Different Levels Of CO2 Research Articles

Estudo preliminar do efeito da cura por carbonatação em geopolímeros

Abstract Carbonation curing differs from weathering carbonation since it is performed intentionally at the early ages of cement hydration. This cure involves applying different levels of CO2 (5% to 99%) to concrete for a short period of time, usually followed by conventional hydration. The objective of this article was to evaluate the carbonation curing in metakaolin-based geopolymer concretes, activated with NaOH and Na2SiO3, and compare them with Portland cement (PC) concrete. The following tests were applied: determination of pH, carbonation depth, water absorption by immersion, void index, and compressive strength. The results showed that after the carbonation curing, the geopolymer concrete had compressive strength and carbonation depth equivalent to the concrete with PC, but with a lower absorbed CO2 content. Although this type of cement absorbs less CO2 but is more sensitive to carbonation. The effect on the void ratio was not remarkable. Furthermore, the alkalinity of concretes can be partially recovered after subsequent curing by water immersion.

Chemical equilibrium based combustion model to evaluate the effects of H2 addition to biogases with different CO2 contents

This research addresses the influence of hydrogen addition on adiabatic flame temperature, and energy-based amounts of biogas combustion products. The evaluations were conducted with the developed solving scheme based on the chemical equilibrium approach for fuel blends of methane (CH4) –carbon dioxide (CO2), and hydrogen (H2) structures. Thus, the biogases, composed of CH4 and CO2, including different levels of CO2 (10, 25 and 40% by volume) were evaluated by blending H2 in the range of 0–40% with a 5% increment by volume. Besides, the analyses were carried out at different equivalence ratios (ϕ) varying from 0.6 to 1.4 to determine the H2 effect in lean, stoichiometric and rich mixture conditions. The results show that the effect of H2 on the adiabatic flame temperatures and the energy-based amounts of CO2, CO, and NO, change heavily depending on the CO2 concentration of biogas and the equivalence ratios. By adding a 40% H2 to biogas involving 40% CO2, the adiabatic flame temperatures enhanced by 55.8 K, 67.9 K, and 114.7 K at φ = 0.6, 1.0, and 1.4, respectively. The H2 addition significantly contributes to decreasing the energy-based amount of CO2. The maximum improvements in the CO2 amounts were obtained as 25.36%, 26.86%, and 32.38% at φ = 0.8, 1.0, and 1.4, respectively, by 40% H2 addition. The CO amounts are tendency to decrease with H2 addition at φ = 1.0 to 1.4 corresponding to stoichiometric and rich mixtures. However, the H2 addition slightly increased the CO amount at the lean mixtures in which the amounts of CO are already quietly low level. Regarding the energy-based amounts of NO, the H2 addition gave rise to increasing the NO amounts. However, the effect of H2 on the NO amount decreased at rich mixtures independent of CO2 content in biogas. The maximum increase in the NO amount by 40% H2 addition is about 0.3 g/MJ at the φ = 0.6 while 0.006 g/MJ at φ = 1.4.

Effects of Increasing Indoor Negative Air Ions on Cognitive Performance and Health of High Pure CO2 Level-Exposed College Students

Cognitive performance is essential to foster learning. High CO2 concentrations are common in classrooms and can lead to reduced cognitive performance. Negative air ions (NAIs) can improve cognitive performance. This study explored the effects of indoor NAIs on the cognitive performance and health of college students exposed to a high pure CO2 environment. Forty college students were exposed to four sets of conditions (NAIs+500 ppm CO2, 500 ppm CO2, NAIs+2500 ppm CO2, and 2500 ppm CO2). Participants’ cognitive performance, including reasoning, short-term memory, concentration, and verbal ability, was assessed under each condition using the Cambridge Brain Sciences tool. Acute health symptoms were investigated using a subjective questionnaire, and simultaneously, participants’ blood pressure, heart rate, and lung function were tested. Analysis of variance (ANOVA) in a repeated-measures design was used to analyze the effects of different conditions on cognitive performance and health symptoms. The results revealed that the different levels of CO2 and NAIs had a significant effect on cognitive performance after one hour of exposure and had no significant effect after three hours of exposure. Compared with 500 ppm CO2, 500 ppm CO2+NAIs resulted in better reasoning skills, short-term memory, and verbal skills, and 2500 ppm CO2 led to poorer reasoning skills. The addition of NAIs to 2500 ppm CO2 improved reasoning skills, short-term memory, and verbal skills. The benefits of adding NAIs to high pure CO2 condition on cognitive performance are more noticeable than those to low CO2 condition. Moreover, adding NAIs can reduce nasal irritation or dryness, skin irritation or dryness, sleepiness symptoms, and heart rate elevation caused by pure CO2. However, the benefits of NAIs on health symptoms and physiology were not observed under the 500 ppm CO2 condition. Adding NAIs to a high pure CO2 level is an effective means to improve the cognitive performance and health of college students.

Assessing optimal nitrate/ ammonium- ratios in baby-leaf lettuce to enhance the heat stress tolerance under elevated CO2 conditions.

In recent years, the interest on baby-leaf lettuce has grown steadily, because it is richer in bioactive compounds than other traditional vegetables. However, the quality of lettuce is being increasingly affected by climate change. It is very rare for a climatic effect to occur in isolation. Even then, a large body of work has only focused on the effect of isolated heat stress, fertilization, and elevated CO2, on morphological, physiological and biochemical parameters. Thus, very few works have focused on how the combination of several of these factors can affect these parameters. For first time, the present work studied the combined effect derived from the application of two different levels of CO2 (400 and 1000 ppm of CO2), four different NO3-/ NH4+ ratios (100/0 (T-I), 100/0 before the short-term heat stress and finally without NO3- (T-II), 80/20 (T-III) and 50/50 (T-IV)), and a short-term heat stress (25 and 43°C), on some physiological and quality parameters (dry biomass, photosynthetic parameters, pigments content, lipid peroxidation and total soluble proteins content) of baby-leaf lettuce cv Derbi. Additionally, a comparison of that combined effect of all these parameters between inner and outer leaves was also performed. The results obtained indicated that the interaction between the nutrient solution containing a 50/50 NO3-/ NH4+ ratio and a high concentration of CO2 (1000 ppm) improved the biomass, photosynthesis, intercellular/external CO2 concentration ratio (ci/ca), stomatal conductance (gs), evapotranspiration (E) and lipid peroxidation, and protein content in this baby-leaf lettuce. The results obtained in this work lead us to conclude that this existing interaction between the NO3-/ NH4+ ratio and the elevated CO2 concentration may be considered as a new strategy for making baby-leaf lettuce more resistant to heat stress, in other words, stronger against the ever more frequent heat waves.

Management of Pulse Beetle in Green Gram Seed Using Modified Atmosphere

The experiment was conducted at Seed Research and Technology Center, PJTSAU, Rajendranagar, Hyderabad, Telangana State, India during June, 2019 under laboratory conditions using modified atmosphere with elevated levels of CO2 in two varieties of green gram namely LGG-460 and LGG-407. The study indicated that biological parameters of the test insect and the seed quality parameters were highly influenced by different levels of CO2 and storage intervals and varied between the two accessions of green gram. Emergence of adults decreased with increased concentrations of CO2. Among the two accessions, LGG-460 had least adult emergence with comparatively less insect damage than LGG-407. Higher concentrations of CO2 (45%) significantly reduced the per cent insect infestation and weight loss of both the accessions. The efficacy of different concentrations of CO2 on seed infestation and population build up revealed that exposing the bruchid infested green gram seed to 45% and higher concentrations of CO2 not only checked seed infestation but also checked the progeny production of the pest even after prolonged periods of storage up to 2 MAS. The green gram seeds stored in CO2 rich atmosphere also maintained seed quality with high germination percentage and seedling vigor up to 2 MAS. Two months storage period was effective for control of insect infestation and weight loss. Among the 2 accessions, seedling vigour I and II were found to be high in LGG 460 even at 6 months storage interval.

Proteolytic Development and Volatile Compounds Profile of Domiati Cheese under Modified Atmosphere Packaging

This study explored the impacts of modified atmosphere packaging (MAP) treatment on the proteolytic development and volatile compounds of Domiati cheese during storage. Domiati cheese samples were kept for 75 days at refrigerator temperature, under aerobic packaging (C1) or vacuum (C2). In parallel, other Domiati cheese samples were kept under MAP, at different levels of CO2 and N2, as follows: 10% CO2/90% N2 (D1), 15% CO2/85% N2 (D2), 25% CO2/75% N2 (D3), 100% CO2 (D4), and 100% N2 (D5). The normal control (C1) treatment showed the highest reduction in pH from 6.64 at zero time to 6.23 and 6.01 after 40 and 75 days of storage, respectively. On the other hand, the under-vacuum samples (C2) showed the lowest reduction in pH, from 6.64 at zero time to 6.49 and 6.28 after 40 and 75 days of storage, respectively. Proteolysis during cheese storage was lower in MAP of cheeses than in the C1 treatment. Total free amino acids (FAAs) were higher in C1 treatment than other cheeses during the whole storage period. The lowest level of total FAA was detected in D4 treatment after 75 days of storage. Volatile acids, aldehydes, ketones, and esters compounds were detected in all treatments during storage, but particularly higher in aerobic packaging than the other treatments after 75 days. The level of each acid compound increased with storage period, and the increases were particularly clear in pentanoic acid, hexanoic acid, heptanoic acid, benzoic acid, and n-decanoic acid. The normal control (C1) showed high contents of the different volatile ketone compounds. However, the samples packaged under 100% N2 (D5) showed the significantly highest levels of all the volatile ketones after 75 days of storage, particularly 2-pentanone, acetoin, methyl isobutyl ketone, 2-heptanone, 2-nonanone, and 2-undecanone. Some important compounds contributing to the good flavor of the cheese are acetic acid, butanoic acid, pentanal, benzaldehyde, acetoin, and 2,3-butanedione. The CO2 and N2 treatments exerted significant changes in all groups during the storage of cheese. All cheese samples showed gradual increases in CO2 co-occurring with parallel decreases in N2 during refrigerated storage periods, except for D4 treatment (100% CO2), which showed a decrease. A significant decrease in O2 level occurred in C1 treatment during cold storage.

Applying Dialysis Bags to Grow Microalgae and Measure Grazing Rates by Secondary Producers

Traditional methods using sealed bottles to determine the grazing rates by secondary producers neglect chemical changes induced by biological activities during the incubation, giving rise to instable levels of nutrients, pH, pCO2, pO2 and other chemicals along with changing microalgal cell concentrations and grazers’ metabolism. Here, we used dialysis bags, which allows exchanges of nutrients and gases, to grow microalgae and to determine grazing rates of secondary producers. The specific growth rate of diatom within the dialysis bags increased with increasing water velocities, indicating its suitability to grow microalgae under dynamic water conditions. Then, we compared the grazing rates by the heterotrophic dinoflagellate Noctiluca scintillans measured with the traditional method using polycarbonate (PC) bottles and the approach with the dialysis bags, and found that these two methods gave rise to comparable grazing rates. Nevertheless, the concentrations of inorganic nitrogen and phosphate in the closed PC bottles were about 89–94% lower than those in the dialysis bags due to the microalga’s assimilation. Subsequently, we applied it to determine the grazing rates by a copepod and an oyster (in the presence of other grazers). Consistent results were obtained using the dialysis bags to determine grazing rates by copepods. During the mesocosm (3000 L) experiment in the presence of primary and secondary producers, the grazing rates by the oyster Crassostrea angulata were determined based on the difference of phytoplankton biomass within and outside of the dialysis bags that held all organisms in the mesocosm except the oyster. Since the dialysis bags are permeable to gases, the grazing rates by the oyster under 410 (AC) and 1,000 (HC) μatm CO2 were successfully measured, with a promising result that HC significantly increased the oyster’s grazing. We concluded that using dialysis bags to grow microalgae and to determine grazing rates is a reliable approach, especially under different levels of CO2 and O2.

Unraveling the nutritional and bioactive constituents in baby-leaf lettuce for challenging climate conditions

The isolated effects of heat stress, fertilization and elevated CO2 on the content of several health-promoting compounds in plants have been quite studied. However, few studies have focused on two of these three factors together. This work provides information on how two different levels of CO2, four different NO3−/NH4+ ratios in the nutrient solution, and a short-term heat stress affect the biomass and nutritional quality of baby-leaf lettuce cv Derbi. Furthermore, the nutritional quality of the inner and outer leaves was also studied and compared. Results indicated that the strategy used led to a bigger and healthier baby-leaf lettuces. So, this lettuces contained a higher content of sugars, minerals and phenolic compounds and showed an enhanced antioxidant activity. On the other hand, results exhibited that whilst in inner leaves the biosynthesis of antioxidant compounds were favored, in outer leaves was favored the biosynthesis of sugars and mineral content.

Drought and Elevated Carbon Dioxide Impact the Morphophysiological Profile of Basil (Ocimum basilicum L.)

Treating plants with elevated carbon dioxide (eCO2) can increase their drought tolerance. Increased atmospheric CO2, a fundamental factor in climate change, may compensate for the drought-induced reduction in crop growth and yield. Basil, being moderately sensitive to drought stress (DS), experiences several morphological changes under DS. Thus, we designed an experiment that addresses how DS and different levels of CO2 affect the overall morphological growth patterns during basil’s early and late-season growth. The experiment was conducted under four different growth conditions: two water treatments, (1) a full-strength Hoagland’s solution was added to the basil plants at 120% of the evapotranspiration each day, and (2) 50% of the full-strength Hoagland’s solution was added to basil plants for the drought treatment, alongside two levels of CO2 application [ambient 420 ppm (aCO2) and elevated 720 ppm (eCO2)]). The DS had a severe impact on the morphological traits of the shoot and root systems. Compared to control, DS reduced the marketable fresh mass (FM) by 31.6% and 55.2% in the early and late stages of growth. FM was highest under control + eCO2 (94.4–613.7 g) and lowest under DS + aCO2 (67.9–275.5 g). Plant height under DS + aCO2 and DS + eCO2 reduced by 16.8% and 10.6% during the late season. On the other hand, dry mass percent (DM%) increased by 31.6% and 55.2% under DS + eCO2 compared to control in the early and late stages of growth, respectively. This study suggested that eCO2 during DS significantly impacts basil morphological traits compared to aCO2. Besides, anthocyanin decreased by 10% in DS + aCO2 and increased by 12.6% in DS + aCO2 compared to control. Similarly, nitrogen balance index, a ratio of chlorophyll and flavonoids, was recorded to be the highest in DS + aCO2 (40.8) compared to any other treatments. Overall, this study indicates that the suppression of basil’s morphophysiological traits by DS is more prominent in its later growth stage than in the earlier stages, and eCO2 played an important role in alleviating the negative effect of DS by increasing the DM% by 55%.

Deep mitigation of CO2 and non-CO2 greenhouse gases toward 1.5\u2009\xb0C and 2\u2009\xb0C futures

Stabilizing climate change well below 2 °C and towards 1.5 °C requires comprehensive mitigation of all greenhouse gases (GHG), including both CO2 and non-CO2 GHG emissions. Here we incorporate the latest global non-CO2 emissions and mitigation data into a state-of-the-art integrated assessment model GCAM and examine 90 mitigation scenarios pairing different levels of CO2 and non-CO2 GHG abatement pathways. We estimate that when non-CO2 mitigation contributions are not fully implemented, the timing of net-zero CO2 must occur about two decades earlier. Conversely, comprehensive GHG abatement that fully integrates non-CO2 mitigation measures in addition to a net-zero CO2 commitment can help achieve 1.5 °C stabilization. While decarbonization-driven fuel switching mainly reduces non-CO2 emissions from fuel extraction and end use, targeted non-CO2 mitigation measures can significantly reduce fluorinated gas emissions from industrial processes and cooling sectors. Our integrated modeling provides direct insights in how system-wide all GHG mitigation can affect the timing of net-zero CO2 for 1.5 °C and 2 °C climate change scenarios.

The Bloom-Forming Dinoflagellate Karenia mikimotoi Adopts Different Growth Modes When Exposed to Short or Long Period of Seawater Acidification.

Impacts of ocean acidification (OA) on noncalcifying organisms and the possibly responsible mechanism have aroused great research interests with the intensification of global warming. The present study focused on a noxious, noncalcifying, bloom-forming dinoflagellate, Karenia mikimotoi (K. mikimotoi), and its variation of growth patterns exposed to different periods of seawater acidification with stressing gradients was discussed. The dinoflagellates under short-time acidifying stress (2d) with different levels of CO2 presented significant growth inhibition (p < 0.05). The cell cycle was obviously inhibited at S phase, and the photosynthetic carbon fixation was also greatly suppressed (p < 0.05). Apoptosis was observed and the apoptotic rate increased with the increment of pCO2. Similar tendencies were observed in the key components of mitochondrial apoptotic pathway (the mitochondrial membrane potential (MMP), Caspase-3 and -9, and Bax/Bcl-2 ratio). However, under prolonged stressing time (8 d and 15 d), the growth of dinoflagellates was recovered or even stimulated, the photosynthetic carbon fixation was significantly increased (p < 0.05), the cell cycle of division presented little difference with those in the control, and no apoptosis was observed (p > 0.05). Besides, acidification adjusted by HCl addition and CO2 enrichment resulted in different growth performances, while the latter had a more negative impact. The results of present study indicated that (1) the short-time exposure to acidified seawater led to reduced growth performance via inducing apoptosis, blocking of cell cycle, and the alteration in photosynthetic carbon fixation. (2) K. mikimotoi had undergone adaptive changes under long-term exposure to CO2 induced seawater acidification. This further demonstrated that K. mikimotoi has strong adaptability in the face of seawater acidification, and this may be one of the reasons for the frequent outbreak of red tide. (3) Ions that dissociated by the dissolved CO2, instead of H+ itself, were more important for the impacts induced by the acidification. This work thus provides a new perspective and a possible explanation for the dominance of K. mikimotoi during the occurrence of HABs.

Higher Atmospheric CO2 Levels Favor C3 Plants Over C4 Plants in Utilizing Ammonium as a Nitrogen Source.

Photosynthesis of wheat and maize declined when grown with NH4+ as a nitrogen (N) source at ambient CO2 concentration compared to those grown with a mixture of NO3– and NH4+, or NO3– as the sole N source. Interestingly, these N nutritional physiological responses changed when the atmospheric CO2 concentration increases. We studied the photosynthetic responses of wheat and maize growing with various N forms at three levels of growth CO2 levels. Hydroponic experiments were carried out using a C3 plant (wheat, Triticum aestivum L. cv. Chuanmai 58) and a C4 plant (maize, Zea mays L. cv. Zhongdan 808) given three types of N nutrition: sole NO3– (NN), sole NH4+ (AN) and a mixture of both NO3– and NH4+ (Mix-N). The test plants were grown using custom-built chambers where a continuous and desired atmospheric CO2 (Ca) concentration could be maintained: 280 μmol mol–1 (representing the pre-Industrial Revolution CO2 concentration of the 18th century), 400 μmol mol–1 (present level) and 550 μmol mol–1 (representing the anticipated futuristic concentration in 2050). Under AN, the decrease in net photosynthetic rate (Pn) was attributed to a reduction in the maximum RuBP-regeneration rate, which then caused reductions in the maximum Rubisco-carboxylation rates for both species. Decreases in electron transport rate, reduction of electron flux to the photosynthetic carbon [Je(PCR)] and electron flux for photorespiratory carbon oxidation [Je(PCO)] were also observed under AN for both species. However, the intercellular (Ci) and chloroplast (Cc) CO2 concentration increased with increasing atmospheric CO2 in C3 wheat but not in C4 maize, leading to a higher Je(PCR)/ Je(PCO) ratio. Interestingly, the reduction of Pn under AN was relieved in wheat through higher CO2 levels, but that was not the case in maize. In conclusion, elevating atmospheric CO2 concentration increased Ci and Cc in wheat, but not in maize, with enhanced electron fluxes towards photosynthesis, rather than photorespiration, thereby relieving the inhibition of photosynthesis under AN. Our results contributed to a better understanding of NH4+ involvement in N nutrition of crops growing under different levels of CO2.

Modelling the effects of CO2 on C3 and C4 grass competition during the mid-Pleistocene transition in South Africa

Palaeoenvironmental reconstructions of the interior of South Africa show a wetter environment than today and a non-analogous vegetation structure in the Early Pleistocene. This includes the presence of grasses following both C3 and C4 photosynthetic pathways, whereas C3 grasses decline after the mid-Pleistocene transition (MPT, c. 1.2–0.8 Ma). However, the local terrestrial proxy record cannot distinguish between the potential drivers of these vegetation changes. In this study we show that low glacial CO2 levels, similar to those at the MPT, lead to the local decline of C3 grasses under conditions of decreased water availability, using a vegetation model (LPX) driven by Atmosphere–Ocean coupled General Climate Model climate reconstructions. We modelled vegetation for glacial climates under different levels of CO2 and fire regimes and find evidence that a combination of low CO2 and changed seasonality is driving the changes in grass cover, whereas fire has little influence on the ratio of C3:C4 grasses. Our results suggest the prevalence of a less vegetated landscape with limited, seasonal water availability, which could potentially explain the much sparser mid-Pleistocene archaeological record in the southern Kalahari.

Effect of Greenhouse CO2 Supplementation on Yield and Mineral Element Concentrations of Leafy Greens Grown Using Nutrient Film Technique

Carbon dioxide (CO2) concentration is reported to be the most important climate variable in greenhouse production with its effect on plant photosynthetic assimilation. A greenhouse study was conducted using a nutrient film technique (NFT) system to quantify the effect of two different levels of CO2 (supplemented at an average of 800 ppm and ambient at ~410 ppm) on growth and nutritional quality of basil (Ocimum basilicum L.) ‘Cardinal’, lettuce (Lactuca sativa L.) ‘Auvona’, and Swiss chard (Beta vulgaris L.) ‘Magenta Sunset’ cultivars. Two identical greenhouses were used: one with CO2 supplementation and the other serving as the control with an ambient CO2 concentration. The results indicate that supplemented CO2 could significantly increase the height and width of hydroponically grown leafy greens. Supplemented CO2 increased the fresh weight of basil ‘Cardinal’, lettuce ‘Auvona’, and Swiss chard ‘Magenta Sunset’ by 29%, 24.7%, and 39.5%, respectively, and dry weight by 34.4%, 21.4%, and 40.1%, respectively. These results correspond to a significant reduction in Soil Plant Analysis Development (SPAD) and atLEAF values, which represent a decrease in leaf chlorophyll content under supplemented CO2 conditions. Chlorophyll, nitrogen (N), phosphorus (P), and magnesium (Mg) concentrations were generally lower in plants grown in supplemented CO2 conditions, but the results were not consistent for each species. Supplemented CO2 reduced tissue N concentration for basil ‘Cardinal’ and lettuce ‘Auvona’ but not Swiss chard, while Mg concentration was reduced in supplemented CO2 for Swiss chard ‘Magenta Sunset’ only. In contrast, Fe concentration was increased under supplemented CO2 for basil ‘Cardinal’ only. These findings suggest CO2 supplementation could increase yield of leafy greens grown with hydroponics and have varying impact on different mineral concentrations among species.

Improving the representation of stomatal responses to CO2 within the Penman–Monteith model to better estimate evapotranspiration responses to climate change

An increase in atmospheric CO2 concentration (CO2) affects stomatal conductance (gs). Since gs is an important parameter in the Penman–Monteith model (P-M), an accurate estimate of gs can improve the accuracy of the estimation of evapotranspiration (ET) by P-M when CO2 increases. This paper identifies three models of the relationship between gs and CO2 (the linear model, L, the hyperbolic model, H, and the modified hyperbolic model, MH), and compares their estimations of ET when they are incorporated into P-M. A two-year experiment which included four levels (400, 550, 700, and 900 μmol mol−1) and three levels (400, 550, and 700 μmol mol−1) of CO2 in 2015 and 2016, respectively, was conducted in order to obtain validation data. Fifty papers that had studied the effect of increased CO2 on gs, over a 45-year period, were analyzed to obtain calibration data. After being calibrated and validated, each of the three models was in turn included as a component of P-M to estimate ET under increased CO2, followed by the comparison between estimated and observed ET. The sensitivity of P-M to the parameters in three models was also analyzed. Our results show that gs decreased and the reduction rate gradually lessened as CO2 increased. Of the three models, MH gave the best estimate of gs, having the largest values of the coefficient of determination (R2), 0.97, the Nash–Sutcliffe efficiency coefficient (NSE), 0.96, and the modified affinity index (d), 0.93, and the smallest values of the root mean square error (RMSE), 0.03, and the Akaike information criterion (AIC), −47.48. Each of the three models gave different ET results for different levels of CO2 when used as a component of P-M. The MH had better ET estimations than L and H when compared to observed ET across all CO2 concentration levels, with the highest R2, NSE, and d, and the lowest RMSE and AIC. The sensitivity of P-M to the empirical parameters varied among the three models, for instance, ±40 and ±20% changes of parameter p in L, gsmaxp and Cs0 in H, and b in MH resulted in −15 to 4%, −13 to 7%, −9 to 4%, and −3 to 3% changes in predicted ET, respectively. Thus, changes of parameter b in MH had minimum effect on predicted ET, indicating greater stability of P-M in ET estimation by incorporating MH. Therefore, using MH to model the response of gs to increased CO2 when incorporated into P-M to estimate ET not only represents a more appropriate stomata physiological reaction to higher CO2, but also results in a more accurate estimate of ET, and making the model more broadly applicable.

CO2 Enrichment with Higher Light Level Improves Flowering Quality of Phalaenopsis Queen Beer ‘Mantefon’

We investigated the flowering and photosynthetic responses of Phalaenopsis Queen Beer ‘Mantefon’ to CO2 enrichment and light level. Potted plants at the flowering stage were supplied with low light level (LL; 90 ± 10 μmol m−2 s−1) or high light level (HL; 260 ± 40 μmol m−2 s−1) using three−wave cool white fluorescent lamps and metal halide lamp and different levels of CO2. Carbon dioxide was supplied to the plants, which perform crassulacean acid metabolism, during their dark period at three concentrations: 400 (control), 800, and 1200 μmol mol−1 CO2. More flowers and lateral branches were produced by plants grown under HL than the control plants grown under LL, and there were more visible floral buds in the plants grown under HL than those grown LL, regardless of CO2 concentration. Net CO2 assimilation rate was higher in plants exposed to 800 and 1200 μmol mol−1 CO2 under LL and 1200 μmol mol−1 CO2 than the control plants under LL and HL. We conclude that photosynthesis is enhanced in CO2-enriched plants, and lateral branch and floral bud production are maximized at the high light level used here in Phalaenopsis Queen Beer ‘Mantefon’.

Genetic responses to carbon and nitrogen availability in Anabaena.

Heterocyst-forming cyanobacteria are filamentous organisms that perform oxygenic photosynthesis and CO2 fixation in vegetative cells and nitrogen fixation in heterocysts, which are formed under deprivation of combined nitrogen. These organisms can acclimate to use different sources of nitrogen and respond to different levels of CO2 . Following work mainly done with the best studied heterocyst-forming cyanobacterium, Anabaena, here we summarize the mechanisms of assimilation of ammonium, nitrate, urea and N2 , the latter involving heterocyst differentiation, and describe aspects of CO2 assimilation that involves a carbon concentration mechanism. These processes are subjected to regulation establishing a hierarchy in the assimilation of nitrogen sources -with preference for the most reduced nitrogen forms- and a dependence on sufficient carbon. This regulation largely takes place at the level of gene expression and is exerted by a variety of transcription factors, including global and pathway-specific transcriptional regulators. NtcA is a CRP-family protein that adjusts global gene expression in response to the C-to-N balance in the cells, and PacR is a LysR-family transcriptional regulator (LTTR) that extensively acclimates the cells to oxygenic phototrophy. A cyanobacterial-specific transcription factor, HetR, is involved in heterocyst differentiation, and other LTTR factors are specifically involved in nitrate and CO2 assimilation.

Numerical study of CO2 effects on laminar non-premixed biogas flames employing a global kinetic mechanism and the Flamelet-Generated Manifold technique

Numerical simulations of flames employing detailed kinetic mechanisms are computationally demanding problems. For this reason, reduced mechanisms and techniques of chemical kinetic reduction have been developed and used in both research and industrial applications. The objective of the present work is to compare the prediction of a global kinetic mechanism and the Flamelet-Generated Manifold (FGM) reduction technique with a detailed mechanism in numerical simulations of laminar non-premixed flames. The fuel was a biogas-like mixture modelled as methane diluted with carbon dioxide. First, the effect of CO2 addition into fuel stream was studied in one-dimensional counterflow flames. Flame structure and chemical kinetics were investigated for different levels of CO2. A new approach for evaluating the dilution effect is introduced based on the CO2 content in a stoichiometric mixture. With this definition, the effect of pure dilution on major species and temperature peak values tends to be linear. The comparisons among solutions obtained with a detailed, a skeleton and a 4-step global mechanism for different strain rates and dilution levels reveals the capabilities of these chemical kinetic approaches for modelling biogas flames. Then, the 4-step mechanism and the FGM technique were compared with a skeleton kinetic model in two-dimensional coflow flames. It was observed that the 4-step mechanism presented good results for temperature and major chemical species, being a good choice when these fields are desired. On the other hand, the FGM technique presented better quantitative results with the advantage of providing detailed information about the flame composition with lower computational time. For the FGM technique, the capability of different progress variable definitions in reproducing the composition space of CO2 diluted flames is investigated and discussed in detail. The chemical and pure dilution effects of CO2 addition to the fuel stream are also discussed for the two-dimensional results.

High concentration CO2 sequestration by using microalgae in staged cultivation

The acclimated fresh water microalga Chlorella vulgaris has the excellent growing capability in the process of staged cultivation (SC). In this study, the alga solutions with low (106/mL) and high (107/m) cell densities showed different abilities of growth with different levels of CO2–air mixture gases[5%, 10%, 15% (v/v)]. The SC process can improve the algal mass productivity rapidly by the aerating increased concentrations of CO2 of mixed gases into the algae solution in a short time. The results showed that the cell density was improved to 1.72 g L−1 within 7 days, showing 3.1, 1.48, and 1.70 times improvement compared to that in the biomass from the culture with separate 5, 10, and 15% CO2–air mixture gases. Besides, there were not the obvious distinctions on the contents of biochemicals (carbohydrate, protein, and lipid) from these algae. This study proved that SC process was an efficient method to improve biomass productivity of Chlorella sp. in a short time with low initial cell density. © 2016 American Institute of Chemical Engineers Environ Prog, 35: 1862–1867, 2016

Growth, photosynthesis and nutrient uptake by Grateloupia livida (Halymeniales, Rhodophyta) in response to different carbon levels

:Grateloupia livida is a commercially important red macroalgal species. In the present study, thalli of G. livida, collected from Nan'ao Island, China, were cultured at different levels of CO2 (c. 1000, 390 and 50 ppm) to examine the growth and physiology and how its plasticity may affect photosynthesis at different carbon levels. The pH-drift experiments showed that G. livida could reach a final pH value of 9.75. Carbonic anhydrase (CA) activity was detected potentiometrically with both thalli and homogenates of G. livida. These implied that G. livida used HCO3− as a source of inorganic carbon for photosynthesis and that this was mediated by extracellular CA activity. Thalli of G. livida grown at low CO2 reduced the relative growth rate (RGR), both the PO43− and NO3− uptake rates, nitrate reductase activity and photochemical activity compared with the algae grown at ambient CO2. Moreover, the RGR and the initial slope of the rapid light curves (α) were inhibited by the high CO2 level in the seawater. The results indicated that either raised or lowered CO2 in culture were unfavourable environmental factors for growth and photosynthesis of G. livida.