The 50 most-cited articles in Environmental Science & Technology, 2019

Microplastics are ubiquitous across ecosystems, yet the exposure risk to humans is unresolved. Focusing on the American diet, we evaluated the number of microplastic particles in commonly consumed foods in relation to their recommended daily intake. The potential for microplastic inhalation and how the source of drinking water may affect microplastic consumption were also explored. Our analysis used 402 data points from 26 studies, which represents over 3600 processed samples. Evaluating approximately 15% of Americans' caloric intake, we estimate that annual microplastics consumption ranges from 39000 to 52000 particles depending on age and sex. These estimates increase to 74000 and 121000 when inhalation is considered. Additionally, individuals who meet their recommended water intake through only bottled sources may be ingesting an additional 90000 microplastics annually, compared to 4000 microplastics for those who consume only tap water. These estimates are subject to large amounts of variation; however, given methodological and data limitations, these values are likely…

Microplastics can affect biophysical properties of the soil. However, little is known about the cascade of events in fundamental levels of terrestrial ecosystems, i.e., starting with the changes in soil abiotic properties and propagating across the various components of soil-plant interactions, including soil microbial communities and plant traits. We investigated here the effects of six different microplastics (polyester fibers, polyamide beads, and four fragment types: polyethylene, polyester terephthalate, polypropylene, and polystyrene) on a broad suite of proxies for soil health and performance of spring onion ( Allium fistulosum). Significant changes were observed in plant biomass, tissue elemental composition, root traits, and soil microbial activities. These plant and soil responses to microplastic exposure were used to propose a causal model for the mechanism of the effects. Impacts were dependent on particle type, i.e., microplastics with a shape similar to other natural soil particles elicited smaller differences from control. Changes in soil structure and water dynamics…

Environmental contamination by microplastics is now considered an emerging threat to biodiversity and ecosystem functioning. Soil ecosystems, particularly agricultural land, have been recognized as a major sink of microplastics, but the impacts of microplastics on soil ecosystems (e.g., above and below ground) remain largely unknown. In this study, different types of microplastics [biodegradable polylactic acid (PLA)], conventional high-density polyethylene (HDPE), and microplastic clothing fibers were added to soil containing the endogeic Aporrectodea rosea (rosy-tipped earthworm) and planted with Lolium perenne (perennial ryegrass) to assess the biophysical soil response in a mesocosm experiment. When exposed to fibers or PLA microplastics, fewer seeds germinated. There was also a reduction in shoot height with PLA. The biomass of A. rosea exposed to HDPE was significantly reduced compared to control samples. Furthermore, with HDPE present there was a decrease in soil pH. The size distribution of water-stable soil aggregates was altered when microplastics were present, suggesting…

On account of environmental concerns, the fate and adverse effects of plastics have attracted considerable interest in the past few years. Recent studies have indicated the potential for fragmentation of plastic materials into nanoparticles, i.e., "nanoplastics," and their possible accumulation in the environment. Nanoparticles can show markedly different chemical and physical properties than their bulk material form. Therefore possible risks and hazards to the environment need to be considered and addressed. However, the fate and effect of nanoplastics in the (aquatic) environment has so far been little explored. In this review, we aim to provide an overview of the literature on this emerging topic, with an emphasis on the reported impacts of nanoplastics on human health, including the challenges involved in detecting plastics in a biological environment. We first discuss the possible sources of nanoplastics and their fates and effects in the environment and then describe the possible entry routes of these particles into the human body, as well as their uptake mechanisms at the…

The increasing presence of micro- and nano-sized plastics in the environment and food chain is of growing concern. Although mindful consumers are promoting the reduction of single-use plastics, some manufacturers are creating new plastic packaging to replace traditional paper uses, such as plastic teabags. The objective of this study was to determine whether plastic teabags could release microplastics and/or nanoplastics during a typical steeping process. We show that steeping a single plastic teabag at brewing temperature (95 °C) releases approximately 11.6 billion microplastics and 3.1 billion nanoplastics into a single cup of the beverage. The composition of the released particles is matched to the original teabags (nylon and polyethylene terephthalate) using Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The levels of nylon and polyethylene terephthalate particles released from the teabag packaging are several orders of magnitude higher than plastic loads previously reported in other foods. An initial acute invertebrate toxicity…

Antibiotics, the most frequently prescribed drugs of modern medicine, are extensively used for both human and veterinary applications. Antibiotics from different wastewater sources (e.g., municipal, hospitals, animal production, and pharmaceutical industries) ultimately are discharged into wastewater treatment plants. Sorption and biodegradation are the two major removal pathways of antibiotics during biological wastewater treatment processes. This review provides the fundamental insights into sorption mechanisms and biodegradation pathways of different classes of antibiotics with diverse physical-chemical attributes. Important factors affecting sorption and biodegradation behavior of antibiotics are also highlighted. Furthermore, this review also sheds light on the critical role of extracellular polymeric substances on antibiotics adsorption and their removal in engineered biological wastewater treatment systems. Despite major advancements, engineered biological wastewater treatment systems are only moderately effective (48-77%) in the removal of antibiotics. In this review, we…

In the environment, microplastics are subjected to multiple aging processes; however, information regarding the impact of aging on the environmental behavior of microplastics is still lacking. This study investigated the alteration properties of polystyrene and high-density polyethylene microplastics by heat-activated K 2 S 2 O 8 and Fenton treatments to improve the understanding of their long-term natural aging in aquatic environments. Our results indicated that the O/C ratio was an alternative parameter to the carbonyl index (CI) to quantitatively describe the surface alteration properties of microplastics. The correlation model of the O/C ratio or CI versus alteration time was developed and compared by natural alteration of microplastics in freshwater samples. Moreover, the regression equation of the equilibrium adsorption capacity of altered microplastics versus the O/C ratio and average size was proposed. This study is the first effort in differentiating the relationships between the alteration properties and alteration time/adsorption capacity of microplastics, which would be…

As an important reactive oxygen species (ROS) with selective oxidation, singlet oxygen ( 1 O 2 ) has wide application prospects in biology and the environment. However, the mechanism of 1 O 2 formation, especially the conversion of superoxide radicals (·O 2 – ) to 1 O 2, has been a great controversy. This process is often disturbed by hydroxyl radicals (·OH). Here, we develop a molybdenum cocatalytic Fenton system, which can realize the transformation from ·O 2 – to 1 O 2 on the premise of minimizing ·OH. The Mo 0 exposed on the surface of molybdenum powder can significantly improve the Fe 3+ /Fe 2+ cycling efficiency and weaken the production of ·OH, leading to the generation of ·O 2 – . Meanwhile, the exposed Mo 6+ can realize the transformation of ·O 2 – to 1 O 2 . The molybdenum cocatalytic effect makes the conventional Fenton reaction have high oxidation activity for the remediation of organic pollutants and prompts the inactivation of Staphylococcus aureus, as well as the adsorption and reduction of heavy metal ions (Cu 2+, Ni 2+, and Cr 6+ ). Compared with iron powder,…

Fungicides are indispensable to global food security and their use is forecasted to intensify. Fungicides can reach aquatic ecosystems and occur in surface water bodies in agricultural catchments throughout the entire growing season due to their frequent, prophylactic application. However, in comparison to herbicides and insecticides, the exposure to and effects of fungicides have received less attention. We provide an overview of the risk of fungicides to aquatic ecosystems covering fungicide exposure (i.e., environmental fate, exposure modeling, and mitigation measures) as well as direct and indirect effects of fungicides on microorganisms, macrophytes, invertebrates, and vertebrates. We show that fungicides occur widely in aquatic systems, that the accuracy of predicted environmental concentrations is debatable, and that fungicide exposure can be effectively mitigated. We additionally demonstrate that fungicides can be highly toxic to a broad range of organisms and can pose a risk to aquatic biota. Finally, we outline central research gaps that currently challenge our ability to…

Eutrophication of water bodies is a serious and widespread environmental problem. Achieving low levels of phosphate concentration to prevent eutrophication is one of the important goals of the wastewater engineering and surface water management. Meeting the increasingly stringent standards is feasible in using a phosphate-selective sorption system. This critical review discusses the most fundamental aspects of selective phosphate removal processes and highlights gains from the latest developments of phosphate-selective sorbents. Selective sorption of phosphate over other competing anions can be achieved based on their differences in acid-base properties, geometric shapes, and metal complexing abilities. Correspondingly, interaction mechanisms between the phosphate and sorbent are categorized as hydrogen bonding, shape complementarity, and inner-sphere complexation, and their representative sorbents are organic-functionalized materials, molecularly imprinted polymers, and metal-based materials, respectively. Dominating factors affecting the phosphate sorption performance of these…

This study proposed an electrochemical technique for investigating the mechanism of nonradical oxidation of organics with peroxydisulfate (PDS) activated by carbon nanotubes (CNT). The electrochemical property of twelve phenolic compounds (PCs) was evaluated by their half-wave potentials, which were then correlated to their kinetic rate constants in the PDS/CNT system. Integrated with quantitative structure-activity relationships (QSARs), electron paramagnetic resonance (EPR), and radical scavenging tests, the nature of nonradical pathways of phenolic compound oxidation was unveiled to be an electron-transfer regime other than a singlet oxygenation process. The QSARs were established according to their standard electrode potentials, activation energy, and pre-exponential factor. A facile electrochemical analysis method (chronopotentiometry combined with chronoamperometry) was also employed to probe the mechanism, suggesting that PDS was catalyzed initially by CNT to form a CNT surface-confined and -activated PDS (CNT-PDS*) complex with a high redox potential. Then, the CNT-PDS*…

Carbon-driven advanced oxidation processes are appealing in wastewater purification because of the metal-free feature of the carbocatalysts. However, the regime of the emerging nonradical pathway is ambiguous because of the intricate carbon structure. To this end, this study was dedicated to unveil the intrinsic structure-performance relationship of peroxydisulfate (PDS) activation by carbon nanotubes (CNTs) toward nonradical oxidation of organics such as phenol (PE) via electron transfer. Eighteen analogical CNTs were synthesized and functionalized with different categories and contents of oxygen species. The quenching tests and chronopotentiometry suggest that an improved reactivity of surface-regulated CNTs was attributed to the reinforced electron-transfer regime without generation of free radicals and singlet oxygen. The quantitative structure-activity relationships were established and correlated to the Tafel equation, which unveils the nature of the nonradical oxidation by CNT-activated PDS complexes (CNT-PDS*). First, a decline in the concentration of oxygen groups in CNTs…

Abstract An accurate fine-resolution surface of the chemical composition of fine particulate matter (PM2.5) would offer valuable information for epidemiological studies and health impact assessments. We develop geoscience-derived estimates of PM2.5 composition from a chemical transport model (GEOS-Chem) and satellite observations of aerosol optical depth, and statistically fuse these estimates with ground-based observations using a geographically weighted regression over North America to produce a spatially complete representation of sulfate, nitrate, ammonium, black carbon, organic matter, mineral dust, and sea-salt over 2000–2016. Significant long-term agreement is found with cross-validation sites over North America (R2 = 0.57─0.96), with the strongest agreement for sulfate (R2 = 0.96), nitrate (R2 = 0.90), and ammonium (R2 = 0.86). We find that North American decreases in population-weighted fine particulate matter (PM2.5) concentrations since 2000 have been most heavily influenced by regional changes in sulfate and organic matter. Regionally, the relative importance of several…

Oxidative stress is a potential mechanism of action for particulate matter (PM) toxicity and can occur when the body's antioxidant capacity cannot counteract or detoxify harmful effects of reactive oxygen species (ROS) due to an excess presence of ROS. ROS are introduced to the body via inhalation of PM with these species present on and/or within the particles (particle-bound ROS) and/or through catalytic generation of ROS in vivo after inhaling redox-active PM species (oxidative potential, OP). The recent development of acellular OP measurement techniques has led to a surge in research across the globe. In this review, particle-bound ROS techniques are discussed briefly while OP measurements are the focus due to an increasing number of epidemiologic studies using OP measurements showing associations with adverse health effects in some studies. The most common OP measurement techniques, including the dithiothreitol assay, glutathione assay, and ascorbic acid assay, are discussed along with evidence for utility of OP measurements in epidemiologic studies and PM characteristics that…

Abstract This study investigates critical structure–reactivity relationships within 34 representative per- and polyfluoroalkyl substances (PFASs) undergoing defluorination with UV-generated hydrated electrons. While CnF2n+1–COO– with variable fluoroalkyl chain lengths (n = 2 to 10) exhibited a similar rate and extent of parent compound decay and defluorination, the reactions of telomeric CnF2n+1–CH2CH2–COO– and CnF2n+1–SO3– showed an apparent dependence on the length of the fluoroalkyl chain. Cross comparison of experimental results, including different rates of decay and defluorination of specific PFAS categories, the incomplete defluorination from most PFAS structures, and the surprising 100% defluorination from CF3COO–, leads to the elucidation of new mechanistic insights into PFAS degradation. Theoretical calculations on the C–F bond dissociation energies (BDEs) of all PFAS structures reveal strong relationships among (i) the rate and extent of decay and defluorination, (ii) head functional groups, (iii) fluoroalkyl chain length, and (iv) the position and number of C–F bonds…

A nonradical oxidation process via metal-free peroxymonosulfate (PMS) activation has recently attracted considerable attention for organic pollutant degradation; however, the origin of singlet oxygen ( 1 O 2 ) generation still remains controversial. In this study, nitrogen-doped carbon nanosheets (NCN-900) derived from graphitic carbon nitride were developed for activation of PMS and elucidation of 1 O 2 production. With a large specific surface area (1218.7 m 2 g –1 ) and high nitrogen content (14.5 at %), NCN-900 exhibits superior catalytic activity in PMS activation, as evidenced by complete degradation of bisphenol A within 2 min using 0.1 g L –1 NCN-900 and 2 mM PMS. Moreover, the reaction rate constant fitted by pseudo-first-order kinetics for NCN-900 reaches an impressive value of 3.1 min –1 . Electron paramagnetic resonance measurements and quenching tests verified 1 O 2 as the primary reactive oxygen species in the NCN-900/PMS system. Based on X-ray photoelectron spectroscopy analysis and theoretical calculations, an unexpected generation pathway of 1 O 2 involving PMS…

Fe(II) is an excellent promoter for advanced oxidation processes (AOPs) because of its environmental ubiquity and low toxicity. This study is among the first to characterize the reaction of peracetic acid (PAA) with Fe(II) ion and apply the Fe(II)/PAA AOP for degradation of micropollutants. PAA reacts with Fe(II) ( k = 1.10 × 10 5 –1.56 × 10 4 M –1 s –1 at pH 3.0–8.1) much more rapidly than H 2 O 2 and outperforms the coexistent H 2 O 2 for reaction with Fe(II). While PAA alone showed minimal reactivity with methylene blue, naproxen, and bisphenol-A, significant abatement (48–98%) of compounds was observed by Fe(II)/PAA at initial pH of 3.0–8.2. The micropollutant degradation by Fe(II)/PAA exhibited two kinetic phases (very rapid then slow) related to PAA and H 2 O 2, respectively. Based on experimental evidence, formation of carbon-centered radicals (CH 3 C(O)O •, CH 3 C(O) •, and • CH 3 ), • OH, and Fe(IV) reactive intermediate species from the PAA and Fe(II) reactions in the presence of H 2 O 2 is hypothesized. The carbon-centered radicals and/or Fe(IV) likely played an important…

An advanced oxidation process of combining cobalt and peracetic acid (Co/PAA) was developed to degrade sulfamethoxazole (SMX) in this study. The formed acetylperoxy radical (CH 3 CO 3 • ) through the activation of PAA by Co (Co 2+ ) was the dominant radical responsible for SMX degradation, and acetoxyl radical (CH 3 CO 2 • ) might also have played a role. The efficient redox cycle of Co 3+ /Co 2+ allows good removal efficiency of SMX even at quite low dosage of Co (<1 μM). The presence of H 2 O 2 in the Co/PAA process has a negative effect on the degradation of SMX due to the competition for reactive radicals. The SMX degradation in the Co/PAA process is pH dependent, and the optimum reaction pH is near-neutral. Humic acid and HCO 3 – can inhibit SMX degradation in the Co/PAA process, while the presence of Cl – plays a little role in the degradation of SMX in this system. Although transformation products of SMX in the Co/PAA system show higher acute toxicity, the low Co dose and SMX concentration in aquatic solution can efficiently weaken the acute toxicity. After reaction in the…

Microplastics (MPs) are presumed to be inert during aging under ambient conditions. In this study, four types of virgin MPs, including polystyrene (PS), phenol-formaldehyde resin (PF), polyethylene (PE), and polyvinyl chloride (PVC), were aged under simulated solar light irradiation. Surprisingly, several environmentally persistent free radicals (EPFRs), which are considered to be a type of emerging contaminant, were detected on the irradiated PS and PF, rather than PE and PVC, by electron paramagnetic resonance (EPR) spectroscopy. Depending on the photoaging duration time, the characteristic g-factors of the EPFRs produced on PS and PF were 2.0044–2.0049 and 2.0043–2.0044, respectively. The generated EPFRs on PS and PF decayed rapidly at the initial stage and then slowly disappeared with the elapsed aging time. Analyses by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS), nuclear magnetic resonance (NMR), and gel permeation chromatography (GPC) suggested that MPs might experience chemical chain scission, O 2 /H…

Although atmospheric transport and deposition could be an important pathway of terrestrial pollutants to the ocean, little information concerning the presence and distribution of these suspended atmospheric microplastics in marine air is available. We investigated, for the first time, the occurrence and distribution of suspended atmospheric microplastics (SAMPs) in the west Pacific Ocean. In this study, the spatial distribution, morphological appearance, and chemical composition of suspended atmospheric microplastics were studied through continuous sampling during a cruise. SAMPs abundance ranged from 0 to 1.37 n/m 3, the median of 0.01 n/m 3 . Fiber, fragment, and granule SAMPs quantitively constituted 60%, 31%, and 8% of all MPs, respectively. Interestingly, plastic microbeads with numerical proportion of 5% were also observed. A high suspended atmospheric microplastics abundance was found in the coastal area (0.13 ± 0.24 n/m 3 ), while there was less amount detected in the pelagic area (0.01 ± 0.01 n/m 3 ). The amount of suspended atmospheric microplastics collected during the…

sp. strain A6 (A6), an autotroph that oxidizes ammonium to nitrite while reducing ferric iron, were conducted in the presence of PFOA or PFOS at 0.1 mg/L and 100 mg/L. Buildup of fluoride, shorter-chain perfluorinated products, and acetate was observed, as well as a decrease in Fe(III) reduced per ammonium oxidized. Incubations with hydrogen as a sole electron donor also resulted in the defluorination of these PFAS. Removal of up to 60% of PFOA and PFOS was observed during 100 day incubations, while total fluorine (organic plus fluoride) remained constant throughout the incubations. To determine if PFOA/PFOS or some of their degradation products were metabolized, and since no organic carbon source except these PFAS was added, dissolved organic carbon (DOC) was tracked. At concentrations of 100 mg/L, PFOA/PFOS were the main contributors to DOC, which remained constant during the pure A6 culture incubations. Whereas in the A6 enrichment culture, DOC decreased slightly with time, indicating that as defluorination of PFOS/PFOA occurred, some of the products were being metabolized by…

Cl • and Cl 2 •– radicals contribute to the degradation of trace organic contaminants (TrOCs) such as pharmaceutical and personal care products and endocrine-disrupting chemicals. However, little is known about their reaction rate constants and mechanisms. In this study, the reaction rate constants of Cl • and Cl 2 •– with 88 target compounds were determined using laser flash photolysis. Decay kinetics, product buildup kinetics, and competition kinetics were applied to track the changes in their transient spectra. Cl • exhibited quite high reactivity toward TrOCs with reaction rate constants ranging from 3.10 × 10 9 to 4.08 × 10 10 M –1 s –1 . Cl 2 •– was less reactive but more selective, with reaction rate constants varying from <1 × 10 6 to 2.78 × 10 9 M –1 s –1 . Three QSAR models were developed, which were capable of predicting the reaction rate constants of Cl 2 •– with TrOCs bearing phenol, alkoxy benzene, and aniline groups. The detection of Cl • -adducts of many TrOCs suggested that Cl • addition was an important reaction mechanism. Single electron transfer (SET)…

There is clear evidence that discarded single-use carrier bags are accumulating in the environment. As a result, various plastic formulations have been developed which state they deteriorate faster and/or have fewer impacts on the environment because their persistence is shorter. This study examined biodegradable, oxo-biodegradable, compostable, and high-density polyethylene (i.e., a conventional plastic carrier bag) materials over a 3 year period. These materials were exposed in three natural environments; open-air, buried in soil, and submersed in seawater, as well as in controlled laboratory conditions. In the marine environment, the compostable bag completely disappeared within 3 months. However, the same compostable bag type was still present in the soil environment after 27 months but could no longer hold weight without tearing. After 9 months exposure in the open-air, all bag materials had disintegrated into fragments. Collectively, our results showed that none of the bags could be relied upon to show any substantial deterioration over a 3 year period in all of the…

Microplastic (MP) contaminates terrestrial, aquatic, and atmospheric environments. Although the number of river sampling studies with regard to MP concentrations is increasing, comprehension of the predominant transport processes of MP in the watercourse is still very limited. In order to gain a better process understanding, around 500 physical experiments were conducted to shed more light on the effects of particle shape, size and density on the rise and settling velocities of MP. The determined velocities ranged between 0.39 cm/s for polyamide fibers (settling) and 31.4 cm/s for expanded polystyrene pellets (rise). Subsequently, the determined velocities were compared with formulas from sediment transport and, as there were large differences between theoretically and experimentally determined velocities, own formulas were developed to describe settling and rise velocities of MP particles with a large variety of shapes, sizes and densities. This study shows that MP differs significantly from sediment in its behavior and that a transfer of common sediment transport formulas should…

Abstract Microplastic contamination was studied along a freshwater continuum from inland streams to the Milwaukee River estuary to Lake Michigan and vertically from the water surface, water subsurface, and sediment. Microplastics were detected in all 96 water samples and 9 sediment samples collected. Results indicated a gradient of polymer presence with depth: low-density particles decreased from the water surface to the subsurface to sediment, and high-density particles had the opposite result. Polymer identification results indicated that water surface and subsurface samples were dominated by low-density polypropylene particles, and sediment samples were dominated by more dense polyethylene terephthalate particles. Of the five particle-type categories (fragments, films, foams, pellets/beads, and fibers/lines), fibers/lines were the most common particle-type and were present in every water and sediment sample collected. Fibers represented 45% of all particles in water samples and were distributed vertically throughout the water column regardless of density. Sediment samples were…

Byproducts produced when treating perfluorooctanoic acid (PFOA) and perfluorooctanesulfonate (PFOS) in water using a plasma treatment process intentionally operated to treat these compounds slowly to allow for byproduct accumulation were quantified. Several linear chain perfluoroalkyl carboxylic acids (PFCAs) (C4 to C7) were identified as byproducts of both PFOA and PFOS treatment. PFOA, perfluorohexanesulfonate (PFHxS), and perfluorobutanesulfonate (PFBS) were also found to be byproducts from PFOS degradation. Significant concentrations of fluoride ions, inorganic carbon, and smaller organic acids (trifluoroacetic acid, acetic acid, and formic acid) were also identified. In addition to PFCAs, PFHxS, and PFBS, trace amounts of 43 PFOA-related and 35 PFOS-related byproducts were also identified using a screening and search-based algorithm. Minor concentrations of gas-phase byproducts were also identified (<2.5% of the F originally associated with the parent molecules) some of which are reported for the first time in perfluoroalkyl substance degradation experiments including cyclic…

Plastic debris, in particular, microplastics and nanoplastics, is becoming an emerging class of pollutants of global concern. Aging can significantly affect the physicochemical properties of plastics, and therefore, may influence the fate, transport, and effects of these materials. Here, we show that aging by UV or O 3 exposure drastically enhanced the mobility and contaminant-mobilizing ability of spherical polystyrene nanoplastics (PSNPs, 487.3 ± 18.3 nm in diameter) in saturated loamy sand. Extended Derjaguin–Landau–Verwey–Overbeek calculations and pH-dependent transport experiments demonstrated that the greater mobility of the aged PSNPs was mainly the result of surface oxidation of the nanoplastics, which increased not only the surface charge negativity, but more importantly, hydrophilicity of the materials. The increased mobility of the aged PSNPs significantly contributed to their elevated contaminant-mobilizing abilities. Moreover, aging of PSNPs enhanced the binding of both nonpolar and polar contaminants, further increasing the contaminant-mobilizing ability of PSNPs.…

The retention of polyvinyl chloride (PVC) microplastics in sewage sludge during wastewater treatment raises concerns. However, the effects of PVC microplastics on methane production from anaerobic digestion of waste activated sludge (WAS) have never been documented. In this work, the effects of PVC microplastics (1 mm, 10–60 particles/g TS) on anaerobic methane production from WAS were investigated. The presence of 10 particles/g TS of PVC microplastics significantly ( P = 0.041) increased methane production by 5.9 ± 0.1%, but higher levels of PVC microplastics (i.e., 20, 40, and 60 particles/g TS) inhibited methane production to 90.6 ± 0.3%, 80.5 ± 0.1%, and 75.8 ± 0.2% of the control, respectively. Model-based analysis indicated that PVC microplastics at >20 particles/g TS decreased both methane potential (B 0 ) and hydrolysis coefficient (k) of WAS. The mechanistic studies showed that bisphenol A (BPA) leaching from PVC microplastics was the primary reason for the decreased methane production, causing significant ( P = 0.037, 0.01, 0.004) inhibitory effects on the…

The preharvest drainage of rice paddy fields during the grain filling stage can result in a substantial mobilization of Cd in soil and, consequently, elevated grain Cd concentration. However, the processes controlling the mobilization of Cd remains poorly understood. Using 12 field-contaminated paddy soils, we investigated the factors controlling the temporal changes in Cd solubility in paddy soils that were incubated anaerobically for 40 d followed by a 20 d oxidation period. Soluble and extractable Cd concentrations decreased rapidly upon flooding but increased during the oxidation phase, with Cd solubility (aqueous Cd/soil Cd) largely depending upon porewater pH. Furthermore, inhibiting sulfate reduction or inhibiting oxidation dissolution of Cd-sulfides had little or no effect on the mobilization of Cd in the subsequent oxidation phase. Both sequential extraction and X-ray absorption spectroscopy (XAS) analyses revealed that changes in Cd solubility were largely dependent upon the transformation of Cd between the Fe-Mn (oxyhydro)oxide fraction and exchangeable fraction.…

Plastics are known sources of chemical exposure and few, prominent plastic-associated chemicals, such as bisphenol A and phthalates, have been thoroughly studied. However, a comprehensive characterization of the complex chemical mixtures present in plastics is missing. In this study, we benchmark plastic consumer products, covering eight major polymer types, according to their toxicological and chemical signatures using in vitro bioassays and nontarget high-resolution mass spectrometry. Most (74%) of the 34 plastic extracts contained chemicals triggering at least one end point, including baseline toxicity (62%), oxidative stress (41%), cytotoxicity (32%), estrogenicity (12%), and antiandrogenicity (27%). In total, we detected 1411 features, tentatively identified 260, including monomers, additives, and nonintentionally added substances, and prioritized 27 chemicals. Extracts of polyvinyl chloride (PVC) and polyurethane (PUR) induced the highest toxicity, whereas polyethylene terephthalate (PET) and high-density polyethylene (HDPE) caused no or low toxicity. High baseline toxicity…

Manganese oxides have been recently investigated as excellent catalysts for peroxymonosulfate (PMS) activation, and the reported mechanisms are mostly forming reactive oxygen species (ROSs). This study investigated the use of iron-doped manganese oxide, synthesized via air oxidation under strong alkaline conditions. The oxidation of three substrates was affected by their adsorption at the catalyst surface, solution pH, and co-solutes. Common ROS scavengers inhibited the oxidation of bisphenol A (BPA), suggesting the possible involvement of ROSs; however, the PMS decomposition tests with and without BPA and the comparison with a 1 O 2 -generation system ruled out the formation of ROSs and pointed to direct electron transfer between the adsorbed BPA and complexed PMS as the mechanism. To prove this mechanism, the catalyst was coated to graphite sheets and a galvanic oxidation process (GOP) was developed to separate BPA and PMS into two half cells. Upon PMS addition into one cell, BPA was quickly oxidized in the other cell, confirming the occurrence of electron transfer. The GOP system…

Spent lithium ion battery (LIB) recovery is becoming quite urgent for environmental protection and social needs due to the rapid progress in LIB industries. However, recycling technologies cannot keep up with the exaltation of the LIB market. Technological improvement of processing spent batteries is necessary for industrial application. In this paper, spent LIB recovery processes are classified into three steps for discussion: gathering electrode materials, separating metal elements, and recycling separated metals. Detailed discussion and analysis are conducted in every step to provide beneficial advice for environmental protection and technology improvement of spent LIB recovery. Besides, the practical industrial recycling processes are introduced according to their advantages and disadvantages. And some recommendations are provided for existing problems. Based on current recycling technologies, the challenges for spent LIB recovery are summarized and discussed from technological and environmental perspectives. Furthermore, great effort should be made to promote the development of…

Abstract Cobalt-mediated activation of peroxymonosulfate (PMS) has been widely investigated for the oxidation of organic pollutants. Herein, we employ cobalt-doped Black TiO2 nanotubes (Co-Black TNT) for the efficient, stable, and reusable activator of PMS for the degradation of organic pollutants. Co-Black TNTs induce the activation of PMS by itself and stabilized oxygen vacancies that enhance the bonding with PMS and provide catalytic active sites for PMS activation. A relatively high electronic conductivity associated with the coexistence of Ti4+ and Ti3+ in Co-Black TNT enables an efficient electron transfer between PMS and the catalyst. As a result, Co-Black TNT is an effective catalyst for PMS activation, leading to the degradation of selected organic pollutants when compared to other TNTs (TNT, Co-TNT, and Black TNT) and other Co-based materials (Co3O4, Co-TiO2, CoFe2O4, and Co3O4/rGO). The observed organic compound degradation kinetics are retarded in the presence of methanol and natural organic matter as sulfate radical scavengers. These results demonstrate that sulfate…

Research has already demonstrated the toxic effects of microplastics (MPs) on different biota. However, the underlying toxic mechanism of MPs remains to be elucidated, especially the effect of particle size and the presence of dissolved organic matter in water. This study investigated the impact on Scenedesmus obliquus exposed in five types of polystyrene particle suspensions with different sizes and surface charges, in the presence and absence of humic acid (HA). Results indicated that the 50% growth inhibition rate of S. obliquus showed no significant difference between the five types of MPs, but the toxic mechanism varied with particle size. Larger size MPs caused adverse effects by blocking the light transport and affecting photosynthesis, while smaller ones destroyed the cell wall by adsorbing onto the algae surface. Also, the addition of HA significantly alleviated the toxicity of smaller size MPs, but not of the larger ones. Scanning electron microscopy images and the reactive oxygen species assay demonstrated that the HA could form a corona on the surface of MPs, reduce the…

Microplastics (MPs) are considered as a pollutant of marine environments and have become a global environmental problem in recent years. A number of studies have demonstrated that MPs can enter the human food chain, and MPs have even been detected in human stools. Therefore, there is increasing concern about the potential risks of MPs to human and animal health. Here, we investigated maternal polystyrene MPs exposure during gestation and lactation and evaluated the potential effects on dams and the F1 (both PND 42 and 280) and F2 (PND 42) generations. The results of transcriptome and 16S rRNA sequencing indicated that MPs caused the metabolic disorder in maternal MPs associated with gut microbiota dysbiosis and gut barrier dysfunction. Simultaneously, maternal MPs exposure also had the intergenerational effects and even caused long-term metabolic consequences in the F1 and F2 generations. In addition, in F1 (PND 42), the composition of gut microbiota did not change significantly, while the hepatic transcriptome and serum metabolite changes showed the potential risk in metabolic…

Yellow mealworms (larvae of Tenebrio molitor, Coleoptera: Tenebrionidae) have been proven to be capable of biodegrading polystyrene (PS) products. Using four geographic sources, we found that dark mealworms (larvae of Tenebrio obscurus ) ate PS as well. We subsequently tested T. obscurus from Shandong, China for PS degradation capability. Our results demonstrated the ability for PS degradation within the gut of T. obscurus at greater rates than T. molitor . With expanded PS foam as the sole diet, the specific PS consumption rates for T. obscurus and T. molitor at similar sizes (2.0 cm, 62–64 mg per larva) were 32.44 ± 0.51 and 24.30 ± 1.34 mg 100 larvae –1 d –1, respectively. After 31 days, the molecular weight ( M n ) of residual PS in frass (excrement) of T. obscurus decreased by 26.03%, remarkably higher than that of T. molitor (11.67%). Fourier transform infrared spectroscopy (FTIR) indicated formation of functional groups of intermediates and chemical modification. Thermo gravimetric analysis (TGA) suggested that T. obscurus larvae degraded PS effectively based on the…

Use of legacy brominated flame retardants (BFRs), including polybrominated diphenyl ethers (PBDEs) and hexabromocyclododecane (HBCD), has been reduced due to adverse effects of these chemicals. Several novel brominated flame retardants (NBFRs), such decabromodiphenyl ethane (DBDPE) and bis(2,4,6-tribromophenoxy) ethane (BTBPE), have been developed as replacements for PBDEs. NBFRs are used in various industrial and consumer products, which leads to their ubiquitous occurrence in the environment. This article reviews occurrence and fate of a select group of NBFRs in the environment, as well as their human exposure and toxicity. Occurrence of NBFRs in both abiotic, including air, water, dust, soil, sediment and sludge, and biotic matrices, including bird, fish, and human serum, have been documented. Evidence regarding the degradation, including photodegradation, thermal degradation and biodegradation, and bioaccumulation and biomagnification of NBFRs is summarized. The toxicity data of NBFRs show that several NBFRs can cause adverse effects through different modes of action, such as…

This study describes a promising sunlight-driven photocatalyst for the treatment of ofloxacin and other fluoroquinolone antibiotics in water and wastewater. Perylene diimide (PDI) supramolecular nanofibers, which absorb a broad spectrum of sunlight, were prepared via a facile acidification polymerization protocol. Under natural sunlight, the PDI photocatalysts achieved rapid treatment of fluoroquinolone antibiotics, including ciprofloxacin, enrofloxacin, norfloxacin, and ofloxacin. The fastest degradation was observed for ofloxacin, which had a half-life of 2.08 min for the investigated conditions. Various light sources emitting in the UV–vis spectrum were tested, and blue light was found to exhibit the fastest ofloxacin transformation kinetics due to the strong absorption by the PDI catalyst. Reactive species, namely, h +, 1 O 2, and O 2 •–, comprised the primary photocatalytic mechanisms for ofloxacin degradation. Frontier electron density calculations and mass spectrometry were used to verify the major degradation pathways of ofloxacin by the PDI–sunlight photocatalytic system…

Microplastics were demonstrated to be an environmental sink for hydrophobic organic pollutants, while they can also serve as a potential source of such pollutants. In this study, the sorption and release of bisphenol A in marine water were investigated through laboratory experiments. Sorption and desorption isotherms were developed, and the results reveal that sorption and desorption depend on the crystallinity, elasticity, and hydrophobicity of the polymer concerned. The adsorption and partition of bisphenol A can be quantified using a dual-mode model of the sorption mechanisms. Polyamide and polyurethane were found to exhibit the highest sorption capacity for bisphenol A, and it was almost irreversible, probably due to hydrogen bonding. Polyethylenes and polypropylene exhibited high and reversible sorption without noticeable desorption hysteresis. Glassy polystyrene, poly(vinyl chloride), poly(methyl methacrylate), and poly(ethylene terephthalate) exhibited low sorption capacity and only partial reversibility. Low-density polyethylene and polycarbonate microplastic particles were…

Polyethylene (PE) microplastics retained in sewage sludge inevitably enter the anaerobic digestion system. To date, no information has been reported on the mechanisms of PE microplastics affecting anaerobic digestion of waste activated sludge (WAS). This study evaluated the mechanisms using batch and continuous tests. Short exposure to PE microplastics at lower levels (i.e., 10, 30, and 60 particles/g-TS) did not significantly affect the methane production, but higher levels of PE microplastics (i.e., 100 and 200 particles/g TS) significantly ( P = 0.006 and 0.0003) decreased methane production by 12.4–27.5%, with a lower methane potential and hydrolysis coefficient. In continuous test over 130 days, feeding WAS with 200 particles PE microplastics/g TS decreased vs destruction by up to 27.3% ( P = 2.18 × 10 –18 ) and resulted in a 9.1% ( P = 0.002) increase in the volume of digested sludge for disposal. Correspondingly, the microbial community was shifted in the direction against anaerobic digestion. A mechanisms study revealed that the negative effect of PE microplastics was likely…

Tailoring the interfaces between active metal centers and supporting materials is an efficient strategy to obtain a superior catalyst for a certain reaction. Herein, an active interface between Ru and CeO 2 was identified and constructed by adjusting the morphology of CeO 2 support, such as rods (R), cubes (C), and octahedra (O), to optimize both the activity and the stability of Ru/CeO 2 catalyst for propane combustion. We found that the morphology of CeO 2 support does not significantly affect the chemical states of Ru species but controls the interaction between the Ru and CeO 2, leading to the tuning of oxygen vacancy in the CeO 2 surface around the Ru–CeO 2 interface. The Ru/CeO 2 catalyst possesses more oxygen vacancy when CeO 2 -R with predominantly exposed CeO 2 {110} surface facets is used, providing a higher ability to adsorb and activate oxygen and propane. As a result, the Ru/CeO 2 -R catalyst exhibits higher catalytic activity and stability for propane combustion compared with the Ru/CeO 2 -C and Ru/CeO 2 -O catalysts. This work highlights a new strategy for the design…

Microplastics (MP; 1 μm to 1 mm) of various shapes and compositions are ingested by numerous marine animals. Recently, proposals have been made to adopt bivalve molluscs as bioindicators of MP pollution. To serve as indicators of MP pollution, however, the proposed organisms should ingest, without bias, the majority of plastic particles to which they are exposed. To test this premise, eastern oysters, Crassostrea virginica, and blue mussels, Mytilus edulis, were offered variously sized polystyrene microspheres (diameters 19–1000 μm) and nylon microfibers (lengths 75–1075 × diameter 30 μm), and the proportion of each rejected in pseudofeces and egested in feces was determined. For both species, the proportion of microspheres rejected increased from ca. 10–30% for the smallest spheres to 98% for the largest spheres. A higher proportion of the largest microsphere was rejected compared with the longest microfiber, but similar proportions of microfibers were ingested regardless of length. Differential egestion of MP also occurred. As a result of particle selection, the number and types…

The effect of Cr(VI) and bisphenol A (BPA) on U(VI) photoreduction by C 3 N 4 photocatalyst was demonstrated by the batch experiments, electron spin resonance (ESR), X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES), and extended X-ray absorption fine structure (EXAFS) techniques. The batch experiments manifested that Cr(VI) and BPA enhanced the photocatalytic activity of C 3 N 4 for U(VI) photoreduction, whereas U(VI) photoreduction was significantly diminished with increased pH from 4.0 to 8.0. According to radical scavengers and ESR analysis, U(VI) was photoreduced to U(IV) by photogenerated electrons of conduction band edge, whereas Cr(VI) was reduced to Cr(III) by H 2 O 2 . BPA and its products such as organic acid and alcohols can capture photoinduced holes, which resulted in the enhancement of U(VI) photoreduction to U(IV). XPS and XANES analyses demonstrated that U(VI) was gradually photoreduced to U(IV) by C 3 N 4 within irradiation 60 min, whereas U(IV) was reoxidized to U(VI) with increasing irradiation time. EXAFS analysis determined…

Our understanding of the fate and distribution of micro- and nano- plastics in the marine environment is limited by the intrinsic difficulties of the techniques currently used for the detection, quantification, and chemical identification of small particles in liquid (light scattering, vibrational spectroscopies, and optical and electron microscopies). Here we introduce Raman Tweezers (RTs), namely optical tweezers combined with Raman spectroscopy, as an analytical tool for the study of micro- and nanoplastics in seawater. We show optical trapping and chemical identification of sub-20 μm plastics, down to the 50 nm range. Analysis at the single particle level allows us to unambiguously discriminate plastics from organic matter and mineral sediments, overcoming the capacities of standard Raman spectroscopy in liquid, intrinsically limited to ensemble measurements. Being a microscopy technique, RTs also permits one to assess the size and shapes of particles (beads, fragments, and fibers), with spatial resolution only limited by diffraction. Applications are shown on both model…

Particulate matter with aerodynamic diameters ≤1 μm (PM 1 ) has a greater impact on the human health but has been less studied due to fewer ground observations. This study attempts to improve the retrieval accuracy and spatial resolution of satellite-based PM 1 estimates using the new ground-based monitoring network in China. Therefore, a space-time extremely randomized trees (STET) model is first developed to estimate PM 1 concentrations at a 1 km spatial resolution from 2014 to 2018 across mainland China. The STET model can derive daily PM 1 concentrations with an average across-validation coefficient of determination of 0.77, a low root-mean-square error of 14.6 μg/m 3, and a mean absolute error of 8.9 μg/m 3 . PM 1 concentrations are generally low in most areas of China, except for the North China Plain and Sichuan Basin where intense human activities and poor natural conditions are prevalent, especially in winter. Moreover, PM 1 pollution has greatly decreased over the past 5 years, benefiting from emission control in China. The STET model, incorporating the spatiotemporal…

Abstract The first spatially and temporally resolved inventory of BDE28, 47, 99, 153, 183, and 209 in the anthroposphere and environment is presented here. The stock and emissions of PBDE congeners were estimated using a dynamic substance flow analysis model, CiP-CAFE. To evaluate our results, the emission estimates were used as input to the BETR-Global model. Estimated concentrations were compared with observed concentrations in air from background areas. The global (a) in-use and (b) waste stocks of ∑5BDE(28, 47, 99, 153, 183) and BDE209 are estimated to be (a) ∼25 and 400 kt and (b) 13 and 100 kt, respectively, in 2018. A total of 6 (0.3–13) and 10.5 (9–12) kt of ∑5BDE and BDE209, respectively, has been emitted to the atmosphere by 2018. More than 70% of PBDE emissions during production and use occurred in the industrialized regions, while more than 70% of the emissions during waste disposal occurred in the less industrialized regions. A total of 70 kt of ∑5BDE and BDE209 was recycled within products since 1970. As recycling rates are expected to increase under the circular…

The maximization of the numbers of exposed active sites in supported metal catalysts is important to achieve high reaction activity. In this work, a simple strategy for anchoring single atom Fe on SBA-15 to expose utmost Fe active sites was proposed. Iron salts were introduced into the as-made SBA-15 containing the template and calcined for simultaneous decomposition of the iron precursor and the template, resulting in single atom Fe sites in the nanopores of SBA-15 catalysts (SAFe-SBA). X-ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy (UV–vis DRS), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM), and extended X-ray absorption fine structure (EXAFS) imply the presence of single atom Fe sites. Furthermore, EXAFS analysis suggests the structure of one Fe center with four O atoms, and density functional theory calculations (DFT) simulate this structure. The catalytic performances of SAFe-SBA were evaluated in Fenton-like catalytic oxidation of p -hydroxybenzoic acid (HBA) and phenol. It was found that the single atom SAFe-SBA…

Humins (HMs) play a very important role in various environmental processes and are crucial for regulating global carbon and nitrogen cycles in various ecosystems. Composting is a controlled decomposition process accompanied by the stabilization of organic solid waste materials. During composting, active fractions of organic substances can be transformed into HMs containing stable and complex macromolecules. However, the structural heterogeneity and formation mechanisms of HMs during composting with various substrates have not been clarified. Here, the structure and composition of HMs extracted from livestock manure (LM) and straw (SW) during composting were investigated by excitation-emission matrices spectroscopy and Fourier transform infrared spectroscopy. The results showed that the stability and humification of LM-HM were lower than that of SW-HM. The parallel factor analysis components of the HM in LM composting contained the same fluorescent unit, and the intermediate of cellulose degradation affected the structure of the HM from SW composting. Structural equation modeling…

The agricultural use of conventional, polyethylene-based mulch films leads to the accumulation of remnant film pieces in agricultural soils with negative impacts for soil productivity and ecology. A viable strategy to overcome this accumulation is to replace conventional with biodegradable mulch films composed of polymers designed to be degraded by soil microorganisms. However, understanding polymer biodegradation in soils remains a significant challenge due to its dependence on polymer properties, soil characteristics, and prevailing environmental conditions. This perspective aims to advance our understanding of the three fundamental steps underlying biodegradation of mulch films in agricultural soils: colonization of the polymer film surfaces by soil microorganisms, depolymerization of the polymer films by extracellular microbial hydrolases, and subsequent microbial assimilation and utilization of the hydrolysis products for energy production and biomass formation. The perspective synthesizes the current conceptual understanding of these steps and highlights existing knowledge…

Semiconductor photocatalytic technology has great potential for the removal of dilute gaseous NO in indoor and outdoor atmospheres but suffers from unsatisfactory NO-removal selectivity due to undesirable NO 2 byproduct generation. In this study, we demonstrate that the 99% selectivity of photocatalytic NO oxidation toward nitrate can be achieved over blue TiO 2 bearing oxygen vacancies (OVs) under visible-light irradiation. First-principles density functional theory calculation and experimental results suggested that the OVs of blue TiO 2 with localized electrons could facilitate the molecular oxygen activation through single-electron pathways to generate ·O 2 – and simultaneously promote the photogenerated hole annihilation. The generated ·O 2 – directly converted NO to nitrate, while the hole annihilation inhibited the side-reaction between holes and NO to avoid toxic NO 2 byproduct formation, resulting in the highly selective removal of NO. This study reveals the dual functions of OVs in defective photocatalysts and also provides fundamental guidance for the selective…