同步辐射软X射线近边吸收谱方法研究长期施肥对黑土有机氮官能团的影响

有机态氮是土壤氮素的主要存在形式,在农田生态系统氮循环中占有重要地位。了解土壤有机氮官能团组成,可为制定合理的农田管理措施提供科学依据。同步辐射软X射线近边吸收谱(N K-edge XANES)技术,是原位测定土壤有机氮官能团组成最有效的方法,但利用该技术对长期施肥条件下土壤有机氮官能团组成的研究尚未见报道。本试验利用N K-edge XANES方法,研究了长期(18年)不同施肥措施[即休闲(Fallow)、不施肥(CK)、施氮磷钾化肥(NPK)、有机肥配施化肥(NPKM)、1.5倍量的有机肥配施化肥(1.5NPKM)和玉米秸秆配施化肥(NPKS)]对黑土全土及粘粒中有机氮官能团的影响。结果表明：各处理均在401.2～401.6和402.7～403.1 eV范围内出现特征吸收峰,分别归属为酰胺/胺和吡咯类化合物,粘粒中特征吸收峰通常较全土更为明显。半定量分析结果指出,全土和粘粒均以酰胺/胺的相对比例最高,是有机氮官能团的主要存在形态;与休闲处理相比,对照处理中酰胺/胺的相对比例较低,而吡咯类氮的相对比例较高;有机无机配施条件下,酰胺/胺的相对比例随有机肥量的增加而下降,而吡咯类氮的相对比例则呈相反的变化趋势;全土中以NPKS处理的酰胺/胺相对比例最高,而粘粒中则以休闲处理的腈类/芳香氮相对比例最高。利用N K-edge XANES方法原位测定不同施肥措施下土壤有机氮官能团组成的变化是可行的。     

同步辐射软X射线近边吸收谱方法研究长期施肥对黑土有机碳官能团的影响

以定位20年的黑土肥料试验为平台,利用同步辐射软X射线近边吸收谱(C-1s NEXAFS)方法,研究了长期施用化肥以及化肥配施玉米秸秆对土壤有机碳官能团的影响。结果表明：与不施肥的空白处理(CK)相比,单施化肥(N,NPK)后土壤的芳香C和羧基C含量增加,脂族C和羰基C含量下降,脂族C/芳香C比值降低;与单施化肥处理相比,化肥配施玉米秸秆后芳香C含量下降而脂族C含量增加,脂族C/芳香C比值增加,并随玉米秸秆用量增加表现的更为明显;无论配施玉米秸秆与否,NPK肥混施处理的芳香C、脂族C以及脂族C/芳香C比值均高于单施N肥处理。上述结果说明,单施化肥比不施肥使土壤有机碳官能团中芳香类化合物的相对比例增加,而脂肪烃类化合物的相对比例下降;化肥配施玉米秸秆则比单施化肥增加了脂肪烃类化合物的相对比例,配施高量比低量玉米秸秆的增加趋势更为明显,同时NPK肥混施比单施N肥有利于提高脂肪烃类化合物的相对比例。C-1s NEXAFS方法能够原位表征长期定位施肥条件下土壤有机碳官能团组成的变化。     

有机官能团的太赫兹光谱特征研究

采用傅里叶远红外光谱仪(FTIR),在室温条件下测量了多种饱和直链有机小分子的太赫兹光谱。测试结果显示,有机官能团的差异导致有机物的太赫兹光谱特征显著不同。其中,有机物的晶格振动吸收峰和分子间氢键的振动吸收峰分别位于太赫兹高频和低频波段。而且,饱和直链一元醇的—OH官能团产生的分子间氢键的特征峰位于57 cm-1,而三十烷酸的—COOH官能团产生的分子间氢键的特征峰则位于74 cm-1。分子间氢键使三十烷醇和三十烷酸对太赫兹辐射的吸收能力明显地强于三十烷烃。相比于三十烷醇,三十烷酸的太赫兹特征峰还发生有规律的红移和蓝移现象。此外,还采用密度泛函理论B3LYP/6-311G(d, p)基组对饱和直链烷烃、烷醇和烷酸的太赫兹光谱进行了仿真计算,发现分子间氢键作用越强的有机物的单体分子的仿真结果与实测光谱的吻合程度越低。二聚体结构的仿真结果与实测光谱的吻合程度明显地高于单分子结构。研究结果对利用FTIR研究其他有机官能团的太赫兹光谱特征、探索有机分子内部的振动模式、探究有机物太赫兹响应的物理原理及器件应用等具有重要意义。     

基于Raman与FTIR对掺甲烷乙烯/氢气扩散火焰碳烟有序度和官能团的研究

以甲烷、乙烯、氢气混合扩散火焰碳烟为研究对象,采用激光共聚焦拉曼光谱（Raman）和傅里叶红外光谱（FTIR）研究了不同掺甲烷比例下乙烯、氢气混合火焰碳烟有序度及官能团的分布特性,分析了碳烟石墨化和官能团分布,揭示了掺甲烷对乙烯/氢气（氢气比例30%）层流扩散火焰的碳烟生成影响规律。Raman研究表明在甲烷掺混比为3%和7%时,在火焰高度低于4cm位置生成的碳烟有序程度显著降低,表明在此区域存在明显的碳烟生成协同效应;甲烷掺混比增大超过10%时,协同效应基本消失,碳烟有序度上升。FTIR研究表明掺混甲烷对碳烟官能团组成影响明显。掺混甲烷后脂肪族官能团相对含量整体提高。随着甲烷掺杂比的增大,CH₂相对含量增大到一峰值后减小。碳烟中芳香族官能团含量随着火焰高度的上升含量下降明显。掺混3%和7%甲烷,芳香族官能团在2和3 cm火焰高度时,芳香族官能团的含量明显上升。掺混甲烷比高于10%时,芳香族官能团的含量则有所降低。表明少量甲烷掺混使得CH₃和C₃H₃生成有了新的途径,CH₃和C₃H₃增加,而C₂H₄和C₂H₂减少不明显,从而促进了多环芳香烃(PAHs)的生成。继续增加甲烷因为稀释作用会抑制C₂H₂生成从而减少PAHs的生成,芳香族相对含量降低,因而降低了碳烟的生成。研究揭示了甲烷对乙烯/氢气层流扩散火焰中碳烟形成的相互作用：在低甲烷掺混比时存在协同效应促进碳烟生成,而在高甲烷掺混比时协同效应消失。     

雅鲁藏布江源区高寒草地退化光谱响应变化研究

雅鲁藏布江源区的草地退化监测研究对于揭示全球变化影响下的区域生态系统响应特征、 探讨其驱动因子及评价西藏高寒生态环境质量具有重要意义。基于高寒草甸、 高寒草原和荒漠等不同类型和不同退化程度草地的地面实测数据,对雅鲁藏布江源区高寒草地的典型植物光谱特征和草地退化过程中的光谱响应变化进行了分析。结果表明作为高寒沼泽草甸、 高寒草甸、 高寒草原和高寒灌丛等类型的典型优势种藏北嵩草、 小嵩草、 紫花针茅和金露梅具有明显的光谱特征差异,主要体现在红边位置、 红边形状、 红谷和纤维素吸收波段处,与植物的生长形态和枯叶鞘固有特性密切相关。在草地退化过程中,光谱反射率整体上持续降低,叶绿素吸收造成的“红谷”特征弱化,近红外水分吸收谷变弱,土壤背景光谱特征渐渐凸显。通过对比常见的植被指数,发现那些能够充分描述植物红边或者叶绿素吸收特征的指数具有更高的可分性,表明可能对草地退化具有更好的表征能力,为西藏高寒草地退化遥感监测提供了参考依据。     

光谱技术在草地土壤检测中的应用和展望

光谱技术检测具有、省时、成本低、可以无损伤、直接分析等特点,可以同时检测多种土壤成分、在野外检测具有实时性。文章对光谱技术应用于检测草地土壤水分含量、土壤有机质、各种营养元素、土壤质地等方面进行了总结,使用该技术可以及时快捷获取各种土壤数据,有效提高草地管理水平。当前需要解决的问题是对草地植物地下生物量的检测,这对于预测牧草生长状况具有重要作用。另外,能够应用于野外检测草地土壤的光谱仪器还不多,需要开发更多便携式、可野外使用的实时检测仪器。     

氮化碳的高压同步辐射研究

 采用金刚石对顶砧及原位同步辐射实验技术,对高温高压有机催化反应制备的氮化碳材料,进行了室温及直到44 GPa压力条件下的原位高压同步辐射X射线衍射研究,并用最小二乘法拟合了样品的Murnaghan型等温状态方程。结果表明,在室温及直到44 GPa压力条件下,石墨相C₃N₄和待定的正交相CN材料都是稳定的,没有发生明显的相变,推测正交相CN材料可能是原始材料三聚氰胺和三聚氰氯在高温高压条件下催化热解产生的某种高分子有机聚合物。     

基于高光谱数据的高寒草地营养状况的研究

高寒草地牧草营养状况的遥感监测是草地合理利用的基础,是草地动态监测的难点。通过对高寒草地牧草营养成分和对应时间高光谱数据的分析,探讨草地营养状况与植被高光谱数据间的关系。结果表明,两波段比高光谱指数模型与草地营养biomass,air-DM,P,CF,CP指标间显著相关;MAXR多元回归模型,当选取波段数达到五个,模型与各营养指标均显著相关。总体上,MAXR回归模型要优于两波段比模型,MAXR模型对air-DM,P,CF进行反演,可获得较高的精度。     

顾及粗糙度的土壤有机碳成像高光谱估测模型

可见近红外非成像光谱分析技术已被广泛用于土壤有机碳（SOC）含量估测,然而该技术的使用受土壤粗糙度的影响,对样本的前处理要求较高,导致模型的实用性受限。针对这一问题,以美国爱荷华州农田土壤为研究对象,使用成像及非成像光谱仪获取土壤样本研磨前后的可见近红外反射光谱,采用去包络线（CR）、吸光度变换（AB）、S-G平滑（SG）、标准正态变换（SNV）、多元散射校正（MSC）5种光谱预处理手段,利用偏最小二乘回归（PLSR）和支持向量回归（SVR）算法构建并对比土壤SOC光谱估算模型,探究利用成像光谱数据估测高粗糙度样本SOC含量的可行性。实验结果表明,使用成像光谱数据能够实现高粗糙度样本的SOC含量估算,而使用非成像光谱数据则无法估算高粗糙度样本的SOC含量;基于成像光谱数据建立的高粗糙度SOC最优PLSR估算模型R2能够达到0.739以及最优SVR估算模型R2为0.712,而基于非成像光谱数据建立的高粗糙度SOC最优PLSR和SVR估算模型R2仅仅分别为0.344和0.311。基于AB,SG,SNV和MSC这4种预处理手段之后的成像光谱数据建立的土壤样本研磨前的PLSR模型性能优于样本研磨之后建立的PLSR模型,而SVR模型性能正好相反。而对于非成像光谱数据来说,土壤样本研磨后建立PLSR和SVR模型精度总是强于样本研磨前建立的模型精度。对于这两种光谱数据和两个估算模型而言,不同的光谱预处理方法提高模型估算精度的能力不同。土壤样本研磨前后,基于成像光谱数据建立的PLSR和SVR模型性能均优于非成像光谱数据所构建的模型。成像光谱技术能够增强高粗糙度土壤样本可见近红外光谱与SOC的相关性,从而提高模型估算精度;能够克服土壤粗糙度的影响;为野外大尺度估测SOC含量提供了新的手段。     

用FTIR研究聚酰胺树脂固化过程中官能团的变化

通过红外光谱分析对其反应过程中官能基的变化进行初步的探讨.红外光谱分析得出的结论为:环氧树脂的固化剂聚酰胺树脂,随着温度的升高,酰胺羰基C=O的伸缩振动及NH2的变角振动与C-N的伸缩振动发生耦合作用是引起1640-1657cm-1吸收峰强度显著变化的原因.聚合反应过程中,影响聚合物微观结构变化的因素很多,本文重点讨论温度的影响.     

东北黑土不同组分有机碳的近红外光谱测定

不同颗粒组分的土壤有机碳(soil organic carbon,SOC)具有不同的化学组成且对不同农艺措施响应不同,因此了解其信息有助于深入理解SOC对土壤肥力的贡献。本研究旨在评价近红外光谱(near Infraredspectroscopy,NIRS)预测黑土不同颗粒组分SOC(水稳性团聚体结合碳、颗粒态有机碳及不同大小粒级有机碳)的潜力。土壤样品(n=136)采集于东北典型黑土带上,利用偏最小二乘法建立定量模型(n=100),并用独立样本对模型进行检验(n=36)。结果表明:NIRS可以在一定程度上预测水稳性团聚体结合碳含量(R2=0.69-0.82,RPD=1.2-1.8);对矿质结合态SOC(<53μm)(R2=0.97,RPD=5.4)及细粒级SOC(<20μm)(R2=0.93,RPD=3.8)预测结果较好,对颗粒态有机碳(>53μm)和粗粒级SOC(>20μm)预测结果不理想。NIRS在简化黑土不同颗粒组分SOC的测定,特别是矿质结合态(<53μm)SOC,具有很好的应用前景。     

Wettability modification of pitch-based spherical activated carbon by air oxidation and its effects on phenol adsorption

The surface chemistry of pitch-based spherical activated carbon (PSAC) was modified by air oxidation to enhance its wettability as well as adsorption properties. Changes of PSAC after modification in texture, surface chemistry and wettability were studied by different techniques including N₂ adsorption, X-ray photoelectron spectroscopy (XPS) and dynamic contact angle analyzer (DCA). Phenol adsorption characteristics in different solvents on PSAC were also investigated. When PSAC was modified under an atmosphere with 20 vol.% oxygen at 400 and 450 °C for 5 h, surface acidic groups increased from 0.11 to 1.22 and 1.60 meq/g, while basic groups decreased from 0.52 to 0.03 and 0.02 meq/g, respectively. After PSAC was modified, the increase of the oxygen-containing groups, especially carboxylic and phenolic ones, is responsible for the increasing of the surface acidity and the significant improvement of the wettability of PSAC. PSAC with a relatively high oxygen content provided a low adsorption capacity to phenol in aqueous solution, and the adsorption isotherms change from Langmuir class (L) to the S-shaped curve; while the solvent is changed into cyclohexane, all adsorption isotherms are type L, and the adsorption capacity to phenol increases with increasing oxygen-containing groups. Possible reasons, including the solvent effect, π-π dispersion and donor-acceptor interactions are discussed.     

Time-resolved observation of structural change of copper induced by laser shock using synchrotron radiation with dispersive XAFS

ABSTRACT

We report a single-shot nanosecond time-resolved dispersive XAFS measurement of copper foil under laser-induced shock compression. Obtained EXAFS results indicated clearly the structural evolution, though XANES spectra showed that the laser irradiation does not affect the copper electronic state. The nearest (ca. 0.22 nm) and longer (ca. 0.44 nm) Cu–Cu distances are changed at 4 and 200 ns, respectively, in the radial structure functions (RSFs). It was revealed that an average compression of 2% occurs at 4 ns and is released within 200?ns. It was found that the fragmentation of the copper begins at around 200 ns according to the increase in distance of the RSF.     

Evaluation of spectral pretreatments,spectral range,and regression methods for quantitative spectroscopic analysis of soil organic carbon composition

Although there is an increasing interest in using infrared spectroscopy for the simple, rapid, and inexpensive prediction of soil organic carbon content, few studies have used this technique to measure organic carbon chemistry. In this paper, based on both near-infrared and mid-infrared diffuse reflectance spectroscopy, we compared the use of instrumentation, spectral pretreatment, and regression method for the prediction of three parameters related to organic carbon content, one related to isotopic composition, and five related to organic carbon chemistry. A total of 140 soil samples collected from seven oriental oak forest sites across East China were used as the data set for the calibration-validation procedure. Calibrations using sample set partitioning based on joint x-y distances method significantly outperformed those using Kennard-Stone method. Compared to models using linear method (i.e., partial least squares), those using non-linear regression method (i.e., support vector machines) greatly improved the prediction precision of the alkyl-to-O-alkyl ratio and performed slightly better for the other organic carbon chemical compositions. Instrumentation had a large effect as mid-infrared models had higher average prediction accuracies than near-infrared models. We finally proposed a model using second derivative preprocessing, joint x-y distances based sample set partitioning, mid-infrared spectra, and support vector machines regression to quantify organic carbon chemistry in this study. The results are helpful for the further study of soil composition measurement.     

单壁纳米碳管的声子谱研究

通过五步旋转操作方便地得到了不同位置原子间的力常数矩阵，从而可以使对各种不同类型管的声子谱的计算变得简便. 计算表明，非螺旋的扶手椅型（n, n）管与锯齿型(n, 0)管的非简并和二重简并模式数分别为12和6(n-1)，这与从群论等方法所得结果相符. 关键词： 纳米碳管 声子谱 振动模式密度 动力学矩阵     

碳纳米管辐射太赫兹波的理论分析与数值验证

基于简单紧束缚方法理论,利用一维碳纳米管的量子化周期边界条件得到了碳纳米管的电子能级结构关系.并结合已报道的碳纳米管中电子与声子相互作用的实验结果,得到了碳纳米管能够辐射太赫兹波的结论.通过数值结果验证了碳纳米管在外场作用下能够产生太赫兹波,并对数值计算结果中太赫兹波的振荡现象给予合理的解释.其结果为进行碳纳米管产生太赫兹辐射的实验研究提供深入的理论基础. 关键词： 太赫兹波 碳纳米管     

Study of the growth of fullerene-carbonized epitaxial SiC thin films by synchrotron radiation

 Thin SiC films have been deposited on silicon(0 0 1) substrates by fullerene-carbonization. Using synchrotron radiation X-ray diffraction pole figure measurements have been employed in order to study the texture of the layers. It is qualitatively shown that the films contain epitaxially aligned β-SiC crystallites with the same orientation as the underlying substrate and their twins of first and second order. The orientational spread of the epitaxial crystallites in terms of tilt against and rotation around the substrate normal is smaller than 3°. The formation of twins as a growth defect plays a major role which is even more pronounced at a higher substrate temperature. Furthermore, an additional preferred orientation has been identified which can only be explained by a non-cubic SiC phase. The portion of these crystallites in the film can be considerably reduced by an increase of the deposition temperature. Received: 18 April 1996/Accepted: 12 August 1996     

水体有机污染物浓度检测中的紫外光谱分析方法

水体中的大多数有机污染物在紫外区域有较强的吸收,因此可利用紫外吸光度检测水体中的有机污染物浓度。在检测过程中,通过平滑、导数、标准正态变量变换等光谱预处理后,采用主元回归、偏最小二乘、支持向量机等方法建立回归模型,并由该模型依据待测样本的紫外光谱数据计算出有机污染物浓度。为了探究不同的预处理方法、建模方法在有机污染物浓度检测中的特点及内在联系,本文对一组来自污水厂进出水的光谱数据采用不同的预处理和建模方法进行实验研究,研究结果表明:当获得的原始数据较好时,可以直接进行建模,进行光谱预处理反而会使模型效果下降;由于本实验中污水的样本数小于光谱数据点数,所以最小二乘支持向量机更适合于本组实验样本。     

Preparation and structural properties of thin carbon films by very-high-frequency magnetron sputtering

Growth and structural properties of thin a-C films prepared by the 60 MHz very-high-frequency(VHF) magnetron sputtering were investigated. The energy and flux of ions impinging the substrate were also analyzed. It is found that the thin a-C films prepared by the 60 MHz sputtering have a lower growth rate, a smooth surface, and more sp~3 contents.These features are related to the higher ion energy and the lower ions flux onto the substrate. Therefore, the 60 MHz VHF sputtering is more suitable for the preparation of thin a-C film with more sp~3 contents.     

Determination of carbon in soil by laser spectral analysis

We have used a combination laser/electrospark method for fast determination of carbon content in soil. Excitation of the spectra is carried out both directly in a laser ablation plume and when a pulsed electric discharge is applied to it. We have plotted a calibration curve that is linear for the major concentration range of practical importance for the analyte element, all the way up to 8.6%. The carbon detection limit for the combination discharge approach is 0.07%. We have analyzed the ratio of the nitrogen and carbon contents, and also the hydrogen and carbon contents as a function of the carbon concentration in the studied soils samples. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 2, pp. 262–268, March–April, 2008.