Biomass Burning Aerosols: Characteristics and Potential Impacts

Transcription

1 Biomass Burning Aerosols: Characteristics and Potential Impacts L.-W. Antony Chen 1, Paul Verburg, Rajan Chakrabarty 1, Hans Moosmüller 1, and Judith C. Chow 1 1 Division of Atmospheric Sciences, Desert Research Institute, Reno, NV Division of Earth and Ecosystem Sciences, Desert Research Institute, tute, Reno, NV 5/13/010 A&WMA International Specialty Conference: Leapfrogging Opportunities for Air Quality Improvement

2 Objectives of Our Biomass Burning Study Characterize the properties of primary biomass burning aerosol through laboratory combustion experiments Physical Chemical Optical Document the emission factors as functions of fuel and combustion conditions Assess the potential impact of biomass burning on a regional and global scale. Pic: Athens, Greece, Aug 17, 007

3 What are in the Biomass Burning Smoke? Soot aggregate Soot monomer CO, CO, H, H O, CH 4, volatile HC PM.5, 10 Organic carbon Non-volatile HC (saccharides, humic-like substances) char and ashes (inorganics) NH 4 NO 3, (NH 4 ) SO 4 NO, NO, N O, N, NH 3, HCN, SO Green house gases Criteria pollutants Air toxics Ozone precursors Visibility Cloud condensation nuclei Secondary organic aerosol precursors Potential nutrients Mineral Inclusion Biomass Fuel cellulous, hemi-cellulous, lignin Soil Humus C,O,H,N,S,Cl,Si,Al,Ca,Fe,K,Mg,Mn,Na,P,Ti,Zn

4 Laboratory Combustion Experiment Exhaust Fan Measured Variables: 8 m Fuels m Ceramic Heater/ Hotplate 10 LPM Mixing Plenum Dekati ELPI Particle Sizer Cyclone Inlet Filter Channel 5 LPM Filter Channel 1 5 LPM TSI Mass Flow Meter Pump 50 LPM TECO NH 3 Analyzer MIDAC FTIR TECO NO x Analyzer Particle Filter Gases Mass, C/N/H fraction, moisture content, extractable NO 3- and NH + 4 CO, CO, NO, NO, N O, NO x, NH 3, VOC s Particles FSL DRI DRI Mass, number, size distribution, light absorption, light scattering, C/N/H fraction, elements, ions, organic and elemental carbon, PAHs

5 Pros and Cons of Laboratory Pros: Experiments Better control and test individual parameters for combustion More comprehensive measurements at higher time resolution More replicate experiments Cons: Representativeness of large-scale burns with complex matrix?

6 Particle emissions throughout the burn with different properties *CE: C CO + C C CO CO + C **MCE : C CO C CO + C HC CO + C PM Mass Extinction/Scattering/Absorption Efficiency (m g -1 ) Extinction Scattering Absorption MCE Modified Combustion Efficiency (MCE) Flaming Smoldering 0 10:33 10:35 10:36 10:37 10:39 Time (PST) 0.8 *Burning Ponderosa Pine Needles Chen et al. (006)

7 Angora Fire -Lake Tahoe, 007 Flaming Flaming Phase: hot and dark; high combustion efficiency (complete combustion) Smoldering Smoldering Phase: not- so-hot and white; low combustion efficiency (incomplete combustion)

8 Relation of Combustion Efficiency and PM.5 Emission Factors Manzanita 900 PM.5 Emission Factors (g/kgc) 800 Bitterbrush Squaw Carpet 500 R = Stems 300 Leaves Litter 00 Litter Duff 100 R = Combustion Efficiency (CE) Chen et al. (010) Duff

9 Relation of Combustion Efficiency and NH 3 Emission Factors Stems NH 3 Emission Factors (g/kgc) Leaves Litter Duff R = 0.68 R = Combustion Efficiency (CE)

10 Moisture Effects Cl- NO3- SO4= 1% NH4+ Na+ Biomass Burning Combustion Efficiency Crustal Res 15% K+ 3% EC 3% OC 49% Dry Manzanita Leaves MCE = 0.91 Res 11% K+ Crustal EC 4% Wet Manzanita Leaves MCE = 0.7 Cl- NO3- SO4= NH4+ Na+ OC 85%

11 The Natural of Organic Matter from Biomass Burning PM.5 TH/TC Ratio TH/TC Ratio Absorption Exponent Lignin Cellulous Sugar Absorption Exponent (370/880 nm) Brown Carbon 0.00 Elemental Carbon OC/TC Ratio 0.0 Organic Carbon Black Carbon

12 Particle Size and Morphology Revealed by SEM Images Some large (d ~100 00nm) spheres Tar Balls from smoldering phase? Mostly uniform primary spheres, d = nm for various fuels (Chakrabarty et al., 006) Tar balls in pure smoldering combustion (Chakrabarty et al., 010)

13 Two Pure Smoldering Combustion (Alaskan Tundra & Ponderosa Pine Duff) dn/dlog(dp) 3.5E E+05.5E+05.0E E+05 Ponderosa Pine Duff (ELPI) Ponderosa Pine Duff (SMPS) Alaskan Tundra Duff (ELPI) Alaskan Tundra Duff (SMPS) dv/dlog(dp) 3.5E+0 3.0E+0.5E+0.0E+0 1.5E+0 Ponderosa Pine Duff (ELPI) Ponderosa Pine Duff (SMPS) Alaskan Tundra Duff (ELPI) Alaskan Tundra Duff (SMPS) 1.0E E+0 5.0E E E Size Dp (um) 0.0E Size Dp (um) Refractive index λ B sca B abs Real Imag Tundra? Refractive index λ B sca B abs Real Imag Pine? (Chakrabarty et al., 010)

14 Optical Properties Alaskan Duff Particles Absorption Exponent ( nm) Single Scattering Albedo (53 nm) Real Refractive Index (53 nm) Imaginary Refractive Index (53 nm) Ponderosa Duff Particles HULIS (Hoffer et al. 006) ~7 (in acetone) ~ Soot/BC (Bond & Bergstrom, 006)

15 F TOA τ Potential Radiative Effects 1 SSA = SD(1 Acld ) Tatm (1 Rsfc ) [Rsfc (1 R ) Radiative Forcing (W/m nm) Radiative Forcing (W/m nm) 405 nm 53 nm 780 nm PP Duff OC -30 Wavelength 405 nm 53 nm 780 nm AK Duff OC -30 Solar constant: 1370 W/m Wavelength Day Fraction: 0.5 sfc β (SSA)] Cloud cover: 0.6 Solar Transmittance: 0.76 Surface albedo: 0.15 SSA: Single Scattering Albedo

16 Take Home Messages Combustion efficiency decreases with increasing moisture content. Lower combustion efficiency results in more PM, NH 3, and VOCs emissions. Combustion efficiency (CE) and modified combustion efficiency (MCE) may be used to infer PM and NH 3 emission factors. Flaming combustion of high CE produces less PM, but the PM consists of fine soot particles, which, along with PAHs, could be of great health concern. Brown carbon is produced from smoldering combustion, predominantly in the form of tar ball and with optical properties similar to HULIS. Brown carbon may produce substantial direct radiative forcing in the near-uv region compared to conventional organic carbon.

17 Moisture Effects: Some Results Plant Species Downed Material Aboveground Shrub Composite Bitterbrush Manzanita Squaw Carpet Parameter\Fuel Type Litter Duff Soil Leaves Stems Leaves Stems Leaves Stems Carbon % b 5 3% 3% 5% 48% 49% 48% 47% 5 Burned % c 9% 5% 9% 9% 81% 9 98% 83% 93% Moisture Level I (Dry f ) Moisture Level II CE CO OC e.5 (9.3) (1.) EC e NO x NH 3 (1.3) (3.7) e NO e NH OPN e (0.4) (0.44) (0.31) Moisture d % 39% 4 39% 48% 44% Burned % c 7% 47% 1 88% 66% 73% 53% 69% 9% CE CO (97.5) (77.7) (108.1) OC e (66.6) 36.0 (6.8) EC e (7.3) NO x (.) (.9) (4.0) (10.7) NH (6.7) e NO e NH (0.03) 0.31 (0.05) OPN e (1.07) (7.70).73 Moisture d 84% 57% 6 5% 66% 57% Burned % c 8 45% 9% 86% 78% 68% 9% 65% 9 CE Moisture Level III CO (133.1) OC e (61.5) EC e (7.6) NO x (.7) NH (4.5) e NO e NH (0.05) OPN e