Environmental Engineering Reference
In-Depth Information
Dry Deposition
The average mass concentrations of fine and coarse particle material were 31 ± 13
and 33 ± 22 mg/m, respectively
[10]
. The dry deposition was evaluated for copper, lead
and cadmium. Tables
2
and
3
show the mean concentrations (standard deviation),
minimum and maximum values of copper, lead and cadmium in fine (d < 2.5 mm)
and coarse mode aerosol (2.5 < d < 10 mm) for diurnal and nocturnal periods.
The results show high variability, suggesting influence of emissions and meteoro-
logical conditions. During the aerosol sampling period, the meteorological conditions
in São Paulo showed 31 days with unfavorable conditions for pollutant dispersion
and 59 days with thermal inversion (height < 400 m). The mean metal concentra-
tions were higher in aerosols collected during night compared to samples collected
during the day. This might be explained by the evolution of a stable nocturnal
boundary layer and with intense vehicular traffic at the beginning of evenings.
Lead was the predominant metal, followed by copper and cadmium in the fine
particle fraction (Table
2
). On the other hand, in the coarse fraction, copper was the
metal found in higher concentration (Table
3
). The relative contribution of Cd, Pb
and Cu in fine and coarse particulate matter is presented in Fig.
1
, suggesting that
metals are emitted from different sources. Lead contamination in the atmosphere
can be attributed to industrial emissions, mainly non-ferrous smelters; while
copper can be associated with emissions from motor vehicles using ethanol and
gasohol (mixture of 22-25% in ethanol + gasoline) as fuels. In urban areas, like
São Paulo, cadmium sources can be associated with both worn out tires and the white
paint used for marking lines on pavement (asphalt) on streets and avenues
[11]
.
The significant contribution of lead to PM
2.5
may be an indicative of the toxicity of
inhalable particle matter, which has been correlated with pulmonary diseases.
Table 2
Average concentrations (standard deviation), and minimum and maximum values of the
metals in ine particle (d < 2.5 mm) samples
Diurnal
Nocturnal
Average (sd)
Min.
Max.
Average (sd)
Min.
Max.
ng/m
ng/m
Cd
0.61 (0.81)
0.13
2.4
1.5 (2.7)
0.17
8.2
Pb
13 (6.6)
5.7
27
25 (33)
4.5
111
Cu
4.7 (4.1)
1.7
14
12 (19)
1.9
63
Table 3
Average concentrations (standard deviation), and minimum and maximum values of the
metals in
coarse particle samples (2.5 < d < 10 mm)
Diurnal
Nocturnal
Average (sd)
Min.
Max.
Average (sd)
Min.
Max.
ng/m
ng/m
Cd
0.49 (0.77)
0.17
2.4
0.60 (0.83)
0.17
2.3
Pb
8.6 (7.9)
2.1
27
10 (14)
2.6
48
Cu
11 (6.8)
2.3
26
18 (17)
8.2
62
