Interpretation of groundwater recharge mechanisms is problematic because of the muted instantaneous response of subsurface water to rainfall and limited recharge rates, particularly in semi-arid ...environments with deep loess deposits. Here we identify the possible groundwater recharge mechanisms in 200-m thick loess deposits with unsaturated zone thickness of over 40 m. We collected soil samples up to 15 m deep under four land use types (one grassland and three apple orchards with stand ages 15, 24 and 30 years old), and used three-year precipitation and groundwater samples to determine the contents of stable water isotopes, chloride, and tritium. Our overarching goal is to determine the relative importance of piston and preferential flow in groundwater recharge using multiple tracers and quantify the effects of land use change on groundwater recharge. We find that while both piston and preferential flows are important in groundwater recharge, the unsaturated and saturated zones have yet to come to hydraulic equilibrium. This suggests different groundwater recharge mechanisms: tracers in the unsaturated zone suggest piston flow, while the detectable tritium in the saturated zone implies preferential flow. Recharge rates in the unsaturated zones range between 23 and 82 mm year−1, accounting for 4%–14% of mean annual precipitation, and increasing with depth presumably because of land use and/or climatic conditions. Total recharge rate in the saturated zone is 112.6 ± 44.1 mm year−1, accounting for 19 ± 9% of mean annual precipitation. Overall, our study finds that piston flow contributes more to total recharge (53%–69%) than does preferential flow. Nevertheless, piston flow may become less important because of land use change (farmland to apple orchard conversion). Our findings have implications for the need to strike a delicate balance between the economic gains from afforestation and the possible risks to groundwater supply sustainability.
•We used multiple tracers to explore recharge mechanisms.•Piston and preferential flows recharge groundwater with different contributions.•Recharge increases with depth, underlining climate and vegetation controls on groundwater recharge.•The conversion of grasslands to apple orchards reduces groundwater recharge.
•Stable and radioactive isotopes were combined to reveal sources of deep soil water.•Extreme wet events in rainy seasons recharge deep soil water through piston flow.•Deep-rooted plants require ...rainfall with higher intensities than farmland.•Deep-rooted plants prevent rainfall from replenishing deep soil water.
Deep soil water (DSW) is of utmost importance for plant growth and groundwater recharge, but the depletion of DSW has been largely reported due to land use change, especially because of the conversion from shallow- to deep-rooted plants. To answer the question whether DSW can be replenished, it is important to reveal the recharge mechanism of DSW under different vegetation types. China’s Loess Plateau has experienced drastic land use change resulting in soil water depletion in deep vadose zones, which provides a good platform to explore these issues. We collected 380 soil samples from five boreholes up to 18 m deep covered by five plants (grassland, apricot, pine, poplar, and peashrub), and determined the contents, stable and radioactive isotopes (δ2H, δ18O, and 3H) of soil water. DSW, defined as soil water below 3 m in this study, was mainly recharged by the wet events in rainy season, especially those with intensities ≥ 50 mm/day, through piston flow. But they were significantly influenced by land use types. Specifically, the forestland and shrubland had lower evaporation effects and higher precipitation offset, and their soil water was recharged by wet events with higher intensities than those under grassland. Nevertheless, the deep-rooted plants substantially reduced recharge rates due to excessive root water uptake, and thus prevented rainfall from replenishing DSW. This study has implications to groundwater sustainability in those regions with limited water resources, drastic land use change, and thick unsaturated zones.
•Implementation costs are a more relevant constraint to afforestation than opportunity costs.•Financial incentives for afforestation are constrained by market access and market prices.•Carbon-neutral ...and food multi-oriented land policies need further exploration.•Collaboration among global carbon markets can enhance CO2 removal efficiency.
Afforestation is a promising nature-based climate solution for mitigating climate change, but it is subject to a complex web of biophysical, cost-benefit, market, and policy processes. Although its biophysical feasibility has been established, the cost, market, and policy constraints that affect climate change mitigation through afforestation are still unclear. Here, we estimate such cost, market, and policy constraints on the basis of biophysical feasibility. Our findings reveal that implementation costs are a more relevant constraint than opportunity costs on mitigating climate change through afforestation. The China Certified Emission Reduction market currently provides only a 0.308 % incentive for climate change mitigation through afforestation, due to market access constraints. The current market prices of China Certified Emission Reduction, China Carbon Emissions Trading Exchange, and Nature Based Carbon Offset in Voluntary Carbon Market constrain 88.15 %, 87.95 %, and 85.75 % of CO2 removal actions through afforestation, compared to the carbon price scenario (US$62.97 tCO2-1) of the EU Emissions Trading System. Moreover, land policy under the scenarios of prohibiting conversion of cultivated land to forest and forest restoration in degraded areas exhibit 8.87–29.59 % and 65.16–74.10 % constraints, respectively, on mitigating climate change through afforestation compared to land-use freedom conversion scenarios from 2020 to 2060. Thus, enhancing the incentive price of CO2 removal, addressing the market access barrier, strengthening cooperation between global carbon markets, and exploring carbon–neutral and food multi-oriented land policies can be valuable sources of mitigation efforts over the next 40 years.
Size, shape, and protein corona play a key role in cellular uptake and removal mechanisms of gold nanoparticles (Au NPs). The 15 nm nanoparticles (NP1), the 45 nm nanoparticles (NP2), and the ...rod‐shaped nanoparticles (NR) enter into cells via a receptor‐mediated endocytosis (RME) pathway. The star‐shaped nanoparticles (NS) adopt not only clathrin‐mediated, but also caveolin‐mediated endocytosis pathways. However, the 80 nm nanoparitcles (NP3) mainly enter into the cells by macropinocytosis pathway due to the big size. Furthermore, the results indicate that the presence of protein corona can change the uptake mechanisms of Au NPs. The endocytosis pathway of NP1, NP2, and NS changes from RME to macropinocytosis pathway and NR changes from RME to clathrin and caveolin‐independent pathway under the non‐fetal bovine serun (FBS)‐coated condition. Both FBS‐coated and non‐FBS‐coated of five types of Au NPs are released out through the lysosomal exocytosis pathway. The size, shape, and protein corona have an effect on the exocytosis ratio and amount, but do not change the exocytosis mechanism. The systematic study of the endocytosis and exocytosis mechanism of Au NPs with different sizes and shapes will benefit the toxicology evaluation and nanomedicine application of Au NPs.
Size, shape, and protein corona play the key role in cellular uptake and removal mechanisms of gold nanoparticles (Au NPs). The uptake mechanisms of five types of Au NPs are different. Size, shape, and protein corona decrease the uptake amount and affect the endocytosis mechanism. However, all of them are released through the lysosomal exocytosis pathway.
•Understanding groundwater recharge is important in arid region with thick vadose zone.•Piston flow recharges groundwater accounting for < 7% of mean annual precipitation.•Deep-rooted plants prevent ...connectivity between unsaturated and saturated zones.•Multiple tracers and methods enhance the understanding of groundwater recharge.
Accurate estimation of groundwater recharge in regions with limited water and thick unsaturated zones is challenging because of the limited water flux. This study aims to employ multiple tracers and methods to investigate the mechanism of groundwater recharge in the thick loess deposits of China. We collected soil samples under different vegetation, unconfined groundwater, and precipitation to determine the water isotopes (δ2H, δ18O, and 3H), chloride (Cl-), nitrate (NO3–). Then, these tracers were employed to estimate recharge rates with methods considering the differences in shallow- and deep-rooted vegetation, as well as those in unsaturated and saturated zones. Results indicated that local precipitation predominantly recharges groundwater through matrix flow at a velocity of 14.5 cm year−1 with the residence time of > 200 years. The recharge rates range from 0 to 37 mm year−1, equivalent to 0–7% of annual average precipitation. However, the deep-rooted vegetation greatly reduced deep drainage compared with shallow-rooted vegetation, which will perturb the current hydraulic connectivity between unsaturated and saturated zones. The multiple tracers and methods can complement each other to enhance the understanding of groundwater recharge mechanisms. The indicated relationship between recharge form and land use suggests the urgency in developing strategies to balance the agroforestry system and water resource sustainability.
In this paper, porous Ni-substituted Co3O4 (ternary NiCo2O4) nanowires are synthesized via a simple microemulsion technique combined with a post thermal treatment. The as-prepared NiCo2O4 exhibits ...porous one-dimensional (1D) nanostructure, which preserves the morphology of the precursor. Moreover, the NiCo2O4 nanowires possess large surface area (53.6m2g−1), pore volume (0.241cm3g−1) and pore size (16.5nm). The porous 1D nanostructures and large surface area have huge benefits for practical applications in supercapacitors. Due to the well-aligned 1D nanowire microstructure and a higher electrical conductivity, these ternary NiCo2O4 electrodes possess high specific capacities of 1197Fg−1 at 1Ag−1 and capacitance retentions of 625Fg−1 at 8Ag−1. After 2000 cycles, the NiCo2O4 electrode can maintain 91.4% of its highest value, which demonstrates its superior cyclic stability performance. Also, the NiCo2O4 electrode exhibits high capacity retention when fast charging. These results show that the porous NiCo2O4 nanowires may be a promising electrode material for high performance electrochemical capacitors.
1D porous NiCo2O4 nanowires with excellent electrochemical performance have been successfully synthesized via a simple microemulsion technique. Display omitted
•Porous NiCo2O4 nanowires were prepared via a simple microemulsion method.•The obtained NiCo2O4 nanowires are assembled by numerous nanoparticles.•The electrode possesses a high specific capacitance and good cycling performance.
•Self-cleanable TiO2/nanocellulose membranes were developed for the first time.•TiO2 nanoparticles in situ generated on the surface of cellulose nanocrystals.•The nanocomposite membrane could ...effectively separate oil/water emulsions.•UV-light induced the improvement of water flux and underwater OCA of membrane.•The membrane could rapidly degrade oil acid under UV-light irradiation.
Emulsified oily wastewater threated to human health seriously, and traditional technologies are unable to separate the emulsion for the small size of oil droplets. Membranes with special wettability are considered as an efficient way for oil/water emulsions separation, but challenges remain in terms of high material costs, complex processing, and easy to be fouled. Herein, novel self-cleanable membranes composed of nanocellulose and TiO2 nanoparticles were developed through a facile and sustainable vacuum-assisted filtration process. TiO2 nanoparticles in situ generated on the surface of tunicate cellulose nanocrystals (TCNC), a kind of nanocellulose, by hydrolysis of titanium oxysulfate. The prepared nanocomposite membrane showed hierarchical architecture, high roughness, superhydrophilicity and underwater oleophobicity. After UV-light irradiation, the resulting membrane exhibited improved underwater oil contact angles and water fluxes, beneficial for the selective oil/water emulsions separation. Importantly, the TiO2/nanocellulose membrane could rapidly degrade contaminant (oleic acid) under UV-light irradiation, suggesting excellent self-cleaning property. This works provided a facile strategy for development of self-cleanable membrane from nanocellulose for oil/water emulsion separation.
•Straw incorporation improved soil aggregation and aggregate-associated organic C content.•Straw incorporation induced the transformation of iron (hydr)oxides in the aggregates.•Straw incorporation ...had different effects on O-alkyl and alkyl C at two experiment sites.•Amorphous Fe (oxyhydr)oxides were positively correlated with soil organic carbon.
The association of soil organic carbon (SOC) with Fe (oxyhydr)oxides is a major SOC stabilization process. However, the effects of straw incorporation on the role of Fe (oxyhydr)oxides in stabilization of SOC composition in aggregates have not been fully explored. The objective of this study was to explore the effect of straw incorporation on the relationship between iron oxides and SOC in soil aggregates in the rice-rape cropping system. In this study, SOC concentration, soil iron fractions and SOC composition in soil aggregates were analyzed. Soil samples were collected under two treatments, conventional tillage without straw incorporation (T) and conventional tillage with straw incorporation (TS), from surface 0–20 cm layer in 10-year and 6-year experiments in Wuxue City (WX) and Jingzhou City (JZ) in China. Compared with the T treatment, the TS treatment increased the proportion of >2 mm aggregates and decreased the proportion of aggregates of other sizes. Except for the 0.25–2 mm aggregates at WX, TS treatment increased the SOC concentration in the aggregates by 36–39% and 20–40% at WX and JZ, respectively, compared with the T treatment. Straw incorporation increased the abundance of alkyl C and the alkyl C/O-alkyl C ratio (an SOC decomposition index), but it slightly decreased the abundance of O-alkyl C at WX, which was opposite to the trend at JZ. Meanwhile, TS treatment increased the abundance of aromatic C in the silt + clay fraction (<0.053 mm) at WX and in aggregates (>0.25 and 0.053–0.25 mm) at JZ. Additionally, straw incorporation decreased the aliphatic C/aromatic C ratio (an SOC complexity index) in the <0.25 mm fraction at WX and in the >0.25 mm fraction at JZ. Furthermore, straw incorporation promoted the accumulation of poorly crystalline (Feo) and organically complexed (Fep) Fe (oxyhydr)oxides in aggregates. Feo was also significantly and positively correlated with the proportion of aromatic C (r = 0.617, P < 0.05) and carbonyl C (r = 0.801, P < 0.05) in the organic matter at WX experimental site. In conclusion, straw incorporation drives the formation of SOC-Fe (oxyhydr)oxides association in aggregates, thus contributing to soil organic carbon stabilization in paddy soils.
•Combined effects of multiple factors were explored for soil water and nitrate.•Land use is the key factor regulating deep soil water and nitrate reservoirs.•Soil water was influenced by magnetic ...susceptibility and sand.•Nitrate was affected by soil water, pH, and soil organic carbon.
Identifying the environmental factors controlling deep soil water and nitrate is important for the sustainability of vegetation and ecosystems. However, the combined effects of multiple factors at varying scales have been poorly understood, especially in those regions with thick vadose zones and deep-rooted plants. The aim of this study is to identify the multivariate controls of water and nitrate in seven > 13 m deep boreholes under different land use types on China’s Loess Plateau. After measuring soil water and nitrate contents, the combined effects of climatic factors (precipitation, temperature, and potential evapotranspiration) and soil properties (soil texture, magnetic susceptibility, pH, EC, and soil organic carbon) were explored by wavelet analysis. Land use is the key factor regulating deep soil water and nitrate reservoirs, with high water deficit and low nitrate accumulation within 0–10 m under non-fertilized forestlands and shrublands. The positive and negative standardized ratios respectively suggested the synergistic and antagonistic relationships of water and nitrate under shallow- and deep-rooted vegetation. As the important agent for nitrate leaching, soil water is influenced by magnetic susceptibility and sand. Furthermore, soil water, pH, EC, and soil organic carbon are individually or simultaneously responsible for nitrate transport and transformation, especially at large scales (> 7.5 m). This study provides novel insights for vegetation and environmental management, and benefits the parameterizing of process-based hydrological and biogeochemical models at regional or global scales, especially in the deep unsaturated zones.
Finger vein recognition methods, as emerging biometric technologies, have attracted increasing attention in identity verification due to their high accuracy and live detection capabilities. However, ...as privacy protection awareness increases, traditional centralized finger vein recognition algorithms face privacy and security issues. Federated learning, a distributed training method that protects data privacy without sharing data across endpoints, is gradually being promoted and applied. Nevertheless, its performance is severely limited by heterogeneity among datasets. To address these issues, this paper proposes a dual-decoupling personalized federated learning framework for finger vein recognition (DDP-FedFV). The DDP-FedFV method combines generalization and personalization. In the first stage, the DDP-FedFV method implements a dual-decoupling mechanism involving model and feature decoupling to optimize feature representations and enhance the generalizability of the global model. In the second stage, the DDP-FedFV method implements a personalized weight aggregation method, federated personalization weight ratio reduction (FedPWRR), to optimize the parameter aggregation process based on data distribution information, thereby enhancing the personalization of the client models. To evaluate the performance of the DDP-FedFV method, theoretical analyses and experiments were conducted based on six public finger vein datasets. The experimental results indicate that the proposed algorithm outperforms centralized training models without increasing communication costs or privacy leakage risks.
