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Fine particulate matter (PM 2.5) pollution is still one of China's most important environmental issues, especially in northern cities during wintertime. In this study, intensive real-time measurement campaigns were conducted in Xi'an, Shijiazhuang, and Beijing to investigate the chemical characteristics and source contributions of PM 2.5 and explore the formation of heavy pollution for policy implications. The chemical compositions of PM 2.5 in the three cities were all dominated by organic aerosol (OA) and nitrate (NO 3-). Results of source apportionment analyzed by a hybrid environmental receptor model (HERM) showed that the secondary formation source contributed more to PM 2.5 compared to other primary sources. Biomass burning was the dominant primary source in the three pilot cities. The contribution of coal combustion to PM 2.5 is non-negligible in Xi'an and Shijiazhuang but is no longer an important contributor in the capital city of Beijing due to the execution of a strict coal-banning policy. The potential formation mechanisms of secondary aerosol in the three cities were further explored by establishing the correlations between the secondary formation sources and aerosol liquid water content (ALWC) and Ox (O3+NO2) , respectively. The results showed that photochemical oxidation and aqueous-phase reaction were two important pathways of secondary aerosol formation. According to source variations, air pollution events that occurred in campaigns were classified into three types: biomass-combustion-dominated, secondary-formation-source-dominated, and a combination of primary and secondary sources. Additionally, this study compares the changes in chemical composition and source contributions of PM 2.5 in past decades. The results suggest that the clean-energy replacements for rural households should be urgently encouraged to reduce the primary source emissions in northern China, and collaborative control on ozone and particulate matter needs to be continuously promoted to weaken the atmosphere oxidation capacity for the sake of reducing secondary aerosol formation. [ABSTRACT FROM AUTHOR]

Fine particulate matter (PM2.5) pollution is still one of China's most important environmental issues, especially in northern cities during wintertime. In this study, intensive real-time measurement campaigns were conducted in Xi'an, Shijiazhuang, and Beijing to investigate the chemical characteristics and source contributions of PM2.5 and explore the formation progress of heavy pollution for policy implications. The chemical compositions of PM2.5 in the three cities were all dominated by organic aerosol (OA) and nitrate (NO3-). Results of source apportionment analyzed by the hybrid environmental receptor model (HERM) showed that the secondary nitrate plus sulfate contributed higher to PM2.5 compared to other primary sources. Biomass burning was the dominant primary source in the three pilot cities. The contribution of coal combustion to PM2.5 is non-negligible in Xi'an and Shijiazhuang but is no longer the important contributor in the capital city of Beijing due to the execution of a strict coal-banning policy. The potential formation mechanisms of secondary aerosol in three cities were further explored by establishing the correlations between the secondary nitrate plus sulfate and aerosol liquid water content (ALWC), and O x (O3 + NO2), respectively. The results showed that photochemical oxidation and aqueous-phase reaction were two important pathways of secondary aerosol formation. According to the source variations, air pollution events that occurred in campaigns were classified into three types: biomass combustion dominated, secondary nitrate plus sulfate dominated, and a combination of primary and secondary sources. Additionally, this study compared the changes in chemical composition and source contributions of PM2.5 in past decades. The results suggested that the clean energy replacements for the rural household should be urgently encouraged to reduce the primary source emissions in northern China, and collaborative control on ozone and particulate matter need to be continuously promoted to weaken the atmosphere oxidation capacity for the sake of reducing secondary aerosol formation. [ABSTRACT FROM AUTHOR]

Brown carbon (BrC) is a unique category of organic carbon aerosol that absorbs ultraviolet–visible light, influencing the radiative budget and climate change. An intensive observational study was conducted in a representative river-valley city in China to investigate the contributions of various organic aerosols (OA) to BrC light absorption. The influence of each OA component on BrC absorption exhibited fluctuations across different air quality levels and diurnal cycles, reflecting changes in emissions and meteorological conditions. Our results demonstrate that biomass-burning OA (BBOA) accounted for 33% of the BrC absorption at a wavelength of 370 nm, surpassing the contributions of coal combustion OA (CCOA) at 30% and cooking OA (COA) at 29% during the observation period. Notably, BBOA's contribution to BrC absorption intensified as air quality deteriorated from excellent to polluted, whereas COA's contribution decreased. The impact of CCOA on BrC absorption showed minor variations with air quality. Additionally, the source contributions to BrC absorption differed between daytime and nighttime, with CCOA dominating during daytime and BBOA leading at night. This study enhances our comprehension of BrC's optical characteristics and the array of sources influencing its light absorption in river-valley regions. [Display omitted] • Absorption Ångström exponent of brown carbon (BrC) indicates a rapid absorption decline during good air quality period. • Biomass-burning organic aerosol accounted for the largest fraction of BrC absorption. • BrC absorption sources varied, with CCOA dominated by day and BBOA by night. [ABSTRACT FROM AUTHOR]

The spontaneous combustion of coal gangue dumps after reclamation causes severe harm to the ecological environment surrounding mining areas. Using remote sensing technology to determine vegetation heat stress levels is an important way to evaluate the probability of a spontaneous combustion disaster. The canopy spectra and chlorophyll fluorescence (ChlF) parameters of alfalfa were collected through pot experiments to simulate different heat stress levels. Time series analyses of three ChlF (chlorophyll fluorescence) parameters showed that the regularity of the quantum efficiency of photosystem II (PSII) in light-adapted conditions ( Fv ′ / Fm ′ ) was stronger during the monitoring period. The correlation coefficients between the three ChlF parameters and the canopy raw spectrum, first derivative spectrum, and vegetation indices were calculated, and the spectral features were found to be more correlated. Lasso regression was used to further screen spectral features, and the optimal spectral features were the raw spectral value at 741 nm (abbreviated as RS (741)) and NDVI (652, 671). To discriminate among heat stress levels accurately and automatically, we built a time convolution neural network. The classification results showed that when the sequence length is 3, the heat stress is divided into three categories, and the model obtains the highest accuracy. In combination with relevant research conclusions on the temperature distribution law of spontaneous combustion in coal gangue dumps, three heat stress levels can be used to assess the potential of spontaneous combustion in coal gangue dumps after reclamation. The research results provide an important theoretical basis and technical support for early warnings regarding spontaneous combustion disasters in reclaimed coal gangue dumps. [ABSTRACT FROM AUTHOR]

Black carbon (BC) is one of the most important short-lived climate forcers, and atmospheric motions play an important role in determining its mass concentrations of pollutants. Here an intensive observation was launched in a typical river-valley city to investigate relationships between atmospheric motions and BC aerosols. Equivalent BC (e BC) source apportionment was based on an aethalometer model with the site-dependent absorption Ångström exponents (AAEs) and the mass absorption cross sections (MACs) retrieved using a positive matrix factorization (PMF) model based on observed chemical components (i.e., EC, POC, K + , Mg, Al, Si, S, Cl, Ca, V, Mn, Fe, Ni, Cu, As, Se, Br, Sr, Pb, Ga, and Zn) and primary absorption coefficients at selected wavelengths from λ=370 to 880 nm. The derived AAEs from 370 to 880 nm were 1.07 for diesel vehicular emissions, 2.13 for biomass burning, 1.74 for coal combustion, and 1.78 for mineral dust. The mean values for e BC fossil and e BC biomass were 2.46 and 1.17 µ g m -3 , respectively. Wind run distances and the vector displacements of the wind in 24 h were used to construct a self-organizing map, from which four atmospheric motion categories were identified (local-scale dominant, local-scale strong and regional-scale weak, local-scale weak and regional-scale strong, and regional-scale dominant). BC pollution was found to be more likely when the influence of local-scale motions outweighed that of regional-scale motions. Cluster analysis for the back-trajectories of air mass calculated by the Hybrid Single-Particle Lagrangian Integrated Trajectory model at the study site indicated that the directions of air flow can have different impacts for different scales of motion. The direct radiative effects (DREs) of source-specific e BC were lower when the influence of regional-scale motions outweighed that of the local ones. However, due to chemical aging of the particles during transport – the DRE efficiencies under regional-scale motions were ∼ 1.5 times higher than those under more local influences. The finding that the DRE efficiency of BC increased during the regional transport suggested significant consequences in regions downwind of pollution sources and emphasizes the importance of regionally transported BC for potential climatic effects. [ABSTRACT FROM AUTHOR]

Due to the complexity of emission sources, a better understanding of aerosol optical properties is required to mitigate climate change in China. Here, an intensive real-time measurement campaign was conducted in an urban area of China before and during the COVID-19 lockdown in order to explore the impacts of anthropogenic activities on aerosol light extinction and the direct radiative effect (DRE). The mean light extinction coefficient (bext) decreased from 774.7 ± 298.1 Mm -1 during the normal period to 544.3 ± 179.4 Mm -1 during the lockdown period. A generalised additive model analysis indicated that the large decline in bext (29.7 %) was due to sharp reductions in anthropogenic emissions. Chemical calculation of bext based on a ridge regression analysis showed that organic aerosol (OA) was the largest contributor to bext in both periods (45.1 %–61.4 %), and the contributions of two oxygenated OAs to bext increased by 3.0 %–14.6 % during the lockdown. A hybrid environmental receptor model combined with chemical and optical variables identified six sources of bext. It was found that bext from traffic-related emissions, coal combustion, fugitive dust, the nitrate and secondary OA (SOA) source, and the sulfate and SOA source decreased by 21.4 %–97.9 % in the lockdown, whereas bext from biomass burning increased by 27.1 %, mainly driven by the undiminished need for residential cooking and heating. An atmospheric radiative transfer model was further used to illustrate that biomass burning, rather than traffic-related emissions, became the largest positive effect (10.0 ± 10.9 W m -2) on aerosol DRE in the atmosphere during the lockdown. Our study provides insights into aerosol bext and DRE from anthropogenic sources, and the results imply the importance of controlling biomass burning for tackling climate change in China in the future. [ABSTRACT FROM AUTHOR]

PM2.5 is widely regarded as a major air pollutant due to its adverse health impacts and intimate relationship with the climate system. This study aims to characterize the chemical components (e.g., organic carbon (OC), elemental carbon (EC), water soluble ionic species (WSIS) and polycyclic aromatic hydrocarbons (PAHs) in PM2.5 collected at Doi–Inthanon in Chiang-Mai, Thailand, the highest mountain in Thailand. All samples (n = 50) were collected by MiniVolTM portable air samplers from March 2017 to March 2018. In this study we found the average PM2.5 concentration was 100 ± 48.6 μg m−3. The OC/EC ratio was 6.8 ± 3.0, and the decreasing order of the WSIS concentrations was SO42->Na+>Ca2+>NH4+>NO3->K+>Cl−>NO2->Mg2+> F-. The total concentrations of nineteen PAHs were defined as the sum of Ace, Fl, Phe, Ant, Fluo, Pyr, B[a]A, Chry, B[b]F, B[k]F, B[a]F, B[e]P, B[a]P, Per, Ind, B[g,h,i]P, D[a,h]A, Cor, and D[a,e]P. The concentration of total PAHs was 2.361 ± 2.154 µg m−3. Principal component analysis (PCA) highlights the importance of vehicular exhaust, biomass burning, diesel emissions, sea-salt aerosols and volatilization from fertilizers as the five dominant potential sources that accounted for 51.6%, 16.2%, 10.6%, 5.20% and 3.70% of the total variance, respectively. The rest of the 12.7% variance probably is associated with unidentified local and regional sources such as incinerators, joss paper/incense burning, and domestic cooking. Interestingly, the results from the source estimations from the PCA underlined the importance of vehicular exhaust as the major contributor to the PM2.5 concentrations in the ambient air of Don-Inthanon, Chiang-Mai province. However, it is crucial to emphasize that the impacts of agricultural waste burning, fossil fuel combustion, coal combustion and forest fires on the variations of OC, EC and WSIS contents were not negligible. [ABSTRACT FROM AUTHOR]

The impacts of anthropogenic emissions on the reduction of source‐specific equivalent black carbon (eBC) aerosols and their direct radiative effects (DREs) were investigated during the lockdown of the coronavirus outbreak in a megacity of China in 2020. Five eBC sources were identified using a hybrid environmental receptor model. Results showed that biomass burning, traffic‐related emissions, and coal combustion were the dominant contributors to eBC. The generalized additive model indicated that the reduction of traffic‐related eBC during the lockdown was entirely attributed to the decrease of emissions. Decreased biomass‐burning activities and favorable meteorological factors are both important drivers for the biomass‐burning eBC reduction during the lockdown. A radiative transfer model showed that the DRE efficiency of eBC from biomass burning was the strongest, followed by coal combustion and traffic‐related emissions. This study highlights that aggressive reduction in the consumption of residential solid fuels would be effective in achieving climate change mitigation. Plain Language Summary: Due to the lockdown of Coronavirus Disease 2019 (COVID‐19), anthropogenic activities were drastically reduced in China. A field campaign was conducted before and during the lockdown in a megacity of China. The results showed that equivalent black carbon (eBC) decreased by 51% during the lockdown compared with the normal days. The source apportionment of eBC indicated that traffic‐related emissions, biomass burning and coal combustion were the main eBC sources. The reduction of anthropogenic emissions brought a decrease of 1.4 ± 0.16 μg m−3 of traffic‐related eBC (eBCtraffic), 0.68 ± 0.23 μg m−3 of biomass‐burning eBC (eBCbiomass), and 0.3 ± 0.05 μg m−3 of coal combustion eBC (eBCcoal). In contrast, the meteorological factors barely contributed to eBCtraffic, but lowered 0.42 ± 0.48 μg m−3 of eBCbiomass, and raised eBCcoal by 0.1 ± 0.23 μg m−3. Although, eBCtraffic decreased most among all source‐specific BC in the lockdown, direct radiative effect (DRE) of eBCbiomass had the greatest decrease due to its high DRE efficiency. This study indicates that controlling traffic emissions is an effective approach for BC emission reduction, but aggressive reduction in the consumption of residential solid fuels would also make an effective contribution to climate change mitigation. Key Points: Equivalent black carbon (eBC) from traffic‐related emissions has decreased the mostthe most decrement in the COVID‐19 lockdownContribution of emission reduction to decreased BC concentration was greater than that of meteorological factors during COVID‐19 lockdownAggressive reduction in the consumption of residential solid fuels would be effective on climate change mitigation [ABSTRACT FROM AUTHOR]

To investigate the chemical composition, size distribution, and mixing state of aerosol particles on heavy pollution days, single-particle aerosol mass spectrometry was conducted during 9–26 October 2015 in Xi'an, China. The measured particles were classified into six major categories: biomass burning (BB) particles, K-secondary particles, elemental carbon (EC)–related particles, metal-containing particles, dust, and organic carbon (OC) particles. BB and EC-related particles were the dominant types during the study period and mainly originated from biomass burning, vehicle emissions, and coal combustion. According to the ambient air quality index, two typical episodes were defined: clean days (CDs) and polluted days (PDs). Accumulation of BB particles and EC-related particles was the main reason for the pollution in Xi'an. Most types of particle size were larger on PDs than CDs. Each particle type was mixed with secondary species to different degrees on CDs and PDs, indicating that atmospheric aging occurred. The mixing state results demonstrated that the primary tracers were oxidized or vanished and that the amount of secondary species was increased on PDs. This study provides valuable information and a dataset to help control air pollution in the urban areas of Xi'an. Graphical abstract [ABSTRACT FROM AUTHOR]

A single particle aerosol mass spectrometer was deployed in a heavily polluted area of China during a coronavirus lockdown to explore the impact of reduced anthropogenic emissions on the chemical composition, size distributions, mixing state, and secondary formation of urban aerosols. Ten particle groups were identified using an adaptive resonance network algorithm. Increased atmospheric oxidation during the lockdown period (LP) resulted in a 42.2%–54% increase in the major NaK-SN particle fraction relative to the normal period (NP). In contrast, EC-aged particles decreased from 31.5% (NP) to 23.7% (LP), possibly due to lower emissions from motor vehicles and coal combustion. The peak particle size diameter increased from 440 nm during the NP to 500 nm during LP due to secondary particle formation. High proportions of mixed 62NO 3 − indicate extensive particle aging. Correlations between secondary organic (43C 2 H 3 O+, oxalate) and secondary inorganic species (62NO 3 −, 97HSO 4 − and 18NH 4 +) versus oxidants (O x = O 3 + NO 2) and relative humidity (RH) indicate that increased atmospheric oxidation promoted the generation of secondary species, while the effects of RH were more complex. Differences between the NP and LP show that reductions in primary emissions had a remarkable impact on the aerosol particles. This study provides new insights into the effects of pollution emissions on atmospheric reactions and the specific aerosol types in urban regions. [Display omitted] • Different responses of the major species of NaK-SN and EC-aged to the COVID-19 lockdown. • Individual particles have larger size distribution during lockdown period than normal period. • NO 3 − was more widely mixed the whole particle type than HSO 4 − in Xiangyang • The atmospheric oxidation capacity was the domination pathway of secondary formation. [ABSTRACT FROM AUTHOR]

Residential coal combustion is a prominent source of brown carbon (BrC) aerosols, but knowledge of their molecular structures and optical absorption were limited, which have notable used in ambient BrC source identification and radiative forcing calculation. In this study, the Fourier transform–ion cyclotron resonance mass spectrometry combined with partial least squares regression analysis as well as Fourier transform infrared spectroscopy analysis were used to insight the molecular compounds and structures of BrC from anthracite and bituminous coal combustions between traditional and improved stoves. The absorption Ångström exponents (AAE) and mass absorption efficiency (MAE) values for the BrC emitted from the combinations of bituminous were both 1.2–2.5 times lower than those of anthracite, interpreting that the BrC from the anthracite emissions had greater light-absorbing capacity. In contrast, the emission factor of light absorption (EF Abs) at 365 nm for the bituminous coal combusted in the traditional stove was the highest among all the tested scenarios, which revealed that the incomplete combustion of bituminous coal could emit more BrC. It was noted that primary BrC emitted from the coal combustion with traditional stoves contains higher aromaticity groups of C–C and C＝O and higher S containing organics, whereas more aliphatic groups were found in BrC using the improved stoves. N-containing (CHON and CHONS) compounds were dominated in the total molecular formula of BrC, whereas the sum of CHON and CHO groups had high double-bond equivalent (DBE) values contributed 53.5%–87.1% to the total BrC absorption. Moreover, for CHOS, the lowest of estimated molecular absorption, DBE, and DBE/C should attribute to the non-chromophoric or weak absorptive S-containing compounds. This study supplied an effective evaluation method to compare BrC emissions and their absorption for coal combustion on regional scale. [Display omitted] • The BrC emitted from anthracite coal presented high light-absorbing capacity. • Calculated CHON and CHO compounds showed dominated light absorptions in BrC. • S-containing compounds present the less absorption of BrC. [ABSTRACT FROM AUTHOR]

Comparisons of aerosol composition and sources in different cities or regions are rather limited, yet important for an in-depth understanding of the spatial diversity of aerosol pollution in China. In this study, the data originating from 25 different winter aerosol mass spectrometer (AMS)/aerosol chemical speciation monitor (ACSM) studies were used to provide spatial coverage of the Beijing-Tianjin-Hebei (BTH), Guanzhong (GZ), Yangtze River Delta (YRD), and Pearl River Delta (PRD) regions. The spatial distribution and diurnal variations in aerosol composition and organic sources were analyzed to investigate the aerosol characteristics in the four regions. It was found that there were differences in the compositions of non-refractory particulate matter across the regions, e.g., more sulfate in the PRD versus more nitrate in the YRD, as well as in the organic sources, e.g., more coal combustion in BTH versus more biomass burning in GZ. The characteristics of the composition of NR-PM are similar when the campaigns were classified according to the winter of different years or the cities of different regions. The diurnal variation of the PRD-sulfate indicated its regional nature, whereas the organics from burning sources in two regions of northern China exhibited local characteristics. Based on these findings, we suggest that strict control policies for coal combustion and biomass burning emissions should be enforced in the BTH and GZ regions, respectively. [ABSTRACT FROM AUTHOR]

In this study, daily PM 2.5 samples were collected at an urban site in Yulin of Northern China during a winter season. Eight carbon fractions, 13 kinds of polycyclic aromatic hydrocarbons (PAHs), and nine water-soluble ions in PM 2.5 were measured. The light-absorption characteristics of brown carbon (BrC) both in water and in methanol extracts were evaluated and quantified. The total quantified PAHs exhibited high concentrations (228.4 ± 52.6 ng m −3 ), contributing 0.2% of the PM 2.5 mass. High indeno[1,2,3- cd ]pyrene/(indeno[1,2,3- cd ]pyrene + benzo[ghi]-perylene) ratio but low NO 3 − /SO 4 2− ratio revealed the important contribution of coal combustion to PM 2.5 . The absorption coefficient (b abs ) for methanol extracts measured at 365 nm averaged 27.5 ± 12.0 Mm −1 . Light absorption by methanol extracts exhibited strong wavelength dependence, with an average absorption Ångström exponent of 5.2 in the 330–400 nm range. The mass absorption cross section (for methanol extracts averaged 1.4 ± 0.4 m 2  g −1 by normalizing b abs measured at 365 nm to organic carbon mass. A relatively strong positive relationship between b abs, methanol and benzo[ a ]pyrene as well as with six carbon fractions indicated the important contribution of coal burning to BrC. Source apportionment based on the positive matrix factorization receptor model and multiple linear regression showed that residential coal combustion accounted for 37.4% of b abs365,methanol . The estimated relative radiative forcing by methanol-soluble organic carbon relative to elemental carbon was 36.9% at 300–400 nm. [ABSTRACT FROM AUTHOR]

Polycyclic aromatic hydrocarbons (PAHs) in urban fugitive dust, known for their toxicity and ability to generate reactive oxygen species (ROS), are a major public health concern. This study assessed the spatial distribution and health risks of 15 PAHs in construction dust (CD) and road dust (RD) samples collected from June to November 2021 over the cities of Tongchuan (TC), Baoji (BJ), Xianyang (XY), and Xi'an (XA) in the Guanzhong Plain, China. The average concentration of ΣPAHs in RD was 39.5 ± 20.0 μg g−1, approximately twice as much as in CD. Four-ring PAHs from fossil fuels combustion accounted for the highest proportion of ΣPAHs in fugitive dust over all four cities. Health-related indicators including benzo(a)pyrene toxic equivalency factors (BAP TEQ), oxidative potential (OP), and incremental lifetime cancer risk (ILCR) all presented higher risk in RD than those in CD. The multilayer perceptron neural network algorithm quantified that vehicular and industrial emissions contributed 86 % and 61 % to RD and CD BAP TEQ , respectively. For OP, the sources of biomass and coal combustion were the key generator which accounted for 31–54 %. These findings provide scientific evidence for the direct efforts toward decreasing the health risks of fugitive dust in Guanzhong Plain urban agglomeration, China. [Display omitted] • Fossil fuels combustion was the dominate source to PAHs in fugitive dust. • Monte Carlo simulated that dermal contact in dust was the main exposure pathway for human health risks. • Vehicle exhausts were the main source to RD BAP TEQ while industrial-related sources were dominated in CD BAP TEQ. • Biomass and coal combustion promoted the dust oxidation potential (OP) generation. [ABSTRACT FROM AUTHOR]

The 'extreme' emission abatement during the lockdown (from the end of 2019 to the early 2020) provided an experimental period to investigate the corresponding source-specific effects of aerosol. In this study, the variations of source-specific light absorption (b abs) and direct radiative effect (DRE) were obtained during and after the lockdown period by using the artificial neural network (ANN) and source apportionment environmental receptor model. The results showed that the b abs decreased for all sources during the two periods. The most reductions were observed with ∼90% for traffic-related emissions (during the lockdown) and ∼85% for coal combustion (after the lockdown), respectively. Heightened b abs (370 nm) values were obtained for coal and biomass burning during the lockdown, which was attributed to the enhanced atmospheric oxidization capacity. Nevertheless, the variations of b abs (880 nm) after the lockdown was mainly due to the weakening of oxidation and reduced emissions of secondary precursors. The present study indicated that the large-scale emission reduction can promote both reductions of b abs (370 nm) and DRE (34–68%) during the lockdown. The primary emissions decrease (e.g., Traffic emission) may enhance atmosphere oxidation, increase the ultraviolet wavelength light absorption and DRE efficiencies. The source-specific emission reduction may be contributed to various radiation effects, which is beneficial for the adopting of control strategies. • Source-specific babs and DRE were obtained during and after the lockdown. • The most reductions were observed with ∼90% for traffic-related emissions during the lockdown. • The environmental conditions were favorable to the increase of b abs in both periods. [ABSTRACT FROM AUTHOR]

Abstract In response to severe haze pollution, the Chinese State Council set PM 2.5 improvement targets for the Beijing-Tianjin-Hebei (BTH) region in 2013. To achieve the targets for the residential sector, semi-coke briquettes are being considered as a replacement for traditional raw coals with the help of financial subsidy, but information on the emission from them and the impacts on the air quality is limited. Laboratory experiments were conducted to determine emission factors (EFs) for a typical semi-coke briquette, its parent material (bituminous raw-coal-chunk) and three types of traditional coals (bituminous raw-coal-chunk, anthracite raw-coal-chunk and anthracite coal-briquette) extensively used in BTH. Compared with the parent material, significant lower EFs of primary PM 2.5 , organic carbon (OC), element carbon (EC), the sum of 16 polycyclic aromatic hydrocarbon components (PAHs), SO 4 2−, NO 3 −, hazardous trace elements (HTEs) and NO x were found in semi-coke briquette. A scenario for the BTH region in 2015 in which raw coals were replaced with the semi-coke briquette showed that amounts of pollutants emitted from residential coal combustion could decrease by 91.6% for primary PM 2.5 , 94.0% for OC, 99.6% for EC, 99.9% for PAHs, 94.2% for NO 3 −, 45.6% for HTEs, 70.9% for NO x and 22.3% for SO 2. However, SO 4 2− loadings evidently would increase if raw coals were replaced with either semi-coke briquette or anthracite coal-briquette. Geographic distributions of modeled reductions were developed to identify emission-reducing hot-spots and aid in the development of clean energy policies. Replacement of traditional raw coals with the semi-coke briquette apparently could lead to significant environmental improvements in BTH and other regions in China. Highlights • PM 2.5 and trace gases EFs for semi-coke briquette combustion were determined. • Semi-coke briquette had significant lower EFs than its parent material. • EFs for semi-coke briquette and traditional coal combustion in BTH were compared. • Emission reductions by switching to semi-coke briquette were estimated for BTH. • High-resolution spatial distribution of reduced emissions was modeled. [ABSTRACT FROM AUTHOR]