Quantitative Analysis Of Reduced Nitrogen Processing In Marine Aerosols By Fog And The Indoor Air Of New Canadian Homes

Abstract

Reduced nitrogen species, including ammonia (NH3) and alkylamines (NR3), are ubiquitous in the atmosphere and play important roles in new particle formation, aerosol growth, multiphase chemical processing, and air quality. However, their quantitative analysis across aerosol and gas phases remains analytically challenging. This thesis develops and applies ion chromatographic (IC) methods to quantify reduced nitrogen to investigate its processing in marine aerosols during fog events and in the indoor air of newly built Canadian homes. An IC method was developed to separate and quantify NH3 and the ten most abundant atmospheric NR3 with high selectivity and separation efficiency using 4 µm packed columns and resin-based suppressors, alongside stabilized NR3 calibration standards. Suppressor performance was improved by stepped-current operation and an external water supply, resulting in enhanced linearity, accuracy, precision, and lower detection limits than conventional suppression modes. The optimized IC method was applied to marine aerosol samples collected during the Fog and Turbulence Interactions in the Marine Atmosphere (Fatima) 2022 campaign over the Northwest Atlantic Ocean. Aerosol chemistry, microphysics, physical processing, and meteorological conditions were analyzed to investigate fog–aerosol interactions. Size-resolved chemical measurements showed a reduction in coarse mode sea salt ions during fog, attributed to their growth into fog droplets, while fine mode processed-S (e.g., nss-SO42- and MSA-) and reduced-N species increased due to enhanced aqueous-phase processing. Consistent reductions in coarse sea salt mass loading across more than a dozen fog events confirm their role as effective fog condensation nuclei and demonstrate the impact of fog processing on aerosol mass loading. The developed IC method was further applied to quantify indoor gas-phase reduced nitrogen in 48 newly built Canadian homes as part of the New Home Air Quality Study (NHAQS) from 2019 to 2024. Indoor NH3 mixing ratios decreased from pre- to post-occupancy and remained relatively stable over 12 months following, consistent with reduced emissions from new materials and increased partitioning surface area upon occupancy. Overall, this thesis develops a new analytical method to quantify reduced nitrogen in marine fog aerosols and indoor air, improving understanding of aerosol–fog chemistry, fog forecasting models, and indoor air quality.