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Particle Number Size Distributions at an Urban Site in southern Sweden: Estimates of the Contribution of Urban Particle Sources. Paper 8A1, Session 8, IAC 2006. - PowerPoint PPT PresentationTRANSCRIPT
Particle Number Size Distributions at an Urban Site in southern Sweden:
Estimates of the Contribution of Urban Particle Sources
Erik Swietlicki1, Andreas Massling1, Ingela Dahlberg1, Jakob Löndahl1, Adam Kristensson2, Henric Nilsson3, Susanna
Gustafsson3 and Matthias Ketzel4
1Division of Nuclear Physics, Lund University, Lund, Sweden2Department of Chemistry, Copenhagen University, Copenhagen, Denmark3Environment and Health Protection Board, City of Malmö, Malmö, Sweden
4Department of Atmospheric Environment, National Environmental Research Institute, Roskilde, Denmark
Research funded by the Swedish FORMAS
Paper 8A1, Session 8, IAC 2006
Motivation – Human Health
•CAFE estimates that fine particles (PM2.5) and ozone combined are responsible for 370,000 premature deaths each year in EU25, and the loss of 3.6 millions years of life annually.
(CAFE: Impact Assessment of the Thematic Strategy on Air Pollution and the Directive on “Ambient Air Quality and Cleaner Air for Europe”, SEC(2005)1133, Brussels, 21 Sept. 2005 (http://www.cafe-cba.org/)
•WHO estimates that exposure to fine particulate matter in outdoor air leads to about 100 000 deaths (and 725 000 years of life lost) annually in Europe. (WHO, World Health Report 2002, Geneva)
• For Sweden, Forsberg et al. (2005) estimated that the current population exposure to PM10 results in 5000 premature deaths annually.
RIP
(RIP = Respired Inhalable Particles … and died!)
Motivation – Climate
•Size-resolved emission data are often close to source (tunnels, tail-pipe, street canyons…).
•Regional/global scale models need the size distributions of the urban plume crossing over the city limits.
•Are aerosol dynamics (coagulation, condensation…) fast enough to significantly modify the urban plume aerosol size distribution?
0.01 0.1d p in µm
0x10 0
4x10 3
8x10 3
1x10 4
2x10 4
dN
/dlo
g(d
p)
AER O 3
1.E-04
1.E-03
1.E-02
1.E-01
1 10 100 1000Particle diameter (nm)
dN/d
logd
p (rel
ativ
e sc
ale)
Wood combustion
Traffic
Measurements sites – Southern Sweden
Vavihill
Malmö
Court House
Malmö
55 36' 23'' N, 13 0' 9'' E
Malmö SMPS system•Own design, manufacture and calibration
•Medium-long DMA (Vienna-type, own manufacture)
•Particle counter: TSI CPC 3760A
•10-551 nm
•Closed-loop (driers and filters in loop)
•Scanning mode (up and downscan, Labview software)
•CPC desmearing to improve time resolution
•Time resolution: 3 min
•RH and T sensors for data QA
•Measurements started April 2005
Court House, Malmö, Sweden(Urban Roof-top Measurement Site)
• Gas phase: NO, NO2, SO2, CO
• PM2.5, PM10
• Meteorological data, nearby mast
Environment and Health Protection Board,
City of Malmö, Sweden
The Vavihill siteRegional background – Southern Sweden
•Twin-DMPS (3-900 nm)
Aerosol Size DistributionsUrban Roof-top – Malmö, Sweden
April 2005 – April 2006
Mean Percentiles
Median
70%
90%
30%
10%
6 980 cm-3
StatisticsApril 2005 – April 2006
Particle concentration
Mean Median Max Min
Number (cm-3) 6 980 5820 89 200 559
Surface (µm2/cm3) 187 153 2 230 12.6
Volume (µm3/cm3) 7.27 5.44 102 0.12
Aerosol Size DistributionsUrban Roof-top – Malmö, Sweden
Mean PM2.5 10 µg/m3
National holidays have been omitted.
Aerosol Size DistributionsUrban Roof-top – Malmö, Sweden
April 2005 – April 2006Average Size Distributions
50 nm
Weekdays
Average size distributions for the various wind sectors.
Aerosol Size DistributionsUrban Roof-top – Malmö, Sweden
Harbour
Malmö
Harbour
Malmö city
Court House, Malmö(urban roof-top measurement site)
Sources to the urban aerosol (size distribution):
• Long-range transported regional background
• Urban sources (road traffic, ship traffic, industry,…)
• Heating: oil and wood combustion (minor sources in Malmö)
+ aerosol dynamics transforming the size distribution within the city limits (condensation, coagulation, deposition, dilution)
Attempt to separate:
•Urban contribution to the urban roof-top concentrations (Urban measurements – Regional Background)
• Local traffic contribution (Highest 20% [NO]/[NO2] ratios)
• Ship plumes (High [SO2], wind direction from harbour area)
Estimated Traffic ContributionMalmö Urban Roof-top
July 2005
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
10 100 1000Dp (nm)
dE
/dlo
gD
p (
x 10
14 k
m-1)
0
500
1000
1500
2000
2500
dn
/dlo
gD
p (
cm-3)
Average fleet, tunnel
Traffic model
Method suggested by Janhäll et al. (2004)
Local traffic contribution: Cases with highest 20% [NO]/[NO2] ratiosUrban background: Cases with lowest 20% [NOx] subtracted
Size-dependent emission factors derived from a Swedish tunnel study (Kristensson et al., 2004) are shown for comparison.
Tunnelstudy
EstimatedTraffic
Derived Traffic Contribution
Traffic distribution - Number
0
1000
2000
3000
4000
5000
6000
7000
8000
1 10 100 1000
Dp in nm
dN
/dlo
gD
p (
cm-3
)
Mode 12.9
Mode 25.3
Mode 67.7
Mode 1000
Mode 80
Mode 70
Sum
Mode GMDs: 13 nm, 25 nm, 68 nm
Rådhuset
Ship Traffic Contribution
Ship plumes from Malmö City
Harbour
0
20
40
60
80
100
120
140
160
00:00 02:00 04:00 06:00 08:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 00:00
SO
2 co
ncen
tratio
n (µ
g/m
3 )
SO2
ShipPlumes
Nucleation mode particlesfrom homogeneous nucleation
of H2SO4 + H20 ?
Urban Roof-top – Regional BackgroundVavihill – Malmö
Urban site(Malmö)
Backgrund(Vavihill)
Malmö City Contribution to the Urban Roof-top Aerosol
Mode GMDs: 8 nm, 38-39 nm, 95-100 nmFresh aerosol (traffic, ships,..) + processed within city limits
Weekdays Weekends
Malmö CityContribution
MalmöCity
Contr.
Malmö City Contribution to the Urban Roof-top Aerosol
Mode GMDs: 8 nm, 38-39 nm, 95-100 nmFresh aerosol (traffic, ships,..) + processed within city limits
Malmö CityContribution
Weekdays July 2005
Malmö CityContribution
Traffic
Ship?
Harbour Inlet
Tetramodal distribution
0
5000
10000
15000
20000
25000
30000
35000
10 100 1000
Dp
dN
/dlo
gD
p
Original distr.
Mode 1
Mode 2
Mode 3
Mode 4
Mode 1-4
Mode 1
N1(cm-3)
CMD1 (nm)
Sigma1
12500 8 1.64
Mode 2
N2(cm-3)
CMD2 (nm)
Sigma2
11100 47 1.45
Mode 3
N3(cm-3)
CMD3 (nm)
Sigma3
2300 115 1.6
Mode 4
N4(cm-3)
CMD4 (nm)
Sigma4
5100 24 1.6
The urban contribution seems to be from road traffic plus ship movements in the harbour.Could the size shift from 25 nm to 40 nm be caused by aerosol dynamics instead?
Method
Ketzel, M. and Berkowicz, R. (2005): Multi-plume aerosol dynamics and transport model for urban scale particle pollution. Atmospheric Environment 39, 3407-3420.
AERO3 Model (E. Vignati, JRC)
InputAssumptions:The background size distribution at Vavihill (3-modal)The estimated traffic emission size distribution (4-modal)Average wind speed = 4 m/sEmission density for Malmö = 230 (pt/cm3) m/s
Modelling Urban Aerosol Dynamics
Question: Can particles grow from 25 to 40 nm in the urban background?
0.01 0.1d p in µm
0.0x10 0
4.0x10 3
8.0x10 3
1.2x10 4
1.6x10 4
2.0x10 4
dN
/dlo
g(d
p)
AER O 3
t= 0 , 1 , 3 , 5 H O U R S
Regional background, Urban Traffic Emissions and Dilution,No Aerosol Removal process
Modelling Urban Aerosol Dynamics
0 h
1 h
3 h
5 h
Emissions
0.01 0.1d p in µm
0.0x10 0
4.0x10 3
8.0x10 3
1.2x10 4
1.6x10 4
2.0x10 4
dN
/dlo
g(d
p)
AER O 3
t= 0 , 1 , 3 , 5 H O U R S
0.01 0.1d p in µm
0.0x10 0
4.0x10 3
8.0x10 3
1.2x10 4
1.6x10 4
dN
/dlo
g(d
p)
AER O 3
Regional background, Urban Traffic Emissions and Dilution,No Aerosol Removal process
Regional background, Traffic Emissions, Dilution, Coagulation,Deposition with u*=1.33 m/s, No condensation
Modelling Urban Aerosol Dynamics
0 h
1 h
3 h
5 h
0.01 0.1d p in µm
0.0x10 0
4.0x10 3
8.0x10 3
1.2x10 4
1.6x10 4
2.0x10 4
dN
/dlo
g(d
p)
AER O 3
t= 0 , 1 , 3 , 5 H O U R S
0.01 0.1d p in µm
0.0x10 0
4.0x10 3
8.0x10 3
1.2x10 4
1.6x10 4
dN
/dlo
g(d
p)
AER O 3
0.01 0.1d p in µm
0x10 0
4x10 3
8x10 3
1x10 4
2x10 4
dN
/dlo
g(d
p)
AER O 3
Regional background, Urban Traffic Emissions and Dilution,No Aerosol Removal process
Regional background, Traffic Emissions, Dilution, CoagulationDeposition with u*=1.33 m/s, No condensation
Regional background, Traffic Emissions, Dilution, Coagulation, DepositionCondensation, Growth rate=6 nm/h, Condensing vapour conc. = 1.85 x 108 molec cm-3
Modelling Urban Aerosol Dynamics
0 h
1 h
3 h
5 h
Regional background, emissions, dilution, coagulation, deposition, condensation
0.01 0.1d p in µm
0x10 0
4x10 3
8x10 3
1x10 4
2x10 4
dN
/dlo
g(d
p)
AER O 3
0.01 0.1d p in µm
0.0x10 0
4.0x10 3
8.0x10 3
1.2x10 4
1.6x10 4
2.0x10 4
dN
/dlo
g(d
p)
AER O 3
t= 0 , 1 , 3 , 5 H O U R S
Modelling Urban Aerosol Dynamics
0 h 0 h
1 h1 h
Regional background, urban traffic emissions and dilution only
• Aerosol dynamics alone can not grow the 25 nm traffic mode to 40 nm. This latter mode is probably caused by ship traffic.
• Aerosol dynamics is nevertheless likely to affect the urban size distribution even within the city limits of a medium-sized city.
• The urban plume contribution to the rural bakground is not simply a linear combination of regional background plus urban emissions and dilution.
Particle Number Size Distributions at an Urban Site in southern Sweden: Estimates of the Contribution of Urban
Particle SourcesErik Swietlicki, Andreas Massling, Ingela Dahlberg, Jakob Löndahl, Adam
Kristensson, Henric Nilsson, Susanna Gustafsson and Matthias Ketzel
> Conclusions <
• The dominant sources to the urban roof-top aerosol size distribution were determined
and were identified as
• Long-range transport
• Local road traffic
• Ship traffic
• Aerosol dynamics play a role
Thank you for your attention!