Measurement of biomass burning aerosol with an Aerodyne Q-AMS during DABEX

(and DODO)Gerard Capes, Hugh Coe, Paul Williams

AMS main result: the CO plot

Increasing distance from source (N and W) moves along the curve

Scatterplots of all data from all flights DABEX & DODO1

Inorganic mass fraction is insignificant in comparison

Contrast with anthropogenic pollution

Data from the Po Valley in northern Italy (ADRIEX) shows an increase in the Organic to CO ratio as the aerosol ages. A similar trend has been observed for UK pollution during photochemical outbreaks (AMPEP experiment).

Does anything else follow the CO plot?

Scattering coefficients change over the plot – do the optical properties (SSA) of the aerosol change over time?

Total number concentration suggests this is just dilution, i.e. not losing particles to coagulation: any coagulation has likely already occurred before FAAM measured it

PCASP size distributions as function of CO

B158

B166 B162

The shape of the distribution doesn’t correlate strongly with the CO concentration – also points to dilution

Mass spectra – key fragments

• m/z43 Both saturated (C3H7+ ) and oxidised compounds (aldedhydes and ketones

CH2CHO+ CH3CO+)

• m/z44 CO2+ Oxidised compounds

• m/z57 C4H9+ Saturated hydrocarbons (fresh aerosol)

• m/z60 Levoglucosan marker

100

80

60

40

20

0

Rel

ativ

e In

ten

sity

(%

)

20018016014012010080604020m/z

29

43

44

55

60

7369

91115 137 167

181

Domestic Wood Burning Emissions, Switzerland

Rami Alfarra, PSI

Ageing of the aerosol: changes in chemical functionality 43

44

57

60

43

44

5760

43

44

5760

Ongoing work…

• Compare AMS size distributions from SLRs with PCASP to derive relationship between vol and mass distribution – hence get a check on effective density and real part of refractive index

• Any evidence for photochemistry? Check whether chemical changes correlate with ozone formation

• Why do we not see SOA in BB layers?

• Collaborative work with climate models