Chemosphere 91 (2013) 751–757
Contents lists available at SciVerse ScienceDirect
Chemosphere
journal homepage: www.elsevier.com/locate/chemosphere
Perfluorinated compounds in soils from Liaodong Bay with concentrated
fluorine industry parks in China
Pei Wang a,b, Tieyu Wang a,⇑, John P. Giesy c, Yonglong Lu a,⇑
a
State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
University of Chinese Academy of Sciences, Beijing 100049, China
c
Toxicology Centre and Department of Veterinary Biomedical Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
" Mass balance analysis provided a
better understanding of fluorine in
soils.
" The production of OC was
investigated in two fluorine industry
parks.
" Distribution of PFC and EOF was
correlated with OC and pH in soil,
respectively.
" Direct emission accounted for the
presence of PFCs in the study area.
a r t i c l e
i n f o
Article history:
Received 5 July 2012
Received in revised form 30 January 2013
Accepted 9 February 2013
Available online 15 March 2013
Keywords:
PFCs
PFOA
Mass balance
Soil
Source
Fluorine industry
a b s t r a c t
With the shift of manufacturing plants from more industrialized countries to China, occurrences of Perfluorinated compounds (PFCs) in the environment has attracted more attention. Concentrations of PFCs in 14
soils collected from the coast of Liaodong Bay were determined and spatial distributions used to identify
potential sources of PFCs. A mass balance approach was introduced to quantify concentrations of Total FluoP
rine (TF) and Extractable Organic Fluorine (EOF). Concentrations of
PFCs ranged from <MDL to
1
3.14 ng g . Perfluorooctanoic acid (PFOA) and Perfluoroundecanoic acid (PFUdA) were predominant with
P
maximum concentrations of 0.47 ng g1 and 0.42 ng g1. Statistical analysis indicated that PFCs and EOF
P
account for a very small portion in TF and there is limited correlation among PFCs, EOF and TF in soils. Two
fluorine industry parks have recently been established in the vicinity of the study site, where electrochemical fluorination (ECF) is used to synthesize ammonium perfluorooctanoate (APFO) and PFOA. The majority
of the PFCs detected had chain lengths of 8 carbons or more, which suggests that direct emission from plants
in the two parks was a major source of PFCs in soils of the coastal area of Liaodong Bay.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
Perfluorinated compounds (PFCs) have been used worldwide in
various industries such as polymers, surfactants, lubricants,
pesticides, textile coatings, nonstick coatings, stain repellent, food
⇑ Corresponding authors. Tel.: +86 10 62849466; fax: +86 10 62918177.
E-mail addresses: wangty@rcees.ac.cn (T. Wang), yllu@rcees.ac.cn (Y. Lu).
0045-6535/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.chemosphere.2013.02.017
packaging, firefighting foams in consumer products for more than
60 years. PFCs have unique and useful chemical properties including
surface activity, thermal and acid resistance, and repellency of water
and oil (Giesy and Kannan, 2001; Paul et al., 2009; Wang et al., 2009).
However, the high energy C–F bond also renders PFCs extremely
stable on hydrolysis, photolysis, microbial degradation, and metabolism by vertebrates (Giesy and Kannan, 2002). Owing to persistence, potentials for bioaccumulation and long-range transport,
752
P. Wang et al. / Chemosphere 91 (2013) 751–757
perfluorooctane sulfonate (PFOS) is the mostly detected PFCs in the
environment. Due to these properties as well as toxic potency, in
2009 chemicals containing PFOS, its salts, and perfluorooctane sulfonyl fluoride (PFOSF), which is the primary intermediate used to
manufacture compounds containing PFOS, have been added to Annex B of the Stockholm Convention on Persistent Organic Pollutants
(POPs) (UNEP), inclusion in this list means that production and use of
chemicals containing PFOS should be minimized.
Legislation in some countries such as those in Europe, North
America as well as Japan has either eliminated or restricted production of chemicals containing PFOS, which has resulted in a shift of
production to other countries including China, where, controls over
production efficiency and releases to the environment are less well
developed (Bao et al., 2009; Wang et al., 2009). In 2003, soon after
3 M, which had been the primary producer phased out production
of the PFOS-based chemistry, companies in China began large-scale
production of chemicals containing PFOS, with a total production of
less than 50 ton by 2004 to over 200 ton in 2006, of which 100 ton
was designated for export (Wang et al., 2011a,b,c).
Given the water solubility and negligible vapor pressure of most
PFCs, water and sediments are considered final sinks of PFCs and
aquatic systems are an important media for their transport (Hansen et al., 2002; Taniyasu et al., 2003). However, recent research
indicates that long-range transport of chemicals containing
longer-chain PFCs is the predominant mechanism by which PFCs
are distributed in the environment, and volatilization of the
neutral species, such as Perfluorooctanesulfonamide (PFOSA),
N-ethylperfluorooctanesulfonamide (N-EtFOSA) and Perfluorobutylethanol (FTOH), is the most important pathway for mobilization
of longer chain homologues from soil (Ellis et al., 2004; Armitage
et al., 2009).
Liaodong Bay (LDB) is part of Bohai Bay, which is adjacent to
one of the most industrialization regions in Northern China. Since
2008, the authors have conducted a systematic research on POPs
including organo-chlorine pesticides (OCPs), Dioxin and PFCs in
this region (Hu et al., 2010a,b; Chen et al., 2011; Naile et al.,
2011; Wang et al., 2011a,b,c), which indicated that the greatest
concentrations of PFCs observed in North Bohai area were found
in LDB, where much of the industry producing PFCs is located. Concentrations of PFCs in surface waters were compared to the level of
industrialization in Northern China. The greatest concentrations of
PFCs, such as PFOA and PFOS, which are the terminal degradation
products of a range of chemicals containing PFCs, were also observed in the Liaoning region (Wang et al., 2011a,b,c). Other studies have reported concentrations of PFCs within and around this
area to be greater than most of other regions of China (Ju et al.,
2008; Bao et al., 2009; Li et al., 2011; Sun et al., 2011).
The object of the present study was to study Total Fluorine (TF),
Extractable Organic Fluorine (EOF), and other environmental factors as a clue to determine the distribution of PFCs in soil of a relatively contaminated area, and to determine if there is a
relationship between the occurrence of PFCs in soils, sediment, surface waters and biota and the presence of manufacturing plants.
The present study is an extension of a systematic research to trace
sources and fates of toxic substances in various environmental
media from adjacent riverine and estuarine areas including the Bohai Sea of China and the West Sea of Korea, to provide scientific
support for PFCs management and risk assessment.
Perfluoro-hexanoic acid (PFHxA), Perfluoro-heptanoic acid
(PFHpA), Perfluoro-octanoic acid (PFOA), Perfluoro-nonanoic
acid (PFNA), Perfluoro-decanoic acid (PFDA), Perfluoro-undecanoic
acid (PFUdA), Perfluoro-dodecanoic acid (PFDoA), Perfluorotridecanoic acid (PFTrDA), Perfluoro-tetradecanoic acid (PFTeDA),
Perfluoro-hexadecanoic acid (PFHxDA), Perfluoro-octadecanoic
acid (PFODA), Potassium Perfluoro-butanesulfonate (PFBS), Sodium
Perfluoro-hexanesulfonate (PFHxS), Sodium Perfluoro-octanesulfonate (PFOS), Sodium Perfluoro-decanesulfonate (PFDS), N-ethylperfluoro-octanesulfonamido-ethanol
(N-EtFOSE),
N-methylperfluoro-octanesulfonamido-ethanol (N-MeFOSE), Perfluoro-octanesulfonamido-acetic (FOSAA), N-methyl-perfluoro-octanesulfonamido-acetic (N-MeFOSAA) and N-ethyl-perfluoro-octanesulfonamido-acetic (N-EtFOSAA) were quantified. Soils were extracted
by use of a previously published method with some modifications
(Naile et al., 2010). Information of target analytes and detailed analytical procedures of PFCs in soils are provided in Supplemental
Materials.
2.2. Collection of soils
Soils were collected from 14 estuarine and coastal areas along
the coast of 4 cities: Huludao, Jinzhou, Panjin and Yingkou in Liaoning Province during May of 2008 (Fig. 1 and Table S2). Surface
(top 0–10 cm) soil samples LS1–LS14 were collected by use of a
stainless steel trowel that had been rinsed with methanol. Each
sample was a composite of five sub-samples collected from the
center and four corners of an area of 10 m 10 m. Samples were
then transferred and stored in clean PP bags. Duplicates and field
blanks were collected at each city, and were analyzed along with
lab and procedural blanks with each group of samples. After arriving at the laboratory, samples were transferred to PP boxes, dried
in air, homogenized with a porcelain mortar and pestle, sieved
with a 2 mm mesh, and stored in 250 mL PP bottles at room temperature until extraction.
2.3. Identification and quantification
A sample of 0.2 g of un-extracted soil was analyzed directly for Total Fluorine (TF) by use of combustion ion chromatography (CIC), and
0.2 mL of each extract was analyzed for Extractable Organic Fluorine
(EOF) by use of CIC. The remaining 0.8 mL of each extract was
analyzed for identification and quantification of PFCs by use of high
performance liquid chromatography coupled with triple qudrapole
tandem mass spectrometry (HPLC-MS/MS). More detailed Instrumental conditions are presented in Supplemental Materials.
Concentrations of EOF, and TF detected here are presented as
corresponding concentrations of F (CF ng F g1 dw). For comparison, concentrations of CF were calculated from concentrations of
individual PFC (Eq. (1)) (Miyake et al., 2007):
CF ¼
nMF
C PFC
M PFC
ð1Þ
where CPFC is concentration of PFC (ng g1 dw), MPFC is molecular
weight of corresponding PFC (g mol1), n is the number of fluorines
in the compound, and MF is the molecular weight of fluorine
(g F mol1).
2.4. Quality assurance and control
2. Materials and methods
2.1. Target chemicals and pretreatment
Twenty-two PFCs (>98%, Wellington Laboratories), including
Perfluoro-butanoic acid (PFBA), Perfluoro-pentanoic acid (PFPeA),
In order to ensure the accuracy of sampling, extraction, and
quantification, the following procedures were used. Field blanks
were collected with each set of samples analyzed, procedural
blanks and recoveries were determined for each set of extractions.
All gases (high purity oxygen, argon and nitrogen) were cleaned by
an active carbon column before injection. Five-point standard
P. Wang et al. / Chemosphere 91 (2013) 751–757
753
Fig. 1. Map of study area. Soil collected from 14 locations in coastal areas of Liaodong Bay. Sampling design and sample information is given in Table S2.
calibration curve was prepared at 0.2, 1, 5, 25, 100 lg mL1 for the
analysis of TF and at 0.01, 0.05, 0.1, 0.5, 1 lg mL1 for the analysis
of EOF with the injection volume at 1.5 mL. Calibration curves were
prepared routinely to check for linearity. Quantification was based
on the response of the external standard that bracketed the responses found in samples. Quantification of PFCs was performed
using external calibration curves which were constructed using a
concentration series of 0.1, 0.5, 2, 5, 10 and 50 ng mL1. Surrogate
standards were used as a reference material to check for the overall
matrix recoveries in soils for every batch of extraction. To reduce
instrument background contamination arising from HPLC or
solvents, a ZORBEX (Thermo Scientific, 50 2.1 mm, 5 lm particle
size) column was inserted directly before the injection-valve, as
adapted from (Benskin et al., 2007). All field and laboratory blanks
were less than the limit of quantification (LOQ), which was defined
as 5 times the background signal of solvent blanks. The use of
Teflon coated lab-ware was avoided during all steps of sample
preparation and analysis to minimize contamination of the
samples. The ions monitored, method detection limit (MDL), and
matrix spike recoveries for all the target chemicals are summarized
in Table S1.
2.5. Statistical analysis
All statistical analyses were performed with SPSS Statistics
V20.0. A statistical distribution test called P–P plots was carried
out to test the normal distribution of raw data in order to ensure
that the raw data was sufficient for further
analysis. Concentrapffiffiffi
tions below LOQ were assigned as LOQ/ 2 during summary statistics. Spatial distributions of PFCs were analyzed using ArcGIS V10.0
software (ESRI).
3. Results and discussion
3.1. Occurrence and spatial distribution of PFCs in soil
Among the 22 PFCs investigated, only PFOA, PFDA, PFUdA,
PFTrDA, PFOS and FOSAA were detected (Table 1 and Fig. 2), no
individual sample containing all of the PFCs was detected. PFOA
(mean = 0.12 ng g1 dry weight (dw)) and PFUdA (mean =
0.17 ng g1 dw) were found to be the predominant PFCs with concentrations of PFOA and PFUdA in soil ranging from <MDL to 0.47
and from <MDL to 0.42 ng g1 dw, respectively. PFDA (LS14) and
PFOS (LS4) were found in soils at only one site. PFTrDA was found
at 3 sites at a relatively greater concentration, which ranged from
0.53 to 0.65 ng g1 dw. However, FOSAA was a precursor detected
in soil from only one site (LS11) with a maximum concentration of
3.14 ng g1 dw. This site was located in a reclaimed area, near the
harbor.
The sampling design was not arranged to investigate any particular facilities that could have been sources of PFCs, such as
manufacturing plants, WWTP or refuse landfills. To provide a
general characterization of PFCs contamination within the LDB,
soils were collected from agricultural fields along the coast
(Table S2). Even though information on concentrations of PFCs
in soils is scarce, concentrations of PFCs measured in this study
were compared to those for other regions of China and other
countries. Concentrations were comparable to those previously
reported to occur in the vicinity of Guanting Reservoir (Wang
et al., 2011a,b,c), west coast of South Korea (Naile et al., 2010)
and tested soil (Washington et al., 2008). However, greater concentrations of Trifluoroacetic acid (TFA), with concentrations
ranging from 92.7 to 188 ng g1 dw and PFOS with concentrations
754
P. Wang et al. / Chemosphere 91 (2013) 751–757
Table 1
Concentrations (ng g1 F dw) of PFCs, EOF and TF in soils from the coast of Liaodong Bay.
Sample ID
LS1
LS2
LS3
LS4
LS5
LS6
LS7
LS8
LS9
LS10
LS11
LS12
LS13
LS14
PFCAs
PFSAs
Precursors
PFOA
PFDA
PFUdA
PFTrDA
PFOS
FOSAA
nd
nd
0.11
0.32
0.10
0.12
0.22
0.14
nd
nd
nd
0.12
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.06
0.18
0.30
nd
0.26
0.20
0.22
0.28
0.09
nd
nd
nd
0.11
0.08
nd
nd
nd
nd
nd
0.41
nd
0.38
nd
0.46
nd
nd
nd
nd
nd
nd
nd
nd
0.28
nd
nd
nd
nd
nd
nd
nd
nd
nd
0.42
nd
nd
nd
nd
nd
nd
nd
nd
nd
nd
1.82
nd
nd
nd
P
PFCs
EOF
TF
0.18
0.30
0.11
0.86
0.71
0.33
0.88
0.23
0.46
nd
1.82
0.23
0.08
0.48
53.7
49.9
30.8
91.4
121.6
31.0
56.2
88.1
205.4
159.9
47.7
208.5
50.7
66.4
607,867
504,100
449,084
738,504
544,586
398,772
269,201
294,452
464,195
567,231
219,468
458,293
587,004
508,948
nd: Below the MDL.
Fig. 2. Mass balance concept and spatial distribution of TF, EOF and PFCs detected in soil samples collected from 14 locations in coastal areas of Liaodong Bay. With
concentrations of individual PFCs converted to corresponding CF (Eq. (1)).
ranging from 8.58 to 10.4 ng g1 dw have been reported for soils
collected from agricultural, residential and industrial areas of
Shanghai, China (Li et al., 2010). PFOS was mostly detected in
soil from suburban districts of Tianjin, China with concentration
ranged from 0.023 to 2.36 ng g1 dw (Pan et al., 2011). These results indicate the complexity on identification of sources and
fates of PFCs for different soil types.
3.2. Mass balance of fluorine in soils
P
Total concentrations of PFCs ( PFCs) in soils expressed as
equivalent concentrations of fluorine (F) ranged from <MDL to
1.82 ng F g1 dw (mean = 0.48 ng F g1 dw), while concentrations
of EOF ranged from 30.8 ng F g1 dw to 208.5 ng F g1 dw
(mean = 90.09 ng F g1 dw) and concentrations of TF ranged from
P. Wang et al. / Chemosphere 91 (2013) 751–757
219,468 ng F g1 dw to 738,504 ng F g1 dw (mean = 472,265
ng F g1 dw), respectively (Table 1 and Fig. 2). These results indicated that EOF accounted for a small proportion of the TF, while
Inorganic Fluorine (IF) and Non-Extractable Organic Fluorine
(NEOF) comprised the major portion of TF. The same trend has
been investigated in water (Miyake et al., 2007), different trophic
levels of wildlife (Loi et al., 2011) and livers of marine mammals
(Yeung et al., 2009).
Fluorine is a basic element of natural soils. The average concentration of TF in this study is comparable to the mean background
concentrations of F reported from soils in China (Wei et al.,
1991). The result indicates that the occurrence of PFCs and EOF is
a small proportion of the total content of F in natural soils. Previous
studies have found strong, positive correlation between TF and
water-soluble fluorine with r = 0.927 (a = 0.01) (Zhang et al.,
2006). In this study we also found that there was strong negative
correlation between TF and pH (r = 0.552, a = 0.05). However, as
for EOF and PFCs, rTF-EOF and rTF-PFCs were 0.301 and 0.339, respectively, neither of which was significantly correlated. Considering
the chemical properties of PFCs and the organic solvent extraction
method applied in this study, the results suggested that the correP
lation for PFCs and EOF with TF was also limited.
In this study, the contribution of known PFCs to EOF was small,
with an average contribution in concentration of 0.8% and weak
correlations (rPFCs-EOF = 0.013). However, polyfluorinated substances such as perfluoroalkyl sulfonamides (FASA) and perfluoroalkyl sulfonamidoethanols (FOSE) are precursors of PFSAs under
environmental conditions (Fischer et al., 2012), where EOF might
comprise these unanalyzed compounds. In biota, the contribution
of known PFCs to EOF was found to be decreased with decreasing
Trophic Levels (TLs), and large portion of unidentified organic fluorine (OF) might undergo biotransformation in forms of intermediates or metabolites of PFCs such as PFOS precursors (Loi et al.,
2011). The present study suggests that although PFCs could resist
microbial degradation in soil, considering the similarity in solubility for EOF and PFCs, they might undergo similar bioconcentration
after entering the food chain and food web. Therefore, it is necessary to take account of large proportion of unknown OF for risk
assessment and management together with PFCs.
3.3. Production and use of PFCs within the study area
There are two large fluorine industry parks located less than
100 km to the north of the city Jinzhou, in the nearby city Fuxin.
Construction on Park 1 started in 2004 and park 2 in 2006. The region has abundant mineral fluorite (CaF2) and large investment, to
make the city the capital of the fluorine industry in China.
Although construction of these industrial parks is incomplete, the
effects of PFCs on the environment in this region have already attracted the attention of the public as well as scientists. Previous
studies conducted at park 1 revealed three trends: (1) the greatest
concentration of PFOA was in the effluent water and sediment released from the park; (2) concentrations of PFOA were inversely
proportional to depth in a core of sediment taken near the effluent;
and (3) concentrations of PFOA in blood serum of residents of the
region were the greatest observed among all PFCs investigated,
which suggests a similar source of exposure in this region (Bao
et al., 2010). All of these observations are consistent with the fact
that PFOA and its derivatives, especially its ammonium salt,
ammonium perfluorooctanoate (APFO), are important processing
aids in the production of fluoropolymers and fluoroelastomers.
For example, high purity of APFO is necessary to produce Polytetrafluoroethylene (PTFE) (European Commission, 2010), and by
the end of 2011 park 1 was producing 3000 tons of TFE monomer
and 1700 tons of PTFE resin annually (Fig. 3). Therefore, there is a
local source in the region that can account for the relatively great
755
concentration of PFOA observed in blood serum of people in the
region.
Under the US EPA 2010/2015 PFOA Stewardship Program,
developed countries are working toward elimination of PFOA and
related chemicals from emissions and products by 2015. While
some industrialized countries are trying to develop alternatives,
plants within these two parks in China are scaling up production
to meet domestic and international demand. As of the end of
2011 Park 2 was annually producing 3100 tons of fluorinated organic compounds (FOCs) (Fig. 3). PFC products are produced by
electrochemical fluorination (ECF) including Perfluoroheptane
(PFHp), Perfluorobutyric acid, Petfluorooctanoic acid (PFOA), Potassium perfluorobutane sulfonate (KPFBS), Perfluorobutanesulfonyl
fluoride (PFBSF), Trifluoromethanesulfonic acid, 2, 2, 3, 3, 4, 4,
4-Heptafluoro-1-butanol and Perfluorooctanoic acid ammonium
salt (APFO). Systemic, long-term monitoring of PFCs in ambient
and local residents, especially those near park 2 is suggested to
assure that exposure does not exceed those which are expected
to result in adverse health outcomes. Another important issue is
the scale of contamination of the regional environment and potential effects on wildlife. Meanwhile, there are a number of consumer
products that contain PFOA (European Commission, 2010), that
could be released to the environment during various parts of the
life cycles of these products. Therefore detailed scientific investigations and regulatory consideration should be given to these sources
even though they are not major sources of contamination as are
manufacturing plants in the region of China investigated in this
study. Especially lacking is information on sources and fates of
PFCs among multimedia.
3.4. Principal component analysis (PCA)
Distribution patterns among Organic Carbon (OC), pH, individual PFCs, EOF and TF in soil were determined using PCA. The components were ranked by their eigenvalues. The results were shown
in Table S4. The first three components explained over 80% of the
total variance. Analysis of the PCA indicated that the distribution
pattern of the most frequently detected PFCs: PFOA and PFUdA,
were associated with organic carbon contents of soils in the LDB
(Fig. S1). Previous studies have reported that sorption of PFCs onto
sediments is strongly correlated with OC fraction (fOC) (Higgins and
Luthy, 2006) and log KOC increased linearly with increasing chain
length (Labadie and Chevreuil, 2011). In this study, the limited
detection of other PFCs restricted the ability to examine this relationship in soils of the LDB.
3.5. Potential source identification
It is notable that all PFCs detected in the present study have a
carbon chain length equal to or greater than 8, such as PFOA
(C8), PFDA (C10), PFUdA (C11), PFTrDA (C13) and PFOS (8 carbons
in the tail) (Table 1), with PFOA and PFUdA predominant. Previous
studies have assessed the fate and transport pathways of longerchain PFCs directly emitted from sources (Armitage et al., 2009),
and long-range transport potential is greater for longer-chain PFCs.
However, there is no direct linkage through water transport to soils
in the vicinity of the two parks. Since the history of production at
the two parks is short, concentrations of PFCs in soils of the region
are still relatively small. Based on the information and analyses
presented above, it is suggested that direct emission from plants
located in the two parks contributes PFCs to soils of the coastal
area of LDB through atmospheric transport, wet and dry deposition
and subsequently to sedimentation and association with OC. In the
agricultural lands, applications of pesticide and irrigation are also
hypothesized to be potential sources of PFCs to soils (Pan et al.,
2011; Wang et al., 2011a,b,c), but until now there is no evidence
756
P. Wang et al. / Chemosphere 91 (2013) 751–757
Fig. 3. Location, main products, annual capacity (ton) and status of the two fluorine industry parks. (Data is available at http://www.f-china.gov.cn/)
of this. Moreover, bioaccumulation potential is positively correlated with numbers of carbons in the tails of PFCs. Additional
investigation of concentrations of PFCs and their potential effects
on biota should be performed for a better understanding of the fate
of known PFCs within this area.
Research Council of Canada (Project No. 326415-07) and a grant
from the Western Economic Diversification Canada (Project Nos.
6971 and 6807). Professor Giesy was supported by the Canada Research Chair program, and the Einstein Professorship Program of
the Chinese Academy of Sciences.
4. Conclusion
Appendix A. Supplementary material
As one of the most industrialized regions in northern China,
PFCs were found widespread in soil in this region in addition to
other environmental media like water and sediment. PFOA and
PFUdA were predominant with maximum concentrations of
0.47 ng g1 and 0.42 ng g1. Mass balance analysis indicated that
there was limited correlation among PFCs, EOF and TF in soil. The
large portions of unknown OF should be taken into consideration
for risk assessment and management together with PFCs. Continuous growth in fluorine industry has led to great exposure of PFOA
to local water and residents. Direct emission from the production
plants contributes PFCs to the study area through atmospheric
transport, wet and dry deposition and subsequently to sedimentation and association with OC. More attention should be paid to the
fluorine industry parks as they may impose impact beyond the local environment. Furthermore, with the elimination of PFOS and
PFOA, their substitutes, mostly known as PFBS and PFBA, have been
widely produced and used in these parks. Although these substitutes are less accumulative and toxic, but they are highly mobile
and there are high concentrations reported in our study area and
other regions. In this regard, more attention should be paid to
short-chain PFCs on their toxicology, environmental behaviors
and potential risks to human health.
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.chemosphere.
2013.02.017.
Acknowledgement
This study was supported by the National Natural Science Foundation of China under Grant Nos. 41071355 and 41171394, and the
International Scientific Cooperation Program with Grant No.
2012DFA91150. Portions of the research were supported by a
Discovery Grant from the National Science and Engineering
References
Armitage, J.M., MacLeod, M., Cousins, I.T., 2009. Comparative assessment of the
global fate and transport pathways of long-chain perfluorocarboxylic acids
(PFCAs) and perfluorocarboxylates (PFCs) emitted from direct sources.
Environmental Science and Technology 43 (15), 5830–5836.
Bao, J., Jin, Y., Liu, W., Ran, X., Zhang, Z., 2009. Perfluorinated compounds in
sediments from the Daliao River system of northeast China. Chemosphere 77
(5), 652–657.
Bao, J., Liu, W., Liu, L., Jin, Y., Dai, J., Ran, X., Zhang, Z., Tsuda, S., 2010. Perfluorinated
compounds in the environment and the blood of residents living near
fluorochemical plants in fuxin, China. Environmental Science and Technology
45 (19), 8075–8080.
Benskin, J.P., Bataineh, M., Martin, J.W., 2007. Simultaneous characterization of
perfluoroalkyl carboxylate, sulfonate, and sulfonamide isomers by liquid
chromatography-tandem mass spectrometry. Analytical Chemistry 79 (17),
6455–6464.
Chen, C.L., Wang, T.Y., Khim, J.S., Luo, W., Jiao, W.T., Lu, Y.L., Naile, J.E., Hu, W.Y.,
Zhang, X.A., Geng, J., Bi, C.C., Li, J., Giesy, J.P., 2011. Perfluorinated compounds in
water and sediment from coastal regions of the northern Bohai Sea, China.
Chemistry and Ecology 27 (2), 165–176.
Ellis, D.A., Martin, J.W., De Silva, A.O., Mabury, S.A., Hurley, M.D., Sulbaek Andersen,
M.P., Wallington, T.J., 2004. Degradation of fluorotelomer alcohols: a likely
atmospheric source of perfluorinated carboxylic acids. Environmental Science
and Technology 38 (12), 3316–3321.
European Commission, D.E. a. I., 2010. Analysis of the risks arising from the
industrial use of Perfuorooctanoic acid (PFOA) and Ammonium
Perfluorooctanoate (APFO) and from their use in consumer articles.
Evaluation of the risk reduction measures for potential restrictions on the
manufacture, placing on the market and use of PFOA and APFO.
Fischer, K., Fries, E., Körner, W., Schmalz, C., Zwiener, C., 2012. New developments in
the trace analysis of organic water pollutants. Applied Microbiology and
Biotechnology, 1–18.
P. Wang et al. / Chemosphere 91 (2013) 751–757
Giesy, J.P., Kannan, K., 2001. Global distribution of perfluorooctane sulfonate in
wildlife. Environmental Science and Technology 35 (7), 1339–1342.
Giesy, J.P., Kannan, K., 2002. Peer reviewed: perfluorochemical surfactants in the
environment. Environmental Science and Technology 36 (7), 146A–152A.
Hansen, K.J., Johnson, H.O., Eldridge, J.S., Butenhoff, J.L., Dick, L.A., 2002. Quantitative
characterization of trace levels of PFOS and PFOA in the Tennessee River.
Environmental Science and Technology 36 (8), 1681–1685.
Higgins, C.P., Luthy, R.G., 2006. Sorption of perfluorinated surfactants on sediments.
Environmental Science and Technology 40 (23), 7251–7256.
Hu, W.Y., Wang, T.Y., Khim, J.S., Luo, W., Jiao, W.T., Lu, Y.L., Naile, J.E., Chen, C.L.,
Zhang, X., Giesy, J.P., 2010a. HCH and DDT in Sediments from marine and
adjacent Riverine areas of north Bohai Sea, China. Archives of Environmental
Contamination and Toxicology 59 (1), 71–79.
Hu, W.Y., Wang, T.Y., Khim, J.S., Luo, W., Jiao, W.T., Lu, Y.L., Naile, J.E., Giesy, J.P.,
2010b. Organochlorine pesticides (HCHs and DDTs) in soils along the north
coastal areas of the Bohai Sea, China. Chemistry and Ecology 26 (5), 339–352.
Ju, X.D., Jin, Y.H., Sasaki, K., Saito, N., 2008. Perfluorinated surfactants in surface,
subsurface water and microlayer from Dalian Coastal waters in China.
Environmental Science and Technology 42 (10), 3538–3542.
Labadie, P., Chevreuil, M., 2011. Partitioning behaviour of perfluorinated alkyl
contaminants between water, sediment and fish in the Orge River (nearby Paris,
France). Environmental Pollution 159 (2), 391–397.
Li, F., Zhang, C.J., Qu, Y., Chen, J., Chen, L., Liu, Y., Zhou, Q., 2010. Quantitative
characterization of short- and long-chain perfluorinated acids in solid matrices
in Shanghai, China. Science of the Total Environment 408 (3), 617–623.
Li, F.S., Sun, H.W., Hao, Z.N., He, N., Zhao, L.J., Zhang, T., Sun, T.H., 2011.
Perfluorinated compounds in Haihe River and Dagu Drainage Canal in Tianjin,
China. Chemosphere 84 (2), 265–271.
Loi, E.I.H., Yeung, L.W.Y., Taniyasu, S., Lam, P.K.S., Kannan, K., Yamashita, N., 2011.
Trophic magnification of poly- and perfluorinated compounds in a subtropical
food web. Environmental Science and Technology 45 (13), 5506–5513.
Miyake, Y., Yamashita, N., Rostkowski, P., So, M.K., Taniyasu, S., Lam, P.K.S., Kannan,
K., 2007. Determination of trace levels of total fluorine in water using
combustion ion chromatography for fluorine: a mass balance approach to
determine individual perfluorinated chemicals in water. Journal of
Chromatography A 1143 (1–2), 98–104.
Naile, J.E., Khim, J.S., Wang, T.Y., Chen, C.L., Luo, W., Kwon, B.O., Park, J., Koh, C.H.,
Jones, P.D., Lu, Y.L., Giesy, J.P., 2010. Perfluorinated compounds in water,
sediment, soil and biota from estuarine and coastal areas of Korea.
Environmental Pollution 158 (5), 1237–1244.
Naile, J.E., Khim, J.S., Wang, T.Y., Wan, Y., Luo, W., Hu, W.Y., Jiao, W.T., Park, J., Ryu, J.,
Hong, S., Jones, P.D., Lu, Y.L., Giesy, J.P., 2011. Sources and distribution of
polychlorinated-dibenzo-p-dioxins and -dibenzofurans in soil and sediment
from the yellow sea region of China and Korea. Environmental Pollution 159 (4),
907–917.
757
Pan, Y.Y., Shi, Y.L., Wang, J.M., Jin, X.L., Cai, Y.Q., 2011. Pilot investigation of
perfluorinated compounds in river water, sediment, soil and fish in Tianjin,
China. Bulletin of Environmental Contamination and Toxicology 87 (2), 152–
157.
Paul, A.G., Jones, K.C., Sweetman, A.J., 2009. A first global production, emission, and
environmental inventory for perfluorooctane sulfonate. Environmental Science
and Technology 43 (2), 386–392.
Sun, H.W., Li, F.S., Zhang, T., Zhang, X.Z., He, N., Song, Q., Zhao, L.J., Sun, L.N., Sun,
T.H., 2011. Perfluorinated compounds in surface waters and WWTPs in
Shenyang, China: mass flows and source analysis. Water Research 45 (15),
4483–4490.
Taniyasu, S., Kannan, K., Horii, Y., Hanari, N., Yamashita, N., 2003. A survey of
perfluorooctane sulfonate and related perfluorinated organic compounds in
water, fish, birds, and humans from Japan. Environmental Science and
Technology 37 (12), 2634–2639.
Wang, T., Wang, Y.W., Liao, C.Y., Cai, Y.Q., Jiang, G.B., 2009. Perspectives on the
Inclusion of perfluorooctane sulfonate into the stockholm convention on
persistent organic pollutants. Environmental Science and Technology 43 (14),
5171–5175.
Wang, T.Y., Khim, J.S., Chen, C.L., Naile, J.E., Lu, Y.L., Kannan, K., Park, J., Luo, W., Jiao,
W.T., Hu, W.Y., Giesy, J.P., 2011a. Perfluorinated compounds in surface waters
from Northern China: comparison to level of industrialization. Environment
International.
Wang, T.Y., Lu, Y.L., Chen, C.L., Naile, J.E., Khim, J.S., Park, J., Luo, W., Jiao, W.T., Hu,
W.Y., Giesy, J.P., 2011b. Perfluorinated compounds in estuarine and coastal
areas of north Bohai Sea, China. Marine Pollution Bulletin 62 (8), 1905–1914.
Wang, T.Y., Chen, C.L., Naile, J.E., Khim, J.S., Giesy, J.P., Lu, Y.L., 2011c. Perfluorinated
compounds in water, sediment and soil from Guanting Reservoir, China.
Bulletin of Environmental Contamination and Toxicology 87 (1), 74–79.
Washington, J.W., Henderson, W.M., Ellington, J.J., Jenkins, T.M., Evans, J.J., 2008.
Analysis of perfluorinated carboxylic acids in soils ii: optimization of
chromatography and extraction. Journal of Chromatography A 1181 (1–2),
21–32.
Wei, F.S., Chen, J.S., Wu, Y.Y., Zheng, C.J., 1991. Study on the background contents on
61 elements of soils in China. Environmental Science 12 (04), 8.
Yeung, L.W.Y., Miyake, Y., Wang, Y., Taniyasu, S., Yamashita, N., Lam, P.K.S., 2009.
Total fluorine, extractable organic fluorine, perfluorooctane sulfonate and other
related fluorochemicals in liver of Indo-Pacific humpback dolphins (Sousa
chinensis) and finless porpoises (Neophocaena phocaenoides) from South China.
Environmental Pollution 157 (1), 17–23.
Zhang, Y.H., Zhou, X., Wang, C.Q., Shi, Y.Y., 2006. Correlation among dissolved
fluorine, total fluorine and property of soil in fluoride-polluted soil.
Environmental Science & Technology in Chinese 29 (5), 3.
<Supplemental Materials>
Perfluorinated Compounds in Soils from Liaodong Bay with
Concentrated Fluorine Industry Parks in China
Pei Wang a, b, Tieyu Wang a, *, John P. Giesy c, Yonglong Lu a, *
* Corresponding author: Tel: +86 10 62849466; Fax: +86 10 62918177
E-mail address: yllu@rcees.ac.cn (Y. LU)；wangty@rcees.ac.cn (T. Wang)
Analytical methods
Standards and reagents
Extraction and clean-up
Analysis of Organic Carbon (OC) and pH
Instumental analysis
References
Supplemental table
Table S1 Target analytes of 22 PFCs measured in the present study with QA/QC
information including monitoring transitions (MT), limit of quantification
(LOQ), matrix spike recovery (MSR) for soil samples (Mean±SD), method
detection limit (MDL) and sample detected ratio (DR) within 14 sampling sites.
Table S2 Sampling information including location, Organic Carbon (OC) and pH.
Table S3 Spearman rank correlation coefficients among PFCs, EOF, TF, OC and
pH.
Table S4 The result of PCA analysis.
Supplemental figures
Figure S1 The component plot of individual PFC, EOF, TF, OC and pH.
Analytical methods
Standards and reagents
The
22
PFCs,
including
Perfluorobutanoic
Perfluorohexanoic acid (PFHxA) [1,2
acid
(PFNA)
[1,2,3,4,5
13
C],
13
acid
(PFBA)
C], PFOA [1,2,3,4
Perfluorodecanoic
acid
[1,2,3,4
13
C],
13
C], Perfluorononanoic
(PFDA)
[1,2
13
C],
Perfluoroundecanoic acid (PFUdA) [1,2 13C], Perfluorododecanoic acid (PFDoA) [1,2
13
C], Sodium Perfluorohexanesulfonate [18O] and Sodium Perfluorooctanesulfonate
[1,2,3,4 13C] that were used as either external or surrogate standards (Table S1), had
purities of >98% (Wellington Laboratories, Guelph, Ontario, Canada). HPLC grade
methanol, methyl tert-butyl ether (MTBE) and ammonium acetate were purchased
from J.T. Baker (Phillipsburg, NJ, USA). Analytical grade sodium thiosulfate was
purchased from EMD Chemicals (Gibbstown, NJ, USA). Nano-pure water was
obtained from a Milli-Q gradient A-10 (Millipore, Bedford, MA, USA).
Extraction and clean-up
2.5 g of soil was weighed into a 50 mL PP centrifuge tube, and then moistened with 2
mL cleaned Milli-Q water while vortex mixing. 1 mL of 0.5 M TBAHS and 2 mL of
25 mM sodium acetate buffer were added for extraction. Samples were spiked with
internal standards that were labeled with 13C or 18O with shaking for 5 min at 700 rpm.
Subsequently, 5 mL MTBE was added and shaken for 20 min at 400 rpm. After
centrifuging for 20 min at 3500 rpm, the supernatant of MTBE was collected. The
remnant aqueous mixture was rinsed with 5 mL MTBE, followed by shaking and
centrifuging, the two supernatants were combined in a 15 mL PP centrifuge tube. The
MTBE solvent was evaporated to dryness under a gentle flow of high purity nitrogen,
and reconstituted in 1 mL methanol. After 0.2 mL solution was taken for
quantification of EOF, the remaining 0.8 mL was added with 40 mg Envi-carb and 1
mL methanol, followed by sonication and centrifuging for 10 min at 3500 rpm. The
supernatant was transferred to a new 15 mL PP tube. The remnant was rinsed twice
with 1 mL methanol, followed by sonication and centrifuging, and the supernatants
combined. The solution was reduced to 0.5 mL under nitrogen. Then filtered through
a 13 mm/0.2 um nylon filter, and transferred into a 1.5 mL PP snap top vial with
polyethylene (PE) cap.
Analysis of Organic Carbon (OC) and pH
OC in soil was determined using external heating potassium dichromate method
according to the Agricultural Standard of China (NY/T 1121.6-2006) with some
modifications. Briefly, 0.3g soil ground through 0.15mm sieve was weighed into a
150mL triangular flask, with 5mL 0.8mol/L potassium dichromate solution and 5mL
concentrated sulfuric acid added. After shaking the mixture well and put a
crookneck funnel over the flask, heat the flask to 170-180℃ and kept boiling 5
min and then cooled off. Washing the funnel with Milli-Q water to keep the volume of
solution 60-70mL, here the color of the solution should be orange yellow or jasmine.
Then Phenanthroline indicator 3-4 drops were added and titrated with 0.198mol/L
green copperas solution to turn the color of the solution to green, pea green and finally
redbrown. Two blanks were necessary for each set of samples and 0.5g mealiness
silicon-dioxide was used for surrogate. The OC content was calculated using the
following formula:
OC(g⁄𝑘𝑘) =
𝐶 × (𝑉0 − 𝑉) × 3 × 1.1 × 10−3
𝑚
Where C is 0.198mol/L green copperas solution, V0 is the volume (mean value) of bla
nks used to titrate green copperas solution (mL), V is the volume of samples used to ti
trate green copperas solution (mL), 3 stands for a quarter mole mass of a carbon atom
(g/mol), 1.1 is oxidation correction factor and m is the weight of a sample (kg).
pH in soil was determined using potentiometry according to t h e Agricultural
Standard of China (NY/T 1377-2007) with some modifications. Briefly, 10g soil
ground through 2mm sieve was weighed into a 50mL beaker and added 25mL CO2
free Milli-Q water, followed by vigorous agitation using a glass rod for 1-2 min, then
left for 30min. Corrected the pH meter using buffer solution and cleaned it. Put the
bulb of glass electrode underneath the suspension of the sample with slightly shaking
and the saturated calomel electrode supernatant fluid, recorded when reading is stable.
Recorrected the pH meter after 5-6 samples.
Instumental analysis
The CIC was a combination of an automated combustion unit (AQF-100 type AIST;
Dia Instruments Co., Ltd.) and an ion chromatography system (ICS-3000 type AIST;
Dionex Corp., Sunny-vale, CA). The details for analytical conditions are given
elsewhere (Miyake et al. 2007). 0.2g of soil or 0.2mL of extract was set on a slica
boat and then combusted in a furnace at 900-1000℃, where organic and inorganic
fluoride were converted into hydrogen fluoride (HF). The HF was then absorbed into
sodium hydroxide solution (0.2 mmol/L). The concentration of F- was determined
using IC. Sodium fluoride (99% purity; Sigma-Aldrich Co. LLC, St. Louis, United
States) was used as a standard for the quantification.
The HPLC was fitted with a Thermo Scientific Betasil C18 (100×2.1 mm, 5 μm
particle size) analytical column, and a guard column was used for separation of
background from analytes in samples. An aliquant of 2 mM ammonium acetate was
used as an ionization aid. Water and methanol were used as mobile phases. Gradient
conditions were: 300 ml/min flow rate and 10 μl of the sample was injected, starting
with 60% A (2mM ammonium acetate) and 40% B (100% methanol). Initial
conditions were held for 2 min and then ramped to 20% A at 18 min, held until 20
min, decreased to 0% A at 21 min, increased to 100% A at 22 min, held until 22.5 min,
returned to initial conditions at 23 min, and finally held constant until 26min. The
temperature of the column oven was kept constant at 35 ℃.
Mass spectra were collected using an Applied Bioscience SCIEX 3000 (Foster City,
CA) tandem mass spectrometer, fitted with an electrospray ionization source, operated
in negative ionization mode. Chromatograms were recorded in multiple reaction
monitoring mode (MRM) with a dwell time of 40 ms. The following instrument
parameters were used: desolvation temperature (450 ℃), desolvation (curtain) gas
6.0 arbitrary units (AU), nebulizer gas flow5 AU, ion spray voltage−3500 V, and
collision gas 12 AU. Optimal settings for collision energies and declustering potential
were determined for each analyte's MRM transitions. Quantification using these
transitions was performed using Analyst 1.4.1 software (Applied Bioscience, Foster
City, CA).
References
Naile, J.E., Khim, J.S., Wang, T.Y., Chen, C.L., Luo, W., Kwon, B.O., Park, J.,
Koh, C.H., Jones, P.D., Lu, Y.L., Giesy, J.P., 2010. Perfluorinated compounds
in water, sediment, soil and biota from estuarine and coastal areas of Korea.
Environmental Pollution 158 (5), 1237-1244.
Higgins, C.P., Field, J.A., Criddle, C.S., Luthy, R.G., 2005. Quantitative
Determination of Perfluorochemicals in Sediments and Domestic Sludge.
Environmental Science and Technology 39 (11), 3946-3956.
Miyake, Y., Yamashita, N., Rostkowski, P., So, M. K., Taniyasu, S., Lam, P.K.S.,
Kannan, K., 2007. Determination of trace levels of total fluorine in water using
combustion ion chromatography for fluorine: A mass balance approach to
determine individual perfluorinated chemicals in water.
Chromatography A 1143 (1-2), 98-104.
Journal of
Supplemental table
Table S1 Target analytes of 22 PFCs measured in the present study with QA/
QC information including monitoring transitions (MT), limit of quantification(L
OQ), matrix spike recovery (MSR) for soil samples (Mean±SD), method detecti
on limit (MDL) and sample detected ratio (DR) within 14 sampling sites.
LOQ
Acronym
MT
MSR%
(ng/g )
MDLa(ng/g)
DRb%
Perfluoro-n-butanoic acid (C4)
PFBA
213→169
76±7
0.6
0.6
0(0)
Perfluoro-n-pentanoic acid (C5)
PFPeA
263→219
94±11
1.0
1.0
0(0)
Perfluoro-n-hexanoic acid (C6)
PFHxA
313→269
83±5
0.1
0.1
0(0)
Perfluoro-n-heptanoic acid (C7)
PFHpA
363→319
96±10
0.1
0.1
0(0)
Perfluoro-n-octanoic acid (C8)
PFOA
413→369
89±3
0.5
0.5
7(50)
Perfluoro-n-nonanoic acid (C9)
PFNA
463→419
92±5
1.0
1.0
0(0)
Perfluoro-n-decanoic acid (C10)
PFDA
513→469
86±4
0.1
0.1
1(7)
Perfluoro-n-undecanoic acid (C11)
PFUdA
563→519
88±8
0.5
0.5
9(71)
Analyte
Perfluioroalkyl compounds
Perfluoro-n-dodecanoic acid (C12)
PFDoA
613→569
92±7
0.1
0.1
0(0)
Perfluoro-n-tridecanoic acid (C13)
PFTrDA
663→619
93±11
1.0
1.0
3(21)
Perfluoro-n-tetradecanoic acid (C14)
PFTeDA
713→669
72±4
1.0
1.0
0(0)
Perfluoro-n-hexadecanoic acid (C16)
PFHxDA
813→769
107±14
0.5
0.3
0(0)
Perfluoro-n-octadecanoic acid (C18)
PFODA
913→869
c
Potassium Perfluoro-1-butanesulfonate (C4)
PFBS
299→99
76±9
1.0
1.0
0(0)
Sodium Perfluoro-1-hexanesulfonate (C6)
PFHxS
399→99
94±8
0.5
0.5
0(0)
Sodium Perfluoro-1-octanesulfonate (C8)
PFOS
499→99
97±9
0.5
0.5
2(14)
Sodium Perfluoro-1-decanesulfonate (C10)
PFDS
599→99
95±11
0.5
0.5
0(0)
IS
IS
IS
IS
Perfluorinated precursors
2-N-ethylperfluoro-1-octanesulfonamido-ethanlo
N-EtFOSE
616→59
85±6
1.0
1.0
0(0)
2-N-methylperfluoro-1-octanesulfonamido-ethanlo
N-MeFOSE
630→59
75±8
0.8
0.8
0(0)
Perfluoro-1-octanesulfonamidoacetic
FOSAA
556→498
107±12
0.6
0.6
1(7)
N-methylperfluoro-1-octanesulfonamidoacetic
N-MeFOSAA
570→419
91±4
1.0
1.0
0(0)
N-ethylperfluoro-1-octanesulfonamidoacetic
N-EtFOSAA
584→419
93±8
1.5
1.5
0(0)
Table S2. Sampling information including location, Organic Carbon (OC) and pH.
Sample ID
Location
OC(g/kg)
pH
LS1
Agriculture fields(corn), small River, 5km from sea, lots of trash
10.46
5.36
LS2
Agriculture fields(corn), 1km to River Wangbao
11.17
5.03
LS3
Agriculture fields(corn), near river Wuli, many factories around, lots of air pollution
7.77
6.91
LS4
On cliff, Beach(open sea, close to harbor), near downtown
27.99
6.09
LS5
Agriculture fields(corn), close to salt/shrimp ponds
9.53
5.07
LS6
Green area, downtown river bank
7.93
7.34
LS7
Agriculture fields(corn), Daling River (upstream)
5.13
7.29
LS8
Agriculture fields(corn), Daling River(middle stream), papermill around
3.67
7.73
LS9
Agriculture fields(corn), Daling River(downstream), lots of oil wells
4.75
7.95
LS10
Agriculture fields(rice), close to downtown, factories in the distance upstream
5.94
7.55
LS11
Reclaimed land, close to open sea (harbor)
3.23
7.84
LS12
Tree farm, Daliao River(midstream), near a heavy traffic bridge, large construction
5.25
8.12
LS13
Tree farm, Daliao River(downstream), downtown, lots of industry, busy harbor
3.32
6.55
LS14
Agriculture fields, beach(open sea), downtown, huge plants around
7.67
5.67
Table S3 Spearman rank correlation coefficients among PFCs, EOF, TF,
OC and pH.
PFCs
EOF
TF
0.013
-0.339
0.013
-0.022
0.301
-0.064
0.305
0.530
-0.552
EOF
OC
TF
pH
*
**
-0.697
OC
*. Correlation is significant at the 0.05 level (2-tailed).
**. Correlation is significant at the 0.01 level (2-tailed).
Table S4 The result of PCA analysis.
Component
1
2
3
PFOA
.526
.535
.550
PFUdA
.743
.333
-.039
PFCs
-.050
.765
-.048
EOF
-.280
-.391
.761
TF
.674
-.661
.155
OC
.894
.043
.264
pH
-.724
.267
.539
Eigenvalue
2.688
1.644
1.270
Percentage of variance
38.406
23.492
18.144
Cumulative percentage
38.406
61.898
80.042
Extraction Method: Principal Component Analysis.
a. 3 components extracted.
a
Supplemental figures
Fig.S1. The component plot of individual PFC, EOF, TF, OC and pH.