Estimation and Congener-Specific
Characterization of Polychlorinated
Naphthalene Emissions from
Secondary Nonferrous Metallurgical
Facilities in China
T E B A , M I N G H U I Z H E N G , * B I N G Z H A N G ,
W E N B I N L I U , G U I J I N S U , G U O R U I L I U ,
A N D K E X I A O
State Key Laboratory of Environmental Chemistry and
Ecotoxicology, Research Center for Eco-Environmental
Sciences, Chinese Academy of Sciences, P.O. Box 2871,
Beijing 100085, China
Received November 2, 2009. Revised manuscript received
February 8, 2010. Accepted February 10, 2010.
Secondary nonferrous production is addressed as one of the
pollutants (UP-POPs) due to the impurity of raw material.
nonferrous metallurgical facilities, release inventories of
polychlorinated naphthalenes (PCNs) are scarce. This study
selected typical secondary copper, aluminum, zinc, and lead
plants to investigate the emissions of PCNs in secondary
nonferrous production in China. The toxic equivalency (TEQ)
emission factor for PCNs released to the environment is highest
for secondary copper production, at 428.4 ng TEQ t-1, followed
by secondary aluminum, zinc, and lead production, at 142.8,
copper, aluminum, lead, and zinc production in China are
Analysis of stack gas emission from secondary nonferrous
homologues, with mono- to tri-CNs making the most important
contributions to the concentration. However, for fly ash, the
Polychlorinated naphthalenes (PCNs) are ubiquitous envi-
ronmental pollutants that are structurally similar to poly-
chlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans
(PCDFs). There are 75 possible congeners based on the
naphthalene ring with one to eight chlorine atoms. It has
their structural similarity (1, 2). PCNs have been used as
ingredients in cable insulation, wood preservatives, engine
oil additives, electroplate masking compounds, and dye
production (3-5). The production and use of PCNs were
banned in the United States and Europe in the 1980s owing
Fs and polychlorinated biphenyls (PCBs), and eventually be
control measures to reduce PCN sources is not as great as
the interest in measures to control PCDD/Fs and PCBs. The
toxic emissions of PCNs from industrial sources should also
be considered when evaluating treatment strategies for the
control of unintentionally produced persistent organic pol-
In recent years, there has been a growing demand for
metallurgy industries (9-12). Although some inventories of
are scarce. It is commonly considered that the formation
mechanism of PCNs is rather similar to that of PCDD/Fs.
Conditions that have been shown to promote the formation
of PCDD/Fs include (i) the presence of elemental chlorine
including nonferrous metal that can catalyze UP-POP
of UP-POPs being reached in steps of the smelting process
(3, 13). Because these conditions are met in secondary
nonferrous metallurgical facilities, they are generally con-
sidered to be potential sources of PCNs.
Although the smelting process in secondary nonferrous
metallurgy is believed to be one of the pathways of the
formation of PCNs, few data about PCN emissions by
secondary nonferrous metallurgical facilities have been
reported. As a part of the national UP-POP emission
inventory, this study focuses on the PCN inventories for
secondary copper, aluminum, zinc, and lead production in
China. The combined production of these four secondary
nonferrous metals was 5,295,000 t in 2007 (14). On the basis
of a primary survey, 11 typical plants with end of pipe
technologies were selected from secondary nonferrous
oriented method was adopted in the investigation of the
emission of PCNs in secondary nonferrous production. The
(TEQs) of specific CN congeners in each sample were
estimated according to relative potency factors (15). Con-
centrations and congener compositions of PCNs were
chromatography and high-resolution mass spectrometry
(HRGC/HRMS). The total emission is calculated using the
emission factors obtained from the selected plants and the
In this study, a total of 33 stack gas and 22 fly ash samples
were collected from 11 plants of secondary copper, alumi-
num, lead, and zinc recycling industries in China. For each
plant, three stack gas samples and two fly ash samples were
The smelting process of secondary zinc production consists
the smelting process of secondary lead production consists
of liquid lead, and casting. Three samples of stack gas were
collected during processes where PCNs might be uninten-
tionally produced and emitted, and special attention was
given to the feeding and melting steps of secondary nonfer-
Environ. Sci. Technol. 2010, 44, 2441–2446
Published on Web 03/04/2010
2010 American Chemical SocietyVOL. 44, NO. 7, 2010 / ENVIRONMENTAL SCIENCE & TECHNOLOGY92441
steps contain residual chlorine. Basic information on the
smelting processes is given in Table S1 in the Supporting
The stack gas samples were collected using an automatic
isokinetic sampling system (TCR TECORA, Italy). The sam-
pling point was set downstream of all air pollution control
devices. Prior to collection, O2, CO2, and CO levels in the
(Madur, Austria). Particles in the stack gas were trapped by
a microfiber thimble filter (25 mm i.d., 90 mm length;
Whatman International Ltd., Whatman, UK). Gases were
cooled in a condensing system and then adsorbed in a trap
with Amberlite XAD-2 resin (Supleco International Ltd.,
and/or quenching tower outlets during the stack gas sam-
pling. Both the stack gas and fly ash samples were spiked
extraction with toluene for 24 h. The extract was purified
gel column (from top to bottom: anhydrous sodium sulfate,
gel, 5 g of 33% silica gel-sodium hydroxide, 1 g of silica gel,
column. Before HRGC/HRMS analysis, the samples were
(13C10-CN-64). All pesticide-grade solvents were purchased
Cambridge Isotope Laboratories (Cambridge, USA). The
parameters of the HRGC/HRMS analysis were as follows.
PCNs were analyzed using a gas chromatograph coupled
with a DFS mass spectrometer (Thermo Fisher Scientific,
USA) with an electron impact ion source. The HRMS was
operated in selected ion monitoring mode with a resolution
greater than 10,000. A 1 µL quantity of sample solution was
injected with an autosampler in the splitless mode. A DB-5
fused silica capillary column (60 m × 0.25 mm i.d. × 0.25
µm) was used for the separation of PCN congeners. The
electron emission energy was set to 45 eV. The source
temperature was 270 °C. The column temperature was
initially 80 °C (for 2 min) and increased to 180 °C (for 1 min)
at 20 °C/min, 280 °C at 2.5 °C/min, and 290 °C (for 5 min)
at 10 °C/min. The carrier gas was helium with a flow rate of
1 mL min-1.
were defined as 3 and 10 times the signal-to-noise ratio,
respectively.13C10-labeled PCN internal standards and re-
covery standard were used for the assurance of analytical
recovery. Detailed data of the quality control are given in
Tables S2-S4 in the SI.
Principal component analysis using SPSS for Windows
Release 13.0 (SPSS Inc.) was applied to evaluate the distribu-
tion pattern of PCNs in this study.
13C10-labeled standards, were purchased from
Results and Discussion
Concentration of PCNs Released from the Secondary
Nonferrous Metallurgical Facilities. The concentrations of
PCNs in stack gas and fly ash of secondary nonferrous
metallurgical facilities are given in Table 1. Concentrations
varied considerably among different metallurgies and also
among different plants for a given metal. Among the four
types of metallurgy, the highest concentration of PCNs in
ng Nm-3). Investigations of unintentionally released PCNs
have been very limited. Existing studies mainly focused on
Abad et al. (7) assessed the release of PCNs from five
municipal solid waste incinerators and found that the levels
of total PCNs (mono- to octachlorinated) varied from 1.08
secondary metal smelting were higher than those of mu-
nicipal waste incineration.
plant 4 have relatively even distributions. However, for each
of the remaining plants investigated, the stack gas congener
particularly mono- to tetra-CNs.
The PCN homologues in fly ash of secondary nonferrous
metallurgical facilities distributed evenly for secondary
aluminum and copper plants 1 through 3. However, PCN
congener profiles in the fly ash for the remaining facilities
were dominated by octa-CN.
distributions in solid phase and gas phase was observed. In
stack gas, the lower chlorination PCNs are the dominant
homologues, with mono- to tri-CNs making the most
important contributions to the concentration. However, for
fly ash, the higher chlorination PCNs, like octa-CN, are the
dominant homologues. This result is similar to the pattern
metallurgical facilities, which are dominated by mono- to
di-CBs. The pattern of PCNs released from the secondary
homologues for secondary copper, aluminum, and lead
is dominated by tetra-CD/Fs (16, 17).
The primary aims of principal component analysis are to
evaluate the distribution pattern and determine possible
groupings with similar emissions characteristics among the
plants in this study. The homologues from mono-CNs to
octa-CN were selected as variables for principal component
two components were selected, which together accounted
for 97.7% of the squared loading.
has higher loading for homologue mono- to hexa-CNs than
PC2, while PC2 has higher loading for homologue hepta- to
octa-CN than PC1. Thus PC1 and PC2 are aggregative
to octa-CN, respectively.
The principal component scores for each plant are
displayed in Figure 3. The plants were divided into three
groups on the basis of component scores: (1) secondary
zinc plants, (2) secondary copper plant 4, and (3) all other
TABLE 1. Concentrations and TEQs of PCNs in Stack Gas and
stack gas fly ash
ng TEQ Nm-3
ng TEQ g-1
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PC2 score, indicating that the pattern is dominated by the
copper plant 4 has the highest PC2 score and lower PC1
score, indicating that the pattern is dominated by higher
chlorination homologues. The third group of plants can
be divided into three subgroups on the basis of similar
properties: (1) secondary aluminum plant 4, secondary
copper plant 1, and the secondary lead plant, which are
all similar to the secondary zinc plant in that they have
plant 1, which is similar to secondary copper plant 4, and
of higher and lower chlorination homologues for these
TEQ of PCNs in Stack Gas and Fly Ash from the
Secondary Nonferrous Metallurgical Facilities. Table 1
collected from the secondary nonferrous plants. The TEQ of
stack gas and fly ash released from secondary copper plant
4 is higher than that of any other secondary nonferrous
The TEQ patterns of PCN congeners in stack gas and fly
patterns are quite different among plants from the different
secondary nonferrous metallurgical facilities. The most
abundant congeners in stack gas from the secondary
aluminum, copper, lead, and zinc plants are CN-73 (30.6%),
CN-73 (44.6%), CN-2 (39%) and CN-66/67 (59.1%) respec-
tively. In contrast, the TEQ patterns of PCN congeners in fly
ash samples are quite similar; CN-66/67 and CN-73 are the
main contributors for all four types of metallurgy.
Estimation of PCN Emission Factors and Total Release
from Secondary Nonferrous Metallurgical Facilities in
the emission factors and total release of PCNs.
FIGURE 1. PCN homologue profiles in stack gas (a) and fly ash (b) of secondary nonferrous metallurgical facilities.
Emission factor of stack gas in concentration (ng/ton)
) Concentration of PCNs (ng/m3) ×
Dry stack gas flow rate (m3)
Metal production (ton)
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The emission factors of the stack gas concentration and
were calculated using eqs 1 and 2, respectively. The data are
metallurgy and also among different plants for a given metal.
The PCN emission factors of the stack gas concentration
of aluminum plants 1-4 are 575, 835, 1306, and 13,610 µg
in raw materials. The raw material of aluminum plant 1 is
impurities. The raw materials of the other three plants are
waste aluminum profile and crushed vehicle material with
a higher content of organic impurities to different degree.
When the technological processes for aluminum plants are
raw material also affects the congener patterns. As shown in
Figure 1, the pattern of aluminum plant 1 has an even
distribution, while the patterns of aluminum plants 2-4 are
dominated by lower chlorination congeners like 1-MoCN,
FIGURE 2. Loading plot of PC1 and PC2 for PCN principal component matrix.
FIGURE 3. Score plot of PCA for the secondary nonferrous metallurgical facilities.
Emission factor of stack gas in TEQ (ng TEQ/ton)
) TEQ of PCNs (ng TEQ/m3) ×
Dry stack gas flow rate (m3)
Metal production (ton)
Total Emission amount (g TEQ/year)
) Emission factor (ng TEQ/ton) ×
activity level of reference year (ton/year)
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2-MoCN, 1,2-DiCN, 1,4,6/1,2,4-TiCN, and 1,2,5,7/1,2,4,6/
The PCN emission factors of stack gas concentration of
copper plants 1-5 are 624, 246, 141, 7014, and 1237 µg t-1,
respectively. The raw material of copper plants 1-3 has a
higher content of copper scrap than copper plants 4-5 and
the raw material of copper plants 4-5 contains many
impurities of oil and enameled wire. The difference in raw
material leads to a lower concentration of PCN emission
from copper plants 1-3 than from copper plants 4-5. The
air pollution control technology of copper plant 5 is more
advanced than the technology of the other copper plants.
Copper plant 5 has a tilting furnace for smelting and after-
combustion chamber for the purification of exhaust gas.
Although the raw material composition of copper plant 5 is
low. As shown in Figure 1, the pattern of copper plant 4 is
dominated by 1,2,3,4,5,6,8-HpCN and octa-CN, and the
congener patterns of copper plants 1-3 are dominated by
lower chlorination homologues mono-CN, di-CN, and tri-
CN. It seems that the high emission factor of the PCN
of a higher chlorination homologue, which is opposite from
the case for aluminum plants.
The mean TEQ emission factors for PCNs are presented
copper production at 428.4 ng TEQ t-1. For secondary
FIGURE 4. TEQ congener patterns of PCNs in stack gas (a) and fly ash (b) from the secondary nonferrous metallurgical facilities.
TABLE 2. Emission Factors of PCNs in Concentration and TEQ
for the Secondary Nonferrous Metallurgical Facilities
ng TEQ t-1
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aluminum, lead, and zinc production, the mean emission Download full-text
factors are 142.8, 20.1, and 125.7 ng TEQ t-1, respectively.
The total emission amounts of PCNs released to air can
be determined using mean emission factors and the total
3. Secondary copper production has the highest emission
aluminum, lead, and zinc production are 0.39, 0.009, and
0.01 g TEQ a-1, respectively. These values are much lower
released from Cu and Al facilities in former studies (16, 17).
emission from secondary zinc and lead production on the
investigation on PCN emissions from secondary zinc and
lead production is needed.
In a secondary nonferrous plant, fly ash is recycled to
recover residual metal, and the final emission in fly ash per
ton of product is therefore very small. As a result, although
factors of fly ash are somewhat less than those of stack gas
and were not calculated in this study. The values in Table
3 can thereby be considered as total emission amounts of
PCNs released to the environment. The total emissions
estimated from emission factors developed in this study are
based on data from large- and medium-sized companies
that use necessary pollution control equipment. Smaller
secondary nonferrous plants in China are usually equipped
could not fulfill the requirements of isokinetic sampling. It
is speculated that the emission factors for smaller plants are
higher than those summarized in this study. Therefore, the
reported values may be considered as the minimum PCN
facilities in China in 2007.
This study was supported by the Chinese Academy of
Sciences (Grant KZCX2-YW-420), the National Natural
Science Foundation of China (20677070, 20921063), and
the National 973 program (2009CB421606).
Note Added after ASAP Publication
This paper published ASAP March 4, 2010 noting incorrect
units in the fly ash sample column of Table 1; the corrected
version published ASAP March 10, 2010.
Supporting Information Available
via the Internet at http://pubs.acs.org.
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TABLE 3. Average Emission Factors and Total PCN Release
from the Secondary Nonferrous Metallurgical Facilities
(ng TEQ t-1)
(thousand t a-1)
(g TEQ a-1)
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