Optical properties of low molecular weight and colloidal organic matter: Application of the ultrafiltration permeation model to DOM absorption and fluorescence   总被引：4，自引：1，他引：4  

Claude Belzile  Laodong Guo   《Marine Chemistry》2006,98(2-4):183-196

Cross-flow ultrafiltration (CFF) is often used to obtain separation and concentration of colloids from bulk natural water samples. Application of the ultrafiltration permeation model allows the quantitative determination of the low molecular weight material (LMW, < 1 kDa) and colloids in bulk dissolved organic matter (DOM) from measurements of time series permeate samples obtained from CFF. Detailed analysis of a Yukon River water sample shows that DOM absorption coefficient and fluorescence follow the permeation model and that the complex spectral optical properties of LMW DOM can be reconstructed from CFF data. A combination of measured and modeled data indicates that the LMW contribution to bulk DOM optical properties obtained from CFF can be grossly underestimated by the use of a low concentration factor (CF, the ratio of initial sample volume to retentate volume). Even at a relatively high CF of 19, optical properties of LMW DOM calculated from measurements of the retentate or integrated permeate would underestimate true values by 5–36%. In the Yukon River sample, LMW dissolved organic carbon represented 26% of the bulk concentration, but only 3–14% of the colored DOM was in the LMW fraction while 31–33% of bulk DOM florescence was due to LMW DOM. The contrasting optical properties of LMW and colloidal DOM support the concept that analysis of bulk DOM absorption and fluorescence properties reveals information about DOM molecular weight.  相似文献   

Spectrophotometric pH measurement in estuaries using thymol blue and m-cresol purple     

Luke M. Mosley  Shamus L.G. Husheer  Keith A. Hunter   《Marine Chemistry》2004,91(1-4):175-186

The conditional acid dissociation constants (pK_a′) of two sulfonephthalein dyes, thymol blue (TB) and m-cresol purple (mCP), were assessed throughout the estuarine salinity range (0<S<40) using a tris/tris–HCl buffer and spectrophotometric measurement. The salinity dependence of the pK_a′ of both dyes was fitted to the equations (25 °C, total proton pH scale, mol kg soln⁻¹):The estimated accuracy of pH measurements using these calculated pK_a′ values is considered to be comparable to that possible with careful use of a glass electrode (±0.01 pH unit) but spectrophotometric measurements in an estuary have the significant advantage that it is not necessary to calibrate an electrode at different salinities. pH was measured in an estuary over a tidal cycle with a precision of ±0.0005 pH unit at high (S>30) salinity, and ±0.002 pH unit at low (S<5) salinity. The pH increased rapidly in the lower salinity ranges (0<S<15) but less rapidly at higher salinities.  相似文献   

Analysis and classification of hyperspectral data for mapping land degradation: An application in southern Spain     

《International Journal of Applied Earth Observation and Geoinformation》2005,7(2):85-96

Desertification is a severe stage of land degradation, manifested by “desert-like” conditions in dryland areas. Climatic conditions together with geomorphologic processes help to mould desert-like soil surface features in arid zones. The identification of these soil features serves as a useful input for understanding the desertification process and land degradation as a whole. In the present study, imaging spectrometer data were used to detect and map desert-like surface features. Absorption feature parameters in the spectral region between 0.4 and 2.5 μm wavelengths were analysed and correlated with soil properties, such as soil colour, soil salinity, gypsum content, etc. Soil groupings were made based on their similarities and their spectral reflectance curves were studied. Distinct differences in the reflectance curves throughout the spectrum were exhibited between groups. Although the samples belonging to the same group shared common properties, the curves still showed differences within the same group.Characteristic reflectance curves of soil surface features were derived from spectral measurements both in the field and in the laboratory, and mean reflectance values derived from image pixels representing known features. Linear unmixing and spectral angle matching techniques were applied to assess their suitability in mapping surface features for land degradation studies. The study showed that linear unmixing provided more realistic results for mapping “desert-like” surface features than the spectral angle matching technique.  相似文献   

岩矿石吸收系数的算和测定方法     

刘海滨 《吉林地质》1996,(2)

岩矿石吸收系数是钻孔电磁波法解决地质问题的重要的物性参数。岩矿石有无吸收系数的差异，是开展钻孔电磁波法能否奏效的前提．了解岩矿石的吸收系数可对钻孔电磁波法的透距和分辨力作出估计，并可为钻孔电磁波的反演解释提供重要的依据．本文不但给出了岩矿石吸收系数的计算方法，也给出了室内岩矿石标本吸收系数的测定方法和野外实测岩矿石吸收系数的方法。  相似文献   

Re-parameterization of a quasi-analytical algorithm for colored dissolved organic matter dominant inland waters     

《International Journal of Applied Earth Observation and Geoinformation》2016

Quasi-Analytical Algorithms (QAAs) are based on radiative transfer equations and have been used to derive inherent optical properties (IOPs) from the above surface remote sensing reflectance (R_rs) in aquatic systems in which phytoplankton is the dominant optically active constituents (OACs). However, Colored Dissolved Organic Matter (CDOM) and Non Algal Particles (NAP) can also be dominant OACs in water bodies and till now a QAA has not been parametrized for these aquatic systems. In this study, we compared the performance of three widely used QAAs in two CDOM dominated aquatic systems which were unsuccessful in retrieving the spectral shape of IOPS and produced minimum errors of 350% for the total absorption coefficient (a), 39% for colored dissolved matter absorption coefficient (a_CDM) and 7566.33% for phytoplankton absorption coefficient (a_phy). We re-parameterized a QAA for CDOM dominated (hereafter QAA_CDOM) waters which was able to not only achieve the spectral shape of the OACs absorption coefficients but also brought the error magnitude to a reasonable level. The average errors found for the 400–750 nm range were 30.71 and 14.51 for a, 14.89 and 8.95 for a_CDM and 25.90 and 29.76 for a_phy in Funil and Itumbiara Reservoirs, Brazil respectively. Although QAA_CDOM showed significant promise for retrieving IOPs in CDOM dominated waters, results indicated further tuning is needed in the estimation of a(λ) and a_phy(λ). Successful retrieval of the absorption coefficients by QAA_CDOM would be very useful in monitoring the spatio-temporal variability of IOPS in CDOM dominated waters.  相似文献   

粉色水晶内针状包裹体的成分与分布特征研究   总被引：1，自引：1，他引：0  

胡哲  郭颖 《岩矿测试》2018,37(3):306-312

粉色水晶内部的针状包裹体常被认为是三组呈三方对称的金红石或蓝线石,至今未有定论。本文选取含有针状包裹体的4颗星光粉晶,利用宝石学显微镜、激光拉曼光谱仪及紫外可见分光光度计对样品进行观察与测试,以确定包裹体的分布特征及矿物种类。无损拉曼测试发现包裹体的特征振动峰949 cm-1、999 cm-1与蓝线石标准峰相匹配,可确定针状包裹体为蓝线石或与其极为相近的矿物。放大检查发现,包裹体直径约0.5μm,长度可达毫米级,近定向分布,整体上呈汇聚状,在某些位置可粗略分为三组,同组针状包裹体近似平行分布。造成六射星光的三组蓝线石立体相交,未观察到明显的三方对称关系,与水晶的结晶习性无直接关系,故认为蓝线石为先成包裹体,在水晶的生长过程中被捕获。紫外可见分光光谱仅显示粉色蓝线石的特征吸收,表明大量的粉色蓝线石包裹体对粉色水晶的粉色有一定贡献。  相似文献   

A Screening Procedure for Heavy Metals in Soil Extracts by Alcohol Dehydrogenase and Urease Inhibition Eine Screening-Methode für Schwermetalle in Extrakten aus Bodenproben,basierend auf der Inhibierung der Enzyme Alkoholdehydrogenase und Urease     

A. Prell-Swaid  G. Schwedt 《洁净——土壤、空气、水》1994,22(2):70-75

A screening method for heavy metals in aqueous extracts of soil is presented which is based on inhibition of the enzymes urease and alcohol dehydrogenase. The method is suitable to detect cupric and mercury ions in concentrations below 0.01 mg/L and several other heavy metal ions in 1000 fold higher concentration. It is shown that the test may be used for screening of mercury ion concentrations exceeding 0.03 mg/L in aqueous solution when copper chelators are added to the test system. The usefulness of the presented tests to detect heavy metals eluted from soil was verified with samples from ore mining waste. The concentration of copper, lead, and zinc eluted from these samples to different amount was determined by atomic absorption spectrometry and was in good agreement with the enzyme inhibition data obtained with these samples.  相似文献   

闾阳－海城－东沟剖面深地震波动力学特征初探   总被引：1，自引：0，他引：1  

朱兆言  崔德鹏 《东北地震研究》1995,(3)

本文利用国内外有关深地震波动力学特征的研究方法，结合现有原始资料的实际条件，对闾阳－海城－东沟深地震测深剖面某些地段的主要波组的动力学特征进行了定性或半定量的分析与研究。在频谱分析，速度振幅的计算与相对理论振幅的对比等方面，获得了一些有益信息。为进一步合理解释深地震测深资料提供依据。  相似文献   

云南临沧地区帮卖盆地含铀煤中锗矿的研究   总被引：8，自引：0，他引：8  

张淑苓  王淑英  尹金双 《铀矿地质》1987,(5)

帮卖盆地是一个不对称山间向斜盆地,其基底为海西·燕山期(γ~3_4-γ~2_5)花岗岩体。盖层为新第三纪的含煤碎屑岩。锗矿体大部分存在于N_1~2煤层中。含铀煤主要为变质程度低的褐煤,属于半暗-半亮煤、暗亮煤及亮暗煤。锗在煤中的存在形式:1.主要为腐植酸锗络合物及锗的有机化合物;2.一部分呈吸附状态;3.极少数呈类质同象。  相似文献   

Location and quantitative analysis of OH in coesite     

M. Koch-Müller  Y. Fei  E. Hauri  Z. Liu 《Physics and Chemistry of Minerals》2001,28(10):693-705

 The incorporation of hydrogen (deuterium) into the coesite structure was investigated at pressures from 3.1 to 7.5 GPa and temperatures of 700, 800, and 1100 °C. Hydrogen could only be incorporated into the coesite structure at pressures greater 5.0 GPa and 1100 °C . No correlation between the concentration of trace elements such as Al and B and the hydrogen content was observed based on ion probe analysis (1335 ± 16 H ppm and 17 ± 1 Al ppm at 7.5 GPa, 1100 °C). The FTIR spectra show three relatively intense bands at 3575, 3516, and 3459 cm⁻¹ (ν₁ to ν₃, respectively) and two very weak bands at 3296 and 3210 cm⁻¹ (ν₄ and ν₅, respectively). The band at 3516 cm⁻¹ is strongly asymmetric and can be resolved into two bands, 3528 (ν_2a) and 3508 (ν_2b) cm⁻¹, with nearly identical areas. Polarized infrared absorption spectra of coesite single-crystal slabs, cut parallel to (0 1 0) and (1 0 0), were collected to locate the OH dipoles in the structure and to calibrate the IR spectroscopy for quantitative analysis of OH in coesite (ɛ _{i ,tot}=190 000 ± 30 000 l mol⁻¹ _H2O cm⁻²). The polarized spectra revealed a strong pleochroism of the OH bands. High-pressure FTIR spectra at pressures up to 8 GPa were performed in a diamond-anvil cell to gain further insight into incorporation mechanism of OH in coesite. The peak positions of the ν₁, ν₂, and ν₃ bands decrease linearly with pressure. The mode Grüneisen parameters for ν₁, ν₂, and ν₃ are −0.074, −0.144 and −0.398, respectively. There is a linear increase of the pressure derivatives with band position which follows the trend proposed by Hofmeister et al. (1999). The full widths at half maximum (FWHM) of the ν₁, ν₂, and ν₃ bands increase from 35, 21, and 28 cm⁻¹ in the spectra at ambient conditions to 71, 68, and 105 in the 8 GPa spectra, respectively. On the basis of these results, a model for the incorporation of hydrogen in coesite was developed: the OH defects are introduced into the structure by the substitution Si^4+(Si2)+4O²⁻= ^[4]□^(Si2) + 4OH⁻, which gives rise to four vibrations, ν₁, ν_2a, ν_2b, and ν₃. Because the OH(D)-bearing samples do contain traces of Al and B, the bands ν₄ and ν₅ may be coupled to Al and/or B substitution. Received: 19 December 2000 / Accepted: 23 April 2001  相似文献