Ministry of National infrastructures
Energy and Water Resources
Geological Survey of Israel
Levels and distribution of Platinum
Group Metals (PGM) in Israel
Nadya Teutsch, Yehudit Harlavan, Ludwik Halicz
GSI/23/2013
Jerusalem, October 2013
Table of Contents
Abstract ....................................................................................................................................... 3
1. Introduction ............................................................................................................................ 4
2. Research Objectives ................................................................................................................ 5
3. Materials and Procedures ....................................................................................................... 6
3.1 Sites and Sampling ............................................................................................................ 6
3.1.1 Soils ............................................................................................................................ 6
3.1.2 Road dust ................................................................................................................... 7
3.2 Sample Preparation .......................................................................................................... 7
3.2.1 Soil processing............................................................................................................ 7
3.2.2 Road dust processing ................................................................................................. 8
3.3 Analytical Methods ........................................................................................................... 8
3.3.1 PGM analysis .............................................................................................................. 8
3.3.2 Trace elements and Pb IC analysis ............................................................................. 9
4. Results and Discussion .......................................................................................................... 10
4.1 Methodology Verification ............................................................................................... 10
4.2 The distribution of PGM in Roadside Soils...................................................................... 10
4.3 The distribution of traffic related metals in Road Dust .................................................. 11
5. Summary and conclusions .................................................................................................... 14
Acknoweldgements................................................................................................................... 15
References ................................................................................................................................ 15
Tables ........................................................................................................................................ 19
Figures ....................................................................................................................................... 24
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List of Ta bles
Table 1: Road dust samples collected west of Shoresh Interchange. .................................. 19
Table 2: Measured and certified values of BCR-723. ............................................................ 20
Table 3: PGM and trace element concentrations in the Jerusalem hills roadside soils ...... 21
Table 4: PGM and trace element concentrations in road dust ............................................ 22
Table 5: Metal enrichment (EF) in the road dust.................................................................. 23
List of Figures
Fig. 1: Scheme of an automotive catalytic converter.. .................................................... 24
Fig. 2: Typical PGM concentrations in the urban environment.. ...................................... 25
Fig. 3. The sampling sites along the Tel-Aviv – Jerusalem highway. ................................. 26
Fig. 4: Average Annual Daily Traffic at the sampling locations. ........................................ 27
Fig. 5: Sampling location of soil samples K6 and WA-1.. .................................................. 28
Fig. 6: Platinum, Pb and Zn concentrations in the soil profile SHN-1 at Shoeva. ............... 29
Fig. 7: Platinum, Pb and Zn concentrations in the soil profile at Sha'ar Hagay .................. 30
Fig. 8: Platinum versus Rh concentrations in surface samples at Sha'ar Hagay ................ 31
Fig. 9: Platinum versus Rh concentrations in road dust section on highway 1 ................. 32
Fig. 10: Platinum versus road related metals in the road dust section. ........................... 33
Fig. 11:
602
Pb/207Pb versus 208Pb/206Pb values of the road dust section. ........................... 34
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Abstract
The main source of Platinum Group Metals (PGM) contamination of the environment
comes from the emission of automobile exhaust catalysts. These converters which are
compulsory in Israel (since 1993) contain Pd and Pt to catalyze the oxidation of carbon
monoxide and hydrocarbons, and Rh to induce the reduction of nitrous oxides. Though
still under debate, these metals are considered harmful to human beings. In order to
investigate these newly introduced metals to the Israeli environment, we examined their
presence in road dust and soils adjacent to roads.
Direct determination of Pt and Rh concentrations by ICPMS after mathematical
correction of interferences was applied. In this method, concentrations of several
interfering metals are measured alongside the PGMs and their relative contributions to
the PGMs concentrations are used for corrections. Nevertheless, Pd could not be
determined as it suffers from extremely high interferences that cannot be resolved.
Roadside soil concentrations were examined in four locations adjacent to heavy load of
traffic roads: two along the Tel-Aviv – Jerusalem highway in the Jerusalem hills (SHN and
KS) and two in the north of Israel (highway 6 - K6 and road 65 - WA). In all locations the
traffic is the main source of anthropogenic contamination. In all sites, Rh concentrations
were below limit of detection (3 µg/kg) while those of Pt were relatively low and could
be detected only in surface samples. Nevertheless, Pt concentrations were found to be in
correlation with other road related contaminants such as Pb and Zn.
The presence of PGM in road dust was examined in five locations along a half km of the
Jerusalem – Tel-Aviv road west of Shoresh interchange. All Road dust (< 150 μm)
samples contained high concentrations of both Pt and Rh ranging from 250 to 1500
µg/kg and 80 to 450 µg/kg, respectively. In addition, road dust contains high
concentrations of other traffic related metals resulting in high enrichment factors (EF) of
Cr, Cu, Pb and Zn and to a lesser degree of Ni. All metals (except Cu) exhibit positive
correlations with Pt and Rh concentrations suggesting a common source or cause.
A remarkable difference between the two sides of the road at each location was
observed for both Pt and Rh. Uphill concentrations are 4-fold higher than on the downhill
side indicating significant rise in PGM emission with increased engine activity. Other
traffic related elements (such as Pb and Zn) show only a 2-fold increase.
The isotopic composition of Pb (Pb IC) in the road dust shows a distinctive anthropogenic
signature, which is in agreement with the high Pb enrichment factors, both suggesting
that the contribution of natural Pb to these samples is minor.
In addition to the road dust samples, the Pb IC of the certified environmental reference
material for the platinum-group elements (BCR-723, road dust collected in an Austrian
tunnel in 1998) was measured for the first time and was found to be similar to European
Pb petrol values.
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The data obtained suggest a clear association between traffic in general and engine
activity in particular, to the emission of the platinum group metals. This connection is
strongly apparent in road dust and less so in roadside soils. Thus, results suggest that
while soil along road sides can be regarded as free of PGM, road dust not only has
detectable concentrations of Pt and Rh but it also reflects traffic load.
1. Introduction
The increase in population and subsequent higher levels of urbanization,
industrialization, and transportation causes contamination problems which have greater
effect on small and fragile environments such as Israel. A new environmental
contamination source is the Platinum-group metals (PGM) which are used in various
applications such as jewelry, dental implants, and electronics. Predominantly, the
automobile exhaust catalysts are the main source of PGM contribution to the
environment. These converters contain Pd and Pt to catalyze the oxidation of carbon
monoxide and hydrocarbons, and Rh to induce the reduction of nitrous oxides (Fig. 1).
Automobile catalysts were introduced in the USA in the 1970s, in the European Union in
the 1980s and are mandatory in new cars in Israel since 1993. Due to abrasion of the
catalyst surface, small amounts of particulate PGM are released into the environment.
Concentrations of Pt, Pd and Rh in the continental crust are very low (0.4, 0.4 and 0.06
µg/kg, respectively; (Wedepohl, 1995). These figures are similar to upper crust values
derived from loess measurements (Pt: 0.51 ng/g, Pd: 0.52 ng/g, Peucker-Ehrenbrink and
Jahn, 2001). Estimated PGM particulate emissions from automobile catalysts are in the
nanogram range per traveled kilometer (Moldovan et al., 2002). Worldwide PGM
production has been increasing steadily in the last few decades (Rauch and Morrison,
2008). For example, global mining supply of Pt in 1975 was 71.2 ton compared to 163 ton
mining supply and addition of recycled 60 tons in 2013 (Varrica et al., 2003).
The increasing concentrations of PGM have raised concern over potential risks for
the environment and to humans in particular, which depend on exposure, bioavailability,
and toxicity. The toxicity and health effects on humans of PGM emitted into the
environment are still under study. For instance, Pt- chloride complexes have been
associated with serious health problems in humans such as asthma, increased hair loss,
increased spontaneous abortion, and dermatitis (Ravindra et al., 2004). However, PGM
health effects have been documented only in settings where exposure is high and have
not been determined under regular low concentration environmental conditions (Rauch
and Morrison, 2008). Yet, in a recent experimental study, it has been demonstrated that
human beings can uptake up to ~90% of PGM emitted from vehicle exhaust via
inhalation exposure (Colombo et al., 2008).
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In the last decade, extensive efforts have been dedicated to determine
concentrations, transport and availability of PGM in the environment worldwide (Ek et
al., 2004; Rauch and Morrison, 2008; Ravindra et al., 2004; Zimmermann and Sures,
2004). Indeed, elevated PGM levels have been found in various environmental settings
(Fig. 2) mainly associated with traffic such as airborne particles (e.g., Rauch et al., 2001),
roadside soils (e.g., Zereini et al., 2007), and sewage sludge (e.g., Schafer et al., 1999).
Even in a remote location such as Greenland, elevated concentrations of PGM have been
found in snow and ice indicating that the atmosphere of the Northern Hemisphere is
contaminated with PGM (Barbante et al., 2001).
The emission of PGM into the environment from the vehicle exhaust is mainly in the
particulate form (Moldovan et al., 2002) and hence, it could be assumed that the PGM
are inert and immobile. However, it has been found that a fraction of PGM, especially
Pd, emitted from cars is in a soluble form and is mobile (e.g., Jarvis et al., 2001). In soils,
PGM can be transformed into soluble species by complexation with natural organic
material such as humic acids (Ek et al., 2004). In experiments under natural growing
conditions, traffic emitted PGM get into plants with transfer coefficients decreasing in
the order Pd>Pt>Rh: Pd was as mobile as Zn, while Pt and Rh were as mobile as Cu
(Schafer et al., 1998).
Previous PGM data in Israel includes only several preliminary analyses of Pt (but not
Rh and Pd) have been previously measured in Israel (Shirav et al., 2007). Although the Pt
data set is small, it indicates that there is a variation in Pt concentrations from <10 µg/kg
to 430 µg/kg in road dust where the higher levels of Pt have been found in samples
collected close to heavy traffic. In addition, the measured concentrations are way above
the average continental crust level of ~0.5 µg/kg which was based on loess
measurements (Peucker-Ehrenbrink and Jahn, 2001).
2. Research Objectives
Though it is obvious that the utilization of automobile exhaust catalysts has caused a
great improvement in the emission of toxic gases emitted to the atmosphere from
vehicles, it has also introduced a new contamination source to the environment. As a
result, in the last decade the research of PGM levels in various environmental settings
has gained increased interest.
The proposed research is aimed at developing the analytical procedures for
measuring the PGM concentrations in various types of samples in order to assess the
increase and impact of anthropogenic PGM on the environment in Israel.
The main objectives are:
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(1) to develop accurate analytical methods to measure PGM in various types of samples
including soil and street dust.
(2) to ascertain the PGM levels in roadside soils and street dust.
(3) to quantify the increase in PGM levels in the last few decades in roadside soils.
3. Materials and Procedures
3.1 Sites and Sampling
3.1.1 Soils
In order to determine PGM levels in local soils, we aimed at sampling contaminated
soils adjacent to roads. However, finding undisturbed soil profiles along main roads in
Israel is relatively difficult as in many cases there are no soil profiles along the road side
in addition to much roadwork taking place which affects the road surroundings. In
addition, the studied location should be affected only by traffic with no other major
contamination sources. As PGM levels in roadside soils in Israel were not known, the
first site that was chosen was in the Jerusalem Hills opposite Shoeva adjacent to the
Jerusalem-Tel Aviv (Jer-TA) highway (SHN, Fig. 3a). This location has been previously
thoroughly investigated in 1982 (Foner, 1990; Teutsch et al., 2001) and in 1996-7 (Foner,
1990; Teutsch et al., 2001). Hence samples from the 1982 campaign should represent
pre automobile catalyst use and are expected to have background levels of PGM while
those of the 1996-7 campaign should represent the early days of the convectors.
Unfortunately, it was found that this location has been strongly transformed over the
last few years due to road works (Shoresh interchange) and park development (Rabin
Park). Thus, the current sampling (2011-2013) in this location is limited to a soil profile
sampled 5 m from the road verge (northern Jer-TA lane). The sampled profile is a
naturally occurring soil pocket exposed in a road cut with a total depth of 35 cm, which is
typical to soil profiles in this area (Teutsch et al., 2001).
Since the Pt levels in the SHN soil profile were found to be relatively low (see section
4.2), another area expected to be more contaminated was chosen for sampling in the
Jerusalem hills. The second soil sampling site is located in the traffic island opposite the
Sha'ar Hagay Kennels (KS, Fig. 3a). This area is a preferred location as there are no other
major contamination sources except traffic along highway 1 which is a major road with
high volume of traffic (Fig. 4). The main part of this site was disturbed over the years due
to ploughing of the olive grove at the site. Consequently, sampling of a detailed soil
profile (KS-1, Fig. 3b) took place at the eastern side of the traffic island beyond a Muslim
grave tomb where it was not expected to be disturbed. This profile is located 6 m and
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17 m from the northern (Jer-TA) and southern (TA-Jer) road verges, respectively.
Because of its location between two lanes, PGM concentrations were expected to be
significant higher due to the greater traffic effect. In addition to the 20 cm deep soil
profile sampled (Fig. 3b), four surface samples (KS-2) were also collected in the vicinity of
this detailed profile, in higher proximity to the traffic lanes. These samples were taken
from the top one cm at the wedge of the traffic island were the distance from the traffic
lane is 6-7 m to each side. These samples are a mixture of soil, organic matter (mainly
pine needles) and dust.
Two additional roadside soils from the north of Israel have been sampled - Highway
6 south of Iron Interchange (K6; Figs. 5a and 5b) and Road 65 west of Megido junction
(WA-1, Figs. 5a and 5c). These locations were chosen as they are located on main roads
with high volume of traffic (Fig. 4) with no expected other major contamination sources.
In addition, Highway 6 is a relatively young road and the section in which sampling took
place has opened only in 2004 and its traffic volume has increased over the years (Fig. 4).
As the highest concentrations were expected and found to be (in the Jerusalem hills) in
the upper most cm of the soil profiles, sampling was emphasized on mostly collecting
topsoil samples. At Highway 6 (K6, Fig. 5b), only surface samples were collected. At
Road 65, the sampling site WA-1 located 2.5 km southwest of Megiddo junction (Fig. 5a)
is a road cut and a whole soil profile could be sampled emphasizing on the top soil.
3.1.2 Road dust
Road dust was collected in the Jerusalem hill along a half km of highway 1, the Jer-TA
road west of Shoresh interchange (Road section, Fig. 3a). Sampling was done by
sweeping the inner margins on both sides of the center crash barrier, along five 10 m
stretches (Table 1; Fig. 3c). This enabled comparison at the same location between uphill
and downhill lanes of this heavy traffic road. The sampling took place in the middle of
the night when the traffic load is the lowest with the help of the traffic police.
3.2 Sample Preparation
3.2.1 Soil processing
Soil samples were dried in the laboratory at 45 °C (until they reached a constant
weight), lightly crushed, sieved through 2-mm plastic sieve, and homogenized.
Homogenization was performed by several stages of sample splitting and finally a few
grams were ground using an agate mortar. Prior to digestion, the samples were heated
at 650 °C for several hours in order to get rid of organic matter. The most common way
for PGM digestion is by reaction with aqua regia (HCl+HNO3) as this reagent dissolves
these metals. However, it does not cause silicate phase's breakdown, and therefore,
does not represent the total concentration of other trace metals. Sample processing
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tests included the necessary amount of soil sample, volume of aqua regia and time of
digestion. Procedural blanks were monitored alongside with the samples and it was
found that there contribution is negligible as their concentrations was in the range of the
calibration blanks.
3.2.2 Road dust processing
In order to avoid road and other materials, road dust samples were sieved through
150 μm plastic sieve and only the fine fraction (below 150 μm) was further treated.
Aqua-regia extraction was conducted similarly to the soil samples process. Explicitly, 20
mL of aqua-regia were added to 1 g of sample and the quartz crucibles were heated for
several hours. Most of the liquid was evaporated to minimize acidity and the remaining
was transferred to a 50 mL centrifuge tube, completed to 40 mL, centrifuged and a
portion of the decanted solution was diluted 1:2 for analysis.
To further explore the road dust samples, they were fully digested with a mixture of
clean concentrated acids (HNO3, HF, HCl) for trace metal concentrations and Pb isotopic
composition (Pb IC). An aliquot of the digestion solution was purified for Pb IC by ion
chromatography (Ehrlich et al., 2004). In summary, dissolved samples were loaded on an
anionic resin column (Dowex® 1X8; 200–400 mesh; chloride form) in 3.1 M HCl, matrix
eluted in 3.1 M HCl and double distilled water (DDW) and Pb was eluted with 6 M HCl.
Following elution, the sample was evaporated to dryness and dissolved with 0.1 M HNO3.
For methodology verification and to ascertain the accuracy of analysis, the only
environmental certified reference material for Pt, Rh and Pd analysis - BCR-732
(Sutherland, 2007) was treated in the same manner as the road dust samples for PGM
analysis. In addition, this standard was fused with Na2O2 for examination of elemental
analysis and also processed (acid dissolution and column purification) for Pb IC
determination.
3.3 Analytical Methods
3.3.1 PGM analysis
The conventional method for PGM determination in environmental samples is by
ICP-MS (Bencs et al., 2003). The main problem in PGM analysis (especially Rh and Pd) is
their very low concentrations, even in contaminated samples, compared to high
concentration of elements that form large spectral interferences on the PGM major
isotopes (Moldovan et al., 1999). To overcome these interferences, various procedures
have been reported in the literature, such as chemical modification in the introduction
system (Riepe et al., 2001), mathematical correction (Gomez et al., 2000), dynamic
reaction cell (Kan and Tanner, 2004), high-resolution ICP-MS (Rauch et al., 2000) and
cloud point extraction (Meeravalia and Jiang, 2008). The choice of method depends on
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the type of sample, the necessary concentration level and obviously available
instrumentation. We followed the direct determination of PGM levels in using the
mathematical correction of interferences (Gomez et al., 2000). In this method, the
interfering signals that overlap the analyte signals are quantified and subtracted by
mathematical equations.
The advantages of this approach are direct PGM
determination, less sample manipulation and no need in HR-ICPMS instrumentation.
However, using this approach totally eliminates Pd determination as it is present in small
quantities and is subjected to extremely high spectral interferences. Hence, in this study
Pd concentrations were not detected.
Platinum was analysed using its highest abundance mass of 195 (33.8%) among the
six stable isotopes of Pt. The 195Pt is affected by only one interference of the oxide ion
HfO+ (179Hf16O+). Although the interference of the Hf oxide on the 195Pt is relatively large
(around 1 %), the absolute correction is quite small as there is not much Hf in
contaminated roadside soils and road dust. On the other hand, Rh is a monoisotopic
element with mass 103 which is affected strongly from the combination of several
spectral interferences. These include Cu and Zn argides (40Ar63Cu+, 36Ar67Zn+), Sr and Rb
oxides (87Sr16O+, 87Rb16O+) and the double charged Pb ion (206Pb++). Although in roadside
contaminated soils, Rh level is expected to be much higher than background
concentrations, it is strongly hampered by higher levels of other traffic related
contaminants especially Pb. Among the Rh interferences, the two major corrections
influencing Rh determination are Pb and Sr. The limit of detection for Pt and Rh in
solution analysis is quite low around 10 ng/L, which corresponds to <1 µg Rh and Pt per
kg sample. However, due to matrix effects and interference corrections, reliable
concentration determination of soil and road dust samples is higher and could vary from
ca. 1 µg/kg up to ca. 10 µg/kg. As in catalytic derived contamination the expected Rh
concentrations are much lower than Pt, it is expected that only highly contaminated
samples will show meaningful Rh concentrations.
3.3.2 Trace elements and Pb IC analysis
Trace elements concentrations of the samples and standard dissolved by either acids
or fusion with Na2O2 were measured with an ICP-MS (DRC II Sciex, Perkin Elmer).
Accuracy and precision were monitored by use of standard reference materials (SRM).
The Pb IC was measured using an MC-ICP-MS (Nu-Plasma, Nu Instruments) with Tl as
internal standard (Ehrlich et al., 2001). The purified sample solutions were diluted to
appropriate concentrations (ca. 100 µg/L). They were doped with Tl (isotopes 203 & 205)
of approximately half the concentrations of Pb to yield similar beams. Accuracy and
precision were monitored using SRM 981 (Platzner et al., 2001).
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4. Results and Discussion
4.1 Methodology Verification
Platinum concentration measured in the reference material BCR-723 was in
excellent agreement with the certified value, while Rh values were below the certified
concentration (Table 2). The excellent value of Pt points to the high reliability of our
method with a relatively small error of the Pt determination. However, values around 10
ng/g of Rh in the samples are difficult to measure accurately because of the high
concentrations of the interfering elements. Rhodium concentrations are reported in
samples with higher content. Thus, it is unlikely that the Rh concentrations in the road
dust are highly underestimated. The trace metal values measured after Na2O2 fusion or
acid digestion were found to be in good agreement with the published values (Table 2).
For future work, it is suggested that sample dilution should be decreased in order to
increase the Rh concentration in solution and thus lower the quantification limit for Rh.
4.2 The distribution of PGM in Roadside Soils
In the soil pocket sampled opposite Shoeva (SHN, Fig. 3a), Pt concentrations could
be detected only at the upper most part of the profile up to a depth of three cm (Table 3
and Fig. 6a). The highest Pt concentration at the top of the soil profile was 10 μg/kg. The
Pt profile pattern is similar to Pb and Zn profiles which are also known to be road
contaminated related (Table 3 and Fig. 6b). However, with the shift to unleaded Petrol in
Israel during the 1990's, it would have been expected to view a Pb decrease in the upper
most part of the soil profile which has not been observed. This could be a result of the
nature of the pocket sample in which the upper most part of the soil has been removed.
Also, in order for the decrease shift to be observed, a high resolution sampling has to be
employed (Teutsch et al., 2001) and this was impossible in the soil pocket. The Pb
concentrations at the bottom of the profile of 15-16 μg Pb/g soil are typical background
values (Teutsch et al., 2001) compared to ~600 μg/g at the surface sample.
The second soil profile sampled in the traffic island opposite the Sha'ar Hagay
Kennels (KS-1, Fig. 3a and 3b), the soil profile was found to be disturbed. This disturbance
could be viewed by several metal concentrations along the profile including those of Pt,
Zn and Pb. At a few cm depth anomalous high concentrations of Pt were observed
(Table 3 and Fig. 7a) while other traffic related elements (such as Pb and Zn) show only a
moderate increase (Table 3 and Fig. 7b). This high concentration could be attributed to a
piece of converter that was caught in the soil. Rhodium was also not detected at this
depth although it would have been expected considering the high Pt concentrations. The
four surface samples (KS-2) collected at the wedge of the traffic island and contain a
mixture of soil, organic matter (mainly pine needles) and dust were found to be highly
contaminated. All four samples display high concentrations of both Pt and Rh (Table 3
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and Fig. 8) with a very high correlation between them (R2=0.996). Although these
surface samples were collected very close to each other, the variability in concentrations
within them is large. Moreover, the high correlations between Zn, Pb, Pt and Rh which
are all traffic related elements confirm their common source. The differences in the
concentrations of the above elements are due to various amounts of this source. In
addition, the Pt/Rh ratio value found in these samples (Fig. 8) is 10.6±1.0 which is in the
range of published catalytic convertors (Ely et al., 2001) and of road dust and surface
samples affected by them (Jarvis et al., 2001).
Platinum concentrations in surface samples (0-1 cm) at the K6 sampling sites vary
between 9 and 25 µg/kg and are slightly lower than concentrations measured at site WA1 with 11 and 38 µg/kg Pt. These values are similar and somewhat higher than the
surface samples of SHN-1 (10 µg Pt/kg soil), the roadside soil sampled opposite Shoeva.
The overall concentrations of Pt found in the upper most part of the studied
roadside soils adjustment to major traffic routes spans from ca. 5 to ca. 40 µg/kg. This
concentration range is somewhat lower than the compilation data reported by Rauch
and Morrison (2008) for urban roadside soil concentrations (25-250 µg/kg; Fig. 2). This
lower PGM concentration level is probably related to the period of catalytic convertors
use. In Israel, utilization of the convertors started only in 1993, while their use was
introduced in the USA in the 1970s and in the European Union in the 1980s (mandatory
for new cars since 1993) from where most of the compiled data is based upon. Indeed,
the relationship between the period of use and the concentrations found in top roadside
soils can be viewed by comparison between different countries. Platinum concentrations
of urban topsoils from China where catalytic convertors were introduced since 2000
exhibit low values (up to 4.7 µg/kg with an average of 2.6 µg/kg; Wang and Sun, 2009).
These low values express the relatively short use of the convertors in China. On the other
hand, in a recent study from Seoul where catalytic convertors are in use since the late
1980s much higher values of Pt were measured for surface soils (up to 221 µg/kg with an
average of 50 µg/kg; Lee et al., 2012). Hence, it appears that although Pt concentrations
and subsequently the other catalytic convertor PGM Rh and Pd are still relatively scarce
in topsoils in the Israeli roadside environment, it is expected to rise in coming years.
4.3 The distribution of traffic related metals in Road Dust
In order to directly examine traffic related element distribution, road dust was swept
from highway 1. Road dust was collected on both sides of the center crash barrier with a
width of one m (out of five m width) along a 10 m section and from outer bands (Table 1
and Fig. 3c). While the inner samples represent accumulation of dust since the last rains,
namely a period ~5 months, the outer width bands samples represent a much shorter
period of a few weeks since the last mopping of the road by the National Roads
Company. The amount of material swept from the inner band was found to be sufficient
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for processing and analyzing. However, the outer band samples yielded only 1-2 g of the
< 150 µm fraction which was found to produce non reliable results and thus will not be
further discussed.
High concentrations of both Pt and Rh were measured for all road dust samples
ranging from 250 to 1500 µg/kg and 80 to 450 µg/kg, respectively (Table 4) with a high
correlation (R2=0.985) between their concentrations (Fig. 9). These high values are above
typical published road dust concentrations of 50-300 µg/kg Pt and 10-60 µg/kg Rh (Rauch
and Morrison, 2008). Expectedly, they are also considerably higher than the mixed soildust surface samples from the sampling site at Sha'ar Hagay traffic island (30-150 µg/kg
Pt and 3-12 µg/kg Rh). Most interesting is the uniform Pt/Rh ratio of 3.3±0.2 (Fig. 9)
which is much lower than the 10.6 ratio of the mixed dust-soil samples. One way of
interpreting the difference in these two sites which are located on the same traffic road
is that these two sites represent diverse deposition periods. The road dust was built up
during the summer months with probably very little mobility (no rain) in contrast to the
soil-dust surface samples which probably represent at least several years of
accumulation with annual cycles of rainy periods. Hence, the different Pt/Rh ratios
obtained for the road dust and the surface mixed soil-dust samples could be either
attributed to higher mobility of Rh compared with Pt or reflects different ratios of
variable catalytic converters. Indeed, the Pt/Rh ratio in catalytic converters which are
not reported by the manufactures, are known to vary largely between manufacturers
around the world, and are regularly altered to optimize performance (Ely et al., 2001).
Based on published data Ely et al. (2001) determined a wide range of Pt/Rh ratio from 5
to 16. The mixed surface samples fall within this range while the road dust ratios are
lower than this range. The lower Pt/Rh ratio in road dust samples (3.3) are within the
range found in urban aerosols (Boston, Massachusetts, USA) that were attributed to
catalyst convertors (Rauch et al., 2005). To further complicate the matter, it has been
documented that the proportion of particulate PGM emissions from fresh and aged
catalyst convertors could change with engine age and type of catalyst (Moldovan et al.,
2002) resulting in a change in Pt/Rh ratios. Hence, it is concluded that the very presence
of Pt and Rh in road dust points to their catalytic source, whereas the Pt/Rh ratio
depends largely on the automobile exhaust catalysts’ age and manufacturer.
A remarkable difference was observed among traffic related elemental
concentrations between the two sides of the road at each location (Table 4). Both Pt and
Rh concentrations at the uphill side were 4-fold higher than on the downhill side
indicating significant rise in PGM emission with increased engine activity (Fig. 9).
Similarly, other traffic related elements (e.g., Pb and Zn) show a 2-fold increase (Table 4;
Fig. 10) while non-traffic related elements (e.g., Sr) show no difference between both
sides of the road. Interestingly, Cu which is also considered a traffic related element
shows no increase of the uphill side (Table 4). Unlike Zn, which is a contaminant
originating in the tire rubber matrix, Cu is an alloying constituent of the metallic
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reinforcing material (Steel cord). Hence, Cu release to the environment probably does
not change as a function of engine activity as Zn, which is released due to higher road
friction.
Enrichment factors (EF) are a common practice to emphasize anthropogenic input
over natural levels (e.g., Weiss et al., 1999; Yongming et al., 2006). It has been reported
that PGM abundances in a natural background sample were found to be similar to
literature values for the upper crust (Ely et al., 2001). Therefore, upper continental crust
(UCC) values (Wedepohl, 1995) were chosen for calculating the EF of the road dust
samples. Several elements are used for normalization of EF values and Al is commonly
used as a normalizing element in general and for dust inputs in particular (e.g., Cloquet
et al., 2006; Erel et al., 2006; Harlavan et al., 2010). However, as all Al values are
relatively similar and small compared to the UCC (Table 4), EF values are strongly
amplified. Therefore, EF values were determined as the ratio between the metal and the
UCC:
EF = [metal] sample/[metal]UCC
There is no established classification for EF values and several suggestions have been
presented in previous literature. A detailed ranking has been proposed by Sutherland
(2000). He presented a five-category system: (1) EF<2 (depletion to minimal
enrichment); (2) EF=2–5 (moderate enrichment); (3) EF=5–20 (significant enrichment);
(4) EF=20–40 (very high enrichment); and (5) EF>40 (extremely high enrichment). In a
much simpler manner, Erel et al. (2006) defined that EF values above 5 unequivocally
represent anthropogenic enrichment. The high concentrations of the traffic related
metals results in extremely high EF values of Pt and Rh (Table 5; ~2000 and ~4000,
respectively) compared to high values of Cu (46), Zn (21), Cr (11), Pb (9), and Cd (7) and
to a lesser degree of Ni (2). The EF value calculated for Sr (0.5) points to its natural
uncontaminated source. Hence, the newly introduced catalytic elements exhibit a
relatively much higher enrichment factor than other traffic related elements.
The Pb IC in road dust shows a distinctive anthropogenic signature on a plot of
potential Pb sources (Fig. 11). The Pb IC values of potential end members are divided into
natural and anthropogenic sources. Natural sources include local soils with the highest
radiogenic values (Erel et al., 1997; Teutsch et al., 2001) and Saharan dust value derived
from the Al-silicates of a high dust load storm which had a natural EF value (Erel et al.,
2006). Similar to other countries, the main source of anthropogenic Pb in Israel has been
from petrol Pb additives (tetraethyl-Pb) and has been previously documented (e.g., Erel
et al., 1997; Teutsch et al., 2001). The Pb IC values form a mixing line stretching from
pre-1992 American petrol-Pb additives used until 1992 (Sherrell and Boyle, 1992) to
post-1992 European petrol-Pb additives used since 1992 (Erel et al., 1997).
Transboundary sources of Pb have been previously identified in aerosols reaching Israel
(Erel et al., 2006; Erel et al., 2007) and their Pb IC values plot on the petrol mixing line
-13-
between pre- and post- 1992 petrol Pb (Fig. 11). All the road dust samples are slightly
shifted from the petrol mixing line (between pre- and post-1992 emissions) and seem to
fall on a mixing line between Cairo's emission and an additional yet undefined
anthropogenic source. The Pb IC exhibited no hill slope pattern. Judging from the Pb IC
and from the high Pb enrichment factors, the contribution of natural Pb to these samples
is minor. In addition, the concentrations of Pb do not exhibit a clear hill slope affect
suggesting current Pb is mainly a result of re-suspension of previously traffic
contamination.
In addition to the road dust samples, the Pb IC of the certified environmental
reference material for the platinum-group elements (BCR-723) was measured. This
standard is road dust collected from the ceiling of an Austrian tunnel (Tanzenberg,
located 50 km north of the city of Graz) in 1998 (Zischka et al., 2002a; Zischka et al.,
2002b). To the best of our knowledge, no Pb IC values have yet been published. The
ratios obtained (206Pb/207Pb = 1.1190 and 208Pb/206Pb = 2.1385) are similar to aerosols
values collected in the 1990s in several parts of Europe including Spain and France
(Bollhofer and Rosman, 2002; Shotyk et al., 1998).
5. Summary and conclusions
Roadside soils as close as 5 m from traffic lanes of major highways in Israel with
heavy load of traffic exhibited relatively low concentrations of PGM. Similar PGM values
were found in various roadside soils. Platinum could be detected only in top soil
samples and concentrations varied up to 25 µg/kg and mostly up to 10 µg/kg. Hence, to
date, no significant PGM levels reside in soils. Mixed soil and dust surface samples
collected close to traffic lanes contain much higher Pt concentrations (tens and up to 250
µg/kg).
In contrary to the soils, very high concentrations of both Pt and Rh were measured in
road dust samples. The high content of PGM in the road dust points to current extensive
pollution of this newly introduced traffic related contaminant. Consequently, increasing
concentrations of PGM in the Israeli environment should be expected in years to come.
-14-
Acknoweldgements
This project was financed by the Ministry of Energy & Water Resources.
We are thankful to Hallel Lutzky for joining and helping in most sampling campaigns
including the night one and appreciate his help and good photos. Udi Coddington, Sagiv
Cohen and two policemen are thanked for the road dust night sampling and Shlomo
Ashkenazi for day sampling. All GSI geochemistry members are appreciated for creating
a supportive working environment.
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-18-
Tables
Table 1: Road dust samples collected west of Shoresh Interchange.
Sample name
Distance1
length
up hill
down hill
m
m
012-1
022-1
0-3.5
11.3
013-1
021-1
0-1
10
014-1
020-1
0-1
10
016-1
019-1
0-1
10
017-1
018-1
0-1
10
013-2
021-2
1-2
10
013-3
021-3
2-3
10
013-4
021-4
3-4
10
014-2
020-2
3-4
10
1
Sampling band presented as distance from the road barrier located in the middle of the
road.
-19-
Table 2: Measured and certified values of Pt (µg/kg), Rh (µg/kg) and other trace metal
(mg/kg) of BCR-723. Platinum and Rh were measured in the aqua regia digestion and the
other metals after Na2O2 fusion.
Element
Certified/Indicative1 ±
Measured2
measured/value
Pt
81.3
2.5
80.9±1.33
1.00
Rh
12.8
1.3
9.4±1.34
0.73
Ba
460
40
573
1.25
Cd
2.5
0.4
2.2
0.88
Co
29.8
1.6
30
1.00
Cr
440
18
450
1.02
Mn
1280
40
1280
1.00
Mo
40.0
0.6
43
1.07
Ni
171
3
175
1.02
Pb
866
16
862
1.00
Sb
28.2
2.3
24
0.86
Sr
254
19
252
0.99
Zn
1660
100
1630
0.98
1
The Pt and Rh values are certified, while other elements are indicative values obtained
by XRF (Zischka et al., 2002a).
2
ICP-MS analyses following aqua regia digestion for Pt and Rh, and either acid digestion
or Na2O2 fusion for the other elements.
3
Average of 6 analyses from two different dilutions.
4
Two measured values of the same solution.
-21-
Table 3: PGM (µg/kg) and trace element (mg/kg) concentrations of the Jerusalem hills
roadside soils
sample
depth
Pt
Rh As Ba Cd Co
Cr
Cu
Mn Mo Ni
SHN-1-1
SHN-1-2
SHN-1-3
SHN-1-4
SHN-1-5
SHN-1-6
0-1
1-3
6-8
10-14
16-19
30-35
10
3
< 1.5
< 1.5
< 1.5
≤ 1.5
<3
<3
<3
<3
<3
<3
9
11
11
12
11
13
218
250
272
273
248
231
3
4
4
4
2
5
15
19
22
22
19
21
111
143
158
163
149
166
59
42
43
41
35
41
520
727
975
757
762
669
2
2
2
2
2
2
KS-1-1
KS-1-3
KS-1-4
KS-1-5
KS-1-6
KS-1-7
KS-1-8
KS-1-9
KS-1-10
KS-1-11
0-1
1-2
2-3
3-4
4-6
6-8
8-11
11-15.5
15.5-18.5
18-19
6
6
4
≤ 1.5
44
8
< 1.5
< 1.5
< 1.5
< 1.5
<3
<3
<3
<3
<3
<3
<3
<3
<3
<3
4
5
6
6
5
5
5
6
6
5
284
316
327
341
328
320
380
342
324
288
7
2
2
2
4
2
4
2
2
2
13
17
17
16
18
17
15
20
20
17
93
111
117
107
107
105
90
116
116
108
62
57
52
45
50
47
44
35
35
31
595
745
766
756
779
769
715
898
909
781
KS-2-a1
KS-2-a2
KS-2-b1
KS-2-b2
top 1 cm
top 1 cm
top 1 cm
top 1 cm
4
3
7
12
<3
<3
<3
<3
2
7
3
3
274
421
219
224
6
8
7
7
6
6
5
7
-21-
Pb
Sr
V
Zn
59 586
72 164
82 30
78 21
69 15
81 16
143
130
114
117
105
98
135
178
202
202
188
230
254
157
159
123
108
118
2
6
2
2
2
2
2
2
1
1
44
54
51
55
50
49
44
59
53
46
254
320
290
302
387
436
424
84
56
67
202
216
218
212
216
214
192
205
204
196
89
111
111
113
114
114
102
128
128
117
231
217
196
179
210
213
196
110
100
93
51 67 256 4
52 81 309 3
60 128 213 8
80 171 274 10
34
37
31
36
447
383
643
1146
154
168
167
155
37
43
38
46
353
341
837
1404
Table 4: Trace metals concentrations in the road dust samples. Upper Continental Crust
(UCC) values (Wedepohl, 1995) are also presented. Trace metal data arranged by
increasing uphill/downhill ratios.
Upper CC
Al
Cu
Sr
Co
Ni
Cr
Cd
Pb
Zn
Pt
Rh
wt.% mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg mg/kg µg/kg µg/kg
8.04 14.3 316 11.6 18.6
35 0.102 17
52
0.4 0.06
012-1
013-1
014-1
016-1
017-1
1.54
1.72
1.57
1.53
1.66
720
683
430
386
575
161
161
158
152
167
6.2
5.9
5.0
5.6
5.2
38
41
37
40
36
445
460
460
457
408
1.6
1.0
0.7
0.6
0.8
218
196
216
187
128
1519
1614
1390
1422
1412
1281
1417
1031
1482
940
406
441
356
421
279
022-1
021-1
020-1
019-1
018-1
1.48
1.51
1.63
1.71
1.63
609
720
762
771
980
160
160
180
184
163
4.5
4.5
4.9
5.2
5.5
31
31
28
40
30
344
317
374
359
348
0.5
0.5
0.7
< 0.05
0.5
82
161
79
78
108
696
706
1029
691
690
304
342
406
336
260
88
108
112
107
80
ave. uphill
1.61
ave. downhill 1.59
up/down
1.01
559
768
0.7
160
169
0.9
5.6
4.9
1.1
38
32
1.2
446
348
1.3
0.9
0.5
1.8
189
102
1.9
1471 1230
762 330
1.9
3.7
381
99
3.8
-22-
Table 5: Metal enrichment factors (EF). Data arranged by increasing EF values.
Sample
Co
Sr
Ni
Cd
Pb
Cr
Zn
Cu
Pt
Rh
012-1
0.5
0.5
2.1
16
13
13
29
50
3203
6763
013-1
0.5
0.5
2.2
10
12
13
31
48
3542
7346
014-1
0.4
0.5
2.0
7
13
13
27
30
2577
5942
016-1
0.5
0.5
2.1
6
11
13
27
27
3706
7018
017-1
0.4
0.5
2.0
8
8
12
27
40
2350
4648
022-1
0.4
0.5
1.7
5
5
10
13
43
760
1471
021-1
0.4
0.5
1.7
5
9
9
14
50
855
1798
020-1
0.4
0.6
1.5
7
5
11
20
53
1015
1873
019-1
0.4
0.6
2.2
0
5
10
13
54
840
1779
018-1
0.5
0.5
1.6
5
6
10
13
69
650
1338
EF average
0.5
0.5
1.9
7
9
11
21
46
1950
3998
ave. uphill
0.5
0.5
2.1
9
11
13
28
39
3075
6343
ave. downhill
0.4
0.5
1.7
4
6
10
15
54
824
1652
-23-
Figures
Fig. 1: Scheme of an automotive catalytic converter. The catalytic converter
reduces the emission of the three harmful pollutants carbon monoxide
(CO), hydrocarbons (HC) and nitrogen oxides (NOx) by converting them into
the harmful pollutants carbon dioxide (CO2), water (H2O) and nitrogen (N2).
The converter consists of honeycomb structure coated with the metals Pt,
Pd and Rh which are responsible for catalyzing the polluting gas conversion
processes.
-24-
Fig. 2: Typical PGM concentrations in the urban environment
compiled for various environmental compartments. Source:
(Rauch and Morrison, 2008).
-25-
a
Road
section
KS
SHN
to Jerusalem
b
c
Fig. 3. The sampling sites along the Tel-Aviv – Jerusalem highway. (a) SHN soil: the soil pocket
sampled opposite Shoeva at the location sampled previously (Foner, 1990; Teutsch et al., 2001).
KS soil: soil profile and surface samples collected in the traffic island opposite Sha'ar Hagay
Kennels. Road dust: five 10 m stretches taken along a road distance of half a km on both sides of
the road. (b) The soil profile pit at KS loated 6m from the northern lane (seen in picture and 17 m
from the southern lane. (c) Enlargement of the road dust sampling location west of Shoresh
Interchange. Numbers represent sampling locations in the uphill south lane (yellow arrow) and in
the downhill north lane (pink arrow).
-26-
Fig. 4: Average Annual Daily Traffic at the sampling locations. Data obtained from the Central
Bureau of Statistics. The traffic volume of road highway 1 (#1) is presented for the two lanes
and also only for the northern side (Jerusalem – Tel-Aviv direction) at the Shoeva section. The
traffic volume presented for highway 6 (Kvish 6) and road 65 (#65) are of the traffic sections in
which the sampling took place.
-27-
a
b
c
Fig. 5: (a) Sampling location of soil samples K6 and WA-1. (b) K6 sampling sites adjacent to the
highway 6 verge are located 1.5 km to the south of Iron Interchange. Several 0-1 cm depth
samples were taken. (c) Sampling site WA-1 is a soil exposed during roadwork on road 65
located 2.5 km southwest of Megiddo junction. A soil profile and several 0-1 cm depth samples
were taken.
-28-
Fig. 6: Platinum (a) and Pb and Zn (b) concentrations in the soil profile SHN-1 at
Shoeva. Platinum concentrations smaller than detection limit (1.5 ng/g) are plotted as
0.
-29-
Fig. 7: Platinum (a) and Pb and Zn (b) concentrations in the soil profile KS-1 sampling
site at Sha'ar Hagay traffic island. Platinum concentrations smaller than detection
limit (< & ≤ 1.5 ng/g) are plotted as 0.
-31-
Fig. 8: Platinum versus Rh concentrations in surface samples of KS-2 sampling site
at Sha'ar Hagay traffic island. The high consistent correlation between these
elements with a ratio of 10.6 is within the range typical to catalytic convertors.
-31-
Fig. 9: Platinum versus Rh concentrations in road dust sampled in five locations along a ~400
m transect on highway 1 west of Shoresh Interchange (Fig. 3). The data points fall within two
groups; uphill higher PGM values and lower downhill values. The positive correlation
between these elements with a ratio of 3.2 is within the range attributed to particulate PGM
emissions (Moldovan et al., 2002).
-32-
Fig. 10: Platinum versus road related metals (i.e., Cr, Pb and Zn) measured in road dust
section. The traffic related trace metals also plot into the uphill and downhill groups. Non
anthropogenic Sr is plotted for comparison.
-33-
Fig. 11: 602Pb/207Pb versus 208Pb/206Pb values of the road dust samples. The samples viewed
together with possible sources of natural (green) and anthropogenic (red) Pb in Israel
(references 1-4). The road dust shows distinctive anthropogenic signature of post-1992 Pb
contamination with another undefined anthropogenic source (empty circle).
-34-
‫תקציר‬
‫מרבית המתכות מקבוצת הפלטינה (‪ )PGM‬המצויות בסביבה מקורן בממירים הקטליטיים של רכבים‪.‬‬
‫ממירים אלו שהשימוש בהם הוא חובה (החל מ‪ )1993-‬מכילים פלדיום ופלטינום המשמשים כזרזים‬
‫לחמצון של פחמן חד חמצני והידרוקרבונים וכן רודיום המאיץ חיזור של תחמוצות חנקן‪ .‬למרות‬
‫שהדעות עדיין חלוקות‪ ,‬מתכות אלה ככל הנראה מזיקות לבני אדם‪ .‬על מנת לחקור את תפוצת‬
‫המתכות מקבוצת הפלטינה בישראל שהנן מזהם סביבתי חדש יחסית‪ ,‬בדקנו את נוכחותם באבק‬
‫כבישים ובקרקעות בצידי כבישים‪.‬‬
‫ריכוזי פלטינה ורודיום נקבעו באמצעות מדידה ב‪ ICPMS-‬והפחתה של ההפרעות על האיזוטופים‬
‫הנמדדים‪ .‬בשיטה זו‪ ,‬נמדדים ריכוזי מספר מתכות הגורמות להפרעה על המתכות מקבוצת הפלטינה‬
‫וההפרעה היחסית שלהם מחושבת עבור התיקון‪ .‬לפלדיום הפרעות גדולות מדי על כל האיזוטופים ולכן‬
‫לא ניתן למדידה בשיטה הישירה שיושמה במחקר זה‪.‬‬
‫ריכוזי מתכות מקבוצת הפלטינה בקרקעות נבדקו בארבעה מקומות הסמוכים לכבישים בעלי עומס‬
‫תנועה כבד‪ :‬שניים בצידי כביש ירושלים ‪ -‬תל אביב בהרי ירושלים (‪ SHN‬ו‪ )KS-‬ושניים בצפון הארץ‬
‫(כביש ‪ K6 - 6‬וכביש ‪ .)WA - 65‬בכל אתרי הדגימה מקור הזיהום העיקרי הוא תחבורה‪ .‬בכל הקרקעות‪,‬‬
‫ריכוזי הרודיום היו מתחת לסף הגילוי (‪ 3‬מק"ג ‪ /‬ק"ג) ואילו ריכוזי פלטינה היו נמוכים יחסית וניתן‬
‫היה לכמתם רק בדוגמאות פני שטח‪ .‬עם זאת‪ ,‬נמצאה קורלציה בין ריכוזי פלטינה וריכוזי מזהמים‬
‫תחבורתיים אחרים כגון עופרת ואבץ‪.‬‬
‫הנוכחות של מתכות מקבוצת הפלטינה באבק כבישים נבדקה בחמישה מקומות לאורך חצי קילומטר‬
‫בכביש ירושלים ‪ -‬תל אביב ממערב למחלף שורש‪ .‬כל דוגמאות אבק הכבישים (הפרקציה הקטנה מ‪-‬‬
‫‪ 151‬מיקרומטר) הכילו ריכוזים גבוהים של פלטינה (‪ 251-1,511‬מק"ג ‪ /‬ק"ג) ורודיום (מק"ג ‪ /‬ק"ג ‪81-‬‬
‫‪ .)451‬בנוסף‪ ,‬אבק הכבישים מכיל ריכוזים גבוהים של מזהמים תחבורתיים אחרים הגורמים למקדמי‬
‫העשרה (‪ )EF‬גבוהים של כרום‪ ,‬נחושת‪ ,‬אבץ ועופרת ובמידה פחותה יותר של ניקל‪ .‬מתאמים חיוביים‬
‫של כל המתכות הללו (מלבד נחושת) עם ריכוזי פלטינה ורודיום מצביעים על מקור או גורם משותפים‪.‬‬
‫הבדל משמעותי בריכוזי פלטינה ורודיום בין שני צידי הכביש נצפה בכל אחד מחמשת האתרים‬
‫שנדגמו‪ .‬ריכוזי המתכות בצד העולה גבוהים פי ארבעה מאשר בצד היורד ומצביעים על עלייה‬
‫משמעותית בפליטת מתכות מקבוצת הפלטינה עם עלייה בפעילות המנוע‪ .‬מתכות אחרות הקשורות‬
‫בפעילות תחבורתית (כגון עופרת ואבץ) מצביעים על גידול בריכוז של פי שניים בלבד‪.‬‬
‫ההרכב האיזוטופי של עופרת (‪ )Pb IC‬באבק הכבישים מראה חתימה אנתרופוגנית ברורה‪ .‬זאת‪,‬‬
‫והממצא שמקדמי ההעשרה של העופרת גבוהים‪ ,‬מצביע על כך שהתרומה האנתרופוגנית של העופרת‬
‫לדגימות אלה היא הדומיננטית וזו הטבעית הינה שולית‪.‬‬
‫בנוסף לאבק הכבישים‪ ,‬ההרכב האיזוטופי של עופרת נמדד לראשונה בסטנדרט הבינלאומי הסביבתי‬
‫היחיד למתכות מקבוצת הפלטינה (‪ ,BCR-723‬אבק כבישים שנאסף במנהרה אוסטרית ב‪ )1998 -‬ונמצא‬
‫דומה לערכי דלק אירופאי (אין הרכב איזוטופי מפורסם בספרות)‪.‬‬
‫הנתונים שנאספו מצביעים על קשר ברור בין ריכוזי מתכות מקבוצת הפלטינה לבין תנועת רכבים בכלל‬
‫ופעילות המנוע בפרט‪ .‬קשר זה הינו מובהק ביותר באבק כבישים ופחות בקרקעות בצידי כבישים‪.‬‬
‫תוצאות המחקר מראות כי בעוד הקרקעות בצידי כבישים יכולות להיחשב כנטולות מתכות מקבוצת‬
‫הפלטינה‪ ,‬באבק הכבישים‪ ,‬לא רק שניתן למדוד ריכוזים של פלטינה ורודיום‪ ,‬אלא שהריכוזים‬
‫משקפים עומסי תנועה‪.‬‬
‫‪-35-‬‬
‫משרד התשתיות הלאומיות‬
‫האנרגיה והמים‬
‫המכון הגיאולוגי‬
‫ריכוזי מתכות מקבוצת הפלטינה ותפוצתן בישראל‬
‫נדיה טויטש‪ ,‬יהודית הרלבן ולודויג הליץ‬
‫דוח מס' ‪GSI/23/2013‬‬
‫ירושלים‪ ,‬אדר א' תשע"ד‪ ,‬פברואר ‪1024‬‬