In the context of global warming, the increasing frequency of compound dry–hot extremes pose varying degrees of threats to the natural environment and human society. However, due to the lack of ...long‐term and high‐accuracy meteorological observations, the characteristics and drivers of compound dry–hot extremes over a century‐long period is still poorly investigated in China. Here we characterize the spatiotemporal variations of growing‐season (May–September) compound dry–hot events (CDHEs) over China using Standardized Dry and Hot Index (SDHI) calculated by monthly temperature and precipitation during 1901–2017. The influences of precipitation and temperature extremes, as well as large‐scale climate indices (i.e., El Niño–Southern Oscillation Index ENSO, Atlantic Multidecadal Oscillation AMO, North Atlantic Oscillation NAO, Pacific Decadal Oscillation PDO and North Pacific NP) on CDHEs were then explored using the relative contribution analysis, Pearson correlation analysis and cross‐wavelet spectrum analysis. Our findings reveal a significant increase in the occurrence of different severity levels of CDHEs in China with their spatial extent gradually increase, practically since the end of the 20th century. Due to the exacerbation of drought conditions in China since the mid‐20th century, the regions where the Standardized Precipitation Index (SPI) has a more prominent contribution to the SDHI have gradually expanded, predominantly in the eastern, northern and northwestern parts of China. The significant influence of large‐scale climate indices, particularly ENSO and AMO, on the occurrence of compound dry–hot extremes in China is noteworthy, as these indices control the variability of precipitation and temperature, respectively. The study findings demonstrate that AMO exhibits a more significant correlation with SDHI in all subregions of China, while ENSO exhibits marginally stronger periodic coherence with SDHI than the other indices. This study offers valuable insights and references for unravelling long‐term development process of and the underlying influence mechanisms of significant climate patterns on the growing‐season CDHEs in China.
The occurrence and spatial extent of different level compound dry–hot extremes increased significantly in China over a century‐long period. All five large‐scale climate patterns consistently exhibit periodic coherence with SDHI, where ENSO exhibits stronger periodic coherence than the others.
For achieving the goal of peaking carbon dioxide emissions and achieving carbon neutrality, developing hydrogen energy, the green and clean energy, shows a promising perspective for solving the ...energy and ecological issues. Herein, firstly, we used the hydrothermal method to synthesize the ZnS(en)0.5 as the precursor. Then, ZnS/ZnO composite was obtained by the in situ transformation of ZnS(en)0.5 with heat treatment under air atmosphere. The composition, optical property, morphology, and structural properties of the composite were characterized by X-ray photoemission spectroscopy (XPS), Ultraviolet-visible absorption spectra (Uv-vis Abs), Scanning electron microscopy (SEM) and Transmission electron microscopy image (TEM). Moreover, the content of ZnO in ZnS/ZnO was controlled via adjustment of the calcination times. The visible-light response of ZnS/ZnO originated from the in situ doping of N during the transformation of ZnS(en)0.5 to ZnS/ZnO under heat treatment, which was verified well by XPS. Photocatalytic hydrogen evolution experiments demonstrated that the sample of ZnS/ZnO-0.5 h with 6.9 wt% of ZnO had the best H2 evolution activity (1790 μmol/h/g) under visible light irradiation (λ > 400 nm), about 7.0 and 12.3 times that of the pure ZnS and ZnO, respectively. The enhanced activities of the ZnS/ZnO composites were ascribed to the intimated hetero-interface between components and efficient transfer of photo-generated electrons from ZnS to ZnO.
•Ecohydrological responses to the 1987 fire were re-examined in three forested basins.•A significant decline in most ecohydrological variables was detected in the 1987 fire.•The hydrological systems ...need longer time to recover from fire than NDVI, LAI and GPP.
Understanding how bushfire affects basin-wide ecohydrological processes is critical for ecological restoration and water supply. However, the mechanisms responsible for post-fire streamflow remain poorly explored in forested basins of China due to complex scale-dependent relationships between fire-induced forest changes and ecohydrological processes, lack of reasonable design of paired watershed experiments, and especially data scarcity. Here, we re-examine ecohydrological responses of the Black Dragon fire (one of the largest and most damaging forest fires on record globally) on an annual scale in three forest basins (two fire-impacted basins, namely Emuer and Pangu, and a nearly unimpacted basin, Huma) in the Daxing’an Mountains using multiple most recent datasets and methods. We found that the Black Dragon fire decreased annual- and basin-averaged vegetation leaf area, evapotranspiration, interception loss, transpiration, soil moisture, runoff, and discharge capacity in 1987 in the two fire-impacted basins compared with the unimpacted basin. The annual- and basin-averaged evapotranspiration (runoff) did not reduce (increase) as much as that expected with decreased LAI given the precipitation amount in 1987 in the two fire-impacted basins, which properly linked to the quick postfire regrowth of vegetation in the growing season. Vegetation leaf area and productivity can quickly recover in the following two to three years postfire, but the hydrological systems need more than 10 years to adapt this disturbance. These findings improve the understanding of ecohydrological responses to bushfire disturbance and provide scientific evidence for ecological protection and water resources management under intensified natural and anthropogenic disturbances.
Changes in the land use/cover alter the Earth system processes and affect the provision of ecosystem services, posing a challenge to achieve sustainable development. In the past few decades, the ...Yellow River (YR) basin faced enormous social and environmental sustainability challenges associated with environmental degradation, soil erosion, vegetation restoration, and economic development, which makes it important to understand the long-term land use/cover dynamics of this region. Here, using three decades of Landsat imagery (17,080 images) and incorporating physiography data, we developed an effective annual land use/cover mapping framework and provided a set of 90 m resolution continuous annual land use/cover maps of the YR basin from 1986 to 2018 based on the Google Earth Engine and the Classification and Regression Trees algorithm. The independent random sampling validations based on the field surveys (640 points) and Google Earth (3456 points) indicated that the overall accuracy of these maps is 78.3% and 80.0%, respectively. The analysis of the land system of the YR basin showed that this region presents complex temporal and spatial changes, and the main change patterns include no change or little change, cropland loss and urban expansion, grassland restoration, increase in orchard and terrace, and increase in forest during the entire study period. The major land use/cover change has occurred in the transitions from forests, grasslands, and croplands to the class of orchard and terrace (19.8% of all change area), which not only increase the greenness but also raised the income, suggesting that YR progress towards sustainable development goals for livelihood security, economic growth, and ecological protection. Based on these data and analysis, we can further understand the role of the land system in the mutual feedback between society and the environment, and provide support for ecological conservation, high-quality development, and the formulation of sustainable management policies in this basin, highlighting the importance of continuous land use/cover information for understanding the interactions between the human and natural systems.
For achieving the goal of peaking carbon dioxide emissions and achieving carbon neutrality, developing hydrogen energy, the green and clean energy, shows a promising perspective for solving the ...energy and ecological issues. Herein, firstly, we used the hydrothermal method to synthesize the ZnS(en)sub.0.5 as the precursor. Then, ZnS/ZnO composite was obtained by the in situ transformation of ZnS(en)sub.0.5 with heat treatment under air atmosphere. The composition, optical property, morphology, and structural properties of the composite were characterized by X-ray photoemission spectroscopy (XPS), Ultraviolet-visible absorption spectra (Uv-vis Abs), Scanning electron microscopy (SEM) and Transmission electron microscopy image (TEM). Moreover, the content of ZnO in ZnS/ZnO was controlled via adjustment of the calcination times. The visible-light response of ZnS/ZnO originated from the in situ doping of N during the transformation of ZnS(en)sub.0.5 to ZnS/ZnO under heat treatment, which was verified well by XPS. Photocatalytic hydrogen evolution experiments demonstrated that the sample of ZnS/ZnO-0.5 h with 6.9 wt% of ZnO had the best Hsub.2 evolution activity (1790 μmol/h/g) under visible light irradiation (λ > 400 nm), about 7.0 and 12.3 times that of the pure ZnS and ZnO, respectively. The enhanced activities of the ZnS/ZnO composites were ascribed to the intimated hetero-interface between components and efficient transfer of photo-generated electrons from ZnS to ZnO.
For achieving the goal of peaking carbon dioxide emissions and achieving carbon neutrality, developing hydrogen energy, the green and clean energy, shows a promising perspective for solving the ...energy and ecological issues. Herein, firstly, we used the hydrothermal method to synthesize the ZnS(en)0.5 as the precursor. Then, ZnS/ZnO composite was obtained by the in situ transformation of ZnS(en)0.5 with heat treatment under air atmosphere. The composition, optical property, morphology, and structural properties of the composite were characterized by X-ray photoemission spectroscopy (XPS), Ultraviolet-visible absorption spectra (Uv-vis Abs), Scanning electron microscopy (SEM) and Transmission electron microscopy image (TEM). Moreover, the content of ZnO in ZnS/ZnO was controlled via adjustment of the calcination times. The visible-light response of ZnS/ZnO originated from the in situ doping of N during the transformation of ZnS(en)0.5 to ZnS/ZnO under heat treatment, which was verified well by XPS. Photocatalytic hydrogen evolution experiments demonstrated that the sample of ZnS/ZnO-0.5 h with 6.9 wt% of ZnO had the best H2 evolution activity (1790 μmol/h/g) under visible light irradiation (λ > 400 nm), about 7.0 and 12.3 times that of the pure ZnS and ZnO, respectively. The enhanced activities of the ZnS/ZnO composites were ascribed to the intimated hetero-interface between components and efficient transfer of photo-generated electrons from ZnS to ZnO.
Spirulina platensis were chosen as templates to produce microscopic helical soft-core magnetic particles by way of depositing ferromagnetic alloy onto their surface using electroplating technique,and ...the process of electroplating ferromagnetic alloy onto microorganism cells was studied.The morphology and appearance of the coated Spirulina platensis were analyzed with optical microscopy and scanning electron microscopy,respectively,and the ingredients and phase structure of the alloy coating were analyzed with energy dispersive X-ray detector（EDX） and X-ray diffractive analysis（XRD）,respectively.The result showed that the particles were successfully coated with uniform metal coating and their initial helical shape was perfectly replicated.The coating was NiFe alloy,and its phase structure was face-centered cubic structure.The magnetic properties of the coated particles were tested with vibrating sample magnetometer（VSM）,and the result showed that the particles were ferro-magnetic,which means the magnetic electroplating of the microorganism cells was successfully achieved.The electrochemical reaction mechanism of the magnetic plating process was also analyzed;the result showed that the deposition of NiFe on the microorganism cells was anomalous codeposition,and that Fe2＋ ion was preferential deposited when magnetic stirring was applied.
Unactivated alkyl chlorides are abundant building blocks in organic synthesis, but they have been rarely engaged in cross-electrophile coupling. Herein, we report a Ni/Ti-cocatalyzed reductive ...allylic defluorinative cross-coupling between trifluoromethyl alkenes and unactivated alkyl chlorides and bromides, enabling the efficient preparation of diverse functional-group-rich gem-difluoroalkenes. Notably, synthesis of the gem-difluoroalkene analogues of azaperone, haloperidol, and benperidol was also accomplished using our method as a key step.
By merging C–O and C–F bond cleavage in cross-electrophile coupling, we developed a method for efficient synthesis of gem-difluoroalkenes with an alkoxy-substituent on the homoallylic position using ...easily accessible acetals as coupling partners with α-trifluoromethyl alkenes. Remarkably, this Ni-catalyzed allylic defluorinative cross-coupling reaction demonstrates high tolerance of a wide range of sensitive functional groups and proves to be applicable in late-stage functionalization of structurally complex compounds.
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