Analysis of Summertime PM2.5 and haze in the Mid-Atlantic Region
Analysis of Summertime PM2.5 and haze in the Mid-Atlantic Region
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Date
2003
Authors
Chen, L.-W. Antony
Chow, Judith C.
Doddridge, Bruce G.
Dickerson, Russell R.
Ryan, William F.
Mueller, Peter K.
Advisor
Citation
Analysis of Summertime PM2.5 and haze in the Mid-Atlantic Region, L-W.A. Chen, B.G. Doddridge, J.C. Chow, R.R. Dickerson, W.F. Ryan, and P.K. Mueller; JAWMA, 53(8), 946-956, 2003.
DRUM DOI
Abstract
Observations of the mass and chemical composition of
particles less than 2.5 µm in aerodynamic diameter
(PM2.5), light extinction, and meteorology in the urban
Baltimore-Washington corridor during July 1999 and July
2000 are presented and analyzed to study summertime
haze formation in the mid-Atlantic region. The mass fraction
of ammoniated sulfate (SO4^2-) and carbonaceous
material in PM2.5 were each ~50% for cleaner air (PM2.5 <
10 µg/m3) but changed to ~60% and ~20%, respectively,
for more polluted air (PM2.5 > 30 µg/m3). This signifies
the role of SO4^2- in haze formation. Comparisons of data
from this study with the Interagency Monitoring of Protected
Visual Environments network suggest that SO4^2- is
more regional than carbonaceous material and originates
in part from upwind source regions. The light extinction
coefficient is well correlated to PM2.5 mass plus water
associated with inorganic salt, leading to a mass extinction
efficiency of 7.6 ± 1.7 m2/g for hydrated aerosol. The
most serious haze episode occurring between July 15 and 19, 1999, was characterized by westerly transport and
recirculation slowing removal of pollutants. At the peak
of this episode, 1-hr PM2.5 concentration reached ~45
µg/m3, visual range dropped to ~5 km, and aerosol water
likely contributed to ~40% of the light extinction coefficient.