Reflective metasurfaces are utilized as a bridge linking propagating waves and surface waves. However, the effective constitutive parameters (permittivity and permeability) cannot be retrieved by conventional theory without transmission coefficients. In this paper, an innovative method based on a quasi-one-port network model is proposed to robustly retrieve the effective electromagnetic parameters (εeff, μeff, neff, and zeff) for reflective metasurfaces with isotropic unit cells. The validity of the method is demonstrated by imping TE-polarized terahertz waves normally and obliquely (10°) on the multiple-layer unit cells. The effective boundary of the multiple-layer cells is determined by minimizing the deviation of the effective refractive indices from 0.1018 to 0.0260 using a genetic algorithm, which increases the consistency of the retrieval results. The sensitivity of the effective constitutive parameters to the accuracy of reflection coefficients and nonzero incident angle θi is also discussed. This method is beneficial for the design of reflective metasurfaces or multichannel reflectors, the coupling of spoof space plasmon polaritons, and other applications of anomalous reflection.
Water-saving irrigation (WSI) is a promising management practice for sustainable rice production. Shallow-wet irrigation (SWI), controlled irrigation (CI), intermittent irrigation (II), and rain-gathering irrigation (RGI) are four common WSI regimes used in China. Their water saving, pollutant reducing, and yield increasing effects were analysed based on literature survey from multi-site field studies across China. An index system considering the applicability and effect of different WSI regimes was developed to identify their potential distributions across China. The potential overall effect of WSI practices at the country level was then estimated. Results showed that CI had the highest average water saving rate (WSR) of 35.12% and the highest average pollutant reducing rate (PRR) of 54.97%, followed by RGI, SWI, and II; while CI had the lowest average yield increasing rate (YIR) (0.79%), followed by II (5.40%), SWI (8.12%), and RGI (11.80%). Overall, the larger the WSR, the larger higher PRR; but the yield increasing effect will be diminished when the WSR is increased to a certain extent due to the resulting rice water stress. About 94.19% of the total paddy area in China are suitable for WSI practices and the unsuitable ones are mainly due to soil structure deterioration and low soil fertility. SWI is the most applicable WSI regime, suitable for 90.03% of paddy fields, followed by CI and II (23.33%), and RGI (4.16%). By full implementation of appropriate WSI regimes at the country level, the total WSR, PRR, and YIR are likely to reach 22.06–26.41%, 32.11–39.11%, and 5.39–6.87%, respectively. The application of WSI practices in China has noticeable potential to alleviate water shortage and non-point source pollution while ensuring high yield.
Previous studies on large-scale patterns in plant richness and underlying mechanisms have mostly focused on forests and mountains, while drylands covering most of the world's grasslands and deserts are more poorly investigated for lack of data. Here, we aim to 1) evaluate the plant richness patterns in Inner Asian drylands; 2) compare the relative importance of contemporary environment, historical climate, vegetation changes, and mid-domain effect (MDE); and 3) explore whether the dominant drivers of species richness differ across growth forms (woody vs herbaceous) and range sizes (common vs rare). Distribution data and growth forms of 13 248 seed plants were compiled from literature and species range sizes were estimated. Generalized linear models and hierarchical partitioning were used to evaluate the relative contribution of different factors. We found that habitat heterogeneity strongly affected both woody and herbaceous species. Precipitation, climate change since the mid-Holocene and climate seasonality dominated herbaceous richness patterns, while climate change since the Last Glacial Maximum dominated woody richness patterns. Rare species richness was strongly correlated with precipitation, habitat heterogeneity and historical climatic changes, while common species richness was strongly correlated with MDE (woody) or climate seasonality (herbaceous). Temperature had little effects on the species richness patterns of all groups. This study represents the first evaluation of the large-scale patterns of plant species richness in the Inner Asian drylands. Our results suggest that increasing water deficit due to anthropogenic activities combined with future global warming may increase the extinction risk of many grassland species. Rare species (both herbaceous and woody) may face severe challenges in the future due to increased habitat destruction caused by urbanization and resource exploitation. Overall, our findings indicate that the hypotheses on species richness patterns based on woody plants alone can be insufficient to explain the richness patterns of herbaceous species.
To enhance the long-term immobilization of radioactive wastes, ferrihydrite nanoparticles were incorporated into cementitious materials. The effects of ferrihydrite nanoparticles on the physicochemical and mechanical properties of cementitious materials and the immobilization of uranium (U), strontium (Sr) and cesium (Cs) were investigated. Adding ferrihydrite nanoparticles at 0.65%, 1.30%, 3.90% and 6.50% of cement weight slightly improved compressive strength by 5–11%, but dramatically reduced U leaching by 50–57%. The enhanced U immobilization was attributed to the strong adsorption of U by ferrihydrite nanoparticles, and the structural incorporation of U into hematite formed during ferrihydrite recrystallization. Although ferrihydrite nanoparticles had weaker effect than hematite nanoparticles on improving cement hydration and reducing permeability, they exhibit stronger U immobilization capacity. In contrast, incorporating ferrihydrite nanoparticles into cementitious materials had no significant effects on Cs and Sr leaching and no detectable adsorption of Sr and Cs. This study elucidated the fundamental differences in the interactions between ferrihydrite nanoparticles and U, Sr or Cs within cementitious systems that led to the distinctive immobilization mechanisms for these radionuclides. It generated new mechanistic understandings of U, Sr and Cs leaching from cementitious barriers modified by Fe-based nanoparticles, and proposed a new approach for enhancing long-term immobilization of U.
With the extensive application of graphene oxide (GO), its leakage and release into wastewater treatment plants become inevitable. However, the toxicity of graphene oxide (GO) on nitrification process and the underlying mechanisms still remain unclear. In this study, the toxic effects of GO at concentration of 10 and 100 mg/L in 4 h and 10 days were evaluated with sealed reactors operated in sequencing batch mode. In the initial 4 h, both GO concentrations showed no negative effect on nitrogen conversion. However, the exposure to 100 mg/L GO significantly weakened the NH+ 4-N and NO- 2-N conversion capabilities and intensified the nitrous oxide (N2O) generation after 10 days. Extracellular polymeric substance (EPS) analysis suggested that 100 mg/L GO decreased the protein content of the nitrifying activated sludge. Moreover, reactive oxygen species (ROS) level was promoted by 100 mg/L GO owing to the impaired endogenous antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT), which caused oxidative stress to bacteria. Finally, quantitative PCR results confirmed that nitrite-oxidizing bacteria (NOB) and complete ammonia oxidizing bacteria (CAOB) were more sensitive to GO, which was the primary cause for the significant promotion of N2O generation in the high GO concentration. This study offered new insights in the toxicity of GO on nitrification and N2O generation in the terms of dose and exposure time.
Hollow microsphere structure cobalt hydroxide (h-Co(OH)2) was synthesized via an optimized solvothermal-hydrothermal process and applied to activate peroxymonosulfate (PMS) for degradation of a typical pharmaceutically active compound, ibuprofen (IBP). The material characterizations confirmed the presence of the microscale hollow spheres with thin nanosheets shell in h-Co(OH)2, and the crystalline phase was assigned to α-Co(OH)2. h-Co(OH)2 could efficiently activate PMS for radicals production, and 98.6% of IBP was degraded at 10 min. The activation of PMS by h-Co(OH)2 was a pH-independent process, and pH 7 was the optimum condition for the activation-degradation system. Scavenger quenching test indicated that the sulfate radical (SO4• −) was the primary reactive oxygen species for IBP degradation, which contributed to 75.7%. Fukui index (f −) based on density functional theory (DFT) calculation predicted the active sites of IBP molecule for SO4• − attack, and then IBP degradation pathway was proposed by means of intermediates identification and theoretical calculation. The developed hollow Co(OH)2 used to efficiently activate PMS is promising and innovative alternative for organic contaminants removal from water and wastewater.
High-efficiency organic-inorganic hybrid perovskite solar cells have experienced rapid development and attracted significant attention in recent years. However, instability to an ambient environment such as moisture is a facile challenge for the application of perovskite solar cells. Herein, 1,8-octanediammonium iodide (ODAI) is employed to construct a two-dimensional modified interface by in situ combined with residual PbI2 on the formamidinium lead iodide (FAPbI(3)) perovskite surface. The ODA(2+ )ion seems to lie horizontally on the surface of a three-dimensional perovskite due to its substitution for two FA(+) ions, which could protect the bulk perovskite more effectively. The unencapsulated perovskite solar cells showed notably improved stability, which remained 92% of its initial efficiency after storing in an ambient environment for 120 days. In addition, a higher open-circuit voltage of 1.13 V compared to that of the control device (1.04 V) was obtained due to the interface energy level modification and defect passivation. A champion power conversion efficiency of 21.18% was therefore obtained with a stabilized power output of 20.64% at the maximum power point for planar perovskite solar cells.
Effective removal of dyes has been widely investigated by the adsorption of powder activated carbon and photodegradation by titanate nanotubes (TNTs). In this study, a facile one-step alkaline-hydrothermal method was applied to synthesize powder activated charcoal–supported TNTs (TNTs@PAC). Adsorption of three representative dyes, i.e., cationic methylene blue (MB), cationic rhodamine B (RhB), and anionic methyl orange (MO), onto TNTs@PAC was evaluated by the adsorption kinetic experiments and adsorption isotherms. The first 30 min is the main time phase of adsorption, and MB, RhB, and MO obtained the experimental equilibrium uptake of 173.30, 115.06, and 106.85 mg/g, respectively, indicating their final removal efficiencies of 100%, 69.36%, and 64.11%, respectively. The increase of pH value reduced adsorption capacity of MO (from 149.35 mg/g at pH of 2 to 96.99 mg/g at pH of 10), but facilitated MB adsorption, which was attributed to the charge distribution on the surface of TNTs@PAC and the charge of dyes at different pH. Furthermore, good capacity recoveries of MB by TNTs@PAC (>þinspace}99%) were observed after UV irradiation treatment, indicating the used TNTs@PAC can be easily recycled for the adsorption of MB by UV irradiation. Overall, TNTs@PAC is an effective process for remediation of dye-contaminated water because of its adsorption performance for all selected dyes and good regeneration capacity for MB.