Showing papers in "Environmental Science and Technology Letters in 2019"
TL;DR: Given the large number of OPFRs in use, manufacturers can move towards healthier and safer products by developing innovative ways to reduce fire hazard for electronics enclosures, upholstered furniture, building materials and other consumer products without adding flame retardant chemicals.
Abstract: As the use of polybrominated diphenyl ethers (PBDEs), and the entire class of organohalogen flame retardants, is declining, the use of organophosphate esters flame retardants (OPFRs) is increasing. In this paper, we ask whether OPFRs are a better choice than PBDEs. To address this question, we compared OPFRs with PBDEs for a wide range of properties. OPFRs exposure is ubiquitous in people and in outdoor and indoor environments, and are now often found at higher levels compared to PBDE peak exposure levels. Furthermore, data from toxicity testing, epidemiological studies, and risk assessments all suggest that there are health concerns at current exposure levels for both halogenated and non-halogenated OPFRs. Obtaining the scientific evidence needed for regulation of OPFRs can take many years. Given the large number of OPFRs in use, manufacturers can move towards healthier and safer products by developing innovative ways to reduce fire hazard for electronics enclosures, upholstered furniture, building materials and other consumer products without adding flame retardant chemicals.
270 citations
TL;DR: In this article, a 3D probability distribution of environmental versus ingested microplastic is proposed to simplify microplastics by fully defining them through a three-dimensional probability distribution, with size, shape and density as dimensions.
Abstract: Because of their diverse sizes, shapes and densities, environmental microplastics are often perceived as complex. Many studies struggle with this complexity, and either address only a part of this diversity, or present data using discrete classifications for sizes, shapes and densities. We argue that such classifications will never be fully satisfactory, as any definition using classes does not capture the essentially continuous nature of environmental microplastic. Therefore, we propose to simplify microplastics by fully defining them through a 3D probability distribution, with size, shape and density as dimensions. Besides introducing the concept, we parameterize these probability distributions, using empirical data. This parameterization results in an approximate yet realistic representation of ‘true’ environmental microplastic. This approach to simplify microplastic could be applicable to exposure measurements, effect studies and fate modelling. Furthermore, it allows for easy comparison between studies, irrespective of sampling or laboratory setup. We demonstrate how the 3D probability distribution of environmental versus ingested microplastic can be helpful in understanding bioavailability of and exposure to microplastic. We argue that the concept of simplified microplastic will also be helpful in probabilistic risk modelling, which would greatly enhance the understanding of the risk that microplastics pose to the environment.
245 citations
TL;DR: In this paper, a method that extracts plastics magnetically, taking advantage of their hydrophobic surface to magnetize the plastics, allowing magnetic recovery, was developed and applied to a simple method, which recovered 92% of 10-20 μm polyethylene and polystyrene beads and 93% of > 1 mm MPs (polyethylene, polyylene terephthalate, poly styrene, polyurethane, polyvinyl chloride and polypropylene) from seawater.
Abstract: Separating microplastics (MPs) from environmental samples is challenging, but necessary to determine their environmental prevalence. Current methods are not standardized across environmental sample type, and it is unclear how well they recover smaller sized MPs. In response, we developed a method that extracts plastics magnetically, taking advantage of their hydrophobic surface to magnetize the plastics. We created hydrophobic Fe nanoparticles that bind to plastic, allowing magnetic recovery. With this principle applied to a simple method, we recovered 92% of 10–20 μm polyethylene and polystyrene beads and 93% of >1 mm MPs (polyethylene, polyethylene terephthalate, polystyrene, polyurethane, polyvinyl chloride, and polypropylene) from seawater. We also recovered 84% and 78% of MPs (polyethylene, polystyrene, polyurethane, polyvinyl chloride, and polypropylene) ranging from 200 μm to 1 mm from freshwater and sediments, respectively. Overall, the procedure is efficient for various sizes, polymer types, and ...
180 citations
TL;DR: In this article, an energy-efficient Magneli phase Ti4O7 reactive electrochemical membrane (REM) was applied for the oxidation of perfluorooctanoic acid (PFOA) and perfluorsulfonic acid (PFOS).
Abstract: An energy-efficient Magneli phase Ti4O7 reactive electrochemical membrane (REM) was applied for the oxidation of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). Approximately...
151 citations
TL;DR: This paper showed that polystyrene is completely photochemically oxidized and showed that it can be oxidized to polycarbonate polyethylene (PEG) polycarbonates.
Abstract: Numerous international governmental agencies that steer policy assume that polystyrene persists in the environment for millennia. Here, we show that polystyrene is completely photochemically oxidiz...
132 citations
TL;DR: In this paper, the authors provide critical analysis of the development and application of amine-containing sorbents for PFAS removal, and also provide an outlook on the next generation of next-generation sorbent.
Abstract: Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are a group of persistent and mobile fluoro-organic chemicals that have been detected in many water supplies, and their recommended safe concentrations in drinking water are as low as 6 ng/L. Current technological advances suggest that amine-containing sorbents can provide alternative solutions to PFAS control in the treatment of municipal water and wastewater at relatively low PFAS concentrations. The objective of this review is to provide critical analysis of the development and application of amine-containing sorbents for PFAS removal. The removal of PFAS by aminated sorbents relies on the combined effects of three main factors: (i) electrostatic interactions with functional groups of the sorbent, (ii) hydrophobic interactions with the sorbent and between PFAS molecules, and (iii) sorbent morphology. The design of next-generation sorbents should take into consideration these three factors and their relative contribution. We also provide an outlook an...
127 citations
TL;DR: Application of the total oxidizable precursor (TOP) assay in its proposed enhanced form revealed high levels of PFEAs, the presence of precursors that form perfluoroalkyl carboxylic acids, and the absence of precursor that form P FEAs in surface water impacted by PFAS-containing wastewater discharges.
Abstract: Per- and polyfluoroalkyl substances (PFASs) are widely used anthropogenic chemicals. The PFAS class includes almost 5000 registered compounds, but analytical methods are lacking for most PFASs. The total oxidizable precursor (TOP) assay was developed to indirectly quantify unknown PFASs that are precursors to commonly measured perfluoroalkyl acids. To understand the behavior of recently identified per- and polyfluoroalkyl ether acids (PFEAs), including fluorinated replacements and manufacturing byproducts, we determined the fate of 15 PFEAs in the TOP assay. Ten perfluoroalkyl ether acids and a chlorinated polyfluoroalkyl ether acid (F-53B) were stable in the TOP assay and represent terminal products that are likely as persistent as historically used PFASs. Adding perfluoroalkyl ether acids and F-53B to the target analyte list for the TOP assay is recommended to capture a higher percentage of the total PFAS concentration in environmental samples. In contrast, polyfluoroalkyl ether acids with a -O-CFH- moiety were oxidized, typically to products that could not be identified by liquid chromatography and high-resolution mass spectrometry. Application of the TOP assay in its proposed enhanced form revealed high levels of PFEAs, the presence of precursors that form perfluoroalkyl carboxylic acids, and the absence of precursors that form PFEAs in surface water impacted by PFAS-containing wastewater discharges.
108 citations
TL;DR: For example, micro-and nanoplastics derived from environmental degradation of larger plastic debris can be ingested and accumulate in aquatic organisms, raising growing global ecological concerns as mentioned in this paper, which is a concern.
Abstract: Micro- and nanoplastics derived from environmental degradation of larger plastic debris can be ingested and accumulate in aquatic organisms, raising growing global ecological concerns. Toxicology s...
102 citations
TL;DR: In this article, the fate of microplastics in the environment, organisms, and food webs is investigated using manipulation experiments. But labeling microplastic with labels is difficult and time-consuming.
Abstract: Observing microplastics in manipulative experiments is of paramount importance for understanding the fate of microplastics in the environment, organisms, and food webs. Labeling microplastics with ...
97 citations
TL;DR: Heterogeneous oxidation of sulfur dioxide (SO2) is suggested to be one of the most important pathways for sulfate formation during extreme haze events in China, yet the exact mechanism remains high.
Abstract: Heterogeneous oxidation of sulfur dioxide (SO2) is suggested to be one of the most important pathways for sulfate formation during extreme haze events in China, yet the exact mechanism remains high...
95 citations
TL;DR: Knowledge of perfluorooctanoic acid (PFOA) accumulation at the air-water interface is critical to understanding the fate and transport of these substances in... as discussed by the authors.
Abstract: Knowledge of perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) accumulation at the air–water interface is critical to understanding the fate and transport of these substances in...
TL;DR: In this article, a promising new strategy for achieving rapid and complete destruction of perfluorooctanesulfonate (PFOS) through the application of hydrothermal conditions (condensed water, 200-350...
Abstract: Here, we report a promising new strategy for achieving rapid and complete destruction of perfluorooctanesulfonate (PFOS) through the application of hydrothermal conditions (condensed water, 200–350...
TL;DR: The presence of microplastic particles (<5 mm) in the environment has generated considerable concern across public, political, and scientific platforms as mentioned in this paper, however, the diversity of micro-plastics that...
Abstract: The presence of microplastic particles (<5 mm) in the environment has generated considerable concern across public, political, and scientific platforms. However, the diversity of microplastics that...
TL;DR: This work presents the first application of machine learning on per- and polyfluoroalkyl substances (PFAS) for predicting and rationalizing carbon–fluorine (C–F) bond dissociation energies to aid in their efficient treatment and removal.
Abstract: We present the first application of machine learning on per- and polyfluoroalkyl substances (PFAS) for predicting and rationalizing carbon–fluorine (C–F) bond dissociation energies to aid in their ...
TL;DR: It is concluded that partitioning to phospholipids is an important mechanism of bioaccumulation for long-chained PFASs in marine mammals.
Abstract: Exposure to poly- and perfluoroalkyl substances (PFASs) has been linked to many negative health impacts in humans and wildlife. Unlike neutral hydrophobic organic pollutants, many PFASs are ionic a...
TL;DR: In this article, 14 OPEs were measured in 100 breast milk samples collected from the United States during the period of 2009-2012, using high-performance liquid chromatography and tandem mass spectrometry.
Abstract: Organophosphate esters (OPEs) are used in consumer products as flame retardants and plasticizers. Little is known, however, about the occurrence and profiles of OPEs in human milk. In this study, 14 OPEs were measured in 100 breast milk samples collected from the United States during the period of 2009-2012, using high-performance liquid chromatography and tandem mass spectrometry. The sum concentrations of 14 OPEs in human milk ranged from 0.670 to 7.83 ng/mL, with a mean value of 3.61 ng/mL. The highest mean concentration was found for tris-2-butoxyethyl phosphate (TBOEP, 1.44 ± 0.789 ng/mL), followed by tri-iso-butyl phosphate (TIBP, 0.569 ± 0.272 ng/mL) and tri-n-butyl phosphate (TNBP, 0.539 ± 0.265 ng/mL), which were the dominant OPEs found in breast milk at detection frequencies of >80%. No significant differences were observed between various maternal/infant characteristics and OPE concentrations (p > 0.05), except for TBOEP, for which the median concentrations in Hispanic mothers (0.765 ng/mL) were 2 times lower than those in non-Hispanic mothers (1.48 ng/mL) (p < 0.05). On the basis of the recommended daily milk ingestion rate, the average and the highest daily intakes of total OPEs were calculated to be in the range of 300-542 and 504-911 ng (kg of body weight)-1 day-1, respectively. The estimated daily intakes of OPEs did not exceed the current reference doses. Our study establishes baseline data for OPE exposure in breast-fed American children.
TL;DR: In this paper, a sink for MPs that originate from domestic sources and can provide an indication of the maggots are emerging pollutants of public health and environmental concern, is described.
Abstract: Microplastics (MPs) are emerging pollutants of public health and environmental concern. Sewage sludge is a sink for MPs that originate from domestic sources and can provide an indication of the mag...
TL;DR: Membrane distillation (MD) is a thermal desalination process with the capability of harnessing low-grade waste heat to treat hypersaline brine as discussed by the authors, which has been actively explored as a p...
Abstract: Membrane distillation (MD) is a thermal desalination process with the capability of harnessing low-grade waste heat to treat hypersaline brine. For this reason, MD has been actively explored as a p...
TL;DR: In this article, the initial discovery of neonicotinoid pesticides in drinking water and their potential for transformation through chlorination and alkaline hydrolysis during water treatment was reported.
Abstract: We recently reported the initial discovery of neonicotinoid pesticides in drinking water and their potential for transformation through chlorination and alkaline hydrolysis during water treatment. ...
TL;DR: In this paper, the authors compared three analytical techniques for total fluorine determination: combustion ion chromatography (CIC), particle-induced γ-ray emission spectroscopy (PIGE), and instrumental neutron activation analysis (INAA).
Abstract: Per- and polyfluoroalkyl substances (PFASs) represent a class of more than 4000 compounds. Their large number and structural diversity pose a considerable challenge to analytical chemists. Measurement of total fluorine in environmental samples and consumer products is therefore critical for rapidly screening for PFASs and for assessing the fraction of unexplained fluorine(i.e., fluorine mass balance). Here we compare three emerging analytical techniques for total fluorine determination: combustion ion chromatography (CIC), particle-induced γ-ray emission spectroscopy (PIGE), and instrumental neutron activation analysis (INAA). Application of each method to a certified reference material (CRM), spiked filters, and representative food packaging samples revealed good accuracy and precision. INAA and PIGE had the advantage of being nondestructive, while CIC displayed the lowest detection limits. Inconsistencies between the methods arose due to the high aluminum content in the CRM, which precluded its analysis...
TL;DR: In this paper, nighttime atmospheric processing enhances the formation of brown carbon aerosol (BrC) in biomass burning plumes, a group of volatile organic compounds (VOCs) abundant in bio-energy plants.
Abstract: Nighttime atmospheric processing enhances the formation of brown carbon aerosol (BrC) in biomass burning plumes. Heterocyclic compounds, a group of volatile organic compounds (VOCs) abundant in bio...
TL;DR: In this paper, the authors discuss the changes in gas and aerosol chemical composition due to aggressive air pollution mitigation measures in northern China. But it is unclear whether aerosol composition has changed.
Abstract: During recent years, aggressive air pollution mitigation measures in northern China have resulted in considerable changes in gas and aerosol chemical composition. But it is unclear whether aerosol ...
TL;DR: In this article, the organic fraction of municipal solid waste (OFMSW) creates a nutrient rich soil amendment and reduces the amount of wastes going to landfills or incineration.
Abstract: Composting the organic fraction of municipal solid waste (OFMSW) creates a nutrient rich soil amendment and reduces the amounts of wastes going to landfills or incineration. However, the occurrence...
TL;DR: A crAssphage qPCR marker was detected in 21 sewage samples in Thailand with 100% sensitivity and a 99.2% specificity was observed using feces from swine, cattle, chicken, duck, goat, sheep, buffalo, and fish, with cross-detection only occurring for one composite swine sample.
Abstract: The human gut bacteriophage crAssphage has been proposed as a human-specific microbial source tracking (MST) marker for impacted water bodies. However, its global use as a human-specific MST marker requires validation in a tropical region. In this study, a crAssphage qPCR marker (CPQ_056) was detected in 21 sewage samples in Thailand with 100% sensitivity. The marker was detected in sewage from hospitals and residential buildings at 5.28–7.38 log10 copies/100 mL and in four influent and four effluent samples of municipal wastewater treatment plants at 4.23–6.19 and 3.78–4.89 log10 copies/100 mL, respectively. Furthermore, a 99.2% specificity (n = 127) was observed using feces from swine, cattle, chicken, duck, goat, sheep, buffalo, and fish, with cross-detection only occurring for one composite swine sample. The crAssphage marker was present in 56.25% (27 out of 48) of river samples at 3.20–7.29 log10 copies/100 mL. The concentrations of the crAssphage marker and a prevalidated human-specific Bacteroidale...
TL;DR: In this paper, the authors show how ROL spatiotemporally evolves and correlates with Fe-redox transformations in a transparent artificial soil and apply non-invasive measurements to visualize opposing O2 and Fe(II) gradients.
Abstract: Although water-logged rice paddies are characterized by anoxic conditions, radial oxygen loss (ROL) from rice roots temporarily oxygenates the soil rhizosphere. ROL not only triggers the abiotic oxidation of ferrous iron (Fe(II)) but also provides the electron acceptor for microaerophilic Fe(II)-oxidizing bacteria (microFeOx). Both processes contribute to the formation of ferric (Fe(III)) iron plaque on root surfaces. Redox interactions at single roots have been studied intensively. However, temporally resolved spatial changes of ROL in the entire rhizosphere and the impact on redoximorphic biogeochemistry are currently poorly understood. Here, we show how ROL spatiotemporally evolves and correlates with Fe-redox transformations. Applying noninvasive measurements in a transparent artificial soil, we were able to visualize opposing O2 and Fe(II) gradients that extend from the root surface 10–25 mm into the rhizosphere. The microoxic zone expanded exponentially in size throughout the entire rhizosphere crea...
TL;DR: Perfluorooctanoic acid (PFOA) and perfluorOOctanesulfonate (PFOS) are groundwater contaminants of emerging concern due to their toxicity and persistence as discussed by the authors.
Abstract: Perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) are groundwater contaminants of emerging concern due to their toxicity and persistence. Currently, there are limited destructive tr...
TL;DR: Temperature swing solvent extraction (TSSE) as discussed by the authors utilizes low-temperature heat and a low-polarity solvent with temperature-dependent water solubility for the selective extraction of water over salt from saline feeds.
Abstract: Hypersaline brines are of growing environmental importance but are technologically under-served by today’s desalination methods. Temperature swing solvent extraction (TSSE) is a radically different desalination technology that is membrane-less and not based on evaporative phase change. TSSE utilizes low-temperature heat and a low-polarity solvent with temperature-dependent water solubility for the selective extraction of water over salt from saline feeds. This study demonstrates TSSE desalination of high-salinity brines simulated by NaCl solutions with three amine solvents: diisopropylamine (DIPA), N-ethylcyclohexylamine (ECHA), and N,N-dimethylcyclohexylamine (DMCHA). We show that TSSE can desalinate brines with salinities as high as ≈234000 ppm total dissolved solids (i.e., 4.0 M NaCl) and achieve salt removals up to 98.4%. Among the solvents, DIPA exhibited the highest water extraction efficiency whereas ECHA and DMCHA produced water with the lowest salt content and solvent residue content, respectivel...
TL;DR: XPS is a useful technique for characterizing PFASs in consumer products because it can precisely quantify the surficial fluorine content of materials and allows identification of CF2 and CF3 groups in materials and can elucidate the depth dependent distribution of fluorine in products.
Abstract: Exposures to poly- and perfluoroalkyl substances (PFASs) have been linked to metabolic disruption, immunotoxicity and cancer in humans. PFASs are known to be present in diverse consumer products including textiles and food packaging. Here we present a new method for quantifying the atomic percent fluorine (% F) in the surficial 0.01 μm of consumer products using X-ray photoelectron spectroscopy (XPS). The surface of food contact materials and textiles measured in this study contained up to 28% F and 45% F, respectively. PTFE tape was measured to demonstrate XPS accuracy and precision. Depth profiles of fluorine content in consumer products measured using XPS showed highest levels at the upper-most surface in contact with the surrounding environment and a decrease below the surface. PFASs released in methanol extracts and quantified using traditional liquid chromatography-tandem mass spectrometry typically accounted for <1% of the fluorine measured with XPS in consumer products. We conclude that XPS is a useful technique for characterizing PFASs in consumer products because it can precisely quantify the surficial fluorine content of materials. XPS also allows identification of CF2 and CF3 groups in materials and can elucidate the depth dependent distribution of fluorine in products.
TL;DR: In this article, the reaction of green rusts with chlorinated ethylenes (CEs) has been investigated and shown to be a fast reductant for chlorinated methanes.
Abstract: Layered iron(II)–iron(III) hydroxides [green rusts (GRs)] constitute fast reductants for chlorinated methanes, but most studies of the reaction of GRs with chlorinated ethylenes (CEs) have reported...
TL;DR: Inverse modeling (top-down) analyses of atmospheric methane observations can help improve the emission estimates but require reliabl... as mentioned in this paper, which may not be the case in coal mine emissions.
Abstract: China has large but uncertain coal mine methane (CMM) emissions. Inverse modeling (top-down) analyses of atmospheric methane observations can help improve the emission estimates but require reliabl...