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

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 Switzerland 1 1 (Alfarra et al., 2007 Environ. Sci. Technol)

Incomplete combustion C,H,O + O 2 +→ CO 2 + H 2 O + CO + C x H y O z N 2 + impuritiesNO x + salts + minerals + BC Complete combustion C,H,O + O 2 +→ CO 2 + H 2 O N 2 + impuritiesNO x + salts + minerals Wood combustion Cellulose, hemicellulose and lignin are the main constituents of wood

Wood combustion markers Levoglucosan has been reported as major constituent of fine particulate emissions 2 and its prominent fragment at m/z 60 has been used as marker ion 3 2 (Reid et al., 2005 Atmos. Chem. Phys) 3 (Alfarra et al., 2007 Environ. Sci. Technol) Fragment m/z 60 is not unique for levoglucosan!

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 Particle Inlet (1 atm) Quadrupole Mass Spectrometer Aerodynamic Lens (2 Torr ) Chopper (150 Hz) Turbo Pump (~1E-3 Torr) TOF Region AERODYNAMIC SIZING CHAMBER Turbo Pump (~1E-5 Torr) Turbo Pump (~1E-8 Torr) Flow ~ 2.2 cm3/sec Detector Q-AMS TOF Spectrometer Flow ~ 1.3 cm3/sec (Jayne et al., 2000; De Carlo et al., 2006) Thermal Vaporization (600°C) and Electron Ionization (70 eV) eˉeˉ Critical orifice (130 µm) Critical orifice (100 µm) 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

Clean air generator Heated Diluter (150°C) Scheme of the setup TOF-AMS Excess air Diluter MAAP CO, CO 2,O 2 analyzer FMPS CVS Dilution ratio ~150x

Dilution ratio calculations

Pellet burner 10x

Start automatic burner Start peak Wood burning markers m/z 60, 73, 137

Stable burning automatic burner Stable burning Wood burning markers m/z 60, 73, 137 m/z 44 is the base peak (like in OOA) (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 1st load 2nd load Start Flaming

First load of beech

End of the fire

Clean air generator Heated Diluter Excess air Heated line (150°C) 1:8 ~4 L/min Smog chamber setup Aethalometer CO,CO 2,NO x,O 3 TOF-AMS CPC + SMPS CO 2

Smog chamber experiment Humidification of the chamber Background measurements Start the burner Filling the chamber Measurement primary emissions Lights on

Organics and black carbon

Wood burning markers

Oxidation CO 2 + C2H4O+C2H4O+

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… Thank you for your attention Roberto Chirico, Peter DeCarlo, Agnes Richard, Torsten Tritscher, Marco Steiger, Rami Alfarra, Andre Prévôt & Urs Baltensperger Michael Sattler & Christian Gaegauf Nickolas Meyer & Heinz Burtcher