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

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 themore » evolution of the physical mixing state and organic bonding in individual particles in a photochemically active environment.« less
Authors:
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Publication Date:
OSTI Identifier:
973571
Report Number(s):
LBNL-2576E
TRN: US201006%%776
DOE Contract Number:
DE-AC02-05CH11231
Resource Type:
Journal Article
Resource Relation:
Journal Name: Atmospheric Chemistry and Physics; Journal Volume: 10; Related Information: Journal Publication Date: February 1, 2010
Research Org:
Ernest Orlando Lawrence Berkeley National Laboratory, Berkeley, CA (US)
Sponsoring Org:
Advanced Light Source Division; Chemical Sciences Division; Directorate
Country of Publication:
United States
Language:
English
Subject:
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