Environmental Pollution 238 (2018) 111e120

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Environmental Pollution

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Spatial and vertical variations of perfluoroalkyl acids (PFAAs) in the Bohai and Yellow Seas: Bridging the gap between riverine sources and marine sinks

* Yunqiao Zhou a, b, Tieyu Wang a, b, , Qifeng Li a, b, Pei Wang a, b, Lei Li a, b, Shuqin Chen a, b, Yueqing Zhang a, b, Kifayatullah Khan a, Jing Meng a, b a State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, b University of Chinese Academy of Sciences, Beijing, 100049, China article info abstract

Article history: Perfluoroalkyl acids (PFAAs) are being increasingly reported as emerging contaminants in riverine and Received 12 January 2018 marine settings. This study investigated the contamination level and spatial distribution of 17 PFAAs Received in revised form within the depth profile of the Bohai and Yellow Seas using newly detected sampling data from 49 sites 28 February 2018 (June 29 to July 14, 2016). Moreover, the riverine flux of 11 selected PFAAs in 33 rivers draining into the Accepted 9 March 2018 Bohai and Yellow Seas was estimated from previous studies (2002e2014) in order to establish the Available online 20 March 2018 relationship between riverine sources and marine sinks. The results showed that the Bohai and Yellow Seas were commonly contaminated with PFAAs: total concentrations of PFAAs in the surface, middle, and Keywords: 1 e 1 e 1 PFAAs bottom zones ranged from 4.55 to 556 ng L , 4.61 575 ng L , and 4.94 572 ng L , respectively. The e 1 < 1 < Stratified seawater predominant compounds were PFOA (0.55 449 ng L ), PFBA ( LOQ-34.5 ng L ), and PFPeA ( LOQ- 1 e e e Spatial distribution 54.3 ng L ),P accounting for 10.1 87.0%, 5.2 59.5%, and 0.6 68.6% of the total PFAAs, respectively. In Riverine input general, the PFAA concentrations showed a slightly decreasing trend with sampling depth. Contami- Bohai and Yellow Seas nation was particularly severe in Laizhou Bay, fed by the Xiaoqing River and an industrial park known for PFAA production. The total riverine PFAA mass flux into the Bohai and Yellow Seas was estimated to be 72.2 t y 1, of which 94.8% was carried by the and Xiaoqing Rivers. As the concentration of short- chain PFAAs begins to rise in seawater, further studies on the occurrence and fate of short-chain PFAAs with special focus on effective control measures would be very timely, particularly in the Xiaoqing River and Laizhou Bay. © 2018 Elsevier Ltd. All rights reserved.

1. Introduction direct human influence (Giesy and Kannan, 2002; Zhang et al., 2017), due to their extensive application, strong persistence, and Perfluoroalkyl acids (PFAAs) are a class of manufactured chem- ability to be transported over long distances. icals widely used in fields such as textiles, metal plating, fire- As the biotoxicity and bioaccumulation properties of PFAAs with fighting and semiconductors because of their hydrophobic and long carbon chains (which generally increase their residence time lipophobic properties (Lindstrom et al., 2011; Xie et al., 2013). This in the human body) were gradually discovered and reported (Borg, family includes Perfluorooctane sulfonate (PFOS), Per- et al., 2013; Lescord et al., 2015; Liu et al., 2015), that why their risk fluorooctanoic acid (PFOA), and other related compounds. Nowa- towards ecologic and human health was became of greater concern, days PFAAs have been detected in many environments (Su et al., leading to their listing as Persistent Organic Pollutants (POPs) in 2017; Wang et al., 2012; Zhou et al., 2017), even in areas far from Stockholm Convention (Gorrochategui et al., 2014; Wang et al., 2009; Xu et al., 2013). In recent years, restrictions and voluntary withdrawals of long-chain PFAAs from production and usage have been implemented, particularly in developed countries. To meet * Corresponding author. State Key Laboratory of Urban and Regional Ecology, continued industrial demand, PFAAs with shorter carbon chains Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, and considerably lower toxicity were introduced as alternatives; Beijing, 100085, China. fl fl E-mail address: [email protected] (T. Wang). these included Per uorobutanoic acid (PFBA) and Per uorobutane https://doi.org/10.1016/j.envpol.2018.03.027 0269-7491/© 2018 Elsevier Ltd. All rights reserved. 112 Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120 sulfonate (PFBS) (Gorrochategui et al., 2014; Wang et al., 2015c). As the 33 target rivers were reported previously. the production and use of PFAAs gradually shifted from developed At each marine sampling site, 3 stratified seawater samples to developing countries, China emerged as one of the largest PFAA were collected using a SBE 32 Carousel Water Sampler (Sea-Bird, producers in the world (Xie et al., 2013; Zhang et al., 2012), ulti- USA). The sampler was programmed to close the sample bottles at mately resulting in serious regional PFAA contamination. For the target depths, where real-time data for seawater conductivity, example, extremely high levels of PFAAs were reported in the temperature, and depth (CTD) were acquired. The stratification of Daling and Xiaoqing Rivers in the prefecture-level cities of Fuxin water column was divided mainly according to the total water and Zibo, respectively, home to several active and well-known depth of the sampling site. Detailed descriptions including total fluorochemical industrial parks (Liu et al., 2017; Shi et al., 2015; depth of the seawater column, sampling date sampling depth, and Wang et al., 2016a; Zhu et al., 2015). parameters measured with in-situ seawater samples are summa- PFAAs can be easily transported by water due to their relatively rized in Table S2. A total of 147 seawater samples were collected in high polarity and solubility (Prevedouros et al., 2006; Sharma et al., 1 L polypropylene bottles (wide-mouth bottle, PP; Thermo Fisher 2016), finally collecting in oceans and seas (Zhao et al., 2015). For Scientific, USA) and kept at room temperature in dark on board. this reason, the Bohai and Yellow Seas, surrounded by prosperous Prior to colleting seawater samples, these bottles were firstly rinsed and intensely populated coastal areas of eastern China and the by methanol and cleaned with in-situ seawater 3 times to remove Korean Peninsula, are of particular concern for PFAA contamination the potential PFAA contamination. The samples were transported to (Cai et al., 2011; Gonzalez-Gaya et al., 2014; Yeung et al., 2017). our laboratory after landing with the least possible delay. Before Daily, hundreds of rivers from the surrounding area directly empty taking the 400 mL supernatants for onward analysis, all seawater industrial and domestic effluents containing PFAAs into the Bohai samples were left to stand for 24 h to precipitate the probable and Yellow Seas. Several studies have been conducted on the spatial suspension using the same procedure of previous studies (Liu et al, distribution of PFAAs in the region’s coastal rivers and surface 2016; Wang et al, 2014). Dissolved phase of PFAAs were analyzed in seawater (Chen et al., 2016; Chen et al., 2017; Wang et al., 2014; the present study. Zhao et al., 2017), but the vertical profile and transportation char- acteristics of PFAAs are still undefined in neritic areas of these ba- 2.3. Extraction, identification, and quantification of target analytes sins (less than 81 m depth). There is a further lack of studies bridging the gap between riverine PFAA inputs and marine sinks; Seawater samples were spiked with internal standards before correcting this could help policy-makers properly manage PFAA extraction using the solid phase extraction (SPE) technique contamination in this significant region. following previous methods (Liu et al., 2016; Taniyasu et al., 2005; This study’s main objectives were to: 1) define the contamina- Zhou et al., 2017) with minor modifications. Briefly, after sequen- tion level and spatial distribution of PFAAs in the Bohai and Yellow tially preconditioning with 4 mL 0.1% NH4OH in methanol, 4 mL Seas; 2) explore vertical transport mechanisms of PFAAs in a large methanol, and 4 mL Milli-Q water, Oasis WAX cartridges (6 cc3, epicontinental sea; and 3) bridge the gap between riverine PFAA 150 mg, 30 mm; Waters, Milford, MA) were loaded with the pre- sources and their marine sinks. The results provide an improved pared 400 mL seawater to extract the target analytes at approxi- understanding of PFAA contamination and vertical transmission in mately 1 drop per second. After successful loading of the the Bohai and Yellow Seas and assess the contribution of riverine supernatant, the cartridge was washed with 4 mL 25 mM ammo- inputs, providing scientific support to governmental efforts nium acetate (pH ¼ 4). The washed cartridges were then put in a regarding the control of PFAA pollution in this rapidly developing lyophilizer overnight at 30 C temperature to dry out thoroughly. coastal area. Next, 4 mL of methanol and 4 mL of 0.1% NH4OH in methanol were successively passed through the cartridges to elute the target 2. Materials and methods analytes into 15 mL PP centrifuge tubes. The eluents were concen- trated up to 0.5 mL under a constant and stable high-purity nitro- 2.1. Standards and reagents gen (99.999%, Haidian District, Beijing, China) air flow, then passed through a nylon filter (13 mm, 0.2 mm, Chromspec, Ontario, Canada) All standards were purchased from Wellington Laboratory Inc. before being transferred into a 1.5 mL PP snap-top brown glass vial (Guelph, Ontario, Canada). These standards included 17 native via a sterile syringe. Finally, the individual PFAAs were separated PFAAs and 9 mass-labeled internal standards with ˃98% purity. and quantified via an Agilent 1290 Infinity HPLC System equipped Chromatographic grade methanol (MeOH) and acetonitrile (ACN) with an Agilent 6460 Triple Quadrupole LC/MS System (Agilent were obtained from J.T. Baker (Phillipsburg, NJ, USA), ammonium Technologies, Palo Alto, CA, USA) in negative electrospray ioniza- acetate (~98%) from Sigma-Aldrich Co. (St. Louis, MO, USA) and tion (ESI-) mode. Detailed descriptions of instrument conditions ammonium hydroxide solution (28%e30% NH3 basis) from Sino- are shown in Table S3. pharm Chemical Reagent Beijing Co., Ltd (Haidian District, Beijing, China). The integrant Milli-Q water was acquired from Milli-Q 2.4. Quality assurance and quality control synthesis A10 (Millipore, Bedford, MA, USA). Detailed information about standards and MS/MS parameters are listed in Table S1. A 9-point native standard curve was established for the quan- tification of each individual PFAA with coefficients (r2) exceeding 2.2. Sample collection 0.99. The concentration gradients of the curves were 0.01, 0.05, 0.1, 0.5, 1, 5, 10, 50, and 100 mgL 1, spiked with 5 ng internal standards. The locations of 33 selected rivers and 49 sampling sites in the The limit of detection (LOD) was determined using a signal-to- Bohai and Yellow Seas are shown in Fig. 1. The maritime samples noise ratio of 3:1 and the limit of quantification (LOQ) was identi- were collected by the research vessel Dongfanghong-2 from June 29 fied as the analyte peak that yielded a signal-to-noise ratio of 10:1. to July 14, 2016. Although the Bohai and Yellow Seas are surrounded The range of matrix spike recoveries and quality assurance and by three countries (China, North Korea, and South Korea), only quality control (QA/QC) information is shown in Table S4. coastal rivers in China (n ¼ 30) and South Korea (n ¼ 3) were The use of polytetrafluoroethylene (PTFE) or other fluoropol- studied; North Korean rivers were excluded due to the absence of ymer materials was avoided during sample collection and extrac- PFAA-related data. All the data of PFAA concentrations in estuary of tion to minimize background contamination. Field blanks, Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120 113

Fig. 1. Locations of 49 sampling sites within the Bohai and Yellow Seas as well as the 33 surrounding rivers considered in this study. transport blanks, procedure blanks, and solvent blanks were consistently below LOD (Table S4), which indicated that no new collected and prepared with every sample batch to check for PFAA contamination was introduced. The QA/QC procedures used possible contamination during the sampling and indoor extraction were described in more detail in our previous study (Liu et al., processes. All the individual PFAA in these blank samples were 2017). 114 Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120

2.5. Statistical and spatial analysis this industrial park was extremely high (up to 1.86 mg L 1) and the maximum PFOA concentration (1.71 mg L 1) was the highest in the Statistical analysis was carried out using SPSS Statistics V22.0 world. In addition to surface water, this region’s PFAA concentra- (SPSS Inc. Quarry Bay, HK). During calculating, graphing and tions in sediments (Li et al., 2017; Zhu et al., 2014), crops (Liu et al., analyzing, the concentrationspffiffiffi of individual PFAA lower than LOD 2017), and even dust (Su et al., 2016) were very high when were assigned as LOD/ 2, while those lower than LOQ were compared with other regions. calculated as half of the LOQ (Bao et al., 2011; Hornung and Reed, As PFAAs have a certain solubility, they can be transported by 1990; Liu et al., 2017; Wang et al., 2014). Spatial distributions of the Xiaoqing River into the , especially Laizhou Bay (Wang PFAAs were analyzed using the ArcMap module of ArcGIS V10.4 et al., 2014). Preceding studies systematically reported PFAA software (ESRI, Redland, CA, USA). Rivers in Fig. 1 were drawn in the contamination in the Xiaoqing River and seawater near the estuary. Google Earth computer package 7.1.8.3036 (32-bit) (Google Inc., The average total PFAA concentration in seawater near the estuary USA) and imported into ArcGIS V10.4 software through the KML file was measured as up to 2390 ng L 1 (Shi et al., 2015). Even seawater format. Other layers, including the bathymetric digital elevation collected 25 km away from the Xiaoqing River’s mouth contained model (DEM), were obtained from the National Geomatics Center the total PFAA concentrations ranging from 899 to 1084 ng L 1. of China (Haidian District, Beijing, China). Moreover, in this study PFOA was the predominant compound among the total PFAAs collected from seawater at B65, in accor- 2.6. Riverine input analysis dance with previous results in Xiaoqing River. Therefore, the Xiaoqing River was a significant source of PFAA contamination in Riverine inputs of PFAAs for each target river were calculated Laizhou Bay and the Bohai Seas with regards to both total con- based on previously reported methods (Chen et al., 2017). The centration and composition. Meanwhile, salting-out effect also average mass flux of each PFAA for a given river in a year (365 days plays an important role in controlling the sediment-water in- in this study) was calculated by: teractions and the fate or transport of PFAAs (C 8) in the aquatic P environment (You et al., 2010). Long-chain PFAAs rather than short- n chain PFAAs are largely scavenged by adsorption to suspended i MFi MF v ¼ (1) a erage n particles due to the salting-out effect especially in river estuary (Hong et al., 2013). Therefore, the PFAA concentration near the fl where MFi is one data point of the PFAA mass ux for the same river estuary of the Xiaoqing River may be influenced by the salting-out i (kg y 1) and n is the number of data points. The riverine input of effect and it is worth further studying. PFAAs was then calculated by: In Laizhou Bay, the spatial distribution of total PFAA concen- tration in surface seawater shows a rapid decline from coastal areas ¼ : MFi F C 0 031536 (2) (such as B65) toward open waters (Fig. 2). The concentration value 1 at B65 (556 ng L ) decreased approximately 10 fold by sites B68 ’ fl 3 1 where F is the river s ow rate (m s ) and C is the riverine PFAA (44.9 ng L 1) and B39 (55.0 ng L 1), declining even further to the 1 concentration (ng L ). east. Although site B42 is approximately the same distance from B65 as B68 and B39, its much lower concentration (15.4 ng L 1) 3. Results and discussion may be attributed to sea current movements. However, it is not clear that PFAAs decrease from coastal to open water overall in the 3.1. Spatial distribution of PFAAs in surface seawater of the Bohai Bohai Sea (Chen et al., 2016). and Yellow Seas Interestingly, PFAA concentrations in surface seawater collected near the demarcation line between the Bohai Sea and the Yellow Of the 17 PFAA analytes, the concentrations of PFDA (C10), Sea were low, ranging from 5.87 to 9.56 ng L 1 (B23, B25, B30, B33, PFTrDA (C13), PFTeDA (C14), and PFDS (C10) were less than the LOQ B36 and B51). This pattern may be influenced by seawater ex- in all seawater samples, whereas the detection frequencies of long- change. The total PFAA concentrations surface seawater samples chain PFAAs, including PFUnDA (C11, 0.7%), PFDoDA (C12, 2.7%), collected east and southeast of the Peninsula were PFHxDA (C16, 5.4%), and PFODA (C18, 1.4%) were very low. The relatively high, possibly indicating local sources of PFAAs. More- concentrations of PFOA (C8) ranged from 0.55 to 449 ng L 1, all over, PFAA concentration in the junction area of Bohai and Yellow exceeding the LOQ value. The detection frequencies of PFBA (C4) Seas (B1-B10 and BS1-BS5) were higher than surrounding sea area and PFBS (C4) were 93.9% and 98.6%, respectively. PFPeA (C5), may be affected by ocean currents and local circulation. In broader PFHxA (C6), and PFOS (C8) had comparatively higher detection areas of the Yellow Sea, the decrease in PFAA concentrations from frequencies as 89.1%, 70.7%, and 70.7%, respectively. Overall, PFAAs coastal to open waters was more obvious, consistent with results with carbon chains shorter than 8 were more likely to be detected from Zhao et al. (2017). in the Bohai and Yellow Seas, consistent with previously-reported The PFAA concentrations in surface seawater near sampling site results from the East China Sea (Zheng et al., 2017), indicating (B65) were 118 ng L 1 and 94.4 ng L 1 in 2012 and 2013, respec- that short-chain PFAAs were easier to transport in the sea (Yeung tively (Chen et al., 2016; Zhao et al., 2017); this study showed a et al., 2017). rapid increase in PFAA concentrations in Laizhou Bay. In compari- The total PFAA concentration in surface seawater samples son with global marine PFOA and PFOS concentrations (Table S5), ranged from 4.55 to 556 ng L 1, with an average of 27.6 ng L 1 and a those in the Bohai and Yellow Seas were relatively high. Coastal median of 13.9 ng L 1, suggesting that significant spatial variation seawater in Japan and Korea had high levels of PFOA and PFOS in PFAA concentration exists in the Bohai and Yellow Seas (Fig. 2). contamination almost 10 years ago (Naile et al., 2010; So et al., Although most values ranged from 4.55 to 55.0 ng L 1, one outlier 2004; Yamashita et al., 2005), which confirmed that there was a value was over one hundred times higher from Laizhou Bay (B65) in period of PFAA pollution in Japan and Korea. Decreases of PFOA and the southwestern Bohai Sea. There is a mega fluorochemical in- PFOS concentrations in Tokyo Bay were recorded in more recent dustrial park located in Zibo City, Shandong province, approxi- years, which indicated that PFAA emissions reduced in the catch- mately 200 km upstream from this sampling site. According to Liu ment basins (Sakurai et al., 2016). While, the contamination level of et al. (2016), the total PFAA concentration in surface water around PFOA and PFOS in seawater around China was still increasing, with Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120 115

Fig. 2. Spatial distribution of total PFAA concentrations in surface seawater of the Bohai and Yellow Seas. contamination levels ranked as Bohai Sea > Yellow Sea > East China shown in Figs. S1 and S2. Sea > South China Sea. These relatively high PFAA concentrations The overall depth of the Bohai and Yellow Seas is relatively may affect the bioaccumulation of PFAAs in marine organisms such shallow, not exceeding 81 m within the sampling region (Table S2). as oceanic plankton (Casal et al., 2017). Thus, more attention is The sampling depths of the surface, middle, and bottom zones needed toward the control of potential ecological risks from PFAAs ranged from 1.5 to 4.1 m, 6.2e41.3 m, and 11.0e76.0 m, respectively. in the marine environment of the Bohai and Yellow Seas. Within these zones, variations in the sampling depth had a great influence on temperature and little effect on salinity: the temper- ature ranged from 16.5 to 32.4 C, 6.8e26.8 C, and 6.2e26.8 Cin 3.2. Vertical profile of PFAA concentrations in the Bohai and Yellow the surface, middle, and bottom zones, respectively, while the Seas salinity remained stable for all depths. The concentration of individual PFAAs changed only little be- Three stratified seawater samples were collected at each marine tween the three zones, which may indicate that vertical exchange sampling site and defined as surface, middle, and bottom zones. of seawater was relatively weak at each site. Of the 17 target PFAAs, The average and range for CTD and concentration of individual only the average concentrations of PFBA, PFPeA, PFHxA, and PFOA PFAAs at different depths is shown in Fig. 3(a) and Fig.3(b), whereas exceeded 1 ng L 1 in each zone: 5.39, 2.93, 1.46, and 17.4 ng L 1 at full data are listed in Table S6. The spatial distribution of total PFAA the surface; 4.75, 2.99, 1.36 and 15.5 ng L 1 at the middle; and 4.44, concentrations in the middle and bottom seawater samples is 116 Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120

Fig. 3. (a) Depth (m), temperature (C), salinity (‰) and (b) concentrations (ng L 1) of individual PFAAs in different vertical zones of the Bohai and Yellow Seas.

3.07, 1.31, 15.2 ng L 1 at the bottom, respectively. As all these PFAAs In terms of the PFAA composition at different depths (Fig. 4(b)), are confirmed perfluoroalkyl carboxylic acids (PFCAs), PFCAs may the three predominant components at all levels were PFOA, PFBA, be easier to transport into seawater compared with perfluoroalkyl and PFPeA, ranging from 28 to 50%, 19e33%, and 8e33%, respec- sulfonic acids (PFSAs). tively. Overall, with increasing depth the composition ratio of PFOA As the sampling depths changed vertically, the concentrations declined, that of PFPeA increased slightly, and that of PFBA fluctu- and compositions of total PFAAs in the seawater changed as well ated. Thus, the short-chain PFAAs, such as PFBA and PFPeA, were (Fig. 4). The extraordinarily high concentrations of total PFAAs from easier to transport vertically due to their higher solubility and site B65 were excluded from this figure for clarity. To better show vertical sea disturbance. changes in PFAA composition with depths, these data were divided into 9 different groups, with the first two divided in 5 m intervals 3.3. Riverine sources and mass flux of PFAAs into the Bohai and and the rest in 10 m intervals. Yellow Seas In general, a slight downward trend in the total PFAA concen- trations (Fig. 4(a)) occurred with increasing of sampling depth, River inputs are usually considered the dominant source of similar to vertical PFAA profiles in the Arctic Ocean (Yeung et al., PFAAs into marine environments (Chen et al., 2017; Filipovic et al., 2017). The highest and lowest average PFAA concentrations were 2013; Lindim et al., 2016). The estimation of riverine PFAA mass flux found at depths between 5 and 10 m (19.9 ng L 1) and 60e70 m into the Bohai and Yellow Seas is notable for its comprehensive (12.0 ng L 1), respectively, a difference of ~40%. The total PFAA summary of the occurrence, distribution, and fate of PFAAs in these concentration may decrease faster at depths exceeding 100 m marine environments (Wang et al., 2015b). The estimated annual (Lohmann et al., 2013). average riverine flux for 11 PFAAs in the 33 target rivers is

Fig. 4. Vertical depth profiles of PFAA (a) concentrations and (b) composition, excluding the extreme outlier values from site B65. Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120 117 presented in Table 1, using data collected from available reports as sequentially decreased from Laizhou Bay > Liaodong Bay > Bohai listed in Tables S7 and S8. The total annual mass flux of the chosen Bay > other areas as influenced by the different riverine inputs. PFAAs in all rivers was approximately 72.2 t y 1, little lower than another estimated flux of 87.3 t y 1 into the Bohai Sea alone (Chen et al., 2017). 3.4. Bridging the gap between riverine inputs and marine sinks of Of the 33 rivers, the PFAA mass flux of the Xiaoqing River PFAAs along the Bohai and Yellow Seas (33.8 t y 1) and Yangtze Rivers (34.7 t y 1) accounted for 94.8% of the total. Although the latter was higher, the PFAA contamination As riverine inputs are the major source of PFAAs in the Bohai and level at the Yangtze River estuary was much lower than at the Yellow Seas, differences between rivers may cause variations in the Xiaoqing River estuary. This may be due to the Xiaoqing River concentrations and compositions of PFAAs in the seawater. Fig. 5(a) fl estuary’s location in the semi-enclosed Laizhou Bay, whereas the shows the total riverine PFAA mass uxes and the average PFAA Yangtze River estuary meets the open sea. Moreover, the dilution compositions at each marine sampling site, while Fig. 5(b) shows fl characteristics of seawater may have a greater influence on the the PFAA compositions of each riverine mass ux. In general, PFOA Yangtze River, whereas this effect is very limited in the Bohai Sea and PFBA were the predominant components in the southern rivers (Chen et al., 2017). In addition, the high PFAA mass flux of the of the Bohai and Yellow Sea, while the ratio of PFBS and PFPeA Yangtze River may be credited to higher flow rate rather than high increased in northern rivers such as the Xiaoling River (Wang et al., PFAA concentration; the average flow rate of the Xiaoqing River is 2016b), Daling River (Wang et al., 2016a), and Shuangtaizi River almost 500 times smaller than the Yangtze River. Thus, the PFAA (Shao et al., 2016). Unlike river emission characteristics from the contamination level near the Xiaoqing River estuary is worth spe- western side, those from South Korea contained more PFOS and fl cial attention. had a distinctly different composition. The total mass ux of PFAAs 1 1 The Daling, Yellow, and Yalu Rivers also contributed higher PFAA in these rivers was 529 kg y , including (234 kg y ) 1 fl (Kim et al., 2011), Geum River (232 kg y )(Hong et al., 2015; Kim emissions into the Bohai and Yellow Seas, with mass uxes esti- 1 mated as 893, 448, and 347 kg y 1, respectively. Although there are et al., 2011; Naile et al., 2010) and Yeongsan River (62.5 kg y ) two fluorochemical industrial parks located along Daling River in (Hong et al., 2013; Hong et al., 2015; Kim et al., 2011; Lam et al., fl Fuxin City, the estimated mass fluxes were much lower than 2014; Naile et al., 2010). Interestingly, rivers owing into the Xiaoqing River. As these high-emission rivers flow into different northern part of the Yellow Sea (R28-R30) also had compositions fl areas (Fig. 1), the riverine sources of PFAAs in the Bohai and Yellow distinct from those owing into the Bohai Sea. Seas have obvious spatial differences which may direct relate to Detailed average marine concentrations of individual PFAAs are local human activities, especially industrial production and emis- given in Table S9 and the PFAA compositions of samples collected sions. The mass flux of PFAAs in the Bohai and Yellow Seas from site B65 are shown in Fig. S3. There was a strong correlation relationship of PFAAs between B65 and the Xiaoqing River

Table 1 Average flow rate (m3 s 1) and annual mass flux (kg y 1) of 11 PFAAs for the 33 target rivers, estimated from studies listed in Tables S7 and S8. P No. River Flow rate PFBA PFPeA PFHxA PFHpA PFOA PFNA PFDA PFUnDA PFBS PFHxS PFOS PFAAs

R1 Yangtze River 29100 1991.40 922.29 1229.71 1000.29 22352.05 856.52 449.67 252.37 3404.66 195.78 2000.58 34655.32 R2 Xinyanggang River 66 e 1.77 3.12 2.91 97.82 1.75 0.33 0.52 e 2.29 52.03 162.56 R3 Sheyang River 127 e 1.48 3.08 3.84 84.11 3.68 2.08 2.32 e 12.02 9.49 122.11 R4 Jia River 14 1.96 0.49 0.49 0.51 1.48 0.26 0.13 eee0.24 5.56 R5 Huangshui River 3.07 0.10 <0.1 <0.1 <0.1 0.30 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.40 R6 Jie River 1.17 0.10 <0.1 <0.1 <0.1 0.10 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.20 R7 Wang River 1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 e R8 Sha River 8 0.60 0.10 0.20 0.20 1.70 0.20 <0.1 <0.1 <0.1 <0.1 0.20 3.20 R9 Jiaolai River 14.48 2.00 1.40 1.10 0.40 2.10 0.30 0.10 <0.1 <0.1 0.10 1.50 9.00 R10 Wei River 116.2 24.20 4.50 6.20 5.80 37.00 6.80 2.30 0.30 0.70 2.20 38.00 128.00 R11 13.95 1.20 0.40 0.60 0.50 3.90 0.30 0.10 <0.1 0.10 <0.1 1.40 8.50 R12 Xiaoqing River 60.265 595.80 673.16 1449.01 1360.44 29643.87 15.54 6.03 2.01 3.19 2.06 7.41 33758.51 R13 989.84 144.07 43.71 29.27 28.11 103.80 21.86 5.02 0.60 12.80 5.20 53.61 448.04 R14 Tuhai River 107.64 26.40 15.00 26.10 13.60 128.00 14.90 5.40 1.00 9.40 <0.1 18.50 258.30 R15 Majia River 55.83 6.20 3.20 3.70 3.60 18.80 1.40 0.50 0.04 1.00 0.20 4.70 43.34 R16 Zhangweixin River 8.27 1.20 0.50 0.40 0.30 3.40 0.40 0.10 <0.1 <0.1 <0.1 0.90 7.20 R17 Ziya River 45 eeee4.26 e 0.63 eee0.41 5.30 R18 Duliujian River 27.9 eee2.29 9.51 4.31 3.34 eee1.41 20.87 R19 69.35 30.07 19.90 32.48 6.75 25.92 3.48 1.80 e 5.95 1.57 14.26 142.18 R20 48.3 12.19 10.66 10.21 3.47 17.75 1.98 1.31 eee9.84 67.40 R21 91 4.74 1.79 2.30 5.74 11.62 0.72 1.00 eee3.37 31.28 R22 Liugu River 9.2 eeee2.63 eeeee1.06 3.69 R23 Xiaoling River 21.95 45.93 2.30 4.57 1.07 6.15 0.54 1.02 e 23.99 0.83 0.92 87.31 R24 Daling River 44.9 340.71 18.04 30.54 7.89 108.39 2.18 0.60 0.05 380.57 0.39 3.28 892.65 R25 Shuangtaizi River 67.07 77.40 78.43 13.39 21.24 48.32 1.13 0.21 e 4.20 0.20 1.17 245.69 R26 Daliao River 141.8 15.20 10.24 5.14 27.12 24.72 1.90 0.78 eee8.38 93.50 R27 Fuzhou River 10.5 eee0.60 eeeeeee0.60 R28 Biliu River 27.3 e 1.98 e 1.89 eeeeeee3.87 R29 Dayang River 82.15 eee2.33 17.10 20.73 25.91 eee23.83 89.90 R30 1038.8 eee26.21 34.40 24.57 65.52 eee196.56 347.25 R31 Han River 613 eee16.05 65.73 10.44 e 6.77 21.26 34.80 79.26 234.30 R32 Geum River 132 4.68 13.02 12.77 14.83 87.42 10.22 7.89 5.18 6.58 10.30 58.86 231.74 R33 Yeongsan River 48 3.11 3.82 3.97 10.29 10.01 2.69 1.27 0.73 3.83 5.01 17.78 62.51 Total flux 3329.26 1828.19 2868.35 2568.27 52952.34 1008.78 583.06 271.88 3878.22 272.94 2608.98 72170.27

Note: “-” indicates data are not available. 118 Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120

Fig. 5. Comparison of riverine and marine PFAA concentrations and mass fluxes: (a) Concentration (ng L 1) and composition (%) of average PFAAs in the Bohai and Yellow Seas with total riverine mass fluxes entering the seas (kg y 1) and (b) PFAA compositions of the total mass flux from each river.

(r2 > 0.99, p < 0.01). Results of Pearson correlation analysis were list et al., 2011), suggesting it may migrate more easily in marine en- in Table S10. Moreover, marine PFAAs concentrations were gener- vironments compared with other PFAAs. Finally, the movement and ally much higher closer to the coast than those away from it, further mixture of sea currents may also play an important role in affecting proving the significant influence of riverine inputs. This may also the final concentrations of PFAAs. The PFAA compositions at B19, indicate an increase in the composition ratio of PFBA, as this B27, and B33 were much different from those in the surrounding gradually became a dominant PFAA in the Yellow Sea. PFBA was water (Fig. 5(a)), suggesting that other sources of PFAAs may exist also observed to be the dominant PFAA in the Arctic Ocean (Cai in these areas. Although two Fluorine Industrial Parks locates along Y. Zhou et al. / Environmental Pollution 238 (2018) 111e120 119 the Daling River, PFAA concentrations in the Daling River did not Dachs, J., 2017. Accumulation of perfluoroalkylated substances in oceanic e show a strong relationship with those in seawater at B54 plankton. Environ. Sci. Technol 51, 2766 2775. Chen, H., Sun, R., Zhang, C., Han, J., Wang, X., Han, G., He, X., 2016. Occurrence, (Table S11). The reason may be that the location of B54 is relatively spatial and temporal distributions of perfluoroalkyl substances in wastewater, far away from the estuary of the Daling River and PFAA riverine seawater and sediment from Bohai Sea, China. Environ. Pollut 219, 389e398. fl 1 Chen, H., Wang, X., Zhang, C., Sun, R., Han, J., Han, G., Yang, W., He, X., 2017. mass ux of the Daling River (893 kg y ) was still less compared fl 1 Occurrence and inputs of per uoroalkyl substances (PFASs) from rivers and with the Xiaoqing River (33759 kg y ). 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Total e and South Korea should fulfill their respective obligation to control Environ 445, 136 145. Hong, S., Khim, J.S., Wang, T., Naile, J.E., Park, J., Kwon, B.-O., Song, S.J., Ryu, J., PFAA contamination in the Bohai and Yellow Seas. Codling, G., Jones, P.D., 2015. Bioaccumulation characteristics of perfluoroalkyl acids (PFAAs) in coastal organisms from the west coast of South Korea. Che- e 4. Conclusion mosphere 129, 157 163. Hornung, R.W., Reed, L.D., 1990. Estimation of average concentration in the pres- ence of nondetectable values. Appl. Occup. Environ. Hyg 5, 46e51. This study confirmed that the Bohai and Yellow Seas were Kim, S.K., Kho, Y.L., Shoeib, M., Kim, K.-S., Kim, K.-R., Park, J.-E., Shin, Y.-S., 2011. fl fl widely contaminated with PFAAs: the total concentration in the Occurrence of per uorooctanoate and per uorooctanesulfonate in the Korean 1 water system: implication to water intake exposure. Environ. Pollut 159, surface, middle, and bottom zones ranged from 4.55 to 556 ng L , 1167e1173. 4.61e575 ng L 1, and 4.94e572 ng L 1, respectively. The predomi- Lam, N.H., Cho, C.R., Lee, J.S., Soh, H.Y., Lee, B.C., Lee, J.A., Tatarozako, N., Sasaki, K., e 1 < Saito, N., Iwabuchi, K., 2014. Perfluorinated alkyl substances in water, sediment, nant compounds were PFOA (0.55 449 ng L ), PFBA ( LOQ- fi 1 < 1 plankton and sh from Korean rivers and lakes: a nationwide survey. Sci. Total 34.5 ng L ), and PFPeA ( LOQ-54.3 ng L ), accounting for Environ 491, 154e162. 10.1e87.0%, 5.2e59.5% and 0.6e68.6%, respectively. A slight Lescord, G.L., Kidd, K.A., De Silva, A.O., Williamson, M., Spencer, C., Wang, X., downward trend of PFAA concentration was observed with vertical Muir, D.C., 2015. Perfluorinated and polyfluorinated compounds in lake food webs from the Canadian high arctic. Environ. Sci. Technol 49, 2694e2702. sampling depth. Spatial distributions of PFAAs were greatly affected Li, L., Wang, T., Sun, Y., Wang, P., Yvette, B., Meng, J., Li, Q., Zhou, Y., 2017. Identify by riverine inputs, sea current movements, salting-out effect and biosorption effects of Thiobacillus towards perfluorooctanoic acid (PFOA): pilot other potential sources. Total PFAA mass flux from 33 rivers study from field to laboratory. Chemosphere 171, 31e39. Lindim, C., Van Gils, J., Cousins, I.T., 2016. Europe-wide estuarine export and surface draining into the Bohai and Yellow Seas was estimated to be water concentrations of PFOS and PFOA. Water Res. 103, 124e132. 1 72.2 t y with two main contributors: the Yangtze and Xiaoqing Lindstrom, A.B., Strynar, M.J., Libelo, E.L., 2011. Polyfluorinated compounds: past, River. These two rivers accounting for up to 94.8% of the total mass present, and future. Environ. Sci. Technol 45, 7954e7961. flux. As the concentration of short-chain PFAAs such as PFBA is Liu, S., Lu, Y., Xie, S., Wang, T., Jones, K.C., Sweetman, A.J., 2015. Exploring the fate, transport and risk of Perfluorooctane Sulfonate (PFOS) in a coastal region of rising in these areas, further studies on the occurrence and fate of China using a multimedia model. Environ. Int 85, 15e26. short-chain PFAAs in marine environment should be conducted. Liu, Z., Lu, Y., Shi, Y., Wang, P., Jones, K., Sweetman, A.J., Johnson, A.C., Zhang, M., Zhou, Y., Lu, X., 2017. Crop bioaccumulation and human exposure of per- fluoroalkyl acids through multi-media transport from a mega fluorochemical Acknowledgments industrial park, China. Environ. Int 106, 37e47. Liu, Z., Lu, Y., Wang, T., Wang, P., Li, Q., Johnson, A.C., Sarvajayakesavalu, S., fi This study was supported by the National Key R&D Program of Sweetman, A.J., 2016. Risk assessment and source identi cation of per- fluoroalkyl acids in surface and ground water: spatial distribution around a China (Grant No. 2017YFC0505702), the National Natural Science mega-fluorochemical industrial park, China. Environ. Int 91, 69e77. Foundation of China (Grant No. 41571478), and the National Water Lohmann, R., Jurado, E., Dijkstra, H.A., Dachs, J., 2013. Vertical eddy diffusion as a fl Pollution Control and Treatment Science and Technology Major key mechanism for removing per uorooctanoic acid (PFOA) from the global surface oceans. Environ. Pollut 179, 88e94. Project (Grant No. 2015ZX07203-005). We would also like to Naile, J.E., Khim, J.S., Wang, T., Chen, C., Luo, W., Kwon, B.-O., Park, J., Koh, C.H., acknowledge support from the Youth Innovation Promotion Asso- Jones, P.D., Lu, Y., 2010. Perfluorinated compounds in water, sediment, soil and e ciation of the Chinese Academy of Sciences. biota from estuarine and coastal areas of Korea. Environ. 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