title: Physical state and acidity of inorganic sulfate can regulate the production of secondary organic material from isoprene photooxidation products.
abstract: The production of secondary organic material (SOM) by the reactive uptake of isoprene photooxidation products was investigated using partially to wholly neutralized sulfuric acid particles. The experiments were performed at a relative humidity (RH) of <5% and a temperature of 20 °C. The extent X of neutralization was adjusted from that of sulfuric acid (X = 0) to that of ammonium sulfate (X = 1). Significant SOM production was observed only for X < 0.7. The threshold of 0.7 corresponded to the transition point of the sulfate particles from aqueous to solid for <5% RH. The phase transition of inorganic sulfate therefore regulated the particle-phase reactions that produce isoprene SOM, at least for the investigated conditions. For aqueous particles, a decreasing extent of neutralization was associated with increasing production of SOM, including increased production of oligomers and organosulfates. These results can underpin treatments of phase-dependent SOM production within chemical transport models, thereby improving the accuracy of simulations of biogenic-anthropogenic interactions in the atmosphere and the associated impacts of aerosol particles on climate and air quality.
authors.affiliation: School of Engineering and Applied Sciences & Department of Earth and Planetary Sciences, Harvard University, Cambridge, Massachusetts 02138, USA. scot_martin@harvard.edu.
authors.forename: Mikinori
authors.initials: M
authors.lastname: Kuwata
authors.forename: Yingjun
authors.initials: Y
authors.lastname: Liu
authors.forename: Karena
authors.initials: K
authors.lastname: McKinney
authors.forename: Scot T
authors.initials: ST
authors.lastname: Martin
mesh_terms: D000645:Ammonium Sulfate / Q000737:chemistry; D002070:Butadienes / Q000737:chemistry*; D045782:Hemiterpenes / Q000737:chemistry*; D007536:Isomerism; D008027:Light; D010084:Oxidation-Reduction; D010420:Pentanes / Q000737:chemistry*; D044367:Phase Transition; D013431:Sulfates / Q000737:chemistry*; D013464:Sulfuric Acids / Q000737:chemistry
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D010420:Pentanes; D013431:Sulfates; D013464:Sulfuric Acids; C005059:isoprene; C033158:sulfuric acid; D000645:Ammonium Sulfate