Global Constraints on Biogenic Particles
PBAP SOA
E=? P=~100 Tg/yr
biogenic?
Colette L. Heald
Dominick V. Spracklen (Leeds), Kateryna Lapina (CSU)
Photo courtesy: Cam McNaughton (taken from NASA’s DC-8)
Goldschmidt Conference
August 19, 2011
PRIMARY BIOLOGICAL AEROSOL PARTICLES (PBAP)
BACTERIA VIRUSES
POLLEN
FUNGUS
PLANT ALGAE
DEBRIS
Jaenicke [2005] suggests may be large (1000s Tg/yr)
Elbert et al. [2007] suggest emission of fungal spores ~ 50 Tg/yr
PBAP estimates ~1000 Tg/yr would swamp all other sources of organic aerosol.
KEY QUESTION: what is the size (lifetime) of these particles??
FIRST SIMULATION OF FUNGAL SPORE PBAP
I. Mannitol is a unique tracer for fungal spores [Bauer et al., 2008; Elbert et al.,
2007]: 1 pg mannitol = 38 pg OM
II. Optimize model emissions as a function of meteorological and phenological
parameters (wind, T, humidity, radiation, surface wetness, precipitation, leaf area
index, water vapour concentrations, boundary layer depths) to match global
observations of mannitol in PM
Emission of 28 Tg/yr, but only 25% in
fine mode (upper limit).
Constant Emission
Optimized Emission = f(LAI, H2O)
Global Model: GEOS-Chem(2x2.5)
WHERE ARE FUNGAL SPORES AN IMPORTANT SOURCE
OF ORGANIC AEROSOL?
Generally contribute ~10% to fine mode surface OA, but > 30% in tropics.
Gilardoni et al. (2011) report coarse PBAP ~2.4 gm-3 in Amazon (good agreement).
WHEN ARE FUNGAL SPORES AN IMPORTANT SOURCE
OF ORGANIC AEROSOL?
Hyytiala
GEOS-Chem simulation
unpublished data, Hanna Manninen
Taiwan
[Ho et al., 2005]
Pronounced seasonality in extratropics
(corresponding to vegetation cover),
peaking in late-summer/fall as in
measurements.
Porto, Portugal
[Sousa et al., 2008]
RELEVANCE TO GLOBAL OA BUDGET…
FINE OA SOURCES COARSE OA SOURCE
(Tg yr-1) (Tg yr-1)
[Heald and Spracklen, GRL, 2009]
Fungal spores make a modest (7%), but regionally important contribution to OA budget.
Most larger than PM2.5. More observations needed to test…
What about other PBAP types?
BACTERIA AS A SOURCE OF PBAP?
Simulated as 1 m particles (ECHAM/MESSy). Inverted for ecosystem emissions.
x 103 m-3
[Burrows et al., ACP, 2009]
Estimate global emissions of bacteria = 0.4-1.8 Tg/yr. Not significant by MASS.
Lifetime suggests potential long-range transport.
Jacobson and Streets [2009] estimate 84.5 Tg/yr pollen (but 30 m)
BIOGENIC ORGANIC AEROSOL OVER THE AMAZON
These observations confirm that there is very little PBAP (mass or number) in the fine mode.
But lots in the coarse mode (IN?)
*10 day pristine period in March 2008. [Poschl et al., Science 2010]
ICE NUCLEATION EFFICIENCY OF PBAP
Amazon: Prenni et al. [2009] show that local biological particles
contribute to IN and becomes dominant (over dust) at warmer
temperatures (> -25°C)
Wyoming (ICE-L): Pratt et al. [2009] estimated that 1/3 of IN
were PBAP.
Model study of relative IN efficiency
(PBAP from Burrows et al, 2009; Heald and Spracklen 2009; Jacobson and Streets, 2009)
[Hoose et al., ERL, 2010]
Observations suggest that significant fraction of IN are biological, but model estimate that
even with max IN efficiency PBAP contributes < 1% to mean total immersion freezing rate.
Perhaps regionally important?
FUNGAL PBAP IS A REGIONALLY IMPORTANT
CONTRIBUTOR TO SUPER-MICRON NUMBER
Fraction of super-micron
PBAP super-micron number (surface) aerosol number at surface
DUST
Fraction of super-micron
aerosol number aloft (7km)
While (fungal) PBAP only contributes
< 1 % of total super-micron aerosol
number globally, regionally can exceed
50% at surface (20% aloft)
[Spracklen and Heald, in prep]
Global Model: GLOMAP (2.8x2.8 )
MARINE PBAP
WIND
Sea-spray emission
Surfactant Layer (with Organics)
Ocean
SPRING (high biological activity)
SeaWIFS
Under biologically active conditions, OA has been observed to dominate sub-micron
aerosol mass.
[O’Dowd et al., 2004]
IS THE OCEAN AN IMPORTANT SOURCE OF PBAP?
Previous estimates range from 2.3 to 75 TgC/yr
No marine OA With marine OA OA Emissions
Observations from 5 ship cruises show
that marine OA from 2 schemes
(based on MODIS / SeaWIFS
chlorphyll-a) of ~8 TgC/yr are more
than sufficient to reproduce sub-
micron OA.
[Lapina et al., ACP, in press]
Measurements from: J.D. Allan, H. Coe, G. McFiggans, S.R.
Zorn, F. Drewnick, T.S. Bates, L.N. Hawkins, L.M. Russell
FUNGUS AS A SOURCES OF SESQUITERPENES TOO!
Horvath et al, [JGR, in press] measured significant SQ emissions from soil (210-570 g/mol CO2).
Is this an important source?
Global Model: NCAR-CLM (2 x2.5 )
We estimate fungal biomass in soil emits ~1 Tg/yr of sesquiterpenes (6% of global source).
Regionally/seasonally important source of SOA?
+ FEEDBACKS FROM
CLIMATE CHANGE
(moisture, precipitation, T, hv)
?
SOA
+
oxidants
↓ OH = ↑ CH4 lifetime
PBAP EMISSIONS:
Particles C5H8
Organics
NOx
…
+
oxidation
O3
DISTURBANCE:
Fires, beetles, ANTHROPOGENIC
land use change INFLUENCE