scholarly journals Distinctions in source regions and formation mechanisms of secondary aerosol in Beijing from summer to winter

2019 ◽  
Vol 19 (15) ◽  
pp. 10319-10334 ◽  
Author(s):  
Jing Duan ◽  
Ru-Jin Huang ◽  
Chunshui Lin ◽  
Wenting Dai ◽  
Meng Wang ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Aqueous Phase ◽  
Regional Scale ◽  
Late Summer ◽  
Photochemical Oxidation ◽  
Formation Mechanisms ◽  
Early Winter ◽  
Secondary Aerosol ◽  
Haze Pollution ◽  
Sulfate Formation

Abstract. To investigate the sources and evolution of haze pollution in different seasons, long-term (from 15 August to 4 December 2015) variations in chemical composition of PM1 were characterized in Beijing, China. Positive matrix factorization (PMF) analysis with a multi-linear engine (ME-2) resolved three primary and two secondary organic aerosol (OA) sources, including hydrocarbon-like OA (HOA), cooking OA (COA), coal combustion OA (CCOA), local secondary OA (LSOA) and regional SOA (RSOA). The sulfate source region analysis implies that sulfate was mainly transported at a large regional scale in late summer, while local and/or nearby sulfate formation may be more important in winter. Meanwhile, distinctly different correlations between sulfate and RSOA or LSOA (i.e., better correlation with RSOA in late summer, similar correlations with RSOA and LSOA in autumn, and close correlation with LSOA in early winter) confirmed the regional characteristic of RSOA and local property of LSOA. Secondary aerosol species including secondary inorganic aerosol (SIA – sulfate, nitrate, and ammonium) and SOA (LSOA and RSOA) dominated PM1 during all three seasons. In particular, SOA contributed 46 % to total PM1 (with 31 % as RSOA) in late summer, whereas SIA contributed 41 % and 45 % to total PM1 in autumn and early winter, respectively. Enhanced contributions of secondary species (66 %–76 % of PM1) were also observed in pollution episodes during all three seasons, further emphasizing the importance of secondary formation processes in haze pollution in Beijing. Combining chemical composition and meteorological data, our analyses suggest that both photochemical oxidation and aqueous-phase processing played important roles in SOA formation during all three seasons, while for sulfate formation, gas-phase photochemical oxidation was the major pathway in late summer, aqueous-phase reactions were more responsible during early winter and both processes had contributions during autumn.

scholarly journals Distinctions in source regions and formation mechanisms of secondary aerosol in Beijing from summer to winter

2019 ◽  
Author(s):  
Jing Duan ◽  
Ru-Jin Huang ◽  
Chunshui Lin ◽  
Wenting Dai ◽  
Meng Wang ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Meteorological Data ◽  
Regional Scale ◽  
Late Summer ◽  
Photochemical Oxidation ◽  
Formation Mechanisms ◽  
Early Winter ◽  
Secondary Aerosol ◽  
Haze Pollution ◽  
Sulfate Formation

Abstract. To investigate the sources and evolution of haze pollution in different seasons, long-term (from 15 August to 4 December 2015) variations of chemical composition of PM1 were characterized in Beijing, China. Positive matrix factorization (PMF) analysis with multi-linear engine (ME-2) resolved three primary and two secondary OA sources, including hydrocarbon-like OA (HOA), cooking OA (COA), coal combustion OA (CCOA), local secondary OA (LSOA) and regional SOA (RSOA). Distinctly different correlations between RSOA and sulfate were found in our study, with tight correlation (R2 = 0.71) in late summer, decreased correlation (R2 = 0.62) in autumn and almost no correlation (R2 = 0.02) in early winter. This difference implies that sulfate was mainly transported at a large regional scale in late summer, while local and/or nearby sulfate formation may be more important in winter. Secondary aerosol species including SIA (sulfate, nitrate and ammonium) and SOA (LSOA and RSOA) dominated PM1 during all three seasons. In particular, SOA contributed 46 % to total PM1 (with 31 % as RSOA) in late summer, whereas SIA contributed 41 % and 45 % to total PM1 in autumn and early winter, respectively. Enhanced contributions of secondary species (66–76 % of PM1) were also observed in pollution episodes during all three seasons, further emphasizing the importance of secondary formation processes in haze pollution in Beijing. Combining chemical composition and meteorological data, our analyses suggest that photochemical oxidation dominated SOA formation during all three seasons, while for sulfate formation, gas-phase photochemical oxidation was the major pathway in late summer and heterogeneous processes were likely more important in autumn and early winter.

Summertime and wintertime atmospheric processes of secondary aerosol in Beijing

2020 ◽  
Author(s):  
Jing Duan ◽  
Rujin Huang ◽  
Chunshui Lin ◽  
Haiyan Ni ◽  
Meng Wang
Keyword(s):  
Aqueous Phase ◽  
Liquid Water ◽  
Fine Particles ◽  
Photochemical Oxidation ◽  
Formation Mechanisms ◽  
Phase Reaction ◽  
Aerosol Formation ◽  
Secondary Aerosol ◽  
Atmospheric Processes ◽  
Sulfate Formation

<p>Secondary aerosol constitutes a large fraction of fine particles in urban air of China. However, its formation mechanisms and atmospheric processes remain largely uncertain despite considerable studies in recent years. To elucidate the seasonal variations of fine particles composition and secondary aerosol formation, an Aerodyne quadrupole aerosol chemical speciation monitor (Q-ACSM) combined with other online instruments were used to characterize the submicron particulate matter (diameter < 1 μm, PM<sub>1</sub>) in Beijing during summer and winter 2015. Our results suggest that the photochemical oxidation was the major pathway for sulfate formation during summer, whereas aqueous-phase reaction became an important process for sulfate formation during winter. High concentration of nitrate (17% of the PM<sub>1</sub> mass) was found during winter explained by enhanced gas-to-particle partitioning at low temperature, while high nitrate concentration (19%) was also observed under the conditions of high relative humidity (RH) during summer likely due to the hydrophilic property of NH<sub>4</sub>NO<sub>3</sub> and hydrolysis of N<sub>2</sub>O<sub>5</sub>. As for SOA formation, photochemical oxidation perhaps played an important role for summertime oxygenated OA (OOA) formation and wintertime less oxidized OOA (LO-OOA) formation. The wintertime more oxidized OOA (MO-OOA) showed a good correlation with aerosol liquid water content (ALWC), indicating more important contribution of aqueous-phase processing than photochemical production to MO-OOA. Meanwhile, the dependence of LO-OOA and the mass ratio of LO-OOA to MO-OOA on atmospheric oxidative tracer (i.e., O<sub>x</sub>) both degraded when RH were greater than 60%, suggesting that RH or aerosol liquid water may also affect the LO-OOA formation.</p>

scholarly journals Summertime and wintertime atmospheric processes of secondary aerosol in Beijing

2020 ◽  
Vol 20 (6) ◽  
pp. 3793-3807 ◽  
Author(s):  
Jing Duan ◽  
Ru-Jin Huang ◽  
Yongjie Li ◽  
Qi Chen ◽  
Yan Zheng ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Liquid Water ◽  
Fine Particles ◽  
Photochemical Oxidation ◽  
Formation Mechanisms ◽  
Phase Reaction ◽  
Aerosol Formation ◽  
Secondary Aerosol ◽  
Atmospheric Processes ◽  
Sulfate Formation

Abstract. Secondary aerosol constitutes a large fraction of fine particles in urban air of China. However, its formation mechanisms and atmospheric processes remain largely uncertain despite considerable study in recent years. To elucidate the seasonal variations in fine-particle composition and secondary aerosol formation, an Aerodyne quadrupole aerosol chemical speciation monitor (Q-ACSM), combined with other online instruments, was used to characterize the sub-micrometer particulate matter (diameter < 1 µm, PM1) in Beijing during summer and winter 2015. Our results suggest that photochemical oxidation was the major pathway for sulfate formation during summer, whereas aqueous-phase reaction became an important process for sulfate formation during winter. High concentrations of nitrate (17 % of the PM1 mass) were found during winter, explained by enhanced gas-to-particle partitioning at low temperature, while high nitrate concentrations (19 %) were also observed under the conditions of high relative humidity (RH) during summer, likely due to the hydrophilic property of NH4NO3 and hydrolysis of N2O5. As for organic aerosol (OA) sources, secondary OA (SOA) dominated the OA mass (74 %) during summer, while the SOA contribution decreased to 39 % during winter due to enhanced primary emissions in the heating season. In terms of the SOA formation, photochemical oxidation perhaps played an important role for summertime oxygenated OA (OOA) formation and less-oxidized wintertime OOA (LO-OOA) formation. The wintertime more-oxidized OOA (MO-OOA) showed a good correlation with aerosol liquid water content (ALWC), indicating a more important contribution of aqueous-phase processing over photochemical production to MO-OOA. Meanwhile, the dependence of LO-OOA and the mass ratio of LO-OOA to MO-OOA on atmospheric oxidative tracer (i.e., Ox) both degraded when RH was greater than 60 %, suggesting that RH or aerosol liquid water may also affect LO-OOA formation.

scholarly journals Multiphase MCM–CAPRAM modeling of the formation and processing of secondary aerosol constituents observed during the Mt. Tai summer campaign in 2014

2020 ◽  
Vol 20 (11) ◽  
pp. 6725-6747 ◽  
Author(s):  
Yanhong Zhu ◽  
Andreas Tilgner ◽  
Erik Hans Hoffmann ◽  
Hartmut Herrmann ◽  
Kimitaka Kawamura ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Aqueous Phase ◽  
Glyoxylic Acid ◽  
Northern China ◽  
Chemical Mechanism ◽  
Radical Mechanism ◽  
Formation Mechanisms ◽  
Major Pathway ◽  
Voc Emissions ◽  
Secondary Aerosol

Abstract. Despite the high abundance of secondary aerosols in the atmosphere, their formation mechanisms remain poorly understood. In this study, the Master Chemical Mechanism (MCM) and the Chemical Aqueous-Phase Radical Mechanism (CAPRAM) are used to investigate the multiphase formation and processing of secondary aerosol constituents during the advection of air masses towards the measurement site of Mt. Tai in northern China. Trajectories with and without chemical–cloud interaction are modeled. Modeled radical and non-radical concentrations demonstrate that the summit of Mt. Tai, with an altitude of ∼1.5 km a.m.s.l., is characterized by a suburban oxidants budget. The modeled maximum gas-phase concentrations of the OH radical are 3.2×106 and 3.5×106 molec. cm−3 in simulations with and without cloud passages in the air parcel, respectively. In contrast with previous studies at Mt. Tai, this study has modeled chemical formation processes of secondary aerosol constituents under day vs. night and cloud vs. non-cloud cases along the trajectories towards Mt. Tai in detail. The model studies show that sulfate is mainly produced in simulations where the air parcel is influenced by cloud chemistry. Under the simulated conditions, the aqueous reaction of HSO3- with H2O2 is the major contributor to sulfate formation, contributing 67 % and 60 % in the simulations with cloud and non-cloud passages, respectively. The modeled nitrate formation is higher at nighttime than during daytime. The major pathway is aqueous-phase N2O5 hydrolysis, with a contribution of 72 % when cloud passages are considered and 70 % when they are not. Secondary organic aerosol (SOA) compounds, e.g., glyoxylic, oxalic, pyruvic and malonic acid, are found to be mostly produced from the aqueous oxidations of hydrated glyoxal, hydrated glyoxylic acid, nitro-2-oxopropanoate and hydrated 3-oxopropanoic acid, respectively. Sensitivity studies reveal that gaseous volatile organic compound (VOC) emissions have a huge impact on the concentrations of modeled secondary aerosol compounds. Increasing the VOC emissions by a factor of 2 leads to linearly increased concentrations of the corresponding SOA compounds. Studies using the relative incremental reactivity (RIR) method have identified isoprene, 1,3-butadiene and toluene as the key precursors for glyoxylic and oxalic acid, but only isoprene is found to be a key precursor for pyruvic acid. Additionally, the model investigations demonstrate that an increased aerosol partitioning of glyoxal can play an important role in the aqueous-phase formation of glyoxylic and oxalic acid. Overall, the present study is the first that provides more detailed insights in the formation pathways of secondary aerosol constituents at Mt. Tai and clearly emphasizes the importance of aqueous-phase chemical processes on the production of multifunctional carboxylic acids.

scholarly journals Multiphase MCM/CAPRAMmodeling of formation and processing of secondary aerosol constituents observed at the Mt. Tai summer campaign 2014

2019 ◽  
Author(s):  
Yanhong Zhu ◽  
Andreas Tilgner ◽  
Erik Hans Hoffmann ◽  
Hartmut Herrmann ◽  
Kimitaka Kawamura ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Aqueous Phase ◽  
Glyoxylic Acid ◽  
Formation Mechanisms ◽  
Major Pathway ◽  
Voc Emissions ◽  
Secondary Aerosol ◽  
Model Studies ◽  
Huge Impact ◽  
Sensitivity Studies

Abstract. Despite the high abundance of secondary aerosols in the atmosphere, their formation mechanisms remain poorly understood. In this study, MCM/CAPRAM mechanism is used to investigate the multiphase formation and processing of secondary aerosol constituents during the advection of air masses towards the measurement site of Mt. Tai in North China. Trajectories with and without chemical cloud interaction are modeled. Modeled radical and non-radical concentrations demonstrate that the summit of Mt. Tai, with an altitude of ∼1.5 km a.m.s.l., is characterized by a sub-urban oxidants budget. The modeled maximum gas-phase concentrations of OH radical are 3.2 × 106 molecules cm−3 and 3.5 × 106 molecules cm−3 in simulations with and without cloud passages in the air parcel, respectively. Different to previous studies at Mt. Tai, this study has modeled chemical formation processes of secondary aerosol constituents under day vs. night and cloud vs. non-cloud cases along the trajectories to Mt. Tai in detail. The model studies show that sulfate is mainly produced in simulations where the air parcel is influenced by cloud chemistry. Under the simulated conditions, the aqueous reaction of HSO3− with H2O2 is the major contributor to sulfate formation, contributing 67 % and 60 % in the simulations with cloud and non-cloud passages, respectively. The modeled nitrate formation is higher at nighttime than at daytime. The major pathway is aqueous-phase N2O5 hydrolysis, with a contribution of 72 % when cloud passages are considered and 70 % when not. Secondary organic aerosol (SOA) compounds, e.g. glyoxylic, oxalic, pyruvic and malonic acid, are found to be mostly produced from the aqueous oxidations of hydrated glyoxal, hydrated glyoxylic acid, nitro 2-oxopropanoate and hydrated 3-oxopropanoic acid, respectively. Sensitivity studies reveal that gaseous VOC emissions have a huge impact on the concentrations of modeled secondary aerosol compounds. Increasing the VOC emissions by a factor of two leads to linearly increased concentrations of the corresponding SOA compounds. Studies using the relative incremental reactivity (RIR) method have identified isoprene, 1,3-butadiene and toluene as the key precursors for glyoxylic and oxalic acid, but only isoprene is found to be a key precursor for pyruvic acid. Additionally, the model investigations demonstrate that an increased aerosol partitioning of glyoxal can play an important role in the aqueous-phase formation of glyoxylic and oxalic acid. Overall, the present study is the first that provides more detailed insights in the formation pathways of secondary aerosol constituents at Mt. Tai and clearly emphasizes the importance of aqueous-phase chemical processes on the production of multifunctional carboxylic acids.

Aerosol chemical composition and formation of secondary aerosol during haze events at the SORPES station in China

2020 ◽  
Author(s):  
Jiaping Wang ◽  
Jinbo Wang ◽  
Wei Nie ◽  
Xuguang Chi ◽  
Jiandong Wang ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Eastern China ◽  
Cold Season ◽  
Particle Dispersion ◽  
Dispersion Modeling ◽  
Formation Processes ◽  
Aerosol Formation ◽  
Secondary Aerosol ◽  
Haze Pollution ◽  
Aerosol Chemical Composition

&lt;p&gt;Haze pollution is a serious air quality concern in China up to now, which occurs frequently in mega city clusters, e.g. Beijing-Tianjin-Hebei and Yangtze River Delta region, especially in the cold season. Understanding the dominating secondary aerosol formation processes is vital for improving the prediction and emission control strategy of haze pollution. In this study, we reported measurements of aerosol chemical composition using the soot particle aerosol mass spectrometer (SP-AMS) at a regional background station, the Station for Observing Regional Processes of the Earth System (SORPES), in Nanjing, eastern China. Characteristics of aerosol chemical composition and dominating secondary aerosol formation processes were analyzed during typical haze events and compared with that in clean episodes. Sources and transportation of organic aerosol were performed using positive matrix factorization (PMF) together with backward Lagrangian particle dispersion modeling (LPDM).&lt;/p&gt;

scholarly journals Formation mechanisms of atmospheric nitrate and sulfate during the winter haze pollution periods in Beijing: gas-phase, heterogeneous and aqueous-phase chemistry

2019 ◽  
Author(s):  
Pengfei Liu ◽  
Can Ye ◽  
Chaoyang Xue ◽  
Chenglong Zhang ◽  
Yujing Mu ◽  
...  
Keyword(s):  
Gas Phase ◽  
Aqueous Phase ◽  
Sampling Period ◽  
Convincing Evidence ◽  
Formation Mechanisms ◽  
Phase Reaction ◽  
So2 Oxidation ◽  
Mean Values ◽  
Sulfate Production ◽  
Haze Pollution

Abstract. A vast area in China is currently going through severe haze episodes with drastically elevated concentrations of PM2.5 in winter. Nitrate and sulfate are main constituents of PM2.5 but their formations via NO2 and SO2 oxidation are still not comprehensively understood, especially under different pollution or atmospheric relative humidity (RH) conditions. To elucidate formation pathways of nitrate and sulfate in different polluted cases, hourly samples of PM2.5 were collected continuously in Beijing during the wintertime of 2016. Three serious pollution cases were identified reasonably during the sampling period and the secondary formations of nitrate and sulfate were found to make a dominant contribution to atmospheric PM2.5 under the relatively high RH condition. The significant correlation between NOR and NO2 × O3 during the nighttime under the RH ≥ 60 % condition indicated that the heterogeneous hydrolysis of N2O5 involving aerosol liquid water was responsible for the nocturnal formation of nitrate at the extremely high RH levels. The more coincident trend of NOR and HONO × DR (direct radiation) × NO2 than Dust × NO2 during the daytime under the 30 % < RH < 60 % condition provided convincing evidence that the gas-phase reaction of NO2 with OH played a pivotal role in the diurnal formation of nitrate at moderate RH levels. The extremely high mean values of SOR during the whole day under the RH ≥ 60 % condition could be ascribed to the evident contribution of SO2 aqueous-phase oxidation to the formation of sulfate during the severe pollution episodes. Based on the parameters measured in this study and the known sulfate production rate calculation method, the oxidation pathway of H2O2 rather than NO2 was found to contribute greatly to the aqueous-phase formation of sulfate.

scholarly journals Vertical distribution of atmospheric particulate matters within urban boundary layer in southern China: size-segregated chemical composition and secondary formation through cloud processing and heterogeneous reactions

2019 ◽  
Author(s):  
Shengzhen Zhou ◽  
Luolin Wu ◽  
Junchen Guo ◽  
Weihua Chen ◽  
Xuemei Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Vertical Distribution ◽  
Aqueous Phase ◽  
Urban Boundary Layer ◽  
Water Soluble ◽  
Heterogeneous Reactions ◽  
Formation Mechanisms ◽  
Haze Pollution ◽  
Adverse Weather ◽  
Autumn And Winter

Abstract. Great progress has been made recently in the understanding of the sources and formation mechanisms of atmospheric aerosols at the ground level. However, vertical profiles and sources of size-resolved particulate matter within the urban boundary layer are still lacking. In this study, vertical distribution characteristics of size-segregated particles were investigated at three observation platforms (ground, 118 m and 488 m) on the 610-meter-high Canton Tower in Guangzhou, China. Size-segregated aerosol samples were simultaneously collected at the three levels on the Canton Tower in autumn and winter, respectively. Major aerosol components, including water-soluble ions, organic carbon and elemental carbon, were measured. The results showed that daily average fine-particle concentrations generally decreased with height. Concentrations of sulfate and ammonium in fine particles displayed small vertical gradients and nitrate concentrations increased with height in autumn, while the above chemical components showed greater variations in winter than in autumn. The size distributions of sulfate and ammonium in both seasons were characterized by dominant unimodal droplet modes with a peak at the size range of 0.44–1.0 μm. In autumn, the nitrate size distribution was bi-modal, peaking at 0.44–1.0 μm and 2.5–10 μm, while it was unimodal in winter, implying that the formation mechanisms for nitrate particles were different in the two seasons. Our results suggest droplet mode sulfate and nitrate are likely formed from aqueous-phase reactions and coarse mode nitrate formation is attributed to heterogeneous reactions of gaseous nitric acid on existing sea-derived coarse particles in autumn at the measurement site. The results from pollution cases study further showed that atmospheric aqueous-phase and heterogeneous reactions together with adverse weather conditions, such as temperature inversion and calm wind, resulted in the autumn and winter haze pollution in the PRD region.

scholarly journals Formation mechanisms of atmospheric nitrate and sulfate during the winter haze pollution periods in Beijing: gas-phase, heterogeneous and aqueous-phase chemistry

2020 ◽  
Vol 20 (7) ◽  
pp. 4153-4165 ◽  
Author(s):  
Pengfei Liu ◽  
Can Ye ◽  
Chaoyang Xue ◽  
Chenglong Zhang ◽  
Yujing Mu ◽  
...  
Keyword(s):  
Gas Phase ◽  
Aqueous Phase ◽  
Sampling Period ◽  
Convincing Evidence ◽  
Formation Mechanisms ◽  
Phase Reaction ◽  
So2 Oxidation ◽  
Mean Values ◽  
Sulfate Production ◽  
Haze Pollution

Abstract. A vast area in China is currently going through severe haze episodes with drastically elevated concentrations of PM2.5 in winter. Nitrate and sulfate are the main constituents of PM2.5, but their formations via NO2 and SO2 oxidation are still not comprehensively understood, especially under different pollution or atmospheric relative humidity (RH) conditions. To elucidate formation pathways of nitrate and sulfate in different polluted cases, hourly samples of PM2.5 were collected continuously in Beijing during the wintertime of 2016. Three serious pollution cases were identified reasonably during the sampling period, and the secondary formations of nitrate and sulfate were found to make a dominant contribution to atmospheric PM2.5 under the relatively high RH condition. The significant correlation between NOR, NOR = NO3-/(NO3-+NO2), and [NO2]2 × [O3] during the nighttime under the RH≥60 % condition indicated that the heterogeneous hydrolysis of N2O5 involving aerosol liquid water was responsible for the nocturnal formation of nitrate at the extremely high RH levels. The more often coincident trend of NOR and [HONO] × [DR] (direct radiation) × [NO2] compared to its occurrence with [Dust] × [NO2] during the daytime under the 30 % < RH < 60 % condition provided convincing evidence that the gas-phase reaction of NO2 with OH played a pivotal role in the diurnal formation of nitrate at moderate RH levels. The extremely high mean values of SOR, SOR = SO42-/(SO42-+SO2), during the whole day under the RH≥60 % condition could be ascribed to the evident contribution of SO2 aqueous-phase oxidation to the formation of sulfate during the severe pollution episodes. Based on the parameters measured in this study and the known sulfate production rate calculation method, the oxidation pathway of H2O2 rather than NO2 was found to contribute greatly to the aqueous-phase formation of sulfate.

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