氧化铁矿物催化分解苯酚的动力学速率及其产物特征   总被引：3，自引：0，他引：3  

吴大清  刁桂仪  袁鹏 《矿物岩石地球化学通报》2006,25(4):293-298

本文研究了针铁矿、纤铁矿、赤铁矿和磁铁矿在过氧化氢参与下催化分解苯酚的动力学速率与溶液pH值的关系,并用紫外吸收谱测定了反应产物的谱学特征。结果表明,纤铁矿反应体系催化分解苯酚的速率常数(k)最大,其余依次为磁铁矿、针铁矿和赤铁矿。在纤铁矿反应体系中又以pH=3.8时反应速率常数最大。除赤铁矿反应体系外,当溶液pH=3~4时苯酚被完全分解,并有50%~65%的有机碳(TOC)被矿化。在pH=3.25的赤铁矿反应体系中,苯酚大多仅被转化为多酚,小部分苯环被打开形成己烯酸。当溶液pH=4~5时,苯酚一般仅被转化为多酚类化合物,但TOC基本不变。当溶液pH>5时,苯酚没有发生明显的转化和矿化现象。  相似文献   

沉积盆地超压系统内油气的生成与保存   总被引：1，自引：0，他引：1  

肖七林  孙永革 《地球化学》2007,36(4):375-382

沉积盆地内的超压系统是一个相对独立的封闭-半封闭体系,与油气生成、保存关系密切.超压系统内矿物介质、有机质、水相互作用过程以及有效应力对有机质演化的作用机理研究揭示了超压对有机质演化具有显著的阶段性和差异性,具体表现在:(1)压力的影响程度是有机质演化程度的函数;(2)超压/压力效应对有机质演化发生显著影响需要达到某一最小值,即门限值;(3)在有机质演化不同阶段发育的超压对生烃的影响不同;(4)同一超压系统内,不同类型有机质对超压的响应具有差异性.迄今,已经建立了超压/压力对有机质演化影响程度的定量化模型,包括化学动力学模型和热力学模型两类.化学动力学模型仍有许多需要改进的地方,如压力影响的阀值、指前因子和活化能随反应时间的变化规律等,相对而言,热力学模型似乎更简单、易用,但其可靠性和普适性还有待时间的检验.由于异常高压对超压系统储层内原油的热裂解反应具有抑制效应,有利于深部高温高压储层内液态烃的保存,因此,含油气盆地深部高温高压地层已成为一个较为有利的石油勘探领域.  相似文献   

二甲基硫光化学氧化反应的动力学研究   总被引：1，自引：1，他引：1  

杨桂朋  张正斌  刘心同  刘莲生 《中国海洋大学学报(自然科学版)》1997,(2)

实验研究水溶液中二甲基硫（ＤＭＳ）的光化学氧化反应的动力学。结果表明，在入射光频率与强度一定条件下，ＤＭＳ进行光化学氧化反应的速率会受到介质、ｐＨ、重金属离子的影响。Ｈｇ２＋能显著加快人工海水介质中ＤＭＳ的光氧化速率。ＤＭＳ进行光氧化的一级速率常数为４．４６×１０－５～３０．４×１０－５ｓ－１，其在光照下的人工海水介质中的半寿期为３．６ｈ。这说明光化学过程对于影响和控制ＤＭＳ在海洋中的浓度和分布起着十分重要的作用  相似文献   

Organotin accumulation in an estuarine food chain: comparing field measurements with model estimations     

Veltman K  Huijbregts MA  van den Heuvel-Greve MJ  Vethaak AD  Hendriks AJ 《Marine environmental research》2006,61(5):511-530

The bioaccumulation model OMEGA (optimal modelling for ecotoxicological applications) is used to explore accumulation of organotins in the Western Scheldt food chain, consisting of herbi-detritivores, primary and secondary carnivorous fish and a piscivorous bird. Organotins studied are tributyltin (TBT) and triphenyltin (TPT) and the respective di- and mono-organotin metabolites. Empirical elimination rate constants are compared to model predictions for organic substances and metals. It is found that field bioaccumulation ratios are higher than predicted based on elimination kinetics relevant for organic compounds. The results indicate that uptake of organotins mainly occurs via hydrophobic mechanisms, whereas elimination may occur via metal-like kinetics. This results in very low elimination rates, which are comparable to model predictions for metals.  相似文献   

新疆哈密库姆塔格沙垄北段韧性剪切带特征及其地质意义     

魏刚锋  聂江涛  辛红刚  李赛赛  张洪瑞  杜志刚  李新光 《大地构造与成矿学》2007,31(1):21-30

通过野外调研和显微构造测试,分析了新疆哈密库姆塔格沙垄北段韧性剪切带几何学、运动学和动力学特征,探讨了韧性剪切带的演化及其地质意义,详细研究了韧性剪切带S-C面理、波状消光、变形条带、变形纹、机械双晶、亚颗粒、动态重结晶颗粒、核幔结构、压力影、旋转碎斑系、显微裂隙和石英、方解石c轴组构等显微构造特征,并对其形成机制进行了解析。  相似文献   

Mechanodestruction of minerals at the crack tip (<Emphasis Type="Italic">Overview</Emphasis>): 1. Experiment     

Farit Khisamutdinovich Urakaev 《Physics and Chemistry of Minerals》2007,34(5):351-361

The kinetics of the amount of volatiles emitted from synthetic and natural calcite single crystals while cleaving and grinding are determined using time-of-flight mass spectrometry. It is revealed that the CO₂ emission is a product of mechano destruction rather than the release of impurities trapped in the crystal. Irradiation of calcite increases the CO₂ emission. A diffusion–desorption model is suggested to explain the kinetics of volatile emission from cleaved surfaces and experimental results on the emission of volatile products during the mechano destruction of various single crystals are summarized. The effects of several sources of systematic errors are discussed. The yield of volatiles is correlated with the speed of the brittle crack propagation and the physicochemical properties of minerals.  相似文献   

Changes of acoustic emission and strain in hard coal during gas sorption–desorption cycles     

Zofia Majewska  Jerzy Zi&#x;tek 《International Journal of Coal Geology》2007,70(4):305-312

The cylindrical coal samples were subjected to three successive cycles of sorption–desorption processes of a single gas (CO₂, CH₄). Acoustic emission (AE) and strains were simultaneously recorded during the sorption and desorption processes.Tests were conducted on medium-rank coal from the Upper Silesia Basin, Poland. Follow-up tests for gas sorption–desorption consistently showed significant changes of AE characteristics for re-runs on the same sample. The AE level decreased in each successive test. The most spectacular differences were observed between AE generated during the first cycle of gas sorption and the subsequent cycle. This phenomenon could be due to structural changes in the coal taking place substantially on its first exposure to the sorbate. The AE results indicate, that each cycle of gas sorption–desorption was run on the same coal though with a somewhat different structure.In those tests, the swelling of coal by CO₂ or/and CH₄ was anisotropic (greater in the direction perpendicular to the bedding plane than parallel) in each cycle of the gas sorption–desorption process.  相似文献   

Bacterial responses in activity and community composition to photo-oxidation of dissolved organic matter from soil and surface waters   总被引：1，自引：0，他引：1  

Kristin E. Judd  Byron C. Crump  George W. Kling 《Aquatic Sciences - Research Across Boundaries》2007,69(1):96-107

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Jurassic septarian concretions from NW Scotland record interdependent bacterial, physical and chemical processes of marine mudrock diagenesis   总被引：3，自引：0，他引：3  

JAMES P. HENDRY  MICHAEL J. PEARSON†  NIGEL H. TREWIN‡  ANTHONY E. FALLICK§ 《Sedimentology》2006,53(3):537-565

Septarian concretions in the Staffin Shales Formation (Kimmeridgian, Isle of Skye) allow controls on concretion rheology and septarian cracking to be investigated. Stratabound concretions consist of anhedral ferroan calcite microspar enclosing clay and minor pyrite. Intergranular volumes range from 77% to 88%, and calcite δ¹³C and δ¹⁸O values in most concretion bodies range from ?10·0‰ to ?17·3‰ and +0·3‰ to ?0·6‰ respectively, consistent with rapid and pervasive cementation in marine pore fluids. Septarian rupture occurred during incipient cementation, with a sediment volume reduction of up to 43%. Crack‐lining brown fibrous calcite records pore fluid re‐oxygenation during a depositional hiatus, followed by increasing Fe content and δ¹³C related to bacterial methanogenesis. Brown colouration results from an included gel‐like polar organic fraction that probably represents bacterially degraded biomass. A new hypothesis for concretion growth and septarian cracking argues that quasi‐rigid ‘proto‐concretions’ formed via binding of flocculated clays by bacterial extracellular polysaccharide substances (EPS). This provided rheological and chemical conditions for tensional failure, subcritical crack growth, volume contraction, calcite nucleation, and incorporation of degraded products into crack‐lining cements. Bacterial decay of EPS and syneresis of host muds provided internal stresses to initiate rupture at shallow burial. Development of septarian (shrinkage) cracks in muds is envisaged to require pervasive in situ bacterial colonization, and to depend on rates of carbonate precipitation versus EPS degradation and syneresis. Subsequent modification of septarian concretions included envelopment by siderite and calcite microspar, hydraulic fracturing associated with Cretaceous shallow burial or Palaeogene uplift; and cementation by strongly ferroan, yellow sparry calcite that records meteoric water invasion of the host mudrocks. An abundance of fatty acids in these spars indicates aqueous transport of organic breakdown products, and δ¹³C data suggest a predominantly methanogenic bicarbonate source. However, the wide δ¹⁸O range for petrographically identical cement (?1·3‰ to ?15·6‰) is difficult to explain.  相似文献   

Heterogeneous growth of cordierite in low P/T Tsukuba metamorphic rocks from central Japan     

K. Miyazaki 《Journal of Metamorphic Geology》2001,19(2):155-164

This paper examines the spatial statistics of matrix minerals and complex patterned cordierite porphyroblasts in the low‐pressure, high‐temperature (low P/T) Tsukuba metamorphic rocks from central Japan, using a density correlation function. The cordierite‐producing reaction is sillimanite + biotite + quartz = K‐feldspar + cordierite + water. The density correlation function shows that quartz is distributed randomly. However, the density correlation functions of biotite, plagioclase and K‐feldspar show that their spatial distributions are clearly affected by the formation of cordierite porphyroblasts. These observations suggest that cordierite growth occurred through a selective growth mechanism: quartz adjacent to cordierite has a tendency to prevent the growth of cordierite, whereas other matrix minerals adjacent to cordierite have a tendency to enhance the growth of cordierite. The density correlation functions of complex patterned cordierite porphyroblasts show power‐law behaviour. A selective growth mechanism alone cannot explain the origin of the power‐law behaviour. Comparison of the morphology and fractal dimension of cordierite with two‐dimensional sections from a three‐dimensional diffusion‐limited aggregation (DLA) suggests that the formation of cordierite porphyroblasts can be modelled as a DLA process. DLA is the simple statistical model for the universal fractal pattern developed in a macroscopic diffusion field. Diffusion‐controlled growth interacting with a random field is essential to the formation of a DLA‐like pattern. The selective growth mechanism will provide a random noise for the growth of cordierite due to random distribution of quartz. Therefore, a selective growth mechanism coupled with diffusion‐controlled growth is proposed to explain the power‐law behaviour of the density correlation function of complex patterned cordierite. The results in this paper suggest that not only the growth kinetics but also the spatial distribution of matrix minerals affect the progress of the metamorphic reaction and pattern formation of metamorphic rocks.  相似文献