Abstract View
Asphalt-related Emissions are a Large Urban Source of Secondary Organic Aerosol Precursors
DREW GENTNER, Peeyush Khare, Jo Machesky, Megan He, Ricardo Soto, Albert Presto, Andrew Lambe, Jordan Krechmer, Manjula Canagaratna, Yale University
Abstract Number: 383
Working Group: Missing contributors to SOA: The Role of Volatile Chemical Products (VCPS)
Abstract
Recent studies show that non-traditional emissions (e.g. volatile chemical products; VCPs) are becoming dominant contributors of reactive organic gases in developed megacities. Asphalt is a heavily used, non-combustion-related source of gas-phase precursors to urban secondary organic aerosol (SOA). Yet, its emissions are largely absent from inventories due to their complex mixture of predominantly intermediate- and semi-volatile organic compounds (IVOCs, SVOCs), which emit over long timescales (e.g. days to weeks), are not present in the “product formulation”, and also closely resemble motor vehicle emissions. We constrained their emissions via a combination of laboratory tests of commonly used PG 64-22 road asphalt and roofing materials under environmentally-relevant thermal, solar irradiation and ozone stresses, and supplement these observations with multi-city field measurements. To further investigate the SOA formation potential, we oxidized asphalt-related emissions in a potential aerosol mass (PAM) reactor under daytime and nighttime conditions and measured the SOA formation and chemical composition using an aerosol mass spectrometer (AMS), a scanning mobility particle sizer (SMPS), and a high-resolution proton transfer reaction time-of-flight mass spectrometer (PTR-TOF).
We report emission factors for total emissions and their distribution of aliphatic, aromatic, and sulfur/oxygen-functionalized compounds as a function of typical temperatures for asphalt while in-use, storage, and during paving. We also evaluate changes over time and provide the most detailed chemical speciation of asphalt-related emissions to date using both a high-resolution atmospheric pressure chemical ionization quadrupole time-of-flight mass spectrometer (APCI-QTOF) and a vacuum electron ionization mass spectrometer (EI-MS) coupled to a gas chromatograph. Together, this combination of laboratory emission experiments, oxidation experiments, and field measurements demonstrate that asphalt is a major non-combustion source of reactive intermediate- and semi-volatile SOA precursors with significant implications for urban air quality.