scholarly journals Chemical and Optical Characteristics and Sources of PM2.5 Humic-Like Substances at Industrial and Suburban Sites in Changzhou, China

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 276
Author(s):  
Ye Tao ◽  
Ning Sun ◽  
Xudong Li ◽  
Zhuzi Zhao ◽  
Shuaishuai Ma ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Inorganic Ions ◽  
Absorption Efficiency ◽  
Control Measures ◽  
Chemical Compositions ◽  
Air Pollution Control ◽  
Industrial Region ◽  
Secondary Sources ◽  
Secondary Formation

The chemical and optical properties and sources of atmospheric PM2.5 humic-like substances (HULIS) were investigated from October to December 2016 in both industrial and suburban areas in Changzhou, China, during polluted and fair days. The average PM2.5 concentration in the industrial region was 113.06 (±64.3) μg m−3, higher than 85.27 (±41.56) μg m−3 at the suburban site. The frequency of polluted days was significantly higher in the industrial region. In contrast, the chemical compositions of PM2.5 at the two sampling sites exhibited no statistically significant differences. Rapidly increased secondary inorganic ions (SNA = NH4+ + SO42− + NO3−) concentrations suggested secondary formation played an important role in haze formation. The daily mean concentration of humic-like substance (HULIS) was 1.8–1.9 times that of HULIS-C (the carbon content of HULIS). Our results showed that HULIS accounted for a considerable fraction of PM2.5 (industrial region: 6.3% vs. suburban region: 9.4%). There were no large differences in the mass ratios of HULIS-C/WSOC at the two sites (46% in the industrial region and 52% in the suburban region). On average, suburban HULIS-C constituted 35.1% of organic carbon (OC), higher than that (21.1%) in the industrial region. Based on different MAE (mass absorption efficiency) values under different pollution levels, we can infer that the optical properties of HULIS varied with PM levels. Moreover, our results showed no distinct difference in E2/E3 (the ratio of light absorbance at 250 nm to that at 365 nm) and AAE300–400 (Absorption Angstrom Exponent at 300–400 nm) for HULIS and WSOC. the MAE365 (MAE at 365 nm) value of HULIS-C was different under three PM2.5 levels (low: PM2.5 < 75 μg m−3, moderate: PM2.5 = 75–150 μg m−3, high: PM2.5 > 150 μg m−3), with the highest MAE365 value on polluted days in the industrial region. Strong correlations between HULIS-C and SNA revealed that HULIS might be contributed from secondary formation at both sites. In addition, good correlations between HULIS-C with K+ in the industrial region implied the importance of biomass burning to PM2.5-bound HULIS. Three common sources of HULIS-C (i.e., vehicle emissions, biomass burning, and secondary aerosols) were identified by positive matrix factorization (PMF) for both sites, but the contributions were different, with the largest contribution from biomass burning in the industrial region and secondary sources in the suburban region, respectively. The findings presented here are important in understanding PM2.5 HULIS chemistry and are valuable for future air pollution control measures.

scholarly journals Primary and secondary organic aerosols in 2016 summer of Beijing

2017 ◽  
Author(s):  
Rongzhi Tang ◽  
Zepeng Wu ◽  
Xiao Li ◽  
Yujue Wang ◽  
Dongjie Shang ◽  
...  
Keyword(s):  
Gasoline Engine ◽  
Control Measures ◽  
High Mass ◽  
Urban Site ◽  
Back Trajectory ◽  
Air Pollution Control ◽  
Secondary Sources ◽  
Peking University ◽  
Catalyzed Reactions ◽  
Engine Emission

Abstract. To improve the air quality, Beijing government has employed several air pollution control measures since 2008 Olympics. In order to investigate the organic aerosol sources after the implementation of these measures, ambient fine particulate matters were collected at a regional site Changping (CP) and an urban site Peking University Atmosphere Environment MonitoRing Station (PKUERS) during the Photochemical Smog in China field Campaign in summer of 2016. A chemical mass balance (CMB) modeling and the tracer yield method were used to apportion the primary and secondary organic sources. Our results showed that the particle concentration decreased significantly during the last a few years. The apportioned primary and secondary sources explained 62.8 ± 18.3 % and 80.9 ± 27.2 % of the measured OC at CP and PKUERS, respectively. Vehicular emissions served as the dominant sources. Except gasoline engine emission, the contributions of all the other primary sources decreased. Besides, the anthropogenic SOC, i.e. toluene SOC, also decreased, implying that deducting primary emission can reduce anthropogenic SOA. Different from the SOA from other regions in the world, where biogenic SOA was dominant, anthropogenic SOA was the major contributor to SOA, implying that deducting anthropogenic VOCs emissions is an efficient way to reduce SOA in Beijing. Back trajectory cluster analysis results showed that high mass concentrations of OC were observed when the air mass was from south. However, the contributions of different primary organic sources were similar, suggesting the regional particle pollution. The ozone concentration and temperature correlated well with the SOA concentration. Different correlations between day and night samples suggested the different SOA formation pathways. Significant enhancement of SOA with increasing particle water content and acidity were observed in our study, suggesting the aqueous phase acid-catalyzed reactions may be the important SOA formation mechanism in summer of Beijing.

scholarly journals Modelling the optical properties of fresh biomass burning aerosol produced in a smoke chamber: results from the EFEU campaign

2007 ◽  
Vol 7 (4) ◽  
pp. 12657-12686 ◽  
Author(s):  
K. Hungershöfer ◽  
K. Zeromskiene ◽  
Y. Iinuma ◽  
G. Helas ◽  
J. Trentmann ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Atmospheric Chemistry ◽  
Absorption Efficiency ◽  
Max Planck ◽  
Fresh Biomass ◽  
Biomass Burning Aerosol ◽  
Smoke Chamber ◽  
The Impact ◽  
Mass Absorption Efficiency

Abstract. A better characterisation of the optical properties of biomass burning aerosol as a function of the burning conditions is required in order to quantify their effects on climate and atmospheric chemistry. Controlled laboratory combustion experiments with different fuel types were carried out at the combustion facility of the Max Planck Institute for Chemistry (Mainz, Germany) as part of the 'Impact of Vegetation Fires on the Composition and Circulation of the Atmosphere' (EFEU) project. Using the measured size distributions as well as mass scattering and absorption efficiencies, Mie calculations provided mean effective refractive indices of 1.60−0.010i and 1.56−0.010i (λ=0.55 μm) for smoke particles emitted from the combustion of savanna grass and an African hardwood (musasa), respectively. The relatively low imaginary parts suggest that the light-absorbing carbon of the investigated fresh biomass burning aerosol is only partly graphitized, resulting in strongly scattering and less absorbing particles. While the observed variability in mass scattering efficiencies was consistent with changes in particle size, the changes in the mass absorption efficiency can only be explained, if the chemical composition of the particles varies with combustion conditions.

scholarly journals Simultaneous Measurements of Chemical Compositions of Fine Particles during Winter Haze Period in Urban Sites in China and Korea

Atmosphere ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 292 ◽  
Author(s):  
Minhan Park ◽  
Yujue Wang ◽  
Jihyo Chong ◽  
Haebum Lee ◽  
Jiho Jang ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Fine Particles ◽  
Chemical Compositions ◽  
Aerosol Formation ◽  
Wind Speeds ◽  
Simultaneous Measurements ◽  
Dust Sources ◽  
Secondary Formation ◽  
Combustion Sources ◽  
Burning Coal

We performed simultaneous measurements of chemical compositions of fine particles in Beijing, China and Gwangju, Korea to better understand their sources during winter haze period. We identified PM2.5 events in Beijing, possibly caused by a combination of multiple primary combustion sources (biomass burning, coal burning, and vehicle emissions) and secondary aerosol formation under stagnant conditions and/or dust sources under high wind speeds. During the PM2.5 events in Gwangju, the contribution of biomass burning and secondary formation of nitrate and organics to the fine particles content significantly increased under stagnant conditions. We commonly observed the increases of nitrogen-containing organic compounds and biomass burning inorganic (K+) and organic (levoglucosan) markers, suggesting the importance of biomass burning sources during the winter haze events (except dust event cases) at both sites. Pb isotope ratios indicated that the fraction of Pb originated from possibly industry and coal combustion sources increased during the PM2.5 events in Gwangju, relative to nonevent days.

scholarly journals The characteristics of atmospheric brown carbon in Xi'an, inland China: sources, size distributions and optical properties

2020 ◽  
Vol 20 (4) ◽  
pp. 2017-2030 ◽  
Author(s):  
Can Wu ◽  
Gehui Wang ◽  
Jin Li ◽  
Jianjun Li ◽  
Cong Cao ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Isotope Composition ◽  
Stable Carbon Isotope ◽  
Urban Atmosphere ◽  
Semiarid Region ◽  
Chemical Compositions ◽  
Brown Carbon ◽  
Polycyclic Aromatic ◽  
Fine Mode

Abstract. To investigate the characteristics of atmospheric brown carbon (BrC) in the semiarid region of East Asia, PM2.5 and size-resolved particles in the urban atmosphere of Xi'an, inland China, during the winter and summer of 2017 were collected and analyzed for optical properties and chemical compositions. Methanol extracts (MeOH extracts) were more light-absorbing than water extracts (H2O extracts) in the optical wavelength of 300–600 nm and well correlated with nitrophenols, polycyclic aromatic hydrocarbons (PAHs) and oxygenated PAHs (r > 0.78). The light absorptions (absλ=365 nm) of H2O extracts and MeOH extracts in winter were 28±16 and 49±32 M m−1, respectively, which are about 10 times higher than those in summer, mainly due to the enhanced emissions from biomass burning for house heating. Water-extracted BrC predominately occurred in the fine mode (< 2.1 µm) during winter and summer, accounting for 81 % and 65 % of the total absorption of BrC, respectively. The light absorption and stable carbon isotope composition measurements showed an increasing ratio of absλ=365 nm-MeOH to absλ=550 nm-EC along with an enrichment of 13C in PM2.5 during the haze development, indicating an accumulation of secondarily formed BrC (e.g., nitrophenols) in the aerosol aging process. Positive matrix factorization (PMF) analysis showed that biomass burning, fossil fuel combustion, secondary formation, and fugitive dust are the major sources of BrC in the city, accounting for 55 %, 19 %, 16 %, and 10 % of the total BrC of PM2.5, respectively.

Brown carbon aerosol in urban Beijing: Significant contributions from biomass burning and secondary formation

2020 ◽  
Author(s):  
Ting Wang ◽  
Rujin Huang ◽  
Lu Yang ◽  
Wei Yuan ◽  
Yuquan Gong
Keyword(s):  
Biomass Burning ◽  
Light Absorption ◽  
Coal Combustion ◽  
Absorption Efficiency ◽  
Traffic Emission ◽  
Brown Carbon ◽  
Factorization Model ◽  
Secondary Formation ◽  
Vis Spectroscopy ◽  
The Impact

&lt;p&gt;Atmospheric brown carbon (BrC) has significant impact on Earth&amp;#8217;s radiative budget. However, due to our very limited knowledge about the relationship between BrC light absorption and the associated sources, the estimation for radiative effects of BrC is still largely constrained. In this study, we combine ultraviolet&amp;#8722;visible (UV&amp;#8722;vis) spectroscopy measurements and chemical analyses of BrC samples collected from January to December 2015 in urban Beijing, to investigated the sources of atmospheric BrC. The multiple liner regression model was applied to apportion the contributions of individual primary and secondary organic aerosol (OA) source components to light absorption of BrC. Our results indicated that biomass burning emission and secondary formation are highly absorbing up to 500 nm, and their contributions increased with the wavelengths. In contrast, the contribution of traffic emission and coal combustion to total absorption decreased with the wavelength and the large contributions were mostly found at shorter wavelengths. Then the mass absorption efficiency (MAE) of major light-absorbing components were estimated, which can provide a support to estimate the impact of BrC from these sources on the climate. The positive matrix factorization model were also used to verify the contributions of different source components of BrC absorption at 365 nm. The results consistently demonstrate that the biomass burning and secondary formation contributes significantly to the overall absorption, followed by coal combustion and traffic emission.&lt;/p&gt;

scholarly journals Physical and optical properties of aged biomass burning aerosol from wildfires in Siberia and the Western USA at the Mt. Bachelor Observatory

2016 ◽  
Vol 16 (23) ◽  
pp. 15185-15197 ◽  
Author(s):  
James R. Laing ◽  
Daniel A. Jaffe ◽  
Jonathan R. Hee
Keyword(s):  
Optical Properties ◽  
Pacific Northwest ◽  
Biomass Burning ◽  
Geometric Mean ◽  
Fine Particulate Matter ◽  
Single Scattering ◽  
Absorption Efficiency ◽  
Size Distributions ◽  
Scanning Mobility Particle Sizer ◽  
Scattering Coefficients

Abstract. The summer of 2015 was an extreme forest fire year in the Pacific Northwest. Our sample site at the Mt. Bachelor Observatory (MBO, 2.7 km a.s.l.) in central Oregon observed biomass burning (BB) events more than 50 % of the time during August. In this paper we characterize the aerosol physical and optical properties of 19 aged BB events during August 2015. Six of the 19 events were influenced by Siberian fires originating near Lake Baikal that were transported to MBO over 4–10 days. The remainder of the events resulted from wildfires in Northern California and Southwestern Oregon with transport times to MBO ranging from 3 to 35 h. Fine particulate matter (PM1), carbon monoxide (CO), aerosol light scattering coefficients (σscat), aerosol light absorption coefficients (σabs), and aerosol number size distributions were measured throughout the campaign. We found that the Siberian events had a significantly higher Δσabs∕ΔCO enhancement ratio, higher mass absorption efficiency (MAE; Δσabs∕ΔPM1), lower single scattering albedo (ω), and lower absorption Ångström exponent (AAE) when compared with the regional events. We suggest that the observed Siberian events represent that portion of the plume that has hotter flaming fire conditions and thus enabled strong pyroconvective lofting and long-range transport to MBO. The Siberian events observed at MBO therefore represent a selected portion of the original plume that would then have preferentially higher black carbon emissions and thus an enhancement in absorption. The lower AAE values in the Siberian events compared to regional events indicate a lack of brown carbon (BrC) production by the Siberian fires or a loss of BrC during transport. We found that mass scattering efficiencies (MSE) for the BB events ranged from 2.50 to 4.76 m2 g−1. We measured aerosol size distributions with a scanning mobility particle sizer (SMPS). Number size distributions ranged from unimodal to bimodal and had geometric mean diameters (Dpm) ranging from 138 to 229 nm and geometric standard deviations (σg) ranging from 1.53 to 1.89. We found MSEs for BB events to be positively correlated with the geometric mean of the aerosol size distributions (R2 = 0.73), which agrees with Mie theory. We did not find any dependence on event size distribution to transport time or fire source location.

scholarly journals Measurement Report: Optical properties and sources of water-soluble brown carbon in Tianjin, North China: insights from organic molecular compositions

2022 ◽  
Author(s):  
Junjun Deng ◽  
Hao Ma ◽  
Xinfeng Wang ◽  
Shujun Zhong ◽  
Zhimin Zhang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Light Absorption ◽  
Radiative Forcing ◽  
North China ◽  
Water Soluble ◽  
Formation Mechanisms ◽  
Chemical Compositions ◽  
Brown Carbon ◽  
Near Ultraviolet

Abstract. Brown carbon (BrC) aerosols exert vital impacts on climate change and atmospheric photochemistry due to their light absorption in the wavelength range from near-ultraviolet (UV) to visible light. However, the optical properties and formation mechanisms of ambient BrC remain poorly understood, limiting the estimation of their radiative forcing. In the present study, fine aerosols (PM2.5) were collected during 2016–2017 on a day/night basis over urban Tianjin, a megacity in North China, to obtain seasonal and diurnal patterns of atmospheric water-soluble BrC. There were obvious seasonal but no evident diurnal variations in light absorption properties of BrC. In winter, BrC showed much stronger light absorbing ability since mass absorption efficiency at 365 nm (MAE365) (1.54 ± 0.33 m2 g−1), which was 1.8 times larger than that (0.84 ± 0.22 m2 g−1) in summer. Direct radiative effects by BrC absorption relative to black carbon in the UV range were 54.3 ± 16.9 % and 44.6 ± 13.9 %, respectively. In addition, five fluorescent components in BrC, including three humic-like fluorophores and two protein-like fluorophores were identified with excitation-emission matrix fluorescence spectrometry and parallel factor (PARAFAC) analysis. The lowly-oxygenated components contributed more to winter and nighttime samples, while more-oxygenated components increased in summer and daytime samples. The higher humification index (HIX) together with lower biological index (BIX) and fluorescence index (FI) suggest that the chemical compositions of BrC were associated with a high aromaticity degree in summer and daytime due to photobleaching. Fluorescent properties indicate that wintertime BrC were predominantly affected by primary emissions and fresh secondary organic aerosol (SOA), while summer ones were more influenced by aging processes. Results of source apportionments using organic molecular compositions of the same set of aerosols reveal that fossil fuel combustion and aging processes, primary bioaerosol emission, biomass burning, and biogenic and anthropogenic SOA formation were the main sources of BrC. Biomass burning contributed much larger to BrC in winter and at nighttime, while biogenic SOA contributed more in summer and at daytime. Especially, our study highlights that primary bioaerosol emission is an important source of BrC in urban Tianjin in summer.

Optical properties of atmospheric brown carbon (BrC) for photochemical and biomass burning-dominated aerosol regimes in India.

2020 ◽  
Author(s):  
Archita Rana ◽  
Supriya Dey ◽  
Sayantan Sarkar
Keyword(s):  
Optical Properties ◽  
Biomass Burning ◽  
Global Climate ◽  
Strong Association ◽  
Absorption Efficiency ◽  
Water Soluble ◽  
Tropospheric Chemistry ◽  
Gangetic Plain ◽  
Brown Carbon ◽  
Fluorescence Measurements

&lt;p&gt;Black and brown carbon (BC and BrC) are potent climate forcing agents with pronounced effects on global climate and tropospheric chemistry. Given the large heterogeneities in BC emission inventories from India and the paucity of studies on BrC characteristics, field-based measurements of BC and BrC sources and optical properties are essential to understand their impacts on regional climate. To address this issue, we report the first ground-based measurements of BC and BrC from a rural location in the highly polluted eastern Indo-Gangetic Plain (IGP) during May-November 2018 encompassing the photochemistry-dominated summer (May-June) and regional biomass burning (BB)-dominated post-monsoon (October-November) periods. A 7-wavelength Aethalometer was used for time-resolved measurements of BC mass and was supplemented by UV-Vis and fluorescence measurements of time-integrated (24 h) aqueous and organic BrC fractions, and measurements of OC, EC, WSOC, and ionic species.&lt;br&gt;The daily averaged BC increased 4 times during the BB regime (12.3 &amp;#177; 3.9 &amp;#956;g m&lt;sup&gt;-3&lt;/sup&gt;) as compared to summer (4.2 &amp;#177; 0.8 &amp;#956;g m&lt;sup&gt;-3&lt;/sup&gt;), while aqueous and organic BrC fractions demonstrated light absorption (babs_365) enhancements of 3-5 times during BB. For aqueous BrC, the averaged AE of 5.9-6.2 and a prominent fluorescence peak at ~420 nm suggested the presence of humic-like substances (HULIS), potentially from secondary photochemical formation during summer and primary emission during BB periods. Fluorescence and UV-Vis spectra also indicated the presence of nitroaromatic compounds, presumably from OH oxidation in summer and nighttime NO3- oxidation in the presence of enhanced NOx and precursor emission during BB. The latter was supported by the strong association between water-soluble organic carbon (WSOC; a proxy for aqueous BrC) and aerosol NO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; (r=0.70, p&lt;0.05). During BB, the fraction of water-insoluble (i.e., organic) BrC increased from 41% at 330 nm to 59 % at 550 nm while during the photochemistry-dominated summer period, the water-insoluble BrC fraction decreased from 73% at 400 nm to 41% at 530 nm, possibly due to photobleaching in the presence of OH. The BB-related BrC aerosol was also characterized by higher aromaticity and increased molecular weights of organic components as evidenced by mass absorption efficiency (MAE) ratios (MAE&lt;sub&gt;250&lt;/sub&gt;/MAE&lt;sub&gt;365&lt;/sub&gt;). Overall, this study established that BrC is a significant component of light-absorbing aerosol in the eastern IGP and that BrC optical properties may vary significantly in this region depending on the relative dominance of aerosol emissions and atmospheric processes.&lt;/p&gt;

scholarly journals Seasonal variations in high time-resolved chemical compositions, sources, and evolution of atmospheric submicron aerosols in the megacity Beijing

2017 ◽  
Vol 17 (16) ◽  
pp. 9979-10000 ◽  
Author(s):  
Wei Hu ◽  
Min Hu ◽  
Wei-Wei Hu ◽  
Jing Zheng ◽  
Chen Chen ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Coal Combustion ◽  
Fine Particles ◽  
Liquid Water Content ◽  
Urban Site ◽  
Chemical Components ◽  
Chemical Compositions ◽  
Average Mass ◽  
Four Seasons ◽  
Secondary Formation

Abstract. A severe regional haze problem in the megacity Beijing and surrounding areas, caused by fast formation and growth of fine particles, has attracted much attention in recent years. In order to investigate the secondary formation and aging process of urban aerosols, four intensive campaigns were conducted in four seasons between March 2012 and March 2013 at an urban site in Beijing (116.31° E, 37.99° N). An Aerodyne high-resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) was deployed to measure non-refractory chemical components of submicron particulate matter (NR-PM1). The average mass concentrations of PM1 (NR-PM1+black carbon) were 45.1 ± 45.8, 37.5 ± 31.0, 41.3 ± 42.7, and 81.7 ± 72.4 µg m−3 in spring, summer, autumn, and winter, respectively. Organic aerosol (OA) was the most abundant component in PM1, accounting for 31, 33, 44, and 36 % seasonally, and secondary inorganic aerosol (SNA, sum of sulfate, nitrate, and ammonium) accounted for 59, 57, 43, and 55 % of PM1 correspondingly. Based on the application of positive matrix factorization (PMF), the sources of OA were obtained, including the primary ones of hydrocarbon-like (HOA), cooking (COA), biomass burning OA (BBOA) and coal combustion OA (CCOA), and secondary component oxygenated OA (OOA). OOA, which can be split into more-oxidized (MO-OOA) and less-oxidized OOA (LO-OOA), accounted for 49, 69, 47, and 50 % in four seasons, respectively. Totally, the fraction of secondary components (OOA+SNA) contributed about 60–80 % to PM1, suggesting that secondary formation played an important role in the PM pollution in Beijing, and primary sources were also non-negligible. The evolution process of OA in different seasons was investigated with multiple metrics and tools. The average carbon oxidation states and other metrics show that the oxidation state of OA was the highest in summer, probably due to both strong photochemical and aqueous-phase oxidations. It was indicated by the good correlations (r = 0.53–0.75, p < 0.01) between LO-OOA and odd oxygen (Ox =  O3 + NO2), and between MO-OOA and liquid water content in aerosols. BBOA was resolved in spring and autumn, influenced by agricultural biomass burning (e.g., field preparation burnings, straw burning after the harvest). CCOA was only identified in winter due to domestic heating. These results signified that the comprehensive management for biomass burning and coal combustion emissions is needed. High concentrations of chemical components in PM1 in Beijing, especially in winter or in adverse meteorological conditions, suggest that further strengthening the regional emission control of primary particulate and precursors of secondary species is expected.

scholarly journals Seasonal variations of high time-resolved chemical compositions, sources and evolution for atmospheric submicron aerosols in the megacity Beijing

2017 ◽  
Author(s):  
Wei Hu ◽  
Min Hu ◽  
Wei-Wei Hu ◽  
Jing Zheng ◽  
Chen Chen ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Coal Combustion ◽  
Fine Particles ◽  
Urban Site ◽  
Chemical Components ◽  
Chemical Compositions ◽  
Average Mass ◽  
Four Seasons ◽  
Secondary Formation ◽  
Autumn And Winter

Abstract. Severe regional haze problem in the megacity Beijing and surrounding areas, caused by fast formation and growth of fine particles, has attracted much attention in recent years. In order to investigate the secondary formation and aging process of urban aerosols, four intensive campaigns were conducted in four seasons between March 2012 and March 2013 at an urban site in Beijing (116.31° E, 37.99° N). An Aerodyne high resolution time-of-flight aerosol mass spectrometry (HR-ToF-AMS) and other relevant instrumentations for gaseous and particulate pollutants were deployed. The average mass concentrations of submicron particulate matter (PM1) were 45.1±45.8, 37.5±31.0, 41.3±42.7, and 81.7±72.4 μg m−3 in spring, summer, autumn and winter, respectively. Organic aerosol (OA) was the most abundant component in PM1, accounting for 31, 33, 44 and 36 % seasonally, and secondary inorganic aerosol (SNA, sum of sulfate, nitrate and ammonium) accounted for 59, 57, 43, and 55 % of PM1 correspondingly. Based on the application of positive matrix factorization (PMF), the sources of OA were obtained, including the primary ones of hydrocarbon-like (HOA), cooking (COA), biomass burning OA (BBOA) and coal combustion OA (CCOA), and secondary component oxygenated OA (OOA). OOA, usually composed of more-oxidized (MO-OOA) and less-oxidized OOA (LO-OOA), accounted for 63, 69, 47 and 50 % in four seasons, respectively. Totally, the fraction of secondary components (OOA+SNA) contributed about 60–80 % to PM1, suggesting that secondary formation played an important role in the PM pollution in Beijing, and primary sources were also non-negligible. The evolution process of OA in different seasons was investigated with multiple metrics and tools. The average carbon oxidation states and other metrics show that the oxidation state of OA was the highest in summer, probably due to both strong photochemical and aqueous-phase oxidations. BBOA and CCOA were only resolved in autumn and winter, respectively, consistent with the agricultural activities (e.g., straw burning after the harvest in suburban areas) in autumn and domestic heating in winter, signifying that the comprehensive management for the emissions from biomass burning and coal combustion are needed. High concentrations of chemical components in PM1 in Beijing, especially in winter or in adverse meteorological conditions, suggest that further strengthening the regional emission control of primary particulate and precursors of secondary species is expected.

Sign in / Sign up

Export Citation Format

Share Document