Biofuel Combustion Research Articles

Source profiling of air pollution and its association with acute respiratory infections in the Himalayan-bound region of India.

The studies related to air pollutants and their association with human health over the mountainous region are of utmost importance and are sparse especially over the Himalayan region of India. The linkages between various atmospheric variables and clinically validated data have been done using various datasets procured from satellite, model reanalysis, and surface observations during 2013-2017. Aerosol optical depth, air temperature, and wind speed are significantly related (p < 0.001) to the incidence of acute respiratory infections with its peak during winter. Model-derived particulate matter (PM2.5) shows high contributions of black carbon, organic carbon, and sulfate during winter. The wind roses show the passage of winds from the south-west and southern side of the region. Back trajectory density plot along with bivariate polar plot analyses have shown that most of the winds coming from the western side are taking a southward direction before reaching the study area and may be bringing pollutants from the Indo-Gangetic Plain and other surrounding regions. Our study shows that the accumulation of pollutants in the Himalayan valley is owing to the meteorological stability with significant local emissions from burning of biomass and biofuels along with long-range and mid-range transport during the winter season that significantly correlated with the incidence of acute respiratory infections in the region.

Modeling Investigation of Brown Carbon Aerosol and Its Light Absorption in China

Brown carbon (BrC) is a type of organic carbon with light-absorbing abilities, especially in ultraviolet (UV) radiation, which could significantly contribute to global warming. Observations have shown high BrC concentrations and absorption in China, suggesting potentially large BrC emissions. The potential contribution of fossil fuel combustion to BrC emission has been ignored in most previous studies. Here, we use GEOS-Chem to simulate BrC distribution and absorption in China, accounting for three major primary BrC sources: residential coal and biofuel combustion, vehicle exhausts, and open biomass burning. Based on the literature and related energy consumption data, we estimate the specific emission ratio of BrC versus BC, and BrC mass absorption efficiency (MAE) for each source. Combined with BC emission, total BrC emission in China is then estimated to be 3.42 Tg yr−1 in 2018, of which 71% is from residential combustion, 14% is from vehicle exhaust, and 15% is from open biomass burning. Residential combustion is the main source of surface BrC in China, accounting for 60% on average, followed by open biomass burning (23%) and vehicle exhaust emissions (17%). There is a clear seasonality in surface BrC concentrations with the maximum in winter (5.1 µg m−3), followed by spring (2.8 µg m−3), autumn (2.3 µg m−3), and summer (1.3 µg m−3). BrC AAOD at 365 nm ranges from 0.0017 to 0.060 in China, mainly dominated by residential combustion (73%), followed by open biomass burning (16%), and vehicle exhaust emissions (11%). It is also estimated that BrC accounts for 45–67% (52% on average) of total carbonaceous aerosol AAOD at 365 nm, implying an equal importance of BrC and BC regarding the absorption in UV radiation.

Laminar Burning Velocity and Ignition Delay Time of Oxygenated Biofuel

The need for lowering the environmental impacts has incentivized the investigation of biomass and biofuels as possible alternative sources for energy supply. Among the others, oxygenated bio-derived molecules such as alcohols, esters, acids, aldehydes, and furans are attractive substances as chemical feedstock and for sustainable energy production. Indeed, the presence of oxygen atoms limits the production of aromatic compounds, improves combustion efficiency (thus heat production) and alleviates the formation of carbon soot. On the other hand, the variability of their composition has represented one of the major challenges for the complete characterization of combustion behaviour. This work gives an overview of the current understanding of the detailed chemical mechanisms, as well as experimental investigations characterizing the combustion process of these species, with an emphasis on the laminar burning velocity and the ignition delay time. From the review, the common intermediates for the most relevant functional groups and combustion of biofuels were identified. The gathered information can be intended for the sake of core mechanism generation.

Replacing liquid fossil fuels and hydrocarbon chemical feedstocks with liquid biofuels from large-scale nuclear biorefineries

Liquid fossil fuels (1) enable transportation and (2) provide energy for mobile work platforms and (3) supply dispatchable energy to highly variable demand (seasonal heating and peak electricity). We describe a system to replace liquid fossil fuels with drop-in biofuels including gasoline, diesel and jet fuel. Because growing biomass removes carbon dioxide from the air, there is no net addition of carbon dioxide to the atmosphere from burning biofuels. In addition, with proper management, biofuel systems can sequester large quantities of carbon as soil organic matter, improving soil fertility and providing other environmental services. In the United States liquid biofuels can potentially replace all liquid fossil fuels. The required system has two key features. First, the heat and hydrogen for conversion of biomass into high-quality liquid fuels is provided by external low-carbon energy sources--nuclear energy or fossil fuels with carbon capture and sequestration. Using external energy inputs can almost double the energy content of the liquid fuel per unit of biomass feedstock by fully converting the carbon in biomass into a hydrocarbon fuel. Second, competing effectively with fossil fuels requires very large biorefineries—the equivalent of a 250,000 barrel per day oil refinery. This requires commercializing methods for converting local biomass into high-density storable feedstocks that can be economically shipped to large-scale biorefineries.

Development of a compact and robust kinetic mechanism for furan group biofuels combustion in internal combustion engines

A compact kinetic reaction mechanism for simulating the oxidation of the unsaturated furanic fuels including furan, 2-methylfuran (MF2) and 2,5-dimethylfuran (DMF) is proposed in this work. The mechanism is developed by integrating the major reaction pathways for the three furanic fuel components into a toluene reference fuel reaction mechanism. The sub-mechanism describing the formation and growth of polycyclic aromatic hydrocarbons up to pyrene is also incorporated so that the prediction of soot formation is enabled. The major reaction pathways for these furanic fuels are derived from the detailed furanic fuel reaction mechanism in the literature via a systematic selection and extraction procedure. An advanced genetic algorithm is applied to automatically optimize the rate parameters for the major furanic fuel reaction pathways. In addition, a simplified empirical soot model is embedded in the mechanism for simulating the soot formation process in the oxidation of the furanic fuels. The resulting mechanism, consisting of 145 species and 643 reactions, has been evaluated against the ignition delays, speciation profiles, laminar flame speeds as well as the soot mass measured from the combustion of the furanic fuels in the literature. The simulation results in general match satisfactorily well with the experimental data, suggesting the high performance of the proposed mechanism. The performance of the reaction mechanism for engine combustion simulation is also tested. A four-cylinder compression ignition engine is simulated using a coupled KIVA4-CHEMKIN code package. The influences of DMF on the engine combustion characteristics and soot emissions are investigated.

Mass absorption cross-section of black carbon from residential biofuel stoves and diesel trucks based on real-world measurements

Black carbon (BC) as an important part of atmospheric aerosols imposes adverse effects on atmospheric visibility, health, and climate change. Mass absorption cross-section (MACBC) is an essential parameter in BC quantitative and model research, which is of growing concern in recent decades. In this study, we conducted real-world measurements on BC emissions from two major sources of residential biofuel stoves and diesel trucks. BC emissions and MACBC values are quantified based on the photoacoustic and thermo-optical methods. The impacts of typical factors from biofuel stoves (biofuel and stove types) and diesel trucks (vehicle types, emission standards, and driving conditions) on BC/EC, MACBC values, and the relationships between BC and EC, BC/PM2.5 and MACBC are analyzed comprehensively. We find the BC and EC emissions from these two sources present good correlations, and those emissions are almost equal from diesel trucks, while the EC emissions from biofuel burning are slightly higher than BC. The typical factors for analysis may affect the optical properties of BC, and then will affect the mass ratio of BC/EC, indirectly. We have calculated the equivalent MACBC values and compared those with previous studies. Then, we further divided the equivalent MACBC values under several typical factors, which are 5.84 and 2.71 m2/g for improved and simple biofuel stoves, and 5.91 and 4.64 m2/g for light-duty and heavy-duty diesel trucks, respectively. Furthermore, the MACBC and BC/PM2.5 under the main operational metrics generally present good correlations. Our results will help to enhance the understanding of MACBC and provide effective data support for BC quantification and atmospheric model research.

Aging of mechanically activated wood: Effect on the burning ability

One of the aspects for optimizing the powdered biofuel combustion technology is to ensure proper relationship between powder production and its delivery into the reactor. This paper focuses on the effect of a time delay between production and use of powdered fuel on its combustion efficiency using pine sawdust as an example. It was established that the ignition delay time increases with an increasing delay between powdered fuel production and use (i.e., the effect of sample aging takes place). A correlation between the ignition delay time, the amount of lignin radicals, and the sample?s ability to release volatile combustible matter is demonstrated.

Inorganic PM and K emissions during ashing of solid biofuels and Kaolinite – Data measurement in laboratory scale

During combustion of solid biofuels, a broad variety of particulate matter (PM) is released into the atmosphere. Combustion systems are constantly being further improved according to the 3‑T rule (time, temperature and turbulence), thus further reducing the proportion of organic compounds in the PM. The inorganic share in PM is affected by this optimization in a rather small amount and therefore gains relevance. Woody and herbaceous biofuels are characterized by a varying elemental composition responsible for a different ash chemistry and thus for various amounts of emitted particles. To estimate the potential PM emissions as well as the corresponding K content related to the respective elements in the solid biofuels during combustion a new inorganic PM sampling method in the laboratory scale has been developed and tested. This method can forecast the amount of released inorganic PM and K during ashing of different biomasses. Here the inorganic PM of five different biomasses (i.e., spruce wood, wheat straw, spruce bark, corn cob and miscanthus) is measured. In addition, the influence of the additive Kaolinite (1 mas-%) is tested regarding the inorganic PM and K emissions during ashing of the biomasses spruce wood and miscanthus. Based on the obtained results from the ash analyses, conclusions concerning the applicability of the presented inorganic PM sampling method are derived. It can be shown, that the addition of 1 mas-% Kaolinite reduces the amount of K in the inorganic PM in the spruce wood and miscanthus sample by 55% and by 78%, respectively.

A Review of Torrefaction Technology for Upgrading Lignocellulosic Biomass to Solid Biofuels

The utilization of lignocellulosic biomass is closely related to one of the renewable sources of energy. However, a few inherent properties of lignocellulosic biomass such as high moisture content, low density, high volume, and heterogeneous composition make it unfavorable for bulk transportation, storage, handling, and conversion. The pretreatment of biomass is found to resolve a few of the aforementioned limitations while increasing the conversion efficiency of lignocellulosic biomass into biofuels. This article reviews the opportunities, challenges, and state-of-art research on torrefaction as a widely used biomass upgrading technique for solid fuel production and thermochemical biomass conversion. Some notable applications of such pretreatments in high-value solid biofuel production, densification, combustion, co-firing, gasification, and metallurgy have been reviewed. The broad changes in physicochemical characteristics and structural chemistry of lignocellulosic biomass because of torrefaction have been thoroughly described. This review also comprehends the effects of different process parameters and operating conditions of torrefaction of lignocellulosic biomass to produce high-value solid fuel. This article attempts to highlight some recent advancements in biomass torrefaction technology concerning the fundamental characteristics of biomass and process operation and optimization as well as the evolution of physicochemical features of torrefied biomass. Lastly, the value-added industrial applications of torrefaction technology and torrefied biomass are also elucidated.

Global and national assessment of the incidence of asthma in children and adolescents from major sources of ambient NO2

Pediatric asthma incidence has been associated with exposure to nitrogen dioxide (NO2) in ambient air. NO2 is predominantly emitted through fossil fuel use in land transportation, power generation and the burning of solid biofuels in households. We simulated NO2 with a global atmospheric chemistry model, combined with a land use regression model, to estimate NO2 exposure in all countries worldwide. The global asthma incidence among children and adolescents attributable to NO2 was estimated by deriving an exposure-response function from a meta-analysis which included epidemiological studies from multiple countries, baseline incidence rates from the Global Burden of Disease and gridded population data. The sectoral contribution to pediatric asthma from NO2 exposure (NO2-related asthma incidence: NINC) was estimated for different source categories to provide guidance to mitigation policies. We estimate 3.52 (2.1–6.0) million NINC per year globally, being about 14% of the total asthma incidence cases among children and adolescents. We find that emissions from land transportation are the leading contributor to NINC globally (∼44%), followed by the domestic burning of solid fuels (∼10.3%) and power generation from fossil fuels (∼8.7%). Biogenic emissions which are not anthropogenically induced may contribute ∼14% to the total NINC. Our results show large regional differences in source contributions, as the domestic burning of solid fuels is a main contributor to NINC in India and Nepal (∼25%), while emissions from shipping are the leading source in Scandinavian countries (∼40%), for example. While only 5% of all children and adolescents live in areas where NO2 exceeds the WHO annual guideline of 21.25 ppb (40 μg m−3) for NO2, about 90% of the NINC is found in regions that meet the WHO guideline, related to the uneven distribution of children and adolescents in the population. This suggests the need for stricter policies to reduce NO2 exposure, and revisiting the current WHO guideline to reduce the health risks of children and adolescents.

The mixtures of bio-oil derived from different biomass and coal/char as biofuels: Combustion characteristics

Bio-oil is produced as a promising fuel for improving the economics of biomass. However, bio-oil utilizations suffer from challenges due to its complex compositions. In this research three bio-oil samples (BSR, BPA and BFT) were blended with coal/char to prepare slurries as biofuels. The thermogravimetric analysis of combustion and ash compositions of biofuels were investigated. Results showed that bio-oils have more weight loss peaks than coal/char, and the Tm is concentrated in the range from 476.4 °C to 495.2 °C, which are much lower than char. The contribution of coal/char and bio-oils to biofuel blendings can be clearly seen in the combustion profiles. There is a synergistic effect between bio-oils and coal/char improving the combustion performance. Tb of lignite BSR slurry reduced up to around 40 °C in comparison with lignite. The temperature range for combustion became narrow. By blending BSR, the Ea of lignite, long flame coal and char reduced 5.65 kJ mol−1, 13.56 kJ mol−1 and 6.31 kJ mol−1, respectively. Lignite BSR slurry with the lowest activation energy presented best combustion characteristics among all biofuels. The improved performance may attribute to AAEMs contained in bio-oil and microexplosions occurred in combustion, and AAEMs also help form lower fusion temperature of ashes.

Selective Catalytic Reduction: From Basic Science to deNOx Applications

The combustion of coal, petroleum and biofuel for energy generation has resulted in unprecedented benefits to the prosperity of our modern society and will continue to do so in the future [...]

Source identification and global implications of black carbon

Black carbon (BC) is one of the short-lived air pollutants that contributes significantly to aerosol radiative forcing and global climate change. It is emitted by the incomplete combustion of fossil fuels, biofuels, and biomass. Urban environments are quite complex and thus, the use of mobile jointly with fixed monitoring provides a better understanding of the dynamics of BC distribution in such areas. The present study addresses the measurement of BC concentration using real-time mobile and ambient monitoring in Barranquilla, an industrialized urban area of the Colombian Caribbean. A microaethalometer (MA200) and an aethalometer (AE33) were used for measuring the BC concentration. The absorption Ångström exponent (AAE) values were determined for the study area, for identifying the BC emission sources. The results of the ambient sampling show that vehicle traffic emissions prevail; however, the influence of biomass burning was also observed. The mean ambient BC concentration was found to be 1.04 ± 1.03 μg/m3 and varied between 0.5 and 4.0 μg/m3. From the mobile measurements obtained in real traffic conditions on the road, a much higher average value of 16.1 ± 16.5 μg/m3 was measured. Many parts of the city showed BC concentrations higher than 20 μg/m3. The spatial distribution of BC concentration shows that vehicle emissions and traffic jams, a consequence of road and transport infrastructure, are the factors that most affect the BC concentration. A comparison of results obtained from two aethalometers indicates that the concentrations measured by MA200 are 9% lower than those measured by AE33. The AAE obtained was found to vary between 1.1 and 1.6, indicating vehicular emissions as the most crucial source. In addition, it was observed that the BC concentration on working days was 2.5 times higher than on the weekends in the case of mobile monitoring and 1.5 times higher in the case of ambient monitoring.

The interaction of the complex transfer processes in the phase transformations regimes of a water droplets

In this article the phase transformations of the water droplets in humid air flow are numerically modelled. The air temperature varies from 20°C to 1000°C, and the volume fraction of water vapor reaches up to 0.4. The droplet surface temperature dynamics defined by a numerical scheme which is based on by the fastest descent method. The interaction of complex heat and mass transfer processes has been investigated in the consistently changing water droplets condensation, transit and equilibrium evaporation regimes. Determination of droplets instantaneous temperatures in the iteration cycles is controlled by calculated heat fluxes balance condition, flowing toward and from the droplet surface, which must correspond to 99.95%. The reliability of the numerical method was confirmed when comparing the calculated water droplets equilibrium evaporation temperature in humid air with the wet bulb thermometer temperature, and with the experiments data. In the case of combined heating a calculated water droplets equilibrium evaporation vapor flux correlates well with other author's experimental data and modeling results. The numerical researches are emphasized specially for cases of water vapor condensate spraying in biofuel combustion technologies. The water droplet heat transfer as well as phase transformations transit and equilibrium evaporation processes were modelled in cases of convective and combined convective-radiative heating. In semi-transparent liquid the impact of absorbed radiation flux for water droplet complex transfer processes interaction was evaluated.

Effect of nanoparticles on the droplet combustion of rice bran oil biodiesel

The present study is dealt with the phenomenon of combustion for rice bran oil (RBO) methyl ester blends with diesel along with nanoparticles of magnelium. Nanoparticles composition of 25 ppm, 50 ppm, and 75 ppm are added to blends of B20, B40, and B60 in the study. A conversion rate of 89.64 ± 2.8% is observed during the transesterification reaction performed at 5 wt% of potassium hydroxide (KOH) catalyst, 10:1 alcohol to oil ratio (methanol), 75 °C reaction temperature, and 60 min reaction time. During the combustion study, few samples displayed the puffing characteristics, which are caused by popping of bubbles at lower pressure. The summary of the present study suggested that blend B20 with 25 ppm nanoparticles has the potential to be used as fuel and further proposed that the fuel will be more economical if the injection droplet diameter is 0.77 mm. Other blends like B20 with 75 ppm are also likely to be used as fuel due to its exhibition of lesser threat towards combustion. Bubble formation followed by micro-explosion is observed in B60 with 25 ppm blend. The present study hoped to enrich future researchers working in similar area for signifying the importance of understanding droplet combustion of biofuels.

Performance and emission analysis on the effect of exhaust gas recirculation in a tractor diesel engine using pine oil and soapnut oil methyl ester

The combustion of biofuel in compression ignition engines produces lower carbon monoxide and unburnt hydrocarbon emissions compared to diesel fuel but higher NOx emissions. In view of reducing NOx emission, the exhaust gas recirculation (EGR) technique was used in the present investigation to study its effect on engine performance and emission characteristics of a twin cylinder off-road vehicle diesel engine (Simpson S217-tractor). The blends of pine oil - soapnut oil methyl ester (P75SNB25), diesel - soapnut oil methyl ester (SNB20) were prepared on volume basis and used in the test engine with a fixed rate of 10% EGR under various loads. The soapnut oil was extracted from the soapnut seeds and trans-esterified in two stages using methanol and catalysts. The high viscosity of soapnut oil methyl ester is compensated by blending it with low viscous pine oil. The experiments were conducted in a four stroke, twin cylinder tractor diesel engine to study the performance and emission characteristics of the prepared biofuel blends. The results showed that the specific fuel consumption, exhaust gas temperature and HC emission of the hybrid biofuel blend P75SNB25 with 10% EGR rate decreased by 3.44%, 3.90% and 20% respectively than diesel operation without EGR at full load condition. The increase in brake thermal efficiency and CO emission of about 4.44% and 8% was also observed. For the blend SNB20 with 10% EGR, the reduction in HC, NOx emission and EGT was about 20%, 10.55% and 3.12% respectively at full load than diesel operation without EGR.

Impacts of chlorine emissions on secondary pollutants in China

The identified components of fine particulate matter with dynamic diameters less than 2.5 μm (PM2.5) suggests the remarkable increase in Cl− in PM2.5 during autumn and winter over North China. Anthropogenic chlorine emissions, including those from biomass burning, coal combustion and biofuel burning, are the main sources of Cl−, which could potentially affect the formation of secondary pollutants in the troposphere. In this study, we resolve the effect of chlorine emissions on PM2.5 and O3 by using the Weather Research and Forecasting (WRF) model coupled with Chemistry (WRF-Chem model) with an updated chemistry mechanism that includes the gaseous chemistry of chlorine, N2O5 heterogeneous reactions and detailed aqueous chemistry. Additionally, the biomass burning emissions of chlorine are derived from the Fire Inventory of the National Center for Atmospheric Research (NCAR) (FINN), which are considered the main contributor to atmospheric chloride over inland areas. The improved model is able to simulate the atmospheric Cl− in PM2.5 with reasonable agreement with the available observations in China. In addition, this model reduces the mean bias of ground-level PM2.5 concentrations from −7.5% to 3.2% over the BTH area and from −11.6% to −0.4% over the Northeast China Plain (NEP). The model also slightly improves O3 simulations by reducing the mean bias from 25.3% to 23.9% over mainland China. The anthropogenic chlorine emissions are estimated to increase the monthly average PM2.5 by 7.5 μg/m3 (9.1%), whereas ozone decreases slightly by up to 2.1 ppbv (4.3%) in November 2014. The influence of ozone was more significant in summer, reaching 2–8 ppbv over the biomass burning regions in 2014. The increase in Cl− and NH4+ accounted for the impacts on PM2.5, and the decline in O3 could be explained by the cycle between chlorine radicals and gases and changes in precursor concentrations. Our results suggest the importance of chlorine emissions and their chemical processes in the formation of PM2.5 and O3 over high-emission regions in China.

Poisoning of SCR Catalysts by Alkali and Alkaline Earth Metals

SCR still represents the most widely applied technique to remove nitrogen oxides from flue gas from both stationary and mobile sources. The catalyst lifetime is greatly affected by the presence of poisoning compounds in the exhaust gas that deactivate the catalysts over time on stream. The progressive and widespread transition towards bio-derived fuels is pushing research efforts to deeply understand and contrast the deactivating effects of some specific poisons among those commonly found in the emissions from combustion processes. In particular, exhaust gases from the combustion of bio-fuels, as well as from municipal waste incineration plants and marine engines, contain large amounts of alkali and alkaline earth metals that can severely affect the acid, redox, and physical properties of the SCR catalysts. This review analyzes recent studies on the effects of alkali and alkaline earth metals on different types of SCR catalysts divided into three main categories (conventional V2O5-WO3/TiO2, supported non-vanadium catalysts and zeolite-based catalysts) specifically focusing on the impact of poisons on the reaction mechanism while highlighting the different type of deactivation affecting each group of catalysts. An overview of the different regeneration techniques aimed at recovering as much as possible the original performance of the catalysts, highlighting the pros and cons, is given. Finally, current research trends aiming to improve the tolerance towards alkali-poisoning of SCR catalysts are reported.

A global anthropogenic emission inventory of atmospheric pollutants from sector- and fuel-specific sources (1970–2017): an application of the Community Emissions Data System (CEDS)

Abstract. Global anthropogenic emission inventories remain vital for understanding the sources of atmospheric pollution and the associated impacts on the environment, human health, and society. Rapid changes in today's society require that these inventories provide contemporary estimates of multiple atmospheric pollutants with both source sector and fuel type information to understand and effectively mitigate future impacts. To fill this need, we have updated the open-source Community Emissions Data System (CEDS) (Hoesly et al., 2019) to develop a new global emission inventory, CEDSGBD-MAPS. This inventory includes emissions of seven key atmospheric pollutants (NOx; CO; SO2; NH3; non-methane volatile organic compounds, NMVOCs; black carbon, BC; organic carbon, OC) over the time period from 1970–2017 and reports annual country-total emissions as a function of 11 anthropogenic sectors (agriculture; energy generation; industrial processes; on-road and non-road transportation; separate residential, commercial, and other sectors (RCO); waste; solvent use; and international shipping) and four fuel categories (total coal, solid biofuel, the sum of liquid-fuel and natural-gas combustion, and remaining process-level emissions). The CEDSGBD-MAPS inventory additionally includes monthly global gridded (0.5∘ × 0.5∘) emission fluxes for each compound, sector, and fuel type to facilitate their use in earth system models. CEDSGBD-MAPS utilizes updated activity data, updates to the core CEDS default scaling procedure, and modifications to the final procedures for emissions gridding and aggregation. Relative to the previous CEDS inventory (Hoesly et al., 2018), these updates extend the emission estimates from 2014 to 2017 and improve the overall agreement between CEDS and two widely used global bottom-up emission inventories. The CEDSGBD-MAPS inventory provides the most contemporary global emission estimates to date for these key atmospheric pollutants and is the first to provide global estimates for these species as a function of multiple fuel types and source sectors. Dominant sources of global NOx and SO2 emissions in 2017 include the combustion of oil, gas, and coal in the energy and industry sectors as well as on-road transportation and international shipping for NOx. Dominant sources of global CO emissions in 2017 include on-road transportation and residential biofuel combustion. Dominant global sources of carbonaceous aerosol in 2017 include residential biofuel combustion, on-road transportation (BC only), and emissions from the waste sector. Global emissions of NOx, SO2, CO, BC, and OC all peak in 2012 or earlier, with more recent emission reductions driven by large changes in emissions from China, North America, and Europe. In contrast, global emissions of NH3 and NMVOCs continuously increase between 1970 and 2017, with agriculture as a major source of global NH3 emissions and solvent use, energy, residential, and the on-road transport sectors as major sources of global NMVOCs. Due to similar development methods and underlying datasets, the CEDSGBD-MAPS emissions are expected to have consistent sources of uncertainty as other bottom-up inventories. The CEDSGBD-MAPS source code is publicly available online through GitHub: https://github.com/emcduffie/CEDS/tree/CEDS_GBD-MAPS (last access: 1 December 2020). The CEDSGBD-MAPS emission inventory dataset (both annual country-total and monthly global gridded files) is publicly available under https://doi.org/10.5281/zenodo.3754964 (McDuffie et al., 2020c).

Seasonal Cycle of Isotope‐Based Source Apportionment of Elemental Carbon in Airborne Particulate Matter and Snow at Alert, Canada

AbstractElemental carbon (EC) is a major light‐absorbing component of atmospheric aerosol particles. Here, we report the seasonal variation in EC concentrations and sources in airborne particulate matter (PM) and snow at Alert, Canada, from March 2014 to June 2015. We isolated the EC fraction with the EnCan‐Total‐900 (ECT9) protocol and quantified its stable carbon isotope composition (δ13C) and radiocarbon content (∆14C) to apportion EC into contributions from fossil fuel combustion and biomass burning (wildfires and biofuel combustion). Ten‐day backward trajectories show EC aerosols reaching Alert by traveling over the Arctic Ocean from the Russian Arctic during winter and from North America (&gt;40°N) during summer. EC concentrations range from 1.8–135.3 ng C m−3 air (1.9–41.2% of total carbon [TC], n = 48), with lowest values in summer (1.8–44.5 ng C m−3 air, n = 9). EC in PM (Δ14C = ‐532 ± 114‰ [ave. ± SD, n = 20]) and snow (−257 ± 131‰, n = 7) was depleted in 14C relative to current ambient CO2 year‐round. EC in PM mainly originated from liquid and solid fossil fuels from fall to spring (47–70% fossil), but had greater contributions from biomass burning in summer (48–80% modern carbon). EC in snow was mostly from biomass burning (53–88%). Our data show that biomass burning EC is preferentially incorporated into snow because of scavenging processes within the Arctic atmosphere or long‐range transport in storm systems. This work provides a comprehensive view of EC particles captured in the High Arctic through wet and dry deposition and demonstrates that surface stations monitoring EC in PM might underestimate biomass burning and transport.