Polissar AV, Hopke PK, Poirot RL.
Department of Chemical Engineering, Clarkson University, Potsdam,
New York
13699-5810, USA.
Aerosol chemical composition data for PM2.5 samples collected
during the period
from 1988 to 1995 at Underhill, VT, were analyzed. Sulfur and
black carbon mass
concentrations ranged from 0.01 to 6.5 microg m(-3) and from 0.05
to 2.2 microg
m(-3), respectively, while the total fine aerosol mass concentration
ranged from
0.2 to 51.1 microg m(-3). Seasonal variations with maxima during
the summer and
minima in winter/spring were observed for sulfur and the fine
mass
concentrations. No annual pattern was observed for black carbon.
Seasonal
variations for most of the other anthropogenic species had maxima
in winter and
spring and minima in the summer. A factor analysis method, positive
matrix
factorization (PMF), utilizing error estimates of the data to
provide optimum
data point scaling was used to obtain information about possible
sources of the
aerosol. An 11-factor solution was obtained. The six sources
representing wood
burning, coal and oil combustion, coal combustion emissions plus
photochemical
sulfate production, metal production plus municipal waste incineration,
and
emissions from motor vehicles were identified. Emissions from
smelting of
nonferrous metal ores, arsenic smelting, and soil particles and
particles with
high concentrations of Na were also identified by PMF. Potential
source
contribution function (PSCF) analysis combines the aerosol data
with the air
parcel backward trajectories. PSCF was applied to identify possible
source areas
and pathways that give rise to the observed high particulate mass
concentrations
from these 11 sources. The CAPITA Monte Carlo trajectory model
was used to
obtain 10 sets of 5-day air parcel back trajectories arriving
every 2 h for the
7-yr period from 1988 to 1995. The PSCF plot for the black
carbon factor shows
high probabilities in the area surrounding the sampling site,
indicating a
strong local influence from residential wood combustion in northern
New England and southwestern Quebec. Similar large potential
source areas in the midwestern
United States were identified for the two coal combustion factors.
The
midwestern United States was also identified as the source region
for the Zn-Pb
factor. The oil combustion factor was associated with the east
coast of the
United States. The results for the Pb-Mn factor suggests high
probability over
the nearby Montreal urban area and the areas in the midwestern
United States.
The windblown dust emissions from the areas to the north are significant
contributors for the soil factor. Canadian Ni smelters are the
main sources for
the As factor, although there is some contribution from coal-fired
power plants
to the south and west of Underhill, VT. It is concluded that the
combination of
the two receptor modeling methods, PMF and PSCF, provides an effective
way in
identifying atmospheric aerosol sources and their likely locations.
Emissions
from different anthropogenic activities as well as secondary aerosol
production
are the main sources of aerosol measured in Vermont. Fuel combustion,
local wood
smoke, municipal waste incineration, and the secondary sulfate
production
collectively accounted for about 87% of the fine mass concentrations
measured in
Vermont.
PMID: 11770762 [PubMed - in process]
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