1. science
2. ecology
3. pollution

How to handle wintertime
road dust and resuspension
Christer Johansson
Associate Professor
Department of Applied Environmental Science, Stockholm university, Stockholm,
Sweden
also Environm Officer at City of Stockholm, Environment and Health Administration
Outline
• ”The road dust system”
– Road dust formation
– Road dust suspension
• List of potential control options
• Results from lab and field studies on the
fomration and suspension of road dust
Ref.:Mats Gustafsson, VTI, Sweden
”The road dust system”
Deposition onto road
surface
Surroundings
• Composition
Surroundings
Direct emissions
Material properties
• Resistability
• Surface structure
• Age
Exhaust
• Etc.
Traffic data
Studded tyre use
• Share
Traffic data
Pavement wear
Depot of
PM10
on road
surface
• Mean stud weight
• Number of studs/tyre
Tyre wear
Traffic data
• Traffic amount
• Composition
Brake wear
• Composition
• Vehicle type
Meteorology
• Humidity
• Speed
(Re)Suspension
• Wind
PM10
in air
Meteorology
• Wind
• Turbulence
Road condition
• Speed
• Driving
characteristsics
• Traffic amount
• Speed
• Humidity
• Precipitation
Sand/salt
Road maintenance
• Gritting
• Salting
• Ploughing
Traffic data
Meteorology
• Traffic amount
• Precipitation
• Composition
• Speed
Airborne removal
Run off
System losses
•Resistability
•Surface structure
Surroundings
•Composition
Direct emissions
Material properties
FORMATION OF
ROAD DUST &
DIRECT EMISSION
•Age
•Etc.
Studded tyre use
Exhaust
•Share
•Mean stud weight
•Number of studs/tyre
Pavement wear
Traffic data
•Traffic amount
•Composition
Tyre wear
•Speed
•Driving
characteristsics
Road maintenance
Brake wear
•Gritting
•Salting
•Ploughing
Sand/salt
Depot of
PM10
on road
surface
Direct emissions
Surroundings
Surroundings
SUSPENSION
OF
ROAD DUST
Traffic data
Depot of
PM10
on road
surface
•Speed
•Vehicle
type
Meteorology
•Humidity
•Wind
Road
condition
- Wetness
- Structure
- Texture
(Re)Suspension
PM10
in air
Potential controling options for road dust production and
suspension
Measure
Action, potential efficiency
Reduce studded tyre use
Reduction of use of studded tyres very important. Prohibition,
fees, information to the public.
Use dust suppressants
Effective during some periods and for some road conditions.
Road sweeping
Not efficient with current machinery for PM10. Removes
material that might otherwise contribute to PM10.
Use sand of low potential for dust
formation
Use filtered/washed crushed stone material (not natural
sand), but impact not quantified in real world conditions.
Plant hedges as ”particle filters”
Minor effects (not well quantified). Hedges likely not feasible
on densely trafficked roads.
Reduce brake wear contribution
Material development? Driving behaviour, speed limits? traffic
regulations? Regenerative brake systems (for electric and
hybrid vehicles)
Speed limits
Effective for studded tyre vehicles. Potentially effective also
for non-studded tyres.
HDV restrictions in populated
areas
Use wear resistant pavement
HDV cause higher suspension and wear than LDV (if nonstudded)
Stone size, stone material, binder. Potentially effective
especially if studded tyres are used.
Reduce tyre wear contribution
Driving behaviour, speed limits? traffic regulations? Type of
tyres, pavement surface structure, tyre air pressures.
Road pavement
Potentially important. Stone material, stone size. Porous
asphalt.
Road test facilities:
Importance of tyres, pavements, sanding for PM formation
Finnish
E.g. Kupiainen (2007) Road
dust from pavement wear and
traction sanding. Monograph of
the Boreal Environment
research, FMI, Finland.
4 tyres driven
by elecrtical
motor
Swedish
E. g. Gustafsson et al. (2008). Properties
and toxicological effects of particles from
the interaction between tyres, road
pavement and winter traction material.
Science of the Total Environ., 393, 226240
Exchangable
pavement
Gustafsson et al. (2008). Properties and toxicological effects of particles from the
interaction between tyres, road pavement and
winter traction material. Science of the Total Environ., 393, 226-240.
Particle production for different pavements
STUDDED versus NON-STUDDED TYRES
2
Quartzite (Kärr), ABS11 STUDDED tyre
PM10 [mg/m3]
1.6
1.2
0.8
0.4
0
0:00
0:05
0:10
0:15
0:20
0:25 0:30 0:35
Tid efter start
0:40
0:45
0:50
0:55
1:00
Particle production for different pavements
STUDDED versus NON-STUDDED TYRES
2
Quartzite (Kärr), ABS11 STUDDED tyre
PM10 [mg/m3]
1.6
1.2
60 – 100 times lower
with non-studded!
0.8
0.4
Quartzite (Kärr), ABS11 NON- STUDDED tyre
0
0:00
0:05
0:10
0:15
0:20
0:25 0:30 0:35
Tid efter start
0:40
0:45
0:50
0:55
1:00
PM10 in a road tunnel
(Stockholm)
Red: Årsta, Blue: Hammarby
PM10
Black: Studded tyre share (% of all cars, right axis)
µg/m3
Feb 2006
Dubbandel
%
Nov 2007
Means to control
Use of studded tyres
Information campaigns
Example from Tornheim, Norway
Norway as an example
Studded tyre fee in Oslo and Trondheim
• Started 1 november 2001
• Now 1200 NOK per year, 400 NOK per month or 30
NOK per day
• ”Pledge” has been used (250 NOK per studded tyre)
• for vehicles > 3,5 ton fee is double
• Aim was 20% studded tyre share
Works well…
Different strategies in different
countries
• Total prohibition
– E.g. Japan, Germany, Holland, Belgium, several states of
USA, Ontario (Canada)
• Seasonal prohibitions
– E.g. Nordic countries, states in USA,
• Technical stud restrictions (Weight, number of
studs per tyre)
– Nordic countries
• Fees on studded tyre usage
– Norway (Oslo, Trondheim, Bergen)
• Information to the public
Studded tyres
•
•
•
Reduced studd weight
Reduced number of studs per tyre
Softened fixing
Dubbkärna i
hårdmetall
Dubbkärna i
hårdmetall
Hölje av
termoplast,
aluminium eller
lättmetallegering
Total höjd 11 mm
Hölje av stål
Stiftlängd
5,8 mm
Total vikt
1,8 - 2,3 g
Stiftlängd
6,6 mm
Total vikt
0,7 - 1 g
c : \ eget \ exc el _9804\ ot her s\ dubb. x l s
Eco stud system (Nokian)
Vehicle speed
-Increased road wear (esp If studded tyres are used)
-Increases suspension (vehicle induced turbulence)
-Increases dilution (vehicle induced turbulence)
-Increases rate of drying of roads (=> increased
suspension)
Increased vehicle speed
1.4
70 km/h
1.2
50 km/h
dm/dlogDp [mg/m³]
1.0
30 km/h
0.8
0.6
0.4
0.2
0.0
0.1
1
Geometric diameter [µm]
10
100
4
0.05
3
0.04
2
0.03
1
0.02
0
0.01
20
30
40
50
60
vsimulator [km h-1]
70
80
PM10/vsimulator
PM10 [mg m-3]
Increased vehicle speed
Vehicle speed important for road wear
ROAD WEAR INCREASE WITH SPEED (IF STUDDED TYRES ARE USED)
Increased vehicle speed
Type of
Share
measurement studded
tyre
Lab. road
100%
test facility
Change in
PM10
Reference
Increase by
factor 3.6
Gustafsson
et al., 2005
Lab. road
test facility
Change Road
in speed condition
Km/h
30 to 50 Dry, no
sand,
quartsite
100%
50 to 70 Dry, no
sand,
quartsite
Ca 70% 72 to 82 Dry
mainly, no
sand
Quartsite
Increase by
factor 1.3
Gustafsson
et al., 2005
Increase by
factor 2
24%
Decrease
with 35%
Johansson
et al.,
2001;
Kristensson
et al., 2004
Hagen et
al., 2005
Road tunnel
Stockholm
Main road
ambient
Oslo
77 to 67 Variabel
Tyre induced
suspension of
particles
Efficiency might
depend on tyre
construction
Kupiainen, 2006
Vehicle speed important for
PM suspension
Mobile tyre-road suspension
20
18
Mass concentration ratio
Swedish: EMMA
Hussein et al., (2007)
May 10; studded/friction
16
September 10; studded/summer
14
September 27; studded/summer
Factors affecting non-tailpipe
aerosol particle emissions from
paved roads: on road
measurements in Stockholm,
Sweden. Atmos. Environ.
42 688-702
12
10
8
Finnish: SNIFFER
6
Pirjola et al., 2008.
Atmosph Environ
4
2
0
0
10
20
30
40
50
60
Vehicle speed (km/h)
70
80
90
100
Road wetness
Affects
- Suspension of particles (reduced if wet)
- Wear rate (higher on wet roads if studded tyres are
used)
- Size of depot (run-off may reduce depot)
Road wetness crucial for PM10
(compare NOx)
200
PM10 µg/m
3
Hornsgatan Dry
150
Hornsgatan Wet
100
50
NOx µg/m
3
0
150
100
50
0
jan2003
feb2003
mar2003
apr2003
maj2003
jun2003
jul2003
aug2003
sep2003
okt2003
nov2003
dec2003
jan2004
feb2004
mar2004
After long period of wet roads: Very high levels of
PM10
PERIODS WITH WET STREETS
PM10 (street-UB)
µg/m3
600
2
Sveavägen
Norrlandsg
Fukt_väg
500
400
1
300
200
1
100
0
Indicates that PM accumulates in depot when roads are wet
24 feb
22 feb
20 feb
18 feb
16 feb
14 feb
12 feb
10 feb
08 feb
06 feb
04 feb
02 feb
31 jan
29 jan
27 jan
0
Dust suppression already 1877:
To reduce suspension due to the horses!
Horse driven
saltwater
carriage
from 1877
(Modern) ”saltwater carriage”
Calcium Magnesium Acetate (CMA)
Daytime (06 – 20)
PM10 concentration reductions
Percentage change in PM10 after treatment of highway CMA or MgCl2
Datum
10 mars
% minskning vid
CMA sträckan
-30%
% minskning vid
MgCl2 sträckan
-
19 mars
-33%
-28%
23 mars
-14%
-23%
6 april
12 april
-24%
-38%
-37%
-44%
See also Norman & Johansson (2006)
Studies of some measures to reduce road dust emissions
from paved roads in Scandinavia. Atmospheric Environment, 40, 6154-6164.
Use of dust suppressants
• Potentially efficient
• Only for special periods and places
• Efficiency may be short lasting
– Dry and hot climate => low efficiency
• Number of different agents with different
properties
Road pavement properties
of potential importance for PM production
Type of pavement (ABT, ABS)
Stone type (granite, quartz etc.)
Stone size (maximum stone diameter)
Stone content
Type of binder
Particle production for different pavements
using studded tyres
6
Granite, ABT16
PM10 [mg/m3]
4
2
0
0:00
0:05
0:10
0:15
0:20
0:25 0:30 0:35
Tid efter start
0:40
0:45
0:50
0:55
1:00
Particle production for different pavements
using studded tyres
6
Granite, ABT16
PM10 [mg/m3]
4
2
Quartzite (Kärr), ABS11
0
0:00
0:05
0:10
0:15
0:20
0:25 0:30 0:35
Tid efter start
0:40
0:45
0:50
0:55
1:00
Particle production for different pavements
using studded tyres
6
Granite, ABT16
PM10 [mg/m3]
4
Quartzite (Hornsberg), ABS16
2
Quartzite (Kärr), ABS11
0
0:00
0:05
0:10
0:15
0:20
0:25 0:30 0:35
Tid efter start
0:40
0:45
0:50
0:55
1:00
Hedges as particle filters
Gritting using sand
- Natural sand or crushed stone
- Washed or unwashed
- Studied mainly in road test
facilities
Sand particle size affects PM10 production
(2-5.6 mm jämförd med 1-5.6 mm)
grain
size of och
traction
sand
10 vs
PM10PM
avsatt
mot
sandmängd
olika storleksfraktioner
10
Grain size
Size
2/5.6 mm
Grain size
Size
1/5.6
3
PM 10 [mg/m ]
12
8
6
4
2
0
Sand: 300 g/m2
Tervahattu & Kupiainen, Nordic Envicon
Sand: 1000 g/m2
Sand: 2000 g/m2
Studded versus non-studded tyres
Tire
type
vs PM 10och olika däcktyper
PM10 avsatt
mot
sandmängd
PM10 [mg/m 3]
3
Studded
tire
Dubbdäck
2
Friction
tire
Friktionsdäck
1
0
Without
sand
Utan sand
Tervahattu & Kupiainen, Nordic Envicon
Sand: 300 g/m2
Sand: 1000 g/m2
Road test lab. studies
8
Unwashed
natural sand,
studded
tyres
Otvättad natursand
0-8 mm,
dubbdäck
Unwashed
natural sand,
non-studded
tyres
Otvättad natursand
0-8 mm,
friktionsdäck
Washed
2-4 mm, studded tyres
Tvättad crushed
kross 2-4stone
mm, dubbdäck
dm/dlogDp [mg/m³]
6
Washed
2-4 mm, studded tyres
Tvättad crushed
kross 2-4stone
mm, friktionsdäck
• Unwashed natural sand produces more PM10 than washed
4
• Studded tyres produces more PM10 than non-studded
2
0
0.1
1
10
Diameter [µm]
100
Road cleaning
Many studies show that sweeping
is inefficient for reducing PM10
PM10 emission potential
– Idaho, sopning efter sandning
Several studies using the TRAKER system by Kuhns et al
Sweepers often inefficient
Road tunnel:
No effect on PM of
high pressure flushing
& vacuuming
200 bar
1400
1200
Supersug
800
Supersug
Tvättåg &
underhållsavstängnin
600
400
200
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
00
:0
0
12
:0
0
PM10 (ug/m3)
1000
06-11-15
06-11-17
06-11-19
06-11-20
06-11-22
06-11-24
06-11-26
06-11-28
06-11-30
Train of road dust cleaning and dust
suppressing, Helsinki
Vehicle
removal
Dust binding
Mech sweeping
Vacuuming
Flushing
Contribution of tyre wear to PM
(non-studded)
Contribution
Paul Boulter, TRL, England
Brake wear
contributes via
direct emission & subsequent
deposition
-Material development?
-Information on driving behaviour?
- Speed restrictions?
-Congestion charging?
Potential controling options for road dust production and
suspension
Measure
Action, potential efficiency
Reduce studded tyre use
Reduction of use of studded tyres very important. Prohibition,
fees, information to the public.
Use dust suppressants
Effective during some periods and for some road conditions.
Road sweeping
Not efficient with current machinery for PM10. Removes
material that might otherwise contribute to PM10.
Use sand of low potential for dust
formation
Use filtered/washed crushed stone material (not natural
sand), but impact not quantified in real world conditions.
Plant hedges as ”particle filters”
Minor effects (not well quantified). Hedges likely not feasible
on densely trafficked roads.
Reduce brake wear contribution
Material development? Driving behaviour, speed limits? traffic
regulations? Regenerative brake systems (for electric and
hybrid vehicles)
Speed limits
Effective for studded tyre vehicles. Potentially effective also
for non-studded tyres.
HDV restrictions in populated
areas
Use wear resistant pavement
HDV cause higher suspension and wear than LDV (if nonstudded)
Stone size, stone material, binder. Potentially effective
especially if studded tyres are used.
Reduce tyre wear contribution
Driving behaviour, speed limits? traffic regulations? Type of
tyres, pavement surface structure, tyre air pressures.
Road pavement
Potentially important. Stone material, stone size. Porous
asphalt.
Thanks for your attention!
Wind speed
- Increases suspension from road
- Speeds up drying of roads
- => possibly more suspension to air
- Increases dilution of PM in air
- Increases deposition of particles onto the road
Wind speed effect
PM10-2.5 & NOx
(Hornsgatan, only dry road)
30
PMcoarse
NOx
25
400
20
300
15
200
10
100
5
0
0
0
2
4
6
Vindhastighet m/s
8
10
12
NOx ug/m3
PMcoarse ug/m3
500
Wind speed effect
Ratio (PM10-2.5)/Nox
dry road (Hornsgatan)
1,8
Ratio PM(10-2.5)/Nox (g/g)
1,6
1,4
1,2
y = 0,0522x + 0,8018
2
R = 0,5542
1
0,8
0,6
0,4
0,2
Wind speed 20 m (m/s)
0
0
2
4
6
8
10
12
Temperature
• Lower temperatures
– make pavement binder less elastic
• cause a more effective abrasion of the more firmly
fixed pavement stones.
– make tyre rubber harder
• may cause larger abrasion
Abatement measures
- Studded tyre restrictions
- Road cleaning (sweeping)
- Gritting practice – sand, salt
- Hedges as PM filters
- Road dust binding
- Vehicle speed restrictions
- Congestion
- Driving behaviour (brake, tyre, road wear)
- Pavement type and construction
there is a potential
for improving air quality along roads and streets where
high concentrations of particles are related to wear particles,
through improving pavement material,
The pavements tested have constructions normal for Nordic
conditions and comparatively durable stone materials typical
for Swedish conditions. In countries where studded tyres
are not used, smaller stone sizes and different constructions
are used as well as local stone material. The durable crystalline
rocks found in the Nordic countries are sparse in
the rest of Europe. Instead, sedimentary rocks, not as durable
are common and used in pavements. How these differences
affects particle production is unknown. Particle production
from pavements is likely to be related to both construction
and material properties and should be studied together
with how pavement properties, such as surface texture
and total wear, vary during the year.
this study strongly support the point that
studded tyres contribute to high particle levels in road and
street environments and give a 60–100 times higher concentration
than friction tyres.
Tyre
?
Exempel Kalifornien
•Mycket damm från omgivningen men även slitage
•Svåra luftkvalitetsproblem, hårda regler
• Rule 1186: renhållningsfordon skall vara PM10-certifierade
• Omtvistad certifieringsmetod
•Metodutveckling (ex.)
• Regenerativluftsponing
• Vaccumassisterad torrsopning
Exempel på PM10-effektiv(?) sopning
Schwartze Enviro Whirl