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This study analyzes the characteristics of near-surface atmospheric CO 2 concentrations on the southern slope of Tomur Peak from 2013 to 2022. Utilizing the Boughton two-parameter algorithm, we determined the CO 2 background and non-background concentrations. Additionally, the Hysplit model was employed to investigate the potential contributing areas of the CO 2 non-background concentration. Our findings that the CO 2 concentration in the study area was approximately 17% lower than the global average, with an annual growth rate that was only about 47% of the global rate. The CO 2 non-background concentration accounted for only 6.25% of the observed concentration, but was largely unaffected by near-ground meteorological factors. The source of the CO 2 non-background was mainly controlled by the westerly belt, with potential source area mainly located in Central Asia. However, the WPSCF values in the modern ice and snow distribution area south of Tomur Peak and west of the monitoring station were significantly elevated, suggesting a strong wind transport of CO 2 after accumulation under the influence of the elevated terrain. The local supplying path accounted for only 12.87%, indicating that human activities in the oasis areas of the Tarim Basin had a limited influence on the study area. Due to the blocking effect of the Baikal high-pressure system and the towering topography of the Tianshan Mountains, the influence of human emissions from higher latitudes was likely negligible., (© 2024. The Author(s).)

Mesophyll resistance for CO 2 diffusion (r m ) is one of the main limitations for photosynthesis and plant growth. Breeding new varieties with lower r m requires knowledge of its distinct components. We tested new method for estimating the relative drawdowns of CO 2 concentration (c) across hypostomatous leaves of Fagus sylvatica. This technique yields values of the ratio of the internal CO 2 concentrations at the adaxial and abaxial leaf side, c d /c b , the drawdown in the intercellular air space (IAS), and intracellular drawdown between IAS and chloroplast stroma, c c /c bd . The method is based on carbon isotope composition of leaf dry matter and epicuticular wax isolated from upper and lower leaf sides. We investigated leaves from tree-canopy profile to analyse the effects of light and leaf anatomy on the drawdowns and partitioning of r m into its inter- (r IAS ) and intracellular (r liq ) components. Validity of the new method was tested by independent measurements of r m using conventional isotopic and gas exchange techniques. 73% of investigated leaves had adaxial epicuticular wax enriched in 13 C compared to abaxial wax (by 0.50‰ on average), yielding 0.98 and 0.70 for average of c d /c b and c c /c bd , respectively. The r IAS to r liq proportion were 5.5:94.5% in sun-exposed and 14.8:85.2% in shaded leaves. c c dropped to less than half of the atmospheric value in the sunlit and to about two-thirds of it in shaded leaves. This method shows that r IAS is minor but not negligible part of r m and reflects leaf anatomy traits, i.e. leaf mass per area and thickness., (© 2024 The Authors. Plant Biology published by John Wiley & Sons Ltd on behalf of German Society for Plant Sciences, Royal Botanical Society of the Netherlands.)

This article focuses on the influence of occupants on the concentration of contaminants (radon Rn-222 and CO 2 ) as well as the thermal comfort parameters. A series of sensors were placed to measure the concentration of the contaminants, temperature, and relative humidity in the test room at the Institute of Nuclear Physics PAN in Krakow (IFJ PAN), Poland. The test room is an office that is typical of the offices used in the facility. The occupants that used the space kept a detailed diary of their entry, exit, and number of people entering. The results showed that the accumulation of contaminants in such spaces may be severe and risks the health and safety of occupants. The accumulation of CO 2 was extremely noticeable and did not diminish to the background level between the re-entry of the occupants to the office. The same was consistent for the radon concentration. The study shows how ventilation methods and small changes in occupant work strategy may influence the contaminant concentration within a test zone.

Health problems and respiratory diseases are associated with poor indoor air ventilation. We investigated the air quality inside a classroom-laboratory where no ventilation is provided. The case of study, consisting of an internal enclosure, is located at the Escuela Técnica Superior de Edificación (ETSEM) of Madrid (Spain). The high height favours air stratification which is analysed in terms of temperature and CO 2 spatial distribution. Temperature, air humidity, atmospheric pressure and CO 2 concentration measurements were taken in time at three different height locations. A CFD numerical model was established to analyse air quality. Flow circulation is derived by solving full 3D Navier - Stokes governing equations, coupled with the thermal problem. The diffusion problem of the CO 2 produced by the inner occupants is then derived from the kinematics solution. Three scenarios were taken into account: occupants seated (1), standing (2), half seated, half standing (3). Results clearly show the air stratification as a result of density gradient, which is in turn determined by temperature difference between the occupants and the surrounding air. Temperature prediction maximum relative error is contained to 3.5 %. As expected, CO 2 concentration increases over time, reaching maximum values depending on the configuration considered and height location., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

Climate change, characterized by rising atmospheric CO 2 levels and temperatures, poses significant challenges to global crop production. Sweet sorghum, a prominent C 4 cereal extensively grown in arid areas, emerges as a promising candidate for sustainable bioenergy production. This study investigated the responses of photosynthesis and leaf-scale water use efficiency (WUE) to varying light intensity ( I ) in sweet sorghum under different temperature and CO 2 conditions. Comparative analyses were conducted between the A n - I , g s - I , T r - I , WUE i - I , and WUE inst - I models proposed by Ye et al. and the widely utilized the non-rectangular hyperbolic (NRH) model for fitting light response curves. The Ye's models effectively replicated the light response curves of sweet sorghum, accurately capturing the diminishing intrinsic WUE (WUE i ) and instantaneous WUE (WUE inst ) trends with increasing I . The fitted maximum values of A n , g s , T r , WUE i , and WUE inst and their saturation light intensities closely matched observations, unlike the NRH model. Despite the NRH model demonstrating high R 2 values for A n - I , g s - I , and T r - I modelling, it returned the maximum values significantly deviating from observed values and failed to generate saturation light intensities. It also inadequately represented WUE responses to I , overestimating WUE. Across different leaf temperatures, A n , g s , and T r of sweet sorghum displayed comparable light response patterns. Elevated temperatures increased maximum A n , g s , and T r but consistently declined maximum WUE i and WUE inst . However, WUE inst declined more sharply due to the disproportionate transpiration increase over carbon assimilation. Critically, sweet sorghum A n saturated at current atmospheric CO 2 levels, with no significant gains under 550 μmol mol -1 . Instead, stomatal closure enhanced WUE under elevated CO 2 by coordinated g s and T r reductions rather than improved carbon assimilation. Nonetheless, this response diminished under simultaneously high temperature, suggesting intricate interplay between CO 2 and temperature in modulating plant responses. These findings provide valuable insights into photosynthetic dynamics of sweet sorghum, aiding predictions of yield and optimization of cultivation practices. Moreover, our methodology serves as a valuable reference for evaluating leaf photosynthesis and WUE dynamics in diverse plant species., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Yang, Ma, Ye, Yang, Shi, Wang, Zhou, Wang and Deng.)

The phenology has gained considerably more attention in recent times of climate change. The transition from vegetative to reproductive phases is a critical process in the life history of plants, closely tied to phenology. In an era of climate change, understanding how environmental factors affect this transition is of paramount importance. This study consisted of field surveys and a greenhouse experiment on the reproductive biology of Northern pipevine ( Aristolochia contorta Bunge). During field surveys, we investigated the environmental factors and growth characteristics of mature A. contorta , with a focus on both its vegetative and reproductive phases. In its successful flowering during the reproductive phase, A. contorta grew under the conditions of 40% relative light intensity and 24% soil moisture content, and had a vertical rhizome. In the greenhouse experiments, we examined the impact of increased CO 2 concentration on the growth and development of 10-year-old A. contorta , considering the effect of rhizome direction. Planted with a vertical rhizome direction, A. contorta exhibited sufficient growth for flowering under ambient CO 2 concentrations. In contrast, when planted with a horizontal rhizome direction, it was noted to significantly impede successful growth and flowering under elevated CO 2 concentrations. This hindered the process of flowering, highlighting the pivotal role of substantial vegetative growth in achieving successful flowering. Furthermore, we observed a higher number of underground buds and shoots under the conditions of elevated CO 2 concentration and a horizontal rhizome direction instead of flowering. Elevated CO 2 concentrations also exhibited diverse effects on mature A. contorta 's flower traits, resulting in smaller flower size, shorter longevity, and reduced stigma receptivity, and pollen viability. The study shed light on elevated CO 2 concentrations can hinder growth, potentially obstructing sexual reproduction and diminishing genetic diversity., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The author(s) declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Park and Kim.)

The practice of aquaculture is associated with the generation of a substantial quantity of effluent. Microalgae must effectively assimilate nitrogen and phosphorus from their surrounding environment for growth. This study modeled the algal biomass film, NO 3 -N concentration, and pH in the membrane bioreactor using the response surface methodology (RSM) and an artificial neural network (ANN). Furthermore, it was suggested that the optimal condition for each parameter be determined. The results of ANN modeling showed that ANN with a structure of 5-3 and employing the transfer functions tansig-logsig demonstrated the highest level of accuracy. This was evidenced by the obtained values of coefficient (R 2 ) = 0.998, R = 0.999, mean squared error (MAE) = 0.0856, and mean square error (MSE) = 0.143. The ANN model, characterized by a 5-5 structure and employing the tansig-logsig transfer function, demonstrates superior accuracy when predicting the concentration of NO 3 -N and pH. This is evidenced by the high values of R 2 (0.996), R (0.998), MAE (0.00162), and MSE (0.0262). The RSM was afterward employed to maximize the performance of algal film biomass, pH levels, and NO 3 -N concentrations. The optimal conditions for the algal biomass film were a concentration of 2.884 mg/L and a duration of 6.589 days. Similarly, the most favorable conditions for the NO 3 -N concentration and pH were 2.984 mg/L and 6.787 days, respectively. Therefore, this research uses non-dominated sorting genetic algorithm II (NSGA II) to find the optimal NO3-N concentration, algal biomass film, and pH for product or process quality. The region has the greatest alkaline pH and lowest NO 3 -N content., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

In the northern high latitudes, warmer spring temperatures generally lead to earlier leaf onsets, higher vegetation production, and enhanced spring carbon uptake. Yet, whether this positive linkage has diminished under climate change remains debated. Here, we used atmospheric CO 2 measurements at Barrow (Alaska) during 1979-2020 to investigate the strength of temperature dependence of spring carbon uptake reflected by two indicators, spring zero-crossing date (SZC) and CO 2 drawdown (SCC). We found a fall and rise in the interannual correlation of temperature with SZC and SCC (R SZC-T and R SCC-T ), showing a recent reversal of the previously reported weakening trend of R SZC-T and R SCC-T . We used a terrestrial biosphere model coupled with an atmospheric transport model to reproduce this fall and rise phenomenon and conducted factorial simulations to explore its potential causes. We found that a strong-weak-strong spatial synchrony of spring temperature anomalies per se has contributed to the fall and rise trend in R SZC-T and R SCC-T , despite an overall unbroken temperature control on net ecosystem CO 2 fluxes at local scale. Our results provide an alternative explanation for the apparent drop of R SZC-T and R SCC-T during the late 1990s and 2000s, and suggest a continued positive linkage between spring carbon uptake and temperature during the past four decades. We thus caution the interpretation of apparent climate sensitivities of carbon cycle retrieved from spatially aggregated signals., (© 2023 John Wiley & Sons Ltd.)

Nitrogen (N) resorption is an important pathway of N conservation, contributing to an important proportion of plant N requirement. However, whether the ratio of N resorption to N requirement may be affected by environmental factors, mycorrhizal types or atmospheric CO 2 concentration remains unclear. Here, we conducted a meta-analysis on the impacts of environmental factors and mycorrhizal types on this ratio. We found this ratio in ectomycorrhizal (EM) trees decreased with mean annual precipitation, mean annual temperature, soil total N content and atmospheric CO 2 concentration and was significantly lower than that in arbuscular mycorrhizal (AM) trees. An in situ 15 N tracing experiment further confirmed that AM trees have a stronger reliance on N resorption than EM trees. Our study suggests that AM and EM trees potentially have different strategies for alleviation of progressive N limitation, highlighting the necessity of incorporating plant mycorrhizal types into Earth System Models., (© 2023 John Wiley & Sons Ltd.)

In a layer house, the CO 2 (carbon dioxide) concentration above the upper limit can cause the oxygen concentration to be below the lower limit suitable for poultry. This leads to chronic CO 2 poisoning in layers, which manifests as listlessness, reduced appetite, weak constitution, decreased production performance, and weakened resistance to disease. Regulating ventilation may ensure a suitable CO 2 concentration in layer houses. Predicting the changes in CO 2 concentration and regulating the CO 2 concentration in advance are key to ensuring healthy large-scale breeding of layers. In recent years, machine learning and deep learning methods have been increasingly applied to this field. A CO 2 prediction model for layer house is proposed based on a GRU (gated recurrent unit) and LSTM (long short-term memory). The temperature, humidity, and CO 2 were determined as inputs to the model by the correlation coefficient. The datasets of the experimental layer house were continuously measured during June-July 2023, using a self-developed environmental monitor, and the monitored data were used as samples for model inputs. There were 22,000 time series data in the datasets. In this study, multivariate time series data were standardized via data pre-processing to improve model training. GRU and LSTM models were constructed. The models were trained using a training set. Then, these trained models were used to provide predictions on a test set. The prediction errors were calculated using the true values of the test set and the predicted values provided by the models. To test the performance of the model and accuracy of the predictions, predictions were made for different numbers of datasets. The results demonstrated that the combined prediction model had good generalization, stability, and convergence with high prediction accuracy. Due to the structure of the model, the stability of the LSTM model was higher than that of the GRU model, and its prediction accuracy and speed were lower than those of the GRU model. When the datasets of the GRU model were 15,000 to 17,000, The MAE of the GRU was 70.8077 to 126.7029 ppm, and the prediction time of the GRU is 16 to 24 ms. When the LSTM model's datasets were 15,000-20,000, the MAE of LSTM was 78.8596 to 136.0896 ppm, and the prediction time of the GRU was 17 to 26 ms.

In the face of global warming, the photosynthesis and transpiration of plants will change greatly, which will ultimately affect the water use efficiency (WUE) of plants. In order to study the coupling effects of CO 2 and temperature on WUE of maize at ear stage, 'Zhengdan 958' was taken as the research object, and 5 temperatures (20 °C, 25 °C, 30 °C, 35 °C and 40 °C) and 11 CO 2 concentration (400, 300, 200, 150, 100, 50, 400, 400, 600, 800 and 1000 μmol mol -1 ) were set to measure the parameters such as net photosynthetic rate ( P n ), transpiration rate ( T r ), stomatal conductance ( G s ) and intercellular CO 2 concentration ( C i ) of single leaves. The response of WUE ( P n / T r ) to CO 2 and temperature was evaluated by a CO 2 response model. The results show that at the same temperature, P n and WUE increased with CO 2 level, while T r decreased as CO 2 level increases; at the same CO 2 concentration, P n and T r were both positively correlated with temperature, while WUE decreased with the increase of temperature. The maximum value of WUE was obtained when the CO 2 concentration was 1000 μmol mol -1 and the temperature was 20.0 °C. The results suggest that global warming will not improve WUE of maize, which will bring more severe challenges to water-saving agriculture and food security., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2023 The Authors. Published by Elsevier Ltd.)

Artificial lighting is complementary and single-source lighting for controlled Environment Agriculture (CEA) to increase crop productivity. Installations to control CO 2 levels and luminaires with variable spectrum and intensity are becoming increasingly common. In order to see the net assimilation of CO 2 based on the relationship between the three factors: intensity, spectrum and CO 2 concentration, tests are proposed on tomatoes seedling with combinations of ten spectra (100B, 80B20G, 20B80G, 100G, 80G20R, 20G80R, 100R, 80R20B, 20R80B, 37R36G27B) seven light intensities (30, 90, 200, 350, 500, 700 and 1000 μmol·m -2 s -1 ) and nine CO 2 concentrations (200, 300, 400, 500, 600, 700, 800 and 900 ppm). These tomato seedlings grew under uniform conditions with no treatments applied up to the moment of measurement by a differential gas analyzer. We have developed a model to evaluate and determine under what spectrum and intensity of light photosynthesis the Net assimilation of CO 2 (A n ) is more significant in the leaves of tomato plants, considering the CO 2 concentration as an independent variable in the model. The evaluation of the model parameters for each spectrum and intensity shows that the intensity has a more decisive influence on the maximum A n rate than the spectra. For intensities lower than 350 μmol·m -2 s -1 , it is observed that the spectrum has a greater influence on the variable A n . The spectra with the best behaviour were 80R20B and 80B20R, which maintained A n values between 2 and 4 (μmol CO 2 ·m -2 ·s -1 ) above the spectra with the worst behaviour (100G, 80G20R, 20G80R and 37B36G27R) in practically all situations. Photosynthetic Light-Use Efficiency (PLUE) was also higher for the 80B20R and 20R80B spectra with values of 36,07 and 33,84 mmol CO 2 ·mol photon -1 , respectively, for light intensities of 200 μmol·m -2 s -1 and 400 ppm of CO 2 that increased to values of 49,65 and 48,38 mmol CO 2 ·mol photon -1 for the same light intensity and concentrations of 850 ppm. The choice of spectrum is essential, as indicated by the data from this study, to optimize the photosynthesis of the plant species grown in the plant factory where light intensities are adjusted for greater profitability., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Moratiel, Jimenez, Mate, Ibánez, Moreno and Tarquis.)

Introduction: Our aim was to gain insight into the effect of COVID-19 measures on SARS-CoV-2 incidence in secondary schools and the association with classroom CO 2  concentration and airborne contamination., Methods: Between October 2020-June 2021, 18 schools weekly reported SARS-CoV-2 incidence and completed surveys on school-initiated COVID-19 measures (e.g. improving hygiene or minimizing contacts). CO 2 was measured in occupied classrooms twice, and SARS-CoV-2 air contamination longitudinally using electrostatic dust collectors (EDC) and analyzed using RT-qPCR. National COVID-19 policy measures varied during pre-lockdown, lockdown and post-lockdown periods. During the entire study, schools were recommended to improve ventilation. SARS-CoV-2 incidence rate ratios (IRR) were estimated by Generalized Estimating Equation (GEE) models., Results: During 18 weeks follow-up (range: 10-22) SARS-CoV-2 school-incidence decreased during national lockdown (adjusted IRR: 0.41, 95%CI: 0.21-0.80) and post-lockdown (IRR: 0.60, 0.39-0.93) compared to pre-lockdown. School-initiated COVID-19 measures had no additional effect. Pre-lockdown, IRRs per 10% increase in time CO 2 exceeded 400, 550 and 800 ppm above outdoor level respectively, were 1.08 (1.00-1.16), 1.10 (1.02-1.19), and 1.08 (0.95-1.22). Post-lockdown, CO 2- concentrations were considerably lower and not associated with SARS-CoV-2 incidence. No SARS-CoV-2 RNA was detected in any of the EDC samples., Conclusion: During a period with low SARS-CoV-2 population immunity and increased attention to ventilation, with CO 2 levels most of the time below acceptable thresholds, only the national policy during and post-lockdown of reduced class-occupancy, stringent quarantine, and contact testing reduced SARS-CoV-2 incidence in Dutch secondary schools. Widespread SARS-CoV-2 air contamination could not be demonstrated in schools under the prevailing conditions during the study., (© 2023. The Author(s).)

The climatological seasonal maximum and minimum CO 2 concentrations in East Asia for 1987-2020 have been recorded at April and August, respectively. We found that the CO 2 concentration in East Asia during July, August, and September (JAS) is lower than normal before the late 1990s and after the early 2010s (Low_CO 2 period), and higher than normal from the late 1990s to the early 2010s (High_CO 2 period). The low-frequency variability of CO 2 concentration in East Asia during JAS correlates with both Pacific Decadal Oscillation (PDO) and Atlantic Multi-decadal Oscillation (AMO)-related sea surface temperatures (SSTs). We analyzed atmospheric and oceanic conditions during JAS between the two periods, finding that precipitation in East Asia decreased during JAS in High_CO 2 period than that in Low_CO 2 period, possibly due to PDO and AMO-related SST forcing, which decreases vegetation's photosynthetic activity. This may lead to a higher CO 2 concentration than normal in East Asia in High_CO 2 period through reduced uptake of CO 2 from the atmosphere. This implies that terrestrial vegetation activity influenced by remote SST forcings should be monitored to better understand regional carbon cycles in East Asia., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

C 4 plants supply concentrated CO 2 to bundle sheath (BS) cells, improving photosynthetic efficiency by suppressing photorespiration. Mesophyll chloroplasts in C 4 plants are redistributed toward the sides of the BS cells (aggregative movement) in response to environmental stresses under light. Although this chloroplast movement is common in C 4 plants, the significance and mechanisms underlying the aggregative movement remain unknown. Under environmental stresses, such as drought and salt, CO 2 uptake from the atmosphere is suppressed by closing stomata to prevent water loss. We hypothesized that CO 2 limitation may induce the chloroplast aggregative movement. In this study, the mesophyll chloroplast arrangement in a leaf of finger millet, an NAD-malic enzyme type C 4 plant, was examined under different CO 2 concentrations and light conditions. CO 2 limitation around the leaves promoted the aggregative movement, but the aggregative movement was not suppressed, even at the higher CO 2 concentration than in the atmosphere, under high intensity blue light. In addition, mesophyll chloroplasts did not change their arrangement under darkness or red light. From these results, it can be concluded that CO 2 limitation is not a direct inducer of the aggregative movement but would be a promoting factor of the movement under high intensity blue light., (© 2023 German Society for Plant Sciences, Royal Botanical Society of the Netherlands.)

Phytoremediation technology is an effective method to remove formaldehyde indoors, but the purification capacity and physiological response of plants to formaldehyde under the simultaneous influence of light and CO 2 have not been examined in previous studies. In this study, formaldehyde fumigation experiments were conducted on the C 3 plants Epipremnum aureum A. and Chlorophytum comosum L., and the crassulacean acid metabolism (CAM) plant Dieffenbachia maculate A. The phytoremediation performance and physiological response of plants were studied. The initial concentration of formaldehyde was established at 11.950 ± 1.442 [Formula: see text]; the light intensities were 448 ± 7 [Formula: see text], 1628 ± 22 [Formula: see text], and 3259 ± 22 [Formula: see text], respectively; and the concentrations of CO 2 were 455 ± 29 [Formula: see text], 978 ± 50 [Formula: see text], 2020 ± 66 [Formula: see text], and 3006 ± 95 [Formula: see text], respectively. The results indicated that the highest purification rates of formaldehyde by E. aureum, D. maculata, and C. comosum were 55.8%, 43.7%, and 53.2%, respectively. The light intensity had a positive effect on the formaldehyde purification rates of all three plants and positively stimulated peroxidase (POD) activity, while the CO 2 concentration had no significant impact on the formaldehyde purification capacity and plants' physiological characteristics. Exposure to formaldehyde inhibited formaldehyde dehydrogenase (FADH) activity and positively stimulated catalase (CAT) activity. The superoxide dismutase (SOD) activity positively correlated with the formaldehyde purification capacity of plants., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Objectives: To review the risk of airborne infections in schools and evaluate the effect of intervention measures reported in field studies., Background: Schools are part of a country's critical infrastructure. Good infection prevention measures are essential for reducing the risk of infection in schools as much as possible, since these are places where many individuals spend a great deal of time together every weekday in a small area where airborne pathogens can spread quickly. Appropriate ventilation can reduce the indoor concentration of airborne pathogens and reduce the risk of infection., Methods: A systematic search of the literature was conducted in the databases Embase, MEDLINE, and ScienceDirect using keywords such as school, classroom, ventilation, carbon dioxide (CO 2 ) concentration, SARS-CoV-2, and airborne transmission. The primary endpoint of the studies selected was the risk of airborne infection or CO 2 concentration as a surrogate parameter. Studies were grouped according to the study type., Results: We identified 30 studies that met the inclusion criteria, six of them intervention studies. When specific ventilation strategies were lacking in schools being investigated, CO 2 concentrations were often above the recommended maximum values. Improving ventilation lowered the CO 2 concentration, resulting in a lower risk of airborne infections., Conclusions: The ventilation in many schools is not adequate to guarantee good indoor air quality. Ventilation is an important measure for reducing the risk of airborne infections in schools. The most important effect is to reduce the time of residence of pathogens in the classrooms.

The measurement of the CO 2 concentration has a wide range of applications. Traditionally, it has been used to assess air quality, with other applications linked to the experimental assessment of occupancy patterns and air renewal rates. More recently, the worldwide dissemination of COVID-19 establishing a relationship between infection risk and the mean CO 2 level has abruptly led to the measurement of the CO 2 concentration in order to limit the spread of this respiratory disease in the indoor environment. Therefore, the extensive application of this measurement outside of traditional air quality assessment requires an in-depth analysis of the suitability of these sensors for such modern applications. This paper discusses the performance of an array of commercial wall-mounted CO 2 sensors, focusing on their application to obtain occupancy patterns and air renovation rates. This study is supported by several long-term test campaigns conducted in an in-use office building located in south-eastern Spain. The results show a spread of 19-101 ppm, with a drift of 28 ppm over 5 years, an offset of 2-301 ppm and fluctuations up to 80 ppm in instantaneous measurements not related to concentration changes. It is proposed that values averaged over 30 min, using a suitable reference value, be used to avoid erroneous results when calibration is not feasible.

Indoor air quality (IAQ) in houses is often deteriorated by chemical substances emitted from heating, building materials, or other household goods. Since it is difficult for occupants to recognize air pollution, they rarely understand the actual conditions of the IAQ. An investigation into the actual condition of IAQ in houses was therefore conducted in this study. Carbon dioxide (CO2) concentrations in 24 occupied houses was measured, and the results from our analysis showed that the use of combustion heaters increased the concentration of CO2 and led to indoor air pollution. Results indicate that as outdoor temperature decreased, the frequency of ventilation decreased simultaneously, and CO2 concentration increased. Results of the questionnaire survey revealed that the actual IAQ in each house did not match the level of awareness its occupants had regarding ventilation. Along with this difficulty in perceiving air pollution, the lack of knowledge about ventilation systems and the effects of combustion heating may be additional barriers to IAQ awareness.

Carbonation seriously deteriorates the durability of existing reinforced concrete structures. In this study, a thermodynamic model is used to investigate the carbonation reactions in cement-based materials. The effects of the concentration and amounts of CO 2 on the carbonation behaviors of mortar are discussed. The simulation results show that the mechanisms of the carbonation reaction of cement-based materials at different CO 2 concentrations may be different. Nearly all of the hydrate phases have a corresponding CO 2 concentration threshold, above which the corresponding carbonation reaction can be triggered. The thresholds of the C-S-H phases with different Ca/Si ratios are different. The calculation results also show that the phase assemblages in cement paste after being completely air-carbonated, primarily consist of a low-Ca/Si ratio C-S-H, strätlingite, CaCO 3 and CaSO 4 . The pH of the pore solution exhibits a significant decrease when a higher Ca/Si ratio C-S-H phase is completely decalcified into a lower Ca/Si ratio C-S-H phase, by increasing the CO 2 uptake. Additionally, the experimental results and the previously published investigations are used to validate the simulation results.

The low-carbon city has become an important global urban development-oriented goal. One important aspect of urban space is low-carbon urban planning, which has a vital role in urban carbon emissions. Which types of urban form and function allocations are conducive to reducing carbon emissions is therefore a key issue. In this study, the Futian and Luohu Districts of Shenzhen, Guangdong Province, China, are taken as an example to investigate this issue. Firstly, a "head/tail" breaks method based on the third fractal theory is adopted to obtain the minimum evaluation parcel of urban space. Then, the Landscape Shape Index (LSI), Fragmentation Index (C), Shannon's Diversity Index (SHDI), and Density of Public Facilities (Den) are used to evaluate the form and function allocation of each parcel. In addition, the CO 2 concentration distribution in this study area is acquired from remote sensing satellite data. Finally, the relationships between urban form, function allocation, and CO 2 concentration are obtained. The results show that the lower the urban form index or the higher the urban function index, the less the CO 2 concentration. To verify this conclusion, three experiments are designed and carried out. In experiment A, the CO 2 concentration of the tested area is reduced by 14.31% by decreasing the LSI and C by 6.1% and 9.4%, respectively. In experiment B, the CO 2 concentration is reduced by 15.15% by increasing the SHDI and Den by 16.3% and 12.1%, respectively. In experiment C, the CO 2 concentration is reduced by 27.72% when the urban form and function are adjusted in the same was as in experiments A and B.

Ventilation is of critical importance to containing COVID-19 contagion in indoor environments. Keeping the ventilation rate at high level is recommended by many guidelines to dilute virus-laden respiratory particles and mitigate airborne transmission risk. However, high ventilation rate will cause high energy use. Demand-controlled ventilation is a promising technology option for controlling indoor air quality in an energy-efficient manner. This paper proposes a novel CO 2 -based demand-controlled ventilation strategy to limit the spread of COVID-19 in indoor environments. First, the quantitative relationship is established between COVID-19 infection risk and average CO 2 level. Then, a sufficient condition is proposed to ensure COVID-19 event reproduction number is less than 1 under a conservative consideration of the number of infectors. Finally, a ventilation control scheme is designed to make sure the above condition can be satisfied. Case studies of different indoor environments have been conducted on a testbed of a real ventilation system to validate the effectiveness of the proposed strategy. Results show that the proposed strategy can efficiently maintain the reproduction number less than 1 to limit COVID-19 contagion while saving about 30%-50% of energy compared with the fixed ventilation scheme. The proposed strategy offers more practical values compared with existing studies: it is applicable to scenarios where there are multiple infectors, and the number of infectors varies with time; it only requires CO 2 sensors and does not require occupancy detection sensors. Since CO 2 sensors are very mature and low-cost, the proposed strategy is suitable for mass deployment in most existing ventilation systems., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 Elsevier Ltd. All rights reserved.)

During COVID-19 lockdowns less people were able to fulfill the WHO recommendations on physical activity. Also, fitness centers were associated to SARS-CoV-2 superspreader events. However, the risk of infection can be strongly reduced by outdoor air ventilation. To investigate whether a reopening of fitness centers can be justified, CO 2 concentration was measured during four days in a fitness center. Except for one room, the observed CO 2 concentrations were mainly under 800 ppm, which stands for high air quality. The strong decrease of CO 2 concentration during the 15 min evacuations following each hour of workout, speaks for the functionality of the ventilation system. In particular, the number of people present in the studio has a strong impact on the estimated CO 2 value. In a linear mixed model, an additional CO 2 concentration of 2.24 ppm (95 % confidence interval [2.04, 2.43]) was estimated for this setting with a total volume of 4065 m 3 in the fitness center and a possible air change rate per hour up to 10. This means, that for 45 visitors, 100 ppm can be added to the predicted concentration. To summarize, a combination of ventilation, restriction of the number of visitors and surveying the CO 2 concentration allowing for further restrictions in case of need, seems to be an adequate means to reduce the risk of SARS-CoV-2 infection in fitness centers., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 Elsevier Ltd. All rights reserved.)

The distribution of agricultural and livestock products has been limited owing to the recent rapid population growth and the COVID-19 pandemic; this has led to an increase in the demand for food security. The livestock industry is interested in increasing the growth performance of livestock that has resulted in the need for a mechanical ventilation system that can create a comfortable indoor environment. In this study, the applicability of demand-controlled ventilation (DCV) to energy-efficient mechanical ventilation control in a pigsty was analyzed. To this end, an indoor temperature and CO 2 concentration prediction model was developed, and the indoor environment and energy consumption behavior based on the application of DCV control were analyzed. As a result, when DCV control was applied, the energy consumption was smaller than that of the existing control method; however, when it was controlled in an hourly time step, the increase in indoor temperature was large, and several sections exceeded the maximum temperature. In addition, when it was controlled in 15-min time steps, the increase in indoor temperature and energy consumption decreased; however, it was not energy efficient on days with high-outdoor temperature and pig heat., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 Elsevier B.V. All rights reserved.)

This paper aims to study the evolution of CO 2 concentrations and emissions on a conventional farm with weaned piglets between 6.9 and 17.0 kg live weight based on setpoint temperature, outdoor temperature, and ventilation flow. The experimental trial was conducted during one transition cycle. Generally, the ventilation flow increased with the reduction in setpoint temperature throughout the cycle, which caused a reduction in CO 2 concentration and an increase in emissions. The mean CO 2 concentration was 3.12 g m -3 . Emissions of CO 2 had a mean value of 2.21 mg s -1 per animal, which is equivalent to 0.195 mg s -1 kg -1 . A potential function was used to describe the interaction between 10 min values of ventilation flow and CO 2 concentrations, whereas a linear function was used to describe the interaction between 10 min values of ventilation flow and CO 2 emissions, with r values of 0.82 and 0.85, respectively. Using such equations allowed for simple and direct quantification of emissions. Furthermore, two prediction models for CO 2 emissions were developed using two neural networks (for 10 min and 60 min predictions), which reached r values of 0.63 and 0.56. These results are limited mainly by the size of the training period, as well as by the differences between the behavior of the series in the training stage and the testing stage.

The effects of modified atmosphere packaging (MAP) with various CO 2 concentrations on the bacterial community and shelf-life of smoked chicken legs during 25 d of storage at 4 °C were evaluated herein. Four treatments were stored in pallets (PAL) and MAP under 20% (M20), 60% (M60), and 100% (M100) CO 2 , respectively. The results indicated that the MAP treatments provided the legs with higher redness and hardness and lower yellowness, luminance, and lipid oxidation, compared with the PAL treatment. In addition, the MAP treatments effectively inhibited the growth of viable bacteria, delayed bacterial spoilage, and extended the shelf-life of the samples. The M60 and M100 treatments had a better inhibition effect on bacteria. In terms of bacterial community, Carnobacterium , Pseudomonas , Brochothrix , and Lactococcus were the most predominant genera in the 25 d-stored MAP samples, with Carnobacterium maltaromaticum , Pseudomonas fragi , Shewanella baltica , and Lactococcus piscium being the dominant species. However, while the inhibition effects of the M60 and M100 treatments on the bacterial community at Day 25 were similar, the outer package of the M100 treatment collapsed. Overall, the M60 treatment may be a promising approach to improving the quality and extending the shelf-life of smoked chicken legs.

Decorative plants can efficiently purify formaldehyde and improve the quality of indoor air. The existing studies primarily revealed that the aerial and underground parts of plants' capacity to purify formaldehyde, while the performance of stems is unclear. A formaldehyde fumigation experiment was conducted on Epipremnum aureum and Rohdea japonica in a sealed chamber. Results showed the stems could remove formaldehyde. The efficiency of removal by the stems of each plant was 0.089 and 0.137 mg∙m -3 ∙h -1 , respectively, the rate of purification was 40.0 and 61.6%, respectively. Both were related to plant species and the latter was affected by other factors like exposed area. To further explore the mechanism of phytoremediation, the correlation between the concentration of formaldehyde and CO 2 during the experiment was investigated. Results showed when leaves of plants were exposed to formaldehyde, the concentration of CO 2 increased with the decrease in concentration of formaldehyde, and the change in concentration of CO 2 could be used as an indicator of the degree of decontamination of formaldehyde by the plants., (© 2021. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Many (inter)national standards exist to evaluate the resistance of mortar and concrete to carbonation. When a carbonation coefficient is used for performance comparison of mixtures or service life prediction, the applied boundary conditions during curing, preconditioning and carbonation play a crucial role, specifically when using latent hydraulic or pozzolanic supplementary cementitious materials (SCMs). An extensive interlaboratory test (ILT) with twenty two participating laboratories was set up in the framework of RILEM TC 281-CCC 'Carbonation of Concrete with SCMs'. The carbonation depths and coefficients determined by following several (inter)national standards for three cement types (CEM I, CEM II/B-V, CEM III/B) both on mortar and concrete scale were statistically compared. The outcomes of this study showed that the carbonation rate based on the carbonation depths after 91 days exposure, compared to 56 days or less exposure duration, best approximates the slope of the linear regression and those 91 days carbonation depths can therefore be considered as a good estimate of the potential resistance to carbonation. All standards evaluated in this study ranked the three cement types in the same order of carbonation resistance. Unfortunately, large variations within and between laboratories complicate to draw clear conclusions regarding the effect of sample pre-conditioning and carbonation exposure conditions on the carbonation performance of the specimens tested. Nevertheless, it was identified that fresh and hardened state properties alone cannot be used to infer carbonation resistance of the mortars or concretes tested. It was also found that sealed curing results in larger carbonation depths compared to water curing. However, when water curing was reduced from 28 to 3 or 7 days, higher carbonation depths compared to sealed curing were observed. This increase is more pronounced for CEM I compared to CEM III mixes. The variation between laboratories is larger than the potential effect of raising the CO 2 concentration from 1 to 4%. Finally, concrete, for which the aggregate-to-cement factor was increased by 1.79 in comparison with mortar, had a carbonation coefficient 1.18 times the one of mortar., Supplementary Information: The online version contains supplementary material available at 10.1617/s11527-022-01927-7., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest., (© RILEM 2022.)

Concepts of semi-closed greenhouses can be used to save energy, whereas their technical equipment often causes a decrease in the light received by the plants. Nevertheless, higher yields are achieved, which are presumably triggered by a higher CO 2 concentration in the greenhouse and associated higher photosynthesis because of the technical cooling and the longer period of closed ventilation. Therefore, we examined the effects of photosynthetic photon flux density (PPFD) and CO 2 concentration on plant photosynthesis and transpiration in tomato using a multiple cuvette gas exchange system. In a growth chamber experiment, we demonstrated that a light-mediated reduction in photosynthesis can be compensated or even overcompensated for by rising CO 2 concentration. Increasing the CO 2 concentration from 400 to 1000 µmol mol -1 within the PPFD range from 303 to 653 µmol m -2 s -1 resulted in an increase in net photosynthesis of 51%, a decrease in transpiration of 5 to 8%, and an increase in photosynthetic water use efficiency of 60%. Estimations showed that light reductions of 10% can be compensated for via increasing the CO 2 concentration by about 100 µmol mol -1 and overcompensated for by about 40% if CO 2 concentration is kept at 1000 instead of 400 µmol mol -1 .

In view of the current and expected future rise in atmospheric CO 2 concentrations, we examined the effect of elevated CO 2 on photoinhibition of photosystem I (PSI) under fluctuating light in Arabidopsis thaliana . At 400 ppm CO 2 , PSI showed a transient over-reduction within the first 30 s after transition from dark to actinic light. Under the same CO 2 conditions, PSI was highly reduced after a transition from low to high light for 20 s. However, such PSI over-reduction greatly decreased when measured in 800 ppm CO 2 , indicating that elevated atmospheric CO 2 facilitates the rapid oxidation of PSI under fluctuating light. Furthermore, after fluctuating light treatment, residual PSI activity was significantly higher in 800 ppm CO 2 than in 400 ppm CO 2 , suggesting that elevated atmospheric CO 2 mitigates PSI photoinhibition under fluctuating light. We further demonstrate that elevated CO 2 does not affect PSI activity under fluctuating light via changes in non-photochemical quenching or cyclic electron transport, but rather from a rapid electron sink driven by CO 2 fixation. Therefore, elevated CO 2 mitigates PSI photoinhibition under fluctuating light at the acceptor rather than the donor side. Taken together, these observations indicate that elevated atmospheric CO 2 can have large effects on thylakoid reactions under fluctuating light.

To investigate the need of allergic population for indoor environment quality, exposure effects of poor air quality on subjects with respiratory allergies were compared with those on healthy people, including perceptual responses, health symptoms, mental performance, and physiological responses. The experimental intervention was with and without ventilation at thermally neutral rooms, creating two exposure conditions indicated by CO 2 concentration ranges of 502 to 3297 ppm (2438 ± 1527 ppm) and 517 to 5687 ppm (3615 ± 1527 ppm). 63 subjects (32 allergic subjects and 31 non-allergic subjects) were exposed to both conditions for 3 hours. The main results suggested that, compared with healthy people, people with respiratory allergy seem to be more sensitive or less acceptable to reduced air quality polluted by occupants during instantaneous exposure. Besides, the allergic group performed worse in cognitive tests than non-allergic group. After 3 hours of continuous exposure, people with respiratory allergy reported stronger intensity of respiratory irritations and seemed to suffer more inflammation indicated by a higher level of interleukin 1L-1β., (© 2021 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

In this study, 30 subjects were exposed to different combinations of air temperature (T a : 24, 27, and 30°C) and CO 2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to T a  = 24°C, exposure to 30°C at all CO 2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of T a on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO 2 from 8000 to 12 000 ppm at all T a caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of T a and CO 2 concentration on human responses was identified., (© 2020 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

This paper describes the in situ monitoring of indoor air quality (IAQ) in two dwellings, using low-cost IAQ sensors to provide high-density temporal and spatial data. IAQ measurements were conducted over 2-week periods in the kitchen and bedroom of each home during the winter, spring, and summer seasons, characterized by different outside parameters, that were simultaneously measured. The mean indoor PM 2.5 concentrations were about 15 μg m -3 in winter, they dropped to values close to 10 μg m -3 in spring and increased to levels of about 13 μg m -3 in summer. During the winter campaign, indoor PM 2.5 was found mainly associated with particle penetration inside the rooms from outdoors, because of the high outdoor PM 2.5 levels in the season. Such pollution winter episodes occur frequently in the study region, due to the combined contributions of strong anthropogenic emissions and stable atmospheric conditions. The concentrations of indoor volatile organic compounds (VOCs) and CO 2 increased with the number of occupants (humans and pets), as likely associated with consequent higher emissions through breathing and metabolic processes. They also varied with occupants' daily activities, like cooking and cleaning. Critic CO 2 levels above the limit of 1000 ppm were observed in spring campaign, in the weeks close to the end of the COVID-19 quarantine, likely associated with the increased time that the occupants spent at home.

Indoor air pollutants comprise both polar and non-polar volatile organic compounds (VOCs). Indoor potted plants are well known for their innate ability to improve indoor air quality (IAQ) by detoxification of indoor air pollutants. In this study, a combination of two different plant species comprising a C3 plant (Zamioculcas zamiifolia) and a crassulacean acid metabolism (CAM) plant (Sansevieria trifasciata) was used to remove polar and non-polar VOCs and minimize CO 2 emission from the chamber. Z. zamiifolia and S. trifasciata, when combined, were able to remove more than 95% of pollutants within 48 h and could do so for six consecutive pollutant's exposure cycles. The CO 2 concentration was reduced from 410 down to 160 ppm inside the chamber. Our results showed that using plant growth medium rather than soil had a positive effect on decreasing CO 2 . We also re-affirmed the role of formaldehyde dehydrogenase in the detoxification and metabolism of formaldehyde and that exposure of plants to pollutants enhances the activity of this enzyme in the shoots of both Z. zamiifolia and S. trifasciata. Overall, a mixed plant of Z. zamiifolia and S. trifasciata was more efficient at removing mixed pollutants and reducing CO 2 than individual plants.

This research was conducted to investigate the dynamics of airborne fungi using viable culture collection and in respect to different abiotic variables, including seasonal and intra-diurnal variations. A gravimetric method was used to sample airborne fungal deposition on potato dextrose agar plates on alternate days, for a year between April 2015 to March 2016. From 176 settle plate exposures, a total of 1197 mould and 283 yeast colony-forming units (CFU), 21 genera and 62 species were retrieved. The highest fungal spore count was recorded in February 2016, whereas the lowest count occurred in August 2015. The main constituents of the fungal airspora were attributed to Cladosporium (60.2%), Aspergillus (10.4%), Fusarium (9.4%), Alternaria (8.5%), and Ganoderma spp. (2.3%). Temperature was negatively correlated with total colony count ( r = -0.231, p ≤ 0.05) or species richness ( r = -0.267, p ≤ 0.001), while wind speed was positively correlated with total colony count ( r = 0.484, p ≤ 0.001) or species richness ( r = 0.257, p ≤ -0.001). The highest dispersal of fungal spores was obtained at 18:00, whereas the lowest fungal spores release was recorded at 00:00 (midnight). There were no significant differences in species composition and richness of the airborne fungal population between two study sites, the Industrial area and Qatar University Campus. The count of Alternaria spp. and Fusarium spp. were significantly higher at the Industrial area site, which corresponds to a higher CO 2 level than the Qatar University site. This study lays the foundation for future work to assess the implications of such aeromycological data on public health.

Premise: A CO 2 control system is important for investigating how elevated CO 2 affects plant growth. Our automatic CO 2 monitoring and control system offers an inexpensive and flexible way to make CO 2 -enriched environments., Method and Results: Using microcontrollers paired with non-dispersive infrared CO 2 sensors, relays, and valves, we developed a low-cost system for monitoring and controlling CO 2 levels in growth chambers., Conclusions: Compared with existing commercially available CO 2 control systems, Arduino-based microcontrollers offer affordable access to the data logging of CO 2 levels in growth chambers, thereby reducing budget limitations for creating growth conditions with highly controlled CO 2 concentrations., (© 2020 Chen and Markham. Applications in Plant Sciences published by Wiley Periodicals LLC on behalf of Botanical Society of America.)

During the first outbreak of the SARS-CoV-2 pandemic the population, focusing primarily on the risk of infection, was generally inattentive to the quality of indoor air. Spain, and the city of Madrid in particular, were among the world's coronavirus hotspots. The country's entire population was subject to a 24/7 lockdown for 45 days. This paper describes a comparative longitudinal survey of air quality in four types of housing in the city of Madrid before and during lockdown. The paper analysed indoor temperatures and variations in CO 2 , 2.5 μm particulate matter (PM 2.5 ) and total volatile organic compound (TVOC) concentrations before and during lockdown. The mean daily outdoor PM 2.5 concentration declined from 11.04 µg/m 3 before to 7.10 µg/m 3 during lockdown. Before lockdown the NO 2 concentration values scored as 'very good' 46% of the time, compared to 90.9% during that period. Although the city's outdoor air quality improved, during lockdown the population's exposure to indoor pollutants was generally more acute and prolonged. Due primarily to concern over domestic energy savings, the lack of suitable ventilation and more intensive use of cleaning products and disinfectants during the covid-19 crisis, indoor pollutant levels were typically higher than compatible with healthy environments. Mean daily PM 2.5 concentration rose by approximately 12% and mean TVOC concentration by 37% to 559%. The paper also puts forward a series of recommendations to improve indoor domestic environments in future pandemics and spells out urgent action to be taken around indoor air quality (IAQ) in the event of total or partial quarantining to protect residents from respiratory ailments and concomitantly enhanced susceptibility to SARS-CoV-2, as identified by international medical research.

Due to their slow movement and closure upon shade, partially closed stomata can be a substantial limitation to photosynthesis in variable light intensities. The abscisic acid deficient flacca mutant in tomato ( Solanum lycopersicum ) displays very high stomatal conductance ( g s ). We aimed to determine to what extent this substantially increased g s affects the rate of photosynthetic induction. Steady-state and dynamic photosynthesis characteristics were measured in flacca and wildtype leaves, by the use of simultaneous gas exchange and chlorophyll fluorometry. The steady-state response of photosynthesis to CO 2 , maximum quantum efficiency of photosystem II photochemistry ( F v /F m ), as well as mesophyll conductance to CO 2 diffusion were not significantly different between genotypes, suggesting similar photosynthetic biochemistry, photoprotective capacity, and internal CO 2 permeability. When leaves adapted to shade (50 µmol m -2 s -1 ) at 400 µbar CO 2 partial pressure and high humidity (7 mbar leaf-to-air vapour pressure deficit, VPD) were exposed to high irradiance (1500 µmol m -2 s -1 ), photosynthetic induction was faster in flacca compared to wildtype leaves, and this was attributable to high initial g s in flacca (~0.6 mol m -2 s -1 ): in flacca , the times to reach 50 ( t 50 ) and 90% ( t 90 ) of full photosynthetic induction were 91 and 46% of wildtype values, respectively. Low humidity (15 mbar VPD) reduced g s and slowed down photosynthetic induction in the wildtype, while no change was observed in flacca ; under low humidity, t 50 was 63% and t 90 was 36% of wildtype levels in flacca . Photosynthetic induction in low CO 2 partial pressure (200 µbar) increased g s in the wildtype (but not in flacca ), and revealed no differences in the rate of photosynthetic induction between genotypes. Effects of higher g s in flacca were also visible in transients of photosystem II operating efficiency and non-photochemical quenching. Our results show that at ambient CO 2 partial pressure, wildtype g s is a substantial limitation to the rate of photosynthetic induction, which flacca overcomes by keeping its stomata open at all times, and it does so at the cost of reduced water use efficiency., (Copyright © 2020 Kaiser, Morales, Harbinson, Heuvelink and Marcelis.)

To investigate the effect of different CO 2 concentrations on the carbonation results of slag blended cement pastes, carbonation experiments under natural (0.03% CO 2 ) and accelerated conditions (3, 20, and 100% CO 2 ) were investigated with various microscopic testing methods, including X-ray diffraction (XRD), 29 Si magic angle spinning nuclear magnetic resonance ( 29 Si MAS NMR) and scanning electron microscopy (SEM). The XRD results indicated that the major polymorphs of CaCO 3 after carbonation were calcite and vaterite. The values of the calcite/(aragonite + vaterite) (c/(a + v)) ratios were almost the same in all carbonation conditions. Additionally, NMR results showed that the decalcification degree of C-S-H gel exposed to 0.03% CO 2 was less than that exposed to accelerated carbonation; under accelerated conditions, it increased from 83.1 to 84.2% when the CO 2 concentration improved from 3% to 100%. In SEM observations, the microstructures after accelerated carbonation were denser than those under natural carbonation but showed minor differences between different CO 2 concentrations. In conclusion, for cement pastes blended with 20% slag, a higher CO 2 concentration (above 3%) led to products different from those produced under natural carbonation. A further increase in CO 2 concentration showed limited variation in generated carbonation products.

Dark, that is, nonphototrophic, microbial CO 2 fixation occurs in a large range of soils. However, it is still not known whether dark microbial CO 2 fixation substantially contributes to the C balance of soils and what factors control this process. Therefore, the objective of this study was to quantitate dark microbial CO 2 fixation in temperate forest soils, to determine the relationship between the soil CO 2 concentration and dark microbial CO 2 fixation, and to estimate the relative contribution of different microbial groups to dark CO 2 fixation. For this purpose, we conducted a 13 C-CO 2 labeling experiment. We found that the rates of dark microbial CO 2 fixation were positively correlated with the CO 2 concentration in all soils. Dark microbial CO 2 fixation amounted to up to 320 µg C kg -1  soil day -1 in the Ah horizon. The fixation rates were 2.8-8.9 times higher in the Ah horizon than in the Bw1 horizon. Although the rates of dark microbial fixation were small compared to the respiration rate (1.2%-3.9% of the respiration rate), our findings suggest that organic matter formed by microorganisms from CO 2 contributes to the soil organic matter pool, especially given that microbial detritus is more stable in soil than plant detritus. Phospholipid fatty acid analyses indicated that CO 2 was mostly fixed by gram-positive bacteria, and not by fungi. In conclusion, our study shows that the dark microbial CO 2 fixation rate in temperate forest soils increases in periods of high CO 2 concentrations, that dark microbial CO 2 fixation is mostly accomplished by gram-positive bacteria, and that dark microbial CO 2 fixation contributes to the formation of soil organic matter., (© 2019 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

One of the most important functions of air conditioning systems in operating rooms is to protect occupants against pathogenic agents transported by air. This protection is done by simultaneously controlling the air distribution, temperature, humidity, filtration and infiltration from other areas etc. Due to their low price, simple installation, operation and maintenance, window/wall air conditioning system have largely been used in operating rooms in Brazil, even if these types of equipment only recirculate the air inside the room without appropriate filtration and renovation with outdoor air. In this context, this work aims to analyse the performance of the window/wall air conditioning systems on indoor air ventilation in operating rooms by measuring particle number concentrations and carbon dioxide concentrations during different surgical procedures, in a single surgical room and in the nearby areas (corridor) for two cases: single surgery and two subsequent surgeries. In addition, the efficiency of the analysed air conditioning system was evaluated by comparing the ventilation level calculated in the surgical room with the ventilation required in order to maintain the carbon dioxide concentration within acceptable levels. The results showed that this type of air conditioning system is not appropriate for use in operating rooms since it cannot provide an adequate level of ventilation. The CO 2 concentrations during surgeries, in fact, significantly exceeded acceptable values and a simultaneous increase in particle number concentration was observed. The results also showed that there is a high risk of contamination between subsequent surgeries in the same surgical room, due to residues of contaminants transported by the particles emitted during the surgeries that were not removed from the operating room by the air conditioning system. The particle number concentration measured in the second surgery, in fact, was approximately six times higher than in the first surgery., Competing Interests: The authors declare no conflict of interest.

Modeling stomatal control is critical for predicting forest responses to the changing environment and hence the global water and carbon cycles. A trait-based stomatal control model that optimizes carbon gain while avoiding hydraulic risk has been shown to perform well in response to drought. However, the model's performance against changes in atmospheric CO2, which is rising rapidly due to human emissions, has yet to be evaluated. The present study tested the gain-risk model's ability to predict the stomatal response to CO2 concentration with potted water birch (Betula occidentalis Hook.) saplings in a growth chamber. The model's performance in predicting stomatal response to changes in atmospheric relative humidity and soil moisture was also assessed. The gain-risk model predicted the photosynthetic assimilation, transpiration rate and leaf xylem pressure under different CO2 concentrations, having a mean absolute percentage error (MAPE) of 25%. The model also predicted the responses to relative humidity and soil drought with a MAPE of 21.9% and 41.9%, respectively. Overall, the gain-risk model had an MAPE of 26.8% compared with the 37.5% MAPE obtained by a standard empirical model of stomatal conductance. Importantly, unlike empirical models, the optimization model relies on measurable physiological traits as inputs and performs well in predicting responses to novel environmental conditions without empirical corrections. Incorporating the optimization model in larger scale models has the potential for improving the simulation of water and carbon cycles., (© The Author(s) 2019. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

The influence of temperature, CO₂ concentration and relative humidity on the carbonation depth and compressive strength of concrete was investigated. Meanwhile, phase composition, types of hydration products and microstructure characteristics of samples before and after the carbonation were analyzed by XRD and ESEM. Research results demonstrate that temperature, CO₂ concentration and relative humidity influence the carbonation depth and compressive strength of concrete significantly. There is a linear relationship between temperature and carbonation depth, as well as the compressive strength of concrete. CO₂ concentration and relative humidity present a power function and a polynomial function with carbonation depth of concrete, respectively. The concrete carbonation depth increases with the increase of relative humidity and reaches the maximum value when the relative humidity is 70%. Significant differences of phase composition, hydration products and microstructure are observed before and after the carbonation. Carbonization products of samples are different with changes of temperatures (10 °C, 20 °C and 30 °C). The result of crystal structure analysis indicates that the carbonation products are mainly polyhedral spherical vaterite and aragonite.

Horticultural crop production and changes in physiological aspects during the growing season may be affected by climate change factors (CC), which include increased temperature and the associated doubling or tripling of atmospheric CO 2 concentrations. However, the potential effects are complex and many parameters might impact on the observed effects. To evaluate the effects of CC, the growth, yield, fruit characteristics, photosynthetic traits, and morphological characteristics of hot peppers were investigated. The hot peppers were grown under two CC scenarios, with the Representative Concentration Pathway (RCP) of 4.5 (Temp.; +3.4°C, CO 2 conc.; 540 μmol/mol, Precipitation +17.3%) and RCP 8.5 (Temp.; +6.0°C and CO 2 conc.; 940 μmol/mol, Precipitation +20.3%), respectively, using extreme weather simulators. This was compared with existing weather conditions occurring in Jeonju, South Korea in terms of air temperature, relative humidity, radiation, and precipitation. Overall, the plant height showed the highest under moderate CC conditions (RCP 4.5) among all the treatments tested. The number of leaves in the RCP 8.5 condition showed 7,739/plants, which was 2.2 times higher than that of the control. In addition, fruit shape was shortened and percentage dry matter was also the highest. The yield of hot pepper in the CC RCP 4.5 and 8.5 conditions were decreased by 21.5% and 89.2% when compared with that of the control, respectively. The days to harvest in the condition of CC scenarios were shortened from 5 to 13 compared with that of control, predominantly due to the increased air temperature. The results indicated that the severe RCP CC scenarios made reduction in the yields and negative affection on the fruit qualities. Overall, hot pepper was tolerant of mild CC scenarios of temperature × CO 2 but was significantly affected by more extreme CC interacting parameter concentrations (or similar).

The aim of this laboratory experiment was to study the effects of ventilation rate, and related changes in air quality, predominantly bioeffluents, on work performance, perceived indoor air quality, and health symptoms in a typical conditions of modern open-plan office with low material and equipment emissions. In Condition A, outdoor air flow rate of 28.2 l/s person (CO 2 level 540 ppm) was applied and in Condition B, outdoor air flow rate was 2.3 l/s person (CO 2 level 2260 ppm). CO 2 concentration level was used as an indicator of bioeffluents. Performance was measured with seven different tasks which measure different cognitive processes. Thirty-six subjects participated in the experiment. The exposure time was 4 hours. Condition B had a weak negative effect on performance only in the information retrieval tasks. Condition B increased slightly subjective workload and perceived fatigue. No effects on health symptoms were found. The intensity of symptoms was low in both conditions. The experimental condition had an effect on perceived air quality and observed odor intensity only in the beginning of the session. Although the room temperature was controlled in both conditions, the heat was perceived to impair the performance more in Condition B., (© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

The climate has important influences on the distribution and structure of forest ecosystems, which may lead to vital feedback to climate change. However, much of the existing work focuses on the changes in carbon fluxes or water cycles due to climate change and/or atmospheric CO 2 , and few studies have considered how and to what extent climate change and CO 2 influence the ecosystem structure (e.g., fractional coverage change) and the changes in the responses of ecosystems with different characteristics. In this work, two dynamic global vegetation models (DGVMs): IAP-DGVM coupled with CLM3 and CLM4-CNDV, were used to investigate the response of the forest ecosystem structure to changes in climate (temperature and precipitation) and CO 2 concentration. In the temperature sensitivity tests, warming reduced the global area-averaged ecosystem gross primary production in the two models, which decreased global forest area. Furthermore, the changes in tree fractional coverage (Δ F tree ; %) from the two models were sensitive to the regional temperature and ecosystem structure, i.e., the mean annual temperature (MAT; °C) largely determined whether Δ F tree was positive or negative, while the tree fractional coverage ( F tree ; %) played a decisive role in the amplitude of Δ F tree around the globe, and the dependence was more remarkable in IAP-DGVM. In cases with precipitation change, F tree had a uniformly positive relationship with precipitation, especially in the transition zones of forests (30% <  F tree  < 60%) for IAP-DGVM and in semiarid and arid regions for CLM4-CNDV. Moreover, Δ F tree had a stronger dependence on F tree than on the mean annual precipitation (MAP; mm/year). It was also demonstrated that both models captured the fertilization effects of the CO 2 concentration.

Background and Aims: Plants depend on photosynthesis for growth. In nature, factors such as temperature, humidity, CO 2 partial pressure, and spectrum and intensity of irradiance often fluctuate. Whereas irradiance intensity is most influential and has been studied in detail, understanding of interactions with other factors is lacking., Methods: We tested how photosynthetic induction after dark-light transitions was affected by CO 2 partial pressure (20, 40, 80 Pa), leaf temperatures (15·5, 22·8, 30·5 °C), leaf-to-air vapour pressure deficits (VPD leaf-air ; 0·5, 0·8, 1·6, 2·3 kPa) and blue irradiance (0-20 %) in tomato leaves (Solanum lycopersicum)., Key Results: Rates of photosynthetic induction strongly increased with CO 2 partial pressure, due to increased apparent Rubisco activation rates and reduced diffusional limitations. High leaf temperature produced slightly higher induction rates, and increased intrinsic water use efficiency and diffusional limitation. High VPD leaf-air slowed down induction rates and apparent Rubisco activation and (at 2·3 kPa) induced damped stomatal oscillations. Blue irradiance had no effect. Slower apparent Rubisco activation in elevated VPD leaf-air may be explained by low leaf internal CO 2 partial pressure at the beginning of induction., Conclusions: The environmental factors CO 2 partial pressure, temperature and VPD leaf-air had significant impacts on rates of photosynthetic induction, as well as on underlying diffusional, carboxylation and electron transport processes. Furthermore, maximizing Rubisco activation rates would increase photosynthesis by at most 6-8 % in ambient CO 2 partial pressure (across temperatures and humidities), while maximizing rates of stomatal opening would increase photosynthesis by at most 1-3 %., (© The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

The Paleocene-Eocene Thermal Maximum (PETM) is a remarkable climatic and environmental event that occurred 56 Ma ago and has importance for understanding possible future climate change. The Paleocene-Eocene transition is marked by a rapid temperature rise contemporaneous with a large negative carbon isotope excursion (CIE). Both the temperature and the isotopic excursion are well-documented by terrestrial and marine proxies. The CIE was the result of a massive release of carbon into the atmosphere. However, the carbon source and quantities of CO2 and CH4 greenhouse gases that contributed to global warming are poorly constrained and highly debated. Here we combine an established oxygen isotope paleothermometer with a newly developed triple oxygen isotope paleo-CO2 barometer. We attempt to quantify the source of greenhouse gases released during the Paleocene-Eocene transition by analyzing bioapatite of terrestrial mammals. Our results are consistent with previous estimates of PETM temperature change and suggest that not only CO2 but also massive release of seabed methane was the driver for CIE and PETM.