Microfluidic-oriented synthesis of enriched iridium nanodots/carbon architecture for robust electrocatalytic nitrogen fixation

Electrocatalytic nitrogen reduction reaction(NRR)is considered as a promising candidate to achieve ammonia synthesis because of clean electric energy,moderate reaction condition,safe operating process and harmless by-products.However,the chemical inertness of nitrogen and poor activated capacity on catalyst surface usually produce low ammonia yield and faradic efficiency.Herein,the microfluidic technology is proposed to efficiently fabricate enriched iridium nanodots/carbon architecture.Owing to in-situ co-precipitation reaction and microfluidic manipulation,the iridium nanodots/carbon nanomaterials possess small average size,uniform dispersion,high conductivity and abundant active sites,producing good proton activation and rapid electrons transmission and moderate adsorption/desorption capacity.As a result,the as-prepared iridium nanodots/carbon nanomaterials realize large ammonia yield of 28.73 μg h^(-1) cm^(-2) and faradic efficiency of 9.14%in KOH solution.Moreover,the high ammonia yield of 11.21 μg h^(-1) cm^(-2) and faradic efficiency of 24.30%are also achieved in H_(2)SO_(4) solution.The microfluidic method provides a reference for large-scale fabrication of nano-sized catalyst materials,which may accelerate the progress of electrocatalytic NRR in industrialization field.

Magnesium fertilizer application increases peanut growth and pod yield under reduced nitrogen application in southern China

This study investigated the effect of magnesium application on peanut growth and yield under two nitrogen(N)application rates in acidic soil in southern China.The chlorophyll content,net photosynthetic rate and dry matter accumulation of the N-sensitive cultivar decreased under reduced N treatments,whereas no effect was observed on the relevant indicators in the N-insensitive variety GH1026.Mg application increased the net photosynthetic rate by increasing the expression of genes involved in chlorophyll synthesis and Rubisco activity in the leaves during the pegging stage under 50%N treatment,while no effect on the net photosynthetic rate was observed under the 100%N treatment.The rate of dry matter accumulation at the early growth stage,total dry matter accumulation and pod yield at harvest increased after Mg application under 50%N treatment by increasing the transportation of assimilates from stems and leaves to pods in both peanut varieties,whereas no effect was found under 100%N treatment.Moreover,Mg application increased the NUE under 50%N treatment.No improvement of NUE in either peanut variety was found under 100%N treatment,while Mg application under the 50%N treatment can obtain a higher economic benefit than the 100%N treatment.In acidic soil,application of 307.5 kg ha^(-1)of Mg sulfate fertilizer under 50%reduced nitrogen application is a suitable fertilizer management measure for improving carbon assimilation,NUE and achieve high peanut yields in southern China.

Plasma nitrogen fixation system with dual-loop enhancement for improved energy efficiency and its efficacy for lettuce cultivation

Plasma nitrogen fixation(PNF)has been emerging as a promising technology for greenhouse gasfree and renewable energy-based agriculture.Yet,most PNF studies seldom address practical application-specific issues.In this work,we present the development of a compact and automatic PNF system for on-site agricultural applications.The system utilized a gliding-arc discharge as the plasma source and employed a dual-loop design to generate NO_(x)from air and water under atmospheric conditions.Experimental results showed that the system with a dualloop design performs well in terms of energy costs and production rates.Optimal operational parameters for the system were determined through experimentation,resulting in an energy cost of 13.9 MJ mol^(-1)and an energy efficiency of 16 g kWh^(-1)for NO_(3)^(-)production,respectively.Moreover,the concentration of exhausted NO_(x)was below the emission standards.Soilless lettuce cultivation experiments demonstrated that NO_(x)^(-)produced by the PNF system could serve as liquid nitrate nitrogen fertilizer.Overall,our work demonstrates the potential of the developed PNF system for on-site application in the production of green-leaf vegetables.

Sustainable nitrogen fixation by bubble discharge plasma:Performance optimization and mechanism

Sustainable nitrogen fixation driven by renewable energy sources under mild conditions has been widely sought to replace the industrial Haber-Bosch process.The fixation of nitrogen in the form of NO_(x)^(-)and NH_4^(+)into aqueous solutions using electricity-driven gas-liquid discharge plasma is considered a promising prescription.In this paper,a scalable bubble discharge excited by nanosecond pulse power is employed for nitrogen fixation in the liquid phase.The nitrogen fixation performance and the mechanisms are analyzed by varying the power supply parameters,working gas flow rate and composition.The results show that an increase in voltage and frequency can result in an enhanced NO_(3)^(-)yield.Increases in the gas flow rate can result in inadequate activation of the working gas,which together with more inefficient mass transfer efficiencies can reduce the yield.The addition of O_(2) effectively elevates NO_(3)^(-)production while simultaneously inhibiting NH_4^(+) production.The addition of H_(2)O vapor increases the production of OH and H,thereby promoting the generation of reactive nitrogen and enhancing the yield of nitrogen fixation.However,the excessive addition of O_(2) and H_(2)O vapor results in negative effect on the yield of nitrogen fixation,due to the significant weakening of the discharge intensity.The optimal nitrogen fixation yield was up to 16.5 μmol/min,while the optimal energy consumption was approximately 21.3 MJ/mol in this study.Finally,the mechanism related to nitrogen fixation is discussed through the optical emission spectral(OES) information in conjunction with the simulation of energy loss paths in the plasma by BOLSIG+.The work advances knowledge of the effect of parameter variations on nitrogen fixation by gas-liquid discharge for higher yield and energy production.

Assessment of Nitrogen Fixation, Uptake, and Leaching in Maize/Soybean Intercropping System at Varied Soil Depths and under Phosphorus Application in Chinese Agricultural Settings

The study of Nitrogen fixation, uptake, and leaching at different soil depths in the co-cultivation of maize and soybean under phosphorus fertilization is important for sustainable agriculture. This study was conducted in Quzhou, Hebei Province, China, with MC812 maize and Jidou12 soybean varieties. Soil samples were taken from each plot to create a composite sample. The results show that nitrogen concentration varies at different depths and is higher in all treatments between 40 and 100 cm. Incorporating intercropping of maize and soybeans into farming practices can lead to more sustainable and environmentally friendly agriculture in China.

Facile preparation of Ag_(2)S/KTa_(0.5)Nb_(0.5)O_(3) heterojunction for enhanced performance in catalytic nitrogen fixation via photocatalysis and piezo-photocatalysis

In this work, a novel heterojunction composite Ag_(2)S/KTa_(x)Nb_(1-x)O_(3)was designed and synthesized through a combination of hydrothermal and precipitation procedures. The Ta/Nb ratio of the KTa_(x)Nb_(1-x)O_(3)and the Ag_(2)S content were optimized. The best 0.5% Ag_(2)S/KTa_(0.5)Nb_(0.5)O_(3)(KTN) sample presents an enhanced photocatalytic performance in ammonia synthesis than KTN and Ag_(2)S. Under simulated sunlight, the NH_(3)generation rate of 0.5% Ag_(2)S/KTN reaches 2.0 times that of pure KTN. Under visible light, the reaction rate ratio of the two catalysts is 6.0.XRD, XPS, and TEM analysis revealed that Ag2S was intimately decorated on the KTN nanocubes surface, which promoted the electron transfer between the two semiconductors. The band structure investigation indicated that the Ag_(2)S/KTN heterojunction established a type-Ⅱ band alignment with intimate contact, thus realizing the effective transfer and separation of photogenerated carriers. The change in charge separation was considered as the main reason for the enhanced photocatalytic performance. Interestingly, the Ag_(2)S/KTN composite exhibited higher NH3generation performance under the combined action of ultrasonic vibration and simulated sunlight. The enhanced piezo-photocatalytic performance can be ascribed that the piezoelectric effect of KTN improved the bulk separation of charge carriers in KTN. This study not only provides a potential catalyst for photocatalytic nitrogen fixation but also shows new ideas for the design of highly efficient catalysts via semiconductor modification and external field coupling.

Optimum Application Rate of Nitrogen in Summer Peanut in Southern Shandong Area

[Objectives]To study the effect of nitrogen(N)on the growth demand of summer peanuts under a certain level of phosphorus and potassium fertilizers,and to carry out experiments on nitrogen fertilizer control of summer peanuts.[Methods]Four treatments were set up in the experiment:no-nitrogen plot(N 0P_(4)K_(4)),optimized nitrogen plot(N_(7)P_(4)K_(4)),70%optimized nitrogen plot(N_(5)P_(4)K_(4)),130%optimized nitrogen plot(N 9P 4K 4),repeated 3 times,and arranged in random blocks.The area of the plot was 42 m^(2),ridges were set between the plots,and protective rows of more than 1 m were set around the experimental site.The types of fertilizers were urea,superphosphate,and imported potassium chloride,and the variety of peanuts was Linhua 5.Except for the level of fertilization,other agricultural operations were the same,and soil sampling tests,field records,and yield testing were carried out according to the requirements of the plan.[Results]On the basis of 60 kg/ha of phosphorus and potassium fertilizer application,the optimum economical fertilizer application rate and the highest application rate of pure nitrogen were about 115.20 and 131.25 kg/ha,respectively.[Conclusions]This study is expected to provide a certain basis for the high-quality and high-yield summer peanuts in southern Shandong area.

Oxygen defect modulating the charge behavior in titanium dioxide for boosting photocatalytic nitrogen fixation performance

Extremely high-temperature and high-pressure requirement of Haber-Bosch process motivates the search for a sustainable ammonia synthesis approach under mild conditions.Photocatalytic technology is a potential solution to convert N2 to ammonia.However,the poor light absorption and low charge carrier separation efficiency in conventional semiconductors are bottlenecks for the application of this technology.Herein,a facile synthesis of anatase TiO_(2)nanosheets with an abundance of surface oxygen vacancies(TiO_(2)-OV)via the calcination treatment was reported.Photocatalytic experiments of the prepared anatase TiO_(2)samples showed that TiO_(2)-OV nanosheets exhibited remarkably increased ammonia yield for solar-driven N2 fixation in pure water,without adding any sacrificial agents.EPR,XPS,XRD,UV-Vis DRS,TEM,Raman,and PL techniques were employed to systematically explore the possible enhanced mechanism.Studies revealed that the introduced surface oxygen vacancies significantly extended the light absorption capability in the visible region,decreased the adsorption and activation barriers of inert N2,and improved the separation and transfer efficiency of the photogenerated electronhole pairs.Thus,a high rate of ammonia evolution in TiO_(2)-OV was realized.This work offers a promising and sustainable approach for the efficient artificial photosynthesis of ammonia.

Estimation of Biological Nitrogen Fixation Capacity by Sugarcane Using 15N

[ Objective] The study aimed to reveal the biological nitrogen fixation capacity by sugarcane from Brazil under the ecological conditions of Guangxi, and to provide reference for study on the biological nitrogen fixation capacity by sugarcane and related generalization and application. [ Method] The ^15N isotopic fertilizer was solely applied on plants of three sugarcane cultivars planted in greenhouse with no other fertilizer forms applied, meanwhile virus-free stem seedling was regarded as control, to measure their biological nitrogen fixation capacity using ^15N isotope. [ Result ] The nitrogen fixation rate of B8 from Brazil reached 26.91%, while Guitang 11 and RIC16 presented no or poor nitrogen fixation capacity. [ Conclusion] The sugarcane eultivar B8 from Brazil showed some nitrogen fixation capacity under the ecological conditions of Guangxi.

Timing and splitting of nitrogen fertilizer supply to increase crop yield and efficiency of nitrogen utilization in a wheat–peanut relay intercropping system in China

Agronomically optimizing the timing and rates of nitrogen(N) fertilizer application can increase crop yield and decrease N loss to the environment. Wheat(Triticum aestivum L.)–peanut(Arachis hypogaea L.) relay intercropping systems are a mainstay of economic and food security in China. We performed a field experiment to investigate the effects of N fertilizer on N recovery efficiency, crop yield, and N loss rate in wheat–peanut relay intercropping systems in the Huang-Huai-Hai Plain, China during 2015–2017. The N was applied on the day before sowing, the jointing stage(G30) or the booting stage(G40) of winter wheat, and the anthesis stage(R1) of peanut in the following percentage splits: 50-50-0-0(N1), 35-35-0-30(N2), and 35-0-35-30(N3), using 300 kg N ha-1, with 0 kg N ha-1(N0) as control. ^(15)N-labeled(20.14 atom %) urea was used to trace the fate of N in microplots. The yields of wheat and peanut increased by 12.4% and 15.4% under the N2 and N3 treatments, relative to those under the N1 treatment. The ^(15)N recovery efficiencies( ^(15)NRE) were 64.9% and 58.1% for treatments N2 and N3, significantly greater than that for the N1 treatment(45.3%). The potential N loss rates for the treatments N2 and N3 were23.7% and 7.0%, significantly lower than that for treatment N1(30.1%). Withholding N supply until the booting stage(N3) did not reduce the wheat grain yield; however, it increased the N content derived from ^(15)N-labeled urea in peanuts, promoted the distribution of ^(15)N to pods, and ultimately increased pod yields in comparison with those obtained by topdressing N at jointing stage(N2). In comparison with N2, the N uptake and N recovery efficiency(NRE) of N3 was increased by 12.0% and 24.1%,respectively, while the apparent N loss decreased by 16.7%. In conclusion, applying N fertilizer with three splits and delaying topdressing fertilization until G40 of winter wheat increased total grain yields and NRE and reduced N loss. This practice could be an environment-friendly N management strategy for wheat–peanut relay intercropping systems in China.

“Biological Nitrogen Fixation” Book Summary

Biological nitrogen fixation is a very valuable alternative to nitrogen fertilizer. This process will be discussed in the “Biological Nitrogen Fixation” book. A wide array of free-living and associative nitrogen fixing organisms (diazotrophs) will be covered. The most extensively studied and applied example of biological nitrogen fixation is the symbiotic interaction between nitrogen fixing “rhizobia” and legume plants. While legumes are important as major food and feed crops, cereals such as wheat, maize and rice are the primary food crops, but do not have this symbiotic nitrogen fixing interaction with rhizobia. It has thus been a “holy grail” to transfer the ability to fix nitrogen to the cereals and this topic will be also addressed in these books.

Nitrogen Dioxide Fumigation for Microbial Control on Unshelled Peanuts*

Stored peanuts often need treatments to control microbial infections as well as insects to maintain postharvest quality. Nitric oxide (NO) is a recently discovered fumigant for postharvest pest control. NO fumigation must be conducted under ultralow oxygen condition to preserve NO and always contains NO2 due to NO reaction with oxygen and NO2 has antimicrobial property. Therefore, NO fumigation has potential to control both pests and pathogens. In this study, we evaluated antimicrobial effects of NO2 fumigation on unpasteurized unshelled peanuts. Peanuts were fumigated with 0.3%, 1.0%, and 3.0% NO2 for three days at 25˚C by injecting NO gas into glass jars to react with O2 in the atmosphere. After fumigation, wash-off microbial samples were collected from intact peanut samples and, then, cracked open peanut samples with non-selective tryptic soy broth medium. The wash-off samples were then diluted with both the non-selective medium and a fungal-selective potato dextrose broth medium and were tested on GreenLight™ rapid enumeration test based on oxygen depletion on culture medium. All three NO2 fumigation treatments showed significant antibacterial and antifungal effects on intact peanuts as well as on cracked peanuts with complete inhibition with 3.0% NO2. Fumigation did not have obvious effects on appearance of skinned peanut kernels. These results suggested that NO2 fumigation has potential to control microbes on stored products, and NO fumigation with the combination of NO and NO2 has potential to control both insects and microbes on stored products.

Boron Nitride Quantum Dots/Ti_(3)C_(2)T_(x)-MXene Heterostructure For Efficient Electrocatalytic Nitrogen Fixation

Electrocatalytic N_(2) fixation through N_(2) reduction reaction(NRR)has been regarded as a promising route for sustainable NH_(3) synthesis,while exploring high-performing NRR catalysts is pivotal yet challenging.Herein,BN quantum dots/Ti_(3)C_(2)T_(x)-MXene(BNQDs/Ti_(3)C_(2)T_(x))heterostructure is demonstrated as an efficient and durable NRR catalyst,exhibiting a high NH_(3) yield of 52.8±3.3μg h^(-1) mg^(-1) with an FE of 19.1±1.6%at0.4 V(vs.RHE),which stand at the high level among all reported BN-and MXene-based NRR catalysts.Theoretical computations reveal that the electronic interactions between BNQDs and Ti_(3)C_(2)T_(x) enrich the electron density of B atoms at the heterointerface and endow them with enhanced electron-donating capability for N_(2) activation and protonation.Meanwhile,the decorated BNQDs can block the active sites of Ti_(3)C_(2)T_(x) for hydrogen evolution,rendering a high N_(2)-to-NH_(3) selectivity.

Physiological Characteristics of Nitrogen Nutrition in Peanut and Efficient Nitrogen Application Technology

Nitrogen plays a very important role in peanut nutrition and fertilization.For peanuts,the nitrogen nutrition comes from root nodules,soil and fertilizer,which are separately referred to as root nodule nitrogen,soil nitrogen and fertilizer nitrogen.The research obtained following findings.(ⅰ)The nitrogen supply ratio of the three nitrogen sources for peanut is about 5∶3∶2.There are significant differences in the nitrogen supply capacity of the three nitrogen sources.The root nodules have the largest variation in nitrogen fixation and have a high potential for development.Nitrogen fixation in root nodules is closely related to carbon metabolism indicators such as photosynthesis in peanut leaves.Phosphorus application could increase the accumulation of three nitrogen sources,and the increase in nodule nitrogen accumulation is greater than that of soil nitrogen and fertilizer nitrogen.(ⅱ)Nitrogen fertilizer has a significant effect on nitrogen nutrition of peanuts.Different forms of nitrogen fertilizers,such as amide nitrogen,ammonium nitrogen,nitrate nitrogen and mixed ammonium nitrate nitrogen,have significant effects on nitrogen metabolism and nitrogen accumulation in peanuts.Amide nitrogen fertilizer is beneficial to improving the activity of enzymes related to nitrogen metabolism and nitrogen accumulation.Controlled-release fertilizer can significantly increase the content of soluble protein and improve the activities of NRase,GDH,GS,GPT,etc.in roots and leaves at the pod setting and mature stages of peanuts,which is favorable for delaying the plant senescence and increasing the yield of peanuts.Mixed application of common nitrogen fertilizer and slow-release fertilizer can increase the soil nitrate nitrogen level at the later growth stage,which is beneficial to the development of the root system at the later stage of growth,increasing the distribution ratio of nitrogen in the pods,and also favorable for increasing the yield and nitrogen utilization rate.(ⅲ)Increasing the ploughing depth,improving fertilization methods,selecting nitrogen-efficient varieties,paying attention to foliar topdressing,and adopting fertilizer-water integrated cultivation are conducive to increasing the nitrogen utilization rate of peanuts,reducing the amount of nitrogen fertilizers,accordingly saving costs,increasing efficiency and realizing sustainable development of agricultural production.

Effects of Different Proportions of Controlled Release Urea and Ordinary Urea on Peanut Yield

[Objectives]To study the effects of different proportions of controlled release urea and ordinary urea on peanut yield.[Methods]A total of 5 treatments were set up according to different proportions of controlled release urea and ordinary urea,randomly arranged in blocks and repeated 3 times.[Results]The test results of field districts showed that different proportions of controlled release urea and conventional urea had different effects on peanut yield.On the basis of applying 50 kg/666.7 m^(2)of calcium superphosphate and 17 kg/666.7 m^(2)of potassium sulfate,13.34 kg/666.7 m^(2)of pure nitrogen was applied.The optimal ratio of controlled release urea to ordinary urea was 75:25,followed by 50:50.The output was 379.83 and 371.83 kg/666.7 m^(2),separately increased by 6.74%and 4.50%compared to the application of ordinary urea.[Conclusions]The combined application of controlled release urea and ordinary urea in peanuts can significantly increase peanut yield compared to just applying ordinary urea.

Optimized nitrogen application methods to improve nitrogen use efficiency and nodule nitrogen fixation in a maize-soybean relay intercropping system

In China, the abuse of chemical nitrogen （N） fertilizer results in decreasing N use efficiency （NUE）, wasting resources and causing serious environmental problems. Cereal-legume intercropping is widely used to enhance crop yield and improve resource use efficiency, especially in Southwest China. To optimize N utilization and increase grain yield, we conducted a two-year field experiment with single-factor randomized block designs of a maize-soybean intercropping system （IMS）. Three N rates, NN （no nitrogen application）, LN （lower N application： 270 kg N ha-1）, and CN （conventional N application： 330 kg N ha-1）, and three topdressing distances of LN （LND）, e.g., 15 cm （LND1）, 30 cm （LND2） and 45 cm （LND3） from maize rows were evaluated. At the beginning seed stage （R5）, the leghemoglobin content and nitrogenase activity of LND3 were 1.86 mg plant-1 and 0.14 mL h-1 plant-1, and those of LND1 and LND2 were increased by 31.4 and 24.5%, 6.4 and 32.9% compared with LND3, respectively. The ureide content and N accumulation of soybean organs in LND1 and LND2 were higher than those of LND3. The N uptake, NUE and N agronomy efficiency （NAE） of IMS under CN were 308.3 kg ha-1, 28.5%, and 5.7 kg grain kg-1 N, respectively; however, those of LN were significantly increased by 12.4, 72.5, and 51.6% compared with CN, respectively. The total yield in LND1 and LND2 was increased by 12.3 and 8.3% compared with CN, respectively. Those results suggested that LN with distances of 15-30 cm from the topdressing strip to the maize row was optimal in maize-soybean intercropping. Lower N input with an optimized fertilization location for IMS increased N fixation and N use efficiency without decreasing grain yield.

Effect of nitrogen fertilization on yield, N content, and nitrogen fixation of alfalfa and smooth bromegrass grown alone or in mixture in greenhouse pots

Planting grass and legume mixtures on improved grasslands has the potential advantage of realizing both higher yields and lower environmental pollution by optimizing the balance between applied N fertilizer and the natural process of legume biological nitrogen fixation. However, the optimal level of N fertilization for grass-legume mixtures, to obtain the highest yield, quality, and contribution of N2 fixation, varies with species. A greenhouse pot experiment was conducted to study the temporal dynamics of N2 fixation of alfalfa （Medicago sativa L.） grown alone and in mixture with smooth bromegrass （Bromus inermis Leyss.） in response to the addition of fertilizer N. Three levels of N （0, 75, and 150 kg ha-1） were examined using 15N-labeled urea to evaluate N2 fixation via the 15N isotope dilution method. Treatments were designated NO （0.001 g per pot）, N75 （1.07 g per pot） and N150 （2.14 g per pot）. Alfalfa grown alone did not benefit from the addition of fertilizer N; dry matter was not significantly increased. In contrast, dry weight and N content of smooth bromegrass grown alone was increased significantly by N application. When grown as a mixture, smooth bromegrass biomass was increased significantly by N application, resulted in a decrease in alfalfa biomass. In addition, individual alfalfa plant dry weight （shoots＋roots） was significantly lower in the mixture than when grown alone at all N levels. Smooth bromegrass shoot and root dry weight were significantly higher when grown with alfalfa than when grown alone, regardless of N application level. When grown alone, alfalfa＇s N2 fixation was reduced with N fertilization （R2=0.9376,P=0.0057）. When grown in a mixture with smooth bromegrass, with 75 kg ha-1 of N fertilizer, the percentage of atmospheric N2 fixation contribution to total N in alfalfa （%Ndfa） had a maximum of 84.07 and 83.05% in the 2nd and 3rd harvests, respectively. Total 3-harvest %Ndfa was higher when alfalfa was grown in a mixture than when grown alone （shoots： ｜t｜=3.39, P=0.0096; root： ｜t｜=3.57, P=0.0073）. We believe this was due to smooth bromegrass being better able to absorb available soil N （due to its fibrous root system）, resulting inlower soil N availability and allowing alfalfa to develop an effective N2 fixing symbiosis prior to the 1st harvest. Once soil N levels were depleted, alfalfa was able to fix N2, resulting in the majority of its tissue N being derived from biological nitrogen fixation （BNF） in the 2nd and 3rd harvests. When grown in a mixture, with added N, alfalfa established an effective symbiosis earlier than when grown alone; in monoculture BNF did not contribute a significant portion of plant N in the N75 and N150 treatments, whereas in the mixture, BNF contributed 17.90 and 16.28% for these treatments respectively. Alfalfa has a higher BNF efficiency when grown in a mixture, initiating BNF earlier, and having higher N2 fixation due to less inhibition by soil-available N. For the greatest N-use-efficiency and sustainable production, grass-legume mixtures are recommended for imDrovino orasslands, usino a moderate amount of N fertilizer （75 kq N ha-l） to provide optimum benefits.

Photocatalytic nitrogen fixation: An attractive approach for artificial photocatalysis

Ammonia synthesis via the Haber-Bosch process, which has been heralded as the most important invention of the 20 th century, consumes massive amounts of energy, around 1%–2% of the world’s annual energy consumption. Developing green and sustainable strategies for NH3 synthesis under ambient conditions, using renewable energy, is strongly desired, by both industrial and sci-entific researchers. Artificial photosynthesis for ammonia synthesis, which has recently attracted significant attention, directly produces NH3 from sunlight, and N2 and H2O via photocatalysis. This has been regarded as an ideal, energy-saving and environmentally-benign process for NH3 produc-tion because it can be performed under normal temperature and atmospheric pressure using re-newable solar energy. Although sustainable developments have been achieved since the pioneering work in 1977, many challenging issues（e.g., adsorption and activation of nitrogen molecules on the surface of photocatalysts under mild conditions） have still not been well solved and the photocata-lytic activities are generally low. In this miniature review, I summarize the most recent progress of photocatalytic N2 fixation for ammonia synthesis, focusing specifically on two attractive aspects for adsorption and activation of nitrogen molecules： one is engineering of oxygen vacancies, and the other is mimicking natural nitrogenase for constructing artificial systems for N2 fixation. Several representative works focusing on these aspects in artificial systems have been reported recently, and it has been demonstrated that both factors play more significant roles in photocatalytic N2 re-duction and fixation under ambient conditions. At the end of the review, I also give some remarks and perspective on the existing challenges and future directions in this field.

SWAT Modeling of Nitrogen Dynamics Considering Atmospheric Deposition and Nitrogen Fixation in a Watershed Scale

The Soil and Water Assessment Tool (SWAT) nitrogen (N) water quality model considers the artificial inputs associated with human activities, including point and nonpoint source pollution loads. Although SWAT has the ability to simulate atmospheric N deposition and fixation, they were not considered in the modeling research. N deposition from the air is an important and considerable pathway for the input of N species into watersheds and water bodies, causing soil and water body acidification and the leaching of N into surface and groundwater, resulting in eutrophication and degraded water quality. The goal of this study is to assess the effects of atmospheric and agricultural N loads on stream water quality at the watershed scale. For a 6642 km2 Chungju dam watershed, SWAT was calibrated for 4 years (2003-2006) and validated for another 4 years (2007-2010) using daily anthropogenic N data (sewage discharge pollutants and fertilizer) and monthly measured atmospheric deposition data for NO3ˉ, NH4+, and dissolved organic N (DON). At the watershed outlet, the Nash-Sutcliffe (1970) efficiency (NSE) of daily streamflow during the validation period was 0.74. The coefficient of determination (R2) of total N was 0.69 considering atmospheric deposition, whereas it was 0.33 when removing the deposition effect. The results of this study demonstrate the potential for using the N dynamics between the atmosphere and land for SWAT assessments of nonpoint source pollution and for modeling stream water quality.

Influences of frequency on nitrogen fixation of dielectric barrier discharge in air

The influences of frequency on nitrogen fixation of dielectric barrier discharge in air were studied by electrical diagnostics, gas detection and infrared detection methods. The system power, nitrogen oxide concentration, voltage-current waveform, dielectric surface temperature distribution and filamentous discharge pictures were measured, and then the energy yield was calculated; paper studied their changing tendencies in the presence of frequency. Results show that frequency has strong influences on nitrogen fixation. When the parameters of reaction chamber and amplitude of applied voltage is fixed, with the increasing of frequency, the system power increases; in 5-10 kHz, nitrogen oxide gas concentration up to 1113.7 mg m-3, and 7 kHz is the optimal nitrogen fixation frequency whose energy yield is 20.5 mR （m3 W）-1.