Chemistry Reference
In-Depth Information
In dry climates such as South European countries, the low and infrequent
precipitations hamper the wash-out and the moistening of road surface, favouring
road dust resuspension by traffic-induced turbulence. Moreover additional inputs of
dust come from the urban soil resuspension due to the little vegetal covering and
from sporadic intensive deposition of Saharan dust outbreaks or uncontrolled
construction/demolition activities.
The experimental evidence is given by the higher suspended PM
10
mineral
matter at the urban areas of Southern Europe as compared to Central Europe [
34
,
44
,
89
,
118
-
124
]). In a comparative study between European sites, Querol et al.
[
44
] highlighted that in Central Europe, the mineral contribution increases from
3-5
gm
3
at kerbside sites. In Spain
the increase found induced by traffic resuspension was much higher: from 10 to
16
gm
3
from urban background sites to 4-7
m
m
gm
3
. In Sweden the mineral aerosol accounts for 7-9
gm
3
in urban
m
m
gm
3
at the traffic sites, as a
result of the sanding and salting of roads during the winter and spring period and
the use of studded tyres. Consequently, the local road dust emissions account for
up to 9-24
background but increases dramatically to 17-36
m
gm
3
for the rest
of countries studied: England, Switzerland, UK, Germany and Austria. These
differences in levels of crustal components may be attributed largely to the higher
dust accumulation and resuspension effect during dry conditions in the southern EU
countries and to the high emission during winter-spring times in Scandinavian
regions, whereas higher rainfall in the central EU countries may help to clean the
road dust from streets.
The application of receptor models permitted to better quantify the contribution
of road dust emissions. At the urban background of Barcelona Amato et al. [
32
]
applied a constrained PMF (by means of the ME-2 scripting) revealing that road
dust emissions were responsible on average for 16% of PM
10
concentrations. An
interesting outcome of this study was that the contribution did not change over the
5 years of study, contrary to industrial emissions, for example, revealing the
existence of a non-controlled sector of transport emissions [
32
]. The same ME-
2 approach was followed by the US EPA that implemented it in EPA PMF v5.0 (of
soon release). In Madrid (Spain) similar contributions from vehicular exhaust and
road dust emissions (31% and 29% respectively) to kerbside daily PM
10
measurements were estimated by PMF [
125
] over 1 month measurements. In
Greece, Karanasiou et al. [
51
] resolved road dust, motor exhaust and a soil factors
by coupling PMF2 and PMF3 models on multiple size fractions in Athens,
estimating the road contribution to be between 12% and 34% of PM
10
. Manoli
et al. [
50
] applied in Thessaloniki (Greece) multiple regression on absolute princi-
pal component scores estimating that road dust was responsible of 28% and 57% of
PM
10
and coarse PM, respectively.
In Scandinavian countries road dust emissions generate large quantities of coarse
particles by enhanced pavement abrasion and mechanical fragmentation of traction
sand grains [
126
-
130
].
Measurement of road dust emission potentials after road sanding on dry roads
indicated a 75% increase in PM
10
emissions after 2.5 h. This effect was short-lived
gm
3
in Sweden, 6
gm
3
in Spain and for 1-5
m
m
m
