{"id":{"repo_id":"toronto-retro","oai_identifier":"oai:utoronto.scholaris.ca:1807/144857"},"canonical_url":"https://search.dev.ndltd.org/etd/toronto-retro/oai:utoronto.scholaris.ca:1807/144857","repository":{"repo_id":"toronto-retro","name":"University of Toronto","base_url":"https://utoronto.scholaris.ca/server/oai/request"},"display":{"title":"Multiphase Aging of Atmospheric Biomass Burning Brown Carbon","abstract":"Brown carbon (BrC) is a type of carbonaceous aerosol, primarily emitted from biomass burning sources such as wildfires. These aerosol particles have significant implications on climate through their ability to absorb light, and potentially contributing to warming effects. Due to the expected increase of wildfire activity in the upcoming years, this source of particulate emission is also expected to increase. Oxidative and photochemical aging in the atmosphere, however, can change BrC’s light absorbing properties as well as its chemical composition. Significant uncertainties remain when estimating BrC’s impact on climate due to its chemical complexity and the range of atmospheric aging processes that can change its composition and optical properties.This thesis focused on elucidating the changes in absorption and chemical composition of biomass burning brown carbon aerosol from atmospheric aging. Targeting daytime photochemical aging by light exposure, we found that UVA light enhanced the ability of the particles to absorb visible light on short timescales of hours or less. This was accompanied by an increase in the oxidation state of the organic aerosols. The role that oxygen, and the subsequent reactive species formed by the presence of oxygen, plays in this absorption enhancement was also investigated. In particular, UV light exposure in the absence of oxygen does not lead to absorption enhancement in the visible region of the spectrum, pointing to the central role it plays in this photochemistry in the atmosphere. Using a singlet oxygen scavenger, we found that around 33% of the absorption increase was due to the formation of this reactive species, with no indication of OH radical formation. This has implications for anoxic, solid-like particles, where oxygen availability is low. Lastly, the enhancement in the absorption properties of biomass burning aerosols by short-term (1 hour) aging with low mixing ratios of NO3 radicals, one of the most important nighttime oxidants. We found that prior aging by either OH radicals or UVB light exposure significantly suppresses the subsequent absorption enhancement from NO3 radical aging, indicating that the aging mechanisms are in competition with each other. Overall, this thesis highlights the rapid optical and chemical transformations of BrC via photochemical and oxidative processing, and advances our understanding of how such particles evolve, with associated impacts on climate.","abstract_html":"Brown carbon (BrC) is a type of carbonaceous aerosol, primarily emitted from biomass burning sources such as wildfires. These aerosol particles have significant implications on climate through their ability to absorb light, and potentially contributing to warming effects. Due to the expected increase of wildfire activity in the upcoming years, this source of particulate emission is also expected to increase. Oxidative and photochemical aging in the atmosphere, however, can change BrC’s light absorbing properties as well as its chemical composition. Significant uncertainties remain when estimating BrC’s impact on climate due to its chemical complexity and the range of atmospheric aging processes that can change its composition and optical properties.This thesis focused on elucidating the changes in absorption and chemical composition of biomass burning brown carbon aerosol from atmospheric aging. Targeting daytime photochemical aging by light exposure, we found that UVA light enhanced the ability of the particles to absorb visible light on short timescales of hours or less. This was accompanied by an increase in the oxidation state of the organic aerosols. The role that oxygen, and the subsequent reactive species formed by the presence of oxygen, plays in this absorption enhancement was also investigated. In particular, UV light exposure in the absence of oxygen does not lead to absorption enhancement in the visible region of the spectrum, pointing to the central role it plays in this photochemistry in the atmosphere. Using a singlet oxygen scavenger, we found that around 33% of the absorption increase was due to the formation of this reactive species, with no indication of OH radical formation. This has implications for anoxic, solid-like particles, where oxygen availability is low. Lastly, the enhancement in the absorption properties of biomass burning aerosols by short-term (1 hour) aging with low mixing ratios of NO3 radicals, one of the most important nighttime oxidants. We found that prior aging by either OH radicals or UVB light exposure significantly suppresses the subsequent absorption enhancement from NO3 radical aging, indicating that the aging mechanisms are in competition with each other. Overall, this thesis highlights the rapid optical and chemical transformations of BrC via photochemical and oxidative processing, and advances our understanding of how such particles evolve, with associated impacts on climate.","abstract_has_math":false,"creators":["Liu-Kang, Carolyn"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":"Chemistry","school":null,"contributors":[],"advisors":["Abbatt, Jonathan"],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-06","date_published":"2025-06","updated_at":"2026-07-27T21:27:52Z","subjects":[],"languages":[],"rights":["Attribution 4.0 International"],"rights_urls":["http://creativecommons.org/licenses/by/4.0/"],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/1807/144857","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor.advisor","label":"Advisor","values":["Abbatt, Jonathan"]},{"key":"dc:contributor.department","label":"Department","values":["Chemistry"]},{"key":"dc:creator","label":"Author","values":["Liu-Kang, Carolyn"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-06"]},{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2025-07-30T15:41:16Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2025-07-30T15:41:16Z"]},{"key":"dc:date.issued","label":"Date","values":["2025-06"]},{"key":"dc:type","label":"Dc Type","values":["Thesis"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:rights","label":"Dc Rights","values":["Attribution 4.0 International"]},{"key":"dc:rights.uri","label":"Rights URI","values":["http://creativecommons.org/licenses/by/4.0/"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["https://hdl.handle.net/1807/144857"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["Brown carbon (BrC) is a type of carbonaceous aerosol, primarily emitted from biomass burning sources such as wildfires. These aerosol particles have significant implications on climate through their ability to absorb light, and potentially contributing to warming effects. Due to the expected increase of wildfire activity in the upcoming years, this source of particulate emission is also expected to increase. Oxidative and photochemical aging in the atmosphere, however, can change BrC’s light absorbing properties as well as its chemical composition. Significant uncertainties remain when estimating BrC’s impact on climate due to its chemical complexity and the range of atmospheric aging processes that can change its composition and optical properties.This thesis focused on elucidating the changes in absorption and chemical composition of biomass burning brown carbon aerosol from atmospheric aging. Targeting daytime photochemical aging by light exposure, we found that UVA light enhanced the ability of the particles to absorb visible light on short timescales of hours or less. This was accompanied by an increase in the oxidation state of the organic aerosols. The role that oxygen, and the subsequent reactive species formed by the presence of oxygen, plays in this absorption enhancement was also investigated. In particular, UV light exposure in the absence of oxygen does not lead to absorption enhancement in the visible region of the spectrum, pointing to the central role it plays in this photochemistry in the atmosphere. Using a singlet oxygen scavenger, we found that around 33% of the absorption increase was due to the formation of this reactive species, with no indication of OH radical formation. This has implications for anoxic, solid-like particles, where oxygen availability is low. Lastly, the enhancement in the absorption properties of biomass burning aerosols by short-term (1 hour) aging with low mixing ratios of NO3 radicals, one of the most important nighttime oxidants. We found that prior aging by either OH radicals or UVB light exposure significantly suppresses the subsequent absorption enhancement from NO3 radical aging, indicating that the aging mechanisms are in competition with each other. Overall, this thesis highlights the rapid optical and chemical transformations of BrC via photochemical and oxidative processing, and advances our understanding of how such particles evolve, with associated impacts on climate."]},{"key":"dc:description.degree","label":"Dc Description Degree","values":["Ph.D."]},{"key":"dc:title","label":"Title","values":["Multiphase Aging of Atmospheric Biomass Burning Brown Carbon"]}]}],"canonical_facts":{"dc:contributor.advisor":["Abbatt, Jonathan"],"dc:contributor.department":["Chemistry"],"dc:creator":["Liu-Kang, Carolyn"],"dc:date":["2025-06"],"dc:date.accessioned":["2025-07-30T15:41:16Z"],"dc:date.available":["2025-07-30T15:41:16Z"],"dc:date.issued":["2025-06"],"dc:description.abstract":["Brown carbon (BrC) is a type of carbonaceous aerosol, primarily emitted from biomass burning sources such as wildfires. These aerosol particles have significant implications on climate through their ability to absorb light, and potentially contributing to warming effects. Due to the expected increase of wildfire activity in the upcoming years, this source of particulate emission is also expected to increase. Oxidative and photochemical aging in the atmosphere, however, can change BrC’s light absorbing properties as well as its chemical composition. Significant uncertainties remain when estimating BrC’s impact on climate due to its chemical complexity and the range of atmospheric aging processes that can change its composition and optical properties.This thesis focused on elucidating the changes in absorption and chemical composition of biomass burning brown carbon aerosol from atmospheric aging. Targeting daytime photochemical aging by light exposure, we found that UVA light enhanced the ability of the particles to absorb visible light on short timescales of hours or less. This was accompanied by an increase in the oxidation state of the organic aerosols. The role that oxygen, and the subsequent reactive species formed by the presence of oxygen, plays in this absorption enhancement was also investigated. In particular, UV light exposure in the absence of oxygen does not lead to absorption enhancement in the visible region of the spectrum, pointing to the central role it plays in this photochemistry in the atmosphere. Using a singlet oxygen scavenger, we found that around 33% of the absorption increase was due to the formation of this reactive species, with no indication of OH radical formation. This has implications for anoxic, solid-like particles, where oxygen availability is low. Lastly, the enhancement in the absorption properties of biomass burning aerosols by short-term (1 hour) aging with low mixing ratios of NO3 radicals, one of the most important nighttime oxidants. We found that prior aging by either OH radicals or UVB light exposure significantly suppresses the subsequent absorption enhancement from NO3 radical aging, indicating that the aging mechanisms are in competition with each other. Overall, this thesis highlights the rapid optical and chemical transformations of BrC via photochemical and oxidative processing, and advances our understanding of how such particles evolve, with associated impacts on climate."],"dc:description.degree":["Ph.D."],"dc:identifier.uri":["https://hdl.handle.net/1807/144857"],"dc:rights":["Attribution 4.0 International"],"dc:rights.uri":["http://creativecommons.org/licenses/by/4.0/"],"dc:title":["Multiphase Aging of Atmospheric Biomass Burning Brown Carbon"],"dc:type":["Thesis"]},"updated_at":"2026-07-27T21:27:52Z"}