High CO2 Levels Research Articles

Gasification Plants for Chemical Production: The Impact of Carbon Utilization on CO2 Capture from the Facility

Coal and other disadvantaged fuels such as petroleum coke and refinery bottoms can be used for the production of chemicals around the world. Coal is an established feedstock in gasification and has been the primary focus in markets like China, where the use of coal to chemicals is needed due to limited access to oil and natural gas reserves. Disadvantaged feedstocks such as petroleum coke and heavy residues are currently experiencing a shift in market utilization. New legislation on criteria pollutants in countries like India and IMO2020 legislation are reducing the size of petroleum coke and residue feedstock end markets. The need to dispose of these disadvantaged feedstocks has created new project opportunities for gasification plants. However, with the new opportunities come increasing pressures to lower the CO2 but also increasing the opportunity to take advantage of CO2 emission reduction benefits and/or to deploy the CO2 for enhanced oil recovery. Air Products provides high quality technical solutions as a technology supplier, process integrator and operator. This paper will present our unique perspective on the amenable streams for CO2 capture within the gasification plant, thoughts on how the technologies are developing to further reduce the overall CO2 footprint of a coal to syngas facility, and what the major driving forces are present in selecting technologies and process options. Gasification produces CO2 as a natural byproduct of the reactions taking place in the gasifier to produce syngas as well as downstream water gas shift reactions. The high temperatures and pressures that various gasification and shift processes can operate under provide potential capture points in the plant flowsheet depending on the quantity and purity of CO2 needed. In addition, product syngas requirements dictate the purity and CO to H2 ratio of the product syngas which has a direct influence over the amount of CO2 available to capture from the product syngas streams. Pressurized CO2 sources are a more cost effective way to capture high levels of CO2. As compared to SMR technologies in which approximately 50% of the CO2 is at pressure, solid and liquid gasification technologies contain almost all of the CO2 within the pressurized syngas stream. The amenable product stream locations vary in quantity, purity, and pressure of CO2. Therefore, the degree of capture from the plant is an important variable when selecting the location and technology employed to capture at a specific facility. Gasification also has the advantages of heat recovery from the process to produce steam which can offset the steam demand from low pressure CO2 sources like on purpose boilers. Heat recovery and integration options are core to producing an economic solution to the CO2 capture. Various technologies exist for the removal of CO2 from gasification plants. The methanol based Rectisol process is one technology employed in gasification plants for the effective removal of CO2 from the pressurized gasification syngas streams. It is a proven technology for purifying the syngas stream, but it is not the only technology which can be employed to capture CO2. Numerous studies on decarbonized fuels have outlined Rectisol as well as other acid gas removal technologies for power production. In this paper, the focus will be on revisiting these standby technology options and introducing additional technologies, like Air Products Sour PSA technology, that provide options to capture various levels and purities of CO2, for the solid or liquid feedstock to syngas markets. Currently, Air Products has formed a joint venture with the Luan Coal Group to operate a large-scale gasification plant which converts coal to liquids. The carbon in the coal does not leave the facility as CO2 as in decarbonized power production processes. A significant portion of the carbon is incorporated into the final product from the syngas. This utilization of carbon in the products influences the amenable envelope of technologies that can be used to capture CO2 from the plant. Maximizing the carbon that resides in product molecules provides an interesting twist on previous decarbonized power carbon capture studies. Maximizing carbon utilization provides insight into how to design the balance of plant and what technologies could be developed that would directly impact the material balance as well as the CO2 emissions from the overall facility. Air Products is uniquely positioned to analyze the technical challenges of capturing CO2 from gasification facilities. Identifying cost effective solutions to individual opportunities and the technical driving force influencing design choices will be discussed in this paper.

ABA signalling and metabolism are not essential for dark-induced stomatal closure but affect response speed

Stomata are microscopic pores that open and close, acting to balance CO2 uptake with water loss. Stomata close in response to various signals including the drought hormone abscisic acid (ABA), microbe-associated-molecular-patterns, high CO2 levels, and darkness. The signalling pathways underlying ABA-induced stomatal closure are well known, however, the mechanism for dark-induced stomatal closure is less clear. ABA signalling has been suggested to play a role in dark-induced stomatal closure, but it is unclear how this occurs. Here we investigate the role of ABA in promoting dark-induced stomatal closure. Tracking stomatal movements on the surface of leaf discs we find, although steady state stomatal apertures are affected by mutations in ABA signalling and metabolism genes, all mutants investigated close in response to darkness. However, we observed a delayed response to darkness for certain ABA signalling and metabolism mutants. Investigating this further in the quadruple ABA receptor mutant (pyr1pyl1pyl2pyl4), compared with wild-type, we found reduced stomatal conductance kinetics. Although our results suggest a non-essential role for ABA in dark-induced stomatal closure, we show that ABA modulates the speed of the dark-induced closure response. These results highlight the role of ABA signalling and metabolic pathways as potential targets for enhancing stomatal movement kinetics.

Assessing roles of geochemical reactions on CO2 plume, injectivity and residual trapping

With increasing CO2 concentration in the atmosphere, CO2 geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO2 in the atmosphere. This paper examins sequestration parameters such as CO2 plume behaviour, residual gas trapping and injectivity as a means of achieving safe and successful CO2 storage in saline aquifers. Mineral precipitation/dissolution rates are used to establish a relationship between these parameters and geochemical reactions in saline aquifers. To achieve this, mechanistic models (6 models with different inputs, created using CMG – GEM, 2016 and WINPROP, 2016) are simulated using input data from literature and studying changes in fluids and formation properties as well as mineral precipitation/dissolution rates in aquifers when subjected to different conditions in the different models.The results from the models show that high CO2 dissolution, which creates large CO2 plume, leads to high mineral dissolution/precipitation as results of increased fluid-rock interactions (geochemical reactions); whereas injectivity, although enhanced by CO2-water cyclic injection, does not show much increase in bottom hole pressure when mineral trapping (thus geochemical reactions) is introduced into the model. Sensitivity study on residual gas trapping shows that high residual gas saturation leads to reduced mineral precipitation/dissolution due to the reduced amount of dissolved CO2 in brine. Also, rapid changes in the bottom hole pressure at high residual gas saturation means that a formation that fosters high residual gas trapping, rather than CO2 dissolution in brine, is more likely to experience injectivity issues during the sequestration process.

End-tidal capnography monitoring in infants ventilated on the neonatal intensive care unit

ObjectiveTo assess whether end-tidal capnography (EtCO2) monitoring reduced the magnitude of difference in carbon dioxide (CO2) levels and the number of blood gases in ventilated infants.Study designA case–control study of a prospective cohort (n = 36) with capnography monitoring and matched historical controls (n = 36).ResultThe infants had a median gestational age of 31.6 weeks. A reduction in the highest CO2 level on day 1 after birth was observed after the introduction of EtCO2 monitoring (p = 0.043). There was also a reduction in the magnitude of difference in CO2 levels on days 1 (p = 0.002) and 4 (p = 0.049) after birth. There was no significant difference in the number of blood gases.ConclusionContinuous end-tidal capnography monitoring in ventilated infants was associated with a reduction in the degree of the magnitude of difference in CO2 levels and highest level of CO2 on the first day after birth.

The Interactive Effect of Elevated CO2 and Herbivores on the Nitrogen-Fixing Plant Alnus incana ssp. rugosa.

Many studies have found that future predicted CO2 levels can increase plant mass but dilute N content in leaves, impacting antiherbivore compounds. Nitrogen-fixing plants may balance their leaf C:N ratio under elevated CO2, counteracting this dilution effect. However, we know little of how plants respond to herbivores at the higher CO2 levels that occurred when nitrogen-fixing plants first evolved. We grew Alnus incana ssp. rugosa was grown at 400, 800, or 1600 ppm CO2 in soil collected from the field, inoculated with Frankia and exposed to herbivores (Orgyia leucostigma). Elevated CO2 increased nodulated plant biomass and stimulated the nitrogen fixation rate in the early growth stage. However, nitrogen-fixing plants were not able to balance their C:N ratio under elevated CO2 after growing for 19 weeks. When plants were grown at 400 and 1600 ppm CO2, herbivores preferred to feed on leaves of nodulated plants. At 800 ppm CO2, nodulated plants accumulated more total phenolic compounds in response to herbivore damage than plants in the non-Frankia and non-herbivore treatments. Our results suggest that plant leaf defence, not leaf nutritional content, is the dominant driver of herbivory and nitrogen-fixing plants have limited ability to balance C:N ratios at elevated CO2 in natural soil.

Extracellular carotenoid production and fatty acids profile of Parachlorella kessleri under increased CO2 concentrations

Large-scale cultivations of photoautotrophic microorganisms represent a very promising and potentially cost-effective alternative for climate change mitigation, when associated to the co-production of high value bioproducts, such as fatty acids and carotenoids, considering the growing demand for natural products. During microalgae cultivation, CO2 enrichment is a requirement to reach high productivities, although high CO2 levels are normally stressful to microalgae. On the other hand, cellular stress is a well reported strategy to induce carotenoid and fatty acids production. This work evaluated extracellular carotenoid production from the mangrove-isolated microalga Parachlorella kessleri cultivated under 5, 15 and 30% CO2 in stirred tank photobioreactors. In the 10th day of cultivation, CO2 supply was interrupted until the end of the cultivation (14th day), causing a stressful and imperative condition for microalgae cells to release the red pigment. Growth kinetics, physiological parameters and bioproducts production were evaluated. Growth kinetics were similar under all tested conditions and differences were not statistically significant, with the highest values of μmax, biomass concentration, lipid content and CO2 fixation rate of 0.77 d−1, 1.24 g L−1, 241 mg g−1 (dw) and 165 mg L−1 d−1, respectively. In contrast, total carotenoid concentrations varied significantly (p < 0.01), with the highest concentration of 0.030 μg mL-1 under 5% CO2. The produced red pigment presented antioxidant activity and characteristics of carotenoids confirmed by UV–vis and tandem mass spectrometry (MS/MS). The fatty acid profiles in the biomass varied in response to CO2 levels in the cultivations. In general, higher CO2 concentrations (15 and 30%) favored the production of saturated and mono-unsaturated fatty acids, suitable as biodiesel feedstock, while drastically decreased the production of the polyunsaturated.

Effects of Modified Atmosphere Packaging and Chitosan Treatment on Quality and Sensorial Parameters of Minimally Processed cv. ‘Italia’ Table Grapes

Table grape is a non-climacteric fruit, very sensitive to water loss and gray mold during postharvest handling and storage. The aim of this work was to evaluate the effects of modified atmosphere packaging and chitosan treatment on quality and sensorial parameters of minimally processed cv. ‘Italia’ table grape during cold storage (14 days at 5 °C) and shelf-life (7 and 14 days of cold storage plus 5 days at 20 °C), reproducing a retail sales condition. Our data showed a significant effect of high CO2-modified atmosphere in combination with chitosan and alone on preserving quality, sensorial parameters, and delaying decay of minimally processed table grape. The most effective treatment in terms of preservation of quality, sensory, and nutritional quality was high-CO2 modified atmosphere packaging plus chitosan treatment. The overall results showed that when a proper modified atmosphere packaging is combined with a postharvest chitosan treatment, gray mold growth can effectively be controlled in ready-to-eat cv. ‘Italia’ table grape and that modified atmosphere packaging (MAP) with high levels of CO2 and reduced concentration of O2 in combination with chitosan treatment could prevent the negative effect of high-CO2 in-packages level, like berry browning and rachis browning and dehydration.

Effect of high levels of CO2 and O2 on membrane fatty acid profile and membrane physiology of meat spoilage bacteria

The membrane is the major protective barrier separating the cell from the environment and is thus important for bacteria to survive environmental stress. This study investigates changes in membrane lipid compositions and membrane physiology of meat spoiling bacteria in response to high CO2 (30%) and O2 (70%) concentrations, as commonly used for modified atmosphere packaging of meat. Therefore, the fatty acid profile as well as membrane fluidity, permeability and cell surface were determined and correlated to the genomic settings of five meat spoiling bacteria Brochothrix (B.) thermosphacta, Carnobacterium (C.) divergens, C. maltaromaticum, Leuconostoc (L.) gelidum subsp. gelidum and L. gelidum subsp. gasicomitatum cultivated under different gas atmospheres. We identified different genomic potentials for fatty acid adaptations, which were in accordance with actual measured changes in the fatty acid composition for each species in response to CO2 and/or O2, e.g., an increase in saturated, iso and cyclopropane fatty acids. Even though fatty acid changes were species-specific, the general physiological responses were similar, comprising a decreased membrane permeability and fluidity. Thus, we concluded that meat spoiling bacteria facilitate a change in membrane fatty acids upon exposure to O2 and CO2, what leads to alteration of membrane fluidity and permeability. The observed adaptations might contribute to the resistance of meat spoilers against detrimental effects of the gases O2 and CO2 and thus help to explain their ability to grow under different modified atmospheres. Furthermore, this study provides fundamental knowledge regarding the impact of fatty acid changes on important membrane properties of bacteria.

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

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

ABA and BAP improve the accumulation of carbohydrates and alter carbon allocation in potato plants at elevated CO2.

Elevated CO2 interactions with other factors affects the plant performance. Regarding the differences between cultivars in response to CO2 concentrations, identifying the cultivars that better respond to such conditions would maximize their potential benefits. Increasing the ability of plants to benefit more from elevated CO2 levels alleviates the adverse effects of photoassimilate accumulation on photosynthesis and increases the productivity of plants. Despite its agronomic importance, there is no information about the interactive effects of elevated CO2 concentration and plant growth regulators (PGRs) on potato (Solanum tuberosum L.) plants. Hence, the physiological response and source-sink relationship of potato plants (cvs. Agria and Fontane) to combined application of CO2 levels (400 vs. 800µmolmol-1) and plant growth regulators (PGR) [6-benzylaminopurine (BAP) + Abscisic acid (ABA)] were evaluated under a controlled environment. The results revealed a variation between the potato cultivars in response to a combination of PGRs and CO2 levels. Cultivars were different in leaf chlorophyll content; Agria had higher chlorophyll a, b, and total chlorophyll content by 23, 43, and 23%, respectively, compared with Fontane. The net photosynthetic rate was doubled at the elevated compared with the ambient CO2. In Agria, the ratio of leaf intercellular to ambient air CO2 concentrations [Ci:Ca] was declined in elevated-CO2-grown plants, which indicated the stomata would become more conservative at higher CO2 levels. On the other hand, the increased Ci:Ca in Fontane showed a stomatal acclimation to higher CO2 concentration. The higher leaf dark respiration of the elevated CO2-grown and BAP + ABA-treated plants was associated with a higher leaf soluble carbohydrates and starch content. Elevated CO2 and BAP + ABA shifted the dry matter partitioning to the belowground more than the above-media organs. The lower leaf soluble carbohydrate content and greater tuber yield in Fontane might indicate a more efficient photoassimilate translocation than Agria. The results highlighted positive synergic effects of the combined BAP + ABA and elevated CO2 on tuber yield and productivity of the potato plants.

Adaptation of a marine diatom to ocean acidification and warming reveals constraints and trade-offs

Ocean acidification and warming are recognized as two major anthropogenic perturbations of the modern ocean. However, little is known about the adaptive response of phytoplankton to them. Here we examine the adaptation of a marine diatom Thalassiosira weissflogii to ocean acidification in combination with ocean warming. Our results show that ocean warming have a greater effect than acidification on the growth of T. weissflogii over the long-term selection experiment (~380 generations), as well as many temperature response traits (e.g., optimum temperatures for photosynthesis, maximal net photosynthetic oxygen evolution rates, activation energy) in thermal reaction norm. These results suggest that ocean warming is the main driver for the evolution of the marine diatom T. weissflogii, rather than oceanacidification. However, the evolution resulting from warming can be constrained by ocean acidification, where ocean warming did not impose any effects at high CO2 level. Furthermore, adaptations to ocean warming alone or to the combination of ocean acidification and warming come with trade-offs by inhibiting photochemical performances. The constrains and trade-offs associated with the adaptation to ocean acidification and warming demonstrated in this study, should be considered for parameterizing evolutionary responses in eco-evolutionary models of phytoplankton dynamics in a future ocean.

Severity assessment of non-cystic fibrosis bronchiectasis by the FACED score

Objectives: Bronchiectasis (BE) is a major health problem associated with a high morbidity and mortality. This study aimed to determine the relation of the FACED score (a multidimensional score contributing to stratify patients into risk categories) with the severity of non-cystic fibrosis bronchiectasis (NCFB) among our population. Materials and Methods: This is a retrospective single center study of 105 consecutive patients with NCFB hospitalized for acute exacerbations (AE) at the Department of Respiratory Medicine of Fattouma Bourguiba Teaching Hospital in Monastir (Tunisia) between January 2005 and December 2017. Patients were divided into two groups (G): G1: FACED Score ≤ 2 and G2: FACED score ≥3. We compared different severity parameters of BE between the two groups. Results: The study included 105 patients with NCFB. Patients of G2 had more comorbidities (P = 0.028), an altered respiratory function with a lower forced vital capacity (G1:2.73, G2:1.33 L; P &lt; 0.001), a decreased PaO2 (88 vs. 68 mmHg; P &lt; 0.001), a high CO2 level (P &lt; 0.001), and a higher number of AE/year (0.96, 2.12 AE/year;P &lt; 0.001). Hospitalizations for AE of G2 were characterized by a lower PaO2, a higher PaCO2 (P &lt; 0.001), a longer course of antibiotic (P &lt; 0.001) with an extended hospitalization (P = 0.007). An ultimate evolution toward chronic respiratory failure was more common in G2 (P &lt; 0.001). Conclusion: A high FACED score is associated with more symptoms, an altered respiratory function, a higher number and more severe AE, more health-care utilization with worse outcomes. Further studies are necessary to evaluate the impact of such scales in clinical practice.

X-ray CT and porosity mapping to determine the effect of ‘Fuji’ apple morphological and microstructural properties on the incidence of CO2 induced internal browning

There is considerable variability in the distribution of porosity within a fruit, hence non-destructive methods to map porosity of the entire fruit are essential. The objective of this study was to use X-ray computed tomography (CT) to map the porosity of ‘Fuji’ apple and help determine the extent to which different fruit morphological and microstructural properties influence the susceptibility of the fruit to CO2 stress-induced internal browning (IB). X-ray CT based porosity mapping and high-resolution X-ray CT were used to determine porosity changes in fruit tissue following exposure to an atmosphere enriched with 50 % CO2 at room temperature (21 °C) for 3 d after harvest. Low-resolution X-ray CT scans enabled the construction of porosity maps for intact fruit based on a linear regression model and a juice scan which acted as a 0 % porosity reference. Short-term exposure of fruit to a high level of CO2 markedly induced IB in the core region of the fruit. Axial porosity profiles measured before the CO2 stress treatment showed that porosity along the axial plane was usually lower in fruit that developed IB. Larger sized fruit were more susceptible to the CO2 stress-induced IB disorder. The porosity in the IB affected fruit tissue declined from 8.6 to 5.4 % following the CO2 stress treatment. It is recommended to ensure that levels of CO2 and O2 in the controlled atmosphere (CA) storage environment are carefully controlled to minimize the risk of IB incidence.

Non-invasive MRI Studies of Ventilatory and Cardiovascular Performance in Edible Crabs Cancer pagurus During Warming Under Elevated CO2 Levels.

The thermal tolerance of marine decapod crustacea is defined through their capacities for oxygen uptake and distribution. High ambient CO2 levels were previously shown to reduce hemolymph oxygen levels at enhanced cardiac performance during warming. This study investigated the impacts of warming under two CO2 levels on ventilation and hemolymph circulation in edible crabs Cancer pagurus. It also highlights changes in the ventilatory and cardiac pauses displayed by Decapoda under routine metabolism. Animals were exposed to step-wise, sub-critical warming (12–20°C over 5 days) under control (470 μatm) and high (1,350 μatm) water PCO2. Flow-through respirometry was combined with magnetic resonance imaging and infra-red photoplethysmography to allow for simultaneous, non-invasive measurements of metabolic rates (), ventilation and cardiovascular performance. Crabs spent significantly more time in a low state (metabolic pause), when experiencing high CO2 conditions above 16°C, compared to normocapnic warming. Heart rates leveled off beyond 18°C at any CO2 level. Cardiac output continued to increase with high-CO2-warming, due to elevated cardiac stroke volumes. Consequently, temperature-dependent branchial hemolymph flow remained unaffected by CO2. Instead, a suppressing effect of CO2 on ventilation was found beyond 16°C. These results indicate constrained oxygen uptake at stable cardiovascular performance in a decapod crustacean.Cancer pagurus: urn:lsid:zoobank.org:act:B750F89A-84B5-448B-8D80-EBD724A1C9D4

Nano- and Micro- Carnauba Wax Emulsions versus Shellac Protective Coatings on Postharvest Citrus Quality

Coatings are generally applied to fruit as microemulsions, but nanoemulsions are still experimental. ‘Nova’ mandarins (Citrus reticulata) were coated with shellac or carnauba (Copernica cerifera) microemulsions or an experimental carnauba nanoemulsion; these were compared with an uncoated control during storage for 7 days at 20 °C. Coatings were also tested on ‘Unique’ tangors (C. reticulata × C. sinensis) stored for 14 days at 10 °C followed by a simulated marketing period of 7 days at 20 °C. Fruit quality evaluations included weight loss, gloss, soluble solids (SS), titratable acidity (TA), pH, SS/TA ratio, internal CO2, O2, fruit juice ethanol, and other aroma volatile content. Sensory visual shine and tangerine (C. reticulata) flavor rank tests after storage were conducted, followed by an off-flavor rating. The carnauba waxes resulted in less weight loss compared with the uncoated control and shellac coating during both experiments. There were no differences in gloss measurements of ‘Nova’ mandarins; however, shellac-coated fruit ranked highest for shine in a sensory test. For ‘Unique’ tangors, initially, shellac showed the highest gloss (shine) measurement; however, at the end of storage, the nanoemulsion exhibited the highest gloss, although it was not different from that of the microemulsion. Similarly, after storage, the nanoemulsion ranked highest for visual shine, although it was not different from that of the microemulsion. There were only minor differences in SS, TA, pH, and SS/TA among treatments. The internal CO2 gas concentration and juice ethanol content generally increased and internal O2 decreased during storage. The highest levels of CO2 and ethanol were found for the shellac treatment, as was the lowest O2, indicating anaerobic respiration. There were only minor differences among the other coating treatments; however, they were only sometimes different from those of the control, which generally had the highest O2, lowest CO2, and lowest ethanol. Shellac and the carnauba microemulsion also altered the volatile profile more than the control and the nanoemulsion did, especially for ‘Unique’ tangors. For ‘Unique’ tangors, the control and nanoemulsion ranked highest for tangerine flavor and had the least off-flavor at the end of storage. Among the coatings tested, the carnauba emulsions demonstrated less water loss, imparted more sustainable gloss, and caused less ethanol production than shellac, with the nanoemulsion exhibiting higher gloss measurements, less modifications of the atmosphere and volatile profile, and, consequently, better flavor compared with the microemulsion.

Indoor air quality in natural-ventilated bedrooms in renovated Norwegian houses

The objective of this work is to investigate the indoor environment in bedrooms ventilated by window opening during night-time. How window opening behaviour affects indoor air quality (IAQ), and how window opening behaviour and IAQ is influenced by external factors, are important questions. The context is renovation of detached wooden houses in Norway. To motivate building owners to renovate their ventilation system, it is important to know the typical indoor environment in bedrooms of existing buildings with natural ventilation. Ten bedrooms in six case houses were investigated by measuring temperature, relative humidity, CO2, particulate matter, formaldehyde and TVOC. The window opening angle was also logged with an accelerometer. The measurements were conducted over 2 to 3 weeks, during March and April. The dwellings were renovated single-family and terraced houses from 1950 – 80, in Trondheim. All the bedrooms had natural ventilation, and the occupants stated they used to open bedroom windows at night. Participants answered a questionnaire about motivations and habits regarding window opening. The most common reason given for not opening was low outdoor temperatures. The window opening behaviour was both predictable and continuous. Windows were open every night in most of the bedrooms, and most of the windows were opened to the same position every night. High CO2 levels during night were found in two bedrooms. In the other bedrooms, the CO2 concentration was satisfying during night-time, although higher concentrations were found in some bedrooms during daytime. Finally, indoor temperature measurements confirmed that many occupants prefer a low bedroom temperature.

Carbon sequestration: counterintuitive feedback of plant growth

Interaction between the atmosphere, plants and soils plays an important role in the carbon cycle. Soils contain vast amounts of carbon, but their capacity to keep it belowground depends on the long-term ecosystem dynamics. Plant growth has the potential of adding or releasing carbon from soil stocks. Since plant growth is also stimulated by higher CO2 levels, understanding its impact on soils becomes crucial for estimating carbon sequestration at the ecosystem level. A recent meta-analysis explored the effect CO2 levels have in plant versus soil carbon sequestration. The integration of 108 experiments performed across different environments revealed that the magnitude of plant growth and the nutrient acquisition strategy result in counterintuitive feedback for soil carbon sequestration.

Identification of candidate genes associated with JA under elevated CO2 in carrot (Daucus carota L.)

CO2 application is one of the important ways to promote crop growth and increase yield, especially for facility crop cultivation. Since carrot is a widespread vegetable, the area of off-season facility cultivation has been increasing in recent years. Jasmonic acid (JA) is a signal molecule that responds quickly to external stimulation in plants, so it is very important to study the JA metabolism under CO2 enrichment. In this study, the JA content and the biomass were measured during the growth and development of carrots under natural conditions and CO2 enrichment in greenhouse. The results showed that the JA content in carrot leaves under CO2 enrichment was higher than that of the control at all stages except harvest stage, but the leaf biomass and root yield were increased at all stages. RNA sequencing identified 482 differentially expressed genes (DEGs). By analyzing the JA synthesis pathway, five DEGs were obtained. In addition, GO annotation found 21 genes that respond to JA or are related to JA-mediated signal transduction. Among them, seven genes are directly related to growth and development, five genes are related to hormonal regulation, and six genes are related to stress. This study showed that JA was highly responsive to CO2 enrichment: JA not only regulated carrot growth, but also responded to abiotic stress. This research provides new insights into the process of plants adapting to high levels of CO2.

Ocean acidification increases phytobenthic carbon fixation and export in a warm-temperate system

The response of photosynthetic organisms to rising CO2 levels is a key topic in ocean acidification research. Most of the work in this field has focused on physiological responses in laboratory conditions which lack ecological realism. Studies using seeps as natural analogues for ocean acidification have demonstrated shifts in algal community composition, but the effect of CO2 on carbon fixation and export remains unclear. Here, we deployed artificial substrata in a warm-temperate region of Japan to collect algal communities using a CO2 seep off Shikine Island. Diatoms became dominant on settlement substrata in areas with elevated CO2 levels, whereas macroalgae dominated at present-day levels of CO2 (reference site). This was supported by pigment composition; fucoxanthin content, characteristic of diatoms, was higher at the high CO2 site, while more Chlorophyll b, which is characteristic of Chlorophyta, was found in the reference site. Algal communities that recruited in water with high levels of CO2 had elevated rates of photosynthesis. Algal biomass was similar on all settlement panels, regardless of CO2 concentration. Much of the carbon that was fixed by algae in the high CO2 conditions was exported, likely due to detachment from the substratum. Diatoms that dominated under high CO2 conditions are more easily transported away as they have no holdfast, whereas newly settled macroalgae became firmly attached at present-day levels of CO2. These results show that ocean acidification may fundamentally alter coastal carbon cycling, increasing photosynthesis and carbon export from coastal ecosystems in warm-temperate biogeographic regions due to a shift in community composition from perennial to ephemeral algae.

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.