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Fs emissions from secondary nonferrous smelting plants and towards to their source emission reduction
Journal Pre-proof Variations of PCDD/Fs emissions from secondary nonferrous smelting plants and towards to their source emission reduction Yuanping Yang, Guanglong Wu, Cheng Jiang, Minghui Zheng, Lili Yang, Jiahong Xie, Qingjie Wang, Minxiang Wang, Cui Li, Guorui Liu PII:
S0269-7491(19)35315-1
DOI:
https://doi.org/10.1016/j.envpol.2020.113946
Reference:
ENPO 113946
To appear in:
Environmental Pollution
Received Date: 16 September 2019 Revised Date:
25 November 2019
Accepted Date: 7 January 2020
Please cite this article as: Yang, Y., Wu, G., Jiang, C., Zheng, M., Yang, L., Xie, J., Wang, Q., Wang, M., Li, C., Liu, G., Variations of PCDD/Fs emissions from secondary nonferrous smelting plants and towards to their source emission reduction, Environmental Pollution (2020), doi: https://doi.org/10.1016/ j.envpol.2020.113946. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Ltd.
1
Variations of PCDD/Fs emissions from secondary nonferrous
2
smelting plants and towards to their source emission reduction
3
Yuanping Yang a,b, Guanglong Wu c, Cheng Jiang c, Minghui Zheng
4
Jiahong Xie c, Qingjie Wang a, Minxiang Wang a, Cui Li a,b, Guorui Liu a,b,*
5
a
（
Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box
7
2871, Beijing, 100085, China
8
b
9
c
10
a,b
, Lili Yang
a,b
,
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research
University of Chinese Academy of Sciences, Beijing, 100049, China International Environmental Cooperation Center, Ministry of Ecology and
Environment of People’s Republic of China, Beijing, China, 100035
11 12
*
13
E-mail: [email protected]
14
Co-authors’
15
[email protected] (G.L.Wu); Cheng Jiang: [email protected]
1（
(C.Jiang); Minghui Zheng: [email protected] (M.H.Zheng); Lili Yang:
17
[email protected] (L.L.Yang); Jiahong Xie: [email protected] (J.H.Xie);
18
Qingjie
19
[email protected] (M.X. Wang); Cui Li: [email protected] (C.Li).
Corresponding author: Tel: +86-10-6284-9356; Fax: +86-10-6284-9356
email:
Wang:
Yuanping
Yang:
[email protected]
20 21 22
Declarations of interest: none
1
[email protected]
(Q.J.Wang);
(Y.P.Yang);
Minxiang
Wang:
23 24
Abstract Polychlorinated
dibenzo-p-dioxins
and
dibenzofurans
(PCDD/Fs)
are
25
cancerogenic organic pollutants that priority controlled by Stockholm Convention
2（
with globally 182 signatories now. Secondary nonferrous smelting plants are
27
confirmed to be important sources in China due to its large industrial activities and
28
high emissions of PCDD/Fs. It is important to prioritize source to achieve source
29
emission reduction by conducting field monitoring on typical case plants. Here, the
30
emission profiles and levels of PCDD/Fs were investigated in 25 stack gas samples
31
collected from three secondary copper production (SeCu), two secondary zinc
32
production (SeZn) and two secondary lead production (SePb). Both average mass
33
concentration and toxic equivalency quantity (TEQ) concentrations of PCDD/Fs all
34
generally decreased in the order: SeCu >SeZn > SePb. It is noteworthy that the mean
35
TEQ concentration in stack gas from SeCu with oxygen-enrich melting furnace
3（
technology, at 2.7 ng I-TEQ/Nm3, was much higher than the concentrations of other
37
smelting processes. The average emission factors and annual release amounts of
38
PCDD/Fs from SeCu, SePb and SeZn investigated were 28.4, 1.5, 10.4 µg I-TEQ/t
39
and 1.03, 0.023, 0.17 g I-TEQ/year, respectively. The ratios of 2,3,7,8-TCDF to
40
1,2,3,7,8-PeCDF and OCDD to 1,2,3,7,8,9-HxCDD varied to large extent for three
41
metal smelting, which could be used as diagnostic ratios of tracing specific
42
PCDD/Fs sources. Addition of copper-containing sludge into the raw materials might
43
lead to higher PCDD/Fs emissions. It is important to emphasize and reduce the
44
PCDD/Fs emissions from oxygen-enrich melting furnace from secondary copper 2
45
productions.
4（ 47
Capsule abstract
48
Copper smelting with oxygen-enrich melting furnace had the highest PCDD/F
49
emissions. Diagnostic ratios of specific congeners were suggested for smelters to
50
tracing PCDD/F sources.
51 52
Keywords: PCDD/Fs; secondary metallurgy industry; persistent organic pollutants;
53
oxygen-enrich melting furnace; copper sludge
54
3
55 5（
1. Introduction Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs)
57
are classified as persistent organic pollutants (POPs) which have acute and chronic
58
effects may pose enormous possible risks to the environment and human health
59
(Knutsen et al., 2018; Van den Berg et al., 1998; Van den Berg et al., 2006). PCDD/Fs
（0
are unintentionally formed and released from many thermal industrial sources such as
（1
waste incineration (Kanan and Samara, 2018; UNEP, 2013; Zhu et al., 2018) and
（2
secondary metallurgy production (Lv et al., 2011), which can result in the
（3
contamination of the environment with long term contamination of soils (Weber et al.,
（4
2018) and food producing animals in the surrounding with associated human exposure
（5
(Weber et al., 2019). The secondary metallurgy manufacture including secondary
（（
copper (SeCu), zinc (SeZn) and lead production (SePb) have been addressed to be
（7
major sources of PCDD/Fs in environment (Ba et al., 2009a; Ba et al., 2009b),
（8
especially secondary zinc smelters can have extreme high releases of PCDD/Fs above
（9
100 ng TEQ/Nm3 (Chi et al., 2007). Tracing the PCDD/Fs emissions from secondary
70
metallurgy manufacture is an activity of great importance to metallurgy plants
71
management and plays an important role in our country's implementation of the
72
Stockholm Convention.
73
Several researchers focused on the emission factors and homolog and congener
74
profiles of PCDD/Fs from secondary metallurgy industry (Altarawneh et al., 2009;
75
Chin et al., 2011; Wang et al., 2016; Wu et al., 2018). Yu et al., (2006) reported the
7（
release levels of PCDD/Fs from various secondary metal smelting industries in Korea. 4
77
It was reported that the emission concentration of PCDD/Fs in flue gas of different
78
secondary metal smelting industries varied greatly. The emission factor of PCDD/Fs
79
during the process of secondary copper smelting was 24.4 µg TEQ/t, which was much
80
higher than that of secondary lead and zinc industries (Yu et al., 2006). Ba et al.,
81
(2009) investigated the emission levels of PCDD/Fs in stack gas of several secondary
82
copper smelters in China (Ba et al., 2009b). The concentrations of PCDD/Fs releases
83
varied from 0.043 to 15.8 ng TEQ/Nm3. At the same time, the total PCDD/Fs
84
emissions of China's secondary copper smelting industry in 2009 were estimated at
85
37.5 g TEQ/year, which was higher than that of PCDD/Fs in the recycled lead and
8（
zinc smelting industries (Ba et al., 2009a). Besides, Nie et al., (2011) studied the
87
effects of different raw materials, pretreatment technology and production scale on
88
PCDD/Fs emissions in the process of secondary copper smelting, indicating that the
89
pretreatment of raw materials can effectively reduce PCDD/Fs emissions in the
90
process of reclaimed copper smelting (Nie et al., 2011). Subsequently, Hu et al., (2013)
91
surveyed the stack gas levels of PCDD/Fs from different smelting stages of secondary
92
copper (feeding-fusion stage, oxidation stage and deoxidization stage). It was found
93
that feeding-fusion stage was the dominate discharge stage of PCDD/Fs in the process
94
of reclaimed copper smelting (Hu et al., 2013).
95
Many secondary copper smelting enterprises currently use oxygen-enriched
9（
smelting furnace to process copper-containing sludge, low-grade waste copper and
97
other raw materials to produce crude copper, which is used as raw material for copper
98
production in converter, thereby improving the grade of copper (Ministry of ecology 5
99
and environment of the people's Republic of China, 2017). To the best of our
100
knowledge, the data about the release of PCDD/Fs in oxygen-enrich smelting furnaces
101
is scarce. In the other hand, the emission limits and regulations of PCDD/Fs in stack
102
gases from secondary metallurgy industry continued to be more and more stringent in
103
the recent years (Ministry of Industry and Information Technology of the People's
104
Republic of China, 2006). Nevertheless, there is no survey on PCDD/Fs emissions
105
from oxygen-enriched smelting furnace, leading to the absence of data about release
10（
concentration and profile of PCDD/Fs in this facility of secondary copper smelting
107
processes. Such a gap indicated urgently need for case studies with the aim of better
108
recognizing and evaluating the major emission stages and source emission control of
109
PCDD/Fs for secondary nonferrous smelting industries. This is significant for towards
110
to the source emission control of secondary copper smelting industries. Moreover,
111
much more data about PCDD/Fs levels and profiles from secondary zinc and lead
112
production is also needed for accurately evaluating their emissions on national scale.
113
In this study, 25 stack gas samples from secondary nonferrous productions including
114
SeCu, SeZn and SePb were isokinetic collected and quantified for seventeen toxic
115
PCDD/Fs congeners. The congener profiles of PCDD/Fs from the investigated
11（
facilities were evaluated for exploring potential formation mechanisms. Additionally,
117
the emission factors and annual release amounts of PCDD/Fs expressed in the toxic
118
equivalency (TEQ) were also calculated for comprehensively evaluating the PCDD/Fs
119
emission from secondary metallurgy industries in China.
120 （
121
2. Materials and methods
122
2.1. Basic information on the investigated plants and stack gas sample collection
123
Seven typical secondary metallurgy plants were investigated, including three
124
SeCu, two SePb, and two SeZn (basic information of these plants are provided in
125
Table 1). In order to understand the release of PCDD/Fs from different smelting
12（
furnaces of secondary copper smelting industry, the flue gas samples from converter
127
furnace (SeCu(1), SeCu(2)-A) and oxygen-enriched smelter furnace (SeCu(2)-B,
128
SeCu(3)) were collected. 25 stack gas samples were collected from investigated
129
plants by an automatic isokinetic sampling system, Isostack Basic (TCR TECORA,
130
Milan, Italy), in accordance with the European Standard EN-1948-1 which was the
131
sampling procedure. Before sampling the stack gas samples, 13C12-labelled PCDD/Fs
132
was spiked into the XAD-2 resin as surrogate sampling standards.
133
2.2. Stack gas sample preparation and instrumental analysis of PCDD/Fs
134
The extraction and purification, identification and quantification of PCDD/Fs
135
congeners were accomplished in accordance with EN-1948-2 and EN-1948-3,
13（
respectively. Briefly,
137
spiked into stack gas samples. The stack gas samples were then Soxhlet extracted for
138
about 24 hours by using 250 mL of toluene. The extracts were evaporated to
139
approximately 1-2 mL using the rotary evaporator. After concentration, the extracts
140
were sequentially purified by a series of adsorption columns, including acidified
141
silica gel, a multilayer silica gel, and activated-charcoal columns. Finally,
13
C12-labelled PCDD/Fs internal quantification standards were
7
142
13
143
chromatography/high resolution mass spectrometry (HRGC/HRMS) analysis.
144
Congener specific analysis of PCDD/Fs were performed by using a gas
145
chromatograph coupled to a DFS mass spectrometer (Thermo Fisher Scientific,
14（
Waltham, MA, USA), and a DB-5 capillary column (60 m × 0.25 mm × 0.25 µm)
147
was selected to separate the analytes. The HRMS was equipped with a positive
148
electron impact source and HRMS was tuned and operated at a mass resolution of
149
around 10,000. The ion source was specified at 250
150
to be 37 eV.
151
2.3. Quality assurance and quality control (QA/QC)
152
C-labelled recovery standards were added to the extracts before high resolution gas
The recoveries of
13
and the electron energy is set
C12-labelled PCDD/Fs internal standards in the stack gas
153
samples were range 58 to 120%, meeting the analytical method requirements. Three
154
QC criteria were employed in the determination of the target compounds: (a) the GC
155
retention time matched to the available corresponding
15（
the signal-to-noise ratio was >3:1; and (c) the isotopic ratios of two monitored ions
157
for the analyte should be within ±15% of the theoretical values. Furthermore, there
158
was a blank in each batch of samples, and no obvious interference was detected in
159
the blank samples. When calculating the concentration of PCDD/Fs in stack gas, the
1（0
collection volume will be converted to the standard state (0
13
C12-labelled standards; (b)
and 1 atm).
1（1
Statistical analysis was employed by SPSS version 25 software (IBM, USA). In
1（2
order to minimize the influence of total concentrations, the congener concentrations
1（3
were normalized to the percentage of total concentrations. Pearson correlation 8
1（4
analysis was conducted by SPSS to explore possible relationships between the target
1（5
compounds and total TEQs. Statistical significance of p < 0.05 was set for correlation
1（（
analysis.
1（7 1（8
3. Results and Discussion
1（9
3.1. Emission levels and variations of PCDD/Fs from different secondary
170
metallurgy facilities and different smelting stages
171
The mass concentrations and I-TEQ of PCDD/Fs were determined in stack gas
172
samples sampled from the seven secondary nonferrous smelting plants investigated
173
are presented in Fig.1. Obviously, there was a large concentrations variations of
174
PCDD/Fs among the different metallurgy smelting industries (SeCu, SeZn and
175
SePb) and among different plants in the same nonferrous smelting category. In
17（
general, the average concentrations of PCDD/Fs in stack gas samples of three
177
category of sources ranged from high to low as follow: SeCu > SeZn > SePb, the
178
corresponding mass concentrations were 53.35, 24.47, 1.53 ng/Nm3 and the
179
corresponding I-TEQ concentrations were 0.84, 0.48, 0.05 ng TEQ/Nm3,
180
respectively. As seen in Fig. 1, the tendencies of mass concentrations of PCDD/Fs
181
from different plants were generally consistent with those of PCDD/Fs TEQ
182
concentrations. The TEQ concentrations of PCDD/Fs in this study were
183
significantly lower than that reported by Ba et al. in 2009, where corresponding
184
concentration were 2.84, 98.02, 0.35 ng TEQ/Nm3 for SeCu, SeZn, and SePb,
9
185
respectively (Ba et al., 2009a; Ba et al., 2009b), indicating that the metal smelting
18（
techniques and stack gas removal technology have been obviously upgraded or
187
improved and achieved remarkable achievements in recent years in China.
188
There are multiple process stages and different types of furnaces for secondary
189
copper smelting. In order to recognize the dominant stages of PCDD/Fs emissions
190
from secondary copper smelting sources, we aim to compare the PCDD/Fs
191
concentrations in the stack gas collected from different smelting furnaces in the
192
secondary copper smelting industry. Firstly, the flue gas samples from converter
193
furnace and oxygen-enriched smelter were collected and analyzed. The converter
194
furnace usually had three main smelting stages: feeding-fusion (FF), oxidation
195
(OX) and deoxidization (DO), and the corresponding dioxin concentrations in the
19（
flue gas were sequentially reduced, which were in the range of 0.11-0.80, 0.07-0.19,
197
0.06-0.07 ng I-TEQ/Nm3, respectively. These trends were similar to the previous
198
report in the stack gas of different stages of secondary copper production (Hu et al.,
199
2013) . However, it was noteworthy that the mean TEQ in stack gas from
200
SeCu(2)-B (oxygen-enrich melting furnace) was 2.7 ng TEQ/Nm3. This value is far
201
higher than the concentrations of PCDD/Fs released from the converter furnace in
202
the same plant, which suggested that PCDD/Fs emissions from oxygen-enrich
203
melting furnace should be emphasized. This is the first measurement of PCDD/Fs
204
released from oxygen-enrich melting furnace and the results are significant for
205
further control and reduction of PCDD/Fs from secondary copper smelting sources.
10
20（
The mean TEQ concentration in stack gas from SeCu(2)-B was approximately
207
21 times higher than that in SeCu(3) using the same type of furnace. After
208
comparing the raw materials, smelting processes and pollution control facilities of
209
the above two secondary copper smelters, it might be attributable to the difference
210
in raw materials: SeCu(2)-B were 30% copper-containing sludge and 70% scrap
211
copper, while SeCu(3) was 100% scrap copper. The carbon source, chlorine source,
212
and catalytically metal elements are widely recognized as important factors in the
213
formation of PCDD/Fs (Heeb et al., 2013; Kakuta et al., 2007; Kuzuhara et al.,
214
2003; Vallejo et al., 2013; Wu et al., 2018). It is widely recognized that ash from
215
secondary copper smelters have the high PCDD/Fs formation potential (Cagnetta et
21（
al., 2016; Liu et al., 2015), since copper is more likely to catalyze the formation of
217
PCDD/Fs during thermal processes (Hung et al., 2015; Stieglitz et al., 1989).
218
Therefore, the TOC contents (3.3%), Cu element (25.1%) and chlorine (4.3%) in
219
the copper-containing sludge from electroplating industry may explicate that the
220
PCDD/Fs concentration of SeCu(2)-B was higher than that of SeCu(3). It was
221
obvious that different raw material compositions can affect the formation amounts
222
of the PCDD/Fs in the secondary metal smelting processes.
223
3.2. Congener profiles and homolog distributions of PCDD/Fs from different
224
industries
225
Homolog patterns and congener profiles of PCDD/Fs were compared for
22（
understanding their emission characteristics in stack gas from different
11
227
metallurgical industries. Fig. 2 presents the congener profiles of 2,3,7,8-substitude
228
PCDD/Fs in the stack gas samples from various industries. In most of stack gas
229
samples, OCDD and 1,2,3,4,6,7,8-HpCDD were the major congeners. The
230
contributions of PCDDs to total PCDD/Fs increased with chlorination degree
231
elevation. Those general patterns were consistent with those for incinerators (Abad
232
et al., 2006; Li et al., 2017), cement kilns (Ames et al., 2012; Zou et al., 2018), and
233
coke plants (Liu et al., 2009). The congener 1,2,3,4,6,7,8-HpCDF was dominant in
234
the PCDFs in the samples and this is similar to that in previous studies (Li et al.,
235
2015; Liu et al., 2009). Meanwhile, the proportion of OCDD increases with the
23（
process of smelting in the samples collected from secondary copper production
237
converter furnace, with the ratio in FF, OX and DO stages was 9.5-13.9%,
238
16.7-20.7% and 25.4-27.5%, respectively (Fig. 2a). The ratios of specific PCDD/Fs
239
congeners can provide important information on source apportioning of PCDD/Fs
240
in the environment (Liu et al., 2015). To further assess the differences in congener
241
profiles of different secondary metallurgy industries, we calculated the
242
concentration ratios of the specific congeners with clear discrepancy. The average
243
ratios of 2,3,7,8-TCDF to 1,2,3,7,8-PeCDF were 0.82, 3.2 and 0.39 for SeCu
244
oxygen-enrich melting furnace, SeZn and SePb, respectively. The average ratios of
245
OCDD to 1,2,3,4,6,7,8-HpCDD were 1.8, 1.1 and 0.41 for SeCu oxygen-enrich
24（
melting furnace, SeZn and SePb, respectively. Those ratios could be used as
247
diagnostic values of tracing the sources of PCDD/Fs in the environment. Moreover,
248
to obtain comprehensive fingerprinting of PCDD/Fs, a more detailed assessment of 12
249
congener patterns including the non-2,3,7,8-substituted congeners should be done in
250
future (Hagenmaier et al., 1994; Ooi et al., 2018).
251
Pearson correlation analysis was conducted to study the correlations among
252
the congener concentrations of PCDD/Fs and total TEQ (Fig. 3). Positive
253
correlations (R2>0.9, p < 0.05) between 2,3,4,6,7,8-HxCDF, 1,2,3,4,6,7,8-HpCDF,
254
1,2,3,4,7,8,9-HpCDF, OCDF, 1,2,3,4,6,7,8-HpCDD, OCDD and TEQ were
255
observed.
25（
1,2,3,4,6,7,8-HpCDD, display much significant correlation with TEQ, with R2 of
257
0.975 and 0.972, respectively, which can act as indicators for estimating PCDD/Fs
258
emissions in TEQ from secondary metal smelting processes.
Two
congeners
comprised
of
1,2,3,4,7,8,9-HpCDF
and
259
The homolog contributions to PCDD/Fs TEQ in the stack gases from the 7
2（0
plants investigated are presented in Fig. 4. For PCDD/Fs homolog profiles, lower
2（1
chlorinated PCDD/Fs homologs (tetra-, and penta-) were dominant in the stack gas
2（2
from SeCu converter furnace and SePb, while higher chlorinated PCDD/Fs
2（3
homologs were dominant in SeCu oxygen-enrich melting furnace and SeZn. The
2（4
different homolog pattern may arise from the different formation mechanisms of
2（5
PCDD/Fs homologs under different metal catalysts (Liu et al., 2015; Oh et al.,
2（（
2004).
2（7
3.3. Emission factors, annual emission amounts and implication for source
2（8
emission reduction
2（9
Derivation of the emission factors (EFs) is significant for compiling emission 13
270
inventories and estimating PCDD/Fs emission amounts from whole industries on
271
national scale based on available monitoring data from studies on case plants. It is
272
also important to recognize the priority sources and assist regulatory agencies to
273
develop best control technique and strategy for reducing overall emissions. The
274
following formula was used for deriving emission factors and calculating the total
275
release of unintentional POPs (UNEP, 2013).
27（
( / ) =
277
/ ( /!"# ) × %& '()* ( +, %('- (!"# /. )
278
= > ( /?@ ) = Emission
279
activity level of reference year (t/year)
1
/0123 4567891:6; (1/<)
factor
(ng
TEQ/t) × 2
280
The emission factors varied among different categories of metallurgy industries
281
and also among different smelting plants for a given metal category. The derived
282
emission factors and evaluated annual emission amounts of PCDD/Fs from flue gas of
283
the secondary nonferrous metal smelters are presented in Table 2. The emission
284
factors ranged from 0.79 to 106.8 µg TEQ/t. The emission factors derived in our study
285
were consistent with those previous publications for metallurgical plants (Antunes et
28（
al., 2012; Ba et al., 2009a; Ba et al., 2009b; Lv et al., 2011). For secondary copper
287
smelters, the emission factors of SeCu(1), SeCu(2)-A and SeCu(3) were all lower than
288
the emission factor of UNEP toolkit’s (5 µg TEQ/t for classification with optimized
289
for PCDD/PCDF control), indicating that the optimization control was carried out for
290
the PCDD/Fs emissions, such as the pretreatment of raw materials or the treatment of
291
flue gas with activated carbon (UNEP, 2013). However, the highest EFs were 14
292
estimated for a secondary copper production plant with oxygen-enrich melting
293
furnace technology (SeCu(2)-B; 106.8 µg TEQ/t), which located between the
294
classification of the well controlled (50 µg TEQ/t) and the basic technology (800 µg
295
TEQ/t) in the UNEP Toolkit. The secondary lead smelter's emission factors were
29（
lower than the UNEP toolkit’s emission factor (8 µg TEQ/t for removing PVC plants
297
and 80 µg TEQ/t for scrap containing PVC). For the investigated secondary zinc
298
smelters, bag filters or electrostatic precipitators were adopted for control dioxins
299
emissions into air, the emission factors were lower than the UNEP toolkit’s emission
300
factor (100 ug TEQ/t for classification of hot briquetting/rotary furnaces, basic dust
301
control; e.g., fabric filters/electrostatic precipitation) (UNEP, 2013). The emission
302
amounts represented the emission level and activity intensity of the specific industries.
303
In this study, the estimated total annual stack gas emissions of the 7 investigated
304
plants ranged from 11.9 to 3847.2 mg TEQ/year.
305
There are about a thousand secondary nonferrous smelting plants being operation
30（
in China. Due to the high emission factors and total emission amounts, it is important
307
to pay attention to the PCDD/Fs emissions from secondary nonferrous productions.
308
This field study on the case plants found that the PCDD/Fs emissions from
309
oxygen-enrich melting furnace were much higher than that in the three stages of
310
converter furnaces. Thus, it is important to optimize the operation parameters in this
311
stage and reduce PCDD/Fs formation and emissions from the oxygen-enrich melting
312
furnace, which was scarcely recognized before this study. We also found that the
313
addition of copper sludge into the raw materials could increase the PCDD/Fs 15
314
emissions. These findings in this study might provide important knowledge for the
315
considerations of PCDD/Fs control, reduction and regulations by the enterprise or
31（
policy makers, which could contribute to the reduction of human exposure in China.
317
Our results also pointed out that the estimated PCDD/Fs emission amount decreased
318
compared to that evaluated in 2009.
319 320
4. Conclusions
321
In this study, the emission characteristics of PCDD/Fs in 25 stack gas samples
322
collected from secondary nonferrous productions were investigated. The results
323
indicated that PCDD/Fs concentrations in stack gas were in the order of SeCu >SeZn
324
> SePb. The average TEQ concentration in stack gas from SeCu with oxygen-enrich
325
melting furnace technology was higher than the concentrations of other smelting
32（
processes. The highest EFs and EAs were also estimated for SeCu(2)-B, at 106.8 µg
327
TEQ/t and 3847.20 mg TEQ/year, respectively. It was found that addition of
328
copper-containing sludge into the raw materials might result in higher PCDD/Fs
329
formation and emissions. Ratios of specific congeners could be used for the
330
diagnostic ratios for identifying their specific sources in the environment. These
331
results might provide important knowledge for the considerations of PCDD/Fs
332
control, reduction and regulations in secondary nonferrous smelting plants, and also
333
emphasize that high emissions of PCDD/Fs from the secondary metal industries and
334
the potential long-term risk to the surrounding areas should attract more attention.
335
Besides, a more comprehensive fingerprinting is available including the 1（
33（
non-2,3,7,8-substituted congeners and need to be applied for source assessment in
337
future.
338 339 340
Acknowledgments
341
This work was supported by the National Natural Science Foundation of China
342
(21936007; 21777172), Beijing Natural Science Foundation (8182052), Youth
343
Innovation Promotion Association of the Chinese Academy of Sciences (2016038).
344 345
Competing financial interest
34（
The authors declare no competing financial interest.
347 348
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Captions of Figures and Tables: Fig. 1. Mass concentrations of PCDDs and PCDFs, I-TEQ concentration of PCDD/Fs in stack gas from different secondary metallurgy industries. Fig 2. Contributions of PCDD/Fs congeners to the total PCDD/Fs concentrations in the stack gas samples from different smelting stages of secondary copper (SeCu) converter furnace (a), SeCu oxygen-enrich melting furnace (b), secondary lead production (c) and secondary zinc production (d). Fig 3. Pearson correlation of PCDD/Fs congeners and I-TEQ. Fig 4. PCDD/Fs homologue distribution for the stack gas samples from the 7 plants investigated.
Table 1. Basic information on the investigated plants. Table 2. Derivation of emission factors and estimation of annual emission amounts of PCDD/Fs form the investigated plants.
24
Fig. 1. Mass concentrations of PCDDs and PCDFs, I-TEQ concentration of PCDD/Fs in stack gas from different secondary metallurgy industries.
25
Fig. 2. Contributions of PCDD/Fs congeners to the total PCDD/Fs concentrations in the stack gas samples from different smelting stages of secondary copper production (SeCu) converter furnace (a), SeCu oxygen-enrich melting furnace (b), secondary lead production(c) and secondary zinc production (d).
2（
Fig. 3. Pearson correlation of PCDD/Fs congeners and I-TEQ.
27
Fig. 4. PCDD/Fs homologue distribution for the stack gas samples from the 7 plants investigated.
28
Table 1. Basic information on the investigated plants. Abbreviation of investigated plants
SeCu(1)
SeCu(2)-A
SeCu(2)-B
SeCu(3)
SePb(1)
SePb(2)
SeZn(1)
SeZn(2)
category of metallurgical
Furnace type
plants secondary copper production
secondary copper production
production secondary zinc production
crude copper + copper
converter furnace
120
activated carbon + bag filter
3
55
bag filter
2
140
bag filter
3
copper scrap
3
lead scrap
lead slag + lead scrap
oxygen-enrich melting
furnace
secondary zinc
Raw material
5
production
production
samples
activated carbon + bag filter
oxygen-enrich melting
secondary lead
Number of
110
secondary copper
production
(t/day)
Air Pollution Control Devices
converter furnace
furnace
secondary lead
Capacity
electrostatic precipitation + gravity
rotary furnace
50
rotary furnace
20
bag fliter
3
rotary furnace
60
gravity settling + bag fliter
3
rotary furnace
64
29
settling + bag filter
electrostatic precipitation + bag fliter
3
scrap crude copper + copper scrap copper sludge + copper scrap
dust of steel mill + zinc dross zinc ore + zinc dross
Table 2. Derivation of emission factors and estimation of annual emission amounts of PCDD/Fs form the investigated plants. Abbreviation of
Emission factors
Annual emission amounts
investigated plants
(ug TEQ/t )
(mg TEQ/year)
SeCu(1)
2.57
92.56
SeCu(2)-A
3.42
171.11
SeCu(2)-B
106.86
3847.20
SeCu(3)
0.79
11.93
SePb(1)
2.18
30.59
SePb(2)
0.89
17.55
SeZn(1)
9.54
177.61
SeZn(2)
11.22
168.33
30
Highlights
PCDD/Fs emitted from seven secondary metallurgical plants were investigated
Copper smelting with oxygen-enrich melting furnace had the highest PCDD/F emissions
Copper-containing sludge in raw materials might cause higher PCDD/F formation
Diagnostic ratios of specific congeners were suggested for different metal smelters
Author Contribution Statement Yuanping Yang: Formal analysis, Investigation, Writing - Original Draft. Guorui Liu: Conceptualization, Investigation, Writing - Review & Editing. Minghui Zheng: Resources, Writing - Review & Editing, Supervision. Guanglong Wu: Investigation, Project administration. Cheng Jiang: Project administration. Jiahong Xie: Investigation. Minxiang Wang: Investigation, Methodology. Cui Li: Investigation, Methodology. Lili Yang: Data Curation, Formal analysis. Qingjie Wang: Data Curation, Methodology.
Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
S0269-7491(19)35315-1
DOI:
https://doi.org/10.1016/j.envpol.2020.113946
Reference:
ENPO 113946
To appear in:
Environmental Pollution
Received Date: 16 September 2019 Revised Date:
25 November 2019
Accepted Date: 7 January 2020
Please cite this article as: Yang, Y., Wu, G., Jiang, C., Zheng, M., Yang, L., Xie, J., Wang, Q., Wang, M., Li, C., Liu, G., Variations of PCDD/Fs emissions from secondary nonferrous smelting plants and towards to their source emission reduction, Environmental Pollution (2020), doi: https://doi.org/10.1016/ j.envpol.2020.113946. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 Published by Elsevier Ltd.
1
Variations of PCDD/Fs emissions from secondary nonferrous
2
smelting plants and towards to their source emission reduction
3
Yuanping Yang a,b, Guanglong Wu c, Cheng Jiang c, Minghui Zheng
4
Jiahong Xie c, Qingjie Wang a, Minxiang Wang a, Cui Li a,b, Guorui Liu a,b,*
5
a
（
Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box
7
2871, Beijing, 100085, China
8
b
9
c
10
a,b
, Lili Yang
a,b
,
State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research
University of Chinese Academy of Sciences, Beijing, 100049, China International Environmental Cooperation Center, Ministry of Ecology and
Environment of People’s Republic of China, Beijing, China, 100035
11 12
*
13
E-mail: [email protected]
14
Co-authors’
15
[email protected] (G.L.Wu); Cheng Jiang: [email protected]
1（
(C.Jiang); Minghui Zheng: [email protected] (M.H.Zheng); Lili Yang:
17
[email protected] (L.L.Yang); Jiahong Xie: [email protected] (J.H.Xie);
18
Qingjie
19
[email protected] (M.X. Wang); Cui Li: [email protected] (C.Li).
Corresponding author: Tel: +86-10-6284-9356; Fax: +86-10-6284-9356
email:
Wang:
Yuanping
Yang:
[email protected]
20 21 22
Declarations of interest: none
1
[email protected]
(Q.J.Wang);
(Y.P.Yang);
Minxiang
Wang:
23 24
Abstract Polychlorinated
dibenzo-p-dioxins
and
dibenzofurans
(PCDD/Fs)
are
25
cancerogenic organic pollutants that priority controlled by Stockholm Convention
2（
with globally 182 signatories now. Secondary nonferrous smelting plants are
27
confirmed to be important sources in China due to its large industrial activities and
28
high emissions of PCDD/Fs. It is important to prioritize source to achieve source
29
emission reduction by conducting field monitoring on typical case plants. Here, the
30
emission profiles and levels of PCDD/Fs were investigated in 25 stack gas samples
31
collected from three secondary copper production (SeCu), two secondary zinc
32
production (SeZn) and two secondary lead production (SePb). Both average mass
33
concentration and toxic equivalency quantity (TEQ) concentrations of PCDD/Fs all
34
generally decreased in the order: SeCu >SeZn > SePb. It is noteworthy that the mean
35
TEQ concentration in stack gas from SeCu with oxygen-enrich melting furnace
3（
technology, at 2.7 ng I-TEQ/Nm3, was much higher than the concentrations of other
37
smelting processes. The average emission factors and annual release amounts of
38
PCDD/Fs from SeCu, SePb and SeZn investigated were 28.4, 1.5, 10.4 µg I-TEQ/t
39
and 1.03, 0.023, 0.17 g I-TEQ/year, respectively. The ratios of 2,3,7,8-TCDF to
40
1,2,3,7,8-PeCDF and OCDD to 1,2,3,7,8,9-HxCDD varied to large extent for three
41
metal smelting, which could be used as diagnostic ratios of tracing specific
42
PCDD/Fs sources. Addition of copper-containing sludge into the raw materials might
43
lead to higher PCDD/Fs emissions. It is important to emphasize and reduce the
44
PCDD/Fs emissions from oxygen-enrich melting furnace from secondary copper 2
45
productions.
4（ 47
Capsule abstract
48
Copper smelting with oxygen-enrich melting furnace had the highest PCDD/F
49
emissions. Diagnostic ratios of specific congeners were suggested for smelters to
50
tracing PCDD/F sources.
51 52
Keywords: PCDD/Fs; secondary metallurgy industry; persistent organic pollutants;
53
oxygen-enrich melting furnace; copper sludge
54
3
55 5（
1. Introduction Polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans (PCDD/Fs)
57
are classified as persistent organic pollutants (POPs) which have acute and chronic
58
effects may pose enormous possible risks to the environment and human health
59
(Knutsen et al., 2018; Van den Berg et al., 1998; Van den Berg et al., 2006). PCDD/Fs
（0
are unintentionally formed and released from many thermal industrial sources such as
（1
waste incineration (Kanan and Samara, 2018; UNEP, 2013; Zhu et al., 2018) and
（2
secondary metallurgy production (Lv et al., 2011), which can result in the
（3
contamination of the environment with long term contamination of soils (Weber et al.,
（4
2018) and food producing animals in the surrounding with associated human exposure
（5
(Weber et al., 2019). The secondary metallurgy manufacture including secondary
（（
copper (SeCu), zinc (SeZn) and lead production (SePb) have been addressed to be
（7
major sources of PCDD/Fs in environment (Ba et al., 2009a; Ba et al., 2009b),
（8
especially secondary zinc smelters can have extreme high releases of PCDD/Fs above
（9
100 ng TEQ/Nm3 (Chi et al., 2007). Tracing the PCDD/Fs emissions from secondary
70
metallurgy manufacture is an activity of great importance to metallurgy plants
71
management and plays an important role in our country's implementation of the
72
Stockholm Convention.
73
Several researchers focused on the emission factors and homolog and congener
74
profiles of PCDD/Fs from secondary metallurgy industry (Altarawneh et al., 2009;
75
Chin et al., 2011; Wang et al., 2016; Wu et al., 2018). Yu et al., (2006) reported the
7（
release levels of PCDD/Fs from various secondary metal smelting industries in Korea. 4
77
It was reported that the emission concentration of PCDD/Fs in flue gas of different
78
secondary metal smelting industries varied greatly. The emission factor of PCDD/Fs
79
during the process of secondary copper smelting was 24.4 µg TEQ/t, which was much
80
higher than that of secondary lead and zinc industries (Yu et al., 2006). Ba et al.,
81
(2009) investigated the emission levels of PCDD/Fs in stack gas of several secondary
82
copper smelters in China (Ba et al., 2009b). The concentrations of PCDD/Fs releases
83
varied from 0.043 to 15.8 ng TEQ/Nm3. At the same time, the total PCDD/Fs
84
emissions of China's secondary copper smelting industry in 2009 were estimated at
85
37.5 g TEQ/year, which was higher than that of PCDD/Fs in the recycled lead and
8（
zinc smelting industries (Ba et al., 2009a). Besides, Nie et al., (2011) studied the
87
effects of different raw materials, pretreatment technology and production scale on
88
PCDD/Fs emissions in the process of secondary copper smelting, indicating that the
89
pretreatment of raw materials can effectively reduce PCDD/Fs emissions in the
90
process of reclaimed copper smelting (Nie et al., 2011). Subsequently, Hu et al., (2013)
91
surveyed the stack gas levels of PCDD/Fs from different smelting stages of secondary
92
copper (feeding-fusion stage, oxidation stage and deoxidization stage). It was found
93
that feeding-fusion stage was the dominate discharge stage of PCDD/Fs in the process
94
of reclaimed copper smelting (Hu et al., 2013).
95
Many secondary copper smelting enterprises currently use oxygen-enriched
9（
smelting furnace to process copper-containing sludge, low-grade waste copper and
97
other raw materials to produce crude copper, which is used as raw material for copper
98
production in converter, thereby improving the grade of copper (Ministry of ecology 5
99
and environment of the people's Republic of China, 2017). To the best of our
100
knowledge, the data about the release of PCDD/Fs in oxygen-enrich smelting furnaces
101
is scarce. In the other hand, the emission limits and regulations of PCDD/Fs in stack
102
gases from secondary metallurgy industry continued to be more and more stringent in
103
the recent years (Ministry of Industry and Information Technology of the People's
104
Republic of China, 2006). Nevertheless, there is no survey on PCDD/Fs emissions
105
from oxygen-enriched smelting furnace, leading to the absence of data about release
10（
concentration and profile of PCDD/Fs in this facility of secondary copper smelting
107
processes. Such a gap indicated urgently need for case studies with the aim of better
108
recognizing and evaluating the major emission stages and source emission control of
109
PCDD/Fs for secondary nonferrous smelting industries. This is significant for towards
110
to the source emission control of secondary copper smelting industries. Moreover,
111
much more data about PCDD/Fs levels and profiles from secondary zinc and lead
112
production is also needed for accurately evaluating their emissions on national scale.
113
In this study, 25 stack gas samples from secondary nonferrous productions including
114
SeCu, SeZn and SePb were isokinetic collected and quantified for seventeen toxic
115
PCDD/Fs congeners. The congener profiles of PCDD/Fs from the investigated
11（
facilities were evaluated for exploring potential formation mechanisms. Additionally,
117
the emission factors and annual release amounts of PCDD/Fs expressed in the toxic
118
equivalency (TEQ) were also calculated for comprehensively evaluating the PCDD/Fs
119
emission from secondary metallurgy industries in China.
120 （
121
2. Materials and methods
122
2.1. Basic information on the investigated plants and stack gas sample collection
123
Seven typical secondary metallurgy plants were investigated, including three
124
SeCu, two SePb, and two SeZn (basic information of these plants are provided in
125
Table 1). In order to understand the release of PCDD/Fs from different smelting
12（
furnaces of secondary copper smelting industry, the flue gas samples from converter
127
furnace (SeCu(1), SeCu(2)-A) and oxygen-enriched smelter furnace (SeCu(2)-B,
128
SeCu(3)) were collected. 25 stack gas samples were collected from investigated
129
plants by an automatic isokinetic sampling system, Isostack Basic (TCR TECORA,
130
Milan, Italy), in accordance with the European Standard EN-1948-1 which was the
131
sampling procedure. Before sampling the stack gas samples, 13C12-labelled PCDD/Fs
132
was spiked into the XAD-2 resin as surrogate sampling standards.
133
2.2. Stack gas sample preparation and instrumental analysis of PCDD/Fs
134
The extraction and purification, identification and quantification of PCDD/Fs
135
congeners were accomplished in accordance with EN-1948-2 and EN-1948-3,
13（
respectively. Briefly,
137
spiked into stack gas samples. The stack gas samples were then Soxhlet extracted for
138
about 24 hours by using 250 mL of toluene. The extracts were evaporated to
139
approximately 1-2 mL using the rotary evaporator. After concentration, the extracts
140
were sequentially purified by a series of adsorption columns, including acidified
141
silica gel, a multilayer silica gel, and activated-charcoal columns. Finally,
13
C12-labelled PCDD/Fs internal quantification standards were
7
142
13
143
chromatography/high resolution mass spectrometry (HRGC/HRMS) analysis.
144
Congener specific analysis of PCDD/Fs were performed by using a gas
145
chromatograph coupled to a DFS mass spectrometer (Thermo Fisher Scientific,
14（
Waltham, MA, USA), and a DB-5 capillary column (60 m × 0.25 mm × 0.25 µm)
147
was selected to separate the analytes. The HRMS was equipped with a positive
148
electron impact source and HRMS was tuned and operated at a mass resolution of
149
around 10,000. The ion source was specified at 250
150
to be 37 eV.
151
2.3. Quality assurance and quality control (QA/QC)
152
C-labelled recovery standards were added to the extracts before high resolution gas
The recoveries of
13
and the electron energy is set
C12-labelled PCDD/Fs internal standards in the stack gas
153
samples were range 58 to 120%, meeting the analytical method requirements. Three
154
QC criteria were employed in the determination of the target compounds: (a) the GC
155
retention time matched to the available corresponding
15（
the signal-to-noise ratio was >3:1; and (c) the isotopic ratios of two monitored ions
157
for the analyte should be within ±15% of the theoretical values. Furthermore, there
158
was a blank in each batch of samples, and no obvious interference was detected in
159
the blank samples. When calculating the concentration of PCDD/Fs in stack gas, the
1（0
collection volume will be converted to the standard state (0
13
C12-labelled standards; (b)
and 1 atm).
1（1
Statistical analysis was employed by SPSS version 25 software (IBM, USA). In
1（2
order to minimize the influence of total concentrations, the congener concentrations
1（3
were normalized to the percentage of total concentrations. Pearson correlation 8
1（4
analysis was conducted by SPSS to explore possible relationships between the target
1（5
compounds and total TEQs. Statistical significance of p < 0.05 was set for correlation
1（（
analysis.
1（7 1（8
3. Results and Discussion
1（9
3.1. Emission levels and variations of PCDD/Fs from different secondary
170
metallurgy facilities and different smelting stages
171
The mass concentrations and I-TEQ of PCDD/Fs were determined in stack gas
172
samples sampled from the seven secondary nonferrous smelting plants investigated
173
are presented in Fig.1. Obviously, there was a large concentrations variations of
174
PCDD/Fs among the different metallurgy smelting industries (SeCu, SeZn and
175
SePb) and among different plants in the same nonferrous smelting category. In
17（
general, the average concentrations of PCDD/Fs in stack gas samples of three
177
category of sources ranged from high to low as follow: SeCu > SeZn > SePb, the
178
corresponding mass concentrations were 53.35, 24.47, 1.53 ng/Nm3 and the
179
corresponding I-TEQ concentrations were 0.84, 0.48, 0.05 ng TEQ/Nm3,
180
respectively. As seen in Fig. 1, the tendencies of mass concentrations of PCDD/Fs
181
from different plants were generally consistent with those of PCDD/Fs TEQ
182
concentrations. The TEQ concentrations of PCDD/Fs in this study were
183
significantly lower than that reported by Ba et al. in 2009, where corresponding
184
concentration were 2.84, 98.02, 0.35 ng TEQ/Nm3 for SeCu, SeZn, and SePb,
9
185
respectively (Ba et al., 2009a; Ba et al., 2009b), indicating that the metal smelting
18（
techniques and stack gas removal technology have been obviously upgraded or
187
improved and achieved remarkable achievements in recent years in China.
188
There are multiple process stages and different types of furnaces for secondary
189
copper smelting. In order to recognize the dominant stages of PCDD/Fs emissions
190
from secondary copper smelting sources, we aim to compare the PCDD/Fs
191
concentrations in the stack gas collected from different smelting furnaces in the
192
secondary copper smelting industry. Firstly, the flue gas samples from converter
193
furnace and oxygen-enriched smelter were collected and analyzed. The converter
194
furnace usually had three main smelting stages: feeding-fusion (FF), oxidation
195
(OX) and deoxidization (DO), and the corresponding dioxin concentrations in the
19（
flue gas were sequentially reduced, which were in the range of 0.11-0.80, 0.07-0.19,
197
0.06-0.07 ng I-TEQ/Nm3, respectively. These trends were similar to the previous
198
report in the stack gas of different stages of secondary copper production (Hu et al.,
199
2013) . However, it was noteworthy that the mean TEQ in stack gas from
200
SeCu(2)-B (oxygen-enrich melting furnace) was 2.7 ng TEQ/Nm3. This value is far
201
higher than the concentrations of PCDD/Fs released from the converter furnace in
202
the same plant, which suggested that PCDD/Fs emissions from oxygen-enrich
203
melting furnace should be emphasized. This is the first measurement of PCDD/Fs
204
released from oxygen-enrich melting furnace and the results are significant for
205
further control and reduction of PCDD/Fs from secondary copper smelting sources.
10
20（
The mean TEQ concentration in stack gas from SeCu(2)-B was approximately
207
21 times higher than that in SeCu(3) using the same type of furnace. After
208
comparing the raw materials, smelting processes and pollution control facilities of
209
the above two secondary copper smelters, it might be attributable to the difference
210
in raw materials: SeCu(2)-B were 30% copper-containing sludge and 70% scrap
211
copper, while SeCu(3) was 100% scrap copper. The carbon source, chlorine source,
212
and catalytically metal elements are widely recognized as important factors in the
213
formation of PCDD/Fs (Heeb et al., 2013; Kakuta et al., 2007; Kuzuhara et al.,
214
2003; Vallejo et al., 2013; Wu et al., 2018). It is widely recognized that ash from
215
secondary copper smelters have the high PCDD/Fs formation potential (Cagnetta et
21（
al., 2016; Liu et al., 2015), since copper is more likely to catalyze the formation of
217
PCDD/Fs during thermal processes (Hung et al., 2015; Stieglitz et al., 1989).
218
Therefore, the TOC contents (3.3%), Cu element (25.1%) and chlorine (4.3%) in
219
the copper-containing sludge from electroplating industry may explicate that the
220
PCDD/Fs concentration of SeCu(2)-B was higher than that of SeCu(3). It was
221
obvious that different raw material compositions can affect the formation amounts
222
of the PCDD/Fs in the secondary metal smelting processes.
223
3.2. Congener profiles and homolog distributions of PCDD/Fs from different
224
industries
225
Homolog patterns and congener profiles of PCDD/Fs were compared for
22（
understanding their emission characteristics in stack gas from different
11
227
metallurgical industries. Fig. 2 presents the congener profiles of 2,3,7,8-substitude
228
PCDD/Fs in the stack gas samples from various industries. In most of stack gas
229
samples, OCDD and 1,2,3,4,6,7,8-HpCDD were the major congeners. The
230
contributions of PCDDs to total PCDD/Fs increased with chlorination degree
231
elevation. Those general patterns were consistent with those for incinerators (Abad
232
et al., 2006; Li et al., 2017), cement kilns (Ames et al., 2012; Zou et al., 2018), and
233
coke plants (Liu et al., 2009). The congener 1,2,3,4,6,7,8-HpCDF was dominant in
234
the PCDFs in the samples and this is similar to that in previous studies (Li et al.,
235
2015; Liu et al., 2009). Meanwhile, the proportion of OCDD increases with the
23（
process of smelting in the samples collected from secondary copper production
237
converter furnace, with the ratio in FF, OX and DO stages was 9.5-13.9%,
238
16.7-20.7% and 25.4-27.5%, respectively (Fig. 2a). The ratios of specific PCDD/Fs
239
congeners can provide important information on source apportioning of PCDD/Fs
240
in the environment (Liu et al., 2015). To further assess the differences in congener
241
profiles of different secondary metallurgy industries, we calculated the
242
concentration ratios of the specific congeners with clear discrepancy. The average
243
ratios of 2,3,7,8-TCDF to 1,2,3,7,8-PeCDF were 0.82, 3.2 and 0.39 for SeCu
244
oxygen-enrich melting furnace, SeZn and SePb, respectively. The average ratios of
245
OCDD to 1,2,3,4,6,7,8-HpCDD were 1.8, 1.1 and 0.41 for SeCu oxygen-enrich
24（
melting furnace, SeZn and SePb, respectively. Those ratios could be used as
247
diagnostic values of tracing the sources of PCDD/Fs in the environment. Moreover,
248
to obtain comprehensive fingerprinting of PCDD/Fs, a more detailed assessment of 12
249
congener patterns including the non-2,3,7,8-substituted congeners should be done in
250
future (Hagenmaier et al., 1994; Ooi et al., 2018).
251
Pearson correlation analysis was conducted to study the correlations among
252
the congener concentrations of PCDD/Fs and total TEQ (Fig. 3). Positive
253
correlations (R2>0.9, p < 0.05) between 2,3,4,6,7,8-HxCDF, 1,2,3,4,6,7,8-HpCDF,
254
1,2,3,4,7,8,9-HpCDF, OCDF, 1,2,3,4,6,7,8-HpCDD, OCDD and TEQ were
255
observed.
25（
1,2,3,4,6,7,8-HpCDD, display much significant correlation with TEQ, with R2 of
257
0.975 and 0.972, respectively, which can act as indicators for estimating PCDD/Fs
258
emissions in TEQ from secondary metal smelting processes.
Two
congeners
comprised
of
1,2,3,4,7,8,9-HpCDF
and
259
The homolog contributions to PCDD/Fs TEQ in the stack gases from the 7
2（0
plants investigated are presented in Fig. 4. For PCDD/Fs homolog profiles, lower
2（1
chlorinated PCDD/Fs homologs (tetra-, and penta-) were dominant in the stack gas
2（2
from SeCu converter furnace and SePb, while higher chlorinated PCDD/Fs
2（3
homologs were dominant in SeCu oxygen-enrich melting furnace and SeZn. The
2（4
different homolog pattern may arise from the different formation mechanisms of
2（5
PCDD/Fs homologs under different metal catalysts (Liu et al., 2015; Oh et al.,
2（（
2004).
2（7
3.3. Emission factors, annual emission amounts and implication for source
2（8
emission reduction
2（9
Derivation of the emission factors (EFs) is significant for compiling emission 13
270
inventories and estimating PCDD/Fs emission amounts from whole industries on
271
national scale based on available monitoring data from studies on case plants. It is
272
also important to recognize the priority sources and assist regulatory agencies to
273
develop best control technique and strategy for reducing overall emissions. The
274
following formula was used for deriving emission factors and calculating the total
275
release of unintentional POPs (UNEP, 2013).
27（
( / ) =
277
/ ( /!"# ) × %& '()* ( +, %('- (!"# /. )
278
= > ( /?@ ) = Emission
279
activity level of reference year (t/year)
1
/0123 4567891:6; (1/<)
factor
(ng
TEQ/t) × 2
280
The emission factors varied among different categories of metallurgy industries
281
and also among different smelting plants for a given metal category. The derived
282
emission factors and evaluated annual emission amounts of PCDD/Fs from flue gas of
283
the secondary nonferrous metal smelters are presented in Table 2. The emission
284
factors ranged from 0.79 to 106.8 µg TEQ/t. The emission factors derived in our study
285
were consistent with those previous publications for metallurgical plants (Antunes et
28（
al., 2012; Ba et al., 2009a; Ba et al., 2009b; Lv et al., 2011). For secondary copper
287
smelters, the emission factors of SeCu(1), SeCu(2)-A and SeCu(3) were all lower than
288
the emission factor of UNEP toolkit’s (5 µg TEQ/t for classification with optimized
289
for PCDD/PCDF control), indicating that the optimization control was carried out for
290
the PCDD/Fs emissions, such as the pretreatment of raw materials or the treatment of
291
flue gas with activated carbon (UNEP, 2013). However, the highest EFs were 14
292
estimated for a secondary copper production plant with oxygen-enrich melting
293
furnace technology (SeCu(2)-B; 106.8 µg TEQ/t), which located between the
294
classification of the well controlled (50 µg TEQ/t) and the basic technology (800 µg
295
TEQ/t) in the UNEP Toolkit. The secondary lead smelter's emission factors were
29（
lower than the UNEP toolkit’s emission factor (8 µg TEQ/t for removing PVC plants
297
and 80 µg TEQ/t for scrap containing PVC). For the investigated secondary zinc
298
smelters, bag filters or electrostatic precipitators were adopted for control dioxins
299
emissions into air, the emission factors were lower than the UNEP toolkit’s emission
300
factor (100 ug TEQ/t for classification of hot briquetting/rotary furnaces, basic dust
301
control; e.g., fabric filters/electrostatic precipitation) (UNEP, 2013). The emission
302
amounts represented the emission level and activity intensity of the specific industries.
303
In this study, the estimated total annual stack gas emissions of the 7 investigated
304
plants ranged from 11.9 to 3847.2 mg TEQ/year.
305
There are about a thousand secondary nonferrous smelting plants being operation
30（
in China. Due to the high emission factors and total emission amounts, it is important
307
to pay attention to the PCDD/Fs emissions from secondary nonferrous productions.
308
This field study on the case plants found that the PCDD/Fs emissions from
309
oxygen-enrich melting furnace were much higher than that in the three stages of
310
converter furnaces. Thus, it is important to optimize the operation parameters in this
311
stage and reduce PCDD/Fs formation and emissions from the oxygen-enrich melting
312
furnace, which was scarcely recognized before this study. We also found that the
313
addition of copper sludge into the raw materials could increase the PCDD/Fs 15
314
emissions. These findings in this study might provide important knowledge for the
315
considerations of PCDD/Fs control, reduction and regulations by the enterprise or
31（
policy makers, which could contribute to the reduction of human exposure in China.
317
Our results also pointed out that the estimated PCDD/Fs emission amount decreased
318
compared to that evaluated in 2009.
319 320
4. Conclusions
321
In this study, the emission characteristics of PCDD/Fs in 25 stack gas samples
322
collected from secondary nonferrous productions were investigated. The results
323
indicated that PCDD/Fs concentrations in stack gas were in the order of SeCu >SeZn
324
> SePb. The average TEQ concentration in stack gas from SeCu with oxygen-enrich
325
melting furnace technology was higher than the concentrations of other smelting
32（
processes. The highest EFs and EAs were also estimated for SeCu(2)-B, at 106.8 µg
327
TEQ/t and 3847.20 mg TEQ/year, respectively. It was found that addition of
328
copper-containing sludge into the raw materials might result in higher PCDD/Fs
329
formation and emissions. Ratios of specific congeners could be used for the
330
diagnostic ratios for identifying their specific sources in the environment. These
331
results might provide important knowledge for the considerations of PCDD/Fs
332
control, reduction and regulations in secondary nonferrous smelting plants, and also
333
emphasize that high emissions of PCDD/Fs from the secondary metal industries and
334
the potential long-term risk to the surrounding areas should attract more attention.
335
Besides, a more comprehensive fingerprinting is available including the 1（
33（
non-2,3,7,8-substituted congeners and need to be applied for source assessment in
337
future.
338 339 340
Acknowledgments
341
This work was supported by the National Natural Science Foundation of China
342
(21936007; 21777172), Beijing Natural Science Foundation (8182052), Youth
343
Innovation Promotion Association of the Chinese Academy of Sciences (2016038).
344 345
Competing financial interest
34（
The authors declare no competing financial interest.
347 348
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Captions of Figures and Tables: Fig. 1. Mass concentrations of PCDDs and PCDFs, I-TEQ concentration of PCDD/Fs in stack gas from different secondary metallurgy industries. Fig 2. Contributions of PCDD/Fs congeners to the total PCDD/Fs concentrations in the stack gas samples from different smelting stages of secondary copper (SeCu) converter furnace (a), SeCu oxygen-enrich melting furnace (b), secondary lead production (c) and secondary zinc production (d). Fig 3. Pearson correlation of PCDD/Fs congeners and I-TEQ. Fig 4. PCDD/Fs homologue distribution for the stack gas samples from the 7 plants investigated.
Table 1. Basic information on the investigated plants. Table 2. Derivation of emission factors and estimation of annual emission amounts of PCDD/Fs form the investigated plants.
24
Fig. 1. Mass concentrations of PCDDs and PCDFs, I-TEQ concentration of PCDD/Fs in stack gas from different secondary metallurgy industries.
25
Fig. 2. Contributions of PCDD/Fs congeners to the total PCDD/Fs concentrations in the stack gas samples from different smelting stages of secondary copper production (SeCu) converter furnace (a), SeCu oxygen-enrich melting furnace (b), secondary lead production(c) and secondary zinc production (d).
2（
Fig. 3. Pearson correlation of PCDD/Fs congeners and I-TEQ.
27
Fig. 4. PCDD/Fs homologue distribution for the stack gas samples from the 7 plants investigated.
28
Table 1. Basic information on the investigated plants. Abbreviation of investigated plants
SeCu(1)
SeCu(2)-A
SeCu(2)-B
SeCu(3)
SePb(1)
SePb(2)
SeZn(1)
SeZn(2)
category of metallurgical
Furnace type
plants secondary copper production
secondary copper production
production secondary zinc production
crude copper + copper
converter furnace
120
activated carbon + bag filter
3
55
bag filter
2
140
bag filter
3
copper scrap
3
lead scrap
lead slag + lead scrap
oxygen-enrich melting
furnace
secondary zinc
Raw material
5
production
production
samples
activated carbon + bag filter
oxygen-enrich melting
secondary lead
Number of
110
secondary copper
production
(t/day)
Air Pollution Control Devices
converter furnace
furnace
secondary lead
Capacity
electrostatic precipitation + gravity
rotary furnace
50
rotary furnace
20
bag fliter
3
rotary furnace
60
gravity settling + bag fliter
3
rotary furnace
64
29
settling + bag filter
electrostatic precipitation + bag fliter
3
scrap crude copper + copper scrap copper sludge + copper scrap
dust of steel mill + zinc dross zinc ore + zinc dross
Table 2. Derivation of emission factors and estimation of annual emission amounts of PCDD/Fs form the investigated plants. Abbreviation of
Emission factors
Annual emission amounts
investigated plants
(ug TEQ/t )
(mg TEQ/year)
SeCu(1)
2.57
92.56
SeCu(2)-A
3.42
171.11
SeCu(2)-B
106.86
3847.20
SeCu(3)
0.79
11.93
SePb(1)
2.18
30.59
SePb(2)
0.89
17.55
SeZn(1)
9.54
177.61
SeZn(2)
11.22
168.33
30
Highlights
PCDD/Fs emitted from seven secondary metallurgical plants were investigated
Copper smelting with oxygen-enrich melting furnace had the highest PCDD/F emissions
Copper-containing sludge in raw materials might cause higher PCDD/F formation
Diagnostic ratios of specific congeners were suggested for different metal smelters
Author Contribution Statement Yuanping Yang: Formal analysis, Investigation, Writing - Original Draft. Guorui Liu: Conceptualization, Investigation, Writing - Review & Editing. Minghui Zheng: Resources, Writing - Review & Editing, Supervision. Guanglong Wu: Investigation, Project administration. Cheng Jiang: Project administration. Jiahong Xie: Investigation. Minxiang Wang: Investigation, Methodology. Cui Li: Investigation, Methodology. Lili Yang: Data Curation, Formal analysis. Qingjie Wang: Data Curation, Methodology.
Declaration of interests ☒ The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. ☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: