Soil Water Movement and Groundwater Recharge Under Different Land Uses in a Flood-Irrigated Area.

The water shortage in agriculture area in China requires to reduce the consumption of excessive water in flood irrigation. Therefore, the dynamics of soil water regime is needed to investigate and water-saving irrigation is necessary to alleviate water shortage. This study investigated the impact of flood irrigation on soil water movement and recharge to groundwater in the Yellow River irrigation area of Yinchuan Plain, China. Combining comprehensive field observation, stable isotopic techniques and water balance simulation, we described the soil water mechanism in vadose zone covered with bare soil in 2019 and planted with maize in 2020. The soil layers affected by precipitation infiltration and evaporation were mainly 0-50 cm, while the soil influenced by irrigation was the entire profile in the mode of piston flow. The maize root took up the soil water up to the depth of 100 cm during the tasseling period. The infiltration and capillary rise in 2020 were similar with those in 2019. However, the total deep percolation was 156.5 mm in 2020 which was about 50% of that in 2019 because of the maize root water uptake. The leakage of ditch water was the major recharge resource of groundwater for the fast water table rise. Precise irrigation is required to minimize deep percolation and leakage of ditch water and reduce excessive unproductive evapotranspiration. Therefore, understanding the soil water movement and groundwater recharge is critical for agricultural water management to improve irrigation efficiency and water use efficiency in arid regions.

Health risk assessment of groundwater nitrogen pollution in Yinchuan plain.

High nitrogen concentration of groundwater poses a threat to human health. This study evaluated the potential health risk of nitrogen pollution in Yinchuan plain by geostatistical analysis and triangular stochastic model considering different land use types, and identified the uncertainties of the parameters. 163 samples were collected from groundwater wells in different land use types. The results show that the concentration of NO3--N ranges from 0.059 to 450 mg/L, with an average of 22.439 mg/L. Approximately 32% of the samples exceed Grade III threshold (20 mg/L of N). The concentration of NH4+-N ranges from 0.011 to 11 mg/L, with an average of 0.456 mg/L. The concentration of NO2--N ranges from 0.003 to 9.09 mg/L The NO3--N and NH4+-N concentration in the groundwater of the unutilized land use is significantly lowest among all the land types. The concentration of nitrogen is highest in farmland use. The ranking of non-carcinogenic risk under different land types for infants, children, adult males and females is: farmland use > residential land use> unutilized land use. The non-carcinogenic risk value of farmland use is three times as much as that of the residential land use. Drinking groundwater can be potentially harmful to human health, and nitrogen pollutants pose an even greater threat to infant. At the same time, considering the impact of different land use types on groundwater would avoid overestimating or underestimating regional risk value. Triangular stochastic model is more sensitive to data changes and can reduce uncertainty. The contribution rate of nitrate concentration to risk is more than 83%, indicating that random sampling is needed to improve the reliability of evaluation results. The research results of this study will provide a new way to solve the uncertainty in groundwater security management.

One-Step Route to Fe2O3 and FeSe2 Nanoparticles Loaded on Carbon-Sheet for Lithium Storage.

Iron-based anode materials, such as Fe2O3 and FeSe2 have attracted widespread attention for lithium-ion batteries due to their high capacities. However, the capacity decays seriously because of poor conductivity and severe volume expansion. Designing nanostructures combined with carbon are effective means to improve cycling stability. In this work, ultra-small Fe2O3 nanoparticles loaded on a carbon framework were synthesized through a one-step thermal decomposition of the commercial C15H21FeO6 [Iron (III) acetylacetonate], which could be served as the source of Fe, O, and C. As an anode material, the Fe2O3@C anode delivers a specific capacity of 747.8 mAh g-1 after 200 cycles at 200 mA g-1 and 577.8 mAh g-1 after 365 cycles at 500 mA g-1. When selenium powder was introduced into the reaction system, the FeSe2 nano-rods encapsulated in the carbon shell were obtained, which also displayed a relatively good performance in lithium storage capacity (852 mAh g-1 after 150 cycles under the current density of 100 mA·g-1). This study may provide an alternative way to prepare other carbon-composited metal compounds, such as FeNx@C, FePx@C, and FeSx@C, and found their applications in the field of electrochemistry.

Construction of direct Z-scheme system for enhanced visible light photocatalytic activity based on Zn0.1Cd0.9S/FeWO4 heterojunction.

A novel direct Z-scheme Zn0.1Cd0.9S/FeWO4 (ZCS/FW) photocatalyst was prepared by a facile calcination method. The photocatalytic performance was investigated by photodegradation rhodamine B (RhB) and photocatalytic production hydrogen (H2) under visible light irradiation. Compared with the pure ZCS, the ZCS/FW composites show considerably improved photocatalytic activity for degradation RhB and production H2. Noticeably, the ZCS/FW with 7 wt% of FW exhibits optimal photocatalytic activity with the H2 evolution rate of 34.6 mmol g-1 h-1 and photodegradation of about 98% of RhB solution (10 mg l-1) in 60 min. These outstanding photocatalytic performances were found to be ascribed to the formation of direct Z-scheme heterojunction, resulting in effective separation and transfer of photogenerated charge carriers. Moreover, active species trapping experiments further demonstrate the electrons transfer followed Z-scheme system, and the photocatalytic mechanism was proposed.