Assessment of CO2 and aerosol (PM2.5, PM10, UFP) concentrations during the reopening of schools in the COVID-19 pandemic: The case of a metropolitan area in Central-Southern Spain

CO2 concentration monitoring inside educational buildings as a strategic tool to reduce the risk of Sars-CoV-2 airborne transmission

This study aimed to assess the seasonal fluctuation of heavy metal contamination in the sediments and surface water of the Narmada River. In this context, samples were gathered from six stations along the river in 2021–2022 and their concentrations were determined by utilizing Inductively Coupled Plasma-Mass Spectrometry (ICP-MS). The results in sediments, the average concentrations of As, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were 0.05, 1.03, 2.47, 1.64, 750.17, 17.75, 0.54, 0.13, and 1.12 mg/kg and in water, the average concentrations of Co, Fe, Ni, and Zn were 0.03 μg/l, 0.01 mg/l, 0.08 μg/l, and 0.39 μg/l. Seasonal fluctuation in sediments revealed that concentration of metals As, Cu, Fe, Ni, and Zn peaked during the rainy climate, while Co and Cr peaked during the post-monsoon and Mn and Pb peaked during the summer climate. Seasonal fluctuation in water, Co, Ni, and Zn exhibits their highest concentrations during the post-monsoon. The finding of pollution indices revealed that the contamination level was low to moderate. Cluster analysis revealed anthropogenic and agricultural runoff water as a contributor to contamination. The findings of this research enhance comprehension of heavy metal contamination in sediment and water of the Narmada River.

One of the aims of the environmental and energy policy of the European Union is to reduce the emission of air pollutants, primarily from heat and electricity production, e.g., using renewable energy sources. An example of such a fuel is agricultural biomass including animal manure, which can be used to produce energy in many ways, inter alia direct combustion. The aim of the study was to measure the concentration of NO, NOx, CO, dust and boiler efficiency during the combustion and co-combustion of wood and manure pellets. The research was conducted in the laboratory of the Poznań University of Technology using a 15 kW domestic boiler at maximum power. Manure pellets had higher moisture—9.2%, lower high heating value—17.25 MJ·kg−1, lower low heating value—16.45 MJ·kg−1, and higher ash content—11.23% than wood pellets. The average concentrations of CO, NO, NOx and dust for 100% wood pellets were 198 ± 27 mg·m−3, 129 ± 5 mg·m−3, 198 ± 8 mg·m−3 and 8.7 ± 0.5 mg·m−3, respectively. For this, the fuel boiler power was 13.6 kW (air–fuel ratio 1.48), and it was close to the maximal nominal power. Increasing the share of manure pellets in the burning mixture worsened the stability of the combustion process, and the occurrence of incomplete combustion was observed, which resulted in an increased concentration of CO and dust. Additionally, NO and NOx concentrations also increased. The average boiler power during the combustion of 100% manure pellets was 7.8 kW (air–fuel ratio 2.2), and the average concentrations of CO, NO, NOx and dust were 1548 ± 555 mg·m−3, 355 ± 53 mg·m−3, 554 ± 88 mg·m−3 and 482 ± 63 mg·m−3, respectively.

CO2 concentration as an indicator of indoor ventilation performance to control airborne transmission of SARS-CoV-2

Summary1. Climate change may significantly influence lake carbon dynamics and consequently the exchange of CO2 with the atmosphere. Warming will accelerate multiple processes that either absorb or release CO2, making predicting the net effect of warming on CO2 exchange with the atmosphere difficult. Here we experimentally test how the CO2 flux of deep and shallow systems responds to warming. To do this, we conducted a greenhouse experiment using mesocosms of two depths, experiencing either ambient or warmed temperatures.2. Deeper mesocosms were found to have a lower average CO2 concentration than shallower mesocosms under ambient temperature conditions. In addition, warming interacts with mesocosm depth to affect the average CO2 concentration; there was no effect of warming on the average CO2 concentration of deep mesocosms, but shallow mesocosms had significantly lower average CO2 concentrations when warmed.3. The difference in CO2 concentration resulting from the depth manipulation was due to varying loss rates of particulate carbon to the sediments. There was a strong negative correlation between CO2 and sedimentation rates in the deep mesocosms suggesting that high particulate carbon loss to the sediments lowered the CO2 concentration in the water column. There was no correlation between CO2 and sedimentation rates observed for shallow mesocosms suggesting enhanced carbon regeneration from the sediments was maintaining higher CO2 concentrations in the water column.4. Relationships between CO2 and algal concentrations indicate that the reduction in CO2 concentrations resulting from warming is due to increased per capita algal turnover rates depleting CO2 in the water column. Our results suggest that the carbon dynamics and CO2 flux of shallow systems will be affected more by climate warming than deep systems and the net effect of warming is to increase CO2 uptake.

In-kitchen air pollution is a leading environmental issue, attributable to extensive cooking, poor ventilation and the use of polluting fuels. We carried out a week-long monitoring of CO2, temperature and relative humidity (RH) in five low-income residential kitchens of 12 global cities (Dhaka, Chennai, Nanjing, Medellín, São Paulo, Cairo, Sulaymaniyah, Addis Ababa, Nairobi, Blantyre, Akure and Dar-es-Salaam). During cooking, the average in-kitchen CO2 concentrations were 22.2% higher than the daily indoor average. Also, the highest CO2 was observed for NVd (natural ventilation-door only; 711 ± 302 ppm), followed by NVdw (natural ventilation-door + window; 690 ± 319 ppm) and DVmn (dual ventilation-mechanical + natural; 677 ± 219 ppm). Using LPG and electric appliances during cooking exhibited 32.2% less CO2 than kerosene. Larger kitchens (46–120 m3) evinced 28% and 20% less CO2 than medium (16–45 m3) and small (4–15 m3) ones, respectively. In-kitchen CO2 with >2 occupants during cooking was 7% higher than that with one occupant. 87% of total kitchens exceeded the ASHRAE standard (RH >40%, temperature >23 °C) for thermal comfort. Considering the ventilation type, both the ACH (air change rate per hour) and ventilation rate followed the order: NVdw > NVd > DVmn, while the trend for weekly average CO2 concentration was NVd > DVmn > NVdw. Larger kitchens presented 22% and 28% less ACH, and 82% and 190% higher ventilation rate than medium- and small-volume ones, respectively. Forty-three percent kitchens had ACH <3 h−1 and ventilation rate <4 L/s/person, hence violated the conditions for ideal ventilation. Moreover, 10% of the Hazard Ratio values for 25% kitchens exceeded the CO2 reference value (1000 ppm). Consequently, our findings prompted several recommendations towards improving in-kitchen ventilation and environmental conditions of low-income homes.

Ventilation and laboratory confirmed acute respiratory infection (ARI) rates in college residence halls in College Park, Maryland

Using a portable CO2 sensor, the CO2 concentration in a classroom at Wakayama University was measured and “natural ventilation”, the open door or window effect was evaluated based upon the number of persons, room size, door or window condition and CO2 concentration. Under no ventilation condition in the classroom, increase of CO2 concentration was 2,000 to 4,000 ppm after 90 minutes and CO2production per person per hour due to respiration was 0.005 to 0.015 m3/hour/person during a lecture.Comparing CO2 concentration under no ventilation condition with under natural ventilation condition, effect of natural ventilation to reduce CO2 concentration per open space size was calculated. The amount of CO2gas exchanged outside through doors or windows by natural ventilation was in agreement with the amount of CO2 gas produced by respiration in the room when sizes of open doors or windows were 2.3 to 12.8 m2or ratios of total room volumes per open door or window sizes were 40 to 180 m.

Prediction of seasonal extremes of one-hour average urban CO concentrations

As an important source of greenhouse gases, the changes in greenhouse gas concentrations of aquaculture ponds are not only the basis for accurate quantification of greenhouse gases emissions but are also important for identifying their influencing factors. The spatial and temporal variation characteristics of CH4, CO2, and N2O concentrations and the influencing factors in a typical small aquaculture pond in the Yangtze River Delta were analyzed based on the headspace equilibrium-gas chromatograph method. Except in spring, the concentrations of CH4, and N2O appeared high at noon or afternoon and were influenced by water temperature. Impacted by water temperature and aquatic plant photosynthesis, the concentrations of CO2 were high in the morning when photosynthesis was weak. The concentrations of CH4 and CO2 were the highest in autumn and the lowest in winter. The mean concentrations of CH4 in autumn and winter were 176.34 nmol·L-1 and 32.75 nmol·L-1, respectively, which were mainly affected by air temperature, water temperature, and dissolved oxygen. The average CO2 concentrations in autumn and winter were 134.37 μmol·L-1 and 23.10 μmol·L-1, respectively, and were mainly affected by aquatic vegetation photosynthesis and pH. N2O concentration was the highest in summer and the lowest in winter, with mean values of 97.05 nmol·L-1 and 19.41 nmol·L-1, respectively, which were mainly affected by air temperature and water temperature. In terms of the vertical spatial variations of the three greenhouse gases, the concentration of CH4decreased with water depth in summer, and the concentration differences between the surface layer and the bottom and middle layers were 71.28 nmol·L-1 and 42.80 nmol·L-1, respectively. The concentration of CH4 increased with water depth in autumn, and the concentration difference between the bottom layer and surface layer was 163.94 nmol·L-1. The CO2 concentration increased with water depth in summer and autumn. The concentration differences between the bottom and surface concentrations were 18.69 μmol·L-1 and 29.90 μmol·L-1, respectively. N2O concentration showed no obvious change in the vertical direction. For the horizontal variations, the concentrations of CH4, CO2, and N2O in the feeding area in summer and in chicken manure in spring were approximately 1.34-1.98 times and 1.95-2.42 times those in other areas, respectively, and the concentrations of N2O and CO2 in spring and summer were approximately 1.13-1.26 times and 1.39-1.74 times those in other areas.

The increasing quantity of air pollutants generated by automobiles can cause significant harm in relatively enclosed indoor environments. Studying the distribution of pollutants under different conditions in underground parking garages is of great significance for improving indoor air quality and reducing casualties in the event of a fire. This article presents a geometric model of an underground parking garage based on PHOENICS modeling. The related results of CO concentration distribution and fire temperature distribution under ventilation and fire conditions are obtained. Based on the CO concentration and velocity distribution as well as the temperature distribution during a fire, reasonable suggestions are proposed to improve indoor air quality and reduce casualty rates in fire incidents. The results show that under ventilation conditions, adjusting the position of the induced ventilation fan can maintain CO concentrations below 30 ppm in partitions one to three and below 37 ppm in partitions four to six. The temperature of smoke gases remained below 50 °C during the evacuation time, and only a small area exhibited CO levels exceeding 2000 ppm. The existing ventilation exhaust system provides effective fire protection, as it minimally affects personnel evacuation due to the relatively lower smoke temperature.

CO2 concentration is one air quality parameter set by WHO. High concentrations of carbon dioxide will have an impact on human health. CO2 is a gas that can cause a greenhouse effect in a city like Surabaya. This study aims to reveal the dynamics of CO2 concentration in northern Surabaya, which is a center of urban activity in Surabaya. This type of research is descriptive analytic with a quantitative approach. The population used is based on the division of administrative regions in Surabaya u tara section. Sampling is carried out in a purposive way, where each land use is taken five locations. Data collection techniques use measurement and observation. The data analysis technique used is descriptive. The results of the data analysis showed that there was a difference in the average CO2 concentration in the morning and evening. All research sites have CO2 concentrations above the safe threshold of CO2 concentrations set by WHO. There is an increase in CO2 concentrations in the morning and evening variably. The average CO2 concentration in the morning was recorded at 436.05 ppm and increased at night to 518 ppm. The highest CO2 concentration in the morning occurred on Colombo road at 467 ppm and the lowest at 345 ppm on Bangunsari road. The highest average CO2 concentration at night occurred on Morokrembangan road, which was 558 ppm and the lowest on Bangunsari road was 460 ppm.&#x0D; Keywords: CO2 concentration, air pollution, northern Surabaya

Spatio-temporal variability of Atmospheric CO2 and CH4 concentrations over Antarctica using Ground and Space-based measurements

During the COVID-19 pandemic, the importance of ventilation was widely stressed and new protocols of ventilation were implemented in school buildings worldwide. In the Netherlands, schools were recommended to keep the windows and doors open, and after a national lockdown more stringent measures such as reduction of occupancy were introduced. In this study, the actual effects of such measures on ventilation and thermal conditions were investigated in 31 classrooms of 11 Dutch secondary schools, by monitoring the indoor and outdoor CO2 concentration and air temperature, both before and after the lockdown. Ventilation rates were calculated using the steady-state method. Pre-lockdown, with an average occupancy of 17 students, in 42% of the classrooms the CO2 concentration exceeded the upper limit of the Dutch national guidelines (800 ppm above outdoors), while 13% had a ventilation rate per person (VRp) lower than the minimum requirement (6 l/s/p). Post-lockdown, the indoor CO2 concentration decreased significantly while for ventilation rates significant increase was only found in VRp, mainly caused by the decrease in occupancy (average 10 students). The total ventilation rate per classrooms, mainly induced by opening windows and doors, did not change significantly. Meanwhile, according to the Dutch national guidelines, thermal conditions in the classrooms were not satisfying, both pre- and post-lockdown. While opening windows and doors cannot achieve the required indoor environmental quality at all times, reducing occupancy might not be feasible for immediate implementation. Hence, more controllable and flexible ways for improving indoor air quality and thermal comfort in classrooms are needed.

The air quality in educational campuses affects the health and work efficiency of teachers and students. Studies into this matter are of great significance for optimizing the management of campus living environments. Low-cost online sensors to monitor PM2.5 and CO2 levels were used in typical functional areas of a university campus in Beijing, China, including offices, dormitories, leisure spaces, canteens, and laboratories. By comparing the findings with data from nearby national monitoring stations, the seasonal and spatial variations in PM2.5 and CO2 concentrations were analyzed. Findings indicate PM2.5 levels within the campus were notably lower compared to the surrounding urban environment. There was variation in PM2.5 and CO2 concentrations across different functional areas. Typically, indoor PM2.5 levels were lower than outdoor ones, while CO2 concentrations in enclosed indoor spaces with human activities progressively escalated. The main internal emission sources affecting the PM2.5 level on campus included traffic emissions, dust generated by human activities, and emissions from catering. In contrast, in areas with better green coverage or where a lake system participates in the atmospheric circulation, the PM2.5 level and CO2/PM2.5 were lower. This indicates that the cleansing impact of plants and aquatic systems is instrumental in lowering PM2.5 concentrations, offering healthier leisure spaces. Seasonal variations also impact PM2.5 levels. During the non-heating period, less pollution source emissions led to decreased outdoor PM2.5 concentrations. The campus monitoring sites experienced an approximate 5 µg/m3 and 29 µg/m3 reduction in the average PM2.5 levels as compared to the PM2.5 of the surrounding urban environment, respectively, during the non-heating and heating period. During indoor activities or sleep, CO2 levels can build up to as high as 2303 ppm due to breathing. It is advisable to stay indoors on days when pollution levels are high, whereas on days with clean air, it is healthier to be outdoors or to air out indoor areas by opening windows. Our research provides clearer scientific evidence for incorporating behavioral strategies for improving air quality into both daily work and life. Moreover, the findings are quite meaningful for the widespread adoption of low-cost sensor monitoring in various environments, with applications beyond just the campus settings.