Primary Sources and Secondary Formation of Organic Aerosols in Beijing, China

2012 ◽  
Vol 46 (18) ◽  
pp. 9846-9853 ◽  
Author(s):  
Song Guo ◽  
Min Hu ◽  
Qingfeng Guo ◽  
Xin Zhang ◽  
Mei Zheng ◽  
...  
Keyword(s):  
Organic Aerosols ◽  
Primary Sources ◽  
Secondary Formation ◽  
Beijing China

scholarly journals Characteristics, primary sources and secondary formation of water-soluble organic aerosols in downtown Beijing

2021 ◽  
Vol 21 (3) ◽  
pp. 1775-1796
Author(s):  
Qing Yu ◽  
Jing Chen ◽  
Weihua Qin ◽  
Siming Cheng ◽  
Yuepeng Zhang ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Aqueous Phase ◽  
Critical Role ◽  
Organic Aerosols ◽  
Sampling Period ◽  
Water Soluble ◽  
Photochemical Oxidation ◽  
Primary Sources ◽  
Secondary Formation ◽  
The Impact

Abstract. Water-soluble organic carbon (WSOC) accounts for a large proportion of aerosols and plays a critical role in various atmospheric chemical processes. In order to investigate the primary sources and secondary production of WSOC in downtown Beijing, day and night fine particulate matter (PM2.5) samples in January (winter), April (spring), July (summer) and October (autumn) 2017 were collected and analyzed for WSOC and organic tracers in this study. WSOC was dominated by its moderately hydrophilic fraction and showed the highest concentration in January and comparable levels in April, July and October 2017. Some typical organic tracers were chosen to evaluate the emission strength and secondary formation of WSOC. Seasonal variation of the organic tracers suggested significantly enhanced formation of anthropogenic secondary organic aerosols (SOAs) during the sampling period in winter and obviously elevated biogenic SOA formation during the sampling period in summer. These organic tracers were applied into a positive matrix factorization (PMF) model to calculate the source contributions of WSOC as well as its moderately and strongly hydrophilic portions. The secondary sources contributed more than 50 % to WSOC, with higher contributions during the sampling periods in summer (75.1 %) and winter (67.4 %), and the largest contributor was aromatic SOC. In addition, source apportionment results under different pollution levels suggested that controlling biomass burning and aromatic precursors would be effective to reduce WSOC during the haze episodes in cold seasons. The impact factors for the formation of different SOA tracers and total secondary organic carbon (SOC) as well as moderately and strongly hydrophilic SOC were also investigated. The acid-catalyzed heterogeneous or aqueous-phase oxidation appeared to dominate in the SOC formation during the sampling period in winter, while the photochemical oxidation played a more critical role during the sampling period in summer. Moreover, photooxidation played a more critical role in the formation of moderately hydrophilic SOC, while the heterogeneous or aqueous-phase reactions had more vital effects on the formation of strongly hydrophilic SOC.

scholarly journals Improving the representation of HONO chemistry in CMAQ and examining its impact on haze over China

2021 ◽  
Author(s):  
Shuping Zhang ◽  
Golam Sarwar ◽  
Jia Xing ◽  
Biwu Chu ◽  
Chaoyang Xue ◽  
...  
Keyword(s):  
Nitrogen Dioxide ◽  
Hydroxyl Radical ◽  
Nitrous Acid ◽  
Organic Aerosols ◽  
Model Reaction ◽  
Heterogeneous Reactions ◽  
Displacement Reaction ◽  
Model Predictions ◽  
Volatile Organic ◽  
Beijing China

Abstract. We compare Community Multiscale Air Quality (CMAQ) model predictions with measured nitrous acid (HONO) concentrations in Beijing, China for December 2015. The model with the existing HONO chemistry in CMAQ severely under-estimates the observed HONO concentrations with a normalized mean bias of −97 %. We revise the HONO chemistry in the model by implementing six additional heterogeneous reactions in the model: reaction of nitrogen dioxide (NO2) on ground surfaces, reaction of NO2 on aerosol surfaces, reaction of NO2 on soot surfaces, photolysis of aerosol nitrate, nitric acid displacement reaction, and hydrochloric acid displacement reaction. The model with the revised chemistry substantially increases HONO predictions and improves the comparison with observed data with a normalized mean bias of −5 %. The photolysis of HONO enhances day-time hydroxyl radical by almost a factor of two. The enhanced hydroxyl radical concentrations compare favorably with observed data and produce additional sulfate via the reaction with sulfur dioxide, aerosol nitrate via the reaction with nitrogen dioxide, and secondary organic aerosols via the reactions with volatile organic compounds. The additional sulfate stemming from revised HONO chemistry improves the comparison with observed concentration; however, it does not close the gap between model prediction and the observation during polluted days.

scholarly journals Measurement report: Online measurement of gas-phase nitrated phenols utilizing a CI-LToF-MS: primary sources and secondary formation

2021 ◽  
Vol 21 (10) ◽  
pp. 7917-7932
Author(s):  
Kai Song ◽  
Song Guo ◽  
Haichao Wang ◽  
Ying Yu ◽  
Hui Wang ◽  
...  
Keyword(s):  
Gas Phase ◽  
Regional Scale ◽  
Primary Sources ◽  
Phenoxy Radical ◽  
Vehicle Exhaust ◽  
Composition Variation ◽  
Secondary Formation ◽  
Long Time ◽  
Heavy Pollution ◽  
Non Negative Matrix Factorization

Abstract. To investigate the composition, variation, and sources of nitrated phenols (NPs) in the winter of Beijing, gas-phase NPs were measured by a chemical ionization long time-of-flight mass spectrometer (CI-LToF-MS). A box model was applied to simulate the secondary formation process of NPs. In addition, the primary sources of NPs were resolved by a non-negative matrix factorization (NMF) model. Our results showed that secondary formation contributed 38 %, 9 %, 5 %, 17 %, and almost 100 % of the nitrophenol (NP), methyl-nitrophenol (MNP), dinitrophenol (DNP), methyl-dinitrophenol (MDNP or DNOC), and dimethyl-nitrophenol (DMNP) concentrations. The phenol–OH reaction was the predominant loss pathway (46.7 %) during the heavy pollution episode, which produced the phenoxy radical (C6H5O). The phenoxy radical consequently reacted with NO2 and produced nitrophenol. By estimating the primarily emitted phenol from the ratio of phenol/CO from freshly emitted vehicle exhaust, this study proposed that oxidation of primary phenol contributes much more nitrophenol (37 %) than that from benzene oxidation (<1 %) in the winter of Beijing. The latter pathway was widely used in models and might lead to great uncertainties. The source apportionment results by NMF indicated the importance of combustion sources (>50 %) to the gas-phase NPs. The industry source contributed 30 % and 9 % to DNP and MDNP, respectively, which was non-negligible. The concentration weighted trajectory (CWT) analysis demonstrated that regional transport from provinces that surround the Yellow and Bohai seas contributed more primary NPs to Beijing. Both primary sources and secondary formation at either local or regional scale should be considered when making control policies of NPs.

scholarly journals Molecular Characterization and Seasonal Variation in Primary and Secondary Organic Aerosols in Beijing, China

2018 ◽  
Vol 123 (21) ◽  
pp. 12,394-12,412 ◽  
Author(s):  
Linjie Li ◽  
Lujie Ren ◽  
Hong Ren ◽  
Siyao Yue ◽  
Qiaorong Xie ◽  
...  
Keyword(s):  
Seasonal Variation ◽  
Molecular Characterization ◽  
Secondary Organic Aerosols ◽  
Organic Aerosols ◽  
Beijing China

scholarly journals Characteristics, primary sources and secondary formation of water soluble organic aerosols in downtown Beijing

2020 ◽  
Author(s):  
Qing Yu ◽  
Jing Chen ◽  
Weihua Qin ◽  
Siming Cheng ◽  
Yuepeng Zhang ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Dominant Role ◽  
Critical Role ◽  
Correlation Coefficients ◽  
Water Soluble ◽  
Primary Sources ◽  
Formation Mechanisms ◽  
Secondary Sources ◽  
Pmf Model ◽  
Secondary Formation

Abstract. Water soluble organic compounds (WSOC) account for a large proportion of aerosols and play a critical role in various atmospheric chemical processes. In order to investigate the primary sources and secondary production of WSOC in downtown Beijing, the day and night PM2.5 samples in January (winter), April (spring), July (summer) and October (autumn) of 2017 were collected and analyzed for WSOC and organic tracers in this study. WSOC showed the highest concentration in winter and comparable levels in the other seasons, and dominated by its hydrophobic fraction (HULIS-C). Some typical organic tracers were chosen to evaluate the emission strength and secondary formation for the major sources of WSOC. According to the diurnal patterns and correlation coefficients with the key influencing factors, most SOA tracers were closely related to gaseous photooxidation in summer, but mainly generated via aqueous-phase processing in other seasons. These organic tracers were applied into the positive matrix factorization (PMF) model to calculate the source contributions of WSOC as well as its hydrophobic and hydrophilic portions. The secondary sources contributed over 50 % to WSOC, with higher contributions in summer (75.7 %) and winter (67.7 %), and the largest contributor was aromatic SOC. Besides, the source apportionment results under different pollution levels suggested that controlling biomass burning and the aromatic precursors would be effective to reduce WSOC during the haze episodes in cold seasons. The possible formation mechanisms of the total secondary organic carbon (SOC) as well as hydrophobic and hydrophilic SOC were also explored in this study. The aqueous-phase process appeared to dominate in the SOC formation in winter and spring, while gas-phase photooxidation played a dominant role in summer. Besides, the gaseous photooxidation played a major role in the generation of hydrophobic SOC, whereas aqueous-phase reactions posed vital effects on the formation of hydrophilic SOC.

scholarly journals Improving the representation of HONO chemistry in CMAQ and examining its impact on haze over China

2021 ◽  
Vol 21 (20) ◽  
pp. 15809-15826
Author(s):  
Shuping Zhang ◽  
Golam Sarwar ◽  
Jia Xing ◽  
Biwu Chu ◽  
Chaoyang Xue ◽  
...  
Keyword(s):  
Nitric Acid ◽  
Nitrogen Dioxide ◽  
Hydroxyl Radical ◽  
Nitrous Acid ◽  
Organic Aerosols ◽  
Heterogeneous Reactions ◽  
Displacement Reaction ◽  
Model Predictions ◽  
Volatile Organic ◽  
Beijing China

Abstract. We compare Community Multiscale Air Quality (CMAQ) model predictions with measured nitrous acid (HONO) concentrations in Beijing, China, for December 2015. The model with the existing HONO chemistry in CMAQ severely underestimates the observed HONO concentrations with a normalized mean bias of −97 %. We revise the HONO chemistry in the model by implementing six additional heterogeneous reactions in the model: the reaction of nitrogen dioxide (NO2) on ground surfaces, the reaction of NO2 on aerosol surfaces, the reaction of NO2 on soot surfaces, the photolysis of aerosol nitrate, the nitric acid displacement reaction, and the hydrochloric acid displacement reaction. The model with the revised chemistry substantially increases HONO predictions and improves the comparison with observed data with a normalized mean bias of −5 %. The photolysis of HONO enhances daytime hydroxyl radical by almost a factor of 2. The enhanced hydroxyl radical concentrations compare favorably with observed data and produce additional sulfate via the reaction with sulfur dioxide, aerosol nitrate via the reaction with nitrogen dioxide, and secondary organic aerosols via the reactions with volatile organic compounds. The additional sulfate stemming from revised HONO chemistry improves the comparison with observed concentration; however, it does not close the gap between model prediction and the observation during polluted days.

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