Aerosol formation pathways from aviation emissions
Author(s)
Prashanth, Prakash; Eastham, Sebastian D; Speth, Raymond L; Barrett, Steven RH
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Aviation emissions are responsible for an estimated 24,000 premature mortalities annually and 3.5%
of anthropogenic radiative forcing (RF). Emissions of nitrogen and sulfur oxides(NOx and SOx)
contribute to these impacts. However, the relative contributions and mechanisms linking these
emissions to formation and impacts of secondary aerosols(as opposed to direct aerosol emissions)
have not been quantified, including how short-lived aerosol precursors at altitude can increase
surface-level aerosol concentrations. We apply global chemistry transport modeling to identify and
quantify the different chemical pathways to aerosol formation from aviation emissions, including the
resulting impact on radiative forcing. We estimate a net aerosol radiative forcing of –8.3 mWm−2
, of
which –0.67 and –7.8 mWm−2 result from nitrate and sulfate aerosols respectively. We find that
aviation NOx causes –1.7 mWm−2 through nitrate aerosol forcing but also –1.6 mWm−2 of sulfate
aerosol forcing by promoting oxidation of SO2 to sulfate aerosol. This accounts for 21% of the total
sulfate forcing, and oxidation of SO2 due to aviation NOx is responsible for 47% of the net aviation
NOx attributable RF. Aviation NOx emissions in turn account for 41% of net aviation-aerosolattributable RF (non-contrail). This is due to ozone-mediated oxidation of background sulfur and the
‘nitrate bounce-back’ effect, which reduces the net impact of sulfur emissions. The ozone-mediated
mechanism also explains the ability of cruise aviation emissions to significantly affect surface aerosol
concentrations. We find that aviation NOx emissions cause 72% of aviation-attributable, near-surface
aerosol loading by mass, compared to 27% from aviation SOx emissions and less than 0.1% from
direct emission of black carbon. We conclude that aviation NOx and SOx emissions are the dominant
cause of aviation-attributable secondary inorganic aerosol radiative forcing, and that conversion of
background aerosol precursors at all altitudes is amplified by enhanced production of aviation
attributable oxidants at cruise altitudes.
Date issued
2022Department
Massachusetts Institute of Technology. Department of Aeronautics and Astronautics; Massachusetts Institute of Technology. Laboratory for Aviation and the Environment; Massachusetts Institute of Technology. Joint Program on the Science & Policy of Global ChangeJournal
Environmental Research Communications
Publisher
IOP Publishing
Citation
Prashanth, Prakash, Eastham, Sebastian D, Speth, Raymond L and Barrett, Steven RH. 2022. "Aerosol formation pathways from aviation emissions." Environmental Research Communications, 4 (2).
Version: Final published version