Ⅲ. RESULTS AND DISCUSSION
3.3 Distribution of indicator PCBs in soils and pine needles
31
3.3 Distribution of indicator PCBs in soils and pine needles
32 3.3.2 Spatial distribution of indicator PCBs
The spatial distributions of total seven indicator PCB levels in soil and pine needle samples are displayed in Figure 22. In general, industrial areas were shown the higher concentrations of indicator PCBs in soils than those from suburban and urban areas. The industrial site I8 was having the highest concentration owing to the area where automobile industries are located, whereas sites such as indicator PCB levels in I2 and I3 were relatively low due to the areas near the non-ferrous industries.
The stacked bar graphs of indicator PCB congeners in concentrations at all sites are shown in Figure 23. In Figure 23a, most industrial sites showed higher concentrations of indicator PCBs in soils than those in other areas, and this result is consistent with those from the previous study taken in the same place, Ulsan, and I8 had the highest concentration of indicator PCBs among the sampling sites owing to the influence on automobile activities (Nguyen et al., 2016).
In Figure 23b, the patterns of indicator PCBs in pine needles among the sampling sites have not appeared. In comparisons with sampling sites, some industrial sites such as I1 and I7 had relatively low indicator PCB levels in pine needles. Those sites may be less polluted due to the locations where the canopy effect had happened (Simonich et al., 1995).
Figure 22. Contour maps of ∑7PCBs in two media in Ulsan, Korea.
– 120 120– 140 140– 160 160– 180 180– 200 200– 240 240– 280 280– 320 320– 360 360– 400 Conc. of I-PCBs (pg/g ww) 024 8
Km 024 8
Km
– 300 300– 600 600– 900 900– 1,200 1,200– 1,500 1,500– 1,800 1,800– 2,100 2,100– 2,400 2,400– 2,700 2,700– 3,000 Conc. of I-PCBs (pg/g dw)
S8 S9 S3 S4
S10 S13
S11
S7
U4
U3
S2 S1
U7
U5U6 U2
U1
I1 I2 I3 I4 I5 I6
I7 I8
I9 I10
S12 S5
S6
S8 S9 S3 S4
S10 S13
S11
S7
U4
U3
S2 S1
U7
U5U6 U2
U1
I1 I2 I3 I4 I5 I6
I7 I8
I9 I10
S12 S5
S6
(a) Soil (b) Pine needle
33 Figure 23. Levels of ∑7PCBs in two media in Ulsan, Korea.
0 1000 2000 3000 4000
#180
#153
#138
#118
#101
#52
#28
(a) Soil
(b) Pine needle
0 100 200 300 400
#180
#153
#138
#118
#101
#52
#28
C onc ent ra tio n (pg /g dw ) Conc ent ra tio n (pg /g ww )
Suburban Urban Industrial
34
3.3.3 Average and individual profiles of indicator PCBs
The average and individual profiles of the indicator PCB congeners for three areas and each sampling site are illustrated in Figure 24 and 25, respectively. In Figure 24a, soil samples generally had the higher contents of two higher chlorinated PCB congener groups, PCB 138, PCB 153 (hexa-CBs), accounting for 44% of the normalized concentrations. Based on these results, it can be referred that dry and wet deposition between soil and PCBs was well performed due to the physicochemical properties of soil.
The lower chlorinated PCB congener groups, especially tri-CBs (PCB 28) and tetra-CBs (PCB 52), were volatilized back into the atmosphere, leading to the lowest ratio compared to other PCB congener groups.
In Figure 24b, pine needle, on the contrary, had a high proportion of tri-CBs (38% of ∑7PCBs), which leads to the different distribution pattern of indicator PCBs in soil (17% of ∑7PCBs). This result implies that lower chlorinated PCBs are more likely absorbed into the pine needles, but higher chlorinated PCBs are normally washed off from the needles due to the dry deposition in the particulate phase (Chun, 2009).
Figure 24. Average congener profiles of indicator PCBs in two media in Ulsan, Korea.
0.0 0.2 0.4 0.6 0.8 1.0
Suburban Urban Industrial
0.0 0.2 0.4 0.6 0.8 1.0
Suburban Urban Industrial
#180
#153
#138
#118
#101
#52
#28
(a) Soil (b) Pine needle
Fraction
35
Figure 25. Individual congener profiles of indicator PCBs in two media in Ulsan, Korea.
(a) Soil
0.0 0.2 0.4 0.6 0.8 1.0
#180
#153
#138
#118
#101
#52
#28
0.0 0.2 0.4 0.6 0.8 1.0
#180
#153
#138
#118
#101
#52
#28
(b) Pine needle
Suburban Urban Industrial
FractionFraction
36
3.3.4 Principal component analysis of indicator PCBs
The PCA score and loading plots for indicator PCBs in soils and pine needles from the sampling sites are shown in Figure 26 and Figure 27, including the commercial products called Aroclor 1254 and 1260 as input data for PCA to compare the contamination profiles of each medium and to identify the potential PCB emission sources on the basis of PCA results (Frame et al., 1996; Nguyen et al., 2016).
The PCA score and loading plots for indicator PCBs in soils from the sampling sites are shown in Figure 26, and the PC 1 and PC 2 accounted for 64% and 26% of the total variance. I7, located on the top right side of the score plot, was characterized by high loadings of PCB 101 and PCB 118 in the loading plot, and Aroclor 1254 was located in the same position, which was out of range in the score plot (X: 0.20, Y: 4.17). It was suggested that soil samples from this site were mainly affected by the usage or leakage of transformer oil from petrochemical plants. Since the transformer oil had used for transferring electrical power as an energy supply especially in petrochemical industries, Aroclor 1254 was the main component of transformer oil (Hong et al., 2005; Nguyen et al., 2016). Moreover, soil samples from automobile (I8) and shipbuilding industrial complexes (I9 and I10) were clustered into the same group as Aroclor 1260, with similar congener profiles of higher chlorinated PCBs including PCB 138, PCB 153, and PCB 180. This reflects that anti-fouling paints containing PCBs had been used for ships as extenders for preventing microbial spoilage, and a massive amount of higher chlorinated PCBs had been deposited into the soil due to the spillage of PCB-containing product (Edge et al., 2001; Nguyen et al., 2016).
Figure 26. Principal component analysis results of indicator PCBs in soils (Aroclor 1254, X: 0.20, Y:
4.17).
(a) Score plot (b) Loading plot
Component 1 (64%)
Component 2 (26%)
#28
#52
#153
#138
#180
#101 #118
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
S2 S1 S3
S4 S5
S6 S8
S9
S10S12 S13
U1 U2
U4 U5
I1 U7 I2
I3 I4 I5 I6
I7
I8 I9
A1260
-3 -2 -1 0 1 2 3
-3 -2 -1 0 1 2 3
Industrial Suburban Urban
A1260 A1254
A1254
37
The PCA score and loading plots for indicator PCBs in pine needles from the sampling sites are shown in Figure 27, and the PC 1 and PC 2 accounted for 62% and 31% of the total variance. The pine needle sample from I7, as mentioned earlier, had a similar tendency of indicator PCBs in soil. The commercial product called Aroclor 1254 was in the same position as I7, which was out of range in the score plot (X:
1.16, Y: 2.96). It can be referred that the main source of soil and pine needle samples in this site was derived from the petrochemical industrial complex, in which the usage of Aroclor 1254 as transformer oil was suspected. Unlike soil, pine needle samples collected from I9 and I10 were positioned on the bottom left side of the score plot, whereas Aroclor 1260 was on the opposite side. It was expected the deposition of organic pollutants in the soil for a long period would be possible to identify the historical uses of commercial products that had been banned since the mid-90s. In that case, this result implied that the application in the commercial product for shipbuilding and automobile industries had stopped for recent years.
Figure 27. Principal component analysis results of indicator PCBs in pine needles (I7, X: 1.16, Y: 2.96;
Aroclor 1254, X: 0.65, Y: 4.00; Aroclor 1260, X: 5.03, Y: -1.69).
U2 U3
U5
S1 S2
S3
S5 S6 S10
I1
I2 I5 I3
I6 I8 I9 I10
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
#153
#52 #180
#138
#28
#118 #101
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
-1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
Component 1 (62%)
Component 2 (31%)
Industrial Suburban Urban
A1260 A1254
(a) Score plot (b) Loading plot
A1254 I7*
A1260
38