Agriculture Reference
In-Depth Information
For source identification by comparison of PCDD/Fs homologue/congener patterns
between soil and MWI emissions, stack gas and fly ash were collected from this MWI. The
stack gas samples were collected with an isostack sampler (M5, KNJ Engineering, Korea)
according to USEPA method 23A. The sample collection components included a glass fiber
filters, in line with a condenser, the sorbent (XAD-2 resin) module and four impingers. The
sampling labelled-
13
C
12
standard was spiked into the XAD-2 resin before the sampling of
flue gas. And the clean procedure was conducted as EPA23 method, including Soxhlet
extraction by toluene for 24 h, wash with sulfuric acid (H
2
SO4), a multi-layer silica gel
column and an alumina column. The final clean extracts were blow-down to 20 µl under a
gentle stream of nitrogen (N
2
).The fly ash was collected at the exit of the bag filter. The clean
procedure was conducted as EPA1613. The difference between EPA23 and EPA1613 is just
using different labeled-
13
C
12
standard solution as EPA1613 without sampling standard
solution, and the clean process is generally the same. All of these samples were analyzed by
HRGC/HRMS. The more detailed procedure of clean-up flue gas and fly ash samples can be
found in the previous report (Chen et al., 2008).
2.4 Data analysis
All the experimental results were expressed on a dry weight basis. The 2,3,7,8-TeCDD toxic
equivalents (I-TEQ) were calculated using NATO/CCMS factors (1988). Data was
normalized before comparison of homologue and the multivariate analysis. Principal
component analysis (PCA) was used to evaluate the similarities and differences of the
PCDD/Fs homologue patterns and HxCDF isomer profile in soil samples, flue gas and fly
ash. Each sample was assigned a score after PCA, allowing the summarized data to be
further plotted and analyzed. PCA was performed using the SPSS 16.0 software package.
3. Results and analysis
The analysis results are present in table 1, including amount and TEQ concentration.
Amount refers the concentration of total PCDD/Fs homologue from Tetra- to Octa-
chlorinated species. PCDD/Fs level displays significant variation during these four years.
Amount, pg·g
-1
TEQ, pg I-TEQ·g
-1
Sites
2007
2008
2009
2010
2007
2008
2009
2010
S1
58.26
439.84
258.96
290.41
0.78
2.21
3.17
4.74
S2
848.34
1981.89
1155.45
1279.39
2.63
5.78
3.54
5.11
S3
397.04
465.10
374.05
669.21
1.78
3.51
2.37
6.07
S4
78.44
626.59
170.45
293.11
0.97
4.83
2.55
4.35
S5
433.77
546.01
551.95
1012.10
1.04
1.04
1.84
3.34
S6
66.48
89.55
123.51
164.73
0.64
0.94
1.34
1.41
S7
44.34
175.91
66.82
97.59
0.46
1.77
0.85
0.98
S8
263.18
273.81
252.84
329.64
1.91
1.99
1.47
3.30
S9
81.64
133.31
125.84
159.62
1.08
1.25
0.91
1.07
S10
57.18
78.51
67.49
92.80
0.45
0.88
0.69
1.12
S11
76.71
163.60
106.04
269.31
0.71
0.98
1.01
1.87
SB
55.94
55.72
79.42
85.01
0.60
0.53
0.73
0.65
Mean
205.11
419.15
277.73
395.24
1.09
2.14
1.70
2.83
Median
77.57
224.86
148.14
279.86
0.87
1.51
1.40
2.59
Table 1. PCDD/Fs amount and I-TEQ concentration in soil samples.
