title: Chemical Reactivity and Liquid/Nonliquid States of Secondary Organic Material.
abstract: The reactivity of secondary organic material (SOM) of variable viscosity, ranging from nonliquid to liquid physical states, was studied. The SOM, produced in aerosol form from terpenoid and aromatic precursor species, was reacted with ammonia at variable relative humidity (RH). The ammonium-to-organic mass ratio (MNH4+/MOrg) increased monotonically from <5% RH to a limiting value at a threshold RH, implicating a transition from particle reactivity limited by diffusion at low RH to one limited by other factors at higher RH. For the studied size distributions and reaction times, the transition corresponded to a diffusivity above 10-17.5 ± 0.5 m2 s-1. The threshold RH values for the transition were <5% RH for isoprene-derived SOM, 35-45% RH for SOM derived from α-pinene, toluene, m-xylene, and 1,3,5-trimethylbenzene, and >90% for β-caryophyllene-derived SOM. The transition RH for reactivity differed in all cases from the transition RH of a nonliquid to a liquid state. For instance, for α-pinene-derived SOM the transition for chemical reactivity of 35-45% RH can be compared to the nonliquid to liquid transition of 65-90% RH. These differences imply that chemical transport models of atmospheric chemistry should not use the SOM liquid to nonliquid phase transition as one-to-one surrogates of SOM reactivity.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.|Department of Civil and Environmental Engineering, Faculty of Science and Technology, University of Macau , Avenida da Universidade, Taipa, Macau, China.
authors.forename: Yong Jie
authors.initials: YJ
authors.lastname: Li
authors.affiliation: School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Pengfei
authors.initials: P
authors.lastname: Liu
authors.affiliation: School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Zhaoheng
authors.initials: Z
authors.lastname: Gong
authors.affiliation: Department of Environmental Health, Harvard T.H. Chan School of Public Health , Boston, Massachusetts 02115, United States.
authors.forename: Yan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Bateman
authors.affiliation: School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.|Department of Energy and Environment, National Institute of Applied Science of Lyon , Villeurbanne 69100, France.
authors.forename: Clara
authors.initials: C
authors.lastname: Bergoend
authors.affiliation: Department of Chemistry, University of British Columbia , Vancouver, British Columbia V6T 1Z1, Canada.
authors.forename: Allan K
authors.initials: AK
authors.lastname: Bertram
authors.affiliation: School of Engineering and Applied Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.|Department of Earth and Planetary Sciences, Harvard University , Cambridge, Massachusetts 02138, United States.
authors.forename: Scot T
authors.initials: ST
authors.lastname: Martin
mesh_terms: D000336:Aerosols / Q000737:chemistry*; D000641:Ammonia / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D000081008:Bicyclic Monoterpenes; D002070:Butadienes / Q000737:chemistry; D004058:Diffusion; D045782:Hemiterpenes / Q000737:chemistry; D006813:Humidity; D039821:Monoterpenes / Q000737:chemistry; D010420:Pentanes / Q000737:chemistry; D044367:Phase Transition; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes / Q000737:chemistry; D013729:Terpenes / Q000737:chemistry*; D014050:Toluene; D014783:Viscosity; D014992:Xylenes / Q000737:chemistry
chemical_list: C482494:1,3,5-trimethylenebenzene; D000336:Aerosols; D001555:Benzene Derivatives; D000081008:Bicyclic Monoterpenes; D002070:Butadienes; D045782:Hemiterpenes; D039821:Monoterpenes; D010420:Pentanes; D000081223:Polycyclic Sesquiterpenes; D012717:Sesquiterpenes; D013729:Terpenes; D014992:Xylenes; C005059:isoprene; D014050:Toluene; D000641:Ammonia; C024714:caryophyllene; C005451:alpha-pinene; C031285:3-xylene