Environmental Engineering Reference
In-Depth Information
2.27 Closing the Peroxy Acetyl (PA) Radical Budget:
Observations of Acyl Peroxy Nitrates (PAN, PPN,
and MPAN) During BEARPEX 2007
1
2
3
3
B.W. LaFranchi , G.M. Wolfe , J.A. Thornton , S.A. Harrold ,
E.C. Browne , K.E. Min , P.J. Wooldridge , J.B. Gilman , W.C. Kuster ,
P.D. Goldan , J.A. de Gouw , M. McKay
1
4
1
5
5
5
5
6
*
6
7
**
,
, A.H. Goldstein , X. Ren
J. Mao
7
***
1,4
, and R.C. Cohen
1
Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA
2
Department of Chemistry, University of Washington, Seattle, WA, USA
3
Department of Atmospheric Sciences, University of Washington, Seattle, WA, USA
4
Department of Earth and Planetary Science, University of California, Berkeley, CA, USA
5
NOAA/ESRL Chemical Sciences Division, Boulder, CO, USA
6
Department of Environmental Science, Policy, and Management, University of California,
Berkeley, Berkeley, CA, USA
7
Department of Meteorology, Penn State University, University Park, PA, USA
Acyl peroxy nitrates (APNs, also known as PANs) are an important class of
reactive nitrogen species having the general structure: RC(O)OONO
2
. In urban source
regions, APN production acts as a net sink for NO
x
(NO
x
= NO + NO
2
). Under
high NO
x
(VOC-limited) conditions this temporary sink results in increased ozone
production rates by slowing the rate of OH reaction with NO
2
, and thus extending
the HO
x
(HO
x
= OH + HO
2
) chain length. Downwind of the source region, where
total NO
x
levels have decreased, APN decomposition injects NO
x
into the atmo-
sphere under low NO
x
conditions resulting in increased ozone prouction rates.
Acyl peroxy nitrates are formed from the oxidation of aldehydes and other
oxygenated VOC (oVOC) in the presence of NO
2
. There are both anthropogenic
and biogenic oVOC precursors to APNs, but a detailed evaluation of their chemistry
against observations has proven elusive. Here we describe measurements of PAN,
PPN, and MPAN along with the majority of chemicals that participate in their pro-
duction and loss, including OH, HO
2
, numerous oVOC, and NO
2
. Observations were
made during the Biosphere Effects on AeRosols and Photochemistry Experiment
(BEARPEX 2007) in the outflow of the Sacramento urban plume. BEARPEX 2007
took place at a site on a ponderosa pine plantation owned and managed by
*
Now at California Air Resources Board, Sacramento, CA, USA
**
Now at Rubenstein School of Marine and Atmospheric Science, University of Miami, Miami,
FL, USA
***
Now at School of Engineering and Applied Sciences, Harvard University, Cambridge, MA, USA
