[Characteristics and drivers of vegetation temporal dynamics in Hunan Province of China during 2002-2020]. / 湖南省2002­2020å¹´æ¤è¢«åŠ¨æ€æ¼”å˜ç‰¹å¾åŠå½±å“å› å­.

Understanding the influences of climate change and human activities on vegetation change is the foundation for effective ecosystem management. Based on the 250 m MODIS-NDVI data from 2002 to 2020, we employed Theil-Sen Median trend analysis and the Mann-Kendall test to quantify vegetation change in Hunan Province. By combining with meteorological, nighttime light index, land cover and other data, residual analysis and correlation analysis, we examined the impacts of human activities and climate change on vegetation dynamics at both the pixel level and the county level. The results showed that the normalized difference vegetation index (NDVI) in Hunan Province exhibited a spatial pattern of "overall improvement with localized degradation" during 2002-2020. Approximately 64.9% of the study area experienced significant vegetation improvement, mainly occurring in the western and central-southern parts of Hunan Province. 1.4% of the study area experienced significant vegetation degradation, mostly in the newly developed urban areas and the farmland in the Dongting Lake Plain. Human activities and climate change jointly promoted vegetation improvement in 67.9% of the study area. Human activities and climate contributed to 96% and 4% of the NDVI change, respectively. At the county level, human activities contributed to over 80% of the NDVI change in each district or county. The impacts of human activities on vegetation change exhibited significant spatial heterogeneity. Urban expansion led to vegetation degradation in the newly developed areas, while vegetation growth appeared in the old developed urban areas. The ecological restoration projects promoted vegetation restoration in the western part of Hunan Province. This study could help us better understand the spatiotemporal variations of vegetation and their responses to climate change and human activities, which would offer scientific basis for effective ecological restoration policy.

The efficient degradation of organic pollutants in an aqueous environment under visible light irradiation by persulfate catalytically activated with kaolin-Fe2O3.

In recent years, persulfate (PS) has been widely studied as a promising oxidant. In this work, a new K-Fe2O3 catalyst was synthesized via a facile impregnation method. K-Fe2O3 samples were utilized as heterogeneous photocatalysts for the degradation of aquatic organic pollutants (rhodamine, RhB, and ciprofloxacin, CIP). The catalysts showed excellent catalytic activity in the presence of PS under the irradiation of visible light, owing to the generation of SO4˙- and ·OH active radicals. The degradation ratio and COD removal ratio for RhB were 99.8% and 88.3%. More importantly, the system retained a high degradation activity for RhB within a wide operating pH range of 2.9-10. The results of cycling degradation experiments confirmed that the K-Fe2O3 catalyst was stable and recoverable. Large-scale experiments for treating dye wastewater under irradiation by natural sunlight were carried out, showing that this study can provide a new perspective for the treatment of wastewater.