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Organic Aerosol: Budgets, Beetles and Bewilderment

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Organic Aerosol: Budgets, Beetles and Bewilderment Colette L. Heald with contributions from Bonne Ford, Ashley Berg and Qi Chen With thanks to : many individuals for ... – PowerPoint PPT presentation

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Title: Organic Aerosol: Budgets, Beetles and Bewilderment


1
Organic Aerosol Budgets, Beetles and Bewilderment
Colette L. Heald with contributions from Bonne
Ford, Ashley Berg and Qi Chen With thanks to
many individuals for invaluable field and
satellite measurements
Dalhousie University August 24, 2012
2
THE DISPROPORTIONATE IMPACT OF PARTICULATE MATTER
ON THE GLOBAL ENVIRONMENT
Global radiative forcing
Global premature deaths from environmental risk
OECD, 2012
IPCC, 2007
By 2030 PM surpasses unsafe water as the leading
environmental cause of premature deaths. PM is
the largest source of uncertainty in global
radiative forcing.
3
ORGANIC AEROSOL MAKES UP AN IMPORTANT/DOMINANT
FRACTION OF OBSERVED AEROSOL
Sulphate Organics
Zhang et al., 2007
Globally makes up 25-75 of total fine aerosol at
the surface (ignoring dust here). Could become
more even more important in the future with
sulphate clean-up?
4
WHAT IS AN ORGANIC AEROSOL? (THE CHALLENGE OF
CHEMICAL COMPLEXITY)
YES
NO
Sulfuric acid always looks like this
And also things like this
H2SO4
Soot consists only of carbon (just in different
configurations)
Each peak is an individual molecule (i.e. organic
chemistry is crazy)
Composition is largely UNKNOWN and VARIABLE.
Composition is KNOWN and CONSTANT
5
A LARGE MISSING SOURCE OF ORGANIC AEROSOL?
Obs (Maria et al., 2003) GEOS-Chem
ACE-Asia (2001) 3 groups measured high OA off
Asia. GEOS-Chem simulation factor of 10-100 too
low Heald et al., 2005
Goldstein and Galbally 2007 suggest that SOA
source may be anywhere from 140-910 TgC/yr.
Models drastically underestimate SOA from 4
campaigns Volkamer et al., 2006
Models are woefully inadequate. Could be up to
10x more OA in atmosphere than sulphate!
6
MY TALK TODAY
Part 1 Constraints on the global budget of OA
Part 2 Impacts of the pine beetle infestation
Part 3 Bewildering aerosol in the Southeastern US
7
AN UNDERCONSTRAINED PROBLEM THAT REQUIRES A
TOP-DOWN APPROACH
All units in TgCyr-1
910
  • Despite lack of mechanistic understanding of OA
    formation/loss, we have made progress in the last
    couple of years by using multiple dimensions of
    ambient measurements to evaluate/probe models
  • Mass de Gouw et al., 2005 Heald et al., 2005
    Volkamer et al., 2006, etc, etc.
  • Correlation / variability Heald et al., 2006
    Carlton et al., 2008
  • Spatial distribution Heald et al., 2010
  • Source signatures from mass spectra Hodzic et
    al., 2009 Spracklen et al., 2011
  • Vertical profile Heald et al., 2005 2006 2011
    Carlton et al., 2008
  • Elemental composition Murphy et al., 2011 Chen
    et al., in prep

Our satellite top-down estimate
140
150
82
SOA (optimized)
Existing GEOS-Chem sources
47
24
POA (fixed)
Bottom-up estimate Goldstein and Galbally, 2007
AMS surface-based optimization Spracklen et al.,
2011
Satellite-based estimate Heald et al., 2010
8
EXPLORING THE VERTICAL DIMENSION
17 aircraft field campaigns (2001-2009)
All AMS measurements, except ITCT-2K4 (PILS)
and ACE-Asia (filters).
Aircraft constraints on the organic aerosol
distribution through depth of troposphere in
remote, polluted and fire influenced
regions. GOAL investigate vertical profile and
compare with one CONSISTENT model.
GEOS-Chem SOA simulation 2 product model,
monoterpenes/sesquiterpenes OH/O3/NO3 (Griffin
et al, 1999), low-NOx isopreneOH (Kroll et al.,
2006), NOx dependent aromatics OH(Ng et al.,
2007) ? latest description Henze et al., 2008
Measurements PIs Hugh Coe (ITOP, ADRIEX, DABEX,
DODO, AMMA, ADIENT, EUCAARI, OP3, VOCALS-UK,
TROMPEX), Jose Jimenez, (MILAGRO, IMPEX, ARCTAS),
R. Weber (ITCT-2K4), Ann Middlebrook (TexAQS),
Lynn Russell (ACE-Asia)
9
COMPARISON OF VERTICAL PROFILE
General profile drops off with altitude, with BB
plumes aloft. Over remote regions, little
structure to profile. Outliers AMMA,
ACE-Asia. Model roughly captures
profile. Reasonable assumption on profiles
made in Heald et al. 2010 looking at satellite
10
CAN WE ATTRIBUTE THE MODEL UNDERESTIMATE?
Adding 100 Tg/yr source of ASOA (as suggested by
Spracklen et al., 2011) improves comparison in
polluted regions, but leads to too much OA aloft
and in remote regions. OA sink?
ASOA anthropogenically controlled SOA
11
A POSSIBLE ORGANIC AEROSOL SINK
FUNCTIONALIZATION (Adding oxygen)
Lots (too much?) particle formation
Oxidation in atmosphere ? volatility more
particle
mass
time
FRAGMENTATION (Breaking into smaller molecules)
Oxidation in atmosphere ? volatility ?
volatility
mass
Acts like a sink of particles
time
For the first time, test the impact of this
fragmentation sink in a model.
12
IMPACT OF ADDING BOTH SOURCES AND FRAGMENTATION
SINK ON COMPARISONS WITH FIELD DATA
ASOAx30 fragmentation sink
Baseline
ASOAx30
Estimate that gas-phase fragmentation can
decrease global SOA burden by up to 50.
Heterogeneous oxidation impact less
(16). Adding 100 Tg/yr of ASOA and a gas
fragmentation sink brings model simulation to
within 1 ?g/m3 of observed concentrations in 15
of 17 campaigns. Model may need SOURCES and SINKS.
Gas-phase oxidation, kOH2x10-11
cm3/molecules/s Heterogeneous oxidation
kOH1x10-12 cm3/molecules/s 5 lost to
fragmentation
Heald et al., 2011
13
ADDING ANOTHER DIMENSION THE OXYGEN CONTENT OF OA
Is OC a useful constraint?
Example of fitting 2 product elemental
composition (isoprene OH, low NOx)
Estimated initial OC from fitting/literature (for
species in GEOS-Chem)
POA Biogenic SOA Aromatic SOA
Significant range in OC, even without accounting
for aging. Is it enough to account for observed
OC?
Qi Chen (MIT)
14
SIMULATING THE OC OF ORGANIC AEROSOL
Surface OC
January 2006
June 2006
Without aging surface OC ranges from 0.2-0.8
(0.4 0.1 for 60S to 60N), with little
seasonal difference. Dominated by POAi and
isoprene SOA.
15
COMPARISON WITH OBSERVATIONS
Base GEOS-Chem Simulation POAo OC0.05,
HC1.8 POAi OC0.30, HC1.5 t 1.15 days
OC values captured near-source, but
underestimated in aged environments. Mass
underestimated in all environments
Thanks to several groups for providing data.
More data from Jimenez Group and Qi Zhang will
become available.
16
HOW DOES INCREASING ASOA CHANGE THE PICTURE?
Revised Simulation (ASOA x 30) POAo OC0.05,
HC1.8 POAi OC0.30, HC1.5 t 1.15 days
Addition of ASOA improves model simulation of
mass (as in Spracklen et al., 2011 Heald et al.,
2011). OC better captured in aged regions (BUT
suggests we may need to invoke aging mechanisms),
but OC in source regions can now be
overestimated (ASOA actually a source with lower
OC?) Bottom line what mechanisms/sources can
improve simulation of both mass and OC?
17
MY TALK TODAY
Part 1 Constraints on the global budget of OA
Part 2 Impacts of the pine beetle infestation
Part 3 Bewildering aerosol in the Southeastern US
18
PINE BEETLE INFESTATION IN WESTERN NORTH AMERICA
Worst beetle outbreak in recorded history peaked
in BC in 2007 and in the Western US in 2009
Over 100,000 km2 of forest killed, continued
expansion. Impacts carbon cycling, fire
susceptibility. What about air quality?
Kurz et al., 2008
19
PINE BEETLES PERTURBING MONOTERPENE EMISSIONS
O3
VOCs?
VOCs
?Mortality Effect
?Attack Effect
Very few quantitative studies have been
done Amin et al. (2012) measure emissions from
Lodgepole pine (and spruce) under attack by
mountain pine beetle, see significant
enhancements of some emissions.
Ashley Berg (CSU)
20
ESTIMATED IMPACTS ON MONOTERPENE EMISSIONS
VEGETATION DISTRIBUTIONS (CLM4)
ANNUAL MORTALITY (Meddens et al., in press)
EXPERIMENTAL VOC INCREASES (Amin et al., 2012)
VOC EMISSIONS IN CLM4 (MEGAN2.1) (Guenther et
al., in press)
Mortality Effect
Mortality Effect Attack Effect
2004
Largest impact of MPB on monoterpene emissions in
British Columbia in 2004 (increase up to 70) and
in 2008 in US (increase up to 104).
2008
ß-pinene, ß-phellandrene, 3-carene, P-cymene
21
ESTIMATED IMPACTS ON MONOTERPENE EMISSIONS
VEGETATION DISTRIBUTIONS (CLM4)
CHAMBER SOA YIELDS (6-55) (Lee et al., 2006)
ANNUAL MORTALITY (Meddens et al., in press)
EXPERIMENTAL VOC INCREASES (Amin et al., 2012)
VOC EMISSIONS IN CLM4 (MEGAN2.1) (Guenther et
al., in press)
Mortality Effect
Mortality Effect Attack Effect
More muted impact on SOA (30-40 max increases)
but also more regional. Dependent on very
uncertain species-variable response scenario
using spruce data shows up to doubling of SOA (1
µgm-3 increase). Evidence of importance of land
use change in air quality.
2004
2008
Berg et al., in prep
22
MY TALK TODAY
Part 1 Constraints on the global budget of OA
Part 2 Impacts of the pine beetle infestation
Part 3 Bewildering aerosol in the Southeastern US
23
IS OA CONTRIBUTING TO CLIMATE TRENDS IN
SOUTHEASTERN US?
Summertime trend in Maximum T (1950-2006)
MISR summer-winter AOD
Data Global Historical Climate Network Daily
(GHCND)
Although clearly speculative, increasing
biogenic secondary organic aerosol/cloud effects
linked to forest regrowth and/or interactions
with anthropogenic pollution is one possibility
that is qualitatively consistent, not only with
the spatial structure, but also with the
seasonality of the correlation of the unusual
negative temperature trends with precipitation
found in the southeastern United States.
Seasonal maximum in AOD consistent with biogenic
emissions (implication biogenic SOA). Part of
the motivation for SOAS field campaign (summer
2013)!
Portmann et al., 2009
Goldstein et al., 2009
24
IS THIS CONSISTENT WITH OUR UNDERSTANDING OF
AEROSOL IN THE REGION?
Bonne Ford (CSU)
NO! Model shows significantly less seasonal
enhancement over SE. But note (a) diversity of
satellite observations (b) model reproduces
surface PM2.5
25
IS THERE SEASONALITY IN SURFACE OA IN THE
SOUTHEAST?
NO. Seasonality in observed PM2.5 is largely
driven by sulfate and dust. Consistent with
Zhang et al. 2012 who suggest that seasonality
is driven by meteorology, transport and
photochemistry.
Assumed OMOC2 year-round
26
A ROLE FOR WATER UPTAKE?
Average nephelometer data at IMPROVE SE sites
(2009)
Mean diurnal RH in the SE(2009)
A-train overpass
Very modest seasonality in surface layer RH,
translates to very little seasonality in mass
extinction efficiency. Not an artifact of the
satellite overpass time (impact of water uptake
on AOD is actually greater on 24-hr mean)
27
POSSIBLE MEANS OF RECONCILIATION AEROSOL ALOFT
JJA
Extinction km-1
CALIOP profiles over 3 years (2007-2009) show a
summertime enhancement aloft could be
associated with fine inorganic or organic
aerosol. Need an aircraft to tell! SENEX!
Ford and Heald, in prep
28
CONCLUSIONS
  • Models underestimate OA, but observations can
    narrow the range suggest the missing source is
    anthropogenic and that additional sinks
    (fragmentation) may also be required.
  • Oxygen content of aerosol is a useful constraint
    suggests that aging mechanism required only in
    remote enviro.
  • Pine beetle infestation in W North America
    estimated to be responsible for up to 40
    increases in SOA.
  • Required better characterization of
    species-specific response
  • Models consistent with observed surface PM2.5
    loading and seasonality in the SE US, but
    underestimate summertime AOD (and seasonality) by
    a factor of 2-3.
  • Possibly resolved by aerosol aloft (suggested by
    CALIOP)
  • ? aircraft observations during SOAS to
    solve the mystery!
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