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A hierarchical core–shell architecture of vertically arrayed ultrathin CuSe nanosheets decorating on hollow CuS microcages affords exceptional sodium storage performance with an admirable 303.1 mA h g−1 at 20.0 A g−1 after 1500 cycles.

The search for new topological materials that are realistic to synthesize has attracted increasing attention. In this study, we systematically investigated the electronic, mechanical, and topological semimetallic properties, as well as the interesting surface states, of the tetragonal monoxide of platinum, which is realistic to synthesize, via a first-principles approach. Our calculated results indicate that PtO is a novel topological semimetal with double nodal lines in the kz = 0 plane and a pair of triple topological nodal points along the A'-M-A directions. Obvious surface states, including Fermi arc and drum-head-like surfaces, could be found around nodal points and nodal lines. The dynamic and mechanical stabilities of P42/mmc-type PtO were examined in detail via calculation of the phonon dispersion and determination of elastic constants, respectively. Some other mechanical properties, including the bulk modulus, Young's modulus, shear modulus, Poisson's ratio, and Pugh's index, were considered in this study. P42/mmc-type PtO provides a good research platform for investigation of novel behaviors that combine mechanical properties and rich topological elements.

The aggregation kinetics of fragmental polyethylene glycol terephthalate (PET) nanoplastics under various chemistry conditions in aqueous environment were firstly investigated in this work. The aggregation of PET nanoplastics increased with increasing electrolyte concentrations and decreasing solution pH, which became stronger with the presence of divalent cations (e.g. Ca2+ and Mg2+) than that of monovalent cations (e.g. Na+ and K+). The effect of cations with the same valence on the aggregation of PET nanoplastics was similar. The measured critical coagulation concentrations (CCC) for PET nanoplastics at pH 6 were 55.0 mM KCl, 54.2 mM NaCl, 2.1 mM CaCl2 and 2.0 mM MgCl2, which increased to 110.4 mM NaCl and 5.6 mM CaCl2 at pH 10. In addition, the aggregation of PET nanoplastics was significantly inhibited with the presence of humic acid (HA), and the CCC values increased to 558.8 mM NaCl and 12.3 mM CaCl2 (1 mg L−1 HA). Results from this study showed that the fragmental PET nanoplastics had the quite higher CCC values and stability in aqueous environment. In addition, the aggregation behaviors of PET nanoplastics can be successfully predicted by the Derjguin Landau Verwey Overbeek (DLVO) theory.

As an important part of the riparian zone, bars are an important barrier for the interception of phosphorus (P) originated from leaching and runoff. The spatial variation in P as well as the influence of factors on the said spatial variation in mountainous river (Lingshan River) bars was investigated. A total of 100 soil samples were collected from 11 sampling sites. Soil total phosphorus (TP) and soil available P were determined to explore the spatial variation of soil P in mountainous river bars. One-way analysis of variance, Pearson's correlation analyses, stepwise multiple linear regressions and curve fitting were used to explore the dominant factors affecting the spatial variation of soil P in mountainous river bars. Affected by erosion effect of flowing water, the TP of the bar soils decreased in the longitudinal direction, the TP and available P of the bar soils increased in the cross-sectional direction and the variation in TP between the surface and deep soils firstly increased and then decreased as the height of the bar above the water surface increased. The stronger the erosion effect of flowing water, the more P releases to the water, which may cause the spatial variation of soil P in mountainous river bars, and the results of this study facilitated control of non-point source pollution in mountainous river and restoration of the ecosystems in mountainous river bars.

In this study, zeta potentials of graphitic carbon nitride (g-C3N4) nanoparticles were detailedly investigated under various electrolytes, solution pH, and humic acid (HA) concentration conditions. The hydrodynamic radius of g-C3N4 nanoparticles was measured to be 388.9 ± 24 nm, and the specific surface area of the g-C3N4 nanoparticles was measured to be 46.2 m2 g−1. The absolute values of g-C3N4 zeta potentials significantly decreased with the increasing ionic strength (IS) due to the charge screening. Compared to the monovalent cation, the zeta potentials of g-C3N4 were less negative with the presence of divalent cations. In addition, K+ was more effective than Na+ in decreasing the absolute values of g-C3N4 zeta potentials, and Ca2+ was more effective than Mg2+ in decreasing the absolute values of g-C3N4 zeta potentials. When NaCl and CaCl2 were used as the electrolytes, the zeta potentials of g-C3N4 became less negative with the decreasing pH conditions. When FeCl3 and AlCl3 were used as the electrolytes, the zeta potentials of g-C3N4 became more positive with increasing solution pH due to the changing species of Fe3+ and Al3+. The zeta potentials of g-C3N4 were significantly more negative with the presence of HA. The results from this work indicated electrolytes, solution pH, and HA concentration conditions play a complex role in zeta potentials of g-C3N4 nanoparticles in aqueous environment.

Transport characteristics of fragmental polyethylene glycol terephthalate (PET) microplastics in porous media were elucidated via column experiments under a series combination of electrolytes, pH, and humic acid (HA) conditions. Fragmental PET microplastics showed low mobility in porous media with a small mass recovery rate (50.1%) even under unfavorable retention conditions. The electrolyte, pH, and HA showed combined impact on PET microplastic transport. PET microplastics mobility was enhanced with decreasing electrolyte concentration, increasing pH, and increasing HA concentration. Basic properties (e.g. destiny and shape) of PET microplastics showed stronger effect on their transport behaviors in porous media rather than the experimental chemical conditions. In general, both environmental factors and basic properties played important roles in controlling the retention and transport of PET microplastics in porous media. A numerical model considering the second order kinetic deposition sites was applied to depict the retention and transport of PET microplastics in porous media. Model simulations well matched the experimental breakthrough curves. Given the fragmental PET microplastics have more realistic and irregular shapes, results from this study can improve present knowledge of the environmental fate and risk of microplastics in underground soil and water systems.

Vegetation filter strips (VFS) have been shown to effectively intercept water flow and remove nitrogen. Studies of the vegetation effects on water flow and nitrogen transport are typically studied based on qualitative analyses with species, layouts, growth stage, seasonal changes, and other vegetation conditions and did not considered quantification based on plant traits. In this study, the transport path and retention efficiency of nitrate nitrogen (NO3-N) in VFSs are investigated from the view of the plant specific trait effects by simulating runoff experiments using three grassed VFSs (centipede grass, tall fescue, and vetiver grass), as well as a bare VFS under different slope gradients (2%, 7%, and 12% slope gradients). The primary grass traits (stem spacing, root depth, root length density, and nitrogen total uptake) were measured, and the responses of water flow and NO3-N loss above and below ground to those were quantitatively assessed using the grey correlation analysis method. Results indicated that grasses and slope gradient significantly influenced the water flow and NO3-N loss in general, except the NO3-N loss concentration of the surface flow, in which the tall fescue VFS showed the highest NO3-N total retention rates under each slope condition. Considering the impact of specific grass traits, stem density and root length density has the greatest effects on the surface flow and the subsurface flow respectively, while the effect of roots was lower than that of stems on NO3-N loss below ground. Additionally, the NO3-N loss mass in the surface and subsurface flow were mostly related to the water flow volume and the NO3-N loss concentration respectively. This indicated that grass traits that reduce water flow should be considered more to control the NO3-N loss mass above ground, whereas the grass traits reducing NO3-N loss concentration should be considered more to control the NO3-N loss mass below ground.

The environmental behaviors of graphitic carbon nitride (g-C3N4) have drawn increasing attention in recent. Understanding the fate and transport of g-C3N4 in porous media is necessary for evaluating its environmental risks. Column experiments were used in this study to investigate the combined effect of ionic strength (IS) and other common physicochemical factors (i.e. sand grain size, solution pH, and humic acid concentration) on g-C3N4 transport. The one-site kinetic models were applied to simulate the retention and transport of g-C3N4 in porous media, which fitted the breakthrough curves very well. Experimental and model results showed that g-C3N4 had a weak mobility with the transport mass recovery (TMR) less than 39.6% at pH 6.0 in absence of humic acid (HA). The mobility of g-C3N4 was inhibited with decreasing sand grain size, and the inhibited efficiency was enhanced with IS. However, g-C3N4 transport was significantly enhanced with increasing pH and HA concentration, and the enhanced efficiency was more obviously at high IS. The maximum TMR (78.3%) of g-C3N4 was observed with the presence of 5 mg L−1 HA. These results indicated that physicochemical factors played an important and combined role in controlling g-C3N4 transport in porous media, which would lead to the more complex evaluation on the environmental behaviors of g-C3N4.

The aggregation behaviors of graphitic carbon nitride (g-C3N4) nanosheets under various electrolytes and pH conditions were systematically investigated. The aggregation of g-C3N4 nanosheets was significantly enhanced with increasing electrolyte concentrations. The divalent electrolytes (CaCl2 and MgCl2) were more effective than monovalent electrolytes (NaCl and KCl) in promoting the aggregation of g-C3N4 nanosheets. At the same valence, cations with higher atomic weight were more effective in enhancing the aggregation of g-C3N4 nanosheets. The measured critical coagulation concentrations (CCC) of g-C3N4 nanosheets were 4.7 mM KCl, 9.2 mM NaCl, 1.0 mM CaCl2 and 1.9 mM MgCl2 at pH 6.0, which were lower than some of other two-dimensional nanoparticles. The CCC values of g-C3N4 nanosheets were decreased to 5.5 mM NaCl at pH 2.0, but increased to 29.0 mM NaCl and 2.1 mM CaCl2 at pH 10.0, indicating that the aggregation degree of g-C3N4 nanosheets was decreased with increasing pH. The Fe/Al hydrated complexes generated at the specific pH inhibited the aggregation of g-C3N4 nanosheets and enhanced the stability. Overall, findings from this study demonstrated that the electrolytes and pH conditions played important and combined roles on the aggregation of g-C3N4 nanosheets. In addition, the aggregation behaviors of g-C3N4 nanosheets could be well predicted with the DLVO theory.

Embankments are common structures along rivers or lakes in riparian zones in plain areas. They should have natural slopes instead of slopes covered by concrete or other hard materials, in order to rebuild sustainable ecosystems for riparian zones. This study was conducted to evaluate the effects of vegetative slopes on water flow and pollutant transport through the embankments. Three embankments with different slope treatments (a bare slope, a slope covered in centipede grass, a slope covered in tall fescue) were examined, and three inflow applications of pollute water with different concentration of total nitrogen (TN) and total phosphorus (TP) used to simulate different agricultural non-point pollution levels. The results showed that the water flux rates of the three embankments were relatively stable under all inflow events, and almost all values were higher than 80%. The embankments with vegetative slopes had better nitrogen removal than the bare slope under all events, and the one with tall fescue slope was best, but the benefits of vegetative slopes decreased with increasing inflow concentration. Moreover, there were no significant differences between the embankments on phosphorus removal, for which the reductions were all high (above 90%) with most loads remaining in the front third of embankment bodies. Overall, the embankments with vegetative slopes had positive effects on water exchange and reducing non-point pollutant into lake or river water, which provides a quantitative scientific basis for the actual layout of lakeshores.