1. JRC-ISPRA 28 April 2011
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F. KARAGULIAN1, L. Clarisse2,
F. Lagler1, M. Barbiere1, R. Connolly1 and, C. A. Belis1
PM formation during a photochemical
episode in the Po Valley: measurements,
mechanisms and source apportionment
European Commission - JRC Institute for Environment and Sustainability, Ispra, Italy
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Université Libre de Bruxelles, Brussels, Belgium
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2. JRC-ISPRA 28 April 2011
Is there any influence of photochemistry
on PM2.5 concentration in the Po valley?
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3. Limito di Pioltello and the Po valley, Italy
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Site of the field campaign:
Limito di Pioltello
Milano
Limito di Pioltello
Date: 17-20 Jun 2009
08-17 July 2009
Po Valley
Limito di Pioltello is located in the Po valley
near the city of Milan
 Large agricultural areas
 Industrial area
 Large residential area
~ 30.000 inhabitants

4. 4-hour experimental time resolution
JRC-ISPRA 28 April 2011
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 Sequential samplers (FAI Instruments and Leckel SEQ47/50) for gravimetric
measurements of PM1 (24h) PM2.5 (4h, 24h) and PM10 (24h), respectively
 Sampling: quartz filter for ion chromatography and offline carbon analysis,
Teflon® filter, (PTFE) for gravimetric and elemental analysis,
on-line semi-continuous OC/EC analyzer Sunset (on hourly basis)
 VOCs sampled on air for 24 hours with CARBOPACK tubes made of activated
charcoal cartridges and analyzed with GC-MS
 Carbonyls groups sampled with 2,4-Dinitrophenylhydrazine-coated (DNPH)
cartridges and analyzed with HPLC
 Size distribution of particles were also collected with an optical particle
counter (OPC, Grimm)

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Results

6. What causes the PM2.5, PM10 summer EPISODE?
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EPISODE
15-16 July 2009
less polluted
NO input ?
increase of O3 levels
EPISODE

7. Ions (PM2.5) correlated with absolute humidity
JRC-ISPRA 28 April 2011
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EPISODE
 Night-early morning: NO3- and NH4+
 Evening:SO4- -

8. NO3- and SO4-- are balanced by NH4+
JRC-ISPRA 28 April 2011
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EPISODE
less polluted
SO 24
3
NO
NH 4+
particles
(secondary inorganic aerosols, SIA)
Seinfeld, J. H., and S. N. Pandis (2006), John Wiley & Sons, Inc.
Vecchi, R., et al. (2009), Environ. Monit. and Assess., 154(1-4), 283-300
Zhang, K., et al. (2007), Atmos. Res., 84, 67-77

9. Secondary Inorganic Aerosols (SIA)
JRC-ISPRA 28 April 2011
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Aqueous phase photochemistry of SO2 and NO2
photochemistry
SO2(g)
NO2(g) + NO3( g )
nighttime
OH •
SO3(g)
N 2O5( g )
H 2O(l )
H 2O(l )
H 2 SO4
HNO3
Aerosol
formation
Heterogeneous
processes
NH 3(g)
Seinfeld, J. H., and S. N. Pandis (2006), John Wiley & Sons, Inc.
Zhang, K., et al. (2007), Atmos. Res., 84, 67-77
Dickerson, R. R. (2003), Nat. Atmos. Dep Progr. Ammonia Workshop
Finlayson-Pitts, B. J., and J. N. Pitts, (2000), Academic Press: San Diego
Karagulian, F., and M. J. Rossi, (2005), 7(17), Phys. Chem. Chem. Phys. 3150-3162
SIA
(NH 4 )2 SO4
(NH 4 )HSO4
NH 4 NO3

10. NH3 in the Po Valley: 7-19 July 2009
satellite observation in the boundary layer
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Large reservoir of NH3
in the Po valley (Italy)
Milano
major NH3 sources:
 fertilizers
 animal waste
Limito di Pioltello
Po Valley
major NH3 sinks:
 wet and dry deposition
volatilization:
 temperature
 relative humidity - - - > nucleation
Averaged NH3 total column
from 7 to 17 July 2009
(data are provided by IASI on the MetOp-A
Meteorological payload)
Clarisse, L., et al. (2009), Nature Geoscience, 2(7), 479-483
The aerial background photographs are © 2008 Google-Imagery © 2008 Terrametrics (http://maps.google.com)

11. PM2.5 dominated by SIA during the EPISODE
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 Si, Fe, Al, Zn, Na, contributed for
less than 1% to the total PM2.5 mass
OM = 1.6 x OC
EPISODE
16th July 2009
Less OM = 1.4 x OC
polluted
8th July 2009
OM = 2.0 x OC
Turpin, B. J., and H. J. Lim (2001), Aerosol Science and Technology, 35(1), 602-610
Vecchi, R., et al. (2009), Environ. Monit. and Assess., 154(1-4), 283-300

12. Fine particles dominate the EPISODE
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Fine particles
Coarse-crustal
(transport, re-suspension)
(2.0-15.0 µm)
ev
en
ing
n ig
ht
(0.25-0.58 µm)
* Data are from ARPA Lombardia (Italy)

13. Wind direction coherent with trends for wind speed
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Coarse particles during
afternoon
(advection + traffic)
Fine particles during
nighttime (local)
00-04h
04-08h
08-12h
12-16h
16-20h
20-24h

14. Photochemical formation of carbonyls
during the EPISODE
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O3
O3
OH •
formation
Sampling on air!
O3 + VOCs → Aldehydes
 vehicle exhausts
 gasoline vapor
•
VOCs + OH → R + H 2O
Lau, A. K. H. et al. (2010), 408(19), Science of the Total Environment 4138-4149.
Photochemical smog
daytime
Atkinson, R., et al. (1984), Journal of Physical Chemistry, 88(6), 1210-1215
Donahue, N. M., et al. (2009), Atmos. Environ., 43(1), 94-106

15. The most volatile OC fraction of PM2.5 correlates with
photochemical oxidation products
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EPISODE
Oxygenated organic
compounds
RT Quartz temperature protocol
for OC/EC thermal desorption
(OC1)
oxygenated
organic compounds
Correlation: r2 ~ 0.7
Matuschek, G., et al. (2007), Environmental Science and Technology, 41(24), 8406
Streibel, T., et al. (2006), Analytical Chemistry, 78(15), 5354

16. JRC-ISPRA 28 April 2011
Comparison between EPA PMF 3.0 and
Multilinear Engine (ME-2)
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17. Source apportionment and receptor models
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Contribution of the kth source
in the jth sample
Mass conservation principle….
p
xij =
∑g
ik f kj
two way model
k =1
Concentration of the jth specie
in the ith sample
i = 1,2,….m (samples)
Concentration of the ith specie
in the kth source
j = 1,2,….n (species) uij is the measured uncertainty
When both gik and fkj are unknown, the Positive matrix Factorization (PMF) model is used (EPA PMF 3.0)
Q
main
=
n
∑∑
i =1
object function
p


 xij −
g ik f kj 
m


k =1


u ij
j =1 





∑
2
min Q main (x, f)
f
best fit

18. Multilinear Engine ME-2
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We can also use a PMF which includes constraints
and pulling equations
 Introducing the Multilinear Engine ME-2
Q = Q main + Q aux
Q
aux
V
=
∑
v =l
aux
Qv
V
=
∑
2
(av − f pj )2 /sv
v =l
softness of the pulling
pulling value

19. Source Contribution Estimation to PM2.5
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Factors
Measured Local Source Profiles
Autopull ME-2 2-way model with
constraints and pulling equations
Paatero and Hopke, PMF-CD, 2010. YP-Tekniikka Ky Rikalantie 6 FI-00970 Helsinki FINLAND
EU Report, Regione Lombardia (under revision)
Amato, F. et al., (2009), 43(17), Atmospheric Environment, 2770-2780
Viana, M., et al. (2008), Journal of Aerosol Science, 39(10), 827-849

20. Wind direction factors for each source
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Nitrate
Sulfate
Traffic
Predominant
from Po Valley
Predominant
from Milano area
Limito
Milano
Enhanced ME-2 2-way model with
constraints
and pulling equations
Po Valley
Uniformly distributed
around the receptor site

21. Higlights
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Diurnal Trend Analysis
Night:
 Low wind speed from East with high RH
 High concentration of sec. nitrate
 Local nucleation and heterogeneous reactions
Afternoon-evening:
 Breeze mainly form South-East
 Traffic re-suspension
 PM likely advected from rural areas
Traffic:
 Maximum values during rush hours

22. PM2.5 diurnal profiles
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23. Conlusions
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 Photochemistry mainly occurs during the EPISODE
 Multilinear Engine with constraints, pulling equation and,
wind direction analysis resulted to be an efficient approach for
data processing
 ME-2 factors resemble source profile more
than PMF factors
 The constraints did not lead to a significant
increase in Q
 ME-2 factors more coherent with advection
and particle properties (size distribution)

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Thanks for your attention
Acknowledgment
Data: Michel Gerboles, Sinan Yatkin, Bo Larsen
Programming: Luca Spano’
General Support: all my friends
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