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What features of bushfire smoke should be considered in the assessment of public health risk?

CSIRO OCEANS AND ATMOSPHERE FLAGSHIP

Fabienne Reisen| Senior Research Scientist

Australia & New Zealand Aerosol Workshop, Wellington, 10-11 July 2014

Features that influence smoke exposure

1. Fire and fuel characteristics

Features of bushfire smoke & public health risk | Fabienne Reisen2 |

3. Pollutants

2. Smoke plume distribution near populated areas

Fire characteristics – Type, size, intensity


Fires in savannas (grassland) are less intense and have short duration

Fires in eucalypt forest range from surface to crown fires with varying intensitiesPeat lands possess high fuel

loads and can burn over extended periods of time

Fires 06/07 Fires 07/08 Burns

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Fires 06/07 Fires 07/08 Burns

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10-25 g/m3

25-50 g/m3

>50 g/m3

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10-25 g/m3

25-50 g/m3

50-75 g/m3

75-100 g/m3

>100 g/m3

Smoke events in Northeast VIC (2006-2008)


Prescribed burns Wildfires

Duration 3-48 hrs (average of 15 hours) 69 days

Intensity PM2.5: 2-30 fold increase

Max hourly PM2.5: 39-377 mg/m3

Max daily PM2.5: 540 mg/m3

Max hourly PM2.5: 1780 mg/m3

Combustion process

Ignition Flaming Smouldering Extinction


Oxygen supply

Heat transfer

Fuel characteristics (size, structure,

moisture)

Flammable mixture of tar & gas products

CO2 and H20VOCs, NOx, N2O

EC or BC

CO, CH4

NMOC, NH3

PM

)COCO(

COMCE

2

2

Emission factors (g/kg) for species emitted

Tropical forest Savanna Boreal forest Temperate forest

CO2 1643 ± 58 1686 ± 38 1489 ± 121 1637 ± 71

CO 93 ± 27 63 ± 17 127 ± 45 89 ± 32

CH4 5.1 ± 2.0 1.9 ± 0.9 6.0 ± 3.1 3.9 ± 2.4

N2O 0.41 0.16 ± 0.21

PM2.5 9.1 ± 3.5 7.2 ± 3.4 15.3 ± 5.9 12.7 ± 7.5

PM10 18.5 ± 4.1

BC 0.52 ± 0.28 0.37 ± 0.20

OC 4.7 ± 2.7 2.6 ± 1.2


Adapted from Agaki et al (2011) Emission factors for open and domestic biomass burning for use inatmospheric models , Atmos. Chem. Phys., 11, 4039-4072.

Emissions measurements

Laboratory studies – Controlled conditions

– Detailed studies of chemistry

– BUT: assume that fire properties in the lab represent combustion properties in the field

Field studies – ground level sampling– Sample real fires in undisturbed fuel beds

– BUT: issue of heterogeneity of smoke

Aircraft plume sampling– No heterogeneity of smoke

– BUT: expensive, complex and requires extensive plumes; need to take into account ageing of the plume


Ground level sampling at prescribed burns


Flaming combustion of fine fuels

Smouldering combustion of coarse fuels

Controlled experiments in the field


Experimental burning of pure samples of each fuel/size class

Laboratory studies


Pyrotron – 25 m long fire-proof wind tunnel- heading/backing fires- fuel/size class

Working section1.5 m wide and 4.8 m long

Emission factors


Volkova et al. (2014) Fuel reduction burning mitigates wildfire effects on forest carbon and greenhouse gas emission, IJWF.

Fuel load and fuel moisture used to determine MCEMCE used to determine EFs

PM2.5 measurements


Leaf litter burn more slowly and produces more smoke

with lower MCE

Well-aerated grass burns fiercely and efficiently

Feature of bushfire smoke - Emission source

Much of the variation in combustion products between fires is due to the way the fuel burns rather than the composition of the fuel

Combustion properties are critical to determine emission characteristics and are driven by fuel characteristics


Smoke plumes and exposures


Fresh smoke plumeComplex mixture of toxic air contaminants (gases & particles)

CO, PM, VOCs and SVOCs, NOY, Hg

Smoke dispersion and dilution

Atmospheric reactions

Aged smoke plumeOzone formed by photochemical reactionsSecondary organic aerosolsCO, fine particles

Thick smoke (limited photochemistry)

11/12/06 18/12/06 25/12/06 1/01/07 8/01/07 15/01/07

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Hourly PM2.5

(Max hourly PM2.5 = 1.8 mg/m3)

Daily PM2.5

(Max daily PM2.5 = 1.1 mg/m3)

Victorian Alpine fires 2006/07


• Fires started by lightning on Dec 1, 2006

• Area burned: 1,048,238 hectares

• Duration: 69-days

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Bushfire season

2005/2006

Bushfire season

2006/2007

Melbourne (~200km from fires)

Ozone concentrations in smoke plumes


Victorian Alpine fires 2006/07

• Photochemical formation of ozone in smoke trapped in valley

• Max hourly O3 = 150 ppb

• Max hourly PM2.5 = 1893 g/m3

Burn ~ 60 km from Manjimup (WA)

• Photochemical formation of ozone in smoke plume

• Elevated PM2.5 concentrations for 7-9 hrs

• Max hourly O3 = 65.2 ppb

• Max hourly PM2.5 = 227 g/m3

Reisen et al. (2011), Atmos Environ, 45, 3944

Southern California wildfires 2003 (Phuleria et al. (2005) J Geophys Res 110, D07S20)

• Limited photochemistry due to thick smoke

• Hourly O3 decreased from 29 ppb to 15 ppb

Features of bushfire smoke & public health risk | Fabienne Reisen

What pollutants should we consider?

17 |

Particle levels during wildfire events

Location Max hourly

PM [g/m3]

Max daily

PM [g/m3]

Duration

Southern CA (2003) 769 (PM10) ~ 400 (PM10) 7 days

Montana (2000) 340 (PM2.5) > 30 days

British Columbia (2003) 200 (PM2.5)

250 (PM10)> 30 days

Portugal (2003) 500 (PM10)

Northern CA (1999) > 1000 (PM10) > 500 (PM10)

Indonesia (1997) 1800 (PM10)

Sydney (1994) 250 (PM10) 210 (PM10) 8 days

Victorian Alpine fires (2006/07)

Melbourne

1800 (PM2.5) 1100 (PM2.5)

~ 120 (PM2.5)

69 days


Chemical composition of particles

• ToF- Aerosol Chemical Speciation Monitor

• Unit mass resolution, no sizing


`

Particle Inlet (1 atm)

Thermal Vaporization &

Electron Impact

Ionization

Aerodynamic Lens40-1000 nm

eTOFMass Spec

Particle Composition

Gunn Point – Savanna fire season


expect to see ~ 80-90% of PM1 through ACSM lens

Deconvolution of mass spectra into component spectra

• HOA – Hydrocarbon-like organic aerosol

• OOA – Oxidized organic aerosol

• BBOA – Biomass burning organic aerosol

• COA – Cooking organic aerosol

PMF analysis applied to ACSM data sets


Summary

Combustion and fuel characteristics influence smoke production and composition

Emission factors are critical to determine amount of toxic compounds released into the atmosphere

Plume distribution is affected by meteorological conditions and topography

The main hazardous component for public health is fine particulate matter (size and composition)

Impact of other pollutants (e.g. mercury, VOCs) on public health is uncertain


CSIRO Oceans and Atmosphere FlagshipFabienne ReisenSenior Research Scientist

t +61 3 9239 4435e [email protected]

OCEANS & ATMOSPHERE FLAGSHIP

Thank you

Size distribution of bushfire smoke particles


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Number distributions on a bushfire day and on a day without strong smoke impact

24-hour MOUDI distributions on two bushfire days and two days without strong smoke impact

what features of bushfire smoke should be considered in ... reisen, what... · ozone concentrations...

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