Distribution and seasonal variations of perfluoroalkyl substances (PFAS) in streams within the Changwon region
Article information
Abstract
This study investigates the distribution and seasonal variations of Poly- and Perfluoroalkyl Substances (PFAS) concentrations in local streams within the Changwon area, aiming to quantify the total PFAS load entering Masan Bay. Using solid-phase extraction (SPE) cartridges for pretreatment, we analyzed 36 types of Perfluorinated carboxylic acids (PFCAs), Perfluorinated sulfonates (PFSAs), and precursor compounds via liquid chromatography-high resolution mass spectrometry (LC-HRMS). The study observed varying concentration levels across different streams, with notable detections of Perfluorohexanoic acid (PFHxA), Perfluorooctanoic acid (PFOA), Perfluorobutanesulfonic acid (PFBS), Perfluoropentanoic acid (PFPeA), and Perfluoroheptanoic acid (PFHpA) at quantifiable levels. Except for the Sogye Stream (SGC), PFCA-based compounds comprised over 50% of the total PFAS detected, predominantly featuring shorter-chain compounds with fewer than eight carbon atoms. Seasonal trends indicated that PFAS concentrations were lowest during the high rainfall period in summer and peaked in winter and spring. The Nam Stream (NC) contributed the highest PFAS inflow into Masan Bay, attributed to its elevated flow rates, while Sum B had high concentrations but lower emissions due to its limited flow. The total annual PFAS discharge was estimated at 1.9 kg. These findings highlight the urgent need for targeted management and comprehensive countermeasures to protect environmental health.
Abstract
Graphical Abstract
1. Introduction
Rapid industrial growth and the evolution of chemical materials used on the daily basis have led to the proliferation of compounds that can have devastating effects on ecosystems. Some of these pollutants are toxic, persistent, bioaccumulative, and capable of long-distance transport, known as Persistent organic pollutants (POPs), remaining in ecosystems for extended periods and causing significant damage. Poly- and Perfluoroalkyl Substances (PFAS), a class of POPs, have been widely used in both daily life and industrial applications over the past 70 years. As a result, PFAS are now ubiquitous in aquatic environments, posing serious threats to wildlife by adversely affecting developmental, immune, metabolic, and endocrine systems. PFAS are characterized by carbon-fluorine bonds, where one or more carbon-hydrogen bonds in a hydrocarbon are replaced with carbon-fluorine bonds, typically forming when a carboxylic or sulfonic acid group is attached to the hydrocarbon’s charged portion.
PFAS are non-flammable at high temperatures and resistant to decomposition by strong acids, strong alkalis, and oxidizing agents, and hardly undergo photolysis [1]. Their low polarizability and high ionization potential result in low surface tension and minimal intermolecular and intramolecular interactions [2]. Due to its hydrophobic and hydrophilic properties, it is used as a surfactant and lubricant in paper products, polishes, food packaging, and digestive agents across various industrial and commercial applications [2–4]. Unlike conventional POPs, it exhibits high water solubility and low octanol-air distribution coefficient (Koa) [5], which lasts more in water than in gas or solid phases.
Human biomonitoring of PFAS began globally in 2000 [6], leading to the detection of compounds such as Perfluorooctanesulfonamide (PFOSA), Perfluorononanoic acid (PFNA), and Perfluorodecanoic acid (PFDA) in human tissues. Once these compounds enter the human body, typically through food consumption or respiratory exposure, they tend to accumulate in serum and liver due to their limited excretion via urine or feces. Moreover, PFASs are non-biodegradable, which contributes to their significant environmental accumulation. For example, PFOS has a half-life of 8.76 years, while PFOA has a half-life of 3.5 years. PFAS have been detected in the livers and blood of various vertebrates worldwide. Considerable concentrations of PFAS have been found in the livers of fish-eating animals near industrialized areas [7]. The detection of PFAS in the Arctic suggests a global spread, even affecting non-industrialized areas, with significant environmental impacts [8].
According to the 2018 World Aquaculture Status report, South Korea is the 14th largest fish producer globally, with an annual production of approximately 3.3 million tons. By 2019, the per-capita- seafood-consumption in South Korea was projected to reach 70 kg per year, surpassing that of many other countries, including Japan and France [9]. Studies have detected PFOA and PFOS in all blood and liver samples of oysters and fish collected off the coasts of Taiwan and Japan [10,11]. In Masan Bay, Korea, a semi-enclosed area with limited seawater exchange, restricted water flow intensifies pollutant buildup, significantly threatening local fisheries and aquaculture. On Korea west coast, concerning PFAS concentrations have been recorded, reaching several hundred ng/L in some cases, indicating substantial contamination of surrounding waters [12].
Currently, PFAS research in Korea has been focused on measuring the concentrations in the environment, particularly in streams and rivers. PFOA and PFOS have been detected in the waters and sediments of the Han, Geum, Yeongsan, and Nakdong River [13,14]. In the Nakdong River, PFAS concentrations are higher in tributaries or in the receiving waters of wastewater treatment plants (WWTPs) compared to the mainstream, suggesting that PFAS are predominantly discharged through wastewater effluents [2]. According to domestic data from 2020, 13 types of PFAS were still being discharged from industries domains or transferred to outsourced treatment facilities [15]. However, most research have focused on measuring PFAS concentrations near sewage treatment plants in large rivers or urbanized areas, leaving a gap in comprehensive studies on the overall influx of these contaminants into the ocean.
This study aims to measure the distribution and concentration of PFAS in small streams within the Changwon and Masan areas, regions characterized by dense residential and industrial activity. Additionally, we aim to profile the specific types of PFAS in each stream and monitor their seasonal variations. By integrating PFAS concentration data with water flow measurements, we estimate the total PFAS load entering Masan Bay and assess the potential environmental risks.
2. Materials and Methods
2.1. Sample Collection
Samples were collected from 14 streams in total in Changwon and Masan area. The details of the streams are shown in Table 1. Since the 1970s, Changwon has developed as an industrial hub with facilities for machinery, electronics, and petrochemicals. In contrast, Masan, originally a port city, has transitioned into a residential and trade-focused area, particularly within the Masan Free Trade Zone. Due to these developments, industrial wastewater primarily flows into Changwon’s streams, while Masan’s streams receive domestic sewage. Between October 2021 and May 2023, we collected 280 samples from these 14 streams. To avoid sample contamination, we used sterile polypropylene (PP) bottles for PFAS collection, as glass bottles can cause sample losses [16]. Detailed sampling locations are shown in Fig. 1 below.
Descriptions of sampling site
River brunch in Changwon and Masan area.
2.2. Reference Standards Material
2.2.1. Reference standards for target chemicals
The standard solution used in the study included substances from both the PFCA and PFSA families. The PFCA family consisted of 13 compounds Perfluorobutanoic acid (PFBA), PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, Perfluoroundecanoic acid (PFUnDA), Perfluorododecanoic acid (PFDoDA), Perfluorotridecanoic acid (PFTrDA), Perfluorotetradecanoic acid (PFTeDA), PFHxA and Perfluorooctadecanoic acid (PFOcDA). The PFSA family included PFBS, Perfluorohexanesulfonic acid (PFHxS), PFOS, Perfluoropentanesulfonic acid (PFPeS), Perfluoroheptanesulfonic acid (PFHpS), Perfluorononanesulfonic acid (PFNS), Perfluorodecanesulfonic acid (PFDS), and Perfluorododecanesulfonic acid (PFDoDS). Additionally, the solution contained various precursor compounds, such as 3:3 FTCA (FPrPA), 5:3 FTCA (FPePA), 6:2 FTUCA (FHUEA), 6:2 FTCA (FHEA), 6:2 PAP, FOSA, 7:3 FTCA (FHpPA), 8:2 FTUCA (FOUEA), 8:2 FTCA (FOEA), 8:2 PAP, FOSAA, n-MeFOSAA, N-EtFOSAA, 10:2 FTUCA (FDUEA), and 6:2 diPAP, along with 15 other precursors.
2.2.2. Internal standards
The internal standards used in this study were MPFHxA-[13]C2 (Perfluoro-n-[1,2,-13C2]hexanoic acid), MPFHxS-[18]O2 (Sodium perfluoro-1-hexane[18O2]sulfonate), MPFOA-[13]C4 (Perfluoro-n-[1,2,3,4-13C4] octanoic acid), and MPFOS-[13]C4 (Sodium perfluoro-1-[1,2,3,4-13C4]octane sulfonate). Detailed information on the standard and internal standard materials is provided in Table 2.
Standard materials and internal standard materials
2.3. Sample Preparation Methods
Various solid phase extraction methods exist for the extraction of the target substances used in LC-MS analysis, among which the method proposed by EDWAG was used for pretreatment. The cartridges used for the pretreatment were prepared using HLB sorbent (200 mg), Strata-XCW (100 mg) and Strata-XAW (100 mg). Pretreatment was performed as follows. Filter 1 L sample through a 0.7 μm GF/F filter, add 80 μL of Citrate buffer (pH 7) and 100 μL of internal standard, and flow through the SPE cartridge at a rate of 10 to 15 mL/min. The SPE cartridge through which the material passed was dried by blowing nitrogen gas and extracted using an alkaline (ethylacetate: methanol=50: 50 + 0.5% ammonia) and acidic (ethylacetate: methanol=50: 50 + 1.7% formic acid) solution. The extraction solution was again concentrated under nitrogen gas and finalized using a 9:1 ratio of water and methanol solvent to a final volume of 1 mL. A detailed schematic diagram is shown in Fig. S1 in the supplementary materials.
2.4. Instrument Analysis Conditions
The instrumentation used to analyze PFAS in the samples included a Thermo Fisher Scientific U 3000 with UHPLC-ESI-HRMS and Q Exactive + Orbitrap mass spectrometry (Thermo Fisher Scientific, Waltham, USA). The column used was an Xbridge C18 column (3.5 μm, 2.1 x 50 mm; Waters, Milford, USA). Distilled water and methanol supplemented with 10% ammonium acetate were used as mobile phases. The initial ratio of 90% water to 10% methanol was increased to 95% methanol, and then returned to a final ratio of 90% water to 10% methanol. The injection volume was 10 μL, and the flow rate was 0.2 mL/min. The conditions of the instrumental analysis are detailed in Table 3.
LC and HRMS instrument analysis conditions
3. Results and Discussion
3.1. PFAS Concentrations
The analysis included 21 PFAS and 15 precursor compounds, primarily from the PFCA family (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, and PFDA) and five PFSA families (PFBS, PFPeS, PFHxS, PFHpS, and PFOS). The average concentrations for each substance were as follows: PFBA, 3.54 ng/L; PFPeA, 6.27 ng/L; PFHxA, 12.62 ng/L; PFHpA, 3.93 ng/L; PFOA, 11.73 ng/L; PFNA, 0.56 ng/L; PFDA, 0.003 ng/L; PFBS, 5.60 ng/L; PFPeS, 0.39 ng/L; PFHxS, 3.62 ng/L; PFHpS, 0.16 ng/L; and PFOS, 6.42 ng/L. The concentration ranges observed were 0.00 to 43.25 ng/L for PFAS, 0.00 to 21.80 ng/L for PFCA, and 0.00 to 43.25 ng/L for PFSA. Detailed data are provided in the supplementary materials, as shown in Fig. S2.
In comparison, a 2018 study also found PFOA to be the dominant PFAS component in Masan Bay, with long-chain PFAS present at very low levels. Significant proportions of PFHxS (31%), PFHpA (17%), and PFOA (23%)—all compounds with four to eight carbon atoms—were detected, with an overall average concentration of over 23%. The total PFAS concentration ranged from 1.92 to 7.67 ng/L, with an average of 4.90 ng/L. Compared to the current study, these previous findings show a difference ranging from at least 2 times to approximately 60 times higher.
PFAS were detected in all 14 streams studied, with the highest concentration observed in SGC, followed by YDC, SNHC, HWC, and CWC. In contrast, JGC exhibited the lowest PFAS concentration, which was over five times lower than that in SGC. These findings are visually represented in Fig. 2, where a pie chart indicates detection levels, and a bar chart on the right illustrates the substances using different colors. Over the one year and five months measurement period, PFAS concentrations in the streams remained relatively stable, with fluctuations generally within ±10% of the average concentration for each substance, except for a significant spike at SGC between February and April 2022. In addition to the 12 commonly observed substances (PFBA, PFPeA, PFHxA, PFHpA, PFOA, PFNA, PFDA, PFBS, PFPeS, PFHxS, PFHpS, and PFOS), 8:2 FTUCA was detected in JGC in January 2022, and the long-chain PFDA was detected in KBC in March 2023. However, 8:2 FTUCA, being a precursor, was converted into other substances and did not maintain its concentration. PFDA was detected intermittently, averaging 0.02 ng/L, and thus had a negligible impact.
Average percentage distribution of PFAS by river.
From October 2021 to May 2023, PFAS was consistently detected at all sites without significant fluctuations in concentration, suggesting a continuous source of contamination over time. Interestingly, PFAS levels in rivers within the residential Masan area were generally higher than those in the commercial Changwon area, except for SGC. This anomaly can likely be attributed to the widespread use of PFAS in household products, such as water repellents, kitchenware, and disposable container coatings [17]. The elevated PFAS levels at the SGC may be linked to the presence of nearby industries, including mechanical equipment manufacturing, automobile parts production, electronic components, and metal surface processing, all within a 2 km radius. This observation aligns with previous studies, which have shown that various industries, beyond just semiconductor and display manufacturing, contribute significantly to PFAS contamination [15]. Among the detected compounds, PFOS and PFBS were the most prevalent. Their dominance is likely due to their application in metal plating and as coatings for film, paper printing, and their use as PFOS substitutes, chosen for their comparatively lower toxicity and persistence [17].
The most frequently detected PFAS compounds were PFHxA, PFOA, PFBS, PFPeA, and PFHpA. These compounds dominated in most streams, with PFCAs being more prevalent than PFSAs. Specifically, PFHxA, PFOA, and PFPeA together constituted over 50% of the total PFAS content. In contrast, SGC had the highest concentration of PFOS and the combined percentages of PFHxA, PFOA, and PFPeA were less than 50%. Among the detected substances, PFDA and PFPeS appeared at very low concentrations. Typically, compounds with fewer than eight carbon atoms were predominant in both the PFCA and PFSA families. Notably, within the PFSA family, compounds with even numbers of carbon atoms were more prevalent. This distribution is consistent with findings from other industrialized regions, such as Las Vegas Wash, where PFCAs also dominated over PFSAs, and short-chain PFAS (fewer than eight carbon atoms) were more frequently detected than long-chain PFAS [18]. This suggests that PFAS distribution trends in streams within industrialized areas are comparable across different geographic locations.
In Korea, high concentrations of PFOA and PFOS were found in both the mainstream and tributaries of the Nakdong River. PFOA in the Han River ranged up to approximately 37 ng/L, while PFOS ranged to about 67 ng/L. These compounds were detected in nearly 98–99% of streams in major river systems, aligning with the levels seen in Changwon [2,13,14]. Seasonal analysis of PFAS concentrations from December 2021 to May 2023, segmented into spring (March to May), summer (June to August), fall (September to November), and winter (December to February), revealed higher concentrations in winter and spring and lower in summer. This pattern likely reflects variations in rainfall, with winter and spring experiencing average daily rainfall of 205.0 mm/day, compared to summer’s higher rainfall of 586.5 mm/day, which leads to dilution effects. This seasonal trend is illustrated in Fig. 3.
Seasonal concentration and precipitation.
3.2. Total Load of PFAS Entering Masan Bay
The average PFAS load delivered by each stream was estimated by multiplying the stream’s average PFAS concentration by its flow rate. This approach allowed for the calculation of daily, monthly, and annual PFAS discharges into Masan Bay. Of the 14 streams studied, eight were selected for detailed analysis: three in the Changwon area (CWC, NC, and NDC) and five in the Masan area (SMHC, SNHC, YDC, HWC, and KBC). For SNHC, SMHC, and YDC, discharges were measured at their confluence (Sum A), as these tributaries merge into a single stream. Similarly, the confluence of KBC and HWC (Sum B) was used for assessment.
In instances where flow data were unavailable (December 2022, January, and February 2023), average flow rates were used for the calculations. The results indicated that CWC and NC, the largest streams in the Changwon area, contributed the highest PFAS loads, followed by Sum A, NDC, Sum B, and JGC. These findings are presented in detail in Table 4.
Changwon on monthly flow rate
The average daily discharge of PFAS from each monitoring point was as follows: 723.5 mg/day (PFCA: 547.7 mg/day, PFSA: 175.9 mg/day) for Changwon, 1,725.5 mg/day (PFCA: 1,293.5 mg/day, PFSA: 432.0 mg/day) for Sum A, 43.8 mg/day (PFCA: 33.7 mg/day, PFSA: 10.1 mg/day) for Janggun, 2,324.1 mg/day (PFCA: 1,772.4 mg/day, PFSA: 551.7 mg/day) for Nam, 162.9 mg/day (PFCA: 112.7 mg/day, PFSA: 50.2 mg/day) for Naedong, and 431.6 mg/day (PFCA: 326.9 mg/day, PFSA: 104.7 mg/day) for Sum B.
When considering total PFAS emissions, streams such as NC, Sum A, CWC, NDC, and JGC consistently ranked high or low depending on both concentration and flow rate. However, Sum B, despite having a high PFAS concentration, exhibited a lower overall ranking due to its reduced flow rate. The industrial complex near NC is a significant contributor to PFAS emissions. Although other sites may show smaller relative emissions, the high flow rate at NC results in the highest daily PFAS discharge among all measured locations. These findings highlight the critical need for thorough investigation and regulation of PFAS emissions from industrial areas, as substantial amounts can enter marine environments. The results are visually represented in Fig. 4.
Average daily outflow in Changwon area.
To estimate the average annual PFAS load entering Masan Bay, we extrapolated the average daily discharge rates for each stream over a year, assuming a 12-month period. The calculated annual discharge rates are as follows: CWC: 260.5 g/year, Sum A: 621.2 g/year, JGC: 5.3 g/year, NC: 836.7 g/year, NDC: 11.4 g/year, and Sum B: 155.4 g/year. Consequently, the total estimated PFAS discharge into Masan Bay is approximately 1,108.6 g/year from the Changwon area and 781.9 g/year from the Masan area.
In Tokyo Bay, a similarly urbanized coastal region, surface seawater samples have shown PFOA concentrations ranging from 1.8 to 192.0 ng/L and PFOS concentrations from 0.4 to 57.7 ng/L. Off the coast of Taiwan, PFBS has been detected in relatively high concentrations, ranging from 130 to 920 ng/L. Globally, PFOS and PFOA are prevalent in coastal waters of the Pacific and Atlantic Oceans and across various Asian countries [11,19]. Given the estimated 2 grams per year of PFAS flowing from Changwon into Masan Bay, it is plausible that PFAS contamination is already present in the surrounding waters of Korea.
PFAS tend to bioaccumulate in marine life due to their persistent nature and slow elimination rates. They often concentrate in the liver, blood, and gallbladder of fish, with shorter-chain PFAS being more readily absorbed through gills compared to their long-chain counterparts [16,20]. PFAS have been detected in the blood and liver of fish in Tokyo Bay, Japan, and in oysters and fish off the coast of Taiwan, with concentrations ranging from 110 to 350 ng/g (dry weight) for PFOA, PFOS, and PFDA. This contamination extends to higher trophic levels; PFOS has been found in the blood of herring gulls near Fukkai Island, likely due to their fish-based diet [21].
PFAS exhibit strong protein-binding properties and are known to accumulate in the bodies of aquatic animals, often reaching higher concentrations than those found in the environment [2]. In Korea, between 1994 and 2008, PFOS levels in women’s serum remained steady, despite a reduction in PFOS production by 3M. Conversely, PFOA levels increased, with average PFOS concentrations at 8.43 ng/mL and PFOA at 3.48 ng/mL in 2007–2008 [22]. For individuals consuming fish and shellfish, the presence of PFAS in seawater poses a significant health risk due to bioaccumulation. This is particularly concerning for communities reliant on aquaculture or fishing, where the potential for PFAS exposure through diet is elevated.
4. Conclusions
In this study, we analyzed 21 perfluorinated compounds and 15 precursors across streams in the Changwon and Masan areas, identifying the presence of 12 key perfluorinated compounds. Notably, except for SGC Stream, PFCA-based substances constituted nearly 50% of the total detected compounds, significantly surpassing PFSA-based substances. The predominant compounds were PFOA and PFHxA, with PFOS showing the highest concentration among the PFSA congeners.
In most streams, PFCA-based substances, such as PFOA and PFHxA, were more prevalent than PFSA-based substances. However, SGC Stream displayed a unique profile with elevated concentrations of PFOS, a PFSA. While no clear seasonal trends in PFAS concentrations were observed across the streams, streams with higher flow rates emerged as major contributors to pollutant loads in Masan Bay. This is particularly evident for NC (Nam Stream), which, despite not having the highest PFAS concentration, contributed over 75% of the total annual PFAS discharge due to its elevated flow rate. This highlights the critical role of NC and CWC in the overall pollutant load entering Masan Bay.
Given the persistent presence and increasing concentrations of perfluorinated compounds, especially in high-flow streams, it is essential to implement continuous and comprehensive monitoring of PFAS in both major and regional rivers. This will aid in understanding their environmental impact and potential health risks. In conclusion, this study emphasizes the need to address PFAS contamination in the Changwon and Masan areas, with a particular focus on high-flow streams that significantly contribute to Masan Bay’s pollutant load. Establishing a robust monitoring and management system is crucial to mitigating both long-term and ongoing impacts.
Supplementary Information
Acknowledgments
This research was supported by Changwon National University in 2023~2024.
Notes
Conflict-of-Interest Statement
The authors declare that they have no conflict of interest.
Author Contributions
C.R.J. (Master student) conducted all the experiments and wrote the manuscript. H.W.J. (PhD student) conducted all the experiments. J.H.J. (Professor) supervised and revised the edited manuscript.