Environmental Engineering Reference
In-Depth Information
Kupiainen 2007; Patra
et al
. 2008), agricultural
activities, street sweeping (Yuan
et al
. 2003), and
construction operations also contribute to this
process. Soil resuspension is probably the main
source of K, Mg, and Mn in an urban aerosol, and
together with coal combustion (whose emission
profi le, as discussed above, is very similar and diffi -
cult to individualize) should provide a signifi cant
amount of Al, Ca, Ce, Cr, Fe, La, Sc, Sr, Ti, and Th
(Kowalczyk
et al
. 1978; Boni
et al
. 1988). Street dust
and the fi ne soil fraction are enriched in anthropo-
genic trace elements relative to coarser soil particles.
If resuspended, they can make a notable contribution
to the trace element load of the inhalable fraction of
an urban aerosol, for instance a study by Laidlaw &
Filippelli (2008) found signifi cant health risks to
young people from resuspended soil contaminated
with Pb both outside and in the home, leading to
blood lead levels (BLLs) in children in excess of
10
here, however, that Gatz (1975) has used Ca as a
tracer of suspended cement dust. According to
Kowalczyk
et al.
(1982), airborne cement particles
should exhibit concentration ratios K/Ca of approxi-
mately 0.006 and Mg/Ca of approximately 0.16.
Possibly associated with pulses of construction activ-
ity, high activities of radioactive nuclides have been
found in some urban dusts in Coventry, UK
(Charlesworth & Foster 2005). The highest activities
were found in road gutter and street dusts where
some samples approached, and even exceeded, the
ICRP (1991) guidelines of 1 mSv yr
−1
for members of
the public.
In northern countries, the use of spiked tires in
the cold season results in the abrasion of the road
surface. Dust particles thus generated are a major
source of atmospheric particulate matter in clear
winter days. Lastly, depending on the location and
urban characteristics of a city, other specifi c sources
of airborne particles might exert a signifi cant infl u-
ence. As an example, sea spray supplies considerable
amounts of Na to the atmosphere of coastal cities
(Kowalczyk
et al.
1978) and studies such as that by
Pryor
et al
. (2008) suggest that neglecting the inter-
actions of sea spray in considerations of urban air
quality may lead to misleading conclusions being
drawn.
1
in some US cities. In Cairo, Egypt, Sharaf
et al.
(2008) found BLLs up to 14.3
μ
m dL
−
m dL
−1
in chil-
dren living by heavily traffi cked roads, and asserted
than the CDC (2007) 10
μ
m dL
−1
advisory level is too
high. However, soil particles that enter the urban
aerosol can have their origin outside the city limits.
The fi nest fraction of these “natural” particles that
result from crustal erosion can travel long distances
and their chemical makeup refl ects the mineral com-
position of the original soil (Cornille
et al
. 1990).
μ
4.2.2 Source apportionment
The terms “source apportionment” and “receptor
modelling” are used to describe the attempt to
apportion the aerosol measured at a receptor site to
its likely sources, making use of various mathemati-
cal models. The two most widely used categories of
mathematical models are chemical mass balance
(CMB) and multivariate models. The latter use mul-
tivariate analyses techniques (i.e. factor analysis,
target transformation factor analysis, Q-mode factor
analysis) to predict the number of relevant emission
sources in the area and their individual contributions
to a series of aerosol measurements (Harrison
et al.
1997). Receptor models based on factor analysis,
however, are not well suited for source apportion-
ment when two or more emission sources in the
study area have similar “signatures” or elemental
emission profi les. Furthermore, an infi nite number of
models can be produced that will satisfy a given
aerosol composition and all natural constraints, i.e.
4.2.1.4 Other urban sources
Traffi c, domestic heating, and soil resuspension do
not account for all the particulate matter that is
emitted to the atmosphere in an urban environment.
Other sources include specifi c industrial sources,
incineration, construction activities, road weathering
and maintenance, etc. The emission profi le of refuse
incineration depends on several factors (refuse com-
position, design of combustion chamber, effi ciency
of fi lters, and other particle collection equipment),
but it has been reported that incineration is a major
source of Zn, Cd, and Sb in the urban aerosol
(Kowalczyk
et al.
1978, 1982; Pacyna 1983). Wadge
et al.
(1986) found high levels of Pb and Cd in the
fi nest fraction of refuse incineration fl y-ash. The
effects of building construction and renovation, and
weathering of building materials are discussed in
detail in the following section. It should be noted
