Chemosphere 114 (2014) 203–209
Contents lists available at ScienceDirect
Chemosphere
journal homepage: www.elsevier.com/locate/chemosphere
Historical trends of inorganic and organic fluorine in sediments of Lake
Michigan
Garry Codling a,⇑, Anja Vogt a, Paul D. Jones a, Tieyu Wang a,b, Pei Wang a,b, Y.-L. Lu b, Margaret Corcoran d,
Solidea Bonina d, An Li c, Neil C. Sturchio d, Karl J. Rockne e, Kyunghee Ji a,j, Jong-Seong Khim f,
Jonathan E. Naile a, John P. Giesy a,f,g,h,i
a
Toxicology Centre, University of Saskatchewan, Saskatoon, SK S7N 5B3, Canada
State Key Lab of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
Environmental and Occupational Health Sciences, School of Public Health, University of Illinois at Chicago, 2121 West Taylor St., Chicago, IL 60612, USA
d
Department of Earth and Environmental Sciences (MC 186), University of Illinois at Chicago, 845 W. Taylor Street, Chicago, IL 60607, USA
e
Department of Civil and Materials Engineering (MC 246), University of Illinois at Chicago 842 West Taylor Street, Chicago, IL 60607-7023, USA
f
Department Veterinary Biomedical Sciences, University of Saskatchewan, 44 Campus Drive, Saskatoon SK S7N 5B3, Canada
g
Department of Biology & Chemistry and State Key Laboratory in Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong Special Administrative Region
h
Department of Zoology, and Center for Integrative Toxicology, Michigan State University, East Lansing, MI 48824, USA
i
School of Biological Sciences, University of Hong Kong, Hong Kong Special Administrative Region
j
School of Public Health, Seoul National University, Seoul 152-742, Republic of Korea
b
c
h i g h l i g h t s
We took 8 sediment cores and 27 ponar grabs from Lake Michigan in 2010.
Samples were extracted for total fluorine, extractable fluorine and 25 PFCs.
PFOS and PFOA are the predominant PFCs in sediment cores.
PFBS and PFBA are appearing in upper sections at concentrations similar to PFOS and PFOA.
TF and EOF concentrations are orders of magnitude higher than PFCs.
a r t i c l e
i n f o
Article history:
Received 14 November 2013
Received in revised form 14 March 2014
Accepted 21 March 2014
Handling Editor: Gang Yu
Keywords:
Sediment
PFCs
PFOS
PFOA
Perfluorinated chemicals
Lake Michigan
a b s t r a c t
Total fluorine (TF), extractable organic fluorine (EOF) and poly- and per-fluorinated compounds (PFCs)
were measured in eight dated cores of sediment taken along with 27 surface sediments from Lake MichP
igan in 2010. Based on rates of sedimentation, total concentrations of PFCs ( PFCs) reached a maximum
in the later 1990s and early 2000s. This result is consistent with rapid changes in production and subsequent sedimentation. Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) are still the predominant PFCs in the cores, but in surface sediments, concentrations of perfluorobutane sulfonate
(PFBS) and perfluorobutanoic acid (PFBA) are now occurring at concentrations comparable to those of
PFOS and PFOA. This observation is consistent with shifts in patterns of production and use in the US
and Canada. Concentrations of TF in sediments were greater than those of EOF. This result is consistent
with a larger proportion of un-extractable fluorinated material in both surface sediments and in cores.
Ó 2014 Elsevier Ltd. All rights reserved.
1. Introduction
Per- and poly-fluorinated compounds (PFCs) are chemically and
thermal stable and have the ability to lessen surface tension and
⇑ Corresponding author. Tel.: +1 3069664978.
E-mail address: garrycodling@yahoo.co.uk (G. Codling).
http://dx.doi.org/10.1016/j.chemosphere.2014.03.080
0045-6535/Ó 2014 Elsevier Ltd. All rights reserved.
create stable foams, which make them ideal for a range of
industrial and home uses (Prevedouros et al., 2005). Though first
manufactured in the late 1940s, production of PFCs began to
increase dramatically in the 1970s with global production of perfluorosulfonate (PFOS) based compounds increasing from 500
tonnes per annum in the 1970s to an annual production of
4500 tonnes by the 1990s (Paul et al., 2008).
204
G. Codling et al. / Chemosphere 114 (2014) 203–209
Advances in mass spectrometry in the 1990s allowed identification and quantification of PFCs in the environment. Giesy and
Kannan (2001) showed that PFC contamination in biota is a global
issue, and some degradation products are toxic at environmentally
relevant concentrations. This resulted in ever-increasing interest in
the environmental occurrence, chemodynamics and potential
effects of perfluorinated alkyl carboxylates and sulphonates
(Renner, 2001). Presence of PFCs in air (Ahrens et al., 2011), water
(Ahrens et al., 2010), snow (Young et al., 2007), and humans
(Yeung et al., 2005) have been reported, which has improved
understanding of chemical transport of PFCs. But there is limited
understanding of their long-term environmental fate, although
they are found to have been deposited into sediments of natural
rivers, lakes and estuaries (Stock et al., 2007; Naile et al., 2010).
In Europe, North America and Japan, PSOF and its related compounds has come under restriction (USEPA, 2000; CEC, 2002). Since
the production was reduced, concentrations in some environmental matrices have decreased (Kannan et al., 2005; Young et al.,
2007).
Temporal trends in concentrations of PFCs have been characterized in human blood serum (Harada et al., 2007; Haug et al.,
2009), biota (Holmström et al., 2004; 2010), snow (Young et al.,
2007), and sediment (Stock et al., 2007; Zushi et al., 2010). In
all matrices specific PFCs such as PFOA and PFOS have increased
until the late 1990s. In Japan, PFCs in human blood samples from
1983–1999 on average increased by 3.5 times while in guillemot
eggs from 1960 to 2003 showed a 50 fold increase (Haug et al.,
2009).
This study is one of the most detailed investigations of PFCs,
total fluorine (TF) and extractable organic fluorine (EOF) in the sediment of Lake Michigan. The objectives of this work were to reveal
the spatial and temporal trends of PFC contamination recorded in
the sediment of this freshwater lake of the North America.
2. Methods
2.1. Chemicals
Omni-Solv grade methanol (MeOH), methyl tert-butyl ether
(MTBE), and sodium thiosulphate were purchased from EMD
Chemicals (Gibbstown, NJ, USA), HPLC grade ammonium acetate
was purchased from J.T. Baker (Phillipsburg, NJ, USA). Perfluorinated standards were purchased from Wellington Laboratories,
and included 9 mass labelled recovery standards. A list of native
and mass labelled PFC compounds is given in the Supporting Information along with compound name abbreviations (SI Table S1).
2.2. Sample collection
Both Ponar and core samplers were used during September
2010 to collect sediments from the R/V Lake Guardian. See Supporting Information for detailed sampling methods (SI 1.1). The sampling locations are shown in Fig. 1, (additional location
information is given in Table SI. 2).
2.3. Sample extraction, identification and quantification of PFCs
A total of 192 samples were analysed, including 159 core layers,
27 Ponar samples and 6 blanks, using the method described by
Naile et al. (2010). Briefly Each sample was lyophilized, and
homogenized, fortified with surrogate standard extracted by replicates of MTBE. Samples were cleaned using Envi Carb and reconstituted in MeOH, before analysis by LC-MSMS (See SI 1.2 for detailed
extraction method, and SI 1.3 for instrumental operating conditions). Selection of PFCs in this study was based environmental
relevance and physical chemical properties that imply their potential presence in the overlying water and some propensity for particles (Ahrens et al., 2009).
2.4. TF and EOF analysis
Total fluorine and extractable fluorine were measured by use of
combustion ion chromatography (CIC). TF was measured using a
0.01 g aliquot of dried sediment and EOF a fraction of the extracted
sample used for PFC identification (additional detail is given in the
SI 1.4).
2.5. Rate of sedimentation
Gamma spectroscopy using two well-type HPGe detectors
yielded radioactivity profiles for 210Pb, 241Am, 226Ra, and 137Cs for
all cores. Rates of sedimentation were calculated by use of methods
described by Appleby (2001), and are within the range of those
obtained in previous studies (Robbins and Edgington, 1975;
Hermanson et al., 1991; Zhang et al., 1993). See SI 1.5 and SI
Table S3 for further information.
2.6. Quality control and assurances
Background contamination was assessed through the use of
field and travel blanks. Individual PFCs in the blanks were below
the limits of detection, which were calculated as 5 the background method detection limits (MDLs) and ranged from 1 to
0.1 ng mL 1 (SI Table S4). Matrix spike recoveries were calculated
from the mean response of the mass labelled standard, and averaged 82% for individual compounds with a range of 31–130% and
low standard deviations (SI Table S4).
Statistical modelling to determine interrelationships between
surface Ponar grabs (n = 27) using standardized squared Euclidean
cluster analysis to calculate distance between samples, and clustered by nearest neighbour (single linkage) and analysis of variance
(ANOVA), was performed using software Statgraphics Centurion
XVI of StatPoint Technologies, Inc. (Warrenton, Virginia).
3. Results and discussion
Of the 25 PFCs characterized in this study, PFODA, N-MeFOSA,
and N-EtFOSA were not detected in either Ponar grab samples or
cores. FOSA and FOSAA were observed in <20% of samples, at concentrations near or less than the MDL.
3.1. PFCs in surface sediments
Dry weight (dw) based concentrations of PFCs which were
detected in >60% of Ponar grab sediments are summarized in
Table 1. The concentrations are comparable to those previously
reported from other locations in the Northern Hemisphere with
the exception of Resolute Lake, Cornwallis Island Canada, where
local discharge sources were suspected (Stock et al., 2007) (See SI
Table S5). While not exhaustive, this comparison indicates the paucity of information on PFCs in sediments. Differences in measured
concentrations among studies, especially for individual compounds, may be related to geographical locations, different methods used during sample collection, chemical analysis, and the
sampling time periods. During 1997–2003, a reduction in production and use of both PFOA and PFOS as well as their precursor
chemicals was implemented alongside the increased use of the
4-C PFCs (Prevedouros et al., 2005; Paul et al., 2008).
The spatial distribution of selected PFCs in surface sediments of
P
Lake Michigan is illustrated in Fig. 2. Concentrations of 25PFCs
G. Codling et al. / Chemosphere 114 (2014) 203–209
205
Fig. 1. Sampling locations in Lake Michigan. Stars represent locations where both Ponar grab and core were taken, while circles indicate Ponar samples only.
Table 1
Mean concentrations of PFC, extractable organic fluorine (EOF) and total fluorine (TF)
in sediments of Lake Michigan from 1900 to 2010 sediment cores and surface Ponar
samples, the 48 core sections represent all sections from 1900 to 2010.
Compound
ng g 1 (dw)
PFBA
PFPeA
PFOA
PFTeDA
PFBS
PFOS
FOSA
N-MeFOSE
N-EtFOSE
P
25PFC
mg g
EOF
TF
1
Ponar-surface samples (n = 27)
0.57
0.17
0.21
0.05
0.19
0.45
0.05
0.30
0.23
2.33
(n.d.–0.97)
(n.d.–1.30)
(n.d.–0.42)
(n.d.–0.15)
(n.d.–0.52)
(n.d.–1.15)
(n.d.–0.083)
(n.d.–0.93)
(0.06–0.45)
(0.89–4.94)
Sediment cores (n = 48)
0.37
0.15
0.75
0.14
0.52
2.70
0.48
0.29
0.26
4.4
(n.d.–1.32)
(n.d.–0.82)
(n.d.–3.66)
(n.d.–0.29)
(n.d.–7.93)
(n.d.–12.78)
(n.d.–0.78)
(n.d.–0.98)
(n.d.–0.86)
(0.4–24.1)
2.16
782
(0.8–4.8)
(375–1322)
(dw)
1.60
571
(0.6–4.8)
(96–1181)
were greater at northern (M120, M050 and M103) and southern
(M002, M010) regions compared with locations in the centre of
the lake. The distribution of the 8 most commonly detected
compounds (PFBS, PFPeA, PFTeDA, PFOS, PFBA, PFOA, N-MeFOSE
and N-EtFOSE) differed at the two ends of the lake. The major feature of water currents within Lake Michigan is a southern gyre and
a northern gyre creating two basins and limited mixing on the east
coast. This is somewhat reflected in the observed spatial pattern of
PFCs. The southern Great Lakes region has a high population density with an estimated 5.5 million people and heavy industry, compared to 1 million in the northern region. Studies have indicated
that some atmospheric contaminants across Lake Michigan may be
traced to the sources in the southern region (Gratz et al., 2013).
Concentrations of PFOS and N-EtFOSE were greatest in sediments
from the northern portion of Lake Michigan. Biotransformation of
N-EtFOSE results in PFOS as one of the terminal products, it might
be considered that they come from the same source, though no significant correlation was observed (Rhoads et al., 2008). N-EtFOSAA,
though not among the 10 PFCs with the greatest concentration/
detection, was observed most frequently in sediments in the northern basin, this has been linked to a degradation pathway of NEtFOSE.
In Lake Michigan, PFOA and PFOS were among the predominant
PFCs in most samples. PFBA was found in 21/27 grab samples at a
206
Fig. 2. Concentrations of
G. Codling et al. / Chemosphere 114 (2014) 203–209
P
25PFCs
and the 5 most frequently detected PFCs in surface sediment of Lake Michigan. The base of each column represents the sampling location.
mean concentration of 0.57 ng g 1, similar to the mean concentration of PFOS (0.44 ng g 1). This result differs from those of previous
studies (e.g. Stock et al., 2007; Zushi et al., 2010), where PFBA was
often not noted. However, since PFBS and PFBA have been used as
substitutes for C-8 PFCs, their production has increased during the
last decade. Studies have found PFBA, and PFBS in the waters of
North Sea, North Bohai Sea, and the River Rhine in Germany; at
some locations C-4 PFCs are now predominant (Ahrens et al.,
2009; Möller et al., 2010; Wang et al., 2012).
PFBA and PFBS had greater concentrations than PFOS or PFOA in
sediments from the southern region of Lake Michigan. For instance,
at M002 the concentration of PFBA was 1.2 ng g 1 dw, but that of
PFOS was < LOQ. Location M010, which is located further south,
exhibited the greatest concentration of PFOA (0.42 ng g 1 dw)
and one of the greatest concentrations of PFOS (0.76 ng g 1 dw).
Cluster analysis for PFBS, PFPeA, PFTeDA, PFOS, PFBA, PFOA, NMeFOSE, and N-EtFOSE (SI Fig. S1) indicate site M002 close to Chicago and M030 near Milwaukee both appear different than all
other sample sites. Site M020 between Chicago and Milwaukee
also differs somewhat from other sites though not as strongly.
The remaining Ponar grab sites are set into 3 distinct groups.
Sites in deep water of the north and south basin are similar,
such as M009, M010 in the south and M032 and M041 in the north,
in keeping with predictions for contaminant movement
(Robbins and Edgington, 1975). The other two groups appear at
intermediate and shallower depths closer to the shoreline though
there is no significant separation, i.e., not all close to shore in shallow water are similar nor are the intermediate depths. There were
no significant correlations between PFC concentrations in sediments and the depth of overlying water. A weak correlation
between concentrations of TF and depth was observed, but this
association was not statistically significant (P > 0.05).
3.2. PFCs in sediment cores
Depending on the location each core represents between 150
and 1200 years of sedimentation. A 1 cm upper sediment layer presents from 4 years to 20 years, with compaction of deeper sediment resulting in a core section covering a greater period.
Differences in sedimentation rate result in different temporal resolution of layers among cores. Because the use of fluorinated compounds, such as additives to drinking water, began prior to the
mass production of PFCs began in the 1940s, a 100 year period
was examined. Through dating cores M008 and M032 indicate
missing the upper 16 and 13 years respectively. While there can
be downward diffusion of organic compounds, detectable concen-
G. Codling et al. / Chemosphere 114 (2014) 203–209
trations of PFCs observed deeper than the year 1900 is likely due to
bioturbation, or pore water movement (Ahrens et al., 2009).
P
Concentrations of
10PFCs (PFBA, PFOA, PFNA, PFBS, PFHxS,
PFOS, PFDS, N-MeFOSE, N-EtFOSE and N-EtFOSAA) ranged from
10 ± 3.9 ng g 1 dw in layers within cores dated at approximately
2000 to 2.1 ± 0.9 ng g 1 dw in those from 1900 to 1910. The general exponential increase in concentrations of PFC from deeper sediment to layers approximating to the 1990s is consistent with
known history of production and use of PFCs in the U.S. and Canada
(Paul et al., 2008; SI Fig. S2). This is due primarily to the increases
in PFOS, PFOA, and PFHxA, (Fig. 3 and SI Fig. S3).
Location M018 and to a lesser extent locations M032, M011 and
M009 all contained measureable concentrations of a range of PFCs
in the 1920s and early 1930s. Even when greater concentrations of
P
PFBS at location M018 were eliminated, the concentration of 10PFCs was greater in this decade than those in sediments deposited
between 1900–1920 and 1930–1940. The cause of this is unknown,
though industry at the time was not actively creating PFCs, some
might have been by-products of industrialization.
Locations M008, M024, M009 and M047 exhibited an increase
P
in concentration of 10PFCs in the late 1950s, compared to concentrations measured prior to and just after that time. Mostly this
was due to greater concentrations of PFOA. Since this pattern was
observed in multiple samples from the southern region of Lake
Michigan, and in the region of deposition predicted due to the
north basin gyre, it might be evidence of initial larger-scale manufacture of PFCs prior to improved waste treatment that began to be
implemented in the 1960s and was reflected in the decrease of
detectable concentrations observed in the subsequently deposited
core sections. Another factor might be that in 1958 one of the largest storms with winds in excess of 100 km h 1 resulted in mixing
of sediments and additional runoff (Hermanson et al., 1991). The
1958 storm differed from subsequent large storms on Lake Michigan, because the wind was predominantly from the southwest,
while wind in later storms was from the north or northeast (NOAA,
2010).
Location M050, situated within Green Bay, exhibited lesser concentrations of PFCs in both surface samples and cores, and thus dif-
Fig. 3. Concentration versus core depth of
P
10PFCs
207
fered from the rest of Lake Michigan. Sedimentation rate at this
location was high 4 year cm 1, but M009 had 3 times greater
sedimentation than M050, but shows concentrations similar to
the rest of the lake. Concentrations of N-EtFOSAA were greater
than those of other PFCs, with a peak concentration of 4.4 ng g 1
in the core section dated at 1980. N-EtFOSAA is a degradation
product of N-EtFOSE, Historically, Green Bay has had paper mills
that might have used N-EtFOSE attached to a phosphate ester in
protective paper coatings. Due to the volatility of this compound,
it is likely to have entered the atmosphere during production or
use and thus been subject to photo-degradation to terminal products like PFOS at locations remote from sources (Martin et al.,
2004). The greater concentrations of N-EtFOSAA at M050 might
be indicative of treated wastewater being a significant source. In
activated sludge of sewage treatment plants, N-EtFOSE was
detected (3M, 2000). A proposed scheme for biotransformation of
N-EtFOSE in activated sludge process is that N-EtFOSAA is a major
degradation product with a proportion not degraded further
towards a terminal product like PFOS and remained as N-EtFOSAA
(Rhoads et al., 2008). Our measurements at M050 are consistent
with this hypothesis.
Previously published estimates of global production of perfluorooctane sulfonyl fluoride from 1970 to 2005 are closely related to
observed trends in sediment contamination (Prevedouros et al.,
2005; Paul et al., 2008). This is also consistent with the expectation
that much of the PFOS was released during production, rather than
through use, and that there is a rapid environmental turnover from
release to sedimentation. Additional measurements in the future
are needed to confirm if the decrease observed from the late
1990s in the majority of cores is statistically significant.
3.3. TF and EOF
Mean concentrations of total fluorine (TF) and extractable
organic fluorine (EOF) are summarized (Table 1). In this study
the proportion of TF represented by EOF was 0.30% and 0.44%
in sediment cores and Ponar grabs, respectively. The mass of unquantified organic fluorine is not unique; a study of surface water
(bars), TF (dotted lines) and EOF (solid lines). The bars include the 10 most frequently detected individual PFCs.
208
G. Codling et al. / Chemosphere 114 (2014) 203–209
after a spill of fire retardant showed that the total mass of PFCs
identified was significantly less than that the 19F measured by
NMR (Moody et al., 2001). There are other instances where for
non-biological matrices EOF has occurred in significantly greater
abundance than that identified by the commonly described PFCs
(Trojanowicz et al., 2011). In comparison, EOF was 63% (n = 10)
and 38% (n = 10) of TF, respectively, for two cetacean species
(Yeung et al., 2009). Ponar samples contained, on average, greater
concentrations of TF within the central basins of Lake Michigan
(Fig. SI 4). This result is consistent with predictions that sediment
is deposited towards the central gyre (Robbins and Edgington,
1975). Concentrations of EOF across the southern basin were similar, though with a slight elevation on the eastern side in keeping
with water flow. Greatest concentrations of EOF were observed
at site M093(b,c), in the northern basin collected near to a river
input. M093 sites also had the greatest concentrations of PFOS
within the northern basin (Fig. 2).
In this study, elemental fluorine accounted for by quantified
PFCs represented 0.16% and 0.09% of EOF in sediment cores and
Ponar samples, respectively. In contrast, molar concentrations of
F accounted for 24% and 22% of the EOF for Indo-pacific humpback
dolphin and finless porpoise, respectively (Yeung et al., 2009). For
human blood serum in the US and Japan, Miyake et al. (2007) was
able to determine all but 20% of the EOF as being PFCs. In a study in
China, unknown EOF material accounted for 30% of the EOF in samples from cities of Beijing, Shenyang, and Guiyang, while it was
70% in Jintan (Yeung et al., 2008).
Concentrations of TF in cores from some locations, such as
M041 and M024, indicate limited changes over the last 100 years,
though fluctuations and low resolution make trends difficult to
interpret. There is some evidence of a decrease in TF within cores
from locations M050, M008 and M018 during the last 20 years
(Fig. 3), and this may be indicative of the improved water quality
after the 1978 Great Lakes Water Quality Agreement that created
a zero discharge policy.
At some locations, there appeared to be a relationship between
concentrations of TF and EOF, such that peaks of TF and EOF both
increased. A lag was observed at some locations such as M009
and M008 both of which have greater sedimentation rates and
hence greater resolution of their chronological profiles. The
significance of this might be that some forms of non-extractable
fluorine could be converted to an EOF form over a period in
sediment, though further analysis is needed to identify unknown
compounds.
Acknowledgements
This research was part of the Great Lakes Sediment Surveillance
Program (GLSSP), which is supported by a Cooperative Agreement
from the U.S. EPA Great Lakes Restoration Initiative with Assistance
No. GL-00E00538 (EPA Program Officer Todd Nettesheim). The
research was also supported, in part, by a Discovery Grant from
the Natural Science and Engineering Research Council of Canada
(Project # 326415-07) and a grant from the Western Economic
Diversification Canada (Project # 6578 and 6807). The authors
wish to acknowledge the support of an instrumentation grant
from the Canada Foundation for Infrastructure. We thank the
Captain and crew of the R/V Lake Guardian for the assistance in
sampling.
Appendix A. Supplementary material
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.chemosphere.
2014.03.080.
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1
5
Supporting Information:
6
SI1.1 Sample collection
7
From each core site location, four cores were collected in polycarbonate tubes (10 cm (ID) x 58
8
cm). Cores were sectioned immediately using into 10 mm layers, with the outer 2 mm carefully
9
trimmed off to minimize smearing. Corresponding layers from multiple cores were combined
10
and hand mixed in pre-cleaned glass containers. PONAR grab samples were taken at the same
11
time as cores plus at 19 other locations (Figure 1 and SI Table S2) and mechanically mixed in a
12
pre-cleaned bucket. Depths of water from which samples were collected ranged from 18 m
13
(M030) to 257 m (M032). Samples were separated into aliquots for differing analyses, and those
14
for PFC analyses were placed in amber glass jars with aluminium foil liner caps. Samples were
15
stored in the dark at -20 °C and shipped on ice in coolers to the laboratory.
16
SI1.2 Individual PFC Analysis
17
Each sample was lyophilized, and homogenized by hand before being passed through a 1 mm
18
sieve to remove stones and large organic matter. A 2.5 g (±0.5) aliquant was transferred to a 50
19
mL polypropylene (PP) centrifuge tube along with 2 mL of nanopure water and vortexed to mix.
20
One mL of tetrabutylammonium hydrogen sulphate, 2 mL of 25 mM sodium acetate, and 100 µL
21
of 100 ng mL-1 recovery standard and vortexed at 700 rpm for 5 min. MTBE (5 mL) was added
22
to the sample and vortexed for a further 20 min at 400 rpm and centrifuged for 20 min at 1300G.
2
3
4
Perfluorinated alky carboxylates and sulphonates within the Sediments of
Lake Michigan, a mass balance approach
23
The supernatant ~5 mL was taken off and the MTBE extraction repeated twice, with the
24
supernatant fractions combined in a 15 mL PP centrifuge tube. Samples are evaporated to
25
dryness under nitrogen and re-dissolved in 1 mL MeOH, forty mg of envi-carb was added and an
26
additional 1 mL of MeOH and the sample was sonicated for 30 s, centrifuged at 2700 G for 20
27
min, and the supernatant taken off. Addition of 1 mL of MeOH followed by sonication, and
28
centrifugation was repeated twice, and the supernatant combined and reduced to 0.5 mL under
29
nitrogen and filtered through a 13 mm/02 µm nylon filter into a 1.5 mL pp GC vial. During
30
extraction fractions were taken for total fluorine (TF), and extractable organic fluorine (EOF).
31
Samples for determination of TF were taken from sieved sediment and that for determination of
32
EOF from an aliquot taken after the extract had been re-dissolved in MeOH.
33
SI1.3 Identification, Quantification and Operating Conditions for PFCs
34
Separation of analytes was by HPLC (Agilent Technologies) through a Beatacil C18 column,
35
(Thermo Scientific, 100 X 2.1 mm, 5 µm particle size), operating at 35 °C, with a flow rate of
36
300 µL min-1. Solvent gradients were initially 60% 2 mM ammonium acetate (A) and MeOH
37
(B) held for 2 min, then ramped to 80% B over 16 min held for 2 min before increasing B to
38
100% over 2 min. It was then switched to 100% A for 30 s and returned to initial conditions by
39
23 min of the run and held stable until 26 min. Mass spectra were measured by a tandem mass
40
spectrometer fitted with an electrospray ionization source (Applied Biosciences SCIEX 3000)
41
operating in negative ionization mode with chromatograms recorded using MRM mode. A
42
desolation temperature was set at 450 °C, ion spray voltage was -3500V, collision gas set at 12
43
arbitrary units (AU) with curtain gas set at 6 AU, nebulizer gas was set to 5 AU and dwell times
44
of 40 ms. Quantification was done by use of Analyst 1.4.1 software (SCIEX, Applied
45
Biosciences Foster City, CA). A list of ions used in quantification is given in SI.
46
SI 1.4 Combustion Ion Chromatography
47
CIC was operated following the method described by Yeung et al (2008). Samples were
48
combusted in an AQF-100 automatic quick furnace, collected in a GA100 Gas Absorption Unit,
49
and measured on a Dionex CD20 Conductivity Detector, using sodium fluoride as standard
50
solution with calibration range for F- at 1 to 100 mg L-1. The operating conditions are given in SI
51
Table S2.
52
In this study we cannot quantify the efficiency of combustion of TF. The results of
53
quantification of TF describe the CIC concentration of fluorine using a liquid calibration curve,
54
sediment spiked with calibration solutions gave poor reproducibility (~40%) between replicates,
55
however replicates of sample material were reproducible (<10%). Therefore, though in this
56
study TF in sediment is considered to be derived from CIC, and might be less than actual
57
concentrations of elemental fluorine in sediment. EOF represents the organic fluorine extracted
58
by this method and may not represent the total sum of organic fluorine present in the sample.
59
SI 1.5 Core Sample Dating
60
Gamma spectroscopy using two well-type HPGe detectors yielded radioactivity profiles for
61
210
62
standards DL-1a (CANMET, U-Th ore) and SRM-4357 (NIST, ocean sediment). Uncertainties
63
in sample activities were obtained from counting statistics, including uncertainties in background
64
subtraction. Rates of sedimentation were calculated by use of methods described by Appleby
65
(2001), and are within the range of those obtained in previous studies (Robbins and Edgington,
66
1975; Zhang et al., 1993; Hermanson et al., 1991). Assignment of calendar year date ranges by
67
use of calculated sedimentation rates was normalized to the peak deposition of 137Cs and 241Am,
68
from testing nuclear weapons in the atmosphere, which occurred in 1963. Apparent near-surface
Pb, 241Am, 226Ra, and
137
Cs for all cores. Detector efficiencies were calibrated using certified
69
mixing observed in some core profiles added an uncertainty of 5 to 20 years in assignment of
70
calendar date ranges to each segment of cores (see SI Table 2 for further information).
71
72
Table S1: PFCs and mass labelled compounds used in this study
Carbon
Number
Name
Abbreviation
Molecular Formula
Molecular
Weight
Perfluoroalkyl compounds
Perfluoro-n-butanoic acid
C4
PFBA
C4HF7O2
214.0396
Perfluoro-n-pentanoic acid
C5
PFPeA
C5HF9O2
264.0474
Perfluoro-n-hexanoic acid
C6
PFHxA
C6HF11O2
314.0552
Perfluoro-n-heptanoic acid
C7
PFHpA
C7HF13O2
364.0630
Perfluoro-n-octanoic acid
C8
PFOA
C8HF15O2
414.0708
Perfluoro-n-nonanoic acid
C9
PFNA
C9HF17O2
464.0786
Perfluoro-n-decanoic acid
C10
PFDA
C10HF19O2
514.0864
Perfluoro-n-undecanoic acid
C11
PFUnA
C11HF21O2
564.0942
Perfluoro-n-dodecanoic acid
C12
PFDoA
C12HF23O2
614.1020
Perfluoro-n-tridecanoic acid
C13
PFTrDA
C13HF25O2
664.1098
Perfluoro-n-tetradecanoic acid
C14
PFTeDA
C14HF27O2
714.1176
Perfluoro-n-hexadecanoic acid
C16
PFHxDA
C16HF31O2
814.1332
Perfluoro-n-octadecanoic acid
C18
PFODA
C18HF35O2
914.1488
Potassium Perfluoro-1-butanesulfonate
C4
PFBS
C4F9SO3K
338.1901
Sodium Perfluoro-1-hexanesulfonate
C6
PFHxS
C6F13SO3Na
422.0972
Sodium Perfluoro-1-octanesulfonate
C8
PFOS
C8F17SO3Na
522.1129
Sodium Perfluoro-1-decanesulfonate
C10
PFDS
C10F21SO3Na
622.1285
Perfluorinated precursors
Perfluoro-1-octanesulfonamide
C8
FOSA
C8H2F17NO2S
499.15
N-methylperfluoro-1-octanesulfonamide
C9
MeFOSA
C9H4F17NO2S
513.17
N-ethylperfluoro-1-octanesulfonamide
C10
EtFOSA
C10H6F17NO2S
527.20
2-N-ethylperfluoro-1-octanesulfonamidoethanol
C12
EtFOSE
C12H10F17NO3S
571.25
2-N-methylperfluoro-1-octanesulfonamido –
ethanol
C11
MeFOSE-M
C11H8F17NO3S
557.23
Perfluoro-1-octanesulfonamidoacetic acid
C10
FOSAA
C10H4F17NO4S
557.18
N-methylperfluoro-1octanesulfonamidoacetic acid
C11
MeFOSAA
C11H8F17NO4S
571.21
N-ethylperfluoro-1-octanesulfonamidoacetic
acid
C12
EtFOSAA
C12H8F17NO4S
585.24
Mass Labelled Recovery Standards
18
16
C6
NaPFHxS [M+4]
C6F13S O2 ONa
426.0968
sodium perfluoro-1- [1,2,3,413
C4]octanesulfonate
C8
NaPFOS [M+4]
13
526.0823
C4
PFBA [M+4]
13
C6
PFHxA [M+2]
13
12
316.0399
C8
PFOA [M+4]
13
12
418.0402
C9
PFNA [M+5]
13
12
469.0404
perfluoro-n-[1,2- C2] decanoic acid
13
C10
PFDA [M+2]
13
12
516.0711
13
C11
PFUdA [M+2]
13
12
566.0789
13
C12
PFDoA [M+2]
13
12
616.0867
13
perfluoro-n-[1,2,3,4- C4] butanoic acid
13
perfluoro-n-[1,2- C2] hexanoic acid
13
perfluoro-n-[1,2,3,4- C4] octanoic acid
13
perfluoro-n-[1,2,3,4,5- C5] nonanoic acid
perfluoro-n-[1,2- C2] undecanoic acid
perfluoro-n-[1,2- C2] dodecanoic acid
73
18
sodium perfluoro-1-hexane [ O2]sulfonate
12
C4 C4F17SO3Na
C4HF7O2
C2 C4HF11O2
C4 C4HF15O2
C5 C4HF17O2
C2 C8HF19O2
C2 C9HF21O2
C2 C10HF23O2
218.0090
Table S2: Locations and Sedimentation Rates Derived from Gamma Spectroscopy
Sedimentation Rate
(g cm yr )
Uncertainty
in dating
(±years)
65
0.011
19.7
-86.59111
60
0.055
42.06583
-87.38
51
M011*
42.38333
-87
128
0.039
M018*
42.73333
-87
161
0.021
M019
42.36694
-86.44278
45
M020
42.36667
-87.66667
45
M024*
43.483
-87.48817
150
M028
43.80033
-86.79983
137
M030
42.66
-87.73806
18
M032*
44.3715
-86.93334
257
0.017
M041
42.87861
-86.35722
58
0.019
M044
42.95278
-87.31528
93
M047*
45.17833
-86.375
186
M048
43.0585
-86.66301
107
M050*
45.11667
-87.41667
20
M061
43.47417
-86.78472
138
M083
44.47367
-86.706
M088
44.71889
-87.17389
94
M093A
44.96217
-86.05517
100
M093B
44.77117
-86.11684
60
M093C
44.85617
-86.243
129
M103
45.06233
-86.49183
207
M113
45.32694
-87.00861
37
LATITUDE
LONGITUDE
Water Depth
(m)
M002
41.78972
-87.29278
20
M008*
41.98417
-87.01417
M009*
42.385
M010
Location
-2
0.023
-1
6.7
6.0
0.025
9.0
0.02
4.9
The sample label, location and depth of all samples * denotes locations where both cores and grab samples were
taken all other locations were surface grabs only. Sedimentation rates were only calculated for core samples
using estimates.
74
Table S3: Conditions for operating the CIC
Combustion Instrument
AQF-100 (type AIST)
Furnace temperature (inlet / outlet)
950 ℃ / 1000 ℃
-1
Carrier gas
150 mL min (Argon)
inlet boat (5 min hold)
switch over to Oxygen gas (3 min hold)
Water supply gas (Argon)
a
150 mL min
-1
Combustion gas (Oxygen)
300 mL min
-1
Injection volume of sediment
0.2ml (EOF) & 0.01g (TF)
Ion chromatograph
ICS-3000 (type AIST); Dionex Co. Ltd
Detector
Conductivity detector
Column
IonPac AS20 (2mm i.d.)
Mobile phase
Potassium hydroxide solution
mM (2 min hold)
5.4 mM/min (7 min)
40mM (4 min hold)
2mM (8 min hold)
Flow rate
0.25 mL/min
Column oven temperature
35 ◦C
Injection volume of absorbent
1500uL
a
The Instrumental operating conditions for the CIC for optimal detection of fluorine. Water (0.2 to 0.3 mL/min) is
supplied with argon gas in the furnace for complete hydride generation and to improve the recovery of total
fluorine.
75
76
Figure S4: Recoveries of PFCs
Compound
Method Detection Limits (MDL)
Recovery
MIN（%）
SD
(ng mL )
PFBA
87.8
51.3
1.7
1
PFPeA
52.1
27.6
1.2
1
PFHxA
87.8
60.6
1.2
0.1
PFHpA
77.3
57.2
0.9
0.1
PFOA
81
52.8
1.3
0.5
PFNA
68.4
56.8
0.5
1
PFDA
83.4
52.8
1.5
0.1
PFUdA
82.2
55.9
1.1
1
PFDoA
105.8
70.7
1.3
0.1
PFTrDA
104.1
71.2
1.3
1
PFTeDA
75.3
61.3
0.6
1
PFHxDA
130.2
91.4
1.6
1
PFBS
30.8
10.1
0.9
1
PFHxS
100.5
60.3
1.8
1
PFOS
70.8
43.1
1
0.5
PFDS
111
60.4
2.3
0.5
FOSA
88.6
57.3
1.3
1
N-MeFOSE
98.7
55.8
1.5
1
N-EtFOSE
46.4
22.7
0.7
1
FOSAA
14.5
87.2
1.7
1
N-MeFOSAA
111.8
50.9
2
1
N-EtFOSAA
99.1
55.9
1.9
1
82.2
55.1
1.3
Average
The recovery for PFCs calculated from all samples (n=192) extracted in this study.
77
-1
MAX（%）
Table S5: Comparison of concentrations of PFCs in surface sediments (ng g-1)
Location
Year
of
collect
ion
PFBS
PFOS
PFOA
PFHxS
Tokyo Bay,
Japan
2004
1.66
0.45
San Francisco
Bay
2004
n.d. 3.76
n.d. 0.63
n.d. 0.07
Hun River
,China
2008
0.19
0.21
0.14
Taizi River,
China
2008
<0.10
0.27
Daliao River,
China
2008
<0.10
West Coast
of Korea
2008
Resolute
Lake,
Cornwallis
Island,
Canada
PFDS
PFNA
PFDA
PFDoA
∑PFC
Ref
Zushi et al
2010
n.d. 2.7
n.d. 0.24
n.d. 1.11
n.d. 0.58
0.14 16
Higgings,
2006
<0.13
<0.10
0.1
0.12
1.31
Bao et al
2009
0.11
<0.13
<0.11
<0.09
<0.09
1.25
Bao et al
2010
0.21
0.11
<0.13
<0.10
<0.09
<0.09
1.06
Bao et al
2011
n.d
< LOQ
< LOQ
n.d.
n.d.
n.d.
< LOQ
< LOQ
<1
Naile et al
2010
2003
n.d
85
7.5
3.5
n.d
3.2
<0.46
n.d
100
Stock et
al, 2007
Char Lake,
Cornwallis
Island,
Canada
2003
<1.1
1.1
1.7
n.d
<0.53
<0.55
0.6
<0.55
5
Stock et
al, 2007
Amituk Lake,
Cornwallis
Island,
Canada
2003
0.047
0.062
0.96
1
n.d
0.35
0.12
<0.29
7
Stock et
al, 2007
Lake
Michigan
2010
0.19
0.45
0.21
0.53
0.35
0.08
0.03
0.07
2.35
This study
(n.d0.56)
(n.d1.15)
(n.d0.42)
(n.d.
1.89)
(n.d0.74)
(n.d0.42)
(n.d0.09)
(n.d0.18)
(0.894.93)
Surface sediment samples analyzed for PFCs, this is not an exhaustive literature review but
highlights the concentrations observed at a range of locations, there is paucity of sediment PFC
data sets and many studies have focussed on PFOA and PFOS. Recently however PFBS and PFBA
have been noted in concentrations greater than PFOS and PFOA in some locations indicating
shifts in production and use.
M002
M008
M024
M009
M088
M088b
M018
M041
M050
M028
M047
M083
M061
M011
M032
M010
M019
M048
M113
M093b
M103
M120
M093a
M093c
M044
M020
M030
Distance
20
16
78
12
8
4
0
Figure SI1: Standardized squared Euclidean Cluster analysis of PONAR samples of surface sediments.,
79
-1
Sum PFC (ng g )
20
15
10
5
0
1880
1900
1920
1940
1960
1980
2000
Year
Figure S2. Trend in concentrations of ∑10PFCs in sediment from ~1910 to 2010.
80
81
82
PFOS
40
30
M008
20
60
PFOA
40
30
80
3E-33e0.0392x
M008 =
R² = 0.9509
60
40
20
10
1950
2000
M008 = 9E-10e0.012x
R² = 0.6899
20
10
0
1900
PFHxS
100
50
M008 = 9E-10e0.012x
R² = 0.6899
0
1900
1950
2000
0
1900
1920
1940
1960
1980
M024
25
40
20
30
M024 = 1E-18e0.0221x
R² = 0.8806
15
20
10
0
1900
1950
2000
y = 5E-25e0.0296x
R² = 0.4566
40
30
y = 9E-32e0.0373x
R² = 0.8753
20
10
5
10
0
1900
1950
2000
0
1900
1920
1940
M018
50
40
40
40
30
30
M018 = 1E-36e0.043x
R² = 0.8418
30
20
20
y = 7E-17e0.0202x
R² = 0.6938
0
1900
1950
2000
0
1900
1960
1980
2000
y = 1E-29e0.0348x
R² = 0.6127
20
10
10
2000
10
1950
2000
0
1900
1920
1940
1960
1980
2000
M009
40
30
120
M009 = 9E-68e0.0784x
R² = 0.6812
100
80
60
20
0
1900
50
40
30
40
10
20
20
1950
2000
y = 2E-15e0.0183x
R² = 0.2972
60
y = 5E-85e0.0988x
R² = 1
10
0
1900
1950
2000
1950
2000
0
1900
1920
1940
1960
1980
2000
MO32
30
25
60
M032 = 1E-12e0.0152x
R² = 0.699
50
20
40
15
30
10
20
5
0
1900
y = 5E-55e0.0641x
R² = 0.6892
10
1950
2000
0
1900
M011
25
20
40
M011 = 2E-12e0.0148x
R² = 0.9331
30
15
20
10
10
5
0
1900
y = 3E-22e0.0264x
R² = 0.9424
1950
2000
0
1900
1950
2000
M047
30
25
50
M047 = 7E-21e0.0246x
R² = 0.9267
40
20
15
M050
1950
2000
0
1900
120
M050 = 3E-30e0.0351x
R² = 0.6194
100
20
10
1950
2000
2000
1960
1980
2000
1980
2000
y = 5E-129e0.1491x
R² = 1
40
20
20
1950
1940
60
40
0
1900
1920
80
60
5
0
1900
100
y = 7E-89e0.1033x
R² = 0.8061
80
10
0
1900
30
10
5
20
40
20
10
0
1900
50
30
15
y = 7E-86e0.0995x
R² = 0.8235
60
y = 9E-31e0.0359x
R² = 0.3912
1950
2000
0
1900
1920
1940
1960
Figure S3: Concentrations of 3 PFCs in cores of sediments with fitted exponetial trends.
83
a)
b)
Figure S4. The distribution of (a) total fluorine (mg g-1) and (b) extractable organic fluorine
(mg g-1) in Lake Michigan surface sediment samples.
84
85
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