Measurement of the interaction force between two materials provides important information on various properties, such as adsorption, binding or compatibility for coatings, adhesion, and composites. The interaction forces of zwitterionic and ionic monomers with graphite platelets (G) and reduced graphene oxide (rGO) surfaces were systematically investigated using atomic force microscopy (AFM) in air and water. The monomers examined were 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (MPC), [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide (SBE), [2-(acryloyloxy)ethyl]trimethylammonium chloride (ATC), and 2-methyl-2-propene-1-sulfonic acid sodium (MSS). The AFM studies revealed that MSS and SBE monomers with sulfonate units have stronger interaction forces with G surface in air, and MPC and ATC monomers with quaternary ammonium units have higher interaction forces in water. In the case of rGO surface, the monomers with quaternary ammonium units showed stronger interactions regardless of the medium. These interactions could be rationalized by the interaction mechanism between the monomers with graphene surfaces, such as cation-π for MPC and ATC, anion-π for MSS and SBE, respectively. Overall, cation-π interactions were effective in water, while anion-π interactions are effective in the air with G surface. The adhesion values of MPC, SBE, ATC, and MSS on rGO were lower than the values measured on G surface. Among the monomers, MPC showed the highest dispersibility for aqueous graphene dispersions. Further, the adsorption of MPC on G and rGO surfaces was verified by high-resolution transmission electron microscopy and X-ray diffraction patterns.

Ammonia is recognised as a major pollutant worldwide, originating from natural and anthropogenic sources. Studies have reported that freshwater mussels are amongst the most sensitive taxa to ammonia, but there is a lack of data available on ammonia toxicity for the early life stages of freshwater mussels from tropical regions. This paper reports the modification of a 24-h acute toxicity test protocol for tropical freshwater mussels and application of the test using ammonia. Velesunio spp. from three different sites were used to assess the toxicity of ammonia at a targeted pH of 6.0 and water temperature of 27.5°C, which were the average annual values for some slightly to moderately acidic, soft water (3-6 mg/L as CaCO3 ) creeks of tropical northern Australia. The valve closure responses of mussel glochidia (larvae) to a sodium chloride solution were used to measure the survival endpoint. Acute toxicity estimates indicate that tropical Velesunio spp. were highly sensitive to ammonia with 24-h exposures to ammonium sulfate generating LC50 estimates ranging from 6.8-14.2 mg/L Total Ammonia Nitrogen (TAN), which when adjusted to pH 7 and 20°C, were amongst the highest sensitivities yet reported for any freshwater mussel species, and amongst the highest in sensitivity for any tropical taxon. These toxicity estimates can contribute to the derivation or refinement of ammonia Guideline Values for freshwater ecosystems globally. This article is protected by copyright. All rights reserved.

A novel and green deep eutectic solvent based liquid phase microextraction (DES-LPME) methodology has been proposed for the assessment of rhodamine B from cosmetic products and water samples. A deep eutectic solvent (DES) consist of tetrabutyl ammonium chloride-decanoic acid (1:2) as extraction solvent and tetrahydrofuran as emulsification agent were used for the microextraction of rhodamine B. The quantitative recoveries were achieved at pH 3 by using 0.3 mL of DES and 0.3 mL of THF. The rhodamine B concentration in last volume was analyzed by mirco-cuvette UV-VIS spectrophotometer at 550 nm. The limit of detection (LOD), limit of quantification (LOQ), preconcentration factor (PF) and relative standard deviation (RSD %) were found as 2.2 μg L-1, 7.3 μg L-1, 25 and 2.3%, respectively. Accuracy and validity of the developed method was verified by addition-recovery studies for water and cosmetic samples.

The results from a 1 1/2-year study of ground-water quality in the vicinity of Milwaukee, Wisconsin, support the suggestion by other researchers, that chloride and sulfate are the principal products of urbanization which alter ground-water chemistry. In addition to chloride and sulfate, ground-water samples, from the Menomonee River Watershed contained relatively high concentrations of ammonium, fecal coliform and fecal streptococci bacteria. Field data suggest that contamination of ground water is caused by infiltration of surface water polluted by municipal and industrial wastes and (or) leakage from sewer lines. Some additional chloride contamination by infiltration of road salt is also suggested.

Chitosan derivative-based self-healable hydrogels with enhanced mechanical properties are reported, which were prepared by polymerization of acrylic acid (AAc) in 2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC) solution. The PAAc/HACC hydrogels exhibit tensile fracture stress as high as 3.31 MPa and a Young's modulus of 2.53 MPa. They can maintain their original shape after 30 repeated compression cycles under various strain conditions, with a compression stress of more than 60 MPa at 99% strain. The damaged PAAc/HACC hydrogels can heal together in the presence of a NaCl salt solution with a self-healing efficiency of up to 61%. In addition, the PAAc/HACC hydrogels have high ionic conductivity and can serve as electrolytes for supercapacitors. The analysis suggests that all these good properties of the PAAc/HACC hydrogels mainly result from their high-density dynamic ionic interactions structure.

Indium tin oxide (ITO) is widely used as a transparent conducting electrode in photoelectron devices. Because ITO production has soared, the potential health hazards caused by occupational exposure to this material have attracted much attention. However, little is known about the mechanisms of the toxic action of ITO nanoparticles (NPs). The present study was designed to examine the genotoxic mechanisms of ITO NPs using human lung epithelial A549 cells. We found that exposing A549 cells to ITO NPs triggered the intracellular accumulation of ITO NPs, the generation of reactive oxygen species (ROS), and the induction of DNA damage. Treatment of the cells with N-acetyl-l-cysteine (NAC), an ROS quenching agent, decreased intracellular ROS levels but not DNA damage, indicating that the genotoxic effect of ITO NPs is not mediated by intracellular ROS. Interestingly, treatment with ammonium chloride, a lysosomotropic agent, decreased intracellular solubility of ITO NPs and attenuated DNA damage. Nuclear accumulation of indium ions in ITO-NP-exposed cells was confirmed by inductively coupled plasma-mass spectrometry. Our results indicate that the ITO-NP-mediated genotoxicity is caused by indium ions that are solubilized in the acidic lysosomal condition and accumulated in the nucleus where they damage DNA, without the involvement of ROS.

The ability of the fungus Aureobasidium pullulans ATCC 42023 to produce pullulan from yeast extract-supplemented xylan hydrolysates of the prairie grass prairie cordgrass was examined relative to polysaccharide and cell biomass production, yield, and pullulan content of the polysaccharide. A pullulan concentration of 11.2 g L-1 and yield of 0.79 g g-1 was produced by ATCC 42023 when grown for 168 h at 30°C on the phosphate-buffered hydrolysate supplemented with yeast extract. The highest biomass level being 8.8 g L-1 was produced by ATCC 42023 after 168 h on a yeast extract-supplemented, hydrolysate-containing complete medium lacking sodium chloride. The highest pullulan content of the polysaccharide produced by ATCC 42023 after 168 h on the hydrolysate medium supplemented with yeast extract and ammonium sulfate was 70%. The findings indicate that a polysaccharide with a high pullulan content can be produced at a relatively high yield by the fungus grown on a yeast extract-supplemented xylan hydrolysate, suggesting that pullulan could be produced using a biomass-based process.

Pervasive particulate pollution has been observed over large areas of the North China Plain. The high level of sulfate, a major component in fine particles, is pronounced during heavy pollution periods. Being different from source apportionments by atmospheric chemistry-transport model and receptor modeling methods, here we utilize sulfur isotopes to discern the potential emission sources. Sixty-five daily PM2.5 samples were collected at an urban site in Beijing between September 2013 and July 2014. Inorganic ions, organic/elemental carbon and stable sulfur isotopes of sulfate were analyzed. The "fingerprint" characteristics of stable sulfur isotopic composition, together with trajectory clustering modeled by HYSPLIT-4 (HYbrid Single-Particle Lagrangian Integrated Trajectory) and FLEXPART ("FLEXible PARTicle dispersion model"), was employed to identify potential aerosol sources in Beijing. Results exhibited a distinctive seasonality with sulfate, nitrate, ammonium, organic matter, and element carbon being the dominant species of PM2.5. Elevated concentrations of chloride with high organic matter were found in autumn and winter as a result of enhanced fossil fuel (mainly coal) combustion. The δ34S values of the Beijing aerosols ranged from 2.8‰ to 9.9‰ with an average of 6.0 ± 1.8‰, further indicating that the major sulfur source was direct coal burning emission. Owing to the changing patterns between oxidation pathways of S(IV) in different seasons, δ34S values varied with a winter maximum (8.2 ± 1.1‰) and a summer minimum (4.9 ± 1.9‰). The results of trajectory clustering and FLEXPART demonstrated that higher concentrations of sulfate with lower sulfur isotope ratios (4.6 ± 0.8‰) were associated with air masses from the south or east, whereas lower sulfate concentrations with heavier sulfur isotope ratios (6.7 ± 1.6‰) were observed when the air masses were mainly from the north or northwest. These results suggested that the fine aerosol pollution in Beijing, especially sulfate pollution, was mainly due to coal combustion sources from regional and local regions.