products in leaves showed a trend from high to low at different carbon treatment stages, but the opposite trend was observed in stems. What's more, the main photosynthetic parameters of high concentration CO2 treatments were significantly increased, especially the photosynthetic fluorescence parameters of CS were the highest, and the relative expression of photosynthesis related genes were significantly up-regulated during acclimation and transplantation. Comprehensive principal component analysis method speculated that exogenous CO2 mainly laid a good foundation for the acclimation and transplantation by promoting the photosynthesis of plantlets and adjusting the source-sink relationship of leaf and stem photosynthetic products.

A meta-analysis of the combined effects of elevated carbon dioxide and chronic warming on plant %N, protein content and N-uptake rate.

Elevated CO2 (eCO2) and high temperatures are known to affect plant nitrogen (N) metabolism. Though the combined effects of eCO2 and chronic warming on plant N relations have been studied in some detail, a comprehensive statistical review on this topic is lacking. This meta-analysis examined the effects of eCO2 plus warming on shoot and root %N, tissue protein concentration (root, shoot and grain) and N-uptake rate. In the analyses, the eCO2 treatment was categorized into two classes (<300 or ≥300 ppm above ambient or control), the temperature treatment was categorized into three classes (<1.5, 1.5–5 and >5 °C above ambient or control), plant species were categorized based on growth form and functional group and CO2 treatment technique was also investigated. Elevated CO2 alone or in combination with warming reduced shoot %N (more so at ≥300 vs. <300 ppm above ambient CO2), while root %N was significantly reduced only by eCO2; warming alone often increased shoot %N, but mostly did not affect root %N. Decreased shoot %N with eCO2 alone or eCO2 plus warming was greater for woody and non-woody dicots than for grasses, and for legumes than non-legumes. Though root N-uptake rate was unaffected by eCO2, eCO2 plus warming decreased N-uptake rate, while warming alone increased it. Similar to %N, protein concentration decreased with eCO2 in shoots and grain (but not roots), increased with warming in grain and decreased with eCO2 and warming in grain. In summary, any benefits of warming to plant N status and root N-uptake rate will generally be offset by negative effects of eCO2. Hence, concomitant increases in CO2 and temperature are likely to negate or decrease the nutritional quality of plant tissue consumed as food by decreasing shoot %N and shoot and/or grain protein concentration, caused, at least in part, by decreased root N-uptake rate.

Effects of elevated CO2 treatment of Populus davidiana × P. bolleana on growth and detoxifying enzymes in gypsy moth, Lymantria dispar

To date, elevated CO2 concentrations in the environment caused by various human activities influence diverse areas of life, including the interactions between insects and plants. The Lymantria dispar is one of the most severely destructive pests, which further could inflict ecological and economical damage. In this experiment, one-year-old Populus davidiana × P. bolleana plants were grown in CO2-enhanced environments for one month at three different CO2 concentrations: 397 ppm (atmospheric CO2 concentration), 550 ppm and 750 ppm (two predicted elevated CO2 concentrations). The 3rd instar L. dispar larvae then fed on the treated poplar seedlings covered in a nylon bag. The L. dispar larvae fed on poplar seedling treated for 96 h showed the highest growth rate at all CO2 concentrations. Enzymatic activity of treated larvae showed the highest GST and P450 activity at 750 ppm CO2. The relative expressions of seven CYP and ten GST genes in L. dispar larvae were analyzed quantitatively using real-time RT-PCR, which the results were expressed variably. Compared to 397 ppm CO2, the expression of CYP4L23 was down-regulated, while the expressions of other CYP genes were up-regulated. Meanwhile, only GSTo1 gene showed down-regulated at 48 h and 96 h in 750 ppm CO2 treatment, while GST expression level for the other nine GST genes showed up-regulated at 48 h and 72 h. These results offer the insight into plant-insect interactions under global climate change and furthermore will provide essential information for strategic pest control based on biochemical and molecular levels changes in gypsy moths.

Identification of miRNAs in sea urchin Strongylocentrotus purpuratus larvae response to pH stress

MicroRNAs (miRNAs) are a class of small, endogenous, non-coding RNAs that regulate gene expression through transcriptional repression of messenger RNA. They play significant roles in many physiological and biochemical processes in eukaryotes. Ocean acidification can impact the development, survival, growth and physiology of many marine organisms. Here, we performed miRNA transcriptome analysis of the sea urchin Strongylocentrotus purpuratus larvae exposed to CO2-driven seawater acidification. We generated 10.6 and 10.8 million clean reads from the malformed S. purpuratus larva after CO2 treatment and the larvae with the normal bone development respectively. A total of 682 conserved and 17 novel miRNAs were identified. Target genes of the differential expression miRNAs were also predicted, which contained growth-related genes (collagenase, collagen and HSP70-binding protein 1), spicule formation-related gene (carbonic anhydrase transcript variant X1) and skeletogenesis-related genes (breast carcinoma amplified sequence 2). Target genes of the differentially expressed miRNAs were used to perform KEGG pathway analysis and were found to be involved in the proteasome and oxidative phosphorylation. These results provide a relatively large number of miRNAs transcriptome resource and provide a foundation for further analyses on the functional and molecular mechanisms of S. purpuratus larvae impacted by ocean acidification.

Effects of Sulfur Dioxide Exposure on Leaf Mass per Area of Selected Gymnosperms and Implications for Interpreting the Plant Fossil Record

Premise of research. The role of sulfur dioxide (SO2) in plant responses to large igneous province volcanism is difficult to determine but important in relation to understanding ecosystem responses during mass extinction events. Leaf mass per area (LMA) is an important leaf measure for tracking plant responses to environmental pressures in the fossil record, but how it responds to SO2 exposure is unclear, particularly for nonangiosperm taxa.Methodology. Five gymnosperm species were grown in simulated paleoatmospheric conditions that included SO2 to determine how the plants responded.Pivotal results. All plants’ growth in high SO2 showed a significant decrease in LMA compared with the control (with no SO2). When grown in a high CO2, low O2, and high SO2 treatment, most plants continued to show a decrease in LMA compared with the control but an increase compared with the high SO2 treatment with ambient CO2 and O2.Conclusions. These findings suggest that exposure to SO2 significantly decreases LMA, potentially reducing preservation potential in the fossil record. Exposure to combined SO2 and high CO2 reduces this effect, but this may also obscure the effects of SO2, leading to interpretations that ecosystem instability is primarily driven by increasing CO2, which may not be the case.

Fractionated Carbon Dioxide Laser for the Treatment of Vulvar Lichen Sclerosus: A Randomized Controlled Trial.

To estimate the efficacy of fractionated carbon dioxide (CO2) laser therapy for vulvar lichen sclerosus. We conducted a prospective, double-blind, randomized, sham-controlled, trial conducted in a clinic specializing in vulvar disorders. The study participants were 40 women with active vulvar lichen sclerosus confirmed with biopsy who were abstaining from topical and systemic treatments for at least 4 weeks before enrollment. Women were randomized in a 1:1 ratio to receive either five sham laser treatments or five fractionated CO2 treatments in a 24-week period. Study participants, treating clinicians, and the evaluating pathologist were blinded. The primary endpoint was the change in the histopathology scale score between pretreatment and posttreatment biopsies. We estimated 20 per group for 80% power to detect a 40% reduction in the histopathology scale score with up to 10% attrition. A secondary endpoint was the change in the validated CSS (Clinical Scoring System for Vulvar Lichen Sclerosus). From November 2018 to June 2020, 40 women were randomized to participate in the trial, and 37 women (19 fractionated CO2, 18 sham) were included in an intention-to-treat (ITT) analysis. Three women were excluded from the ITT analysis because they did not have posttreatment biopsies and, therefore, a posttreatment histopathology scale score could not be obtained. There was a 0.20 reduction (improvement) in histopathology scale score from baseline in the active treatment group (95% CI -1.1, 0.80, P=.74) and a 0.1 increase from baseline in the sham treatment group (95% CI -0.90, 1.0, P=.91). The change in histopathology scale score between the active and sham arm was not statistically significant (95% CI -1.14, 1.06, P=.76). Fractionated CO2 is not an effective monotherapy treatment for vulvar lichen sclerosus. ClinicalTrials.gov, NCT03665584. Additional funding for this study was supplied by El.En Group, Florence, Italy, the manufacturer of the laser used in this study. In addition, El.En Group supplied the laser used in the study.

Considering coasts: Adapting terrestrial models to characterize coastal wetland ecosystems

The Energy Exascale Earth System Model (E3SM) simulates fully coupled processes and interactions among water, energy, carbon and nutrient cycles. E3SM connects vegetation and soil dynamics through nutrient uptake, plant production, litterfall and decomposition as a function of abiotic parameters (e.g. temperature and moisture). However, E3SM is designed to characterize terrestrial ecosystems and connects land and open ocean systems using a single streamflow transport term, ignoring the complex dynamics of energy, water, carbon, and nutrients in coastal systems. The goals of our project were to: (1) Parameterize a point version of E3SM to capture coastal wetland habitats and (2) Determine marsh community responses to increased temperature and elevated CO2. We adapted a version of the E3SM land model, previously configured to represent forested bog hydrology to a coastal ecosystem using datasets from field experiments conducted at the Smithsonian Environmental Research Center's Global Change Research Wetland (GCReW). Tidal forcing in a marsh environment was simulated using a two-column system in which the columns are connected by lateral hydrologic flows. One column simulates interactions between vegetation and soil while a second column simulates variation in water level (both tidal and sea level rise). The updated model captures many aspects of the field experiments, showing that plant community responses to environmental change are non-linear, non-additive and different between plant types. Elevated CO2 treatments increased C3 plant biomass more than C4 (33% vs 17%). Temperature exacerbated CO2 responses in C3 plants (0 °C: 26%, 5.1 °C: 56%). We were more successful at characterizing C3 than C4 responses and simulating above rather than belowground biomass production. Next steps will include updates to key physiological parameters such as root:shoot carbon allocation and the addition of mechanistic feedbacks between vegetation and biogeochemical processes.

Transcriptome Analysis of Pre-Storage 1-MCP and High CO2-Treated 'Madoka' Peach Fruit Explains the Reduction in Chilling Injury and Improvement of Storage Period by Delaying Ripening.

Cold storage of peach fruit at low temperatures may induce chilling injury (CI). Pre-storage 1-MCP and high CO2 treatments were reported among the methods to ameliorate CI and reduce softening of peach fruit. However, molecular data indicating the changes associated with pre-storage 1-MCP and high CO2 treatments during cold storage of peach fruit are insufficient. In this study, a comparative analysis of the difference in gene expression and physico-chemical properties of fruit at commercial harvest vs. stored fruit for 12 days at 0 °C (cold-stored (CS), pre-storage 1-MCP+CS, and pre-storage high CO2+CS) were used to evaluate the variation among treatments. Several genes were differentially expressed in 1-MCP+CS- and CO2+CS-treated fruits as compared to CS. Moreover, the physico-chemical and sensory data indicated that 1-MCP+CS and CO2+CS suppressed CI and delayed ripening than the CS, which could lead to a longer storage period. We also identified the list of genes that were expressed commonly and exclusively in the fruit treated by 1-MCP+CS and CO2+CS and compared them to the fruit quality parameters. An attempt was also made to identify and categorize genes related to softening, physiological changes, and other ripening-related changes. Furthermore, the transcript levels of 12 selected representative genes from the differentially expressed genes (DEGs) in the transcriptome analysis were confirmed via quantitative real-time PCR (qRT-PCR). These results add information on the molecular mechanisms of the pre-storage treatments during cold storage of peach fruit. Understanding the genetic response of susceptible cultivars such as ‘Madoka’ to CI-reducing pre-storage treatments would help breeders release CI-resistant cultivars and could help postharvest technologists to develop more CI-reducing technologies.

Elevated Atmospheric CO2 and Nitrogen Fertilization Affect the Abundance and Community Structure of Rice Root-Associated Nitrogen-Fixing Bacteria.

Elevated atmospheric CO2 (eCO2) results in plant growth and N limitation, yet how root-associated nitrogen-fixing bacterial communities respond to increasing atmospheric CO2 and nitrogen fertilization (eN) during the growth stages of rice is unclear. Using the nifH gene as a molecular marker, we studied the combined effect of eCO2 and eN on the diazotrophic community and abundance at two growth stages in rice (tillering, TI and heading, HI). Quantitative polymerase chain reaction (qPCR) showed that eN had no obvious effect on nifH abundance in rice roots under either ambient CO2 (aCO2) or eCO2 treatment at the TI stage; in contrast, at the HI, nifH copy numbers were increased under eCO2 and decreased under aCO2. For rhizosphere soils, eN significantly reduced the abundance of nifH under both aCO2 and eCO2 treatment at the HI stage. Elevated CO2 significantly increased the nifH abundance in rice roots and rhizosphere soils with nitrogen fertilization, but had no obvious effect without N addition at the HI stage. There was a significant interaction [CO2 × N fertilization] effect on nifH abundance in root zone at the HI stage. In addition, the nifH copy numbers in rice roots were significantly higher at the HI stage than at the TI stage. Sequencing analysis indicated that the root-associated diazotrophic community structure tended to cluster according to the nitrogen fertilization treatment and that Rhizobiales were the dominant diazotrophs in all root samples at the HI stage. Additionally, nitrogen fertilization significantly increased the relative abundance of Methylosinus (Methylocystaceae) under eCO2 treatment, but significantly decreased the relative abundance of Rhizobium (Rhizobiaceae) under aCO2 treatment. Overall, the combined effect of eN and eCO2 stimulates root-associated diazotrophic methane-oxidizing bacteria while inhibits heterotrophic diazotrophs.

Changes in N2-fixation activity, abundance and composition of diazotrophic communities in a wheat field under elevated CO2 and canopy warming

Global climate change with elevated atmospheric CO2 concentrations and warming may potentially influence microbial function and nitrogen (N) cycling in various ecosystems. Despite the significance of diazotrophic mediation in soil N cycling within agricultural ecosystems, little is known about the impacts of climate change on diazotrophic abundance and community composition. An open-air field experiment growing wheat was conducted under four treatments: ambient condition (CK), CO2 enrichment up to 500 ppm (CE), warming of canopy air by 2 °C over ambient (WA), and the combined CO2 enrichment and canopy warming (CW). Quantitative real-time PCR and high-throughput pyrosequencing were used to analyze diazotrophic abundance and community composition in the bulk and rhizosphere soils. Results showed that both N2-fixation activity and nifH gene abundance were higher in the rhizosphere than those in bulk soil. N2-fixation activity and nifH gene abundance were significantly increased under elevated CO2 treatments, while no significant change was observed under warming treatment. Elevated CO2 levels altered the diazotrophic community composition and increased the alpha diversity. A redundancy analysis indicated that soil organic carbon, total nitrogen and available potassium were the most important factors in shaping diazotrophic communities in the wheat rhizosphere and bulk soil. These findings suggest that N2-fixation and diazotrophic community in wheat soil are more impacted by elevated CO2 compared with warming. Therefore, understanding how simultaneous elevated CO2 and temperature levels influences the microbial ecology of soil diazotrophs, can provide novel insights into the sustainability of agricultural production under future climate scenarios.

NOx Reduction Using Pilot-Scale SCR Under Oxyfuel Conditions

This paper presents a comprehensive experimental study of selective catalytic reduction (SCR) of nitrogen oxides formed in the oxyfuel combustion of lignite coal in a 500 kWth pilot-scale bubbling fluidized bed (BFB) boiler using the V2O5 over TiO2 honeycomb catalyst and the ammonia as the reducing agent. The study also compares the performance of the SCR between oxyfuel and air combustion modes. The SCR unit is placed in the tail-end position of the flue gas processing scheme after the cyclone particle separator. Experiments were realized both in air- and oxyfuel combustion regime, evaluating the impact of relevant process conditions on the NOx reduction. The dependence of the NOx reduction efficiency on the catalyst temperature and on the normalized stoichiometric ratio (NSR) of the reducing agent molar flow to the molar flow of NOx were studied. The efficiency of the NOx reduction was evaluated based on the NOx concentration measured simultaneously before and after the SCR unit. In the off-gas, the concentration of unreacted reducing agent (ammonia slip) was measured as well. For evaluation of real NSR, ammonia and flue gas flow rates were measured during each experiment. The catalyst temperature was regulated within the experiments in the range of 260 to 300 °C and the NSR was chosen in the range of 0 to 1.2. From this experimental setup, the correlations of the NOx reduction efficiency related to the different NSR and catalyst temperature were evaluated. The results show the fundamental information about the differences between air and oxyfuel conditions in a real combustion environment. In general, the NOx conversion efficiency was significantly higher during air combustion. In order to get similar results of maximum NOx conversion as reached during air combustion, it was necessary to increase NSR up to 1.8 and more, however at the cost of significantly increased ammonia slip. Although the SCR performance is lower in oxyfuel combustion, it was possible to decrease NOX under 100 ppmv with NSR about 1 and without any significant ammonia slip, which is important prior to further CO2 treatment.

Carbon Dioxide Pretreatment and Cold Storage Synergistically Delay Tomato Ripening through Transcriptional Change in Ethylene-Related Genes and Respiration-Related Metabolism.

The effects of CO2 pretreatment before cold storage on tomato quality were investigated using physicochemical and transcriptome changes. Harvested tomatoes were treated with 30% or 60% CO2 for 3 h before storage at 4 °C for 14 d (cold storage), followed by transfer to 20 °C for 8 d (ambient conditions). The CO2-treated fruits were firmer with a better appearance than untreated fruits, even after being transferred from 4 °C storage to 20 °C for 8 d. CO2 pretreatment coupled with cold storage synergistically delayed tomato ripening by reducing respiration and lowering lycopene production. The tomatoes treated with 30% and 60% CO2 had fewer pits than untreated fruits after cold storage, even after being transferred to ambient conditions. Moreover, the 60% CO2 treatment significantly suppressed the decay rate. Transcriptome and metabolome functional enrichment analyses commonly showed the involvement of CO2-responsive genes or metabolites in sucrose and starch metabolism, as well as biosynthesis of secondary metabolites—in particular, glycolysis reduction. The most frequently detected domain was the ethylene-responsive factor. These results indicate that altered ethylene biosynthesis and ethylene signaling, via ethylene-responsive transcription factors and respiration-related pathways, appear to control CO2-induced fruit quality.

In-situ preparation of MIL-88A(Fe)/MIL-100(Fe)/PVA-Co-PE nanofiber membranes for efficient photocatalytic reduction of CO2

In this paper, we tend to ready a polyvinyl alcohol-polyethylene (PVA-Co-PE) composite nanofiber membrane catalyst decorated by bimetallic organic framework MIL-100(Fe)/MIL-88A(Fe). The experimental results of the performance of photocatalytic reduction of CO2 show that it exhibits glorious photocatalytic activity for the reduction of CO2 underneath actinic ray irradiation, and also the best conversion rate of CO2 is 8.3 mL/h. Through SEM, XRD, BET, DRS, FTIR, and alternative characterization ways, the factors touching the photocatalytic CO2 reduction method of the composite nanofiber membrane were investigated. Studies have found that the bimetallic framework structure increases the photocurrent density and significantly reduces the photoluminescence intensity. The versatile composite nanofiber membrane has high photocatalytic activity and smart reusability and features a smart prospect within the photocatalytic reduction of CO2 treatment.

RETRACTED: Mixed-ligand coordination polymers: Catalytic CO2 fixation and treatment activity on the intestinal polyps by inducing the intestinal epithelial cells apoptosis

Abstract By virtue of a dual-ligand strategy, two transition metal coordination polymers of {[Ni2(NDC)2(L1)(H2O)2(H2O)]·(DMF)2(H2O)}n (1, L1 = 3,3′-azobis pyridine) and [Mn(NDC)(L2)(H2O)]n (2, L2 = 1,4-bis(1H-benzo[d]imidazol-1-yl)butane) have been synthesized via the corresponding metal salts reacting with the 1,4-naphthalene dicarboxylic acid (H2NDC) in the existence of distinct nitrogen-donor co-ligands. Given the permanently microporous nature, moderate CO2 sorption capacity as well as high density of the open metals positions, the activated 1 revealed the chemical fixation of the cyclic carbonates and carbon dioxide or an efficient activity of catalysis in the existence of the cocatalyst under the mild and solvent-free conditions. To evaluate the activity of the compound against intestinal polyps, following experiments were conducted. The Cell Counting Kit-8 (CCK-8) method was implemented to evaluate the inhibitory effects of these two compounds against the intestinal epithelial cells. Next, the western blotting was conducted and the apoptotic protein Bcl-2 expression levels was determined as well.

Bicarbonate for microalgae cultivation: a case study in a chlorophyte, Tetradesmus wisconsinensis isolated from a Norwegian lake

Bicarbonate was evaluated as an alternative carbon source for a green microalga, Tetradesmus wisconsinensis, isolated from Lake Norsjø in Norway. Photosynthesis, growth, and lipid production were studied using four inorganic carbon regimes: (1) aeration only, (2) 20 mM NaHCO3, (3) 5% (v/v) CO2 gas, and (4) combination of 20 mM NaHCO3 and 5% CO2. Variable chlorophyll a fluorescence analysis revealed that the bicarbonate treatment supported effective photosynthesis, while the CO2 treatment led to inefficient photosynthetic activity with a PSII maximum quantum yield as low as 0.31. Conversely, bicarbonate and CO2 treatments gave similar biomass and fatty acid production. The maximum growth rate, the final cell dry weight, and total fatty acids under the bicarbonate-only treatment were 0.33 (± 0.06) day−1, 673 (± 124) mg L−1 and 75 (± 5) mg g−1 dry biomass, respectively. The most abundant fatty acid components were α-linolenic acid and polyunsaturated fatty acids constituting 69% of the total fatty acids. The fatty acid profile eventuated in unsuitable biodiesel fuel properties such as high degree of unsaturation and low cetane number; however, it would be relevant for food and feed applications. We concluded that bicarbonate could give healthy growth and comparative product yields as CO2.

Hyperspectral Estimation Models of Winter Wheat Chlorophyll Content Under Elevated CO2.

Chlorophyll content is an important indicator of winter wheat health status. It is valuable to investigate whether the relationship between spectral reflectance and the chlorophyll content differs under elevated CO2 condition. In this open-top chamber experiment, the CO2 treatments were categorized into ambient (aCO2; about 400 μmol⋅mol–1) or elevated (eCO2; ambient + 200 μmol⋅mol–1) levels. The correlation between the spectral reflectance and the chlorophyll content of the winter wheat were analyzed by constructing the estimation model based on red edge position, sensitive band and spectral index methods, respectively. The results showed that there was a close relationship between chlorophyll content and the canopy spectral curve characteristics of winter wheat. Chlorophyll content was better estimated based on sensitive spectral bands and difference vegetation index (DVI) under both aCO2 and eCO2 conditions, though the accuracy of the models varied under different CO2 conditions. The results suggested that the hyperspectral measurement can be effectively used to estimate the chlorophyll content under both aCO2 and eCO2 conditionsand could provide a useful tool for monitoring plants physiology and growth.

Elevated extracellular CO&lt;sub&gt;2&lt;/sub&gt; level affects the adaptive transcriptional response and survival of human peripheral blood mononuclear cells toward hypoxia and oxidative stress

BACKGROUND High carbon dioxide (CO2) level from indoor environments, such as classrooms and offices, might cause sick building syndrome. Excessive indoor CO2 level increases CO2 level in the blood, and over-accumulation of CO2 induces an adaptive response that requires modulation of gene expression. This study aimed to investigate the adaptive transcriptional response toward hypoxia and oxidative stress in human peripheral blood mononuclear cells (PBMCs) exposed to elevated CO2 level in vitro and its association with cell viability.&#x0D; METHODS PBMCs were treated in 5% CO2 and 15% CO2, representatives a high CO₂ level condition for 24 and 48 hours. Extracellular pH (pHe) was measured with a pH meter. The levels of reactive oxygen species were determined by measuring superoxide and hydrogen peroxide with dihydroethidium and dichlorofluorescin-diacetate assay. The mRNA expression levels of hypoxia-inducible factor (HIF)-1α, HIF-2α, nuclear factor (NF)-κB, and manganese superoxide dismutase (MnSOD) were analyzed using a real-time reverse transcriptase-polymerase chain reaction (qRT-PCR). Cell survival was determined by measuring cell viability.&#x0D; RESULTS pHe increased in 24 hours after 15% CO₂ treatment, and then decreased in 48 hours. Superoxide and hydrogen peroxide levels increased after the 24- and 48-hour of high CO₂ level condition. The expression levels of NF-κB, MnSOD, HIF-1α, and HIF-2α decreased in 24 hours and increased in 48 hours. The increased antioxidant mRNA expression in 48 hours showed that the PBMCs were responsive under high CO2 conditions. Elevated CO2 suppressed cell viability significantly in 48 hours.&#x0D; CONCLUSIONS After 48 hours of high CO₂ level condition, PBMCs showed an upregulation in genes related to hypoxia and oxidative stress to overcome the effects of CO2 elevation.

Mechanisms of shale water wettability alteration with chemical groups after CO2 injection: Implication for shale gas recovery and CO2 geo-storage

Supercritical carbon dioxide (Sc-CO2) has been used in shale gas exploitation for efficient fracturing and the added benefit of CO2 geo-storage. Many studies have suggested that the water wettability of shale significantly influences the success of shale gas recovery. The aim of this work was to investigate the effect of CO2 treatment on shale water wettability. X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) were used to analyze the raw and CO2-treated shale samples using peak fitting and grey relational (GR) analyses. The results showed that the CO2-treated shale surface showed weaker hydrophilicity than the raw shale sample. The GR analysis results indicated that Si–OH contributed most to shale water wettability because Si–OH formed hydroxyl bonds with the water molecules on the shale surface, significantly enhancing shale hydrophilicity. The proportion of Si–OH in the shale chemical groups decreased, and fewer hydroxyl bonds were formed after the CO2 treatment, weakening shale hydrophilicity. The content of hydrophilic –OH groups was lower in the CO2-treated shale samples than the raw samples, and increases and decrease were observed in the content of the C–O groups. A decrease in the contents of hydrophilic calcite, dolomite, and clay minerals also contributed to shale hydrophilicity weakening. These results imply that the injection of CO2 into shale reservoirs weakens shale hydrophilicity, improving shale gas recovery because the water blocking effect is minimized. The findings in this research can be used for shale wettability reversal by chemical reagents, which is of great significance for improving gas productivity and CO2 geological storage.

The dose makes the poison: Non-linear behavioural response to CO2-induced aquatic acidification in zebrafish (Danio rerio).

CO2-induced aquatic acidification is predicted to affect fish neuronal GABAA receptors leading to widespread behavioural alterations. However, the large variability in the magnitude and direction of behavioural responses suggests substantial species-specific CO2 threshold differences, life history and parental acclimation effects, experimental artifacts, or a combination of these factors. As an established model organism, zebrafish (Danio rerio) can be reared under stable conditions for multiple generations, which may help control for some of the variability observed in wild-caught fishes. Here, we used two standardized tests to investigate the effect of 1-week acclimatization to four pCO2 levels on zebrafish anxiety-like behaviour, exploratory behaviour, and locomotion. Fish acclimatized to 900 μatm CO2 demonstrated increased anxiety-like behaviour compared to control fish (~480 μatm), however, the behaviour of fish exposed to 2200 μatm CO2 was indistinguishable from that of controls. In addition, fish acclimatized to 4200 μatm CO2 had decreased anxiety-like behaviour; i.e. the opposite response than the 900 μatm CO2 treatment. On the other hand, exploratory behaviour did not differ among any of the pCO2 exposures that were tested. Thus, zebrafish behavioural responses to elevated pCO2 are not linear; with potential important implications for physiological, environmental, and aquatic acidification studies.