CO2 Measurements Research Articles

Mediator-Free Self-Powered Bioassay for Wide-Range Detection of Dissolved Carbon Dioxide.

Electrochemical sensors for the dissolved CO2 (dCO2) measurement have attracted great interest because of their simple setup and the resulting low costs. However, the developed sensors suffer from the requirement of the external electrical power supply throughout the sensing. Here, the fabrication and evaluation of a self-powered biosensor based on biofuel cells (BFCs) for dCO2 measurements are described. In this device, AuNPs-multiwalled carbon nanotubes/GOx-modified carbon paper (CP) served as a bioanode for the oxidation of glucose, while imine-linked covalent triazine framework (I-CTF)-modified CP was employed as the cathode for the reduction of Fe(CN)63-. I-CTF is a porous organic polymer with a high CO2 capture capacity. Voltammetry and electrochemical impedance spectroscopy confirmed that the electron transfer of Fe(CN)63- on the I-CTF-modified electrode decreases after contacting I-CTF with dCO2. In the designed BFC, by capturing CO2 by the I-CTF-modified cathode, a significant decrease in open-circuit voltage (EOCV) of the BFC was observed, which can be used for the sensitive measurement of dCO2. In addition to the self-powering feature, the EOCV of the BFC sensor can be restored when the captured CO2 is desorbed from the I-CTF-modified cathode by increasing the temperature of the cathode. Finally, the BFC is integrated into a circuit containing a matching capacitor; the charges generated by the BFC are accumulated on the capacitor, and then the instantaneous current is quickly detected using a switching regulator and a digital multimeter. Under optimal conditions, the instantaneous current of the BFC sensor was found to sensitively respond to dCO2 in a wide concentration range from 1.3 × 10-5 to 0.252 atm with a low detection limit of 5 × 10-6 atm.

Social knowledge of symptoms, risk factors, causes, and preventive measures of CO poisoning among Saudi Arabia's general population

Social knowledge of symptoms, risk factors, causes, and preventive measures of CO poisoning among Saudi Arabia's general population

A Survey of CO, CO2, and H2O in Comets and Centaurs

CO and CO2 are the two dominant carbon-bearing molecules in comae and have major roles in driving activity. Their relative abundances also provide strong observational constraints to models of solar system formation and evolution but have never been studied together in a large sample of comets. We carefully compiled and analyzed published measurements of simultaneous CO and CO2 production rates for 25 comets. Approximately half of the comae have substantially more CO2 than CO, about one-third are CO-dominated, and about 1/10 produce a comparable amount of both. There may be a heliocentric dependence to this ratio with CO dominating comae beyond 3.5 au. Eight out of nine of the Jupiter Family Comets in our study produce more CO2 than CO. The six dynamically new comets produce more CO2 relative to CO than the eight Oort Cloud comets that have made multiple passes through the inner solar system. This may be explained by long-term cosmic-ray processing of a comet nucleus’s outer layers. We find (Q CO/Q )median = 3 ± 1% and (Q /Q )median = 12 ± 2%. The inorganic volatile carbon budget was estimated to be (Q CO+Q )/Q ∼ 18% for most comets. Between 0.7 and 4.6 au, CO2 outgassing appears to be more intimately tied to the water production in a way that the CO is not. The volatile carbon/oxygen ratio for 18 comets is C/Omedian ∼ 13%, which is consistent with a comet formation environment that is well within the CO snow line.

Performance and Emission of Diesel Engine Fuelled by Commercial Bio-Diesel Fuels in Indonesia

Abstract The performance and emission of a small diesel engine fuelled by commercial diesel fuel in Indonesia are present in this paper. Various commercial diesel fuels in Indonesia are produced and marketed by Pertamina. As the largest oil company in Indonesia, Pertamina has developed various diesel fuels, namely Solar, Biosolar (B30), Dexlite, and Pertadex. This study explains in more detail the performance, fuel consumption, and emission produced by the four types of fuels, and they were investigated experimentally using a single-cylinder diesel engine at various engine speeds, from 1,000 rpm to 4,500 rpm. The result shows the engine fuelled by Pertadex generates the highest power and torque, while the lowest is generated by the Biosolar fuelled engine. The maximum torque and power generated by the Pertadex fuelled engine are about 25.5 Nm and 7200 W, respectively. The engine fuelled by Pertadex has the lowest brake specific fuel consumption (BSFC) of 0.3037 kg·kW·h, compared to the engines fuelled by the Dexlite, Solar, and Biosolar fuels, with values around 0.3127, 0.3215, and 0.3338 kg·kW·h, respectively. At the same time, the measurement of gas emissions, including CO2, CO, NOx, and HC was conducted simultaneously.

Temperature, soot, and OH*/CH* chemiluminescence measurements of partially-premixed CO2-diluted propane flames on a linear Hencken burner

Recent studies highlight the need for further examination of partially-premixed diffusion flames with applications in modern burner configurations that increasingly rely on technologies such as flue gas recirculation and oxy-fuel combustion, which increase the CO 2 content in the combustion environment. The partially-premixed nature of the linear Hencken burner (LHB) offers a unique platform with many advantages over comparable slot-type or radially-symmetric burner configurations. In this work, partially-premixed laminar propane flames were examined under increasing CO 2 percentages (0 to 50% v ). Prosumer grade digital CMOS cameras were calibrated and used to determine two-dimensional, quantitative measurements of soot, temperature, and OH* and CH* chemiluminescence. Soot values were additionally supported via laser extinction measurements using a 532 nm continuous wavelength laser. The peak soot volume fraction was found to decrease from 318 ppbv for the pure propane case down to 37 ppbv for the 50% v CO 2 case, while the corresponding temperature decreased from 1876 K down to 1742 K. The data also suggested that soot maturity decreased in conjunction with overall concentration. The regions of peak OH* and CH* concentrations maintained their transverse positions as well as their relative positions with respect to one another for all flame conditions, though moved axial further away from the flame base with increasing CO 2 . Additionally, the peak OH* region remained closer to the central flame axis across all conditions, a result that is counter to other studies that examined CO 2 dilution in purely non-premixed flames. • 2D quantitative soot and temperature measurements of CO2 diluted partially-premixed propane flames. • Laser extinction measurements bolster 2D soot values. • Fuel dilution over 40%v CO2 starts to significantly lower soot maturity. • 2D quantitative chemiluminescence measurements of OH* and CH* in CO2 diluted partially-premixed propane flame. • Movement of peak chemiluminescent regions show significant differences versus premixed and dilution flames.

Analisis Kualitas Udara Berdasarkan Volume Lalu Lintas di Jalan Kedung Cowek Surabaya

The increasing number of people in the world has caused the air to be increasingly polluted. In everyday time of day the exhaust gases from transportation are mostly inhaled from the combustion output using fuel whichhas relatively high levels. Carbon monoxide has a negative influence on the body because CO is able to bind through blood cells or hemoglobin which transports oxygen to all the body and interferes with the distribution of oxygen to the blood. This study aims to find out the average picture of the level of CO concentration and the influence of the number of motorized vehicles on the level of CO concentration on Jalan Kedung Cowek Surabaya.In this study, the CO measurement used aeroaqual tools. The results of research conducted for 1 week on Tuesday (representing weekdays), Saturdays (representing half-working days) and Sundays (representing holidays) showed differences in CO concentration and vehicle volume at each time”. In the morning and evening, the average CO concentration tends to be higher than during the day. From the results of the Multivariate Anova analysis, it can be concluded that the existing time difference greatly affects the concentration of CO and the volume of the vehicle produced. In addition, CO concentration is also influenced by meteorological factors such as temperature, direction and wind speed.

Air quality assessment in biosphere reserves close to emission sources. The case of the Spanish “Tablas de Daimiel” national park

This work shows that biosphere reserves, national parks and other protected natural areas require in situ tools to monitor and detect local and remote air pollution sources which are a threat to flora, fauna water and soil. Industries in surrounding areas, traffic and long-range transport of air pollution, can change with time and meteorology and so each national park should also have a historical database of the air quality in the site. This study reports surface measurements of ozone, NO, NO2, CO, SO2 and PM2.5 acquired from March 2020 to July 2021 in “Las Tablas de Daimiel”, a wetland Mediterranean National Park bordered by different cities and new industries in the field of the revalorization of agricultural wastes. Simultaneous data from a background station in a rural area isolated from air pollution are considered as reference.Twelve campaigns of one week duration were also performed to sample air in sorbent tubes to analyse volatile organic compounds from anthropogenic sources. Data are discussed considering meteorology, especially wind speed and direction together with the assessment of back-trajectories of air masses from distant sources. The results show that the effects of pollution from local and faraway sources on air quality in the park were weak. Thus, except for the high levels of ozone, with a mean value of 71 μg.m−3, measured mass loadings for pollutants were low and not in exceedance of the air quality standards. Saharan dust events were frequent and contributed to PM2.5 levels in the site. NOx and SO2 average concentrations (3.2 and 0.4 μg.m−3, respectively) were below the recommended critical levels for vegetation and all the quantified VOCs were found in average concentration levels below 0.5 μg.m−3.

Flow measurement challenges for carbon capture, utilisation and storage

Carbon Capture, Utilisation and Storage (CCUS) is a key element in the United Kingdom Government strategy for reducing carbon dioxide (CO2) emissions. The UK aims to capture and store 10 million tonnes of CO2 each year by 2030.At each stage in the CCUS infrastructure, accurate measurement of the CO2 flow rate is required, over a range of temperatures, pressures, flow rates and fluid phases, where the flow measurement must be validated through a credible traceability chain. The traceability chain provides the underpinning confidence required to verify meter performance, financial and fiscal transactions, and environmental compliance. The UK equivalent of the EU Emissions Trading System (EU ETS) specifies a maximum uncertainty value for CO2 flow measurement. Accordingly, the provision of accurate and traceable flow measurement of CO2 is a prerequisite for an operational CCUS scheme.However, there are currently no CO2 flow measurement facilities, nationally or internationally, providing traceable flow calibrations of gas phase, liquid/dense phase and supercritical phase CO2 that replicate real-world CCUS conditions. This lack of traceable CO2 gas and liquid flow measurement facilities and associated flow measurement standards is a significant barrier to the successful implementation of CCUS projects worldwide.This paper presents an overview of the traceability chain required for CO2 flow measurement in the UK and globally. Current challenges are described along with potential solutions and opportunities for the flow measurement community.

Smart Wireless CO2 Sensor Node for IoT Based Strategic Monitoring Tool of The Risk of The Indoor SARS-CoV-2 Airborne Transmission

A close correlation between CO2 concentration and aerosol enables the wide utilization of CO2 concentration as a good representation of Severe Acute Respiratory Syndrome-Coronavirus-2 infection airborne transmission. On the other side, many indoor air-quality monitoring devices have been developed for indoor monitoring applications. However, most of them are multiparameter air-quality sensor systems and tend to consume relatively high power, are relatively large devices, and are fairly expensive; therefore, they not meet the requirement for indoor monitoring applications. This paper presents a smart wireless sensor node that can measure and monitor CO2 concentration levels. The node was designed to meet the requirements of indoor air-quality monitoring applications by considering several factors, such as compact size, low cost, and low power, as well as providing real-time, continuous, reliable, and remote measurement. Furthermore, the commercial off-the-shelf and low-power consumption components are chosen to fit with the low-cost development and reduce energy consumption. Moreover, a low-power algorithm and cloud-based data logger also were applied to minimize the total power consumption. This power strategy was applied as a preliminary development toward an autonomous sensor node. The node has a compact size and consumes low energy for one cycle of CO2 measurement, accompanied by high accuracy with very low measurement error. The experiment result revealed the node could measure and monitor in real-time continuous, reliable, and remote CO2 concentration levels in indoor and outdoor environments. A user interface visualizes CO2 concentration graphically and numerically using the Adafruit platform for easy accessibility over the Internet of Things. The developed node is very promising and suitable for indoor CO2 monitoring applications with the acquired data that could be utilized as an indicator to minimize the risk of indoor Severe Acute Respiratory Syndrome-Coronavirus-2 airborne transmission.

Enhancing crop growth in rooftop farms by repurposing CO2 from human respiration inside buildings

Integrating cities with the surrounding environment by incorporating green spaces in creative ways would help counter climate change. We propose a rooftop farm system called BIG GRO where air enriched with carbon dioxide (CO2) produced through respiration from indoor spaces is applied through existing ventilation systems to produce a fertilization effect and increased plant growth. CO2 measurements were taken inside 20 classrooms and at two exhaust vents on a rooftop at Boston University in Boston, MA. Exhausted air was directed toward spinach and corn and plant biomass and leaf number were analyzed. High concentrations of CO2 persisted inside classrooms and at rooftop exhaust vents in correlation with expected human occupancy. CO2 levels averaged 1,070 and 830 parts per million (ppm), reaching a maximum of 4,470 and 1,300 ppm CO2 indoors and at exhaust vents, respectively. The biomass of spinach grown next to exhaust air increased fourfold compared to plants grown next to a control fan applying atmospheric air. High wind speed from fans decreased growth by approximately twofold. The biomass of corn, a C4 plant, experienced a two to threefold increase, indicating that alternative environmental factors, such as temperature, likely contribute to growth enhancement. Enhancing growth in rooftop farms using indoor air would help increase yield and help crops survive harsh conditions, which would make their installation in cities more feasible.

Observation of atmospheric CO2 and CO in a low-carbon pilot city: insight into CO2 sources and regional transport

The first batch of eight low-carbon pilot cities in China includes Tianjin, Hangzhou and Nanchang etc., in which Nanchang is the only one located in center China. In this study, two-year in-situ measurements of atmospheric CO2 and CO were conducted at Nanchang station. The yearly averages of CO2 and CO mole fraction were 426.2 ppm and 449.2 ppb in 2019, 430.8 ppm and 384.4 ppb in 2020, respectively. We confirmed the significant influence of local sources on distributing the profile of CO2 and CO based on the serial analysis of their diurnal and seasonal pattern and the impacts of surface wind. The enhancements of CO2 (△CO2) and CO (△CO) in polluted conditions relative to the regionally representative conditions showed significant positive correlation in winter, with the average CO2/CO emission ratio of 54.1 ppm/ppm, suggesting their common-source from anthropogenic emissions. Specifically, we found the yearly averaged anthropogenic CO2 enhancement decreased from 7.07 ppm in 2019 to 6.72 ppm in 2020, probably due to higher fossil fuel combustion efficiency and more use of clean energy in center China. In addition, results from cluster analysis, weighted potential source contribution function, and the contribution ratio calculation demonstrated that the significant sources mainly distributed in the central and eastern Hubei in spring, Jiangxi, Guangdong and Fujian province in summer, eastern Hubei, southern Henan, central and western Shandong, northern Anhui and Jiangxi in autumn, and southern Henan, eastern Hubei, eastern and northern of Hunan, central and southern Jiangxi, northern Anhui and Jiangsu in winter.

Utility of arterial CO2 - End-tidal CO2 gap as a mortality indicator in the surgical ICU

BackgroundEnd-tidal CO2 (ETCO2) measurements have been an established tool for assessing critically ill patients. We aim to show that PaCO2-ETCO2 gap can be used as a predictor of mortality over a 7-day ICU stay. MethodsA retrospective chart review was performed on intubated surgical/trauma patients with documented ETCO2. We performed a univariate analysis and a receiver operating characteristic (ROC) curve. ResultsThirty-four patients were included. Patients who died were found to have longer days on vasopressors, and higher lactic acid levels on days 2–5, and 7. PaCO2-ETCO2 gap was higher on days 2–4 in those that died. Using ROC, days 2 and 4 PaCO2-ETCO2 gaps had good sensitivities, comparable to lactic acid sensitivity, in predicting mortality. ConclusionsPaCO2-ETCO2 gap was shown to be comparable to lactic acid in predicating mortality. Using this surrogate may aid to predict the clinical course in the ICU.

Comparison of discrete and underway CO2 measurements: Inferences on the temperature dependence of the fugacity of CO2 in seawater

The fugacity or partial pressure of CO2 in surface water (fCO2w) is a key parameter to determine air-sea CO2 fluxes and the evolution of ocean acidification. Despite its importance some key physical chemical characteristics are not fully resolved, notably its dependence on temperature. The fCO2w is mostly measured by autonomous underway systems near in situ sea surface temperature (SST). Subsurface measurements are commonly carried out on individual (discrete) samples at a fixed temperature, normally 20 °C. Here, the underway system observations are compared with co-located discrete observations to determine the consistency of these types of measurements. The co-located discrete fCO2w at 20 °C and underway fCO2w measurements at SST are used to infer the temperature dependence of CO2. In addition, calculated fCO2w from total alkalinity (TA) and total dissolved inorganic carbon (DIC) are compared with the underway and discrete fCO2w measurements. For 21 cruises spanning the major ocean basins from 1992 to 2020 a temperature dependence of 4.13 ± 0.01% °C−1 is determined in close agreement with a widely used previous empirical estimate of 4.23 ± 0.02% °C−1 for North Atlantic surface water. The temperature dependency of calculated fCO2w from TA and DIC using recommended constants is 4.10% °C−1 for 17 cruises where there are co-located measurements of fCO2w, TA and DIC.

Uniformitarian Prediction of Early‐Pleistocene Atmospheric CO2

AbstractDespite recent empirical and modeling advances, atmospheric CO2 concentrations during the early Pleistocene remain uncertain. Using a recently‐developed Bayesian paleoclimate model, an ensemble of seven different CO2 records is inferred conditional on reconstructions of past sea level. Five ensemble members give a consensus prediction that CO2 concentrations averaged 241 ppm (238–245 ppm 95% CI) between 2 and 0.8 Ma. Uncertainty estimates account for contributions from orbital forcing, age uncertainties, and other factors. Our consensus prediction aligns well with a compilation of previously published δ11B‐based CO2 reconstructions after calibration to late‐Pleistocene ice‐core CO2 values, as well as with 60 early‐Pleistocene CO2 measurements from the Allan Hills in East Antarctica. Our consensus prediction can be definitively tested by obtaining continuous ice‐core atmospheric CO2 records that extend into the early Pleistocene.

Monitoring of Atmospheric Carbon Dioxide over a Desert Site Using Airborne and Ground Measurements

Accurate monitoring of atmospheric carbon dioxide (CO2) is of great significance for studying the carbon cycle. Compared to ground observational sites, airborne observations cover a wider area, which help in effectively monitoring the distribution of CO2 sources and sinks. In this study, an airborne campaign was carried out in June and July 2021 to measure the atmospheric CO2 concentration over a desert site, Dunhuang, located in western China. The dry-air column-averaged CO2 mole fraction (XCO2) inversion results obtained from the Atmospheric Carbon Dioxide Lidar (ACDL) system were compared with the Orbiting Carbon Observatory 2 (OCO-2) retrievals, portable Fourier Transform Spectrometer (EM27/SUN) measurement results, and with the XCO2 estimates derived using the airborne Ultraportable Greenhouse Gas Analyzer (UGGA) and the Copernicus Atmosphere Monitoring Service (CAMS) model measurements. Moreover, the vertical CO2 profiles obtained from the OCO-2 and the CAMS datasets were also compared with the airborne UGGA measurements. OCO-2 and CAMS CO2 measurements showed a vertical distribution pattern similar to that of the aircraft-based measurements of atmospheric CO2. In addition, the relationship of atmospheric CO2 with the aerosol optical depth (AOD) was also determined and the results showed a strong and positive correlation between the two variables.

Local-Scale Horizontal CO2 Flux Estimation Incorporating Differential Absorption Lidar and Coherent Doppler Wind Lidar

A micro-pulse lidar system incorporating differential absorption lidar (DIAL) and coherent Doppler wind lidar (CDWL) is proposed and demonstrated. Due to the high signal-to-noise ratio (SNR) of the superconducting nanowire single-photon detector (SNSPD), the DIAL channel achieves high sensitivity in CO2 measurement. Meanwhile, the CDWL channel is used to obtain the horizontal wind field. In the process of the optimization and calibration of the DIAL receiver, specifically, mode scrambling and temperature control of the connecting fiber between the telescope and the SNSPD enhance the stability and robustness of the system. Horizontal scanning of the CO2 concentration and the wind field is carried out in a 6 km range over a scanning span of 60° with a radial resolution of 150 m and 15 s. The results show that the hybrid lidar system captures the spatial distribution of CO2 concentration and the wind field simultaneously. The horizontal net CO2 flux in a radius of 6 km is estimated by integrating the CO2 concentration and the wind transport vector, indicating different characteristics of horizontal net CO2 fluxes in an industrial area, a university campus, and a park. During most of the experiment, CO2 flux remained positive in the industrial area, but balances fell to nearly zero on the campus and in the park. The horizontal net fluxes averaged over 24 h in the three areas are 3.5 × 105 ppm·m2·s−1, 0.7 × 105 ppm·m2·s−1, and 0.1 × 105 ppm·m2·s−1.

(Invited) Electrical, Thermal, and H2o and CO2 Poisoning Behaviors of PrNi0.5Co0.5O3-δ Cathode for Proton Conducting Intermediate Temperature Solid Oxide Fuel Cell

PrNi0.5Co0.5O3-δ (PNC) cathode material demonstrates total electrical conductivity on the order of ~300 S/cm at 400-600oC in air, and the conductivity shows a slight increase as temperature increases with an activation energy (from ln(σT) vs 1/T plot) of 10.9 kJ/mol. The introduction of water vapor (H2O) leads to a small (~0.16%) increase in total resistivity, which is reversible upon water removal and explained, tentatively, by the defect reaction of H2O + 2Oo x + 2h• = 2(OH)O • + 0.5O2. The thermal expansion coefficient (TEC) of PNC is measured to be 17.6×10-6/K by dilatometry and 18.43×10-6/K by in situ XRD up to 800oC. On the other hand, despite bulk chemical stability for both PNC and BZCYYb4411 powders against low percentage H2O and CO2, a PNC cathode symmetrical cell over proton conducting BaZr0.4Ce0.4Y0.1Yb0.1O3-δ (BZCYYb4411) electrolyte shows degradation (or increase) in interfacial resistance upon introduction of 3% moisture or 5% CO2 into simulated air at temperature in the range of 650 to 450oC. In comparison, oxygen ion conducting symmetrical cells with PNC cathode and Ce0.9Gd0.1O2-δ (GDC) electrolyte show no change upon H2O and CO2 introduction. The observed sensitivity of the PNC cathode proton conducting symmetrical cell to H2O and CO2 is attributed to the preferred adsorption of H2O and CO2 molecules onto the BZCYYb4411 proton conducting electrolyte surface than on the PNC cathode, and such an explanation is supported by temperature programmed desorption (TPD) measurements for H2O and CO2 on both PNC and BZCYYb4411 powders.

Improving the Performance for Direct Electrolysis of CO2 in Solid Oxide Electrolysis Cell with Sr1.9Fe1.5Mo0.5 O6 - δ Electrode Via Infiltration of Pr6O11 Nanoparticles

High temperature direct CO2 electrolysis based on solid oxide electrolysis cell (CO2-SOEC) is a promising technology to convert carbon dioxide to carbon monoxide with a high current density and Faradaic efficiency. The exploration for suitable cathodes with desirable catalytic activity is a grand challenge for the development of CO2-SOEC. Sr2Fe1.5Mo0.5O6 - δ is often used as the cathode material for SOEC, but suffers from insufficient activity for CO2 reduction reaction (CO2RR). In this work, nanoscale Pr6O11 was infiltrated into the Sr1.9Fe1.5Mo0.5O6 - δ (SFM) electrode to promote the CO2RR performance in SOEC. The optimal loading of Pr6O11 is systematically investigated. At 800°C, the current density of the Pr6O11 infiltrated SFM cathode with a Pr6O11 loading of 13.4wt.% reaches 1.58 A/cm2 at 1.5V, which is 2.5 times higher than that of SFM cathode (0.63 A/cm2) at the same operating conditions. X-ray photoelectron spectroscopy characterization and temperature-programmed desorption of CO2 measurements indicate that the adsorption and desorption ability of CO2 of SFM cathode are improved by the infiltration of Pr6O11. Further, the polarization resistance of SFM cathode has significantly decreased with the infiltrated Pr6O11. These results demonstrate that the infiltration of Pr6O11 is a promising approach for increasing CO2RR activity. Acknowledgements Financial support from the U.S. Department of Energy (DE-EE0009427) and NASA EPSCoR (Grant # 80NSSC20M0233) is greatly appreciated.

Shock-tube study on high-temperature CO formation during dry methane reforming

The use of natural-gas-fueled combustion engines at unusual operating conditions to provide electrical and/or chemical energy on demand emphasizes the need for fundamental research on decomposition and formation of base chemicals at these conditions. In this work, the CO formation behind reflected shock waves from the pyrolysis of CO2/CH4 mixtures was investigated for the first time in the context of engine-based dry methane reforming, to understand the interaction of CO2 and CH4 at high temperatures and to test the validity of literature reaction mechanisms. Different CO2/CH4 mixtures at atmospheric pressure and temperatures between 1900 K and 2700 K were investigated. Time-resolved CO measurements were performed by laser absorption using a quantum cascade laser.With increasing CO2 addition later reaction onset was observed, showing a reduction in the overall reactivity. Rate of production and sensitivity analyses highlight competing reactions in the pyrolysis and oxidation pathways and that the number of available H radicals is limited, which is attributed to the reduced reactivity. However, the analysis shows that CO2 is also a source for OH radicals (via CO2 + H ⇌ CO + OH), which enhance methane decomposition. The comparison with literature reaction mechanisms showed that none of the tested mechanisms can perfectly predict the time-resolved CO formation, highlighting the need for the validation of detailed kinetics models under nontypical conditions.

Low-complexity methods to mitigate the impact of environmental variables on low-cost UAS-based atmospheric carbon dioxide measurements

Abstract. This article assesses the individual and joint impact of pressure, temperature, and relative humidity on the accuracy of atmospheric CO2 measurements collected by unmanned aerial systems (UASs) using low-cost commercial non-dispersive infrared (NDIR) sensors. We build upon previous experimental results in the literature and present a new dataset with increased gradients for each environmental variable to match the abrupt changes found in UAS-based atmospheric vertical profiles. As a key contribution, we present a low-complexity correction procedure to mitigate the impact of these variables and reduce errors in this type of atmospheric CO2 measurement. Our findings support the use of low-cost NDIR sensors for UAS-based atmospheric CO2 measurements as a complementary in situ tool for many scientific applications.