Maximum CO2 Concentration Research Articles

Understanding landfill gas behavior at elevated temperature landfills

Landfill gas (LFG) wellhead data were compared to understand the range of observations due to unique conditions at five elevated temperature landfills (ETLFs) in the U.S. Correlations of the primary gas ratio, CH4:CO2, show distinct compositional indicators for (1) typical operation, (2) subsurface exothermic reactions (SERs), (3) high moisture content, and (4) air intrusion that can help operators and regulators diagnose conditions across gas extraction wells. ETLFs A, B, D, and E showed similar trends, such as decreasing CH4 and increasing CO2, CO, and H2 that have been previously described. ETLF C uniquely exhibited elevated CH4 and temperatures simultaneously due to carbonation (i.e., CO2 consumption) of a steel slag which was used as alternative daily cover (ADC). At the maximum gas well temperature, T = 82 °C/180 °F, CH4 and CO2 concentrations were 47% and 28%, respectively. At ETLFs A, B, and E, H2 > 50% were regularly observed in affected gas wells for several years. At the five ETLFs, maximum CO concentrations ranged from 1400–16,000 ppmv. Like the analysis of CH4:CO2, it is hypothesized here that H2 (%):CO (ppmv) may infer the types of waste that are thermally degrading. Co-disposal of industrial wastes and MSW and the use of potentially reactive ADCs should remain an important consideration for landfill operators and regulators because of their potential long-term impacts to LFG quality.

Impacts of different biomass burning emission inventories: Simulations of atmospheric CO2 concentrations based on GEOS-Chem

Biomass burning has substantial spatiotemporal variabilities. It contributes significantly to the dynamics of global CO2 distributions and variances. Quantifying the impacts of biomass burning emissions on atmospheric CO2 concentrations is essential for global and regional carbon cycles and budgets. In this study, we performed several numerical experiments by switching and replacing inventories to estimate the impacts of four biomass burning emission inventories on atmospheric CO2 concentration simulations in 2006–2010 based on the global chemical transport model, GEOS-Chem. The results highlighted similarities and differences in the annual and seasonal variability of biomass burning emissions and simulated CO2 concentrations at global and regional scales. Based on four different biomass burning emission inventories, we found that biomass burning emissions could lead to a global CO2 concentration increase of 2.4 ppm annually. Africa contributed the largest global CO2 emissions among all continental regions, where the maximum CO2 concentration increase could reach 7.9–13.0 ppm in summer. Model evaluation results showed that simulation using the Quick Fire Emissions Database (QFED) as the model priori biomass burning emission inventory had the best performance compared with the satellite and surface observations. The sensitivity of simulated CO2 concentrations to the uncertainties in different biomass burning emission inventories was high in southern South America and most areas of the Eurasian continent, and low in central Africa and Southeast Asia. This study furthers our understanding of the critical role of biomass burning in atmospheric CO2 and indicates an urgent need to improve the accuracy of biomass burning emission estimates in CO2 simulations.

Effect of non-thermal plasma dielectric barrier discharge reactor on the quality of biomass gasification product gas from the gasifier

The primary goal of this research is to determine the effect of key processing parameters of dielectric barrier discharge (DBD) reactor on the components concentration of the fuel gas produced during the biomass gasification. By changing key processing parameters such as plasma input power, flow rate, and temperature, the performance of the DBD reactor is assessed. When the power is increased from 5 to 40 W, the concentrations of CO2 and H2 decrease to 12.9% and 18.5%, respectively, while the concentration of CO increases to 17.2%. At 40 W and 65 ml/min, the amount of tar compound significantly drops from 33 g/Nm3 to less than 1 g/Nm3. However, as input power increases, the concentration of C1–C5 hydrocarbons also tends to rise. The highest concentration of C1–C5 was around 0.60% at 40 W. As the flow rate increases, the concentration of CO2 increases while the concentration of CO tends to decrease at all measured power levels, the maximum concentration of CO2 was at 120 ml/min, whereas the minimum concentration of CO is seen under same conditions. With an increase in flow rate, the concentration of CH4 shows a decreasing tendency. It is seen that at 40 W, the concentration of CO and H2 drops as the temperature rises up to 400 °C. In contrast, there is a rising trend in the concentration of CO2, CH4, and tar compounds while increasing temperature. Hence, the DBD reactor appears to have a profound influence on a gas component produced during biomass gasification.

Contamination and risk surveillance of potentially toxic elements in different land-use urban soils of Osogbo, Southwestern Nigeria.

The concentrations of potentially toxic elements (PTEs) and their contamination indices were determined in urban soil from five different land-use zones, namely municipal solid waste landfill (MWL), industrial area (INA), heavy traffic area (TRA), residential area with commercial activities (RCA), and farmland (FAL) in Osogbo Metropolis. Ecological and human health risk assessments were also evaluated. Based on the average concentrations, the highest values of As, Cr, Cu, Fe, Mn, Ni, Pb, V, and Zn were found at INA, while the maximum concentrations of Ba, Cd, and Co were observed at MWL. The average enrichment factor (EF) values of Cd, Cu, Pb, and Zn showed very high to extremely high enrichment in the soils of INA, MWL, TRA, and RCA, while the EF values of Ba, Co, Cr, Fe, Ni, and V were significantly to moderately enriched in the aforementioned land-use zones. This trend was consistent with the average contamination factor (Cf) values of Cd, Cu, Pb, and Zn, which indicated considerable to very high contamination at INA, MWL, TRA, and RCA. However, Cf values of Ba, Co, Cr, Fe, Ni, and V had moderate contamination variously at the different land-use zones. Furthermore, the potential ecological risk factor (Eri) values for all the PTEs were < 40, which indicated low Eri, except for Cd and to some extent Pb. The Eri value of Cd was high to very high at MWL, INA, TRA, and RCA, and low at FAL, while Eri of Pb was only moderate at INA. Assessment of health quotient (HQ) of non-carcinogenic health risks was within acceptable limit (< 1) for most of the PTEs in the different zones for adults and children, except the maximum HQ value of Pb at INA (HQ = 1.0), which was beyond the acceptable limit for children. The carcinogenic risk was within the acceptable limit (1.0 × 10-6) in all the zones, except INA. This may pose health challenges to children in the vicinity of the pollution sources. Continuous monitoring of PTEs to reduce exposure to PTE should be considered.

Low frequency changes in CO2 concentration in East Asia related to Pacific decadal oscillation and Atlantic multi-decadal oscillation for mid-summer and early fall

The climatological seasonal maximum and minimum CO2 concentrations in East Asia for 1987–2020 have been recorded at April and August, respectively. We found that the CO2 concentration in East Asia during July, August, and September (JAS) is lower than normal before the late 1990s and after the early 2010s (Low_CO2 period), and higher than normal from the late 1990s to the early 2010s (High_CO2 period). The low-frequency variability of CO2 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_CO2 period than that in Low_CO2 period, possibly due to PDO and AMO-related SST forcing, which decreases vegetation's photosynthetic activity. This may lead to a higher CO2 concentration than normal in East Asia in High_CO2 period through reduced uptake of CO2 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.

Bismuth Manganese Catalysts for Soot Oxidation in Diesel Engine Exhaust: Effect of Preparation Methods on Active Oxygen Species

AbstractTo manufacture efficient and cost‐effective catalysts for soot combustion, a series of MnxBiOy catalysts with different molar ratios of manganese bismuth (x=1,3,6,9) were prepared by hydrolysis driven redox, coprecipitation and hydrothermal synthesis methods (named R−MnxBiOy, Cop−MnxBiOy and H−MnxBiOy, respectively). The physicochemical properties of the as‐prepared catalysts were characterized via powder X‐ray diffraction (XRD), transmission electron microscope (TEM), temperature‐programmed reduction by hydrogen (H2−TPR), X‐ray photoelectron spectroscopy (XPS), and so on. The catalytic performance results show that R−Mn3BiOy catalyst obtained by hydrolysis‐driven redox method exhibited highest catalytic activity with a maximum concentration of CO2 at 390 °C (T10=330 °C, T50=385 °C, and T90=425 °C). Meanwhile, the reaction mechanism of R−Mn3BiOy catalysts was also proposed based on the characterization results. The reason for high catalytic is related to the uniform distribution of Bi on the surface of Mn, which forms more lattice defects, thereby generating a large number of oxygen vacancies and providing more active sites for catalytic reactions. This provides a reference for the design of efficient and stable soot catalysts.

The Experimental Study of the Efficiency of the Gasification Process of the Fast-Growing Willow Biomass in a Downdraft Gasifier

In this work, a study was performed on the influence of the ratio of height to the diameter of the reduction zone of a small-size downdraft gasifier as well as of the fuel fraction sizes on the gas quality (the quality was evaluated for CO content). The ratio of a full side area to the volume of a fuel fraction (SVR) was used as a fuel parameter. The maximum CO concentration was observed when using a small fuel fraction with SVR—0.7–0.72 mm−1 and when adhering to the ratio of height to the diameter of the reduction zone H/D—0.5–0.6. The maximum electric power for gasoline generators (nominal power equaled 4 kW) when using the gas received from the fast-growing hybrid willow biomass equaled 2.4 kW. This power is 37.5% lower than when using gasoline and 7.0% lower than when using the gas received from the hardwood biomass. The emissions of harmful gases into the atmosphere by the gasoline generator engine equaled 0.12–0.14% CO and 24–27 mln−1 CxHy. The emissions were 64.8 times less for CO and 8.5 times less for CxHy when compared with using gasoline.

Air quality investigation and research for various types of student-oriented indoor environments on a university campus

This study investigated suspended particles (PM2.5 and PM10), formaldehyde, TVOC, ozone, carbon dioxide, and carbon monoxide in seven student-oriented indoor environments, which are inclusive of the library study room (A), computer classroom (B), teacher and student compound office (C), classroom-1 (D), classroom-2 (E), student cafeteria (F), and underground motorcycle parking lot (G) on a university campus. We monitored each indoor environment during the open hours for at least three weekdays. The averaged concentrations of CO2 in environments A, B, C, and D all exceeded the standard (1000 ppm) with values of 2,628±375, 1,908±613, 1,752±495, and 1,076±280 ppm. The corresponding minimum and maximum CO2 concentrations were 1,101 and 3,314, 836 and 3,272, 672 and 2,667, and 752 and 2,040 ppm, respectively. Sites A, B, C, D, F, and G are the environments where the concentrations of TVOC exceeded the standard (560 ppb) with the averaged values of 829±21, 920±192, 582±8, 607±15, 640±102 and 815±205 ppb, respectively. Both concentrations of PM2.5 and PM10 in site F exceeded the standards (i.e., 35 μg/m3 and 75 μg/m3) with averaged values of 39±13 μg/m3 and 103±51 μg/m3, respectively. Three target compounds, CO, O3, and HCHO, were below their respective standards.

Measurement and rapid assessment of indoor air quality at mass gathering events to assess ventilation performance and reduce aerosol transmission of SARS-CoV-2.

To assess risk factors for COVID-19 transmission and address the closure of mass gathering events since March 2020, the UK Government ran the Events Research Programme (ERP), following which it reopened live events in sports, music, and culture in July 2021. We report the rapid post-occupancy evaluation of Indoor Air Quality (IAQ) and associated long-range airborne transmission risk conducted in the Environmental Study of the ERP. Ten large venues around the UK were monitored with CO2 sensors at a high spatial and temporal resolution during 90 events. An IAQ Index based on CO2 concentration was developed, and all monitored spaces were classified in bands from A to G based on their average and maximum CO2 concentrations from all events. High resolution monitoring and the IAQ Index depicted the overall state of ventilation at live events, and allowed identification of issues with ventilation effectiveness and distribution, and of spaces with poor ventilation and the settings in which long-range airborne transmission risk may be increased. In numerous settings, CO2 concentrations were found to follow patterns relating to event management and specific occupancy of spaces around the venues. Good ventilation was observed in 90% of spaces monitored for given occupancies. Practical applications: High-resolution monitoring of indoor CO2 concentrations is necessary to detect the spatial variation of indoor air quality (IAQ) in large mass gathering event venues. The paper summarises COVID-19 ventilation guidance for buildings and defines a methodology for measurement and rapid assessment of IAQ during occupancy at live events that can be implemented by venue managers. Comparisons of the CO2 concentrations measured during the events identified the spaces at high risk of long-range transmission of airborne pathogens. Building operators should be mindful of the ventilation strategies used relative to the total occupancy in different spaces and the occupant's activities.

Numerical study on the effects of primary air ratio on ultra-low-load combustion characteristics of a 1050 MW coal-fired boiler considering high-temperature corrosion

Primary air significantly impacts the ultra-low-load combustion of coal-fired utility boilers. In this study, eleven combustion scenarios with varied primary air ratios (the flowrate ratio of primary air to the total air, PAR) were numerically investigated for a 1050 MW double-tangential circular coal-fired boiler under ultra-low load. The effects of PAR on temperature distribution, coal burnout, and gas species were thoroughly examined. Meanwhile, special attention was paid to the reducing atmosphere near furnace walls for alleviating the problem of high-temperature corrosion. Results show that a relatively large high-temperature region in the furnace is achieved at PAR = 0.153, contributing to combustion stability under ultra-low load conditions. Although the residence time tends to be shortened as PAR increases from 0.123 to 0.275, the amount of unburned carbon in coal particles has a general trend of decreasing because of more available oxygen from primary air. Due to the high excess air coefficient at ultra-low load, strong reducing atmosphere and high-temperature regions mostly concentrate around the operating coal burners, posing corrosion hazard there. As PAR increases to 0.275, the area of high CO concentration regions near furnace walls and the maximum CO concentration decrease noticeably, indicating less pronounced high-temperature corrosion at large values of PAR. NO emissions increase from 294.4 mg/Nm3 to 823.7 mg/Nm3 with increasing PAR from 0.123 to 0.275. This is shown to be related to the weakened reducing atmosphere as well as the reduced residence time of the coal particles as PAR increases.

Particle-scale modelling of injected hydrogen and coke co-combustion in the raceway of an ironmaking blast furnace

Hydrogen is an environmentally friendly fuel that does not produce greenhouse gas (GHG) emissions. Its applications have attracted significant attention from many industries, especially the ironmaking industry, which consumes massive amounts of fossil energy. The injection of hydrogen into a blast furnace (BF) is one of the most promising low-carbon ironmaking routines. In this study, an experimentally validated CFD-DEM model is adopted to investigate the dynamics, microstructure and thermochemical behaviours in the raceway of a BF with hydrogen injection operations (HIOs), which include raceway evolution, force distribution and the co-combustion characteristics of hydrogen and coke. Some significant features are obtained through comparison analyses between HIOs and air injection operations (AIOs). In particular, the effects of the hydrogen injection concentration on the raceway size, gas temperature and components are studied. The simulation results show that a smaller raceway is formed under HIOs in comparison with that of AIOs. In addition, the gas temperature is higher near the tuyere but lower along the tuyere axis, and the oxygen consumption is larger and produces more CO. As the hydrogen injection concentration increases: (i) the raceway size and gas temperature decrease; (ii) the CO is generated at the early stage and the maximum CO2 concentration moves to inlet direction along the tuyere axis. The results provide new insights into the fundamental understanding of low-carbon ironmaking BF technology.

Effects of increased recirculation air rate and aircraft cabin occupancy on passengers’ health and well-being – Results from a randomized controlled trial

BackgroundAircraft cabins are special environments. Passengers sit in close proximity in a space with low pressure that they cannot leave. The cabin is ventilated with a mixture of outside and recirculated air. The volume of outside air impacts the carbon footprint of flying. Higher recirculation air rates could be considered to save energy and divert less kerosene from producing thrust. ObjectivesTo investigate whether higher recirculation air rates in aircraft cabins negatively affect passengers' health and well-being and if occupancy plays a role in this. MethodsIn a 2 (occupancy: full and half-occupied) X 4 (ventilation regime) factorial design with stratified randomization, participants were exposed in an aircraft segment in a low-pressure tube during a 4-h simulated flight. Ventilation regimes consisted of increasing proportions of recirculated air up to a maximum CO2 concentration of 4200 ppm. Participants rated comfort, health symptoms, and sleepiness multiple times. Heart rate (variability), as stress marker, was measured continuously. Results559 persons representative of flight passengers regarding age (M = 42.7, SD = 15.9) and sex (283 men) participated. ANCOVA results showed hardly any effect of both factors on self-reported health symptoms, strong main effects of occupancy on comfort measures, and interaction effects for sleepiness and physiological stress parameters: Participants in the half-occupied cabin hardly reacted to increased recirculation air rates and show overall more favorable responses. Participants in the fully occupied cabin reported higher sleepiness and had stress reactions when the recirculation air rate was high. DiscussionThis large-scale RCT shows the importance of occupancy, a previously neglected factor in indoor air research. The proximity of other people seems to increase stress and exacerbate reactions to air quality. Further studies on causal pathways are needed to determine if recirculation air rates can be increased to reduce the carbon footprint of flying without detrimental effects on passengers.

Analysis of Air and Soil Quality around Thermal Power Plants and Coal Mines of Singrauli Region, India.

Singrauli region is known as the energy capital of India, as it generates nearly 21 GW of electricity, supplied to various parts of the northern India. Many coal-based Thermal Power Plants (TPPs) using coal from several nearby coal mines, and numerous industries are set up in this region which has made it as one of the highly polluted regions of India. In the present study, detailed temporal analysis and forecast of carbon dioxide (CO2), nitrogen dioxide (NO2), sulfur dioxide (SO2), and methane (CH4) concentrations retrieved from satellite data have been carried out for the periods 2005–2020. Based on the classical multiplicative model and using linear regression, the maximum concentration of CO2, NO2, SO2, and CH4 in the year 2025 is found to be 422.59 ppm, 29.28 ppm, 0.23 DU, and 1901.35 ppbv, respectively. Detailed analysis shows that carbon dioxide has a 95% correlation with all other trace gases. We have also carried out the geo-accumulation index for the presence of various contaminants in the soil of this region. The geo-accumulation index shows that soil in and around thermal power plants and coal mines is contaminated by heavy metals. The cumulative index shows that soil around Hindalco industries, Bina coal mines, Khadia coal mines, and coal-based TPPs (Anpara and Vindhayachal) are highly polluted and a threat to human population living in the region.

Numerical Study on Combustion Behavior of Semi-Coke in Blast Furnace Blowpipe-Tuyere-Combustion Zone

Injecting low-cost semi-coke is critical to reducing blast furnace production costs. The combustion behavior of the co-injection of semi-coke and undersized coke powder is still rarely studied. In this work, a three-dimensional CFD mathematical model was established to simulate the gas velocity, temperature, composition distribution and burnout of semi-coke during the combustion of pulverized semi-coke. The influence of mass fraction of semi-coke on the composition and burnout in the combustion zone of blast furnace was also studied. The results show that the maximum concentrations of CO and H2 in the combustion zone are 36% and 8%, respectively. With the decrease of the semi-coke ratio in the blended coal, the fixed carbon content and the calorific value of the blended coal increase, but the burnout of the blended coal reduces. When bituminous coal is single injected, the burnout reaches 70%, which is higher than that of semi-coke. In actual production, for the semi-coke and coke powder injecting into the blast furnace, a proportion of bituminous coal can be appropriately added to improve the burnout rate of the coal blends and increase the H2 content in reducing gas.

Natural hydrogen migration along thrust faults in foothill basins: The North Pyrenean Frontal Thrust case study

The existence of geological fluids rich in natural hydrogen (H2) raises the question about the energy potential of this carbon-free resource. However, to date there is no exploration strategy based on robust methodologies and pathfinders. Therefore, it is important to develop an exploration guide that is not only focused on surface gas monitoring, but that also considers the local deep geological setting integrating the entire hydrogen system from source to trap or leakage into the atmosphere.The northwestern Pyrenees, and particularly the Mauléon Basin, represent a promising geological environment for natural H2 exploration for at least four reasons. First, an ultramafic mantle body is emplaced at shallow depth below the basin under pressure-temperature conditions favorable to serpentinization. Second, major faults such as the North Pyrenean Frontal Thrust constitute large-scale fluid flow convergence and drainage. Third, hydraulic gradients imposed by sharp reliefs and combined with temperature and pressure gradients trigger fluid migration. Fourth, impermeable sedimentary formations or caprocks such as evaporites or claystones overly porous reservoir rocks that could constitute traps for accumulating H2.To investigate H2 migration at the fault scale, we present new geochemical and geophysical data recorded along the North Pyrenean Frontal Thrust. Based on both soil gas and electromagnetic transects, we reveal the presence of a gas-draining fault. Soil gas concentration (H2, CO2, CH4 and 222Rn) recorded at 1 m depth increases when approaching the North Pyrenean Frontal Thrust. The maximum H2, CO2 and 222Rn concentrations recorded in the fault zone are 822 ppmv, 10.3 vol% and 57 kBq.m−3, respectively - whereas their local background concentrations are by 1–2 orders of magnitude lower: 10 ppmv, 0.2 vol% and 0.3 kBq.m−3 respectively. Our geochemical and geophysical data support the concept of a deep-fluid migration along the detected fault plane. In addition, the study of historical well data combined with the most recent geological and geophysical surveys carried out in the region, highlights zones where H2 could accumulate at depth. The Triassic salt formations, located at 2800 to 4000 m deep beneath the Mauléon Basin, represent the most promising trap for H2 in the northwestern Pyrenees.

Alternative strategies to perform solid-state cultivation in a multilayer packed-bed bioreactor: Continuous and cyclic operations

The packed-bed bioreactor (PBB) is one of the equipment most used in solid-state cultivation (SSC) processes. However, PBBs present problems in the removal of metabolic heat generated by microorganisms, making difficult to scale up these equipment, that are usually operated in batches. Aiming to minimize the overheating problems and to provide more versatility for biorefineries, this work aimed to evaluate alternative modes of operation of a multilayer PBB applied in the production of endoglucanase by SSC, namely cyclic and continuous operations. For this purpose, the fungus Myceliophthora thermophila I-1D3b was used as inoculum and sugarcane bagasse and wheat bran were used as substrates. In the cyclic operation, the layers had their positions changed every 24 h. In the continuous process, newly inoculated layers were added and spent layers fermented were removed every 24 h, leading to a regular flow of layers. Maximum temperatures reached 48.1, 48.2 and 48.3 °C and endoglucanase productivities were 2.85, 3.18 and 3.35 U/g of dry solid/h for classical, cyclic and continuous operations, respectively. These results showed no significant difference according to the Tukey test (α = 0.05). Despite that, in the continuous operation, the maximum CO2 concentration recorded was 60% lower than in batch operations. In addition, it was possible to estimate the biomass production rate in continuous operation, which was 5.32 g/h. Therefore, the continuous operation proved to be applicable and advantageous, being able to contribute to the scale up and operational versatility of PBBs and, consequently, to the industrial advancement of SSC.

Patient tilt improves efficacy of CO2 field-flooding in minimally invasive cardiac surgery

ObjectiveSpace limitations during minimally invasive cardiac surgery impede consistent use of CO2 field-flooding. We compared different gas delivery methods, flow rates and the effect of patient inclination.MethodsA gastight model of MICS surgery with internal organs and right thoracotomy wound was created from a mannequin and equipped with a CO2 concentration sensor in the left ventricle. Maximum achievable CO2 concentration was compared for gas delivery via three commercial CO2 diffusors (CarbonMini, Temed, Andocor) and also via a trocar with side port. Gas flow rates of 1, 3, 5 and 8 L per minute were tested. The model was placed either in supine position or with 20° oblique tilt. A simplified transparent model was also created and placed in an optical test bench to evaluate the gas cloud motions via real-time visualization.ResultsThe trocar consistently achieved higher CO2 concentrations inside the left ventricle. At 1 l/min, approximately 2.5 min were needed to fill the supine model to its maximum CO2 concentration, which was limited to a range of 48–82% in the left ventricle. At higher flow rates, filling time and concentration were significantly improved. In a tilted model, all devices and all flow rates generated on average 99% CO2 in the ventricle. Imaging revealed constant gas exchange via the main incision, with CO2 outflow via bottom and air inflow via the top of the incision.ConclusionsCO2 field flooding in minimally invasive cardiac surgery is highly effective if the patient is tilted. Else a flow rate of 5 l/min is recommended to achieve the same protection.

Mitigation of lead toxicity in Vigna radiata genotypes by silver nanoparticles

Heavy metal (HM) contamination of the soil through anthropogenic activities influences the living systems and drastically impacts food chain. This study examined the application of silver nanoparticles (AgNPs) in two genotypes (G1 and G2) of Mung bean (Vigna radiata) for ameliorating the Pb toxicity. Different doses of Pb (0, 25, 50 μM) were differentially tackled by AgNPs with the aim of ameliorating the plant attributes. Both genotypes displayed statistically significant quantitative and qualitative modulations for Pb tolerance. In G2, the most prominent increase in plant height (43.79%), fresh biomass (49.56%) and total chlorophyll (20%) was observed at L2 (AgNPs 10 mg/L) in comparison with the control. Overall, photosynthetic rate was increased by 26% in G2 at L6 (AgNPs 25 mg/L + Pb 25 μM). In addition, the results presented 78.5% increase in water use efficiency of G2 while G1 experienced a maximum internal CO2 concentration (209.8%) at L8 (Pb 50 μM). AgNPs triggered balanced uptake of minerals and improved growth of Vigna genotypes. 50 μM Pb was most hazardous and caused maximum reduction in growth of Vigna plants along with a significant suppression in photosynthetic activity, increase in MDA (199.7%) in G1 and H2O2 (292.8%) in G2. In comparison to control, maximum superoxide dismutase (376%), peroxidase (659.8%) and catalase (9.3%) activity was observed in G2 at L11. The application of AgNPs substantially enhanced plant growth and helped them in surviving well in absence as well as presence of Pb. G2 genotype exhibited substantial tolerance capability and revealed less impairment in the studied attributes than G1 and treatment of AgNPs i.e. 25 mg/L was the best level that yielded best results in both genotypes. The results demonstrate that AgNPs mediate response(s) of plants under Pb stress and particularly contributed to HM tolerance of plants and thus showing great promise for use in phytoremediation.

How Safe is Singing Under Pandemic Conditions? - CO[formula omitted]-Measurements as Simple Method for Risk Estimation During Choir Rehearsals

The SARS-CoV-2 pandemic has forced choirs to pause or at least to restrict rehearsals and concerts. Nevertheless, an uncertainty about the risks of infection while singing remains, especially with regard to distances, duration of singing, number of singers and their positions in the room, size of the room as well as ventilation strategies. Based on the assumption that CO2 is a suitable indicator for the exhaled aerosols in a room, it is the aim of this study to deduce recommendations for a choir rehearsal with a minimum risk of infection. During two choir rehearsals in a typical, nonventilated classroom, we installed 30 CO2 sensors, which allow spatial and temporal evaluation of the CO2 dispersion during singing. Various singing and ventilation phases were applied and the rates of CO2 increase during singing as well as its decrease during ventilation phases were evaluated and compared for different scenarios. The measurements reveal a linear relation between the duration of singing, size of the room and number of persons. For our size of the room of 200 m3 the average CO2 increase is 1.83 ppm/min per person. Masks or pure breathing without singing do - in contrast to aerosol dispersion - not influence the rate of CO2 increase. CO2 disperses fast and homogeneously on horizontal planes. However, a vertical layering with a maximum CO2 concentration is observed near the ceiling. Shock ventilation shows the largest CO2 decrease within the first 5 min, after 10 min of ventilation the outside base concentration of 400 ppm is reached again. The evaluated relations allow to calculate safe singing times for a defined number of singers and size of the room until a critical threshold of 800 ppm is reached. Furthermore, in order to monitor the actual CO2 concentration during choir rehearsal, just one CO2 sensor is representative for the air quality and CO2 concentration of the whole room and thus considered sufficient. For an early warning, it should be installed near the ceiling. Direct singing into a sensor should be avoided. A ventilation time of just 5 min is recommended which represents a compromise between strong CO2 reduction and still sufficient room temperature during winter time.

Preparation of 3DOM ZrTiO4 Support, WxCeMnOδ/3DOM ZrTiO4 Catalysts, and Their Catalytic Performance for the Simultaneous Removal of Soot and NOx.

As an efficient and durable engine, a diesel engine has a broad application. However, soot particles (PM) and nitrogen oxides (NOx) coming from diesel engines are the main causes of air pollution, so it is necessary to design and prepare an effective catalyst for the simultaneous elimination of PM and NOx. In this work, a novel 3DOM ZrTiO4 support and a series of WxCeMnOδ/3DOM ZrTiO4 catalysts (where x indicates the wt% of W) were designed and fabricated by the colloidal crystal template technique. Among the as-prepared catalysts, the W1CeMnOδ/3DOM ZrTiO4 catalyst exhibits the highest NO conversion rate (52%) at the temperature of maximum CO2 concentration (474°C) and achieves 90% NO conversion in the temperature range of 250–396°C. The excellent catalytic performance is associated with the macroporous structure, abundant oxygen vacancies, sufficient acid sites, and the synergistic effect among the active components. The possible reaction mechanisms of WxCeMnOδ/3DOM ZrTiO4 catalysts were also discussed based on the characterization results.