To What Extent Can Biogenic
SOA be Controlled?
Annmarie Carlton, Rob Pinder, Prakash Bhave,
George Pouliot
CMAS – Chapel HIll, NC
Office of Research and Development
National Exposure Research Laboratory
Atmospheric Modeling Division, Research Triangle Park, NC
April 9, 2015
Important Findings
CMAQ Simulations indicate anthropogenic
pollution enhances predicted biogenic SOA
concentrations in the U.S. substantially ~ 50%
–Effects are largest in eastern U.S.
–POC and NOx are largest individual
pollutant classes contributing to overall
biogenic SOA
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MOTIVATION
Non-fossil (biogenic) carbon is a dominant component of
atmospheric organic aerosol
Substantial portion of PM2.5 carbon is ‘modern’ even in urban areas
(Lewis et al., 2004; Szidat et al., 2006; Bench et al., 2007; Gelencsér, et al., 2007)
Tracer-based ambient SOA ‘measurements’ dominated by
contributions from biogenic hydrocarbons (Edney et al., 2003; Kleindienst et
al., 2007)
Ambient WSOC, AMS OOA spectra and other indicators of SOA
correlate strongly with tracers of anthropogenic pollution (Weber et
al., 2007; de Gouw et al., 2005; Goldstein et al., 2009)
If anthropogenic pollution is enhancing biogenic SOA how can
this contribution be quantified?
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Anthropogenic/Biogenic Interactions in SOA Formation
POA
SOAA
SOAB
SOAA
SVOC
anthropogenic
VOCs
POA
SOAB
SVOC
oxidants
SVOC
SVOC
oxidants
biogenic
VOCs
controllable emissions
non-controllable
(e.g., anthropogenic VOCs)
(e.g., biogenic VOCs)
H+ effects not shown
3
Estimating Anthropogenic Contribution
to “Biogenic” SOA
• Difficult to directly measure in the atmosphere
–O3, OH ambient measurements – no insight as to
whether the precursor was anthropogenic or biogenic
–PM mass - can make estimates only about organic
precursors with detailed chemical analysis
• Can investigate large scale trends and
relationships with an atmospheric model
(CMAQ) by manipulating emissions
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accumulation mode
organic PM
cloud water
monoterpene
AORGC
ATRP1, ATRP2
dissolution
SV_TRP1
SV_TRP2
AOLGB
sesquiterpenes
ASQT
or NO3
POA
SV_SQT
AISO1, AISO2
AISO3
∙OH
SV_ISO1, SV_ISO2
O3,O3P, or NO3
Pathways do not contribute to SOA
Non-volatile
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EMISSIONS
VOCs
EMISSIONS
EMISSIONS
isoprene
H+
glyoxal
methylglyoxal
EMISSIONS
∙OH,O ,
3
∙OH
Modeling experiment
• Simulation of August 15 - September 4, 2003
• Continental US
• Time period has high biogenic contribution to SOA
• Emissions: controllable versus not controllable
Not Controllable
Wildfire
Prescribed burning
VOCs from plants / trees
Soil NOx
Lightning NOx
Controllable
Everything else:
Power plants
Vehicles
Agricultural burning
Area sources
6
Percent of emitted species from controllable and uncontrollable sources
controllable sources – gray
uncontrollable sources - white
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Carlton et al., ES&T (2010)
Biogenic SOA at the Surface (<~34 m): 18 day average
Base CMAQ simulation
all emissions
Fraction of biogenic SOA from
controllable pollution
non-controllable emissions =
biogenic emissions + wildfires + prescribed
burns
fraction
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Results averaged from Aug. 18th – Sep. 4th, 2003
Carlton et al., ES&T (2010)
Difference in predicted biogenic SOA mass concentrations
Maxima for time period
Average for time period
On Average ~ 1 ug/m3
of Biogenic
SOA in SE is
(All Sources - Biogenic
Only)
from controllable sources
• Additional simulations to estimate effects and contributions of individual species
•
POC, NOx, VOC, SO2, NH3
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To control biogenic SOA – what should regulators
focus on?
• What emitted species are most important?
• What locations are most impacted?
• Group the anthropogenic emissions into
– VOC: Volatile Organic Carbon
– POC: Primary Organic Carbon Particles
– NOx
• Remove one of these species at a time
• Calculate change in biogenic SOA
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Regional Influence of Controllable Emissions on
“Biogenic” SOA
Controllable POC
Controllable NOx
Controllable SO2
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Surface (<~34 m) Concentration; 18 day average
Change in population-weighted AQ metrics
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Cloud SOA
2003 Monthly-Averaged CMAQ Results at RTP
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Cloud SOA Precursors
glyoxal
methylglyoxal
2003 Monthly-Averaged CMAQ Results at RTP
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Cloud SOA Precursors
∙OH
SOA formation is photochemistry
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Conclusions
• Used CMAQ to estimate fraction of biogenic SOA that is
controllable.
• In the Eastern US, ~50% of the biogenic SOA can be
controlled by reducing anthropogenic emissions
• To reduce concentrations of biogenic SOA, focus on
–primary organic carbonaceous particles (POC) and NOx
–SO2 impacts biogenic SOA in the southeastern US
• Cloud-produced SOA exhibits seasonal cycle similar to
∙OH
and biogenic VOCs
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Acknowledgements
• Sergey Napelenok
• Marc Houyoux
• Alice Gilliland
• Rohit Mathur
• Golam Sarwar
• Ed Edney, Tad Kleindist, John Offenburg, Michael Lewandowski
• Charles Chang & Ryan Cleary
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