Air CO2 Concentration Research Articles

3-D Geological Mapping of Rocks Potentially Suitable for Capturing Carbon Dioxide from the Atmosphere

Rapid increase of the Anthropocene ambient air CO2 concentration value is the main cause of the 1.2 o C global temperature rise creating the recent adverse climate and weather changes. Promising new methods to capture CO2 from the air are being developed but remain too expensive for worldwide applications. Mantle-derived rocks, primarily basalts, peridotites and serpentinites are likely to play an important role in future CO2 reduction because of relatively rapid disintegration of minerals (including olivine and serpentine) in these rocks potentially resulting in widespread CO2 capture. Examples to be discussed include artificially enhanced carbonization of water emitted from ophiolites, and acid dissolution of serpentinites resulting in indirect mineral carbonation by optimizing temperature and pressure conditions. Reconstruction of a large cone-shaped body of serpentinite situated within the Mount Albert peridotite intrusion in Québec is presented as an example of the rôle 3-D geologic mapping can play in future CO2 reduction efforts.

The result of the comparative use of OCO-2 information to find the relationship between changes in the atmospheric concentration of CO2 and air temperature in the Argentine Islands and Ukraine.

The results of comparative analysis of data of data of changes CO2 concentrations in the atmosphere over the polar regions adjacent to the "Akademik Vernadsky" station (the size of the study area 1.5° × 1.5°, or approximately 166 km by 75 km) were obtained satellite Orbiting Carbon Observatory (OCO-2) and air temperature according to ground meteorological observations at the "Akademik Vernadsky" station for 2014-2020. From obtained graph, we can see that the air temperature and CO2 concentration in the atmosphere over the study area tend to increase slowly. In addition, the analysis of the above results showed that in this way it is possible to determine the integrated trends in the impact of greenhouse gas content in the atmosphere on air temperature. A comparative analysis of data of data of changes CO2 concentrations according to OCO-2 between regions where there is a direct anthropogenic impact (Ukraine) and the region where anthropogenic impact is minimized (areas adjacent to the "Akademik Vernadsky" station) for 2014-2020. It was found that CO2 concentrations over areas with direct anthropogenic impact are growing much faster than over areas where there is no such impact at all. However, we see that CO2 concentrations tend to increase in both cases. Based on the obtained results, it was determined that conducting a comprehensive, simultaneous and consistent with satellite observations measurements of various series of variables, will provide an opportunity to optimize information of changes in climatic parameters (air temperature) in the polar regions.

Association of bedroom environment with the sleep quality of elderly subjects in summer: A field measurement in Shanghai, China

Sleep is essential for the health of elderly people, but few studies have made connection between their sleep quality and their bedroom environment. This study performed field measurements in Shanghai, China, to investigate the bedroom thermal environment and ventilation and their associations with the sleep quality of elderly subjects in summer. Forty-five elderly subjects participated in this study for six consecutive days. Their bedroom air temperature, relative humidity and CO2 concentration were measured continuously and their sleep quality was objectively measured using a wrist-worn sleep tracker. Wrist skin temperature was measured continuously at night. Each morning after waking up the subjects assessed their sleep quality, recalled their thermal sensation, and recorded their bed covering, sleepwear and cooling/ventilation arrangements during that night. The results show that higher air temperature and CO2 concentration were both negatively correlated with objective sleep quality. Air temperature was the key factor influencing objective sleep quality. When air temperature increased by 1 °C, sleep efficiency (SE) decreased by 0.7%, duration of Rapid Eye Movement (REM) sleep decreased by 2.1min, and time awake increased by 2.3min. The sleep quality of elderly subjects was more negatively affected by heat exposure than has been previously reported for younger subjects. As CO2 concentration increased by 100 ppm, the Total Sleep Time (TST) decreased by 11min. The combined effects of air temperature, relative humidity and CO2 concentration were analyzed: TST and duration of REM sleep were reduced at higher air temperature, relative humidity and CO2 concentration.

A field study on summertime overheating of six schools in Montreal Canada

Due to global climate change, the world has been experiencing significant increases in average temperatures and the frequency and intensity of extreme weather events such as heatwaves. The overheating problem in indoor spaces of buildings has become a concern to the comfort and health of building occupants, especially vulnerable populations such as the elderly, children, or the sick. A field monitoring network consisting of rooftop weather stations and indoor sensors has been set up on 11 buildings of different types in Montreal, Canada. This paper presents the results of field measurements of indoor thermal conditions of six school buildings to assess the risks of summertime overheating. These six primary school buildings were built in 1930-1966 with window-wall-ratios between 10-30% and limited mechanical ventilation. The indoor dry-bulb air temperature, relative humidity, and CO2 concentrations are measured by indoor wireless sensors. The weather conditions, including dry-bulb temperature, relative humidity, solar radiation, rainfall, wind speed, and wind direction, are measured by rooftop weather stations. Measurements presented in this paper are collected from July to September 2020, which include four different time intervals: (a) during two heatwaves, (b) during summer break when schools were closed, and (c) when schools were reopened, and windows were intermittently opened. Data analysis shows that the indoor and outdoor temperature difference has a strong linear correlation with the outdoor temperature observed for all school buildings. This correlation is also affected by building operations, such as opening windows, closing blinds, and the micro-climate of their surroundings.

On reducing CO2 concentration in buildings by using plants

The article deals with the implementation of plants in the indoor environment of buildings to reduce the concentration of CO2. Based on a specified model representing the internal environment of an office space, it was studied whether the requirement for the total amount of ventilated air could be reduced by using plants, thereby achieving savings of operating costs in the building ventilation sector. The present research describes the effect of plant implementation according to different levels of CO2 concentration of the supply air, specifically with values of 410 ppm corresponding to the year 2020, 550 ppm to the year 2050 and 670 ppm to the year 2100, as well as according to different levels of CO2 concentration in the indoor environment, namely 1000 ppm and 1500 ppm, the illumination of plants in the indoor environment is constant in the model, PPFD equals to 200 μmolm−2 s−1. Based on the computational model, it was found that the implemented plants can positively influence the requirement for the total amount of ventilated air, the most significant effect is in the case of a low indoor environment quality, with the CO2 concentration of 1500 ppm, and a high supply air quality 410 p˙pm. The simulation also showed that compared to 2020, by the year 2100, it will be necessary to increase the ventilation of the indoor environment by 25.1% to ensure the same quality of the indoorenvironment.

Monitors to improve indoor air carbon dioxide concentrations in the hospital: A randomized crossover trial

BackgroundVentilation has emerged as an important strategy to reduce indoor aerosol transmission of coronavirus disease 2019. Indoor air carbon dioxide (CO2) concentrations are a surrogate measure of respiratory pathogen transmission risk. ObjectivesTo determine whether CO2 monitors are necessary and effective to improve ventilation in hospitals. MethodsA randomized, placebo (sham)-controlled, crossover, open label trial. Between February and May 2021, we placed CO2 monitors in twelve double-bed patient rooms across two geriatric wards. Staff were instructed to open windows, increase the air exchange rate and reduce room crowding to maintain indoor air CO2 concentrations ≤800 parts per million (ppm). ResultsCO2 levels increased during morning care and especially in rooms housing couples (rooming-in). The median (interquartile range, IQR) time/day with CO2 concentration > 800 ppm (primary outcome) was 110 min (IQR 47–207) at baseline, 82 min (IQR 12–226.5) during sham periods, 78 min (IQR 20–154) during intervention periods and 140 min (IQR 19.5–612.5) post-intervention. The intervention period only differed significantly from the post-intervention period (P = 0.02), mainly due to an imbalance in rooming-in. Significant but small differences were observed in secondary outcomes of time/day with CO2 concentrations > 1000 ppm and daily peak CO2 concentrations during the intervention vs. baseline and vs. the post-intervention period, but not vs. sham. Staff reported cold discomfort for patients as the main barrier towards increasing ventilation. DiscussionIndoor air CO2 concentrations in hospital rooms commonly peaked above recommended levels, especially during morning care and rooming-in. There are many possible barriers towards implementing CO2 monitors to improve ventilation in a real-world hospital setting. A paradigm shift in hospital infection control towards adequate ventilation is warranted. Trial registrationClinicalTrials.gov Identifier: NCT04770597

Enhancing Electrochemically Driven CO2 Separator Using Hydroxide Exchange Membranes

In a hydroxide exchange membrane fuel cell (HEMFC), hydroxide produced at the cathode readily reacts with CO2 in air due to its acid-base reaction. The CO2 then transports across the hydroxide exchange membrane to the anode where bicarbonates build up lowering the local pH until CO2 evolution reactions become favorable. The pH gradient across the cell results in lower voltage output; however, it can act as an effective CO2 separator from air. By focusing on CO2 separation, rather than power output, an electrochemically-driven CO2 separator (EDCS) was developed using a poly(aryl piperidinium) membrane.1 Efficient and continuous CO2 separation technologies are needed for various applications including upstream of HEMFC stacks in vehicles2 as well as life support systems in submarines3 and manned spacecrafts.4 Previously, the EDCS was demonstrated as an effective and continuous method to remove CO2 from ambient air using minimal hydrogen flow to power the separation, and various operating conditions and cell build configurations were investigated.5 This work seeks to further optimize the EDCS through improvements in ionomer, flow fields, temperature, and relative humidity for various CO2 concentrations. Figure 1 shows the improvements in CO2 removal from ambient air of a 25 cm2 EDCS from the initial design inspired by fuel cells to the latest design using a nickel metal mesh as the combined flow field and gas diffusion layer at the cathode. The EDCS operating conditions and design is also evaluated for different applications as their requirements for air flow, CO2 concentrations, operating conditions, energy and size restraints differ and must be taken into account. Additionally, this work explores methods to scale the EDCS for these high throughput operations such as planar stacks or spiral wound modules.

Development and Analysis of a Dynamic Energy Model of an Office Using a Building Management System (BMS) and Actual Measurement Data

Calibration of the energy model of a building is one of the essential tasks required to determine the efficiency of building management systems, and both their own and other systems’ improvement potential. In order to make the building energy model as accurate as possible, it is necessary to collect comprehensive data on its operation and sometimes to assess the missing information. This paper represents the process of developing an energy model for an administrative building and its calibration procedure, using detailed long-term measurement and building management system (BMS) data. Indoor air temperature, CO₂ concentration, and relative humidity were experimentally measured and evaluated separately. Such dual application of data reduces the inaccuracy of the assumptions made and assesses the model’s accuracy. The DesignBuilder software developed the building model. During the development of the model, it was observed that the actual energy consumption needs to be assessed, as the assumptions made during the design about the operation and management of HVAC systems often do not coincide with the actual situation. After integrating BMS information on HVAC management into the building model, the resulting discrepancy between the model results and the actual heat consumption was 6.5%. Such a model can be further used to optimize management decisions and assess energy savings potential.

Effects of elevated air CO2 concentrations on the carbon and nitrogen contents of rice and winter wheat

Investigating the effects of different air CO2 concentrations on the carbon (C) and nitrogen (N) contents of straw and roots of different generations of crops is crucial to predict crop responses to elevated CO2. We performed a field experiment with open-top chambers (OTCs) and applied consecutively elevating CO2 concentrations (120 ppm and 160 ppm during the investigated 2018 rice and 2018–2019 winter wheat seasons, respectively, with a consecutive increase of 40 ppm per year beginning from the first winter wheat–rice rotation season in November 2015) and a continuously elevated CO2 concentration of 200 ppm during each season. The results indicated that elevated CO2 concentrations generally increased the root C content of both rice and winter wheat. The most obvious effects between the treatments appeared in the crops grown from seeds harvested in the OTCs each season. An elevated CO2 concentration increased the rice root N content, with more obvious effects over multiple generations that had been planted in the OTCs for three or four growing seasons than on a single generation that was planted in the OTCs for only one growing season. An elevated CO2 concentration also induced an increase in the ratio of C to N (C/N) in the roots of rice and in the straw and roots of winter wheat. The C content of the rice and winter wheat roots increased significantly with increasing root N content. The enhancement effect of an elevated CO2 concentration on the C and N content and the C/N ratios in rice and winter wheat is more significant for multiple generations than for one generation.

The triple oxygen isotope composition of phytoliths, a new proxy of atmospheric relative humidity: controls of soil water isotope composition, temperature, CO<sub>2</sub> concentration and relative humidity

Abstract. Continental atmospheric relative humidity is a major climate parameter whose variability is poorly understood by global climate models. Models' improvement relies on model–data comparisons for past periods. However, there are no truly quantitative indicators of relative humidity for the pre-instrumental period. Previous studies highlighted a quantitative relationship between the triple oxygen isotope composition of phytoliths, particularly the 17O excess of phytoliths, and atmospheric relative humidity. Here, as part of a series of calibrations, we examine the respective controls of soil water isotope composition, temperature, CO2 concentration and relative humidity on phytolith 17O excess. For that purpose, the grass species Festuca arundinacea was grown in growth chambers where these parameters were varying. The setup was designed to control the evolution of the triple oxygen isotope composition of phytoliths and all the water compartments of the soil–plant–atmosphere continuum. Different analytical techniques (cavity ring-down spectroscopy and isotope ratio mass spectrometry) were used to analyze water and silica. An inter-laboratory comparison allowed to strengthen the isotope data matching. Water and phytolith isotope compositions were compared to previous datasets obtained from growth chamber and natural tropical sites. The results show that the δ′18O value of the source water governs the starting point from which the triple oxygen isotope composition of leaf water, phytolith-forming water and phytoliths evolves. However, since the 17O excess varies little in the growth chamber and natural source waters, this has no impact on the strong relative humidity dependency of the 17O excess of phytoliths, demonstrated for the 40 %–80% relative humidity range. This relative humidity dependency is not impacted by changes in air temperature or CO2 concentration either. A relative humidity proxy equation is proposed. Each per meg of change in phytolith 17O excess reflects a change in atmospheric relative humidity of ca. 0.2 %. The ±15 per meg reproducibility on the measurement of phytolith 17O excess corresponds to a ±3.6 % precision on the reconstructed relative humidity. The low sensitivity of phytolith 17O excess to climate parameters other than relative humidity makes it particularly suitable for quantitative reconstructions of continental relative humidity changes in the past.

Efficient CO sensing by a CuO:Au nanocomposite thin film deposited by PLD on a Pyrex tube

Carbon monoxide gas is a highly toxic, poison gas in air that can lead to death, if inhaled by humans for a prolonged time. It is produced from incomplete various combustion processes (natural gas, gasoline of cars, outdoor fires, etc.), and circulates the same way as air as its density is close to air density. Moreover, it is a tasteless, colorless and odorless gas. Therefore, efficient CO sensors are necessary with high efficiency, low cost and easily production, low power consumption, simplicity and robustness in their operation. Such sensors can be realized by electrochemical, semiconducting metal oxide thin films. A p-type pure CuO and CuO:Au compound thin film sensor has been grown by Pulsed Laser Deposition on the surface of a Pyrex tube (Din = 8 mm, thickness 1 mm) and CO sensing has been performed with a concentration as low as ca. 60 ppm/air. A cheap, home-made and with low power consumption ceramic heater was inserted into the tube reaching operating temperature up to 450 °C. A granular film surface revealed by AFM and SEM measurements, indicating a large effective surface for gas sensing. EDS surface mapping indicated the Au existence on the CuO:Au compound film homogeneously covering the whole film surface. CO sensing measurements were performed for 305, 325, 345 °C operating temperatures and for a large number of CO concentrations in air.

Alternating Wet-Dry Cycles Rather than Sulfate Fertilization Control Pathways of Methanogenesis and Methane Turnover in Rice Straw-Amended Paddy Soil.

Alternate wet-drying (AWD) and sulfate fertilization have been considered as effective methods for lowering CH4 emissions from paddy soils. However, there is a clear knowledge gap between field studies that focus on the quantification of emissions and laboratory studies that investigate mechanisms. To elucidate mechanisms of CH4 production and oxidation under field conditions, rice was planted in straw-amended mesocosms with or without sulfate fertilization under continuously flooded conditions (FL) or two wet-dry cycles. CO2 and CH4 concentrations in soil air and their natural C isotope compositions were measured at stem elongation, booting, and flowering stages. CH4 concentration reached 51 mg C L-1 at the flowering stage under FL, while it decreased to 0.04 mg C L-1 under AWD. Relative 13C enrichment in CH4 and depletion in CO2 under AWD indicated CH4 oxidation. Ample organic substrate supply may have reduced competition between sulfate-reducing bacteria and methanogenic archaea, and therefore, it explains the absence of a decrease in CH4 concentrations in sulfate treatments. 13C enrichment in CO2 over time (6 and 7‰ with and without sulfate fertilizers, respectively) under FL indicates continuous contribution of hydrogenotrophic methanogenesis to CH4 production with ongoing rice growth. Overall, AWD could more efficiently reduce CH4 production than sulfate fertilization in rice straw-amended paddy soils.

Use of optimised MLP neural networks for spatiotemporal estimation of indoor environmental conditions of existing buildings

Controlling the indoor environmental quality in real time is essential for the health, well-being and productivity of occupants of a building. In recent years, research has focused on improving monitoring devices and strategies and developing techniques for estimating indoor conditions. The use of machine learning algorithms in this context has increased considerably. However, monitoring data in real time from large multizone working areas is challenging. The aim of this work is to provide an interpolation methodology based on the use of optimised multilayered perceptron neural networks to estimate the indoor environmental conditions of a building in real time. These estimations are obtained without the need for neither monitoring in the occupied working area nor human intervention and considering low-cost sensors. The neural network is optimised by implementing the multiobjective genetic algorithm NSGA-II to find the best architecture in terms of error and complexity. This method was applied to the building of a research centre in north-western Spain, where interpolated values for indoor air temperature, relative humidity and CO2 concentration were obtained. The results of this case study yielded relative errors close to 6% for temperature, 5% for relative humidity, and 12% for CO2 concentration. These values validate the methodology developed for the estimation of indoor environmental conditions and the contribution of this research to the improvement of the monitoring and control of the indoor environmental quality of a building.

Building pathology and environment: Weathering and decay of stone construction materials subjected to a Csa mediterranean climate laboratory simulation

Building stone materials have to satisfy long-term durability requirements in different environments in terms of mechanical strength and resistance to aggressive conditions. Several studies and field observations show that weathering on geo-materials is related to average annual precipitation and temperature.The decay also depends on salts air/soil concentrations and biological agents, but the more harmful impact is given by greenhouse gas (e.g. CO2, SOX, NOX, O3). These last induce the acidification of the rain and runoff waters. Nowadays, decay prediction is required in order to estimate the behaviour of stone materials over time. This research represents a second part of a previous work where the response to weathering of some construction materials used in ancient and contemporary architecture and cultural heritage has been evaluated by a laboratory simulation of hot-summer Csa Mediterranean climate. Simulation consists of accelerate ageing test on climate chamber by reproducing macro (e.g. daily and seasonal cycles of temperature, relative humidity, CO2 air concentration) and micro (e.g. rain, soil capillary rising) environments. Some non-destructive testing were executed to evaluate some physical–mechanical “decay markers” before and after the ageing. Test caused both decreasing and increasing of Leeb D hardness, decreases of permeability and a general decrease of ultrasonic speed, mainly due to the formations of patinas, crusts and efflorescences on the surfaces.

Air Quality Monitoring During High-Level Biocontainment Ground Transport: Observations From Two Operational Exercises.

Stretcher transport isolators provide mobile, high-level biocontainment outside the hospital for patients with highly infectious diseases, such as Ebola virus disease. Air quality within this confined space may pose human health risks. Ambient air temperature, relative humidity, and CO2 concentration were monitored within an isolator during 2 operational exercises with healthy volunteers, including a ground transport exercise of approximately 257 miles. In addition, failure of the blower unit providing ambient air to the isolator was simulated. A simple compartmental model was developed to predict CO2 and H2O concentrations within the isolator. In both exercises, CO2 and H2O concentrations were elevated inside the isolator, reaching steady-state values of 4434 ± 1013 ppm CO2 and 22 ± 2 mbar H2O in the first exercise and 3038 ± 269 ppm CO2 and 20 ± 1 mbar H2O in the second exercise. When blower failure was simulated, CO2 concentration exceeded 10000 ppm within 8 minutes. A simple compartmental model predicted CO2 and H2O concentrations by accounting for human emissions and blower air exchange. Attention to air quality within stretcher transport isolators (including adequate ventilation to prevent accumulation of CO2 and other bioeffluents) is needed to optimize patient safety.

Assessment of Nutritional and Quality Properties of Leaves and Musts in Three Local Spanish Grapevine Varieties Undergoing Controlled Climate Change Scenarios.

The market demand together with the need for alternatives to withstand climate change led to the recovery of autochthonous grapevine varieties. Under climate change, the summer pruning of vineyards may lead to an increase of vegetative residuals of nutritional and medicinal interest. The objectives of our study were (1) to evaluate the nutritional properties of the leaves of three local Spanish grapevines (Tinto Velasco, TV, Pasera, PAS, and Ambrosina, AMB) when grown under climate change conditions, and (2) to test the potentiality of these grapevines as suitable candidates to be cultivated under climate change scenarios based on the quality of their must. Experimental assays were performed with fruit-bearing cuttings grown in temperature gradient greenhouses that simulate rising CO2 (700 μmol mol−1) and warming (ambient temperature +4 °C), either acting alone or in combination. TV and AMB were the most and the least affected by air temperature and CO2 concentration, respectively. The interaction of elevated CO2 with high temperature induced the accumulation of proteins and phenolic compounds in leaves of TV, thus enhancing their nutritional properties. In PAS, the negative effect of high temperature on protein contents was compensated for by elevated CO2. Warming was the most threatening scenario for maintaining the must quality in the three varieties, but elevated CO2 exerted a beneficial effect when acting alone and compensated for the negative effects of high temperatures. While TV may be a candidate to be cultivated in not very warm areas (higher altitudes or colder latitudes), PAS behaved as the most stable genotype under different environmental scenarios, making it the most versatile candidate for cultivation in areas affected by climate change.

Consecutive 4-year Elevated Atmospheric CO2 on Shaped Microbial Communities in the Rhizosphere Soil of Robinia pseudoacacia L. Seedlings Grown in Pb-contaminated Soils

Elevated atmospheric CO2 could affect the speciation of heavy metals in rhizosphere soils by changing root exudates, thereby influencing soil microecosystem in the rhizosphere. Therefore, understanding the function of heavy metals in soils on rhizospheric ecology under elevated atmospheric CO2 scenarios is highly important. Here, we investigated the combined effects of a four-year period of elevated air CO2 concentrations[(700±27) μmol·L-1] and Pb-contamination (15.6 mg·kg-1 and 515.6 mg·kg-1) on the soil rhizopheric microbial community of Robinia pseudoacacia L. seedlings. Significant (P<0.05) effects of CO2, Pb, and their interaction on bacterial richness and fungal diversity were observed. Relative to Pb exposure alone, elevated CO2 significantly increased pH, total C, total N, and water-soluble organic carbon, and the C/N ratio under Pb exposure (P<0.05) and significantly decreased total and soluble Pb content (P<0.05). The richness and diversity of bacteria increased (P<0.05), fungal richness decreased (P<0.05), and microbial diversity increased (P<0.05) under the combined treatments relative to Pb contamination alone. The changes in the relative abundance of the top two dominant bacterial and fungal genera were not significant; however, differences in the relative abundances of other groups, such as Anaerolineaceae, Solirubrobacterales, Eurotiomycetes, Aspergillus, and Trichocomaceae, were significant between the different treatments. According to a redundancy analysis, total C and soluble Pb had a significant influence (P<0.05) on the dominant bacterial genera, and total C affected (P<0.05) the dominant genera in the fungal community. These results suggest that the responses of soil environmental factors to the combination of elevated atmospheric CO2 and Pb could shape soil microbial community structure in the rhizosphere of R. pseudoacacia seedlings.

Environmental factors affecting sleep quality in summer: a field study in Shanghai, China.

Although the environment can greatly influence an individual's sleep quality, China is yet to conduct comprehensive research on the topic. This study investigated the bedroom environment and sleep quality of 41 households during summer in Shanghai. Bedroom environments were comprehensively evaluated through environmental perception questionnaires filled by participants after waking up every morning. Parameters, such as air temperature, relative humidity, CO2 concentration, and noise level were continuously monitored. Furthermore, participants' sleep quality was observed using both subjective questionnaires and physiological measures. Environmental measurements showed that the most comfortable air temperature and relative humidity was 24.8°C and 64%, respectively. Physiological measurements showed that the average duration of slow wave sleep (SWS) and sleep efficiency (SE) was 73.8min and 86.7%, respectively. Additionally, SWS was negatively correlated with air temperature (r=-0.377, p=0.015) and CO2 concentration (r=-0.362, p=0.02), and SE was negatively correlated with noise level (r=-0.32, p=0.042). The subjective and objective results consistently indicated that higher air temperature, CO2 concentration, and noise level leads to poor sleep quality in summer. In addition, air temperature and CO2 concentration had a greater impact on the sleep quality of males, while noise level had a greater impact on the sleep quality of females.

Effects of Climatic Conditions, Season and Environmental Factors on CO2 Concentrations in Naturally Ventilated Primary Schools in Chile

Between the ages of 6 and 18, children spend between 30 and 42 h a week at school, mostly indoors, where indoor environmental quality is usually deficient and does not favor learning. The difficulty of delivering indoor air quality (IAQ) in learning facilities is related to high occupancy rates and low interaction levels with windows. In non-industrialized countries, as in the cases presented, most classrooms have no mechanical ventilation, due to energy poverty and lack of normative requirements. This fact heavily impacts the indoor air quality and students’ learning outcomes. The aim of the paper is to identify the factors that determine acceptable CO2 concentrations. Therefore, it studies air quality in free-running and naturally ventilated primary schools in Chile, aiming to identify the impact of contextual, occupant, and building design factors, using CO2 concentration as a proxy for IAQ. The monitoring of CO2, temperature, and humidity revealed that indoor air CO2 concentration is above 1400 ppm most of the time, with peaks of 5000 ppm during the day, especially in winter. The statistical analysis indicates that CO2 is dependent on climate, seasonality, and indoor temperature, while it is independent of outside temperature in heated classrooms. The odds of having acceptable concentrations of CO2 are bigger when indoor temperatures are high, and there is a need to ventilate for cooling.

External controls on CO2 in Gibraltar cave air and ground air: Implications for interpretation of δ13C in speleothems

The principles of cave ventilation and ground air advection are outlined. CO2 concentrations were monitored every 2–4 h from 2006 to 2012 at twelve locations in two Gibraltar caves, New St. Michael's (240–275 m altitude) and Ragged Staff (0–70 m), providing detailed records of spatial distribution and temporal changes responding to transient meteorological conditions and seasonal cycles. Cave atmospheres are dynamic mixtures of external air and CO2-rich ground air containing soil-respired CO2 augmented by CO2 derived from oxidation of organic matter washed down into the vadose fracture porosity. The dominant feature of the cave air records is seasonal alternation between high and low CO2 states caused by reversals in ventilation and ground air advection into or away from the caves. The high and low pCO2 states are tightly coupled between the two caves in an antiphase relationship, with rapid switching in response to temperature-controlled density differences between external air and isothermal ground air at mean annual surface temperature (18 °C). The diurnal temperature cycle modulates this pattern, producing four ventilation-advection modes. Summer and winter modes occur when diurnal temperatures are respectively entirely above or below the core temperature of the Rock. During transitional modes the core temperature lies within the diurnal range and pCO2 fluctuates rapidly as the flow of low-CO2 external air through cave entrances alters in response. Strong easterly winds reduce CO2 concentrations in ground air entering the caves and progressively lower cave air CO2. The effects of the CO2 regime on δ13C in speleothem are restricted to variations of 2–3‰, suggesting that larger changes of up to 6‰ across major climatic transitions probably reflect changes in production, transport and oxidation rate of organic matter in the vadose zone. Direct observations of these processes would improve future understanding of the climatic significance of δ13C records in speleothems.