Decorating Pd-Au Nanodots Around Porous In2 O3 Nanocubes for Tolerant H2 Sensing Against Switching Response and H2 S Poisoning.

With the recently-booming hydrogen (H2 ) economy by green H2 as the energy carriers and the newly-emerged exhaled diagnosis by human organ-metabolized H2 as a biomarker, H2 sensing is simultaneously required with fast response, low detection limit, and tolerant stability against humidity, switching, and poisoning. Here, reliable H2 sensing has been developed by utilizing indium oxide nanocubes decorated with palladium and gold nanodots (Pd-Au NDs/In2 O3 NCBs), which have been synthesized by combined hydrothermal reaction, annealing, and chemical bath deposition. As-prepared Pd-Au NDs/In2 O3 NCBs are observed with surface-enriched NDs and nanopores. Beneficially, Pd-Au NDs/In2 O3 NCBs show 300 ppb-low detection limit, 5 s-fast response to 500 ppm H2 , 75%RH-high humidity tolerance, and 56 days-long stability at 280 °C. Further, Pd-Au NDs/In2 O3 NCBs show excellent stability against switching sensing response, and are tolerant to H2 S poisoning even being exposed to 10 ppm H2 S at 280 °C. Such excellent H2 sensing may be attributed to the synergistic effect of the boosted Pd-Au NDs' spillover effect and interfacial electron transfer, increased adsorption sites over the porous NCBs' surface, and utilized Pd NDs' affinity with H2 and H2 S. Practically, Pd-Au NDs/In2 O3 NCBs are integrated into the H2 sensing device, which can reliably communicate with a smartphone.

Enhancement of electrokinetic-phytoremediation by Ophiopogon japonicus: stimulation of electrokinetic on root system and improvement of polycyclic aromatic hydrocarbon degradation.

Root systems are sensitive to voltage and tend to improve the degradation of organic pollutants by promoting the root exudates and increasing microbial enzyme activity in the rhizosphere under the effect of electrokinetic. In this study, electrokinetic-assisted phytoremediation (EKPR) was applied for the remediation of soil containing phenanthrene (PHE) and pyrene (PYR). Direct current (DC) voltage (1 V cm-1) was applied across the soils for 30 days following 3 treatment schedules (0 h, 4 h, and 12 h per day), referred to as treatments EK0, EK4, and EK12. Electrokinetic assistance improved phytoremediation. Compared to EK0, the removal of PHE and PYR increased by 51.79% and 45.07% for EK4 and by 43.18% and 38.75% for EK12. The applied voltage promoted root growth, stimulated the root exudate release, and increased accumulation of PHE and PYR by plants, and the effect was most pronounced in treatment EK4. Catalase and urease activities in rhizosphere soil also increased, by respective increments of 44.51% and 40.86% for EK4 and by 28.53% and 21.24% for EK12. In this study, we demonstrated that a low voltage applied for an appropriate duration (4 h per day) improves removal of PAHs by stimulating root growth, promoting the root exudate release and enhancing enzyme activity in the microbiome of rhizosphere soil.

Combined effects of fluoroquinolone antibiotics and organophosphate flame retardants on Microcystis aeruginosa.

As freshwater harmful algal blooms continue to rise in frequency and severity, increasing focus is made on the effects of mixed pollutants and the dominant cyanobacterial species Microcystis aeruginosa (M. aeruginosa). However, few studies have investigated whether M. aeruginosa has a synergistic relationship with two common pollutants, namely, organophosphate flame retardants (OPFRs) and fluoroquinolone antibiotics (FQs). In this paper, three FQs and three OPFRs commonly detected in freshwaters were selected to construct a ternary mixture of FQs, a ternary mixture of OPFRs, and a six-component mixture of OPFRs and FQs. The effects of single substance and mixture on the growth of M. aeruginosa were determined at 24, 48, 72, and 96 h, and the toxicities of the mixture were evaluated by concentration addition model and independent action model. The results showed that the mixture of FQs and the mixture of OPFRs do not show toxicological interaction. However, partial mixtures of OPFRs and FQs showed antagonism or synergism at different concentrations and times. This indicated that combined toxicities of OPFRs and FQs on M. aeruginosa were mixture ratio dependent, concentration dependent and time dependent. This study improves our understanding of the role of OPFRs and FQs in cyanobacterial outbreaks of Microcystis.

Distribution, sources and risk assessment of PAHs in soil from the water level fluctuation zone of Xiangxi Bay, Three Gorges Reservoir.

Information on PAH distribution in the water level fluctuation zone (WLFZ) of Three Gorges Reservoir is limited. In this study, we investigated PAH distribution and sources and assessed PAH risks, over one annual water level fluctuation cycle (June 2017-June 2018) at four elevations spanning the WLFZ (145 m, 155 m, 165 m and 175 m) at seven locations in the water level fluctuation zone along Xiangxi River. The mean total PAH concentration in June 2018 (953 ng g-1) was significantly higher than in June 2017 (494 ng g-1), and the horizontal and vertical distributions of PAHs changed significantly. The changes in distribution patterns provided evidence for the cause of increased PAH levels, which were attributed to construction of the Xiangxi River Bridge. Thus, this study of PAH dynamics in the WLFZ soils of Xiangxi Bay also provided valuable information on the impact of bridge construction on WLFZ soils. The change in PAH levels among stations implicated sediment disturbance resulting from bridge construction as the major contributor to the increased PAH levels. Source characterization, based on the ratios of certain PAHs, indicates that PAHs are mainly from the combustion of petroleum fuels, biomass and coal. These ratios indicated that the proportion of PAHs from fuel combustion increased from 2017 to 2018, implicating the heavy equipment used during bridge construction as another source of the increased PAH levels. The incremental lifetime cancer risk (ILCR) model was used to assess the health risk of the PAHs and the range among all age groups (10-5-10-4) indicates a potential health risk. The mean effects range-median quotient (M-ERM-Q) was used to assess the ecological risk of PAHs and the range (0.1-0.5) indicates low to medium risk. The increase in PAH levels from 2017 to 2018 increased the risk to public health and the environment. The results of this investigation provide a reference for ecological restoration of the WLFZ and support development of effective policies for environmental and public health. Further, the results provide information on the impact of bridge construction on WLFZ soils and identify research needed to more fully understand PAH dynamics in WLFZ soils.

[Temporal-spatial Distribution and Risk Assessment of Polycyclic Aromatic Hydrocarbons in Soil of Xiangxi Bay in Three Gorges Reservoir Area].

The US Environmental Protection Agency has listed 16 polycyclic aromatic hydrocarbons (PAHs) for priority control. Soil samples from Xiangxi Bay in the Three Gorges Reservoir Area (the water fluctuation zone, WLFZ; upper edge of water fluctuation zone, UEWLFZ; sediments) were analyzed for the concentration of these PAHs, using high performance liquid chromatography (HPLC). The results showed that the soil samples of Xiangxi Bay could be ranked, based on the concentration of PAHs, in the following order:UEWLFZ>WLFZ>sediment. The composition of PAHs varied from the three regions, with 3- and 4-ring PAHs dominating in sediments and 4- and 5-ring PAHs dominating in soil from the WLFZ and UEWLFZ. The composition of PAHs in soil from the WLFZ exhibited a higher coefficient of variation and a weaker correlation with the composition of PAHs in soil from the UEWLFZ and sediment. Soil from the three regions showed varying seasonal distributions of PAHs, which is closely related to the quantity and types of energy consumption in each season. PAHs in sediment from sites at the same altitude showed no evident differences, whereas WLFZ and UEWLFZ soil had higher levels of PAHs at the sites near Xiakou Town and the Yangtze River Estuary. Isomer ratio analysis showed that the sources of PAHs in Xiangxi Bay vary between seasons and regions, with incomplete combustion of fossil fuels and biomass forming the main sources in the soil of Xiangxi Bay. The lifetime carcinogenic risk assessment shows that PAHs in sediment, WLFZ, and UEWLFZ have a potential risk to human through ingestion and dermal contact, with PAHs in the soil of UEWLFZ posing the highest carcinogenic risk. The results provide a theoretical reference for the prevention and control of contamination by PAHs in Xiangxi Bay of the Three Gorges Reservoir area.

Heavy metal accumulation and health risk assessment of crayfish collected from cultivated and uncultivated ponds in the Middle Reach of Yangtze River.

Crayfish, an aquatic food consumed globally, has been reported to accumulate heavy metal. To assess the health risk to the crayfish-consuming population, we investigated heavy metals (Cu, Pb, Zn, Fe, Mn, Cd, Cr, Ba, and As) in crayfish tissues (exoskeleton, abdominal muscle, gills, and hepatopancreas) and sediments from uncultivated and cultivated ponds in the middle reach of the Yangtze River. The metals, except for As, were measured by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and As was measured by atomic fluorescence spectrometry. The distribution of heavy metals differed significantly among tissues and concentrations were generally highest in the hepatopancreas. The average concentrations of heavy metals were higher in crayfish from uncultivated ponds than in crayfish from cultivated ponds. Heavy metal concentrations in crayfish correlated positively with sediment concentrations in uncultivated ponds, indicating that heavy metals can accumulate in crayfish. However, this positive correlation between sediment concentration and crayfish concentration was not observed in cultivated ponds. Source identification, using correlation analysis, indicated that heavy metals in the sediments derive from transportation and agriculture. Based on correlations between heavy metal concentration and body weight, and data on metal distribution in organs, heavy metals accumulate in the hepatopancreas of crayfish in uncultivated ponds, but not in cultivated ponds. Heavy metal concentrations were somewhat higher in female crayfish than in male crayfish and the difference was significant for Fe and Pb. The target hazard quotient (THQ) was used to evaluate non-carcinogenic health risk, with THQ < 1 considered to be safe. All THQ values were < 1, except for Cu in the hepatopancreas (THQ = 1.38) of cultured crayfish and Pb (THQ = 1.01) and Cd (THQ = 1.69) in the hepatopancreas of wild crayfish. Thus, the health risk posed by consuming crayfish, particularly cultured crayfish is low. Our research was designed to protect food safety and the results indicate that the health risk posed by heavy metals in crayfish is low.

Nano-SiO2 combined with a surfactant enhanced phenanthrene phytoremediation by Erigeron annuus (L.) Pers.

The objective of this experiment was to evaluate the effects of Triton X-100 (1000 mg kg-1) and nano-SiO2 (500 mg kg-1) on Erigeron annuus (L.) Pers. grown in phenanthrene spiked soil (150 mg kg-1) for 60 days. Results show that untreated groups, groups treated with both Triton X-100 and nano-SiO2, exhibited better phenanthrene degradation rates and improved root biomasses, chlorophyll contents, and soil enzyme activities. This study demonstrates that Triton X-100 combined with nano-SiO2 protects plants, alleviating the stress of polycyclic aromatic hydrocarbons (PAHs), and can provide a means for improving phytoremediation of PAH contaminated soils.

Characteristics of growth and microcystin production of Microcystis aeruginosa exposed to low concentrations of naphthalene and phenanthrene under different pH values.

Here, Microcystis aeruginosa (M. aeruginosa) was studied to analyze the effects of 0.5 mg L-1 naphthalene and 0.05 mg L-1 phenanthrene on profiles of cell growth, chlorophyll-a content and Microcystin-LR (MC-LR) production at different pH values. The results indicated that for both the naphthalene and phenanthrene treatments, the specific growth rates were higher in pH 10.0 than in either pH 7.0 or pH 5.0. In the presence of low concentrations of naphthalene or phenanthrene, chlorophyll-a in medium increased significantly more in pH 10.0 than pH 5.0. chlorophyll-a in cell was significantly lowered when exposed to naphthalene in both pH 10.0 and pH 7.0, and was higher when exposed to phenanthrene in pH 10.0 than pH 5.0. HPLC analysis revealed that the extracellular MC-LR concentrations in M. aeruginosa exposed to either naphthalene or phenanthrene were lower than in control M. aeruginosa at pH 5.0. The intracellular MC-LR levels in toxic M. aeruginosa cells exposed to naphthalene or phenanthrene were higher than in the controls at pH 10.0. Our study suggests that the MC-LR production of M. aeruginosa was affected by the pH value when low concentrations of either naphthalene or phenanthrene were present in the water. These results indicate that the pH value should not be ignored when evaluating the risk of chemicals that promote MC-LR production in eutrophic waters.

Metasurface generated polarization insensitive Fano resonance for high-performance refractive index sensing.

A refractive index sensor can provide refractive index measurement and continuously monitor a dynamic process. Plasmonic nanostructure based sensors suffer from severe metal losses in the optical range, leading to the performance degradation. We design and numerically analyze a high-performance refractive index sensor based on the Fano resonance generated by a dielectric metasurface. The figure of merit (FOM) and the maximum quality factor (Q-factor) of the sensor are 721 and 5126, respectively. The maximum modulation depth can exceed 99% and the enhancement factor of the electric field amplitude can reach a high value of about 100. The uniqueness of the proposed sensor is polarization insensitivity. The transmittance spectra for various polarization states of the incident light can perfectly coincide, which is a rare phenomenon in Fano resonance based sensors and can facilitate experimental measurement.

Effects of lead and cadmium on photosynthesis in Amaranthus spinosus and assessment of phytoremediation potential.

This study assessed the effects of Pb (0, 200, 500, 1000 mg kg-1) and Cd (0, 5, 15, 30, 50 mg kg-1) on photosynthesis in Amaranthus spinosus (A. spinosus), as well as the potential for phytoremediation by pot-culture experiment. Exposure to Pb/Cd produced a concentration-dependent decrease in biomass and all photosynthesis parameters, except for non-photochemical quenching, which increased with the metal concentration. The metals accumulated more in roots compared to shoots. The bioconcentration factor (BCF) of Pb was <1 in shoots at all Pb levels, whereas the BCF was <1 in roots at all but the lowest concentration of Pb. Roots extracted Cd from soil at all treatments. The translocation factor of Cd was larger than that of Pb suggesting that Cd is more mobile than Pb in A. spinosus. Amaranthus spinosus displays a high tolerance for both Pb and Cd with regards to growth and photochemical efficiency, but it is more sensitive to Cd than Pb. Amaranthus spinosus accumulates Pb and Cd primarily in the roots and Cd is more bioconcentrated and translocated in comparison to Pb. This investigation shows that A. spinosus has good potential for phytoremediation of soils contaminated by low levels of Cd and Pb.

Selenium enhanced phytoremediation of diesel contaminated soil by Alternanthera philoxeroides.

Using a 60-day pot culture experiment, we investigated the effect of selenium on phytoremediation of soil containing high-level diesel by Alternanthera philoxeroides (alligator weed). Diesel (20 g kg-1) decreased the growth of A. philoxeroides and induced oxidative stress, as indicated by tissue levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Adding Se (0.5 or 1.5 mg kg-1) to diesel-treated soil alleviated oxidative stress and improved biomass production, and the low dose was as effective as the high dose. After 60 days, the reduction in rhizospheric soil diesel was 20.1 ±â€¯0.55% without Se and 35.2 ±â€¯3.6% with Se, showing a significant increase in efficiency. Again, the low Se dose was as effective as the high dose. These findings advance the field phytoremediation by demonstrating that Se, at 0.5 mg kg-1, enhances removal and increases plant tolerance to petroleum hydrocarbons.

Se enhanced phytoremediation of diesel in soil by Trifolium repens.

A pot-culture experiment was conducted to assess the effects of selenium (Se) (0.5 mg kg-1) on Trifolium repens exposed to various levels of diesel (0, 15, 20, 25 g kg-1) for 30 days and 60 days. Exposure to diesel for 60 day led to concentration-dependent decreases in root morphogenesis, chlorophyll content and CAT activity, and to dose-dependent increases in MDA content and SOD activity. The residual diesel concentration in soil increased and the removal efficiency decreased with soil diesel concentration. The chlorophyll content and residual diesel concentration after were slightly higher at 30 days than at 60days. Application of Se to soil increased Trifolium repens tolerance to diesel and significantly increased the phytoremediation effect at 60 days, with a removal rate of 36 ±â€¯8%, compared to 28 ±â€¯7% in the control. These results contribute to the ongoing effort to develop an effective phytoremediation system for soils highly contaminated by diesel.

Selenium alleviates phytotoxicity of phenanthrene and pyrene in Alternanthera Philoxeroides.

To investigate if selenium can alleviate phytotoxicity of phenanthrene and pyrene, two high molecular weight (HMW) PAHs (polycyclic aromatic hydrocarbons) in Alternanthera philoxeroides are considered. A 60-day pot-culture experiment was carried out to assess the effects of selenium (0.5 mg Se·kg-1 soil) on A. philoxeroides exposed to two PAH pollutants, pyrene (PYR) and phenanthrene (PHE), at levels of 10, 100, and 1000 mg·kg-1. The test index included growth, chlorophyl, gas exchange and chlorophyl fluorescence parameters, and indicators of oxidative stress (H2O2 and malondialdehyde MDA). The response of plants to PAH exposure was concentration dependent; indicators of plant health declined, while indicators of plant stress rose. The maximum values of H2O2 and MDA were recorded at 1000 mg·kg-1 PYR, followed by 1000 mg·kg-1 PHE. However, application of Se (0.5 mg·kg-1) to the soil significantly decreased the phytotoxic response to PAH exposure. This study demonstrated that Se increases the tolerance of A. philoxeroides to PYR and PHE, improving the feasibility of phytoremediating high level PAH contamination and expediting ecological restoration.

Geometric Phase Generated Optical Illusion.

An optical illusion, such as "Rubin's vase", is caused by the information gathered by the eye, which is processed in the brain to give a perception that does not tally with a physical measurement of the stimulus source. Metasurfaces are metamaterials of reduced dimensionality which have opened up new avenues for flat optics. The recent advancement in spin-controlled metasurface holograms has attracted considerate attention, providing a new method to realize optical illusions. We propose and experimentally demonstrate a metasurface device to generate an optical illusion. The metasurface device is designed to display two asymmetrically distributed off-axis images of "Rubin faces" with high fidelity, high efficiency and broadband operation that are interchangeable by controlling the helicity of the incident light. Upon the illumination of a linearly polarized light beam, the optical illusion of a 'vase' is perceived. Our result provides an intuitive demonstration of the figure-ground distinction that our brains make during the visual perception. The alliance between geometric metasurface and the optical illusion opens a pathway for new applications related to encryption, optical patterning, and information processing.

Use of selenium to alleviate naphthalene induced oxidative stress in Trifolium repens L.

Polycyclic aromatic hydrocarbons (PAHs) are among the most dangerous of environmental contaminants, due to their toxicity, carcinogenicity and mutagenicity. This study investigated the use of selenium (Se) to protect plants from the toxic effects of naphthalene (NPH). Exposing Trifolium repens L. (white clover) to a high concentration of NPH (soil spiked to 500mgkg-1) for 60 d significantly decreased biomass, CO2 assimilation rate (Pn), stomatal conductance (Gs) and intercellular CO2 concentration (Ci), while inducing production of H2O2 and malondialdehyde (MDA). Application of Se (soil spiked to 0.5mgkg-1) to plants exposed to NPH clearly protected the plants; biomass, Pn, Gs and Ci were significantly higher and contents of MDA and H2O2 decreased. The protection provided to Trifolium repens L. by Se is attributed primarily to an increase in photosynthesis and a decrease in oxidative stress. This study demonstrates that a low concentration of Se protects plants against oxidative stress induced by NPH and can provide a means for improving phytoremediation in PAHs contaminated soils.

Enantioselective apoptosis induced by individual isomers of bifenthrin in Hep G2 cells.

Bifenthrin (BF) has been used in racemate for agricultural purposes against soil insects, leading to increased inputs into soil environments. However, most of the studies about the toxicology research on BF were performed in its racemic form. The aim of the present study was to evaluate the enantiomer-specific cis-BF-induced apoptosis and intracellular reactive oxygen species (ROS) generation on human hepatocarcinoma cells (Hep G2). The results of cell viability assay and cytoflow assay indicated an obvious enantioselective hepatocyte toxicity of 1S-cis-BF in Hep G2 cells. 1S-cis-BF also induced ROS production, up-regulated Bax protein expression and down-regulated Bcl-2 expression levels. The present study suggested that enantioselective toxicity should be evaluated on currently used chiral pesticides, such as synthetic pyrethroids.

Enantioselective cytotoxicity of isocarbophos is mediated by oxidative stress-induced JNK activation in human hepatocytes.

Recent studies have shown the enantioselectivity of chiral pesticides in environmental fate, aquatic toxicity, endocrine disruption and cytotoxicity. Thus it is of significance to investigate the molecular mechanisms of chiral pesticides enantioselectivity in cytotoxicity. In the present study, we used Hep G2 cells as in vitro model to assay cytotoxicity of enantiomers of isocarbophos (ICP), a widely used chiral organophosphorus pesticide. The results of cell viability assay and cytoflow assay indicated an obvious enantioselective hepatocyte toxicity of ICP: (-)-ICP was about two times more toxic than (+)-ICP in Hep G2 cells. We found that (-)-ICP, but not (+)-ICP, up-regulated Bax protein expression and down-regulated Bcl-2 expression levels, which resulted in an increase in Bax/Bcl-2 ratio with the apoptosis co-ordination. Although (-)-ICP enantioselectively activated both ERK and JNK, only the specific inhibitor for JNK could completely reverse (-)-ICP-induced apoptosis of Hep G2 cells. It suggests that (-)-ICP-induced hepatocyte toxicity was more dominantly through the sustained activation of JNK pathway, but only partially via ERK cascade. Furthermore, (-)-ICP induced ROS production, while (+)-ICP had no effect on ROS generation. The antioxidant MnTBAP attenuated (-)-ICP-induced activation of JNK and ERK, indicating that the outcome from challenge with (-)-ICP enantiomer depends on the oxidative stress-induced activation of a series of signaling cascades that promote hepatocyte apoptosis. In conclusion, (-)-ICP enantioselectively causes the change of Bax/Bcl-2 ratio, triggers the generation of intracellular ROS and sequentially induces sustainable activation of JNK, which in turn, results in a decrease in cell viability and an increase in cell apoptosis. Our observations provide further insight into enantiomers toxicity pathway which is able to differentiate between enantiomer activities at molecular level.

Enantiomer-specific, bifenthrin-induced apoptosis mediated by MAPK signalling pathway in Hep G2 cells.

Enantioselectivity in toxicology, and health risk of chiral xenobiotics have become important topics at the forefront of chemistry and toxicology research. Our previous results showed that cis-bifenthrin (cis-BF) induced cytotoxicity and genotoxicity in human amnion epithelial (FL) cells, in an enantioselective manner. However, the exact molecular mechanisms of synthetic pyrethroid-induced, enantioselective apoptosis and cytotoxicity remain unclear. In this study, enantiomers of the synthetic pyrethroid-based insecticide, cis-BF, were separated on selected chiral columns by HPLC. Enantioselectivity in cytotoxicity and apoptosis, mediated by the mitogen-activated protein kinase (MAPK) signalling pathway, were evaluated in the human hepatocellular liver carcinoma (Hep G2) cell line. Exposure to 1S-cis-BF resulted in increased levels of phosphorylated JNK (Jun-N-terminal Kinases)/MAPKs, while exposure to 1R-cis-BF did not affect phosphorylated JNK levels. Pre-treatment with the JNK inhibitor SP600125, blocked 1S-cis-BF-induced cytotoxicity and apoptosis. In addition, 1S-cis-BF enhanced the production of ROS, while pre-treatment with the antioxidant agent MnTBAP resulted in decreased phosphorylation of JNK. To the best of our knowledge, this is the first report demonstrating that cis-BF-induced apoptosis might occur, at least in part, through the enantioselective activation of JNK/MAPK signalling pathway in Hep G2 cells. The results suggest that enantioselectivity should be considered when evaluating eco-toxicological effects and health risks of chiral contaminants, and could also improve the understanding of molecular mechanisms responsible for chiral chemical-induced cytotoxicity and apoptosis.