全波长扫描式多功能读数仪-分光光度法测定土壤中无机氮

快速准确测定土壤中铵态氮、硝态氮含量对监测土壤肥力水平和生态环境,指导作物氮肥施用非常重要。选择30份土样,利用全波长扫描式多功能读数仪(酶标仪)结合靛酚蓝分光光度法、硫酸肼还原法测定土壤中铵态氮和硝态氮含量,探讨利用酶标仪测定土壤无机氮含量的可行性。结果显示,利用酶标仪测定土壤铵态氮、硝态氮含量与连续流动分析仪测定结果之间无明显差异,彼此间呈显著线性相关。铵态氮回归直线方程为Y(连续流动分析仪-NH_4~+-N)=0.997 6 X(酶标仪-NH_4~+-N)-0.012 3,相关系数R=0.961 9(n=30,P0.01);硝态氮回归方程为Y(连续流动分析仪-NO_3~--N)=0.959 3 X(酶标仪-NO_3~--N)+0.021 9,相关系数R=0.964 0(n=30,P0.01)。酶标仪测定铵态氮回收率在96.2%～108%,相对标准偏差在10%以内;硝态氮测定回收率为94.9%～110%,且相对标准偏差在5%以内,酶标仪测定土壤铵态氮和硝态氮方法检出限分别为0.068mg/L和0.028mg/L。酶标仪测定土壤无机氮速度快,精密度、准确度较高,消耗试剂少,可用于大批量土壤浸提液中铵态氮和硝态氮含量的快速分析。     

全波长扫描式多功能读数仪-分光光度法测定土壤中无机氮

快速准确测定土壤中铵态氮、硝态氮含量对监测土壤肥力水平和生态环境,指导作物氮肥施用非常重要。选择30份土样,利用全波长扫描式多功能读数仪(酶标仪)结合靛酚蓝分光光度法、硫酸肼还原法测定土壤中铵态氮和硝态氮含量,探讨利用酶标仪测定土壤无机氮含量的可行性。结果显示,利用酶标仪测定土壤铵态氮、硝态氮含量与连续流动分析仪测定结果之间无明显差异,彼此间呈显著线性相关。铵态氮回归直线方程为Y(连续流动分析仪-NH_4~+-N)=0.997 6 X(酶标仪-NH_4~+-N)-0.012 3,相关系数R=0.961 9(n=30,P<0.01);硝态氮回归方程为Y(连续流动分析仪-NO_3~--N)=0.959 3 X(酶标仪-NO_3~--N)+0.021 9,相关系数R=0.964 0(n=30,P<0.01)。酶标仪测定铵态氮回收率在96.2%～108%,相对标准偏差在10%以内;硝态氮测定回收率为94.9%～110%,且相对标准偏差在5%以内,酶标仪测定土壤铵态氮和硝态氮方法检出限分别为0.068mg/L和0.028mg/L。酶标仪测定土壤无机氮速度快,精密度、准确度较高,消耗试剂少,可用于大批量土壤浸提液中铵态氮和硝态氮含量的快速分析。     

全自动定氮仪碱解蒸馏法测定植物营养液中硝态氮和铵态氮

建立凯氏定氮仪法测定植物营养液中铵态氮和硝态氮的方法。将10 mL植物营养液置于凯氏定氮管中,加入4.5 mol/L氢氧化钠溶液10 mL,利用锌-硫酸亚铁还原剂将营养液中硝态氮(NO_(3)^(-)-N)转化为铵态氮(NH_(4)^(+)-N),经蒸馏后被定量吸收在硼酸溶液中,用标准酸进行滴定,计算营养液中总氮含量;不加锌-硫酸亚铁还原剂时,测定营养液中的NH_(4)^(+)-N含量,采用差减法计算出营养液中NO_(3)^(-)-N含量。方法的检出限(以铵态氮计)为0.15 mg/L,硝态氮和铵态氮测定结果的相对标准偏差分别为1.23%~2.75%、0.83%~2.84%(n=5),加标回收率为98.7%~100.8%。该方法满足LY/T 1228—2015《森林土壤氮的测定》标准要求。     

利用连续流动分析仪测定水溶肥料硝态氮的方法研究

探讨了利用连续流动分析仪测定水溶肥料中的硝态氮的方法。选择含腐植酸、有机、微量元素、大量元素等4类水溶肥料样品,采用水振荡浸提试样,利用连续流动分析仪对浸提液中硝态氮的含量进行测定,并与紫外分光光度计测定数据进行对比,探讨利用连续流动分析仪测定化学肥料中硝态氮含量可行性。结果表明,流动分析仪法的方法检出限为0.008 g/kg;加标回收率在93.2%~101%;测定结果的相对标准偏差在1.7%~8.3%;所得数据与紫外分光光度计测定结果对比分析,t检验结果表明两种方法无显著差异;两种方法测定数据之间拟合方程为y=0.9782x+0.0768,R²=0.9966。结果表明,连续流动分析仪测试速度快,试剂消耗量少,精密度和准确度满足要求,可用于水溶肥料硝态氮含量的分析测定。     

基于中红外衰减全反射光谱的氮同位素标记硝态氮的快速测定

采用中红外衰减全反射光谱对溶液和土壤样本中硝态氮含量(14NO3-N/15NO3-N)进行快速测定。结果表明,溶液和土壤样本中硝酸盐的特征吸收区在1200~1500 cm!1,进一步发现,与常规14NO!3相比,15NO!3的吸收峰红移约35 cm!1。在硝酸盐特征吸收区内,干扰吸收少,吸收峰与硝态氮浓度成正比,采用该特征波段的第一主成分与硝态氮含量进行线性回归分析,相关系数R2>0.9840,表明中红外衰减全反射光谱可用于溶液和土壤中硝态氮的快速检测。同时,依据15NO!3吸收峰的红移特征,采用偏最小二乘法对溶液和土壤样本不同氮同位素标记的硝态氮进行建模预测,结果表明,溶液和土壤样本的预测模型均达优秀水平;溶液样本中,14NO3-N和15NO3-N相关系数(R2)均为0.998,有RPD值分别为6.44和4.76;而土壤样本中,14NO3-N和15NO3-N相关系数(R2)分别为0.979和0.968,RPD值分别为5.75和4.78。因此,红外衰减全反射光谱可用于溶液和土壤中硝态氮以及氮同位素标记硝态氮的测定,为快速原位研究土壤中氮的硝化过程提供新的手段。     

微流池多光程土壤有效态氮磷测定方法研究

农业面源氮磷污染是当前地表水体污染主要来源,而土壤有效态氮磷测试大都依赖于流动分析仪在实验室完成,无法满足个性化土壤有效态氮磷现场测定需求。建立了一种微流池多光程的土壤有效态氮磷测定技术,通过柔性化参数设置,实现不同土壤有效态氮磷测试规范和现场测试。以广东省韶关市农业科学研究所和北京市农林科学院提供的26个样品为例进行有效态铵态氮、硝态氮和磷测定验证。实验结果表明,微流池多光程土壤有效态氮磷测定方法中有效态铵态氮、硝态氮和磷的检出限(LOD)分别为0.0086、0.0094和0.0078 mg/L,相对标准偏差(RSD)分别为0.80%、5.7%和0.90%,加标回收率在92.0%~103%,平均单样品测试时间6 min。测试过程自动化,极大地提升了土壤有效态氮磷测定效率和测试结果准确性,为农业面源污染防治提供技术支撑。     

离子选择电极阵列土壤中硝态氮测定

土壤硝态氮反映土壤短期氮素供应水平,实时了解土壤硝态氮的含量为精准农业和农业面源污染防控提供支撑,因此,在线实时检测土壤硝态氮方法突破就显得十分迫切。土壤硝态氮中的硝酸根离子在土壤中的高水溶性和流动性为全固态硝酸根离子选择电极高敏感检测土壤中硝态氮提供了条件,固态硝态氮离子选择电极的离子选择膜反应硝酸根离子在被测溶液中的浓度。采用全固态硝酸根离子选择电极,且与温度电极和pH电极融合组成电极阵列对土壤饱和溶液中的硝态根离子进行检测。设计了高输入阻抗运算放大电路对电极信号进行采集,并通过微处理控制蠕动泵完成土壤硝态氮待测溶液连续流动测量及实时传输结果。实验结果表明,电极响应时间≤15 s,斜率-51.63 mV/decade,线性范围10-5-10-2.2 mol/L,最低检测限10-5.23 mol/L。相对标准差在0.78%-4.47%范围内,加标回收率均在90%-110%以内。与国家标准紫外可见分光光度法测试结果相比,相关系数（R2）为0.9952,为土壤硝态氮在现场检测奠定技术基础。     

连续流动分析仪测定水溶肥料硝态氮

探讨了利用连续流动分析仪测定水溶肥料中的硝态氮的方法.选择含腐植酸、有机、微量元素、大量元素等4类水溶肥料样品,采用水振荡浸提试样,利用连续流动分析仪对浸提液中硝态氮的含量进行测定,并与紫外分光光度计测定数据进行对比,探讨利用连续流动分析仪测定化学肥料中硝态氮含量可行性.结果表明,流动分析仪法的方法检出限为0.008 ...     

氮肥增效剂2,5-二氯硝基苯

肥料是农业“八字宪法”的重要内容,施肥是提高农作物单位面积产量的重要内容之一。但是氮肥施用田间以后,由于受土壤中亚硝化和硝化微生物作用,氮肥中不易随雨水流失的铵态氮被氧化成为亚硝态氮和硝态氮,而亚硝态氮和硝态氮不易被土壤吸附,容易被雨水冲淋而流失,致使氮肥利用率大大降低。根据我国农业部门的测定,氮肥利用率一般在50%左右。氮肥增效剂是提高氮肥利用率的化学药剂。又称     

离子选择电极阵列测定土壤中硝态氮

土壤硝态氮反映土壤短期氮素供应水平,实时了解土壤硝态氮的含量为精准农业和农业面源污染防控提供支撑,因此,在线实时检测土壤硝态氮方法突破就显得十分迫切。土壤硝态氮中的硝酸根离子在土壤中的高水溶性和流动性为全固态硝酸根离子选择电极高敏感检测土壤中硝态氮提供了条件,固态硝态氮离子选择电极的离子选择膜反应硝酸根离子在被测溶液中的浓度。采用全固态硝酸根离子选择电极ELIT NO₃^-,且与温度电极和pH电极融合组成电极阵列对土壤饱和溶液中的硝酸根离子进行检测。设计了高输入阻抗运算放大电路对电极信号进行采集,并通过微处理控制蠕动泵完成土壤硝态氮待测溶液连续流动测定及实时传输结果。实验结果表明,电极响应时间≤15 s,斜率-51.63 mV/decade,线性范围10^-5~10^-2.2 mol/L,最低检测限10^-5.23 mol/L。相对标准差在0.78%~4.5%,加标回收率均在90.0%~110%。与紫外可见分光光度法测试结果相比,相关系数(R²)为0.9952,为土壤硝态氮在现场检测奠定技术基础。     

A Comparison of PE Surfaces Modified by Plasma Generated Neutral Nitrogen Species and Nitrogen Ions

The surface modification of polyethylene (PE) by neutral nitrogen species (ground and excited state N₂ as well as atomic N; modified nitrogen plasma treatment) has been compared to the effect of nitrogen ion bombardment using X-ray Photoelectron Spectroscopy (XPS) and contact angle measurements. XPS results indicate that a greater nitrogen concentration was grafted during the modified nitrogen plasma treatment of PE, an effect that was attributed to surface sputtering during ion beam modification. The distribution of nitrogen-containing functionalities was strongly dependent upon the treatment strategy; the modified nitrogen plasma treatment lead predominantly to imine groups being formed at the PE surface, while amine groups were the dominant species produced during ion beam modification. The presence of electron irradiation during the modified nitrogen plasma treatment of PE did not modify the rate of nitrogen incorporation or change the nature of N-containing functional groups produced but did lead to a systematic decrease in contact angle.     

Detection of the Elusive Triazane Molecule (N3H5) in the Gas Phase

We report the detection of triazane (N₃H₅) in the gas phase. Triazane is a higher order nitrogen hydride of ammonia (NH₃) and hydrazine (N₂H₄) of fundamental importance for the understanding of the stability of single‐bonded chains of nitrogen atoms and a potential key intermediate in hydrogen–nitrogen chemistry. The experimental results along with electronic‐structure calculations reveal that triazane presents a stable molecule with a nitrogen–nitrogen bond length that is a few picometers shorter than that of hydrazine and has a lifetime exceeding 6±2 μs at a sublimation temperature of 170 K. Triazane was synthesized through irradiation of ammonia ice with energetic electrons and was detected in the gas phase upon sublimation of the ice through soft vacuum ultraviolet (VUV) photoionization coupled with a reflectron‐time‐of‐flight mass spectrometer. Isotopic substitution experiments exploiting [D₃]‐ammonia ice confirmed the identification through the detection of its fully deuterated counterpart [D₅]‐triazane (N₃D₅).     

Achievements,Challenges, and Perspectives on Nitrogen Electrochemistry for Carbon-Neutral Energy Technologies

Unrestrained anthropogenic activities have severely disrupted the global natural nitrogen cycle, causing numerous energy and environmental issues. Electrocatalytic nitrogen transformation is a feasible and promising strategy for achieving a sustainable nitrogen economy. Synergistically combining multiple nitrogen reactions can realize efficient renewable energy storage and conversion, restore the global nitrogen balance, and remediate environmental crises. Here, we provide a unique aspect to discuss the intriguing nitrogen electrochemistry by linking three essential nitrogen-containing compounds (i.e., N₂, NH₃, and NO₃⁻) and integrating four essential electrochemical reactions, i.e., the nitrogen reduction reaction (N₂RR), nitrogen oxidation reaction (N₂OR), nitrate reduction reaction (NO₃RR), and ammonia oxidation reaction (NH₃OR). This minireview also summarizes the acquired knowledge of rational catalyst design and underlying reaction mechanisms for these interlinked nitrogen reactions. We further underscore the associated clean energy technologies and a sustainable nitrogen-based economy.     

Characterization of the Active Species in the Afterglow of a Nitrogen and Helium Atmospheric-Pressure Plasma

The concentrations of the neutral active species in the afterglow of a nitrogen and helium atmospheric-pressure plasma have been determined by optical emission and absorption spectroscopy and by numerical modeling. For operation with 10 Torr N₂ and 750 Torr He, at 15.5 W/cm³ rf power, 30.4 L/min flow rate, and a neutral temperature of 50°C, the plasma produced 4.8×10¹⁵ cm^–3 of ground state nitrogen atoms, N(⁴S), 2.1×10¹³ cm^–3 of N₂(A³_u), 1.2×10¹² cm^–3 of N₂(B³_g), and 3.2×10⁹ cm^–3 of N₂(C³_u). The concentration of nitrogen atoms and metastable state nitrogen molecules, N₂(A), increased gradually with the rf power and the nitrogen partial pressure. Both the model and experiments indicate that ground-state nitrogen atoms are the dominant active species in the afterglow beyond 2.0 ms.     

Synthesis and Crystal Structure of [Cu(acac)(Hdmpz)_3]Br.EtOH

1 INTRODUCTION Diazoles have both a pyridine-type nitrogen and a pyrrole-type nitrogen (imino group), so they can act as bifunctional groups to coordinate with many metal ions or Lewis acids giving a variety of products[1, 2]. Recently researches on the pyrazole ligand have been focused on the following three sections. (i) The first is that the ligand acts as a bridged ligand and coordinates to metal forming di- and polynuclear complexes. Such system arouses much interest mainly because o…     

基于高性能负载型钼基载氮体的化学链合成氨性能研究

化学链合成氨是一种新型的、环境友好的低压合成氨技术, 其借助于载氮体的传递作用实现固氮与释氮制氨的循环, 已受到产学界的广泛关注. 构建高效、绿色的载氮体是化学链合成氨技术的关键. 本工作通过一步热解法制备了负载型钼基载氮体, 并对其释氮、固氮及稳定性进行了研究. 结果表明: 在释氮阶段, 当热解制备温度为450 ℃时, 钼基载氮体的氢化产氨速率为最大, 可达20000 μmol•g^-1•h^-1; 固氮过程中, 氢气的引入加快了钼基载氮体从氮气中补充晶格氮的速率, 实现了载氮体的高效再生; 历经12次循环后, 负载型钼基载氮体(制备温度为600 ℃)的产氨速率基本稳定在1500 μmol•g^-1•h^-1. 本研究探索了负载型钼基载氮体化学链合成氨的可行性, 结果可为新型过渡金属基载氮体的开发及其化学链合成氨研究提供理论基础.     

Highly Dense Nitranilates‐Containing Nitrogen‐Rich Cations

High density energetic salts containing nitrogen‐rich cations and the nitranilic anion were readily synthesized in high yield by metathesis reactions of sodium nitranilate 2 and an appropriate halide. All of the new compounds were fully characterized by elemental, spectral (IR, ¹H, ¹³C NMR), and thermal (DSC) analyses. The structure of hydrazinium nitranilate ( 4 ) was also determined by single‐crystal X‐ray analysis. The high symmetry and oxygen content of the anion give these salts extensive hydrogen bonding capability which further results in the high densities, low water solubilities, and high thermal stabilities (T_d> 200 °C) of these compounds. Theoretical performance calculations were carried out by using Gaussian 03 and Cheetah 5.0. The calculated detonation pressures (P) for these new salts fall between 17.5 GPa ( 10 ) and 31.7 GPa ( 4 ), and the detonation velocities (νD) range between 7022 m s^?1 ( 13 ) and 8638 m s^?1 ( 4 ).     

Recent Advances in Noble‐Metal‐Free Catalysts for Electrocatalytic Synthesis of Ammonia under Ambient Conditions

Ammonia is an essential chemical for producing fertilizers and energy carriers. However, the industrial Haber–Bosch process causes huge CO₂ emissions and energy waste. As a promising alternative for Haber‐Bosch process, electrochemical synthesis of ammonia has drawn much attention. Catalysts, as a vital part of electrochemical nitrogen reduction reaction (NRR), have developed rapidly in recent years. Compared to noble‐metal catalysts, noble‐metal‐free catalysts possess a low‐cost advantage. In this review, noble‐metal‐free catalysts, including metal‐based materials, metal organic frameworks (MOFs), MXenes, and metal‐free materials, are summarized. In addition, effective design strategies are discussed, along with the main problems and some potential directions of noble‐metal‐free NRR catalysts.