PM2.5 Sourcing: A Multi-System Geochemical Approach for

PM2.5 Sourcing: A Multi-System Geochemical Approach for Improving AerosolTracking Algorithms
Jeffrey Steiner,1 Elizabeth Rudolph,1 A. Katz2, and Alexandra Alimova2
Department of Earth and Atmospheric Sciences & NOAA-CREST at CCNY
Department of Physics & IUSL at CCNY
The City College of New York
138th and Convent Ave., NYC, NY 10031
The creation of precise aerosol sourcing models depends to a significant degree on the
development of improved methods for aerosol speciation. We present an overview of
ongoing speciation studies focusing on organo-sulfate, organic, and dust aerosols
collected in New York City using an E-BAM beta-attenuation impactor system. Issues of
speciation, surface properties, and optical characteristics are investigated by a multisystem approach emphasizing scanning electron microscope (SEM) and energy
dispersive micro-analysis (EDS). Preliminary characterizations of the easily volatilized
aerosol fraction by environmental scanning electron microscopy (ESEM) show more than
a fifty percent substitution of light element and ammonium populations with heavy
metals, including iron. Complementary analyses by high resolution scanning electron
microscopy (HRSEM) show that PM2.5 sulfur-based aerosols are commonly associated
with composite nanofilms adhearing to glass fibers. The complex nature of these
associations are discussed in terms of possible models for aggregation during aerosol
transport and regrowth during impaction.
In complementary experiments, the optical properties of aerosols are being investigated
using optical petrography, fluorescence and light scattering experiments. The optical
parameters of aerosols are presently based on simple clay- or bacteria-water systems as
recorded using a Nikon optical fluorescence system with a high resolution Optronics
CCD. These results are used to validate optical spectroscopy experiments. Preliminary
light extinction and angular scattering measurements on colloidal suspensions yield
particle size and shape parameters in good agreement with optical and SEM
measurements. These results encourage the argument that optical spectroscopy can be
used to characterize bacteria-clay aerosol associations as these research methods are
refined for gas phase dispersions.