Biomass Burning Sources Research Articles

Saccharides in atmospheric PM2.5 in tropical forest region of southwest China: Insights into impacts of biomass burning on organic carbon aerosols

Biomass burning (BB) in South and Southeast Asia has a strong impact on regional air quality, yet its impact on atmospheric PM2.5 of tropical rainforest regions, a background region occupying a large area in South Asia, has rarely been investigated. In this work, we performed one-year PM2.5 sampling during December 2018 to October 2019 at a tropical rainforest site in southwest China. PM2.5 mass concentration, major chemical components, and ten saccharides were determined to study seasonal variations of PM2.5 chemical composition, and further to understand possible impacts of BB to organic carbon (OC) aerosols at this background region. The concentration levels of PM2.5, major PM2.5 components, and total saccharides were significantly higher in dry season than in wet season. Besides, PM2.5, OC, and total saccharides were highly correlated (R2 > 0.64, p < 0.001) during the sampling period, suggesting they might share common sources. Source apportionment of saccharides revealed that BB was the main source in both seasons. Furthermore, the contributions of BB to OC (BB/OC) were estimated using levoglucosan as a molecular tracer while levoglucosan's chemical degradation was considered. It was found that over 80% of LG was degraded in both seasons, suggesting BB sources were largely from the transport of external air mass. The estimated BB/OC were over 50%, indicating BB was an important source of OC and likely of PM2.5 in both seasons. The air-mass backward trajectory analysis and active fire spots data indicate intense BB emission sources were from South and Southeast Asia in dry season and the BB emissions in southern region of China could impact on the studied area in wet season.

Policy-driven variations in oxidation potential and source apportionment of PM2.5 in Wuhan, central China

China has implemented several control measures to mitigate PM2.5 pollution and improve air quality, such as the Action Plan for the Prevention and Control of Air Pollution (APPCAP). To comprehensively assess the changes in ambient PM2.5 concentrations and the corresponding health risk with the implementation of APPCAP, this study examined PM2.5 samples collected in Wuhan in 2012/2013 and 2018 for water-soluble ions, carbonaceous fractions, and elements, respectively. Dithiothreitol (DTT) assay was used to determine the oxidation potential (OP) of PM2.5. The positive matrix factorization (PMF) model and the multiple linear regression (MLR) model were used to analyze PM2.5 sources and the contribution of each source to the OP of PM2.5. The results showed that PM2.5 concentrations in Wuhan decreased significantly, however, there was little change in the health risk and a significant increase in intrinsic toxicity. DTTv (the volume-normalized dithiothreitol) showed high correlations (r > 0.5, p < 0.01) with water-soluble organic carbon (WSOC), organic carbon (OC), secondary ions (NO3−, SO42−, and NH4+), and elements. Compared to 2012/2013, the contribution of vehicle emissions and secondary aerosol sources to PM2.5 increased significantly in 2018. Biomass burning sources significantly contribute to DTTv in the summer and autumn, and secondary aerosol sources significantly contribute to DTTv in winter. The human health impacts from coal combustion sources remained high, while vehicle emission sources increased. In the context of decreasing PM2.5 concentrations, the role of vehicle emissions health impacts is increasingly significant due to the large increment in vehicle ownership and high inherent OP. Therefore, targeting vehicle emissions for control is of great importance for human health and needs to be given great attention in future policymaking.

Diurnal variation and source analysis of NMHCs at a background site of Nam Co (4,730 m a.s.l.) in the interior area of Tibetan Plateau

As the highest plateau in the world, the atmospheric environment of the Tibetan Plateau (TP) has a significant influence on the continental and global climate. The non-methane hydrocarbon (NMHC) characteristics at the background site Nam Co (4730 m a.s.l.) on the TP were investigated based on the concentration characteristics, diurnal variations, emission source identification, and transport pathways in the summer of 2020. The concentration of NMHC at the sampling site was 3408 pptv, which was lower than most of global background sites. The diurnal variations in the NMHC concentration at the sampling site were higher at night and noon and lower in the morning and afternoon, which was quite different from that in urban areas. Positive matrix factorization (PMF) and HYSPLIT models were used to identify the NMHC emission sources. The PMF model identified regional transport (40.2%), biomass burning (23.6%), vehicle emissions (22.0%), and biogenic sources (14.2%) as the predominant NMHC sources. The HYSPLIT model indicated the air masses over the sampling site could be clustered in three directions. The analysis of the potential source contribution function (PSCF) and concentration-weighted trajectory (WCWT) indicated the NMHC concentration at the sampling site was primarily influenced by air masses from the southern Tibet. The health risk assessment signified the benzene levels were high enough to cause a potential cancer risk during the sampling period. Research on the NMHC characteristics of background sites could provide the basis for studying the NMHC transport pathway between regions and the global atmospheric motions.

Arctic spring and summertime aerosol optical depth baseline from long-term observations and model reanalyses – Part 1: Climatology and trend

Abstract. We present an Arctic aerosol optical depth (AOD) climatology and trend analysis for 2003–2019 spring and summertime periods derived from a combination of multi-agency aerosol reanalyses, remote-sensing retrievals, and ground observations. This includes the U.S. Navy Aerosol Analysis and Prediction System ReAnalysis version 1 (NAAPS-RA v1), the NASA Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2), and the Copernicus Atmosphere Monitoring Service ReAnalysis (CAMSRA). Spaceborne remote-sensing retrievals of AOD are considered from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Multi-angle Imaging SpectroRadiometer (MISR), and the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Ground-based data include sun photometer data from AErosol RObotic NETwork (AERONET) sites and oceanic Maritime Aerosol Network (MAN) measurements. Aerosol reanalysis AODs and spaceborne retrievals show consistent climatological spatial patterns and trends for both spring and summer seasons over the lower Arctic (60–70∘ N). Consistent AOD trends are also found for the high Arctic (north of 70∘ N) from reanalyses. The aerosol reanalyses yield more consistent AOD results than climate models, can be verified well with AERONET, and corroborate complementary climatological and trend analysis. Speciated AODs are more variable than total AOD among the three reanalyses and a little more so for March–May (MAM) than for June–August (JJA). Black carbon (BC) AOD in the Arctic comes predominantly from biomass burning (BB) sources in both MAM and JJA, and BB overwhelms anthropogenic sources in JJA for the study period. AOD exhibits a multi-year negative MAM trend and a positive JJA trend in the Arctic during 2003–2019, due to an overall decrease in sulfate/anthropogenic pollution and a significant JJA increase in BB smoke. Interannual Arctic AOD variability is significantly large, driven by fine-mode and, specifically, BB smoke, with both smoke contribution and interannual variation larger in JJA than in MAM. It is recommended that climate models should account for BB emissions and BB interannual variabilities and trends in Arctic climate change studies.

Spatial characteristics and source apportionment of urban environmental black carbon concentrations based on mobile monitoring

Black carbon (BC) is an important component of airborne fine particulate matter, with significant impacts on global climate change and human health. Taking Minhang District of Shanghai as the study area, a microaethalometer (MA200) and GPS were installed on the electric taxi to form a mobile observation platform to identify the spatial distribution and hot spots of atmospheric BC in urban environment. We analyzed the sources and influencing factors of BC. The results showed that the overall characteristics of the spatial distribution pattern of near surface atmospheric BC in Minhang District of Shanghai were high in the north and low in the south. The average BC concentration was (4.11±4.87) μg·m-3. The average concentrations of BC in working days and non-working days were (4.22±1.49) and (3.52±2.26) μg·m-3. The variability of BC concentration in the high value area was large, indicating that the increases of BC concentration in mobile observation were related to traffic accidents in the road section. In addition to human activities, large-scale dense vegetation might inhibit BC diffusion. The Absorption ngström Exponent (AAE) was (0.82±0.54), which was closer to that of fossil fuel combustion. The contributions of fossil fuel emissions, biomass combustion, and mixed sources to BC sources were 67.5%, 4.9% and 27.6%, respectively.

Impact of biomass burning sources during the high season on PM2.5 pollution observed at sampling sites in Hanoi, Vietnam and Chiang Rai, Thailand

This study aimed to assess PM&lt;sub&gt;2.5&lt;/sub&gt; concentration and the potential impacts of biomass burning sources on PM&lt;sub&gt;2.5&lt;/sub&gt; measured at the sampling sites in Hanoi, Vietnam and Chiang Rai, Thailand during the high season (from January to April) in 2021 in which intensive biomass burning activities occur in Southeast Asia (SEA) region. For this purpose, an integrated approach of PM&lt;sub&gt;2.5&lt;/sub&gt; in-situ measurement, receptor and trajectory modelling techniques and satellite remote sensing was employed. Results showed that the average value of PM&lt;sub&gt;2.5&lt;/sub&gt; daily concentrations measured at the sampling site in Hanoi was higher than that at the sampling site in Chiang Rai during January–February (winter) periods. In contrast, the average value of PM&lt;sub&gt;2.5&lt;/sub&gt; daily concentrations measured at the sampling site in Hanoi was slightly lower than the counterpart at the sampling site in Chiang Rai during March–April (spring) periods. Elevated concentrations of PM&lt;sub&gt;2.5&lt;/sub&gt; measured in Chiang Rai during March–April periods were largely associated with intensive biomass burning activities in the SEA region. Positive Matrix Factorisation (PMF) receptor model-based source apportionment results indicated a larger contribution of biomass burning sources to the PM&lt;sub&gt;2.5&lt;/sub&gt; measured at the sampling site in Chiang Rai compared to that at the sampling site in Hanoi. Analysis of MODIS cumulative fire radiative power maps in the SEA region and three-day air masses backward trajectories arrived at the sampling sites in Hanoi and Chiang Rai further suggested the potential impacts of biomass burning sources on the PM&lt;sub&gt;2.5&lt;/sub&gt; measured at the sampling sites in Hanoi during the winter periods and in Chiang Rai during the spring periods.

Contrasting source contributions of Arctic black carbon to atmospheric concentrations, deposition flux, and atmospheric and snow radiative effects

Abstract. Black carbon (BC) particles in the Arctic contribute to rapid warming of the Arctic by heating the atmosphere and snow and ice surfaces. Understanding the source contributions to Arctic BC is therefore important, but they are not well understood, especially those for atmospheric and snow radiative effects. Here we estimate simultaneously the source contributions of Arctic BC to near-surface and vertically integrated atmospheric BC mass concentrations (MBC_SRF and MBC_COL), BC deposition flux (MBC_DEP), and BC radiative effects at the top of the atmosphere and snow surface (REBC_TOA and REBC_SNOW) and show that the source contributions to these five variables are highly different. In our estimates, Siberia makes the largest contribution to MBC_SRF, MBC_DEP, and REBC_SNOW in the Arctic (defined as &gt;70∘ N), accounting for 70 %, 53 %, and 41 %, respectively. In contrast, Asia's contributions to MBC_COL and REBC_TOA are largest, accounting for 37 % and 43 %, respectively. In addition, the contributions of biomass burning sources are larger (29 %–35 %) to MBC_DEP, REBC_TOA, and REBC_SNOW, which are highest from late spring to summer, and smaller (5.9 %–17 %) to MBC_SRF and MBC_COL, whose concentrations are highest from winter to spring. These differences in source contributions to these five variables are due to seasonal variations in BC emission, transport, and removal processes and solar radiation, as well as to differences in radiative effect efficiency (radiative effect per unit BC mass) among sources. Radiative effect efficiency varies by a factor of up to 4 among sources (1471–5326 W g−1) depending on lifetimes, mixing states, and heights of BC and seasonal variations of emissions and solar radiation. As a result, source contributions to radiative effects and mass concentrations (i.e., REBC_TOA and MBC_COL, respectively) are substantially different. The results of this study demonstrate the importance of considering differences in the source contributions of Arctic BC among mass concentrations, deposition, and atmospheric and snow radiative effects for accurate understanding of Arctic BC and its climate impacts.

Enhanced Deposition of Atmospheric Soluble Iron by Intrusions of Marine Air Masses to East Antarctica

AbstractBio‐essential iron can relieve nutrient limitation and stimulate marine productivity in the Southern Ocean. The fractional iron solubility of aerosol iron is an important variable determining iron availability for biological uptake. However, estimates of dissolved iron (dFe; iron &lt; 0.2 μm) and the factors driving the variability of fractional iron solubility in pristine air masses are largely unquantified. To constrain inputs of fractional iron solubility to remote East Antarctic waters, dFe, total dissolvable iron (TDFe), trace elements and refractory black carbon were analyzed in a 9‐year‐old snow pit (2005–2014) from a new ice core site at Aurora Basin North (ABN) in Wilkes Land, East Antarctica. Extremely low annual dFe deposition fluxes were estimated (0.2 × 10−6 g m−2 y−1), while annual TDFe deposition fluxes (70 × 10−6 g m−2 y−1) were comparable to other Antarctic sites. TDFe is dominantly sourced from mineral dust. Unlike coastal Antarctic sites where the variability of fractional iron solubility in modern snow is explained by a mixture of dust and biomass burning sources, dFe deposition and fractional iron solubility at ABN (ranging between 0.1% and 6%) is enhanced in episodic high precipitation events from synoptic warm air masses. Enhanced fractional iron solubility reaching the high elevation site at ABN is suggested through the mechanism of cloud processing of background mineral dust that modifies the dust chemistry and increases iron dissolution during long‐range transport. This study highlights a complex interplay of sources and processes that drive fractional iron solubility in pristine air masses.

Spatiotemporal Distribution and Source Apportionment of Suspended Polycyclic Aromatic Hydrocarbons in Surface Water

Polycyclic aromatic hydrocarbons (PAHs) are a type of typical environmental pollutant with carcinogenic effects and high ecological risk. With the development of industry, surface water acts as a primary sink for PAHs. Owing to their low solubility, a significant amount of PAHs are adsorbed onto suspended particulate matter in surface water, which presents a serious risk to human health and the ecological environment. To protect human health and aquatic organisms, a systematic assessment of the trends in PAHs exposure risk is essential. Based on long-term monitoring data from 2002 to 2016, this study systematically evaluated the spatiotemporal distribution and source apportionment of PAHs adsorbed on suspended particulate matter in surface water. The results of the Mann-Kendall test indicated that pollution levels of PAHs decreased from 2012 to 2016. The maximum average content was 6239 μg·kg-1, and the minimum was 2760 μg·kg-1. Benzo(b)fluoranthene, benzo(k)fluoranthene, chrysene, and benzo(a)anthracene showed significant declines from 2002-2016 (P<0.05). Levels of benzo(a)pyrene, dibenzo(a,h)anthracene, and indeno(1,2,3-cd)pyrene were steady. Wavelet analysis showed that the pollution level of PAHs had significant periodic oscillations for surface water. Midstream and downstream Σ16PAHs showed significant declines from 2002-2016 (P<0.05), whereas upstream Σ16PAHs were steady. ANOVA analysis showed that the spatial difference was significant and occurred in the following order:midstream (6168 μg·kg-1)>upstream (5407 μg·kg-1)>downstream (3412 μg·kg-1). Diagnostic ratio analysis and the positive matrix factorization model suggested that the major sources of PAHs were traffic sources, coal burning sources, and biomass combustion sources, which accounted for 40.9%, 33.7%, and 25.4%, respectively. The contribution of traffic sources decreased by 25.9%. The contributions of coal burning sources and biomass combustion sources increased by 4.8% and 21.1% from 2002-2009 to 2010-2016, respectively. These results provide scientific reference for risk analysis and the control of PAHs pollution in surface water.

Characteristics and Source Apportionment of Volatile Organic Compounds in August in the Chang-Zhu-Tan Urban Area

Continuous sampling using the tank sampling method were conducted in Changsha, Zhuzhou, and Xiangtan cities from August 18 to 27, 2020, and 106 VOCs species were analyzed using GC-MS analysis. Then, the regional VOCs concentrations, generation potential, and source of VOCs were studied. The results showed that the average φ(VOCs) was (20.5±10.5)×10-9 in the Changsha-Zhuzhou-Xiangtan area, in which OVOCs (33.5%) and alkanes (28.2%) accounted for the highest proportion. The ozone formation potential (OFP) of VOCs was 118.5 μg·m-3, and the contributions of aromatic hydrocarbons, olefin, and OVOCs to OFP were 37.4%, 24.2%, and 23.6%, respectively. The average secondary organic aerosol formation potential (SOAp) of the VOCs was 0.5 μg·m-3, and the contribution of aromatic hydrocarbons to SOAp was 97.0%, among which C8 aromatic hydrocarbons contributed 41.7%. Toluene, m/p-xylene, and o-xylene were the common dominant species that contributed significantly to OFP and SOAp. The characteristic ratio results showed that VOCs in Changsha were relatively influenced by industrial processes and solvent use, whereas Zhuzhou and Xiangtan were more affected by coal and biomass combustion. The PMF results showed that the VOCs mainly came from vehicle exhaust and oil and gas volatilization (27.2%), coal and biomass combustion (23.7%), industrial processes (20.4%), solvent use (17.2%), and natural sources (11.5%) in the Changsha-Zhuzhou-Xiangtan area.

Particle size-resolved emission characteristics of complex polycyclic aromatic hydrocarbon (PAH) mixtures from various combustion sources

Combustion of domestic solid fuels is a significant source of polycyclic aromatic hydrocarbons (PAHs). Some oxygenated PAHs (o-PAHs) and PAHs with molecular weight of 302 (MW302 PAHs) are more toxic than the traditional 16 priority PAHs, whereas their emissions were much less elucidated. This study characterized the size-dependent emissions of parent PAHs (p-PAHs), o-PAHs, and MW302 PAHs from various combustion sources. The estimated emission factors (eEFs) from biomass burning sources were highest for most of the PAHs (391–8928 μg/kg), much higher than that of anthracite coal combustion (43.0–145 μg/kg), both which were operated in an indoor stove. Cigarette smoking had a high eEF of o-PAHs (240 ng/g). MW302 PAHs were not found in the emissions of smoking, cooking, and vehicular exhausts. Particle-size distributions of PAHs were compound- and source-dependent, and the tendency to associate with smaller particles was observed especially in biomass burning and cigarette smoking sources. Furthermore, the inter-source differences in PAH eEFs were associated with their dominance in fine particles. PAH composition profiles also varied with the particle size, showing increasing contributions of large-molecule PAHs with decreasing sizes in most cases. The size distributions of p-PAHs are much more significantly dependent on their n-octanol/air partition coefficients and vapor pressures than those of o-PAHs, suggesting differences in mechanisms governing their distributions. Several molecular diagnostic ratios (MDRs), including two based on MW302 PAHs, specific to these combustion scenarios were identified. However, the MDRs within some sources are also strongly size-dependent, providing a new explanation for the uncertainty in their application for source identification of PAHs. This work also highlights the necessity for understanding the size-resolved atmospheric behaviors and fate of PAHs after their emission.

Identification and spatiotemporal distribution analysis of global biomass burning based on Suomi-NPP VIIRS Nightfire data

Biomass burning refers to the combustion of various organisms formed through photosynthesis, including natural and man-made biomass burning. Biomass combustion has great impacts on nature and human health. Biomass combustion and industrial heat sources overlap in temperature range, it is difficult to distinguish them with traditional methods. In order to explore the distribution of biomass combustion, the influence of industrial heat sources must be eliminated. This paper used Suomi-NPP (Suomi National Polar-orbiting Partnership) VIIRS (Visible Infrared Imaging Radiometer Suite) Nightfire data to extract 1,457,930 global biomass combustion objects from 2012 to 2018 based on the spatial distribution, occurrence frequency and duration characteristics of biomass combustion. The extracted results were verified using industrial directory Point of Interest (POI) data obtained online from high-resolution remote sensing images and place name maps, and the results showed that 98.37% of the industrial heat sources were successfully removed. The spatial and temporal characteristics of biomass combustion in regions with varying levels of economic development at the intercontinental, international and global levels from 2012 to 2018 were revealed in this paper. It also compares the temporal and spatial differences in biomass burning among different climate zones and land cover types from 2012 to 2018. Overall, global biomass burning showed an upward trend from 2012 to 2018 and increased significantly from 2015 to 2016. Global biomass combustion was mostly distributed in Africa, followed by Oceania and South America. Australia, Brazil, Russia, the United States and Canada were the five countries with the most biomass burning. The proportions of biomass burning in different climatic zones and land cover types also showed obvious regularity. Biomass combustion mostly occurred in low-latitude and high-temperature areas and in areas where the land cover types included shrublands, grasslands and farmlands.

Direct and indirect effects and feedbacks of biomass burning aerosols over Mainland Southeast Asia and South China in springtime

Southeast Asia is one of the largest biomass burning (BB) source regions in the world. In order to promote our understanding of BB aerosol characteristics and environmental impacts, this study investigated the emission, composition, evolution, radiative effects, and feedbacks of BB aerosols from Mainland Southeast Asia during 15 March to 15 April 2019 by using an online-coupled regional chemistry/aerosol-climate model RIEMS-Chem. Model results are compared against a variety of ground and vertical observations, indicating a generally good model performance for meteorology, aerosol chemical compositions, and aerosol optical properties. It is found that BB aerosols contributed significantly to regional particulate matter (PM), accounting for up to 90 % of the near-surface PM2.5, BC, and OC concentrations over the BB source regions of north Mainland Southeast Asia and for approximately 30–70 % over wide downwind areas including most areas of southwest China and portions of south China. At the top of atmosphere (TOA), BB aerosols exerted a positive all-sky radiative effect (DREBB) up to 25 W/m2 over north Vietnam and south China, a negative DREBB up to −10 W/m2 over Myanmar, western Thailand, and southwest China. Meanwhile, the indirect radiative effect (IREBB) was consistently negative, with the maximum of −10 W/m2 over downwind areas with cloud coverage, e.g., from north Vietnam to most of south China. The subregional (95–125°E and 10–30°N) and period mean DREBB and IREBB at TOA were estimated to be 0.69 W/m2 and − 0.63 W/m2, respectively, leading a total radiative effect (TREBB) of 0.06 W/m2 at TOA. The radiative effects of BB aerosols led to decreases in sensible and latent heat fluxes, near-surface temperature, PBL height, and wind speed of 6.0 Wm−2, 9.0 Wm−2, 0.26 °C, 38.7 m, and 0.1 m/s, respectively, accompanied with an increase in RH of 1.9 %, averaged over the subregion and the study period. The accumulated precipitation during the study period was apparently reduced by BB aerosols from east Thailand to south China, with the maximum reduction up to 14 cm (exceeding 40 %) over north Vietnam and south China. TREBB tended to increase mean near-surface PM2.5 and its component concentrations, with the maximum percentage increase up to 24 % over the BB source regions of north Mainland Southeast Asia, resulting from the combined effects of dynamic and chemical feedbacks. DREBB generally dominated over IREBB in the feedback-induced PM2.5 concentration changes.

Analysis on the Characteristics of Oxidation Potential and Influence Sources of PM2.5 in Baoding City in Winter

In order to explore the characteristics of PM2.5 oxidation potential and its impact sources in the suburbs of Baoding City in the winter of 2018, the dithiothreitol (DTT) method was used to determine the reactive oxygen species in PM2.5. Pearson correlation was used to analyze the relationship between the chemical components in PM2.5 and the oxidation potential. PMF was used to analyze the pollution source of DTTv. Firstly, the results showed that the average value of ρ(PM2.5) in Baoding in winter was (140.96±70.67) μg·m-3 higher than the concentration of PM2.5 in Beijing during the same period. Secondly, both the DTTv and DTTm values of the oxidation potential were higher during the day than those at night[DTTv was (2.37±0.76) nmol·(min·m3)-1 during the day and (2.14±1.17) nmol·(min·m3)-1 at night; DTTm was (0.96±0.60) pmol·(min·μg)-1 during the day and (0.76±0.41) pmol·(min·μg)-1 at night]. This showed that the atmospheric environment during the day was more conducive to the generation and survival of active oxygen. In addition, through the analysis of the correlation between DTTv and carbohydrates, inorganic salt ions, OC, EC, and water-soluble metals, it was found that metal Fe, oxalate, and NH4+ had a high correlation with DTTv both day and night (during the day:r=0.790, P<0.01, at night:r=0.960, P<0.01; during the day:r=0.609, P<0.01, at night:r=0.577, P<0.01; during the day:r=0.627, P<0.01, at night:r=0.586, P<0.01), and OC, levoglucan, mannan, and galactan were only highly correlated with DTTv in the daytime (r=0.675, P<0.01; r=0.701, P<0.01; r=0.662, P<0.01; r=0.671, P<0.01). Finally, according to the PMF source analysis, there were five main pollution sources that affected DTTv:secondary sources (29.9%), biomass combustion (29.2%), dust (11.2%), mineral dust and industrial sources (8.6%), and traffic sources (21.1%). The influence of secondary sources and biomass combustion on DTTv was dominant.

Siberian Arctic black carbon: gas flaring and wildfire impact

Abstract. As explained in the latest Arctic Monitoring and Assessment Programme (AMAP) report released in early 2021, the Arctic has warmed 3 times more quickly than the planet as a whole, as well as faster than previously thought. The Siberian Arctic is of great interest mainly because observations are sparse or largely lacking. A research aerosol station has been developed on Bely Island (Kara Sea) in western Siberia. Measurements of equivalent black carbon (EBC) concentrations were carried out at the “Island Bely” station continuously from August 2019 to November 2020. The source origin of the measured EBC and the main contributing sources were assessed using atmospheric transport modeling coupled with the most updated emission inventories for anthropogenic and biomass burning sources of BC. The obtained climatology for BC during the period of measurements showed an apparent seasonal variation with the highest concentrations between December and April (60 ± 92 ng m−3) and the lowest between June and September (18 ± 72 ng m−3), typical of the Arctic haze seasonality reported elsewhere. When air masses arrived at the station through the biggest oil and gas extraction regions of Kazakhstan, Volga-Ural, Komi, Nenets and western Siberia, BC contribution from gas flaring dominated over domestic, industrial and traffic sectors, ranging from 47 % to 68 %, with a maximum contribution in January. When air was transported from Europe during the cold season, emissions from transportation were more important. Accordingly, shipping emissions increased due to the touristic cruise activities and the ice retreat in summertime. Biomass burning (BB) played the biggest role between April and October, contributing 81 % at maximum in July. Long-range transport of BB aerosols appeared to induce large variability to the absorption Ångström exponent (AAE) with values &gt; 1.0 (excluding outliers). As regards the continental contribution to surface BC at the Island Bely station, Russian emissions dominated during the whole year, while European and Asian ones contributed up to 20 % in the cold period. Quantification of several pollution episodes showed an increasing trend in surface concentrations and frequency during the cold period as the station is directly in the Siberian gateway of the highest anthropogenic pollution sources to the Russian Arctic.

Field measurements of PM2.5 emissions from typical solid fuel combustion in rural households in Fenhe Basin, China

Solid fuel is the most widely used energy source for cooking and heating in the rural households in developing countries. In this study, emissions from 13 fuel–stove combinations were studied in two typical rural villages in the Fenhe Basin, Shanxi Province, China. This study gathered data on the emission characteristics of particles with an aerodynamic diameter of ≤2.5 μm (PM2.5), organic carbon (OC), elemental carbon (EC), and 21 parent and oxygenated polycyclic aromatic hydrocarbons (pPAHs and oPAHs, respectively); the mechanism of gas formation was also determined. The PM2.5 EFs of biomass burning ranged from 4.11 ± 2.12 to 138 ± 47.2 g/kg, which was higher than that of coal combustion (1.57 ± 0.89 to 4.11 ± 0.63 g/kg). Notably, the average PM2.5 EFs of biomass burning in a traditional stove and elevated kang were 50.9 ± 13.8 and 23.0 ± 3.99 g/kg, respectively, suggesting that the elevated kang had superior emission mitigation. Wood pellet burning in a biomass furnace yielded lower PM2.5 EFs than firewood burning in the biomass furnace, which demonstrated wood pellet combustion's superior emission reduction effect. The relative contribution of OC4 to OC subfractions may be useable as tools for identifying the sources of coal and biomass burning. Regarding PAHs, biomass with abundant lignin pyrolysis produced numerous hydroxyl radicals that were conducive to the release of greater proportions of oPAHs. By contrast, pPAHs had greater relative contributions in coal combustion. Regarding gaseous pollutants, its formation mechanism varied with combustion phase. Emission differences between the two phases were mainly determined by the relative contributions of volatile C/N and char. Clarifying the pollutant formation mechanism can better guide the implementation of emission control from household solid fuel combustion.

Impacts of severe residential wood burning on atmospheric processing, water-soluble organic aerosol and light absorption, in an inland city of Southeastern Europe

This study examines the concentrations and characteristics of carbonaceous aerosols (including saccharides) and inorganic species measured by PM2.5 filter sampling and a multi-wavelength Aethalometer during two campaigns in a mountainous, medium-sized, Greek city (Ioannina). The first campaign was conducted in summer and used as a baseline of low concentrations, while the second took place in winter under intensive residential wood burning (RWB) emissions. Very high winter-mean OC concentrations (26.0 μg m−3) were observed, associated with an OC/EC ratio of 9.9, and mean BCwb and PM2.5 levels of 4.5 μg m−3 and 57.5 μg m−3, respectively. Simultaneously, record-high levoglucosan (Lev) concentrations (mean: 6.0 μg m−3; max: 15.9 μg m−3) were measured, revealing a severely biomass burning (BB)-laden environment. The water-soluble OC component (WSOC) accounted for 56 ± 9% of OC in winter, exhibiting high correlations (R2 = 0.93–0.97) with BB tracers (nss-K+, BCwb, Lev), nitrate and light absorption, potentially indicating the formation of water-soluble brown carbon (BrC) from fast oxidation processes. The examination of diagnostic ratios involving BB tracers indicated the prevalence of hardwood burning, while the mean Lev/OC ratio (22%) was remarkably higher than literature values. Applying a mono-tracer method based on levoglucosan, we estimated very high BB contributions to OC (∼92%), EC (∼64%) and WSOC (∼87%) during winter. On the contrary, low levels were registered during summer for all carbonaceous components, with winter/summer ratios of 4–5 for PM2.5 and BC, 10 for OC, 30 for BCwb and ∼1100 for levoglucosan. The absence of local BB sources in summer, combined with the photochemical processing and aging of regional organic aerosols, resulted in higher WSOC/OC fractions (64 ± 13%). The results indicate highly soluble fine carbonaceous aerosol fraction year-round, which when considered alongside the extreme concentration levels in winter can have important implications for short- and long-term health effects.

The Cross-Border Transport of PM2.5 from the Southeast Asian Biomass Burning Emissions and Its Impact on Air Pollution in Yunnan Plateau, Southwest China

Southeast Asia is one of the largest biomass burning (BB) regions in the world, and the air pollutants generated by this BB have an important impact on air pollution in southern China. However, the mechanism of the cross-border transport of BB pollutants to neighboring regions is yet to be understood. Based on the MODIS remote sensing products and conventional observation data of meteorology and the environment, the WRF-Chem and FLEXPART-WRF models were used to simulate a typical PM2.5 pollution episode that occurred during 24–26 March 2017 to analyze the mechanism of cross-border transport of BB pollutants over Yunnan Plateau (YP) in southwest China. During this air pollution episode, in conjunction with the flourishing BB activities over the neighboring Indo-China Peninsula (ICP) regions in Southeast Asia, and driven by the southwesterly winds prevailing from the ICP to YP, the cross-border transport of pollutants was observed along the transport pathway with the lifting plateau topography in YP. Based on the proximity to the BB sources in ICP, YP was divided into a source region (SR) and a receptor region (RR) for the cross-border transport, and the negative and positive correlation coefficients (R) between PM2.5 concentrations and wind speeds, respectively, were presented, indicating the different impacts of BB emissions on the two regions. XSBN and Kunming, the representative SR and RR sites in the border and hinterland of YP, respectively, have distinct mechanisms that enhance PM2.5 concentrations of air pollution. The SR site is mainly affected by the ICP BB emissions with local accumulation in the stagnant meteorological conditions, whereas the RR site is dominated by the regional transport of PM2.5 with strong winds and vertical mixing. It was revealed that the large PM2.5 contributions of ICP BB emissions lift from the lower altitudes in SR to the higher altitudes in RR for the regional transport of PM2.5. Moreover, the contributions of regional transport of PM2.5 decrease with the increase in transport distance, reflecting an important role of transport distance between the source–receptor areas in air pollution change.

Characteristics, Source Contributions, and Source-Specific Health Risks of PM2.5-Bound Polycyclic Aromatic Hydrocarbons for Senior Citizens during the Heating Season in Tianjin, China.

Polycyclic aromatic hydrocarbons (PAHs) have carcinogenic impacts on human health. However, limited studies are available on the characteristics, sources, and source-specific health risks of PM2.5-bound PAHs based on personal exposure data, and comparisons of the contributions of indoor and outdoor sources are also lacking. We recruited 101 senior citizens in the winter of 2011 for personal PM2.5 sample collection. Fourteen PAHs were analyzed, potential sources were apportioned using positive matrix factorization (PMF), and inhalational carcinogenic risks of each source were estimated. Six emission sources were identified, including coal combustion, gasoline emission, diesel emission, biomass burning, cooking, and environmental tobacco smoking (ETS). The contribution to carcinogenic risk of each source occurred in the following sequence: biomass burning > diesel emission > gasoline emission > ETS > coal combustion > cooking. Moreover, the contributions of biomass burning, diesel emission, ETS, and indoor sources (sum of cooking and ETS) to PAH-induced carcinogenic risk were higher than those to the PAH mass concentration, suggesting severe carcinogenic risk per unit contribution. This study revealed the contribution of indoor and outdoor sources to mass concentration and carcinogenic risk of PM2.5-bound PAHs, which could act as a guide to mitigate the exposure level and risk of PM2.5-bound PAHs.

Brown Carbon Fuel and Emission Source Attributions to Global Snow Darkening Effect

AbstractSnow and ice albedo reduction due to deposition of absorbing particles (snow darkening effect [SDE]) warms the Earth system and is largely attributed to black carbon (BC) and dust. Absorbing organic aerosol (BrC) also contributes to SDE but has received less attention due to uncertainty and challenges in model representation. This work incorporates the SDE of absorbing organic aerosol (BrC) from biomass burning and biofuel sources into the Snow Ice and Aerosol Radiative (SNICAR) model within a variant of the Community Earth System Model. Additionally, 12 different emission regions of BrC and BC from biomass burning and biofuel sources are tagged to quantify the relative contribution to global and regional SDE. BrC global SDE (0.021–0.056 Wm−2 over land area and 0.0061–0.016 Wm−2 over global area) is larger than other model estimates, corresponding to 37%–98% of the SDE from BC. When compared to observations, BrC simulations have a range in median bias (−2.5% to +21%), with better agreement in the simulations that include BrC photochemical bleaching. The largest relative contributions to global BrC SDE are traced to Northern Asia (23%–31%), Southeast Asia (16%–21%), and South Africa (13%–17%). Transport from Southeast Asia contributes nearly half of the regional BrC SDE in Antarctica (0.084–0.3 Wm−2), which is the largest regional input to global BrC SDE. Lower latitude BrC SDE is correlated with snowmelt, in‐snow BrC concentrations, and snow cover fraction, while polar BrC SDE is correlated with surface insolation and snowmelt. This indicates the importance of in‐snow processes and snow feedbacks on modeled BrC SDE.