Transcript Slide 1

Investigation of primary and secondary aerosols
from wood combustion with a high resolution
time of flight aerosol mass spectrometer
Maarten Heringa
Laboratory of Atmospheric Chemistry
Paul Scherrer Institut, Switzerland
Gothenburg 23-06-2008
Why are we interested in wood burning?

Biomass has the potential to become the world’s largest and most sustainable
renewable energy source. (2004 Survey of Energy Resources World Energy
Council)

Three billion people use small-scale wood fueled appliances that are both
inefficient and highly polluting. (2007 Survey of Energy Resources World
Energy Council)
Examples of wood burning
Wood burning in Roveredo Switzerland
Wood is used as fuel for 75% of the domestic heating installations
in Roveredo Switzerland1
1(Alfarra
et al., 2007 Environ. Sci. Technol)
Wood combustion
Cellulose, hemicellulose and lignin are the main constituents of wood
Complete combustion
Incomplete
combustion
C,H,O + O2 + →
CO2 + H2O + CO + CxHyOz
N2 + impurities
NOx + salts + minerals +
BC
Wood combustion markers
Levoglucosan has been reported as major constituent
of fine particulate emissions2 and its prominent fragment
at m/z 60 has been used as marker ion3
Fragment m/z 60 is not unique for levoglucosan!
2(Reid
et al., 2005 Atmos. Chem. Phys)
3(Alfarra
et al., 2007 Environ. Sci. Technol)
Objectives
• Characterization of primary emissions
– Log wood burners
– Automatic pellet burners
– Wood burning markers m/z 60, 73 and 137
• Investigation of the stability of wood burning
markers m/z 60, 73 and 137
• Investigation of the SOA formation potential of
wood burning emissions in the PSI smog
chamber
HR-ToF-AMS
Q-AMS
TOF Spectrometer
Flow
~ 1.3
2.2 cm3/sec
Quadrupole
Mass Spectrometer
Critical orifice
(100
(130 µm)
Detector
Chopper (150 Hz)
eˉ
TOF Region
Aerodynamic
Lens (2 Torr)
Thermal
Vaporization
(600°C)
and
Electron
Ionization
(70 eV)
Particle Inlet (1 atm)
Turbo Pump
(~1E-3 Torr)
(Jayne et al., 2000; De Carlo et al., 2006)
Turbo Pump
(~1E-5 Torr)
AERODYNAMIC SIZING
CHAMBER
Turbo Pump
(~1E-8 Torr)
DETECTION
CHAMBER
Primary emissions
Pellet burner
80% (7.2 kW), 1.46 kg/h
Log wood burner
0.5kg softwood + 2 x 2.7kg beech
Scheme of the setup
CVS
Clean air
generator
Excess air
Excess air
Dilution ratio
~150x
Heated Diluter
(150°C)
Diluter
FMPS
CO, CO2 ,O2
analyzer
TOF-AMS
MAAP
Dilution ratio calculations
Pellet burner
Org
NO3
SO4
Chl
PAH
-3
Mass Concentration (mg m )
-3
Mass Concentration (mg m )
140
120
100
80
60
12
8
4
0
15:30
22.10.2007
15:40
15:50
Date and Time
40
10x
20
0
15:15
22.10.2007
15:30
Date and Time
15:45
16:00
Start automatic burner
Start peak
40
Species
-3
Nitrate Equivalent Mass Concentration (µg m )
10
Air
Water
Ammonium
Nitrate
Sulphate
Chloride
PAH
Organics
8
30
6
20
4
60
10
73
2
0
137
Wood burning markers
m/z 60, 73, 137
0
20
20
40
40
60
60
80 80
m/z m/z
100 100
120 120
140 140
Stable burning automatic burner
Stable burning
-3
Nitrate Equivalent Mass Concentration (µg m )
10
-3
Nitrate Equivalent Mass Concentration (µg m )
40
30
20
60
Species
Air
Water
Ammonium
Nitrate
Sulphate
Chloride
PAH
Organics
8
m/z 44 is the base peak
(like in OOA)
6
4
2
0
20
10
40
60
73
80
m/z
137
100
120
140
Wood burning markers
m/z 60, 73, 137
0
20
40
60
80
m/z
100
120
140
(Lanz et al., 2008 Environ. Sci. Technol.)
Reproducibility of a log wood burner
2.7kg of beech cut to a standard size and weight
(Weimer et al., 2008 Geophysical Research)
Log wood burner
400
Organics
Ammonium
Nitrate
Sulphate
Chloride
PAH
-3
Mass Concentration (mg m )
1st load
300
Start
200
2nd load
100
Flaming
0
14:00
24.10.2007
15:00
16:00
Date and Time
17:00
Species
-3
Nitrate Equivalent Mass Concentration (µg m )
First load of beech
Air
Water
Ammonium
Nitrate
Sulphate
Chloride
PAH
Organics
60
60
40
73
137
20
0
20
40
60
80
m/z
100
120
140
End of the fire
Species
-3
Nitrate Equivalent Mass Concentration (µg m )
8
Air
Water
Ammonium
Nitrate
Sulphate
Chloride
PAH
Organics
6
4
2
73
60
137
0
20
40
60
80
m/z
100
120
140
Smog chamber setup
Excess air
Clean air
generator
CO,CO2,NOx,O3
Heated line (150°C)
CO2
1:8
Heated
Diluter
~4 L/min
Aethalometer
CPC + SMPS
TOF-AMS
Smog chamber experiment
•
•
•
•
•
Humidification of the chamber
Background measurements
Start the burner
Filling the chamber
Measurement
primary emissions
• Lights on
Organics and black carbon
120
2.0
Org
BC
Org/BC
100
1.5
60
1.0
40
0.5
20
0
0.0
-1
0
1
2
3
Time after lights on (h)
4
5
Org/BC
µg/m3
80
120
3.0
100
2.5
2.5
80
2.0
2.0
M/z 60 µg/m3
60
org
ratio_60_org
org60
3.0
1.5
1.5
40
1.0
1.0
20
0.5
0.5
0
0.0
0.0
0
1
2
3
Time after lights on (h)
4
5
Percentage m/z 60
Org µg/m3
Wood burning markers
Oxidation
0.14
60
1.0
0.12
20
0.10
43.6
0
43.8
44.0
m/z
44.2
0.08
400
6
300
4
200
2
100
0
0
43.6
100
500
org44_to_org start
org44_to_org flaming
8
44.4
43.8
44.0
m/z
44.2
44.4
1.0
50
0.8
40
0.6
30
0.4
20
0.2
10
0.0
0
-3
Nitrate equivalent mass (µg m )
-3
1.5
Org44/org
2.0
40
C2H4O+
0.5
10
-3
80
1.5
0.0
Nitrate equivalent mass (µg m )
100
Nitrate equivalent mass (µg m )
-3
Nitrate equivalent mass (µg m )
CO2+
0.16
2.0
80
0.06
60
1.0
40
0.04
0.5
20
0.02
0.0
59.6
0
59.8
60.0
m/z
60.2
60.4
59.6
59.8
60.0
m/z
60.2
0.00
0
1
2
3
Time after lights on (h)
4
5
60.4
Conclusions
 Automatic pellet burners produce high concentrations of organics during the
ignition
 During stable burning the spectrum of the organics is dominated by m/z 44
which is the dominant signal of OOA
 Log wood burners show large variations in concentration between runs and
during a burning cycle
 The wood burning marker at m/z 60
 is mainly formed during the start
 consist of one molecular formula
 is stable for > 5 hours
 Oxidation of the gas phase emissions of the tested log wood burner increased
the organic aerosol mass with a factor of ~ 2-3
Take home
 Burning automatic pellet burners emit less organics during
stable burning than log wood burners. Nevertheless, high
concentrations of organics are emitted during the ignition.
 Log wood burners show large variations in emissions between
runs and during a single burning cycle. The spectral changes
during the burning cycle makes it more difficult to identify a
representative source profile.
 A particle filter can reduce the primary aerosol emissions.
However, due to SOA formation, only a reduction of 25-40%
can be established (for a particle filter with 80% efficiency)
Thanks to…
Roberto Chirico, Peter DeCarlo, Agnes Richard,
Torsten Tritscher, Marco Steiger, Rami Alfarra,
Andre Prévôt & Urs Baltensperger
Nickolas Meyer & Heinz Burtcher
Michael Sattler & Christian Gaegauf
Thank you for your attention