Wear particles from road traffic – the Nordic experience€¦ · The Nordic situation Snowy and icy roads in winter (October-March) • Studded winter tyres used in Norway, Sweden

Non-exhaust particles

from road traffic – the

Nordic experience

Mats Gustafsson, Ph.D.

Photo: Göran Blomqvist

Outline

• The Nordic situation

• Main sources

• Factors influencing suspension from road surface

• Mitigation

• NORTRIP model

• Knowledge gaps

• Conclusions

The Nordic situation

Snowy and icy roads in winter (October-March)

• Studded winter tyres used in Norway, Sweden and Finland

• Winter road operation with sand and salt

MAIN PARTICLE SOURCES

Main PM10 emission sources

1. pavement wear affected by tyre and pavement properties

2. winter operation affected by use and properties of traction

sanding

3. brake and tyre wear minor sources during the problematic

season (late winter - early spring)

Influence of tyre type on direct PM10

emission

11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00Time [hh:mm]

Studded tyre

Friction tyre (non-studde winter tyre)

Summer tyre

0

1

2

3

4

5

6

PM

10 [m

g m

-3]

30

km/h

50

km/h

70

km/h

Studded winter

tyres

Non-studded

Nordic winter tyres

Summer tyres

11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00Time [hh:mm]

Studded tyre

Friction tyre (non-studde winter tyre)

Summer tyre

0

1

2

3

4

5

6

PM

10 [m

g m

-3]

Stud

ded

tyre share (%

)

Figure: Michael Norman, SLB-Analys, Stockholm

PM10 and studded tyre use in tunnel, Stockholm

Road pavement properties affecting direct PM10

emissions from studded tyre wear

Pavement property Influence on direct emission

Construction No comparable tests. Focus on the most

durable SMA type.

Maximum stone size (Dmax) Higher Dmax results in lower emissions

Rock wear resistance Higher wear resistance results in lower

emissions

Alt 1.: Rubber mixed asphalt Slightly lower emissions than reference

asphalt

Alt. 2.: Porous asphalt No effects yet assigned to the construction.

Low emission, but assigned to more

durable rock

Alt. 3.: Concrete Higher direct emissions than reference

asphalt, but lower total wear.

Lower total emission in reality?

Winter road sanding affects direct and

suspended PM10 emission

Kupiainen et al., 2011, KAPU-project

Uncertainties regarding sources

• The contribution from pavement wear and sand as

well as the interaction (sand wearing pavement)

and its variation in time and space.

• Results from NASTA project (Finland) show that

about 50 % comes from pavement and 25 % from

sand. One street and one sand material in one

season.

FACTORS INFLUENCING

SUSPENTION FROM ROAD

SURFACE

Road surface moisture rules PM10 emission from

road surface Hornsgatan v 12 2008

0

100

200

300

2008-03-13

00:00

2008-03-14

00:00

2008-03-15

00:00

2008-03-16

00:00

2008-03-17

00:00

2008-03-18

00:00

2008-03-19

00:00

Datum

PM

10,

µg

/m3

0

3

6

9

PM10

Vägfukt

Humid Humid Humid

Dry Dry Dry

Christer Johansson, SLB-analys

Winter road salting affects surface humidity

Pavement surface texture influences dust load

0

20

40

60

80

100

120

140

1 1.2 1.4 1.6 1.8 2

DL<

18

0 (

g/m

2)

MTD (mm)

Hjulspår

111021

111220

120302

120316

120413

120525

0

20

40

60

80

100

120

140

0.5 1 1.5 2 2.5

DL<

18

0 (

g/m

2)

MTD (mm)

Mellan hjulspår

111021

111220

120302

120316

120413

120525

Road dust in wheel track

Texture histograms of some Stockholm streets

Traffic?

Direct emission

• Traffic amount and composition

• Studded tyre frequency

• Speed – emission: linear relationship (studded

tyres)

Suspension

• Traffic amount and composition

• Speed

MITIGATION

Mitigation of PM10

1. Minimize the sources

a. Improve wear properties of materials

b. Reduce the wear potential of traffic

2. Minimize suspension to air

a. Remove dust from road surface (sweeping, vacuuming)

b. Bind dust to road surface (dust binding)

c. Adjust traffic (less traffic, lower speed, less heavy vehicles)

3. Optimized strategies combining 1 and 2

Used measures for PM10 mitigation

Measure Norway Sweden Finland

Reduce

studded tyres

Fees in cities

since 2000

Prohibition in

certain streets

since 2010

-

Improved

pavements

Improved since

the 90ies

Tested in

Norrköping

-

Improved sand

material

- - Tests in Helsinki

Dust binding MgCl2 MgCl2, CMA CaCl2

Sweeping/

vacuuming

In combination

with dust

binding

Tests in some

larger cities

Ambitious winter sand

removal. Tests within

KAPU and REDUST

projects

Speed

reductions

Environmental

speed limits

Tests -

Example: mitigation in Stockholm 2011-2012

• Two streets normal operation PLUS treated with

dust binder (CMA), an advanced street scrubber

(high pressure water cleaning, vacuuming and

sweeping) and water flushing.

• Two streets normal operation (references)

Accumulated number of days above 50 µg/m3 PM10

Treated street Hornsgatan

Treated street Sveavägen

Reference street

Folkungagatan

Reference street

Norrlandsgatan

2012

2012

}

} 2012 2009-2011 }

2012 2009-2011 }

Christer Johansson SLB-analys, Stockholm

Acc. num

ber

of

exceedances

2009-2011

2009-2011

Are the Nordic countries reaching limit values?

• Norway – yes, for the last 6 years

• Finland – yes (are using the possibility to subtract

winter sanding/salting events)

• Sweden – no. 2012 was first time ok in Stockholm,

but 2013 looks bad

Seasonal meteorology very important for the

possibilities not to exceed limit values.

Mitigation combination and strategies important for

success.

THE NORTRIP MODEL NON-EXHAUST ROAD TRAFFIC INDUCED PARTICLE

EMISSION MODELLING

The NORTRIP model

Aim:

to gather all relevant information

on non-exhaust emission

processes into a tool for air quality

prediction, planning and

understanding

Denby et al. Atmospheric

Environment 77 (2013) 283-300

Part II recently submitted

The NORTRIP model concept

Surface moisture conditions

Salting

Wearroad, brake and tyre

Sanding

Cle

anin

g

Freezing temperature

Meteorological conditionsParticles

TSPPM10

PM2.5

Deposition

Dra

inag

e

Sand abrasion

Retainedwear

Road surface

Dra

inag

e

Spra

ySp

ray

Plo

ugh

ing

Plo

ugh

ing

Pre

cip

itat

ion

Vapour pressure:

evaporation

Sand crushing

Wetting

Direct

emissions

Surface retention

Temperature, humidity and radiation

Energy balance

Evap

ora

tio

n

con

den

sati

on

Salt

Traf

fic

turb

ule

nce

an

d h

eat

flu

x

Tra

ffic

su

sp

en

sio

n

Win

d s

usp

en

sio

nBruce Denby & Ingrid Sundvor, NILU

Example: Hornsgatan, Stockholm

Bruce Denby & Ingrid Sundvor, NILU

KNOWLEDGE GAPS

Some important knowledge gaps

• How do the wear and winter sand sources

contribute, interact and vary over space and time?

• Interaction between road surface texture –

moisture – chemistry – dust load – dust emission

• Mitigation

• What are the optimal mitigation techniques and

strategies?

• How can winter road operation measures interact

with dust mitigation measures in strategies?

• Modelling: need for data supporting process

modelling including influence of road operation

measures

Conclusions

• Focus on road wear, road operation and

suspension processes

• Sources and processes rather well known but still

lack of data supporting relationships between

influencing factors and emissions

• Mitigation partly successful, but optimized

strategies are missing

• Model NORTRIP promising, but needs further

development

On-going activities

• NRG – Nordic Road dust Group (authorities and researchers)

• NORTRIP II planning

• Finnish REDUST project (Life+) “best practises for road dust mitigation”

• Railroad and road tunnel particle emissions

• Sweeping technologies and strategies

• Stockholm mitigation trials

• Alternative pavement projects (concrete, cinder)

• Pavement grinding project

• Modelling residual salt (MORS I & II) – road moisture modelling input!

• WearTox II (toxicity of wear dust from pavements and brakes)

• …and more.

Thanks for your attention!

Contact: [email protected]

Thanks for your attention!

Contact: [email protected]

Sweeping technologies and strategies

• Street tests

• Controlled tests

• Techniques?

• Strategies – combine sweeping

with other abatement methods

• When, where and how?

EU limit values for PM10 in 2005

Choice of PM10 for the directive means:

• the coarser the particles (within PM10), the more

important for limit values and

• the more effective to mitigate to reach limit values

• Especially important where sources to coarse

fractions of PM10 are strong.

Evaluation of road dust measures in Stockholm

Texture (Sand patch)

RST

PM10 emission from and road dust on concrete

pavement

Asphalt Concrete

Health

• Toxicology show at least as high inflammatory

potential from road wear PM10 as from diesel

particles (Gustafsson et al., 2008)

• Epidemiology show that coarse fraction (PM10-2.5)

in Stockholm has a significant effect on daily

mortality (1.7% per 10 µg/m3) (Meister et al., 2012)

• No reasons NOT to abate the coarse fraction.

0

10

20

30

40

50

60

70

80

Kontroll PM 1 PM 2 PM 3 PM 4 PM 5 PM 6

TN

F-α

pg

/ml

x 1

04 c

ell

s

Inflam

mation p

ote

ntial

PM10 from

granite pavement

PM10 from

quartzite

pavement

PM10 from

Hornsgatan

PM10

from

subway

Diesel particles

Cell studies

Control

Road pavement properties affecting direct PM10

emissions from studded tyre wear

Pavement property Influence on direct emission

Construction No comparable tests. Focus on the most

durable SMA type.

Maximum stone size (Dmax) Lower Dmax results in higher emissions

Rock wear resistance Less wear resistance results in higher

emissions

Alt 1.: Rubber mixed asphalt Slightly lower emissions than reference

asphalt

Alt. 2.: Porous asphalt No effects yet assigned to the construction.

Low emission, but assigned to more

durable rock

Alt. 3.: Concrete Higher direct emissions than reference

asphalt, but lower total wear.

Lower total emission in reality?

Influence of rock material in same pavement construction

worn by studded tyres

Largest stone size (Dmax) and PM

600

500

400

300

200

100

Ef (m

g/f

km

) Rock material properties relates to PM10

emissions

Nordic ball mill value

(wear properties)

0

2

4

6

8

10

12

14

16

18

SMA pavementwith durable rock

Central EuropeanAC diorite

Central EuropeanAC limestone

No

rmal

ize

d c

Pavement type

Studded winter tyres

Studded tyres at 50 km/h on Nordic and C-

European pavements

Non-studded tyres at 50 km/h on Nordic and C-

European pavements

0

1

2

3

4

5

6

7

8

9

10

11


Central EuropeanAC diorite

Central EuropeanAC limestone

No

rmal

ize

d c

Pavement type

Summer tyres

Nordic winter tyres

C-European winter tyres

Dust binding in Nordic cities

Trondheim

Oslo

Gothenburg Linköping

Norrköping

Stockholm Helsinki

MgCl2

CMA

Sugar

CMA/salt

CMA

MgCl2

CMA

CaCl2

+ Austria, the Netherlands, Germany, UK…

Aims:

Investigate what micro-textural properties within

stone material that affect formation of inhalable

particles and to

investigate the toxicity in airways of coarse and fine

pavement wear particles in relation to physical,

chemical and morphological particle properties.

RIVM finances the addition of brake wear particles

to the study

WearTox II

Influence of tyre type (limestone pavement)

Influence of tyre type (limestone pavement)

Influence of tyre type (diorite pavement)

Influence of tyre type (diorite pavement)

Evaluation of road dust measures in Stockholm

WDS

Effect of measures on PM10 on Hornsgatan

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

2009/2010 2010/2011 2011/2012 2011/2012 städning

2011/2012 spolning

2011/2012 CMA

Vägdammsdagar

Förhållande Ho/Fo

Road dust days (dry conditions)

Ratio treated/non-treated street

Sweeping Flushing Dust

binding

CMA

Previous seasons and non-

treated

Road dust (DL<180 µm) on streets

Ions on street surface (Hornsgatan)

0

2

4

6

8

10

12

14

16

18

2011-10-21 2011-12-20 2012-03-02 2012-03-02 2012-03-16 2012-03-16 2012-04-13 2012-05-25

Män

gd (

g/m

2)

Cl

NO3-N

SO4-S

Ca

Mg

Na

K

Fo

Ac

PM10 emission from and road dust on concrete

pavement

Asphalt Concrete

The NORTRIP model concept

Surface moisture conditions

Salting

Wear road, brake and tyre

Sanding

Cle

an

ing

Freezing

temperature

Meteorological conditions

Particles

TSP

PM10 PM2.

5

Deposition

Dra

ina

ge

Sand abrasion

Retained wear

Road surface

Dra

ina

ge

Sp

ray

Sp

ray

Plo

ugh

ing

Plo

ugh

ing

Pre

cip

ita

tio

n

Vapour

pressure:

evaporation

Sand

crushing

Wetting

Direct

emissions

Surface retention

Temperature, humidity

and radiation

Energy

balance

Eva

po

ratio

n

co

nd

ensation

Sa

lt

Tra

ffic

tu

rbu

lence

an

d h

ea

t flu

x

Tra

ffic

su

sp

en

sio

n

Win

d s

usp

en

sio

n


Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May0

200

400

600

Hornsgatan 2010-2011: Emissions and mass balance

Em

issio

n (

g/k

m/h

r)

Date

Total

Direct dust

Direct sand

Suspended


50

100

150

Mass lo

adin

g (

g/m

2 )

Date

Suspendable dust

Road salt(Na)

Dissolv ed salt(Na)

Suspendable sand


100

200

300

400

Mass lo

adin

g (

g/m

2 )Date

Non-suspendable sand

Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May-2000

-1000

0

1000

2000

Rate

s (

g/k

m/h

r)

Date

Road dust production

Road dust sink

Production and sinks of road dust


200

400

600

Hornsgatan 2010-2011: Emissions and mass balanceE

mis

sio

n (

g/k

m/h

r)

Date

Total

Direct dust

Direct sand

Suspended


50

100

150

Mass lo

adin

g (

g/m

2)

Date

Suspendable dust

Road salt(Na)

Dissolv ed salt(Na)

Suspendable sand


100

200

300

400

Mass lo

adin

g (

g/m

2)

Date



-1000

0

1000

2000

Rate

s (

g/k

m/h

r)

Date


Road dust sink


500

1000

1500

Hornsgatan 2010-2011: Traffic

Traf

fic v

olum

e (v

eh/h

r)

Date

Total

Light

Heav y

Light studed

Light winter


30

35

40

45

50

Traf

fic s

peed

(km

/hr)

Date

Light

Heav y


0.5

1

1.5

2

2.5

Saltin

g/sa

nding

(g/m

2 )

Date

Sanding/10

Salting(Na)

Salting(Mg)


200

400

600

Hornsgatan 2010-2011: Emissions and mass balance

Em

issio

n (

g/k

m/h

r)

Date

Total

Direct dust

Direct sand

Suspended


50

100

150

Mass lo

adin

g (

g/m

2)

Date

Suspendable dust

Road salt(Na)

Dissolv ed salt(Na)

Suspendable sand


100

200

300

400

Mass lo

adin

g (

g/m

2)

Date



-1000

0

1000

2000

Rate

s (

g/k

m/h

r)

Date


Road dust sink

Example of NORTRIP model application Studded tyre season

Sanding and salting events

Wet surface retention

Road wear dust loading Suspendable

sand Salt

Dry surface suspension

Direct and suspended emission


Examples: HCAB, Copenhagen


Winter operation strategies for minimized PM

emissions

Normal winter operation, Southern Sweden

Winter

Studded tires

Salting NaCl

Gritting

AprilOctober November December January February March

Example of alternative strategy

Winter

Studded tires

Salting MgCl2 or CaCl2

Gritting

Dust binding

and anti-icing CMA

March AprilOctober November December January February

Relative differences at 50 km/h

1

10

100

1000

10000

100000


AC diorite AC limestone

No

rmal

ize

d c

Pavement type

Summer

Nordic winter

C-European winter

Studded winter

Report on pavements and PM10

Available at www.trafikverket.se

Are the Nordic countries reaching limit values? N

um

ber

of

exceedances (

PM

10)

Year

Oslo

Strategies: REDUST (Finnish Life+ project)

2011-2014

• WP1 Demonstrating and finding the best practices to

mitigate PM10 road dust

• WP1.1 Winter time practices

• WP1.2 Dust binding practices

• WP1.3 Street cleaning practices

• WP1.4 Emission factor development and mitigation

potential of the practices

• WP2 Development of an optimized strategy to mitigate

urban PM10 road dust

• WP3 Dissemination of results

www.redust.fi

Wear particles from road traffic – the Nordic experience€¦ · The Nordic situation Snowy and icy roads in winter (October-March) • Studded winter tyres used in Norway, Sweden

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