Future Changes in Simulated Evapotranspiration across Continental Africa Based on CMIP6 CNRM-CM6.

The main goal of this study was to assess the interannual variations and spatial patterns of projected changes in simulated evapotranspiration (ET) in the 21st century over continental Africa based on the latest Shared Socioeconomic Pathways and the Representative Concentration Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) provided by the France Centre National de Recherches Météorologiques (CNRM-CM) model in the Sixth Phase of Coupled Model Intercomparison Project (CMIP6) framework. The projected spatial and temporal changes were computed for three time slices: 2020-2039 (near future), 2040-2069 (mid-century), and 2080-2099 (end-of-the-century), relative to the baseline period (1995-2014). The results show that the spatial pattern of the projected ET was not uniform and varied across the climate region and under the SSP-RCPs scenarios. Although the trends varied, they were statistically significant for all SSP-RCPs. The SSP5-8.5 and SSP3-7.0 projected higher ET seasonality than SSP1-2.6 and SSP2-4.5. In general, we suggest the need for modelers and forecasters to pay more attention to changes in the simulated ET and their impact on extreme events. The findings provide useful information for water resources managers to develop specific measures to mitigate extreme events in the regions most affected by possible changes in the region's climate. However, readers are advised to treat the results with caution as they are based on a single GCM model. Further research on multi-model ensembles (as more models' outputs become available) and possible key drivers may provide additional information on CMIP6 ET projections in the region.

Spatial Distribution and Environmental Significance of Phosphorus Fractions in River Sediments and Its Influencing Factor from Hongze and Tiaoxi Watersheds, Eastern China.

This study explored the spatial distribution of phosphorus fractions in river sediments and analyzed the relationship between different phosphorus fractions and their environmental influence on the sediments within different watersheds in Eastern China. River sediments from two inflow watersheds (Hongze and Tiaoxi) to Hongze and Taihu Lake in Eastern China were analyzed by the sequential extraction procedure. Five fractions of sedimentary phosphorus, including freely sorbed phosphorus (NH4Cl-P), redox-sensitive phosphorus (BD-P), bound phosphorus metal oxide (NaOH-P), bound phosphorus calcium (HCl-P), and residual phosphorus (Res-P) were all analyzed. The orders of rankings for the P fractions of the rivers Anhe and Suihe were HCl-P > NaOH-P > BD-P > NH4Cl-P and HCl-P > BD-P > NaOH-P > NH4Cl-P, respectively. For the rank order of the Hongze watershed, HCl-P was higher while the NH4Cl-P contents were significantly lower. The rank order for the Dongtiaoxi River was NaOH-P > HCl-P > BD-P > NH4Cl-P, and that of Xitiaoxi River was NaOH-P > BD-P > HCl-P > NH4Cl-P. Compared with the phosphorus forms of the Tiaoxi watershed, NaOH-P contents were significantly higher compared to HCl-P, which was significantly higher in the Hongze watershed. In comparison, NH4Cl-P contents were significantly lower in both. Variations may be attributed to differential discharge of the P form in the watershed due to land-use changes and urban river ambient conditions.

Spatial variations in and environmental significance of nitrogen forms in river sediments from two different watersheds in eastern China.

Nitrogen is considered an essential nutrient element limiting water productivity, and its distribution in sediments directly affects its release potential. This study aimed to analyse the spatial characteristics, distribution, and influence of nitrogen forms in two different river catchments situated in eastern China. Using sequential extraction methods, the study divided sediment nitrogen into four forms, namely, an ion-exchangeable form (IEF-N), weak acid-extractable form (WAEF-N), strong alkali-extractable form (SAEF-N), and strong oxidant-extractable form (SOEF-N). The results for the two catchments showed significant differences in the physicochemical properties as well as variations in space. The mean proportion of total transferable nitrogen (TTN) in the Anhe, Suihe, Dongtiaoxi, and Xitiaoxi rivers accounted for 50.64%, 32.87%, 34.63%, and 40.45%, respectively. The results also revealed a higher total TTN in the Hongze watershed than in the Tiaoxi watershed. The order of mean TTN in sediments from the Hongze watershed was SOEF-N > SAEF-N > IEF-N > WAEF-N, whereas that for the Tiaoxi watershed was SOEF-N > SAEF-N > WAEF-N > IEF-N. The distribution of nitrogen forms in the sediments was significantly impacted by the sediment composition and environmental factors, as shown by correlation and redundancy analysis (RDA).

Lyotropic liquid crystal self-assembly of H2O2-hydrolyzed chitin nanocrystals.

H2O2 hydrolysis of mechanically-defibrillated chitin nanofibrils was explored as a green way of fabricating rod-like chitin nanocrystals (H2O2-hydrolyzed CHNs) that have an average length of 350 nm and width of 40 nm. We investigated the structure and morphology of CHNs as well as the rheology and lyotropic self-assembly behavior of its colloidal dispersions. The results show that although H2O2-hydrolyzed CHNs maintained the crystalline structure of α-chitin, surface charge of the nanorods was switched from positive to negative. As a consequence, the colloidal nanocrystals were well-dispersed in neutral or alkaline aqueous media, and behaved as a lyotropic liquid crystal between two critical concentrations. It is interesting that lyotropic liquid crystal transition was a spontaneously self-assembly from well-aligned nanofibers, to nanobelts, and to multi-layered lamellae. At high critical concentration, H2O2-hydrolyzed CHN colloids exhibited a sol-gel transition, which was discovered to be highly dependent on the storage time, concentration, temperature, and surface charge density. It is also suggested that nematic mesophases rather than gel could be effectively maintained by improving the surface charge density or lowering the aging temperature and colloidal concentration of CHNs.

Fiber Alignment and Liquid Crystal Orientation of Cellulose Nanocrystals in the Electrospun Nanofibrous Mats.

Sulfate cellulose nanocrystal (CNC) dispersions always present specific self-assembled cholesteric mesophases which is easily affected by the inherent properties of particle size, surface charge, and repulsion or affinity interaction, and external field force generated from ionic potential of added electrolytes, magnetic or electric field, and mechanical shearing or stretching. Aiming at understanding the liquid crystal orientation and fiber alignment under high-voltage electric field, randomly distributed, uniform-aligned, or core-sheath nanofibrous mats involving charged CNCs and PVA were electrospun; and among them, specific straight arrayed fine nanofibers with average diameter of 270 nm were manufactured by using a simple and versatile gap collector. Moreover, arrayed composite nanofibers regularly aligned along the vertical direction of gap plates and selectively reflected frequent and continuous birefringence which was regarded as nematic phases of CNCs induced by the uniaxial stretching under high-voltage electric field. As a synergic effect of rigidness of nanocrystals and stretching orientation of nematic phases, the aligned nanofibrous arrays exhibited a higher tensile strength and strain than the randomly oriented or core-sheath nanofibrous mats at the same loading of CNCs. By contrast, mesophase transition of CNCs from cholesteric to nematic occurred in the coaxially spun core-sheath nanofibers at a loss of long-ranged chiral twist. Hence, the structure-effect relationship between liquid crystal orientation of charged nanorods in polymer-based fine nanofibers and the flexibility or mechanical integrity of the aligned fiber array will be favorable for strategic development of functional liquid crystal fabrics.

Cholesteric film of Cu(II)-doped cellulose nanocrystals for colorimetric sensing of ammonia gas.

With the increasing demand of environmental monitoring for toxic and odorous ammonia gas it is desired to develop specific green, cost-effective and in situ passive colorimetric alternatives to current complex instrumentations. In this work, we designed an ammonia gas sensor based on cholesteric liquid crystal films of copper(II)-doped cellulose nanocrystals (CNCCu(II)) whose structure, optical and sensing properties were investigated. The hybrid films using the low doping Cu(II) as a color-tuning agent inherited the chiral nematic signature and optical activity of CNCs, suggesting a strong chelation between copper ions and negatively charged CNCs. The sensing performance illustrates that the CNCCu(II)125 film was sensitive to ammonia gas which could merge into nematic layers of CNCs and trigger-sensed to copper ions chelated on CNCs, consequently arousing a red-shift of reflective wavelength as well as an effective colorimetric transition. Such a hybrid film is anticipated to boost a new gas sensing regime for fast and effective on-site qualitative investigations.

Cellulose Nanocrystal/Poly(ethylene glycol) Composite as an Iridescent Coating on Polymer Substrates: Structure-Color and Interface Adhesion.

The broad utility as an environmentally friendly and colorful coating of cellulose nanocrystal (CNC) was limited by its instability of coloration, brittleness, and lack of adhesion to a hydrophobic surface. In the present work, a neutral polymer, poly(ethylene glycol) (PEG) was introduced into CNC coatings through evaporation-induced self-assembly (EISA) on polymer matrices. The structure-color and mechanical properties of the composite coating or coating film were characterized by UV-vis spectroscopy, polarized light microscopy (PLM), scanning electron microscopy (SEM), wide-angle X-ray diffraction (WXRD), and tensile tests. Results showed that the reflective wavelength of the iridescent CNCs could be finely tuned by incorporation of PEG with varied loadings from 2.5 to 50 wt %, although the high loading content of PEG would produce some side effects because of the severe microphase separation. Second, PEG played an effective plasticizer to improve the ductility or flexibility of the CNC coating or coating film. Furthermore, as a compatibilizer, PEG could effectively and tremendously enhance the adhesion strength between CNCs and neutral polymer matrices without destroying the chiral nematic mesophases of CNCs. Environmentally friendly CNC/PEG composites with tunable iridescence, good flexibility, and high bonding strength to hydrophobic polymer matrices are expected to be promising candidates in the modern green paint industry.