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).