Abstract
JOURNAL OF GEOPHYSICAL RESEARCH,
VOL. 109,
D15S09,
20 PP., 2004
doi:10.1029/2003JD004378
Size distributions and mixtures of dust and black carbon aerosol in Asian outflow: Physiochemistry and optical properties
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
Environmental Fluid Dynamics Program, Arizona State University, Tempe, Arizona, USA
Environmental Fluid Dynamics Program, Arizona State University, Tempe, Arizona, USA
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA
Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, USA
School of the Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
During Transport and Chemical Evolution over the Pacific (TRACE-P) and Asian Aerosol Characterization Experiment (ACE-Asia)
we measured the dry size distribution of Asian aerosols, their state of mixing, and the optical properties of dust, black
carbon (BC) and other aerosol constituents in combustion and/or dust plumes. Optical particle sizing in association with thermal
heating extracted volatile components and resolved sizes for dust and refractory soot that usually dominated light absorption.
BC was internally mixed with volatile aerosol in ∼85% of accumulation mode particles and constituted ∼5–15% of their mass.
These optically effective sizes constrained the soot and dust size distributions and the imaginary part of the dust refractive
index, k, to 0.0006 ± 0.0001. This implies a single-scatter albedo,
(550 nm), for dust ranging from 0.99+ for D
p
<1 μm to ∼0.90 at D
p
= 10 μm and a size-integrated campaign average near 0.97 ± 0.01. The typical mass scattering efficiency for the dust was
∼0.3 m2 g−1, and the mass absorption efficiency (MAE) was 0.009 m2 g−1. Less dust south of 25°N and stronger biomass burning signatures resulted in lower values for
of ∼0.82 in plumes aloft. Chemically inferred elemental carbon was moderately correlated with BC light absorption (R
2 = 0.40), while refractory soot volume between 0.1 and 0.5 μm was highly correlated (R
2 = 0.79) with absorption. However, both approaches yield an MAE for BC mixtures of ∼7 ± 2 m2 g−1 and higher than calculated MAE values for BC of 5 m2 g−1. The increase in the mass fraction of soot and BC in pollution aerosol in the presence of elevated dust appears to be due
to uptake of the volatile components onto the coarse dust. This predictably lowered
for the accumulation mode from 0.84 in typical pollution to ∼0.74 in high-dust events. A chemical transport model revealed
good agreement between model and observed BC absorption for most of SE Asia and in biomass plumes but underestimated BC for
combustion sources north of 25°N by a factor of ∼3.
Received 24 November 2003; accepted 18 March 2004; published 8 June 2004.
Citation: (2004), Size distributions and mixtures of dust and black carbon aerosol in Asian outflow: Physiochemistry and optical properties, J. Geophys. Res., 109, D15S09, doi:10.1029/2003JD004378.
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