Nitrogen Flow in the Rural Ecosystem of Mikasa City in Hokkaido, Japan

This study of Mikasa City in 2001, which analyzed N flow between N production and N load in seven agricultural and settlement subsystems, i.e., paddy, onion, wheat, vegetable, dairy, chicken, and citizen subsystems, aimed to compare N flow in each subsystem, to determine the main sources of the N load, and to evaluate the influence of agricultural production and food consumption on N cycling in a rural area. The results showed that in Mikasa city, 38.5% of the N load came from point sources and the remainder from non-point sources with intensive vegetable farming imparting a serious N load. Because of the internal N cycling in the dairy subsystem, chemical fertilizer application was reduced by 70.2%, and 23.72 Mg manure N was recycled to the field; therefore, the N utilization efficiency was raised from 18.1% to 35.1%. If all the manure N in the chicken subsystem was recycled, chemical fertilizer application would be reduced by 8.1% from the present level, and the point sources of N pollution would be reduced by 20.8%.

Influences of nitrogen flow rate on the structures and properties of Ti and N co-doped diamond-like carbon films deposited by arc ion plating

In this paper, Ti-C-N nanocomposite films are deposited under different nitrogen flow rates by pulsed bias arc ion plating using Ti and graphite targets in the Ar/N2 mixture gas. The surface morphologies, compositions, microstructures, and mechanical properties of the Ti-C-N films are investigated systematically by field emission scanning electron mi- croscopy （FE-SEM）, x-ray photoelectron spectroscopy （XPS）, grazing incident x-ray diffraction （GIXRD）, Raman spectra, and nano-indentation. The results show that the nanocrystalline Ti（C,N） phase precipitates in the film from GIXRD and XPS analysis, and Raman spectra prove the presence of diamond-like carbon, indicating the formation of nanocomposite film with microstructures comprising nanocrystalline Ti（C,N） phase embedded into a diamond-like matrix. The nitrogen flow rate has a significant effect on the composition, structure, and properties of the film. The nano-hardness and elastic modulus first increase and then decrease as nitrogen flow rate increases, reaching a maximum of 34.3 GPa and 383.2 GPa, at a nitrogen flow rate of 90 sccm, respectively.

Tailoring the microstructure,mechanical and tribocorrosion performance of (CrNbTiAlV)N_(x) high-entropy nitride films by controlling nitrogen flow

The(CrNbTiAlV)N_(x)high-entropy nitride films were fabricated by adjusting nitrogen flow via magnetron sputtering.The microstructure,mechanical,electrochemical and tribocorrosion performances of the films were studied.The results show that the films transform from amorphous to nanocrystalline structure as nitrogen flow increased.The nanocrystalline films show super hardness(>40 GPa)and adhesion strength(>50 N).The amorphous film has a pretty anti-corrosion in static corrosion,while not in tribocorrosion condition.The film deposited at nitrogen flow of 38 sccm exhibits the optimal tribocorrosion performance in artificial seawater,with the highest open circuit potential(∼−0.1 V vs.Ag/AgCl),the lowest friction coefficient(∼0.162)and wear rate(∼7.48×10^(−7)mm^(3)N^(−1)m^(−1)).

Influence of Nitrogen Flow Rate on the Microstructure and Properties of N and Me (Me=Cr,Zr) Co-doped Diamond-like Carbon Films

In this paper,Me （Me=Cr,Zr） and N co-doped diamond like carbon （DLC-MeN） composite films were prepared on cemented carbide substrates by pulsed bias arc ion plating.The effect of nitrogen flow rates on the microstructure and properties of the films were investigated by X-ray photoelectron spectroscopy （XPS）,Raman spectra,grazing incident X-ray diffraction （GIXRD）,high resolution transmission electron microscopy （HRTEM） and nano-indentation.Raman,GIXRD and HRTEM results show that the deposited films are nanocomposite films with MeN nanocrystalline phase embedded within DLC amorphous matrix,which are vital for the mechanical properties of the films.The nitrogen flow rate has significant effect on the compositions and structures and hence on the hardness and elastic modulus of the films,and increasing nitrogen flow rate decreases drastically the hardness and elastic modulus of the films.

Effect of nitrogen gas flow and growth temperature on extension of GaN layer on Si

The effect of nitrogen flow and growth temperature on extension of GaN on Si substrate has been studied.By increasing the nitrogen flow whose outlet is located in the center of the MOCVD(metal–organic chemical vapor deposition)gas/particle screening flange and by increasing the growth temperature of HT-AlN and AlGaN buffer layers near the primary flat of the wafer,the GaN layer has extended more adequately on Si substrate.In the meantime,the surface morphology has been greatly improved.Both the AlN and GaN crystal quality uniformity has been improved.X-ray diffraction results showed that the GaN(0002)XRD FWHMs(full width at half maximum)decreased from 579 arcsec~1655 arcsec to around 420 arcsec.

Characteristics of runoff processes and nitrogen loss via surface flow and interflow from weathered granite slopes of Southeast China

Rainfall intensity and slope gradient are two of the most important factors affecting the variations of runoff nitrogen(N).However,the effects of slope gradient and rainfall intensity on N loss via surface flow and interflow on weathered granite slopes are poorly understood.In this study,12 artificial rainfalls(three rainfall intensities and four slope gradients)were simulated to investigate the coupling loss characteristics of surface flow–interflow–total nitrogen(TN),nitrate nitrogen(NO_3^--N)and ammonia nitrogen(NH_4^+-N)on weathered granite slopes.The results show that slope gradient has a greater impact on the surface flow when the rainfall intensity is relatively large.The effect gradually weakens with the decrement of rainfall intensity.The interflow yield increases firstly with the prolongation of rainfall duration,then tends to be stable and finally decreases.The total surface flow percentage increases with rainfall intensity while it decreases with increasing slope gradient with a range of 10.88%-71.47%.The TN loss concentration of the surface flow continually decreases with rainfall duration while that of the interflow shows different fluctuations.However,the TN loss loads of both surface flow and interflow increase with increasing rainfall intensity and slope gradient.The NO_3^--N concentration of interflow is much higher than that of the surface flow.The NH_4^+-N concentration is always less than that of NO_3^--N with no significant difference between surface flow and interflow.The percentages of the TN,NO_3^--N,and NH_4^+-N total loss load and concentration of surface flow and interflow were analyzed.The results show that N loss via both surface flow and interflow occurs mainly in the form of NO_3^--N.Most of the N loss is caused by interflow which is the preferential path of runoff nutrient loss.These findings provide data support and underlying insights for the control of runoff and N loss on the weathered granite slopes.

Effect of Nitrogen on Water Content, Sap Flow, and Tolerance of Rice Plants to Brown Planthopper, Nilaparvata lugens

Water content (WC) and sap flow from leaf sheath of rice plants with varying nitrogen levels at different growth stages, and fluctuations in relative water content (RWC) of rice plants being damaged by brown planthoppcr (BPH), Nilaparvata lugens were determined in the laboratory, and the tolerance of rice plants to BPH at different nitrogen regimes was evaluated in the greenhouse at International Rice Research Institute (IRRI), the Philippines. The results indicated that both WC and RWC were increased significantly, as the amount of sap flow from rice plants was reduced statistically, with the increase of nitrogen content in rice plants. RWC in rice plants applied with high nitrogen fertilizer decreased drastically by the injury of BPH nymphs, while the reduced survival duration of rice plants with the increase of nitrogen content was recorded. These may be considered to be one of the important factors in increasing the susceptibility to BPH damage on rice plants applied with nitrogen fertilizer.

An Experimental Observation of the Thermal Effects and NO Emissions during Dissociation and Oxidation of Ammonia in the Presence of a Bundle of Thermocouples in a Vertical Flow Reactor

Ammonia (NH3) dissociation and oxidation in a cylindrical quartz reactor has been experimentally studied for various inlet NH3 concentrations (5%, 10%, and 15%) and reactor temperatures between 700 K and 1000 K. The thermal effects during both NH3 dissociation (endothermic) and oxidation (exothermic) were observed using a bundle of thermocouples positioned along the central axis of the quartz reactor, while the corresponding NH3 conversions and nitrogen oxides emissions were determined by analysing the gas composition of the reactor exit stream. A stronger endothermic effect, as indicated by a greater temperature drop during NH3 dissociation, was observed as the NH3 feed concentration and reactor temperature increased. During NH3 oxidation, a predominantly greater exothermic effect with increasing NH3 feed concentration and reactor temperature was also evident;however, it was apparent that NH3 dissociation occurred near the reactor inlet, preceding the downstream NH3 and H2 oxidation. For both NH3 dissociation and oxidation, NH3 conversion increased with increasing temperature and decreasing initial NH3 concentration. Significant levels of NOX emissions were observed during NH3 oxidation, which increased with increasing temperature. From the experimental results, it is speculated that the stainless-steel in the thermocouple bundle may have catalysed NH3 dissociation and thus changed the reaction chemistry during NH3 oxidation.

Phosphorus and Nitrogen Removal by Saturated Vertical-Flow Constructed Wetlands (SVCWs) Type Micro-Pilot Using Shale from Ivory Coast as a Substrate

This study evaluates the performance of shale from Ivory Coast used as substrate in vertical-flow constructed wetlands in removal of phosphates and nitrogen. The pilot-scale artificial wetland has been duplicated: filter planted with Panicum maximun and unplanted. They were set up outdoors, and fed with a municipal wastewater. The wetlands have been fed with three batches per week (intermittent) over a period of 3 months. During the operation period, the hydraulic residence time (HRT) 52 h was used, while wastewater temperatures varied from about ~33°C. The removal performance of the constructed wetland units was very good, since it reached on an average 98%, 89.4%, 89.4%, 84%, 80%, 84.8% and 92% for TSS, DOC, BOD5, , TKN, TP and respectively. In addition, the vegetation did not demonstrate superior performance to unplanted controls. Therefore, this study focuses on the role of shale in the phosphorus and nitrogen removal from wastewater by constructed wetland.

黄河流域农业农村氮流时空分布特征及演化规律研究

氮磷等营养元素过剩引发的面源污染问题,是黄河流域水质恶化的重要原因.为应对黄河流域氮素危机,从源头上降低面源污染负荷,本研究基于物质流和空间分析方法,刻画1949-2022年间黄河流域农业农村氮流时空格局演化规律,评估黄河流域面源污染关键氮流和高风险区.结果表明:(1)新中国成立以来,黄河流域的作物收获量整体呈现上升的趋势,2015年之后在氮输入水平持续下降的情况下,仍然能够保持年均2%的增长,黄河流域在氮素利用水平上得到了极大的提升.(2)黄河流域农业农村依然存在严重的氮流失现象,其中存贮和反硝化是氮流失的主要部分,1962年、1992年和2022年这两部分流失量分别占耕地氮输出流的51%、47%和36%.2015开始氮素流失(存储)量逐年下降,2022年比2015年减少了15.55%,但是每年仍有30.12×10^(8)kg氮素流失到大气、水体和土壤中,是当年作物收获氮量的1.64倍,氮素损失率高达62.05%.(3)降雨和地势地形是影响氮径流的决定因素,在高风险区内约有27%~45%的氮剩余流失到附近的地表水中,主要分布在甘肃省的最南部和东南角部分地区、陕西省的最南部和山东省东部地区.研究显示:黄河流域在氮素利用提升和氮污染治理方面取得一定成效,但是仍然存在严重的氮流失现象;需要持续推进化肥减量、粪便还田和农村污水治理,同时需要在高风险区采取构建缓冲带等工程措施,才能实现面源污染等氮危机的有效控制.

潜流人工湿地脱氮除磷基质的应用研究及展望

基质的选择直接影响着潜流人工湿地全生命周期及污水处理效果,不同类型的基质对脱氮除磷具有差异性效果。综述了不同类型潜流人工湿地基质的研究现状,分析了其脱氮除磷机理,总结了各类基质的应用效果,展望了天然矿石基质、固体废弃物基质和人工合成基质研究方向和研究重点,以期为潜流人工湿地脱氮除磷基质的研发提供参考。

农业生产消费系统氮损失特征及其不确定性

准确量化活性氮损失是农业生产消费系统氮管理的重要基础。以长江三角洲地区(长三角地区)为研究区,基于物质流分析法研究农业生产消费系统的氮损失特征,采用误差传播方程量化氮损失的不确定性,并采用多元回归分析对其传播机制进行分析。结果表明,2011—2020年,长三角地区农业生产消费系统活性氮损失总量由2011年的(1841.0±150.4)Gg/a上升至2013年的(1874.1±154.2)Gg/a,随后逐年下降至2020年的(1636.4±144.6)Gg/a。作物种植和畜禽养殖子系统是活性氮损失最大的两个源,10年平均占比分别为37.5%和31.0%。10年间,二者的活性氮损失占比均呈下降趋势,而居民消费和废物管理子系统活性氮损失占比均呈上升趋势。大气环境是系统活性氮损失最主要的汇,10年平均占比为52.2%。不确定性方面,系统活性氮损失总量的不确定性为8.1%—8.8%,其中,废物管理子系统和地表水环境活性氮损失分别为不确定性最高的源和汇。由人类活动水平数据和氮流参数引入的系统氮损失的不确定性分别为1.2%—1.3%和8.0%—8.8%,表明后者是氮损失不确定性的主要来源。畜禽养殖子系统和地表水环境损失对系统氮损失总量不确定性的贡献最大,分别为27.4%和50.0%。多元回归分析结果显示,各组分氮损失通量及其不确定性两个因素均显著影响氮损失总量的不确定性,且各组分氮损失通量是影响不确定性传播的主导因素。研究结果可为降低农业生产消费系统氮损失的不确定性提供参考。

A^(2)/O+反硝化深床滤池在城镇污水处理厂深度经济脱氮的运行优化

脱氮是当前城镇污水处理的重点,其中A^(2)/O+反硝化滤池工艺是生活污水处理主流工艺,四川省岷江流域某城镇污水处理厂通过优化进水流量分配比、调节溶解氧和内回流比、碳源筛选等工艺试验,综合考察了工艺调控措施对系统脱氮效能的提升以及脱氮成本的经济化控制。结果表明,A^(2)/O池进水100%进入厌氧区、内回流比200%、A^(2)/O池末端溶解氧控制在1.5 mg/L、反硝化深床滤池投加液体复合碳源,在有效深度脱氮的同时节约运行费用,总氮指标满足岷沱江标准,脱氮费用降低0.37元/m^(3)。

水力侵蚀作用下坡地土壤碳氮淋溶迁移特征

碳氮随壤中流淋溶下渗是土壤碳氮流失的主要路径之一,然而由于直接观测难度大,土壤碳氮淋溶相关研究相对滞后,特别是由于壤中流的复杂性,一些问题还未得到完全解释。本文基于文献总结分析土壤、环境及壤中流影响下土壤碳氮淋溶迁移特征和观测方法,系统总结碳氮淋溶的研究方法以及各自优劣。结果表明:影响碳氮淋溶的因素众多,最主要的是降水和土壤性质。现场测量方式能真实反映淋溶的自然过程,室内试验能有效便捷地定量研究各因素对淋溶的影响,数学模型通过模拟水和溶质在多孔介质中的流动和输移,能更好地理解碳氮淋溶的物理机理,未来研究可将这些方法有机结合,以实现更好的研究效果。本文旨在为碳氮在物质循环和养分转移过程中的作用提供一定认识,为未来更好地调控生态系统中碳和氮的矿化、固着、淋溶和植物吸收的动态变化提供依据。

朱集西煤矿自燃“三带”分布及注氮参数研究

为了研究朱集西煤矿11503综采工作面采空区自燃“三带”分布规律,在进、回风巷侧埋设束管对采空区内部氧气浓度变化规律进行现场实测,并采用数值模拟的方法研究不同注氮流量下自燃“三带”分布变化规律,确定合理的注氮流量。研究表明:增加注氮流量,采空区氧化带的分布范围和宽度会减小,当注氮流量增加至900 m^(3)/h以上时对减小氧化带宽度效果甚微,据此确定了合理的注氮流量900 m^(3)/h;通过计算得到11503工作面安全通风量为222 m^(3)/min。研究结果为该工作面的后续防灭火工作提供参考。

变重力下低温液氮界面流动及温度分布

为了研究残余重力加速度g对液氮贮箱自加压期间贮箱内流体的流动、相分布、温度分布以及压强分布的影响,针对液氮贮箱,采用流体体积(Volume-of-Fluid,VOF)方法数值模拟了不同g条件下液氮贮箱的自加压过程.研究结果表明:在大g情况下,贮箱内压强沿g的方向逐渐增大,贮箱内气枕的温度随贮箱壁面的持续漏热而不断升高,且靠近壁面区域气体的温度最高,靠近液体区域气体的温度最低;随着g的减小,贮箱内的液体更容易沿贮箱壁面爬升,贮箱内流体温度差异性逐渐减小;在小g情况下,贮箱内流体流动稳定后会将气枕包裹于贮箱中部,形成球形气泡,贮箱内流体温度的差异性随时间先逐渐增大然后逐渐减小.在零重力环境下,贮箱壁面漏热(q_(w)=0.5 W·m^(–2))存在与否对贮箱内流体运动和相分布的影响均不显著,并且在起始一段时间间隔△t_(f)(0≤△t_(f)≤40 s)内,除贮箱壁面附近之外,qw存在与否对贮箱内流体温度分布的影响也不显著.

惰性气体射流协同控制火焰振荡和NO_(x)排放性能研究

预混火焰燃烧通常会出现热声振荡等问题,严重制约了燃气轮机或油气锅炉的安全运行和洁净排放。为此,提出通过惰性气体射流来调控预混燃烧过程,从而实现火焰振荡和NO_(x)排放的协同控制。惰性气体射流将导致预混火焰振荡模态迁移,既可降低火焰振荡幅值,还可使火焰振荡频率发生改变。相对原子质量大的氩气比相对原子质量小的氦气的控制效果好。惰性气体射流能够显著改变火焰结构,使预混火焰长度变短。

低温氮气/液氮射流冷凝振荡特性实验研究

为了探索火箭低频振动特征及其机理,以液氮为工质开展气液掺混射流冷凝的可视化低温实验研究,通过高速相机成功捕捉到了直管段内的低频振荡流型,且利用低温高频动态压力传感器成功测量到了低频压力脉动特性,为火箭低频振动问题提供了事实依据。通过逐帧图像处理技术发现,氮气/液氮相界面以16 Hz的频率周期性波动,与压力脉动主频一致。射流冷凝振荡表现出3种不同流型:间歇回流、过渡流和气羽振荡流。间歇回流频率随着气体流量和液体质量通量的增加而增加,冷凝振荡频率随气体流量的增大而增大,随液体质量通量的增大而减小。整体上间歇回流频率为0.8—2.8 Hz范围,冷凝振荡频率为16.6—17.8 Hz范围,皆表现为典型的低频特性,为低温液体燃料火箭低频振动问题提供了理论基础和技术支撑。

一体化厌氧-变级数缺氧/好氧循环流污水处理装置中试研究

针对现有村镇污水处理技术与装备的不足,开发出适用于村镇污水处理的新型一体化厌氧-变级数缺氧/好氧循环流(A-(AO)_n)同步脱氮除磷、沉淀分离技术与装备,以长沙某污水提升泵站沉砂池的出水作为处理对象开展中试实验。对好氧区不同溶解氧、填料填充比和分区进水条件下装置污水处理效能的变化进行研究,结果表明:当好氧区溶解氧控制在1.5~2.0 mg/L,好氧区填料填充比为30%时,装置的脱氮除磷效果最佳。在不外加碳源且不投加化学除磷药剂的条件下,出水水质优于《城镇污水处理厂污染物排放标准》(GB 18918—2002)的一级A标准。高通量测序结果显示,好氧区投加悬浮球填料后,系统中微生物总量和多样性明显提高,为系统中发生同步硝化反硝化(SND)现象创造了条件。

连续流中氮负荷对好氧颗粒污泥稳定性的影响

考察了连续流反应器中好氧颗粒污泥(AGS)处理无机高氨氮废水的脱氮性能及稳定性。接种成熟AGS启动连续流反应器,运行第1~55 d内进水氮负荷由初始时的1.0 kg/(m~3·d)逐步升至4.0 kg/(m~3·d),第56~125 d内氮负荷逐步降至1.4 kg/(m~3·d),第126~145 d氮负荷再次升至2.0 kg/(m~3·d)。前75 d内观察到明显的AGS破碎及流失现象,且颗粒平均粒径不断减小;虽然多次补充接种AGS可维持系统的稳定性,但前80 d内颗粒的污泥容积指数(SVI)、胞外聚合物(EPS)及比耗氧速率(SOUR)剧烈波动。其中,第91~109 d反应器原位闲置。系统重新运行后,AGS的理化指标逐渐趋于稳定。前45 d内AGS对氨氮去除率逐渐升至98%以上;46~75 d内AGS对氨氮去除率迅速降至50%后又回升至99%以上;总无机氮去除率基本维持为35%~45%。考察了连续流反应器对污泥选择性筛分的效果,利用高通量测序分析污泥菌群组成变化。结果表明,当沉淀池中挡板深度为27 cm时,反应器对污泥截留率在98%以上,出水污泥粒径多为0~0.30 mm。与刚接种AGS相比,运行145 d时AGS中的硝化细菌属(Nitrosomonas)相对丰度明显增大,而反硝化细菌属(unclassified_Bacteria、Thauera、Truepera等)的相对丰度略有降低。