Word version - SUNY College of Environmental Science and Forestry

The Chemical and Physical Characteristics of Fresh Aerosols Produced at
the Ocean Surface
*Long, M S [email protected] Keene, W [email protected] Maben, J [email protected] Department
of Environmental Sciences, University of Virginia, 280 Clark Hall, Charlottesville, VA 22908 US
Kieber, D [email protected] Davis, A J
[email protected] Dahl, E [email protected] State University
of New York College of Environmental Science and Forestry, 1 Forestry Drive, Syracuse, NY 13210 US
Maring, H [email protected] NASA Headquarters, Science Mission Directorate Mail Suite 3F71,
Washington, DC 20546 US
Pszenny, A [email protected] Institute for the Study of Earth, Oceans, and Space, University of
New Hampshire, 39 College Road, Durham, NH 03824 US and Mount Washington Observatory, PO Box
2310, North Conway, NH 03860 US
Izaguirre, M [email protected] University of Miami, Rosenstiel School of Marine and
Atmospheric Science, Miami, FL 33149 US
Zhou, X [email protected] Wadsworth Center, NYS Department of Health, and School of Public
Health, SUNY at Albany, Empire State Plaza P.O. Box 509, Albany, NY 12201-0509 US
Fresh aerosols produced by wind stress at the ocean surface undergo rapid multiphase
chemical and physical transformation. Consequently, it is impossible to unequivocally
differentiate primary versus secondary constituents based on measurements of aerosols
in ambient marine air. However, reliable characterization of the initial aerosol
composition is essential to interpret the nature of subsequent chemical processing,
associated biogeochemical cycles, and related environment influences. Fresh marine
aerosols were generated artificially by bubbling zero-air through a 1.3 m column of
flowing seawater within a 20-cm diameter Pyrex and Teflon chamber deployed at
Bermuda. Aerosols produced by bursting bubbles at the surface were swept with zero-air
hydrated to ~80% RH through isokinetic ports and subsequently sampled in bulk and
with MOUDI cascade impactors for analysis of major ions, total halogens, and organic
carbon (OC) and with Aerodynamic Particle Sizer (TSI Model 3310) and a Scanning
Mobility Particle Sizer (TSI Model 3934L) for characterization of number size
distributions (13 nm to > 15 micrometer diameters). The composition of feed seawater
was measured in parallel. The median OC concentration (65 micrometer) and ratios of
OC to sea-salt constituents in feed water were virtually identical to long-term averages
for surface seawater offshore. Relative size distributions of conservative sea-salt aerosol
constituents were similar to those over the open ocean. Ratios of major ions and of total
Cl and Br in all size fractions were statistically indistinguishable from those in surface
seawater. OC was highly enriched relative to seawater in all size fractions (median factor
for all samples = 387); highest enrichments were associated with sub-micron size aerosols.
Number size distributions were bimodal with peaks at 4 to 5 micrometer and 120 to 130
nm diameter. About 95 % of the inorganic sea-salt mass was associated with super-um
size fractions; OC dominated the sub-micron size fractions. The efficient mechanical
production of primary sub-micron marine aerosols has important implications for
multiphase chemical processes in the marine troposphere and associated radiative effects.