Chemosphere 83 (2011) 806–814
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Occurrence and partition of perﬂuorinated compounds in water and sediment from Liao River and Taihu Lake, China Liping Yang a, Lingyan Zhu a,⇑, Zhengtao Liu b a b
College of Environmental Science and Engineering, Key Laboratory of Pollution Processes and Environmental Criteria, Ministry of Education, Nankai University, Tianjin 300071, China Chinese Research Academy of Environmental Sciences, Beijing 100012, China
a r t i c l e
i n f o
Article history: Received 6 October 2010 Received in revised form 18 January 2011 Accepted 27 February 2011 Available online 23 March 2011 Keywords: Perﬂuorinated compounds (PFCs) Water Sediment Sediment water partition coefﬁcient China
a b s t r a c t The concentrations of four perﬂuorinated sulfonate acids (PFSAs) and 10 perﬂuorinated carboxylate acids (PFCAs) were measured in water and sediment samples from Liao River and Taihu Lake, China. In the water samples from Taihu Lake, PFOA and PFOS were the most detected perﬂuorinated compounds (PFCs); in Liao River, PFHxS was the predominant PFC followed by PFOA, while PFOS was only detected in two of the samples. This suggests that different PFC products are used in the two regions. PFOS and PFOA in both watersheds are at similar level as in the rivers of Japan, but signiﬁcantly lower than in Great Lakes. The contributions of PFOS and long chain PFCAs in sediments were much higher than in water samples of both watersheds, indicating preferential partition of these PFCs in sediment. The concentrations of PFOS and PFOA were three orders of magnitude of lower than that of polycyclic aromatic hydrocarbons in the same sediments. The average sediment–water partition coefﬁcients (log Koc) of PFHxS, PFOS and PFOA were determined to be 2.16, 2.88 and 2.28 respectively. Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction Over the last decades, perﬂuorinated compounds (PFCs), including perﬂuorosulfonates (PFSAs) and perﬂuoroalkyl carboxylic acids (PFCAs), have been widely produced and used as surfactants, lubricants, paints, polishes, ﬁre-retardants and water repellents for leather, paper, and textiles (Prevedouros et al., 2006). Due to the large amount of usage, PFCs are omnipresent in environmental matrices, even in remote areas, such as the Arctic (Martin et al., 2004) and Tibetan Plateau (Shi et al., 2010), China. The presence of these chemicals in the environment is of great concern due to their bioaccumulation and adverse effects to biota and human (Martin et al., 2003, 2004; Higgins et al., 2005, 2007; Kannan et al., 2005; Houde et al., 2006a; Nakata et al., 2006; So et al., 2006; Senthilkumar et al., 2007; Kelly et al., 2009; Liu et al., 2009; Quinete et al., 2009; Rumsby et al., 2009; Suja et al., 2009; Naile et al., 2010; Pan et al., 2010; Shi et al., 2010). Most PFCs exhibit negligible vapor pressure, high solubility in water and moderate sorption to solids (Kelly et al., 2009). As a result, PFCs are expected to accumulate in surface water, especially in oceans. As reported by many studies, PFCs are widely present in surface water of rivers and oceans all over the world (So et al., 2004, 2007; Yamashita et al., 2004; Houde et al., 2006a; Nakata et al., 2006; Senthilkumar et al., 2007; Ju et al., 2008; Takagi et al., 2008;
⇑ Corresponding author. Tel.: +86 22 23500791; fax: +86 22 23503722. E-mail address: [email protected]
(L. Zhu). 0045-6535/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2011.02.075
Quinete et al., 2009; Rumsby et al., 2009; Suja et al., 2009; Naile et al., 2010; Pan et al., 2010). However, the data about the occurrence of PFCs in fresh water in China is very limited. Sediment is an important component in water system and it plays an important role in the environmental transport and fate of organic pollutants. Sediment has been suggested as a ﬁnal sink and reservoir for non-ionic hydrophobic organic pollutants, such as polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). In the contrary, most PFCs exhibit hydrophobic and hydrophilic properties (Martin et al., 2003). Therefore, their partition behavior between water and sediment may be different from the non-ionic hydrophobic chemicals. As compared to surface water, the study of PFCs in sediment is very sparse. Higgins et al. studied the sorption of PFCs on sediment and they found that hydrophobic interaction is very important for their sorption on sediment (Higgins and Luthy, 2006). Arhens et al. investigated the partition behavior of PFCs among water, suspended particulate matter and sediment (Ahrens et al., 2009). They found that longer chain PFCs appear to bind more strongly to particles. There are a few studies reported the occurrence of PFCs in sediments (Higgins et al., 2005; Nakata et al., 2006; Becker et al., 2008; Bao et al., 2009; Naile et al., 2010). But in general, the partition of PFCs in surface water and sediment in ﬁeld is not well understood. Liao River is one of the seven largest rivers in China and located in the northern China, passing through Jilin and Liaoning provinces. The Liao River system, especially its downstream Daliao River, received more than 2 billion tons of industrial and domestic wastewater annually from the neighbouring areas within Liaoning Province (Zhang et al.,
L. Yang et al. / Chemosphere 83 (2011) 806–814
2008), which lies in northeast of China and is an important ﬂuorine industrial base of China specializing in chemical industries and medicine. Taihu Lake is located in southeast of China and currently is the second largest freshwater lake in China. The watershed of Taihu Lake covers several highly dense and industrialized regions in the middle-east of China, including Jiangsu and Zhejiang provinces. To the north and northeast of Taihu Lake within Jiangsu province, there is also an industrial base for ﬂuorinated products. Yeung et al. measured PFCs in human blood from 9 cities in China (Yeung et al., 2008). They found that the level of PFCs in human blood from Shenyang, which is located along Liao River, was the highest among the nine cities. The level of the predominant PFC compound, perﬂuorooctane sulfonate (PFOS) was as high as 79.2 ng mL1. But the level of PFCs in the surface water of Liao River is unknown. Similarly, there is no report of PFCs in Taihu Lake even though these is heavy production of ﬂuorinated chemicals surrounding the lake. The goal of current study was to determine the distributions of PFCs in water and sediment in both Liao River and Taihu Lake. The composition proﬁle of PFCs in water and sediment was compared. Partition coefﬁcients Kd and log Koc were calculated to investigate the partition behavior of these PFCs between water and sediment. 2. Experimental section 2.1. Chemicals and standards The standard solutions of perﬂuorobutane sulfonate (PFBS), PFOS, perﬂuorodecane sulfonate (PFDS), and perﬂuoroundecanoic acid (PFUdA) were purchased from Wellington Laboratories (Guelph, Canada). Perﬂuorohexane sulfonate (PFHxS) was purchased from Sigma–Aldrich (St. Louis, MO, USA). Perﬂuorononanoic acid (PFNA), perﬂuorooctanoic acid (PFOA) and perﬂuoroheptanoic acid (PFHpA) were purchased from Alfa Aesar (Ward Hill, MA). Perﬂuorodecanoic acid (PFDA) and perﬂuoroundecanoic acid (PFDoA) were obtained from Acros Organics (Geel, Belgium). The internal standards of perﬂuoro-1-(1,2,3,4-13C4)octanesulfonate (13C4-PFOS) and perﬂuoro-n-(1,2-13C2) octanoic acid (13C2-PFOA) were also purchased from Wellington Laboratories. Methanol of high-performance liquid chromatography (HPLC) grade was purchased from Tedia Chemical Company (Tianjin, China). Milli-Q water was used throughout the study. 2.2. Sample collection Water and sediment samples were collected from Liao River and Taihu Lake (Fig. 1) in November and December of 2009. Thirteen sites were distributed along the Hun River (HR1-13) and seven were along Liao River (LR1-7). There were 22 sites (T1-22) distributed in Taihu Lake. At each site, water was collected at least 5 m off riverbank and surface sediment was collected with a hand piston sediment sampler. In a few points in Liao River and Taihu Lake, sediment was not available. There were 14 sediments in Liao River and 18 in Taihu Lake. Water was stored in 500 mL Polystyrene (PS) bottle and sediment was stored in polypropylene (PP) plastic bags. The containers were pre-cleaned with methanol and Milli-Q water before each sampling. 2.3. Sample pretreatment Water samples were prepared in less than 6 h after the sampling was performed. Water (300–500 mL) was ﬁltered through 0.45 lm membranes to remove large particles and biota. Then it was solid phase extracted with Oasis HLB cartridge (500 mg,
6 mL volume, Waters Limited, Mississauga, ON). Brieﬂy, the HLB cartridge was conditioned with 10 mL of methanol followed by 10 mL of water. The ﬁltered water samples were passed through the cartridges at a rate of 3 mL min1, which were washed with 5 mL of 40% methanol in water, and pumped until dry. Analytes were eluted with 10 mL of methanol. The extract was blown down to 1 mL under a nitrogen stream and then transferred into an autosampler vial. Mass labeled internal standards (5 ng), 13C4-PFOS and 13 C2-PFOA was added before analysis. Two extraction methods, namely acid method and half dry alkaline method, were compared in present study using spiked sediment samples. For the acid method (Higgins et al., 2005; Ahrens et al., 2009), 5 g sediment was transferred to a 50-mL PP vial, to which 10 mL of 1% acetic acid solution was added. Each vial was vortexed, placed in the preheated sonication bath, and sonicated for 15 min. The vials were then centrifuged at 2000 rpm for 5 min, and the acetic acid solution was decanted into a second 50-mL vial. The extraction was repeated twice with 2.5 mL solvent mixture and the extracts were combined. In the contrary, NaOH in 20% H2O/80% methanol was used in the half dry alkaline method to alkalify the sediment (Ahrens et al., 2009). Five grams of dry sediment was added into a PP tube and soaked with 2 mL of 100 mM NaOH in 20% H2O and 80% methanol for 1 h. Methanol (10 mL) was added and the mixture was vortexed to ensure complete mixing. Each tube was sonicated for 30 min and then centrifuged at 2000 rpm for 5 min. The supernatant was transferred into another PP tube. The extraction procedure was repeated once. All the extracts were combined, acidiﬁed with 1.5 mL of 200 mM HCl, and diluted with H2O to 400 mL. Waters Oasis HLB cartridges were used for further cleanup, following the same method as described above for water samples. 2.4. Determination of the total organic carbon Total organic carbon of the sediments was determined using the wet chemistry techniques suggested by US Environment Protection Agency. The fraction of total organic carbon (foc) in the sediments from Liao River is in the range of 0.3–3.9% and that from Taihu Lake is in the range of 1.3–3.8%. 2.5. Instrumental analysis All sample extracts were analyzed by an Agilent 1200 liquid chromatograph equipped with an Agilent 6310 ion trap mass spectrometer (LC/MS) operated in negative electrospray ionization (ESI) mode. The analytes were separated on a Waters XTerra C-18 column (2.1 i.d. 150 length mm) with 2.5 mM ammonium acetate and methanol as mobile phase starting at 10% methanol at a ﬂow rate of 0.25 mL min1. The gradient increased to 80% methanol at 0.8 min, and then increased to 100% methanol at 12.8 min before reverting to original conditions at 17.8 min, and was then maintained until 19 min. Twenty micro liter of extract was automatically injected and the oven temperature of LC was 40 °C. Chromatograms were recorded using Multiple Reaction Monitoring (MRM) mode, and when possible at least two transitions per-analyte were monitored. PFCs were quantiﬁed with monitoring transitions ions at m/z: 299 ? 99,80; 399 ? 99,80; 499 ? 99,80; 599 ? 99,80 for PFBS, PFHxS, PFOS PFDS, and 363 ? 319, 413 ? 369, 463 ? 419, 513 ? 469, 563 ? 519, 613 ? 569 for PFHpA, PFOA, PFNA, PFDA, PFUdA and PFDoA, respectively. The ion source working parameters were as follows: nebulizer was 20.0 psi; ﬂow of the dry gas was 9.0 L min1; dry temperature was 350 °C; target mass was 613 m/z; compound stability was 100%; trap dive level 100% and optimize was normal.
L. Yang et al. / Chemosphere 83 (2011) 806–814
Fig. 1. Sampling sites in Liao River (right) and Taihu Lake (below), China.
2.6. Quality assurance and statistical analysis Through out the sampling and analytical processes, Teﬂon coated lab wares were avoided to minimize contamination of the samples. Along with each batch of nine samples, one procedure blank was run to make sure the analytical procedure was operating correctly. Three spiked matrix samples were run to monitor the recoveries of the analytical method. The limit of detection (LOD) of the analytes was determined with a signal-to-noise ratio of 3:1, while the limit of quantiﬁcation (LOQ) was determined with a signal-to-noise ratio of 10:1. All the analytical results lower than LOQ were reported as half of the LOQ, while those lower than LOD were reported as n.d. (not detected) and zero was assigned for statistical purpose. The recoveries for water and sediment samples were in the range of 73–128% and 73–121%, depending on different PFC compounds. All PFCs compounds in blanks were well below the LOQ. All concentrations were not recovery corrected. All other statistical analyses were performed using SPSS for Windows (version 16). 3. Results and discussion
Senthilkumar et al., 2007; Ahrens et al., 2009). Higgins et al. (2005) developed an analytical method to analyze PFCs in sediment and sewage samples for the ﬁrst time. They used an acetic acid wash method followed by solvent extraction and this acid method was used in many other studies. While Powley et al. (2005) developed another sample pretreatment for PFCs in solid matrices, which is named half-dry method. In the contrary to the acid method, alkaline is used in the half-dry method, and it is used in several studies (Hawthorne et al., 2006; Ahrens et al., 2009). The recovery was calculated for each chemical in the spiked sediment samples using both acid and half dry alkaline methods and is shown in Table 1. Both methods provide satisﬁed recovery for some of the PFCs such as PFBS, PFHxS, PFHpA, PFOA and PFDA. For other long-chain PFCs, the acid method does not provide good recovery. For example, the recovery of PFDS, PFUdA and PFDoA is only 50 ± 3%, 31 ± 7%, and 51 ± 8%, respectively. However, the recoveries of these PFCs are enhanced to 96 ± 2%, 92 ± 5% and 76 ± 2% by the alkaline method. The results suggest that the half dry alkaline method provides better recovery for most PFCs than the acid method, especially for the longer chain PFCs. Therefore, half-dry method was applied for sediment analysis in present study.
3.1. Comparison of the extraction methods for sediment samples 3.2. PFCs distribution in water samples Due to the special physicochemical properties of PFCs and the heterogeneous characteristic of sediment, there is not a standard method to analyze PFCs in sediment. Two common methods, acid method and half dry alkaline method were reported and used in previous studies (Higgins et al., 2005; Higgins and Luthy, 2006;
The PFCs concentrations in water samples from Liao River and Taihu Lake are summarized in Table 2. A total of 10 PFCs including C4, C6, C8 and C10 PFSAs and C7–12 PFCAs were quantiﬁed in the samples in present study. PFCs were detected in all of the water
L. Yang et al. / Chemosphere 83 (2011) 806–814 Table 1 Recoveries (%), detection frequency, LODs and LOQs for individual PFCs. Analytes
PFBS PFHxS PFOS PFDS PFHpA PFOA PFNA PFDA PFUdA PFDoA
299 ? 99,80 399 ? 99,80 499 ? 99,80 599 ? 99,80 363 ? 319 413 ? 369 463 ? 419 513 ? 469 563 ? 519 613 ? 569
% Recovery (±SD)
Sediment (ng g1 dw)
Water (ng L1)
Sediment (ng g1 dw)
Water (ng L1)
94 ± 2 109 ± 3 108 ± 2 96 ± 2 91 ± 2 103 ± 2 127 ± 3 128 ± 2 88 ± 4 73 ± 4
22/32 17/32 32/32 2/32 23/32 32/32 32/32 29/32 32/32 32/32
1/46 31/46 24/46 0/46 10/46 38/46 2/46 2/46 2/46 6/46
0.02 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01
0.5 0.5 0.2 0.2 0.5 0.5 0.2 0.1 0.2 0.2
0.05 0.05 0.02 0.04 0.05 0.02 0.02 0.02 0.02 0.02
1.0 1.0 0.7 0.7 1.0 0.7 0.8 0.3 0.7 0.7
71 ± 0.3 93 ± 4 66 ± 4 50 ± 3 121 ± 6 103 ± 4 57 ± 1 92 ± 6 31 ± 7 51 ± 8
75 ± 5 93 ± 3 112 ± 4 83 ± 6 101 ± 6 101 ± 3 73 ± 5 121 ± 6 92 ± 5 76 ± 1
Table 2 Concentration (ng L1) of PFCs in water samples from Liao River and Taihu Lake. Liao River
PFBS PFHxS PFOS PFDS PFHpA PFOA PFNA PFDA PFUdA PFDoA RPFSA RPFCA RPFCs
n.d. 27.9 0.33 n.d. 2.89 10.9 n.d. n.d. n.d. n.d. 28.3 13.7 43.6
n.d. 24.0 n.d. n.d. n.d. 11.5 n.d. n.d. n.d. n.d. 25.6 14.2 37.3
n.d. 1.4–94.5 n.d.-6.6 n.d. n.d.-23.3 n.d.-27.9 n.d. n.d. n.d. n.d. 1.4–94.5 n.d.-41.1 1.4–131
n.d 1.3 26.5 n.d. 1.7 21.7 n.d. n.d. n.d. 0.6 27.8 30.0 51.8
n.d. n.d. 5.8 n.d. n.d 19.5 n.d. n.d. n.d. n.d. 7.7 20.0 26.2
n.d. n.d.-6.5 3.6–394 n.d. n.d.-18.4 10.6–36.7 n.d. n.d. n.d. n.d.-3.2 3.9–400 13.4–48.6 17.8–448
n.d. = Not detected.
samples in both watersheds, indicating widespread contamination of PFCs in the surface water of China. In the water samples from Taihu Lake, PFOA and PFOS are the most detected PFCs (see Fig. 2), followed by PFHxS, PFDoA and PFHpA with average detection frequency at 32%, 38% and 14%. PFBS, PFDS, PFDA and PFUdA were not detected in any of the samples while PFNA was only detected in two samples. This is consistent with the results in many other studies, which reported that PFOS and PFOA are the dominating compounds in surface water in many different districts, such as the German Bayreuth (Becker et al., 2008), Pearl River and Yangtze River of China (So et al., 2007), Tennessee of USA (Hansen et al., 2002) and coastal areas in Japan (Takagi et al., 2008; Ahrens et al., 2009) and Korea (Naile et al., 2010). The concentration of PFOA and PFOS varied in the range 10.6–36.7 ng L1 and 3.56– 394 ng L1. The total concentration of PFCs (RPFCs) in water samples is shown in Fig. 3. Generally, the level of RPFCs was similar among the lake except for T8 with relatively higher RPFCs in the north area Meilianghu. The highest concentration of RPFCs was observed at T8 site (448 ng L1), where PFOS (394 ng L1) was the highest and other PFCs were also high. Close to the north of Taihu Lake (Fig. 1) is Wuxi, which is an industrial city and there are several manufactures producing paints, plastic pipes and plastic anticorrosion products containing ﬂuorinated chemicals (Zhang et al., 2010). Changzhou is an industrial base with heavy production of PFCs and it is located to the northeast of Taihu Lake. The discharge of efﬂuent from the municipal waste water treatment plant or direct discharge of waste water to the complex river system may ﬁnally go to Taihu Lake, resulting relatively high levels of RPFCs in the north area of Taihu Lake. Except for T8 site, the level of PFOA
was higher than PFOS in the water of Taihu Lake. The average contribution of PFOA to the RPFCs was 63.9% within a range of 6.72– 81.7%, while that of PFOS was 27.9% within a range of 10.4–87.8%. The concentration of PFHxS was in the range of n.d.-6.54 ng L1 and that of PFDoA was in the range of ng-3.16 ng L1. Even though PFHpA and PFNA were only detected in 2–3 water samples, their concentrations were relatively high, contributing 4.10–29.3% and 2.8–24.9% to the RPFCs in the samples. The total concentration of the four perﬂuoroalkyl sulfonates (RPFSAs) and the six perﬂuoroalkyl carboxylic acids (RPFCAs) were calculated for each water sample. A good correlation (p < 0.05) was found between RPFSAs and RPFCAs (excluding the sample at site T8), suggesting that they may be from similar sources. The PFOS to PFOA ratio was calculated and it is lower than one except for site T8, indicating that PFOA is the predominant PFC in water samples collected in Taihu Lake. For the water samples from Liao River, the RPFCs are at similar level with those in Taihu Lake. However, different composition was found in Liao River (see Fig. 2). PFHxS is the predominant compound with a contribution of 63.6%, followed by PFOA (23.4%), and PFHpA (7.84%), while PFOS was only detected in two of the samples. The other six PFCs including PFBS, PFNA, PFDA, PFUdA, PFDS and PFDoA were not detected at most of the sampling sites in Liao River. The different compositions of PFCs in Liao River and Taihu Lake suggest that there are different sources in the two regions. PFHxS was also observed in Korean coastal water (Naile et al., 2010). The source of PFHxS remains unclear at present. There are foam extinguisher plant, pulp factories, steel and dye manufacturers and sewage treatment plants along the river. The concentration of PFHxS was in the range of 1.41–94.5 ng L1, PFOA in the range of n.d.-27.9 ng L1, and PFHpA in the range of n.d.23.3 ng L1. RPFSAs was also found to correlate with RPFCAs (p < 0.05). HR1 and HR2 are two sites located at Dahuofang Reservoir, which is at the upstream of the Hun River and is also the source of drinking water for Fushun and surrounding population. It is well protected, and the PFCs in the water at these two sites are very low (1.41 and 7.64 ng L1, see Fig. 3). The Hun River goes down and passes through Fushun and Shenyang, which are two biggest industrial cities along the river. Due to the discharge of the efﬂuent from the municipal or industrial waste water treatment plants, PFCs in the river water are relatively high in HR3– HR7 (36.0–88.0 ng L1). High level of RPFCs (88.5 and 131 ng L1) was also found at sites of LR1–LR2 and the highest concentration of RPFCs (131 ng L1) was detected at site LR2, which is not unexpected. LR1–LR2 is the merge point of Liao River and Xiushui River and receives waste water discharge from upstream. At the same sites, other environmental pollutants such as polycyclic aromatic hydrocarbons (PAHs), organochlorine pesticides (OCPs) were also found to be at higher levels than at other sites (data not shown).
L. Yang et al. / Chemosphere 83 (2011) 806–814
T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 T13 T14 T15 T16 T17 T18 T19 T20 T21 T22
HR1 HR2 HR3 HR4 HR5 HR6 HR7 HR8 HR9 HR10 HR12 HR13 LR1 LR2 LR3 LR4 LR5 LR6 LR7
Total PFC concentrations in water samples (ng/L)
Fig. 2. Average contribution of each compound to the total PFCs in water and sediments from Liao River and Taihu Lake.
Fig. 3. Concentrations of PFCs in water samples from Liao River and Taihu Lake.
Since the PFCs reported in the literature are not consistent and different compositions were found in different districts, it does not make much sense to compare the RPFCs in water samples. Usually PFOA and PFOS are the two PFC compounds frequently detected, their concentrations are compared with the results from literatures. As shown in Fig. 4, it can be seen that PFOS in Taihu Lake is comparable to that found in Pearl River and Yangzet River, China (So et al., 2007) and in Tama river and Yodo river, Japan (Senthilkumar et al., 2007), but relatively lower than that in the streams and Shihwa Lake in South Korea (Naile et al., 2010) and in Great Lakes (Kannan et al., 2005). Since PFOS was only detected in two samples in Liao River at low concentration, it is not shown in Fig. 4. This suggests that the contamination of PFOS in the surface water in these two watersheds is relatively lower than South Korea and North America. In case of PFOA, its concentration in Liao River
and Taihu Lake is comparable to that in Yangzet River and rivers in Japan, but higher than in Pearl River in Guangzhou and the Shihwa Lake in South Korea. It is generally lower than that found in Great Lakes. The highest concentration of PFOA detected in Liao River and Taihu Lake is much lower than the highest level found in Yangzet River and the rivers in Japan. In two of the water samples in Taihu Lake, the concentrations of PFOA are as high as 36 ng L1, which is very close to the New Jersey guidance for PFOA in drinking water (Renner, 2007), suggesting that further investigation is needed in this area. 3.3. Distribution of PFCs in sediment samples In contrast to those in water samples, the PFCs in the sediment of both Liao River and Taihu Lake show a different composition
L. Yang et al. / Chemosphere 83 (2011) 806–814
Great Lakes, US Lake Shihwa, Korea Streams, Korea Yodo River Japan Tama River Japan Yangzet River Pearl River in Guangzhou Tai Lake
PFOS concentration in freshwater ng/L
Great Lakes, North America Streams, Korea Shihwa Lake, Korea Rivers in Japan Yangzet River, China Pearl River in Guangzhou, China Tai Lake, Present Study Liao River, Present Study
PFOA concentration in fresh water ng/L Fig. 4. Comparison of PFOS and PFOA in water samples in different districts in the world.
proﬁle, as shown in Fig. 2. More PFCs including the long chain PFCAs such as PFNA, PFDA, PFUdA and PFDoA were detected in the sediments with high detection frequency. This suggests that long-chain PFCs are prone to partition to sediment, which represents a sink for these chemicals in the environment. As compared with water samples, the contribution of PFOA decreased while PFOS increased in the sediments of both watersheds, especially in Liao River (Fig. 2), implying that the partition of PFOS to sediment is higher than PFOA. PFDA, PFUdA, and PFDoA are common in the sediment, and their mean contribution to RPFCs is around 20% in both watersheds. Different from water samples, the concentration of PFOS in the sediment of Liao River is relatively high and its mean contribution is 30.6% while that of PFOA is 16.4%. The detection of PFHxS is much more frequent in Liao River than that in Taihu Lake. PFNA and PFDS make much less contribution. Fig. 5 compares the concentrations of PFOS and PFOA in the sediment of Liao River and Taihu Lake with those of other persistent organic pollutants such as PAHs and OCPs in the same sediment samples. In both watersheds, the concentration of PFOS is slightly higher than that of PFOA in the sediment. This result agrees with that reported by Bao et al. (2009) and Houde et al. (2006b), who also found that PFOS was higher than PFOA in sediments of the Daliao River system (China), the Charleston Harbor and the Stono
River (US). The concentrations of PFOA and PFOS in both watersheds are almost three orders of magnitude lower than that of PAHs in the same sediments. This may be due to the heavy pollution of PAHs in these areas. Another possible reason is that PFOA and PFOS are much more soluble in water than PAHs. As a result, their partition in sediments is relatively lower. Their concentrations are similar to that of hexachlorocyclohexane (HCHs) and dichlorodiphenyl trichloroethane (DDTs). The low levels of HCHs and DDTs are due to the regulation of their use in China since 1980s. The water solubility of HCHs and DDTs are much higher than that of PFOA and PFOS. The similar or slightly higher level of PFOA than HCHs and DDTs in sediment indicates the continuous current release of the related commercial products in these areas. As shown in Table 3, the mean and median concentrations of PFOA in the sediment of Liao River and Taihu Lake are 0.08, 0.05 (range 0.02–0.18) and 0.16, 0.12 (range < 0.02–0.52) ng g1 dw, while those of PFOS are 0.15, 0.11 (range 0.04–0.48) and 0.15, 0.15 (range 0.06–0.31) ng g1 dw. Fig. 6 illustrates the comparison of the concentrations of PFOA and PFOS in the sediments with those reported in other studies. PFOA in the sediments of Liao River and Taihu Lake is comparable to that in the Roter Main River, Germany (Becker et al., 2008) with mean concentration of 0.054 (0.02–0.07) ng g1, slightly higher than that found in the Ariake
L. Yang et al. / Chemosphere 83 (2011) 806–814
PFOA PFOA 100
Liao River PFOS
concentration of organic pollutants in sediment (ng/g dw)
Fig. 5. Comparison of concentrations of PFOS and PFOA with PAHs and OCPs in the sediments of Liao River and Taihu Lake.
.01 Table 3 Concentration (ng g1 dw) of PFCs in sediments from Liao River and Taihu Lake. Liao River
PFBS PFHxS PFOS PFDS PFHpA PFOA PFNA PFDA PFUdA PFDoA RPFSA RPFCA RPFCs
0.06 0.04 0.15 n.d. 0.02 0.08 0.02 0.10 0.02 0.01 0.25 0.26 0.51
0.07 0.03 0.11 n.d. 0.01 0.05 0.02 0.03 0.02 0.01 0.23 0.18 0.43
n.d.-0.13 <0.02–0.10 0.04–0.48 n.d. <0.01–0.13 0.02–0.18 0.01–0.07 0.01–0.50 0.01–0.03 <0.01–0.04 0.13–0.59 0.08–0.68 0.26–1.11
0.07 0.003 0.15 n.d. 0.08 0.16 0.06 0.06 0.07 0.03 0.23 0.46 0.69
0.01 n.d. 0.15 n.d. 0.01 0.12 0.02 0.04 0.06 0.03 0.18 0.41 0.57
n.d.-0.27 n.d.-0.03 0.06–0.31 n.d. n.d.-0.33 <0.02–0.52 <0.01–0.51 n.d.-0.29 0.03–0.18 0.01–0.07 0.07–0.52 0.12–1.08 0.20–1.31
n.d. = Not detected.
Sea, Japan (Nakata et al., 2006), with a mean concentration of 0.96 (0.84–1.1) ng g1 dw, and in the rivers by the San Francisco Bay, USA (Higgins et al., 2005), with a mean concentration of 0.25 (n.d.-0.396) ng g1 dw. It is much lower than that found in the Huangpu river in Shanghai, China (So et al., 2007), where a mean concentration of PFOA was found to be 34.6 (5.20–203) ng g1 dw. Shanghai is an industrial city with high density of population. Along the Yangtze River Delta, there locate some ﬂuorine chemicals plants producing polytetraﬂuoroethylene, which may be responsible for the high level of PFOA in the rivers. Bao et al. (2009) studied PFCs in the sediments from the Daliao River and the concentration of PFOA they found was 0.111 (0.04–
9 8 7 9 4 4 06 00 00 00 00 00 00 , 2 y, 20 n, 2 a, 2 a, 2 r, 2 e, 2 A e n in S in pa iv ak , U ma Ja i, Ch r, Ch o R ai L ea Ger ea, a T r a i e L A , gh Riv S ay iver an ke o Sh alia o B in r Aria D Ma er Fig. 6. Comparison of the concentrations of PFOA and PFOS in the sediments with those reported in other studies.
0.17) ng g1, very similar to the results in present study. As for PFOS, it is comparable to those in the Ariake Sea, Japan [0.11 (0.09–0.14) ng g1 dw] (Nakata et al., 2006), the Roter Main River, Germany [0.201 (0.09–0.348) ng g1] (Becker et al., 2008) and Daliao river [0.21 (0.06–0.37) ng g1] (Bao et al., 2009); but lower than in the San Francisco Bay, USA (n.d.-3.76 ng g1 dw) (Higgins et al., 2005) and in Shanghai, China [2.52 (1.57–8.78) ng g1 dw] (Li et al., 2010). 3.4. Partition of PFCs in water and sediment The partition coefﬁcients of PFCs between sediment and surface water were estimated using the concentration of PFCs in the sediment and in the overlaying water at the same sampling sites. The partition coefﬁcient Kd was calculated using the following equation:
K d ¼ C s =C w
where Cs and Cw are the PFC concentrations in sediment (ng g and in water (ng L1).
L. Yang et al. / Chemosphere 83 (2011) 806–814
K oc ¼ K d 100=foc
where Koc is the organic carbon normalized partition coefﬁcient and foc is the percentage of organic carbon in sediment. Since only PFHxS and PFOA were found in both water and sediment in Liao River, the partition coefﬁcients were calculated for PFHxS and PFOA in Liao River; similarly, those of PFOS and PFOA were calculated in Taihu Lake. The log Kocs of PFHxS and PFOA in Liao River are 2.16 ± 0.54 and 2.28 ± 0.42 cm3 g1, while those of PFOS and PFOA in Taihu Lake are 2.88 ± 0.62 and 2.28 ± 0.55 cm3 g1. These values are similar to that reported by Higgins and Luthy (2006), who studied the sorption of PFCs on sediments and the log Kocs of PFOS and PFOA in their study were 2.68 ± 0.09 and 2.11 cm3 g1. They also reported that perﬂuorocarbon chain length was the dominant structural feature inﬂuencing sorption, with each CF2 moiety contributing 0.50–0.60 log units to log Kocs and the sulfonate moiety contributed additional 0.23 log units compared to carboxylate analogs. In present study, the log Kocs of PFHxS and PFOA are smaller than PFOS with a difference of 0.72 and 0.6 log units. Ahrens et al. (2009) studied the partition of PFCs in water and sediment from Tokyo Bay, Japan. They obtained slightly higher log Kocs of PFHxS and PFOS than in our study, which were 3.6 ± 0.1 and 3.8 ± 0.1 cm3 g1, respectively. These suggest that sediment properties and water conditions may affect the partition of PFCs in real environment. The log Kocs of PFOA and PFOS are 1.4–4.4 log units less than the median log Koc values of naphthalene, pyrene, and benzo[a]pyrene, which were determined as 4.3, 5.8, and 6.7 cm3 g1 respectively by Hawthorne et al. (2006). The log Kocs of HCH and DDT were reported to be 4.02 and 5.63 (Hodson and Williams, 1988), which are also much higher than those of PFOS and PFOA. As compared to the hydrophobic organic pollutants, PFCs are prone to stay in water column and this also explains the fact the concentrations of PFOA and PFOS in sediments are almost 3 orders of magnitude lower than that of PAHs. 4. Conclusions The results present in current study demonstrate that PFCs are widely present in the surface water and sediment of Liao River and Taihu Lake. In the water samples from Taihu Lake, PFOA and PFOS were the most detected PFCs; while in Liao River, PFHxS was the predominant PFC followed by PFOA, suggesting that there might be different sources of PFCs in these two districts. PFOS and PFOA in both watersheds are at similar level as in the rivers of Japan, but signiﬁcantly lower than in Great Lakes. The contributions of PFOS and long chain PFCAs in sediments were much higher than in water samples of both watersheds, which is accounted by their preferential partition to sediment. The sediment–water partition coefﬁcients (log Koc) of PFHxS, PFOS and PFOA are signiﬁcantly lower than those of typical hydrophobic organic chemicals such as PAHs, HCHs and DDTs. As compared to these chemicals, PFCs are prone to stay in water column and this also explains the fact the concentrations of PFOA and PFOS in sediments are almost three orders of magnitude lower than that of PAHs in the same sediments. Acknowledgments The authors gratefully acknowledge the ﬁnancial support of Ministry of Science and Technology (2009DFA92390, 2008ZX08526-003 and 2009DFA91910), Chinese Natural Science Foundation (21077060), Ministry of Education (Grant 708020), Ministry of Environmental Protection (201009026), Tianjin Municipal Science and Technology Commission (08ZCGHHZ01000) and China–US Center for Environmental Remediation and Sustainable Development.
Appendix A. Supplementary material Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.chemosphere.2011.02.075. References
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