RESUMO
Per- and polyfluoroalkyl substances (PFAS) comprise >4000 synthetic substances used in industrial applications and consumer products. PFAS used daily in households and manufacturing plants end up in domestic sewage, and industrial effluents can be discharged to surface water. Urban watersheds located in low and middle-income countries (LMIC), which lack sanitation infrastructure, are potential recipients of waste containing PFAS. Yet, only a few studies report PFAS occurrence in urban reservoirs and lakes, especially those located in the Global South due to resource limitations. This is the first study aimed to assess PFAS occurrence and ecological risks in Pampulha Lake, Brazil, a site which represents the reality of many other urban watersheds in LMIC as it is surrounded by densely populated areas and manufacturing plants. Surface water samples were collected monthly for 1 year from four sampling points at Pampulha Lake. Sample analysis was based on US Environmental Protection Agency Method 1633, which employs solid phase extraction followed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). Species sensitivity distribution (SSD) curves were built to identify potentially susceptible species based on detected water concentrations. Bioaccumulation was estimated for fish tissue. Short-chain (perfluorobutanesulfonic acid, PFBS and perfluorohexanoic acid, PFHxA) and long-chain PFAS (perfluorodecanoic acid, PFDA; perfluorooctanoic acid, PFOA; perfluorododecanoic acid, PFDoA; and perfluorooctanesulfonic acid, PFOS) were detected at the µg L-1 range. Total PFAS concentrations in the wet season were generally higher than in the dry season, likely due to limited capacity of the treatment plant processing water from tributaries which receive raw sewage. More than 5 % of aquatic species are potentially susceptible to chronic effects of PFOS at detected concentrations (0.2-2.2 µg L-1). Predicted bioaccumulation of PFOS in fish was above advisory diet intake levels for humans. Results emphasize the need for studies related to PFAS occurrence in watersheds located in LMIC.
Assuntos
Monitoramento Ambiental , Fluorocarbonos , Lagos , Poluentes Químicos da Água , Fluorocarbonos/análise , Brasil , Lagos/química , Poluentes Químicos da Água/análise , Ácidos Alcanossulfônicos/análise , Animais , Caprilatos/análise , Peixes , Medição de RiscoRESUMO
This study assessed the occurrence of five antibiotics, three hormones, caffeine, and long and short-chain perfluoroalkyl and polyfluoroalkyl substances (PFASs) in surface water and feedstuff samples obtained from aquaculture cages in Três Marias reservoir in Brazil. This is the first work to evaluate the presence of PFAS in surface water used for aquaculture in Brazil. Solid-phase extraction and low temperature partitioning extraction followed by liquid chromatography coupled to mass spectrometry (LC-MS) were performed to process and analyze surface water samples and feedstuff, respectively. The ecotoxicological risk quotient was calculated for target compounds detected in water. Ciprofloxacin and caffeine were detected in all surface water samples. Pharmaceutical drugs ranged from 0.7 ng L-1 (trimethoprim) to 389.2 ng L -1 (ß-estradiol). Estrone (10.24 ng g-1) and ß-estradiol (66.20 ng g-1) were also found in feedstuff. Four PFASs (PFOA, PFDoA, PFTeDA, and PFBS) were detected (9.40-15.2 µg L-1) at levels higher than reported in studies conducted worldwide. Ecotoxicological risk assessment indicated high risks for caffeine and PFOA, PFDoA, and PFTeDA with RQ values from 10 to 103. These findings reveal risks to biodiversity, ecosystem integrity and human health considering possible intake of these contaminants by fish consumption due to potential bioaccumulation of these substances. Hence, it is critical to conduct more studies in this direction in Brazil and other low and middle-low-income countries.
Assuntos
Ácidos Alcanossulfônicos , Ciclídeos , Fluorocarbonos , Poluentes Químicos da Água , Humanos , Animais , Água/análise , Brasil , Monitoramento Ambiental , Antibacterianos/análise , Ácidos Alcanossulfônicos/análise , Cafeína/análise , Ecossistema , Estradiol/análise , Poluentes Químicos da Água/análise , Fluorocarbonos/análiseRESUMO
When performing basic and translational laboratory studies with aquatic organisms, particularly for bioaccumulation, toxicity, or biotransformation experiments, it is imperative to control the route and dose of exposure. Contamination of feed and the organisms prior to study could alter the results of an experiment. Furthermore, if organisms not exposed in the lab are used for quality assurance/quality control, then blank levels, method detection limits, and limits of quantitation can be affected. In an effort to determine the magnitude of this potential issue for exposure studies involving Pimephales promelas, we analyzed a suite of 24 per- and polyfluoroalkyl substances (PFAS) in four types of feed from three different companies and in organisms from five aquaculture facilities. Contamination with PFAS was found in all types of materials and organisms from all aquaculture farms. The most frequently detected PFAS in fish feed and aquaculture fathead minnows were perfluorocarboxylic acids and perfluorooctane sulfonate (PFOS). Concentrations of total and individual PFAS in feed ranged from nondetect to 76 ng/g and from nondetect to 60 ng/g, respectively. Fathead minnows were contaminated with PFOS and perfluorohexane sulfonate as well as several perflourocarboxylic acids. Concentrations of total and individual PFAS ranged from 1.4 to 351 ng/g and from nondetect to 328 ng/g, respectively. The PFOS measured in food was primarily the linear isomer, consistent with greater bioaccumulation of that isomer in organisms raised as fish food. Future studies are necessary to define the extent of PFAS contamination in aquatic culture facilities and aquaculture production operations. Environ Toxicol Chem 2023;42:1463-1471. © 2023 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
Assuntos
Ácidos Alcanossulfônicos , Cyprinidae , Fluorocarbonos , Poluentes Químicos da Água , Animais , Monitoramento Ambiental/métodos , Poluentes Químicos da Água/análise , Ácidos Alcanossulfônicos/análise , Cyprinidae/metabolismo , Aquicultura , Fluorocarbonos/análiseRESUMO
Although freshwater mussels are imperiled and identified as key conservation priorities, limited bioaccumulation information is available on these organisms for contaminants of emerging concern. In the present study we investigated the bioaccumulation of per- and polyfluoroalkyl substances (PFAS) in the model freshwater pond mussel Sagittunio subrostratus because mussels provide important ecosystem services and are important components of aquatic systems where PFAS occur. In the present study we selected four representative perfluorinated carboxylic acids and sulfonic acids, then determined the bioaccumulation kinetics of freshwater mussels in a controlled laboratory study. Because uptake (ku ) and elimination (ke ) rate constants and time to steady state are important parameters for food web bioaccumulation models, we derived bioaccumulation kinetic parameters following exposure to perfluorohexane sulfonic acid (PFHxS), perfluorooctane sulfonic acid (PFOS), and perfluorodecanoic acid (PFDA) at 10 µg/L and perfluoroundecanoic acid (PFUnDA) at 1 µg/L during a 14-day uptake period followed by a 7-day elimination period. Kinetic and ratio-based bioaccumulation factors (BAFs) were subsequently calculated, for example ratio-based BAFs for mussel at day 7 were determined for PFHxS (0.24 ± 0.08 L/kg), PFOS (7.73 ± 1.23 L/kg), PFDA (4.80 ± 1.21 L/kg), and PFUnDA (84.0 ± 14.4 L/kg). We generally observed that, for these four model PFAS, freshwater mussels have relatively low BAF values compared with other aquatic invertebrates and fish. Environ Toxicol Chem 2023;42:1190-1198. © 2023 SETAC. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.
Assuntos
Ácidos Alcanossulfônicos , Bivalves , Fluorocarbonos , Animais , Cinética , Bioacumulação , Ecossistema , Água Doce , Fluorocarbonos/análiseRESUMO
Plastic pollution is a major threat facing our environment. To understand the full effects, we must first characterize how plastics break down in environmental systems. Heretofore, there has been little work examining how exposure to sewage sludge facilitates the degradation of plastics, particularly of plastics that have been previously weathered. Herein, we characterize how the crystallinity, surface chemistry, and morphology of polylactic acid (PLA) and polyethylene (PE) films change due to sludge exposure. In this work, sludge-induced changes in carbonyl index were found to depend on the level of prior exposure to ultraviolet (UV) irradiation. The carbonyl indices of un-irradiated films increased while those of UV-aged films decreased after 35 days of sludge exposure. In addition, the carbonoxygen and hydroxyl bond indices of PE films increased with sludge exposure, suggesting the surface oxidation of PE. As for PLA, crystallinity was found to increase with sludge exposure, consistent with a chain scission mechanism. This work will help to predict the behavior of plastic films after transfer from wastewater to sewage sludge.
Assuntos
Polietileno , Esgotos , Esgotos/química , Poliésteres , PlásticosRESUMO
Pyrolysis as a thermochemical technology is commonly used in waste management and remediation of organic-contaminated soil. This study, for the first time, investigated fluorinated and non-fluorinated compounds emitted from per- and polyfluoroalkyl substances (PFAS) and relevant products upon pyrolysis (200-890 °C) and their formation mechanisms. Approximately 30 non-fluorinated compounds were detected from PFAS-containing aqueous film-forming foams (AFFFs) and commercial surfactant concentrates (SCs) after heating, including glycols and glycol ethers that were predominant at 200 °C. Oxygen (e.g., 1,4-dioxane) and nitrogen heterocycles and benzene were unexpectedly observed at higher temperatures (300-890 °C), which were likely formed as a consequence of the thermal dehydration, dehydrogenation, and intermolecular cyclization of glycols and glycol ethers. Fluorinated volatiles in six major classes were detected at low and moderate temperatures (200-500 °C), including perfluoroalkenes, perfluoroalkyl aldehydes, fluorotelomer alcohols, and polyfluorinated alkanes/alkenes. Several features of the pyrolyses of PFAS suggest that the underlying decomposition mechanism is radical-mediated. Perfluoroheptene thermally decomposed at 200 °C to shorter-chain homologues following a radical chain-scission mechanism. Most of these volatiles observed at low/moderate temperatures were not detected at 890 °C. Ultra-short-chain fluorinated greenhouse gases (e.g., perfluoromethane) were not found.
Assuntos
Fluorocarbonos , Poluentes Químicos da Água , Éteres , Fluorocarbonos/análise , Glicóis , Pirólise , Água , Poluentes Químicos da Água/análiseRESUMO
Per- and polyfluoroalkyl substances (PFASs) have been used in consumer and military products since the 1950s but are increasingly scrutinized worldwide because of inherent chemical properties, environmental contamination, and risks to public health and the environment. The United States Environmental Protection Agency (USEPA) identified 24 PFASs of interest for further study and possible regulation. We examined 371 peer-reviewed studies published since 2001 to understand the occurrence and distribution of 24 priority PFASs in global surface waters and groundwater. We identified 77,541 and 16,246 data points for surface waters and groundwater, respectively, with total PFAS concentrations ranging from low pg/L to low mg/L levels. Most data were from Asia, Europe, and North America with some reports from Oceania. PFAS information from other geographic regions is lacking. PFASs levels are consistently higher in rivers and streams followed by lakes and reservoirs and then coastal and marine systems. When sufficient data were available, probabilistic environmental hazard assessments (PEHAs) were performed from environmental exposure distributions (EEDs) to identify potential exceedances of available guideline values for each compound by matrix, region, and aquatic system. Specifically, exceedances of USEPA drinking water lifetime health advisory levels were up to 74% for PFOS in groundwater from Oceania and 69% for PFOA in North American groundwater. Our findings support selection of environmentally relevant experimental treatment levels for future toxicology, ecotoxicology and bioaccumulation studies, and potable source water exposure investigations, while highlighting PFASs and major geographic locations requiring additional study and inclusion in global monitoring and surveillance campaigns.
Assuntos
Ácidos Alcanossulfônicos , Água Potável , Fluorocarbonos , Água Subterrânea , Poluentes Químicos da Água , Saúde Ambiental , Monitoramento Ambiental , Fluorocarbonos/análise , Fluorocarbonos/toxicidade , Poluentes Químicos da Água/análiseRESUMO
Effects of perfluorooctane sulfonate (PFOS) and a legacy aqueous film-forming foam (AFFF) containing 91% PFOS (AFFF PFOS) on reproduction, chick survivability, and growth of Japanese quail (Coturnix japonica) were determined. Day-old Japanese quail were administered PFOS or AFFF PFOS at 6 dietary concentrations ranging from 0 to 21 mg kg-1 feed for a total of 20 wk. At the age of 4 wk, 16 male/female pairs per treatment were assigned to cages, and egg laying was induced by the age of 10 wk. Eggs were collected daily, set weekly, and incubated for 18 d for the following 10 wk. Hatchlings were fed uncontaminated feed for 2 wk and euthanized to collect blood and liver. After 10 wk of egg collection, adults were euthanized to collect blood, liver, and kidneys. Significantly increased myofiber numbers in the liver and glomerular sclerosis in the kidneys of adults indicated damage at greater doses. Perfluorooctane sulfonate or AFFF PFOS did not significantly affect egg production; however, hatchability was decreased at the highest PFOS dose. The no-observed-adverse-effect levels for chick survivability, considered the critical effect, were 4.1 mg PFOS kg feed-1 (0.55 mg kg body wt-1 d-1 ) and 5.0 mg AFFF PFOS kg feed-1 (0.66 mg kg body wt-1 d-1 ), resulting in calculated average toxicity reference values of 0.25 mg kg feed-1 and 0.034 mg kg body weight-1 d-1 . Environ Toxicol Chem 2021;40:2521-2537. © 2020 SETAC.
Assuntos
Ácidos Alcanossulfônicos , Fluorocarbonos , Ácidos Alcanossulfônicos/análise , Ácidos Alcanossulfônicos/toxicidade , Animais , Coturnix , Exposição Dietética , Feminino , Fluorocarbonos/análise , Fluorocarbonos/toxicidade , Masculino , ReproduçãoRESUMO
As part of an effort to develop avian ecotoxicity information for poly- and perfluoroalkyl substances (PFAS) including perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) associated with aqueous film-forming foam (AFFF) used by the Department of Defense, the subacute toxicity of PFOS, PFOA, PFOS + PFOA, 3M AFFF, and Ansul AFFF to Japanese quail (Coturnix japonica) chicks was determined. Ten-day-old Japanese quail were administered treated feed for 5 d and then fed untreated feed for 18 d. Analyzed concentrations of PFOS, PFOA, and PFOS + PFOA ranged from 62 to 1955, 162 to 1208, and 43 + 45 to 296 + 292 mg kg feed-1 . Analyzed concentrations of PFOS in feed containing the 3M AFFF ranged from 73 to 1399 mg kg feed-1 , and formulated concentrations of 6:2 fluorotelomer thioamido sulfonate in feed containing the Ansul AFFF ranged from 9 to 1118 mg kg feed-1 . Average daily doses resulting in 50% mortality at day 5 were 38 (34-43), 68 (63-74), 55 (51-59), and 130 (103-164) mg PFOS, PFOA, PFOS + PFOA, and PFOS in 3M AFFF kg body weight-1 d-1 . Ansul AFFF did not result in any mortalities. Dietary concentrations resulting in 50% mortality at day 5 were 351 (275-450), 496 (427-575), 398 (339-468), and 467 (390-559) mg PFOS, PFOA, PFOS + PFOA, and PFOS in 3M AFFF kg feed-1 . Environ Toxicol Chem 2021;40:695-710. © 2020 SETAC.
Assuntos
Ácidos Alcanossulfônicos , Fluorocarbonos , Poluentes Químicos da Água , Ácidos Alcanossulfônicos/toxicidade , Animais , Caprilatos/toxicidade , Coturnix , Fluorocarbonos/análise , Fluorocarbonos/toxicidade , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/toxicidadeRESUMO
Recent studies have reported potential neurotoxicity and epigenetic alteration associated with exposure to several per- and polyfluoroalkyl substances (PFASs). However, such information is limited to a few compounds (e.g., perfluorooctane sulfonate), primarily based on rodent experiments, and the underlying toxicological mechanism(s) for many PFAS in the environment remain poorly understood. In the present study, we investigated 8:8 perfluoroalkyl phosphinic acid (8:8 PFPiA), an under-studied PFAS with high persistency in the environment and biota, using the zebrafish model. We exposed zebrafish embryos (<4 hpf) to various concentrations of 8:8 PFPiA (0, 0.0116, 0.112, 0.343, 1.34, 5.79 µM) for 144 h. Although there was no significant change in survival, hatchability and malformations, zebrafish locomotor speed at 120 h significantly decreased in dark photoperiod. At 144 h, several genes related to thyroid hormones that are essential for neurodevelopment, including corticotropin releasing hormone b (crhb), iodothyronine deiodinase 3a (dio3a), thyroid-stimulating hormone receptor (tshr) and nkx2 homeobox1 (nkx 2.1), were up-regulated by 8:8 PFPiA at 5.79 µM. 8:8 PFPiA also significantly down-regulated a neurodevelopmental gene, elav like neuron-specific RNA binding protein (elavl3), at 1.34 and 5.79 µM; in addition, one oxidative stress gene was slightly but significantly up-regulated. Further, global DNA methylation was significantly decreased at higher treatment levels, identifying effects of 8:8 PFPiA on epigenetic regulation. However, promoter DNA methylation of selected genes (dio3, tshr, nkx2.1) were not statistically altered, though dio3 methylation showed a decreasing trend with 8:8 PFPiA exposure. Our results specifically advance an understanding of molecular toxicology of PFPiA and more broadly present an approach to define diverse responses during animal alternative assessments of PFASs.
Assuntos
Fluorocarbonos , Peixe-Zebra , Animais , Metilação de DNA , Epigênese Genética , Ácidos Fosfínicos , Glândula TireoideRESUMO
Remediation of groundwater impacted by per- and polyfluoroalkyl substances (PFAS) is particularly challenging due to the resistance of the molecule to oxidation because of the strength of the carbon-fluorine bond and the need to achieve low nanogram per liter drinking water targets. Previous studies have shown that activated carbon is an effective sorbent for removal of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in conventional water treatment systems. The objective of this study was to evaluate the in situ delivery and sorptive capacity of an aqueous suspension containing powdered activated carbon (PAC) stabilized with polydiallyldimethylammonium chloride (polyDADMAC). Batch reactor studies demonstrated substantial adsorption of PFOA and PFOS by polyDADMAC-stabilized PAC, which yielded Freundlich adsorption coefficients of 156 and 629 L/g-n, respectively. In columns packed with 40-50 mesh Ottawa sand, injection of a PAC (1000 mg/L) + polyDADMAC (5000 mg/L) suspension created a sorptive region that increased subsequent PFOA and PFOS retention by 3 orders of magnitude relative to untreated control columns, consistent with the mass of retained PAC. Experiments conducted in a heterogeneous aquifer cell further demonstrated the potential for stabilized-PAC to be an effective in situ treatment option for PFAS-impacted groundwater.
Assuntos
Fluorocarbonos , Poluentes Químicos da Água , Carvão Vegetal , Fluorocarbonos/análise , Polímeros , Pós , Poluentes Químicos da Água/análiseRESUMO
In situ methods for the sequestration of perfluorooctyl-1-sulfonate (PFOS) that are based on PFOS binding to polyquaternium polymers were reported previously, providing an approach to immobilize and concentrate PFOS in situ. To apply these methods in real life, the concentrations of polymers that permit efficient sequestration must be determined. This is only possible if the stoichiometry and strength of PFOS binding to polyquaternium polymers are known. Here, we report on the use of fluorous-phase ion-selective electrodes (ISEs) to determine the equilibrium constants characterizing binding of PFOS to poly(dimethylamine-co-epichlorohydrin) and poly(diallyldimethylammonium) in simulated groundwater and in soil suspensions. We introduce a new method to interpret potentiometric data for surfactant binding to the charged repeat unit of these polyions by combining a 1:1 binding model with the ISE response model. This allows for straightforward prediction and fitting of experimental potentiometric data in one step. Data fit the binding model for poly(diallyldimethylammonium) and poly(dimethylamine-co-epichlorohydrin) chloride in soil-free conditions and in the presence of soil from Tinker Air Force Base. When the total PFOS concentration in a soil system is known, knowledge of these PFOS binding characteristics permits quantitative prediction of the mobile (free) and polymer-bound fractions of PFOS as a function of the concentrations of the polyquaternium polymer. Because the technique reported here is based on the selective in situ determination of the free ionic surfactant, we expect it to be similarly useful for determining the sequestration of a variety of other ionic pollutants.
RESUMO
Aqueous film forming foams (AFFF) can contain gram per liter concentrations of per- and polyfluoroalkyl substances (PFAS) and are often released in large quantities directly to the environment as they are used to fight fires. AFFF composition is complex and contains many unknown PFAS in addition to ingredients such as hydrocarbons, solvents, and corrosion inhibitors. While biological effects of single PFAS have been studied, the effects of PFAS-containing mixtures, such as AFFF, are unknown. The effect of PFAS on microorganisms is also not well understood; nevertheless, we rely on microorganisms in locations containing elevated PFAS concentrations to perform certain functions, such as carbon cycling and co-contaminant degradation. This study focused on determining the functional consequences of AFFF and PFAS exposure in a microbial community in both the presence and the absence of a co-contaminant. AFFF, select PFAS, and a PFAS mixture were tested to determine the effect of AFFF on an anaerobic microbial community and the characteristics of the PFAS that drive toxicity in such mixtures. To study this, anaerobic digester communities were exposed to PFAS and a co-contaminant (2,4-dichlorophenol, DCP); methane production, as an indicator of toxicity and the community's ability to cycle carbon, and co-contaminant degradation were monitored. Results showed that PFAS and AFFF can alter the toxicity of DCP, inhibit DCP degradation, decrease the number of methanogens present, and change the microbial community structure. DCP was also able to decrease the toxicity of the PFAS perfluorooctane sulfonate (PFOS), possibly by changing the sorption of PFOS to the microorganisms present. Additionally, it was determined that while PFOS was responsible for AFFF toxicity, no single PFAS or simple PFAS mixture accurately accounted for the inhibition of DCP degradation caused by AFFF exposure.
Assuntos
Ácidos Alcanossulfônicos/toxicidade , Retardadores de Chama/toxicidade , Fluorocarbonos/toxicidade , Metano/análise , Microbiota/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , AnaerobioseRESUMO
Perfluoroalkyl substances (PFAS) are ubiquitous and persistent environmental contaminants, yet knowledge of their biological effects and mechanisms of action is limited. The highest aqueous PFAS concentrations are found in areas where bacteria are relied upon for functions such as nutrient cycling and contaminant degradation, including fire-training areas, wastewater treatment plants, and landfill leachates. This research sought to elucidate one of the mechanisms of action of PFAS by studying their uptake by bacteria and partitioning into model phospholipid bilayer membranes. PFAS partitioned into bacteria as well as model membranes (phospholipid liposomes and bilayers). The extent of incorporation into model membranes and bacteria was positively correlated to the number of fluorinated carbons. Furthermore, incorporation was greater for perfluorinated sulfonates than for perfluorinated carboxylates. Changes in zeta potential were observed in liposomes but not bacteria, consistent with PFAS being incorporated into the phospholipid bilayer membrane. Complementary to these results, PFAS were also found to alter the gel-to-fluid phase transition temperature of phospholipid bilayers, demonstrating that PFAS affected lateral phospholipid interactions. This investigation compliments other studies showing that sulfonated PFAS and PFAS with more than seven fluorinated carbons have a higher potential to accumulate within biota than carboxylated and shorter-chain PFAS.
Assuntos
Fluorocarbonos , Poluentes Químicos da Água , Bactérias , Biota , Bicamadas LipídicasRESUMO
A comprehensive method to extract perfluoroalkane sulfonic acids (PFSAs), perfluoroalkyl carboxylic acids (PFCAs), polyfluoroalkyl phosphoric acid diesters (diPAPs), perfluoroalkyl phosphinic acids (PFPiAs) and perfluoroalkyl phosphonic acids (PFPAs) from sediment and analysis by liquid chromatography tandem mass spectrometry (LC-MS/MS) was developed and applied to sediment cores from three small isolated lakes (Plastic Lake, Lake 442, Lake Tettegouche) and Lake Ontario in the Great Lakes Region. Recoveries of the target compounds using the optimized acetonitrile/sodium hydroxide extraction ranged from 73% to 120%. The greatest concentrations of per- and polyfluorinated alkyl substances (PFASs) were recorded in sediment from Lake Ontario (ΣPFASs 13.1 ng/g), where perfluorooctane sulfonic acid (PFOS) contributed over 80% of the total. Concentrations in Lake Ontario were approximately 1-2 orders of magnitude greater than the more remote lakes subject to primarily atmospheric inputs. Whilst the PFAS contribution in Lake Ontario was dominated by PFOS, the more remote lakes contained sediment with higher proportions of PFCAs. Trace amounts of emerging PFASs (diPAPs and PFPiAs) were found in very recent surface Lake Ontario and remote lake sediments.
Assuntos
Ácidos Alcanossulfônicos/análise , Ácidos Carboxílicos/análise , Monitoramento Ambiental/métodos , Fluorocarbonos/análise , Sedimentos Geológicos/análise , Lagos/química , Organofosfatos/análise , Poluentes Químicos da Água/análise , Sedimentos Geológicos/química , Great Lakes Region , Ontário , Espectrometria de Massas em TandemRESUMO
This study compares the fungal growth ratio on loaded ventilation filters under various temperature, relative humidity (RH), and air flow conditions in a controlled laboratory setting. A new full-size commercial building ventilation filter was loaded with malt extract nutrients and conidia of Cladosporium sphaerospermum in an ASHRAE Standard 52.2 filter test facility. Small sections cut from this filter were incubated under the following conditions: constant room temperature and a high RH of 97%; sinusoidal temperature (with an amplitude of 10°C, an average of 23°C, and a period of 24 hr) and a mean RH of 97%; room temperature and step changes between 97% and 75% RH, 97% and 43% RH, and 97% and 11% RH every 12 hr. The biomass on the filter sections was measured using both an elution-culture method and by ergosterol assay immediately after loading and every 2 days up to 10 days after loading. Fungal growth was detected earlier using ergosterol content than with the elution-culture method. A student's t-test indicated that Cladosporium sphaerospermum grew better at the constant room temperature condition than at the sinusoidal temperature condition. By part-time exposure to dry environments, the fungal growth was reduced (75% and 43% RH) or even inhibited (11% RH). Additional loaded filters were installed in the wind tunnel at room temperature and an RH greater than 95% under one of two air flow test conditions: continuous air flow or air flow only 9 hr/day with a flow rate of 0.7 m(3)/s (filter media velocity 0.15 m/s). Swab tests and a tease mount method were used to detect fungal growth on the filters at day 0, 5, and 10. Fungal growth was detected for both test conditions, which indicates that when temperature and relative humidity are optimum, controlling the air flow alone cannot prevent fungal growth. In real applications where nutrients are less sufficient than in this laboratory study, fungal growth rate may be reduced under the same operating conditions.
Assuntos
Filtros de Ar/microbiologia , Cladosporium/crescimento & desenvolvimento , Movimentos do Ar , Biomassa , Ergosterol/análise , Umidade , Temperatura , VentilaçãoRESUMO
Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are emerging anthropogenic compounds that have recently become the target of global concern due to their ubiquitous presence in the environment, persistence, and bioaccumulative properties. This study was carried out to investigate the migration of PFOS and PFOA in soils and groundwater in a U.S. metropolitan area. We observed elevated levels in surface soils (median: 12.2 ng PFOS/g dw and 8.0 ng PFOA/g dw), which were much higher than the soil-screening levels for groundwater protection developed in this study. The measured levels in subsurface soils show a general increase with depth, suggesting a downward movement toward the groundwater table and a potential risk of aquifer contamination. Furthermore, concentrations of PFOS and PFOA in monitoring wells in the source zone varied insignificantly over 5 years (2009-2013), suggesting limited or no change in either the source or the magnitude of the source. The analysis also shows that natural processes of dispersion and dilution can significantly attenuate the groundwater contamination; the adsorption on aquifer solids, on the other hand, appears to have limited effects on the transport of PFOS and PFOA in the aquifer. The probabilistic exposure assessment indicates that ingestion of contaminated groundwater constitutes a much more important exposure route than ingestion of contaminated soil. Overall, the results suggest that (i) the transport of PFOS and PFOA is retarded in the vadose zone, but not in the aquifer; (ii) the groundwater contamination of PFOS and PFOA often follows their release to surface soils by years, if not decades; and (iii) the aquifer can be a major source of exposure for communities living near point sources.
Assuntos
Ácidos Alcanossulfônicos/análise , Caprilatos/análise , Exposição Ambiental/análise , Fluorocarbonos/análise , Água Subterrânea/química , Poluentes do Solo/análise , Solo/química , Poluentes Químicos da Água/análise , Água Potável/química , Geografia , Humanos , MinnesotaRESUMO
The contamination of urban lakes by anthropogenic pollutants such as perfluorooctane sulfonate (PFOS) is a worldwide environmental problem. Large-scale, long-term monitoring of urban lakes requires careful prioritization of available resources, focusing efforts on potentially impaired lakes. Herein, a database of PFOS concentrations in 304 fish caught from 28 urban lakes was used for development of an urban-lake prioritization framework by means of exploratory data analysis (EDA) with the aid of a geographical information system. The prioritization scheme consists of three main tiers: preliminary classification, carried out by hierarchical cluster analysis; predictor screening, fulfilled by a regression tree method; and model development by means of a neural network. The predictive performance of the newly developed model was assessed using a training/validation splitting method and determined by an external validation set. The application of the model in the U.S. state of Minnesota identified 40 urban lakes that may contain elevated levels of PFOS; these lakes were not previously considered in PFOS monitoring programs. The model results also highlight ongoing industrial/commercial activities as a principal determinant of PFOS pollution in urban lakes, and suggest vehicular traffic as an important source and surface runoff as a primary pollution carrier. In addition, the EDA approach was further compared to a spatial interpolation method (kriging), and their advantages and disadvantages were discussed.
Assuntos
Ácidos Alcanossulfônicos/análise , Conservação dos Recursos Naturais/métodos , Peixes , Fluorocarbonos/análise , Lagos/análise , Poluentes Químicos da Água/análise , Animais , Cidades , Análise por Conglomerados , Monitoramento Ambiental/métodos , Sistemas de Informação Geográfica , Minnesota , Modelos Teóricos , Reprodutibilidade dos Testes , Análise EspacialRESUMO
The aqueous solubility (log S) of xenobiotic chemicals has been identified as a key characteristic in determining their bioaccessibility/bioavailability and their fate and transport in aquatic environments. We here explore and evaluate the use of a state-of-the-art data analysis technique (Project to Latent Structures, PLS) to estimate log S of environmentally relevant chemicals. A large number (n = 624) of molecular descriptors was computed for over 1400 organic chemicals, and then refined by a feature selection technique. Candidate predictor descriptors were fitted to data by means of PLS, which was optimized by an internal leave-one-out cross-validation technique and validated by an external data set. The final (best) PLS model with only four variables (AlogP, X1sol, Mv, and E) exhibited noteworthy stability and good predictive power. It was able to explain 91% of the data (n = 1400) variance with an average absolute error of 0.5 log units through the solubilities span over 12 orders of magnitude. The newly proposed model is transparent, easily portable from one user to another, and robust enough to accurately estimate log S of a wide range of emerging contaminants.
Assuntos
Modelos Químicos , Compostos Orgânicos/química , Relação Quantitativa Estrutura-Atividade , Poluentes Químicos da Água/química , Disponibilidade Biológica , Modelos Teóricos , Compostos Orgânicos/farmacocinética , Bifenil Polibromatos/química , Bifenil Polibromatos/farmacocinética , Reprodutibilidade dos Testes , Solubilidade , Água/química , Poluentes Químicos da Água/farmacocinética , Xenobióticos/química , Xenobióticos/farmacocinéticaRESUMO
Perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA) are persistent organic pollutants that have been found to be ubiquitous in the environment. This article, for the first time, delineates removal areas of these polar compounds on a coagulation diagram that associates chemical conditions with different coagulation mechanisms. Variables considered were solution pH, coagulant dosage, coagulants (alum and ferric chloride), natural organic matter (NOM), initial turbidity, and flocculation time. The jar-test results show that conventional coagulation (alum dosage of 10-60 mg/L and final pH of 6.5-8.0) removed ≤20% of PFOS and PFOA. These chemicals tended to be removed better by enhanced coagulation at higher coagulant dosages (>60 mg/L) and (thus) lower final pH (4.5-6.5). A coagulation diagram was developed to define the coagulant dosage and solution pH for PFOS/PFOA removal. The results suggest that the primary PFOS/PFOA removal mechanism is adsorption to fine Al hydroxide flocs freshly formed during the initial stage of coagulation; increasing flocculation time from 2 to 90 min could not further improve PFOS and PFOA removals. Furthermore, the effect of NOM on PFOS/PFOA removal by coagulation was examined, and possible removal mechanisms were discussed.