First report of perfluoroalkyl acids (PFAAs) in the Indus Drainage System: Occurrence, source and environmental risk

Characterization of per- and polyfluoroalkyl substances (PFASs) in Chinese river and lake sediments

Sediment pollution by per- and polyfluoroalkyl substances (PFASs) is an emerging environmental concern with far-reaching implications, attracting considerable public, scientific and regulatory attention. This study analyzed 72 articles published since 2010 to assess the accumulation, sources, spatiotemporal trends, and contributing factors of PFAS pollution in surface sediments across China. The total concentrations of PFASs at the reviewed sites ranged from 0.001 to 10700 ng/g, with the maximum concentration detected in the Xiaoqing River, Shandong province. Excluding the Xiaoqing River, the mean total PFAS concentrations at other sites were below 200 ng/g. Although long-chain PFASs have been frequently associated with sediment phases due to their hydrophobicity, short-chain legacy and emerging PFASs also exhibited high concentrations, often being the dominant analytes at several sites because of their significant partition coefficients in sediments of China. Fluorochemical industries were identified as the most significant contributors to sediment PFAS accumulation, with concentrations up to ten times higher than those in areas affected by other sources. Risk assessments revealed differing outcomes based on chronic and acute toxicological data. Acute data indicated high ecological risks to aquatic organisms-including daphnids, green algae, mysids, and fish-from long-chain PFCAs and PFOS exposure at up to 19 sites. In contrast, chronic data derived from SSD for PFOS and PFOA, considering the maximum concentrations found across sites, suggested high chronic risks at only 1 and 4 sites, respectively. These findings, combined with the widespread occurrence of fluorochemical industries and the adsorption and bioaccumulative behavior of legacy and emerging PFASs in sediments, underscore the need for expanded assessments in underrepresented regions of China to comprehensively evaluate ecological and human health risks.

A global review on perfluoroalkyl acids (PFAAs) in the riverine systems: Environmental behaviours and risks implications

This review provides a comprehensive global overview of the occurrences, distribution, emissions, and associated risks of perfluoroalkyl acids (PFAAs) in riverine systems across both developed and developing countries including the United States (US), Spain, France, Netherlands, Germany, Pakistan, China, Korea, Vietnam, Italy, and Japan. Data for this review were systematically gathered through a comprehensive and structured search process using various databases, search engines, and academic repositories to identify relevant literature and studies. Human health risks were assessed using recommended United States Environmental Protection Agency (USEPA) models, including estimated daily intake (EDI), hazard risk (HR), and hazard index (HI) for each reported PFAA compound in the studied countries. The overall results revealed significant variability in PFAAs contamination from the 1950s to 2023, reflecting extensive industrial usage and increasing environmental concerns, with levels often exceeding the permissible limits set by environmental quality standards established by national or international regulatory authorities, agencies, and organizations. Among the studied countries, Italy exhibited the highest average sum of PFAA compounds (∑PFAAs) concentration in riverine water, ranging from 4.07 to 140.61 ng/L, with an average of 41.37 ng/L, followed by the Netherlands, China, Japan, the US, Pakistan, Spain, France, Germany, Korea, and Vietnam. Similarly, Germany showed the highest average ∑PFAAs concentration in riverine sediments, ranging from 40.25 to 213.00 ng/g, with an average of 126.63 ng/g, followed by China, Spain, the US, Pakistan, Vietnam, and Korea. Whereas, in riverine fish, Spain had the highest average ∑PFAAs concentration, ranging from 0.05 to 144.97 ng/g, with a mean of 15.94 ng/g, followed by Korea, Vietnam, and the US. From a human risk perspective, the highest average EDI of ∑PFAAs via riverine water consumption was observed in the dependent population of Italy (2.02 × 10-3 ng/L/day), followed by the Netherlands (8.24 × 10-4 ng/L/day), the US (5.56 × 10-4 ng/L/day), Pakistan (3.99 × 10-4 ng/L/day), Japan (3.69 × 10-4 ng/L/day), France (3.42 × 10-4 ng/L/day), China (2.58 × 10-4 ng/L/day), Spain (2.43 × 10-4 ng/L/day), Germany (1.17 × 10-4 ng/L/day), Korea (6.01 × 10-5 ng/L/day), and Vietnam (1.28 × 10-5 ng/L/day). For fish consumption, Spain recorded the highest average EDI of ∑PFAAs (9.92 × 100 ng/g/day) in its dependent population, followed by the US (3.44 × 100 ng/g/day), Korea (8.13 × 10-1 ng/g/day), and Vietnam (4.99 × 10-1 ng/g/day). The non-carcinogenic HR values for individual PFAA compounds via riverine water intake in the dependent populations of both developed and developing countries were within acceptable limits (<1). However, the HI values for ∑PFAAs intake via riverine fish consumption in the dependent population exceeded the threshold (>1) in the developed countries, the US and Spain, indicating higher potential risks associated with fish consumption in these countries. Given the inadequate wastewater treatment facilities in many regions, coupled with untreated runoff from urban areas and agricultural fields draining directly into rivers, this study underscores the urgent need for integrated prevention and control measures to mitigate PFAAs contamination in riverine systems and reduce associated risks. Ultimately, stricter regulations, improved monitoring, and enhanced water treatment technologies are crucial to reducing PFAAs contamination and safeguarding public health.

Heavy metals pollution in riverine sediments: Distribution, source, and environmental implications

This research reports heavy metal pollution in riverine sediments from River Kabul, Pakistan, which could endanger human health and ecology via the food web. The results revealed a substantial special variation in the average contents (mg/kg) of chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg), lead (Pb), iron (Fe), and aluminum (Al) in riverine sediments, in the order of Fe (20,234.51) > Al (17,550.86) > Mn (375.45) > Zn (149.08) > Ni (89.11) > Cr (83.36) > Pb (45.29) > Cu (19.86) > Cd (7.48) > Co (6.28) > Hg (0.81). Among the heavy metals, Cd exhibited the highest degree of pollution along the river, followed by Hg > Ni > Zn > Pb > Al > Cr > Mn > Fe > Cu > Co. The overall contamination factor (CF) values for the sum of heavy metals were highest at monitoring site S-9, followed by S-8 > S-10 > S-6 > S-5 > S-7 > S-1 > S-4 > S-12 > S-3 > S-2 > S-1 with pollution load index (PLI) > 1, whereas the geo-accumulation index (Igeo) values of Cd and Hg fluctuated between Levels 3, 4, and 6, suggesting moderate to extreme pollution in the river. The correlation statistics determined the fate and distribution of heavy metals by establishing significant positive correlations between the specific metals of bounded sediments. The cluster analysis separates the correlated metals into Groups A and B, and Groups 1 and 2. While the principal component analysis evaluates the qualitative behavior of clustering by discerning industrial, agrochemicals, mining, and domestic wastewater discharges, leakages of lubricants along with multiple geogenic inputs, erosion of mafic and ultramafic rocks, and minimal atmospheric deposition are all potential sources of Cr, Mn, Co, Ni, Cu, Zn, Cd, Hg, Pb, Fe, and Al contamination. In terms of risk, the contaminations of Mn, Co, Cu, Zn, and Pb in riverine sediments were 85, 100, 100, 17, and 11%, respectively, representing a rare biological influence because their value is less than their corresponding threshold effect concentrations (TECs), whereas the levels of Mn, Ni, Cd, and Hg were above their probable effect concentrations (PECs) of 100, 100, 81, and 52%, respectively, representing prominent adverse biological influence. Based on consensus-based TECs and PECs, the contamination levels of Cr, Mn, Zn, Cd, Hg, and Pb were 100, 85, 83, 19, 48, and 90%, respectively, indicating occasionally exhibited adverse biological effects on the riverine population. Besides, the overall potential ecological risk index (PERI) of Cd and Hg, in particular, exhibited the maximum pollution level ( E r i ≥ 320), suggesting a very high potential ecological risk in the drainage that requires special attention from pollution control authorities.

Pathways and risk analysis of arsenic and heavy metal pollution in riverine water: Application of multivariate statistics and USEPA-recommended risk assessment models

This study analyzed surface water from the River Swat, Pakistan, using inductively coupled plasma mass spectrometry, multivariate statistical techniques, and US-EPA risk assessment models to evaluate the concentrations, distribution, pathways, and potential risks of arsenic (As) and heavy metals, including chromium (Cr), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg), and lead (Pb). The results revealed significant correlations (p ≤ 0.01) among metals that indicated common pollution sources, likely influenced by anthropogenic point and non-point activities. Along the monitored sites (S1-S10), the mass flow of ∑metals showed a dynamic pattern: progressively increasing downstream, decreasing at S6-S7, rising again at S7-S8, and then steadily declining toward S10, with Ni being the most abundant metal, followed by Cr > As> Cu > Mn > Co > Zn > Hg > Cd > Pb. The As and Heavy Metal Pollution Index (HPI), As and Heavy Metal Evaluation Index (HEI), and Pollution Index (PI) revealed variations in pollution levels, ranking the metals in the orders of Co > As> Cr > Cd > Mn > Hg > Ni > Pb > Cu > Zn, As> Cr > Ni > Hg > Cd > Co > Mn > Cu > Zn > Pb, and Hg > Ni > As> Co > Cu > Cd > Mn > Zn > Pb, respectively. However, according to the risk assessment, overall individual metal contamination in the River Swat water was below the ecological risk threshold (ERI 〈110). Where, the Chronic Daily Intakes (CDIs), Hazard Quotients (HQs), Hazard Indices (HIs), Cancer Risks (CRs), and Total Cancer Risks (TCRs) of Cr, Mn, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb associated with daily river water intake and dermal contact indicate that long-term exposure to untreated river water may pose both carcinogenic and non-carcinogenic health risks to residents.

Fate, distribution, and transport dynamics of Per- and Polyfluoroalkyl Substances (PFASs) in the environment

Per- and Polyfluoroalkyl Substances (PFASs) are persistent organic pollutants with significant environmental and health impacts due to their widespread occurrence, bioaccumulation potential, and resistance to degradation. This paper comprehensively reviews current knowledge of PFAS fate and transport mechanisms by correlating PFAS leaching, retention, and movement to their physicochemical properties and environmental factors based on observing PFAS fate and transport in unsaturated zones, surface water, sediments, plants, and atmosphere. The complex and unique physiochemical properties of PFASs, such as their carbon-fluorine bonds and amphiphilic nature, determine their environmental behavior and persistence. Recent studies emphasize that concentration-dependent affinity coefficients predict the transport of diverse PFAS mixtures by considering the impact of the Air-Water Interface (AWI). These studies highlight the complex interactions that influence PFAS behavior in environmental systems and the need for refined modeling techniques to account for transport dynamics. Competitive adsorption at the AWI, influenced by PFAS physicochemical properties and environmental factors, is crucial. PFAS chain length profoundly affects PFAS volatility and mobility, i.e., longer chains show higher solid matrix adsorption, while shorter chains exhibit greater atmospheric deposition potential. Solution chemistry, encompassing pH and ionic strength, variably alters PFAS sorption behaviors. Mathematical models, such as the Leverett Thermodynamic Model (LTM) and Surface Roughness Multipliers (SRM), effectively predict PFAS retention, offering enhanced accuracy for surface-active solutes through empirical adjustments. Co-contaminants' presence influences the transport behavior of PFASs in the environment. Microbial activity alters PFAS retention, while microplastics, especially polyamide, contribute to their adsorption. These complex interactions govern PFAS fate and transport in the environment. The paper identifies critical gaps in current understanding, including the fate of PFASs, analytical challenges, ecological risk assessment methods, and the influence of episodic events on PFAS transport dynamics. This paper also investigates the research gap in refining current models and experimental approaches to predict PFAS transport accurately and enhance risk mitigation efforts. Addressing these gaps is crucial for advancing remediation strategies and regulatory frameworks to mitigate PFAS contamination effectively.

Identification of Emerging Per- and Polyfluoroalkyl Substances (PFAS) in E-waste Recycling Practices and New Precursors for Trifluoroacetic Acid

Electronic waste is an emerging source of per- and polyfluoroalkyl substance (PFAS) emissions to the environment, yet the contribution from hazardous recycling practices in the South Asian region remains unclear. This study detected 41 PFAS in soil samples from e-waste recycling sites in Pakistan and the total concentrations were 7.43-367 ng/g dry weight (dw) (median: 37.7 ng/g dw). Trifluoroacetic acid (TFA) and 6:2 fluorotelomer sulfonic acid emerged as the dominant PFAS, constituting 49% and 13% of the total PFAS concentrations, respectively. Notably, nine CF3-containing emerging PFAS were identified by the high-resolution mass spectrometry (HRMS)-based screening. Specifically, hexafluoroisopropanol and bistriflimide (NTf2) were consistently identified across all the samples, with quantified concentrations reaching up to 854 and 90 ng/g dw, respectively. This suggests their potential association with electronic manufacturing and recycling processes. Furthermore, except for NTf2, all the identified emerging PFAS were confirmed as precursors of TFA with molar yields of 8.87-40.0% by the TOP assay validation in Milli-Q water. Overall, this study reveals significant emission of PFAS from hazardous e-waste recycling practices and emphasizes the identification of emerging sources of TFA from precursor transformation, which are essential for PFAS risk assessment.

Population exposure to emerging perfluoroalkyl acids (PFAAs) via drinking water resources: Application of multivariate statistics and risk assessment models

This study assessed the occurrence, origins, and potential risks of emerging perfluoroalkyl acids (PFAAs) for the first time in drinking water resources of Khyber Pakhtunkhwa, Pakistan. In total, 13 perfluoroalkyl carboxylic acids (PFCAs) with carbon (C) chains C4-C18 and 4 perfluoroalkyl sulfonates (PFSAs) with C chains C4-C10 were tested in both surface and ground drinking water samples using a high-performance liquid chromatography system (HPLC) equipped with an Agilent 6460 Triple Quadrupole liquid chromatography-mass spectrometry (LC-MS) system. The concentrations of ∑PFCAs, ∑PFSAs, and ∑PFAAs in drinking water ranged from 1.46 to 72.85, 0.30-8.03, and 1.76-80.88 ng/L, respectively. Perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA), and perfluoropentanoic acid (PFPeA) were the dominant analytes in surface water followed by ground water, while the concentration of perfluorobutane sulfonate (PFBS), perfluorooctanoic acid (PFOA), perfluoroheptanoic acid (PFHpA), perfluorooctane sulfonate (PFOS), perfluorohexane sulfonate (PFHxS), perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA), perfluoroundecanoic acid (PFUnDA), and perfluorododecanoic acid (PFDoDA) were greater than long-chain PFOA and PFOS. The correlation statistics, which showed a strong correlation (p < 0.05) between the PFAA analytes, potentially indicated the fate of PFAAs in the area's drinking water sources, whereas the hierarchical cluster analysis (HCA) and principal component analysis (PCA) statistics identified industrial, domestic, agricultural, and commercial applications as potential point and non-point sources of PFAA contamination in the area. From risk perspectives, the overall PFAA toxicity in water resources was within the ecological health risk thresholds, where for the human population the hazard quotient (HQ) values of individual PFAAs were < 1, indicating no risk from the drinking water sources; however, the hazard index (HI) from the ∑PFAAs should not be underestimated, as it may significantly result in potential chronic toxicity to exposed adults, followed by children.

First insights into per-and polyfluoroalkyl substance contamination in edible fish species of the Indus water system of Pakistan

Per- and polyfluoroalkyl substances (PFASs) are a group of emerging contaminants, that have a wide range of applications in industrial and commercial products. The direct discharge of untreated industrial and domestic wastewater into freshwater bodies is a common practice in developing countries, which are the main contributors to PFASs in the aquatic environment. The situation is further worsened due to poor wastewater treatment facilities and weak enforcement of environmental regulations in countries like Pakistan. The current study was designed to assess PFASs contamination in muscle tissues of edible fish species from major tributaries of the Indus System, including Head Panjnad (HP), Head Trimmu (HT), Chashma Barrage (CB), Head Blloki (HB) and Head Qadirabad (HQ). The analysis of target PFAS was performed using ultrahigh-performance liquid chromatography coupled with a quadrupole Orbitrap high-resolution mass spectrometry. The highest levels of ∑17PFASs were observed in S. seenghala, C. mirigala from HB, and C. mirigala from HQ with a mean value of 45.4 ng g-1, 43.7 ng g-1, and 40.8 ng g-1, respectively. Overall, the compositional profile of fish samples was predominated by long-chain PFASs such as PFOA, PFOS, PFHpS, and PFDS. The accumulation of PFASs in fish species is dependent on the physiochemical properties of PFASs, characteristics of the aquatic environment, and fish species. Significant associations of PFASs with isotopic composition (p < 0.05), feeding habits (p < 0.05), and zones (p < 0.05) indicate that dietary proxies could be an important predictor of PFASs distribution among species. The C7-C10 PFASs exhibited bio-accumulative tendency with an accumulation factor ranging from 0.5 to 3.4. However, none of the fish samples had sufficiently high levels of PFOS to cause human health risk (HR < 1). For future studies, it is s recommended to conduct seasonal monitoring and the bioaccumulation pattern along trophic levels of both legacy and emerging PFASs.

Combustion of high-calorific industrial waste in conventional brick kilns: An emerging source of PFAS emissions to agricultural soils

The brick kilns in the South Asian region are widely documented to partially combust high-calorific waste components of synthetic-industrial origin, which contain hazardous constituents, including per- and polyfluoroalkyl substances (PFAS). Correspondingly, these establishments are necessarily built on agricultural land to easily acquire clay by excavating soil horizons, thus making cultivation soils vulnerable to PFAS contaminations. In this pioneering study, the occurrence, distribution profile, traceability and human health risk exposure to forty-four legacy and novel PFAS homologues, including two ultrashort-chain (C2-C3) PFAS, were investigated in agricultural soils around thirty-two conventional brick kilns across three districts of Pakistan. ⅀44PFAS concentrations ranged from 14.3 to 465 ng/g (median: 28.2 ng/g), which were 2 to 70 folds higher than those in background soils, and slightly higher than those reported in agricultural soils in the global literature. The highest occurrence was observed for PFAS alternatives, i.e., 6:2 fluorotelomer sulfonate (6:2 FTSA) (40 %) and 6:2 chlorinated polyfluorinated ether sulfonate (6:2 Cl-PFESA) (4.5 %). A significant positive correlation (p < 0.01) was observed among the concentrations of short-chain perfluoroalkyl acids (C4-C7) and novel PFOS substitutes, implying their origin from common sources. Furthermore, ultrashort-chain and short-chain perfluorocarboxylic acids (PFCA) (89 %) and perfluorosulfonic acids (PFSA) (63 %) dominated over long-chain's PFCA (11 %) and PFSA (37 %), respectively. The estimated daily intake to children exposed in surrounding inhabited communities, at 95th percentile concentrations was found to be approaching the European tolerable daily intake limit of 0.63 ng/kg bw/day. Therefore, the brick manufacturing industry is identified as a novel source of PFAS in the adjacent environment and for residents. This suggests the need for further investigations to elucidate the origin of emerging contaminants in the waste streams of the region to safeguard ecological integrity.

Heavy metals in five commonly consumed fish species from River Swat, Pakistan, and their implications for human health using multiple risk assessment approaches

This study analyzed the levels of heavy metals bioaccumulation in commonly consumed riverine fish species, including G. cavia, T. macrolepis, G. gotyla, S. plagiostomus, and M. armatus from River Swat in Pakistan, and quantify their potential risk to children and adults in general and fisherfolk communities using multiple pollution and risk assessment approaches. The highest metal detected by inductive coupled plasma mass spectrometry (ICP-MS) was Zn, which ranged from 49.61 to 116.83 mg/kg, followed by Fe (19.25-101.33 mg/kg) > Mn (5.25-40.35 mg/kg) > Cr (3.05-14.59 mg/kg) > Ni (4.26-11.80 mg/kg) > Al (1.59-12.25 mg/kg) > Cu (1.24-8.59 mg/kg) > Pb (0.29-1.95 mg/kg) > Co (0.08-0.46 mg/kg) > Cd (0.01-0.29 mg/kg), demonstrating consistent fluctuation with the safe recommendations of global regulatory bodies. The average bioaccumulation factor (BAF) values in the examined fish species were high (BAF > 5000) for Pb, Zn, Mn, Cu, Cr, Ni, and Cd, bioaccumulate (1000 > BAF < 5000) for Co, and probable accumulative (BAF <1000) for Fe, and Al, while the overall ∑heavy metals pollution index (MPI) values were greater than one (MPI > 1) indicating sever heavy metals toxicity in G. cavia, followed by S. plagiostomus, M. armatus, G. gotyla, and T. macrolepis. The multivariate Pearson's correlation analysis identified the correlation coefficients between heavy metal pairs (NiCr, CuCr, PbCr, AlCo, CuNi, and PbNi), the hierarchical cluster analysis (CA) determined the origin by categorizing heavy metal accumulation into Cluster-A, Cluster-B, and Cluster-C, and the principal component analysis (PCA) discerned nearby weathering, mining, industrial, municipal, and agricultural activities as the potential sources of heavy metals bioaccumulation in riverine fish. As per human risk perspective, S.plagiostomus contributed significantly to the estimated daily intake (EDI) of heavy metals, followed by G.cavia > M.armatus > G.gotyla > T.macrolepis in dependent children and adults of the fisherfolk followed by the general population. The non-carcinogenic target hazard quotient (THQ) and hazard index (HI) values for heavy metal intake through fish exposure were < 1, while the carcinogenic risk (CR) for individual metal intake and the total carcinogenic risk (TCR) for cumulative Cr, Cd, and Pb intake were within the risk threshold of 10-6-10-4, suggesting an acceptable to high non-carcinogenic and carcinogenic risk for both children and adults in the fisherfolk, followed by the general population.

Analysis of a Passive Sampling Device to Assess the Behavior of Per- and Polyfluoroalkyl Substances in Sediments

Per- and polyfluoroalkyl substances (PFAS) are an emerging class of compounds that cause health and environmental problems worldwide. In aquatic environments, PFAS may bioaccumulate in sediment organisms, which can affect the health of organisms and ecosystems. As such, it is important to develop tools to understand their bioaccumulation potential. In the present study, the uptake of perfluorooctanoic acid (PFOA) and perfluorobutane sulfonic acid (PFBS) from sediments and water was assessed using a modified polar organic chemical integrative sampler (POCIS) as a passive sampler. While POCIS has previously been used to measure time-weighted concentrations of PFAS and other compounds in water, in our study, the design was adapted for analyzing contaminant uptake and porewater concentrations in sediments. The samplers were deployed into seven different tanks containing PFAS-spiked conditions and monitored over 28 days. One tank contained only water with PFOA and PFBS, three tanks contained soil with 4% organic matter, and three tanks contained soil combusted at 550 °C to minimize the influence of labile organic carbon. The uptake of PFAS from the water was consistent with previous research using a sampling rate model or simple linear uptake. For the samplers placed in the sediment, the uptake process was explained well using a mass transport based on the external resistance from the sediment layer. Uptake of PFOS in the samplers occurred faster than that of PFOA and was more rapid in the tanks containing the combusted soil. A small degree of competition was observed between the two compounds for the resin, although these effects are unlikely to be significant at environmentally relevant concentrations. The external mass transport model provides a mechanism to extend the POCIS design for measuring porewater concentrations and sampling releases from sediments. This approach may be useful for environmental regulators and stakeholders involved in PFAS remediation. Environ Toxicol Chem 2023;42:2171-2183. © 2023 SETAC.

An overview on human exposure, toxicity, solid-phase microextraction and adsorptive removal of perfluoroalkyl carboxylic acids (PFCAs) from water matrices

Perfluoroalkyl carboxylic acids (PFCAs) are sub-class of perfluoroalkyl substances commonly detected in water matrices. They are persistent in the environment, hence highly toxic to living organisms. Their occurrence at trace amount, complex nature and prone to matrix interference make their extraction and detection a challenge. This study consolidates current advancements in solid-phase extraction (SPE) techniques for the trace-level analysis of PFCAs from water matrices. The advantages of the methods in terms of ease of applications, low-cost, robustness, low solvents consumption, high pre-concentration factors, better extraction efficiency, good selectivity and recovery of the analytes have been emphasized. The article also demonstrated effectiveness of some porous materials for the adsorptive removal of the PFCAs from the water matrices. Mechanisms of the SPE/adsorption techniques have been discussed. The success and limitations of the processes have been elucidated.

A review on superior advanced oxidation and photocatalytic degradation techniques for perfluorooctanoic acid (PFOA) elimination from wastewater

Perfluorooctanoic acid (PFOA) has been identified as the most toxic specie of the family of perfluorinated carboxylic acids (PFCAs). It has been widely distributed and frequently detected in environmental wastewater. The compound's unique features such as inherent stability, rigidity, and resistance to harsh chemical and thermal conditions, due to its multiple and strong C-F bonds have resulted in its resistance to conventional wastewater remediations. Photolysis and bioremediation methods have been proven to be inefficient in their elimination, hence this article presents intensive literature studies and summarized findings reported on the application of advanced oxidation processes (AOPs) and photocatalytic degradation techniques as the best alternatives for the PFOA elimination from wastewater. Techniques of persulfate, photo-Fenton, electrochemical, photoelectrochemical and photocatalytic degradation have been explored and their mechanisms for the degradation and defluorination of the PFOA have been demonstrated. The major advantage of AOPs techniques has been centralized on the generation of active radicals such as sulfate (SO₄^•-) hydroxyl (•OH). While for the photocatalytic process, photogenerated species (electron (e) and holes (h ⁺ _vb)) initiated the process. These active radicals and photogenerated species possessed potentiality to attack the PFOA molecule and caused the cleavage of the C-C and C-F bonds, resulting in its efficient degradation. Shorter-chain PFCAs have been identified as the major intermediates detected and the final stage entails its complete mineralization to carbon dioxide (CO₂) and fluoride ion (F^-). The prospects and challenges associated with the outlined techniques have been highlighted for better understanding of the subject matter for the PFOA elimination from real wastewaters.

Spatial distribution, compositional profile, sources, ecological and human health risks of legacy and emerging per- and polyfluoroalkyl substances (PFASs) in freshwater reservoirs of Punjab, Pakistan

Per- and polyfluoroalkyl substances (PFASs) are a large group of chemicals reported in global environment and are responsible for various adverse impacts on humans and environment. We report a comprehensive study on occurrence of PFASs, including legacy, substitute and emerging ones, from Pakistan. Surface water samples were collected from five ecologically important freshwater reservoirs in Pakistan, namely, Head Panjnad (HP), Head Trimmu (HT), Chashma Barrage (CB), Head Blloki (HB), and Head Qadirabad (HQ). The detection frequencies of PFASs ranged between 37 %-100 %. The highest concentration of ∑₁₅PFASs was detected at HP (114.1 ng L^-1), whereas the lowest at HQ (19.9 ng L^-1). Among the analyzed PFASs, 6:2 fluorotelomer sulfonic acid (6:2 FTS) and perfluorooctanoic acid (PFOA) showed maximum mean concentrations of 9.1 ng L^-1 and 7 ng L^-1 at HP, followed by Perfluorooctane sulfonic acid (PFOS) with level of 0.99 ng L^-1 at HT. The ecological risk assessment for selected species i.e., daphnid, mysid, fish and green algae showed that PFOS, perfluorononanoic acid (PFNA), perfluorodecanoic acid (PFDA) exhibited moderate risk i.e., Hazard Quotients (HQs) < 1 to the modeled organisms, whereas perfluorobutane sulfonic acid (PFBS) showed the high risk to green algae (HQs = 8.6) and PFOA presented a high risk to all the organisms (HQs ranged between 1.04 and 7.38). The level of ∑PFASs at HP (114.1 ng L^-1) exceed the EU guideline value of ∑PFASs in water (100 ng L^-1), however the risk quotient (RQ_mix) values of all age groups were < 1 implying that the detected PFASs in water do not pose risk to human health. Source apportionment through Positive Matrix Factorization (PMF) showed that industrial effluent is the main source of PFASs in freshwater reservoirs. Comparable concentrations of legacy and substitute PFASs in this study indicate that legacy PFASs are still in use adjacent to ecologically important water reservoirs.

Occurrence, spatial heterogeneity, and risk assessment of perfluoroalkyl acids (PFAAs) in the major rivers of the Tibetan Plateau

The Tibetan Plateau (TP) is home to the headwaters of major rivers in Asia, yet their water quality security on a large spatial scale is scarcely studied, especially in regard to emerging organic pollutants. In this study, a systematic field campaign was carried out along Yarlung Tsangpo River, Nu River, Lancang River and Jinsha River, and 13 perfluoroalkyl acids (PFAAs) were analyzed. The total concentrations of PFAAs in the river waters of the TP were in the range of 0.58-7.46 ng/L, containing a high proportion of perfluorobutanoic acid (PFBA) and perfluorobutane sulfonate (PFBS) with average values of 56.7 %. Elevated PFAA loadings were found for the midstream of Yarlung Tsangpo River in central Tibet. Geodetector results indicated that precipitation, solar radiation and vegetation type were the top three influential factors contributing to the observed spatial heterogeneity. When interactions with human activities were taken into account, the explanatory power was significantly enhanced and rose above 0.70, highlighting the increased risks for TP rivers from the combined effects of natural environments and anthropogenic activities. Risk assessments suggest a low risk is posed to the alpine aquatic ecosystems and human health. The discharge fluxes of PFAAs via riverine export were estimated at 94-425 kg/year, which is one to two orders of magnitude lower than their mass loadings in major rivers worldwide. Our study underlined the need for further attention to the increased risk of water resource quality on the central TP in the context of long-range transport, increased cryosphere melting and local emission.

Perfluorononanoate and Perfluorobutane Sulfonate Induce Cardiotoxic Effects in Zebrafish

Globally, per- and polyfluoroalkyl substances are common artificial ingredients in industrial and consumer products. Recently, they have been shown to be an emerging human health risk. Perfluorononanoic acid (PFNA)/perfluorononanoate and perfluorobutane sulfonic acid (PFBS)/perfluorobutane sulfonate cause reproductive toxicity and hepatotoxicity, disrupt thyroid functions, and damage embryonic development in zebrafish. However, the cardiotoxic effects of PFNA and PFBS have not been fully established. We found that PFNA and PFBS exposures repress hatchability while increasing malformation and mortality in zebrafish embryos. Hematoxylin and eosin staining as well as assessment of the transgenic zebrafish line Tg(myl7:nDsRed) revealed that exposure of embryos to PFNA increases the occurrence of severe cardiac malformations relative to exposure to PFBS. Moreover, we evaluated the differential expressions of cardiac development-associated genes in response to PFNA and PFBS, which validated the potential cardiotoxic effects, consistent with cardiac dysfunctions. Overall, our findings reveal novel cardiotoxic effects of PFNA and PFBS in zebrafish, implying that they may exert some cardiotoxic effect in humans. To the best of our knowledge, ours is the first study to show that PFNA exerts more severe cardiotoxic effects in zebrafish when compared with PFBS. Based on these findings, studies should evaluate the mechanisms of their cardiotoxic effects. Environ Toxicol Chem 2022;41:2527-2536. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.