HR: 11:50h
AN: A52A-07    [Abstracts]
TI: The Fate of Carbon From Isoprene Over West Africa
AU: * Murphy, J G
EM: jmurphy@chem.utoronto.ca
AF: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
AU: * Murphy, J G
EM: jmurphy@chem.utoronto.ca
AF: Department of Chemistry, University of Toronto, Toronto, ON M5S 3H6, Canada
AU: Mills, G P
EM: g.mills@uea.ac.uk
AF: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
AU: Bandy, B J
EM: b.bandy@uea.ac.uk
AF: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
AU: Oram, D E
EM: d.e.oram@uea.ac.uk
AF: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
AU: Reeves, C E
EM: c.reeves@uea.ac.uk
AF: School of Environmental Sciences, University of East Anglia, Norwich, NR4 7TJ, United Kingdom
AU: Capes, G
EM: gerard.capes@postgrad.machester.ac.uk
AF: School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M60 1QD, United Kingdom
AU: Coe, H
EM: hugh.coe@manchester.ac.uk
AF: School of Earth, Atmospheric and Environmental Sciences, University of Manchester, Manchester, M60 1QD, United Kingdom
AB: During the summer of 2006, a comprehensive suite of trace gases and aerosol properties were measured aboard the BAe-146 U.K. research aircraft during the African Monsoon Multidisciplinary Analysis campaign. Good spatial agreement was found between isoprene concentrations measured using a Proton Transfer Reaction Mass Spectrometer and those predicted based on the underlying vegetation. Within minutes to hours following emission, the isoprene is oxidized to form several possible products, many of which were observed from the aircraft, including methyl vinyl ketone, methacrolein, formaldehyde, organic peroxides and carbon monoxide. We use the ratios of isoprene and its oxidation products and a simple box model to calculate a regional average for the flux of carbon derived from isoprene into the atmosphere. Despite these large emissions of isoprene in the region, the average loading of organic aerosol observed by the Aerodyne Aerosol Mass Spectrometer (AMS) was very low (< 1 μg/m³). These observations are in conflict with chamber measurements, which predict a significant yield of secondary organic aerosol (SOA) from isoprene, and observations over the United States and Europe, which show large amounts of biogenically-derived SOA. We explore two other possibilities that isoprene-derived SOA was formed, but 1) partitioned to larger mode aerosol (PM_1.0) not measurable using the AMS, or 2) that the lifetime of SOA in the lower troposphere over West Africa is extremely short (less than a few hours).
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0320 Cloud physics and chemistry
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting