Hydrocarbons in surface sediments from the Changjiang (Yangtze River) Estuary, East China Sea   总被引：9，自引：0，他引：9  

Bouloubassi I  Fillaux J  Saliot A 《Marine pollution bulletin》2001,42(12):1335-1346

Sedimentary aliphatic (AH) and polycyclic aromatic hydrocarbons (PAHs) were studied in the Changjiang Estuary and the adjacent East China Sea. Total AH ranged from 2.20 to 11.82 μg g⁻¹ and consisted of n-alkanes and a dominant petroleum-related unresolved complex mixture (UCM). Within the n-alkanes, terrestrial plant wax compounds prevailed at nearly all stations. Of the PAHs, biogenic perylene dominated at stations receiving riverine inputs. Anthropogenic PAHs originating from combustion/pyrolysis processes varied from 17 to 157 ng g⁻¹, while fossil PAH concentrations ranged from 42 to 187 ng g⁻¹. Both biogenic and anthropogenic hydrocarbons are primarily derived from riverine discharges and accumulate at shallow-water stations. Distinct phase associations lead, nevertheless, to different sedimentation patterns. Fossil PAHs are enhanced at offshore stations where they are introduced directly by shipping activities. Biomarker fingerprints ascribe their source to Chinese crude oils. The overall levels of anthropogenic hydrocarbons are low compared to relevant areas worldwide and reveal a low/moderate level of hydrocarbon pollution.  相似文献   

塔里木盆地西北缘二叠系礁灰岩的时空分布特征及其油气地质意义   总被引：3，自引：0，他引：3       下载免费PDF全文

罗金海车自成  周新源李勇李建立  张敬艺 《地质论评》2007,53(5):600-607

对塔里木盆地西北缘二叠系礁灰岩的岩石、岩相、沉积演化和油气地质特征的分析表明,生物礁主要发育于中二叠统栖霞阶昆克拉契组和巴立克立克组,以亮晶藻粘结灰岩为主,具有堤礁的特点。二叠系礁灰岩较大的厚度表明,当时礁体生长速率与礁基沉降（或水体加深）的速率匹配较好,具有进积型沉积的特点,这与当时塔里木地块内部的退积型沉积特点是不一致的。礁灰岩的原生孔隙较小,可以作为中等烃源岩,在哈拉峻盆地的东南侧和乌什凹陷北缘的覆盖区之下可能构成与礁灰岩相关的油气远景区。  相似文献   

土壤中钙形态的连续浸提方法   总被引：4，自引：0，他引：4  

余海  王世杰 《岩矿测试》2007,26(6):436-440

通过改进的连续浸提技术，把土壤钙的赋存形态划分为5个类型：水溶态、交换态、酸溶态、有机结合态及残渣态，用原子吸收光谱法测定各形态钙含量及总钙量，各形态钙的加和值与测得的总钙量基本相符，且各形态钙8次浸提的相对标准偏差基本在10％以内。探讨了改进的连续浸提方法提取条件（包括浸提剂、水土比、提取时间、离心速率及离心时间等）对提取效果的影响。结果表明，土壤中各形态钙可以满足生态地球化学土壤样品评价需要。  相似文献   

Environmental impact on construction limestone at humid regions with an emphasis on salt weathering,Al-hambra islamic archaeological site,Granada City,Spain: case study     

G. M. E. Kamh 《Environmental Geology》2007,52(8):1539-1547

Al-hambra is an immense and valuable archaeological site in Spain built on Sabika hill with red brick and natural sandy limestone. It exhibits weathering features indicating salt weathering process. The main aim of this study is to examine weathering processes and intensity acting on Al-hambra. Rock petrography and mineralogical composition have been examined using thin sections, scanning electron microscope, X-ray diffraction and X-ray fluorescence; limits of rock’s physical parameters using ultrasonic waves and mercury porosimeter; rock salt content through hydrochemical analysis. Salts attacking this structure are mainly from wet deposition of air pollutants on the long term chemical alteration of rock’s carbonate content to its equivalent salts. The salts’ concentration limit within the examined rock samples is considerably low but it is effective on the long run through hydration of sulphate salts and/or crystallization of chloride salts. Rock texture type and its silica as well as clay content reduces its resistance to internal stresses by salts as well as wetting and drying cycles at such humid area. The recession in limits of physical parameters examined for deep seated and weathered limestone samples quantitatively reflects weathering intensity on Al-hambra.  相似文献   

Leakage below dam sites in limestone terrains by enhanced karstification: a modeling approach     

Douchko Romanov  Franci Gabrovsek  Wolfgang Dreybrodt 《Environmental Geology》2007,51(5):775-779

Unnaturally high hydraulic gradients below dam sites enhance dissolutional widening of fractures in limestone. A model is presented which suggests that under unfavorable conditions, leakage rates could become unbearably high during the lifetime of the dam. At the beginning when water is impounded, leakage rates are low and increase slowly. A positive feedback loop, however, causes a sudden dramatic increase of leakage within a few years. Deep grouting becomes necessary to prevent such failures. Inefficiencies in grouting may leave some open fractures in the grouting curtain. These fractures widen faster than pathways below the grouting curtain, and reduce the effect of the grouted region located below. Therefore, open fractures act in a similar way as reduction of the grouting depth.  相似文献   

Triassic mid-oceanic sedimentation in Panthalassa Ocean: Sambosan accretionary complex, Japan     

Tetsuji  Onoue  Hiroyoshi  Sano 《Island Arc》2007,16(1):173-190

Abstract   The Sambosan accretionary complex of southwest Japan was formed during the uppermost Jurassic to lowermost Cretaceous and consists of basaltic rocks, carbonates and siliceous rocks. The Sambosan oceanic rocks were grouped into four stratigraphic successions: (i) Middle Upper Triassic basaltic rock; (ii) Upper Triassic shallow-water limestone; (iii) limestone breccia; and (iv) Middle Middle Triassic to lower Upper Jurassic siliceous rock successions. The basaltic rocks have a geochemical affinity with oceanic island basalt of a normal hotspot origin. The shallow-water limestone, limestone breccia, and siliceous rock successions are interpreted to be sediments on the seamount-top, upper seamount-flank and surrounding ocean floor, respectively. Deposition of the radiolarian chert of the siliceous rock succession took place on the ocean floor in Late Anisian and continued until Middle Jurassic. Oceanic island basalt was erupted to form a seamount by an intraplate volcanism in Late Carnian. Late Triassic shallow-water carbonate sedimentation occurred at the top of this seamount. Accumulation of the radiolarian chert was temporally replaced by Late Carnian to Early Norian deep-water pelagic carbonate sedimentation. Biotic association and lithologic properties of the pelagic carbonates suggest that an enormous production and accumulation of calcareous planktonic biotas occurred in an open-ocean realm of the Panthalassa Ocean in Late Carnian through Early Norian. Upper Norian ribbon chert of the siliceous rock succession contains thin beds of limestone breccia displaced from the shallow-water buildup resting upon the seamount. The shallow-water limestone and siliceous rock successions are nearly coeval with one another and are laterally linked by displaced carbonates in the siliceous rock succession.  相似文献   

Carbonate deposits on submerged seamounts in the northwestern Pacific Ocean     

Hideko  Takayanagi  Yasufumi  Iryu  Tsutomu  Yamada  Motoyoshi  Oda  Kazuyuki  Yamamoto  Tokiyuki  Sato  Shun  Chiyonobu  Akira  Nishimura  Tsutomu  Nakazawa  Satoshi  Shiokawa 《Island Arc》2007,16(3):394-419

Abstract   The lithology of shallow-water carbonates collected from 19 sites on 16 seamounts in six areas of the northwestern Pacific Ocean using the Deep-sea Boring Machine System are described. The areas include the Amami Plateau, Daito Ridge, Oki-Daito Ridge, Urdaneta Plateau, Kyushu-Palau Ridge and Ogasawara Plateau. Chronological constraint is provided by calcareous nannofossil biostratigraphy, planktonic foraminiferal biostratigraphy, larger foraminiferal biostratigraphy and strontium (Sr) isotope stratigraphy. Large amounts of shallow-water carbonates accumulated on the seamounts during the Oligocene, a relatively cool period, whereas limited carbonate deposits formed during the Early Miocene, a relatively warm period. This might indicate that deposition of shallow-water carbonates on seamounts in the northwestern Pacific Ocean was not necessarily controlled by climatic conditions, but was related to volcanism and tectonics that served as foundations for reef/carbonate-platform formation. Remarkable differences in biotic composition exist between Cretaceous and Cenozoic shallow-water carbonates. Late Cretaceous shallow-water carbonates are distinguished by the occurrence of rudists, solenoporacean algae and microencrusters. Middle Eocene to Early Oligocene shallow-water carbonates are dominated by Halimeda or nummulitid and discocyclinid larger foraminifers. Scleractinian corals became common from the Oligocene onward. Nongeniculate coralline algae and larger foraminifers were common to abundant throughout the Eocene to the Pleistocene. The replacement of major carbonate producers in the shallow-water carbonate factory during post-Cretaceous time is in accordance with previous studies and is considered to reflect a shift in seawater chemistry.  相似文献   

Simulation of the dissolution of weathered versus unweathered limestone in carbonic acid solutions of varying strength     

M. J. Thornbush  H. A. Viles 《地球表面变化过程与地形》2007,32(6):841-852

A simulation was undertaken within a climatic chamber to investigate limestone dissolution under varied carbonic acid (H₂CO₃) strengths as a possible analogue for future increases in atmospheric CO₂ arising from global warming. Twenty‐eight samples cut from a block of Bath (Box Hill) limestone from Somerville College, Oxford, which had been removed during restoration after 150 years in an urban environment, were weighed and placed in closed bottles of thin plastic containing varying concentrations of H₂CO₃. Half of the stone samples were derived from exposed surfaces of the stone block (weathered) while the others were obtained from the centre of the block on unexposed surfaces (unweathered). The purpose of this was to compare dissolution of previously weathered versus unweathered surfaces in strong (pH 4·73) versus weak (pH 6·43) solutions of H₂CO₃. A temperature of c. 19 °C was maintained within the chamber representing a plausible future temperature in Oxford for the year 2200 given current warming scenarios. The simulation lasted 25 days with a few stone samples being removed midway. Stone samples show reduced weight in all cases but one. There was greater dissolution of stone samples in a strong H₂CO₃ solution as conveyed by higher concentrations of total hardness and Ca²⁺ in the water samples as well as enhanced microscopic dissolution features identified using SEM. The simulation confirms that enhanced atmospheric CO₂ under global warming, given adequate moisture, will accelerate dissolution rates particularly of newly replaced limestone building stones. However, previously weathered surfaces, such as those on historical stone exposed for a century or more, appear to be less susceptible to the effects of such increased rainfall acidity. Conservation techniques which remove weathered surfaces, such as stone cleaning, may accelerate future decay of historical limestone structures by increasing their susceptibility to dissolution. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

塔里木盆地西南依格孜牙组与卡拉塔尔组灰岩碳、氧同位素特征     

李滨阳  周瑶琪  吴绍祖  李永安 《新疆地质》2002,20(Z1):88-90

对塔里木盆地西南依格孜牙组和卡拉塔尔组灰岩碳、氧同位素特征研究结果表明,上白垩统依格孜牙组δ13C(PDB标准)平均值为3.79‰,δ18O(PDB标准)平均值为-3.49‰;古近系卡拉塔尔组灰岩δ13C(PDB标准)平均值为2.09‰,δ18O(PDB标准)平均值为-4.54‰.与前人和世界其他剖面数据对比认为,碳同位素比较稳定,能够反映其沉积时的特征,而氧同位素变化较大,可能受沉积后作用的影响.依格孜牙组与卡拉塔尔组灰岩碳同位素具较大差异,主要受陆源环境(？)物质的注入,海水盐度、生物作用和古大气CO2含量等因素的影响.  相似文献   

藏南岗巴—定日地区始新世化石碳酸盐岩微相与沉积环境   总被引：8，自引：0，他引：8       下载免费PDF全文

李国彪万晓樵  其和日格梁定益  刘文灿 《中国地质》2002,29(4):401-406

藏南岗巴-定日地区发育着西藏最晚期的海相沉积，对这套海相沉积的研究，可提供关于西藏特提斯演化晚期的良好信息，本文对岗巴-定日地区始新世遮普惹组的化石碳酸盐岩微相进行了较为详细的分析和研究。参考Wilson(1975)的标准微相，初步识别出10种微相和5种生物相类型。同时对遮普惹组中的砾状灰岩的成因机制作了有益的探讨，它完全是由沉积作用而成；胶结物不是源于物质的重新分配，而是台地边缘斜坡的等深流沉积。以此为基础，对西藏特提斯晚期沉积环境的演变进行了较为详细的分析。笔者认为：岗巴-定日盆地在始新世Ypresian-Lutetian早期接受海侵；自Lutetian晚期开始，区内总体处于一种海退环境，但由于受板块碰撞作用的影响，岗巴地区在Lutetian晚期-Bartonian晚期成为-深水坳陷盆地；至Priabonian早期，海水完全退出本区。  相似文献