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Article

Comprehensive Assessment of Per- and Polyfluoroalkyl Substances (PFAS) Pollution in a Coastal Region: Contributions from Nearshore and Offshore Sources

by
Chenyu Chen
1,†,
Ying Wang
2,†,
Fei Chen
2,
Xinyue Wang
3,
Qiao Zhang
3,
Jialong Sun
1,2,
Si Li
4,
Qiang Chen
5,
Fangze Shang
1 and
Hui Zhang
3,*
1
PowerChina Eco-Environmental Group Co., Ltd., Shenzhen 518101, China
2
VAST Institute of Water Ecology and Environment, Shenzhen 518101, China
3
College of Resources and Environment, Chengdu University of Information Technology, Chengdu 610225, China
4
Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation, College of Resources and Environmental Sciences, China Agricultural University, Beijing 100193, China
5
PowerChina Lingkun Intelligent Creation City Ecological Construction and Development (Wenzhou) Co., Ltd., Wenzhou 325799, China
*
Author to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Water 2025, 17(2), 149; https://doi.org/10.3390/w17020149
Submission received: 22 November 2024 / Revised: 29 December 2024 / Accepted: 4 January 2025 / Published: 8 January 2025
(This article belongs to the Section Oceans and Coastal Zones)
Browse Figures
Versions Notes

Abstract

:
Per- and polyfluoroalkyl substances (PFAS) have become a well-known class of anthropogenic pollutants in coastal regions. It is known that PFAS primarily enter the sea from nearshore sources, dry deposition, and wet deposition. However, the contribution of offshore sources to PFAS pollution in the sea remains poorly understood. Our study aims to investigate the occurrence of 74 PFAS across 15 groups in a coastal region of eastern China and to characterize their spatial distribution by focusing on the critical roles of both nearshore and offshore sources. Results revealed that 26 PFAS were detected in the coastal region (i.e., Ou River and Wenzhou Bay), with detection frequencies ranging from 4.3% to 100.0%. Notably, over 10 PFAS were detected for the first time in the region, such as perfluorooctane sulfonamide (FOSA), hexafluoropropylene oxide dimer acid (HFPO-DA), and 6:2 fluorotelomer sulfonic acid (6:2 FTSA), among others. The concentrations of detected PFAS ranged from 0.0018 to 76.31 ng/L, with perfluorooctanoic acid (PFOA) as the dominant congener. Spatial analysis indicated that the nearshore area was more severely polluted compared to the offshore area, with specific hotspots identified near industrialized areas. However, the distribution of certain PFAS, such as perfluorobutane sulfonic acid (PFBS) and perfluoro-3,6-dioxaheptanoic acid (PFDHA), exhibited a contrasting pattern, with higher concentrations observed in the offshore area and near island perimeters. These findings suggest that PFAS pollution in Wenzhou Bay originates from both nearshore and offshore sources, highlighting a complex interplay between nearshore and island-related activities.

1. Introduction

Per- and polyfluoroalkyl substances (PFAS) are a class of synthetic persistent organic pollutants, whose hydrogen atoms on the carbon chain are wholly or partially replaced by fluorine atoms. Since the 1950s, PFAS have been widely used in various industries, including papermaking, leather processing, textiles, material packaging, and fire protection [1,2,3], due to their high-temperature resistance, strong chemical stability, and amphiphilic properties, which allow them to repel water and oils while interacting with aqueous environments [4]. PFAS have C-F bonds with high bond energy that are resistant to degradation in natural environments. Consequently, PFAS have been detected ubiquitously in various environmental media, including water (e.g., groundwater, surface water, seawater, drinking water, etc.) [5,6,7], dust [8,9], sediment [10,11], soil [12], and air [13]. The occurrence of PFAS in plants [14,15], animals [16,17], and humans [18,19] has also been reported. Extensive studies have demonstrated the genetic toxicity, embryonic toxicity, reproductive toxicity, neurotoxicity, endocrine-disrupting effects, and carcinogenicity of PFAS on living organisms [20,21,22,23,24]. Perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and their salts and related substances have been listed in the Stockholm Convention to limit their production and use since 2009, 2019, and 2022, respectively [25]. Meanwhile, the List of New Pollutants for Priority Control (2023 Edition) (Index Number: 000014672/2022-00530) released in 2022 by China’s Ministry of Ecology and Environment in conjunction with other ministries, imposes restrictions on the production, processing, and use of PFOS, PFOA, their salts and related compounds. In addition, China issued its first restrictions on PFOS and PFOA in drinking water in the Standards for Drinking Water Quality in 2022 [26], which limits the levels of PFOS and PFOA in drinking water to no more than 40 ng/L and 80 ng/L, respectively. In 2024, the USA’s Environmental Protection Agency (EPA) issued the first-ever legally enforceable drinking water standards for PFAS [27]. This regulation sets limits for five individual PFAS in drinking water—PFOA, PFOS, PFHxS, perfluorononanoic acid (PFNA), and hexafluoropropylene oxide dimer acid (HFPO-DA)—as well as for mixtures containing two or more of PFHxS, PFNA, HFPO-DA, and perfluorobutane sulfonic acid (PFBS). Under this regulation, the maximum contaminant levels (MCLs) are set at 4.0 ng/L for PFOA and PFOS, 10 ng/L for PFHxS, PFNA, and HFPO-DA, and the hazard index for the mixtures must be less than 1.
Traditionally, only a limited number of PFAS congeners in the environment have been studied. For example, An et al. [28] quantified 25 PFAS in water and sediment samples from the Jiulong River and Xiamen Bay of China, revealing that pollution levels of PFAS were generally higher in upstream areas compared to downstream, and seasonal changes observably influenced PFAS distribution. Wang et al. [29] found that levels of 20 PFAS in surface water were remarkably higher than in bottom water in the South China Sea, with perfluorobutanoic acid (PFBA) and PFOA being the dominant congeners in seawater. Cai et al. [13] conducted a comprehensive analysis of water samples for 24 PFAS, including snow, lake water, surface runoff water, and coastal seawater from Antarctica, recording the highest PFOA concentration in seawater (15.10 ng/L), and high PFBA concentrations in snow (1.11 ng/L), lake water (2.67 ng/L) and surface runoff water (1.43 ng). The most studied PFAS included PFOS, PFOA, PFBA, PFNA, PFBS, PFHxS, perfluorohexanoic acid (PFHxA), and perfluoropentanoic acid (PFPeA) [6,13,28,29]. The number of well-studied PFAS is far from representing the full extent of PFAS pollution, especially considering the vast number of known PFAS, estimated to be approximately 5000 to 10,000 types [4,30]. Although our knowledge of PFAS is still limited, advancements in analytical technologies for PFAS may help to address this concern [31,32]. A recent study on a comprehensive analysis of PFAS in drinking water highlights the importance of expanding targeted analysis of PFAS to better understand PFAS pollution [33]. The simultaneous analysis of multiple groups of PFAS in environmental samples is both promising and necessary.
To our knowledge, there have been studies on the occurrence of PFAS in water bodies such as rivers, nearshore zones, and oceans [34,35,36,37,38]. However, to date, systematic investigations of PFAS contamination in the aquatic environment containing rivers, nearshore areas, island peripherals, and offshore areas remain lacking. Hence, the sources of PFAS in the sea, especially in coastal areas, may not be properly interpreted. Wenzhou plays a pivotal role in China’s terrestrial and maritime economy and is a key hub for economic development and regional integration in the Economic Zone on the West Coast of the Taiwan Straits [39]. With its fast development, Wenzhou faced severe eco-environmental stress during the period from 2000 to 2010 and was the key area of pollution control in the Economic Zone [40]. The Ou River, the second-largest river in Zhejiang Province, China, flows from west to east over a total length of 388 km. It traverses Wenzhou City before discharging an average annual volume of 20.2 billion cubic meters of water into Wenzhou Bay. The Ou River is also contaminated by various pollutants, including legacy persistent pollutants (e.g., polycyclic aromatic hydrocarbons and polychlorinated biphenyls) [41], flame retardants [42], pharmaceuticals [43], and PFAS [44]. Wenzhou Bay is located in the eastern part of Wenzhou City, Zhejiang Province, China, at the mouth of the Ou River. It is connected to Yueqing Bay to the north and offshore islands, such as Lingkun, Dongtou, and Damen, which are situated within its vicinity, covering an area of approximately 500 km2. The industrial economy in this region is thriving, with important transportation hubs including an international airport and a deep-water port. Studies have shown that Wenzhou Bay is polluted by plastic litter [45], phthalic acid esters [46], and endocrine disrupters, such as bisphenol analogs, triclocarban, and triclosan [47]. However, our knowledge of the status of PFAS pollution in Wenzhou Bay is limited.
In this study, a mass spectrometry-based target analysis method was applied to investigate the pollution profiles of PFAS in the Ou River and Wenzhou Bay, including 74 legacy and novel PFAS across 15 groups. A comprehensive evaluation of the occurrence and distribution of PFAS in rivers, nearshore areas, island perimeters, and offshore areas was conducted to illustrate PFAS pollution characteristics as well as to understand the contribution of offshore sources to PFAS pollution in the coastal region.

2. Materials and Methods

2.1. Chemicals and Materials

The solvent mixture of 27 PFAS standards (20 mg/L in methanol) was purchased from ANPEL Laboratory Technologies (Shanghai, China), including PFBA, PFPeA, 7h-perfluoroheptanoic acid (HPFHpA), PFHxA, perfluoroheptanoic acid (PFHpA), PFOA, PFNA, perfluorodecanoic acid (PFDA), perfluoro-3,7-dimethyloctanoic acid (PF-3,7-DMOA), perfluoroundecanoic acid (PFUnDA), perfluorododecanoic acid (PFDoDA), perfluorotridecanoic acid (PFTrDA), perfluorotetradecanoic acid (PFTeDA), PFBS, PFHxS, perfluoroheptane sulfonic acid (PFHpS), PFOS, perfluorodecane sulfonic acid (PFDS), 8:2 fluorotelomer carboxylic acid (8:2 FTCA), 8:3 fluorotelomer carboxylic acid (8:3 FTCA), 6:2 FTSA, 8:2 fluorotelomer sulfonic acid (8:2 FTSA), FOSA, n-methyl perfluorooctane sulfonamide (MeFOSA), n-ethyl perfluorooctane sulfonamide (EtFOSA), n-methyl perfluorooctane sulfonamidoethanol (MeFOSE), and n-ethyl perfluorooctane sulfonamidoethanol (EtFOSE).
The solvent mixture of 9 PFAS carbon-13 or oxygen-18 labeled standards (2 mg/L in methanol) were purchased as internal standards from Wellington Laboratories (Guelph, ON, Canada), including perfluoro-n-[13C4]butanoic acid (13C4-PFBA), perfluoro-n-[1,2-13C2]hexanoic acid (13C2-PFHxA), perfluoro-n-[1,2,3,4-13C4]octanoic acid (13C4-PFOA), perfluoro-n-[1,2,3,4,5-13C5]nonanoic acid (13C5-PFNA), perfluoro-n-[1,2-13C2]decanoic acid (13C2-PFDA), perfluoro-n-[1,2-13C2]undecanoic acid (13C2-PFUndA), perfluoro-n-[1,2-13C2]dodecanoic acid (13C2-PFDoA), sodium perfluoro-1-hexane[18O2]sulfonate (18O2-PFHxS), and sodium perfluoro-1-[1,2,3,4-13C4]octanesulfonate (13C4-PFOS).
Methanol (LC/MS grade) was purchased from Kelong Chemicals (Chengdu, China). Ammonium acetate (LC/MS grade) was purchased from Aladdin (Shanghai, China). WAX cartridges were purchased from ANPEL Laboratory Technologies (Shanghai, China).

2.2. Sample Collection and Pretreatment

Water samples were collected from the Ou River and Wenzhou Bay, located in southern Zhejiang Province, China (Figure 1). There were 23 sampling sites, including 2 in the Ou River (i.e., S1–S2) and 21 in Wenzhou Bay (i.e., S3–S23). These sites were categorized into nearshore and offshore areas, which included 9 sites (i.e., S1–S5 and S7–S10) and 14 sites (i.e., S6 and S11–S23), respectively. Triplicate samples were collected at each sampling location on 8 and 9 November 2023. Detailed information on the sampling locations and times is shown in Table S1. After collection, the samples were transported on ice packs to the analytical laboratory within 2 days and were analyzed within 3 days.
Solid-phase extraction (SPE) with a WAX cartridge (150 mg, 6 mL) was used to extract PFAS from water samples. Before SPE, water samples were filtered through glass fiber filters (pore size 0.45 μm), then 800 mL of filtrate was spiked with PFAS internal standard (each 5 ng) and homogenized. To condition the WAX cartridge, methanol with 1% ammonium hydroxide (3 × 5 mL), 0.3 M formic acid (5 mL), and ultrapure water (5 mL) were applied in sequence. After loading the water sample, the WAX cartridge was rinsed with ultrapure water (5 mL) and then dried under vacuum for 1 min. After that, methanol with 1% ammonium hydroxide (5 mL) was used to elute PFAS from the WAX cartridge, and then concentrated acetic acid (20 μL) was added into the eluate, which was then concentrated under nitrogen gas to reduce the volume to be 1 mL. After that, the extract was filtered through a nylon syringe filter (pore size 0.2 μm) and stored at −20 °C prior to LC-MS analysis.

2.3. LC-MS/MS Analysis

An Agilent 1290 Infinity II LC coupled with Agilent 6495C Triple Quad MS (Agilent, Santa Clara, CA, USA) was used to analyze PFAS. The Agilent PFAS MRM Database containing analytical information for 72 PFAS was applied to develop a target analysis method, which was validated by analyzing authentic standards of PFAS. The analytical information for 2 PFAS (PF-3,7-DMOA and HPFHpA) and the internal standards used in our study (13C4-PFBA, 13C2-PFHxA, 13C4-PFOA, 13C5-PFNA, 13C2-PFDA, 13C2-PFUndA, 13C2-PFDoA, 18O2-PFHxS, and 13C4-PFOS) were not included in the database. The MRM parameters of these 2 PFAS and internal standards were optimized in our laboratory and incorporated into the analytical method. The developed method can analyze 74 PFAS simultaneously with quantitative analysis of 27 of them and semi-quantitative analysis of the others using the stable isotope dilution method (Table S2).
According to the analytical conditions in the database, a ZORBAX Eclipse Plus C18 column (1.8 μm, 2.1 mm × 100 mm, Agilent) was used to separate PFAS at 55 °C. The mobile phases consisted of 5 mM ammonium acetate in water (phase A) and methanol (phase B). The gradient was as follows: 15% B kept for 1 min, increased to 55% in 0.5 min, then increased to 70% in 4 min, then increased to 80% in 1.5 min, then increased to 100% in 5 min, and then kept at 100% for 2.4 min, finally decreased to 15% in 0.1 min and kept at 15% for 2.5 min. The injection volume was 20 μL, and the flow rate of the mobile phase was 0.4 mL/min. The PFAS was ionized by electrospray ionization (ESI) in negative mode, and MS was operated in multiple reaction monitoring (MRM) mode.

2.4. Method Validation and Quality Assurance/Quality Control

The standards of 27 PFAS and 9 labeled PFAS were spiked into water (n = 4) and then extracted following the aforementioned procedures. The accuracies ranged from 60% to 130% for 22 PFAS, from 34% to 50% for 5 PFAS (i.e., 8:2 FTCA, MeFOSE, MeFOSA, EtFOSA, and EtFOSE), and from 82% to 128% for the 9 labeled PFAS, all with low relative standard deviations (RSDs: 1–14%,). The method detection limits (MDLs) for PFAS were concentrations having a signal-to-noise ratio of 3, which were in the range of 0.01–2.40 ng/L.
PFAS in the samples were identified following these criteria: (1) the signal-to-noise ratio was above 3, (2) the uncertainty of qualifier to quantifier ratio was below 30%, and (3) the retention time shift was within 0.1 min. Blank samples (ultrapure water) were pretreated together with water samples to evaluate background contamination. Several PFAS, such as PFBA, PFPeA, and PFOA, were detected in blank samples at low concentrations, ranging from 0.01 to 0.33 ng/L. For these PFAS, blank-corrected concentrations were reported when the concentration in a sample exceeded the average concentration plus 3 times the standard deviation in the blank samples; otherwise, the PFAS were considered not detected.

2.5. Statistical Data Treatment

Statistical analysis was conducted using R version 4.4.1. Spearman correlations were explored between the detected PFAS with detection frequencies above 50%. To visualize the spatial distribution of the detected PFAS with a heatmap, the concentrations were log-transformed and then normalized between −1 and 1, where −1 represented the lowest or non-detectable concentration, and 1 represented the highest concentration for each PFAS. The Mann–Whitney U Test was applied to compare PFAS concentrations between the nearshore and offshore areas, and the difference was considered statistically significant when the p value was lower than 0.05. For the aforementioned statistical analysis, the non-detectable concentrations of the PFAS were replaced with half the MDLs.

3. Results and Discussion

3.1. Occurrence of PFAS in the Coastal Region

The detection frequencies and concentrations of PFAS in the Ou River and Wenzhou Bay are shown in Table 1 and Figure 2. In this study, 26 of the 74 PFAS were detected in water samples collected from the 23 sampling sites. The detection frequencies (DFs) of these 26 PFAS ranged from 4.3% to 100.0%, with 11 PFAS (i.e., PFBA, PFPeA, PFBS, PFHxA, PFHpA, PFHxS, PFOA, PFHpS, PFNA, PFOS, and HFPO-DA (GenX)) being detected at all the sampling sites. In addition, 6 PFAS were frequently detected with DFs ranging from 56.5% to 91.3%, and the other 9 PFAS had low DFs (<50%). In particular, 6:2 FTSA, 8:2 FTSA, PFMBA, and FOSAA were only detected at one site. Compared with previous studies in nearby areas, including Hangzhou Bay, East China Sea, and Yangtze River Estuary [48,49,50], this study detected more than 10 PFAS that were not reported previously, such as HPFHpA, 6:2 FTSA, 8:2 FTSA, 8:3 FTCA, PFDS, FOSA, PFTrDA, PFTeDA, PFMPA, PFMBA, PFPeS, PFDHA, HFPO-DA (GenX), and FOSAA. This highlights the necessity of expanding the screening scope to understand the status of PFAS pollution [30,33].
Concentrations of the detected PFAS ranged from 0.0018 to 76.31 ng/L, and the concentration of PFOA was the highest at each site, ranging from 13.17 to 76.31 ng/L. The concentrations of PFHxA, PFPeA, PFBS, HPFHpA, PFBA, and PFHpA were also high, and their maximum concentrations were 12.38 ng/L, 10.20 ng/L, 3.22 ng/L, 3.00 ng/L, 2.97 ng/L, and 3.12 ng/L, respectively. In comparison, PFHpS, 8:2 FTSA, FOSA, PFPeS, PFDHA, and FOSAA had low concentrations (mean concentrations: 0.0096–0.052 ng/L). Available data indicate that the studied region has advanced development in industries such as electrical engineering, garment manufacturing, footwear production, pump and valve manufacturing, and the automotive parts industry, suggesting that the presence of PFAS in nearby water bodies is likely closely associated with these industrial activities [28,29].
The correlation between 17 PFAS having DFs above 50% is shown in Figure 3. It can be seen that PFOS, PFNA, PFHpS, PFOA, PFHxS, and PFBA had significant positive correlations with each other (p < 0.05), indicating that they may have common sources and similar environmental behaviors. As typical short-chain PFAS, PFBS, and PFDHA exhibited a significant positive correlation. Notably, PFBS showed significant negative correlations with most PFAS, which are mainly long-chain PFAS. PFDHA was also negatively correlated with most PFAS, but only the correlations with PFPeS, FOSA, PFHpS, and PFHxS were significant. PFDHA is the main component of aqueous film-forming foam (AFFF) used as a firefighting agent [51], while PFBS and its precursor, perfluorobutyl sulfonamido amine, have also been identified in firefighting foams [52]. Therefore, it is highly likely that PFBS and PFDHA may have similar usage patterns in the studied region, potentially reflecting a transition from long-chain to short-chain PFAS usage.

3.2. Spatial Distribution of PFAS in the Coastal Region

The concentrations of PFAS at the 23 sampling sites are shown in Figure 4a. It is noted that PFAS were widely detected in the coastal region, and the total concentrations ranged from 24.14 to 101.66 ng/L. For most of the sampling sites (i.e., S1–S8, S10–S23), the total concentrations of PFAS were comparable (24.14–45.53 ng/L), while S9 had the highest concentration (101.66 ng/L). It is speculated that there were PFAS emission sources near S9, which is located along the coastline of Yueqing City. Known as China’s capital of electrical appliances, Yueqing City has maintained the highest gross domestic product (GDP) in Wenzhou for over 20 years, driven by its diverse and competitive industries, including the production of industrial electrical appliances and electronic components, shipbuilding, garment manufacturing, and automotive parts production. However, these industries may contribute to the emission of PFAS into the environment [28,29]. Further analysis revealed that PFOA was the dominant PFAS at each sampling site (Figure 4b), especially the concentration of PFOA at S9, which was as high as 76.31 ng/L.
The total concentrations of PFAS in the Ou River increased by more than 20 times compared to the data from a study by Lu et al. [49], while concentrations of PFOA, the dominant PFAS both in Lu’s study and our study, increased by a factor of more than 25. This indicates that, with the continuous development and expansion of cities, the impact of human activities on water quality is becoming increasingly apparent.
This study analyzed 15 groups of PFAS in the coastal region, including perfluoroalkyl carboxylic acid (PFCA), perfluoroalkane sulfonic acid (PFSA), fluorotelomer (saturated) carboxylic acids (FTCA), fluorotelomer sulfonic acids (FTSA) and other types (Table S2). The results revealed that PFCA was the main group in the studied area (Figure 4c), accounting for 84.9% to 94.1% of the total PFAS concentrations at the 23 sites. Over the past decades, manufacturers globally have been gradually replacing long-chain PFAS with short-chain PFAS [53]. Some studies have indicated that the contributions of short-chain PFAS to the total PFAS concentrations in the environment are higher than those of long-chain PFAS [5,28,54]. Our results showed that the levels of long-chain PFAS in the coastal region were lower than those of short-chain PFAS at S11 (19.6 vs. 25.9 ng/L) and S13 (18.4 vs. 19.8 ng/L), which are near Xiaomen Island and Damen Island (Figure 1). In contrast, long-chain PFAS were dominant at other sites (Figure 4d), contributing 50.9% to 80.1% of the total PFAS concentrations. This may suggest that the types of PFAS used in this region are still in the process of turnover in general, and island activities may release more short-chain PFAS than long-chain PFAS.
The spatial distribution of 27 PFAS detected in this study is shown in Figure 5. In general, for most PFAS, such as PFOS, PFNA, PFHpS, and PFHxS, the concentrations at nearshore area (S1–S5 and S7–S10) were higher than that in the sea (S6 and S11–S23), which was consistent with previous studies on the South China Sea coastal region, suggesting that PFAS concentrations decreased from the estuaries to the offshore regions due to the dilution effect [29]. Also, most PFAS were detected at S1 and S2 of the Ou River, and their concentrations were relatively higher than at other sites. It is also noted that the concentrations of most PFAS gradually decreased at sampling sites along the direction from the Ou River to the sea, except for S9, which showed abnormally high concentrations of PFAS (Figure 5). This trend revealed that PFAS in Wenzhou Bay may mainly come from the shore, indicating that urban non-point sources and effluent of sewage treatment plants may both play key roles in emitting PFAS to Wenzhou Bay [54,55]. The statistical analysis (Mann–Whitney U Test) showed that the concentrations of 10 PFAS in the nearshore and offshore areas exhibited a significant difference (p < 0.05), including PFBA, PFNA, PFDoDA, PFBS, PFPeS, PFHxS, PFHpS, PFOS, FOSA, and PFDHA, in which only PFBS and PFDHA had higher concentrations in the offshore area (Figure 6). PCA was conducted to further explore the distribution pattern of PFAS across the 23 sampling sites. As shown in Figure 7, PC1 and PC2 explained 30.2% and 20.5% of the total variability in the dataset, respectively. The nearshore sites were primarily clustered on the left side of the plot, while the offshore sites were more scattered on the right side. This suggests that the PFAS profiles at the offshore sites are more consistent than those at the nearshore sites. The broader distribution of the sampling sites and the potential presence of multiple PFAS sources in the nearshore area may account for this difference. Nevertheless, the results revealed that the nearshore and offshore sites were separated in the PCA plot, indicating their distinct characteristics in terms of the PFAS profiles.
The results revealed that 8 PFAS with the highest concentrations were found at S9, including PFBA, PFPeA, PFHxS, PFOA, PFHpS, PFNA, PFOS, and PFMPA (Figure 5). Yueqing City, located near S9, has a developed manufacturing industry that mainly includes electrical appliances, clothing, leather, and small commodities. The high concentrations of PFAS at S9 may be closely related to industrial emissions [28,56,57]. The total concentration of PFAS at S11 was only lower than S9 (Figure 4a), where 4 PFAS (i.e., HPFHpA, PFHxA, PFHpA, and PFMBA) were found to have the highest concentrations compared to other sites (Figure 5). At S4, 4 PFAS (i.e., 8:2 FTSA, PFDS, PFTrDA, and PFTeDA) with the highest concentrations were found (Figure 5), although the total concentration of PFAS at this site was not high (Figure 4). It is worth mentioning that these 4 PFAS were rarely detected at other sites, which suggests that they may be from a potential specific source and might be related to the extensive application of firefighting foams (AFFFs) near the Wenzhou Longwan International Airport [5,28,54], but additional data are necessary for further exploration.
The results also revealed that some PFAS, such as PFBS and PFDHA, exhibited higher concentrations in the offshore area than in the nearshore area (Figure 6). High concentrations of PFBS and PFDHA were usually found near islands, such as at sites S14–S21 near Niyu Island and Dongtou District, with their highest concentrations both occurring at S21 (Figure 1 and Figure 5). This suggests that these 2 PFAS may primarily originate from these islands rather than the shore. It is noted that HPFHpA also had higher concentrations in the offshore area, but they were only detected at S1, S2, S7, and S11 with an increasing trend (Figure 5). It is highly possible that the emission source of HPFHpA was not on the shore but near S11. In the offshore area, the concentrations of PFAS at S14, S15, S19, and S20 were relatively high (Figure 4a). This was possibly due to the presence of a deep-water port near these sampling sites [28], which experiences heavy traffic between Luxi Island and Zhuangyuanao Port. The total concentration of PFAS at S23 in the far sea area of this sampling campaign was not the lowest (Figure 4a), indicating that seawater near the islands has already been contaminated by PFAS. Our results strongly suggest that the distribution of PFAS in Wenzhou Bay was affected by both nearshore and offshore sources, and the islands deserve more attention for their contribution to PFAS pollution in the sea. The environmental impacts of human activities at sea also require greater attention [58]. More comprehensive studies in Wenzhou Bay, focusing on seasonal variations in PFAS distribution, emissions of PFAS from the islands, and the influences of river flow and ocean current directions on PFAS distribution, could provide stronger support for our findings.

3.3. Comparison with Other Studies and Its Implications

A global comparison of the main PFAS in surface water is shown in Table 2. Generally, the PFAS concentrations in Wenzhou Bay were similar to those in the Bohai Sea and Hangzhou Bay in China, as well as Osaka Bay in Japan [34,49,59]. This suggests that pollution sources in these areas may be similar due to industrialization and urbanization. In China’s sea areas, pollution in the northern coastal waters, such as the Bohai Sea and Jiaozhou Bay [34,60], is more severe than in the southern areas, such as Shuidong Bay and the Beibu Gulf [61,62].
Previous studies on coastal areas have found that PFOA concentrations were higher than those of PFOS in most sea areas, except for the United States, Australia, and South Korea [5,63,64,65]. Notably, HPFHpA has not been reported before but was detected at four sites in our study, with concentrations higher than those of most other PFAS, including PFNA, PFDA, PFHxS, PFHpS, and PFOS (Table 1). This indicates the need for more attention to this novel PFAS congener in the future. Additionally, the overall pollution level in remote sea areas, which are less affected by human activities, was generally lower than in nearshore areas [50,66], which is consistent with the results of our study.
Compared to the final recommended aquatic life criteria and benchmarks for select PFAS released by the US EPA in October 2024 [67], PFOA and PFOS concentrations in Wenzhou Bay were much lower than the acute saltwater aquatic life benchmarks (7.0 mg/L and 0.55 mg/L, respectively). While chronic saltwater aquatic life benchmarks have not been provided, a comparison with the chronic freshwater ones (0.10 mg/L and 0.00025 mg/L, respectively) suggests that PFOA and PFOS are unlikely to pose high threats to marine life in Wenzhou Bay. However, the potential risks posed by PFAS in the studied region still deserve significant attention, as domestic and international regulatory limits for most PFAS are not yet available for comprehensive risk assessments, and multiple PFAS, including some novel compounds, were detected for the first time in this region.
Our findings highlight the urgent need to expand surveillance frameworks to include novel PFAS compounds and to implement stricter controls on PFAS emissions. Additionally, our research supports broader efforts to enhance chemical management at both domestic and international levels, providing valuable data to policy makers and relevant stakeholders.
Table 2. Concentrations of PFAS in coastal water from Wenzhou Bay and other coastal areas around the world (ng/L).
Table 2. Concentrations of PFAS in coastal water from Wenzhou Bay and other coastal areas around the world (ng/L).
CountryAreaPFAS SpeciesPFOAPFHxAPFPeAPFBSHPFHpAPFBAPFHpAPFOSReferences
USBiscayne Bay300.29–5.810.29–5.810.63–6.180.4–2.2NA0.68–3.160.48–4.61.16–46.98[5]
AustraliaSydney Harbour134.2–6.42.8–3.2NA1.2–1.5NANA1.4–2.07.5–21[65]
JapanOsaka Bay150.31–70.43–370.48–1.30.76NA1.2–1.80.38–20.89–1.3[59]
Koreaalong the Korean coasts250.21–16.5<0.04–2.18<0.2–2.20<0.04–3.87NANA<0.1–1.50<0.04–1.92[35]
KoreaWest coast120.54–31NANA<0.2–16NANA<1.0–1100.35–47[63]
KoreaWest coast122.95–68.6ND–47.0NAND–39.8NAND–9.55ND–47.24.11–450[64]
ChinaThe entire coastal line12ND–423ND–41.7ND–37.7ND–575NA0.34–283ND–44.4ND–56.0[48]
ChinaBohai Sea213.64–6290.58–11.51.70–8.940.610–30.9NA3.58–18.20.73–10.420.951–14.3[34]
ChinaBohai Sea292.3–1060.40–4.00.31–3.00.12–0.28NA0.15–1.50.19–2.2<0.03–0.12[50]
Yellow Sea290.89–140.16–0.960.12–1.2<0.04–0.22NA<0.05–0.660.06–0.45<0.03–0.11[50]
Yangtze River Estuary290.98–6.90.20–1.40.12–1.30.11–0.94NA0.09–0.500.07–0.23<0.03–0.20[50]
ChinaJiaozhou Bay14<1.0–28.72ND–3.13<1.5<0.8NAND–2.04ND–3.76ND–14.55[60]
Chinacoastal tourist resorts in Shandong Peninsula170.34–23.40.18–11.80.22–15.20.48–3.59NA2.98–43.70.0089–8.552.26–24.5[66]
ChinaHangzhou Bay174525NANANANANA1.0[49]
ChinaShuidong Bay230.32–0.490.16–0.420.18–0.610.27–2.18NA0.91–2.490.17–0.600.077–0.21[61]
ChinaBeibu Gulf180.23–0.840.09–1.000.12–2.970.14–0.56NA0.34–1.300.11–0.35ND–0.37[62]
ChinaWenzhou Bay7413.17–76.312.71–12.382.23–10.201.23–3.22 0.93–2.990.76–2.970.56–3.120.23–2.23This study

4. Conclusions

A target analysis method was applied to study the occurrence and distribution of 74 PFAS in Wenzhou Bay, China, and the findings indicated widespread PFAS pollution. Of the 26 detected PFAS, 11 had a detection frequency of 100.0%. Notably, PFOA was the dominant PFAS congener, with relatively high concentrations observed for other congeners such as PFHxA, PFPeA, PFBS, and HPFHpA. This study revealed that PFBS and PFDHA were negatively correlated with other PFAS, while a significant positive correlation was observed between them. The total concentration of PFAS at the 23 sampling sites ranged from 24.14 to 101.66 ng/L. Notably, the sampling site S9, near a highly developed industrial city, was the most severely polluted site, with eight PFAS having the highest concentrations. The total PFAS concentrations at the other sampling sites fell within a similar range, but the composition of pollutants varied. Long-chain PFAS concentrations were lower than short-chain PFAS at S11 and S13 but were dominant at the other 21 sites, suggesting the types of PFAS used in this region may still be transitioning from short-chain to long-chain PFAS. Most pollutants, such as PFOS and PFNA, exhibited higher concentrations near the shore compared to the sea, while PFBS and PFDHA had higher concentrations in the sea than near the shore. Our study indicates a substantial contribution of human activities on islands to PFAS pollution, emphasizing the necessity for pollution evaluation and control on islands in the future.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/w17020149/s1, Table S1: Descriptions of sampling information in Wenzhou Bay, including location, area, date and time; Table S2: Information on the 74 PFAS analyzed in this study.

Author Contributions

Conceptualization, C.C., Y.W. and H.Z.; Methodology, C.C., Y.W., F.C., X.W. and Q.Z.; Investigation, F.C., X.W., Q.Z. and J.S.; Resources, Q.C.; Writing—original draft, C.C. and Y.W.; Writing—review & editing, S.L. and H.Z.; Visualization, H.Z.; Supervision, H.Z.; Funding acquisition, C.C., Y.W., F.S. and H.Z. All authors have read and agreed to the published version of the manuscript.

Funding

This work was supported by a Research Plan Project from PowerChina Eco-environmental Group Co., Ltd. (Grant No. KYZB2022Z003), the Shenzhen Sustainable Development Project (Grant No. KCXFZ20201221173413037), the Natural Science Foundation of Sichuan Province, China (Grant No. 23NSFSC1019), and the Core Technology Research Project from Power Construction Corporation of China (Grant No. DJ-HXGG-2022-09).

Data Availability Statement

The original contributions presented in this study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.

Conflicts of Interest

Authors Chenyu Chen, Jialong Sun and Fangze Shang were employed by the company PowerChina Eco-Environmental Group Co., Ltd., authors Ying Wang, Fei Chen and Jialong Sun were employed by the company VAST Institute of Water Ecology and Environment, and author Qiang Chen was employed by the company PowerChina Lingkun Intelligent Creation City Ecological Construction and Development (Wenzhou) Co., Ltd. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Water 17 00149 g001
Figure 1. Sampling sites in the Ou River (S1 and S2) and Wenzhou Bay (S3–S23), Zhejiang Province, China.
Figure 1. Sampling sites in the Ou River (S1 and S2) and Wenzhou Bay (S3–S23), Zhejiang Province, China.
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Water 17 00149 g002
Figure 2. PFAS concentrations in the surface water samples from the Ou River and Wenzhou Bay. Median (the middle line), minimum, and maximum values, excluding outliers (upper and lower whiskers), are shown in the boxplots. The black dots represent outliers. The blue dots represent PFAS concentrations at the sampling sites.
Figure 2. PFAS concentrations in the surface water samples from the Ou River and Wenzhou Bay. Median (the middle line), minimum, and maximum values, excluding outliers (upper and lower whiskers), are shown in the boxplots. The black dots represent outliers. The blue dots represent PFAS concentrations at the sampling sites.
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Water 17 00149 g003
Figure 3. Correlations between 17 PFAS detected with high detection frequency (>50%). *: p < 0.05, **: p < 0.01, ***: p < 0.001.
Figure 3. Correlations between 17 PFAS detected with high detection frequency (>50%). *: p < 0.05, **: p < 0.01, ***: p < 0.001.
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Water 17 00149 g004
Figure 4. Spatial distribution of PFAS at the 23 sampling sites. (a) Concentration profiles of individual PFAS; (b) concentration percentages of PFAS; (c) contributions of PFCA and other groups; and (d) contributions of long-chain and short-chain PFAS.
Figure 4. Spatial distribution of PFAS at the 23 sampling sites. (a) Concentration profiles of individual PFAS; (b) concentration percentages of PFAS; (c) contributions of PFCA and other groups; and (d) contributions of long-chain and short-chain PFAS.
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Water 17 00149 g005
Figure 5. Distribution of detected PFAS at the 23 sampling sites (data are normalized between −1.0 and 1.0).
Figure 5. Distribution of detected PFAS at the 23 sampling sites (data are normalized between −1.0 and 1.0).
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Water 17 00149 g006
Figure 6. Concentrations of the 10 PFAS showing significant differences (p < 0.05) between nearshore and offshore sites.
Figure 6. Concentrations of the 10 PFAS showing significant differences (p < 0.05) between nearshore and offshore sites.
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Water 17 00149 g007
Figure 7. PCA plot of the 23 sampling sites based on the detected PFAS.
Figure 7. PCA plot of the 23 sampling sites based on the detected PFAS.
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Table 1. Detection frequencies and concentrations of the detected PFAS.
Table 1. Detection frequencies and concentrations of the detected PFAS.
PFASDetection Frequencies (%)Minimum Concentration
(ng/L)		Maximum Concentration
(ng/L)		Mean Concentration
(ng/L)		Standard Deviation
(ng/L)
PFBA100.00.76192.96591.52010.49
PFPeA100.02.234510.20463.28221.67
HPFHpA17.40.92842.98881.77310.89
PFHxA100.02.712012.38164.72032.37
PFHpA100.00.55693.11811.12420.67
PFOA100.013.166576.312519.006212.67
PFNA100.00.40741.39830.75010.31
PFDA91.30.09710.44730.21440.10
PFDoDA56.50.02790.36520.12030.11
PFTrDA34.80.09990.63950.26270.18
PFTeDA26.10.11310.49570.26330.14
PFBS100.01.22623.21662.60720.49
PFHxS100.00.14270.53810.25320.086
PFHpS100.00.01290.13340.03750.027
PFOS100.00.22752.23380.81910.50
PFDS8.70.10750.12830.11790.015
PFPeS65.20.01110.06670.03780.018
FOSA69.60.01040.16580.05180.053
FOSAA4.30.03780.03780.0378-
8:3 FTCA73.90.04170.61780.26330.17
6:2 FTSA4.30.39500.39500.3950-
8:2 FTSA4.30.03230.03230.0323-
PFMPA8.70.07660.07710.07680.00033
PFMBA4.30.20480.20480.2048-
PFDHA95.70.00180.01470.00960.0036
HFPO-DA (GenX)100.00.02160.49900.10590.10
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Chen, C.; Wang, Y.; Chen, F.; Wang, X.; Zhang, Q.; Sun, J.; Li, S.; Chen, Q.; Shang, F.; Zhang, H. Comprehensive Assessment of Per- and Polyfluoroalkyl Substances (PFAS) Pollution in a Coastal Region: Contributions from Nearshore and Offshore Sources. Water 2025, 17, 149. https://doi.org/10.3390/w17020149

AMA Style

Chen C, Wang Y, Chen F, Wang X, Zhang Q, Sun J, Li S, Chen Q, Shang F, Zhang H. Comprehensive Assessment of Per- and Polyfluoroalkyl Substances (PFAS) Pollution in a Coastal Region: Contributions from Nearshore and Offshore Sources. Water. 2025; 17(2):149. https://doi.org/10.3390/w17020149

Chicago/Turabian Style

Chen, Chenyu, Ying Wang, Fei Chen, Xinyue Wang, Qiao Zhang, Jialong Sun, Si Li, Qiang Chen, Fangze Shang, and Hui Zhang. 2025. "Comprehensive Assessment of Per- and Polyfluoroalkyl Substances (PFAS) Pollution in a Coastal Region: Contributions from Nearshore and Offshore Sources" Water 17, no. 2: 149. https://doi.org/10.3390/w17020149

APA Style

Chen, C., Wang, Y., Chen, F., Wang, X., Zhang, Q., Sun, J., Li, S., Chen, Q., Shang, F., & Zhang, H. (2025). Comprehensive Assessment of Per- and Polyfluoroalkyl Substances (PFAS) Pollution in a Coastal Region: Contributions from Nearshore and Offshore Sources. Water, 17(2), 149. https://doi.org/10.3390/w17020149

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