scholarly journals Source apportionment of organic aerosol from 2-year highly time-resolved measurements by an aerosol chemical speciation monitor in Beijing, China

2018 ◽  
Vol 18 (12) ◽  
pp. 8469-8489 ◽  
Author(s):  
Yele Sun ◽  
Weiqi Xu ◽  
Qi Zhang ◽  
Qi Jiang ◽  
Francesco Canonaco ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Seasonal Variations ◽  
Coal Combustion ◽  
Chemical Speciation ◽  
Function Analysis ◽  
Dominant Role ◽  
Organic Aerosol ◽  
Mass Loading ◽  
Heating Season

Abstract. Organic aerosol (OA) represents a large fraction of submicron aerosols in the megacity of Beijing, yet long-term characterization of its sources and variations is very limited. Here we present an analysis of in situ measurements of OA in submicrometer particles with an aerosol chemical speciation monitor (ACSM) for 2 years from July 2011 to May 2013. The sources of OA are analyzed with a multilinear engine (ME-2) by constraining three primary OA factors including fossil-fuel-related OA (FFOA), cooking OA (COA), and biomass burning OA (BBOA). Two secondary OAs (SOA), representing a less oxidized oxygenated OA (LO-OOA) and a more oxidized (MO-OOA), are identified during all seasons. The monthly average concentration OA varied from 13.6 to 46.7 µg m−3 with a strong seasonal pattern that is usually highest in winter and lowest in summer. FFOA and BBOA show similarly pronounced seasonal variations with much higher concentrations and contributions in winter due to enhanced coal combustion and biomass burning emissions. The contribution of COA to OA, however, is relatively stable (10–15 %) across different seasons, yet presents significantly higher values at low relative humidity levels (RH < 30 %), highlighting the important role of COA during clean periods. The two SOA factors present very different seasonal variations. The pronounced enhancement of LO-OOA concentrations in winter indicates that emissions from combustion-related primary emissions could be a considerable source of SOA under low-temperature (T) conditions. Comparatively, MO-OOA shows high concentrations consistently at high RH levels across different T levels, and the contribution of MO-OOA to OA is different seasonally with lower values occurring more in winter (30–34 %) than other seasons (47–64 %). Overall, SOA (= LO-OOA + MO-OOA) dominates OA composition during all seasons by contributing 52–64 % of the total OA mass in the heating season and 65–75 % in non-heating seasons. The variations in OA composition as a function of OA mass loading further illustrate the dominant role of SOA in OA across different mass loading scenarios during all seasons. However, we also observed a large increase in FFOA associated with a corresponding decrease in MO-OOA during periods with high OA mass loadings in the heating season, illustrating an enhanced role of coal combustion emissions during highly polluted episodes. Potential source contribution function analysis further shows that the transport from the regions located to the south and southwest of Beijing within ∼ 250 km can contribute substantially to high FFOA and BBOA concentrations in the heating season.

scholarly journals Source apportionment of organic aerosol from two-year highly time-resolved measurements by an aerosol chemical speciation monitor in Beijing, China

2018 ◽  
Author(s):  
Yele Sun ◽  
Weiqi Xu ◽  
Qi Zhang ◽  
Qi Jiang ◽  
Francesco Canonaco ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Seasonal Variations ◽  
Coal Combustion ◽  
Chemical Speciation ◽  
Function Analysis ◽  
Dominant Role ◽  
Organic Aerosol ◽  
Mass Loading ◽  
Heating Season

Abstract. Organic aerosol (OA) represents a large fraction of submicron aerosols in the megacity of Beijing, yet long-term characterization of its sources and variations is very limited. Here we present analysis of in situ measurements of OA in submicrometer particles with an aerosol chemical speciation monitor (ACSM) for two years from July 2011 to May 2013. The sources of OA are analyzed with multilinear engine (ME-2) by constraining three primary OA factors including fossil fuel related OA (FFOA), cooking OA (COA), and biomass burning OA (BBOA). Two secondary OA (SOA), representing a less oxidized oxygenated OA (LO-OOA) and a more oxidized (MO-OOA) are identified during all seasons. The monthly average concentration OA varied from 13.6 to 46.7 µg m−3 with a strong seasonal pattern that is usually highest in winter and lowest in summer. FFOA and BBOA show similarly pronounced seasonal variations with much higher concentrations and contributions in winter due to enhanced coal combustion and biomass burning emissions. The contribution of COA to OA, however, is relatively stable (10–15 %) across different seasons, yet presents significantly higher values at low relative humidity levels (RH < 30 %), highlighting the important role of COA during clean periods. The two SOA factors present very different seasonal variations. The pronounced enhancement of LO-OOA concentrations in winter indicates that emissions form combustion-related primary emissions could be a considerable source of SOA under low temperature (T) conditions. Comparatively, MO-OOA shows high concentrations consistently at high RH levels across different T levels, and the contribution of MO-OOA to OA is different seasonally with lower values occurring more in winter (30–34 %) than other seasons (47–64 %). Overall, SOA (= LO-OOA + MO-OOA) dominates OA composition during all seasons by contributing 52–64 % of the total OA mass in heating season, and 65–75 % in non-heating seasons. The variations of OA composition as a function of OA mass loading further illustrates the dominant role of SOA in OA across different mass loading scenarios during all seasons. However, we also observed a large increase in FFOA associated with a corresponding decrease in MO-OOA during periods with high OA mass loadings in heating season, illustrating an enhanced role of coal combustion emissions during highly polluted episodes. Potential source contribution function analysis further shows that the transport from the regions located to the south and southwest of Beijing within ~200 km can contribute substantially to high FFOA and BBOA concentrations in heating season.

scholarly journals Characterization and source apportionment of organic aerosol at 260 m on a meteorological tower in Beijing, China

2017 ◽  
Author(s):  
Wei Zhou ◽  
Qingqing Wang ◽  
Xiujuan Zhao ◽  
Weiqi Xu ◽  
Chen Chen ◽  
...  
Keyword(s):  
Coal Combustion ◽  
Dominant Role ◽  
Ground Level ◽  
Organic Aerosol ◽  
Back Trajectory ◽  
Heating Season ◽  
Aerosol Composition ◽  
Average Mass ◽  
Back Trajectory Analysis ◽  
Combustion Emissions

Abstract. Despite extensive efforts into characterization of submicron aerosols at ground level in the megacity of Beijing, our understanding of aerosol sources and processes at high altitudes remains less understood. Here we conducted a three-month real-time measurement of non-refractory submicron aerosol (NR-PM1) species at a height of 260 m from 10 October 2014 to 18 January 2015 using an aerosol chemical speciation monitor. Our results showed a significant change in aerosol composition from non-heating period (NHP) to heating season (HP). Organics and chloride showed clear increases during HP due to coal combustion emissions, while nitrate showed substantial decreases from 28 % to 15–18 %. We also found that NR-PM1 species in heating season can have average mass differences of 30–44 % under similar emission sources yet different meteorological conditions. Multi-linear engine 2 (ME-2) using three primary organic aerosol (OA) factors, i.e., fossil fuel-related OA (FFOA) dominantly from coal combustion emissions, cooking OA (COA), biomass burning OA (BBOA) resolved from ground high-resolution aerosol mass spectrometer measurements as constrains was performed to OA mass spectra of ACSM. Two types of secondary OA (SOA) that were well correlated with nitrate and chloride/CO, respectively, were identified. SOA played a dominant role in OA during all periods at 260 m although the contributions were decreased from 72 % during NHP to 58–64 % during HP. The SOA composition also changed significantly from NHP to HP. While the contribution of oxygenated OA (OOA) was decreased from 56–63 % to 32–40 %, less oxidized OOA (LO-OOA) showed a large increase from 9–16 % to 24–26 %. COA contributed a considerable fraction of OA at high altitude, and the contribution was relatively similar across different periods (10–13 %). In contrast, FFOA showed a large increase during HP due to the influences of coal combustion emissions. We also observed very different OA composition between ground level and 260 m. Particularly, the contributions of COA and BBOA at ground site were nearly twice those at 260 m, while SOA at 260 m was ~ 15–34 % higher than that at ground level. Bivariate polar plots and back trajectory analysis further illustrated the different source regions of OA factors in different seasons.

scholarly journals Primary and secondary aerosols in Beijing in winter: sources, variations and processes

2016 ◽  
Vol 16 (13) ◽  
pp. 8309-8329 ◽  
Author(s):  
Yele Sun ◽  
Wei Du ◽  
Pingqing Fu ◽  
Qingqing Wang ◽  
Jie Li ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Biomass Burning ◽  
Coal Combustion ◽  
Dominant Role ◽  
Liquid Water Content ◽  
Oxidation States ◽  
Gas Chromatography Mass Spectrometry ◽  
Formation Mechanisms ◽  
Aerosol Composition ◽  
Secondary Aerosols

Abstract. Winter has the worst air pollution of the year in the megacity of Beijing. Despite extensive winter studies in recent years, our knowledge of the sources, formation mechanisms and evolution of aerosol particles is not complete. Here we have a comprehensive characterization of the sources, variations and processes of submicron aerosols that were measured by an Aerodyne high-resolution aerosol mass spectrometer from 17 December 2013 to 17 January 2014 along with offline filter analysis by gas chromatography/mass spectrometry. Our results suggest that submicron aerosols composition was generally similar across the winter of different years and was mainly composed of organics (60 %), sulfate (15 %) and nitrate (11 %). Positive matrix factorization of high- and unit-mass resolution spectra identified four primary organic aerosol (POA) factors from traffic, cooking, biomass burning (BBOA) and coal combustion (CCOA) emissions as well as two secondary OA (SOA) factors. POA dominated OA, on average accounting for 56 %, with CCOA being the largest contributor (20 %). Both CCOA and BBOA showed distinct polycyclic aromatic hydrocarbons (PAHs) spectral signatures, indicating that PAHs in winter were mainly from coal combustion (66 %) and biomass burning emissions (18 %). BBOA was highly correlated with levoglucosan, a tracer compound for biomass burning (r2 = 0.93), and made a considerable contribution to OA in winter (9 %). An aqueous-phase-processed SOA (aq-OOA) that was strongly correlated with particle liquid water content, sulfate and S-containing ions (e.g. CH2SO2+) was identified. On average aq-OOA contributed 12 % to the total OA and played a dominant role in increasing oxidation degrees of OA at high RH levels (> 50 %). Our results illustrate that aqueous-phase processing can enhance SOA production and oxidation states of OA as well in winter. Further episode analyses highlighted the significant impacts of meteorological parameters on aerosol composition, size distributions, oxidation states of OA and evolutionary processes of secondary aerosols.

scholarly journals Spatial and seasonal variations of isoprene secondary organic aerosol in China: Significant impact of biomass burning during winter

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Xiang Ding ◽  
Quan-Fu He ◽  
Ru-Qin Shen ◽  
Qing-Qing Yu ◽  
Yu-Qing Zhang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Seasonal Variations ◽  
Secondary Organic Aerosol ◽  
Organic Aerosol

scholarly journals Primary and secondary aerosols in Beijing in winter: sources, variations and processes

2016 ◽  
Author(s):  
Yele Sun ◽  
Wei Du ◽  
Pingqing Fu ◽  
Qingqing Wang ◽  
Jie Li ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Biomass Burning ◽  
Coal Combustion ◽  
Dominant Role ◽  
Liquid Water Content ◽  
Oxidation States ◽  
Gas Chromatography Mass Spectrometry ◽  
Formation Mechanisms ◽  
Aerosol Composition ◽  
Secondary Aerosols

Abstract. Winter has the worst air pollution in a year in the megacity of Beijing. Despite extensive winter studies in recent years, our knowledge on the sources, formation mechanisms and evolution of aerosol particles is not complete. Here we have a comprehensive characterization of the sources, variations and processes of submicron aerosols that were measured by an Aerodyne high-resolution aerosol mass spectrometer from December 17, 2013 to January 17, 2014 along with offline filter analysis by gas chromatography/mass spectrometry. Our results suggest that submicron aerosols composition was overall similar in winter among different years, which was mainly composed of organics (60 %), sulfate (15 %) and nitrate (11 %). Positive matrix factorization of high- and unit-mass resolution spectra identified four primary organic aerosol (POA) factors from traffic, cooking, biomass burning (BBOA) and coal combustion (CCOA) emissions, and two secondary OA (SOA) factors. POA dominated OA, on average accounting for 56% with CCOA being the largest contributor (20 %). Both CCOA and BBOA showed distinct polycyclic aromatic hydrocarbons (PAHs) spectral signatures indicating that PAHs in winter were mainly from coal combustion (66 %) and biomass burning emissions (18 %). BBOA was highly correlated with levoglucosan, a tracer compound for biomass burning (r2 = 0.93), and made a considerable contribution to OA in winter (9 %). An aqueous-phase processed SOA (aq-OOA) that was strongly correlated with particle liquid water content, sulfate and S-containing ions (e.g., CH2SO2+) was identified. aq-OOA on average contributed 12 % to the total OA and played a dominant role in increasing oxidation degrees of OA at high RH levels (> 50 %). Our results illustrate that aqueous-phase processing can enhance SOA production and oxidation states of OA as well in winter. Further episode analyses highlighted the significant impacts of meteorological parameters on aerosol composition, size distributions, oxidation states of OA, and evolutionary processes of secondary aerosols.

scholarly journals Characterization and source apportionment of organic aerosol at 260 m on a meteorological tower in Beijing, China

2018 ◽  
Vol 18 (6) ◽  
pp. 3951-3968 ◽  
Author(s):  
Wei Zhou ◽  
Qingqing Wang ◽  
Xiujuan Zhao ◽  
Weiqi Xu ◽  
Chen Chen ◽  
...  
Keyword(s):  
Coal Combustion ◽  
Dominant Role ◽  
Ground Level ◽  
Organic Aerosol ◽  
Back Trajectory ◽  
Heating Period ◽  
Aerosol Composition ◽  
Average Mass ◽  
Back Trajectory Analysis ◽  
Combustion Emissions

Abstract. Despite extensive efforts toward the characterization of submicron aerosols at ground level in the megacity of Beijing, our understanding of aerosol sources and processes at high altitudes remains low. Here we conducted a 3-month real-time measurement of non-refractory submicron aerosol (NR-PM1) species at a height of 260 m from 10 October 2014 to 18 January 2015 using an aerosol chemical speciation monitor. Our results showed a significant change in aerosol composition from the non-heating period (NHP) to the heating period (HP). Organics and chloride showed clear increases during HP due to coal combustion emissions, while nitrate showed substantial decreases from 28 to 15–18 %. We also found that NR-PM1 species in the heating season can have average mass differences of 30–44 % under similar emission sources yet different meteorological conditions. Multi-linear engine 2 (ME-2) using three primary organic aerosol (OA) factors as constraints, i.e., fossil-fuel-related OA (FFOA) dominantly from coal combustion emissions, cooking OA (COA), and biomass burning OA (BBOA) resolved from ground high-resolution aerosol mass spectrometer measurements, was applied to OA mass spectra of ACSM. Two types of secondary OA (SOA) that were well correlated with nitrate and chloride–CO, respectively, were identified. SOA played a dominant role in OA during all periods at 260 m although the contributions were decreased from 72 % during NHP to 58–64 % during HP. The SOA composition also changed significantly from NHP to HP. While the contribution of oxygenated OA (OOA) was decreased from 56–63 to 32–40 %, less oxidized OOA (LO-OOA) showed a large increase from 9–16 to 24–26 %. COA contributed a considerable fraction of OA at high altitude, and the contribution was relatively similar across different periods (10–13 %). In contrast, FFOA showed a large increase during HP due to the influences of coal combustion emissions. We also observed very different OA composition between ground level and 260 m. Particularly, the contributions of COA and BBOA at the ground site were nearly twice those at 260 m, while SOA at 260 m was ∼ 15–34 % higher than that at ground level. Bivariate polar plots and back-trajectory analysis further illustrated the different source regions of OA factors in different seasons.

scholarly journals Quantification of organic aerosol and brown carbon evolution in fresh wildfire plumes

2020 ◽  
Vol 117 (47) ◽  
pp. 29469-29477
Author(s):  
Brett B. Palm ◽  
Qiaoyun Peng ◽  
Carley D. Fredrickson ◽  
Ben H. Lee ◽  
Lauren A. Garofalo ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Organic Aerosol ◽  
Brown Carbon ◽  
Airborne Measurements ◽  
Wildfire Smoke ◽  
Secondary Sources ◽  
Western Us ◽  
Smoke Plumes ◽  
Reactive Trace Gases

The evolution of organic aerosol (OA) and brown carbon (BrC) in wildfire plumes, including the relative contributions of primary versus secondary sources, has been uncertain in part because of limited knowledge of the precursor emissions and the chemical environment of smoke plumes. We made airborne measurements of a suite of reactive trace gases, particle composition, and optical properties in fresh western US wildfire smoke in July through August 2018. We use these observations to quantify primary versus secondary sources of biomass-burning OA (BBPOA versus BBSOA) and BrC in wildfire plumes. When a daytime wildfire plume dilutes by a factor of 5 to 10, we estimate that up to one-third of the primary OA has evaporated and subsequently reacted to form BBSOA with near unit yield. The reactions of measured BBSOA precursors contribute only 13 ± 3% of the total BBSOA source, with evaporated BBPOA comprising the rest. We find that oxidation of phenolic compounds contributes the majority of BBSOA from emitted vapors. The corresponding particulate nitrophenolic compounds are estimated to explain 29 ± 15% of average BrC light absorption at 405 nm (BrC Abs405) measured in the first few hours of plume evolution, despite accounting for just 4 ± 2% of average OA mass. These measurements provide quantitative constraints on the role of dilution-driven evaporation of OA and subsequent radical-driven oxidation on the fate of biomass-burning OA and BrC in daytime wildfire plumes and point to the need to understand how processing of nighttime emissions differs.

scholarly journals Brown carbon's emission factors and optical characteristics in household biomass burning: Developing a novel algorithm for estimating the contribution of brown carbon

2020 ◽  
Author(s):  
Jianzhong Sun ◽  
Guorui Zhi ◽  
Regina Hitzenberger ◽  
Yingjun Chen ◽  
Chongguo Tian
Keyword(s):  
Biomass Burning ◽  
Coal Combustion ◽  
Dominant Role ◽  
Combustion Process ◽  
Emission Factors ◽  
Integrating Sphere ◽  
Total Biomass ◽  
Brown Carbon ◽  
Leading Role ◽  
Novel Algorithm

Abstract. Recent studies have highlighted the importance of brown carbon (BrC) in various fields, particularly relating to climate change. The incomplete combustion of biomass in open and contained burning conditions is believed to be a significant contributor to primary BrC emissions. So far, few studies have reported the emission factors of BrC from biomass burning, and few studies have specifically addressed which form of light absorbing carbon, such as black carbon (BC) or BrC, plays a leading role in the total solar light absorption of biomass burning. In this study, the optical integrating sphere (IS) approach was used, with carbon black and humic acid sodium salt as reference materials for BC and BrC, respectively, to distinguish BrC from BC on the filter samples. Eleven widely used biomass types in China were burned in a typical stove to simulate the real household combustion process. (i) Large differences existed in the emission factors of BrC (EFBrC) among the tested biomass fuels, with a geomean EFBrC of 0.71 g/kg (0.24, 2.18). Both the plant type (herbaceous or ligneous) and burning style (raw or briquetted biomass) might influence the value of EFBrC. (ii) The calculated annual BrC emissions from China's household biomass burning amounted to 712 Gg, higher than the contribution from China's household coal combustion (592 Gg). (iii) The average absorption Ångström exponent (AAE) was (2.46 ± 0.53), much higher than that of coal-chunks combustion smoke (AAE = 1.30 ± 0.32). (iv) For biomass smoke, the contribution of absorption by BrC to the total absorption by BC + BrC across the strongest solar spectral range of 350–850 nm (FBrC) was 50.8 %. This was nearly twice that for BrC in smoke from household coal combustion (26.5 %). (v) Based on this study, a novel algorithm was developed for estimating the FBrC for any combustion sources (FBrC = 0.5519 lnAAE + 0.0067, R2 = 0.999); the FBrC value for global entire biomass burning (open + contained) (FBrC-entire) was 64.5 % (58.5–69.9 %). This corroborates the dominant role of BrC in total biomass burning absorption. Therefore, BrC is not optional but indispensable when considering the climate energy budget, particularly for biomass burning emissions (contained and open).

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