Laboratory studies of atmospheric photochemistry in indoor and outdoor environments

Secondary organic aerosol (SOA), fine particulate matter formed through indirect photochemical reactions, influences the climate and contributes to air pollution harmful to human health. While these two effects act at different scales, they are governed by similar chemical processes. This work investigates the atmospheric photochemistry of indoor and outdoor environments, giving particular attention to the reactions that lead to SOA formation, notably those involving oxidant and peroxy radical (RO2) chemistry. First, this thesis examines the oxidation of dimethyl sulfide (DMS), which represents a large natural source of sulfur to the atmosphere and affects the climate. Using varied chemical conditions across numerous environmental chamber experiments, we characterize aerosol formation from the oxidation of DMS, as well as two related compounds, dimethyl sulfoxide and dimethyl disulfide. We also measure key rate constants crucial to understanding the formation and fate of hydroperoxymethyl thioformate, an important recently-discovered DMS product. Second, this work investigates the indoor air quality implications of 222 nm germicidal ultraviolet lamps (GUV222). While these lamps are effective at reducing the spread of airborne pathogens, they lead to the formation of ozone (O3), a harmful air pollutant. Through environmental chamber experiments, we quantify the GUV222-driven production of O3, OH, oxidized products, and SOA, and further demonstrate that GUV222 causes new particle formation. Based on these results, we recommend that GUV222 lights be operated at their lowest effective level. Finally, we pivot to examine assumptions embedded within the relationship between chamber experiments and SOA parameterizations in global chemical transport models. We represent historical laboratory experiments in a box model, enabling explicit estimates of the unmeasured RO2 and oxidant chemistry that influences aerosol formation. This work shows that reaction conditions are dynamic, changing within and between experiments, and demonstrates that RO2 isomerization is implicitly built into SOA parameterizations, even without its explicit representation. Overall, this thesis connects multiple areas of indoor and outdoor atmospheric photochemistry, improving our understanding of marine organosulfur chemistry, the impacts of GUV222 lamps, and the relationship between laboratory chamber measurements and the modeling of aerosol on a global scale.

Name thesis:degree_name

Doctoral

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Civil and Environmental Engineering

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2024

Author dc:creator

• Goss, Matthew B.

Advisor dc:contributor.advisor

• Kroll, Jesse H.

Statement dc:rights

• In Copyright - Educational Use Permitted
• Copyright retained by author(s)

Licence dc:rights.uri

• https://rightsstatements.org/page/InC-EDU/1.0/

Handle dc:identifier.uri

https://hdl.handle.net/1721.1/157732

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/157732