Increase In Carbon Monoxide Concentration Research Articles

The impact of carbon monoxide on years of life lost and modified effect by individual- and city-level characteristics: Evidence from a nationwide time-series study in China

Ambient carbon monoxide (CO) has been linked with mortality and morbidity. Little evidence is available regarding the relation between CO and years of life lost (YLL). Using data from 48 major cities in China from 2013 to 2017, we applied generalized additive models and random effects meta-analyses to explore the effects of CO on YLL from various diseases. Stratified analyses and meta-regression were performed to estimate potential effect modifications of demographic factors, regions, meteorological factors, co-pollutants, urbanization rate, economic level and health service level. Additional life gains due to avoidable YLL under certain scenario were also evaluated. Results indicated that a 1-mg/m³ increase of CO concentrations (lagged over 0–3 d), was associated with 2.08% (95% confidence interval [CI], 1.35%, 2.80%), 2.35% (95% CI: 1.39%, 3.30%), 1.47% (95% CI: -0.01%, 2.93%), 2.28% (95% CI: 1.09%, 3.47%), 2.42% (95% CI: 1.31%, 3.54%), 2.09% (95% CI: 0.47%, 3.72%) increments in daily YLL from non-accidental causes, cardiovascular diseases, respiratory diseases, coronary heart disease, stroke and chronic obstructive pulmonary disease, respectively. These associations were robust to the adjustment of co-pollutants and varied substantially by geography and demographic characteristics. Associations were stronger in the elder people (≥65 years), females, population with low education attainment, and lived in south region, than younger people, males, high educated populations and those lived in north region. Moreover, the harmful impact of increasing CO concentration could be attenuated by city-level characteristics, including the growth of urbanization rate, gross domestic product (GDP), GDP per capita, number of hospital beds, doctors and hospitals. Finally, an estimated life of 0.081 (95% CI: -0.027, 0.190) years would be gained per deceased people if CO concentration could fall to 1 mg/m3. In conclusions, this nationwide analysis showed significant associations between short-term CO exposure and cause-specific YLL. The heterogeneity of both individual- and city-level characteristics should be considered for relevant intervention. These findings may have significant public health implications for the reduction of CO-attributed disease burden in China.

The Relationship between City Size and Carbon Monoxide (CO) Concentration and Their Effect on Heart Rate Variability (HRV).

Generally, larger cities are characterized by traffic congestion, which is associated with higher concentrations of pollution, including Carbon Monoxide (CO) pollution. However, this convention requires empirical support on the basis of accurate and reliable measurements. In addition, the assessment of the effect of CO on the autonomic nervous system (ANS), as measured by heart rate variability (HRV), has yielded conflicting results. A majority of the (few) studies on the topic have shown that increases in CO concentration of up to about 10 parts per million (ppm) are associated with a decrease in stress and risk to health in subjects. Beyond the hypothesis postulating city size as a determinant of increased CO concentration, the hypothesis proposing a causal link between CO concentration and HRV balance also requires empirical support. This article compares CO concentrations in a large metropolis with those in a small town, analyzing the relationship between CO and the HRV responses of young women in terms of city size. Four different types of environments were compared, taking into account mediating variables. The study participants spent 35 min in selected environments (a city center, a residential environment, a park, and a home) wearing Polar devices to measure HRV, and portable devices to measure noise thermal load and CO. The average concentrations of CO in each environment were calculated, along with the time distribution of the CO concentration, and the regression slopes between the concentrations of CO and the ANS balance, as measured by the low frequency power/high frequency power ratio (LF/HF) expressed as an HRV index. The results show that, regardless of size, the cities measured were all characterized by low levels of CO, far below the maximal accepted threshold standards, and that urban residents were exposed to these concentrations for less than half of the daytime hours. Furthermore, in contrast to the common view, larger cities do not necessarily accumulate higher concentrations of CO compared to small cities, regardless of the level of transport congestion. This study confirms the findings of the majority of the other studies on the subject, which showed a decrease in stress (as measured by HRV) as a result of an increase in CO concentrations below 7 ppm. Finally, following the assessment of the differential contribution attributed to the different environmental factors, it appears that noise, thermal load, and congestion all contribute more to a higher level of HRV balance than CO. This finding highlights the importance of a multivariable approach to the study, and a remediation of the effect of environmental factors on stress in urban environments.

APPLICATION OF PORTABLE FLYING ROBOTIC SYSTEMS FOR EARLY DETECTION OF AN IGNITION SOURCE

Recently, the development of modern equipment and early detection of ignition sources has become relevant due to many fires and the material and human damage caused by them. This study aimed to develop a method of searching for the ignition source by moving a mobile gas analyzer towards increasing the concentration of carbon monoxide (CO) emitted in the initial stages of fire. According to the simplex and Kiefer method, an algorithm based on the spatial detection method and guaranteed trajectory definition was used to move the mobile gas analyzer towards increasing concentration. The dependence of the engine speed on the supply voltage, the angular speed of the engine with the supply voltage, the tractive force at the wing flap frequency, the supply voltage as well as the energy consumed by the engine during propulsion were calculated. To determine the direction of the azimuth towards the movement of increasing the concentration of CO, an equation was obtained that made it possible to determine the concentration of CO as a function of the distance from the carbon monoxide source. A diagram of the gradient dependence on the distance to the ignition point was plotted, and the number of points on the trajectory on which the CO concentration is measured was determined. One way to further improve early fire detection methods is to use mobile gas analyzers in the ignition source movement and determine their coordinates with the increase in CO concentration. However, further development is restricted due to insufficient research on design methods for mobile gas analyzers, communication analysis between subsystems, and calculation methods based on mathematical models that adequately describe the basic modes of movement of mobile gas analyzers.

Myocardial infarction triggered by exposure to air pollution – underestimated or overrated issue – 11 years study

Abstract Introduction Currently, the greatest threat to the health and life of people and the leading cause of death in Poland are cardiovascular diseases (CVD). Air quality is a well-known risk factor for the development of them. Purpose The aim of this study is to assess the impact of air pollution on the frequency of hospital admissions due to acute coronary syndrome (ACS). Methods The medical records of 30,695 patients hospitalized in the Department of Invasive Cardiology were analyzed. Patients treated for ACS and living within the borders of the analyzed city met inclusion criteria. Weather conditions such as temperature, humidity, atmospheric pressure, wind speed and the following components of air pollution were analyzed: carbon monoxide (CO), sulfur dioxide (SO2), nitrogen dioxide (NO2), trioxygen (O3), particulate matter with a diameter of 2.5 μm or less (PM2.5) and with a diameter of 10 μm or less (PM10). Poisson regression was used for statistical analysis. Results The study included 3,325 inhabitants of analyzed city (mean age 66.2 years, SD=12.2), male in majority (60.3%). The number of patients admitted for ST-segment elevation myocardial infarction (STEMI), non-ST-segment elevation myocardial infarction (NSTEMI), and unstable angina (UA) was 1002, 1265, and 1058, respectively. An increase of CO concentration by 1 g/m3 was associated with a higher number of admissions due to NSTEMI (RR 1.74; 95% CI, 1.08–2.8; P=0.02), this effect was more noticeable in the female population (RR - 2.8; 95% CI, 1.39–5.65; P=0.004). In male subjects an increase in the concentration of PM2.5 by 10 μg/m3 was associated with a 0.5% increase in the number of admissions for NSTEMI (RR 1.05, 95% CI 1.02–1.22; P=0.02) and UA (OR 1.14, 95% CI 1.02–1.25; P=0.014). An increase in the concentration of SO2 by 1 μg/m3 affected the frequency of admissions in men due to NSTEMI (0.5% increase, RR 1.04, 95% CI 1.01–1.07; P=0.007) and UA (OR 1.17, 95% CI 1.02–1.36; P=0.031). The concentration of 03 and NO2 did not affect admissions rate due to ACS. Conclusions Air quality had an impact on the occurrence of ACS among residents of Bialystok. Increased exposure to air pollution, in particular, elevated PM2.5, SO2 and CO levels, was associated with a higher incidence of NSTEMI and UA. This effect was more noticeable in the male population. Funding Acknowledgement Type of funding source: None

Ambient Carbon Monoxide and Daily Mortality: A Global Time-Series Study in 337 cities

Background Epidemiological evidence on the short-term association between ambient carbon monoxide (CO) and mortality is inconclusive and limited to single cities, regions, or countries. Generalization of results from previous studies is challenged by potential publication bias and different modeling approaches. We, therefore, assessed the associations between short-term exposure to CO and daily mortality in a multi-city multi-country setting.Methods We collected daily data on air pollution, meteorology, and total mortality from 337 cities in 18 countries from the Multi-Country Multi-City Collaborative Research Network. We first estimated city-specific associations using confounder-adjusted generalized additive models with a quasi-Poisson distribution; then, we pooled the estimates using a random-effects multilevel meta-analytical model. We also assessed the overall shape of the exposure-response curve and evaluated the existence of a threshold value.Results Overall, a 1 mg/m3 increase in the average CO concentration of the previous day was associated with a percent increase of 0.91% (95% confidence interval [95% CI]: 0.32%, 1.50%) in daily total mortality. The pooled exposure-response curve showed a continuously elevated mortality risk with increasing CO concentrations, suggesting no evidence for a threshold. Larger mortality risk estimates were found at daily CO levels below 1 mg/m3 and persisted at concentrations as low as below 0.2 mg/m3.Conclusions This international study is, to our knowledge, by far the largest epidemiological study on short-term CO-related mortality. We found significant associations between short-term exposure to ambient CO and daily mortality, even at levels well below the current global and national air quality guidelines.The study was conducted on behalf of the MCC Collaborative Research Network

Atmospheric inverse estimates of CO emissions from Zhengzhou, China

Carbon monoxide (CO) is an important gas that affects human health and causes air pollution. However, the estimates of CO emissions in China are still subject to large uncertainties. Based on the CO mass concentration and the coupled Weather Research and Forecast (WRF) and Stochastic Time-Inverted Lagrangian Transport (STILT) model (WRF-STILT), this study estimates the CO emissions over Zhengzhou, China. The results show that the mean CO mass concentration was 1.17 mg m−3 from November 2017 to February 2018, with a clear diurnal variation. There were two periods of rapidly increasing CO concentration in the diurnal variation, which are 06:00–09:00 and 16:00–20:00 local time. The footprint analysis shows that the observation site is highly influenced by local emissions. The most influential regions to the site observations are northeast and northwest Zhengzhou, which are associated with the geographical barrier of the Taihang Mountains in the north and narrow Fenwei Plain in the west. The inversion result shows that the actual emissions are lower than the inventory estimates. Using the optimal scaling factors, the WRF-STILT simulations of CO concentration agree closely with the CO measurements with the linear fitting regression equation y = 0.87x + 0.15. The slopes of the linear fitting regressions between the WRF-STILT-simulated CO concentrations determined using the optimal emissions and the observations range from 0.72 to 0.89 for four months, and all the fitting results passed the significance test (P < 0.001). These results indicate that the new optimal emissions derived with the scaling factors could better represent the real emission conditions than the a priori emissions if the WRF-STILT model is assumed to be reliable.

Impact of Traffic on Carbon Monoxide Concentrations Near Urban Road Mid-Blocks

An increase in population, number of vehicles and rate of urbanization have happened drastically in the past decades, resulting in deteriorating air quality and a threat to the environment. Vehicular emissions are among the primary and noted sources of air pollution in urban areas. Carbon monoxide (CO) is one of the major pollutants emitted from vehicles, affecting the environment adversely. The present study attempts to develop models to predict CO concentrations at different mid-block sections of urban roads using multiple linear regression (MLR) and artificial neural networks (ANN) methods. The proportional share of vehicles and average traffic speed are considered as inputs to the models. The traffic volume, speed and CO concentrations collected at different mid-block sections have been analyzed. A good correlation between average traffic speed, traffic volume and CO concentrations was observed. The study also shows that the classified traffic volume and average traffic speed in a mid-block could help explain the variance in CO levels significantly, with R2 value of 0.91 and 0.97 for MLR and ANN models, respectively. It has been observed that the CO level would be as high as 14 ppm at or below the average speed of 25 km/h for moving vehicles. The linear increase in CO concentration was found due to decrease in average speed of traffic stream. The model validation illustrates that the estimated CO concentrations match well the observed CO concentrations under the same set of traffic and roadway conditions with an MAPE value of 0.18% and 0.11% for MLR and ANN models, respectively. It seems interesting to see that the ANN model had better predicted the CO values than MLR model. This study considers developing cities to determine the CO levels. The results of the study would help Pollution Control Board officials and traffic control authorities to implement necessary measures for improving air quality in the cities under consideration.

Measurement of carbon monoxide concentration levels within an underground parking lot throughout the day

Background: During the fall and winter months, people opt to using cars as a mode of transportation to and from work, school, or recreation. The ease of access, comfort, and efficiency of travel prompt an increase in drivers. Underground lots are ideal parking spaces during these months, which see an increase in traffic and subsequent rise in emissions, specifically carbon monoxide (CO) that can be hazardous to health at certain concentrations. This study is to determine the levels of CO in a confined parking space Methods: Air quality and composition were determined via passive dosi-tubes that were affixed onto columns within the Langara College underground parking lot in the morning and picked up for analysis in the afternoon. Results: There is an increase in carbon monoxide concentration within the underground parking lot, during peak hours. Traffic within the lot is found to be higher during poor weather conditions which correlate with ease of use and comfort of driving a car. There is also an increase in traffic on Tuesdays and Thursdays, which is likely dictated by class times. Carbon monoxide levels did not fail to meet government regulations during any sampling period. Conclusions: The air composition in the Langara underground parking lot is safe even during periods of high traffic, for the average person. However, individuals with underlying medical conditions should enter with caution, as the recorded CO levels can aggravate pre-existing cardio-pulmonary diseases.&#x0D;

Carbon monoxide: a critical physiological regulator sensitive to light

The mechanism by which humans absorb therapeutic light in winter seasonal and nonseasonal depression is unknown. Bright-light-induced release and generation of blood-borne gasotransmitters such as carbon monoxide (CO) may be one mechanism. Here, 24 healthy female volunteers had peripheral blood samples drawn. Samples were collected in a dimly lit room and protected from light exposure. Samples were analyzed for CO concentrations by gas chromatography after 2 h of continuous exposure to darkness vs. bright white light. In a similar confirmatory study, 11 additional volunteers had samples analyzed for CO concentrations after 2 h of continuous exposure to gentle rocking in darkness vs. in bright white light. In the first study, light-unexposed peripheral blood had a mean CO concentration of 1.8 ± 0.4 SD ppm/g. Identically treated samples with 2 h of rocking and exposure to bright white light at illuminance 10,000 lux had a mean CO of 3.6 ± 1.2 ppm/g (p < 0.0001). Post hoc analysis of that study showed that time of day was significantly inversely associated with increase in CO concentration under bright light vs. dark (p < 0.04). In a smaller confirmatory study of 11 healthy female volunteers, after 2 h of rocking, light-unexposed peripheral blood had a mean CO of 1.4 ± 0.5 SD ppm/g. Identically treated blood samples with 2 h of exposure to bright white light at illuminance 10,000 lux had a mean CO of 2.8 ± 1.7 ppm/g (p < 0.02). In conclusion, bright-light exposure robustly increases human blood CO in vitro. This supports the putative role of CO as a physiological regulator of circadian rhythms and light’s antidepressant effects. This human evidence replicates earlier data from a preclinical in vivo model. This effect may be stronger in the morning than in the afternoon.

Structural Modifications of Nile Red Carbon Monoxide Fluorescent Probe: Sensing Mechanism and Applications.

Carbon monoxide (CO) is a cell-signaling molecule (gasotransmitter) produced endogenously by oxidative catabolism of heme, and the understanding of its spatial and temporal sensing at the cellular level is still an open challenge. Synthesis, optical properties, and study of the sensing mechanism of Nile red Pd-based CO chemosensors, structurally modified by core and bridge substituents, in methanol and aqueous solutions are reported in this work. The sensing fluorescence "off-on" response of palladacycle-based sensors possessing low-background fluorescence arises from their reaction with CO to release the corresponding highly fluorescent Nile red derivatives in the final step. Our mechanistic study showed that electron-withdrawing and electron-donating core substituents affect the rate-determining step of the reaction. More importantly, the substituents were found to have a substantial effect on the Nile red sensor fluorescence quantum yields, hereby defining the sensing detection limit. The highest overall fluorescence and sensing rate enhancements were found for a 2-hydroxy palladacycle derivative, which was used in subsequent biological studies on mouse hepatoma cells as it easily crosses the cell membrane and qualitatively traces the localization of CO within the intracellular compartment with the linear quantitative response to increasing CO concentrations.

The Biotic and Abiotic Carbon Monoxide Formation During Aerobic Co-digestion of Dairy Cattle Manure With Green Waste and Sawdust.

Carbon monoxide (CO), an air pollutant and a toxic gas to humans, can be generated during aerobic digestion of organic waste. CO is produced due to thermochemical processes, and also produced or consumed by cohorts of methanogenic, acetogenic, or sulfate-reducing bacteria. The exact mechanisms of biotic and abiotic formation of CO in aerobic digestion (particularly the effects of process temperature) are still not known. This study aimed to determine the temporal variation in CO concentrations during the aerobic digestion as a function of process temperature and activity of microorganisms. All experiments were conducted in controlled temperature reactors using homogeneous materials. The lab-scale tests with sterilized and non-sterilized mix of green waste, dairy cattle manure, sawdust (1:1:1 mass ratio) were carried out for 1 week at 10, 25, 30, 37, 40, 50, 60, 70°C to elucidate the biotic vs. abiotic effect. Gas concentrations of CO, O2, and CO2 inside the reactor were measured every 12 h. The CO concentrations observed for up to 30°C did not exceed 100 ppm v/v. For 50 and 60°C, significantly (p < 0.05) higher CO concentrations, reaching almost 600 ppm v/v, were observed. The regression analyses showed in both cases (sterile and non-sterile) a statistically significant effect (p < 0.05) of temperature on CO concentration, confirming that the increase in temperature causes an increase in CO concentration. The remaining factors (time, O2, and CO2 content) were not statistically significant (p > 0.05). A new polynomial model describing the effect of temperature, O2, and CO2 concentration on CO production during aerobic digestion of organic waste was formulated. It has been found that the proposed model for sterile variant had a better fit (R2 = 0.86) compared with non-sterile (R2 = 0.71). The model predicts CO emissions and could be considered for composting process optimization. The developed model could be further developed and useful for ambient air quality and occupational exposure to CO.

Evaluating the impacts of updated aerodynamic roughness length in the WRF/Chem model over Pearl River Delta

The aerodynamic roughness length (Z0) plays an important role in the land–air exchange. At present, the atmospheric numerical models cannot accurately describe the Z0 in different underlying surfaces, which affects the simulation performance and the description of the momentum and heat exchange and atmospheric environment. In this study, the regional air quality model WRF/Chem with updated Z0 of the various underlying surface categories is used to study the impacts of Z0 on the boundary layer meteorological conditions and atmospheric environment over the Pearl River Delta (PRD) region. Two numerical experiments are conducted, including default Z0 (Base experiment) and updated Z0 (Case experiment). By comparing the simulations with the observations from 9 meteorological stations and 30 national air quality monitoring stations, the updated Z0 improves the model simulation performance of 10 m wind speed in PRD. The impacts of updated Z0 on 2 m temperature and relative humidity are relatively small, while the influences of updated Z0 on surface skin temperature (TSK), ground heat flux (GRDFLX), sensible heat flux (HFX), friction velocity (U*), 10 m wind speed (WS) and planetary boundary layer height (PBLH) are evident. The impacts of updated Z0 in the urban are greater than that in the evergreen broadleaf forest. In the urban, the updated Z0 reduces TSK, lowers GRDFLX, increases HFX during the daytime, and increases U*, causing the reduction of WS, while the vertical velocity also increases, which is conducive to the elevation of PBLH. With the updated Z0, the surface carbon monoxide (CO) concentrations generally increase, especially in the central urban areas, due to the impact of wind speed, turbulent motion and planetary boundary layer height. The updated Z0 has a little impact on CO concentration profile during the daytime, which is affected by horizontal wind speed and turbulent motion; while at night, the updated Z0 produces an increase of CO concentration below 300 m, which is affected by the horizontal wind speed.

Estimating cardiovascular hospitalizations and associated expenses attributable to ambient carbon monoxide in Lanzhou, China: Scientific evidence for policy making

ObjectivesAir pollution is an important trigger of cardiovascular disease worldwide, but few studies have determined the cardiovascular disease, health, and economic burdens attributable to ambient carbon monoxide (CO). This study aimed to examine the association between CO and CVD hospitalizations, and quantified the attributable CVD hospitalizations, associated hospital stays and hospitalization costs for CO in Lanzhou, one of the most air-polluted Chinese cities historically. MethodsDaily data on CVD hospitalizations, air pollutants, and weather records from 2013 to 2017 were obtained for Lanzhou, China. Generalized additive model with a quasi-Poisson link was used to model the association between CO and CVD hospitalizations, after controlling for other air pollutants, weather conditions, day of week, long-term trend, influenza and pneumonia incidence. The effects of CO on hospital stays and hospitalization expenses from CVD were also quantified. ResultsCO concentrations below the current Chinese ambient air quality standard had a significant impact on CVD hospitalizations. Each 1 mg/m3 increase in CO concentration on the present day and previous 4 days (lag 0–4) was associated with an 11% (95% confidence interval: 3%–20%) increase in total CVD hospitalizations. During the study period, CO was responsible for 11.74% of total CVD hospitalizations, equating to 62,792 inpatient days and 149 million RMB. Each adult patient on average spent approximately 5% of annual salary on medicine from CO-related CVD treatment during hospitalization. Maintaining the historical CO concentration within 1 to 3 mg/m3 could avert hundreds of total CVD hospitalizations and save millions of RMB annually in Lanzhou, China. ConclusionsExposure to low-level ambient CO concentration increased the risk of CVD hospitalizations and resulted in substantial health and economic burdens in Lanzhou, China. Our findings can be used for evidence-based practice and policy making to assess the cost-effectiveness of prevention measures.

Enhancement of carbon monoxide concentration in atmosphere due to large scale forest fire of Uttarakhand.

The richly forested Indian state of Uttarakhand experienced widespread forest fires in April to May 2016. The current study examines dispersion of carbon monoxide (CO) from the source regions of forest fire to distant places, using the Lagrangian particle dispersion model, FLEXPART. Atmospheric Infrared Sounder (AIRS) observations revealed that CO columnar concentrations had increased by almost 28 percentage during 24 April to 02 May 2016 with respect to the previous non-burning period of April 2016 at Uttarakhand. It is also seen that there is considerable enhancement of 45 percentage in average columnar concentration of CO during the burning period, compared to that in the previous 5 years as observed by AIRS. In the present study, concentrations of CO at different pressure levels and columnar CO over Uttarakhand during the forest fire event have been simulated using FLEXPART. The area averaged profile of model derived CO has been compared with the profile from AIRS onboard Aqua. Comparison between model derived columnar CO and satellite observations shows good agreement with coefficient of correlation (r) approximately 0.91 over the burnt areas. Further analysis using FLEXPART reveals that the transport of pollutants is towards north-eastern and eastern regions from the locations of forest fire events. Model derived vertical distribution of CO over Tibet, which is situated at the north-east of Uttarakhand, shows significant increase of CO concentration at higher altitudes around 3 km from the mean sea level during the fire event. FLEXPART results show that the emissions from the Uttarakhand fires were transported to Tibet during the study period.

Dual Fabry–Pérot Interferometric Carbon Monoxide Sensor Based on the PANI/Co3O4 Sensitive Membrane-Coated Fibre Tip

Abstract A novel dual Fabry–Pérot (F-P) interferometric carbon monoxide gas sensor based on polyaniline/Co3O4 (PANI/Co3O4) sensing film coated on the optical fibre end face is proposed and fabricated. Its structure is composed of standard single-mode-fibre (SMF), endlessly photonic crystal fibre (EPCF), and PANI/Co3O4 sensing membrane (PCSM). Therefore, they form three F-P reflectors, the reflector between SMF and EPCF, that between EPCF and PCSM, and interface between PCSM and air. So, the dual F-P interferometer is achieved. The results show that in the range of 0–70 ppm, the interference spectra appear red shift with the increasing carbon monoxide concentration. In addition, the high sensitivity of 21.61 pm/ppm, the excellent linear relationship (R 2 = 0.98476), and high selectivity for carbon monoxide are achieved. The response and recovery time are 35 and 84 s, respectively. The sensor has the advantages of high sensitivity, strong selectivity, low cost, and simple structure and is suitable for sensitive detection of trace carbon monoxide gas.

Influence of hydrogen and various carbon monoxide concentrations on reduction behavior of iron oxide at low temperature

The aims of this study are to produce Fe3O4 from Fe2O3 using hydrogen (H2) and carbon monoxide (CO) gases by focusing on the influence of these gases on reduction of Fe2O3 to Fe3O4 at low temperature (below 500 °C). Low reduction temperature behavior was investigated by using temperature programmed reduction (TPR) with the presence of 20% H2/N2, 10% CO/N2, 20% CO/N2 and 40% CO/N2. The TPR results indicated that the first reduction peak of Fe2O3 at low temperature appeared faster in CO atmosphere compared to H2. Furthermore, reducibility of first stage reduction could be improved when increasing CO concentration and reduction rate were followed the sequence as: 40% CO > 20% CO > 10% CO > 10% H2. All reduction peaks were shifted to higher temperature when the CO concentration was reduced. Although, initial reduction by H2 occurred slower (first peak appeared at higher temperature, 465 °C) compared to CO, however, it showed better reduction with Fe2O3 fully reduced to Fe at temperature below 800 °C. Meanwhile, complete reduction happened at temperature above 800 °C in 10% and 20% CO/N2. Thermodynamic calculation revealed that CO acts as a better reducer than H2 as the enthalpy change of reaction (ΔHr) is more exothermic than H2 and the change in Gibbs free energy (ΔG) at 500 °C is directed to more spontaneous reaction in converting Fe2O3 to Fe3O4. Therefore, formation of magnetite at low temperature was thermodynamically more favorable in CO compared to H2 atmosphere. XRD analysis explained the formation of smaller crystallite size of magnetite by H2 whereas reduction of CO concentration from 40, 20 to 10% enhanced the growth of highly crystalline magnetite (31.3, 35.5 and 39.9 nm respectively). All reductants were successfully transformed Fe2O3 → Fe3O4 at the first reduction peak except for 10% CO/N2 as there was a weak crystalline peak due to remaining unreduced Fe2O3. Overall, less energy consumption needed in reducing Fe2O3 to Fe3O4 by CO. This proved that CO was enhanced the formation of magnetite, encouraged formation of highly crystalline magnetite in more concentrated CO, considered better reducing agent than H2 and these are valid at lower temperature.

How parked cars affect pollutant dispersion at street level in an urban street canyon? A CFD modelling exercise assessing geometrical detailing and pollutant decay rates

Computational fluid dynamics (CFD) is a recognised modelling tool for simulating pollutant dispersion in urban street canyons. These studies require accurate street geometry, sufficient modelling experience and access to software to provide reliable outputs. Parked cars are known to act as a passive barrier and affects pollutant dispersion in an urban street canyon. This modelling study examines the impact of accurate geometrical detailing and suitable mesh sizing on air pollution concentrations measured at street level. Mean steady state concentrations of carbon monoxide (CO) were measured in a reference scenario (without parked cars) and three parked car scenarios. A comparison of the results indicated that individual rectangular blocks and generic car scenarios overestimated pollutant concentrations on the footpaths by up to 25% when compared to the results from the five distinct car designs scenario, with the parked cars acting as a passive barrier in each scenario under different wind conditions. The most notable finding demonstrated how the five distinct car designs scenario presented an increase in CO concentrations on the leeward footpath as opposed to a reduction in the results in the other coarser geometrically detailed scenarios. The parked cars trapped pollutants in each scenario with low wind speeds for perpendicular wind conditions, as higher concentrations were measured on the footpaths. A further examination of pollutant decay rates demonstrated how the geometrical detailing of the parked cars also impacted upon the duration taken for pollutants to escape from the footpath zones. These findings demonstrate how parked cars affects pollutant dispersion and concentrations measured on the footpaths at street level, and the adoption of a suitable meshing scheme is vital to capture results in the zone of interest in an urban street canyon.

Microbial fuel cell-based biosensor for toxic carbon monoxide monitoring

This study presents an innovative microbial fuel cell-based biosensor for carbon monoxide (CO) monitoring. The hypothesis for the function of the biosensor is that CO inhibits bacterial activity in the anode and thereby reduces electricity production. A mature electrochemically active biofilm on the anode was exposed to CO gas at varied concentrations. A proportional linear relationship (R2 = 0.987) between CO concentration and voltage drop (0.8 to 24 mV) in the range of 10% and 70% of CO concentration was observed. Notably, no further decrease of voltage output was observed by with further increasing CO concentration over 70%. Besides, the response time of the biosensor was 1 h. The compact design and simple operation of the biosensor makes it easy to be integrated in existing CO-based industrial facilities either as a forewarning sensor for CO toxicity or even as an individual on-line monitoring device.

A Novel Four-Way Plasma-Catalytic Approach for The After-Treatment of Diesel Engine Exhausts

This study proposes a novel four-way plasma-catalytic removal of particulate matter, nitrogen oxides, hydrocarbons, and carbon monoxide without external heating using a pulsed dielectric barrier discharge reactor combined with Au/CaSO4/γ-Al2O3 catalyst balls. With the optimized amount of Au and CaSO4, over 90% of particulate matter, 40% of nitrogen oxides, and nearly 100% of hydrocarbons were removed from the diesel engine exhaust, while the increase of carbon monoxide concentration due to the oxidation of particulate matter and hydrocarbons and the decomposition of carbon dioxide were minimized. Importantly, the performance of the plasma-catalytic reactor was maintained without decline for the duration of the experiment (7 h) with an attractive cost/performance ratio. These findings offer a new approach to the simultaneous treatment of diesel exhausts and provide a novel concept for the design of a practical and compact after-treatment device for the diesel engine exhaust gases.

Limitation in growth temperature for water-assisted single wall carbon nanotube forest synthesis

ABSTRACTIn this study, we examined the limitations in growth temperatures for single-walled carbon nanotube (SWNT) forest synthesis using a water (H2O) growth enhancer as highlighted by a dramatic decrease in growth efficiency at high temperatures. Comparative synthesis using a carbon monoxide (CO) growth enhancer demonstrated a wider temperature window for SWNT forest synthesis. We found that SWNT forests taller than 100 μm could not been synthesized above 850 °C by using H2O, but by using CO, tall (&gt;800 μm) forests could be synthesized at growth temperatures exceeding 900 °C. The dependency of H2O concentration showed that H2O, itself, was the cause for the reduced growth efficiency observed at higher temperatures. In contrast, increased CO concentrations did not result in any drop in the carbon nanotube (CNT) yield across the entire temperature range. While a severe drop of CNT yield above 950 °C was observed when CO was used, the origin was found to stem from catalyst particle aggregation enhanced by diffusion on the surface rather than CO itself. Therefore, the ability to synthesize at higher growth temperatures is advantageous when using more stable carbon feedstocks, such as methane.