Online Single Particle Chemical Characterization Of Aerosol Populations in Remote Environments

Abstract

Atmospheric aerosols have significant impacts on air quality, climate, and human health, yet analytical and logistical challenges have limited our ability to measure these aerosol particles, particularly in remote regions. In this dissertation, individual atmospheric particles were chemically characterized in rural northern Michigan and remote northern Alaska for the first time. To enable this measurements, Chapter 2 details the construction and characterization of an updated aircraft-capable aerosol time-of-flight mass spectrometer (A-ATOFMS), capable of measuring size-resolved chemical composition of 0.07 – 1.6 µm individual particles up to 40 Hz with lower mass (~25 kg saved) and power (~600 W saved) consumption than the previous A-ATOFMS. Chapter 3 discusses size-resolved chemical composition of atmospheric aerosols in northern Michigan while the site was influenced by Canadian wildfire, urban, and local forest air masses. Throughout the study, long-range transported biomass burning aerosols were the cores of particles primarily consisting, by mass, of secondary organic aerosol from the oxidation of volatile organic compounds emitted from both wildfires and forests. In Chapter 4, we identified 14 periods of ultrafine particle growth at the same field site. Urban air mass influence during the daytime led to the highest observed growth rates, likely due to increased atmospheric oxidant levels producing condensable material. Nighttime wildfire air masses were likely influenced by increased SO2 and NO2 in the plumes leading to NO3 radical oxidation. TEM-EDX showed contributions from sulfur, carbon, and oxygen down to 20 nm particles, suggesting contributions from H2SO4 and SOA. As particle growth was previously thought to be suppressed in this isoprene-rich forest, these measurements represent a source of particles not previously considered in this environment. Chapters 5 – 6 discuss the results from field campaigns conducted in the Alaskan Arctic. In Chapter 5, I show results of A-ATOFMS and scanning electron microscopy with energy-dispersive x-ray spectroscopy (SEM-EDX) analyses of atmospheric particles transported to Utqiaġvik, AK from the Prudhoe Bay oil fields, located hundreds of kilometers to the east, in comparison to the pristine Arctic Ocean background. During Arctic Ocean influence, fresh sea spray aerosol (SSA) was the primary contributor to aerosol number concentrations, compared to transported organic carbon and aged SSA particles during Prudhoe Bay air masses. Chapter 6 details the 2016 field campaign within the Prudhoe Bay oil fields, where we deployed the A-ATOFMS to characterize local oil field combustion plumes and the overall oil field background aerosol population; these were the first single particle measurements within an Arctic oil field. Diesel and natural gas combustion were the major influences on the aerosol population, with unique amine-containing particles identified from the processing of natural gas. Overall, the results from these field campaigns, aided by the newly constructed A-ATOFMS, provided new insights into the chemical composition of local and transported atmospheric particles on rural and remote environments influenced by the changing climate.