基于红外光声光谱的蒙脱石-黄原糖复合体界面层特征研究

黏土矿物-有机物复合体在土壤中具有重要的作用,而土壤黏土矿物-多糖复合体是黏土矿物-有机物复合体形成的前体,有利于复合体的形成和转化,但其具体的作用机制尚不清楚。本研究制备了蒙脱石-黄原糖模型复合体,采用X-衍射分析了复合体的结构信息,并利用傅里叶转换红外光声光谱原位逐层扫描功能,探测了蒙脱石-黄原糖复合体表面下不同深度的光谱信息。结果表明,蒙脱石与黄原糖的相互作用主要发生在蒙脱石的表面,并形成表面界面层;该界面层具有明显的红外光声光谱特征,所形成的复合体有更强的持水能力,且表层与亚表层的光谱信息明显不同;红外光声光谱逐层分析表明,蒙脱石-黄原糖复合体界面层厚度大约在2.05～6.47μm之间。本结果为揭示复杂的矿物-有机物复合体形成过程及其影响因素提供了定量依据。     

蒙脱石-氧化铁复合体的表征及其对不同形态磷的吸附特性

制备了蒙脱石-针铁矿复合体(Mt-Goe)和蒙脱石-非/弱晶质氧化铁复合体(Mt-HFO),研究了它们的结构、表面性质及其对无机磷酸盐(Pi)和植酸(IHP)的吸附特性。结果显示,Mt-Goe中少量羟基铁离子进入了蒙脱石晶层间导致其层间距增大,针铁矿颗粒较好地包被在蒙脱石外表面;Mt-HFO中蒙脱石层间则发生了Fe~(3+)水解,生成了(羟基)铁氧化物,并在蒙脱石表面形成非晶质氧化铁颗粒。蒙脱石、Mt-Goe和Mt-HFO的比表面积分别为258.7、185.4和226.4 m~2·g~(–1),其表面分形度、等电点和表面羟基含量均依次升高,pH5.5时的表面Zeta电位分别为–46.1、–13.6和–19.4 mV。3种样品对Pi和IHP的吸附模式以匀质性表面单层吸附为主,Langmuir饱和吸附量(qmax)和吸附亲和力均表现为由大到小依次为Mt-HFO、Mt-Goe、蒙脱石。3种样品对Pi和IHP的动力学吸附过程适合用准二级动力学模型描述,其速率常数由小到大依次为Mt-HFO、Mt-Goe、蒙脱石。与吸附Pi相比,3种样品吸附IHP的动力学速率常数明显减小,吸附量明显增大;Mt-HFO对IHP的吸附速率尤其缓慢,而吸附量远大于对Pi的吸附量。     

基于近红外光声光谱的土壤有机质含量定量建模方法

该研究的目的在于应用近红外光声光谱技术结合不同的定量分析方法实现5种不同类型土壤有机质含量的快速估测。对中国中、东部地区5种不同类型土壤风干样本进行光谱扫描,经过多元散射校正、一阶导数、二阶导数及平滑等预处理后,应用逐步多元回归(SMLR)、主成分分析(PCR)、偏最小二乘法(PLS)和偏最小二乘法-反向传播神经网络(PLS-BPNN)等方法建立土壤有机质含量的定量估测模型。结果显示,不同预处理方法对所建土壤有机质含量估测模型的预测精度有较大影响,总体表现为多元散射校正+Norris一阶导数>多元散射校正>Norris一阶导数>标准正态化>Norris二阶导数>吸光度>Savitzky-Golay平滑后一阶导数>Savitzky-Golay平滑后二阶导数。对于4种不同建模方法,均以多元散射校正+Norris一阶导数滤波平滑后的光谱建模精度最高,其中采用PLS-BPNN方法建模效果最好,其次是PLS、SMLR和PCR。采用PLS-BPNN建立有机质校正模型具有极高的预测精度,建模决定系数和均方根偏差分别为0.97和1.88,模型测试决定系数和均方根偏差分别为0.97和1.72。因此,基于多元散射校正+Norris一阶导数光谱建立的PLS-BPNN模型可能是土壤有机质含量估测建模的最优方法。     

基于山-谷-水耦合界面的三峡水库地表覆被转换轨迹分析

利用三峡库区多时相LUCC遥感解译数据、水系和DEM数据,考虑淹没时间的连续性和地表覆被的自然特性,构建地表覆被分类体系,对比识别水库不同运行阶段地表覆被转换的宏观时空格局,旨在找出不同覆被转换轨迹的山-谷-水界面分布与地形梯度特征。结果表明:水库不同运行阶段,1库区地表覆被间发生了不同程度的多样化转换,但总体格局不变,均以透水性的季节性绿色覆被和常绿性绿色覆被为主,占整个库区的96%以上;2库区地表覆被间的转换方向和规模呈阶段性差异,但主要地表覆被转换方式在3个运行阶段基本一致,表现为季节性与常绿性绿色覆被间互转、灰色覆被吞噬季节性绿色覆被不断扩张、水位上升淹没绿色覆被和蓝色覆被,只是其空间分布与延展呈现较大阶段性差异;3库区局部山-谷-水界面地表覆被间的转换呈显著差异,前两阶段(1997—2003年和2003—2006年)以山-山界面地表覆被转换为主,后一阶段(2006—2009年)主要是山-谷界面地表覆被间的转换,且同类地表覆被在山-谷-水界面上的转换流向也发生阶段性变化;4库区主要地表覆被转换方式的分布符合自然和人类活动的规律,在海拔和坡度2个地形梯度上具有显著差异性,但坡向仅对淹没区转换有显著影响。研究结果可为库区土地利用规划与生态环境保护提供参考。     

不同傅里叶变换红外光谱法研究土壤光谱特征的比较与应用

为了将傅里叶变换红外光谱技术更好地应用于土壤中官能团的定量分析,通过比较3种不同傅里叶变换技术下土壤特征吸收峰的差异,来选取最佳的光谱技术应用于土壤的相关研究。采用透射(T-FTIR)、衰减全反射(ATR-FTIR)和漫反射(DR-FTIR)3种光谱技术分别对有机物(苯甲酸、硬脂酸)和土壤(辽东栎)进行了分析。并将辽东栎和草地土壤样品按不同比例混合,使用T-FTIR和DR-FTIR对混合土样进行光谱测定,用于定量分析研究。结果表明:(1)有机物样品在3种光谱技术中均出现特征吸收峰,苯甲酸在1 600～1 400 cm^-1出现苯环C=C骨架特征峰,硬脂酸在2 900～2 800 cm^-1显现甲基的特征峰。有机物中羧酸-COOH内羰基-C=O在1 720～1 680 cm^-1出现伸缩振动吸收峰,羟基-OH分别在1 430～1 410 cm^-1,940～930 cm^-1附近出现面内和面外弯曲振动吸收峰。有机物在T-FTIR技术中需要用溴化钾(KBr)对其稀释。(2)辽东栎土壤样品在T-FTIR和DR-FTIR技术测试中发现,其土壤谱图中有较多有效特征吸收峰,土壤样品在T-FTIR技术中也需要用KBr进行稀释并使样品均匀的分布在锭片中; 而ATR-FTIR技术测试中仅出现个别有效特征吸收峰,不利于对土壤谱图鉴别与进一步分析。(3)辽东栎和草地土壤样品按不同比例混合的测试结果表明:T-FTIR和DR-FTIR技术测试中质量分数与峰面积比呈正相关,线性拟合分别为R²=0.70和R²=0.88。土壤在3种不同红外技术中,DR-FTIR光谱具有较好的土壤特征吸收峰,对土壤样品可以不用KBr稀释。测试步骤简单易操作,可用于土壤样品定量分析研究。     

Impact of Bran Addition on Water Properties and Gluten Secondary Structure in Wheat Flour Doughs Studied by Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy

The aim of this work was to elucidate the underlying physical mechanism(s) by which bran influences whole grain dough properties by monitoring the state of water and gluten secondary structure in wheat flour and bran doughs containing 35–50% moisture and 0–10% added bran. The system was studied with attenuated total reflectance (ATR) FTIR spectroscopy. Comparison of the OH stretch band of water in flour dough with that in H₂O‐D₂O mixtures having the same water content revealed the formation of two distinct water populations in flour dough corresponding to IR absorption frequencies at 3,600 and 3,200 cm^–1. The band intensity at 3,200 cm^–1, which is related to water bound to the dough matrix, decreased and shifted to lower frequencies with increasing moisture content of the dough. Addition of bran to the dough caused redistribution of water in the flour and bran dough system, as evidenced by shifts in OH stretch frequency in the 3,200 cm^–1 region to higher frequencies and a reduction in monomeric water (free water). This water redistribution affected the secondary structure of gluten in the dough, as evidenced by changes in the second‐derivative ATR‐FTIR difference spectra in the amide I region. Bran addition caused an increase in β‐sheet content and a decrease in β‐turn (β‐spiral) content. However, this bran‐induced transconformational change in gluten was more significant in the 2137 flour dough than in Overley flour dough. This study revealed that when bran is added to flour dough, water redistribution among dough components promotes partial dehydration of gluten and collapse of β‐spirals into β‐sheet structures. This transconformational change may be the physical basis for the poor quality of bread containing added bran.     

近红外光谱结合小波变换预处理在蜂蜜产地快速检测中的应用

应用近红外光谱结合化学计量学方法对蜂蜜产地进行了判别分析。kennard-Stone法划分训练集和预测集。光谱用一阶导数加自归一化预处理后,再用小波变换（WT）进行压缩和滤噪。结合滤波后光谱信息,分别用径向基神经网络（RBFNN）和偏最小二乘-线性判别分析（PLS-LDA）建立了苹果蜜产地和油菜蜜产地判别模型。对不同小波基和分解尺度进行了详细讨论。对苹果蜜,WT-RBFNN模型和WT-PLS-LDA模型都是小波基为db1、分解尺度为2时的预测精度最好,都为96.2%。对油菜蜜：WT-RBFNN模型在小波基为db4和分解尺度为1时,预测精度最好;WT-PLS-LDA模型在小波基为db9、分解尺度也为1时,预测精度最好,为90.5%;预测精度WT-PLS-LDA模型优于WT-RBFNN模型。研究表明：WT结合线性的PLS-LDA建模比WT结合非线性的RBFNN建模更适于蜂蜜产地鉴别;近红外光谱结合WT-PLS-LDA可实现对蜂蜜产地的快速无损检测,为蜂蜜产地鉴别提供了一种新方法。     

傅里叶红外标准加入法测定银杏叶提取物(EGb)中的总内酯

银杏叶提取物（ＥＧｂ）经ＫＢｒ压片后,在１８４０～１７２６ｃｍ－１区间,用傅里叶变换红外光谱仪测量峰面积,以美国Ｓｉｇｍａ的银杏内酯Ｂ为标准品,用ＦＴＩＲ标准加入法测定ＥＧｂ中的总内酯含量,其结果与ＲＰＨＰＬＣ、ＲＩ法接近,平均回收率９６．８％,ＳＤ０．４,ＲＳＤ５．５％,方法简便,结果可靠,适于ＥＧｂ及其制剂在生产过程中作质量控制的测定方法用。     

Quantitative Analysis of Benzyl Modification in Waxy Maize Starch by Fourier Transform (FT) Raman Spectroscopy

Waxy maize starch was chemically modified to varying benzylation levels and the degree of benzylation substitution was measured using a nuclear magnetic resonance (NMR) method. Fourier Transform (FT) Raman spectra of the chemically modified starches were acquired and aromatic C=C stretch Raman bands characteristic of the benzylation modification were used to derive a calibration curve for the Raman intensity of these marker bands versus the degree of benzylation substitution. The best‐fit linear regression to the plotted data gave a linear correlation coefficient of 0.997. The FT‐Raman technique provides a fast, nondestructive method for the measurement of the degree of benzylation substitution of modified waxy maize starches and should be applicable for use with benzylated starches from other botanical sources.     

Rapid Variety Identification of Pure Rough Rice by Fourier‐Transform Near‐Infrared Spectroscopy

Rice variety is considered as an important factor influencing cooking and processing quality because of variations in size, shape, and constitution. Difficulty in management of rough rice with lower varietal purity becomes a significant problem in rice production and can result in the reduction of rice quality. Fourier‐transform near‐infrared (FT‐NIR) spectroscopy was used to identify the variety of rough rice through whole‐grain techniques. Moist rough rice samples (n = 259) comprising five varieties (Khao Dawk Mali 105 [KDML105], Pathum Thani 1, Suphan Buri 60, Chainat 1, and Pitsanulok 2) were gathered from different locations around Thailand and scanned in the NIR region of 9088–4000 cm^–1 in reflectance mode. Soft independent modeling of class analogies (SIMCA) and partial least squares discriminant analysis (PLSDA) methods were used for identification by utilizing preprocessed spectra. The highest identification accuracy achieved was 74.42% by the SIMCA model and 99.22% by the PLSDA model. The best PLSDA model demonstrated approximately 97% correct identification for KDML105 samples and 100% for the others. This study raises the possibility of applying FT‐NIR spectroscopy as a nondestructive technique for rapidly identifying moist rough rice varieties in routine quality assurance testing.     

中红外光声光谱法测定土壤顶空氨气浓度

利用中红外光声光谱对土壤顶空氨气(NH3)浓度进行测定。结果表明,在动镜速率为0.16 cm/s,分辨率为4 cm–1时获得的NH3光谱噪音较少且信号强度高。利用选定的参数采集不同浓度NH3光谱,其中位于900~1 000 cm–1的特征吸收峰适于定量分析。分别选用该特征吸收的峰高、峰面积和第一主成分与NH3浓度进行回归建模,线性决定系数(R2)均达到0.9以上,表明三者都呈显著线性相关,中红外光声光谱可以用于快速测定土壤顶空中NH3浓度,这为土壤氮素循环研究提供了新手段。     

基于傅里叶红外光谱弃耕地开垦前后土壤有机质结构变化分析

以新疆玛纳斯河流域盐渍化弃耕地为案例,人为开垦(5年)后不同土层土壤为研究对象,以弃耕地土样为对照,采用傅里叶红外光谱(FTIR)对不同土层土壤有机质(SOM)结构进行比较,研究弃耕地开垦前后土壤有机质红外光谱特征,探明开垦对不同土层有机质结构变化的影响,明确有机质结构稳定性变化情况,分析不同深度土层土壤有机质结构稳定性的变化。结果表明:开垦前后土壤红外光谱的特征峰相似,特征峰所代表的官能团主要来源于脂肪族(2925和2854 cm^-1)、芳香族(1623和1432 cm^-1)、糖类(1163、1073、1033和1007 cm^-1)和游离羟基(3620和3421 cm^-1);开垦后农田土壤有机质中脂肪族、芳香族、糖类和游离羟基官能团的峰面积在10~20 cm土层中较弃耕地分别提高1.24、37.64、77.44和27.39;芳香族的相对峰强度增长15.93%,脂肪族的相对峰强度下降9.09%;随着土层深度的增加,弃耕地土壤中来源于糖类和芳香族的峰面积逐渐降低,而开垦后棉田芳香族的官能团峰面积逐渐升高。农田开垦种植后增加了土壤有机质稳定性,尤其在20~40 cm土层表现更为明显。综上所述,弃耕地开垦后土壤有机质结构更为复杂,土壤有机质中芳香族官能团所占比例的提高是土壤有机质结构稳定性提高的重要原因。     

Rapid Analysis of Apple Leaf Nitrogen using Near Infrared Spectroscopy and Multiple Linear Regression

A quick method was developed for diagnosis of nitrogen (N) in apple trees based on multiple linear regressions to establish the relationship between near-infrared reflectance spectra (NIRS) and the N contents of fresh and dry tissue. Spectral pretreatment methods such as derivatives, smoothing, and normalization were used. The derivatives appeared to be the most effective. The best calibration for fresh leaf gave 0.842 for the correlation coefficient of validation (R_v), 1.119 g kg^?1 for the root mean square error of prediction (RMSEP), and 8.311 for the ratio of the range in reference data from the validation samples to the root mean square error of prediction (RER). The best calibration for dried ground samples was obtained with R_v = 0.952, RMSEP = 0.633 g kg^?1, the ratio performance deviation (RPD) = 3.27, and RER = 13.728. The results showed that calibrations of dry-apple leaf are robust enough for an accurate prediction of N.