Modelling the Vegetation Response to Climate Changes in the Yarlung Zangbo River Basin Using Random Forest

Vegetation coverage variation may influence watershed water balance and water resource availability. Yarlung Zangbo River, the longest river on the Tibetan Plateau, has high spatial heterogeneity in vegetation coverage and is the main freshwater resource of local residents and downstream countries. In this study, we proposed a model based on random forest (RF) to predict the Normalized Difference Vegetation Index (NDVI) of the Yarlung Zangbo River Basin and explore its relationship with climatic factors. High-resolution datasets of NDVI and monthly meteorological observation data from 2000 to 2015 were used to calibrate and validate the proposed model. The proposed model was then compared with artificial neural network and support vector machine models, and principal component analysis and partial correlation analysis were also used for predictor selection of artificial neural network and support vector machine models for comparative study. The results show that RF had the highest model efficiency among the compared models. The Nash–Sutcliffe coefficients of the proposed model in the calibration period and verification period were all higher than 0.8 for the five subzones; this indicated that the proposed model can successfully simulate the relationship between the NDVI and climatic factors. By using built-in variable importance evaluation, RF chose appropriate predictor combinations without principle component analysis or partial correlation analysis. Our research is valuable because it can be integrated into water resource management and elucidates ecological processes in Yarlung Zangbo River Basin

Millennial-scale variations in sedimentary oxygenation in the western subtropical North Pacific and its links to North Atlantic climate

The deep-ocean carbon cycle, especially carbon sequestration and outgassing, is one of the mechanisms to explain variations in atmospheric CO2 concentrations on millennial and orbital timescales. However, the potential role of subtropical North Pacific subsurface waters in modulating atmospheric CO2 levels on millennial timescales is poorly constrained. An increase in the respired CO2 concentration in the glacial deep-ocean due to biological pump generally corresponds to deoxygenation in the ocean interior. This link thus offers a chance to study oceanic ventilation and coeval export productivity based on redox-controlled sedimentary geochemical parameters. Here, we investigate a suite of geochemical proxies in a sediment core from the Okinawa Trough to understand sedimentary oxygenation variations in the subtropical North Pacific over the last 50 000 years (50 ka). Our results suggest that enhanced mid-depth western subtropical North Pacific (WSTNP) sedimentary oxygenation occurred during cold intervals and after 8.5 ka, while oxygenation decreased during the Bölling-Alleröd (B/A) and Preboreal. The enhanced oxygenation during cold spells is linked to the North Pacific IntermediateWater (NPIW), while interglacial increase after 8.5 ka is linked to an intensification of the Kuroshio Current due to strengthened northeast tradewinds over the tropics. The enhanced formation of the NPIW during Heinrich Stadial 1 (HS1) was likely driven by the perturbation of sea ice formation and sea surface salinity oscillations in the high-latitude North Pacific. The diminished sedimentary oxygenation during the B/A due to a decreased NPIW formation and enhanced export production, indicates an expansion of the oxygen minimum zone in the North Pacific and enhanced CO2 sequestration at mid-depth waters, along with the termination of atmospheric CO2 concentration increase. We attribute the millennial-scale changes to an intensified NPIW and enhanced abyss flushing during deglacial cold and warm intervals, respectively, closely related to variations in North Atlantic Deep Water formation

Deglacial biogenic opal peaks revealing enhanced Southern Ocean upwelling during the last 513 ka

Strength of Southern Ocean upwelling controls the exchange of carbon dioxide (CO2) between deep ocean reservoirs and atmosphere, as well as the communication of dissolved silicon with the euphotic zone of the Southern Ocean. The silicon supply could limit diatom opal productivity in the high-latitudes of Southern Ocean and the subsequent burial of biogenic opal in underlying sediments. Here we report a record of biogenic opal export off the Prydz Bay south of the polar front of the Southern Ocean, indicating strengthened upwelling during the past five glacial terminations. In all five terminations (Isingle bondV), opal peaks occur in line with Northern Hemisphere summer insolation intensity as well as the existing IRDs, indicating that freshwater injection associated with retreat of the Northern Hemisphere ice sheets could be the cause of enhanced upwelling in the Southern Ocean during terminations. This could in turn promote CO2 outgassing, finally accelerating the completion of the terminations. In addition, the enhanced upwelling could export the Si-rich deep water to low latitudes via Antarctic Intermediate Water (AAIW) and Subantarctic Mode Water (SAMW), potentially leading to deglacial opal peaks in subtropical North Atlantic

Subzero-Temperature Liquid -Liquid Extraction Coupled with UPLC -MS-MS for the Simultaneous Determination of 12 Bioactive Components in Traditional Chinese Medicine Gegen-Qinlian Decoction

Based on the phase separation phenomenon of acetonitrile-water system at subzero temperature, a subzero-temperature liquid -liquid extraction coupled with ultra-performance liquid chromatography tandem quadrupole mass spectrometry (UPLC -MS-MS) method was developed for the simultaneous determination of 12 bioactive components in Gegen-Qinlian decoction. After optimization, the extraction conditions were set as follows: 3.0 mL of aqueous sample solution ( pH 5.86) was extracted with 2 mL of acetonitrile at 2358 8 8 8 8C for 35 min. The separated acetonitrile phase was diluted 10-fold with water before UPLC -MS-MS analysis. Separation was performed on a Waters ACQUITY UPLC w BEH C 18 column (2.1 3 100 mm i.d., 1.7 mm) with ammonium formate buffer solution (20 mmol L 21 , pH 3.2, adjusted by formic acid) and acetonitrile as mobile phase with gradient elution. Twelve target components could be separated within 10 min and quantified in multiple reaction monitoring mode, both positive and negative ionization modes were employed. Limits of detection were in the range of 0.0003 -0.0451 mg mL 21 . Relative standard deviation values for intra-and interday precision were <2.71 and 8.94%, respectively. The established method provides a simple and effective framework for the quality control of Gegen-Qinlian decoction and related traditional Chinese medicinal preparations

Bioleaching of Rare Earth Elements: Perspectives from Mineral Characteristics and Microbial Species

Bioleaching exhibits high potential for the processing of low-grade complex mineral resources. With the development of the economy and an increase in demand, rare earth elements (REEs) in secondary resources, such as phosphogypsum, red mud and coal-related resources, are gaining more and more attention. In this review, the bioleaching performance of diverse microorganisms is summarized and compared for primary (mainly monazite) and secondary REE resources, based on publications from the past decade. The mineral characteristics of these REE resources are different, as they can be found in phosphate, sulfate, or silicate forms. Correspondingly, microbial species suitable for use in bioleaching differ. The most efficient bioleaching microbe for monazite is Paecilomyces sp., while Acidianus manzaensis is effective in processing red mud. Acidophilic sulfur oxidizers are suitable for processing acidic phosphogypsum. Acidithiobacillus thiooxidans could recover a significant amount of REEs from coal fly ash. In particular, monazite has a high REE content but extremely low bioleaching efficiency compared to that of secondary resources, supporting the understanding that bioleaching approaches are more competitive for minerals with low REE contents. Overall, great progress has been made over the last decade, as considerable REE recovery rates have been achieved, and the main metabolites of microbes were identified. However, numerous challenges still exist. Future efforts should focus on improving biorecovery efficiency, reducing the cost of cell-culture media, and exploring the interaction mechanism between cells and minerals, with an emphasis on mineralogical phase transformations and the molecular regulation mechanisms inside cells during the bioleaching process

Bio-Nanotechnology in High-Performance Supercapacitors

The use of bio-nanotechnology for the fabrication of diverse functional nanomaterials with precisely controlled morphologies and microstructures is attracting considerable attention due to its sustainability and renewability. As one of the key energy storage devices, supercapacitor (SC) requires the active electrode material to have high specific surface area, interconnected porous structure, excellent electronic conductivity, and appropriate heteroatom doping for promoting the transfer of electrons and electrolyte ions. The combination of bio-technology and SC will open up a new avenue for the large-scale fabrication of high performance functional energy storage devices. In this review, the most state-of-the-art research progress in bio-nanotechnological fabrication of different nanomaterials, including carbon materials, metal oxides, conducting polymers, and their corresponding composites are reviewed with the following three bio-nanotechnical approaches covered: (1) biomass carbonization technologies; (2) bio-template methods; and (3) bio-complex technologies, while also highlighting their applications as functional SC electrodes

Fast response detection of H2S by CuO-doped SnO2 films prepared by electrodeposition and oxidization at low temperature

Fast response detection of H2S by CuO-doped SnO2 films prepared was prepared by a simple two-step process: electrodeposition from aqueous solutions of SnCl2 and CuCl2, and oxidization at 600 °C. The phase constitution and morphology of the CuO-doped SnO2 films were characterized by X-ray diffraction and scanning electron microscopy. In all cases, a polycrystalline porous film of SnO2 was the product, with the CuO deposited on the individual SnO2 particles. Two types of CuO-doped SnO2 films with different microstructures were obtained via control of oxidation time: nanosized CuO dotted island doped SnO2 and ultra-uniform, porous, and thin CuO film coated SnO2. The sensor response of the CuO doped SnO2 films to H2S gas at 50–300 ppm was investigated within the temperature range of 25–125 °C. Both of the CuO-doped SnO2 films show fast response and recovery properties. The response time of the ultra-uniform, porous, and thin CuO coated SnO2 to H2S gas at 50 ppm was 34 s at 100 °C, and its corresponding recovery time was about 1/3 of the response time

Evaluation of Performance of Three Satellite-Derived Precipitation Products in Capturing Extreme Precipitation Events over Beijing, China

Extreme precipitation events have a more serious impact on densely populated cities and therefore reliable estimation of extreme precipitation is very important. Satellite-derived precipitation products provide precipitation datasets with high spatiotemporal resolution. For improved applicability to estimating urban extreme precipitation, the performance of such products must be evaluated regionally. This study evaluated three satellite-derived precipitation products, the Integrated Multi-satellite Retrievals for GPM (IMERG_V06), Multi-Source Weighted-Ensemble Precipitation (MSWEP V2), and China Meteorological Forcing Dataset (CMFD), in capturing extreme precipitation using observations acquired at 36 rainfall stations during 2001–2016 in Beijing, China. Results showed that MSWEP had the highest accuracy regarding daily precipitation data, with the highest correlation coefficient and the lowest absolute deviation between MSWEP and the rainfall station observations. CMFD demonstrated the best ability for correct detection of daily precipitation events, while MSWEP maintained the lowest rate of detecting non-rainy days as rainy days. MSWEP performed better in estimating precipitation amount and the number of precipitation days when daily precipitation was 50 mm. All three products underestimated extreme precipitation. The Structural Similarity Index, which is a map comparison technique, was used to compare the similarities between the three products and rainfall station observations of two extreme rainstorms: “7.21” in 2012 and “7.20” in 2016. MSWEP and CMFD showed higher levels of similarity in terms of spatial–temporal structure. Overall, despite systematic underestimation, MSWEP performed better than IMERG and CMFD in estimating extreme precipitation in Beijing