title: Isoprene epoxydiols as precursors to secondary organic aerosol formation: acid-catalyzed reactive uptake studies with authentic compounds.
abstract: Isoprene epoxydiols (IEPOX), formed from the photooxidation of isoprene under low-NO(x) conditions, have recently been proposed as precursors of secondary organic aerosol (SOA) on the basis of mass spectrometric evidence. In the present study, IEPOX isomers were synthesized in high purity (>99%) to investigate their potential to form SOA via reactive uptake in a series of controlled dark chamber studies followed by reaction product analyses. IEPOX-derived SOA was substantially observed only in the presence of acidic aerosols, with conservative lower-bound yields of 4.7-6.4% for β-IEPOX and 3.4-5.5% for δ-IEPOX, providing direct evidence for IEPOX isomers as precursors to isoprene SOA. These chamber studies demonstrate that IEPOX uptake explains the formation of known isoprene SOA tracers found in ambient aerosols, including 2-methyltetrols, C(5)-alkene triols, dimers, and IEPOX-derived organosulfates. Additionally, we show reactive uptake on the acidified sulfate aerosols supports a previously unreported acid-catalyzed intramolecular rearrangement of IEPOX to cis- and trans-3-methyltetrahydrofuran-3,4-diols (3-MeTHF-3,4-diols) in the particle phase. Analysis of these novel tracer compounds by aerosol mass spectrometry (AMS) suggests that they contribute to a unique factor resolved from positive matrix factorization (PMF) of AMS organic aerosol spectra collected from low-NO(x), isoprene-dominated regions influenced by the presence of acidic aerosols.
authors: Department of Environmental Sciences and Engineering, Gillings School of Global Public Health,  The University of North Carolina at Chapel Hill , North Carolina, United States of America.
authors: Ying-Hsuan
authors: YH
authors: Lin
authors: Zhenfa
authors: Z
authors: Zhang
authors: Kenneth S
authors: KS
authors: Docherty
authors: Haofei
authors: H
authors: Zhang
authors: Sri Hapsari
authors: SH
authors: Budisulistiorini
authors: Caitlin L
authors: CL
authors: Rubitschun
authors: Stephanie L
authors: SL
authors: Shaw
authors: Eladio M
authors: EM
authors: Knipping
authors: Eric S
authors: ES
authors: Edgerton
authors: Tadeusz E
authors: TE
authors: Kleindienst
authors: Avram
authors: A
authors: Gold
authors: Jason D
authors: JD
authors: Surratt
mesh_terms: D000143:Acids / Q000737:chemistry*; D000336:Aerosols / Q000138:chemical synthesis* / Q000737:chemistry; D001272:Atmosphere / Q000737:chemistry; D002070:Butadienes / Q000737:chemistry*; D002384:Catalysis; D004852:Epoxy Compounds / Q000737:chemistry*; D008401:Gas Chromatography-Mass Spectrometry; D045782:Hemiterpenes / Q000737:chemistry*; D009930:Organic Chemicals / Q000737:chemistry; D010316:Particle Size; D052638:Particulate Matter / Q000737:chemistry; D010420:Pentanes / Q000737:chemistry*; D012015:Reference Standards
chemical_list: D000143:Acids; D000336:Aerosols; D002070:Butadienes; D004852:Epoxy Compounds; D045782:Hemiterpenes; D009930:Organic Chemicals; D052638:Particulate Matter; D010420:Pentanes; C005059:isoprene