Spatial and Vertical Variations of Perfluoroalkyl Acids (Pfaas)
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Environmental Pollution 238 (2018) 111e120 Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol 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, China 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: À1 e À1 e À1 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 À1 < À1 < Stratified seawater predominant compounds were PFOA (0.55 449 ng L ), PFBA ( LOQ-34.5 ng L ), and PFPeA ( LOQ- À1 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 À 72.2 t y 1, of which 94.8% was carried by the Yangtze 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 À30 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.