Wear and Resuspension Particles form Road Traffic - Source and Emissions Factors

Wear and Resuspension Particles

from Road Traffic Sources and Emission Factors

Robert Gehrig, Nicolas Bukowiecki

EMPA Dübendorf (Switzerland)

Urban Air Quality: The Challenge of Non-Exhaust Emissions from Traffic

Sources, Health Risks and Mitigation; Barcelona, Spain July 11-12, 2013

Materials Science & Technolog y

Outline

Emission factors from Swiss field campaigns

Road wear or resuspension?

Tyre wear

Conclusions

R. Gehrig; International Workshop Urban Air Quality, Barcelona, July 2013


Non-exhaust sources

Brake wear

Road wear

Resuspension of road dust

Tyre wear



Motorway in Rural Area (Reiden LU)

MeasuringSite 1

Wind Direction

Road

Background +Traffic Emssions Background Only

MeasuringSite 2

50’000 vehicles per day

Rural Motorway

120 km/h free-flowing

HDV Fraction 15%


cx, motorway traffic = cx, downwind – cx, upwind


Motorway in Rural Area (Reiden LU)



Street Canyon (Zürich Weststrasse)

22’000 vehicles per day

Measuring Site 1

Road

Background Only

Measuring Site 2

Urban TrafficBackground

Background +Traffic Emssions

Urban Street Canyon

Stop and Go Traffic

HDV Fraction 10%


cx, local traffic = cx, street canyon – cx, urban background


Street Canyon (Zürich Weststrasse)



The Empa Rotating Drum Impactor (RDI)

Bukowiecki et al. , Environmental Science and Technology (2005) 39, 5754-5762

Lundgren, D. , J. Air Pollut. Control Assoc. (1969) 17, 225-229.

• Size fractionation by rectangular nozzles

• Aluminum wheels

• Substrate: 6 μm PP

• Bouncing prevention: Apiezon M

1 bar = 1 hour

1 wheel = 4 days

~10 µg total aerosol mass per spot

The Empa RDI is a modification of the original Lundgren impactor:

1.52 x 10 mm

0.68 x 10 mm

0.30 x 10 mm

1.52 x 10 mm

0.68 x 10 mm

0.30 x 10 mm

backup filter for

ultrafine fraction



Concentrations of PM10 and Antimony



Calculation of Emission Factors

Concentration differences

Traffic counts (LDV, HDV) Emission factors

Dilution (from NOx)



Emission factors for selected elements Relative size distribution (Sum=1):

(HDV)


LDV

HDV


PM10 Emission factors Zürich-Weststrasse

Zürich-Weststrasse:

Urban Street Canyon

Stop and Go Traffic

HDV Fraction 10%



PM10 Emission factors Reiden

Reiden:

Rural Main Freeway

120 km/h free-flowing

HDV Fraction 20%



Can this be modelled?




Road wear or resuspension? Tyre wear

Conclusions



How a Mobile Load Simulator works 2400mm

1200mm

940m

m

300mmMMLSMMLS

Model Mobile Load Simulator

Ø

2400mm

1200mm

940m

m

300mmMMLSMMLS

Model Mobile Load Simulator

Ø

direction of moving wheel

and induced air stream

sampling point for dosing of

particles and tracer gas tracer gas



MMLS in operation



View of MLS



Preparation of the test surface

porous asphalt

asphalt concrete



Typical mass size distribution

0.00

0.02

0.04

0.06

0.08

0.10

0.12

0.14

0.1 1 10 100

aerodynamic particle diameter (µm)

dM

/dlo

gD

p

Ambient air

Simulator in operation

Difference (= abraded fraction)



Abrasion from asphalt concrete pavement

0.00

0.05

0.10

0.15

0.20

0.25

0.30

-24

-12

0 12

24

36

48

60

72

84

96

108

120

132

144

156

168

180

min

PM

10 (

µg

/m3)

Red: ambient air concentration

Black: MMLS in operation



PM10 emission factors for fresh particle abrasion

Type of mobile load simulator MMLS

(LDV)

MMLS

(LDV)

MLS

(HDV)

MLS

(HDV)

Type of pavement asphalt

concrete

porous

asphalt

asphalt

concrete

asphalt

concrete

Condition of pavement new new good poor

PM10 emission factor

(mg/km/wheel) 0.25 0 – 0.2 0.7 8

PM10 emission factor (mg/km/LDV) 3 0 - 2

PM10 emission factor (mg/km/HDV) 7 80



PM10 emission factors for resuspension

Type of mobile load simulator MMLS

(LDV)

MMLS

(LDV)

MLS

(HDV)

MLS

(HDV)

Type of pavement asphalt

concrete

porous

asphalt

asphalt

concrete

asphalt

concrete

Condition of pavement new new good poor

PM10 emission factor (mg/km/wheel) 6.3 0.41 11 66

PM10 emission factor (mg/km/LDV) 76 5

PM10 emission factor (mg/km/HDV) 110 660



Resuspension of dust


0

100

200

300

400

500

600

700

0 20 40 60 80

mg

/km

min

porous asphalt

asphalt concrete


Resuspension of dust (detail view)


0

5

10

15

20

25

30

35

40

45

50

0 10 20 30 40 50 60 70

mg

/km

min

porous asphalt

asphalt concrete



Road wear or resuspension?

Tyre wear Conclusions



PM10- emission factors for Fe and Zn

MLS-Messungen (HDV) Fe Zn Tyre

(1% Zn)

Simulator in operation (µg·m-3) 1.68 0.129 12.9

Ambient air (µg·m-3) 0.32 0.008 0.8

Difference (metal abrasion, (µg·m-3) 1.36 0.121 12.1

Emission factor per HDV (mg·km-1) 1.91 0.17 17

MMLS-Messungen (LDV) Fe Zn Tyre

(1% Zn)

Total concentration (µg·m-3) 1 0.02 2.0

Emission factor per LDV (mg·km-1) 0.40 0.008 0.80



Tyre wear particles in PM10

Julie M. Panko et al.; Atmospheric Environment 72 (2013) 192-199



% Tyre wear in PM (Günter Stein et al. VDI 2009)



Tyre abrasion

Photo: V. Dietze, Deutscher Wetterdienst, Referat Lufthygiene Freiburg i.Br.(D)



Conclusions

Abrasion related particles and resuspended road dust were mainly found in

the 1-10 µm particle size range.

In the street canyon and along the motorway, abrasion sources and vehicle

induced dust resuspension made up about 50% of the traffic related PM10

emissions.

Brake wear and resuspension were found to be more mass relevant in the

street canyon than road wear and tire wear.

Road wear was found to be of minor importance for intact pavements, but

damaged pavements can lead to substantial road wear emissions.

Vehicle induced resuspension is not strictly correlated with traffic numbers

but is strongly influenced by available road dust. Difficult to describe with

conventional emission factor models.

Tyre wear seems to be of minor importance.



Acknowledgements

We thank for the financial support by:

Swiss Federal Roads Office (ASTRA)

Swiss Federal Office for the Environment (FOEN)


Wear and Resuspension Particles form Road Traffic - Source and Emissions Factors

Technology

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