Microscopic Characterization of Carbonaceous Aerosol Particle Aging in the Outflow from Mexico City

Journal Article · Wed Sep 16 04:00:00 EDT 2009 · Atmospheric Chemistry and Physics

DOI:https://doi.org/10.5194/acpd-9-16993-2009· OSTI ID:973571

Moffet, R C; Henn, T R; Tivanski, A V; Hopkins, R J; Desyaterik, Y; Kilcoyne, A L. D.; Tyliszczak, T; Fast, J; Barnard, J; Shutthanandan, V; Cliff, S S; Perry, K D; Laskin, A; Gilles, M K

This study was part of the Megacities Initiative: Local and Global Research Observations (MILAGRO) field campaign conducted in Mexico City Metropolitan Area during spring 2006. The physical and chemical transformations of particles aged in the outflow from Mexico City were investigated for the transport event of 22 March 2006. A detailed chemical analysis of individual particles was performed using a combination of complementary microscopy and micro-spectroscopy techniques. The applied techniques included scanning transmission X-ray microscopy (STXM) coupled with near edge X-ray absorption fine structure spectroscopy (NEXAFS) and computer controlled scanning electron microscopy with an energy dispersive X-ray analyzer (CCSEM/EDX). As the aerosol plume evolves from the city center, the organic mass per particle increases and the fraction of carbon-carbon double bonds (associated with elemental carbon) decreases. Organic functional groups enhanced with particle age include: carboxylic acids, alkyl groups, and oxygen bonded alkyl groups. At the city center (T0) the most prevalent aerosol type contained inorganic species (composed of sulfur, nitrogen, oxygen, and potassium) coated with organic material. At the T1 and T2 sites, located northeast of T0 (~;;29 km and ~;;65 km, respectively), the fraction of homogenously mixed organic particles increased in both size and number. These observations illustrate the evolution of the physical mixing state and organic bonding in individual particles in a photochemically active environment.

• Research Organization: Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
• Sponsoring Organization: Advanced Light Source Division; Chemical Sciences Division; Directorate
• DOE Contract Number: AC02-05CH11231
• OSTI ID: 973571
• Report Number(s): LBNL-2576E
• Journal Information: Atmospheric Chemistry and Physics, Journal Name: Atmospheric Chemistry and Physics Vol. 10
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
ABSORPTION
AEROSOLS
AGING
BONDING
CARBON
CARBOXYLIC ACIDS
CHEMICAL ANALYSIS
COMPUTERS
DOUBLE BONDS
FINE STRUCTURE
FUNCTIONALS
MICROSCOPY
NITROGEN
OXYGEN
PLUMES
POTASSIUM
SCANNING ELECTRON MICROSCOPY
SPECTROSCOPY
SULFUR
TRANSFORMATIONS
TRANSPORT
URBAN AREAS
aerosols
STXM
scanning transmission X-ray microscopy
soot
MILAGRO
particles
NEXAFS