Environmental Engineering Reference
In-Depth Information
atmospheric particulates, others monitoring lead
concentrations in urban soils and deposited dust
have reported still signifi cant levels of the element in
solid material (e.g. Charlesworth
et al
. 2003), which
refl ects the storage of historical lead levels. This is
discussed further in the sections on street dusts and
urban soil. As well as the Zn and Cu mentioned
above, traffi c also contributes signifi cant amounts of
Ba, Cd, and Ni, a detailed account of the origin of
which is provided in the next sections, devoted to
street and house dust. The relative contribution of
traffi c to the trace element load in urban particulate
materials has been evaluated alternatively by the
ratios Ba/Pb, Br/Pb, and, using factor analysis, by the
scores on a factor that includes Pb, Cu, Ba, and Zn
(Kowalczyk
et al
. 1982; Sturges & Harrison 1986;
Boni
et al
. 1988; Cornille
et al
. 1990; Paterson
et al.
1996; De Miguel
et al
. 1999; Viana
et al
. 2006).
Recent modifi cations to Factor Analysis, Positive
Matrix Factorization, has been used with multiple
sources to give “signifi cant information on anthro-
pogenic sources” (Mazzei
et al.
2008, p. 87).
However, studies using radioactive isotope ratios,
for instance lead and carbon (Widory
et al.
2004;
Chen
et al
. 2005) have enabled the possibility of fi ner
discrimination with Widory
et al.
(2004) using
carbon isotopes to differentiate between diesel emis-
sions and those of fuel oil, although they do admit
that these conclusions are “subject to debate”
(p. 959).
With the introduction of catalytic converters in the
mid-1970s in the USA and mid-1980s in Europe, and
increasing use of multi-element analytical techniques
such as that afforded by inductively coupled plasma-
atomic emission spectroscopy (ICP-AES), it was real-
ized that the so-called platinum group elements
(PGEs) or platinum group metals (PGMs), which
include Pt, Pd, Rh, Ru, Ir, and Os (Ravindra
et al.
2004) had begun to accumulate in the environment.
In fact, Barbante
et al.
(2001) estimated that Pt from
vehicle catalytic converters alone could release up to
1.4 tonnes of Pt per year globally, and Schäfer
et al.
(1999) found that the daily deposition rate for Pt in
a typical urban site could reach 23 ng m
−2
. It was
found (Palacios
et al.
2000) that these elements
bioaccumulate and are transported in the ultrafi ne
particle sizes, generally less than 0.39
et al.
(2004) provide a detailed review of PGE levels
in environmental materials, including the urban
aerosol and their subsequent health effects which is
beyond the scope of this chapter, but other studies
since then have concentrated on the distribution of
PGEs in deposited road and street dust which will be
covered in the sections which follow.
4.2.1.2 Domestic heating, coal and oil combustion
Depending on the fuel burnt for domestic heating,
its emission profi le can vary noticeably, for instance,
coal combustion is one of the main sources of Mn,
Cr, Cu, Co, As, and Se but its exact emission profi le
depends on the type of coal burnt. Estimates of the
relative contribution of coal combustion to the trace
element load of the urban aerosol are hindered by
the fact that its emission profi le coincides largely with
that of soil resuspension, owing to the similarity
between the alumino-silicate matrix of soil particles
and that of coal fl y ash (Kowalczyk
et al.
1978;
Tomza 1984). However, a differentiating factor
between both sources of particulate material, accord-
ing to these authors, would be the relative enrichment
in As and Se and depletion in Mn of coal fl y ash.
Other elemental markers used to trace the infl uence
of coal combustion include Al, Si, and Ti (Kowalczyk
et al
. 1978; Pacyna 1991; Rose
et al
. 1994).
Vanadium and, to a lesser extent, Ni and S have
been almost universally used as tracers of oil com-
bustion (Kowalczyk
et al
. 1978, 1982; Boni
et al
.
1988; Cornille
et al.
1990; Sadiq & Mian 1994),
although some authors have assigned up to 40% of
all the vanadium in the aerosol of an arid area to
shale-like soil resuspension (Cornille
et al.
1990).
The exact contribution of oil combustion to the
urban aerosol is diffi cult to ascertain because its
emission profi le depends greatly on the origin of the
oil (Kowalczyk
et al.
1978).
4.2.1.3 Resuspension of soil and street
dust particles
Soil and street dust particles can be lifted by wind
currents and incorporated into the urban aerosol,
where they represent a signifi cant proportion of its
coarse fraction (Harrison
et al.
1974). Although
wind is clearly one of the main resuspension agents,
vehicular and pedestrian traffi c (see, for example,
m, at sizes
considered inhalable and therefore of most concern
to human health (Kappos
et al
. 2004). Ravindra
μ
