2011 - Cooperative Institute for Research in Environmental Sciences ...

Joost de Gouw
Sources and Chemistry of Organic Carbon
in the Atmosphere
FUNDING: NOAA
Atmospheric aerosols
play an important role in
air quality and climate:
They scatter and potentially
absorb radiation,
and are damaging to
human health when present
in the air we breathe.
A significant portion
of aerosol consists of
organic material, but the
sources of this material
are poorly understood.
In polluted conditions,
the dominant fraction of
organics is not directly
emitted from combustion
sources, but is formed
from the oxidation of
gas-phase organic compounds from both anthropogenic
and biogenic sources. Determining the relative importance
Scientists used NOAA’s WP-3D aircraft to measure the effect of the Deepwater Horizon Oil Spill on air quality.
32 CIRES Annual Report 2011
of anthropogenic and biogenic sources is an important
component of our current research.
In 2010, we performed the CalNex (Research at the
Nexus of Air Quality and Climate Change) study in
California. One of the goals was to study how emissions
in the Los Angeles basin, where anthropogenic emissions
are large, react to form organic aerosol. Toward that goal,
we made measurements by mass spectrometry and gas
chromatography of gas-phase organic compounds 1) from
a research ship to characterize inflow conditions into the
basin, 2) from a surface site in Pasadena to characterize
emissions and the initial stages of photochemical formation
and 3) from the NOAA WP-3D research aircraft to
follow the urban air masses downwind. Analysis of this
large and detailed data set, in conjunction with numerous
measurements of organic aerosol, is currently ongoing.
The Deepwater Horizon Oil Spill in the Gulf of Mexico
occurred during CalNex, and the NOAA WP-3D aircraft
made two flights over the spill to determine the atmospheric
impact. It was found that a significant fraction
of the oil evaporated and organic aerosol was formed
efficiently from these vapors. Interestingly, the aerosol
appeared to be primarily formed from less volatile
compounds, as opposed to the more volatile compounds
with fewer than 12 carbon atoms, which have traditionally
been considered as precursors. Measurements in this
extreme environment have, thus, given important insight
into organic aerosol formation in other environments,
such as urban atmospheres where these same less-volatile
compounds are emitted.
DAN LACK/CIRES