The Formation and Aging of Secondary Organic Aerosol from Alpha-pinene Oxidation PDF Download

Author: Kaytlin Henry
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

View

Book Description

Author: Emma Louise D'Ambro
Publisher:
ISBN:
Category :
Languages : en
Pages : 129

View

Book Description

Author: Jenny Pui Shan Wong
Publisher:
ISBN:
Category :
Languages : en
Pages : 132

View

Book Description
A new portable flow tube technique, the Toronto Photo-Oxidation Tube v2.0 was developed and characterized to explore its potential to control and monitor the OH-initiated formation and chemical aging of secondary organic aerosol (SOA) in-situ. The first study investigated the different operational parameters of this flow tube technique. TPOT v2.0 can generate oxidizing conditions equivalent to ambient OH exposures of 2.3 -- 10.8 days. The transmission efficiency of a model organic aerosol indicated negligible losses in the oxidation tube. Differences in the residence time distribution curves measured for a gas and model organic aerosol showed that particles were subjected to approximately half of the OH exposure compared to gases.The second study examined the capacity of the TPOT technique to generate secondary aerosols due to OH oxidation. High aerosol yield was observed for H2SO4 particles, whereas a low aerosol yield was observed for alpha-pinene SOA.

Author: Mehrnaz Sarrafzadeh
Publisher:
ISBN:
Category :
Languages : en
Pages : 0

View

Book Description
Atmospheric organic aerosols have a significant impact on climate and human health. However, our understanding of the physical and chemical properties of these aerosols is inadequate, thus their climate and health influences are poorly constrained. In this study, we investigated the secondary organic aerosol (SOA) formation from OH-initiated oxidation of -pinene. The majority of experiments were conducted in the York University smog chamber. The main objective was to identify the gas and particle phase products with an atmospheric pressure chemical ionization mass spectrometer (APCI-MS/MS). A wide variety of products were identified containing various functional groups including alcohol, aldehyde, carboxylic acid, ketone and nitrate. Following the chemical composition characterization of products, the shape, phase state and density of generated particles were determined. Images from a scanning electron microscope (SEM) revealed that SOA particles from -pinene were commonly spherical in shape, and adopted an amorphous semi-solid/liquid state. Additionally, the density was determined for SOA particles generated from -pinene/OH, nopinone/OH and nopinone/NO3 experiments for the first time using a tapered element oscillating microbalance-scanning mobility particle sizer (TEOM-SMPS) method. Our results showed a correlation between the determined particle density and the particle chemical composition of the respective system. This demonstrates that changes in particle density can be indicative of the changes in chemical composition of particles. We also investigated the chemical aging of oxidation products by exposing them to additional OH radicals or ozone. The observed changes in chemical composition of products and additional SOA mass production during OH-induced aging were attributed to further oxidation of gas phase intermediate products. The NOx dependence of SOA formation from -pinene photooxidation was investigated in the York University smog chamber and the Jlich Plant Atmosphere Chamber (JPAC). Consistent with previous NOx studies, SOA yields increased with increasing [NOx] at low-NOx conditions, whereas increasing [NOx] at high-NOx conditions suppressed the SOA yield. This increase was attributed to an increase of OH concentration. After removing the effect of [OH] on SOA yield in the JPAC, SOA yields only decreased with increasing [NOx]. Finally, the formation mechanisms of identified products were probed based on the information acquired throughout our study.

Author: Bethany A. Warren
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 414

View

Book Description

Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 13

View

Book Description

Author: National Aeronautics and Space Administration (NASA)
Publisher: Createspace Independent Publishing Platform
ISBN: 9781723538780
Category :
Languages : en
Pages : 274

View

Book Description
This is the eleventh in a series of evaluated sets of rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation. The primary application of the data is in the modeling of stratospheric processes, with special emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. Demore, W. B. and Sander, S. P. and Golden, D. M. and Hampson, R. F. and Kurylo, M. J. and Howard, C. J. and Ravishankara, A. R. and Kolb, C. E. and Molina, M. J. Jet Propulsion Laboratory NASA-CR-198863, JPL-PUBL-94-26, NAS 1.26:198863 NAS7-1260; RTOP 464-41-04-01-00...

Author: Quentin Gerald James Malloy
Publisher:
ISBN:
Category : Aerosols
Languages : en
Pages : 414

View

Book Description

Author: Celia L. Faiola
Publisher:
ISBN:
Category :
Languages : en
Pages :

View

Book Description
Atmospheric aerosol impact climate by scattering and absorbing radiation and contributing to cloud formation processes. One of the largest uncertainties in climate change predictions is due to limitations in our understanding of the formation of secondary organic aerosol (SOA). This dissertation investigated SOA formation from the oxidation of plant and leaf litter emissions in a laboratory chamber. To accurately measure the biogenic volatile organic compound (BVOC) emissions, a dynamic dilution system was developed and is described in the first study. This system was used to calibrate the GC-MS-FID and improve quantitation with a maximum instrumental error of +/-10%. In the second study, two separate sets of soil and leaf litter samples were transported from the University of Idaho experimental forest and brought back to the lab. The BVOC emissions from these samples were pumped to an aerosol growth chamber where they were oxidized to generate SOA. The resulting SOA composition was similar to SOA formed from the oxidation of other biogenic SOA precursors. Soil/leaf litter BVOC missions were compared to a canopy emission model and contributed from 12-136% of canopy emissions during spring and fall. Results suggest this could be a significiant emission source during those times of the year. In the third and fourth study, coniferous plants were treated with a plant hormone, methyl jasmonate, to simulate herbivory stress. The third study focused on the plant responses to the stress treatment by investigating changes to the BVOC emission profile. There was a high degree of inter- and intra-plant species variability. Some of the compounds most affected by the stress treatment were alpha-pinene, beta-pinene, limonene, 1,8-cineol, beta-myrcene, terpinolene, and the aromatic cymene isomers. The fourth study investigated changes to SOA composition due to changes in the BVOC emission profiles. Most pre-treatment SOA was very similar in composition with Pearson correlation coefficients between the AMS spectra greater than 0.88. The SOA generated after MeJA treatment produced aerosol mass spectra with similar m/z enhancements. This could indicate an herbivory stress mass spectral fingerprint that could be used to identify plant stress at an ecosystem scale.

Author: Lindsay Diana Yee
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages : 466

View

Book Description
The photooxidation of volatile organic compounds (VOCs) in the atmosphere can lead to the formation of secondary organic aerosol (SOA), a major component of fine particulate matter. Improvements to air quality require insight into the many reactive intermediates that lead to SOA formation, of which only a small fraction have been measured at the molecular level. This thesis describes the chemistry of secondary organic aerosol (SOA) formation from several atmospherically relevant hydrocarbon precursors. Photooxidation experiments of methoxyphenol and phenolic compounds and C12 alkanes were conducted in the Caltech Environmental Chamber. These experiments include the first photooxidation studies of these precursors run under sufficiently low NOx levels, such that RO2 + HO2 chemistry dominates, an important chemical regime in the atmosphere. Using online Chemical Ionization Mass Spectrometery (CIMS), key gas-phase intermediates that lead to SOA formation in these systems were identified. With complementary particle-phase analyses, chemical mechanisms elucidating the SOA formation from these compounds are proposed. Three methoxyphenol species (phenol, guaiacol, and syringol) were studied to model potential photooxidation schemes of biomass burning intermediates. SOA yields (ratio of mass of SOA formed to mass of primary organic reacted) exceeding 25% are observed. Aerosol growth is rapid and linear with the organic conversion, consistent with the formation of essentially non-volatile products. Gas and aerosol-phase oxidation products from the guaiacol system show that the chemical mechanism consists of highly oxidized aromatic species in the particle phase. Syringol SOA yields are lower than that of phenol and guaiacol, likely due to unique chemistry dependent on methoxy group position. The photooxidation of several C12 alkanes of varying structure n-dodecane, 2-methylundecane, cyclododecane, and hexylcyclohexane) were run under extended OH exposure to investigate the effect of molecular structure on SOA yields and photochemical aging. Peroxyhemiacetal formation from the reactions of several multifunctional hydroperoxides and aldehyde intermediates was found to be central to organic growth in all systems, and SOA yields increased with cyclic character of the starting hydrocarbon. All of these studies provide direction for future experiments and modeling in order to lessen outstanding discrepancies between predicted and measured SOA.