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ZnO/Cu2S nanotube arrays are fabricated firstly by a facile and capping-agent-free method, and the photo-electrochemical performance has been studied systematically. The results show that ZnO/Cu2S nanotube arrays achieve enhanced photo-electrochemical water splitting performance and the photocurrent densities of ZnO/Cu2S are 7.9 times than that of ZnO at 0 V versus Ag/AgCl. The performance of the ZnO/Cu2S nanotube arrays can be adjusted by changing the amount of Cu2S microcrystals. The results confirm that the enhanced photo-electrochemical performance of ZnO/Cu2S is due to the significantly improved visible light absorption, effective separation of photo-induced carriers due to the well band energy match and the formed p-n junction between ZnO and Cu2S.

The ZnO nanotube arrays were obtained by a simple three-step method, and then Au nanoparticles and Cu2O nanocrystals were decorated onto ZnO nanotube arrays successively. The composition, morphology, optical properties and photoelectrochemical performance of the as-prepared ZnO@Au@Cu2O nanotube arrays were characterized by X-ray diffraction, scanning electron microscopy, UV–vis diffuse reflectance spectra, X-ray photoelectron spectroscopy, and photocurrent densities. The results confirmed that ZnO@Au@Cu2O nanotube arrays showed enhanced response to visible light and achieved an excellent photocurrent under visible light due to the localized surface plasmon resonance effect, visible light harvesting of Cu2O nanocrystals, effective transfer and separation of photo-generated charge carriers induced by p-n junction and well band energy match of the ZnO@Au@Cu2O nanotube arrays.

The application of single-phase ZnO in hydrogen production through photoelectrochemical (PEC) water reduction is limited because of its unability to utilize photon energy of visible light and high carrier recombination rate. Herein, a three-dimensional (3D) plasmonic photoanode consisting of Au nanoparticles/ZnFe2O4 nanosheets coated onto ZnO nanotube arrays (Au/ZnFe2O4/ZnO NTAs) is rationally designed for hydrogen generation via PEC water splitting. The measurements preformed under simulated solar light and visible light irradiation show that the hot-electron injection of Au nanoparticles (NPs) significantly enhances PEC water splitting for hydrogen generation of 3D plasmonic Au/ZnFe2O4/ZnO NTAs photoanode. Benefiting from the outstanding visible light harvesting ability of ZnFe2O4 nanosheets, efficient suppression of carrier recombination by a favorable band alignment, hot-electron injection of Au NPs and large surface area of 3D architecture, the 3D plasmonic Au/ZnFe2O4/ZnO NTAs photoanode exhibits enhanced PEC water splitting for hydrogen generation. The hydrogen generation rate obtained by 3D plasmonic Au/ZnFe2O4/ZnO NTAs photoanode is 1.5 and 5.7-fold of ZnO/ZnFe2O and ZnO NTAs photoanodes, respectively, at 0.6 V versus reference electrode (Ag/AgCl) under simulated solar light irradiation.

Reliable attribution of changes in streamflow is fundamental to our understanding of the hydrological cycle and is needed to enable decision makers to manage water resources in a sustainable way. Here, we used a new attribution method based on the Budyko framework (complementary method) to quantify the contributions of climate change and human activities to the changes in annual streamflow in 22 catchments on China's Loess Plateau during the past three decades. Our results showed that after the Grain-for-Green (GFG) project, the annual streamflow decreased by 36% on average (3–72%), with reductions being more intense in northern catchments. The sensitivity of streamflow to precipitation and potential evapotranspiration also decreased, with a mean rate of −0.7 mm yr−1/mm yr−1 and −0.2 mm yr−1/mm yr−1, respectively. Using the upper and lower bounds of the human effects on streamflow from the complementary method as a reference, we found that these effects at half of the stations were under- or over-estimated by the total differential method. The contribution analysis from the complementary method showed that although human activities decreased streamflow by 26% (or 54% as a relative value) on average, the contribution of potential evapotranspiration alone to the decrease in streamflow was 9% (42%), highlighting the important role of increasing atmospheric moisture demand in the water cycle. In addition, the 5-year incremental analysis showed that the impacts of climate and human activities on streamflow had strong spatiotemporal variability.

In this study, we show for the first time a hierarchical ZnO/ZnFe2O4 nanotube array photoanode for water splitting to produce hydrogen. In this photoanode, the wrinkle-like ZnFe2O4 nanosheets (NSs) are grown onto ZnO nanotube arrays through adsorption and annealing reaction. The hierarchical ZnO/ZnFe2O4 nanotube array photoanode exhibits outstanding PEC water splitting to produce hydrogen due to the remarkable visible-light harvesting ability and the large surface area of wrinkle-like ZnFe2O4 NSs. Under simulated solar light irradiation, the hierarchical ZnO/ZnFe2O4 nanotube arrays (NTAs) achieve a remarkably enhanced photocurrent density of 1.3 mA/cm2, which is 2.2-fold higher than that of pristine ZnO NTAs at 0 V vs Ag/AgCl. Moreover, the hydrogen production rate of the hierarchical ZnO/ZnFe2O4 nanotube array photoanode is 3.6-fold higher than that of pristine ZnO nanotube array photoelectrode at 0.6 V vs Ag/AgCl.

A novel Janus sponge with the ability to remove complex contaminants from water is reported. Firstly, a superhydrophilic sponge (PA@PEI-sponge) is prepared via synthesizing negatively charged phytic acid@polyethyleneimine (PA@PEI) nanoparticles and assembling them on the surface of polydopamine (PDA) and PEI-modified polyurethane (PU) sponge through electrostatic adsorption. The Janus sponge is generated by modifying one side of the PA@PEI-sponge with PDMS, which exhibits superior separation efficiency and high filtration flux toward both water-in-oil and oil-in-water emulsions due to its multiplex selective wettability and the interconnected and tortuous 3D porous channels. The numerous negatively charged active sites of PA@PEI nanoparticles and PDA layer impart the superhydrophilic PA@PEI-sponge with the removal efficiency of 39.95 ± 0.27% for malachite green (MG) via simple flow-through filtration, which can be improved to 99.92 ± 0.07% by Janus modification. More importantly, the Janus sponge exhibits an excellent treatment capacity for complex mixtures containing emulsified oil and dye, with the separation efficiency above 99.59%. The Janus sponge also demonstrates the effective separation of real industrial wastewater collected from an acrylic dyeing plant. Together with a facile and green preparation strategy, this Janus sponge shows excellent application potential for simultaneous dye removal and oil/water emulsion separation.

Recently, relationship between vegetation activity and temperature variability has received much attention in China. However, vegetation-induced changes in water resources through changing land surface energy balance (e.g. albedo), has not been well documented. This study investigates the underlying causes of vegetation change and subsequent impacts on runoff for the Northern Shaanxi Loess Plateau. Results show that satellite-derived vegetation index has experienced a significantly increasing trend during the past three decades, especially during 2000-2012. Large-scale ecological restorations, i.e., the Natural Forest Conservation project and the Grain for Green project, are found to be the primary driving factors for vegetation increase. The increased vegetation coverage induces decrease in surface albedo and results in an increase in temperature. This positive effect can be counteracted by higher evapotranspiration and the net effect is a decrease in daytime land surface temperature. A higher evapotranspiration rate from restored vegetation is the primary reason for the reduced runoff coefficient. Other factors including less heavy precipitation, increased water consumption from town, industry and agriculture also appear to be the important causes for the reduction of runoff. These two ecological restoration projects produce both positive and negative effects on the overall ecosystem services. Thus, long-term continuous monitoring is needed.

Agricultural water resource, mainly consumed through evapotranspiration, plays a critical role in agricultural production of arid and semiarid regions. Quantifying the changes of evapotranspiration in cropland (ETc), and its driving factors, may provide rich information for improving human land-use and water resource management. Here we first investigated the multi-year (2000–2015) changes in the ETc (mm yr−1) and associated driving factors of the Loess Plateau (LP), using a combination of the Vegetation Interfaces Processes model and a factorial analysis of variance. We found that the ETc of the LP showed a significant upward trend of 0.31 km3 yr−2 (3.33 mm yr−2) (p