Overview of the Focused Isoprene eXperiment at the California Institute of Technology (FIXCIT): mechanistic chamber studies on the oxidation of biogenic compounds

The Focused Isoprene eXperiment at the California Institute of Technology(FIXCIT) was a collaborative atmospheric chamber campaign that occurredduring January 2014. FIXCIT is the laboratory component of a synergisticfield and laboratory effort aimed toward (1) better understanding thechemical details behind ambient observations relevant to the southeasternUnited States, (2) advancing the knowledge of atmospheric oxidationmechanisms of important biogenic hydrocarbons, and (3) characterizing thebehavior of field instrumentation using authentic standards. Approximately 20principal scientists from 14 academic and government institutions performedparallel measurements at a forested site in Alabama and at the atmosphericchambers at Caltech. During the 4 week campaign period, a series of chamberexperiments was conducted to investigate the dark- and photo-inducedoxidation of isoprene, α-pinene, methacrolein, pinonaldehyde,acylperoxy nitrates, isoprene hydroxy nitrates (ISOPN), isoprene hydroxyhydroperoxides (ISOPOOH), and isoprene epoxydiols (IEPOX) in a highlycontrolled and atmospherically relevant manner. Pinonaldehyde andisomer-specific standards of ISOPN, ISOPOOH, and IEPOX were synthesized andcontributed by campaign participants, which enabled explicit exploration intothe oxidation mechanisms and instrument responses for these importantatmospheric compounds. The present overview describes the goals, experimentaldesign, instrumental techniques, and preliminary observations from thecampaign. This work provides context for forthcoming publications affiliatedwith the FIXCIT campaign. Insights from FIXCIT are anticipated to aidsignificantly in interpretation of field data and the revision of mechanismscurrently implemented in regional and global atmospheric models