Black Carbon Emission Inventories Research Articles

Emission-Based Machine Learning Approach for Large-Scale Estimates of Black Carbon in China

Tremendous efforts have been made to construct large-scale estimates of aerosol components. However, Black Carbon (BC) estimates over large spatiotemporal scales are still limited. We proposed a novel approach utilizing machine-learning techniques to estimate BC on a large scale. We leveraged a comprehensive gridded BC emission database and auxiliary variables as inputs to train various machine learning (ML) models, specifically a Random Forest (RF) algorithm, to estimate high spatiotemporal BC concentration over China. Different ML algorithms have been applied to a large number of potential datasets and detailed variable importance and sensitivity analysis have also been carried out to explore the physical relevance of variables on the BC estimation model. RF algorithm showed the best performance compared with other ML models. Good predictive performance was observed for the training cases (R2 = 0.78, RMSE = 1.37 μgm−3) and test case databases (R2 = 0.77, RMSE = 1.35 μgm−3) on a daily time scale, illustrating a significant improvement compared to previous studies with remote sensing and chemical transport models. The seasonal variation of BC distributions was also evaluated, with the best performance observed in spring and summer (R2 ≈ 0.7–0.76, RMSE ≈ 0.98–1.26 μgm−3), followed by autumn and winter (R2 ≈ 0.7–0.72, RMSE ≈ 1.37–1.63 μgm−3). Variable importance and sensitivity analysis illustrated that the BC emission inventories and meteorology showed the highest importance in estimating BC concentration (R2 = 0.73, RMSE = 1.88 μgm−3). At the same time, albedo data and some land cover type variables were also helpful in improving the model performance. We demonstrated that the emission-based ML model with an appropriate auxiliary database (e.g., satellite and reanalysis datasets) could effectively estimate the spatiotemporal BC concentrations at a large scale. In addition, the promising results obtained through this approach highlight its potential to be utilized for the assessment of other primary pollutants in the future.

Responses of wildfire-induced global black carbon pollution and radiative forcing to climate change

The impacts of climate change on wildfires have been studied extensively. Along with declining emissions from fossil fuel combustion due to anthropogenic emission control, black carbon (BC) released from wildfires is expected to contribute a more significant portion to its atmospheric burden. However, from a global perspective, little is known about the BC burden and radiative forcing caused by wildfires. Here, we report the results from the long-term wildfire-induced BC concentration and direct radiative forcing (DRF) from 1981 to 2010 globally simulated by an Earth System Model using an updated wildfire BC emission inventory. We show that wildfire-induced BC concentration and DRF varied significantly spatially and temporarily, with the highest in sub-Saharan Africa, attributable to its highest level of wildfire BC emission worldwide. The temporal trends of near-surface air temperature, precipitation, and evapotranspiration and their association with wildfire-induced BC concentration are explored using the multidimensional ensemble empirical mode decomposition. A statistically significant relation between changes in climate parameters and wildfire-induced BC concentration was found for 53% of the land grid cells, explaining on average 33% of the concentration variations. The result suggests that the wildfire-induced BC DRF, with an increasing trend, would be an important contributor to climate change, especially in sub-Saharan Africa. Occurrences of wildfires in the Amazon Basin respond most strongly to climate change and play an increasingly important role in changing the global climate.

A Plant Species Dependent Wildfire Black Carbon Emission Inventory in Northern Eurasia

AbstractWildfire emission inventories are usually applied with biome‐scale emission factors for atmospheric modeling. However, emission factors measured for different plant species vary substantially within the same biome. We apply the species‐specific emission factors and refine the Fire Emission Inventory‐northern Eurasia (FEI‐NE), and derive the wildfire black carbon emission inventory in northern Eurasia from 2002 to 2015. Our new inventory produces 61% more black carbon emissions than current estimates based on Global Fire Emission Database (GFED) and 33% less than FEI‐NE. Model simulations with different inventories are compared with ground‐based and satellite retrievals of aerosol absorption optical depth (AAOD). Compared with the Ozone Monitoring Instrument, the normalized root mean square deviation of AAOD over northern Eurasia is reduced from 1.0 under FEI‐NE to 0.95 through application of the new inventory. This study reveals the importance of applying sub‐biome‐scale emission factors for wildfire inventories development and revisiting emissions uncertainty in atmospheric modeling.

Seasonal transition of Black carbon aerosols over Qinghai-Tibet Plateau: Simulations with WRF-Chem

Black carbon (BC) particles over the Qinghai-Tibet Plateau (Q-TP), whether suspended in the air or deposited on snow, can affect snow melt and accelerate glacier retreat. Since BC over the Q-TP may originate from different regions, it is necessary to understand the transport mechanism of BC and then provide concentrations and spatial-temporal distributions of BC over Q-TP, in order to study its radiative and climatic effects. In this study, Weather Research and Forecasting model with Chemistry (WRF-Chem), with MIX emission inventory (a mosaic Asian anthropogenic emission inventory for the MICS-Asia and the HTAP projects), was used to study the BC transport from South Asia, one of the major BC source regions, to Q-TP in April (pre-monsoon season), July (summer monsoon season) and December (winter monsoon season). The model's ability to simulate the BC transport from South Asia to the Q-TP was firstly evaluate using various reanalysis data, including 2 m temperature, precipitation, 10 m wind speed and direction and BC concentration at surface. The simulated meteorological fields and seasonal distribution and variation of BC are generally in good agreement with reanalysis data. The model showed good performance in simulating transport of BC as well. Our study showed that during pre-monsoon season, BC aerosols accumulated in the foothills of the Himalayas and were transported to southern Q-TP and even Southeast Asia via dry and wet deposition and westerly winds below 200hpa. Although the cyclonic airflow, which was favorable to transport, prevailed in South Asia, slight BC aerosols would be transported to Q-TP through wet deposition due to the efficient wet scavenging by abundant precipitation during summer monsoon season. During winter monsoon season, the prevailing westerly winds at 500hpa would transport BC aerosols from South Asia to Q-TP by dry deposition. A sensitivity simulation using PKU emission inventory (Peking University's global BC emission inventory) was then conducted to investigate the impact of different emission inventory on the modeling results. It is shown that the simulations using the different BC emission inventories overall did not have significant impacts on spatial distributions of surface concentration and column burden during three studies seasons. However, the simulated BC concentrations and burden based on PKU were overall higher than that based on MIX, that is, main differences were found in the southern part of Q-TP (i.e. adjacent to South Asia), especially during pre-monsoon and winter monsoon seasons. The differences of mean BC surface concentration ranging from 0.1 to 1 μg/m3, and burden ranging from 0.1 to 1 mg/m2 due to both higher dry and wet deposition (0.1–2 μg/m2/s for dry deposition flux, and 0.1–3 μg/m2/s for wet deposition flux) during pre-monsoon. During winter monsoon seasons, relatively large differences (0–3 μg/m3 for concentration, and 0–2 mg/m2 for burden, and 0.1–3 μg/m2/s for dry deposition flux) were found in southern Q-TP.

Emission characteristics and light absorption apportionment of carbonaceous aerosols: A tunnel test conducted in an urban with fully enclosed use of E10 petrol

To reduce the heavy dependence on petroleum, bioethanol has been increasingly employed as an alternative and sustainable transportation fuel. However, the characteristics of black carbon (BC) emissions from E10 petrol vehicles (i.e., ethanol-gasoline containing 10% ethanol) are still unclear, especially under real driving conditions. Here, a tunnel test was conducted during a cold winter. This tunnel was characterized by heavy traffic comprising more than 98% E10-fueled gasoline vehicles (GVs). Real-time BC concentrations, traffic parameters and meteorological conditions were recorded during the sampling campaign. The average BC concentration inside the tunnel (10.94 ± 5.02 μg m−3) was almost twice the background concentration. Based on aethalometer AE33 in situ measurements and the minimum R-squared (MRS) method, real-time aerosol light absorption was apportioned. The light absorption proportions of BC, primary brown carbon (BrC1) and secondary brown carbon (BrC2) were 79.86%, 2.78% and 17.36%, respectively, at 370 nm. The BC emission factor (EFBC) of the E10-fueled vehicles was 1.09 ± 0.49 mg km−1·veh−1 and 15.24 ± 6.85 mg·(kg fuel)−1, lower than those of traditional gasoline fueled vehicles in previous studies. This study can support the compilation of vehicular BC emission inventories, provide recommendations for biofuel policies and contribute to comprehensively understanding the climatic impact of E10 petrol.

Using Ice Cores to Evaluate CMIP6 Aerosol Concentrations Over the Historical Era

AbstractThe radiative effect of anthropogenic aerosols is one of the largest uncertainties in Earth's energy budget over the industrial period. This uncertainty is in part due to sparse observations of aerosol concentrations in the pre‐satellite era. To address this lack of measurements, ice cores can be used, which contain the aerosol concentration record. To date, these observations have been under‐utilized for comparison to aerosol concentrations found in state‐of‐the‐art Earth system models (ESMs). Here we compare long term trends in concentrations of sulfate and black carbon (BC) between 15 ice cores and 11 ESMs over nine regions around the world during the period 1850–2000. We find that for sulfate concentration trends model results generally agree with ice core records, whereas for BC concentration the model trends differ from the records. Absolute concentrations of both investigated species are overestimated by the models, probably in part due to representation errors. However, we assume that biases in relative trends are not altered by these errors. Ice cores in the European Alps and Greenland record a maximum BC concentration before 1950, while most ESMs used in this study agree on a post‐1950 maximum. We source this bias to an error in BC emission inventories in Europe. Emission perturbation experiments using NorESM2‐LM support the observed finding that BC concentrations in Northern Greenland ice cores are recording European emissions. Errors in BC emission inventories have implications for all future and past studies where Coupled Model Intercomparison Project Phase 6 historical simulations are compared to observations relevant to aerosol forcing.

Compilation of a city-scale black carbon emission inventory: Challenges in developing countries based on a case study in Brazil

Black carbon (BC) inventories for cities are scarce, especially in developing countries, despite their importance to tackle climate change and local air pollution. Here, we draw on results from a case study in a Brazilian city to discuss the challenges of compiling a BC inventory for different activity sectors. We included traditionally inventoried sectors, such as industries and on-road transportation, other less reported sectors (food establishments and aviation), and open burning of household solid waste (HSW), typically found in developing countries. We present a machine-learning technique (Random Forest) as a novel approach to obtain HSW burning activity using a set of spatial predictors. The BC inventory was based on PM2.5 emissions weighted by the fraction of PM2.5 emitted as BC and developed for the year 2018. We also reported the disaggregated spatial PM2.5 emissions for the same combustion sources, and documented the databases used for activity data and emission factors (EF). The total estimated BC and PM2.5 emissions amounted to 57.88 and 234.75 tons, respectively, with on-road vehicle exhaust emissions and industrial combustion as the main BC sources (63 and 22%, respectively). For PM2.5 emissions, on-road transportation (exhaust and non-exhaust) contributed 48%, followed by industrial combustion (21%) and food establishments (20%). Population density, number of vacant lots, and property tax values were identified as the most important features to predict the HSW fire activity. A comparison with other inventories revealed that the BC emission profile of Londrina is similar to the profile reported for Greater Mexico City, another Latin American city. Thus, the methodology used in this study could be extended to other cities with similar local BC sources. Finally, we highlight that the lack of local activity data, representative EF, and even methodology may undermine the development of reliable BC inventories, and intensive research should be conducted to characterize the emission sources.

Wintertime direct radiative effects due to black carbon (BC) over the Indo-Gangetic Plain as modelled with new BC emission inventories in CHIMERE

Abstract. To reduce the uncertainty in climatic impacts induced by black carbon (BC) from global and regional aerosol–climate model simulations, it is a foremost requirement to improve the prediction of modelled BC distribution, specifically over the regions where the atmosphere is loaded with a large amount of BC, e.g. the Indo-Gangetic Plain (IGP) in the Indian subcontinent. Here we examine the wintertime direct radiative perturbation due to BC with an efficiently modelled BC distribution over the IGP in a high-resolution (0.1∘ × 0.1∘) chemical transport model, CHIMERE, implementing new BC emission inventories. The model efficiency in simulating the observed BC distribution was assessed by executing five simulations: Constrained and bottomup (bottomup includes Smog, Cmip, Edgar, and Pku). These simulations respectively implement the recently estimated India-based observationally constrained BC emissions (Constrainedemiss) and the latest bottom-up BC emissions (India-based: Smog-India; global: Coupled Model Intercomparison Project phase 6 – CMIP6, Emission Database for Global Atmospheric Research-V4 – EDGAR-V4, and Peking University BC Inventory – PKU). The mean BC emission flux from the five BC emission inventory databases was found to be considerably high (450–1000 kg km−2 yr−1) over most of the IGP, with this being the highest (> 2500 kg km−2 yr−1) over megacities (Kolkata and Delhi). A low estimated value of the normalised mean bias (NMB) and root mean square error (RMSE) from the Constrained estimated BC concentration (NMB: < 17 %) and aerosol optical depth due to BC (BC-AOD) (NMB: 11 %) indicated that simulations with Constrainedemiss BC emissions in CHIMERE could simulate the distribution of BC pollution over the IGP more efficiently than with bottom-up emissions. The high BC pollution covering the IGP region comprised a wintertime all-day (daytime) mean BC concentration and BC-AOD respectively in the range 14–25 µg m−3 (6–8 µg m−3) and 0.04–0.08 from the Constrained simulation. The simulated BC concentration and BC-AOD were inferred to be primarily sensitive to the change in BC emission strength over most of the IGP (including the megacity of Kolkata), but also to the transport of BC aerosols over megacity Delhi. Five main hotspot locations were identified in and around Delhi (northern IGP), Prayagraj–Allahabad–Varanasi (central IGP), Patna–Palamu (mideastern IGP), and Kolkata (eastern IGP). The wintertime direct radiative perturbation due to BC aerosols from the Constrained simulation estimated the atmospheric radiative warming (+30 to +50 W m−2) to be about 50 %–70 % larger than the surface cooling. A widespread enhancement in atmospheric radiative warming due to BC by 2–3 times and a reduction in surface cooling by 10 %–20 %, with net warming at the top of the atmosphere (TOA) of 10–15 W m−2, were noticed compared to the atmosphere without BC, for which a net cooling at the TOA was exhibited. These perturbations were the strongest around megacities (Kolkata and Delhi), extended to the eastern coast, and were inferred to be 30 %–50% lower from the bottomup than the Constrained simulation.

Observed and Modeled Black Carbon Deposition and Sources in the Western Russian Arctic 1800-2014.

Black carbon (BC) particles contribute to climate warming by heating the atmosphere and reducing the albedo of snow/ice surfaces. The available Arctic BC deposition records are restricted to the Atlantic and North American sectors, for which previous studies suggest considerable spatial differences in trends. Here, we present first long-term BC deposition and radiocarbon-based source apportionment data from Russia using four lake sediment records from western Arctic Russia, a region influenced by BC emissions from oil and gas production. The records consistently indicate increasing BC fluxes between 1800 and 2014. The radiocarbon analyses suggest mainly (∼70%) biomass sources for BC with fossil fuel contributions peaking around 1960–1990. Backward calculations with the atmospheric transport model FLEXPART show emission source areas and indicate that modeled BC deposition between 1900 and 1999 is largely driven by emission trends. Comparison of observed and modeled data suggests the need to update anthropogenic BC emission inventories for Russia, as these seem to underestimate Russian BC emissions and since 1980s potentially inaccurately portray their trend. Additionally, the observations may indicate underestimation of wildfire emissions in inventories. Reliable information on BC deposition trends and sources is essential for design of efficient and effective policies to limit climate warming.

Quantification and implication of measurement bias of ambient atmospheric BC concentration

Black carbon (BC) aerosols have severe impacts on climate and health. Most atmospheric BC loadings are now predominantly reported for the PM2.5 size cut-off. Based on 39 published set of ambient BC concentrations from around the world where PM2.5 and PM10 were collected in parallel, we demonstrate that BC in PM2.5 was only around 80% of that in PM10. The implication is that around 20% of BC in the global ambient atmosphere is ignored with the now-legacy PM2.5 sampling approach. Correspondingly, BC of freshly emitted particles from combustion activities is dominantly reported in terms of PM2.5, and thus inflicting a bias in the total BC emission inventories. A consequence is that ambient BC is underpredicted when derived from models based on (PM2.5) emission inventories. This consideration contributes to reconcile existing systematic offset between model predictions and observation-based estimates of climate-relevant effects of anthropogenic BC aerosols. We propose that total ambient BC concentration should be considered rather than the PM2.5 portion to reduce the uncertainties in estimates of BC effects on the climate.

Optically Measured Black and Particulate Brown Carbon Emission Factors from Real-World Residential Combustion Predominantly Affected by Fuel Differences

Residential solid fuel use is an important source of black carbon (BC) but also a main source of uncertainty in BC emission inventories, as reliable real-world emission factors (EFs) and data on consumption of noncommercial household fuels are limited. In this study, particulate BC and brown carbon (BrC) for real-world indoor coal and biomass burning were evaluated using a SootScan model OT21 optical transmissometer from a field campaign including 343 biomass/coal combustion events. The highest BC EF from the burning of coal cake (a mixed fuel locally made from coal and clay) was 1.6-6.4 higher than that of other fuels, and BC EFs were higher for coal combustion than for biomass burning. The highest particulate BrC EF was from charcoal burning and was 1.5-4.3 times higher than that from other biomass and coals. Burning fuel in iron stoves had lower BC and BrC EFs, at approximately 15-66% and 40-54%, respectively, compared with burning in other stove types. The difference between heating and cooking activities was statistically insignificant (p > 0.05). A generalized linear model coupled with dominance analysis evidenced that the EFs were significantly associated with fuel and stove types, with the fuel difference being a major influencing factor explaining 68% of the variation. This suggests that a clean fuel transition would have beneficial impacts on air pollution associated with the residential sector in China. The absorption EFs differed by 2-3 orders of magnitude across different fuel-stove combinations. The Absorption Ångström Exponent values for the particulate from residential solid fuel combustions ranged from 0.92 to 3.7.

A 150-year record of black carbon (soot and char) and polycyclic aromatic compounds deposition in Lake Phayao, north Thailand.

An improved understanding of the historical variation in the emissions and sources (biomass burning, BB vs. fossil fuel, FF combustion) of soot and char, the two components of black carbon (BC), and polycyclic aromatic compounds (PACs) may help in assessing the environmental effects of the Atmospheric Brown Cloud (ABC) in SE Asia. We therefore determined historical variations of the fluxes of soot, char, and PACs (24 polycyclic aromatic hydrocarbons (PAHs), 12 oxygenated PAHs (OPAHs), and 4 azaarenes) in a dated sediment core (covering the past ∼150 years) of Phayao Lake in Thailand. The soot fluxes have been increasing in recent times, but at a far lower rate than previously estimated based on BC emission inventories. This may be associated with a decreasing BB contribution as indicated by the decreasing char fluxes from old to young sediments. The fluxes of high- and low-molecular-weight (HMW and LMW) PAHs, OPAHs, and azaarenes all sharply increased after ∼1980, while the ΣLMW-/ΣHMW-PAHs ratios decreased, further supporting the reduction in BB contribution at the expense of increasing FF combustion emissions. We also suggest that the separate record of char and soot, which has up to now not been done in aerosol studies, is useful to assess the environmental effects of ABC because of the different light-absorbing properties of these two BC components. Our results suggest that besides the establishment of improved FF combustion technology, BB must be further reduced in the SE Asian region in order to weaken the ABC haze.

Progress of the stable carbon and radiocarbon isotopes of black carbon aerosol

Black carbon (BC) aerosol derived from incomplete combustion of fossil fuel (e.g., coal and liquid petroleum) and biomass (e.g., agricultural residue, biofuel, and forest) is an important atmospheric pollutant globally. Besides presenting potential risks to public health, BC strongly absorbs solar radiation, decreases atmospheric visibility, heats the air, and is thought to be a key driver of climate warming. However, there is a large discrepancy between observations and models of the source apportionment and climate forcing of atmospheric BC globally, due to uncertain emission estimates. Stable carbon (13C) and radiocarbon (14C) isotope measurements are some of the most objective and accurate tools for apportioning atmospheric BC into key emission sources due to their unique fingerprint features. This review focuses on the principle of source apportionment for BC using 13C and 14C measurements, and the recent important progress in China, one of the largest emitters of BC. As expected, fossil fuel combustion is the largest contributor (70%−90%) of BC in many Chinese cities, mainly due to the huge consumption of coal and petroleum. However, the impact of biomass burning on BC can reach ~50% in some cities and even higher (~70%) in some remote sites, strongly reflecting the regional features of BC emission sources in China. Moreover, the largest and smallest contributions of fossil fuel combustion to BC are generally in summer and winter, respectively, highlighting the important influence of biomass burning on atmospheric BC during the cold season. The combined 13C and 14C measurements show that atmospheric BC in Northern China is mainly associated with coal combustion, followed by the burning of petroleum and biomass, which is very different from other regions where BC is typically dominated by petroleum burning. This implies that coal combustion is much more common and intensive in Northern China than in other regions. A strong correlation ( R 2 = 0.81) is observed between the 14C signal and atmospheric levoglucosan concentration in winter, while the correlation is very weak ( R 2 = 0.19) in summer. These results indicate that levoglucosan is chemically stable in the cold, but is degraded to a large extent in the atmosphere in summer. Compared with the levoglucosan concentration in winter, we roughly estimate that ~24% and ~70% of levoglucosan would be chemically degraded in spring and summer, respectively, which is consistent with chamber-based results (30%–75%). Therefore, we confirm that levoglucosan cannot quantify the impact of biomass burning on atmospheric BC in hot seasons. The source apportionment of BC based on emission-inventory technology is variable. In China, the contribution of biomass burning to BC could be as low as ~20% or as high as ~50%, depending on the emission inventory. Given the excellent ability of 13C and 14C isotopes to quantify atmospheric BC, this review notes that a combined 13C and 14C measurement technique can serve as a good “referee” to guide the improvement of the BC emission inventory and deepen our understanding of the environmental and climatic effects of BC aerosols. Future research should (1) establish a 13C-BC database for different combustion-related emission sources and regions, (2) bridge the emission inventory of BC and isotope-based observations using atmospheric chemistry models, (3) comprehensively explore the atmospheric stability of levoglucosan using carbon isotopes, and (4) build an atmospheric observation network for BC carbon isotopes covering urban, rural, and remote areas in China.

Twentieth Century Black Carbon and Dust Deposition on South Cascade Glacier, Washington State, USA, as Reconstructed From a 158‐m‐Long Ice Core

AbstractLight absorbing particles (LAPs) include black carbon (BC) and mineral dust and are of interest due to their positive radiative forcing and contribution to albedo reductions and snow and glacier melt. This study documents historic BC and dust deposition as well as their effect on albedo on South Cascade Glacier (SCG) in Washington State (USA) through the analysis of a 158‐m (139.5‐m water equivalent [w.e.]) ice core extracted in 1994 and spanning the period 1840–1991. Peak BC deposition occurred between 1940 and 1960, when median BC concentrations were 16 times higher than background, likely dominated by domestic coal and forest fire emissions. Post 1960 BC concentrations decrease, followed by an increase from 1977 to 1991 due to melt consolidation and higher emissions. Differences between the SCG record and BC emission inventories, as well as ice core records from other regions, highlight regional differences in the timing of anthropogenic and biomass BC emissions. Dust deposition on SCG is dominated by local sources and is variable throughout the record. Albedo reductions from LAP are dominated by dust deposition, except during high BC deposition events from forest fires and during 1940–1960 when BC and dust similarly contribute to albedo reductions. This study furthers understanding of the factors contributing to historical snowmelt and glacier retreat in the Cascades and demonstrates that ice cores retrieved from temperate glaciers have the potential to provide valuable records of LAP deposition.

Establishment and evaluation of anthropogenic black and organic carbon emissions over Central Plain, China

The Central China represented by Henan Province is one of the most haze-polluted regions in China with high levels of black carbon (BC) and organic carbon (OC) emissions. In this study, a 2016-based BC and OC emission inventory of Henan Province was developed based on detailed activity data and latest emission factors from different sources involving particulate matter. The total annual emissions of BC and OC were estimated to be 117.6 kt and 162.8 kt, respectively. Industrial process (44.2%) and industrial combustion (17.0%) were the top two contributors for BC emission, whereas OC emission was mainly from biomass burning (36.8%). Typical industrial cities were the major contributors to BC emission, by contrast, relatively higher OC emission was concentrated on agricultural cities in the southeast of Henan Province. The OC/BC ratios of industrial cities were generally lower than those of southeastern agricultural cities. The monthly variations presented that the highest BC and OC emissions were concentrated in January and June, respectively. Overall, in this study, the quantitative uncertainty ranges on the 95% confidence interval were approximately −30%–47% for BC and −38%–65% for OC. The emission inventory was also verified by qualitative comparison with other studies and indirect evaluation of OCpri/EC ratios, and the result was within a reasonable range. The ways of discussion and evaluation in this study can provide reference for other regions.

Simulation of Black Carbon Emissions from Gas Flaring Activities in the Niger Delta Region, Nigeria

There is no Black Carbon emission inventory for Nigeria and no standard Emission factor with which to measure the volume of emissions. This study aims at providing baseline emission inventory for the volume of Black Carbon released into the environment from gas flaring activities in the National Data Repository (NDR) between 1965 to 2016 (52 years) using Nigeria's associated petroleum gas-related emission factors; modelling of the estimated Black Carbon emissions using logistic growth model. The volume of gas produced and flared within this period was sourced from Nigerian National Petroleum Corporation (NNPC) annual bulletins and other literature. The work shows that: for the period under review, 1.8 trillion cubic meters of gas was produced and 0.91 trillion cubic meters was flared, only 11% of gas produced was flared in 2016. Estimated cumulative Black Carbon emission shows that Black Carbon emission from gas flare is decreasing as the volume of gas flared is decreasing. The model shows that 487050 tons, 1116157 tons; 19438 tons, 44544 tons and 0.10 are the respective carrying capacities, initial Black Carbon volumes and growth rate for the upper and lower Black Carbon emissions. Re-injection and Utilization of flared gas for cooking purposes and placing a heavy penalty on gas flaring activities are among solutions given to reduce gas flaring.

Black carbon physical and optical properties across northern India during pre-monsoon and monsoon seasons

Abstract. Black carbon (BC) is known to have major impacts on both climate and human health and is therefore of global importance, particularly in regions close to large populations that have strong sources. The size-resolved mixing state of BC-containing particles was characterised using a single-particle soot photometer (SP2). The study focusses on the Indo-Gangetic Plain (IGP) during the pre-monsoon and monsoon seasons. Data presented are from the UK Facility for Airborne Atmospheric Measurements BAe-146 research aircraft that performed flights during the pre-monsoon (11 and 12 June) and monsoon (30 June to 11 July) seasons of 2016. Over the IGP, BC mass concentrations were greater (1.95 µg m−3) compared to north-west India (1.50 µg m−3) and north-east India (0.70 µg m−3) during the pre-monsoon season. Across northern India, two distinct BC modes were recorded; a mode of small BC particles (core diameter <0.16 µm and coating thickness <50 nm) and a mode of moderately coated BC (core diameter <0.22 µm and coating thickness of 50–200 nm). The IGP and north-east India locations exhibited moderately coated black carbon particles with enhanced coating thicknesses, core sizes, mass absorption cross sections, and scattering enhancement values compared to much lower values present in the north-west. The coating thickness and mass absorption cross section increased with altitude (13 %) compared to those in the boundary layer. As the monsoon arrived across the region, mass concentration of BC decreased over the central IGP and north-east locations (38 % and 28 % respectively), whereas for the north-west location BC properties remained relatively consistent. Post-monsoon onset, the coating thickness, core size, mass absorption cross section, and scattering enhancement values were all greatest over the central IGP much like the pre-monsoon season but were considerably reduced over both north-east and north-west India. Increases in mass absorption cross section through the atmospheric column were still present during the monsoon for the north-west and central IGP locations, but less so over the north-east due to lack of long-range transport aerosol aloft. Across the Indo-Gangetic Plain and north-east India during the pre-monsoon and monsoon seasons, solid-fuel (wood burning) emissions form the greatest proportion of BC with moderately coated particles. However, as the monsoon develops in the north-east there was a switch to small uncoated BC particles indicative of traffic emissions, but the solid-fuel emissions remained in the IGP into the monsoon. For both seasons in the north-west, traffic emissions form the greatest proportion of BC particles. Our findings will prove important for greater understanding of the BC physical and optical properties, with important consequences for the atmospheric radiative forcing of BC-containing particles. The findings will also help constrain the regional aerosol models for a variety of applications such as space-based remote sensing, chemistry transport modelling, air quality, and BC source and emission inventories.

Constraining a Historical Black Carbon Emission Inventory of the United States for 1960–2000

AbstractWe present an observationally constrained United States black carbon emission inventory with explicit representation of activity and technology between 1960 and 2000. We compare measured coefficient of haze data in California and New Jersey between 1965 and 2000 with predicted concentration trends and attribute discrepancies between observations and predicted concentrations among several sources based on seasonal and weekly patterns in observations. Emission factors for sources with distinct fuel trends are then estimated by comparing fuel and concentration trends and further substantiated by in‐depth examination of emission measurements. We recommend (1) increasing emission factors for preregulation vehicles by 80–250%; (2) increasing emission factors for residential heating stoves and boilers by 70% to 200% for 1980s and before; (3) explicitly representing naturally aspired off‐road engines for 1980s and before; and (4) explicitly representing certified wood stoves after 1985. We also evaluate other possible sources for discrepancy between model and measurement, including bias in modeled meteorology, subgrid spatial heterogeneity of concentrations, and inconsistencies in reported fuel consumption. The updated U.S. emissions are higher than the a priori estimate by 80% between 1960 and 1980, totaling 690 Gg/year in 1960 and 620 Gg/year in 1970 (excluding open burning). The revised inventory shows a strongly decreasing trend that was present in the observations but missing in the a priori inventory.

Top-down estimate of black carbon emissions for city clusters using ground observations: a case study in southern Jiangsu, China

Abstract. We combined a chemistry transport model (the Weather Research and Forecasting and the Models-3 Community Multi-scale Air Quality Model, WRF/CMAQ), a multiple regression model, and available ground observations to optimize black carbon (BC) emissions at monthly, emission sector, and city cluster level. We derived top-down emissions and reduced deviations between simulations and observations for the southern Jiangsu city cluster, a typical developed region of eastern China. Scaled from a high-resolution inventory for 2012 based on changes in activity levels, the BC emissions in southern Jiangsu were calculated at 27.0 Gg yr−1 for 2015 (JS-prior). The annual mean concentration of BC at Xianlin Campus of Nanjing University (NJU, a suburban site) was simulated at 3.4 µg m−3, 11 % lower than the observed 3.8 µg m−3. In contrast, it was simulated at 3.4 µg m−3 at Jiangsu Provincial Academy of Environmental Science (PAES, an urban site), 36 % higher than the observed 2.5 µg m−3. The discrepancies at the two sites implied the uncertainty of the bottom-up inventory of BC emissions. Assuming a near-linear response of BC concentrations to emission changes, we applied a multiple regression model to fit the hourly surface concentrations of BC at the two sites, based on the detailed source contributions to ambient BC levels from brute-force simulation. Constrained with this top-down method, BC emissions were estimated at 13.4 Gg yr−1 (JS-posterior), 50 % smaller than the bottom-up estimate, and stronger seasonal variations were found. Biases between simulations and observations were reduced for most months at the two sites when JS-posterior was applied. At PAES, in particular, the simulated annual mean declined to 2.6 µg m−3 and the annual normalized mean error (NME) decreased from 72.0 % to 57.6 %. However, application of JS-posterior slightly enhanced NMEs in July and October at NJU where simulated concentrations with JS-prior were lower than observations, implying that reduction in total emissions could not correct modeling underestimation. The effects of the observation site, including numbers and spatial representativeness on the top-down estimate, were further quantified. The best modeling performance was obtained when observations of both sites were used with their difference in spatial functions considered in emission constraining. Given the limited BC observation data in the area, therefore, more measurements with better spatiotemporal coverage were recommended for constraining BC emissions effectively. Top-down estimates derived from JS-prior and the Multi-resolution Emission Inventory for China (MEIC) were compared to test the sensitivity of the method to the a priori emission input. The differences in emission levels, spatial distributions, and modeling performances were largely reduced after constraining, implying that the impact of the a priori inventory was limited on the top-down estimate. Sensitivity analysis proved the rationality of the near-linearity assumption between emissions and concentrations, and the impact of wet deposition on the multiple regression model was demonstrated to be moderate through data screening based on simulated wet deposition and satellite-derived precipitation.

Black carbon variability since preindustrial times in the eastern part of Europe reconstructed from Mt. Elbrus, Caucasus, ice cores

Abstract. Black carbon (BC), emitted by fossil fuel combustion and biomass burning, is the second largest man-made contributor to global warming after carbon dioxide (Bond et al., 2013). However, limited information exists on its past emissions and atmospheric variability. In this study, we present the first high-resolution record of refractory BC (rBC, including mass concentration and size) reconstructed from ice cores drilled at a high-altitude eastern European site in Mt. Elbrus (ELB), Caucasus (5115 m a.s.l.). The ELB ice core record, covering the period 1825–2013, reflects the atmospheric load of rBC particles at the ELB site transported from the European continent with a larger rBC input from sources located in the eastern part of Europe. In the first half of the 20th century, European anthropogenic emissions resulted in a 1.5-fold increase in the ice core rBC mass concentrations with respect to its level in the preindustrial era (before 1850). The summer (winter) rBC mass concentrations increased 5-fold (3.3-fold) in 1960–1980, followed by a decrease until ∼ 2000. Over the last decade, the rBC signal for summertime slightly increased. We have compared the signal with the atmospheric BC load simulated using past BC emissions (ACCMIP and MACCity inventories) and taken into account the contribution of different geographical regions to rBC distribution and deposition at the ELB site. Interestingly, the observed rBC variability in the ELB ice core record since the 1960s is not in perfect agreement with the simulated atmospheric BC load. Similar features between the ice core rBC record and the best scenarios for the atmospheric BC load support anthropogenic BC increase in the 20th century being reflected in the ELB ice core record. However, the peak in BC mass concentration observed in ∼ 1970 in the ice core is estimated to occur a decade later from past inventories. BC emission inventories for the period 1960s–1970s may be underestimating European anthropogenic emissions. Furthermore, for summertime snow layers of the 2000s, the slightly increasing trend of rBC deposition likely reflects recent changes in anthropogenic and biomass burning BC emissions in the eastern part of Europe. Our study highlights that the past changes in BC emissions of eastern Europe need to be considered in assessing ongoing air quality regulation.