Emissions and Secondary Formation of Organic Aerosols in the ...

Emissions and Secondary Formation of Organic Aerosols
in the Polluted Atmosphere
Joost de Gouw
NOAA Earth System Research Laboratory
&
CIRES, University of Colorado
Boulder, Colorado
With Data From:
AMS Tim Bates, Trish Quinn, Tim Onasch
WSOC Rodney Weber, Amy Sullivan, Rick Peltier
WAS Elliot Atlas
PTR-MS Carsten Warneke, Lori Del Negro
GC-MS Paul Goldan, Bill Kuster, Min Shao
CO Eric Williams, Brian Lerner, Paul Murphy
CO John Holloway

Emissions and Secondary Formation of Organic Aerosols
in the Polluted Atmosphere
Joost de Gouw
NOAA Earth System Research Laboratory
CIRES, University of Colorado
Boulder, Colorado
Outline:
1. Organic aerosol in urban plumes during ICARTT
2. Budget of anthropogenic SOA
3. Carbonyl Sulfide as a tracer for biogenic SOA?

Motivation
De Gouw [JGR 2005]:
1. Organic aerosol in the NE
U.S. mostly associated with
urban emissions
2. In most air masses:
SOA >> POA
3. Growth of SOA >> calculated
from urban precursors
NEAQS 2002
How well does this description hold up for other data sets?

ICARTT 2004
NOAA r/v Ronald H. Brown
OM: Quinn; CO: Williams
OM and CO are correlated
Ratio increases with photo-chemical
age (from toluene to benzene ratio)

From NEAQS 2002:
OM versus Photochemical Age
POA
NEAQS equation works well for ICARTT data!
SOA

Aircraft Measurements During ICARTT 2004
NOAA WP-3D
From: Sullivan [JGR 2006]
Good correlation between watersoluble
organic carbon (WSOC)
and CO

Quasi-Lagrangian Study of SOA Formation
From: de Gouw [JGR submitted]
Benzene is relatively inert
Similar ratio observed on
both days (July 20 and 21)

Quasi-Lagrangian Study of SOA Formation
From: de Gouw [JGR submitted]
Toluene is more reactive
Much smaller ratio observed
on 2 nd day (July 21)

Quasi-Lagrangian Study of SOA Formation
From: de Gouw [JGR submitted]
WSOC is higher on 2nd day
(July 21)
Observed increase:
9 to 23 µgC m -3 ppmv -1
similar to calculated † increase:
7 to 26 µgC m -3 ppmv -1
† assuming OM/WSOC=2.8

Growth of WSOC in Urban Plumes
From: de Gouw [JGR submitted]
Growth of WSOC in urban plumes consistent
with equation derived from NEAQS

New Yields for Aromatic VOCs
Explain Larger Part of SOA
Multiple field studies:
SOA/CO ≈ 40 µg m -3 ppmv -1
SOA yields from Seinfeld & Pandis [1998]:
SOA/CO ≈ 3.7 µg m -3 ppmv -1
New SOA yields from Ng [2007]:
SOA/CO ≈ 14 µg m -3 ppmv -1
Suggests 35% of SOA from measured
aromatics
Remainder may come from:
Unresolved VOCs [Lewis, 2000]?
Semi-volatiles [Robinson, 2007]?
Biogenic VOCs?

Multiple field studies:
∆SOA/∆CO ≈ 40 µg m -3 ppmv -1
Global Anthropogenic CO
(EDGAR) = 244 Tg y -1
=> Global Anthropogenic SOA:
8.0 Tg y -1
Anthropogenic SOA:
9% worldwide
35% in the U.S.
(Most biogenic VOCs and
fires in the tropics; most
fossil-fuel use in the
northern hemisphere
Importance of Anthropogenic SOA
From: de Gouw [JGR submitted]

Teaser: Carbonyl Sulfide (OCS) as Biogenic Tracer?
Problem:
Biogenic VOCs are very short-lived
A long-lived tracer would be useful to quantify biogenic SOA
A potential solution?
OCS is long-lived
Variability of OCS over the U.S. is
controlled by vegetation uptake
[Montzka, JGR 2007]
Here:
Fit ICARTT data for WSOC, methanol and CO to:
(after filtering for biomass burning using acetonitrile)
A + Bx(Acetylene-100pptv) + Cx(480pptv-OCS)
Background Urban POA+SOA Biogenic SOA

WSOC:
Bg = 0.25 µgC m -3
Urban = 95%
Biogenic = 5%
Results of Multivariate Fits
Methanol:
Bg = 750 pptv
Urban = 50%
Biogenic = 50%
CO:
Bg = 85 ppbv
Urban = 76%
Biogenic 24%
De Gouw [JGR 2005]: OM is 86% urban, 14% biogenic
methanol is 62% urban, 38% biogenic

WSOC:
Bg = 0.25 µgC m -3
Urban = 95%
Biogenic = 5%
Results of Multivariate Fits
Methanol:
Bg = 750 pptv
Urban = 50%
Biogenic = 50%
CO:
Bg = 85 ppbv
Urban = 76%
Biogenic 24%
Initial results suggest that WSOC is largely anthropogenic
Not a definitive argument, but another piece of the puzzle

Summary
Significant part of the regional variability in OM explained by:
1. relatively small, direct emissions from cities
2. strong growth of SOA in urban plumes
New yields for aromatic VOCs may explain a significant part
of SOA formation
Anthropogenic SOA could be 35% of total OM in the U.S.
Acknowledgements
Chuck Brock, Ann Middlebrook, Fred Fehsenfeld, Michael Trainer,
Tom Ryerson, David Parrish