Validation and determination of nine PFCS in surface water and sediment samples using UPLC-QTOF-MS

Evidence of the occurrence, detection, and ecotoxicity studies of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in aqueous environments

Perflorochemicals (PFCs), among which are the most commonly detected perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA), are persistent emergent contaminants of concern in recent times. These compounds have been reported for their cytotoxicity, genotoxicity, carcinogenicity, immunotoxicity, and developmental toxicities. Meanwhile, they have been detected in diverse matrices such as soil, sediment, and, surprisingly, in serum and even breastmilk. Worrisomely, these compounds are detected in drinking water across the globe, aquaculture water, and other surface waters. Thus, it was important to appraise the studies conducted on PFOS and PFOA to provide an overview of the environmental status of contamination regarding them. The present review article sought to provide insights into the occurrence patterns and ecotoxic effects of both pollutants in the water ecosystems within five continents of the world. Based on the information gathered in this article, the ∑ P F O S concentration (ng/L) within the five continents is in the order Europe > Asia > Africa > North America > South America, while the ∑ P F O A level (ng/L) is in the order Europe > Asia > South America > Africa > North America. The study also investigated the previous works that have been conducted regarding the diverse elimination technologies employed for the removal of these pollutants from the aqueous environments, with plasma combined with surfactant process being the most efficient. Generally, studies on PFOS/PFOA are still scanty when compared to those on pharmaceuticals and personal care products (PPCPs), especially in North America. The information gathered in this study could be useful in establishing thresholds of PFOA and PFOS environmental levels and be adopted by appropriate authorities as safety guidelines.

Challenges Associated With PFAS Detection Method in Africa

Per- and polyfluoroalkyl substances (PFAS) are a group of man-made chemicals that are widely present in many industries. Monitoring and analyzing PFAS in Africa is challenging due to the limited availability of mass spectrometry (MS), which is an essential technique for detecting PFAS. This review assesses the scope and impact of the shortage of mass spectrometry instruments in Africa, emphasizing the resulting limitations in monitoring environmental and public health threats. The review analyzes the existing PFAS monitoring, the accessibility of MS instruments, and the technical capabilities within the continent. This study suggests that fewer African countries have sufficient MS instruments, resulting in significant underreport of environmental data and related public health issues. The review proposes financial support and programs to address these difficulties to provide necessary MS instruments. The review suggests that it is highly important to develop regional centers of excellence for PFAS monitoring using MS instruments and investing in training programs to address the gap in monitoring efforts. So, enhancing these are crucial for the successful management of the environment and safeguarding public health from the effects of PFAS contamination.

Poly- and per-fluoroalkyl substances (PFAS) in the African environments: progress, challenges, and future perspectives

Per- or poly-fluoroalkyl substances (PFAS) are a group of anthropogenic compounds that are used in a variety of industrial processes and consumer products with their ubiquitous presence in the environment recently gaining relevant attention. Progress and milestones on PFAS contamination within multiple environments from African continent are highlighted in this review. Identification and quantitation of PFAS within African environments is important to the public at large because of their toxicity and possible ecotoxicological risk. Two most studied classes of PFAS are perfluoro carboxylic acid (PFCA) (i.e., perfluorooctanoic acid (PFOA)) and perfluoro sulfonic acid (PFSA) (i.e., perfluoro sulfonic acid (PFOS)) with many more classes of PFAS been created by industry. Within the African continent, studies reported PFAS in water, sediments, soils, fish, dust, breastmilk, infant formulae, dust, atmosphere, marine species and wildlife. Southern Africa contributed more studies on the presence of PFAS in the environment with Central Africa contributing the least. Despite growing awareness of PFAS contamination in Africa, the number of studies, studied compounds, and concentration levels vary significantly across regions and matrices. While some countries in Southern and Western Africa have made progress in PFAS research, the overall disparity in research output highlights the urgency for increased attention, resources, and concerted efforts to comprehensively address PFAS contamination. This review also revealed PFAS contamination within freshwater environments, with non-existent data from marine water environments. Collaboration among scientists, policymakers, industry players as well as regional and international communities are essential to mitigate the impact of PFAS in the African environment.

Per- and poly-fluoroalkyl substances in aquatic ecosystems and wastewater treatment works in Africa: Occurrence, ecological implications, and future perspectives

The increasing levels of industrialization and urbanization have led to the generation of significant amounts of wastewater and waste products, often containing chemicals like per- and poly-fluoroalkyl substances (PFASs) commonly found in consumer products. PFASs are known for their persistence, ubiquity, and ecotoxicological impacts, raising concerns about potential harm to ecosystems. This paper reports the occurrence and evaluates the ecological risks of PFASs in aquatic ecosystems and wastewater treatment works (WWTWs) across Africa. We reviewed 32 papers published in the period 2009-2024 and identified a total of 35 PFAS compounds in surface waters, wastewater, sediments, fish, crocodiles, and invertebrates. Much of the reported studies came from South Africa, followed by Kenya and Nigeria. PFAS concentrations in Africa were <0.7-390.0 ng L-1 in surface waters, 0.05-772 ng g-1 dw in sediments, and <0.2-832 ng L-1 in wastewater, while the highest levels in fish and invertebrates were 460.7 and 35.5 ng g-1 ww, respectively. The PFAS levels were in the same range of data as those reported globally. However, the high concentrations of PFASs in sediments and wastewater suggest areas of point contamination and a growing risk to aquatic ecosystems from effluent discharges. Calculated risk quotients suggested that, in Africa, organisms in river systems face greater risks due to exposure to PFASs compared to those in lakes, while marine organisms might face higher risks compared to freshwater organisms. Future studies should focus on PFAS contamination sources, especially WWTWs, as emerging sources of PFASs in aquatic systems.

Simultaneous and High-Throughput Analytical Strategy of 30 Fluorinated Emerging Pollutants Using UHPLC-MS/MS in the Shrimp Aquaculture System

This study established novel and high-throughput strategies for the simultaneous analysis of 30 fluorinated emerging pollutants in different matrices from the shrimp aquaculture system in eastern China using UHPLC-MS/MS. The parameters of SPE for analysis of water samples and of QuEChERS methods for sediment and shrimp samples were optimized to allow the simultaneous detection and quantitation of 17 per- and polyfluoroalkyl substances (PFASs) and 13 fluoroquinolones (FQs). Under the optimal conditions, the limits of detection of 30 pollutants for water, sediment, and shrimp samples were 0.01-0.30 ng/L, 0.01-0.22 μg/kg, and 0.01-0.23 μg/kg, respectively, while the limits of quantification were 0.04-1.00 ng/L, 0.03-0.73 μg/kg, and 0.03-0.76 μg/kg, with satisfactory recoveries and intra-day precision. The developed methods were successfully applied to the analysis of multiple samples collected from aquaculture ponds in eastern China. PFASs were detected in all samples with concentration ranges of 0.18-0.77 μg/L in water, 0.13-1.41 μg/kg (dry weight) in sediment, and 0.09-0.96 μg/kg (wet weight) in shrimp, respectively. Only two FQs, ciprofloxacin and enrofloxacin, were found in the sediment and shrimp. In general, this study provides valuable insights into the prevalence of fluorinated emerging contaminants, assisting in the monitoring and control of emerging contaminants in aquatic foods.

Per- and polyfluoroalkyl substances contamination of drinking water sources in Africa: Pollution sources and possible treatment methods

Despite the detection of poly- and perfluorinated alkyl substances (PFAS) in the water system in Africa, the effort towards mitigating PFAS in water in Africa needs to be better understood. Therefore, this review evaluated the contamination status and mitigation methods for handling PFAS-contaminated water systems in Africa. The findings revealed the presence of PFAS in wastewater treatment plant (WWTP) effluents, surface water and commercially available bottled and tap water in African countries. The concentration of PFAS in drinking water sources reviewed ranged from < limits of quantification to 778 ng L-1. The sources of PFAS in water systems in Africa are linked to uncontrolled importation of PFAS-containing products, WWTP effluents and inappropriate disposal of PFAS-containing materials. The information on treatment methods for PFAS-contaminated water systems is scanty. Unfortunately, the treatment method is challenged by poor water research infrastructure and facilities, lack of awareness, poor research funding and weak legislation; however, adsorption and membrane technology seem favourable for removing PFAS from water systems in Africa. It is essential to focus on monitoring and assessing drinking water quality in Africa to reduce the disease burden that this may cause. Most African countries' currently implemented water treatment facilities cannot efficiently remove PFAS during treatment. Therefore, governments in Africa need to fund more research to develop an efficient water treatment technique that is sustainable in Africa.

Emergency of per- and polyfluoroalkyl substances in drinking water: Status, regulation, and mitigation strategies in developing countries

The detection of per- and polyfluoroalkyl substances (PFAS) in water presents a significant challenge for developing countries, requiring urgent attention. This review focuses on understanding the emergence of PFAS in drinking water, health concerns, and removal strategies for PFAS in water systems in developing countries. This review indicates the need for more studies to be conducted in many developing nations due to limited information on the environmental status and fate of PFAS. The health consequences of PFAS in water are enormous and cannot be overemphasized. Efforts are ongoing to legislate a national standard for PFAS in drinking water. Currently, there are few known mitigation efforts from African countries, in contrast to several developing nations in Asia. Therefore, there is an urgent need to develop economically viable techniques that could be integrated into large-scale operations to remove PFAS from water systems in the region. However, despite the success achieved with removing long-chain PFAS from water, more studies are required on strategies for eliminating short-chain moieties in water.

Influence of soil composition and environmental factors on the adsorption of per- and polyfluoroalkyl substances: A review

Per- and polyfluoroalkyl substances (PFASs) have garnered considerable scientific and regulatory scrutiny due to their widespread distribution across environments and their potential toxicological impacts on human health. The pedosphere serves as a vital reservoir for these chemicals, significantly determining their environmental trajectory and chemical transformations. This study offers a comprehensive synthesis of the current understanding regarding the adsorption mechanics of PFASs in soil matrices. Due to their unique molecular structure, PFASs predominantly engage in hydrophobic and electrostatic interactions during soil adsorption. This work thoroughly evaluates the influence of various factors on adsorption efficiency, including soil properties, molecular characteristics of PFASs, and the prevailing environmental conditions. The complex nature of soil environments complicates isolating individual impacts on PFAS behavior, necessitating an integrated approach to understanding their environmental destinies better. Through this exploration, we seek to clarify the complex interplay of factors that modulate the adsorption of PFASs in soils, highlighting the urgent need for future research to disentangle the intricate and combined effects that control the environmental behavior of PFAS compounds.

Quantification of perfluorinated compounds in atmospheric particulate shows potential connection with environmental event

A method of quantification of perfluorinated compounds (PFCs) from atmospheric particulate matter (APM) is described. A single step pretreatment method, selective pressurized liquid extraction (SPLE), was developed to reduce the high matrix background and avoid contamination from commonly used multiple sample pretreatment steps. An effective sorbent was selected to purify the PFCs during SPLE, followed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), for quantification of PFCs. Conditions affecting the SPLE efficiency, including temperature, static extraction time, and number of extraction cycles used, were studied. The optimum conditions were found to be 120°C, 10 min, and 3 cycles, respectively. LC-MS/MS method was developed to obtain the optimal sensitivity specific to PFCs. The method detection limits (MDLs) were 0.006 to 0.48 ng/g for the PFCs studied and the linear response range was from 0.1 to 100 ng/g. To ensure accurate values were obtained, each step of the experiment was evaluated and controlled to prevent contamination. The optimized method was tested by performing spiking experiments in natural particulate matter matrices and good rates of recovery and reproducibility were obtained for all target compounds. Finally, the method was successfully used to measure 16 PFCs in the APM samples collected in Beijing over five years from 2015 to 2019. It is observed that some PFCs follow the trend of total PFC changes, and can be attributed to the environment influencing events and policy enforcement, while others don't seem to change as much with time of the year or from year to year.

Overview of African water resources contamination by contaminants of emerging concern

This review look at several classes of contaminants of emerging concern (CECs) in conventional and non-conventional water resources across the African continent's five regions. According to the review, pharmaceuticals, endocrine-disrupting chemicals, personal care products, pesticides, per- and polyfluoroalkyl compounds, and microplastics were found in conventional and non-conventional water resources. Most conventional water resources, such as rivers, streams, lakes, wells, and boreholes, are used as drinking water sources. Non-conventional water sources, such as treated wastewater (effluents), are used for domestic and agricultural purposes. However, CECs remain part of the treated wastewater, which is being discharged to surface water or used for agriculture. Thus, wastewater (effluent) is the main contributor to the pollution of other water resources. For African countries, the prevalence of rising emerging pollutants in water poses a severe environmental threat. There are different adverse effects of CECs, including the development of antibiotic-resistant bacteria, ecotoxicological effects, and several endocrine disorders. Therefore, this needs the urgent attention of the African Union, policymakers, Non-Governmental Organizations, and researchers to come together and tackle the problem.

Distribution of perfluoroalkyl substances (PFASs) in water, sediment, and fish tissue, and the potential human health risks due to fish consumption in Lake Hawassa, Ethiopia

Due to their global distribution, persistence, bioaccumulative potential and toxicity, perfluoroalkyl substances (PFASs) are considered as hazardous chemicals. Although many studies on PFASs pollution in aquatic environments have been done in the Northern hemisphere, less is known on PFASs pollution in African aquatic ecosystems and the risks they pose to humans through consumption of contaminated biota. The objective of this study was to determine the spatial distribution of PFASs in water, sediment, and fish tissue in Lake Hawassa, Ethiopia, and to investigate possible human health risks due to fish consumption. Among the PFASs detected in water and sediment, perfluorooctanoic acid (PFOA) was the most abundant with mean concentrations of 6.93 ng/L and 0.23 ng/g dw respectively. Long-chained PFASs dominated the PFAS accumulation profiles in fish tissues, with higher concentrations measured in liver compared to muscle tissue. The detected concentrations of PFASs were, however, often similar to those reported in other African aquatic ecosystems. This study showed no potential health risk due to consumption of contaminated fish based on mean concentrations and fish consumption. However, it is expected that peoples who consume more fish (fishermen and local peoples living close to Lake Hawassa) may suffer health risks due to PFASs contamination.

Perfluorooctanoic acid exposure in early pregnancy induces oxidative stress in mice uterus and liver

This study aimed to explore the mechanism of perfluorooctanoic acid (PFOA) toxicity on the uterus and liver of mice during early pregnancy. Pregnant mice were given 0, 1, 5, 10, 20, and 40 mg/kg PFOA daily by gavage from gestational day (GD) 1-7 and sacrificed on GD 9. Subsequently, several toxicity parameters were evaluated, including the uterus and liver weights, liver and uterine indexes, histopathological changes of the liver and uterus, and levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-Px) in the liver. We also determined the expressions of FAS, FASL, Bax, Bcl-2, and Caspase-3 in decidual cells by immunohistochemistry and the TUNEL assay to detect apoptosis uterine cells. The results showed that PFOA increased the liver weights and reduced the uterus index in a dose-dependent manner. With increasing doses of PFOA, the levels of SOD and GSH-Px were significantly decreased, and MDA increased substantially in liver tissue. 20 mg/kg and 40 mg/kg of PFOA caused more substantial harm to the uterus, thus a higher probability for congestion and resorption. The expression of FAS, FASL, Bax, and Caspase-3 in decidual cells of the uterus in the PFOA treatment groups significantly increased in a dose-dependent manner. The expression of Bcl-2 was downregulated, decreasing the Bcl-2/Bax ratio. At gestation day 9, the control group had significantly fewer apoptotic cells in the uterus and shallower staining than the 40 mg/kg PFOA group. The findings of this study suggest that oxidative damage may be one of the mechanisms by which PFOA induces liver toxicity, and a subsequent increase in uterine cell apoptosis may cause embryo loss or damage.

Concentrations and human exposure assessment of per and polyfluoroalkyl substances in farmed marine shellfish in South Africa

Although the consumption of seafood is a major route of human exposure to perfluoroalkyl substances (PFAS), data on their concentrations in marine shellfish and the exposure of the African population to PFAS through the consumption of shellfish is lacking. In this study, the concentrations of 15 PFAS were measured in four species of farmed marine shellfish by using a validated UHPLC-MS/MS method. These concentrations were used to determine the human daily intake of PFAS through the consumption of marine shellfish and the hazard quotient thereof. PFPeA, PFOS, PFHxA and PFTeDA were the most prevalent compounds with detection frequencies of 94, 88, 76 and 71%, respectively. The Σ₁₁PFAS concentrations (in ng g^-1 wet weight (ww)) ranged from 0.12 to 0.49, 4.83-6.43, 0.64-0.66 and 0.22 ng g^-1 ww in abalone, mussel, oyster and lobster, respectively. The prevalence of PFCAs reflects the current contamination profile of PFAS in farmed shellfish. The estimated daily intake for Σ₁₀ PFAS through the consumption of marine shellfish ranged from 0.05 to 1.58 ng kg^-1 bw d^-1. Overall, the hazard quotients for these compounds were low, indicating that these compounds do not pose a health risk to the South African population through shellfish consumption. This study provides background data for future studies on the occurrence of PFAS and other emerging contaminants in the African coastal environment.

Risks posed by per- and polyfluoroalkyl substances (PFAS) on the African continent, emphasizing aquatic ecosystems

Per- and polyfluoroalkyl substances (PFAS) are organic pollutants that may have adverse effects on the ecosystem. Despite the global presence of PFAS, knowledge of PFAS on the African continent is limited because monitoring of PFAS is challenging and often not feasible owing to the lack of analytical capacity and high cost. However, it is necessary to understand the environmental risks posed by these chemicals in developing countries, because increasing urbanization will likely increase PFAS contamination in the environment. Although, as far as is known, PFAS concentrations in the African aquatic environment are generally lower than in more developed countries, exceedances of ecological quality standards (EQS) were reported in a few cases, providing evidence of potential ecological risks to these ecosystems. However, the number of ecosystems at risk will likely increase as urbanization and modernization increase in African countries. Therefore, environmental regulations should be updated and implemented to reduce further contamination of the aquatic environment with these chemicals. In addition, analytical laboratories in Africa should develop their capacity to detect PFAS and related compounds regularly and routinely. Local hot spots need to be identified, the influence of these hot spots on the PFAS burden in the environment should be investigated, and environmental regulations should be implemented for these hot spots to reduce their environmental impact. Therefore, we recommend a more routine monitoring of PFAS, including new PFAS that are currently used as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) alternatives, which are not regulated and environmentally concerning. Integr Environ Assess Manag 2021;17:726-732. © 2021 SETAC.

Determination and assessment of human dietary intake of per and polyfluoroalkyl substances in retail dairy milk and infant formula from South Africa

Dairy milk and infant formula play important roles in the diet of adolescents, adults and infants, respectively, in the South African population. However, data on the occurrence of legacy and emerging contaminants such as PFAS in these important food sources is lacking. In this study, the concentration of fifteen PFAS were measured in 23 pooled retail dairy milk and 7 pooled infant formulas by means of an ultrahigh performance liquid chromatography tandem mass spectrometric method. The concentrations of Σ₁₅PFAS ranged from 0.08-15.51 ng mL^-1 and 0.42-5.74 ng mL^-1 in dairy milk and infant formulas, respectively. PFBA, PFPeA, PFuDA, PFTrDA and PFDoA were the most prevalent PFAS in both matrices with detection frequency > 96%. Highest PFAS concentrations of 2.02 ng ml^-1 and 2.76 ng ml^-1 were recorded for PFDoA in infant formulas and dairy milk, respectively. The concentrations of legacy PFAS -PFOA and PFOS, shows resemblance with global data, however, elevated concentrations of long chain C₉ - C₁₄ PFAS were observed in this study. Though, higher concentrations of PFAS were measured in full cream dairy milk, no statistical significant difference (P = 0.546) was observed for the various classes of dairy milk. The EDI of Σ₁₅PFAS through infant formulas were 184.92, 329.47 and 166 ngkg^-1BWday^-1 for partially breastfed, exclusively formula fed and older infants, respectively. Similarly, the EDI of PFAS through dairy milk for toddlers, adolescents, female and male adults for the rural population were 14.17, 1.09, 2.59 and 3.16 ngkg^-1BWday^-1 respectively while they were 20.41, 3.84, 4.13 and 4.26 ngkg^-1BWday^-1 respectively in the urban population. Although, the EDI of PFAS through the consumption of infant formulas and dairy milk are lower than the daily tolerable limits, the relative importance of long-term exposure and the cumulative effects of multiple exposure pathways cannot be overemphasized.

Male reproductive toxicity involved in spermatogenesis induced by perfluorooctane sulfonate and perfluorooctanoic acid in Caenorhabditis elegans

As a persistent organic pollutant, perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) have gained increasing research attention over recent years because of their potential risk to humans and the environment. In this paper, we investigated the reproductive toxicity of these pollutants using a C. elegans model to evaluate spermatogenesis throughout the entire developmental cycle of him-5 mutant by exposing to 0.001, 0.01, and 0.1 mmol/L PFOS or PFOA for 48 h. Experimental results suggested that PFOS and PFOA exposure led to reductions in brood size, germ cell number, spermatid size, and motility, and increases in rate of malformation spermatids. Analysis of variance (ANOVA) showed that exposure to PFOS resulted in higher levels of damage than PFOA in germ cells only in 0.001 mmol/L exposure group. RT-qPCR was used to further investigate the expression of genes associated with different stages of spermatogenesis, such as mitosis and meiosis, fibrous body-membranous organelles (FB-MOs), and sperm activation. The expression levels of wee-1.3, spe-4, spe-6, and spe-17 genes were increased, while those of puf-8, spe-10, fer-1, swm-1, try-5, and spe-15 genes were decreased. Our results suggesting that PFOS or PFOA may cause spermatogenesis damage by disrupting the mitotic proliferation, meiotic entry, formation of the MOs, fusion of the MOs and plasma membrane (PM), and pseudopods. Loss-of-function studies using puf-8 and spe-10 mutants revealed spe-10 gene was specifically involved in PFOS- or PFOA-induced reproductive toxicity via regulating one or more critical palmitoylation events, while puf-8 gene was not direct target of PFOS and PFOA, and PFOS and PFOA may act on the upstream gene of puf-8, thus affecting reproductive ability. Taken together, these results demonstrate the potential adverse impact of PFOS and PFOA exposure on spermatogenesis and provide valuable data for PFC risk assessment. Grapical abstract.

Environmental levels and human body burdens of per- and poly-fluoroalkyl substances in Africa: A critical review

Per- and polyfluoroalkyl substances (PFASs) are known organic pollutants with adverse health effects on humans and the ecosystem. This paper synthesises literature about the status of the pollutants and their precursors, identifies knowledge gaps and discusses future perspectives on the study of PFASs in Africa. Limited data on PFASs prevalence in Africa is available because there is limited capacity to monitor PFASs in African laboratories. The levels of PFASs in Africa are higher in samples from urban and industrialized areas compared to rural areas. Perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) are the dominant PFASs in human samples from Africa. Levels of PFOS and PFOA in these samples are lower than or comparable to those from industrialized countries. PFOA and PFOS levels in drinking water in Africa are, in some cases, higher than the EPA drinking water guidelines suggesting potential risk to humans. The levels of PFASs in birds' eggs from South Africa are higher, while those in other environmental media from Africa are lower or comparable to those from industrialized countries. Diet influences the pollutant levels in fish, while size and sex affect their accumulation in crocodiles. No bioaccumulation of PFASs in aquatic systems in Africa could be confirmed due to small sample sizes. Reported sources of PFASs in Africa include municipal landfills, inefficient wastewater treatment plants, consumer products containing PFASs, industrial wastewater and urban runoff. Relevant stakeholders need to take serious action to identify and deal with the salient sources of PFASs on the African continent.

Removal of COD, NH4-N, and perfluorinated compounds from wastewater treatment plant effluent using ZnO-coated activated carbon

This study investigated the removal of chemical oxygen demand (COD), NH₄-N, and perfluorinated compounds (PFCs) in the effluent from a wastewater treatment plant (WWTP) using ZnO coated activated carbon (ZnO/AC). Results suggested that the optimal dosage of the ZnO/AC was 0.8 g/L within 240 min of contact time, at which the maximum removal efficiency of COD was approximately 86.8%, while the removal efficiencies of PFOA and PFOS reached 86.5% and 82.1%. In comparison, the removal efficiencies of NH₄-N, PFBA, and PFBS were lower, at approximately 47.9%, 44.0%, and 55.4%, respectively. In addition, COD was preferentially adsorbed before PFCs and NH₄-N, when the contact time ranged from 0 to 180 min, and the order of PFCs removal showed a positive correlation with C-F chain length. The kinetic study revealed that the removal of COD, NH₄-N, and PFCs could be better depicted and predicted by the Lagergren quasi-second order dynamic model with high correlation coefficients, which involved liquid membrane diffusion, intraparticle diffusion, and photocatalytic reactions. The saturated ZnO/AC was finally regenerated using ultrasound for 3 h and retained excellent performance, which proved it could be considered as an effective and alternative technology.

The emerging PFOS alternative OBS exposure induced gut microbiota dysbiosis and hepatic metabolism disorder in adult zebrafish

Sodium ρ-perfluorous nonenoxybenzene sulfonate (OBS), as a novel the alternatives of PFASs, is widely used in many fields of life. Here, adult male zebrafish selected were exposed to OBS at concentrations of 3, 30 and 300 μg/L for 7 and 21 days, respectively. Based on the gut microbiota analysis, at genus level, the relative abundance of the Flavobacterium, Hyphomicrobium, Paracoccus, Lawsonia, Plesiomonas and Vibrio changed significantly in the gut of zebrafish after exposure to 300 μg/L OBS. In addition, the liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis suggested that a total of 1077 metabolites in pos-model and a total of 706 metabolites in neg-model changed significantly from the liver, and these changed metabolites were tightly related to several pathways including amino acid, pyrimidine and purine metabolism, etc. Furthermore, the changed gut bacteria including Flavobacterium, Hyphomicrobium, Paracoccus, Lawsonia, Plesiomonas and Vibrio at genus level were significantly correlated with various metabolites (succinic acid, leucine, xanthine, orotic acid, nicotinic acid, etc.). Taken together, all the results showed that low dose of OBS exposure could induce the dysbiosis of gut microbiota and disturbed the hepatic metabolism balance in adult male zebrafish.

Electrooxidation of short and long chain perfluorocarboxylic acids using boron doped diamond electrodes

This study investigates electrooxidation of short (C3-C6) and long (C7-C-18) chain perfluorocarboxylic acids (PFCAs) including perfluorooctane sulfonate (PFOA) using Si/BDD electrode. The effect of operational parameters (supporting electrolyte type, applied current density, and initial pH) were explored for PFOA removal. At the optimized conditions, 74% TOC removal and 37% defluorination ratio were gained for 10 mg L^-1 of PFOA solution which evidences that the shorter chain PFCAs were formed. The PFOA degradation pathway followed one direct electron transfer from PFOA molecule to anode surface. Then two different degradation pathways were proposed. The first proposed degradation mechanism involved the reaction of perfluoroheptyl radical and hydroxyl radical, the release of HF and hydrolysis. The second mechanism involved the reaction between perfluoroheptyl radical and O₂, formation of C₇F₁₅O and perfluorohexyl radical with releasing COF₂. The removal of short- (C3-C6) and long-chain PFCAs (C7-C18) was also characterized. More than 95% of removal efficiency was gained for all long-chain PFCAs, excluding C7. The removal ratios of short-chain PFCAs (C3-C6) were 39%, 41%, 66% and 70% for C3, C4, C5 and C6, respectively. Contrary to long-chain PFCAs, chain-length dependence for short-chain PFCAs were observed. Defluorination ratio of short-chain PFCAs was only 45% signifying that defluorination partially occurred. Water matrix did not significantly affect the degradation of short-chain PFCAs in deionized water (DI), river water and secondary effluent of a wastewater treatment plant (WWTP). In contrast, defluorination ratio of long-chain PFCAs was noticeably affected by water matrix with the order of DI water > WWTP effluent > river water.

Toxicity of perfluorinated compounds to soil microbial activity: Effect of carbon chain length, functional group and soil properties

Perfluorinated compounds (PFCs) have been detected at various concentrations in different environment compartments due to their widespread usage. Nowadays, soil environment has become a prominent sink of PFCs from surface runoff and penetration, but few researches have been conducted in the toxicity of PFCs to soil microorganisms. To address the issue, microcalorimetry was applied to investigate the toxicity of six PFCs with different carbon chain length (4, 8, and 10) and functional group (carboxylic and sulfonic) to microbial activities in three Chinese soils varying widely in soil properties. Adsorption of PFCs by soil matrix was a key factor in controlling the toxicity of PFCs to soil microorganisms. The differences of carbon chain length and functional groups of PFCs have different impacts on soil microbial activity while affecting adsorption progress. Particularly, the sulfonic PFCs expressed higher toxicity than the carboxylic. It is also identified that the longer the chain length, the greater the toxicity of PFCs. Soil pH was another relevant factor of soil adsorption, and with the increase of pH, adsorption capability increased. Soil available P, N and K were essential nutrients in soil, and suggested to improve microbial activity under PFCs stress.