Highly Disperse Aerosols

Fuks, N. A.; Sutugin, A. G.

doi:10.1070/rc1968v037n11abeh001710

“…k d ( r ) can be calculated using the Fuks and Sutugin () interpolation equation:

k_{d} = \frac{4 italicπrDV}{1 + K_{n} ([], λ + 4 ((), 1 - γ) / 3 γ)}

where D is the molecular diffusion coefficient of gaseous species in air; V represents a ventilation factor; K n is the Knudsen number; λ is the effective mean free path of a gas molecule in air; and γ is the uptake coefficient.…”

Section: Methods and Datamentioning

confidence: 99%

Formation and Evolution Mechanisms for Two Extreme Haze Episodes in the Yangtze River Delta Region of China During Winter 2016

Li

¹

,

Wang

²

,

Xie

³

et al. 2019

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Severe haze pollution frequently occurred in China during winter. Mechanisms for the formation and evolution of high PM2.5 (particulate matter with aerodynamic diameter of 2.5 μm or less) episodes, however, remain poorly understood. We characterize two extreme haze episodes in the Yangtze River Delta region of China from 1 to 9 December (Episode I) and 19 to 24 December (Episode II) in 2016 using comprehensive measurements and model analyses. The aqueous sulfur dioxide (SO2) oxidation catalyzed by mineral ions and the heterogeneous uptakes of SO2, sulfuric acid (H2SO4), nitrogen dioxide (NO2), nitrogen trioxide (NO3), nitrogen pentoxide (N2O5), and nitric acid (HNO3) on mineral aerosols are included in the model to better represent the formation of sulfate‐nitrate‐ammonium. The optimized mechanisms substantially improve the simulations of PM2.5 composition, particularly for sulfate and nitrate. The two episodes show different synoptic conditions and evolution stages, with gradual PM2.5 increase under stagnant weather conditions in Episode I (Stage I: Slow Increase Stage, Stage II: Rapid Formation Stage, and Stage III: Dissipation Stage) and with explosive PM2.5 increase mostly associated with cross‐border transport from North China in Episode II (Stage I′: Clean Stage, Stage II′: Fast Transport Stage, and Stage III′: Clear Stage). The concentrations of sulfate‐nitrate‐ammonium increased evidently and became the key components of PM2.5 during haze episodes. The heterogeneous conversion from SO2 to sulfate on mineral aerosols is the main reason for sulfate increase, accounting for more than 50% of sulfate production. This study provides a better understanding of the causes for winter haze in China.

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“…RCAT8.2 also includes biogenic and anthropogenic emissions and the Mainz Isoprene Mechanism (MIM) (Geiger et al, 2003). Aerosol uptake rates in RCAT8.2 are calculated using the mass-transfer equation by Fuks and Sutugin (1971). The uptake rates were calculated based on the vertical profile of the aerosol surface to air volume ratio and a particle diameter of 150 nm.…”

Section: Rcatmentioning

confidence: 99%

Nitrous acid formation in a snow-free wintertime polluted rural area

Tsai

¹

,

Spolaor

²

,

Colosimo

³

et al. 2018

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Abstract. Nitrous acid (HONO) photolysis is an important source of hydroxyl radicals (OH) in the lower atmosphere, in particular in winter when other OH sources are less efficient. The nighttime formation of HONO and its photolysis in the early morning have long been recognized as an important contributor to the OH budget in polluted environments. Over the past few decades it has become clear that the formation of HONO during the day is an even larger contributor to the OH budget and additionally provides a pathway to recycle NO x . Despite the recognition of this unidentified HONO daytime source, the precise chemical mechanism remains elusive. A number of mechanisms have been proposed, including gas-phase, aerosol, and ground surface processes, to explain the elevated levels of daytime HONO. To identify the likely HONO formation mechanisms in a wintertime polluted rural environment we present LP-DOAS observations of HONO, NO 2 , and O 3 on three absorption paths that cover altitude intervals from 2 to 31, 45, and 68 m above ground level (a.g.l.) during the UBWOS 2012 experiment in the Uintah Basin, Utah, USA. Daytime HONO mixing ratios in the 2-31 m height interval were, on average, 78 ppt, which is lower than HONO levels measured in most polluted urban environments with similar NO 2 mixing ratios of 1-2 ppb. HONO surface fluxes at 19 m a.g.l., calculated using the HONO gradients from the LP-DOAS and measured eddy diffusivity coefficient, show clear upward fluxes. The hourly average vertical HONO flux during sunny days followed solar irradiance, with a maximum of (4.9 ± 0.2) × 10 10 molec. cm −2 s −1 at noontime. A photostationary state analysis of the HONO budget shows that the surface flux closes the HONO budget, accounting for 63 ± 32 % of the unidentified HONO daytime source throughout the day and 90 ± 30 % near noontime. This is also supported by 1-D chemistry and transport model calculations that include the measured surface flux, thus clearly identifying chemistry at the ground as the missing daytime HONO source in this environment. Comparison between HONO surface flux, solar radiation, NO 2 and HNO 3 mixing ratios, and results from 1-D model runs suggest that, under high NO x conditions, HONO formation mechanisms related to solar radiation and NO 2 mixing ratios, such as photo-enhanced conversion of NO 2 on the ground, are most likely the source of daytime HONO. Under moderate to low NO 2 conditions, photolysis of HNO 3 on the ground seems to be the main source of HONO.

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“…RCAT8.2 also includes biogenic and anthropogenic emissions and the Mainz Isoprene Mechanism (MIM) (Geiger et al, 2003). Aerosol uptake rates in RCAT 8.2 are calculated using the mass-transfer equation by (Fuks and Sutugin, 1971). …”

Section: Rcatmentioning

confidence: 99%

Nitrous acid formation in a snow-free wintertime polluted rural area

Tsai¹,

Spolaor²,

Colosimo³

et al. 2017

Preprint

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Abstract.Nitrous acid (HONO) photolysis is an important source of hydroxyl radicals (OH) in the lower atmosphere, in particular in winter when other OH sources are less efficient. The nighttime formation of HONO and its photolysis in the early morning have long been recognized as an important contributor to the OH budget in polluted environments. Over the past few decades it has become clear that the formation of HONO during the day is an even larger contributor to the OH budget, and additionally 5 provides a pathway to recycle NO x . Despite the recognition of this unidentified HONO daytime source, the precise chemical mechanism remains elusive. A number of mechanisms have been proposed, including gas-phase, aerosol, and ground surface processes, to explain the elevated levels of daytime HONO. To identify the likely HONO formation mechanisms in a wintertime polluted rural environment we present LP-DOAS observations of HONO, NO 2 , and O 3 on three absorption paths that cover altitude intervals from 2 m to 31 m, 45 m, and 68 m agl during the UBWOS 2012 experiment in the Uintah Basin, Utah, 10 USA. Daytime HONO mixing ratios in the 2 -31 m height interval were, on average, 78 ppt, which is lower than HONO levels measured in most polluted urban environments with similar NO 2 mixing ratios of 1-2 ppb. HONO surface fluxes at 16 m agl, calculated using the HONO gradients from the LP-DOAS and measured eddy diffusivity coefficient, show clear upward fluxes. The hourly average vertical HONO flux during sunny days followed solar irradiance, with a maximum of (4.9±0.2) x10 10 molec. cm

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Highly Disperse Aerosols

Cited by 11 publications

References 0 publications

Formation and Evolution Mechanisms for Two Extreme Haze Episodes in the Yangtze River Delta Region of China During Winter 2016

Formation and Evolution Mechanisms for Two Extreme Haze Episodes in the Yangtze River Delta Region of China During Winter 2016

Nitrous acid formation in a snow-free wintertime polluted rural area

Nitrous acid formation in a snow-free wintertime polluted rural area

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