Simultaneous measurements of particle number size distributions at ground level and 260 m on a meteorological tower in urban Beijing, China

Du, Wei; Zhao, Jian; Wang, Yuying; Zhang, Yingjie; Wang, Qingqing; Xu, Weiqi; Chen, Chen; Han, Tingting; Zhang, Fang; Li, Zhanqing; Fu, Pingqing; Li, Jie; Wang, Zifa; Sun, Yele

doi:10.5194/acp-17-6797-2017

Cited by 55 publications

(49 citation statements)

References 42 publications

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“…It is interesting to note that the fraction of b abs,BrC in b abs increased from ∼ 0.35 to ∼ 0.5 and the ratio of organics between SP-AMS and HR-AMS also increases, suggesting that rBC-related OA materials were more light-absorbing than the total OA. In fact, the organic mass measured by the SP-AMS is dominated by coal combustion and biomass burning emissions (J. , two important sources of BrC (Yan et al, 2015;Sun et al, 2017;Du et al, 2014). Further supporting evidence includes the fact that the mass absorption coefficient of BrC (MAC org,370 nm ) showed a pronounced diurnal cycle, with higher values at nighttime, consistent with the enhanced nighttime primary emissions in winter.…”

Section: Brown Carbonmentioning

confidence: 78%

Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China

Xie

Wang

et al. 2019

Atmos. Chem. Phys.

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Abstract. Aerosol particles are of importance in the Earth's radiation budget since they scatter and absorb sunlight. While extensive studies of aerosol optical properties have been conducted at ground sites, vertical measurements and characterization are very limited in megacities. In this work, we present simultaneous real-time online measurements of aerosol optical properties at ground level and at 260 m on a meteorological tower from 16 November to 13 December in 2016 in Beijing along with measurements of continuous vertical profiles during two haze episodes. The average (±1σ) scattering and absorption coefficients (bsca and babs; λ=630 nm) were 337.6 (±356.0) and 36.6 (±33.9) Mm−1 at 260 m, which were 26.5 % and 22.5 % lower than those at ground level. Single scattering albedo (SSA), however, was comparable between the two heights, with slightly higher values at ground level (0.89±0.04). Although bsca and babs showed overall similar temporal variations between ground level and 260 m, the ratios of 260 m to ground varied substantially from less than 0.4 during the clean stages of haze episodes to > 0.8 in the late afternoon. A more detailed analysis indicates that vertical profiles of bsca, babs, and SSA in the low atmosphere were closely related to the changes in meteorological conditions and mixing layer height. The mass absorption cross section (MAC) of equivalent black carbon (eBC, λ=630 nm) varied substantially from 9.5 to 13.2 m2 g−1 in winter in Beijing, and it was strongly associated with the mass ratio of coating materials on refractory BC (rBC) to rBC (MR), and also the oxidation degree of organics in rBC-containing particles. Our results show that the increases in MAC of eBC in winter were mainly caused by photochemically produced secondary materials. Light absorption of organic carbon (brown carbon, BrC) was also important in winter, which on average accounted for 46 (±8.5) % and 48 (±9.3) % of the total absorption at 370 nm at ground level and 260 m, respectively. A linear regression model combined with positive matrix factorization analysis was used to show that coal combustion was the dominant source contribution of BrC (48 %–55 %) followed by biomass burning (17 %) and photochemically processed secondary organic aerosol (∼20 %) in winter in Beijing.

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Section: Brown Carbonmentioning

confidence: 78%

Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China

Xie

Wang

et al. 2019

Atmos. Chem. Phys.

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“…4). The PM 2.5 mass concentration in urban areas is dominated by accumulation mode particles, with a clearly smaller contribution by ultrafine (cluster, nucleation and Aitken mode) particles (Feng et al, 2010).…”

Section: Calculation Of the Formation Ratementioning

confidence: 93%

Variation of size-segregated particle number concentrations in wintertime Beijing

et al. 2020

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Abstract. The spatial and temporal variability of the number size distribution of aerosol particles is an indicator of the dynamic behavior of Beijing's atmospheric pollution cocktail. This variation reflects the strength of different primary and secondary sources, such as traffic and new particle formation, as well as the main processes affecting the particle population. In this paper, we report size-segregated particle number concentrations observed at a newly developed Beijing station during the winter of 2018. Our measurements covered particle number size distributions over the diameter range of 1.5 nm–1 µm (cluster mode, nucleation mode, Aitken mode and accumulation mode), thus being descriptive of a major fraction of the processes taking place in the atmosphere of Beijing. Here we focus on explaining the concentration variations in the observed particle modes, by relating them to the potential aerosol sources and sinks, and on understanding the connections between these modes. We considered haze days and new particle formation event days separately. Our results show that during the new particle formation (NPF) event days increases in cluster mode particle number concentration were observed, whereas during the haze days high concentrations of accumulation mode particles were present. There was a tight connection between the cluster mode and nucleation mode on both NPF event and haze days. In addition, we correlated the particle number concentrations in different modes with concentrations of trace gases and other parameters measured at our station. Our results show that the particle number concentration in all the modes correlated with NOx, which reflects the contribution of traffic to the whole submicron size range. We also estimated the contribution of ion-induced nucleation in Beijing, and we found this contribution to be negligible.

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“…The particle number size distributions at ground level were obtained using a scanning mobility particle sizer (SMPS) with a time resolution of 5 min. Details regarding this instrumentation can be found in Du et al (2017). All data in this study are presented in Beijing local time (UTC+8 h).…”

Section: Observationsmentioning

confidence: 99%

Modeling of aerosol property evolution during winter haze episodes over a megacity cluster in northern China: roles of regional transport and heterogeneous reactions of SO<sub>2</sub>

Chen

et al. 2019

Atmos. Chem. Phys.

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Regional transport and heterogeneous reactions have been shown to play crucial roles in haze formation over a megacity cluster centered on Beijing. In this study, the updated Nested Air Quality Prediction Model System (NAQPMS) and the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model were employed to investigate the evolution of aerosols -in terms of the number concentration, size distribution, and degree of agingin Beijing during six haze episodes between 15 November and 15 December 2016, as part of the Air Pollution and Human Health-Beijing (APHH-Beijing) winter campaign of 2016. The model exhibited reasonable performance not only with respect to mass concentrations of PM 2.5 and its components in Beijing but also regarding the number concentration, size distribution, and degree of aging. We revealed that regional transport played a non-negligible role in haze episodes, with contributions of 14 %-31 % to the surface PM 2.5 mass concentration. The contribution of regional transport to secondary inorganic aerosols was larger than that to primary aerosols (30 %-63 % and 3 %-12 %, respectively). The chemical transformation of SO 2 along the transport pathway from source regions to Beijing was the major source of SO 2− 4 . We also found that sulfate formed outside Beijing from SO 2 emitted in Beijing; this sulfate was then blown back to Beijing and considerably influenced haze formation. Along the transport pathway, aerosols underwent aging, which altered the mass ratio of the coating of black carbon to black carbon (R BC ) and the size distribution of number concentrations. During the episodes, the geometric mean diameter (GMD) increased from less than 100 nm at the initial site to approximately 120 nm at the final site (Beijing), and the R BC increased from 2-4 to 4-8. During haze episodes with high humidity, the average contributions of gas and aqueous chemistry, heterogeneous chemistry, and primary emission to sulfate were comparable. However, their relative contributions varied with pollution levels. Primary emissions had the greatest impact under light to moderate pollution levels, whereas heterogeneous chemistry had a stronger effect under high pollution levels.

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Simultaneous measurements of particle number size distributions at ground level and 260 m on a meteorological tower in urban Beijing, China

Cited by 55 publications

References 42 publications

Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China

Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China

Variation of size-segregated particle number concentrations in wintertime Beijing

Modeling of aerosol property evolution during winter haze episodes over a megacity cluster in northern China: roles of regional transport and heterogeneous reactions of SO<sub>2</sub>

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Simultaneous measurements of particle number size distributions at ground level and 260 m on a meteorological tower in urban Beijing, China

Cited by 55 publications

References 42 publications

Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China

Vertical characterization of aerosol optical properties and brown carbon in winter in urban Beijing, China

Variation of size-segregated particle number concentrations in wintertime Beijing

Modeling of aerosol property evolution during winter haze episodes over a megacity cluster in northern China: roles of regional transport and heterogeneous reactions of SO&lt;sub&gt;2&lt;/sub&gt;

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Simultaneous measurements of particle number size distributions at ground level and 260 m on a meteorological tower in urban Beijing, China

Modeling of aerosol property evolution during winter haze episodes over a megacity cluster in northern China: roles of regional transport and heterogeneous reactions of SO<sub>2</sub>