Gas- and particle-phase chemical composition measurements onboard the G-1 research aircraft during the CARES campaign

 

Authors

John T Jayne — Aerodyne Research, Inc.
Lizabeth M Alexander — Pacific Northwest National Laboratory
John E Shilling — Pacific Northwest National Laboratory
Ed Fortner — Aerodyne Research, Inc.

Category

Field Campaigns

Description

Chemical evolution of the aerosol plume observed from the G-1 research aircraft on June 28 during the CARES campaign in Sacramento, California. The loss of the gas-phase biogenic precursors isoprene, MVK, and MACR correlates with morning production of particle-phase organic material (OM). The elemental O:C and H:C ratios of the OM are constant through the day, consistent with laboratory observations of SOA formation from isoprene. However, mass of OM that was observed to form from the measured precursors is higher than expected.
An Aerodyne High Resolution Aerosol Mass Spectrometer (AMS) and an Ionicon Proton Transfer Reaction Mass Spectrometer (PTRMS) were deployed on the G-1 research aircraft during the CARES campaign in Sacramento, California, to investigate aerosol gas- and particle-phase chemical composition. Preliminary analysis of PTRMS data suggests that biogenic volatile organic compounds (VOCs), particularly isoprene, dominate the region with anthropogenic VOCs, such as benzene and toluene, providing much smaller contributions to the VOC pool. Data from the AMS shows that the particle phase is dominated by organic material (81% on average) with smaller concentrations of sulfate (10%), nitrate (6%) and ammonium (4%) observed. Organic particle mass concentrations are strongly influenced by SOA generated when isoprene-rich air from the foothills mixed with the Sacramento urban plume. A case study examining the formation and chemical evolution of the organic aerosol on June 28 will also be presented.