Methane-derived authigenic carbonates from the Ulleung basin sediments, East Sea of Korea

Authigenic carbonates were sampled in methane-enriched piston core sediments collected from gas venting sites on the western continental slope of the Ulleung Basin, East Sea of Korea. Multidisciplinary investigations on these carbonates, including the scanning electronic microscope (SEM) observations and mineralogical-geochemical compositions, were carried out to identify the carbon and oxygen sources and the forming mechanism of these carbonates. The authigenic carbonates from the study area correspond to semi-consolidated, compact concretions or nodules ranging from 2 to 9 cm in size. X-ray diffraction and electron microprobe analyses showed that most of the sampled carbonate concretions were composed of almost purely authigenic high-Mg calcite (10.7-14.3 mol% MgCO3). Characteristically, microbial structures such as filaments and rods, which were probably associated with the authigenic minerals, were abundantly observed within the carbonate matrix. The carbonates were strongly depleted in delta C-13 (-33.85 parts per thousand to -39.53 parts per thousand Peedee Belemnite (PDB)) and were enriched in delta O-18 (5.16-5.60 parts per thousand PDB), indicating that the primary source of carbon is mainly derived from the anaerobic oxidation of methane. Such methane probably originated from the destabilization of the underlying gas hydrates as strongly supporting from the enriched O-18 levels. Furthermore, the strongly depleted delta C-13 values (-60.7 parts per thousand to -61.6 parts per thousand PDB) of the sediment void gases demonstrate that the majority of the gas venting at the Ulleung Basin is microbial methane by CO2 reduction. This study provides another example for the formation mechanism of methane-derived authigenic carbonates associated with gas-hydrate decomposition in gas-seeping pockmark environments. (c) 2009 Elsevier Ltd. All rights reserved.

末次冰盛期以来黑潮流域的古环境演化

2005年6月，中法国际合作在西太平洋海域执行IMAGES XII-MD147 Micro Polo1航次科学考察时，由法国极地研究所R/V Marine Dufresne极地考察船利用Calypso重力取样器于冲绳海槽南部钻取了34.2米长MD05-2908柱状样。本文利用AMS14C测年数据建立了该孔的年代模型，对该孔的浮游有孔虫动物群落进行了分析，并利用FP-12E浮游有孔虫转换函数和Q型因子分析方法对该孔浮游有孔虫数据进行了研究，对全新世以来的黑潮流系演化和古环境记录进行了讨论。 结果表明，中晚全新世存在着5次洪水爆发期，洪水爆发期与当时温暖气候相对应，而高海平面对洪水的爆发也产生了影响。进入全新世以来的6790～4000a B.P.期间，黑潮流一直有稳步增强的趋势，黑潮流始终位于冲绳海槽内；4000～3000a B.P.期间，黑潮强度减弱或者发生明显东偏，冲淡水影响增强；3000a B.P.以后黑潮强度逐渐增强，1650～0a B.P.为中晚全新世以来黑潮活动最强的时期,在600a B.P.和140a B.P.左右存在低值，黑潮强度短暂减弱。普林虫低值事件在MD05-2908孔中有很好的体现，对该事件进行了进一步定年，其发生时间为3900～2800a B.P.，持续时间为1100a，该事件的发生可能与东亚冬季风加强有关。 冲绳海槽中晚全新世气候变化可以分为四个阶段： 6790～4800a B.P.低温阶段，4800～4100a B.P.高温阶段，4100～2400a B.P.低温阶段，2400～0a B.P.波动高温阶段。通过与中国及世界其它地方对比可以识别出6.3～5.9、5.5、4.6～4.2、3.6～3.0、2.9～2.4、1.3～1.0、0.5～0.1ka B.P.六个降温事件，为全新世气候波动在深海高分辨率沉积记录中的响应提供了有力支持。该孔SST频谱分析结果显示，存在着3008a、1061a这种千年尺度的周期，以及215a、123a、103～107a、81～78a以及73～71a等周期，表明该孔SST变化与太阳活动强度是密切相关的。 中晚全新世以来，黑潮流在冲绳海槽逐步加强，到4000aB.P.左右达到最大，然后4000～3000a B.P.期间，黑潮强度明显减弱或者发生东偏，3000aB.P.以后，黑潮强度持续增强，在近1000aB.P.波动较大。 对冲绳海槽地区14个柱状样氧同位素以及P.obliquiloculata丰度进行研究，发现LGM以来，黑潮流可能仍然在冲绳海槽地区活动，并没有移出海槽外，但是由于其强度减弱，其流径发生了很大变化。

Light energy conversion into H-2 by Anabaena variabilis mutant PK84 dense cultures exposed to nitrogen limitations

Concentrated cultures (25-86 mg Chl a l(-1)) of Anabaena variabilis PK84 were incubated under 99% Ar+1% CO2 atmosphere in the photobioreactor made of coaxial cylinders. Under illumination equal to 353 mu E m(-2) s(-1) they produced hydrogen with the rate more than 20 ml l(-1) h(-1) for several days. The efficiency of light energy conversion into H-2 was approx. 1% and did not depend significantly on initial Chl a concentration. H-2/O-2 ratio reached 41.5% of theoretical value for water photolysis. Data indicate that dense cultures might be used for outdoor systems under direct sun light. Supra-optimal temperatures 36 degrees C were not harmful for cultures even for 2 days period. Short-term incubation of cultures under 36 degrees C even increased H2 production rate and efficiency of light energy bioconversion by 1.25 times. (c) 2006 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.

Electrochemical, SEM/EDS and quantum chemical study of phthalocyanines as corrosion inhibitors for mild steel in 1 mol/l HCl

The inhibition effect of metal-free phthalocyanine (H2Pc), copper phthalocyanine (CuPc) and copper phthalocyanine tetrasulfuric tetrasodium salt (CuPc center dot S(4)center dot Na-4) on mild steel in I mol/l HCl in the concentration range of 1.0 X 10(-5) to 1.0 X 10(-3) mol/l was investigated by electrochemical test, scanning electron microscope with energy dispersive spectrometer (SEM/EDS) and quantum chemical method. The potentiodynamic polarization curves of mild steel in hydrochloric acid containing these compounds showed both cathodic and anodic processes of steel corrosion were suppressed, and the Nyquist plots of impedance expressed mainly as a capacitive loop with different compounds and concentrations. For all these phthalocyanines, the inhibition efficiency increased with the increase in inhibitor concentration, while the inhibition efficiencies for these three phthalocyanines with the same concentration decreased in the order Of CuPc center dot S(4)center dot Na-4 > CuPc > H2Pc according to the electrochemical measurement results. The SEM/EDS analysis indicated that there are more lightly corroded and oxidative steel surface for the specimens after immersion in acid solution containing 1.0 x 10(-3) mol/l phthalocyanines than that in blank. The quantum chemical calculation results showed that the inhibition efficiency of these phthalocyanines increased with decrease in molecule's LUMO energy, which was different from the micro-cyclic compounds. (c) 2005 Elsevier B.V. All rights reserved.

青海湟水流域植物区系研究

湟水流域位于青海省的东部，约处于北纬35°56′－37°38′，东径100°35′－103°05′。属于青藏高原和黄土高原的过滤地带，海拔1650－4394m，全区面积约16600km^2，属于大陆性气候和高原大陆性气候类型。本区共有野生种子植物83科、400属、1234种。分别占本区所属的青藏高原植物亚区唐古特地区总科数的92．22％、总属数的78．74％、总种数的54．00％。研究表明，湟水流域植物区系特征为：（1）在唐古特地区中种类相对较丰富；（2）温带成分占2．80％，以绝对优势确定了本区系为明显的温带性质（属于以北温带成分，特别是欧亚大陆温、寒地带典型成分为优势的，兼具温性，寒温和高寒类型的温带区系性南，或可称为在温带区第中的过渡区系所具有的“复合型”区系特征）；（3）木本类型少，大多数种类为多年生草本植物，缺乏古老和原始类群，一些中国特有种衍生于其广布的亲缘种中，表明本区系具有年轻和衍生的性质；（4）我国西南高山区系和华北区系对该区系具有双重影响；（5）为青藏高原植物亚区唐古特植物地区同华北植物地区相互过渡的代表区系之一；（6）特有属和特有种少。在中国种子植物区系分区中，本区属于青藏高原植物亚区中的唐古特地区。

青海省湟水地区森林灌丛植被遥感分析及其主要特征

湟水地区地处黄土高原和青藏高原过渡带, 界于北纬36°02′～ 37°28′, 东经100°41′～103°04′之间。海拔1650～ 4395m , 总面积为16120 km2。本研究根据卫星遥感影像资料(以TM 为主) , 结合以往野外调查工作, 研究并综合分析了湟水地区的森林、灌丛植被及其主要特征。森林灌丛植被的遥感解译采用综合分析法。研究表明湟水地区森林灌丛植被具有明显的生态地理分布特征, 其分布多集中于黄土低山丘陵与中高山地形结合地带, 即黄土覆盖的边缘交错区域。这一空间分布特征可能与本区的黄土覆盖边缘地区的多样化生态地理特点存在一定的联系。生境的干湿状况直接影响本地区天然林的分布特征、森林灌丛植被覆盖率的高低、森林的类型结构和种类组成, 并成为人工造林效果的重要环境因素。本区森林灌丛植被长期受到人类活动的深刻影响, 具有人类活动的明显痕迹。人类活动的规模范围、作用方式、影响强度等因素成为本区森林灌丛植被及其生境变化与差异的重要原因之一。

石油二次运移机理物理模拟研究

Oil and gas migration is very important for theoretical hydrocarbon geology study and exploration practice, but related research is weak. Physical simulation is a main method to study oil migration. Systematic experiments were done to quantitatively describe the migration patterns, path characters and oil saturation by adjusting the possible dynamic factors respectively. The following conclusions were drawn. 1. Darcy velocity and pore throat diameter were calculated according to seepage cross-sectional area and glass beads arrangement. With such normalized Darcy velocity and pore throat diameter, the date from one and two dimensional experiments can be reasonably drawn in two phase diagrams. It is found that the migration pattern can be identified using only one dimensionless number L which is defined as the ration of capillary number and Bond number. 2. Oil saturated in the pores between glass beads was used as calibration and oil saturation in the path was measured by magnetic resonance imaging. The results show that oil saturation in the center of migration path can reach 100%, is higher than oil saturation in the edge of migration path. 3. Percolation backbone during secondary oil migration was identified experimentally using Hele-Shaw cell. The backbone formed mainly because of the spatial variation of the cluster conductivity caused by oil saturation heterogeneity, main resistant force change, and path shrinkage and snap-off. Percolation backbone improves hydrocarbon migration efficiency and is a favorable factor for reservoir forming. 4. In the three dimensional filling models, the thickness of the secondary migration path is mall. It is only 2.5cm even for the piston pattern. Inclination of the model is the main influencing factor of the secondary path width.

基于分形和统计理论的地层非均质研究

Basin-scale heterogeneity contains information about the traces of the past sedimentary cycle and tectonic process, and has been a major concern to geophysicists because of its importance in resource exploration and development. In this paper, the sonic data of 30 wells of Sulige field are used to inverse the power-law spectra slope and correlation length which are measures of the heterogeneity of the velocity of the log using fractal and statistic correlation methods. By taking the heterogeneity parameters of different wells interpolated, we get power law spectra slope and correlation length contours reflecting the stratum heterogeneity. Then using correlation and gradient, we inverse the transverse heterogeneity of Sulige field. Reservior-scale heterogeneity influnce the distribution of remaining oil and hydrocarbon accumulation. Using wavelet modulus maximum method to divide the sedimentary cycle using Gr data, therefore we can calculate the heterogeneity parameter in each layer of each log. Then we get the heterogeneity distribution of each layer of Sulige field. Finally, we analyze the relation between the signal sigularity and the strata heterogeneity, and get two different sigularity profiles in different areas.