Laboratory Investigations of Soot Optical Properties and the Hygroscopicity and Production of Sea Spray Aerosol PDF Download

Author: Sara Danielle Forestieri
Publisher:
ISBN: 9780355972436
Category :
Languages : en
Pages : 0

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Author: Dan Zhang
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ISBN:
Category :
Languages : en
Pages :

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Soot particles released from fossil fuel combustion and biomass burning have a large impact on the regional/global climate by altering the atmospheric radiativeproperties and by serving as cloud condensation nuclei (CCN). However, the exact forcing is affected by the mixing of soot with other aerosol constituents, such as sulfuric acid. In this work, experimental studies have been carried out focusing on three integral parts: (1) heterogeneous uptake of sulfuric acid on soot; (2) hygroscopic growth of H2SO4-coated soot aerosols; (3) effect of H2SO4 coating on scattering and extinction properties of soot particles. A low-pressure laminar-flow reactor, coupled to ion drift chemical ionization mass spectrometry (ID-CIMS) detection, is used to study uptake coefficients of H2SO4 on combustion soot. The results suggest that uptake of H2SO4 takes place efficiently on soot particles, representing an important route to convert hydrophobic soot to hydrophilic aerosols. A tandem differential mobility analyzing (TDMA) system is employed to determine the hygroscopicity of freshly generated soot in the presence of H2SO4 coating. It is found that fresh soot particles are highly hydrophobic, while coating of H2SO4 significantly facilitates water uptake on soot even at sub-saturation relative humidities. The results indicate that aged soot particles in the atmosphere can potentially be an efficient source of CCN. Scattering and extinction coefficient measurements of the soot-H2SO4 mixed particles are conducted using a three wave length Nephelometer and a multi-path extinction cell. Coating of H2SO4 is found to increase the single scattering albedo (SSA) of soot particles which has impact on the aerosol direct radiative effect. Other laboratory techniques such as transmission electron microscopy (TEM) and Fourier transform infrared spectrometry (FTIR) are utilized to examine the morphology and chemical composition of the soot-H2SO4 particles. This work provides critical information concerning the heterogeneous interaction of soot and sulfuric acid, and how their mixing affects the hygroscopic and optical properties of soot. The results will improve our ability to model and assess the soot direct and indirect forcing and hence enhance our understanding of the impact of anthropogenic activities on the climate.

Author:
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Category :
Languages : en
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Author: Huaxin Xue
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Category :
Languages : en
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Soot aerosols are well known to be atmospheric constituents, but the hydrophobic nature of fresh soot likely prohibits them from encouraging cloud development. Soot aged through contact with oxygenated organic compounds may become hydrophilic enough to promote water uptake. In this study, the tandem differential mobility analyzer (TDMA) and differential mobility analyzer-aerosol particle mass analyzer (DMA-APM) were employed to measure the changes in morphology and hygroscopicity of soot aerosol particles upon coating with succinic and glutaric acids. The effective densities, fractal dimensions and dynamic shape factors of fresh and coated soot aerosol particles have been determined. Significant size-dependent increases of soot particle mobility diameter, mass, and effective density ([rho]eff) were observed upon coating of aggregates with succinic acid. These properties were restored back to their initial states once the acid was removed by heating, suggesting no restructuring of the soot core had occurred. Coating of soot with glutaric acid, on the other hand, leads to a strong size shrinking with a diameter growth factor ~0.60, even after the acid has been removed by heating suggesting the strong restructuring of the soot agglomerate. The additional 90% RH cycle can evidently enhance the restructuring process. The extinction and scattering properties at 532 nm of soot particles internally mixed with dicarboxylic acids were investigated experimentally using a cavity ring-down spectrometer and an integrating nephelometer, respectively, and the absorption is derived as the difference between extinction and scattering. It was found that the organic coatings significantly affect the optical and microphysical properties of the soot aggregates. The size-dependent amplification factors of light scattering were as much as 3.8 and 1.7 with glutaric and succinic acids coatings, respectively. Additional measurements with soot particles that are first coated with glutaric acid and then heated to remove the coating show that both scattering and absorption are enhanced by irreversible restructuring of soot aggregates to more compact globules. These results reveal the microphysical state of soot aerosol with incomplete restructuring in the atmosphere, and advance the treatment of atmospheric aged soot aerosol in the Mie theory shell-and-core model.

Author: Jonathan Trueblood
Publisher:
ISBN:
Category :
Languages : en
Pages : 223

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Atmospheric aerosols directly impact the Earth's climate by scattering and absorbing solar radiation and indirectly by altering the microphysical properties of clouds. Aerosols formed over the oceans, termed marine aerosols, consist of secondary marine aerosols (SMA) formed upon the oxidation of gas phase species and of primary sea spray aerosols (SSA) that are directly emitted from the surface of the ocean. The climate relevant properties of primary SSA are determined by their size and chemical composition, both of which are functions of the ocean's biological activity as well as atmospheric heterogeneous reactions with trace gas species and photochemical aging reactions. This dissertation investigates the impacts of each of these processes on the chemical complexity of SSA by conducting fundamental laboratory studies involving spectroscopic probing of various SSA systems ranging from simple, single component model systems to authentic SSA produced using an indoor ocean-atmosphere facility that replicates the chemical and biological complexity of the ocean and SSA. First, we identified the various chemical species found in SSA and linked their size and temporal changes to the biological activity of the ocean. Next, we used our improved understanding of the molecular speciation of SSA to look in-depth at the atmospheric reactions that alter the chemical and physical properties of SSA, including the heterogeneous reaction with gas phase nitric acid and OH radicals, as well as photosensitized reactions with chromophoric species. We found that the chemical complexity of SSA due to the organic and biological components alters their reactivity and introduces alternative pathways beyond those previously acknowledged. Finally, to aid in future experiments of photochemical aging reactions of SSA, we constructed and validated an LED incoherent broadband cavity enhanced absorption spectrometer (LED-IBCEAS) to detect various nitrogen oxides (e.g., NO2 and HONO). The findings presented in this dissertation improve our understanding of the various chemical and biological controls on the climate relevant properties of SSA, and can ultimately be used to improve the performance of regional and global climate models.

Author: Kyle William Dawson
Publisher:
ISBN:
Category :
Languages : en
Pages : 55

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Author:
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Languages : en
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The objective of this workshop was to address the most urgent open science questions for improved quantification of sea spray aerosol-radiation-climate interactions. Sea spray emission and its influence on global climate remains one of the most uncertain components of the aerosol-radiation-climate problem, but has received less attention than other aerosol processes (e.g. production of terrestrial secondary organic aerosols). Thus, the special emphasis was placed on the production flux of sea spray aerosol particles, their number concentration and chemical composition and properties.

Author: Rekha Kale
Publisher: Scitus Academics LLC
ISBN: 9781681171326
Category : Aerosols
Languages : en
Pages : 0

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Atmospheric Aerosols is a vital problem in current environmental research due to its importance in atmospheric optics, energetics, radiative transfer studies, chemistry, climate, biology and public health. Aerosols can influence the energy balance of the terrestrial atmosphere, the hydrological cycle, atmospheric dynamics and monsoon circulations. Because of the heterogeneous aerosol field with large spatial and temporal variability and reduction in uncertainties in aerosol quantification is a challenging task in atmospheric sciences. Keeping this in view the present study aims to assess the impact of aerosols on coastal Indian station Visakhapatnam and the adjoining Bay of Bengal. An aerosol is a colloid of fine solid particles or liquid droplets, in air or another gas. Aerosols can be natural or not. Examples of natural aerosols are fog, forest exudates and geyser steam.

Author: Abdur Rasheed
Publisher:
ISBN:
Category :
Languages : en
Pages : 136

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Author: Columbia University. Central Aerosol Laboratories
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 58

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