measurement of aerosol and voc turbulent fluxes and in-canopy particle characterization at a...
TRANSCRIPT
Measurement of aerosol and VOC turbulent fluxes
and in-canopy particle characterization at a pristine forest in Amazonia
Luciana Rizzo
The Amazon forestThe Amazon forest
• Greatest tropical forest in extension (~6 millions km2)
• Biosphere-atmosphere interaction: fluxes of momentum, heat, water vapor, aerosol particles and trace gases
• Natural source of biogenic particles and trace gases like VOC, CO2, H2O etc
• Intense convective activity: transport over large distances, in a way that the forest acts as a natural global source
The Brazilian Amazon
(IPAM, 2004)
Biosphere-atmosphere interactions
Biogenic aerosols in Biogenic aerosols in Amazonia Amazonia • Mass: 10-15 g/m3, Number: 300-500 cm-3
• 70% of the mass on the coarse mode• Organic matter = 60-70% FPM and 70-85% of CPM
LBA/ZF2-2004 LBA/ZF2-2004 ExperimentExperiment
• Cuieiras forest reserve (100 km North of Manaus), Central Amazonia
• Particle and VOC flux measurements
• Conducted during the dry season between August and October
Soil (2m)
Canopy (28m)
Top (40m)
Anemometer (54m)
10
Canopy level: SFU, scattering, number
Top level: SFU, scattering, mass, number, BC, size distribution
Anemometer level: Particle, VOC, CO2 fluxes
oil level: SFU, scatt
oil level: SFU, scatte
oil level: SFU, scatter
oil level: SFU, scatteri
oil level: SFU, scatterin
oil level: SFU, scattering
Hei
ght a
bove
gro
und
[m]
20
30
40
50
60
Soil level: SFU, scattering, mass, number, BC
Measurement of aerosol properties
CPC Datalogger
1,5 m
Sonic Anemometer
Analog output
Counting electrical pulses
at 10 Hz
Particle flux measurement
''''11 1
0
cwcwN
ccwwN
N
iiic
Particle counter (Dp < 1 m)
Measured aerosol FluxesMeasured aerosol Fluxes• Net flux of fine particles close to zero (under optimal sampling conditions)
•Predominance of emission (asc.) during the day and deposition (desc.) during the night
• Consequence of equilibrium between the biosphere and the atmosphere?
• Or most of exchanges occur on the coarse mode?
0.05 106 particles/m2/s
Measured VOC fluxesMeasured VOC fluxes
• Strong diurnal variability: temperature and light dependence
• Comparison with boreal forest (max diurnal flux): 40 g/m2/h for isoprene and 150 g/m2/h for monoterpenes
Fluxo de COVs
-4
-2
0
2
4
6
8
10
12
14
16-Sep 18-Sep 20-Sep 22-Sep 24-Sep 26-Sep 28-Sep
[mg
C/m
2/h
]
isopreno
monoterpenos
.
g
/m2/h
]
Do these VOC emissions Do these VOC emissions lead to the formation of lead to the formation of
new particles?new particles?• No significant correlation between VOC
fluxes and aerosol fluxes• Aerosol size distributions (10-350nm): no
clear nucleation events were observedIsopreno X Partículas Finas
0.00
0.10
0.20
0.30
0.40
0.50
0 60 120 180 240 300 360 420 480 540tempo de atraso [min]
corr
elaç
ão n
orm
aliz
ada
Isoprene X particle conc (30<Dp<350nm)
Nor
mal
ized
co
rrel
atio
n
Delay time [min]
The only clue:
• 7 hour delay
• suggests the influence of isoprene over nucleation and/or growth of particles
Interesting and recurrent Interesting and recurrent nocturnal eventsnocturnal events
• Nocturnal bursts (observed in 15 of 34 days)• Observed in clean days and under the influence of regional fires• No systematic relationship with aerosol and VOC fluxes
0
5
10
15
20
0:00 6:00 12:00 18:00 0:00
Co
nc
. 1
m [
cm
-3]
topodossel
23-set-04
-30
-20
-10
0
10
20
30
0:00 6:00 12:00 18:00 0:00
Flu
xo d
e C
O2
[mm
ol/m
2/s
]
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
Ve
loc.
Atr
ito u
* [m
/s]
Fluxo de CO2
u*
Coeficiente de espalhamento - 23 set
102030405060708090
100110
0:00 6:00 12:00 18:00 0:00
Esp
alh
am
en
to 5
50
nm
[1/M
m]
topo
dossel
solo
• Burst of particles with Dp > 0,5 m
• Emission?
• In-canopy CCN activation?
• CO2 emission: biological activity
• u* peak: indicates turbulent activity at night
• Increased scattering
coefficient at the Canopy level
• Strong gradient of coarse mode P at night• Recurrent observation in Amazonia• Emission of nutrients at coarse mode at night: cycle
only locally, avoiding losses outside the ecosystem via turbulent transportation.
Coarse mode P - Cuieiras forest
0 10 20 30
Soil
Canopy
Top
Average concentration [ng/m3]
Night
Day
SummarySummary
• Net fine particle flux close to zero• Traces of in-canopy particle emissions
were observed, specially at night → the biophysical mechanisms controlling those emissions remain unknown
• No nucleation events • Not significant relationships between VOC
and particle fluxes• Results can not be extrapolated, because
of the heterogeneity of the Amazon region
Remaining questions Remaining questions 1. Net fine particle flux close to zero (Amazonia
and Finland)• Equilibrium between biosphere-atmosphere?• Is this a matter of improving measurement
techniques?• Does that also apply for the coarse particle mode?
Range of particle flux measurements Develop new
techniques to measure size segregated fluxes and coarse mode fluxes
2. No nucleation events observed in the pristine Amazon forest
– What are the limiting factors?– What is the role of VOC on particle growth?– What is the influence of SOA over the physical
properties of aerosol population?
Amazonia Finland
Max isoprene flux [mg/m2/h]
10 2
Max monoterp flux [mg/m2/h]
2 15
SO2 [ppt] 30 400
O3 [ppb] 0.05 30
RH >80% 40-80%
To begin with:
Chamber experiments reproducing typical
Amazonian atmospheric conditions
Amazonia - Annual deforestation rate
0
5000
10000
15000
20000
25000
30000
35000
19
88
19
89
19
90
19
91
19
92
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96
19
97
19
98
19
99
20
00
20
01
20
02
20
03
20
04
20
05
km2
/ye
ar
Cumulative deforestation percentual (raw calculations)
0.0%
1.0%
2.0%
3.0%
4.0%
5.0%
6.0%
7.0%
19
87
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00
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06