Examination of pollution in soil
and water along roads caused by
traffic and the road pavement
Danish Road Institute
Report 104
2000
0 LQLVWU\RI7U DQVSRUW'HQPD UN
1
1
Road Directorate
Danish Road Institute
Elisagaardsvej 5
P.O. Box 235
DK-4000 Roskilde
Denmark
Telephone: +45 46 30 70 00
Telefax:
+45 46 30 71 05
[email protected]
www.vd.dk
Title:
Authors:
Photos:
Dated:
Copyright:
Published by:
ISBN:
ISSN:
2
Examination of pollution in soil and water along
roads caused by traffic and the road pavement
Knud A. Pihl, Jørn Raaberg
Nicolaj Lehmann, DHI, Lars Bo Christensen, Hedeselskabet
December 2000
Road Directorate, All rights reserved
Road Directorate, Danish Road Institute
87-90145-69-0
0909-1386
2
Examination of pollution in soil
and water along roads caused by
traffic and the road pavement
Knud A. Pihl
Jørn Raaberg
Danish Road Institute
Report 104
2000
3
3
4
4
Table of contents
5
Abstract
6
Introduction
7
Criteria for the choice of field sites
8
Choice of locality
9
Instrumentation of field sites
11
Results
13
Conclusion and discussion
18
Further work
19
References
19
5
Abstract
In 1997, the Road Directorate in Denmark decided to start an investigation which
should supply documentation of the type and amount of pollution which is spread
from roads and traffic in Denmark. It was decided to establish two field study sites,
one in eastern Denmark and another one in western Denmark.
During the spring of 1998, two study sites were established. Certain criteria were
drawn up for the placing of the stations of which the following can be mentioned:
traffic density, placing in relation to the most common wind direction, the nature of
the surroundings and the accessibility and safety for the personnel. A screening test of
soil and water samples was made on six possible sites. On the basis of these results,
two suitable sites were chosen.
The Danish field study sites are a part of the European project POLMIT, where six
other countries from Finland in the north to Portugal in the south each have two field
study sites established along similar principles. It is therefore possible to compare
results from 14 field sites in Europe.
When the POLMIT project has been completed, the Road Directorate expects to
continue the pollution measurements in Denmark.
Results are now available from the two field sites taken throughout one year. As
expected, large variations in the contents of chloride and sodium ions during the
course of a year were found, since large amounts of de-icing salts are used in Denmark. Apart from the high concentration of sodium, a high zinc content is also found,
which is one of the metals for which measurements are being made. These two
components are the only ones which exceed the Danish rules for content in drinking
water.
At both field sites increased concentrations of polyaromatic hydrocarbons (PAH) and
NVOC (non-volatile organic compound) have been found in relation to what is
permissible in drinking water. Furthermore at the eastern site, the values of THC (total
hydrocarbon) is too high. It has been noted that all parameters are highest in winter
and that the pollution is greatest closest to the road.
The paper presents the results from the Danish tests.
6
6
Introduction
In a modern public agency it is necessary to take environmental questions into consideration, both due to legal issues and also because the public agency must lead with
a good example. At present there are no demands on Danish road owners to publish
green accounts, environmental statements, etc for a single road stretch or for the entire
road network. However, it should be of importance for road owners to be able to
document that the road network is managed in a responsible manner in relation to the
environment as regards consumption of resources and inconvenience to the
surroundings.
The Road Directorate in Denmark has evaluated in its environmental strategy from
1996 that there is a need to strengthen its knowledge and therefore a number of
projects have been started in order to throw light on the influence of roads on the
environment.
One of these projects, called Environmental Monitoring has examined the amounts of
pollution of the areas near a road (water and soil) by establishing two environmental
study sites at motorway networks in Denmark.
The Road Directorate is also participating in the EU-project “POLMIT - Pollution of
Groundwater and Soil by Road and Traffic Sources: dispersal mechanisms, pathways
and mitigation measures”, in which seven countries participate. Thereby data and
experience from other countries becomes available.
The Road Directorate co-operates with two Danish institutes, DHI - Institute for the
Water and Environment, and with Hedeselskabet in this project concerning the soil
and water environment.
Parameters/polluting compounds
Which polluting compounds can be found in soil and water as a result of roads and
traffic? Previously, there was a great deal of focus on the heavy metal lead, which was
added to petrol. However, lead has not been added to petrol in Denmark since 1994.
Brakes, rust, paint, wear of tyres and exhaust gasses contribute to remains of
polyaromatic hydrocarbons (PAH) and also some heavy metals in the environment.
The maintenance of roads leads to spread of de-icing salts during winter and traffic
itself rubs some of the asphalt layers off, which are spread to the surrounding areas.
In the POLMIT project generally and from the samples of the Danish environmental
field sites it was decided to make analyses of the substances shown in table 1:
Metals
Anions
Organic parameters
Various
Cd, Cu, Cr, Pb, Zn, Ca, K, Mg and Na
Cl- and SO42PAH, NVOC and THC
Suspended substances
Table 1. Parameters which are determined in the POLMIT project, including the Danish field
study sites
7
7
Criteria for the choice of field sites
Some criteria for the field sites were established at the beginning of the project, but
when it became apparent that it would not be possible to comply with all criteria at the
same field site, a priority list of these criteria was made. Table 2 shows the criteria and
the priorities given (3 highest, 1 lowest).
Priority
3
3
3
2
2
2
1
1
Criteria
In order to ensure that effects of traffic can be
measured Annual Daily Traffic (ADT) should be
greater than 10,000.
Drainage system There should be a retention pond, which makes it
possible to make measurements of the cleaning effect
of the pond. Furthermore, it is a criteria that no water
comes into the pond from other areas than run-off
from the road.
The road should run in a north/south direction, since
Direction
the prevailing wind in Denmark is westerly.
Pollution from
No other larger road or railway at a distance of 200 m
other sources
or industry or habitation at a distance of 500 m should
be seen.
Age of road
An attempt should be made to find a road which has
been trafficked for several years, so that it should be
possible to obtain some measurement results. A screening test should prove that analyses show a result.
Surroundings
The areas next to the road should preferably be open,
a meadow or field. The road should be prone to winds.
There should preferably be no noise barrier and
woods, major hedges within 500 m.
Groundwater
Water from drainage of the groundwater, primary as
well as secondary to the pond, should be minimal. The
road should preferably be situated in a very low
embankment.
Road pavement It is preferred that emergency lane during its entire
on emergency
lifetime has been paved. Since most emergency lanes,
lane
however, ordinarily have surface gravel, but have been
asphalted in recent years, such a change in pavement
must be accepted.
Parameter
Traffic density
Table 2. Priorities of the criteria made for the field sites in Denmark
In the POLMIT project the requirement was that the actual road stretches should have
been trafficked for a minimum of ten years.
8
8
Choice of locality
In order to place the two Danish field sites so that they fulfilled the criteria, 17
possible localities were inspected during the summer and autumn of 1997. Three
localities in Jutland and three localities on Zealand were selected which complied with
most of the criteria. Screening tests [1] were carried out on samples of soil from the
shoulder and run-off from the road. Tests were made covering the parameters stated in
the POLMIT project, but also for a number of other compounds, a total of more than
100. The screening showed, that there were traces of compounds, such as softeners
and Methyl Tertiary Butyl Ether (MTBE) from petrol, which must be watched in the
future.
Based on the data found during the screening and the criteria established, it was
decided to choose the localities on motorway 14, km 16.7 (Vejenbrod) and motorway
70, km 197.4 (Rud), (see figure 1).
Danmark
Randers
Rud
Århus
Helsingør
Vejenbrød
København
Figure 1. Placing of the two Danish environmental field sites
The choice fell on Rud, even though this road had only been trafficked for four years,
when the study commenced, and thus did not comply with the criteria of ten years
made by POLMIT. There were however, many other considerations which made the
site extremely suitable. This site makes it possible to follow a “young” road and its
pristine surroundings. The ADT for 1997 was counted at 22,000 vehicles with an lorry
percentage of 19.
9
9
By choosing the of locality at Vejenbrod, a road was selected which has been
trafficked for more than twenty years. It was also the road with the highest lead
content in the soil which was found during the screening test.
The site was in open country, south of Niverød, with a retention pond on the western
side of the road close to the study site. The pond was overgrown, and it is likely that
the sedimented material had not been cleared during the entire running period of the
road. The ADT for 1997 was counted at 29,000 vehicles with a lorry percentage of
6%.
10
10
Instrumentation of field sites
In the POLMIT project it was decided which samples should be taken and which
analyses should be made on these samples. All fourteen field sites in the seven
countries in Europe were constructed in the same way and the analysis data should be
available for a period of 12 months. It was furthermore decided only to take samples
from the one side of the road. The only exception was collection of groundwater,
where samples were taken from both sides of the road.
At the Danish field sites all samples were taken on the eastern side of the road, since
the prevailing direction of the wind is from the west.
Several methods of collecting run-off from the road were discussed, and the choice
fell on the method described below, since the Dutch participants had good experiences
with exactly that type [2]. At each field, site the run-off was caught by a gutter which
was 1 meter in length and 15 cm in width and the gutter was placed alongside the
asphalt edge dug into the top layer of the soil (figure 2). The gutter was separated into
10 sections and the water from each of these sections was collected into a bottle with a
volume of 25 litre. Representative samples were taken from each bottle, the samples
were mixed and analysed every month.
At four different distances from the road pavement, samples were collected, including
splash from the road and rain precipitation in a total deposition sampler (figure 3). The
total deposition sampler consists of four gutters which have an area of 0.016 m2,
where the total precipitation (wet/dry) is led into a collection bottle which is dug into
the ground. The equipment has been used successfully in the Netherlands.
Figure 2. Run-off sampler
Figure 3. Total deposition sampler
Furthermore, in two positions 3 and 6 meters from the edge of the road, samples of the
soil solution at a depth of 0.35 m was taken with an equipment produced in Denmark
(Prenart). The equipment consists of a porous cup situated above ground level which
sucks soil solution with the aid of a mechanical water pump, and in that way
continuously takes samples of soil solution.
11
11
On both sides of the road groundwater pipes were installed to take samples of the
secondary groundwater which at the Danish sites was found two to three meters below
the surface.
The road run-off was analysed every month, whereas the total deposition, soil solution
and groundwater was analysed once every three months. Soil samples were taken once
during the twelve month period. Soil samples were taken three, six and twenty meters
from the edge of the asphalt pavement.
Apart from the equipment mentioned above, a rain gauge was installed at each field
site. It was connected to a data logger which registered rain continuously. For the sake
of comparison, data was also collected from the nearest weather station of the Danish
Metrological Institute.
12
12
Results
This paper presents a summary of the Danish data. All the results from the Danish
study sites will be shown in the final report from POLMIT, where the results from the
other countries also will be available.
Run-off
For the samples of run-off, conductivity was measured. Figure 4 shows a graphic
presentation of the conductivity as a function of time. A considerable increase can be
noted for both field sites during the winter period, which is due to the use of de-icing
salt in Denmark. The amount of de-icing salt used at the sites was almost identical
during the winter 98/99. The responsible authorities state that at Vejenbrod approx.
14 kg/m2 was spread and at Rud 12 kg/m2.
Conductivity, run-off
&RQGXFWLYLW\UXQRII
25000
Vejenbrod
µS/cm
20000
Rud
15000
10000
5000
0
Jul98
O ct98
Jan 99
Apr99
Jul99
Figure 4. Conductivity of road run-off as a function of time
It appears that the use of road salt also has influence on other parameters of the runoff. Table 3 shows some of the parameters from the examination of the run-off from
Vejenbrod. There is an increase in the content of Ca, K, Mg, Zn og organic
compounds (PAH, NVOC and THC) in the period where salting takes place. As can be
expected, there is a sharp increase of chlorides, due to the use of de-icing salts. A
similar increase can be found for sodium.
The results from Rud show the same tendency, however the level of some of the
parameters is different.
13
13
Jul
Aug
Sep
Oct
Nov
Dec
Jan
Feb
Mar
Apr
Maj
Jun
Zn,
µg/l
Pb,
µg/l
Cl-,
µg/l
Sum
PAH,
µg/l
NVOC,
µg/l
THC,
µg/l
069
075
068
047
455
144
210
330
170
075
052
180
8
8
9
12
11
18
25
46
21
13
8
29
3
4
5
4
1,500
2,500
1,500
3,700
1,200
1,210
1,117
1,115
<0.22
<0.22
<0.22
<0.21
<0.36
<0.84
2.0
3.6
2.5
<0.42
2.5
2.0
10,000
11,000
07,100
07,000
12,000
34,000
25,000
49,000
30,000
21,000
23,000
31,000
04,900
04,700
05,000
03,900
05,500
12,000
12,000
19,000
08,400
01,100
0 680
01,200
Table 3. Summary of the analysis results from run-off, Vejenbrod
Total deposition
When analysing the samples from the total deposition samplers, a corresponding
increase in conductivity can be seen for samplers situated three meters from the road
in the period where salting takes place. In general, the concentrations are low;
however, the concentration of zinc is high at both sites.
There was only little water in the sampler at Rud and it was therefore only possible to
to make a few analyses of the organic parameters. The concentrations found from the
analyses are very low. The amounts of water collected at Vejenbrod made more analyses of organic compounds possible. As for the inorganic parameters, the concentrations measured are low, but the analysis of THC gives high values.
Soil solution
In the samples sucked up from a depth of 0.35 m, a considerable difference can be
noted between the two sites as regards conductivity. At Vejenbrod the sample closest
to the road (three meters from the asphaltic edge) shows a considerable increase
during the winter, whereas the samples six meters from the edge are registered with a
constant, high level. This can be seen in figure 5. The increase in conductivity during
the winter is not nearly as pronounced at the site at Rud. The concentration of
chlorides is also lower there than at Vejenbrod.
It applies for both sites that the concentration of other parameters is low; however
there is an increased content of THC at Vejenbrod. This can be explained by the fact
that there is a higher content of THC for the total deposition.
14
14
&RQGXFWLYLW\6RLOVROXWLRQ
Conductivity,
Soil solution
PHWHU
PHWHU
@
P
F
6
—
>
&
(
Jul-98
Oct-98
Jan-99
Apr-99
Jul-99
Figure 5. Conductivity measured on soil solution, Vejenbrod
Groundwater
Both sites show in the results of the analyses of the groundwater a higher content of
sodium and chloride in the samples on the downstream side than for the other side of
the road. The downstream side was at both sites the eastern side of the road. The
values for chloride are higher than for typical values found in groundwater in
The content of chloride, groundwater
7KHFRQWHQWRIFKORULGHJURXQGZDWHU
9HMHQEURGXSVWUHDP
PJO
9HMHQEURG
GRZQVWUHDP
5XGXSVWUHDP
5XGGRZQVWUHDP
-XO
6HS
2FW
'HF
-DQ
0DU
$SU
-XQ
Figure 6. Contents of chlorides in the groundwater
15
15
Denmark. There were no differences in the concentration of chlorides from the two
sites. Figure 6 shows the variation of chloride concentrations for the period.
At the site at Vejenbrod there is a high content of THC in the first sample, whereas
there is a high content of heavy metals at the site at Rud from the first sample. This is
not found again and may be due to disturbances of the soil during the installation of
the pipes.
Soil samples
Soil samples were only taken once during the project. The results represent an
accumulation throughout the period while the roads have been trafficked; for Vejenbrod 25 years, for Rud 4 years. Tables 4 and 5 present a summary of some the
parameters.
Distance from
the road in m
3
6
20
Depth
in cm
0-2
2 -10
10-30
0-2
2 -10
10-30
0-2
2 -10
Vejenbrod
Rud
Sum of PAH, NVOC, Sum of PAH, NVOC,
µg/kg
µg/kg
mg/kg
mg/kg
7,513
23,300
7,920
413
411
80
138
131
49,000
35,000
13,000
30,000
20,000
7,800
24,000
19,000
90
Not detected
Not detected
40
40
60
70
70
3,830
330
210
9,600
5,600
7,900
15,600
6,300
Table 4. Comparison of the content of some organic compounds in soil samples
Distance from
the road in m
3
6
20
Depth
in cm
0-2
2 -10
10-30
0-2
2 -10
10-30
0-2
2 -10
Vejenbrod
Cr,
Pb,
Zn,
mg/kg mg/kg mg/kg
41
28
24
32
33
36
28
29
191
223
83
74
72
35
42
48
314
240
119
89
97
67
53
95
Rud
Cr,
Pb,
mg/kg mg/kg
3
1
2
7
8
12
14
15
6
1
1
7
7
13
11
12
Zn,
mg/kg
25
<5
6
24
24
32
33
30
Table 5. Comparison of the content of some heavy metals in soil samples
16
16
It can be seen from the results in table 4 and 5 that there are great differences in the
concentration found at the two roads. The level in the soil samples from Rud is within
the interval which can be expected in normal undisturbed Danish soil, whereas it is
quite clear that the concentrations in the soil samples from Vejenbrod are very high.
This difference can be explained by the fact that the study site at Vejenbrod has been
exposed to influence from traffic for more than twenty years whereas the motorway in
Rud was opened four years ago.
It is to be expected that the level of lead at Rud will never reach the level from Vejenbrod, as lead is no longer added to petrol since 1994.
17
17
Conclusion and discussion
As expected, the analyses show for inorganic parameters that there are high concentrations of sodium and chloride in the road run-off and soil solution close to the road (3
meters) during the winter, when de-icing salts are used.
The presence of chloride can cause a washing of heavy metals from the soil, since the
chloride ions can form complexes with heavy metals. It is however, not possible to
document this effect, since the concentrations of heavy metals found in the soil solution and groundwater samples is very low.
The analyses show that concentrations of heavy metals in water samples from soil
solution and groundwater samples are low, but it is seen that the zinc content in the
water samples from both stations exceeded the requirement to drinking water in Denmark. The concentrations of the metals examined show a tendency that they are higher
during the winter.
The results of the soil samples at Rud are on level with unpolluted soil samples in
Denmark. There is no influence from the traffic or the road. The analysis results for
soil samples at Vejenbrod, after 25 years of accumulation of low soluble compounds
show much higher values - the closer to the road, the higher the values. As example it
can be mentioned that the highest concentration of lead from soil samples at Vejenbrod
is 223 mg/kg, whereas the highest concentration of lead from samples at Rud is at 15
mg/kg.
The content of organic parameters in soil samples (PAH, NVOH and THC) shows the
same tendency as for heavy metals. The concentration which is determined in the soil
taken from Vejenbrod is much higher than that from Rud. For the organic parameters
in the run-off there is an increase during the winter, in the same way as for heavy
metals. The concentration found in other water samples has generally been low,
however there is a higher THC content in deposition and soil solution at Vejenbrod.
By choosing the two field sites with such different ages, it is confirmed that there is an
increased concentration of heavy metals and organic matter (PAH, NVOH and THC)
as a function of the total traffic volume. Various initiatives, such as use of unleaded
petrol and the requirement of catalysts in new vehicles, have had a positive effect in
the wish to reduce pollution. It must therefore be expected that it will last more than
25 years before the site at Rud will reach the same level of concentration in the soil as
that at Vejenbrod today.
In a way it can be seen that the greatest influence of the soil and water from the road
and traffic is due to de-icing salt in winter.
The results of the study sites show that spreading of pollution from traffic and roads is
on a low level. On the other hand, an accumulation of contaminating compounds near
the roads and also a spread of pollution near the roads can be found to such an extent,
that mitigation must be considered. Continuation of measurements must be considered.
18
18
Further work
As a part of the POLMIT project calculations are made of the sources to the emissions
from vehicles. It is based on the best knowledge of the emission factors and an average composition of the fleet of cars in the individual countries. The first attempts
have shown that it is possible to obtain realistic results compared to what is found in
the environment along the roads. The results from this work will be found in the
complete POLMIT reports.
References
19
[1]
Lehmann N.K.J., et al. (1998): Miljømålinger langs veje – screeningsundersøgelser af jord og vand [In English: Environmental Monitoring in the verges of
roads. Screening test of soil and water] Stads- og havneingeniøren nr. 8, 1998,
Danmark
[2]
Erisman, J.W. et al., (1998): Manual for measuring run-off and total deposition
in the verges of motorways. W-DWW-98-023. DWW, Delft, The Netherlands
19
20
20
Rapporter/Reports
Nr./No
År/Year
81/97
Betonstrækningen
Ølby - Ringsted
Status efter 20 års driftsperiode
(Finn Thøgersen)
94/99
Evolution and Harmonization of Evenness Evaluation
Techniques
(Bjarne Schmidt)
(Electronic edition)
82/97
Friction Test
Comparative testing with 3 different equipments
carried out during the summer 1996
(Bent Lund)
95/99
Investigation of Gyratory Compaction used for Asphalt
Mix Design
(Jørn Raaberg)
(Electronic edition)
83/97
Eighth International Conference on Asphalt
Pavements. Seattle USA, August 10-14, 1997.
Papers.
(H.J. Ertman Larsen, Per Ullidtz, Susanne Baltzer,
Lynne H. Irwin.)
96/99
84/97
TRB Annual Meeting 1997
DRI Paper Presentation at Session 13
Pavement Instrumentation, Part 1.
(Robin A. Macdonald, Wei Zhang)
Development of Models for Economic Evaluation of
Pavement Maintenance: the PAV-ECO Project
Providing an Efficient and Socially Acceptable Road
Transport Network
(Gregers Hildebrand, Philippe Lepert)
(Electronic edition)
97/99
Development of a Laser-Based High Speed Deflectograph
(Gregers Hildebrand, Søren Rasmussen, Raúl Andrés)
(Electronic edition)
85/97
Subgrade Performance Study
Part I: Materials, Construction and Instrumentation
(Robin Macdonald, Susanne Baltzer)
98/99
86/97
Fifth International Conference on the Bearing
Capacity of Roads and Airfields
Trondheim, July 6 - 8, 1998, Papers
(Robin Macdonald, Wei Zhang, Susanne Baltzer,
Per Ullidtz, Jesper L. Lund)
Accelerated Pavement Testing
1999 International Conference
October 18-20, Reno, Nevada
(Carsten Bredahl Nielsen, Per Ullidtz, Wei Zhang,
Susanne Baltzer, Robin A. Macdonald)
(Electronic edition)
99/00
Stabilitet og holdbarhed af danske asfaltbelægninger
(Jeanne Rosenberg, Jørn Raberg)
(Electronic edition)
87/98
Pavements Subgrade Performance Study
Part II: Modeling Pavement Response and
Predicting Pavement Performance
(Wei Zhang, Per Ullidtz, Robin Macdonald)
88/98
Road Unevenness
Paper presented at the 1998 FISITA World
Automobile Congress, Paris
(Bjarne Schmidt)
89/99
Development of improved mechanistic deterioration
models for flexible pavements
(Hans Ertman Larsen, Per Ullidtz)
(Electronic edition)
90/99
Friktionsmålinger
Sammenlignende målinger mellem ROAR og Stradograf
(Bjarne Schmidt)
91/99
Grundere til broisolering
- typegodkendelse
- materialevalg
(Jeanne Rosenberg)
92/99
The Structure of Polymer Modified Binders and
Corresponding Asphalt Mixtures
(Vibeke Wegan, Bernard Brûlé)
93/99
PIARC World Road Association
International Experiment to Harmonise Longitudinal
and Transverse Profile Measurement and Reporting
Procedures, Draft Report
(Bjarne Schmidt, Jim Wambold, Akira Kawamura,
Guy Descornet)
(Electronic edition)
100/00 Response and Performance of a Test Pavement to
two Freeze - Thaw Cycles, Danish Road Testing
Machine RTM2: 1998
(Wei Zhang, Robin Macdonald)
(Electronic edition)
101/00 Responses and Performance of a Rehabilitated Test
Pavement to Accelerated Load Testing
Danish Road Testing Machine RTM3: 1999
(Wei Zhang, Robin Macdonald)
(Electronic edition)
102/00 Responses and Performance of a Rehabilitated Test
Pavement to one Freeze - Thaw Cycle
Danish Road Testing Machine RTM3: 2000
(Wei Zhang, Robin Macdonald)
(Electronic edition)
103/00 PIARC World Road Association
International Experiment to Harmonise Longotudial
and Transverse Profile Measurement and Reporting
Procedures, Final Report
(Bjarne Schmidt, Jim Wambold, Akira Kawamura,
Guy Descornet)
(Electronic edition)
104/00 Examination of pollution in soil and water along roads
caused by traffic and the road pavement
(Knud A. Pihl, Jørn Raaberg)
(Electronic edition)