(263a) Gas-Particle Partitioning of Alkyl Nitrates from Anthropogenic Alkanes
AIChE Annual Meeting
2017
2017 Annual Meeting
Environmental Division
Atmospheric Chemistry and Physics I
Tuesday, October 31, 2017 - 8:00am to 8:17am
Oxidation of volatile organic compounds
(VOC) produces secondary organic aerosol (SOA), increasing the overall fine
particle mass and aggravating the associated negative health effects. Studies
have shown that long-chain anthropogenic VOCs, despite their low ambient
abundance relative to biogenic VOCs, can contribute significantly to the
overall SOA mass. Typical anthropogenic emission sources, such as oil and gas
extraction sites, tend to be environments rich in nitrogen oxides (NOx)
and therefore favorable for the formation of alkyl nitrates (AN), which can
partition to the particle phase and therefore contribute to SOA. The gas-particle
partitioning of AN is known to aid NOx cycling and transport, contributing
to the regional nature of NOx pollution. The gas-particle
partitioning behavior of SOA derived from anthropogenic VOCs remains poorly
characterized.
Here we report results from
environmental chamber experiments conducted to investigate SOA formation from
select linear, branched, and cyclic C8, C10, and C12
anthropogenic alkanes under high NOx conditions. SOA formation was significantly
higher for cyclic alkanes, consistent with previous findings. Aerosol
volatility was determined using a thermodenuder and an aerosol evaporation
kinetics model. The partitioning behavior of ANs was determined based on particle-phase
measurements and total AN concentration estimated using an updated SAPRC box
model with carbon-bond-based reaction mechanisms. The molecular composition of
gas- and particle-phase products was determined using a Filter Inlet for Gases and
AEROsols (FIGAERO)
coupled to a High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer,
where evidence of oligomer formation was observed. Results from this study can
help improve air quality models with respect to SOA loading, NOx
cycling, and NOx transport.
(VOC) produces secondary organic aerosol (SOA), increasing the overall fine
particle mass and aggravating the associated negative health effects. Studies
have shown that long-chain anthropogenic VOCs, despite their low ambient
abundance relative to biogenic VOCs, can contribute significantly to the
overall SOA mass. Typical anthropogenic emission sources, such as oil and gas
extraction sites, tend to be environments rich in nitrogen oxides (NOx)
and therefore favorable for the formation of alkyl nitrates (AN), which can
partition to the particle phase and therefore contribute to SOA. The gas-particle
partitioning of AN is known to aid NOx cycling and transport, contributing
to the regional nature of NOx pollution. The gas-particle
partitioning behavior of SOA derived from anthropogenic VOCs remains poorly
characterized.
Here we report results from
environmental chamber experiments conducted to investigate SOA formation from
select linear, branched, and cyclic C8, C10, and C12
anthropogenic alkanes under high NOx conditions. SOA formation was significantly
higher for cyclic alkanes, consistent with previous findings. Aerosol
volatility was determined using a thermodenuder and an aerosol evaporation
kinetics model. The partitioning behavior of ANs was determined based on particle-phase
measurements and total AN concentration estimated using an updated SAPRC box
model with carbon-bond-based reaction mechanisms. The molecular composition of
gas- and particle-phase products was determined using a Filter Inlet for Gases and
AEROsols (FIGAERO)
coupled to a High-Resolution Time-of-Flight Chemical Ionization Mass Spectrometer,
where evidence of oligomer formation was observed. Results from this study can
help improve air quality models with respect to SOA loading, NOx
cycling, and NOx transport.