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The structure–reactivity relationship of g-C3N4 embedded with 0–2D carbon-based nanomaterials towards photocatalysis of emerging contaminants is presented.

The dynamic biological fate of silver nanoparticles as dissolution and neo-formation in zebrafish influences the number concentration-based versus mass concentration-based toxicokinetics.

Groundwater contamination remains a global threat due to its toxic effects to humans and the environment. The remediation of contaminated groundwater sites can be costly, thus, identifying the priority areas of concern is important to reduce money spent on resources. In this study, we aimed to identify and rank the priority groundwater sites in a contaminated petrochemical district by combining alternative, non-animal approaches - chemical analysis, cell-based high throughput screening (HTS), and Toxicological Priority Index (ToxPi) computational toxicology tool. Groundwater samples collected from ten different sites in a contaminated district showed pollutant levels below the detection limit, however, hepatotoxic bioactivity was demonstrated in human hepatoma HepaRG cells. Integrating the pollutants information (i.e., pollutant characteristics and concentration data) with the bioactivity data of the groundwater samples, an evidence-based ranking of the groundwater sites for future remediation was established using ToxPi analysis. The currently presented combinatorial approach of screening groundwater sites for remediation purposes can further be refined by including relevant parameters, which can boost the utility of this approach for groundwater screening and future remediation.

Silica nanoparticles (SiO2 NPs) are engineered nanomaterials (ENMs) that have a wide range of application. Increased use in manufacturing has led to concerns about their environmental impact and possible adverse health effects. We conducted a comparative toxicity assessment of bare SiO2-NPs and amine-functionalized SiO2 NPs (NH2-SiO2 NPs) utilizing the Caenorhabditis elegans (C. elegans) in vivo model. L1 nematodes were exposed to exposure concentrations of 0.25, 0.5, 2.5, and 5 mg mL–1 until the worms reached the L4 stage. The chronic lethality and lifespan assays revealed a significant decrease in survival rate and lifespan at 2.5 and 5 mg mL–1 for nematodes exposed to bare SiO2 NPs (89% and 88%; 22 days, p < 0.05 and 14 days, p < 0.05) and at 5 mg mL–1 for the NH2-SiO2 NPs-exposed group (86%; 20 days, p < 0.001). Exposure to all SiO2 NP concentrations reduced progeny production to 79–60% while exposure to 2.5 and 5 mg mL–1 of NH2-SiO2 NPs significantly reduced the brood size to 64–63%. Neurobehavioral toxicity was also observed in the SiO2 NP-exposed worms, which displayed significantly decreased head thrashing for up to 92–71% and in the NH2-SiO2 NPs-exposed worms which showed significantly reduced head thrashing movement for up to 91–85% at concentrations of 0.5-5 mg mL–1. Body bending movements were also significantly reduced at 0.5–5 mg mL–1 SiO2 NPs (71–34%) and 2.5–5 mg mL–1 NH2-SiO2 NPs (94–66%). Significant shortening of body size was also observed in nematodes exposed to 0.5–5 mg mL–1 for both SiO2 NPs (93–81%) and NH2-SiO2 NPs (94–88%). Overall, bare SiO2 NPs were observed to be more toxic due to the negatively charged surface OH groups, which may have disrupted protein homeostasis, resulting in the observed toxicities. We suggest that functionality is an important indicator in nanosafety evaluations.

Determining the hotspots and deposition efficiencies (DEs) for aerosols in human airways is important for both research and medical purposes. The complexity of the human airways and the breathing process limit the application of in vitro measurements to only two consecutive branches of the human airway. Herein, in-depth information on in vitro experiments and state-of-the-art review on various computational fluid dynamics (CFD) applications and finite element methods on airflow and aerosol motion in both healthy and obstructed human airways are provided. A brief introduction of the application of one-dimensional and two-dimensional mathematical models to investigate airflow and particle motion in the lungs are further discussed. As evident in this review, aerosol deposition in the upper and central human airway regions has been extensively studied under different inhalation statuses and conditions such as humidity as well as different aerosol sizes, shapes, and properties. However, there is little literature on the lower sections of the human airways. Herein, a detailed review of the fundamentals for both in vitro experiments and numerical simulation at different sections of human airways is done. Exceptional features and essential developments in numerical methods for aerosol motion in healthy and diseased human airways are also discussed. Challenges and limitations associated with the applications of in vitro experiments and CFD methods on both human-specific and idealized models are highlighted. The possibility of airborne transmission pathways for COVID-19 has been discussed. Overall, this review provides the most useful approach for carrying out two-phase flow investigations at different sections of the human lungs and under different inhalation statuses. Additionally, new research gaps that have developed recently on the role of bioaerosols motion in COVID-19 transmission, as well as the deposition of aerosols in impaired human airways due to coronavirus (COVID-19) are underlined.

Characterizing engineered nanoparticles (ENPs) in complex environmental matrices remains a challenging task. This work presents a two-dimensional size analysis method by combining differential mobility analyzer (DMA) and single-particle inductively coupled plasma-mass spectrometry (spICP-MS) with a new atomizer (ATM)-enabled sample introduction that is relatively easy to operate. The tailing of electrical mobility size distributions was solved by heating the aerosol flow, where water-shelled gold nanoparticles (AuNPs) were dehydrated, effectively eliminating the tailing. The improved method has a good sizing performance and can resolve the size fractions of mixed 30 nm and 50 nm AuNPs. It can reliably analyze 7.8 × 10

Single-walled carbon nanotubes (SWCNTs) are widely utilized for industrial, biomedical, and environmental purposes. The toxicity of Carboxylated SWCNTs (SWCNTs−COOH) in in vivo models, particularly Caenorhabditis elegans (C. elegans), and in vitro human cells is still unclear. In this study, C. elegans was used to study the effects of SWCNTs−COOH on lethality, lifespan, growth, reproduction, locomotion, reactive oxygen species (ROS) generation, and the antioxidant system. Our data show that exposure to ≥1 μg·L−1 SWCNTs−COOH could induce toxicity in nematodes that affects lifespan, growth, reproduction, and locomotion behavior. Moreover, the exposure of nematodes to SWCNTs−COOH induced ROS generation and the alteration of antioxidant gene expression. SWCNTs−COOH induced nanotoxic effects at low dose of 0.100 or 1.00 μg·L−1, particularly for the expression of antioxidants (SOD-3, CTL-2 and CYP-35A2). Similar nanotoxic effects were found in human cells. A low dose of SWCNTs−COOH induced ROS generation and increased the expression of catalase, MnSOD, CuZnSOD, and SOD-2 mRNA but decreased the expression of GPX-2 and GPX-3 mRNA in human monocytes. These findings reveal that background-level SWCNTs−COOH exerts obvious adverse effects, and C. elegans is a sensitive in vivo model that can be used for the biological evaluation of the toxicity of nanomaterials.

Single-walled carbon nanotubes (SWCNTs) are widely utilized for industrial, biomedical, and environmental purposes. The toxicity of Carboxylated SWCNTs (SWCNTs-COOH) in in vivo models, particularly

The bioaccumulation and depuration of TiO

As yet, the effect of biodiesels on the emissions of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from heavy-duty diesel engines (HDDEs) has only been studied using limited fuel blend ratios. To clarify the influence of using higher fractions of biodiesel on the emissions of toxic organic pollutants from diesel engines, in this research, the emissions of PM, PAHs, and persistent organic pollutants (POPs) from EURO IV and EURO III HDDEs fueled by low to high waste cooking oil (WCO)-based biodiesel-petrodiesel fuel blends were studied, including D100 (0% biodiesel), B20 (20%), B40 (40%), B60 (60%), B80 (80%), and B100 (100%). The engines were tested according to the US FTP-75 test procedure. The results for the EURO IV diesel engine showed that the PM and toxic organic pollutant emissions were reduced with increases in the blending ratio up until the B60 scenario when compared to the D100 scenario. This is because biodiesel has higher oxygen content and no or lower aromatic content than petrodiesel. Nevertheless, during the B80 and B100 scenarios, the PM and toxic organic pollutant emissions increased due to the high viscosity property of biodiesel, which negatively affected the combustion process. The biodiesel effect on the emissions from EURO III engine was more pronounced because of its lower combustion efficiency, and therefore the improvement in combustion using biodiesel resulted in greater PCDD/F reductions.

Cooking oil fumes (CF) coming from night market stalls exhaust contain substantial amounts of air pollutants such as carbonyl compounds that may contribute to outdoor air pollution and may have adverse health effects on the Taiwanese population. Carbonyl emission characteristics depend on several factors, which include but are not limited to, the cooking style and food material being used. The current study evaluated carbonyl compound emissions from two scenarios: a standard kitchen cooking classroom with a stack gas tunnel and night market food stalls. The different cooking styles and food types cooked using a liquefied petroleum gas (LPG) stove, such as grilled chicken with (GCS) and without sauce (GC), mixed barbecue with sauce (MBS), grilled vegetables with sauce (GVS), stir-fried oyster omelet (OM), fried Taiwanese chicken nuggets (FN) in the kitchen cooking classroom, and grilled chicken with (GCS) and without sauce (GC), stir-fried oyster omelet (OM), grilled vegetables with sauce (GVS), and fried steak (FS) in the night market were evaluated for carbonyl carbon emissions. OM from the kitchen classroom and GCS from the night market showed the highest mean total carbonyl compound concentrations (1850 ± 682 ppb and 1840 ppb). Formaldehyde was found to be the most predominant carbonyl compound, with contribution percentages ranging from 70.9–99.58% of the total carbonyl emission factors in CFs. Grilled vegetables with sauce had the highest emission factor magnitude of 274 µg kg–1 wt. Factors such as the addition of sauce and grilling were also observed to increase carbonyl compound emissions. Corresponding health risks of carbonyl compounds in CFs for the night market vendors were also assessed. All values for cancer risk (R) were above the standard R value for workplace exposure, and HQ values were all greater than 1, suggesting a high risk for adverse health effects. Although our reported values were relatively high due to our sampling conditions, our study was first to be conducted in Taiwan and holds an important contribution to the global existing data of carbonyl compound emissions.

Concerns about the effects of nanoparticles (NPs) on human health are being raised by researchers because the risks of nanocosmetics like sunscreen are unknown. We explored the association between urinary oxidative stress markers and exposure of cosmetics salesclerks to 20 cosmetics that might contain titanium dioxide (TiO2)/zinc oxide (ZnO) NPs. We then recruited 40 cosmetics salesclerks and 24 clothing salesclerks and categorized them based on their exposure to ZnO and TiO2 NPs. Nineteen and 15 samples met the EU definition for TiO2 and ZnO nanomaterials, respectively. Participants with a higher co-exposure index of ZnO and TiO2 NPs had a significantly higher base level of urinary 8-hydroxy-2&prime, deoxyguanosin (8-OHdG) concentrations than the lower co-exposure group (5.82 vs. 2.85 ng/mL, p &lt, 0.001). After potential confounding factors had been adjusted for, the TiO2 and ZnO NP co-exposure index was significantly positively associated with the urinary 8-OHdG base concentration (&beta, = 0.308, 95% CI = 0.106 to 0.510) and the creatinine-adjusted concentration (&beta, = 0.486, 95% CI = 0.017 to 0.954). Current evidence suggests that the likelihood of harm from using sunscreens containing nanoparticles might result in higher urinary 8-OHdG. However, our limited number and types of sample cosmetics might underestimate the risk.

Exposure assessment is a key component in the risk assessment of engineered nanomaterials (ENMs). While direct and quantitative measurements of ENMs in complex environmental matrices remain challenging, environmental fate models (EFMs) can be used alternatively for estimating ENMs’ distributions in the environment. This review describes and assesses the development and capability of EFMs, focusing on surface waters. Our review finds that current engineered nanomaterial (ENM) exposure models can be largely classified into three types: material flow analysis models (MFAMs), multimedia compartmental models (MCMs), and spatial river/watershed models (SRWMs). MFAMs, which is already used to derive predicted environmental concentrations (PECs), can be used to estimate the releases of ENMs as inputs to EFMs. Both MCMs and SRWMs belong to EFMs. MCMs are spatially and/or temporally averaged models, which describe ENM fate processes as intermedia transfer of well-mixed environmental compartments. SRWMs are spatiotemporally resolved models, which consider the variability in watershed and/or stream hydrology, morphology, and sediment transport of river networks. As the foundation of EFMs, we also review the existing and emerging ENM fate processes and their inclusion in recent EFMs. We find that while ENM fate processes, such as heteroaggregation and dissolution, are commonly included in current EFMs, few models consider photoreaction and sulfidation, evaluation of the relative importance of fate processes, and the fate of weathered/transformed ENMs. We conclude the review by identifying the opportunities and challenges in using EFMs for ENMs.

The bioaccumulation and depuration of TiO2 nanoparticles (TiO2NPs) by zebrafish via the dietary exposure following the OECD Test Guideline 305 (OECD TG305) was evaluated using particle size- and number concentration-resolved analysis based on single-particle ICP-MS (spICP-MS). We found that using enzymatic digestion without H2O2 or excessive heating can recover 84.0 ± 4.0% and 94.5 ± 3.5% of TiO2NP mass and number concentrations from fish tissue, respectively, without altering the size distribution of parent TiO2NPs. OECD TG305 can allow for the evaluation of bioaccumulation and depuration of TiO2NPs by fish based on the particle mass and number dose metrics. The toxicokinetic modeling can reasonably describe the mass- and number-based measurement data with the derived absorption efficiency α at ~0.2, depuration rate at ~0.5 d-1, and kinetic biomagnification factor (BMFk) at ~0.007 comparable with available data. The mass concentration- and number concentration-based bioaccumulation metrics including body burdens are correlated for TiO2NPs that remained nano-sized in vivo and exhibited marginal physicochemical alterations upon uptake by fish. The result indicates that the traditional mass concentration metric may be used to represent the fish bioaccumulation potential for chemically inert NPs like TiO2.

In 2017, the seasonal variations in the wet deposition fluxes of total-PCDD/Fs-WHO2005-TEQ in ambient air were evaluated in Taiwan. The results showed the annual wet deposition fluxes of total-PCDD/Fs-WHO2005-TEQ to be 42.5 pg WHO2005-TEQ m–2 month–1, and the seasonal distributions were 53.3, 62.9, 26.7 and 27.1 pg WHO2005-TEQ m–2 month–1 in spring, summer, autumn and winter, respectively. The average Stot of total-PCDD/Fs-WHO2005-TEQ was 12300. There were obvious seasonal variations in Stot, for which the values were 13840, 6540, 8280 and 20540 in spring, summer, autumn, and winter, respectively. The average concentration of total-PCDD/Fs-WHO2005-TEQ in the rain were 0.453, 0.176, 0.218 and 0.649 pg WHO2005-TEQ L–1 in spring, summer, autumn and winter, respectively. Atmospheric deposition is the major removal pathway for PCDD/Fs. The results of this study provide an evaluation of the adverse effects of PCDD/Fs exposure on human health, and provide a reason for the government to be concerned and to enact better control on air pollution.

Air pollution was getting worse and worse with the development of economic, and atmospheric deposition was an important mechanic for the removal of air pollutants. During 2017, the average dry deposition fluxes of total-PCDD/Fs-WHO2005-TEQ in various areas in Taiwan range between 57 (Lienchiang County in autumn) and 589 pg WHO2005-TEQ m–2 month–1 (Keelung City in winter), with an average of 221 pg WHO2005-TEQ m–2 month–1. The average total deposition fluxes of total-PCDD/Fs-WHO2005-TEQ in various areas in Taiwan range between 65 (Lienchiang County in autumn) and 681 pg WHO2005-TEQ m–2 month–1 (Keelung City in winter), with an average of 263 pg WHO2005-TEQ m–2 month–1. The fractions of dry deposition fluxes contribute to the total deposition fluxes range between 37.8% (Yilan County in winter) and 99.9% (Kaohsiung City in winter), with an average of 82.1%.

The emission factor (EF), the weight of potentially toxic elements (PTEs) per unit energy or weight of sinter produced were evaluated for coal-fired boilers and sintering furnaces integrated in a steel plant. From three coal-fired boilers, 15 samples were taken while 22 samples were taken from four sintering furnaces. Investigations were performed on the EF of lead, cadmium, mercury, arsenic and chromium (VI). The coefficient of variance for the first 3 samples from each PTE was used to decide whether 2 more samples were necessary for the investigation. Three samples were sufficient for Cr (VI), however, 5 samples were required for Pb, Cd, Hg, and As, since the variances in concentrations of the first three samples exceeded 20%. The ranges for the ratio of the laboratory-based EF to the default EF applied by the Environment Protection Administration (EPA Taiwan) for Pb, Cd, Hg, and As for the coal-fired boiler were 0.08–0.013, 0.014–0.017, 0.019–0.033, 0.047–0.066 and for the sintering furnaces were 0.059–0.232, 0.05–0.151, 0.05–0.364, and 0.067–0.824. The ratio for Cr (VI)- was constant at 0.005 for all the coal fired boilers while it ranged from 0.057–0.709 for the sintering furnaces. Whilst source identification, enrichment factors, and spatial distributions for PTEs are often studied, laboratory-based investigations on the EFs for PTEs from industrial plants are rarely performed. This study filled the information gap and compared the obtained EFs with the EPA default values. To avoid overcharging industrial plants equipped with the best available technology for emission control, the EPA should apply field investigations and laboratory-based EFs instead of the default EPA EFs to calculate air pollution fees. Insights from this investigation can be applied to promote the adoption of appropriate air pollution control devices to cut down the emission of PTEs.

An integrated cobalt oxide catalyst supported on silica (Co3O4/SiO2) packed in the lumen of tubular alumina (Al2O3) membrane was designed to realize a Fenton-like oxidation coupling with ultrafiltration water treatment technology to remove persistent and hazardous pollutants. We employed a selection of SiO2 support materials with a range micro/mesostructures to immobilize the Co3O4 catalyst. These were evaluated and screened to achieve the highest pollutant decolorization rate and maximum decolorization efficiency. Then, an integrated catalyst-membrane was developed as proof-of-concept for advanced water treatment. Batch degradation results showed acid orange 7 dye (AO7) was effectively removed using Co3O4 deposited on MCM-41 silica, with 97% decolorization efficiency achieved in 15 mins owing to the large surface area and high porosity of the MCM-41 support. In contrast, humic acid (HA) was relatively difficult to degrade using this catalyst, and was however found to inhibit AO7 degradation. The integrated catalyst-membrane successfully removed both AO7 and HA with only a 10% water flux reduction from 25.0 to 22.5 kg m−2 h−1 bar−1 with excellent co-pollutant removal rate of 99% over 40 h. Furthermore, the integrated catalyst-membrane also removed a range of organic pollutants (neutral red, tetracycline hydrochloride, oxytetracycline) achieving > 90% rejection and 30 kg m−2 h−1 bar−1. These results show that the integrated catalyst-membrane can effectively purify a binary pollutant mixture containing both hazardous dye and natural organic matter and other pharmaceutical chemicals whilst producing process water for recycling and reuse.

Composite photocatalysts comprising graphitic carbon nitride (g-C3N4) and graphene materials were synthesized and evaluated in the photocatalysis of bisphenol A (BPA) with a focus on elucidating the reaction mechanism. Embedding reduced graphene oxide (rGO) to g-C3N4 significantly accelerated the photocatalysis rate of BPA by three folds under visible light irradiation at neutral pH. We showed that rGO synthesized in intimate contact with g-C3N4 increased the surface areas and electrical conductivity of the g-C3N4 composites and promoted the electron-hole pair separation. The BPA photodegradation mechanism involved selective oxidants as superoxide (O2•−) and singlet oxygen (1O2) that were formed through one-electron reduction of O2 and the unique oxidation of O2•− by photogenerated hole (h+), respectively. The synthesized photocatalyst exhibited superior visible light photoreactivity to that of N-doped P25 TiO2, good photo-stability and reuse potential, and was operative in complex wastewater. rGO embedded g-C3N4 achieved good photomineralization of BPA at 80% in 4 h compared to 40% of bare g-C3N4. This study sheds light on the photocatalysis mechanism of BPA with a metal-free, promising rGO/g-C3N4 photocatalyst.

Graphene family nanomaterials are emerging, two-dimensional photocatalysts consisting of Earth-abundant elements. This study evaluated the potential of graphene oxide (GO) toward photocatalytic H2O2 production in water driven by renewable sunlight and visible light without synthetic organic electron donors. We reported for the first time that GO can efficiently photocatalyze the generation of H2O2 to millimolar levels under simulated sunlight in a few hours. The concentration of H2O2 produced is among the greatest values reported in current photocatalytic systems without organic electron donors. We showed that dissolved O2 played a pivotal role in the photoproduction of H2O2 by GO and that superoxide (O2•–) was not involved. A 2-fold increase in H2O2 photoproduction can be readily achieved by raising pH from 3 to 7. The addition of oxalate as the electron donor only enhanced H2O2 photoproduction at low pH, but not at high pH where GO suffered greater photocorrosion. As a result, GO had a greater long-term...

Photocatalytic, hollow fiber membranes based on nanocomposites of titania nanoparticles and carbonaceous char were simultaneously fabricated in a single calcination step, and then optimized for the photo-degradation of pollutants and water recovery in an integrated membrane operation in this study. The physicochemical, mechanical and photocatalytic properties along with separation performance of two series of membranes were finely-tuned by systematically changing the calcination temperature (series 1: 500–1000 °C for 8 h holding time) and calcination time (series 2: 2–8 h at 600 °C). The calcined membranes were extensively characterized for morphology, thermal stability, microstructure, modulus and chemical compositions. Both constituents of titania and char are essential in deriving the desirable hollow fiber properties and membrane performance for photocatalysis and water recovery. By controlling the calcination conditions, membranes prepared at 600 °C for the 3 and 6 h duration displayed an optimal balance between enhanced mechanical strength (34 MPa) and high photo-degradation of acid orange 7 (90.4%). Membrane performance demonstrated water fluxes of 6.9 (H2O/dark), 12.9 (H2O/UV) 4.8 (AO7/dark) and 7.9 L m–2 h–1 (AO7/UV) with excellent organic dye rejection. Both membranes exhibited photo-induced super-hydrophilicity and defouling potential under the influence of UV light due to the photo-activation of exposed TiO2 nanoparticles on the membrane surface. The detailed mechanism of property correlation and separation performance for the photocatalytic hollow fibers is proposed and elucidated. This work offers an innovative material for the research avenue of photocatalytic, hollow fiber membrane reactors for advanced membrane treatment applications.\ud \ud

Over the past few years, there has been a strong interest in exploring the potential impact of fullerenes in the environment. Despite that both C 60 and C 70 have been detected in environmental matrices, the research on the impact of higher fullerenes, such as C 70, has been largely missing. This study evaluated and compared the phototransformation of aqueous C 60 and C 70 clusters (nC 60 and nC 70 ) and their 1 O 2 production under sunlight and lamp light irradiation (315 nm, 360 nm and 420 nm). The nC 60 and nC 70 samples formed by direct mixing with water adopted a face-centered cubic (FCC) crystal structure. The apparent quantum yields (AQYs) of fullerene phototransformed were relatively constant over the examined wavelengths, while 1 O 2 production AQYs decreased with increased wavelengths. The long-term fate studies with outdoor sunlight indicated that both nC 60 and nC 70 lost considerable organic carbon contents (>80%) in water after ∼8 months of irradiation and that the intermediate photoproducts of nC 60 and nC 70 exhibited a progressively increased level of oxygen-containing functionalities. Overall, the study indicates that nC 70 can be photochemically removed under sunlight conditions and that the photoreactivity of nC 60 based on AQYs is greater than that of nC 70 .

Graphene-related materials are emerging with a wide range of potential applications. Their possible ecological effect must be properly evaluated before their widespread use. This study examined the antibacterial activity of graphene oxide (GO) before and after solar transformation under two reaction scenarios. GO was directly phototransformed under simulated sunlight or indirectly photolyzed by photochemically generated hydroxyl radical (˙OH). The results indicate that compared to parent GO, directly phototransformed GO showed increased toxicity to bacteria, while the indirectly phototransformed GO became less toxic. The reduced bacterial toxicity of indirectly photolyzed GO correlated with its large decrease in total organic carbon (TOC) concentration after the indirect photoreaction. In contrast, the directly phototransformed GO caused greater membrane disruption and oxidative stress, which is consistent with its increased antibacterial activity. The oxidative stress was likely associated with the intrinsic oxidation capability of the directly photolyzed GO. Given that direct photolysis of GO is expected to occur more rapidly in sunlit surface waters, as predicted in previous research, enhanced antibacterial activity of phototransformed GO will likely dominate the initial solar transformation of GO, while microbial toxicity will decrease in long term photolysis where GO is extensively decomposed by ˙OH-mediated photoreaction.

Silver nanoparticles (AgNPs) have shown to be toxic to freshwater cyanobacterial species, and sodium hypochlorite (NaOCl) is a common oxidant for the treatment of cyanobacterial cells. AgNPs have a high possibility of co-existing with the cyanobacterial cells in the aqueous environments leading to its exposure to NaOCl during water treatment; however, their combined effects on the cyanobacterial cells are largely undocumented. This work compares the individual and combined effect of AgNP and NaOCl on the integrity and toxin (microcystins) release of Microcystis aeruginosa at varying levels. The results show that the AgNP (0.2-0.6 mg/L) alone has negligible effects on the cell lysis, while NaOCl alone shows concentration-dependent (0.2 0.4 0.6 mg/L) rupturing of cells. In contrast, the AgNP + NaOCl (0.2-0.6 mg/L) samples show increasing loss in cell integrity at higher AgNP (0.4 and 0.6 mg/L) levels than the NaOCl only samples. NaOCl exposure results in increasing dissolution of AgNPs with time, releasing silver ions (Ag

To understand the contributions of a raw material storage site for iron ore, coal, limestone, and sinter to ambient air fine particulate matter (PM2.5), the concentrations and chemical fingerprints for resuspended and ambient air PM2.5 were compared. Investigations were done for 15 piles of raw materials, including 5 iron piles, 5 coal piles, 3 stone piles, and a single pile each for coke and sinter. Additionally, four sites, including A, B, C, and D, in the storage site surroundings were chosen to investigate the ambient air PM2.5 concentrations. The concentrations, compositions, and i and j values for PM2.5 varied significantly by season in the four sites under investigation. The chemical fingerprints of the PM2.5 showed that water-soluble ions were the most important component in all sites. Specifically, SO42– and NO3– were the predominant water-soluble ions in winter and summer, respectively. The most dominant components in the iron ore, coal, limestone, coke, and sinter piles were iron, carbon, Ca2+ and carbon, carbon and SO42–, and Fe and Ca2+, respectively. During the summer, PM2.5 concentrations ranged from 13.7–18.0 µg m–3, where the chemical composition of water-soluble ions, metals, carbon accounted for 54.2%, 5.7%, and 23.7% respectively. During winter, the concentrations ranged from 44.7–48.0 µg m–3, where the water-soluble ions, metals, carbon components accounted for 49.2%, 8.1%, and 17.4% respectively. From the chemical mass balance, the main sources of PM2.5 in sites B, C, and D were stationary sources, mobile sources, and secondary organic aerosols. To effectively address the air pollution threat associated with the surroundings of a raw material storage site, the environmental protection agency should formulate measures to effectively reduce the contribution of resuspended dust and other pollution sources to ambient air PM2.5.

This paper probes the role of hydroxyl radicals (·OH) generated by H2O2 photolysis on graphene oxide (GO) phototransformation, under simulated sunlight. It focuses on comparing the photoreaction of GO with (indirect) and without (direct) added H2O2 under simulated sunlight conditions. The biomarker responses of fish epithelial cells in in vitro assays of parent GO and GO photoreacted with H2O2 and their interaction with model biomembranes are also compared. GO was found to be far more extensively photodecomposed in the presence of H2O2, with ∼85% of the initial carbon content converted to CO2 during 48 h of irradiation. Direct and indirect photoreactions occurred concurrently in GO samples containing H2O2, and indirect photoreaction accounted for ∼70% of GO conversion to CO2. Reaction with ·OH causes increases in the concentrations of carboxylic acid groups of photoreacted GO and low-molecular-weight (LMW) species as part of the intermediate photoproducts. Compared to parent GO, intermediate photoproducts exhibited reduced interaction with model cell membranes and altered biomarker responses. Kinetic analysis extrapolating our data to conditions prevalent in sunlit surface waters predicts that initial GO photoreaction is dominated by direct photolysis, while indirect photoreactions involving ·OH determine subsequent conversion of intermediate GO photoproducts to CO2.

This work shows the concept of a simple, single-step, partial pyrolysis approach to prepare inorganic composite hollow fibers at low temperature conditions. Two series of robust, photocatalytic and high-performance membranes were synthesized by changing the pyrolysis temperature (Series 1: 500–600 °C for 8 h) and time (Series 2: 550 °C for 3–12 h), leading to the formation of a composite matrix consisted of carbonaceous char and titania nanoparticles. Chemical composition, phase of crystallinity, mechanical strength, textural characteristics, morphology and photocatalytic activity of the hollow fibers were comprehensively characterized. Mechanical strength of the hollow fibers was found to directly attribute to the amount of char and porosity. Hollow fibers, prepared using 8 h at 550 and 575 °C or 6 h at 550 °C condition, displayed a good balance between the highest mechanical strength of 52 MPa and photo-degradation of 90.4% of acid orange 7 under ultra-violet light. This was attributed to the optimization of degree of char derived from the binder and the exposure of anatase titania nanoparticles on the hollow fiber surface made available for photo-oxidation. This work offers the opportunity for future development of a fully integrated photocatalysis and membrane operation for wastewater treatment applications.

Introduction Exhaled breath condensate (EBC) is an emerging and noninvasive specimen allowing the study of lung processes. EBC could be an ideal biological matrix, as it could provide information about the deposited dose. The purpose of this study is to examine whether exhaled UFP in EBC could be correlated with exposure levels or surrogate of nanoparticle exposure. Methods 18 TiO 2 -exposed nanomaterial workers and 23 non-exposed controls were recruited from nanotechnology factories. A questionnaire was used to collect personal information. EBC was collected by an ECoScreen turbo (Viasys GmbH, Hochberg, Germany) and stored at −80°C until analysis. The particle size-number distribution of ultrafine particles (PM0.1) were assessed in the EBC samples with the NanoSight LM10 HS system (Nanosight Ltd., Salisbury, UK) using the Nanoparticle Tracking Analysis (NTA) method. The results were expressed as average size(nm) mode size(nm) concentration ((x108 #particles/mL), % of UFP and particles number of UFP). Result The average size of particles (nm) in TiO2 exposed worker was smaller than non-exposed workers. The concentration of particles (x10 8 #particles/mL) in TiO2 exposed worker was higher than non-exposed workers. However, there was no significant difference between TiO 2 exposed and controls in the average size(nm), mode size(nm), concentration (x10 8 #particles/mL), % of UFP and particles number of UFP. But we found that the particles number of UFP in females was significantly higher than in males. Discussion The possible reason for no association between nanomaterial exposure and particle concentration in EBC may be due to the storage of EBC in −80°C refrigerator for a period of time which may induce aggregation or agglomeration of nanoparticles. Further study is required to clarify the use of exhaled UFP in fresh EBC as exposure matrix.

In this study, the polychlorinated dibenzo-p-dioxin/furan (PCDD/F) levels in 381 soil samples coming from different background areas (n = 238) and contaminated areas (n = 143) in Taiwan were investigated from 2011 to 2015 using high resolution gas chromatograph/high resolution mass spectrometry (HRGC/HRMS). The contaminated areas showed higher PCDD/F contamination as compared to the background areas (1230 vs 749 pg/g dry weight (dw)); 14.0 vs 6.25 pg WHO2005-TEQ/g dw). The lowest levels were recorded in the outlying islands (1.28 pg WHO2005-TEQ/g dw). PCDD/F congener distribution profiles in the background and contaminated areas as well as on the islands varied. OCDD was the dominant congener in almost all locations, including the northern background (87.7%) and central contaminated (74.2%) areas. Other dominant species included OCDF and 1,2,3,4,6,7,8-HpCDD. Levels of PCDD/F-TEQs in Taiwanese soils, including the background areas, were higher than in some developing countries and regions with global background levels due to high industrialization except for the contaminated areas. Geographic differences in dioxin-contaminated soils were also shown in this study. Higher soil dioxin-TEQs were observed in locations with high populations and population densities. Despite the limitations, the economic status of Taiwan represented by the annual averaged family income (AAFI) was positively correlated to soil dioxin-TEQs.

Single-wall carbon nanotubes (SWCNTs) have a variety of potential and demonstrated applications, and their production rates are increasing rapidly. This increase in production has motivated research on their transport and potential transformation and their toxicity in the environment. In this work, we examined the direct and indirect photoreactivity of SWCNTs under sunlight conditions. We found that the direct photoreactivity of pristine SWCNTs is generally low; however, indirect photoreaction involving ·OH may be significant in natural aquatic environments. Environmental photochemical reactions generating ·OH lead to distinct changes in SWCNT fluorescence efficiency in the near-infrared (NIR) region, Raman spectra, and light attenuation spectra in the UV, visible, and NIR regions, indicating that covalent functionalization of SWCNTs occurs. The reactivity of SWCNTs to ·OH is dependent on the specific chiral structure of the SWCNTs and the surfactant associated with it. An operationally defined second-order rate constant (based on the decrease in NIR fluorescence signals) for all SWCNT chiral species reacting with ·OH was estimated to be (2.91 ± 1.30) × 10(10) M(-1 )s(-1). Our work suggests that photochemical reactions may be a significant transformation pathway of SWCNTs in aquatic systems.

Carbon nanotubes (CNTs) have one of the highest production volumes among carbonaceous engineered nanoparticles (ENPs) worldwide and are have potential uses in applications including biomedicine, nanocomposites, and energy conversion. However, CNTs possible widespread usage and associated likelihood for biological exposures have driven concerns regarding their nanotoxicity and ecological impact. In this work, we probe the responses of planar suspended lipid bilayer membranes, used as model cell membranes, to functionalized multi-walled carbon nanotubes (MWCNT), CdSe/ZnS quantum dots, and a control organic compound, melittin, using an electrophysiological measurement platform. The electrophysiological measurements show that MWCNTs in a concentration range of 1.6–12 ppm disrupt lipid membranes by inducing significant transmembrane current fluxes, which suggest that MWCNTs insert and traverse the lipid bilayer membrane, forming transmembrane carbon nanotubes channels that allow the transport of ions. This paper demonstrates a direct measurement of ion migration across lipid bilayers induced by CNTs. Electrophysiological measurements can provide unique insights into the lipid bilayer–ENPs interactions and have the potential to serve as a preliminary screening tool for nanotoxicity.

Photobiogeochemical reactions involving metal species can be a source of naturally occurring nanoscale materials in the aquatic environment. This study demonstrates that, under simulated sunlight exposure, ionic Ag is photoreduced in river water or synthetic natural water samples that contain natural organic matter (NOM), forming Ag nanoparticles (AgNPs) that transform in size and shape and precipitate out upon extended irradiation. We show that the dissolved oxygen concentration does not appear to affect AgNP formation rates, indicating that reactive transients such as superoxide, hydrated electron, and triplet NOM do not play a large role. By varying pH and NOM concentrations and adding competing cations on the AgNP formation, we present three lines of evidence to show that Ag ion photoreduction likely involves ionic Ag binding to NOM. Our work suggests that photochemical reactions involving ionic Ag and NOM can be a source of nanosized Ag in the environment.

Single-walled carbon nanotubes (SWCNTs) with proper functionalization are desirable for applications that require dispersion in aqueous and biological environments, and functionalized SWCNTs also serve as building blocks for conjugation with specific molecules in these applications. In this study, we examined the phototransformation of carboxylated SWCNTs and associated amorphous carbon impurities in the presence or absence of H2O2 under simulated sunlight conditions. We found that while carboxylated SWCNTs were rather unreactive with respect to direct solar photolysis, they photoreacted in the presence of H2O2, forming CO2 and strongly aggregated SWCNT products that precipitated. Photoreaction caused SWCNTs to lose oxygen-containing functionalities, and interestingly, the resulting photoproducts had spectral characteristics similar to those of parent carboxylated SWCNTs whose amorphous carbon was removed by base washing. These results indicated that photoreaction of the amorphous carbon was likely involved. The removal of amorphous carbon after indirect photoreaction was confirmed with thermogravimetric analysis (TGA). Further studies using carboxylated SWCNTs with and without base washing indicate that amorphous carbon reduced the extent of aggregation caused by photoreaction. The second-order rate constant for carboxylated SWCNTs reacting with (•)OH was estimated to be in the range of 1.7-3.8 × 10(9) MC(-1) s(-1). The modeled phototransformation half-lives fall in the range of 2.8-280 days in typical sunlit freshwaters. Our study indicates that photosensitized reactions involving (•)OH may be a transformation and removal pathway of functionalized SWCNTs in the aquatic environment, and that the residual amorphous carbon associated with SWCNTs plays a role in SWCNT stabilization.

Lipid bilayers are biomembranes common to cellular life and constitute a continuous barrier between cells and their environment. Understanding the interaction of engineered nanomaterials (ENMs) with lipid bilayers is an important step toward predicting subsequent biological effects. In this study, we assess the effect of varying the surface functionality and concentration of 10-nm-diameter gold (Au) and titanium dioxide (TiO(2)) ENMs on the disruption of negatively charged lipid bilayer vesicles (liposomes) using a dye-leakage assay. Our findings show that Au ENMs having both positive and negative surface charge induce leakage that reaches a steady state after several hours. Positively charged particles with identical surface functionality and different core compositions show similar leakage effects and result in faster and greater leakage than negatively charged particles, which suggests that surface functionality, not particle core composition, is a critical factor in determining the interaction between ENMs and lipid bilayers. The results suggest that particles permanently adsorb to bilayers and that only one positively charged particle is required to disrupt a liposome and trigger the leakage of its entire contents in contrast to mellitin molecules, the most widely studied membrane lytic peptide, which requires hundred of molecules to generate leakage.

Biological membranes are one of the important interfaces between cells and pollutants. Many polar and hydrophobic chemicals can accumulate within these membranes. For this reason, artificial biological membranes are appealing surrogates to complex organisms for assessing the bioaccumulation potential of engineered nanomaterials (ENMs). To our knowledge, this work presents the first quantitative study on the distribution of fullerene ENMs between lipid bilayers, used as model biological membranes, and water. We evaluated the lipid bilayer-water association coefficients (K(lipw)) of aqueous fullerene aggregates (nC(60)) and fullerol (C(60)(ONa)(x)(OH)(y), x + y = 24). Kinetic studies indicated that fullerol reached apparent equilibrium more rapidly than nC(60) (2 h versus9 h). Nonlinear isotherms can describe the distribution behavior of nC(60) and fullerol. The lipid bilayer-water distributions of both nC(60) and fullerol were pH-dependent with the accumulation in lipid bilayers increasing systematically as the pH decreased from 8.6 (natural water pH) to 3 (the low end of physiologically relevant pH). This pH dependency varies with the zeta potentials of the ENMs and leads to patterns similar to those previously observed for the lipid bilayer-water distribution behavior of ionizable organic pollutants. The K(lipw) value for nC(60) was larger than that of fullerol at a given pH, indicating a greater propensity for nC(60) to interact with lipid bilayers. For example, at pH 7.4 and an aqueous concentration of 10 mg/L, K(lipw) was 3.5 times greater for nC(60) (log K(lipw) = 2.99) relative to fullerol (log K(lipw) = 2.45). Comparisons with existing aquatic organism bioaccumulation studies suggested that the lipid bilayer-water distribution is a potential method for assessing the bioaccumulation potentials of ENMs.

To construct accurate risk assessment models for engineered nanomaterials, there is urgent need for information on the reactivity (or conversely, persistence) and transformation pathways of these materials in the natural environment. As an important step toward addressing this issue, we have characterized the products formed when aqueous C(60) clusters (nC(60)) are exposed to natural sunlight and also have assessed the wavelengths primarily responsible for phototransformation. Long-wavelength light (λ ≥ 400 nm) isolated from sunlight, was shown to be important in both the phototransformation of nC(60) and in the production of (1)O(2). The significance of visible light in mediating the phototransformation of nC(60) was supported by additional experiments with monochromatic light in which the apparent quantum yield at 436 nm (Φ(436 nm) = (2.08 ± 0.08) × 10(-5)) was comparable to that at 366 nm (Φ(366 nm) = (2.02 ± 0.07) × 10(-5)). LDI-TOF mass spectrometry indicated that most of the photoproducts formed after 947 h of irradiation in natural sunlight retain a 60 atom carbon structure. A combination of (13)C NMR analysis of (13)C-enriched nC(60), X-ray photoelectron spectroscopy and FTIR indicated that photoproducts have olefinic carbon atoms as well as a variety of oxygen-containing functional groups, including vinyl ether and carbonyl or carboxyl groups, whose presence destroys the native π-electron system of C(60). Thus, the photoreactivity of nC(60) in sunlight leads to the formation of water-soluble C(60) derivatives.

The expected rapid expansion of nanotechnology industries has raised concern over the environmental fate and effects of materials created by these industries, including carbon-based fullerenes. In this study, the reaction mechanism responsible for the photochemical transformation of aqueous C60 clusters (nC60) in sunlight has been examined. Evidence is presented that under lamps that emit light only within the solar spectrum, 1O2 is produced via aqueous nC60 suspensions, using furfuryl alcohol (FFA) as an indicator. In air-equilibrated suspensions, the losses of 0.2 mM FFA and 0.8 mg/L C60 were90% and 70% after 15 h, while removing oxygen, the precursor of 1O2, stopped both reactions, indicating that 1O2 was produced and mediated nC60 phototransformation. Similar reactions performed in deuterium oxide and with added azide ion resulted in accelerated and slowed loss of FFA, respectively, as expected if 1O2 is a reaction intermediate. 1O2 production (as measured by FFA loss) increased with time as more water-soluble intermediate products accumulated in solution. In summer sunlight (West Lafayette, IN, 86 degrees 55' W, 40 degrees 26' N), suspensions of 5 mg/L nC60 produced 1O2 concentrations 1 order of magnitude higher thanthe average value typically found in natural waters containing the same mass of natural organic carbon.

C60 is emerging in a variety of potential applications; however, its environmental fate remains largely unknown. Photochemical transformation may be an important fate process of C60 in the aquatic environment due to its strong light absorption within the solar spectrum. In this study, the photochemical transformation of aqueous C60 clusters (nC60) in sunlight (West Lafayette, IN, 86 degrees 55' W, 40 degrees 26' N) and in lamp light (300-400 nm wavelengths) was investigated. When exposed to light, the brown to yellow color of nC60 was lost gradually, and the cluster size decreased as the irradiation time increased. TOC analysis on the water phase of centrifuged samples indicated that water soluble products formed and that with continued light exposure, these intermediates eventually mineralized, volatilized, or were converted to other products not quantified by TOC after centrifugation and filtration. In sunlight at approximately 1 mg/L C60, the decay rate of C60 in small clusters (diameter = 150 nm) was greater than for C60 in larger (500 nm) clusters, with half-lives of 19 and 41 h, respectively. The presence of fulvic acid, changes in pH, and the preparation method of the clusters had minimal effects on the phototransformation rate. Deoxygenated samples resulted in negligible loss after 17 h of lamp exposure, indicating O2 played a role in the phototransformation mechanism. These findings suggested that release of nC60 into surface waters will result in photochemical production of currently unknown products.

Over the past few years, there has been a strong interest in exploring the potential impact of fullerenes in the environment. Despite that both C

Graphene oxide (GO) is promising in scalable production and has useful properties that include semiconducting behavior, catalytic reactivity, and aqueous dispersibility. In this study, we investigated the photochemical fate of GO under environmentally relevant sunlight conditions. The results indicate that GO readily photoreacts under simulated sunlight with the potential involvement of electron-hole pair creation. GO was shown to photodisproportionate to CO2, reduced materials similar to reduced GO (rGO) that are fragmented compared to the starting material, and low molecular-weight (LMW) species. Kinetic studies show that the rate of the initially rapid photoreaction of GO is insensitive to the dissolved oxygen content. In contrast, at longer time points (10 h), the presence of dissolved oxygen led to a greater production of CO2 than the same GO material under N2-saturated conditions. Regardless, the rGO species themselves persist after extended irradiation equivalent to 2 months in natural sunlight, even in the presence of dissolved oxygen. Overall, our findings indicate that GO phototransforms rapidly under sunlight exposure, resulting in chemically reduced and persistent photoproducts that are likely to exhibit transport and toxic properties unique from parent GO.

In this study, we investigate the role of simulated sunlight on the physicochemical properties, aggregation, and deposition of graphene oxide (GO) in aquatic environments. Results show that light exposure under varied environmental conditions significantly impacts the physicochemical properties and aggregation/deposition behaviors of GO. Photo-transformation has negligible effects on GO surface charge, however, GO aggregation rates increase with irradiation time for direct photo-transformation under both aerobic and anaerobic conditions. Under anaerobic conditions, photo-reduced GO has a greater tendency to form aggregates than under aerobic conditions. Aggregation of photo-transformed GO is notably influenced by ion valence, with higher aggregation found in the presence of divalent ions versus monovalent, but adding natural organic matter (NOM) reduces it. QCM-D studies show that deposition of GO on surfaces coated with organic matter decreases with increased GO irradiation time, indicating a potential increase in GO mobility due to photo-transformation. General deposition trends on Suwannee River Humic Acid (SRHA)-coated surfaces are control GO > aerobically photo-transformed GO ≈ anaerobically photo-transformed GO. The release of deposited GO from SRHA-coated surfaces decreases with increased irradiation time, indicating that photo-transformed GO is strongly attached to the NOM-coated surface.

Due to the widespread use of engineered nanomaterials (ENMs) in consumer and industrial products, concerns have been raised over their impacts once released into the ecosystems. While there has been a wealth of studies on the short-term acute toxic effects of ENMs over the past decade, work on the chronic endpoints, such as biological accumulation, has just begun to increase in last 2–3 years. Here, we comprehensively review over 65 papers on the biological accumulation of ENMs under a range of ecologically relevant exposure conditions in water, soil or sediment with the focus on quantitative comparison among these existing studies. We found that daphnid, fish, and earthworm are the most commonly studied ecological receptors. Current evidence suggests that ENM accumulation level is generally low in fish and earthworms with logarithmic bioconcentration concentration factor and biota-sediment accumulation factor ranging from 0.85–3.43 (L kg−1) and −2.21–0.4 (kg kg−1), respectively. ENMs accumulated in organisms at the lower trophic level can transfer to higher trophic level animals with the occurrence of biomagnification varying depending on the specific food chain studied. We conclude the review by identifying the challenges and knowledge gaps and propose paths forward.

Lipid bilayers are biomembranes common to cellular life and constitute a continuous barrier between cells and their environment. Understanding the interaction of nanoparticles with lipid bilayers is an important step toward predicting subsequent biological effects. In this study, we assessed the affinity of functionalized gold nanoparticles (Au NPs) with sizes from 5 to 100 nm to lipid bilayers by determining the Au NP distribution between aqueous electrolytes and lipid bilayers. The Au NP distribution to lipid bilayers reached an apparent steady state in 24 h with smaller Au NPs distributing onto lipid bilayers more rapidly than larger ones. Au NPs distributed to lipid bilayers to a larger extent at lower pH. Tannic acid-functionalized Au NPs exhibited greater distribution to lipid bilayers than polyvinylpyrrolidone-functionalized Au NPs of the same size. Across the various Au NP sizes, we measure the lipid bilayer-water distribution coefficient (K(lipw) = C(lip)/C(w)) as 450 L/kg lipid, which is independent of dosimetric units. This work suggests that the nanoparticle-cell membrane interaction is dependent on solution chemistry and nanoparticle surface functionality. The K(lipw) value may be used to predict the affinity of spherical Au NPs across a certain size range toward lipid membranes.

To construct accurate risk assessment models for engineered nanomaterials, there is urgent need for information on the reactivity (or conversely, persistence) and transformation pathways of these materials in the natural environment. As an important step toward addressing this issue, we have characterized the products formed when aqueous C(60) clusters (nC(60)) are exposed to natural sunlight and also have assessed the wavelengths primarily responsible for phototransformation. Long-wavelength light (λ ≥ 400 nm) isolated from sunlight, was shown to be important in both the phototransformation of nC(60) and in the production of (1)O(2). The significance of visible light in mediating the phototransformation of nC(60) was supported by additional experiments with monochromatic light in which the apparent quantum yield at 436 nm (Φ(436 nm) = (2.08 ± 0.08) × 10(-5)) was comparable to that at 366 nm (Φ(366 nm) = (2.02 ± 0.07) × 10(-5)). LDI-TOF mass spectrometry indicated that most of the photoproducts formed after 947 h of irradiation in natural sunlight retain a 60 atom carbon structure. A combination of (13)C NMR analysis of (13)C-enriched nC(60), X-ray photoelectron spectroscopy and FTIR indicated that photoproducts have olefinic carbon atoms as well as a variety of oxygen-containing functional groups, including vinyl ether and carbonyl or carboxyl groups, whose presence destroys the native π-electron system of C(60). Thus, the photoreactivity of nC(60) in sunlight leads to the formation of water-soluble C(60) derivatives.