Declines in phosphorus concentration in the upper River Thames (UK): Links to sewage effluent cleanup and extended end-member mixing analysis

Phosphorus concentrations in the upper River Thames Basin (southeastern England) are described and linked to sewage effluent sources. Weekly surveys between 1997 and 2007 of the Thames and two of its major tributaries, the Thame and the Kennet indicated that phosphorus was mainly in soluble reactive (SRP) form. Baseflow concentrations in the Thames reduced from 1584 μg/l in 1998 to 376 μg/l in 2006 and from 2655 to 715 μg/l for the Thame. Flow response, flux and endmember mixing analysis indicated that these declines resulted from SRP reductions in sewage treatment works (STW) effluent following phosphorus stripping for the major STWs in the region. This was confirmed by comparing our analysis with direct measurements of SRP in the effluents based on Environment Agency data. A within-river loss under baseflow of ~ 64% (range 56-78%) of the SRP-effluent input was estimated for the Thames, with a near balance for the Thame. SRP concentrations in the Kennet were an order of magnitude lower than the Thames/Thame: non-point sources dominated and were important for all the rivers at high flows. It was concluded that removal of SRP from effluents would be insufficient SRP in the Thames and Thame to meet annual average environmental targets of 50 to 120 μg/l.The paper flags the value of combining hydrological/chemical tracing and concentration/flux approaches to data interrogation and the bonus of having actual measurements of the effluent. It highlights the need for fuller assessment of water storage/sediment/biota interactions for phosphorus and for caution in using boron as a long-term tracer for effluent inputs, its concentrations having declined markedly in response to reduced usage in washing powders: the value of using sodium as a tracer for examining SRP changes is shown.     

Copper(II) Binding by Dissolved Organic Matter: Importance of the Copper-to-Dissolved Organic Matter Ratio and Implications for the Biotic Ligand Model

The ratio of copper to dissolved organic matter (DOM) is known to affect the strength of copper binding by DOM, but previous methods to determine the Cu(2+)-DOM binding strength have generally not measured binding constants over the same Cu:DOM ratios. In this study, we used a competitive ligand exchange-solid-phase extraction (CLE-SPE) method to determine conditional stability constants for Cu(2+)-DOM binding at pH 6.6 and 0.01 M ionic strength over a range of Cu:DOM ratios that bridge the detection windows of copper-ion-selective electrode and voltammetry measurements. As the Cu:DOM ratio increased from 0.0005 to 0.1 mg of Cu/mg of DOM, the measured conditional binding constant ((c)K(CuDOM)) decreased from 10(11.5) to 10(5.6) M(-1). A comparison of the binding constants measured by CLE-SPE with those measured by copper-ion-selective electrode and voltammetry demonstrates that the Cu:DOM ratio is an important factor controlling Cu(2+)-DOM binding strength even for DOM isolates of different types and different sources and for whole water samples. The results were modeled with Visual MINTEQ and compared to results from the biotic ligand model (BLM). The BLM was found to over-estimate Cu(2+) at low total copper concentrations and under-estimate Cu(2+) at high total copper concentrations.     

Demographic differences in presence across seven studies

Virtual Reality - It is often necessary for virtual reality (VR) users to experience a sense of presence for the benefits of VR applications to be realized. However, feelings of presence are...     

Study of polycarbonate–polystyrene interfaces using scanning transmission electron microscopy spectrum imaging (STEM-SI)

Polymer blends are important for both commercial utility and scientific understanding. The degree of interfacial mixing in polymer blends is important since it influences the blends' mechanical properties. Understanding bulk properties in multiphase polymeric materials requires knowledge of the interfacial properties of the materials. The characterization of the interface, in terms of its width and composition profile, provides insight about the bulk behaviour of the material. Chemical microscopy through electron energy-loss spectroscopy (EELS) in a transmission electron microscope is gaining popularity to characterize narrow polymer–polymer interfaces. In this work, we show how scanning transmission electron microscopy spectrum imaging, a spatially resolved energy-loss spectroscopy, can be employed to calculate the interfacial width in a pair of immiscible polymers, taking a polycarbonate–polystyrene (PC-PS) bilayer as an example. By mapping peaks unique to each of the blend constituents at several points across the interface, we show how the interfacial profile concentrations can be determined. With this method we calculated the interfacial width in the PC-PS bilayer sample to be approximately 32 nm, even utilizing low resolution spectrometers, which are more widely available. Using the technique described with higher resolution EELS instruments having a better signal-to-noise ratio, a higher spatial resolution can be achieved. Using EELS chemical fingerprints of polymers that have been developed earlier, the technique presented here has the potential for effective visualization and morphological measurements of phase-differentiated polymer blends. This paper is an attempt to enable a new user to characterize polymer–polymer interfaces using chemical microscopy. © 2022 Society of Industrial Chemistry.     

Gaseous chlorine dioxide inactivation of microbial contamination on whole black peppercorns

Black peppercorn is a common ingredient imported and used in uncooked or ready-to-eat foods in the United States. They might be exposed to fecal coliforms and other microbial contamination due to a lack of good agricultural and manufacturing practices in some developing countries under which they were grown and harvested, thus causing economic losses to the peppercorn industry in the United States. We investigated the effect of gaseous chlorine dioxide (ClO₂) on reducing the microbial population levels of coliforms, aerobic bacteria, yeasts, and molds on unprocessed black peppercorns. Treatments on peppercorns were conducted in a 30-L airtight chamber, and equal amounts of dry media precursors were used to generate gaseous ClO₂. Whole peppercorns (200 g) were exposed to 20, 30, and 40 g of precursor dose for up to 60 min at 21 ± 0.4°C and in combination with mild heat at 40 ± 2°C. Aerobic bacteria, coliforms, yeasts, and molds on peppercorns were enumerated before (7.4, 7.2, and 7.1 log CFU/g, respectively) and after treatments. Results after treatment demonstrated 0.8–1 log₁₀ (90%) reduction for all the microbes post-treatment at 21 ± 0.4°C. The treatments conducted with a 30 g precursor dose for 60 min at 21 ± 0.4°C reduced statistically higher (p < .05) microorganisms than those at 40 ± 2°C. Our work demonstrated that gaseous ClO₂ could be used as a part of an overall hurdle technology to reduce the coliforms, aerobes, yeasts, and molds on black peppercorns without affecting the visual quality.     

Deposition of polymeric sensing materials for gas detection

Once a promising polymeric (detection) material is identified, it needs to be incorporated into a MEMS sensor. In this sensor functionalization step, the deposition of the polymeric material on the sense-plate should be accurate and repeatable. After a quick overview of different deposition methods and related solubility characteristics of polyaniline (and derivatives), drop coating is implemented to deposit polyaniline on sense-plates, moving from a manual deposition technique to a semi-automated deposition procedure with more practical benefits, and identifying an optimal ‘carrier’ mixture of 10–15/90–85 polyaniline/ethylene glycol. A correlation can be established between area coverage and polymer mass, which leaves room for future fully automated deposition using image processing.     

Evaluating the performance of designed terpolymers for polymer flooding

In this work, polymeric materials designed for enhanced oil recovery (EOR) were evaluated for their intended application. Properties including viscosity, flow through porous media (resistance factor and residual resistance factor), and heavy oil displacement (incremental oil recovery) were assessed for designed terpolymers of 2-acrylamido-2-methylpropane sulphonic acid (AMPS), acrylamide (AAm), and acrylic acid (AAc). The same properties were evaluated for two commercially available reference materials (e.g., partially hydrolyzed polyacrylamides or HPAM) with similar characteristics, which allowed for direct comparison between the newly designed terpolymers and materials that are currently on the market for the polymer flooding application. The incremental oil recovery directly associated with polymer flooding, which includes both the polymer flooding and post-polymer waterflooding stages (excluding the initial waterflooding injection (or secondary) oil recovery), demonstrates that the designed terpolymers provided a higher incremental recovery (42% and 58%) than the reference materials (33% and 46%). Therefore, the terpolymers provided a higher contribution to incremental (or enhanced) oil recovery than the typical HPAM. Additionally, both designed terpolymers showed better injectivity in unconsolidated porous media and are less likely to cause plugging than the commercially available reference materials. Therefore, using a targeted design approach ultimately led to polymeric materials with excellent performance for EOR polymer flooding applications.     

Looking Outside the Square: The Growth,Structure, and Resilient Two-Dimensional Surface Electron Gas of Square SnO2 Nanotubes

Nanotechnology has delivered an amazing range of new materials such as nanowires, tubes, ribbons, belts, cages, flowers, and sheets. However, these are usually circular, cylindrical, or hexagonal in nature, while nanostructures with square geometries are comparatively rare. Here, a highly scalable method is reported for producing vertically aligned Sb-doped SnO₂ nanotubes with perfectly-square geometries on Au nanoparticle covered m-plane sapphire using mist chemical vapor deposition. Their inclination can be varied using r- and a-plane sapphire, while unaligned square nanotubes of the same high structural quality can be grown on silicon and quartz. X-ray diffraction measurements and transmission electron microscopy show that they adopt the rutile structure growing in the [001] direction with (110) sidewalls, while synchrotron X-ray photoelectron spectroscopy reveals the presence of an unusually strong and thermally resilient 2D surface electron gas. This is created by donor-like states produced by the hydroxylation of the surface and is sustained at temperatures above 400 °C by the formation of in-plane oxygen vacancies. This persistent high surface electron density is expected to prove useful in gas sensing and catalytic applications of these remarkable structures. To illustrate their device potential, square SnO₂ nanotube Schottky diodes and field effect transistors with excellent performance characteristics are fabricated.     

Site-Selective Aryl Diazonium Installation onto Protein Surfaces at Neutral pH using a Maleimide-Functionalized Triazabutadiene

Aryl diazonium cations are versatile bioconjugation reagents due to their reactivity towards electron-rich aryl residues and secondary amines, but historically their usage has been hampered by both their short lifespan in aqueous solution and the harsh conditions required to generate them in situ. Triazabutadienes address many of these issues as they are stable enough to endure multiple-step chemical syntheses and can persist for several hours in aqueous solution, yet upon UV-exposure rapidly release aryl diazonium cations under biologically-relevant conditions. This paper describes the synthesis of a novel maleimide-functionalized triazabutadiene suitable for site-selectively installing aryl diazonium cations into proteins at neutral pH; we show reaction with this molecule and a surface-cysteine of a thiol disulfide oxidoreductase. Through photoactivation of the site-selectively installed triazabutadiene motifs, we generate aryl diazonium functionality, which we further derivatize via azo-bond formation to electron-rich aryl species, showcasing the potential utility of this strategy for the generation of photoswitches or protein-drug conjugates.