The 50 most-cited articles in Environmental Science & Technology, 2021

Persulfate-based nonradical oxidation processes (PS-NOPs) are appealing in wastewater purification due to their high efficiency and selectivity for removing trace organic contaminants in complicated water matrices. In this review, we showcased the recent progresses of state-of-the-art strategies in the nonradical electron-transfer regimes in PS-NOPs, including design of metal and metal-free heterogeneous catalysts, in situ/operando characterization/analytical techniques, and insights into the origins of electron-transfer mechanisms. In a typical electron-transfer process (ETP), persulfate is activated by a catalyst to form surface activated complexes, which directly or indirectly interact with target pollutants to finalize the oxidation. We discussed different analytical techniques on the fundamentals and tactics for accurate analysis of ETP. Moreover, we demonstrated the challenges and proposed future research strategies for ETP-based systems, such as computation-enabled molecular-level investigations, rational design of catalysts, and real-scenario applications in the complicated…

The rapid increase in both the quantity and complexity of data that are being generated daily in the field of environmental science and engineering (ESE) demands accompanied advancement in data analytics. Advanced data analysis approaches, such as machine learning (ML), have become indispensable tools for revealing hidden patterns or deducing correlations for which conventional analytical methods face limitations or challenges. However, ML concepts and practices have not been widely utilized by researchers in ESE. This feature explores the potential of ML to revolutionize data analysis and modeling in the ESE field, and covers the essential knowledge needed for such applications. First, we use five examples to illustrate how ML addresses complex ESE problems. We then summarize four major types of applications of ML in ESE: making predictions; extracting feature importance; detecting anomalies; and discovering new materials or chemicals. Next, we introduce the essential knowledge required and current shortcomings in ML applications in ESE, with a focus on three important but often…

Human ingestion of microplastics (MPs) is inevitable due to the ubiquity of MPs in various foods and drinking water. Whether the ingestion of MPs poses a substantial risk to human health is far from understood. Here, by analyzing the characteristics of MPs in the feces of patients with inflammatory bowel disease (IBD) and healthy people, for the first time, we found that the fecal MP concentration in IBD patients (41.8 items/g dm) was significantly higher than that in healthy people (28.0 items/g dm). In total, 15 types of MPs were detected in feces, with poly(ethylene terephthalate) (22.3-34.0%) and polyamide (8.9-12.4%) being dominant, and their primary shapes were sheets and fibers, respectively. We present evidence indicating that a positive correlation exists between the concentration of fecal MPs and the severity of IBD. Combining a questionnaire survey and the characteristics of fecal MPs, we conclude that the plastic packaging of drinking water and food and dust exposure are important sources of human exposure to MPs. Furthermore, the positive correlation between fecal MPs…

Annual global satellite-based estimates of fine particulate matter (PM 2.5 ) are widely relied upon for air-quality assessment.Here, we develop and apply a methodology for monthly estimates and uncertainties during the period 1998-2019, which combines satellite retrievals of aerosol optical depth, chemical transport modeling, and ground-based measurements to allow for the characterization of seasonal and episodic exposure, as well as aid air-quality management.Many densely populated regions have their highest PM 2.5 concentrations in winter, exceeding summertime concentrations by factors of 1.5-3.0 over Eastern Europe, Western Europe, South Asia, and East Asia.In South Asia, in January, regional population-weighted monthly mean PM 2.5 concentrations exceed 90 μg/m 3 , with local concentrations of approximately 200 μg/m 3 for parts of the Indo-Gangetic Plain.In East Asia, monthly mean PM 2.5 concentrations have decreased over the period 2010-2019 by 1.6-2.6 μg/m 3 /year, with decreases beginning 2-3 years earlier in summer than in winter.We find evidence that global-monitored…

A variety of chemical substances used in plastic production may be released throughout the entire life cycle of the plastic, posing risks to human health, the environment, and recycling systems. Only a limited number of these substances have been widely studied. We systematically investigate plastic monomers, additives, and processing aids on the global market based on a review of 63 industrial, scientific, and regulatory data sources. In total, we identify more than 10'000 relevant substances and categorize them based on substance types, use patterns, and hazard classifications wherever possible. Over 2'400 substances are identified as substances of potential concern as they meet one or more of the persistence, bioaccumulation, and toxicity criteria in the European Union. Many of these substances are hardly studied according to SciFinder (266 substances), are not adequately regulated in many parts of the world (1'327 substances), or are even approved for use in food-contact plastics in some jurisdictions (901 substances). Substantial information gaps exist in the public domain,…

Abstract Human exposure to microplastic is recognized as a global problem, but the uncertainty, variability, and lifetime accumulation are unresolved. We provide a probabilistic lifetime exposure model for children and adults, which accounts for intake via eight food types and inhalation, intestinal absorption, biliary excretion, and plastic-associated chemical exposure via a physiologically based pharmacokinetic submodel. The model probabilistically simulates microplastic concentrations in the gut, body tissue, and stool, the latter allowing validation against empirical data. Rescaling methods were used to ensure comparability between microplastic abundance data. Microplastic (1–5000 μm) median intake rates are 553 particles/capita/day (184 ng/capita/day) and 883 particles/capita/day (583 ng/capita/day) for children and adults, respectively. This intake can irreversibly accumulate to 8.32 × 103 (90% CI, 7.08 × 102–1.91 × 106) particles/capita or 6.4 (90% CI, 0.1–2.31 × 103) ng/capita for children until age 18, and up to 5.01 × 104 (90% CI, 5.25 × 103–9.33 × 106) particles/capita or…

High Resolution Image Download MS PowerPoint Slide Air pollution has altered the Earth’s radiation balance, disturbed the ecosystem, and increased human morbidity and mortality. Accordingly, a full-coverage high-resolution air pollutant data set with timely updates and historical long-term records is essential to support both research and environmental management. Here, for the first time, we develop a near real-time air pollutant database known as Tracking Air Pollution in China (TAP, http://tapdata.org.cn/ ) that combines information from multiple data sources, including ground observations, satellite aerosol optical depth (AOD), operational chemical transport model simulations, and other ancillary data such as meteorological fields, land use data, population, and elevation. Daily full-coverage PM 2.5 data at a spatial resolution of 10 km is our first near real-time product. The TAP PM 2.5 is estimated based on a two-stage machine learning model coupled with the synthetic minority oversampling technique and a tree-based gap-filling method. Our model has an averaged out-of-bag…

Increasing chemical pollution of aquatic environments is a growing concern with global relevance. A large number of organic chemicals are termed as "micropollutants" due to their low concentrations, and long-term exposure to micropollutants may pose considerable risks to aquatic organisms and human health. In recent decades, numerous treatment methods and technologies have been proposed to remove micropollutants in water, and typically several micropollutants were chosen as target pollutants to evaluate removal efficiencies. However, it is often unclear whether their toxicity and occurrence levels and frequencies enable them to contribute significantly to the overall chemical pollution in global aquatic environments. This review intends to answer an important lingering question: Which micropollutants or class of micropollutants deserve more attention globally and should be removed with higher priority? Different risk-based prioritization approaches were used to address this question. The risk quotient (RQ) method was found to be a feasible approach to prioritize micropollutants in a…

Ubiquitous oxygen vacancies (Vo) existing in metallic compounds can activate peroxymonosulfate (PMS) for water treatment. However, under environmental conditions, especially oxygenated surroundings, the interactions between Vo and PMS as well as the organics degradation mechanism are still ambiguous. In this study, we provide a novel insight into the PMS activation mechanism over Vo-containing Fe–Co layered double hydroxide (LDH). Experimental results show that Vo/PMS is capable of selective degradation of organics via a single-electron-transfer nonradical pathway. Moreover, O 2 is firstly demonstrated as the most critical trigger in this system. Mechanistic studies reveal that, with abundant electrons confined in the vacant electron orbitals of Vo, O 2 is thermodynamically enabled to capture electrons from Vo to form O 2 •– under the imprinting effect and start the activation process. Simultaneously, Vo becomes electron-deficient and withdraws the electrons from organics to sustain the electrostatic balance and achieve organics degradation (32% for Bisphenol A without PMS).…

Oxygen vacancies (OVs) play a crucial role in the catalytic activity of metal-based catalysts; however, their activation mechanism toward peroxydisulfate (PDS) still lacks reasonable explanation. In this study, by taking bismuth bromide (BiOBr) as an example, we report an OV-mediated PDS activation process for degradation of bisphenol A (BPA) employing singlet oxygen ( 1 O 2 ) as the main reactive species under alkaline conditions. The experimental results show that the removal efficiency of BPA is proportional to the number of OVs and is highly related to the dosage of PDS and the catalyst. The surface OVs of BiOBr provide ideal sites for the inclusion of hydroxyl ions (HO – ) to form Bi III –OH species, which are regarded as the major active sites for the adsorption and activation of PDS. Unexpectedly, the activation of PDS occurs through a nonradical mechanism mediated by 1 O 2, which is generated via multistep reactions, involving the formation of an intermediate superoxide radical (O 2 •– ) and the redox cycle of Bi(III)/Bi(IV). This work is dedicated to the in-depth mechanism…

Recently, reactive iron species (RFeS) have shown great potential for the selective degradation of emerging organic contaminants (EOCs). However, the rapid generation of RFeS for the selective and efficient degradation of EOCs over a wide pH range is still challenging. Herein, we constructed FeN 4 structures on a carbon nanotube (CNT) to obtain single-atom catalysts (Fe SA -N-CNT) to generate RFeS in the presence of peroxymonosulfate (PMS). The obtained Fe SA -N-CNT/PMS system exhibited outstanding and selective reactivity for oxidizing EOCs over a wide pH range (3.0–9.0). Several lines of evidences suggested that RFeS existing as an FeN 4 ═O intermediate was the predominant oxidant, while SO 4 ·– and HO · were the secondary oxidants. Density functional theory calculation results revealed that a CNT played a key role in optimizing the distribution of bonding and antibonding states in the Fe 3d orbital, resulting in the outstanding ability of Fe SA -N-CNT for PMS chemical adsorption and activation. Moreover, CNT could significantly enhance the reactivity of the FeN 4 ═O intermediate…

Potassium periodate (PI, KIO 4 ) was readily activated by Fe(II) under acidic conditions, resulting in the enhanced abatement of organic contaminants in 2 min, with the decay ratios of the selected pollutants even outnumbered those in the Fe(II)/peroxymonosulfate and Fe(II)/peroxydisulfate processes under identical conditions. Both 18 O isotope labeling techniques using methyl phenyl sulfoxide (PMSO) as the substrate and X-ray absorption near-edge structure spectroscopy provided conclusive evidences for the generation of high-valent iron–oxo species (Fe(IV)) in the Fe(II)/PI process. Density functional theory calculations determined that the reaction of Fe(II) with PI followed the formation of a hydrogen bonding complex between Fe(H 2 O) 6 2+ and IO 4 (H 2 O) −, ligand exchange, and oxygen atom transfer, consequently generating Fe(IV) species. More interestingly, the unexpected detection of 18 O-labeled hydroxylated PMSO not only favored the simultaneous generation of · OH but also demonstrated that · OH was indirectly produced through the self-decay of Fe(IV) to form H 2 O 2 and…

Peroxymonosulfate (PMS)-based advanced oxidation processes (PMS-AOPs) as an efficient strategy for organic degradation are highly dependent on catalyst design and structured active sites. However, the identification of the active sites and their relationship with reaction mechanisms for organic degradation are not fully understood for a composite catalyst due to the complex structure. Herein, we developed a family of Co encapsulated in N-doped carbons (Co-PCN) with tailored types and contents of active sites via manipulated pyrolysis for PMS activation and ciprofloxacin (CIP) degradation, focusing on the correlation of active sites to generated reactive species and degradation routes of organics. The structure–function relationships between the different active sites in Co-PCN catalysts and reactive oxygen species (ROS), as well as bond breaking position of CIP, were revealed through regression analysis and density functional theory calculation. Co–N x, O–C═O, C═O, graphitic N, and defects in Co-PCN stimulate the generation of 1 O 2 for oxidizing the C–C bond in the piperazine ring…

As two major types of pollutants of emerging concerns, microplastics (MPs) and antibiotics (ATs) coexist in aquatic environments, and their interactions are a source of increasing concern. Therefore, this work examines the interaction mechanisms of MPs and ATs, and the effect of MPs on ATs bioavailability and antibiotic resistance genes (ARGs) abundance in aquatic environments. First, the mechanisms for ATs adsorption on MPs are summarized, mainly including hydrophobic, hydrogen-bonding, and electrostatic interactions. But other possible mechanisms, such as halogen bonding, CH/π interaction, cation-π interaction, and negative charge-assisted hydrogen bonds, are newly proposed to explain the observed ATs adsorption. Additionally, environmental factors (such as pH, ionic strength, dissolved organic matters, minerals, and aging conditions) affecting ATs adsorption by MPs are specifically discussed. Moreover, MPs could change the bioaccumulation and toxicity of ATs to aquatic organisms, and the related mechanisms on the joint effect are reviewed and analyzed. Furthermore, MPs can enrich…

High Resolution Image Download MS PowerPoint Slide Based on the exposure data sets from the Tracking Air Pollution in China (TAP, http://tapdata.org.cn/ ), we characterized the spatiotemporal variations in PM 2.5 and O 3 exposures and quantified the long- and short-term exposure related premature deaths during 2013–2020 with respect to the two-stage clean air actions (2013–2017 and 2018–2020). We find a 48% decrease in national PM 2.5 exposure during 2013–2020, although the decrease rate has slowed after 2017. At the same time, O 3 pollution worsened, with the average April–September O 3 exposure increased by 17%. The improved air quality led to 308 thousand and 16 thousand avoided long- and short-term exposure related deaths, respectively, in 2020 compared to the 2013 level, which was majorly attributed to the reduction in ambient PM 2.5 concentration. It is also noticed that with smaller PM 2.5 reduction, the avoided long-term exposure associated deaths in 2017–2020 (13%) was greater than that in 2013–2017 (9%), because the exposure–response curve is nonlinear. As a result of the…

There is increasing pressure on global agricultural systems due to higher food demand, climate change, and environmental concerns. The design of nanostructures is proposed as one of the economically viable technological solutions that can make agrochemical use (fertilizers and pesticides) more efficient through reduced runoff, increased foliar uptake and bioavailability, and decreased environmental impacts. However, gaps in knowledge about the transport of nanoparticles across the leaf surface and their behavior in planta limit the rational design of nanoparticles for foliar delivery with controlled fate and limited risk. Here, the current literature on nano-objects deposited on leaves is reviewed. The different possible foliar routes of uptake (stomata, cuticle, trichomes, hydathodes, necrotic spots) are discussed, along with the paths of translocation, via the phloem, from the leaf to the end sinks (mature and developing tissues, roots, rhizosphere). This review details the interplays between morphological constraints, environmental stimuli, and physical-chemical properties of…

High Resolution Image Download MS PowerPoint Slide Biomass waste-derived porous carbons (BWDPCs) are a class of complex materials that are widely used in sustainable waste management and carbon capture. However, their diverse textural properties, the presence of various functional groups, and the varied temperatures and pressures to which they are subjected during CO 2 adsorption make it challenging to understand the underlying mechanism of CO 2 adsorption. Here, we compiled a data set including 527 data points collected from peer-reviewed publications and applied machine learning to systematically map CO 2 adsorption as a function of the textural and compositional properties of BWDPCs and adsorption parameters. Various tree-based models were devised, where the gradient boosting decision trees (GBDTs) had the best predictive performance with R 2 of 0.98 and 0.84 on the training and test data, respectively. Further, the BWDPCs in the compiled data set were classified into regular porous carbons (RPCs) and heteroatom-doped porous carbons (HDPCs), where again the GBDT model had R 2 of…

Single-atom catalysts (SACs) have emerged as efficient materials in the elimination of aqueous organic contaminants; however, the origin of high activity of SACs still remains elusive. Herein, we identify an 8.1-fold catalytic specific activity (reaction rate constant normalized to catalyst’s specific surface area and dosage) enhancement that can be fulfilled with a single-atom iron catalyst (SA-Fe-NC) prepared via a cascade anchoring method compared to the iron nanoparticle-loaded catalyst, resulting in one of the most active currently known catalysts in peroxymonosulfate (PMS) conversion for organic pollutant oxidation. Experimental data and theoretical results unraveled that the high-activity origin of the SA-Fe-NC stems from the Fe–pyridinic N 4 moiety, which dramatically increases active sites by not only creating the electron-rich Fe single atom as the catalytic site but also producing electron-poor carbon atoms neighboring pyridinic N as binding sites for PMS activation including synchronous PMS reduction and oxidation together with dissolved oxygen reduction. Moreover, the…

Microplastics are a big and growing part of global pollution, which has aroused increasing concern in recent years because of their large amount, wide distribution, and adverse effects. Microplastics can sorb various pollutants from aquatic environments and act as vectors of pollutants. Most studies mainly focused on the virgin microplastics. However, microplastics in environments can be easily colonized by microorganisms, and form biofilm, which will influence the behaviors and potential risks of microplastics. The formation of biofilm on microplastics and its effects on their properties have been studied before, but their sorption and transport behaviors, and potential risks for pollutants' transfer have not been reviewed. In this paper, the role of biofilm-developed microplastics as vectors of pollutants was thoroughly analyzed and summarized. First, the formation of biofilm on microplastics, the compositions of microorganisms in biofilm, the influencing factors, and the property changes of microplastics after biofilm attachment are thoroughly reviewed. Second, the sorption of…

Herein, a silicate-enhanced flow-through electro-Fenton system with a nanoconfined catalyst was rationally designed and demonstrated for the highly efficient, rapid, and selective degradation of antibiotic tetracycline. The key active component of this system is the Fe 2 O 3 nanoparticle filled carbon nanotube (Fe 2 O 3 -in-CNT) filter. Under an electric field, this composite filter enabled in situ H 2 O 2 generation, which was converted to reactive oxygen species accompanied by the redox cycling of Fe 3+ /Fe 2+ . The presence of the silicate electrolyte significantly boosted the H 2 O 2 yield by preventing the O–O bond dissociation of the adsorbed OOH*. Compared with the surface coated Fe 2 O 3 on the CNT (Fe 2 O 3 -out-CNT) filter, the Fe 2 O 3 -in-CNT filter demonstrated 1.65 times higher k L value toward the degradation of the antibiotic tetracycline. Electron paramagnetic resonance and radical quenching tests synergistically verified that the dominant radical species was the 1 O 2 or HO· in the confined Fe 2 O 3 -in-CNT or unconfined Fe 2 O 3 -out-CNT system, respectively. The…

Selective removal or enrichment of targeted solutes including micropollutants, valuable elements, and mineral scalants from complex aqueous matrices is both challenging and pivotal to the success of water purification and resource recovery from unconventional water resources. Membrane separation with precision at the subnanometer or even subangstrom scale is of paramount importance to address those challenges via enabling "fit-for-purpose" water and wastewater treatment. So far, researchers have attempted to develop novel membrane materials with precise and tailored selectivity by tuning membrane structure and chemistry. In this critical review, we first present the environmental challenges and opportunities that necessitate improved solute-solute selectivity in membrane separation. We then discuss the mechanisms and desired membrane properties required for better membrane selectivity. On the basis of the most recent progress reported in the literature, we examine the key principles of material design and fabrication, which create membranes with enhanced and more targeted…

Volatile organic compounds (VOCs) are one of the main sources of air pollution, which are of wide concern because of their toxicity and serious threat to the environment and human health. Catalytic oxidation has been proven to be a promising and effective technology for VOCs abatement in the presence of heat or light. As environmentally friendly and low-cost materials, manganese-based oxides are the most competitive and promising candidates for the catalytic degradation of VOCs in thermocatalysis or photo/thermocatalysis. This article summarizes the research and development on various manganese-based oxide catalysts, with emphasis on their thermocatalytic and photo/thermocatalytic purification of VOCs in recent years in detail. Single manganese oxides, manganese-based oxide composites, as well as improving strategies such as morphology regulation, heterojunction engineering, and surface decoration by metal doping or universal acid treatment are reviewed. Besides, manganese-based monoliths for practical VOCs abatementare also discussed. Meanwhile, relevant catalytic mechanisms are…

Manganese (Mn) is a biologically important and redox-active metal that may exert a poorly recognized control on carbon (C) cycling in terrestrial ecosystems. Manganese influences ecosystem C dynamics by mediating biochemical pathways that include photosynthesis, serving as a reactive intermediate in the breakdown of organic molecules, and binding and/or oxidizing organic molecules through organo-mineral associations. However, the potential for Mn to influence ecosystem C storage remains unresolved. Although substantial research has demonstrated the ability of Fe- and Al-oxides to stabilize organic matter, there is a scarcity of similar information regarding Mn-oxides. Furthermore, Mn-mediated reactions regulate important litter decomposition pathways, but these processes are poorly constrained across diverse ecosystems. Here, we discuss the ecological roles of Mn in terrestrial environments and synthesize existing knowledge on the multiple pathways by which biogeochemical Mn and C cycling intersect. We demonstrate that Mn has a high potential to degrade organic molecules through…

Despite the vital roles of reactive radical species in the coupled iron–carbon composite/persulfate (PS) system for eliminating pollutants, nonradical contributions are typically overlooked. Herein, we developed two efficient magnetic iron–char composites via low-temperature (BCFe-400) and high-temperature (BCFe-700) pyrolysis. The two composites activated PS through nonradical pathways for sulfamethoxazole (SMX) degradation. In the BCFe-400/PS system, high-valent iron Fe(IV) was the dominant active species for the oxidation, evidenced by methyl phenyl sulfoxide-based probe tests, Mössbauer spectroscopy, and in situ Raman analyses with kinetic evaluation. In the BCFe-700/PS system, surface-mediated electron transfer dominated the oxidation, and the nonradical regime was probed by the electrochemical test and in situ Raman analysis. Furthermore, the BCFe-400/PS system maintained high efficiency in continuous degradation of SMX due to the feasible Fe 2+ generation toward Fe(IV) formation. In the BCFe-700/PS system, the stability of the system was limited due to the hindered electron…

The presence of diverse pollutants in water has been threating human health and aquatic ecosystems on a global scale. For more than a century, chemical oxidation using strongly oxidizing species was one of the most effective technologies to destruct pollutants and to ensure a safe and clean water supply. However, the removal of increasing amount of pollutants with higher structural complexity, especially the emerging micropollutants with trace concentrations in the complicated water matrix, requires excessive dosage of oxidant and/or energy input, resulting in a low cost-effectiveness and possible secondary pollution. Consequently, it is of practical significance but scientifically challenging to achieve selective oxidation of pollutants of interest for water decontamination. Currently, there are a variety of examples concerning selective oxidation of pollutants in aqueous systems. However, a systematic understanding of the relationship between the origin of selectivity and its applicable water treatment scenarios, as well as the rational design of catalyst for selective catalytic…

Dissolved oxygen (DO) reflects river metabolic pulses and is an essential water quality measure. Our capabilities of forecasting DO however remain elusive. Water quality data, specifically DO data here, often have large gaps and sparse areal and temporal coverage. Earth surface and hydrometeorology data, on the other hand, have become largely available. Here we ask: can a Long Short-Term Memory (LSTM) model learn about river DO dynamics from sparse DO and intensive (daily) hydrometeorology data? We used CAMELS-chem, a new data set with DO concentrations from 236 minimally disturbed watersheds across the U.S. The model generally learns the theory of DO solubility and captures its decreasing trend with increasing water temperature. It exhibits the potential of predicting DO in "chemically ungauged basins", defined as basins without any measurements of DO and broadly water quality in general. The model however misses some DO peaks and troughs when in-stream biogeochemical processes become important. Surprisingly, the model does not perform better where more data are available. Instead,…

Graphitized nanodiamonds (ND) exhibit outstanding capability in activating peroxymonosulfate (PMS) for the removal of aqueous organic micropollutants (OMPs). However, controversial observation and interpretation regarding the effect of graphitization degree on ND’s activity and the role of singlet oxygen ( 1 O 2 ) in OMP degradation need to be clarified. Herein, we investigated graphitized ND-mediated PMS activation. Experiments show that the activity of ND increases first and then decreases with the monotonically increased graphitization degree. Further experimental and theoretical studies unveil that the intensified surface graphitization alters the degradation mechanism from singlet oxygenation to an electron-transfer pathway. Moreover, for the first time, we applied a self-constructed, time-resolved phosphorescence detection system to provide direct evidence for 1 O 2 production in the PMS-based system. This work not only elucidates the graphitization degree-dependent activation mechanism of PMS but also provides a reliable detection system for in situ analysis of 1 O 2 in…

Microplastics (size of plastic debris <5 mm) occur in various environments worldwide these days and cause detrimental effects on biota. However, the behavioral responses of fish to microplastics in feeding processes are not well understood. In the present study, juveniles from four fish species and two common shapes of microplastics were used to explore fish feeding responses. We found swallowing-feeding fish ingested more pellets than filtering- and sucking-feeding fish. With high-definition and high-speed observational experiments, we found that all species did not actively capture microfibers; instead, they passively sucked in microfibers while breathing. Surprisingly, fish showed a rejective behavior, which was spontaneously coughing up microfibers mixed with mucus. Nevertheless, some of the microfibers were still found in the gastrointestinal tracts and gills of fish, while abundances of ingested microfibers were increased in the presence of food. Our findings reveal a common phenomenon that fish ingest microplastics inadvertently rather than intentionally. We also provide…

With the increasing severity of global water scarcity, a myriad of scientific activities is directed toward advancing brackish water desalination and wastewater remediation technologies. Flow-electrode capacitive deionization (FCDI), a newly developed electrochemically driven ion removal approach combining ion-exchange membranes and flowable particle electrodes, has been actively explored over the past seven years, driven by the possibility of energy-efficient, sustainable, and fully continuous production of high-quality fresh water, as well as flexible management of the particle electrodes and concentrate stream. Here, we provide a comprehensive overview of current advances of this interesting technology with particular attention given to FCDI principles, designs (including cell architecture and electrode and separator options), operational modes (including approaches to management of the flowable electrodes), characterizations and modeling, and environmental applications (including water desalination, resource recovery, and contaminant abatement). Furthermore, we introduce the…

and their thresholds. We provide evidence that the third criterion could be fulfilled for weathering plastics in sensitive environments and therefore conclude that weathering plastics pose a planetary boundary threat. We suggest future research priorities to better understand (eco)toxicological hazards modulated by increasing exposure and continuous weathering processes, to better parametrize the planetary boundary threshold for plastic pollution.

Pesticides are applied in large quantities to agroecosystems worldwide. To date, few studies assessed the occurrence of pesticides in organically managed agricultural soils, and it is unresolved whether these pesticide residues affect soil life. We screened 100 fields under organic and conventional management with an analytical method containing 46 pesticides (16 herbicides, 8 herbicide transformation products, 17 fungicides, seven insecticides). Pesticides were found in all sites, including 40 organic fields. The number of pesticide residues was two times and the concentration nine times higher in conventional compared to organic fields. Pesticide number and concentrations significantly decreased with the duration of organic management. Even after 20 years of organic agriculture, up to 16 different pesticide residues were present. Microbial biomass and specifically the abundance of arbuscular mycorrhizal fungi, a widespread group of beneficial plant symbionts, were significantly negatively linked to the amount of pesticide residues in soil. This indicates that pesticide residues,…

This is the first study in the last 15 years to analyze per- and polyfluoroalkyl substances (PFAS) in breast milk collected from mothers ( n = 50) in the United States, and our findings indicate that both legacy and current-use PFAS now contaminate breast milk, exposing nursing infants. Breast milk was analyzed for 39 PFAS, including 9 short-chain and 30 long-chain compounds, and 16 of these PFAS were detected in 4–100% of the samples. The ∑PFAS concentration in breast milk ranged from 52.0 to 1850 pg/mL with a median concentration of 121 pg/mL. Perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) were the most abundant PFAS in these samples (medians 30.4 and 13.9 pg/mL, respectively). Two short-chain PFAS, including perfluoro- n -hexanoic acid (PFHxA, C6) and perfluoro- n -heptanoic acid (PFHpA, C7), were detected in most of the samples with median concentrations of 9.69 and 6.10 pg/mL, respectively. Analysis of the available breast milk PFAS data from around the world over the period of 1996–2019 showed that while the levels of the phased-out PFOS and PFOA have…

Abstract Microplastics (MPs) pollution has caused a threat to soil ecosystem diversity and functioning globally. Recently, an increasing number of studies have reported effects of MPs on soil ecosystems. However, these studies mainly focused on soil bacterial communities and a few limited functional genes, which is why MPs effects on soil ecosystems are still not fully understood. Fertilization treatment often coinsides with MPs exposure in practice. Here, we studied effects of an environmentally relevant concentration of polyethylene on soil properties, microbial communities, and functions under different soil types and fertilization history. Our results showed that 0.2% PE MPs exposure could affect soil pH, but this effect varied according to soil type and fertilization history. Long-term fertilization history could alter effects of MPs on soil bacterial and fungal communities in diverse farmland ecosystems (P < 0.05). Soil fungal communities are more sensitive to MPs than bacterial communities under 0.2% PE MPs exposure. MPs exposure has a greater impact on the soil ecosystem…

Abstract Heterogeneous advanced oxidation processes (AOPs) allow for the destruction of aqueous organic pollutants via oxidation by hydroxyl radicals (•OH). However, practical treatment scenarios suffer from the low availability of short-lived •OH in aqueous bulk, due to both mass transfer limitations and quenching by water constituents, such as natural organic matter (NOM). Herein, we overcome these challenges by loading iron oxychloride catalysts within the pores of a ceramic ultrafiltration membrane, resulting in an internal heterogeneous Fenton reaction that can degrade organics in complex water matrices with pH up to 6.2. With •OH confined inside the nanopores (∼ 20 nm), this membrane reactor completely removed various organic pollutants with water fluxes of up to 100 L m–2 h–1 (equivalent to a retention time of 10 s). This membrane, with a pore size that excludes NOM (>300 kDa), selectively exposed smaller organics to •OH within the pores under confinement and showed excellent resiliency to representative water matrices (simulated surface water and sand filtration effluent…

Herein, we report that Co(II)-doped g-C 3 N 4 can efficiently trigger peracetic acid (PAA) oxidation of various sulfonamides (SAs) in a wide pH range. Quite different from the traditional radical-generating or typical nonradical-involved (i.e., singlet oxygenation and mediated electron transfer) catalytic systems, the PAA activation follows a novel nonradical pathway with unprecedented high-valent cobalt–oxo species [Co(IV)] as the dominant reactive species. Our experiments and density functional theory calculations indicate that the Co atom fixated into the nitrogen pots of g-C 3 N 4 serves as the main active site, enabling dissociation of the adsorbed PAA and conversion of the coordinated Co(II) to Co(IV) via a unique two-electron transfer mechanism. Considering Co(IV) to be highly electrophilic in nature, different substituents (i.e., five-membered and six-membered heterocyclic moieties) on the SAs could affect their nucleophilicity, thus leading to the differences in degradation efficiency and transformation pathway. Also, benefiting from the selective oxidation of Co(IV), the…

Abstract Pollutant degradation via periodate (IO4–)-based advanced oxidation processes (AOPs) provides an economical, energy-efficient way for sustainable pollution control. Although single-atomic metal activation (SMA) can be exploited to optimize the pollution degradation process and understand the associated mechanisms governing IO4–-based AOPs, studies on this topic are rare. Herein, we demonstrated the first instance of using SMA for IO4– analysis by employing atomically dispersed Co active sites supported by N-doped graphene (N-rGO-CoSA) activators. N-rGO-CoSA efficiently activated IO4– for organic pollutant degradation over a wide pH range without producing radical species. The IO4– species underwent stoichiometric decomposition to generate the iodate (IO3–) species. Whereas Co2+ and Co3O4 could not drive IO4– activation; the Co–N coordination sites exhibited high activation efficiency. The conductive graphene matrix reduced the contaminants/electron transport distance/resistance for these oxidation reactions and boosted the activation capacity by working in conjunction with…

Understanding the salt-water separation mechanisms of reverse osmosis (RO) membranes is critical for the further development and optimization of RO technology. The solution-diffusion (SD) model is widely used to describe water and salt transport in RO, but it does not describe the intricate transport mechanisms of water molecules and ions through the membrane. In this study, we develop an ion transport model for RO, referred to as the solution-friction model, by rigorously considering the mechanisms of partitioning and the interactions among water, salt ions, and the membrane. Ion transport through the membrane is described by the extended Nernst-Planck equation, with the consideration of frictions between the species (i.e., ion, water, and membrane matrix). Water flow through the membrane is governed by the hydraulic pressure gradient and the friction between the water and membrane matrix as well as the friction between water and ions. The model is validated using experimental measurements of salt rejection and permeate water flux in a lab-scale, cross-flow RO setup. We then…

High Resolution Image Download MS PowerPoint Slide Direct air carbon capture and storage (DACCS) is an emerging carbon dioxide removal technology, which has the potential to remove large amounts of CO 2 from the atmosphere. We present a comprehensive life cycle assessment of different DACCS systems with low-carbon electricity and heat sources required for the CO 2 capture process, both stand-alone and grid-connected system configurations. The results demonstrate negative greenhouse gas (GHG) emissions for all eight selected locations and five system layouts, with the highest GHG removal potential in countries with low-carbon electricity supply and waste heat usage (up to 97%). Autonomous system layouts prove to be a promising alternative, with a GHG removal efficiency of 79–91%, at locations with high solar irradiation to avoid the consumption of fossil fuel-based grid electricity and heat. The analysis of environmental burdens other than GHG emissions shows some trade-offs associated with CO 2 removal, especially land transformation for system layouts with photovoltaics (PV)…

Large quantities of mismanaged plastic waste threaten the health and wellbeing of billions worldwide, particularly in low- and middle-income countries where waste management capacity is being outstripped by increasing levels of consumption and plastic waste generation. One of the main self-management strategies adopted by 2 billion people who have no waste collection service, is to burn their discarded plastic in open, uncontrolled fires. While this strategy provides many benefits, including mass and volume reduction, it is a form of plastic pollution that results in the release of chemical substances and particles that may pose serious risks to public health and the environment. We followed adapted PRISMA guidelines to select and review 20 publications that provide evidence on potential harm to human health from open burning plastic waste, arranging evidence into eight groups of substance emissions: brominated flame retardants; phthalates; potentially toxic elements; dioxins and related compounds; bisphenol A; particulate matter; and polycyclic aromatic hydrocarbons. We…

Studying heavy metal adsorption on soil is important for understanding the fate of heavy metals and properly assessing the related environmental risks. Existing experimental methods and traditional models for quantifying adsorption, however, are time-consuming and ineffective. In this study, we developed machine learning models for the soil adsorption of six heavy metals (Cd(II), Cr(VI), Cu(II), Pb(II), Ni(II), and Zn(II)) using 4420 data points (1105 soils) extracted from 150 journal articles. After a comprehensive comparison, our results showed that the gradient boosting decision tree had the best performance for a combined model based on all the data. The Shapley additive explanation method was used to identify the feature importance and the effects of these features on the adsorption, based on which six independent models were developed for the six metals to achieve better model performance than the combined model. Using these independent models, the global distribution of heavy metal adsorption capacities on soils was predicted with known soil properties. Reversed models,…

The presence of microplastics within the gut of animals is well documented. Whether microplastics bioaccumulate in organisms and biomagnify in food webs remains unclear and relies on the ability of microplastics to translocate to other tissues. Here, we demonstrate the widespread presence of microplastics and other anthropogenic microparticles in the gastrointestinal tract, fillet, and livers of seven species of sportfish from Lake Simcoe, Ontario, Canada. Larger fish had a higher microplastic load compared to smaller fish, but the opposite trend was observed with translocated microplastics standardized by fish mass (i.e., smaller fish contained more translocated particles per gram wet weight than larger fish). Moreover, we observed no evidence of biomagnification as there was no significant relationship between the trophic level and total or translocated microplastics per individual. Overall, this suggests that microplastics are translocating, but that excretion of translocated particles or growth dilution may be occurring rather than bioaccumulation and biomagnification. Moreover,…

Abstract Atmospheric oxidation of sulfur dioxide (SO2) forms sulfate-containing aerosol particles that impact air quality, climate, and human and ecosystem health. It is well-known that in-cloud oxidation of SO2 frequently dominates over gas-phase oxidation on regional and global scales. Multiphase oxidation involving aerosol particles, fog, and cloud droplets has been generally thought to scale with liquid water content (LWC) so multiphase oxidation would be negligible for aerosol particles due to their low aerosol LWC. However, recent field evidence, particularly from East Asia, shows that fast sulfate formation prevails in cloud-free environments that are characterized by high aerosol loadings. By assuming that the kinetics of cloud water chemistry prevails for aerosol particles, most atmospheric models do not capture this phenomenon. Therefore, the field of aerosol SO2 multiphase chemistry has blossomed in the past decade, with many oxidation processes proposed to bridge the difference between modeled and observed sulfate mass loadings. This review summarizes recent advances in…

Microplastics (MPs) exposed to the natural environment provide an ideal surface for biofilm formation, which potentially acts as a reactive phase facilitating the sorption of hazardous contaminants. Until now, changes in the contaminant sorption capacity of MPs due to biofilm formation have not been quantified. This is the first study that compared the capacity of naturally aged, biofilm-covered microplastic fibers (BMFs) to adsorb perfluorooctane sulfonate (PFOS) and lead (Pb) at environmentally relevant concentrations. Changes in the surface properties and morphology of aged microplastic fibers (MF) were studied by surface area analysis, infrared spectroscopy, and scanning electron microscopy. Results revealed that aged MFs exhibited higher surface areas because of biomass accumulation compared to virgin samples and followed the order polypropylene>polyethylene>nylon>polyester. The concentrations of adsorbed Pb and PFOS were 4-25% and 20-85% higher in aged MFs and varied among the polymer types. The increased contaminant adsorption was linked with the altered surface area and the…

Abstract Many reagents as electron sacrificers have been recently investigated to induce decomposition of permanganate (KMnO4) to produce highly reactive intermediate Mn species toward oxidation of organic contaminants; however, this strategy meanwhile causes low KMnO4 utilization efficiency. This study surprisingly found that graphite can mediate direct electron transfer from organics (e.g., sulfamethoxazole (SMX)) to KMnO4, resulting in high KMnO4 utilization efficiency, rather than reductive sites of graphite-induced conversion of KMnO4 to highly reactive intermediate Mn species. The galvanic oxidation process (GOP) and comparative experiments of different organic contaminants prove that the KMnO4/graphite system mainly extracts electrons from organic contaminants via a one-electron pathway instead of a two-electron pathway. More importantly, the KMnO4/graphite system has superior reusability, graphite can keep a long-lasting reactivity, and the KMnO4 utilization efficiency elevates significantly after each cycle of graphite. The transformation of SMX in the KMnO4/graphite system…

Persistent organic pollutants (POPs) and related chemicals are fascinating because of their combination of physical-chemical properties and complex effects. Most are man-made, but some also have natural origins. They are persistent in the environment, but they can be broken down variously by biodegradation, atmospheric reactions, and abiotic transformations. They can exist in the gas or particle phases, or both, in the atmosphere and in the dissolved or particulate phases, or both, in water. These combinations mean that they may undergo long-range transport in the atmosphere or oceans, or they may stay close to sources. Hence, emissions from one country are frequently a source of contamination to another country. They are also usually lipophilic, so-combined with persistence-this means they can accumulate in organisms and biomagnify through food chains. We all have a baseline of POPs residues in our tissues, even the unborn fetus via placental transfer and the newly born baby via mother's milk. POPs in biological systems occur in mixtures, so confirming effects caused by POPs on…

2021 marks 10 years since controlled abiotic synthesis of sulfidated nanoscale zerovalent iron (S-nZVI) for use in site remediation and water treatment emerged as an area of active research. It was then expanded to sulfidated microscale ZVI (S-mZVI) and together with S-nZVI, they are collectively referred to as S-(n)ZVI. Heightened interest in S-(n)ZVI stemmed from its significantly higher reactivity to chlorinated solvents and heavy metals. The extremely promising research outcomes during the initial period (2011-2017) led to renewed interest in (n)ZVI-based technologies for water treatment, with an explosion in new research in the last four years (2018-2021) that is building an understanding of the novel and complex role of iron sulfides in enhancing reactivity of (n)ZVI. Numerous studies have focused on exploring different S-(n)ZVI synthesis approaches, and its colloidal, surface, and reactivity (electrochemistry, contaminant selectivity, and corrosion) properties. This review provides a critical overview of the recent milestones in S-(n)ZVI technology development: (i) clear…

The catalytic activation of peroxymonosulfate (PMS) is under intensive investigation with potentials as an alternative advanced oxidation process (AOP) in wastewater treatment. Among all catalysts examined, Co(II) exhibits the highest reactivity for the activation of PMS, following the conventional Fenton-like mechanism, in which free radicals ( i.e., sulfate radicals and hydroxyl radicals) are reckoned as the reactive species. Herein, we report that the primary reactive species (PRS) is proposed to be a Co(II)–PMS complex (Co(II)–OOSO 3 – ), while free radicals and Co(III) species act as the secondary reactive species (SRS) that play a minor role in the Co(II)/PMS process. This Co(II)–OOSO 3 – exhibits several intriguing properties including ability to conduct both one-electron-transfer and oxygen-atom-transfer reactions with selected molecules, both nucleophilic and electrophilic in nature, and strongly pH-dependent reactivity. This study provides novel insights into the chemical nature of the Co(II)-catalyzed PMS activation process.

High Resolution Image Download MS PowerPoint Slide Plastic products contain complex mixtures of extractable chemicals that can be toxic. However, humans and wildlife will only be exposed to plastic chemicals that are released under realistic conditions. Thus, we investigated the toxicological and chemical profiles leaching into water from 24 everyday plastic products covering eight polymer types. We performed migration experiments over 10 days at 40 °C and analyzed the migrates using four in vitro bioassays and nontarget high-resolution mass spectrometry (UPLC-QTOF-MS E ). All migrates induced baseline toxicity, 22 an oxidative stress response, 13 antiandrogenicity, and one estrogenicity. Overall, between 17 and 8681 relevant chemical features were present in the migrates. In other words, between 1 and 88% of the plastic chemicals associated with one product were migrating. Further, we tentatively identified ∼8% of all detected features implying that most plastic chemicals remain unknown. While low-density polyethylene, polyvinyl chloride, and polyurethane induced most toxicological…

-xylene, toluene, propylene, and formaldehyde. The top five contributors to SOAP were toluene, mineral spirits, benzene, heptadecane, and hexadecane. Mobile and solvent sources were the dominant VOC sources for both OFP and SOAP. The potential increases in biogenic VOC emissions due to future urban greening had significant effects on urban air quality that offset the benefits of reducing anthropogenic VOC emissions. This study demonstrates that urban greening programs in Los Angeles county, and likely other cities as well, need to account for both anthropogenic and biogenic VOC contributions to secondary pollution, and greening cities should consider using vegetation types with low VOC emissions to avoid further degradation to urban air quality.

Heterogeneous electro-Fenton (HEF) reaction has been considered as a promising process for real effluent treatments. However, the design of effective catalysts for simultaneous H 2 O 2 generation and activation to achieve bifunctional catalysis for O 2 toward •OH production remains a challenge. Herein, a core–shell structural Fe-based catalyst (FeNC@C), with Fe 3 C and FeN nanoparticles encapsulated by porous graphitic layers, was synthesized and employed in a HEF system. The FeNC@C catalyst presented a significant performance in degradation of various chlorophenols at various conditions with an extremely low level of leached iron. Electron spin resonance and radical scavenging revealed that •OH was the key reactive species and Fe IV would play a role at neutral conditions. Experimental and density function theory calculation revealed the dominated role of Fe 3 C in H 2 O 2 generation and the positive effect of FeN x sites on H 2 O 2 activation to form •OH. Meanwhile, FeNC@C was proved to be less pH dependence, high stability, and well-recycled materials for practical application in…