Pore-scale removal mechanisms of residual light non-aqueous phase liquids in porous media     

Helian Li  Jiajun Chen  Jian Yang 《Environmental Earth Sciences》2011,64(8):2223-2228

Glass-etched micromodel and visualization technology were used to research the removal mechanisms of residual light non-aqueous phase liquids (LNAPLs) droplets at pore scale. In this research, n-hexadecane was selected as the LNAPL model substance. During the injection of de-ionized water into the pore channel, residual n-hexadecane droplet was removed quickly at first, then gradually became slow and finally remained nearly invariable; the droplet size after a definite time depends on its initial value. The relationship between total volume of residual n-hexadecane and time can be described by a logarithmic equation: V = V ₀ − 0.0152lnt + 0.0360 (0 < t < 9,420, R ² = 0.9621). Based on percolation theory, the relationship between fluid percolation velocity in pores and time was determined through the analysis of residual n-hexadecane droplet size and the flowing characteristics of injected fluid. Gaussian model was used to fit the cumulated dissolved n-hexadecane, the correlation coefficient R ² = 0.97269. The removal process of n-hexadecane in network model experiment is similar to that of the sand column flushing experiment, which indicates that the mass transfer micro-mechanism of network model experiment could be used to interpret the results of column flushing experiment.  相似文献   

Molecular level analysis of long term vegetative shifts and relationships to soil organic matter composition     

《Organic Geochemistry》2013

Soil organic matter (SOM) is one of the earth’s largest reservoirs of actively cycled carbon and plays a critical role in various ecosystem functions. In this study, mineral soils with the same parent material and of similar approximate age were sampled from the same climatic region in Halsey, Nebraska to determine the relationship between overlying vegetation inputs to SOM composition using complementary molecular level methods (biomarker analyses and solid state ¹³C nuclear magnetic resonance (NMR) spectroscopy). Soil samples were collected from a native prairie and cedar and pine sites planted on the native prairie. Free and bound lipids isolated from the pine soil were more enriched in aliphatic and cutin-derived compounds than the other two soils. Cinnamyl type lignin-derived phenols were more abundant in the grassland soil than in the pine and cedar soils. Acid to aldehyde ratios (Ad/Al) for vanillyl and syringyl type phenols were higher for the pine soil indicating a more advanced stage of lignin oxidation (also observed by ¹³C NMR) in the soil that has also been reported to have accelerated carbon loss. In agreement with the more abundant aliphatic lipids and cutin-derived compounds, solid state ¹³C NMR results also indicated that the SOM of the pine soil may have received more aliphatic carbon inputs or may have lost other components during enhanced decomposition. The observed relationship between vegetation and SOM composition may have important implications for global carbon cycling as some structures (e.g. aliphatics) are hypothesized to be more recalcitrant compared to others and their accumulation in soils may enhance below ground carbon storage.  相似文献   

江西省兴源冲铜矿床同位素地球化学特征及成矿机制探讨   总被引：1，自引：0，他引：1  

刘婷  刘成东  严兆彬  陈益平  吴旭铃  凡秀君 《矿床地质》2013,32(3):614-624

兴源冲铜矿床地处九岭南缘铜多金属大型矿集区西段的黄茅地区。文章在成矿地质特征的基础上,通过对矿石进行稳定同位素地球化学研究,重点分析了成矿物质来源,探讨了矿床成矿机制。碳、氧同位素分析结果表明,矿区碳酸盐岩δ13CVPDB为-5·4‰～1·9‰,平均为0·6‰,δ18OSMOW变化范围为9·0‰～13·9‰,平均为10·9‰,主要为海相碳酸盐岩,碳、氧同位素图解表明碳可能主要来源于深部,且受高温变质作用和低温蚀变作用明显;矿石硫化物硫同位素δ34S变化范围主要在1·0‰～6·2‰之间,个别样品同位素比值偏大,对比相似矿床,表明该矿床具有海底喷流沉积和后期岩浆热液叠加作用的特征。上述同位素地球化学特征表明,兴源冲铜矿床是在中元古代海底火山沉积基础上,经新元古代晋宁造山期岩浆热液、动力变质叠加成矿作用所形成。  相似文献   

雅鲁藏布江缝合带西段东波蛇绿岩OIB型玄武岩的厘定及其形成环境   总被引：9，自引：8，他引：1  

刘飞  杨经绥  陈松永  梁凤华  牛晓露  李兆丽  连东洋 《岩石学报》2013,29(6):1909-1932

雅鲁藏布江缝合带(YZSZ)西段分为两支,南带蛇绿岩的成因对整个缝合带的性质和构造背景的探讨起到十分关键作用,但由于地区偏远、交通不便,研究程度一直十分薄弱.本文报道了南带的东波蛇绿岩中洋岛型玄武岩及有关沉积岩的发现和成因探讨.东波蛇绿岩主要由地幔橄榄岩(方辉橄榄岩、含单辉方辉橄榄岩和透镜状纯橄岩)和上覆火山-沉积岩组成,未见堆晶岩和枕状熔岩等典型洋壳端元.火山-沉积岩盖层为一套稳定的海相层序,主要由硅质灰岩、红色硅质岩等沉积岩和玄武岩和玄武火山碎屑岩组成.OIB型玄武岩的特征表现为低SiO2和MgO,高TiO2、P2O5和(K2O+Na2O),富集Nb、Ta,亏损Th、K、Pb、Sr.微量元素和Sr、Nd、Pb同位素数据显示,该玄武质源区来自石榴石尖晶石二辉橄榄岩2％ ～ 5％的部分熔融.成分研究显示,硅质岩形成于大陆边缘环境,为洋岛或海山和大陆边缘物质在生物作用下形成的.以上证据表明,东波火山-沉积岩层序具有典型海山特征,与世界上典型的地幔柱型蛇绿岩可对比,属于地幔柱热点活动的产物.因此,可以认为,地幔柱热点在与冈瓦纳大陆北缘岩石圈地幔相互作用过程中,不但促使YZSZ西段南带(达巴-休古嘎布)特提斯洋盆打开,还可能与YZSZ蛇绿岩中普遍包含金刚石等异常地幔矿物群有直接的动力学关系.  相似文献   

西藏雅鲁藏布江缝合带西段发现高铬型和高铝型豆荚状铬铁矿体   总被引：11，自引：5，他引：6  

熊发挥  杨经绥  刘钊  郭国林  陈松永  徐向珍  李源  刘飞 《岩石学报》2013,29(6):1878-1908

豆英状铬铁矿按其矿物化学组分分为高铝型(Cr#值为20～ 60)和高铬型(Cr#值为60～80)两类(Thayer,1970),在全球已报道的豆英状铬铁矿中普遍为在一岩体内只存一种类型的矿体,而在同一岩体内发现两种类型的铬铁矿体较少见.位于雅鲁藏布江缝合带西段普兰岩体中首次发现同时存在高铬型和高铝型铬铁矿,岩体由地幔橄榄岩、辉长辉绿岩、火山岩等组成.地幔橄榄岩主要为方辉橄榄岩、纯橄岩和少量二辉橄榄岩.在方辉橄榄岩中发现7处透镜状的铬铁矿矿体露头,矿石类型主要有致密块状、稠密浸染状和稀疏浸染状等.矿体长2～6m,厚0.5～2m,矿体的最大延伸方向为北西-南东向,与岩体的展布方向一致,矿石的Cr#=52～88,高铬型铬铁矿包括Cr-2～5矿体,Cr#值为63～89,高铝型铬铁矿有Cr-1和Cr-6矿体,Cr#=52 ～55.矿石中脉石矿物主要为橄榄石、角闪石、蛇纹石等.普兰地幔橄榄岩的矿物结构显示,岩体经历了强烈的部分熔融以及塑性变形作用,地幔橄榄岩的地球化学特征显示岩体形成于MOR,后受到SSZ环境的改造.并且依据铬尖晶石-橄榄石/单斜辉石的矿物化学成分,识别出普兰地幔橄榄岩至少经历了3次不同的部分熔融,包括早期部分熔融(～10％)、晚期部分熔融(20％～30％)和局部的减压部分熔融作用(～15％).对比其他铬铁矿矿体和地幔橄榄岩的矿物组合,矿物化学和地球化学等,显示普兰豆荚状铬铁矿矿体与典型高铬型、高铝型铬铁矿具相似性,并存在较大的找矿空间.  相似文献   

西藏康金拉铬铁矿床刚玉中的包裹体研究   总被引：1，自引：1，他引：0  

徐向珍  杨经绥  郭国林  熊发挥 《岩石学报》2013,29(6):1867-1877

西藏康金拉铬铁矿石的矿物学研究中,发现大量的微粒金刚石和碳硅石等超高压异常地幔矿物,表明它们产在一个强还原的高压环境.本研究在铬铁矿石中还发现了刚玉及其中大量的矿物包裹体.电子探针等方法研究表明,包裹体的种类包括简单氧化物,如金红石;自然钛;Ti-N、Ti-Si、Ti-C、Ti-Si-P、Ti-B等合金类;含稀土元素的硅酸盐矿物,以及一些未知矿物.结合对铬铁矿石中其他矿物的研究成果,认为康金拉铬铁矿石中的刚玉及其中的强还原环境形成的矿物组合形成于深部地幔.因此,康金拉铬铁矿石中的刚玉可以认为是一种新的带有高压环境信息的标志性矿物.  相似文献   

PAH-degrading microbial consortium and its pyrene-degrading plasmids from mangrove sediment samples in Huian,China     

《Marine pollution bulletin》2009,58(6-12):703-706

PAH-degrading microbial consortium and its pyrene-degrading plasmids were enriched from the sediment samples of Huian mangroves. The consortium YL showed degrading abilities of 92.1%, 87.6%, 92.3%, and 95.8% for pyrene, fluoranthene, phenanthrene, and fluoene at 50 mg l⁻¹ after 21 days incubation, respectively. The dynamics of pH changes in the cultures was consistent with that of PAH concentration change. Bacillus cereus Py5 and Bacillus megaterium Py6 were isolated from the consortium and observed consuming 65.8% and 33.7% of pyrene (50 mg l⁻¹) within three weeks, respectively. The enriched Escherichia coli DH5α cells containing the plasmids of YL were demonstrated to degrade 85.7% of the original pyrene concentration at the 21st day.  相似文献   

Distribution and speciation of mercury in surficial sediments from main mangrove wetlands in China   总被引：4，自引：0，他引：4  

Z.H. Ding  J.L. Liu  L.Q. Li  H.N. Lin  H. Wu  Z.Z. Hu 《Marine pollution bulletin》2009,58(9):1319-1325

The purpose of this study was to establish the distribution, speciation and bioavailability of mercury in mangrove sediments. A systemic survey of surficial sediments from 13 mangrove wetlands of China was carried out. Hg concentrations ranged from 2.3–903.6 ng g⁻¹, with an average value of 189.4 ng g⁻¹. Of the 13 areas surveyed, the Hg content in sediments was similar to background levels in 6 areas but was much higher in the other seven areas. Hg levels were affected by natural and anthropogenic factors, including terrestrial pollutants, geomorphic properties, and indirectly by economic status. Hg levels were positively correlated with organic matter, pH, and silt and clay fractions, but Hg was negatively correlated with sand fraction. In most mangrove wetlands, Hg existed primarily in the form of volatile Hg. Hg is easily bioaccumulated in mangrove wetlands and may be the natural source of Hg emissions to the atmosphere.  相似文献   

东昆仑造山带海德乌拉铀矿床成矿流体特征研究     

朱坤贺  王凯兴  刘晓东  段建华  李彦强  吴佳  余驰达  雷勇亮 《地质学报》2024,98(2):467-480

东昆仑造山带海德乌拉铀矿床是近些年西北地区最新探明的与火山岩有关的独立铀矿床,该矿床的发现为东昆仑造山带探寻热液型铀矿床提供了指示意义。本文选择与海德乌拉铀矿成矿期相关的透明矿物（粉红色方解石、紫黑色萤石及石英）作为研究对象,系统地开展C- H- O同位素和流体包裹体研究,查明该矿床成矿流体的来源与性质,并探讨矿床成因。研究结果表明,海德乌拉铀矿床成矿期石英中主要为H2O气液两相包裹体,少见CO2- H2O两相包裹体;在粉红色方解石脉、紫黑色萤石脉中流体包裹体均含H2O气液两相包裹体,在粉红色方解石脉中偶见纯液相包裹体,均未见到纯气相及含固相包裹体。成矿期粉红色方解石、紫黑色萤石及石英中包裹体均一温度范围分别为133~187℃（均值163℃）、127~204℃（均值169℃）、183~287℃（均值219℃）,盐度范围分别为1. 40%~7. 02%NaCleq（均值3. 65%NaCleq）、0. 53%~3. 06%NaCleq（均值1. 26%NaCleq）、7. 17%~17. 26%NaCleq（均值为11. 46%NaCleq）。流体包裹体气相成分以H2O为主,另含少量CO2等。C- H- O同位素实验数据表明,流体中δ13CFluid- V- PDB、δDFluid- V- SMOW、δ18OFluid- V- SMOW值的变化范围分别为1. 59‰~1. 00‰、71‰~63‰、0. 03‰~3. 72‰,表明成矿流体并非单一来源,可能为大气降水与岩浆水混合来源。此外,沥青铀矿的沉淀主要是由于流体与围岩的相互反应所引起的物理化学条件变化加上流体沸腾/CO2去气,最终导致了沥青铀矿等成矿物质发生大规模的卸载与沉淀。  相似文献   

Research on the temperature field of a partially freezing sand barrier with groundwater seepage     

LiYan Lao  ZhiQiang Ji  LiangLiang Huang  ShangJing Li 《寒旱区科学》2017,9(3):280-288

To study the distribution characteristics and variation regularity of the temperature field during the process of seepage freezing,a simulated-freezing test with seepage of Xuzhou sand was completed by using a model test developed in-house equipment.By means of three group freezing tests with different seepage velocities,we discovered the phenomenon of the asymmetry of the temperature field under the influence of seepage.The temperature upstream was obviously higher than that downstream.The temperature gradient upstream was also steeper than that downstream.With a higher seepage velocity,the asymmetry of the temperature field is more pronounced.The asymmetry for the interface temperature profile is more strongly manifest than for the main surface temperature profile.The cryogenic barrier section is somewhat"heartshaped".With the increasing velocity of the seepage flow,the cooling rate of the soil decreases.It takes much time to reach the equilibrium state of the soil mass.In our study,seepage flow velocities of 0 m/d,7.5 m/d,and 15 m/d showed the soilcooling rate of 4.35°C/h,4.96°C/h,and 1.72°C/h,respectively.  相似文献