title: Epoxide pathways improve model predictions of isoprene markers and reveal key role of acidity in aerosol formation.
abstract: Isoprene significantly contributes to organic aerosol in the southeastern United States where biogenic hydrocarbons mix with anthropogenic emissions. In this work, the Community Multiscale Air Quality model is updated to predict isoprene aerosol from epoxides produced under both high- and low-NOx conditions. The new aqueous aerosol pathways allow for explicit predictions of two key isoprene-derived species, 2-methyltetrols and 2-methylglyceric acid, that are more consistent with observations than estimates based on semivolatile partitioning. The new mechanism represents a significant source of organic carbon in the lower 2 km of the atmosphere and captures the abundance of 2-methyltetrols relative to organosulfates during the simulation period. For the parametrization considered here, a 25% reduction in SOx emissions effectively reduces isoprene aerosol, while a similar reduction in NOx leads to small increases in isoprene aerosol.
authors.affiliation: National Exposure Research Laboratory, US Environmental Protection Agency , Research Triangle Park, North Carolina, 27711 United States.
authors.forename: Havala O T
authors.initials: HO
authors.lastname: Pye
authors.forename: Robert W
authors.initials: RW
authors.lastname: Pinder
authors.forename: Ivan R
authors.initials: IR
authors.lastname: Piletic
authors.forename: Ying
authors.initials: Y
authors.lastname: Xie
authors.forename: Shannon L
authors.initials: SL
authors.lastname: Capps
authors.forename: Ying-Hsuan
authors.initials: YH
authors.lastname: Lin
authors.forename: Jason D
authors.initials: JD
authors.lastname: Surratt
authors.forename: Zhenfa
authors.initials: Z
authors.lastname: Zhang
authors.forename: Avram
authors.initials: A
authors.lastname: Gold
authors.forename: Deborah J
authors.initials: DJ
authors.lastname: Luecken
authors.forename: William T
authors.initials: WT
authors.lastname: Hutzell
authors.forename: Mohammed
authors.initials: M
authors.lastname: Jaoui
authors.forename: John H
authors.initials: JH
authors.lastname: Offenberg
authors.forename: Tadeusz E
authors.initials: TE
authors.lastname: Kleindienst
authors.forename: Michael
authors.initials: M
authors.lastname: Lewandowski
authors.forename: Edward O
authors.initials: EO
authors.lastname: Edney
mesh_terms: D000336:Aerosols; D000393:Air Pollutants / Q000737:chemistry*; D002070:Butadienes / Q000737:chemistry*; D004852:Epoxy Compounds / Q000737:chemistry*; D005988:Glyceric Acids / Q000737:chemistry; D045782:Hemiterpenes / Q000737:chemistry*; D008962:Models, Theoretical; D009566:Nitrates / Q000737:chemistry; D010420:Pentanes / Q000737:chemistry*; D013457:Sulfur Compounds / Q000737:chemistry
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D002070:Butadienes; D004852:Epoxy Compounds; D005988:Glyceric Acids; D045782:Hemiterpenes; D009566:Nitrates; D010420:Pentanes; D013457:Sulfur Compounds; C005059:isoprene