Estimation of greenhouse gas emission factors based on observed covariance of CO2, CH4, N2O and CO mole fractions

During the global COVID-19 pandemic, anthropogenic emissions of air pollutants and greenhouse gases, especially traffic emissions in urban areas, have declined significantly. Long-term measurements of trace gas concentrations in urban areas can be used to quantify the impact of emission reductions on local air quality. Open-path Fourier transform infrared (OP-FTIR) spectroscopy is a non-intrusive technique that can be used to simultaneously measure multiple atmospheric trace gases in the boundary layer. This study investigates the reduction of surface CO, CO2 , and CH4 mole fractions during the lockdown in downtown Toronto, Canada, which is the fourth largest city in North America. The mean daily CO mole fraction anomaly (ΔCO) for the period from March 14 to May 18, 2020 declined by 46 ± 16% compared to the period before lockdown from January 13 to March 13, 2020. The mean daily ΔCO during the lockdown also declined relative to the same period in previous years: by 50 ± 20% relative to 2019 and by 44 ± 25% relative to 2018. Changes in the diurnal variations of CO, CO2 and CH4 during the lockdown are also investigated and compared to 2019 and 2018. Both CO and CO2 show early morning maxima on weekdays corresponding to rush hour. The change of the amplitude of the diurnal variation in CO during the lockdown is significant, compared to the period before lockdown. The differences in the diurnal variation in CO during the same two periods in 2019 and 2018 are not significant. Ratios of CO/CO2 anomalies show seasonal variations, which are also likely due to seasonal changes of emissions from local sources. These results show that the COVID-19 lockdown in Toronto modified surface mole fractions, diurnal variations, and ratios of air pollutants monitored by OP-FTIR. In addition, measured CO mole fractions are compared with simulated CO mole fractions by WRF-STILT to assess the relationship between atmospheric measurements and urban emissions from Toronto.

Effect of high-frequency alternating electric fields on the behavior and nitric oxide emission of laminar non-premixed flames

This paper compares the results of emission estimates of trace gases from open vegetation fires in southern hemisphere Africa for the year 2000 using different data sets. The study employs several approaches, deriving carbon monoxide (CO) emissions from a variety of satellite information, measurement data sets, and empirically‐based techniques to estimate burned areas (BA), fuel consumption (FC), and emission factors (EF). Three BA data sets are used: the Moderate Resolution Imaging Spectroradiomter (MODIS) burned area data set, the Global Burned Area data set for the year 2000 (GBA2000), and the Global Burn Scar Atlas (GLOBSCAR) in July and September, 2000. The estimated total BA in southern Africa varies significantly among data sets from 210,000 to 830,000 km2 for the sum of July and September. Temporal and spatial variations associated with CO emissions are analyzed using three different techniques for calculating the FC and EF. The first set of FC and EF extrapolates monthly variations in Zambia to southern Africa, the second extrapolates spatially resolved data for September to July, and the last includes monthly and spatial variations in both FC and EF. This analysis suggests the importance of accounting for the temporal and spatial variations in both FC and EF in order to determine the appropriate temporal and spatial variations of emissions from open vegetation fires. The CO emissions from open vegetation burning for the sum of July and September range from 18 to 31 Tg CO, using the MODIS BA data set and three different techniques for calculating FC and EF. The relative standard deviations (RSD) calculated from the three different methods are 58% for BA, 21% for FC, and 37% for EF. The best estimate of CO emissions from open biomass burning for the sum of the two months is 29 Tg CO, which may be compared to the estimates constrained by numerical models and measurements in 2000 which range from 22 to 39 Tg CO.

Tailpipe emissions of a pool of 13 Euro 6b light-duty vehicles (eight diesel and five gasoline-powered) were measured over an extensive experimental campaign that included laboratory (chassis dynamometer), and on-road tests (using a portable emissions measurement system). The New European Driving Cycle (NEDC) and the Worldwide harmonised Light-duty vehicles Test Cycle (WLTC) were driven in the laboratory following standard and extended testing procedures (such as low temperatures, use of auxiliaries, modified speed trace). On-road tests were conducted in real traffic conditions, within and outside the boundary conditions of the regulated European Real-Driving Emissions (RDE) test. Nitrogen oxides (NOX), particle number (PN), carbon monoxide (CO), total hydrocarbons (HC), and carbon dioxide (CO2) emission factors were developed considering the whole cycles, their sub-cycles, and the first 300 s of each test to assess the cold start effect. Despite complying with the NEDC type approval NOX limit, diesel vehicles emitted, on average, over the WLTC and the RDE 2.1 and 6.7 times more than the standard limit, respectively. Diesel vehicles equipped with only a Lean NOX trap (LNT) averaged six and two times more emissions over the WLTC and the RDE, respectively, than diesel vehicles equipped with a selective catalytic reduction (SCR) catalyst. Gasoline vehicles with direct injection (GDI) emitted eight times more NOX than those with port fuel injection (PFI) on RDE tests. Large NOX emissions on the urban section were also recorded for GDIs (122 mg/km). Diesel particle filters were mounted on all diesel vehicles, resulting in low particle number emission (~1010 #/km) over all testing conditions including low temperature and high dynamicity. GDIs (~1012 #/km) and PFIs (~1011 #/km) had PN emissions that were, on average, two and one order of magnitude higher than for diesel vehicles, respectively, with significant contribution from the cold start. PFIs yielded high CO emission factors under high load operation reaching on average 2.2 g/km and 3.8 g/km on WLTC extra-high and RDE motorway, respectively. The average on-road CO2 emissions were ~33% and 41% higher than the declared CO2 emissions at type-approval for diesel and gasoline vehicles, respectively. The use of auxiliaries (AC and lights on) over the NEDC led to an increase of ~20% of CO2 emissions for both diesel and gasoline vehicles. Results for NOX, CO and CO2 were used to derive average on-road emission factors that are in good agreement with the emission factors proposed by the EMEP/EEA guidebook.

Abstract. Biomass burning (BB) plumes were measured at the Cape Grim Baseline Air Pollution Station during the 2006 Precursors to Particles campaign, when emissions from a fire on nearby Robbins Island impacted the station. Measurements made included non-methane organic compounds (NMOCs) (PTR-MS), particle number size distribution, condensation nuclei (CN) > 3 nm, black carbon (BC) concentration, cloud condensation nuclei (CCN) number, ozone (O3), methane (CH4), carbon monoxide (CO), hydrogen (H2), carbon dioxide (CO2), nitrous oxide (N2O), halocarbons and meteorology. During the first plume strike event (BB1), a 4 h enhancement of CO (max ~ 2100 ppb), BC (~ 1400 ng m-3) and particles > 3 nm (~ 13 000 cm-3) with dominant particle mode of 120 nm were observed overnight. A wind direction change lead to a dramatic reduction in BB tracers and a drop in the dominant particle mode to 50 nm. The dominant mode increased in size to 80 nm over 5 h in calm sunny conditions, accompanied by an increase in ozone. Due to an enhancement in BC but not CO during particle growth, the presence of BB emissions during this period could not be confirmed. The ability of particles > 80 nm (CN80) to act as CCN at 0.5 % supersaturation was investigated. The ΔCCN / ΔCN80 ratio was lowest during the fresh BB plume (56 ± 8 %), higher during the particle growth period (77 ± 4 %) and higher still (104 ± 3 %) in background marine air. Particle size distributions indicate that changes to particle chemical composition, rather than particle size, are driving these changes. Hourly average CCN during both BB events were between 2000 and 5000 CCN cm-3, which were enhanced above typical background levels by a factor of 6–34, highlighting the dramatic impact BB plumes can have on CCN number in clean marine regions. During the 29 h of the second plume strike event (BB2) CO, BC and a range of NMOCs including acetonitrile and hydrogen cyanide (HCN) were clearly enhanced and some enhancements in O3 were observed (ΔO3 / ΔCO 0.001–0.074). A short-lived increase in NMOCs by a factor of 10 corresponded with a large CO enhancement, an increase of the NMOC / CO emission ratio (ER) by a factor of 2–4 and a halving of the BC / CO ratio. Rainfall on Robbins Island was observed by radar during this period which likely resulted in a lower fire combustion efficiency, and higher emission of compounds associated with smouldering. This highlights the importance of relatively minor meteorological events on BB emission ratios. Emission factors (EFs) were derived for a range of trace gases, some never before reported for Australian fires, (including hydrogen, phenol and toluene) using the carbon mass balance method. This provides a unique set of EFs for Australian coastal heathland fires. Methyl halide EFs were higher than EFs reported from other studies in Australia and the Northern Hemisphere which is likely due to high halogen content in vegetation on Robbins Island. This work demonstrates the substantial impact that BB plumes can have on the composition of marine air, and the significant changes that can occur as the plume interacts with terrestrial, aged urban and marine emission sources.

Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV

Remote sensing of PM, NO, CO and HC emission factors for on-road gasoline and diesel engine vehicles in Las Vegas, NV

Characteristics of the real-driving emissions from gasoline passenger vehicles in the Kuala Lumpur urban environment

Abstract. Emissions of greenhouse gases (GHGs) from the Indian subcontinent have increased during the last 20 years along with rapid economic growth; however, there remains a paucity of GHG measurements for policy-relevant research. In northern India and Bangladesh, agricultural activities are considered to play an important role in GHG concentrations in the atmosphere. We performed weekly air sampling at Nainital (NTL) in northern India and Comilla (CLA) in Bangladesh from 2006 and 2012, respectively. Air samples were analyzed for dry-air gas mole fractions of CO2, CH4, CO, H2, N2O, and SF6 and carbon and oxygen isotopic ratios of CO2 (δ13C-CO2 and δ18O-CO2). Regional characteristics of these components over the Indo-Gangetic Plain are discussed compared to data from other Indian sites and Mauna Loa, Hawaii (MLO), which is representative of marine background air. We found that the CO2 mole fraction at CLA had two seasonal minima in February–March and September, corresponding to crop cultivation activities that depend on regional climatic conditions. Although NTL had only one clear minimum in September, the carbon isotopic signature suggested that photosynthetic CO2 absorption by crops cultivated in each season contributes differently to lower CO2 mole fractions at both sites. The CH4 mole fraction of NTL and CLA in August–October showed high values (i.e., sometimes over 4000 ppb at CLA), mainly due to the influence of CH4 emissions from the paddy fields. High CH4 mole fractions sustained over months at CLA were a characteristic feature on the Indo-Gangetic Plain, which were affected by both the local emission and air mass transport. The CO mole fractions at NTL were also high and showed peaks in May and October, while CLA had much higher peaks in October–March due to the influence of human activities such as emissions from biomass burning and brick production. The N2O mole fractions at NTL and CLA increased in June–August and November–February, which coincided with the application of nitrogen fertilizer and the burning of biomass such as the harvest residues and dung for domestic cooking. Based on H2 seasonal variation at both sites, it appeared that the emissions in this region were related to biomass burning in addition to production from the reaction of OH and CH4. The SF6 mole fraction was similar to that at MLO, suggesting that there were few anthropogenic SF6 emission sources in the district. The variability of the CO2 growth rate at NTL was different from the variability in the CO2 growth rate at MLO, which is more closely linked to the El Niño–Southern Oscillation (ENSO). In addition, the growth rates of the CH4 and SF6 mole fractions at NTL showed an anticorrelation with those at MLO, indicating that the frequency of southerly air masses strongly influenced these mole fractions. These findings showed that rather large regional climatic conditions considerably controlled interannual variations in GHGs, δ13C-CO2, and δ18O-CO2 through changes in precipitation and air mass.

Abstract. We developed a new lightweight stratospheric air sampler (LISA). The LISA sampler is designed to collect four bag samples in the stratosphere during a balloon flight for CO2, CH4 and CO mole fraction measurements. It consists of four multi-layer foil (MLF) sampling bags, a custom-made manifold, and a diaphragm pump, with a total weight of ∼2.5 kg. A series of laboratory storage tests were performed to assess the stability of CO2, CH4 and CO mole fractions in both MLF and Tedlar bags. The MLF bag was chosen due to its better overall performance than the Tedlar bag for the three species CO2, CH4 and CO. Furthermore, we evaluated the performance of the pump under low pressure conditions to optimize a trade-off between the vertical resolution and the sample size. The LISA sampler was flown on the same balloon flight with an AirCore in Sodankylä, Finland (67.368∘ N, 26.633∘ E, 179 m a.s.l.), on 26 April and 4–7 September 2017. A total of 15 stratospheric air samples were obtained during the ascent of four flights. The sample size ranges between 800 and 180 mL for the altitude between 12 and 25 km, with the corresponding vertical resolution ranging from 0.5 to 1.5 km. The collected air samples were analysed for CO2, CH4 and CO mole fractions, and evaluated against AirCore retrieved profiles, showing mean differences of 0.84 ppm for CO2, 1.8 ppb for CH4 and 6.3 ppb for CO, respectively. High-accuracy stratospheric measurements of greenhouse gas mole fractions are useful to validate remote sensing measurements from ground and from space, which has been performed primarily by comparison with collocated aircraft measurements (0.15–13 km), and more recently with AirCore observations (0–30 km). While AirCore is capable of achieving high-accuracy greenhouse gas mole fraction measurements, it is challenging to obtain accurate altitude registration for AirCore measurements. The LISA sampler provides a viable low-cost tool for retrieving stratospheric air samples for greenhouse gas measurements that is complementary to AirCore. Furthermore, the LISA sampler is advantageous in both the vertical resolution and sample size for performing routine stratospheric measurements of the isotopic composition of trace gases.

It is a well-known fact that the effects of magnetic fields on combustion can be used to control and optimize the flame deformation and the flame brightness. The kinetics and equilibrium properties of chemical reactions of combustion are influenced by the magnetic force exerted on paramagnetic species. In this study, the effects of non-uniform magnetic fields on one-stage methane combustion reaction are numerically investigated. It is known that NO, OH, and O₂ are paramagnetic species and the other species and methane have diamagnetic behavior. Considering these facts, the effects of non-uniform magnetic field on 10 main product species of methane combustion are studied, by minimization of the Gibbs free energy. The results indicate that variation of non-uniform magnetic fields from 0 to 0.08 Tesla leads to decrease in NO mole fraction by 99.6 % in temperature range 1500-2500 K. Furthermore, the combination of non-uniform magnetic field and raising the pressure have the beneficial result in decreasing NO and CO mole fractions as well as rise in temperature.

Title: Efficiency of improved cookstoves and emission of Carbon Monoxide and Carbon Dioxide: an intervention study in Northern Ghana AbstractBiomass burning for home energy use is a major environmental health concern. Improved cooking technologies could generate environmental health benefits, yet prior results regarding reduced exposure to air pollution from improve cookstoves are mixed. In this study, 20 in-field uncontrolled cooking tests were conducted in domestic settings to assess the emission and efficiency of the Ace and the Jumbo stoves using the Emission Pod (EPOD) to measure emissions in real-time. Carbon Dioxide (CO2) and Carbon Monoxide (CO) emissions, Emission Factors (EF), Modified Combustion Efficiency (MCE) and Cooking time were all calculated across a variety of meal types using the two stoves. Overall average CO emission was estimated at 248.71±44.66 ppm for the Ace stove while that of the Jumbo stove was calculated to be 103.66±24.4 ppm (P=0.024). The Jumbo stove had a higher MCE of 0.93 against the Ace stove (0.84). Using the partial capture Carbon Balance Method (CBM), EF was calculated for both stoves with the Ace recording a CO EF of 1425.04 g/kg and CO2 EF of 1318.35 g/kg. The Jumbo, on the other hand, had a CO EF of 151.57 g/kg and a CO2 EF of 1215.82 g/kg. The study concluded that although the stoves had better performance in most of the parameters studied compared to other stove interventions in the literature, they still fell short when compared with some of the traditional cooking methods. While the Jumbo falls within the International Workshop Agreement (IWA) tier 4 category guidelines for cookstove, the Ace stove which is much fancier falls in WHO-IWA category 0.

Emissions of carbon monoxide and carbon dioxide from uncompressed and pelletized biomass fuel burning in typical household stoves in China

<p>A clear understanding of carbon monoxide (CO) emissions is important at various scales. On the local scale CO is toxic to living organisms, and on the global scale CO plays in role in the budget of  the hydroxyl radical (OH). OH, in turn, is important for the oxidizing capacity of the atmosphere. Additionally, CO is a precursor of the greenhouse gases ozone and carbon dioxide, hence CO influences also climate on a global scale.</p><p>Approximately one quarter of the global atmospheric CO load emanates from wildfires. However, these emissions are sometimes underrepresented in the emission datasets. Among the reasons for this discrepancy are clouds and smoke plumes hampering observations of land cover and active fires and uncertainties in emission factors. These issues are less relevant for top-down approaches like inverse modeling, which allow tracing back an atmospheric signal to its source even if it is only observed days after emission.</p><p>In this study, we attempt to improve the emission estimates of an existing inventory by applying an inverse modeling approach to the CO emissions of the California wildfires in 2018, that devastated more than 7500 square kilometers of forested and residential area. More specifically, we used the Fire Emission Inventory from NCAR (FINN) together with the CO observations from the TROPOMI instrument onboard the Sentinel 5 Precursor (S5P) satellite and the TM5-4dvar inverse model. The high resolution of the TROPOMI observations enables better spatial constraints compared to previous instruments. Preliminary results suggest significant positive emission increments compared to FINN.</p>

Abstract. This paper evaluates the performance of a multirotor uncrewed aircraft and AirCore system (UAAS) for measuring vertical profiles of wind velocity (speed and direction) and the mole fractions of methane (CH4) and carbon dioxide (CO2), and it presents a use case that combines UAAS measurements and dispersion modeling to quantify CH4 emissions from a dairy farm. To evaluate the atmospheric sensing performance of the UAAS, four field deployments were performed at three locations in the San Joaquin Valley of California where CH4 hotspots were observed downwind of dairy farms. A comparison of the observations collected on board the UAAS and an 11 m meteorological tower show that the UAAS can measure wind velocity trends with a root mean squared error varying between 0.4 and 1.1 m s−1 when the wind magnitude is less than 3.5 m s−1. Findings from UAAS flight deployments and a calibration experiment also show that the UAAS can reliably resolve temporal variations in the mole fractions of CH4 and CO2 occurring over periods of 10 s or longer. Results from the UAAS and dispersion modeling use case further demonstrate that UAASs have great potential as low-cost tools for detecting and quantifying CH4 emissions in near real time.