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(2002), a similar result was observed around a MSWI, 40% reduction in soil after technical
alteration in the MSWI. Lee et al. (2007) found PCDD/Fs concentration in air around MSWI
decreased approx. 50% after the introduction of a new flue gas treatment, as well as, 99.98%
reduction of PCDD/Fs in stack gas samples. However, the PCDD/Fs level continues to
increase in 2010 survey. The PCDD/Fs distribution in different sites and the relation of
PCDD/Fs variation with distance from MWI is present in Fig.5. In the baseline, all of the
sites almost stay in the same level of PCDD/Fs, and there is no specific trend with distance.
After operation, the level curve (AO) goes up, particularly in the close sites (S1 to S4). With
the amount comparison, the largest increase of PCDD/Fs (629.31 pg g
-1
) is in S2, which is the
closest point from MWI. Furthermore, S1 is the same distance away the stack as S2, and its
increase (271.47 pg g
-1
) is much lower than S2' increase. The main reason is the different
characteristic surface in these two sites, as the thick grass covers in S1. Grass can reduce the
adsorption of PCDD/Fs in soil, even absorb and degrade these toxic substances. And the
curve (AO) of TEQ after operation displays a slight decline with distance. Meanwhile, the
variation of PCDD/Fs is not significant in the farther sites than S5. So approx. 500 m radius
is thought as the influence area in this case, which is consistent with another study (Kim et
al., 2008). In this possible influenced area, there are no inhabitants except the staff of this
plant, so the workers had better take strict protection to avoid health risk.
2500
2500
2000
2000
S2
S2
1500
1500
S2
S2
S2
S2
1000
1000
S2
S2
600
600
300
300
0
0
07
07
08
08
09
09
10
10
Year
Year
6.0
6.0
4.0
4.0
2.0
2.0
0.0
0.0
07
07
08
08
09
09
10
10
Year
Year
Fig. 4. Box plot of PCDD/Fs concentration in soils.
Figure 6 summarizes the average PCDD/Fs level in soil samples in the 2010 year survey and
the comparison with different sites from Spain (Jiménez et al., 1996; Domingo et al., 2000),
Taiwan (Cheng et al., 2003), Italy (Caserini et al., 2004; Capuano et al., 2005), Switzerland
(Schmid et al., 2005), Norway (Andersson & Ottesen, 2008), South Korea (Kim et al., 2008),
China (Yan et al., 2008), USA (Lorber et al., 1998) and Japan (Takei et al., 2000). The present
PCDD/Fs level in this studied region is in the normal level as shown in Fig.6.
