angeliki karanasiou source apportionment of particulate matter in urban aerosol institute of nuclear...

Angeliki Karanasiou

Source apportionment of particulate matter in urban aerosol

Institute of Nuclear Technology and Radiation Protection, Environmental Radioactivity Laboratory,

N.C.S.R. Demokritos, Athens, Greece

Background

•Athens has significant air pollution problems •Non-attainment of the EU Air Quality Standard for Particulate Matter is frequent

•Receptor models applied to aerosol chemical composition data can identify the source types (Hopke, 2003)

The fundamental principle of receptor modelling isthat mass conservation can be assumed and a mass

balance analysis can be used to identify andapportion sources of airborne particulate matter in

the atmosphere

Receptor Modelling

Sources Known

•Chemical Mass Balance

(Watson et al., 1990)

Sources Unknown

•Principal Component Analysis (Thurston and Spengler, 1985)

•Unmix (Henry, 2000)

•Positive Matrix Factorization (Paatero and Tapper, 1993; Paatero, 1997)

A mass balance equation can be written to account for all m chemical species in the n samples as contributions from p independent sources

1

p

k

ij ik kjx g f

Where i = 1,…, n samples, j = 1,…, m species and k =1,…, p sources

Positive Matrix Factorization

0, 0ik kjg f 2n

2i=1 1

= m ij ik kj

j ij

X G FQ

s

i = 1,…, n samples

j = 1,…, m species

k =1,…, p sources (user specified)

Xn m

= Gn p

Fj p

source profile, μg/μg

source contribution, μg/m3

Sij: uncertainty in Xij

Aerosol Mass Balance

Aerosol Sampling

•Sampling was conducted on three sites located in Athens urban area•Two aerosol-sampling campaigns at each site were performed during March - December 2002 in Athens, covering the cold and warm period of the year•PM10 and PM2.1 samples were collected

simultaneously over a 24 h period (55 samples)•Aerosol components determined: metallic elements, sulphate, black carbon

Positive Matrix Factorization, PMF2Two separate datasets Fine aerosol specie concentration in PM2Coarse aerosol specie concentration in PM10-PM2

Aerosol concentrations

Important steps in PMF

Preliminary runs to select the number of factors

/

i xij j j

j j j j

xij XS N

mDL mDL

S/N>2: strong variables

Sources

Variables

1 2

1

max ,p

ij ij kj ik

k

S C C x f g

C1: Combined standard uncertainty

2 21 R j ijC S a X SR: variable reproducibility

aj: deviation from the true value

C2: Sampling uncertainty

Uncertainty

Aerosol sources

Fine aerosol

•Road dust•Vehicles•Biomass burning•Marine aerosol•Oil combustion

Coarse aerosol

•Road dust •Soil•Marine aerosol

Fine aerosol sources

BC, SO42-, crustal

metals

diesel and gasoline exhaust emissions

Road dust

Vehicles

0.001

0.01

0.1

1

Cd Pb V Ni Mn Cr Cu Fe Al Ca Mg K Na BC SO4

Con

cent

ratio

n, μ

g/μg

0.001

0.01

0.1

1


Conce

ntr

atio

n, μg/μ

g


mixed source?secondary aerosol

Marine aerosol

Biomass burning

0.001

0.01

0.1

1


Con

cent

ratio

n, μ

g/μg

BC pulled towards zero, Fkey

Dall’Osto and Harrison, 2006

0.001

0.01

0.1

1


Co

nce

ntr

atio

n,

μg

/μg

PMF

marine aerosol

(Wilson, 1975)


Fe: fuel oil (V, Ni)Samara et al, 2005, Atm Environ, 39, 6430-6443

Oil combustion

0.001

0.01

0.1

1


Con

cent

ratio

n, μ

g/μg

Coarse aerosol sources

Road dust

Soil

Scheff and Valiozis, Atm Environ, 24, 203-211, 19900.001

0.01

0.1

1

Pb V Ni Mn Cr Cu Fe Al Ca Mg K Na SO4

Coc

entr

atio

n, μ

g/μ

g

PMF

soil

0.001

0.01

0.1

1


Con

cent

ratio

n, μ

g/μ

g

Coarse aerosol sources

Marine aerosol

(Wilson, 1975)0.001

0.01

0.1

1


Con

cent

ration

, ng/

ng

PMF

marine aerosol

Sources – fine and coarse mode

Typical Mass concentration distribution from "Micron" Inverted Berner impactor measurements

0

10

20

30

40

0.01 0.10 1.00 10.00 100.00

Aerodynamic diameter, Dp [m]

Ma

ss

Co

nc

en

tra

tio

n d

M/D

log

(Dp

)

[g

/m3]

Athens suburban Aerosol

PM2.1

PM10

Certain sources existed in both coarse and fine fractions

Fine fraction includes a ‘tail end’ of the coarse mode

Karanasiou et al.,2007. Atmospheric Environment, 41, 2368–2381.

Positive Matrix Factorization in PM10

0.001

0.01

0.1

1

Cd Pb V NiM

n CrCu Fe Al

CaM

g K NaBC

SO4

0.001

0.01

0.1

1

Cd Pb V NiM

n CrCu Fe Al

CaM

g K NaBC

SO4

0.001

0.01

0.1

1

Cd Pb V NiM

n CrCu Fe Al

CaM

g K NaBC

SO40.001

0.01

0.1

1

Cd Pb V NiM

n CrCu Fe Al

CaM

g K NaBC

SO4

0.001

0.01

0.1

1

Cd Pb V NiM

n CrCu Fe Al

CaM

g K NaBC

SO4

0.001

0.01

0.1

1

Cd Pb V NiM

n CrCu Fe Al

CaM

g K NaBC

SO4

Marine aerosol Vehicles

Biomass burningUnidentified

Unidentified Road/Soil dust

Tracers

Pearson correlation coefficient between source contributions and variable concentrations

Road dust: CaBiomass burning: KMarine aerosol: NaOil combustion: FeVehicles: Ni

Coarse aerosol: no significant correlations between source contributions and variable concentrations

Wind direction vs Source contribution

Fuel oil Marine aerosol

-50

50

150

250

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

-1000

0

1000

2000

3000

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

-200

100

400

700

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

Biomass burning

-200

100

400

700

N

NNE

NE

ENE

E

ESE

SE

SSE

S

SSW

SW

WSW

W

WNW

NW

NNW

Vehicles

-200

0

200

400

600

N

NNE

ENE

E

SSE

ESE

SE

SSE

E

SSW

SW

WSW

W

WNW

NW

NNW

Road dust

•No directional dependence•Sources are dispersed in Athens basin

Conclusions

PMF resolved the major source typesFive sources were identified in fine aerosol representing Road dust, Vehicles, Biomass burning, Marine aerosol and Oil combustion Coarse aerosol sources were Road dust, Soil and Marine aerosolAerosol sources were not clearly identified in PM10 data setNi proved to be a good tracer of vehicle emissions in Athens

Take home messages

Receptor models can provide valuable information on aerosol sources PM10 monitoring could not provide adequate information on aerosol sourcesAerosol organic compounds could yield a resolved factor based on the source of the tracer

Acknowledgements Special thanks to Prof. Pentti Paatero for the fruitful discussions and suggestions on PMF

angeliki karanasiou source apportionment of particulate matter in urban aerosol institute of nuclear...

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