Grain yield and N uptake of maize in response to increased plant density under reduced water and nitrogen supply conditions

The development of modern agriculture requires the reduction of water and chemical N fertilizer inputs.Increasing the planting density can maintain higher yields,but also consumes more of these restrictive resources.However,whether an increased maize density can compensate for the negative effects of reduced water and N supply on grain yield and N uptake in the arid irrigated areas remains unknown.This study is part of a long-term positioning trial that started in 2016.A split-split plot field experiment of maize was implemented in the arid irrigated area of northwestern China in 2020 to 2021.The treatments included two irrigation levels:local conventional irrigation reduced by 20%(W1,3,240 m^(3)ha^(-1))and local conventional irrigation(W2,4,050 m^(3)ha^(-1));two N application rates:local conventional N reduced by 25%(N1,270 kg ha^(-1))and local conventional N(360 kg ha^(-1));and three planting densities:local conventional density(D1,75,000 plants ha^(-1)),density increased by 30%(D2,97,500 plants ha-1),and density increased by 60%(D3,120,000 plants ha^(-1)).Our results showed that the grain yield and aboveground N accumulation of maize were lower under the reduced water and N inputs,but increasing the maize density by 30% can compensate for the reductions of grain yield and aboveground N accumulation caused by the reduced water and N supply.When water was reduced while the N application rate remained unchanged,increasing the planting density by 30% enhanced grain yield by 13.9% and aboveground N accumulation by 15.3%.Under reduced water and N inputs,increasing the maize density by 30% enhanced N uptake efficiency and N partial factor productivity,and it also compensated for the N harvest index and N metabolic related enzyme activities.Compared with W2N2D1,the N uptake efficiency and N partial factor productivity increased by 28.6 and 17.6%under W1N1D2.W1N2D2 had 8.4% higher N uptake efficiency and 13.9% higher N partial factor productivity than W2N2D1.W1N2D2 improved urease activity and nitrate reductase activity by 5.4% at the R2(blister)stage and 19.6% at the V6(6th leaf)stage,and increased net income and the benefit:cost ratio by 22.1 and 16.7%,respectively.W1N1D2 and W1N2D2 reduced the nitrate nitrogen and ammoniacal nitrogen contents at the R6 stage in the 40-100 cm soil layer,compared with W2N2D1.In summary,increasing the planting density by 30% can compensate for the loss of grain yield and aboveground N accumulation under reduced water and N inputs.Meanwhile,increasing the maize density by 30% improved grain yield and aboveground N accumulation when water was reduced by 20% while the N application rate remained constant in arid irrigation areas.

MoS_3 loaded TiO_2 nanoplates for photocatalytic water and carbon dioxide reduction

Photocatalytic water splitting and carbon dioxide reduction provide us clean and sustainable energy resources. The carbon dioxide reduction is also the redemption of the greenhouse effect. MoS/TiOphotocatalysts based on TiOnanoplates have been synthesized via a hydrothermal acidification route for water and carbon dioxide reduction reactions. This facile approach generates well dispersed Mo S3 with low crystallinity on the surface of TiOnanoplates. The as-synthesized MoS/TiOphotocatalyst showed considerable activity for both water reduction and carbon dioxide reduction. The thermal treatment effects of TiO, the loading percentage of MoSand the crystalline phase of TiOhave been investigated towards the photocatalytic performance. TiOnanoplate synthesized through hydrothermal reaction with the presence of HF acid is an ideal semiconductor material for the loading of MoSfor photocatalytic water and carbon dioxide reduction simultaneously in EDTA sacrificial solution.

Promoting the charge separation and photoelectrocatalytic water reduction kinetics of Cu_(2)O nanowires via decorating dual-cocatalysts

Developing high activity and low-cost materials to produce hydrogen by the sustainable way of photoelectrochemical is key to social development.The abundance and inexpensive Cu_(2)O has been received increasing research as its suitable energy level for photocatalytic water reduction.However,the fast charge recombination rate and the sluggish catalytic kinetics are the huge challenges facing the Cu_(2)O photoreduction.Here,the highly reactive Cu_(2)O@C-MoS_(2)photocathode is constructed by depositing dual-cocatalysts of the carbon layer and MoS_(2)nanosheets on Cu_(2)O nanowires to realize efficient water reduction.An impressive carrier concentration of 6.59×10^(23)cm^(-3)is received,which is 2.78 times of the bare Cu_(2)O,resulting in remarkable enhancement in photocurrent density of 3.34 times for the Cu_(2)O@CMoS_(2)photocathode.Moreover,the applied bias photon-to-current conversion efficiency of the bare Cu_(2)O enhanced 4.5 times from 0.16%to 0.72%in the Cu_(2)O@C-MoS_(2)photocathode.The analysis shows that the Cu_(2)O as light absorber,the carbon layer as electron transfer promoter,and MoS_(2)nanosheets as catalytic sites,thus facilitating chrage separation and enhancing catalytic kinetics.This system paves a feasible strategy for designing other photoelectrodes to realize efficient charge separation and high catalytic activity.

The Need for Awareness of Drinking Water Loss Reduction for Sustainable Water Resource Management in Rwanda

Drinking water loss or Non-Revenue Water (NRW) threatens the financial viability of water utilities and sustainable natural water resource management. However, little attention has been paid to quantitative assessment of the spatial distribution of water losses in Rwanda. Therefore, this study focused on the magnitude of water losses, the associated environmental and socio-economic consequences, as well as the potential benefits from water loss reduction in Rwanda. Based on water usage records from the Water and Sanitation Corporation (WASAC) of Rwanda, NRW was calculated for 15 WASAC branches and Provinces, from July 2013 to June 2014, by using the International Water Association (IWA) standard water balance approach. The results highlight an annual NRW of 16,502,198 or 41% of the total water produced, inducing a revenue loss of US$ 8,713,156. In 14 of the 15 WASAC water branches and all Rwandan provinces, the NRW ratios exceed the NRW threshold (10%) recommended by the American Water Works Association (AWWA). Because of the lost revenue, the water facilities may not expand quickly enough to meet the demands of the rapidly growing population. The suggested 50% reduction in NRW would provide additional 8,251,100 m3 of treated water yearly, enough to serve extra 41,925 households or irrigate 661 ha of cropland and save US$ 4,356,579, which would reduce the financial gap in Rwanda’s National Water Improvement Project by more than 24%.

Development of a bismuth-based metal-organic framework for photocatalytic hydrogen production

A novel 3 D bismuth-organic framework(called Bi-TBAPy) single crystal was synthesized by employing 1,3,6,8-tetrakis(p-benzoic acid)pyrene(H4TBAPy) as an organic linker. The study demonstrates that the Bi-TBAPy not only possesses good chemical stability and suitable band edge positions for promising photocatalytic H2 evolution, but it also exhibits a typical ligand-to-metal charge transfer for favorable charge separation. The photocatalytic H2 evolution rates on the as-obtained Bi-TBAPy with different cocatalysts modified were examined with triethanolamine as the sacrificial reagent. Based on this, the hydrogen evolution rate of 140 μmol h-1 g-1 was obtained on the optimized sample with a loading of 2 wt% Pt as a cocatalyst. To the best of our knowledge, this is the first bismuth-based metal-organic framework(MOF) that functions as an effective photocatalyst for photocatalytic water reduction. Our study not only adds a new member to the family of photocatalyst materials, but also reveals the importance of cocatalyst modification in improving photocatalytic activity of MOFs.

Impacts of Mau Forest Catchment on the Great Rift Valley Lakes in Kenya

Remote sensing and GIS applications are being widely used for various projects relating to natural resource management. Forests are very important national assets for economic, environmental protection, social and cultural values and should be conserved in order to realize all these benefits. Kenya’s forests are rapidly declining due to pressure from increased population, technological innovation, urbanization human development and other land uses. Mau forest is one of the major forests in Kenya that is a catchment area for many Great Rift Valley lakes within the country and faces a lot of destruction. Continued destruction of the Mau forest will cause catastrophic environmental damage, resulting in massive food crises and compromising the livelihoods of millions of Kenyans, and the possible collapse of the tourism industry. The purpose of this research was to investigate the relationship between the increasing rate of deforestation and the reduction of the volumes of water in the neighboring lakes between the years 1989 to 2010. Satellite images from Landsat-5 Thematic Mapper (TM) and Landsat-7 Enhanced Thematic Mapper (ETM+) were used for the detection of changes in the Mau forest and the dynamics of the neighboring water bodies that included lakes: Naivasha, Baringo, Nakuru, Elementaita and Bogoria. The research showed that from a period of 1989 to 2010 Mau forest has been decreasing due to deforestation and the water bodies have irregular dynamics in that, from 1989 to 2000, there was rise in the volume of water, this is attributed to the El Nino rains experienced in the country during the year 1997 and 1998. But between 2000 and 2010 the volume decreased as the forest is also decreasing. It is recommended that the government creates awareness to sensitize the public on the importance of such forests as catchment areas in Kenya.

Assessing ability of a wet swale to manage road runoff：A case study in Hefei, China

The ability of a wet swale,constructed in an area of poor soil permeability,to manage runoff from a roadway was monitored through 27 storm events over a period of 8 months.During the monitoring period,the wet swale reduced the total runoff volume by 50.4%through exfiltration and evapotranspiration.The wet swale significantly decreased the influent pollutant concentrations,and the effluent mean concentrations of total suspended solids,total phosphorus,chemical oxygen demand,ammonium,oxidized nitrogen,and total nitrogen in the effluent were 31 mg/L,0.10 mg/L,29 mg/L,0.52 mg/L,0.35 mg/L and1.28 mg/L,respectively.Pollutant loads were also substantially reduced from 70%to 85%.Plant uptake played an important role in nutrient removal in the wet swale.Approximately half of the nitrogen(53.8%)and phosphorus(51.5%)that entered the wet swale was incorporated in above-ground plants.It is shown that wet swales are useful for managing runoff from roads in areas of poor soil permeability.

Water-trapping and drag-reduction effects of fish Ctenopharyngodon idellus scales and their simulations

In the last decades, surface drag reduction has been re-emphasized because of its practical values in engineering applications,including vehicles, aircrafts, ships, and fuel pipelines. The bionic study of drag reduction has been attracting scholars' attentions. Here, it was determined that the delicate microstructures on the scales of the fish Ctenopharyngodon idellus exhibit remarkable drag-reduction effect. In addition, the underlying drag-reduction mechanism was carefully investigated. First,exceptional morphologies and structures of the scales were observed and measured using a scanning electron microscope and3-dimensional(3D) microscope. Then, based on the acquired data, optimized 3D models were created. Next, the mechanism of the water-trapping effect of these structures was analyzed through numerical simulations and theoretical calculations. It was determined that there are many microcrescent units with certain distributions on its surface. In fact, these crescents are effective in generating the "water-trapping" effect and forming a fluid-lubrication film, thus reducing the skin friction drag effectively.Contrasting to a smooth surface, the dynamics finite-element analysis indicated that the maximum drag-reduction rate of a bionic surface is 3.014% at 0.66 m/s flow rate. This study can be used as a reference for an in-depth analysis on the bionic drag reduction of boats, underwater vehicles, and so forth.

Fluid–solid coupling analysis of rock pillar stability for concealed karst cave ahead of a roadway based on catastrophic theory

In order to study the mechanism of water inrush from a concealed, confined karst cave, we established a fluid–solid coupling model of water inrush from a concealed karst cave ahead of a roadway and a strength reduction method in a rock pillar for preventing water inrush based on catastrophic theory. Fluid–solid coupling effects and safety margins in a rock pillar were studied. Analysis shows that rock pillar instability, exerted by disturbance stress and seepage stress, is the process of rock pillar catastrophic destabilization induced by nonlinear extension of plastic zones in the rock pillar. Seepage flow emerges in the rock pillar for preventing water inrush, accompanied by mechanical instability of the rock pillar. Taking the accident of a confined karst cave water-inrush of Qiyi Mine as an example, by studying the safety factor of the rock pillar and the relationship between karst cave water pressure and thickness of the rock pillar,it is proposed that rock pillar thickness with a safety factor equal to 1.5 is regarded as the calculated safety thickness of the rock pillar, which should be equal to the sum of the blasthole depth, blasting disturbance depth and the calculated safety thickness of the rock pillar. The cause of the karst water inrush at Qiyi Mine is that the rock pillar was so small that it did not possess a safety margin. Combining fluid–solid coupling theory, catastrophic theory and strength reduction method to study the nonlinear mechanical response of complicated rock engineering, new avenues for quantitative analysis of rock engineering stability evaluation should be forthcoming.

A method for recovery of iron,titanium,and vanadium from vanadium-bearing titanomagnetite

An innovative method for recovering valuable elements from vanadium-bearing titanomagnetite is proposed. This method involves two procedures： low-temperature roasting of vanadium-bearing titanomagnetite and water leaching of roasting slag. During the roasting process, the reduction of iron oxides to metallic iron, the sodium oxidation of vanadium oxides to water-soluble sodium vanadate, and the smelting separation of metallic iron and slag were accomplished simultaneously. Optimal roasting conditions for iron/slag separation were achieved with a mixture thickness of 42.5 mm, a roasting temperature of 1200°C, a residence time of 2 h, a molar ratio of C/O of 1.7, and a sodium carbonate addition of 70 wt%, as well as with the use of anthracite as a reductant. Under the optimal conditions, 93.67% iron from the raw ore was recovered in the form of iron nugget with 95.44% iron grade. After a water leaching process, 85.61% of the vanadium from the roasting slag was leached, confirming the sodium oxidation of most of the vanadium oxides to water-soluble sodium vanadate during the roasting process. The total recoveries of iron, vanadium, and titanium were 93.67%, 72.68%, and 99.72%, respectively.

Fly Ash for Removal of Contaminates from Coal Mine Drainage

In this study, fly ash obtained from a coal burning power plant was used to remove iron from coal mine drainage as well as raising the pH to acceptable limits for natural water using column chromatography. The results of this study indicate that fly ash has the ability to completely remove iron and reduce acidity of coal mine water drainage. This approach can be extended to include other contaminants such as magnesium.

An experimental investigation on sound transmission loss and vibration reduction of a vessel in water

Experimental results of sound transmission loss in a range of frequency through bubbly curtains were obtained, where the air content was in a wide range by means of varying pressure differences and the diameters of the pores of bubble-produce apparatus . Vibration reduction of a vessel in water due to the bubbly curtain was found.

The influence of patterned microporous layer on the proton exchange membrane fuel cell performances

The ordered membrane electrode assembly(MEA)has gained much attention because of its potential in improving mass transfer.Here,a comprehensive study was conducted on the influence of the patterned microporous layer(MPL)on the proton exchange membrane fuel cell performances.When patterned MPL is employed,grooves are generated between the catalyst layer and the gas diffusion layer.It is found that the grooves do not increase the contact resistance,and it is beneficial for water retention.When the MEA works under low humidity scenarios,the MEA with patterned MPL illustrated higher performance,due to the reduced inner resistance caused by improved water retention,leading to increased ionic conductivity.However,when the humidity is higher than 80%or working under high current density,the generated water accumulated in the grooves and hindered the oxygen mass transport,leading to a reduced MEA performance.

Tetrafunctional Cu2S thin layers on Cu2O nanowires for efficient photoelectrochemical water splitting

Photoelectrochemical （PEC） water splitting by photocathodes based on p-type semiconductors is a promising process for direct and efficient hydrogen generation. The identification of ideal photocathode materials with a high photoconversion efficiency and long-term stability is still a significant challenge. Herein, we propose a new photocathode consisting of Cu2S-coated Cu2O nanowires （NWs） supported on a three-dimensional porous copper foam. The Cu2S thin layer is generated in situ on the surface of the Cu2O NWs and has four functions： （1） sensitizer, with a band gap of 1.2 eV, for extending the range of optical absorption into the near-infrared region; （2） electron trapper, with appropriate energy level alignment to Cu2O, for achieving effective electron transfer and trapping; （3） electrocatalyst, with excellent electrocatalytic activity for the hydrogen evolution reaction; and （4） protector, preventing direct contact between Cu2O and the electrolyte in order to significantly increase the stability. A photocathode based on the tetrafunctional Cu2S-coated Cu2O NWs exhibits significantly enhanced PEC performance and remarkably improved long-term stability under illumination. The present strategy, based on the in situ generation of multifunctional layers, opens a new avenue for the rational design of photocathodes for PEC water reduction.

Sintered Ore Sprayed by Acid and Alkaline Waste Water Resulted From Cold Rolling

In order to prevent the powdering of a sintered ore from influencing the smooth operation of a blast furnace,the conventional way to deal with it is that the CaCl2 solution is prepared by tap water,and then the solution is sprayed onto the sintered ore for improving its RDI（low temperature reduction degradation index）.The CaCl2 solution prepared by adding acid and alkaline waste water resulted from cold rolling is sprayed onto the sintered ore to improve its RDI.The values of RDI＋6.3 and RDI＋3.15 of the sintered ore which is sprayed by the CaCl2 solution with the CaCl2 concentration of 3.5%（mass percent） are increased by 17.5% and 11.63%,but the index of RDI-0.5 is decreased by 3.1% when the spraying amount of the solution is making up 0.5% of the total sintered ore sprayed in comparison with those of the sintered ore which is not sprayed by using the CaCl2 solution.Experimental results show that after the CaCl2 solutions prepared by adding the acid and alkaline waste water are sprayed on the sintered ore,RDI of the ore can be remarkably improved and therefore another way for recycling acid and alkaline waste water can be available,by which both cost for treating waste water and cost for producing a sintered ore can be decreased and environment is free of pollution by harmful substances in the waste water.

Magnetic and electro-catalytic properties of a copper complex with 2-(pyridylmethyl)amino-N,N-bis(2-methylene-4,6-difluorophenol)

A new material for both magnetic coupling and electrocatalytic hydrogen generation based on a copper complex,[（HL）CuCl-CuCl（HL）]HCl 1 is prepared by the reaction of 2-（pyridylmethyl）amino-N,N-bis（2-methylene-4,6-difluorophenol）（H2L） and CuCl2·2H2O.In solid,complex 1 is built from two copper units（[（HL）CuCl]）,and exhibits an antiferromagnetic exchange interaction between copper（Ⅱ） ions（J=-160cm^-1）.In liquid,1 can electrocatalyze hydrogen generation both from acetic acid with a turnover frequency（TOF） of 16.3 moles of hydrogen per mole of catalyst per hour at an overpotential（OP）of 941.6 mV（in DMF）,and a neutral buffer with a TOF of 1415.6 moles of hydrogen per mole of catalyst per hour at an OP of 787.6 mV.

The effect of surface electronic structures of Au/TiO_2 on sonophotochemical reactions

Sonophotocatalysis combines ultrasonic and light irradiations to drastically boost the chemical reaction rate and has attracted many interests for its potential applications in the environmental remediation and protection. However, it still remains unclear whether the light irradiation could couple with the ultrasound to prompt the sonophotocatalytic process. Here, we selectively excited the TiO2 and Au to manipulate the electronic structures of Au/TiO2 and studied their influence in sonophotocatalytic water（H2 O） reduction. Surprisingly, no significant increase of the hydrogen（H2） production rate was observed under either the UV light irradiation or the visible light irradiation, suggesting that the change in electronic structures of Au/TiO2 does not prompt the generation of free radicals under sonication and the reaction is dominated by the recovery of active sites through ultrasound. Our findings established an indepth understanding of the origin of the enhanced catalytic activity in sonophotocatalysis.