Environmental Engineering Reference
In-Depth Information
3. Result and Discussion
3.1. Seasonal variation and temporal trends
The concentration of PCDDs/Fs in ambient air samples from 2002 through 2008
ranged from 292 to 9,900 fg/m
3
with a mean 3,300 fg/m
3
. The TEQ value of them
ranged from 22 to 563 fg I-TEQ/m
3
with a mean 142fg I-TEQ/m
3
. The levels were
a bit higher than those of previous studies in urban area but lower than those in
industrial areas (Choi et al., 2008; Raun et al., 2005; Abad et al., 2004). The first
plot in
Fig. 1.
indicates monthly variation of PCDDs/Fs in ambient air. There was
apparently a tendency which the TEQ value in ambient air was higher in the
winter compared to the summer. The PCDDs/Fs concentrations in winter were
approximately double compared to those in summer. The trend of higher levels of
PCDDs/Fs during colder periods has been recognized by other researchers (Raun
et al., 2005; Oh et al., 2001). The seasonal variations of PCDDs/Fs levels are
presumed due to the increase in domestic heating, the presence of temperature
inversion layer in winter and reaction with OH
−
radicals in summer. The second
plot shows temporal trends of PCDDs/Fs in ambient air in Seoul. The plot
indicated that mean TEQ value of PCDDs/Fs in 2002 was 0.187 fg I-TEQ/m
3
and
the mean value tends to decline year by year. The level in 2008 was 0.106 fg I-
TEQ/m
3
.
0.30
0.25
mean
Median
mean
median
0.25
0.20
0.20
0.15
0.15
0.10
0.10
0.05
0.05
0.00
0.00
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
2002
2003
2004
2005
2006
2007
2008
Fig. 1.
Monthly variation and temporal trends of PCDDs/Fs in ambient air
3.2. Congener profile of PCDDs/Fs
The vertical bar chart in
Fig. 2
indicates average congener profiles of PCDDs in
ambient air. This plot presents a similar pattern with hepta- and octa CDDs/Fs
making the major contributions in 2002, 2005, 2008. The ratios of PCDDs/PCDFs
in air were from 0.43 to 0.52. Caserini et al. (2004) reported congener pattern of
PCDDs/Fs in air in Italy. There was no significant difference of congener pattern
