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81.
The photocatalytic degradation of dye Rhodamine B (RhB) in the presence of TiO2 nanostdpe or P25 under visible light irradiation was investigated. The degradation intermediates were identified using Infrared spectra (IR spectra), ^1H nuclear magnetic resonance (^1HNMR) spectra, and gas chromatography-mass spectroscopy (GC-MS). The IR and the ^1HNMR results showed that the large conjugated chromophore structure of RhB was efficiently destroyed under visible light irradiation in both the photocatalytic systems (TiO2 nanostfipe or P25 and Rhodamine B systems). GC-MS results showed that the main identified intermediates were ethanediotic acid, 1,2-benzenedicarboxylic acid, 4-hydroxy benzoic acid and benzoic acid, which were almost the same in the TiO2 nanostdpes and P25 systems. This work provides a good insight into the reaction pathway(s) for the TiO2-assisted photocatalytic degradation of dye pollutants under visible light irradiation. 相似文献
82.
本文研究了近场长周期强地震动加速度的傅氏谱和功率谱模型及其参数估计方法,基于强地震动参数统计上的无向性,提出了一种结合地震学模拟模型和工程学统计回归模型的综合方法。文中定义了强地震动平稳段均方根加速度的计算方法,并通过均方根加速度建立了震源力学参数和强地震动工程参数间的关系。通过对目前使用的主观持时定义的应用分析,指出主观持时定义使得估计的地震动过程的峰值加速度的变异性与实际地震动过程的峰值加速度的变异性有显著不同,明显偏小,这对于结构抗震可靠度分析可能会得到失效概度偏小的结果,应引起工程界的重视。 相似文献
83.
针对矿业废弃地高背景值-历史矿业源相叠加区下土壤重金属Cd污染问题,以西南地区某历史硫磺矿业废弃地重构土壤为研究对象,采集剖面土壤共30个样品,分析测试土壤样品中镉(Cd)、铬(Cr)、镍(Ni)、砷(As)和汞(Hg),利用电镜扫描-能谱分析(SEM-EDS)和重金属形态连续提取的BCR方法,分析不同土层厚度下Cd的赋存形式,运用风险评价编码法(RAC)和次生相与原生相分布比值法(RSP)对其进行有效性评价,以及对不同理化性质下Cd各形态的变化规律进行了初步探讨.结果表明,研究区5种重金属中Cd全量的富集系数最高,达4以上;通过形貌特征可以发现,样品中存在较多的次棱角状、棱角状颗粒,不同深度下的能谱特征显示结果相似,均含有Cd、Fe、S和As等元素,Cd元素是以类质同象形式存在;对Cd进行潜在风险评价,RAC结果显示为中等风险及以下,RSP结果主要为重度污染;重金属全量是影响Cd各形态含量分布的最主要因素,其次pH、有机质和CEC,对垂直深度的土壤Cd赋存形态也表现出不同程度的影响.该研究结果可为进一步了解Cd在剖面土壤的活性、迁移规律、生物毒性和赋存形式提供科学依据. 相似文献
84.
85.
Xin Jin Weijie Zhang Rui Hou Pengkang Jin Jina Song Xiaochang C. Wang 《环境科学学报(英文版)》2019,31(2):289-298
The characteristics of effluent organic matter (EfOM) from a wastewater treatment plant (WWTP) during ozonation were investigated using excitation and emission matrix (EEM) spectra, Fourier transform infrared spectroscopy (FT-IR) and high-performance size exclusion chromatography (HPSEC) at different ozone dosages. The selectivity of ozonation towards different constituents and functional groups was analysed using two-dimensional correlation spectra (2D-COS) probed by FT-IR, synchronous fluorescence spectra and HPSEC. The results indicated that ozonation can destroy aromatic structures of EfOM and change its molecular weight distribution (MWD). According to 2D-COS analysis, microbial humic-like substances were preferentially removed, and then the protein-like fractions. Terrestrial humic-like components exhibited inactivity towards ozonation compared with the above two fractions. Protein-like substances with small molecular weight were preferentially reacted during ozonation based on 2D-COS probed by HPSEC. In addition, the selectivity of ozone towards different functional groups of EfOM exhibited the following sequence: phenolic and alcoholic CO groups?>?aromatic structures containing CC double bonds?>?aliphatic CH. X-ray photoelectron spectroscopy (XPS) further elucidated the preferential reaction of aromatic structures in EfOM during ozonation. 相似文献
86.
87.
A. Peters K. Delhey W. Goymann B. Kempenaers 《Behavioral ecology and sociobiology》2006,59(5):666-673
The proximate basis of sexual traits can suggest mechanisms maintaining honesty in signalling. A central role hereby has been
attributed to testosterone, although its importance for brightly coloured plumage has been questioned. We determined circulating
testosterone levels in male blue tits captured at the start of breeding and demonstrated an age-dependent relationship between
testosterone and male crown UV/blue coloration. In yearling males, testosterone increases with increasing ornamentation (higher
UV chroma, higher chroma, more UV-shifted hue), whereas in older males, this relationship is negative, with less UV-ornamented
males having higher testosterone. This pattern is robust since it occurred in 2 years, before and after egg laying, and in
males sampled during the day and during the night, despite a tenfold difference in testosterone levels. Since more UV-ornamented
young males gain higher within-pair paternity, while less UV-ornamented older males achieve more extra-pair matings, the results
imply that higher testosterone is associated with reproductive success and attractiveness in both age classes. We hypothesise
that this relationship could result from causal effects of testosterone on coloration or through associations with behaviour
and suggest ways to test these hypotheses. Our results caution against premature dismissal of a potential role for testosterone
in maintaining honesty of plumage signals. 相似文献
88.
二甲基硫醚的真空紫外光电子谱 总被引:1,自引:0,他引:1
本文测定了二甲基硫醚(DMS)的真空紫外光电子能谱(UPS),实验测得的DMS的各Iv(cV)值与Kimura的结果一致。8.79,11.29eV峰指认为硫原子孤对电子ng,ns的电子电离,12.62eV峰相应于σcs价电子电离,14.03-15.42eV的四个峰相应于πCH3-,πCH3+电子电离,紫外光辐照影响DMS的UPS,显示在πCH3有变化。微波放电时DMS的UPS有明显的影响,有许多新 相似文献
89.
水相中CCl4和CHCl3的紫外光解机理 总被引:1,自引:0,他引:1
利用瞬态吸收光谱技术研究水体污染物CCl4 和CHCl3 在紫外光照条件下的转化和归宿 ,表明在 2 4 8nm激光作用下 ,CCl4 解离为CCl3 和Cl自由基 ;CHCl3 在此条件下不解离 ,但加入少量的苯后即发生明显解离 ,产生CHCl2 和Cl自由基 .在有氧条件下 ,光解产生的CCl3 和CHCl2 自由基均与O2 反应分别生成CCl3O2 和CHCl2 O2 ;在无氧条件下 ,CCl3 和CHCl2 则发生偶合反应分别生成C2 Cl6和C2 H2 Cl4 .本研究还得出了一些微观速率常数 . 相似文献
90.
Preliminary investigation of submerged aquatic vegetation mapping using hyperspectral remote sensing 总被引:5,自引:0,他引:5
William DJ Rybicki NB Lombana AV O'Brien TM Gomez RB 《Environmental monitoring and assessment》2003,81(1-3):383-392
The use of airborne hyperspectral remote sensing imagery for automated mapping of submerged aquatic vegetation (SAV) in the tidal Potomac River was investigated for near to real-time resource assessment and monitoring. Airborne hyperspectral imagery and field spectrometer measurements were obtained in October of 2000. A spectral library database containing selected ground-based and airborne sensor spectra was developed for use in image processing. The spectral library is used to automate the processing of hyperspectral imagery for potential real-time material identification and mapping. Field based spectra were compared to the airborne imagery using the database to identify and map two species of SAV (Myriophyllum spicatum and Vallisneria americana). Overall accuracy of the vegetation maps derived from hyperspectral imagery was determined by comparison to a product that combined aerial photography and field based sampling at the end of the SAV growing season. The algorithms and databases developed in this study will be useful with the current and forthcoming space-based hyperspectral remote sensing systems. 相似文献