Characteristics, formation mechanisms, and sources of non-refractory submicron aerosols in Guangzhou, China

Chen, Chen; Tan, Haobo; Hong, Yongfeng; Yin, Chengqing; Deng, Xuejiao; Chan, P. W.; Wang, Meng; Bu, Qiaoli; Weng, Jiafeng; Gan, Quan

doi:10.1016/j.atmosenv.2021.118255

Cited by 9 publications

(5 citation statements)

References 54 publications

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“…In general, the volatility distribution from the acid group assumption is very similar to that from the empirical method based on TD‐AMS measurement as shown in Figures 3a and 3b ( R = 0.65, UC = 0.93; Table S5 in Supporting Information ), in contrast to the correlation coefficient with hydroxyl and carbonyl group (R = −0.3–0.4, UC = 0.58–0.84). The acid group assumption of OA is also consistent with the evolution pathway of the functional group found in the Van Krevelen plot of this study, which shows a regression slope of H: C and O: C around −0.78 (C. Chen et al., 2021). Similar ELVOC (34% vs. 40%), LVOC (30% vs. 32%), and SVOC fractions (29% vs. 27%) in both methods are also found (Figure 4).…”

Section: Resultssupporting

confidence: 89%

Quantitative Characterization of the Volatility Distribution of Organic Aerosols in a Polluted Urban Area: Intercomparison Between Thermodenuder and Molecular Measurements

Chen,

Hu,

Tao

et al. 2024

JGR Atmospheres

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To quantify the volatility of organic aerosols (OA), a comprehensive campaign was conducted in the Chinese megacity. Volatility distributions of OA and particle‐phase organic nitrate (pON) were estimated based on five methods: (a) empirical method and (b) kinetic model based on the measurement of a thermodenuder (TD) coupled with an aerosol mass spectrometer; (c) Formula‐based SIMPOL model‐driven method; (d) Element‐based estimations using molecular formula measurements of OA; and (e) gas/particle partitioning. Our results demonstrate that the ambient OA volatility distribution shows good agreement between the two heating methods and the formula‐based method when assuming ambient OA was mainly composed of organic nitrate (pON), organic sulfate and acid groups using the SIMPOL model. However, the element‐based method tends to overestimate the volatility of OA compared to the above three methods, suggesting large uncertainties in the parameterizations or in the representativeness of the molecular measurements that need further refinement. The volatility of ambient OA is generally lower than that of the laboratory‐derived secondary OA, emphasizing the impact of aging. A large fraction at the higher and lower volatility ranges (approximately log C* ≤ −9 and ≥2 μg m−3) was found for pON, implying the importance of both extremely low volatile and semi‐volatile species. Overall, this study evaluates different methods for volatility estimation and gives new insight into the volatility of OA and pON in urban areas.

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Section: Resultssupporting

confidence: 89%

Quantitative Characterization of the Volatility Distribution of Organic Aerosols in a Polluted Urban Area: Intercomparison Between Thermodenuder and Molecular Measurements

Chen,

Hu,

Tao

et al. 2024

JGR Atmospheres

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“…For example, for the episode in which the worst pollution conditions occurred, the daily average NR PM 1 increased from 19 to 143 µg m −3 from 12 to 16 February, with the organic aerosol increasing from 9.3 to 69.8 µg m −3 and nitrate increasing from 5.5 to 44.2 µg m −3 ; however, sulfate only increased from 1.4 to 8.5 µg m −3 . This phenomenon is quite different from the results reported by Guo et al (2020) and W. Chen et al ( 2021) that organic aerosol dominated the aerosol mass increase with a significant increase of both sulfate and nitrate in pollution episodes in autumn of Guangzhou urban area; however, it is generally consistent with the increasing characteristics reported by C. Chen et al (2021). These observations suggest that the aerosol pollution differs much among seasons and years due to the highly variable characteristics of meteorological conditions.…”

Section: Organic Aerosol Hygroscopicity Derivationcontrasting

confidence: 86%

Strong light scattering of highly oxygenated organic aerosols impacts significantly on visibility degradation

et al. 2022

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Abstract. Secondary organic aerosols (SOAs) account for a large fraction of atmospheric aerosol mass and play significant roles in visibility impairment by scattering solar radiation. However, comprehensive evaluations of SOA scattering abilities under ambient relative humidity (RH) conditions on the basis of field measurements are still lacking due to the difficulty of simultaneously direct quantifications of SOA scattering efficiency in dry state and SOA water uptake abilities. In this study, field measurements of aerosol chemical and physical properties were conducted in winter in Guangzhou (lasting about 3 months) using a humidified nephelometer system and aerosol chemical speciation monitor. A modified multilinear regression model was proposed to retrieve dry-state mass scattering efficiencies (MSEs, defined as scattering coefficient per unit aerosol mass) of aerosol components. The more oxidized oxygenated organic aerosol (MOOA) with an O/C ratio of 1.17 was identified as the most efficient light scattering aerosol component. On average, 34 % mass contribution of MOOA to total submicron organic aerosol mass contributed 51 % of dry-state organic aerosol scattering. The overall organic aerosol hygroscopicity parameter κOA was quantified directly through hygroscopicity closure, and hygroscopicity parameters of SOA components were further retrieved using a multilinear regression model by assuming hydrophobic properties of primary organic aerosols. The highest water uptake ability of MOOA among organic aerosol factors was revealed with κMOOA reaching 0.23, thus further enhancing the fractional contribution of MOOA in ambient organic aerosol scattering. In particular, the scattering abilities of MOOA were found to be even higher than those of ammonium nitrate under RH of <70 %, which was identified as the most efficient inorganic scattering aerosol component, demonstrating that MOOA had the strongest scattering abilities in ambient air (average RH of 57 %) during winter in Guangzhou. During the observation period, secondary aerosols contributed dominantly to visibility degradation (∼70 %), with substantial contributions from MOOA (16 % on average), demonstrating significant impacts of MOOA on visibility degradation. The findings of this study demonstrate that more attention needs to be paid to SOA property changes in future visibility improvement investigations. Also, more comprehensive studies on MOOA physical properties and chemical formation are needed to better parameterize its radiative effects in models and implement targeted control strategies on MOOA precursors for visibility improvement.

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“…2d, with rBC mass concentrations ranging from about 0.1 to 20 µg/m³ with an average of 2.3 µg/m³. Resolved POA factors were HOA and COA, which is consistent with results of previous studies in recent years that traffic emissions and cooking emissions are two main sources of primary aerosols in Guangzhou urban area (Guo et al, 2020;Chen et al, 2021a;Chen et al, 2021b) The observed average BC mass size distribution, as shown in Fig. 3a, exhibits a single lognormal mode for diameters greater than 100 nm, with a fitted geometric mean (Dg,BC) of 258 nm ranging from 200 nm to 300 nm.…”

Section: Overview Of Dma-sp2 Measurements and Aerosol Chemical Compos...supporting

confidence: 89%

Black carbon content of traffic emissions impacts significantly on black carbon mass size distributions and mixing states

Luo

Zhai

et al. 2023

Preprint

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Abstract. Both the size and mixing state of black carbon (BC)-containing aerosols are crucial in estimating the environmental, health and climate impacts of BC. Traffic emissions are a major global source of BC, however, parameterization of BC mass size distributions and mixing states associated with traffic remains lacking due to its dependence on vehicle types and driving conditions. To investigate BC mass size distributions and mixing states associated with traffic emissions, a field campaign was conducted in Guangzhou urban area during winter, which used a system coupling a differential mobility analyzer (DMA) and single-particle soot photometer (SP2) to measure BC mass size distributions in the range of 100 to 700 nm. The resolved primary organic aerosols were hydrocarbon-like organic aerosols (HOA) and cooking-like organic aerosols (COA), refractory BC (rBC) which was detected by the DMA-SP2 and correlated highly with HOA (R2=0.88), confirming that traffic emissions are the dominant source of atmospheric BC during the observations. The BC mass size distribution was found to be best fitted by a lognormal distribution, with a geometric mean (Dg,BC) of 258±16 nm, varying between 200 and 300 nm. During daytime, active formation of secondary nitrate and organic aerosols was observed, but it had little effect on the variations of BC mass size distributions. Further analyses revealed that Dg,BC was highly correlated with rBC/HOA (R=0.66) in a linear form of Dg,BC= 34×rBC⁄HOA+177, demonstrating that the BC content of traffic emissions significantly impacts the BC mass size distributions. In addition, the size-dependent fractions of BC-containing aerosols in all types of aerosols (fBCc) and the fraction of identified externally mixed (bare/thinly coated) BC particles in all BC-containing aerosols (fext) were also characterized. It was found that the daytime secondary aerosol formation reduced both fBCc and fext, with the decrease of fext being more pronounced for larger particles, possibly due to the higher relative coating thickness. Variations in fext during nighttime were mainly controlled by the emission conditions. For example, fext for 600 nm particles decreased from 0.82 to 0.46 as rBC/HOA increased from 1 to 3.5 while the mass ratios of secondary aerosols to rBC varied little, demonstrating that the BC content also significantly affects the mixing states of freshly emitted BC from traffic emissions. This study suggests that BC content likely plays a key role in parameterizing both mass size distributions and mixing states of BC from traffic emissions and hence has significant implications for accurate representation of BC from different sources when modeling the impacts of BC.

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Characteristics, formation mechanisms, and sources of non-refractory submicron aerosols in Guangzhou, China

Cited by 9 publications

References 54 publications

Quantitative Characterization of the Volatility Distribution of Organic Aerosols in a Polluted Urban Area: Intercomparison Between Thermodenuder and Molecular Measurements

Quantitative Characterization of the Volatility Distribution of Organic Aerosols in a Polluted Urban Area: Intercomparison Between Thermodenuder and Molecular Measurements

Strong light scattering of highly oxygenated organic aerosols impacts significantly on visibility degradation

Black carbon content of traffic emissions impacts significantly on black carbon mass size distributions and mixing states

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